WO2010119447A1 - Système et procédé d'imagerie - Google Patents

Système et procédé d'imagerie Download PDF

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Publication number
WO2010119447A1
WO2010119447A1 PCT/IL2010/000308 IL2010000308W WO2010119447A1 WO 2010119447 A1 WO2010119447 A1 WO 2010119447A1 IL 2010000308 W IL2010000308 W IL 2010000308W WO 2010119447 A1 WO2010119447 A1 WO 2010119447A1
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WIPO (PCT)
Prior art keywords
optical
light
optical system
elements
window
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PCT/IL2010/000308
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English (en)
Inventor
Doron Shlomo
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Doron Shlomo
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Publication of WO2010119447A1 publication Critical patent/WO2010119447A1/fr

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N23/00—Cameras or camera modules comprising electronic image sensors; Control thereof
    • H04N23/60—Control of cameras or camera modules
    • H04N23/69—Control of means for changing angle of the field of view, e.g. optical zoom objectives or electronic zooming

Definitions

  • the present invention relates to imaging devices and methods for imaging and image analysis.
  • Cameras are typically based on a single aperture focused imaging techniques.
  • Such systems typically utilize an imaging screen/detector and a lens module (e.g. including a set of one or more lenses and/or mirrors) with a single optical aperture through which light is focused on the imaging screen forming thereon an image (an actual image) of a certain portion of the scenery defined by the field of view of the camera.
  • a lens module e.g. including a set of one or more lenses and/or mirrors
  • the lens module of such cameras enables light collection and focusing from a relatively large aperture (larger than that possible with pinhole/direct-ray imaging), thus providing sufficient light intensities on the imaging screen.
  • imaging systems often have a relatively large dimension (large length along their optical axes).
  • Utilizing lens modules with low F numbers (the F-number being the ratio of the focal length of the lens module to its effective aperture diameter) that allow locating an imaging screen in proximity to the lens generally introduces substantial aberrations to image.
  • utilizing focal lens modules with low F- numbers to focus an image on the imaging screen is generally limited in terms of the focal depth of the imaging system, and only parts of the scenery, which are located within a certain narrow distance range from the imaging systems, are focused on the imaging screen.
  • thermal imaging systems for which the dimensions and weight of the imaging device are highly significant are thermal imaging systems.
  • the detector generally a focal plane array FPA detector
  • some parts of a DEWAR assembly enclosing the optical path of light entering towards the detector are maintained at low-temperature conditions (e.g. cooled to down to cryogenic temperatures) in order to reduce the amount of thermal noise in the image.
  • Thermal noise affecting the signal to noise of the image captured by the FPA detector may originate from temperature of the detector itself or from thermal radiation emanating (emitted or reflected) from the inner sidewalls of the DEWAR that define the field of view of the detector.
  • the cooling systems e.g. thermo-electric cooler (TEC) or nitrogen evaporation cooling
  • TEC thermo-electric cooler
  • the present invention provides a novel imaging method and system (e.g. camera) utilizing multi-aperture imaging, while enabling the system to be desirably small and light, while not affecting the image quality.
  • a novel imaging method and system e.g. camera
  • multi-aperture imaging while enabling the system to be desirably small and light, while not affecting the image quality.
  • the imaging system of the invention includes an optical window defining/including multiple optical apertures through which light is projected, from outside scenery to be imaged, onto an imaging surface of the imaging system (e.g. light sensitive surface of an image detector coupled or integrated with the imaging system).
  • an aperture is a light transmitting optical element, or generally a light transmissive region, which may or may not have an optical power.
  • the optical window associated with multiplicity of such apertures presents a certain transmission pattern, variable or static.
  • the optical window and the light detection surface may be formed together as an integrated structure or as separate elements accommodated within an optical enclosure (opaque or diffusive) of said imaging system.
  • one of the drawbacks of single-aperture imaging systems is that operating with small F-numbers introduces various aberrations to the image. Accordingly, most of the known single-aperture imaging systems operate with an imaging lens set having F-number greater F#>2, and thus the detector is located substantially at the focal plane of the lens-set, at a distance of the order of twice the diameter of the lens's effective aperture. Accordingly, the thickness of such imaging systems cannot be reduced below the characteristic size of their effective light collection aperture.
  • the present invention solves the above problem of the single-aperture approach by utilizing multiple optical elements each having a relatively small sized light collection aperture, and further improves the multi-aperture approach by providing a novel arrangement of multiple light collection elements such that this arrangement has a significant light collection area, as each light collection element collects light from a substantially part of the field of view of the imaging system and effectively projects it onto a light sensitive surface of the detector.
  • known multiple apertures imaging systems are designed by mimicking the operational principles of compound insect eyes. According to those designs, each aperture is associated with an optical element (having a single aperture) and with a dedicated light detection region of an image detector and actually operates as in independent imager (camera).
  • a plurality of such independent cameras is then aligned together to form an imaging system of a certain field of view.
  • Each of these cameras (apertures) is designed and aligned with the imaging system and with respect to other cameras to cover a certain partial region (typically a small region) of the entire field of view of the imaging system. Accordingly, an image of the entire field of view of the imaging system is obtained by these systems by joining together (mosaicing) the images of small portions of that field of view that are captured by the different independent cameras.
  • multiple apertures imaging systems manufactured according to the conventional approach can be designed for having shorter optical length and thus smaller dimensions as compared to the single-aperture based systems. This is because the relatively small apertures of the independent cameras allow medium and high F- numbers (e.g. F#>2) to be achieved together with relatively short optical lengths of the cameras (relatively to the width and height dimensions of the imaging systems).
  • medium and high F- numbers e.g. F#>2
  • each of the multiple cameras should have sufficient imaging quality as each of the cameras is alone responsible for imaging a certain part of the field of view of the optical system.
  • the cameras should be carefully arranged and directed with respect to one another such that each camera "sees" a different portion of the field of view of the imaging system without having gaps between the cameras fields of view (sometimes with a small overlap between their fields of view) such that an image, without gaps, of the entire field of view of the system can be generated by mosaicing the images from the different cameras. This requires complicated fabrication and alignment methods making such devices expensive.
  • the optical system of the invention utilizes a novel arrangement of multiple optical elements (i.e. constituting multiple effective optical apertures).
  • the optical elements are arranged such that each of the elements is capable of projecting, onto the imaging surface, a light field (image) of a substantial region of the desired field of view of the optical system. Additionally, the region of the imaging screen, on which light (image) is projected by an individual aperture, is overlapping with other regions on which light is projected by one or more other apertures. It should be noted that with the arrangement of the invention, the overlapping images are not necessarily formed by locally adjacent optical elements (apertures).
  • the image formed on the imaging surface is not a mosaic of independent images each corresponding to a partial field of view of the optical system, but rather is an "indicative image" of the entire field of view of the optical system that is formed by multiple overlapping images from the multiple optical elements.
  • optical elements according to the invention allows for utilizing lower quality optical elements as well as imprecise arrangement of the elements. This certain imprecision and low quality of the elements can be compensated for during the image processing that is carried out according to the invention for generating an actual image of the scenery from the indicative image produced by the optical window.
  • the optical system is characterized by a certain arrangement of the optical properties and/or locations and/or orientations of the optical elements (e.g. light transmissive regions) of the optical window which is irregular with respective to the arrangement of light sensitive pixels in the imaging surface.
  • Said certain arrangement of the optical properties (e.g. transmission, optical power, magnification, field of view, etc.) and/or locations and/or orientations of the optical elements is termed hereinbelow as "irregular respective arrangement" or “irregular arrangement”.
  • This irregular respective arrangement is such that light beams (e.g. collimated), impinging on the optical window from different directions (e.g.
  • the field of view of the imaging system defined by a solid angle of light collection by the optical window, can be regarded as a set of discrete general directions designating a set of light propagation directions, intersecting with and passing through the optical window plane and impinging on the imaging surface. Since light from each of said set of certain general directions is perceived by the detector with a distinct spatial intensity pattern, processing of the readout signals from the detector allows for discriminating between the intensities (and possibly chrominance) of light beams arriving from different general directions.
  • optical window refers to the arrangement of multiple optical elements (having effective apertures corresponding therewith).
  • the optical window can be an integrated bulky unit formed by integral multiple optical elements, or a collection of separate optical elements, arranged according to the invention.
  • optical elements and light transmissive regions are used herein interchangeably and designate transparent regions or optical elements, which may or may not have any optical power.
  • the term irregular respective arrangement of the optical elements should be construed herein as an arrangement of the optical elements, with respect to the locations of light sensitive pixels of a predetermined image detector, designed such that each of the light sensitive pixels perceives a distinct subset of intensities of light arriving from different general directions which is different from the subset of intensities perceived by other pixels of the image detector which output contributes to the processing of the image.
  • the arrangement of the light transmissive regions defines a certain pattern of these regions in the optical window plane.
  • the pattern may be characterized by a spaced apart relationship between the light transmissive regions and/or types (optical properties) of the transmissive regions providing said irregular respective arrangement with respect to one or more designated types of image detectors and with respect the locations of the light sensitive pixels thereon.
  • the optical elements may have no optical power ("plane apertures", perforations, surface relief regions) or may be constituted by one or more optical components (optical units) such as lenses (lenslets) and/or mirrors and/or prisms or from combination of these components.
  • the optical elements used in the invention may be implemented as optical apertures (e.g. pinholes) as well as elements that are capable of manipulating the direction of light passing therethrough.
  • the optical elements have a small dimension in the optical window plane (e.g. their aperture diameter is small) relatively to the dimension of the imaging surface on which an image of the field of view of the imaging system is projected.
  • An optical system of the present invention can be designed for various purposes and can acquire various size scales. Accordingly the optical elements of the invention may be micro- elements having dimensions in the range between a few microns to a few millimeters (micro-lenses, micro-prisms and micro-mirrors), or they may be of macroscopic dimensions of a few millimeters and higher (lenses, lenslets, mirrors and/or prisms).
  • the micro-optical components may be fabricated by any suitable technique such as by photolithography, and may be manufactured from organic materials (photopolymers) and/or inorganic materials.
  • Active (adaptive) micro-optical components which are tunable, i.e. have controllably varying optical properties (e.g. electro-optical elements with changeable optical properties by varying applied voltage), such as their light transmission and focal length, can also be used.
  • optical elements should be interpreted as any elements capable of transferring/reflecting light (not necessarily by specular reflection).
  • Light in this sense may include electro-magnetic (EM) radiation in various wavelength regimes and may include inter alia visible light, ultra-violet light (UV), infra-red light (IR) (e.g. in the Near, Mid, and Far regimes) and also other electromagnetic radiation such as X-ray.
  • EM electro-magnetic
  • UV ultra-violet light
  • IR infra-red light
  • X-ray electromagnetic radiation
  • the arrangement of optical elements of the invention may include electro-optical elements or electronic elements that are configured for applying a lensing effect to light field interacting therewith by manipulating an electro-magnetic field in the vicinity thereof.
  • the irregular respective arrangement of the optical elements and/or pixels may be configured as an optical filter that applies a different spatial intensity/mask to light beams emanating respectively from different general directions (regions of the field of view).
  • each beam from each direction (region of the field of view) projects light with distinct pattern of intensity (or chrominance) on the imaging surface.
  • the distinct patterns are overlaid and/or overlap with one another to form an indicative image of the exterior scenery.
  • An actual image of the exterior scenery within the field of view of the imaging system can be reconstructed from the measured intensities of light captured by the pixels of the imaging surface. Because the different light patterns overlaid/overlapped on the imaging surface are distinct, it is possible to discriminate the intensity in which different patterns are projected and thus to determine the intensity/color of light beams from different directions.
  • the image (indicative of the scenery/light-field) that is formed by the arrangement of optical elements is typically not an actual image of the scenery but it is an indicative image.
  • the latter can be further processed to derive therefrom an actual image of the scenery.
  • Such processing is carried out based on the optical properties of the optical window and more specifically on the optical function matrix of the optical window (as will be described more specifically below) which characterizes the irregular respective arrangement of the optical elements.
  • the actual image of a scenery/light field is an image of the scenery in which the color and/or intensity of each image pixel corresponds respectively to the intensity(ies) and/or color(s) of light ray(s) arriving at the imaging system from about a particular point in the "object" plane in the scenery.
  • the indicative image of the scenery/subject is an image, formed by capturing light rays from the scenery, such that in at least some of the image pixels (typically in all or most of them) the intensity/colors of light rays arriving from about more than one directions are recorded (typically two or more substantially different direction).
  • the indicative image is as image from which an actual image of the scenery can be generated by utilizing the intensities and/or colors recorded in multitude of pixels of the indicative image to devise the intensities and/or colors of light rays arriving at the imaging systems from one or more directions.
  • an irregular arrangement of the optical elements according to the invention can be achieved by varying the pitch/distance between the optical elements and their locations as well as their fields of view and optical properties (such as the magnification and the direction of the principal optical axis) are set such that the images projected by the elements substantially overlap to form an indicative image of the scenery.
  • optical properties such as the magnification and the direction of the principal optical axis
  • optical transfer matrix also referred to herein as optical transfer matrix
  • its optical function matrix is an invertible matrix preferably having multitude of non zero entries in at least some of its rows and columns.
  • optical transfer matrix as it is defined and used herein for the proposes of the present invention should not be confused with the generally known ray transfer matrix (or ABCD matrix) which is sometimes also referred to in the literature as optical transfer matrix.
  • optical function matrix is a matrix representing the optical function of the system.
  • An optical system is generally considered to be located between an input and output reference surfaces/planes (object and image planes) corresponding respectively to the field of view of an imaging system from which light is perceived and to the imaging surface of the imaging system onto which an image of said field of view is projected.
  • the optical function matrix of the optical system allows to determine the intensity (and possibly color) of light distribution that is generated on the output reference plane by said optical system in view of a certain light intensity (and color) distribution emanating from the input reference plane.
  • the distribution of light intensity and/or chrominance emanating from the input reference plane (field of view of the optical system) and the distributions of the light intensity impinging on the output reference plane (imaging surface of the optical system) are represented by the input and output vectors I and O respectively.
  • Each entry in those vectors I and O represents a certain region (point) in the respective input and output planes, and the value in the entry may represent the light intensity and/or chrominance in said certain region.
  • Ideal single-aperture imaging systems of the generally known type can be represented by a diagonal optical function matrix W which is indeed invertible and in some cases, proportional to the unit matrix. This is because light emanating from a single point in the object plane (input plane I) is projected by such systems onto a single point in the image plane (O - output plane). This is also true for known in the art multiple-aperture imaging systems because these systems operate as collection of individual single aperture cameras.
  • an optical function matrix W of a conventional imaging system has substantially only one non-zero entry in each one of its columns and rows as it relates the light intensity (chrominance) emanating from each one region of the input plane with the intensity of light impinging on only one light sensitive pixel of the output plane (the surface of the imaging sensor).
  • the image produced by such systems is an actual image of the scenery because the optical function matrix W of such systems is relatively close to the unit matrix and thus the input and output vectors I and O are very similar.
  • an optical function matrix of a non-imaging optical system such as an optically diffusive bulk/surface
  • a non-imaging optical system such as an optically diffusive bulk/surface
  • Light rays arriving from different regions of the input surface are mixed on the output surface in a way that does not allow reconstructing an image of the input surface therefrom. It is thus impossible to reconstruct the input vector I based on the output vector O.
  • the optical window/system of the present invention is associated with an invertible optical function matrix W having multiple non-zero entries in at least one of its rows and columns.
  • Light from different directions within the field of view of the optical system e.g. different regions of the input plane
  • some of the optical constraints posed by the conventional imaging techniques in which light from different directions is directed to respectively different locations on the imaging surface, are diminished.
  • directional correlation is preserved maintained between the directions of light beams entering the optical window and directions of light beams that are consequently emanating therefrom.
  • the optical transfer matrix W and the input I and output O vectors become infinitely large (with infinite dimension).
  • the output plane is a pixilated surface of an image sensor divided into finite number (e.g. 5 Mega-Pixel) of finite size light sensitive regions.
  • the input plane/field of view which can be sensed by such pixilated surface is also divided into finite numbers of regions. Accordingly, the input I and output O vectors as well as the optical function matrix W, have in practice finite sizes.
  • the optical system of the invention is based on the irregular relative arrangement of the optical elements with respect to the pixel arrangement of the detector.
  • This irregular relative arrangement is configured as an optical filter that applies a different spatial intensity/mask to collimated light beams emanating respectively from directions in the field of view of the optical system for applying different intensity patterns thereto.
  • the different patterns are overlaid/overlap on the imaging surface.
  • the spacing between the exit pupils of the optical elements, from which light is emitted through the optical elements toward the imaging surface is preferably greater than the pitch between light sensitive pixels on the imaging surface.
  • each optical element may collects (through its light collection aperture), light from a substantial part of the field of view of the imaging system and project the collected light onto a substantial part of the imaging surface. Accordingly, an improved light intensity is provided on the imaging surface.
  • the pupil magnification is a ratio between the diameter of the exit pupil (EP), from which light is projected by the optical element on the imaging surface, and the diameter of the entrance pupil (light collection area) from which light is collected by the optical element from the scenery/field of view.
  • EP exit pupil
  • the collected light is condensed to small bundles and emanates from exit pupils of the optical elements which are maintained desirably spaced from one another.
  • optical elements there are various possible arrangements of the optical elements in terms of both the locations and the types of the elements, which can be implemented such that the optical function matrix of the optical window is invertible.
  • different arrangements with different distributions of the optical elements can be realized which are associated with different dynamic ranges and different color depth (color bit rates) of the total image that is projected on the imaging surface.
  • a relatively homogeneous arrangement of the optical elements provides a total image with low dynamic range which requires a detector with high color depth while substantially inhomogeneous arrangement provide an image with high dynamic range which does not require a detector having high color depth bit rate.
  • the optical elements project individual overlapping images on the common image surface (contrary to other multiple-aperture imaging techniques in which each optical element is associated with different part of the imaging surface).
  • the dynamic range of CCD or CMOS image sensors is specified as the maximum achievable signal (defined by the well saturation) divided by the camera noise.
  • the maximum achievable signal or the signal strength is determined by the full-well capacity, and the noise is the sum of dark and read noises.
  • the color depth of an image detector represents the number of bits that are provided by each pixels of the detector to represent the different color or different shades of gray. As higher is the color depth the better is the possible color seperation/descrimination (e.g. between two close colors/light intensities/shades of gray).
  • the arrangements of optical elements in the present invention can be designed differently for effective utilization of image detectors with various dynamic ranges and color depths.
  • the imaging surface in close proximity with the arrangement of the optical elements (close to the optical window).
  • the technique of the invention utilizes multiple apertures and allow for using multiple small optical elements for collecting the same amount of light. The smaller the elements the closer they can be located to the imaging surface of the optical system without requiring use of low F-numbers. Accordingly, an optical system with a thickness of a few millimeters and below can be manufactured according to the invention.
  • utilizing optical elements with optical magnification higher than unity allows locating the imaging surface closer to the optical elements and capturing the same field of view by these optical elements.
  • the optical magnification is considered here as a ratio between the tangents of the maximal angle from which a light beam is projected from the exit pupil of the optical element on the image screen, and the maximal respective angle of incidence (light entry angle through which the light beam had entered the optical element).
  • optical elements which optical magnifications can be controlled or adjusted can also be used for achieving optical zooming.
  • optical zooming does not incur loss of image information and enables to utilize the full extent of the light sensitive surface of the image sensor for imaging variable and controllable fields of view (angles of view).
  • the arrangement of the optical elements, as well as the optical elements themselves present a substantial directional correlated optical system. This provides for wide depth of field (depth of focus) of the imaging system and obviates a need for focus adjustment mechanisms.
  • one or more of the optical elements can operate by the principles of direct rays imaging (e.g. pinhole cameras) which obviate a need for focusing and thus provide an extended depth of focus.
  • the directions of light beams emanating from the exit pupils of such optical elements are maintained relatively correlated with the directions at which they entered the optical elements. Indeed, in direct ray imaging pinhole cameras, the light beams experience no bending at all. However, according to the present invention, the light beams can be bent while passing through the optical window as a result of an optical magnification and/or pupil magnification of the optical elements as well as because of some optical power of the optical elements.
  • the expression direct ray imaging in the context of the imaging system of the invention relates to the directional correlation between the direction of light beams entering and exiting the optical window of the invention. This correlation, referred to herein as directional correlation of the imaging system, may allow utilizing signal processing for identifying/determining the intensities (and chrominance) of light beams from different directions.
  • optical elements with short foal lengths and low F-numbers tend to substantially affect the directions of light beams passing therethrough and to diminish the directional correlation of the imaging system.
  • optical magnifications of the optical elements larger than unity increase the directional correlation as such magnifications operate to direct light entering the optical system from different directions to emanate with more extreme directions.
  • the depth of field (DOF) of an imaging system of the invention utilizing the direct ray imaging principles described above, is increasing with the increase of both the F- numbers of the optical elements and their optical magnification. This is contrary to conventional "focusing based" imaging systems described above in which the depth of field (and focal depth) is reduced when the optical magnification is increased.
  • This feature of the invention allows locating the imaging screen in proximity to the optical window while maintaining a wide DOF.
  • An indicative measure for the directional correlation (DC) of the optical elements of the system of the invention is given by their F-number (F#) multiplied by their optical magnification. The higher this measure is, the better is the directional correlation of the optical elements and also the higher is its DOF.
  • An optical system according to the invention that includes optical elements with high directional correlation (e.g. DC larger than 10 and preferably larger than 100 and more preferably larger than 1000), is referred to herein as directionally correlated optical system. It is preferable that the optical system of the invention has a good directional correlation to enable good measurement of the light intensities from different directions.
  • This can be achieved by utilizing optical elements with large effective focal length associated with high F-numbers (e.g. larger then f/11 and preferably larger than f/100) and also by utilizing optical elements with small F- numbers (e.g. smaller than f/3.8) but having optical magnification (e.g. MA ⁇ x5 magnification).
  • An optical aperture is an example of an afocal optical element that can be used in the present invention. Light rays passing through an optical aperture maintain their direction and hence have high directional correlation.
  • Zooming can be achieved according to the invention by conjugating any one of the above described optical element and telescopic optical element with additional set of optical components (zoom set) that can be operated to control the magnification and condensation of the light beams entering the optical element.
  • additional zoom set may be operated according to known zooming techniques, for example by utilizing an afocal zoom set composed of three lenses that can be actuated to different positions with respect to one another such that in each position different magnification is obtained.
  • zooming can be achieved according to the invention by utilizing electro-optical elements; e.g. by utilizing elements which index of refraction can be controlled to vary their magnification capabilities.
  • zooming of the image formed by the optical window of the invention can also be achieved by conjugating/optically coupling the entire optical window with any of the existing types of zoom lens set system, specifically with afocal zoom lens sets.
  • an afocal zoom lens set system may be located in front of the optical window of the invention
  • the invention in its one aspect provides an optical system including an optical window associated with an invertible optical function matrix W.
  • the optical window includes an irregular setup/arrangement of optical elements which is implemented utilizing either different optical elements such as elements having different sizes and shapes of their optical apertures, different magnification powers or fields of view of the elements and/or it may be achieved by arranging the elements with disordered arrangements (such as a non-periodic or non homogeneous arrangements).
  • the elements may be arranged such that they are oriented with different directions of light collections (their optical axes are directed to different or slightly different directions) such that at least one of the elements captures a different field of view of the scenery.
  • the present invention provides an optical system configured for use with a predetermined light detection surface comprising a multitude of light sensitive pixels.
  • the optical system comprises an optical window defining a predetermined light transmission pattern formed by a multiple spaced apart light transmissive regions, configured in accordance with said multitude of light sensitive pixels, configuration of said multiple spaced apart light transmissive regions defining an irregular arrangement of said regions with respect to said multitude of light sensitive pixels, said optical window with said irregular arrangement being configured for collecting light beams from different directions from a scenery to be imaged and for directing, on each of said light sensitive pixels, the light component formed by a distinct set of light intensities, corresponding to said light beams collected from different directions, thereby providing spatially distinct light intensity patterns overlapped on said light detection surface and corresponding to said light beams collected from different directions.
  • the optical window which is defined by the arrangement of the optical elements, may be planar optical window or it may be curved optical window, as well as may or may not be formed with a surface relief (which may or may not introduce an optical power). Accordingly, the optical axes of the optical elements may be directed to the same or different directions.
  • Colored images can be generated according to the invention by utilizing any of the known in the art technique, e.g. utilizing 3CCD sensors or image sensors with color RGB filtering layer(s)/coatings thereon (RGB filtering).
  • the optical window itself may be associated with (or may include) an arrangement (array) of prisms that split light of different colors to impinge on different locations on the imaging surface.
  • prisms can be each associated with a specific optical element of the optical window (or included therein) or common prisms can serve for several optical elements.
  • color filtering coating or layers can be used to filter the light passing through the different elements.
  • the invention also provides an IR imaging optical window for use with thermal imaging systems (e.g. IR imaging).
  • the optical window includes an arrangement of multiple spaced apart optical elements (light transmission regions) and one or more thermal conduction regions thermally coupled with the spaced apart optical elements.
  • the optical elements are arranged substantially traverse to the principal light propagation direction through the optical window and may operate as a multi-aperture imaging system according to the present invention and also according to any suitable, known in the art, multi-aperture imaging techniques.
  • an optical window for use for thermal imaging, the optical window comprising an arrangement of multiple optical elements and one or more thermal conduction elements; said optical elements are arranged substantially traverse to the general direction of light propagation through the optical window and said one or more thermal conduction elements comprising thermal conduction regions thermally coupled with at least some of the optical elements thereby enabling efficient heat evacuation from said optical window.
  • Such constructed optical window is advantageous for use in thermal (IR) imaging systems because the optical window includes multiple small optical elements that may collectively have smaller thermal mass than a comparable single-aperture optical module (lens-sets) typically used in the conventional thermal detection systems. This is because the thickness of an optical component (e.g.
  • lens of a certain F-number constructed from a certain optical material can be scaled down together with the diameter of its light collection aperture. Accordingly, by utilizing multiple small optical elements instead of a single large optical element, less material mass is used and lower thermal mass is obtained. This enables effective cooling of such optical window to low temperatures with low cooling/energy requirements. Moreover, thermal conduction regions in the optical elements of the present invention can be thermally coupled with each of the spaced apart optical elements. This enables effective heat evacuation from optical elements located at/near the center of the optical window as well as from optical element located in the periphery of the optical window. Accordingly, homogeneous cooling of the optical window can be achieved and thus thermal noise in the IR/thermal imaging system can be reduced.
  • the thermal conduction regions may be regions of the optical window that are thermally coupled to the optical elements in parallel to their optical path (e.g. surrounding the optical elements or coupled to one or more facets of the elements that encircle or enclosing their optical paths), and/or the thermal conducting regions may be thermally conductive layer(s) perpendicular to the optical axes of the elements defining light transmissive apertures through which light passes through the optical elements. Accordingly, the thermal conduction region(s) are thermally coupled with the individual optical elements and is/are accommodated with thermally conductive material (such as metal) which allows effective heat evacuation from the elements.
  • thermally conductive material such as metal
  • Thermal conduction regions are typically associated with thermal coupling regions located at the sides of the optical elements to allow thermal coupling of the optical element to the enclosure of the thermal imaging system for allowing heat evacuation therethrough from the optical window.
  • the optical window according to any one of the embodiments of the present invention can be implemented in different size scales according to the desired dimensions of the optical system sought.
  • the optical window can have wafer scale dimensions.
  • Refractive optical elements, such as lenses or lens arrays may have a plano-convex and/or plano-concave surface or other structures such as biconcave and/or biconvex and/or convexo-concave. Accordingly the optical elements according to the invention may include optical components formed by various techniques and from various materials.
  • suitable arrays of micro-lenses and/or lenslets of small dimensions can be fabricated for example utilizing photosensitve layer and a writing mask as described for example in US patent publication No. 2007/218372 incorporated herein by reference.
  • micro lens arrays with curved surfaces defining an array of convex or concave surface regions of the microlens can be fabricated utilizing sacrificial layer technology as described for example in International (PCT) publication No. WO 08/010219 incorporated herein by reference.
  • Other techniques for fabricating such optical components having small dimensions and adequate optical quality include micro-optic technologies, such as UV replication or hot stamping in plastic. Such techniques are described for example in US patent publication no. 2009/050946 incorporated herein by reference.
  • Optical components suitable for the purposes of the present invention can be manufactured from inorganic materials as well as from polimetric materials.
  • Polymer materials suited for the invention may include polymethylmethacrylate (PMMA), polycarbonate, polystyrene, cycloolefin polymer (COP), cycloolefin copolymer (COC) or other polymers on a polycycloolef ⁇ n basis.
  • Support structures as well as spacer elements may be fabricated from silica/glass as well as from organic polymer materials such as BCB.
  • the spacer layer structure has at least 10 microns thickness and at most 150 microns thickness, and is made either from an inorganic material by a sacrificial layer technology or from one or more organic polymer materials including a BCB layer.
  • Opaque/space-defining elements which can be used to define the apertures of the optical elements of the invention may include for example non-transparent polymer plate having perforations or recess therein.
  • Fig. 1 is a schematic illustration of a two dimensional optical system according to the invention comprising an optical window with multiple light transmissive regions.
  • Fig. 2 is a schematic illustration of an embodiment of a one dimensional optical system according to the invention.
  • Figs. 3A to 3F are six examples of the optical system of the invention in which six different possible arrangements of the optical elements are illustrated suited for projecting respectively six different indicative images of the scenery.
  • Figs. 4A to 4F are six examples of optical elements suited for use, alone or in combinations thereof, in the optical window of the invention.
  • Figs. 5A to 5C exemplify an optical window according to an embodiment of the present invention formed by two arrays of lenses and an aperture defining surface.
  • Figs. 5D and 5G illustrate an embodiment of an optical system according to the invention including an integrated structure integrated with an image detector and exemplify three different configuration of an aperture defining surface of the optical window.
  • Figs. 6A to 6F illustrate zooming principles according to the present invention and exemplify zooming optical elements and an optical system including the same constructed according to the invention.
  • Figs. 7A to 7C illustrate an embodiment of an optical window/system according to the invention suited for use for thermal imaging.
  • FIG. 1 An optical system 100 according to an embodiment of the present invention is illustrated schematically in Fig. 1.
  • the optical system 100 is configured as an imaging device and includes an optical window 120 configured and operable according to the principles of the present invention.
  • the optical window 120 defines an optical surface S2 and is associated with an imaging surface Sl of said imaging device.
  • Light detection surface Sl may be a virtual location designating a location at which an image detector with defined pixel locations is to be installed.
  • the locations Pi - P n marked on the imaging surface Sl designate the location of the pixels of an image detector 110.
  • the active light sensitive region of the image detector 110 presents an imaging surface Sl on to which an indicative image of the scenery is projected by the optical window.
  • the locations Pi - P m are therefore referred to in the following as light sensitive pixels (or just pixels).
  • Image sensor 110 may be any photoelectric sensitive device such as a charge coupled device (CCD), complementary metal oxide semiconductor (CMOS), and focal plane array (FPA) imaging devices.
  • CCD charge coupled device
  • CMOS complementary metal oxide semiconductor
  • FPA focal plane array
  • the pixels Pi - P n are typically arranged with a grid like arrangement.
  • the locations and dimensions of the pixels on the light detection surface (on the imaging surface) can be different to facilitate the respective irregular arrangement discussed above and further illustrated below.
  • Optical window 120 includes a multitude of spaced apart light transmissive regions Ai to A n (e.g. optical elements) arranged with spaced apart relationship across the optical surface and S2.
  • the optical window 120 is adapted for being optically coupled with the imaging surface Sl such that an indicative image of the field of view of the imaging system can be projected on the imaging surface Sl through the spaced apart light transmissive regions Ai - A n of the optical window 120 (the surface S2).
  • the optical system 100 is configured such that the arrangement and types of the optical elements Ai - A n in the optical window 120 together with the respective locations of the pixels on the imaging surface Sl constitutes an irregular respective arrangement in the meaning disclosed above.
  • the optical elements Ai - A n may include focal elements capable of focusing images of an external scenery onto the imaging surface Sl and/or the focusing elements may include afocal elements which maintain the collimation of light passing therethrough and which operate by the principles of direct ray imaging (pinhole camera) for projecting images of an external scenery onto the imaging surface S2. It should be understood that a combination of focal and afocal elements can also be realized in the optical window 120 for providing said irregular respective arrangement.
  • each optical element Aj operates as a miniature imaging aperture projecting an image onto a substantial area of the imaging surface Sl and accordingly an indicative image of the scenery is formed by multiple substantially overlapping images projected by the optical elements Ai - A n on the imaging surface.
  • the indicative image of the scenery formed by the optical window 120 includes multiple distinct light intensity patterns corresponding respectively to light arriving from different directions of the imaged scenery to the optical window 120.
  • the optical window 120 inclusive of the arrangement of optical elements Ai - A n operates by applying spatial patterns to light from different directions such that the intensity of the light from those directions can be determined.
  • the images projected by the optical elements Ai - A n may or may not be actual images of the scenery.
  • the optical elements Ai - A n may be "low quality" optical elements which induce substantial optical aberrations to the light passing therethrough and/or optical elements with various apertures shapes can be utilized.
  • optical elements and/or diffractive optical elements Utilizing "low quality" optical elements and/or diffractive optical elements, significant variations may occur in the optical properties of different optical windows 120 made according to the present invention.
  • the optical elements in the optical window such that the light transmission function matrixes (as defined above) of the different optical windows are invertible matrixes that allow indicative images of an imaged scenery to be projected by the different optical windows on their respective light sensitive surface Sl. Accordingly, in order to enable generation of an actual image of the scenery from those different optical windows, their irrespective light transmission function matrixes corresponding to the different irregular respective arrangement of the optical elements on the optical window should be characterized.
  • the irregular respective arrangement of the optical elements in the optical surface allows reconstruction of sharp actual image of imaged scenery by applying processing to the readout data from the sensor.
  • the multiple optical elements Ai - A n are used for providing sufficient light intensity impinging on the imaging surface Sl which can be measured by the light sensitive pixels Pi - P n , of the image sensor 110.
  • each of the optical elements ⁇ A ⁇ have small light collection aperture as compared with a lens-set of a typical camera, sufficient light intensity impinges the pixels of the imaging surface enabling light detection with adequate signal to noise even in dark scenes.
  • the pixels Pi - P n are exposed to light from more than one optical element Ai (preferably from most or all of the optical elements ⁇ A ⁇ ) which may have a collective light collection area equivalent to a single lens set with F-number 3.5 or lower.
  • Ai optical element
  • ⁇ A ⁇ optical elements
  • multiple n images associated with multiple optical elements Ai - A n are projected and overlap on a particular pixel pp, the light intensity impinging on that pixel would be on average n times greater than the intensity that that pixel would receive from a single optical element Aj.
  • each imaging aperture optical element
  • afocal optical elements e.g. F# > f/1000
  • the invention may utilize afocal lenses while applying principles of direct ray imaging for providing bright enough indicative image of the scenery. This also obviates the need for focusing optics and thereby allowing an extended depth of focus to be obtained.
  • the distance between the lens set and the imaging surface is generally determined by the F-number of the lens set being the focal length of the lens-set over its light collection aperture diameter.
  • F-Number ⁇ 2 allows locating the imaging surface of the typical camera in close proximity to its lens-set (i.e. distanced by the F-Number times its diameter of light collection aperture) but is associated with non desired optical aberrations.
  • a short distance between the light collection surface Sl and the optical window 120 can be realized also with high F-Numbers of the optical elements or with afocal optical element. Accordingly, an imaging system based on the optical system 100 of the invention can have small dimensions as compared with an equivalent imaging system of the typical, single lens-set type, which utilizes an imaging sensor of the same dimensions (e.g. full frame 35mm digital sensor).
  • Light transmissive region Aj is associated with an exit pupil and with an effective light collection aperture.
  • the exit pupil designating an area of the light transmissive region from which light is perceived to emerge towards the imaging surface Sl.
  • the effective light collection aperture designates an area of the light transmissive region Ai through which light is collected and guided towards the exit pupil and thereform to the imaging surface Sl.
  • the effective light collection area of the optical window 120 being the collective area of the effective light collection apertures of the light transmissive regions, is generally proportional to the light intensity impinging on the imaging surface Sl when given scenery is imaged.
  • increasing the intensity of light impinging on the imaging surface Sl is possible by either utilizing greater number of light transmissive regions Ai - A n (optical elements) in the optical window or by increasing the sizes of the effective light collection apertures of the elements or by both.
  • the number of light transmissive regions Ai - A n that can be fitted on an optical window 120 of a given optical surface area S2 is limited. This is because the light transmissive regions ⁇ A ⁇ should be arranged on the optical window 120 with irregular respective arrangement such that respective exit pupils of adjacent light transmissive regions are separated with distance greater than space the distance between adjacent locations (Pj, Pj+i) of light sensitive pixels in light sensitive surface Sl. Such an arrangement is preferable since it provides that images projected, onto the imaging surface Sl, through adjacent light transmissive regions ⁇ A ⁇ are partially overlapping but are shifted from each other with by one or more pixels thus facilitating said spatial light patterning by the optical window 120 and enabling discrimination of images of different light transmissive regions.
  • the invention is carried out utilizing aperture type light transmissive regions Ai - A n .
  • This type of transmissive regions Ai - A n have no light condensing ability an no optical power (no focusing ability) and thus their exit pupil and light collection aperture have the same size (e.g. they coincide).
  • Increasing the light intensity is possible in this case by increasing the areas of the light collection apertures and or the density of the apertures.
  • the density of the apertures is limited by the requirement to maintain a certain minimal distance between the apertures in the order of the characteristic length of one or more pixels apart.
  • increasing the light collection aperture is also limited as in this type of elements it requires increasing the area of the exit pupils of the elements.
  • the exit pupils of the optical elements can be separated from one another with an adequate distance and can be small enough so as not to incur image blur while the effective light collection apertures may be arranged with close packing (e.g. tight packing) to enable to increase the effective light collection area on the optical window 120.
  • close packing e.g. tight packing
  • the space SP between the light transmissive regions Ai to A n may be light diffusive or opaque regions of the optical window 120 (e.g. of the optical surface S2). Light is therefore either blocked these spacing or light is diffused and partially passes the spacing and reaching disordered to the imaging surface Sl. In the later case, light that traverse through these spaces is substantially diffused and thus it impinge with substantially homogeneous intensity on all the light sensitive pixels of the detector 110 and can be accordingly processed out of the image. However, utilizing such light diffusive spaces, increase the amount of light impinging the detector and thus may increase the saturation rate of the light sensitive pixels Pi - P m .
  • the optical elements Ai-A n may also be associated with or may include a transparency adjusting elements (e.g. electro-optical elements) that allow controlling the transparency of one or more of the optical elements.
  • a transparency adjusting elements e.g. electro-optical elements
  • such transparency modulation element may be formed by one or more polarizer layers/elements (such as liquid crystal layer or a constant polarizing layer) which respective polarizations can be actively controlled to affect the amount of light passing through the optical elements Ai-A n .
  • Use of such transparency adjustment elements allows to more effectively utilize the dynamic range of the image sensor 110 coupled with the optical window 120.
  • the optical window of the invention may include optical elements Ai - A n (light transmissive regions) including micro-lenses and/or micro-mirrors components.
  • Optical elements Ai - A n utilizing micro-lenses and/or micro-mirrors components may be designed for increasing the effective light collection area of the optical window 120 (as compared with use of apertures) without adding to the image blur. This is achieved by configuring the optical elements Ai - A n with their exit pupils smaller than their respective light collection apertures such that light passing through the light collection apertures is condensed and guided to the smaller exit pupils.
  • a n utilizing micro-lenses and/or micro-mirrors components may also be designed for providing non-unitary optical magnification. Utilizing optical magnification greater than one allows to locate the imaging surface Sl with greater proximity (with smaller distance) from the optical window 120 (form the optical surface S2) as compared with the case no magnification is used. Also, the optical elements Ai - A n can be designed with adjustable magnification such that optical zooming on an image of imaged scenery is possible with varying the magnifications of the optical elements Ai - A n . Indeed, alternatively or additionally zooming can also be provided by means of digital zooming in the expense of reducing the image resolution.
  • the surfaces Sl and S2 are illustrated as planar parallel surfaces, in general those surfaces need not to be planar neither parallel with respect to each other and an irregular respective arrangement of the light transmission regions can be realized in non planar and not parallel surfaces as well.
  • the surfaces Sl and S2 may be configured to define two dimensional arrangements of pixels and light transmissive regions Ai - A n respectively for providing two dimensional imaging as in the present example.
  • one dimensional arrangement of the pixels Pi - P n , light transmissive regions Ai - A n from which a one dimensional image can be generate can be used.
  • a two dimensional image can be formed in this case by mosaic of multitude of such one dimensional images.
  • variable different distances might be implemented between various pixels and between various apertures.
  • Such an arrangement of variable distances might be used to realize said irregular arrangement of light transmissive regions Ai - A n and to facilitate the generation of an indicative image of the scenery by the optical window 120.
  • the distances dl between the pixels along the X direction can be different from the distances between the pixels along the Y direction.
  • the distances d2 between the apertures might be different along X and the Y directions.
  • those light transmissive regions Ai - A n can be realized by different types of optical elements located on the optical window 120.
  • different optical or optical elements having different optical properties such as different light condensations or magnification, different focal lengths different light collection apertures and exit pupils as well as different principal optical axes directed to different regions/directions in the field of view of the optical window 120.
  • the optical elements may also have different cross- sectional shapes of their tight transmissive regions such that light in different direction passing therethrough "sees" different effective light collection aperture area.
  • Light transmissive regions Ai - A n realized by different types of optical elements can be used to provide different image projections by the optical elements to enable said irregular respective arrangement.
  • Fig. 2 illustrating a one dimensional embodiment of the optical system 200 according to the present invention.
  • module or elements of the invention having similar functional purpose are designated with the same reference numbers in all the figures of different embodiments of the invention.
  • an optical window 120 according to the present invention, defining a one dimensional array of light transmissive regions ai - as and; an imaging surface defining the locations of nine light sensitive pixels pi - p 9 are illustrated.
  • the optical system 200 includes an enclosure 130 (optically opaque in this example) enclosing the imaging surface Sl and the optical window 120.
  • the optical window 120 is located on a facet of the enclosure 130 such that light from within the field of view FOV of the optical window can enter the enclosure through the light transmissive regions ai - as (i.e. light rays that arrive from within a field of view angle ⁇ ).
  • the light transmissive regions aj - as are considered here to be similar apertures with no optical power or magnification having substantially the same effective light collection area for light beams from any direction within the field of view FOV of the optical window. Accordingly, and without loss of generality, these light transmissive regions are referred to in the following as apertures ai - as.
  • the field of view FOV of the optical window 120 is illustrated schematically and divided into nine field of view regions marked FOV1-FOV9. Out of field of view regions OUTl AND OUT2 from which light does not pass through the optical window 120 are also shown.
  • Light rays (beams) Rl, R3, R5 and R9 arriving respectively from field of view regions FOVl, FOV3, FOV5 and FOV9 (from general directions/angles ⁇ l, ⁇ 3, ⁇ 5 and ⁇ 9) with respective intensities I 1 , 1 3 , 1 5 and I 9 are illustrated.
  • the optical system 200 is not drawn in scale with the field of view FOV and is substantially smaller than the field of view. Accordingly each of the light rays Rl, R3, R5 and R9 that impinge from different FOV regions is considered as a collimated beam that traverse through the multitude of the light transmissive regions ai - as with the same direction.
  • general direction or general direction angle a generally refers to all light rays arriving from a certain predetermined solid angle (or just an angle in the one dimensional case of the present example) which is determined by the field of view region (angle of view) FOV1-FOV9 from which the respective light ray is considered.
  • the array of equally distanced apertures (al - a5) is arranged above (at a distance L) and in parallel to the array of pixels (Pl - P9), such that the apertures facing the pixels project thereon multiple images of the scene.
  • the arrays are centered one above the other such the central pixel P5 is directly below the central aperture a3.
  • the field of view of the apertures (al - a5) is configured in accordance with the dimensions of the pixels array.
  • the irregular respective arrangement between the apertures and the pixels and the distances between the apertures d2 as well as the distances between the pixels dl are selected such that each of the pixels is illuminated by a different set of light rays ⁇ R ⁇ from different general directions (e.g. passing through different apertures.
  • the first pixel Pl is illuminated only by the light ray Rl passing through the first aperture al from the general direction ⁇ l (FOVl).
  • Light rays Rl - R9 from the different FOV regions FOV1-FOV9 pass through the apertures al - a5 and hit the light sensitive pixels Pl - P9 on the surface Sl. Because in the present example the effective area of the imaging surface Sl (accommodated with pixels) is larger than the effective area of the apertures surface S2, thus not all the rays Rl-Rn hit all the pixels. (Note that the Rays Rl and R9 were selected to mark the boundaries of the field of view of the apertures.). In the present example only the ray Rl which impinges the device at an angle ⁇ l hits the first pixel Pl.
  • the intensity readout O 1 from the pixel Pl corresponds to the measure of the light intensity Ii of the ray Rl. Since only Rl and R3 hit the pixel P2 and only Rl, R3 and R5 hits pixel P3, the readout O 2 from the pixel P2 correspond to the light intensities Ii + 1 3 of rays Rl and R3 respectively and the readout O 3 from the pixel P3 correspond to the light intensities Ii + I 3 +I 5 of rays Rl, R3 and R5 and so forth.
  • the relationship and relative location between the pixels and the apertures provides for the following set of equations which can be solved to determine the intensities of the light rays Rl, R3 and R5:
  • 0 3 RF(Ii + I 2 + 1 3 )
  • the function RF denotes the pixels response function associating the intensity of the pixel's readout signal with the intensity of light that impinges on that pixel.
  • the above set of equations can be easily solved for a monotonic function RF to determine the intensities ⁇ 1 ⁇ of light rays from different directions based on the readout signals ⁇ O ⁇ from the pixels.
  • the intensities I are regarded here as the surface density of the light energy flux projected on the sensor's surface Sl, i.e. taking into account the angle of arrival of the corresponding ray with respect to the sensor surface.
  • the area of the apertures and thus the amount of light that passes therethrough is not constant to all the apertures and can also vary for light rays impinging the apertures from different directions.
  • a weight factors associated with the corresponding apertures' areas are used to enable analysis of the rays' intensities.
  • the apertures al-a3 are associated respectively with different isotropic light collection regions W 1 , W 2 and W 3 (isotropic with respect to the angle of view ⁇ ), then these may serve also as the weighs for the equations above as follows:
  • the output vector [Oi to O M ] of readouts from the pixels Pi - Pm of the light sensitive surface (imaging surface) of the image sensor (being the output surface) are functions of weight factors ⁇ W ⁇ which are in turn determined by the irregular respective arrangement of the optical elements ⁇ A ⁇ which is implemented by relative locations and configurations ant types of the micro- optical elements through which the light beams are projected on the imaging surface Sl.
  • Each specific micro-optical elements Aj operates to project on each specific pixel P j a weighted cross section Wy of the intensity flux I z of a particular light ray R 2 arriving from a general direction vector ⁇ z .
  • the readouts vector O of the signals (the output vector) received from the sensors is a function of the weights matrix W (referred to herein as optical function matrix or optical transfer matrix of the optical window) multiplied by the input vector I representing the intensities of the light rays from different general directions ⁇ . This is according to the according to the following equation:
  • the function RF here represents the pixels' response function and is assumed here to be similar to all the pixels, hi case the response function is just a linear function RF is just proportionality constant. In which case O ⁇ W-I.
  • the light intensity readout O (output vector) that is measured by analyzed based on the optical function matrix W of the optical window 120 to determine the intensities vector I (input vector) of one or more light beams.
  • the optical function matrix W should be an invertible matrix representing linearly independent set of equations associating the readout intensities by the different pixels with the input light intensities (input vector I) of the light beams (general directions) that should be resolved. This is achieved by the irregular respective arrangement of the optical elements.
  • FIG. 3A to 3E illustrating five embodiments 300A, 300B, 300C, 300D and 300E of the optical system according to the present invention. In those embodiments different irregular respective arrangements of the light transmissive regions of the optical window are exemplified.
  • 300A, 300B, 300C, 300D and 300E each include an optical window 120 defining an optical surface S2 and including spaced apart light transmissive regions ⁇ A ⁇ and an imaging surface Sl (e.g. of a detector 110) defining the locations ⁇ P ⁇ of light sensitive pixels.
  • the optical window 120 and the imaging surface Sl are spaced from one another with a distance L along the z direction designating a principal direction of the field of view of the optical system.
  • the space between the optical window and the optical surface can be empty or it can be formed by a transparent spacer layer 140, in cases where the optical system is implemented as an integrated structure integrated with the detector 110.
  • each of the optical systems 300A, 300B, 300C is formed a grid like arrangement of optical elements ⁇ A ⁇ across the X and Y directions of the optical surface S2 and a parallel grid like arrangement of the arrangement of light sensitive pixels ⁇ P ⁇ across the X and Y directions of the imaging surface Sl.
  • the irregular respective arrangements illustrated in each of the optical systems 300A, 300B, 300C may include light transmissive regions ⁇ A ⁇ implemented by different type of optical elements or by the same type of optical elements (e.g. aperture elements or micro-optical elements) having the same optical properties. In the later case, the irrespective irregular arrangement is realized only by the special locations of the optical elements ⁇ A ⁇ with respect to the pixels ⁇ P ⁇ .
  • the irregular arrangements of the optical systems 300A, 300B, 300C to include the same type of optical elements ⁇ A ⁇ having similar fields of view (similar angles of view ⁇ ).
  • FIG. 3A there is illustrated an optical system 300A with grid like arrangement of optical elements ⁇ A ⁇ designed for providing substantially homogeneous light intensity pattern on the imaging surface Sl. This is achieved by arranging the optical elements ⁇ A ⁇ with respect to the locations of the pixels ⁇ P ⁇ such that all pixels ⁇ P ⁇ are exposed to light from an almost complete set of general directions defined within the desired field of view of the optical system 300A. Actually in this grid like arrangement of optical elements ⁇ A ⁇ a central region Ac designating the absence of a central optical element is blocked for light transmission.
  • each of the pixels ⁇ P ⁇ receive light from substantially all directions within the field of view of the optical system apart from a certain direction, which is different for each pixel, that is determined by the direction from the pixel to the blocked central location Ac.
  • the extent FOV-X of the field of view of the optical system along the X directions is shown in the figure.
  • the angle of view ⁇ x of each of the optical elements ⁇ A ⁇ in the X-Z plane is also shown.
  • each of the pixels ⁇ P ⁇ is exposed to all directions within the field of view FOV-X apart from one distinct general direction that is blocked for the particular pixel by the non light transmissive region Ac of the optical window 120. It should be understood that although not explicitly illustrated, the same arrangement principle are also in effect as regarding light arriving from the extent of the field of view of the optical system along the Y direction.
  • each one pixel P c is not exposed to only a particular piece of information of that scenery which corresponds to the light rays R B coming from a particular general direction associated with the direction of the blocked region Ac with respect to the pixel P c .
  • N being the number where the number of non redundant pixels ⁇ P ⁇ "seeing" distinct light patterns of the scenery.
  • the average variation in the intensities that different pixels ⁇ P ⁇ are subjected to is small. This is because all pixels are exposed to light from almost the same directions (the same regions) in the field of view of the optical system. Accordingly the dynamic rage of the scenery indicative image projected on the imaging surface Sl is very small.
  • a light sensitive sensor and an A/D converter coupled there with should have sufficient color depth bit rate (e.g. 24 or 36 bits).
  • each pixels is exposed to light from (1000x1000-1) optical elements and the difference in light between the light intensity sensed by different pixels the is very low in the order of 1/10 6 .
  • Providing an optical arrangement having higher variability between the light intensities sensed by different pixels is illustrated in Figs. 3B to 3E below.
  • FIG. 3B illustrating an optical system 300B with a grid like arrangement of pixels ⁇ P ⁇ on the imaging surface Sl and with an arrangement, of smaller dimensions, of optical elements ⁇ A ⁇ accommodated in the optical window 120.
  • the arrangement of optical elements ⁇ A ⁇ is centered above the pixels arrangement and is located parallel thereto.
  • the optical elements ⁇ A ⁇ have a field of view angle Bx in the X-Z plain and By (not specifically shown in the figure) in the Y- Z plain.
  • the optical elements ⁇ A ⁇ are arranged with respect to the locations ⁇ P ⁇ of the pixels such that edge pixels in the left side of the X axis (e.g.
  • the central pixel Pc is exposed to light rays from substantially all the directions within the field of view of the optical system 300B.
  • the optical elements ⁇ A ⁇ are arranged in the Y direction with respect to the pixels ⁇ P ⁇ such that pixels at the edjes of the pixels arrangement ⁇ P ⁇ are exposed only to light rays arriving from the opposite "edge" of the field of view.
  • the central pixel Pc is exposed to light from all the field of view of the optical system, while other pixels located closer to the edges of the light sensitive regions are exposed to distinct subsets of light rays from distinct subsets of direction of the field of view of the optical system 300B.
  • This provides that an invertible light function matrix W that allows to determine the intensities (and possibly chrominance of different rays from different directions of the field of view.
  • Figs. 3A and 3B exemplify two irregular respective arrangements of optical elements ⁇ A ⁇ designed for obtaining two extreme results.
  • the embodiment of Fig. 3A is characterized by low variability of light intensity sensed by different pixels. This allows utilizing an image sensor of low dynamic ranges and with relatively low light sensitivity but also requires image sensors with high color depth and bit rates that enable to discriminate minute changes in the light intensity sensed by different pixels.
  • the embodiment of Fig. 3B is characterized by high variability of light intensity sensed by different pixels which allow using image sensors with relatively low color depth and bit rates but with an adequate dynamic range.
  • the optical window 120 includes a pattern of optical element ⁇ A arranged such that the light sensitive pixels ⁇ P ⁇ are exposed to light rays from different subset of directions within the desired field of view of the optical window 120. This is achieved in the example of Fig. 3C by utilizing a disordered arrangement of the optical elements ⁇ A ⁇ of similar types spaced apart by opaque regions ⁇ OP ⁇ of different areas and sizes. In Figs.
  • the disordered patterns of optical elements ⁇ A ⁇ shown in Figs. 3C and 3D are configured for projecting distinct light intensity patterns on the imaging surface Sl. These distinct light patterns correspond respectively to light beams (e.g. collimated light) arriving to the optical window 120 from different directions. Accordingly, since those patterns are distinct, it is possible to determine the light intensity and also the color of light arriving from each different direction by utilizing the readout from the pixels ⁇ P ⁇ . It should be noted that utilizing such an arrangement enables to design the optical window 120 for providing a certain desired levels of light intensities by setting the numbers of optical elements ⁇ A ⁇ within the arrangement as well as by designing the nominal separation between them.
  • the variability of light intensities perceived by the different sensor pixels ⁇ P ⁇ can also be pre-designed such that sensors with different dynamic ranges and light sensitivities can be utilized.
  • the degree of homogeneity of the distribution of the optical elements ⁇ A ⁇ in optical window 120 has a significant effect.
  • Substantially homogeneous distribution of optical elements ⁇ A ⁇ generally results with low variability of light intensity on the pixels ⁇ P ⁇ while substantially inhomogeneous distribution of the optical elements ⁇ A ⁇ across the optical surface S2 of the optical window 120 results with high variability of light intensity on the pixels ⁇ P ⁇ .
  • the imaging system includes an optical system/window 300E furnished with an image detector 110 and; a processing unit 310 that is electrically connected to the read out circuit of the image detector 110.
  • the optical window 120 of the optical system 300E is formed by an optical surface S2 having a substantially disordered distribution/arrangement of transparent and opaque regions with various optical properties and/or sizes and/or shapes.
  • a surface can be in the form of a perforated film or metallic foil as well as a surface made by polymeric materials.
  • the optical surface is characterized in that it defines a pattern of light transmission regions ⁇ A ⁇ arranged such that the light sensitive pixels ⁇ P ⁇ of the detector 110 are exposed to light rays from different subset of directions within the desired field of view of the optical window 120.
  • the imaging system 300Z of the present example include a signal processing unit 310 connected to the read out circuit.
  • the readout signal RS received from the image detector 110 by signal processing unit 310 is generally indicative of the light intensities measured by the light sensitive pixels of the detector. In accordance with the type of image detector used, each pixels provides for 8 to 24 bits of information, regarding to the intensity and possibly color of light that impinges that pixel.
  • This readout signal RS is used by the processing unit to determine a read out vector O described above where each entry of the vector is containing the information provided by a single pixel of the detector 110.
  • Processing unit 310 includes a memory modulell ⁇ and a processor 114.
  • the memory module is equipped with non-volatile memory (such as a flash or ROM) holding data (W "1 ) that is indicative of the inverse of the light transmission/function matrix W corresponding to the optical properties of the optical window 300E and the detector 110 that are coupled with the processing unit.
  • non-volatile memory such as a flash or ROM
  • W "1 data that is indicative of the inverse of the light transmission/function matrix W corresponding to the optical properties of the optical window 300E and the detector 110 that are coupled with the processing unit.
  • Processor 114 is adapted to apply signal processing to the read out vector O by multiplying this vector with the inverse of the light transmission/function matrix W (i.e. multiplying by W "1 ) to determine an actual image of the imaged scenery. It should be also noted that optionally, additional processing is carried out by the processor 114.
  • the operation performed by the processor 114 to determine an actual image from the readout vector O are dependent on parameters of the light transmission/function matrix W of the respective optical system 300E coupled with the processing unit and on the dimensions of the output vector that is obtained from the image detector 110. Accordingly, the optical systems 300E can be modularly replaced different optical systems having different optical properties. This requires replacing in the memory module data relating to the light transmission/function matrix W and the dimensions of the readout vector with suitable data corresponding to the optical properties of the substitute optical system.
  • FIG. 3F in which another example of the optical system 300F according to the present invention is illustrated.
  • the optical elements ⁇ A ⁇ that are arranged in the optical window 120 are divided into several groups of optical elements ⁇ Al ⁇ , ⁇ A2 ⁇ and ⁇ A3 ⁇ .
  • Each group of optical elements includes at least one optical element and is associated with a specific region on the imaging surface on which the optical elements of the group are projecting images of at least a partial part of the scenery.
  • the optical elements ⁇ A ⁇ are devided into in three groups ⁇ Al ⁇ , ⁇ A2 ⁇ and ⁇ A3 ⁇ each associated with only a part of the desired field of view of the optical system 300F.
  • the three groups are associated respectively with only partial field of view angles ⁇ l, ⁇ 2 and ⁇ 3.
  • the extent FOV-X of the field of view of the optical system along the X direction which is defined by the field of view angle ⁇ x, is shown in the figure.
  • the partial extents FOV-Xl, FOV-X2 and FOV-X3 of the fields of view of the respective groups ⁇ Al ⁇ , ⁇ A2 ⁇ and ⁇ A3 ⁇ of optical elements corresponding to the angles of view ⁇ l, ⁇ 2 and ⁇ 3 are illustrated as well.
  • the partial extents FOV- Xl, FOV-X2 and FOV-X3 illustrate the respective portions of the image of the total field of view extent FOV-X of the optical system that are captured and projected by the respective groups of optical elements (Al ⁇ , ⁇ A2 ⁇ and ⁇ A3 ⁇ .
  • each group of elements is associated with a dedicated region on the optical detection surface Sl.
  • the groups ⁇ Al ⁇ , ⁇ A2 ⁇ and ⁇ A3 ⁇ are associated respectively with surface regions SRl, SR2 and SR3. Accordingly, each of the groups ⁇ Al ⁇ , ⁇ A2 ⁇ and ⁇ A3 ⁇ of optical elements together with its respective surface region (SRl, SR2 or SR3 respectively) is operating as an independent optical system (for example similarly to any one of those illustrated above with respect to Figs. 3 A to 3E), and is capable of imaging a certain portion the entire field of view of the optical system 300F.
  • the present example is simplified at least in that it presents only three groups of optical elements and corresponding three surface regions.
  • the number of groups of optical elements is substantially larger in the range of between hundreds to several millions of such groups and corresponding regions. Accordingly, as greater the number of groups of optical elements the narrower the field of view region that is imaged by each group.
  • the spaces between the groups of optical elements and the spaces between the surface regions are illustrated in the figure only for the clarity of the illustration.
  • the groups of elements and the surface regions may be arranged in continuous fashion.
  • optical elements in the different groups may be similar optical elements and may have different directions of their optical axes such that the optical elements of each group are pointing and capturing a different field of view regions different than those captured by the elements of other groups.
  • these regions e.g. FOV-Xl, FOV-X2 and FOV-X3
  • FOV-Xl, FOV-X2 and FOV-X3 may be overlapping regions and accordingly an image of the entire field of view of the optical system can be formed by mosaic of the images that are formed by each of the groups (e.g. ⁇ Al ⁇ , ⁇ A2 ⁇ and ⁇ A3 ⁇ ) of elements on their respective surface regions (e.g. SRl, SR2 and SR3).
  • FIGs. 4A to 4F illustrating few examples of different optical elements (Aa to Af) that can be used as light transmissive regions in the optical window of the present invention.
  • An image plane S and three collimated light beams R arriving from an angle of view ⁇ and passing through the optical elements towards the image plane S are shown to exemplify the effects (e.g. optical magnification and light condensation) of each of the optical elements on the propagation pass of the light beams R.
  • the light beams R and the image plane S are not part of the optical elements and are depicted here only exemplify the operation of the elements.
  • the dimensions and distance of the imaging surface from the optical elements are not necessarily drawn to scale with the optical elements.
  • FIG. 4A illustrating an optical element Aa including an optical aperture AP (e.g. pinhole) with no optical power and no magnification capability.
  • the light collection area CA of the aperture is equal and coinciding with its effective exit pupil EP from which light is perceived to emerge towards the imaging surface Sl.
  • Such an aperture is actually operating as a pinhole camera and thus in order for an image of a scenery to be projected on the image plane S the light collection area CA of the aperture AP should be substantially smaller than both the image plane S and the external scenery which imaging is sought. Therefore, utilizing this type of elements Aa in the optical windows of the invention (e.g.
  • optical windows 120 as those described above in Figs 1, 2 and 3A-3E) may result with a low intensity image(s) on the image plane S and such a configuration is therefore suited for capturing images of relatively bright sceneries (e.g. day light sceneries).
  • sceneries e.g. day light sceneries
  • increasing the light collection area CA of the aperture AP generally results with an image blur and thus there is a tradeoff between the amount of light permitted through the aperture AP and the perceived image blur.
  • Fig. 4B illustrating an optical element Ab including a lens CS (e.g. a lenslet or a micro-lens being part of an array) with a focal length F and with no magnification capability.
  • a lens CS e.g. a lenslet or a micro-lens being part of an array
  • the lens CS (referred to here as collection lens) is configured for collecting light arriving from a certain object plane OB of external scenery to be imaged and to focus that light on the image plane S. Accordingly light, arriving from the object plane OB, is collected by a relatively large collection aperture CA and thus an improved light intensity as compared to that achievable with the optical element Aa of Fig. 4A can be achieved for allowing imaging of low light sceneries (e.g. night sceneries).
  • the lens CS is depicted to be positioned such that the image plane S is located at the focal plane of the lens CS (distant from the lens CS by its focal length F) and is therefore configured for focusing collimated light beams (e.g. arriving from "infinitely" distant object plane OB) on the image plane S.
  • the lens may be positioned with different distances and may also be actuated to move such as to focus light from different object planes.
  • the optical element Ab enable higher light intensities than that achived by the optical element Aa without incurring image blur.
  • this comes on the expanse of a limited depth of focus of the lens CS.
  • utilizing this configuration with lenses CS having medium and low F-numbers e.g. 2.8 ⁇ F# ⁇ 8 or F# ⁇ 2.8
  • medium and low F-numbers e.g. 2.8 ⁇ F# ⁇ 8 or F# ⁇ 2.8
  • these type of lenses of medium-small F-numbers
  • This may be achieved by utilizing lens actuation module(s) (not shown) for moving the lens or by utilizing adaptive lenses with adjustable focal lengths
  • a wide focal depth of the optical elements Ab which obviates the need of focus adjustments can be achieved by utilizing lenses with medium to high focal lengths (e.g. F#>5.6 and preferably F#>11 or higher).
  • medium to high focal lengths e.g. F#>5.6 and preferably F#>11 or higher.
  • utilizing such lenses limit the proximal distance at which the image plane (e.g. and the imaging sensor) can be located with respect to the lens CS and thus may increase the dimensions of the imaging system.
  • the lens CS may be located proximal to the image plane S but a low focal depth is obtained.
  • FIG. 3A we consider for example an embodiments of the optical system of the invention similar to the optical system 300A which is configured for utilizing optical elements ⁇ A ⁇ with no optical magnification capabilities such as the optical elements Aa or Ab illustrated in Figs. 4 A and 4B.
  • Considering such optical system is utilizing a full-frame 35mm digital image sensor 110 and is configured for providing a field of view equivalent to that of a 50mm normal lens installed on a standard 35mm camera.
  • the angle of view ⁇ x and ⁇ y (not shown) with respect to the X and Y (width and height) of the image sensor 110 are respectively 45° and 31° degrees.
  • the width (along the X axis), height (along the Y axis) of the full- frame 35mm digital image sensor are respectively 36 mm, 24 mm. Therefore, in case at least one optical element A (e.g. an optical element A near the center of the arrangement of optical elements ⁇ A ⁇ ) is configured for projecting an image onto substantially all the light sensitive region of the image sensor 110, it should be located at a distance:
  • Figs. 4C to 4F illustrate additional four example of optical elements Ac, Ad, Ae and Af suited for use in the optical window of the invention.
  • These optical elements are compound optical lements that are formed by an arragment of more than one optical component.
  • the optical elements Ac, Ad, Ae and Af provide substantially large light collection apertures CA as well as optical magnifications. It should be noted that examples of optical elements presented in these figures are non exhausting list of examples and other elements with similar properties may be designed for the purposes of the present invention.
  • the optical elements Ac, Ad and Ae illustrated respectively in Figs. 4C, 4D and 4E are substantially afocal elements with on optical power which therefore obviate the need for focusing and provide for wide focal depth (depth of focus) of the optical window.
  • Figs. 4C and 4D both illustrating afocal optical elements Ac and Ad respectively having magnifications greater than one.
  • Both the optical elements include two component lenses which are referred to herein as collection lens CL and surface lens SL with respective focal lengths F and f.
  • the respective focal lengths F and f may be set for providing pupil magnification p m smaller than one to therefore provide concentration (condensation) entering through the optical elements Ac and Ad to the optical system of the invention.
  • the light collection aperture CA presenting an entrance pupil of the optical elements Ac and Ad and the effective exit pupil EP is the exit pupil from which light is perceived to arrive to the image surface S.
  • the pupil magnification p m is the ratio of the diameter of the exit pupil EP to the diameter of the entrance pupil CA. Accordingly, an improvement in the light intensity that passes through the optical elements such as Ac and Ad with pupil magnification p m ⁇ as compared with an aperture based optical elements (such as Aa of Fig.
  • optical lens 4A is achieved with the light intensity increased by a factor of about (1/ p m ) 2 .
  • This can be achieved in the embodiments of optical elements Ac and Ad while maintaining the same dimensions of the exit pupils EP similar to that of the optical element Aa and thus when utilizing such optical elements in the optical window (e.g. 120 in Fig. 1) an increased light intensity is provided without adding image blur.
  • the respective focal lengths F and f of the lenses CL and SL may be also set for providing optical magnification in similar to that of a telescopic lenses. This may be used arranging the image surface (e.g. Sl in Fig. 1) of the imaging system of the invention in proximity to the optical window (e.g. 120 in Fig. 1) and optionally also for providing an imaging system with variable field of view angle (zooming) as described below.
  • the waist of the light beams R, passing through the optical element, Ac are narrow at two places, at the focal plane PF of the collection lens CL and at the plane of the effective exit pupil EP. Accordingly, preventing the entrance of stray light rays through the optical elements Ac can be achieved by accommodating an opaque or translucent layer/surface with an aperture such that the e opaque surface encloses any one or both of the regions of these planes at which undesired light rays may pass (e.g. enclosing effective exit pupil EP and or enclosing the region of the focal plane PF of the lens CS through which light should not pass).
  • the optical element Ad of Fig. 4D can have a smaller form factor as the distance between the two optical lenses SL and CL can be shorter.
  • the optical element Ac includes two lenses with positive foci F>0 and ff>0 while the foci of the lenses CL and SL of the optical element Ad are appositive and negative respectively F>0 and f ⁇ 0.
  • the optical element Ae includes a surface lens SL with positive focal number f and a set of concave an convex mirrors CM and VM.
  • the set of mirrors CM and VM are arranged along an optical axis OX of the optical element Ae and configured for collecting light rays R arriving at the light collection aperture CA (which is defined by concave mirror CM) and for directing and this light, by the aid of the convex mirror VM through a hole in the concaved mirror where it is focused at the focal plane PF of the set of mirrors.
  • the optical element Ae is similar to the optical element Ac described above only having light collection by the set of mirrors CM and VM instead of the collection lens CL of the optical element Ac.
  • a surface lens SL with negative focal length f ⁇ 0 can be used for reducing the size of the optical element Ae and providing the shorter distance De between the set of mirrors and the surface lens SL.
  • an opaque surface (or translucent or diffusive) with an optical aperture can be included in the element at either at the focal plane PF and/or at the effective exit pupil EP (or otherwise at a different locations) in order to prevent, reduce or at least diffuse the transmittance of stray light rays through the optical element.
  • Fig. 4F illustrating an optical element Af according to the invention with both an optical power (focal optical element) and with an optical magnification.
  • the optical element Af is generally similar to the optical element Ad with positive F>0 and negative f>0 foci of the lenses the lenses CL and SL respectively.
  • the distance De between those lenses CL and SL is larger than the sum of those optical lengths of the lenses CL and SL, (De > F + f) and thus the optical element Af is focal optical element with positive focal length and with some net focusing.
  • other types of focal optical elements suited for the purpose of the present invention can be constructed also based on the design of the optical elements of Figs.
  • the focal optical element Af illustrated here can be considered to have substantially high directional correlated elements given that its F-numbet times its magnification is relatively large (e.g. above 11). In which case the directions, of light beams that pass through the optical element Af, are affected more by the optical magnification of the optical elements than by its focal power. Accordingly, as illustrated in the figure, collimated light beams from different directions (e.g.
  • optical elements such as Af having high directional correlation or afocal elements are highly suited for use in the present invention as they provides wide depth of field (depth of focus).
  • FIG. 5A-5C illustrating an optical window 120 according to an embodiment of the present invention.
  • Fig. 5A depicts the optical window 120 and
  • Figs. 5B and 5C illustrate an exemplary optical element Al arranged on the optical window 120 with the illustration of the propagation of perpendicular light beam Rp and diagonal light beam Rd through the optical element respectively.
  • the optical window in this example is formed by a structure of two stacked arrays LAl and LA2 of optical units (i.e. apertures and/or lenses/lens-lets/micro- lenses and/or mirrors/micro-mirrors and/or prisms/micro-prisms) located one above of the other in a stacked structure.
  • the includes in this example an arrangement of light transmissive regions in the optical window 120 of the present example is formed by an arrangement of multiple optical elements ⁇ A ⁇ such that they are capable of providing an indicative image (of a scenery to be imaged) on a respective light sensitive surface of a predetermined image detector(s)/sensor(s).
  • the stacked arrays of lenses LAl and LA2 are substantially aligned one above the other ant the lenses in each array are arranged such that pairs of lenses, e.g. CL and SL, from the two arrays are also substantially aligned with one another (i.e. the their optical axes OX are nearly coinciding).
  • Each of these pairs of lenses are components of an optical element (e.g. Al) of the optical window 120.
  • the arrays LAl and LA2 of lenses may be lens-let arrays and/or micro-lens arrays (MLAs) depending on the desired dimensions needed for the optical window and also on the designed arrangement and number of optical elements ⁇ A ⁇ in the optical window 120.
  • the optical elements ⁇ A ⁇ of the optical window 120 are optically designed such that the directions of light rays Rin that arrive towards (and pass through) the optical window 120 are substantially correlated with the respective directions of the light rays Rout that emanate from the optical window at the othere side.
  • the optical window is presented as a substantially planar continuous structure, the invention is not limited to this example, and the optical window may have curved light collecting surface, and/or may have surface relief in the light collecting surface, and/or may not be a continuous surface but a segmented one formed by spaced-apart separate elements. Additionally, it should be noted that the optical window may include an array of prisms allowing for color separation.
  • optical elements ⁇ A ⁇ are generally of the type illustrated in Fig. 4C. It should be however noted that other type of optical elements can be implemented here as well. In some cases of other types of optical elements, other types of arrays LAl and LA2 may be used.
  • the lens array LAl depicted here would be replaced by two arrays of mirrors (or micro-mirrors) for accommodating the mirrors (CM and VM) of the optical element Ae of Fig. 4E.
  • the two arrays LAl and LA2 illustrated herein are shown to be spaced form on another with an additional aperture surface SPL that includes a perforated opaque surface.
  • the perforations in the opaque surface SPL define an arrangement of apertures (e.g. AP) which are aligned with the light transmission regions of the optical elements ⁇ A ⁇ (e.g. the apertures are centered with respect to the optical axis OX of the optical elements) and are enclosed by opaque regions OP of the perforated surface.
  • the opaque regions OP of the perforated surface SPL operate to block the transmission of undesired light rays through the optical surface.
  • the regions OP or some of them may be translucent or light diffusive regions. Indeed this may result with higher noise on the detection light sensitive surface but in some cases (specifically when light diffusive regions are used that are associated homogeneous light spread on the optical surface) such noise can be accounted for in processing of the image.
  • the opaque surface SPL is located in between the two lens arrays LAl and LA2 in proximity to (or substantially coinciding with) the focal plane (PF in Figs. 4C and 4E) of the lens CL of the optical elements.
  • an opaque or diffusive surface/layer defining light transmissive regions is placed at various locations with respect to the arrays of optical units LAl and LA2.
  • a surface defining light transmissive apertures ban be located in front or behind the arrays of optical units (e.g. near the plane of the effective exit apertures EP as suggested above with reference to Figs. 4C and 4E).
  • FIGs. 5B an 5C an exemplary optical elements Al of the optical window 120 is illustrated.
  • the lenses CL and SL are associated respectively with the arrays LAl and LA2 of the optical window 120 and the aperture AP is formed by the opaque surface SPL.
  • the lenses are arranged such that their focal planes coincide to a common focal plane located within the aperture.
  • Two collimated light rays Rp and Rt arriving from a perpendicular and tilted direction with respect to the optical axis OX of the optical element Al illustrated respectively in these figures. Both light rays Rp and Rt are focused by the collection lens CL onto its focal plane within the aperture AP and collected than collected and collimated by the lens SL.
  • the tilted ray Rt is arriving from the periphery of the field of view of the element Al and, as illustrated, it is partially blocked by the aperture and thus pass with a reduced intensity.
  • This reduced intensity of such periphery light rays can be accounted for in the signal processing of the indicative image formed by the optical window 120. For example it can be compensated for in by the optical function matrix W corresponding to the optical window 120.
  • the optical window 120 depicted herein can be formed as an integrated structure including one or more stacked layers of optical units (micro-lenses and/or micro-mirrors prisms etc 1 ).
  • the optical window can be formed by separate arrays of lenses/mirrors or by a combination of an integrated structure together with additional optical units/layers.
  • the aperture surface SPL can be formed by spacer layer.
  • the light transmissive apertures and light diffusive/opaque regions can be formed by coating of the spacer layer or by any other technique known in the art.
  • an optical system 500 in which the imaging system is formed as an integrated structure including an integrated structure of the optical window 120 integrated with (e.g. formed on top of) a light sensor (detector) 110 integrated circuit.
  • the light sensor 110 may be any type of suitable sensor such as a silicon based CMOS or CCD integrated circuits.
  • the layers structure of the optical system 500 is illustrated in Fig. 5D and the optical elements ⁇ A ⁇ of the optical window 120 formed by this layer structure are illustrated in Fig. 5E.
  • the optical window is spaced from the sensors' integrated circuit 110 by a light transmissive (or translucent) spacer layer SPR2 which thickness is designed for providing the desired distance between the optical elements ⁇ A ⁇ of the optical window 120 and the imaging surface Sl of the detector 110.
  • this spacing/distance should be adjusted such that an indicative image of the scenery to be imaged would be formed by the optical window 120 on the imaging surface Sl of the detector 110.
  • an optical window 120 similar to that of Fig. 5A is formed as an integrated structure.
  • the optical window 120 of this example include three stacked layers including a first micro-lens array layer MLAl, an optional spacer layer SPRl and a second micro-lens layer MLA2.
  • Each of the micro lens layers include a plurality of micro-lenses which are respectively aligned between the two layers.
  • a pacer layer, SPl is optionally used for providing a desired distance between the micro lenses of the two layers MLAl and MLA2. It should be understood that according to some embodiments of the invention the micro-lens arrays are formed directly on the spacer layer SPL from both sides of this layer.
  • the optical window 120 may be formed by the single layer SPl on the front and back facets of which the micro-lens arrays MLAl and MLA2 are defined. This can be achieved for example by patterning the front and back facets of the spacer layer SPl by utilizing any known in the art technique to define micro-lens arrays thereon; for example by utilizing photo resist.
  • Opaque regions OP designed for blocking stray light beams from passing through the optical window 120 are illustrated here to be formed in line with the first micro-lens array MLAl encircling the spaces between the micro lenses of these array.
  • This opaque regions OP can be formed for example by coating the aeries surrounding the micro-lenses with appropriate light opaque or light diffusive coating.
  • Figs. 5F and 5G there are illustrate another two examples of the optical window 120 of the invention similar to that of Figs. 5A or 5D.
  • light diffusive regions LD are arranged in line with at least one of the lenses arrays LAl and LA2. As noted above, these light diffusive regions LD operate to diffuse undesired light beams passing there through such that they impinge on the imaging surface Sl with substantially homogeneous intensity distribution and can be that accounted for and subtracted by processing to the image formed on the imaging surface Sl.
  • Light diffusive regions LD can be formed by utilizing any known technique for roughing the surface/regions surrounding the lenses of the respective array (e.g.
  • an opaque surface defining apertures of the optical elements ⁇ A ⁇ is formed by an additional layer APL located in between the micro lens arrays LAl and LA2. This surface can be formed for example by a thin film or thin metallic foil layer.
  • the opaque or diffusive surface/layer
  • the opaque has a certain thickness and it thus define light transmissive apertures AP with a certain light transmission cross-section.
  • the cross section of the light transmissive regions can be also designed to affect the field of view (e.g. the angles of view ⁇ as well as the light transmission properties through the optical elements.
  • the optical function matrix associated with the optical window 120 is calculated to account for the cross-sectional shape of the apertures AP in this layer.
  • Optical elements ⁇ A ⁇ having different optical properties and or different dimensions and/or different separations between each other can also be formed by the layered array structured illustrated herein. This can be achieved for example by utilizing lenses/mirrors with different optical arranged within the same array. This may be used for providing the irregular respective arrangement of the optical window of the invention and for thus enabling an indicative image of the scenery to be formed by such an arrangement.
  • Fig. 6A illustrates a known in the art configuration of an afocal zooming lens-set AFZ including three lenses Ll, L2 and L3 with, respectively, positive negative and positive focal lengths.
  • Lenses Ll, L2 of the lens-set AFZ can be actuated to move axially (along their optical axes OX) such that a variable optical magnification is obtained while the lens-set AFZ is maintained afocal with no optical power.
  • the lens-set AFZ is illustrated in three positions of different optical magnifications POSl, POS2 and POS3 with different respective magnifications. Different magnification can be obtained by actuating the lenses Ll and L2 to move along the trajectories illustrated by the dashed lines in the figure.
  • Fig. 6B illustrates a zooming optical element AZl according to an embodiment of the invention.
  • This zooming element AZl is constructed by optically coupling of the optical element Aa of Fig. 4A with the afocal zoom lens-set AFZ of Fig. 6 A.
  • the fixed immovable lens L3 of the zoom lens-set AFZ is facing the optical element Aa. Accordingly, by actuating the lenses Ll and L2 of the zoom lens-set AFZ the field of view of rays entering through the aperture of the optical elements Aa is varied and zooming is obtained.
  • Fig. 6C illustrates a zooming optical element AZ2 according to another embodiment of the invention which is constructed by optically coupling of the optical element Ac of Fig.
  • the optical element Ac may have by itself a certain optical magnification as described above.
  • Zooming elements AFZ that is coupled with the optical element Ac may serve for varying (increasing or decreasing the optical magnification of the optical elements Ac. It should also be understood that any of the optical elements depicted in Figs.
  • FIG. 6D a zooming lens-set with similar optical properties as that illustrated in the previous figure 6C is illustrated.
  • an afocal zoom lens-set is integrated with and optical elements such as Ac.
  • the lenses L3 and CL of the zoom lens-set AFZ and the optical elements Ac depicted in the Fig. 6C are integrated here into a single optical lens to thereby reduce the number of required lenses.
  • zooming can be achieved according to the invention by either utilizing a mechanical actuation of certain lenses of the optical elements for varying the optical magnification of the element or alternatively or additionally, adaptive lens-lets or micro-lenses with a controllable optical powers can be used for varying the magnification of the respective optical elements.
  • an electric signal or thermal control is applied to the lenses to very their optical power.
  • the optical elements may be substantially afocal elements i.e. having a certain flexibility in the range of their optical power that does not impaire the images produced thereby). Accordingly, a variable magnification (zooming) of the optical elements can be achieved while allowing the optical power of the optical elements to vary within a certain range and without requiring adjustments to the distance between the elements and the image surface Sl. This allows simpler designs of zooming lenses/optical-units with reduced number of optical units.
  • optical elements operate appropriately also when their vocal bowers are veried within a certain range
  • a combination of the adaptive optical elements with variable optical powers can be used even if adjustments of the optical magnification of these elements results with changes in their focal/optical powers.
  • This provides variable zooming with reduced number of optical units/components (reduced numbers of arrays of optical units and/or without requiring mechanical or thermal actuation assemblies and without impairing the image quality.
  • FIG. 6E and 6F illustrating a perpective and side views of an optical window 120 according to the invention including multiple optical elements ⁇ A ⁇ with zooming capability.
  • the optical window is constructed by similarly to that illustrated in Fig. 5A by utilizing stacked arrays of optical units to that are arranged to form an arrangement of multiple of optical elements ⁇ A ⁇ .
  • two arrays of lenses LAl and LA2 separated by a spacing SPL are constructed similarly to the arrays of Fig. 5 A with only the optical properties of the lenses and the spacing SPL might be different for allowing zooming.
  • Additional, two arrays of lenses LA3 and LA4 are also arranged stacked above the lenses array LAl and separated therefrom and from one another by respectively by separating regions ASPRl and ASPR2.
  • the distances between the arrays of lenses LAl, LA3 and LA4 can be controlled by mechanically controlling the separations between the arrays of lenses LAl, L A3 and LA4 to provide variability of the optical magnifications of the optical elements. This can be for example achieved by utilizing a physical actuation of the positions lens arrays LA3 and LA4 or alternatively or additionally the separating regions ASPRl and ASPR2 may be accommodated with thermally/electrically controlled separation modules or layers.
  • the optical window depicted here with zooming capabilities is implemented as a full integrated structure or as partially integrated structure in which some of the arrays are integrated together (e.g. via spacing layer) and some might be separate elements.
  • the lens arrays LAl and LA2 and the spacing SPL may be formed as integrated structure layers integrated with an image detector 110 and spaced there from by spacer layer SPR.
  • the arrays of lenses LA3 and LA4 and the spacing regions between them may be separate elements or may be also integrated on the structure.
  • zooming is achieved by utilizing single zooming-lens system such as that depicted in Fig. 6A.
  • zooming-lens system is substantially large having the dimensions of the order of the entire optical window 120.
  • Figs. 7A and 7B showing two examples optical windows 120A and 120B respectively configured and operable for thermal imaging of radiation in the infra-red (IR) regime.
  • the optical function and the optical elements of these optical windows may be configured to operate according the imaging principles of the invention as described in any of the embodiments of the invention illustrated above as well as according to other multiple aperture imaging techniques. Accordingly, specific description of the optical function and the optical elements of the optical windows 120A and 120B is omitted here and only description of the special properties making these embodiments suited for use for thermal imaging are described.
  • FIG. 7A illustrating an optical window 120 formed by stacked arrays (e.g. LAl and LA2) of optical units (e.g. MLl and ML2).
  • the arrays (LAl and LA2) of optical units are stacked together and associated with thermal conduction regions thermally coupled thereto.
  • thermal coupling layers that may be located above, below or in between the arrays and or thermally conducted materials can be constructed contact the optical elements from their side facets (e.g. to enclose/encircle the optical elements about their optical axes).
  • One such thermal conduction layer TCL is depicted in the figured located in between the arrays of optical units LAl and LA2.
  • the thermal conduction layer(s) TCL are made from materials, such as metallic materials, having good thermal conductivity and is associated with thermal coupling regions TCRl from which heat can be evacuated from the optical window 120A.
  • the thermal conduction layer(s) TCL defines light transmissive aperture regions AP which may be formed for example by perforations/recesses in the thermal conduction layer(s) TCL. These aperture regions AP are aligned (e.g. substantially centered) about the optical axes of the optical elements of the optical window and thus, light is permitted to pass through the optical elements of the optical window. Accordingly, the dimensions and thickness of the aperture regions AP can be formed to define a desired aperture of the optical elements.
  • the thermal conduction layer TCL can serve also as the spacing SPL depicted in Fig. 5A in which multiple apertures of the optical elements are defined.
  • the thermal conduction layer(s) TCL are also configured and operable for providing substantially homogeneous heat evacuation from the entire light transmissive regions of the optical window 120. This is achieved by thermally coupling these thermal conduction layer(s) TCL to the arrays (e.g. LAl and LA2) of optical units (e.g. utilizing thermally conductive past/binding material or by tight physical attachment).
  • the thermal conduction layer(s) TCL are formed such as to enclose/define the light transmissive regions of each of the optical elements in the thermal window 120A with a thermally conductive material of the thermal conduction layer(s) TCL.
  • optical window of the invention is formed by multiple, relatively small optical elements with low thermal masses, efficient heat evacuation from these elements can be achieved with low energetic expense for cooling.
  • FIG. 7B illustrating another embodiment of an optical window 120B suited for thermal imaging.
  • This optical window 120B is similar to that illustrated in Fig. 7A but it does not include thermal conduction layer(s) TCL depicted in Fig. 7A. Instead, in this example heat evacuation is performed by taking advantage of the small dimensions and thus small thermal masses of the optical elements in the optical window 120B.
  • the present invention allows utilizing multiple small optical elements (small with respect to the dimensions of the image detector e.g. FPA) with thickness and volume smaller than those provided by conventional optics utilizing large optical lenses which dimensions are comparable and often larger than the dimensions of the image sensor. Accordingly, by taking advantage of the small thermal mass of the optical window of the present invention, efficient heat evacuation can also be obtained by arranging thermal conduction regions TCR2 attached to the sides of the optical window 120B through which light does not propagate.
  • TCR2 thermal conduction regions
  • thermal conduction regions TCR2 are also made from materials, such as metallic materials, having good thermal conductivity that allows efficient heat evacuation from the optical window 120B.
  • the thermal conduction regions TCR2 can be thermally coupled and attached to the sides of the optical window by utilizing thermally conductive past/binding material or by tight physical attachment.
  • Fig. 7B may provide less homogeneous heat evacuation with respect to different regions of the optical window 120B (e.g. with respect to the periphery and center regions).
  • this configuration may be highly suited when optical windows 120B is of relatively small dimensions (e.g. formed by micro optical units such as micro-lenses or micro-mirrors) or when at least some of the optical materials from which the optical elements are made have good thermal conductivity.
  • both the optical windows of Figs. 7 A and/or 7B can be configured for installation/integration in a thermal enclosure of the typical thermal imaging systems. Heat in this case would be pumped from the optical window through thermal coupling regions of said thermal conduction regions (layer(s); e.g. TCL or TCR2) through the thermal coupling regions associated therewith through which they are thermally coupled with the thermal enclosure.
  • the optical window 120A is illustrated with an optional cold filter CF element arranged on top of the optical window. It should be noted that this element can be implemented within or on top the optical window by any suitable technique or alternatively it can be provided as a separate element. It should be also understood that this element can also be added or integrated with the optical windows 120B and 120C of Figs 7B and 7C respectively.
  • Fig. 7E illustrating another thermal imaging system 700C according to another embodiment of the present invention.
  • the thermal imaging system 700C is formed as an integrated structure constructed similar to that of Fig. 5D.
  • the thermal imaging system 700C includes and optical window 120C in which light transmissive regions are made of materials suited for transmittance of infra red radiation in the desired range (e.g. Near-, Mid-, and/or Far- IR).
  • the optical window 120C may include thermal conduction regions (e.g. thermal conduction layers) similar to those described above with respect to Figs. 7A or 7B. It should be understood that according to the present invention, optical windows for thermal imaging similar to those exemplified in Figs.
  • optical windows 7A, 7B and 7C can be thermally coupled with and/or accommodated in an enclosure of a thermal imaging systems enclosing the optical path between the optical window and the infra red image detector (e.g. FPA).
  • a thermal imaging systems enclosing the optical path between the optical window and the infra red image detector (e.g. FPA).
  • such optical windows can also be formed as an integrated structures which may or may not be integrated directly (or through a spacer layer) on a suitable infra red image sensor in which case the integrated structure optical window is accommodated within a common optical enclosure of the detector. Cooling of the optical window in any of these cases can be achieved by coupling the thermal coupling regions directly or indirectly with a cooling system of the thermal imaging system.

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Abstract

L'invention concerne un système optique destiné à être utilisé avec une surface de détection de lumière prédéterminée comprenant une multitude de pixels photosensibles. Le système optique comprend une fenêtre optique définissant un diagramme de transmission de lumière prédéterminé formé par de multiples régions de transmission de lumière mutuellement espacées, configurées en conformité avec ladite multitude de pixels photosensibles. La configuration desdites multiples régions de transmission de lumière mutuellement espacées définit un agencement irrégulier desdites régions par rapport à ladite multitude de pixels photosensibles. Ladite fenêtre optique présentant ledit agencement irrégulier est configurée de façon à collecter des faisceaux lumineux provenant de directions différentes d'une scène à mettre en image et à diriger vers chacun desdits pixels photosensibles la composante de lumière formée par un ensemble distinct d'intensités lumineuses, correspondant auxdits faisceaux lumineux collectés en provenance de directions différentes, ce qui permet d'obtenir des diagrammes d'intensité lumineuse spatialement distincts se chevauchant sur ladite surface de détection de lumière et correspondant auxdits faisceaux lumineux collectés en provenance de directions différentes.
PCT/IL2010/000308 2009-04-16 2010-04-18 Système et procédé d'imagerie WO2010119447A1 (fr)

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EP2592823A3 (fr) * 2011-10-12 2013-06-19 Canon Kabushiki Kaisha Dispositif de capture d'image
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CN112799064A (zh) * 2020-12-30 2021-05-14 内蒙古工业大学 柱面孔径非线性渐进式相位迭代成像的方法及装置
CN112835040A (zh) * 2020-12-30 2021-05-25 内蒙古工业大学 球面孔径分区域渐进式相位迭代成像的方法及装置
CN112928588A (zh) * 2021-01-25 2021-06-08 中国科学院上海光学精密机械研究所 一种多波长激光器

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Publication number Priority date Publication date Assignee Title
EP2592823A3 (fr) * 2011-10-12 2013-06-19 Canon Kabushiki Kaisha Dispositif de capture d'image
US9344700B2 (en) 2014-02-06 2016-05-17 University Of Connecticut System and method for imaging with pinhole arrays
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CN112835040A (zh) * 2020-12-30 2021-05-25 内蒙古工业大学 球面孔径分区域渐进式相位迭代成像的方法及装置
CN112799064B (zh) * 2020-12-30 2023-05-26 内蒙古工业大学 柱面孔径非线性渐进式相位迭代成像的方法及装置
CN112928588A (zh) * 2021-01-25 2021-06-08 中国科学院上海光学精密机械研究所 一种多波长激光器
CN112928588B (zh) * 2021-01-25 2022-11-08 中国科学院上海光学精密机械研究所 一种多波长激光器

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