WO2022128337A1 - Filtre angulaire optique - Google Patents
Filtre angulaire optique Download PDFInfo
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- WO2022128337A1 WO2022128337A1 PCT/EP2021/082404 EP2021082404W WO2022128337A1 WO 2022128337 A1 WO2022128337 A1 WO 2022128337A1 EP 2021082404 W EP2021082404 W EP 2021082404W WO 2022128337 A1 WO2022128337 A1 WO 2022128337A1
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- layer
- incidence
- filter according
- microlenses
- radiation
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Classifications
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
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- G02B5/20—Filters
- G02B5/201—Filters in the form of arrays
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B5/00—Optical elements other than lenses
- G02B5/20—Filters
- G02B5/208—Filters for use with infrared or ultraviolet radiation, e.g. for separating visible light from infrared and/or ultraviolet radiation
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B5/00—Optical elements other than lenses
- G02B5/20—Filters
- G02B5/28—Interference filters
- G02B5/281—Interference filters designed for the infrared light
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B2207/00—Coding scheme for general features or characteristics of optical elements and systems of subclass G02B, but not including elements and systems which would be classified in G02B6/00 and subgroups
- G02B2207/123—Optical louvre elements, e.g. for directional light blocking
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B3/00—Simple or compound lenses
- G02B3/0006—Arrays
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B5/00—Optical elements other than lenses
- G02B5/20—Filters
- G02B5/28—Interference filters
- G02B5/285—Interference filters comprising deposited thin solid films
- G02B5/286—Interference filters comprising deposited thin solid films having four or fewer layers, e.g. for achieving a colour effect
Definitions
- TITLE Optical angular filter
- This description relates to an angular optical filter.
- an angular filter intended to be used within an optical system, for example, an imaging system or to be used to collimate the rays of a light source, in particular for a directional lighting application by an organic light-emitting diode (OLED), liquid crystal display (LCD) or by a light-emitting diode, possibly coupled to a waveguide or an optical inspection application, for example, for capturing fingerprints or veins.
- OLED organic light-emitting diode
- LCD liquid crystal display
- a light-emitting diode possibly coupled to a waveguide or an optical inspection application, for example, for capturing fingerprints or veins.
- An angular filter is a device making it possible to filter incident radiation as a function of the incidence of this radiation and thus block the rays whose incidence is greater than a maximum incidence.
- Angle filters are frequently used in conjunction with image sensors.
- One embodiment provides an angular filter for an image acquisition device comprising a stack comprising: a layer comprising media of different refractive indices and transparent to said radiation, the layer allowing only the rays of said radiation to pass whose incidences are less than a first maximum incidence; and a matrix of apertures delimited by walls opaque to visible and/or infrared radiation and an array of microlenses, the assembly formed by the array of apertures and the array of microlenses allowing only the rays of said radiation to pass whose incidences are less than a second maximum incidence less than the first maximum incidence.
- said layer comprises several sub-layers.
- the refractive index of each sub-layer is different from the refractive index of the sub-layer that it covers by at least 0.15, preferably 0.2.
- the layer is an interference filter.
- the layer is a fiber optic panel.
- the layer comprises a group of optical fibers.
- the layer comprises a group of parallel optical fibers each surrounded by an opaque material.
- the layer corresponds to a microstructured layer which can be likened to a photonic crystal, the microstructured layer having a higher resolution than the resolution of the array of microlenses
- the layer comprises a film of a first material transparent to said radiation through which pillars of a second material transparent to said radiation are arranged in a network.
- the network of microlenses is located between the matrix and the layer.
- the layer is located between the network of microlenses and the matrix.
- the matrix is located between the network of microlenses and the layer.
- the first maximum incidence which corresponds to the half-width at half the maximum transmittance is less than 10°, preferably less than 4°.
- the first maximum incidence which corresponds to the half-width at half the maximum transmittance is greater than 15° and less than 60°.
- the first maximum incidence is less than or equal to 30°.
- the openings are filled with air, a partial vacuum or a material that is at least partially transparent in the visible and infrared domains.
- each opening is surmounted by a single microlens; each microlens covers a single aperture; and/or the optical axis of each microlens is aligned with the center of an aperture.
- One embodiment provides an image acquisition device comprising an angular filter as described above and an image sensor.
- Figure 1 illustrates an embodiment of an image acquisition system
- Figure 2 illustrates, in a sectional view, partial and schematic, an embodiment of an image acquisition device comprising an angular filter
- FIG. 3 represents, by a graph, the transmittance of the angular filter of the device illustrated in FIG. 2 as a function of the incidence of the rays reaching the angular filter;
- FIG. 4 illustrates, in a partial and schematic sectional view, another embodiment of an image acquisition device comprising an angular filter
- FIG. 5 illustrates another embodiment of an image acquisition device comprising an angular filter
- FIG. 6 illustrates, in a partial and schematic sectional view, another embodiment of an image acquisition device comprising an angular filter.
- the expressions “all the elements”, “all the elements”, “each element”, mean between 95% and 100% of the elements. [0036] Unless otherwise specified, the expression “it comprises only the elements” means that it comprises, at least 90% of the elements, preferably that it comprises at least 95% of the elements.
- the refractive index of a medium is defined as being the refractive index of the material constituting the medium for the range of wavelengths of the radiation captured by the sensor of pictures.
- the refractive index is considered to be substantially constant over the range of wavelengths of the useful radiation, for example equal to the average of the refractive index over the range of wavelengths of the radiation picked up by the image sensor .
- a layer or a film is said to be opaque to radiation when the transmittance of the radiation through the layer or the film is less than 10%.
- a layer or a film is said to be transparent to radiation when the transmittance of the radiation through the layer or the film is greater than 10%.
- all the elements of the optical system which are opaque to radiation have a transmittance which is less than half, preferably less than a fifth, more preferably less than a tenth, of the transmittance the weakest of the elements of the optical system transparent to said radiation.
- the term "useful radiation” is used to refer to the electromagnetic radiation passing through the optical system in operation.
- optical element of micrometric size refers to an optical element formed on one face of a support whose maximum dimension, measured parallel to said face, is greater than 1 ⁇ m and less than 1 mm.
- each optical element of micrometric size being able to correspond, for example, to a Fresnel lens of micrometric size, to a micron-sized gradient index lens or to a micron-sized diffraction grating.
- visible light is electromagnetic radiation, the wavelength of which is between 400 nm and 700 nm, and, in this range, red light is electromagnetic radiation, therefore the wavelength is between 600 nm and 700 nm.
- Infrared radiation is electromagnetic radiation with a wavelength between 700 nm and 1 mm. In infrared radiation, a distinction is made in particular between near infrared radiation, the wavelength of which is between 700 nm and 1.7 ⁇ m.
- Figure 1 illustrates an embodiment of an image acquisition system 11.
- the image acquisition system 11, illustrated in FIG. 1, comprises: an image acquisition device 13 (DEVICE); and a processing unit 15 (PU).
- DEVICE image acquisition device 13
- PU processing unit 15
- the processing unit 15 preferably comprises means for processing the signals supplied by the device 11, not represented in FIG. 1.
- the processing unit 15 comprises, for example, a microprocessor.
- the device 13 and the processing unit 15 are preferably connected by a connection 17.
- the device 13 and the processing unit 15 are, for example, integrated in the same circuit.
- Figure 2 illustrates, in a sectional view, partial and schematic, an embodiment of an image acquisition device 19 comprising an angular filter.
- the image acquisition device 19 shown in Figure 2 comprises, from bottom to top in the orientation of the figure: an image sensor 21; and an angular filter 23, covering the image sensor 21.
- the embodiments of the devices of FIGS. 2 to 4 are represented in space according to a direct orthogonal XYZ frame, the Y axis of the XYZ frame being orthogonal to the upper face of the image sensor. 21.
- the image sensor 21 comprises an array of photon sensors 25, also called photodetectors.
- the photodetectors 25 are preferably arranged in matrix form.
- the photodetectors 25 may be covered with a protective coating, not shown.
- the photodetectors 25 preferably all have the same structure and the same properties/characteristics. In other words, all the photodetectors 25 are substantially identical except for manufacturing differences.
- the image sensor 21 further comprises conductive tracks and switching elements, in particular transistors, not shown, allowing the selection of the photodetectors 25.
- the photodetectors 25 are preferably made of organic materials.
- the photodetectors 25 are, for example, organic photodiodes (OPD, Organic Photodiode) integrated on a substrate with CMOS transistors (Complementary Metal Oxide Semiconductor, complementary metal oxide semiconductor) or a substrate with thin film transistors (TFT or Thin Film Transistor).
- CMOS transistors Complementary Metal Oxide Semiconductor, complementary metal oxide semiconductor
- TFT or Thin Film Transistor The substrate is for example made of silicon, preferably of monocrystalline silicon.
- the channel, source and drain regions of the TFT transistors are for example made of amorphous silicon (a-Si or amorphous Silicon), of indium, gallium and zinc oxide (IGZO, Indium Gallium Zinc Oxide) or of low temperature polycrystalline silicon (LTPS, Low Temperature Polycrystalline Silicon) .
- a-Si or amorphous Silicon amorphous silicon
- IGZO Indium Gallium Zinc Oxide
- LTPS Low Temperature Polycrystalline Silicon
- the photodiodes 25 of the image sensor 21 comprise, for example, a mixture of organic semiconductor polymers such as poly (3-hexylthiophene) or poly (3-hexylthiophene-2, 5-diyl), known under the name P3HT, mixed with methyl [6,6]-phenyl-C61-butanoate (N-type semiconductor), known as PCBM.
- organic semiconductor polymers such as poly (3-hexylthiophene) or poly (3-hexylthiophene-2, 5-diyl
- P3HT poly (3-hexylthiophene) or poly (3-hexylthiophene-2, 5-diyl
- P3HT poly (3-hexylthiophene-2, 5-diyl
- PCBM methyl [6,6]-phenyl-C61-butanoate
- the photodiodes 25 of the image sensor 21 comprise, for example, small molecules, that is to say molecules having molar masses of less than 500 g/mol, preferably less than 200 g/mol .
- the photodiodes 25 can be inorganic photodiodes, for example, made from amorphous silicon or crystalline silicon.
- the photodiodes 25 comprise quantum dots.
- each photodetector 25 is adapted to detect visible radiation and/or infrared radiation.
- the angular filter 23 comprises: an array 27 of microlenses 29 of micrometric size, for example plano-convex; a matrix 31 or layer of holes or openings 33 delimited by walls 35 that are opaque (for example, absorbent or reflective) in the visible and/or infrared domains; and a layer 41 comprising media of different refractive indices, the layer 41 only allowing the rays of said radiation to pass whose incidences are less than a first maximum incidence.
- the array 27 of microlenses 29 is formed on and in contact with a substrate or support 30, the substrate 30 then being interposed between the microlenses 29 and the matrix 31.
- the substrate 30 can be made of a transparent polymer which does not absorb, at least, the wavelengths considered, here in the visible and/or infrared range.
- This polymer may in particular be poly (ethylene terephthalate)
- the thickness of the substrate 30 can vary between 1 ⁇ m and 100 ⁇ m, preferably between 10 ⁇ m and 100 ⁇ m.
- the substrate 30 can correspond to a colored filter, to a polarizer, to a half-wave plate or to a quarter-wave plate.
- the microlenses 29 can be made of silica, of PMMA, of a positive photosensitive resin, of PET, of poly(ethylene naphthalate) (PEN), of COP, of polydimethylsiloxane (PDMS)/silicone, of epoxy resin or in acrylate resin.
- the microlenses 29 can be formed by creeping blocks of a photosensitive resin.
- the microlenses 29 can additionally be formed by molding on a layer of PET, PEN, COP, PDMS/silicone, epoxy resin or acrylate resin.
- the microlenses 29 are converging lenses each having a focal distance f of between 1 ⁇ m and 100 ⁇ m, preferably between 1 ⁇ m and 70 ⁇ m. According to one embodiment, all the microlenses 29 are substantially identical.
- the microlenses 29 and the substrate 30 are preferably made of transparent or partially transparent materials, that is to say transparent in part of the spectrum considered for the targeted domain, for example , imaging, over the range of wavelengths corresponding to the wavelengths used when exposing an object to be imaged.
- the flat faces of the microlenses 29 face the openings 33.
- the thickness of the walls 35 is called "h".
- the walls 35 are, for example, opaque to the radiation detected by the photodetectors 25, for example absorbing and/or reflecting with respect to the radiation detected by the photodetectors 25.
- the walls 35 absorb and/or reflect in the visible and/or the near infrared and/or the infrared.
- the walls 35 are, for example, opaque to wavelengths between 400 nm and 600 nm, used for imaging (eg biometrics and fingerprint imaging).
- the upper face of the layer 31 is called the face of the layer 31 located at the interface between the layer 31 and the substrate 30. Also called the lower face of the layer 31, the face of the layer 31 located opposite the upper face.
- each opening 33 can be square, rectangular or funnel-shaped.
- Each opening 33 seen from above (that is to say in the XZ plane), can have a circular, oval or polygonal shape, for example triangular, square, rectangular or trapezoidal.
- Each opening 33 viewed from above, has a preferably circular shape.
- the width of an opening 33 is defined as the characteristic dimension of the opening 33 in the plane XZ. For example, for an opening 33 having a square cross-section in the XZ plane, the width corresponds to the dimension of one side and for an opening 33 having a circular cross-section in the XZ plane, the width corresponds to the diameter of the opening 33.
- the width of the openings 33, at the level of the upper face of the layer 31, is greater than the width of the openings 33, at the level of the lower face of the layer 31.
- the center of an opening 33 is called the point situated at the intersection of the axis of symmetry of the openings 33 and of the lower face of the layer 31.
- the center of each opening 33 is located on the axis of revolution of the opening 33.
- the openings 33 are arranged in rows and in columns.
- the openings 33 can all have substantially the same dimensions.
- the width of the openings 33 at the interface with the substrate or the microlenses 29 is called “wl” and the width of the openings 33 at the interface with the layer 37 is called “w2".
- wl The width of the openings 33 at the interface with the substrate or the microlenses 29
- w2 the width of the openings 33 at the interface with the layer 37
- Each aperture 33 is preferably associated with a single microlens 29.
- the optical axes of the microlenses 29 are preferably aligned with the centers of the openings 33 of the matrix 31.
- the diameter of the microlenses 29 is preferably greater than the maximum width (measured perpendicular to the optical axes) of the openings 33.
- the pitch p can be between 5 ⁇ m and 100 ⁇ m, for example equal to approximately 15 ⁇ m.
- the height h can be between 1 ⁇ m and 1 mm, preferably be between 12 ⁇ m and 20 ⁇ m.
- the width wl can preferably be between 5 ⁇ m and 100 ⁇ m, for example be equal to about 10 ⁇ m.
- the width w2 can preferably be between 1 ⁇ m and 100 ⁇ m, for example be equal to about 2 ⁇ m.
- each photodetector 25 is associated with four openings 33 (each photodetector 25 is for example associated with two openings 33 along the X axis and two openings 33 along the Z axis) .
- the resolution of the angular filter 23 may be more than four times greater than the resolution of the image sensor 21. In other words, in practice, there may be more than four times as many apertures 33 as photodetectors. 25, for example eight times more.
- the structure associating the array 27 of microlenses 29 and the matrix 31 is adapted to filter the incident radiation according to the incidence of the radiation relative to the optical axes of the microlenses 29 of the array 27, which, in FIG. 2, are parallel to the Y axis.
- the structure associating the array 27 of microlenses 29 and the matrix 31 is adapted to block at least the majority, preferably substantially all of the rays of the incident radiation whose respective incidences with respect to the optical axes of the microlenses 29 of the filter 23 are greater than a second maximum incidence, less than the first maximum incidence.
- This structure is adapted to allow only rays to pass whose incidence relative to the optical axes of the microlenses 29 is lower than the second maximum incidence.
- the structure only lets through incident rays having an incidence of less than 45°, preferably less than 30°, more preferably less than 10°, even more preferably less than 4°, for example of the order of 3 .5°.
- the openings 33 are, for example, filled with air, with a partial vacuum or with a material that is at least partially transparent in the visible and infrared domains.
- the material filling the openings 33 preferably forms a layer 37 on the lower face of the matrix 31 so as to cover the walls 35 and planarize said lower face of the matrix 31.
- the microlenses 29 are preferably covered by a layer 39 of planarization.
- Layer 39 is made of a material that is at least partially transparent in the visible and infrared domains.
- the layer 39 has a refractive index lower than the refractive index of the material constituting the microlenses 29.
- layer 41 is located above array 27 of microlenses 29. More specifically, layer 41 is located on the upper face of layer 39.
- the layer 41 is adapted to filter the incident radiation as a function of the incidence of the radiation with respect to the Y axis.
- the layer 41 is adapted to only let through rays having an incidence lower than the first maximum incidence. .
- layer 41 is adapted to allow only rays to pass, arriving on the upper face of layer 41, having an incidence less than the first maximum incidence.
- the first maximum incidence is preferably greater than 15°.
- the first maximum incidence is preferably less than 60°, preferably less than or equal to 30°.
- the structure comprising the network 27 of microlenses 29 and the matrix 31 of openings 33 theoretically makes it possible to block all the rays whose incidence is greater than the second maximum incidence.
- certain rays of incidence greater than the second maximum incidence nevertheless manage to cross the matrix 31.
- This phenomenon is called optical crosstalk or parasitic coupling and can lead to a drop in the resolution of the photodetectors 25 or in the contrast of the image obtained.
- the purpose of the layer 41 is to block the rays of incidence greater than the second maximum incidence and which could cause optical crosstalk.
- layer 41 is composed of a stack of several successive sub-layers, four successive sub-layers 411, 413, 415, 417 being represented by way of example in FIG. 2.
- Underlayer 417 is preferably located on layer 39 and in contact with layer 39. Underlayer 417 preferably covers all of layer 39.
- Underlayer 415 covers the upper face of the sub-layer 417.
- the sub-layer 415 is covered by the sub-layer 413 which is itself covered by the layer 411.
- the sub-layers 411, 413, 415 and 417 have, for example, the same thicknesses.
- the sub-layers 411, 413, 415 and 417 preferably have different thicknesses.
- layer 41 comprises a stack of four sub-layers.
- the layer 41 can be composed of a stack of a number of sublayers different from four. By way of example, the number of sub-layers can be two.
- the refractive indices of two successive sub-layers are preferably different, for example by at least 0.15, preferably by at least 0.2.
- the lower sub-layer that is to say the sub-layer closest to the sensor 21
- the refractive index of the upper sub-layer that is to say the sub-layer farthest from the sensor 21.
- the refractive index of the sub-layer 411 is greater by 0.15, preferably 0.2, compared to the refractive index of the sub-layer 413.
- the refractive index of the sub-layer 413 is greater by 0.15, preferably 0.2, compared to the refractive index of the sub-layer 415.
- the refractive index of the sub-layer 415 is 0.15, preferably 0.2, higher than the refractive index of the sub-layer 417.
- the filtering function described above by layer 41 with a multilayer structure can be obtained by combining a single layer covering layer 39.
- This single layer then has a higher refractive index at least 0.15, preferably at least 0.2, relative to the refractive index of layer 39.
- the sub-layers 411, 413, 415 and 417 are preferably made of different materials.
- the sub-layers 411, 413, 415 and 417 can, for example, be composed of the same chemical compounds in different proportions, have decreasing refractive indices from layer 411 to layer 417 in order to deflect the rays.
- layer 41 is composed of several sub-layers made alternately based on silicon nitride (S13N4) and air or a polymer such as polyethylene terephthalate (PET).
- Layer 41 has, for example, a thickness comprised between 10 nm and 10 ⁇ m, preferably between 50 nm and 1 ⁇ m.
- the layer 41 is preferably transparent to the wavelengths of the application considered.
- the filtering comes from the fact that the layer 41 reflects the rays whose incidence is greater than the first maximum incidence. More precisely, with each change of layer, the medium of propagation of the light rays changes. The rays are then, in contact with the interface formed by the interface between the two successive layers, partly refracted and partly reflected. At the output of layer 41, there are almost no more rays whose incidence is greater than the first maximum incidence. In other words, layer 41 is optimized to guarantee maximum transmittance for rays having an incidence less than the first maximum incidence.
- the radiation incident on device 19 comprises: rays 43 of zero incidence with respect to layer 41 (that is to say perpendicular to the upper face of layer 41); rays 45 of incidence a with respect to layer 41, strictly greater than 0° and less than or equal to the first maximum incidence, for example, approximately 30°, the rays 45 having, after passing through layer 41, an angle of attack ⁇ 21, strictly less than the second maximum angle of attack, for example approximately 4°; rays 47 of incidence p with respect to layer 41, strictly greater than a and less than or equal to the first maximum incidence, for example, approximately 30°, the rays 47 having, after passing through layer 41, an incidence P22, greater than or equal to the second maximum angle of attack, for example approximately 4°; and rays 49 of incidence y with respect to layer 41, greater than the first maximum incidence.
- the rays 45 and 47 are represented in the layer 41 by dotted lines which represent only the direction resulting from these rays at the exit from the layer 41. In reality, the rays 45 and 47 are refracted at each change of sub-layers of layer 41 as shown for spokes 49.
- each ray 43 passes through layer 41 and array 27 of microlenses 29 emerging from one of microlenses 29 with an angle S22 so as to pass through the image focus of said microlens 29.
- the image focus of each microlens 29 is located on the underside of the matrix 31 of apertures 33, at the center of the aperture 33 with which the microlens 29 is associated. Neither the layer 41 nor the structure associating the array 27 of microlenses 29 and the matrix 31 blocks the rays 43.
- Each ray 43 is therefore picked up by the image sensor 21 and more precisely by the photodetector 25 underlying the microlens 29 traversed by spoke 43.
- each spoke 45 passes through layer 41 to come out with an angle “21-
- the layer 41 does not block the rays 45 whose incidence is less than the first maximum incidence.
- the structure associating the network 27 of microlenses 29 and the matrix 31 does not block the rays 45 because these arrive on the microlenses 29 with an incidence strictly lower than the second maximum incidence.
- Each ray 45 is therefore picked up by the image sensor 21 and more precisely by the photodetector 25 underlying the microlens 29 through which the ray 45 passes.
- each ray 47 crosses the layer 41 to come out with an angle P22 •
- the layer 41 does not block the rays 47 whose incidence is less than the first maximum incidence.
- the structure associating the network 27 of microlenses 29 and the matrix 31 blocks the rays 47 because these arrive on the microlenses 29 with an incidence greater than or equal to the second maximum incidence. The rays 47 are therefore not picked up by the image sensor 21.
- all the rays 49 having incidences greater than the first maximum incidence are reflected by the accumulation of the sub-layers of the layer 41.
- the rays 49 arrive on the upper face of layer 41, more precisely the upper face of sub-layer 411, with an incidence greater than the first maximum incidence.
- a part 49' of the rays 49 is reflected and the other part 491 of the rays 49 engages in the sub-layer 411 with an angle Y211-
- the rays 491 arrive on the upper face of the sub-layer 413.
- the rays 493 are divided into a reflected part 493' and a refracted part 495 (the rays 495 having an angle Y215 with the rays 213).
- the rays 495 are split into a reflected portion 495' and a refracted portion 497 (the rays 497 having an angle Y217 with the rays 215).
- the rays 497, in contact with the layer 39, are mostly reflected (rays 497').
- the rays 497 are not all reflected and residues of rays 497 propagate, at the output of the layer 41, in the layer 39. These are deflected by the layer 39 and blocked by the association of the microlenses 29 and of the matrix 31 because they arrive at the surface of the microlenses 29 with an incidence much greater than the first incidence.
- the rays 49 therefore do not reach the photodetectors 25.
- the image sensor 21 At the output of the angular filter 23, the image sensor 21 only captures the rays 43 and 45.
- no opaque layer extends above layer 41.
- the layer 41 comprises only transparent materials which, here again, makes it possible to maximize the useful surface for collecting light by the angular filter.
- FIG. 3 represents, by a graph, the transmittance of the angular filter 23 of the device illustrated in FIG. 2 as a function of the incidence of the rays reaching the angular filter 23.
- FIG. 3 illustrates three curves 70, 71 and 73 each representing the normalized transmittance (Transmission) of the rays in different parts of the angular filter 23 as a function of the incidence of said rays (Angles (°)).
- the graph illustrated in FIG. 3 comprises: a curve 70 corresponding to the transmittance of the rays passing through the structure associating the array 27 of microlenses 29 and the matrix 31; a curve 71 corresponding to the transmittance of the rays passing through the layer 41; and a curve 73 corresponding to the transmittance of the rays passing through the assembly of the angular filter 23 as illustrated in FIG. 2.
- the association of the network of microlenses 29 and the matrix 31, respectively the matrix 41 does not make it possible to block clearly the rays whose incidence is greater than the second maximum incidence, respectively the first maximum impact.
- blocking value that is to say the second maximum incidence, respectively the first maximum incidence, as being the half-width at half of the maximum transmittance or half-width at half-height of the curve 70, respectively the curve 71. That is to say that the rays whose incidence is equal to this value are blocked at 50%, the rays whose incidence is greater than this value are mostly unblocked and the rays whose incidence is lower than this value are oritarily blocked by the association of the network of microlenses and the first matrix 31, respectively by the second matrix 41.
- the half-width at half-height of the curve 70 or half-width at half the maximum transmittance of the assembly formed by the array 27 of microlenses 29 and the matrix 31 (HWHM : Half Width High Maximum) is equal to about 3.5° and the half-width at half-height of curve 71 or half-width at half the maximum transmittance of layer 41 is equal to about 20°.
- the first curve 70 includes two second peaks, called secondary peaks, for incidences of about 25° and -25°.
- the transmittance of rays having an incidence equal to approximately 25° is approximately equal to 0.05.
- These secondary peaks correspond to the passage, through the network of microlenses 29 and the matrix 31, of rays having incidences of between about 20° and about 40°, picked up by a photodetector 25 close to the photodetector 25 underlying the microlens 29 or the opening 33 that the ray passes through.
- the second curve 71 is characteristic of a band pass filter allowing the rays whose incidences are between ⁇ 20° and 20° to pass.
- the values of curve 73 correspond to a multiplication of the value of curve 70 and the value of curve 71 for the same given incidence.
- the third curve 73 has, in comparison to curve 70, no secondary peaks.
- the transmittance of the rays beyond 20° then tends towards 0.
- Figure 4 illustrates, by a sectional view, partial and schematic, another embodiment of an image acquisition device 51.
- FIG. 4 illustrates an image acquisition device 51 similar to device 19 illustrated in FIG. 2, except that layer 41 is an interference bandpass filter, that is to say say a filter that only lets through radiation whose wavelengths are within a given range of wavelengths.
- layer 41 is an interference bandpass filter, that is to say say a filter that only lets through radiation whose wavelengths are within a given range of wavelengths.
- an interference filter also behaves like an angular filter because of its angular tolerance. That is to say that the cut-off wavelength range depends on the incidence.
- an interference filter blocks, for each incidence, a different wavelength range.
- a ray 53 having a wavelength i is blocked (reflected and/or absorbed) if its incidence is greater than an angle 0i while a ray 55 having a wavelength ⁇ 2 is blocked ( reflected and/or absorbed) if its incidence is greater than an angle 02 different from angle 01.
- layer 41 is formed by stacking several layers of different refractive indices.
- layer 41 comprises alternating first layers of a first material having a first refractive index and second layers of a second material having a second refractive index different from the first refractive index.
- layer 41 comprises alternating layers made of magnesium fluoride and layers made of alumina or alternating layers made of tantalum pentoxide and layers made of silicon dioxide.
- layer 41 comprises an alternation of layers made of one or more of the materials from the list: magnesium fluoride, alumina, tantane pentoxide, silicon dioxide, trititanium pentoxide, hafnium dioxide.
- Layer 41 may further comprise an alternation of layers made of gold, silver, chromium, nickel or aluminum or one or more of their derivatives. As a variant, layer 41 illustrated in FIG. 4 can be located between array of microlenses 29 and matrix 31 or between matrix 31 and image sensor 21.
- no opaque layer extends above layer 41.
- the layer 41 comprises only transparent layers (in materials that are transparent or thin enough to be transparent) which, here again, makes it possible to maximize the useful surface area for collecting light by the angular filter.
- Figure 5 illustrates another embodiment of an image acquisition device 57.
- FIG. 5 illustrates an image acquisition device 57 similar to device 19 illustrated in FIG. 2, except that layer 41 is a fiber optic plate (FOP, Fiber Optic Plate).
- FOP Fiber Optic Plate
- the layer 41 corresponds to the grouping of several optical fibers joined together and arranged substantially parallel to the Y axis.
- each optical fiber comprises a core 61 surrounded by a sheath 62.
- the core is made of a first material having a first refractive index and the sheath is made of a second material having a first index of refraction, the first and second materials being transparent to incident radiation, and the first index being greater than the second index.
- the spaces between the optical fibers are filled with a black resin 63, preferably absorbent radiation considered.
- layer 41 includes a black resin 63 used to fill the holes between the optical fibers.
- the angular selection of the optical fibers is due to the difference in refractive index between the core 61 and the sheath 63 of the fibers.
- the optical fibers have a numerical aperture which therefore depends on the refractive indices of the core 61 and of the cladding 62.
- the numerical aperture of the fibers is calculated by the following formula:
- the maximum incidence depends in particular on the characteristics of the optical fibers, on the thickness of the layer 41.
- each optical fiber has a substantially cylindrical shape with a circular base.
- the external diameter of an optical fiber is, for example, between 6 ⁇ m and 25 ⁇ m.
- layer 41 is located on the upper face of array 27 of microlenses 29 and is, for example, fixed thereto by means of an adhesive.
- the layer 41 can, as a variant, be located between the microlenses 29 and the matrix 31 or between the matrix 31 and the image sensor 21.
- no opaque layer extends above layer 41. This makes it possible to maximize the useful area for collecting light by the angular filter.
- Figure 6 illustrates another embodiment of an image acquisition device 65.
- FIG. 6 illustrates an image acquisition device 65 similar to the device 19 illustrated in FIG. 2 with the difference that the layer 41 is a structured layer and located between the array of microlenses 29 and the matrix 31.
- the layer 41 preferably corresponds to a structured layer such as a photonic crystal, that is to say it is a layer of a first material having a first refractive index crossed by pillars 67 extending along the Y axis and arranged in a network, the pillars 67 being made of a second material having a second refractive index different from the first refractive index, the first and second materials being transparent to the incident radiation.
- a structured layer such as a photonic crystal
- the pillars 67 have, in FIG. 6, substantially cylindrical shapes, the base of which corresponds to a circle, an ellipse, a square, a rectangle, a parallelogram, a polygon, etc.
- the pillars 67 have shapes substantially of cones, truncated cones, pyramids, or truncated pyramids.
- the pillars 67 can, as a variant, have any shape.
- the properties of the photonic crystal in particular the dimensions of the pillars 67 and the arrangement of the pillars 67 in a network, are chosen so that the combination of the layer 41 and the structure associating the network 27 of microlenses 29 and the matrix 31 d openings 33 completely block the incident rays having an incidence greater than the first maximum incidence.
- the complete blocking of the incident rays having an incidence greater than the first maximum incidence makes it possible to reduce, or even eliminate, the optical crosstalk.
- no opaque layer extends above layer 41.
- the layer 41 comprises only transparent materials which, there Tl again, makes it possible to maximize the useful surface of collection of light by the angular filter
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- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Health & Medical Sciences (AREA)
- Toxicology (AREA)
- Solid State Image Pick-Up Elements (AREA)
- Optical Elements Other Than Lenses (AREA)
- Diffracting Gratings Or Hologram Optical Elements (AREA)
- Studio Devices (AREA)
- Optical Filters (AREA)
Abstract
Description
Claims
Priority Applications (4)
Application Number | Priority Date | Filing Date | Title |
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JP2023536173A JP2024500393A (ja) | 2020-12-14 | 2021-11-22 | 光学角度フィルタ |
EP21815506.7A EP4260104A1 (fr) | 2020-12-14 | 2021-11-22 | Filtre angulaire optique |
CN202180084152.2A CN116685881A (zh) | 2020-12-14 | 2021-11-22 | 光学角度滤波器 |
US18/266,547 US20240045125A1 (en) | 2020-12-14 | 2021-11-22 | Optical angular filter |
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FRFR2013151 | 2020-12-14 | ||
FR2013151A FR3117615B1 (fr) | 2020-12-14 | 2020-12-14 | Filtre angulaire optique |
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WO2022128337A1 true WO2022128337A1 (fr) | 2022-06-23 |
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PCT/EP2021/082404 WO2022128337A1 (fr) | 2020-12-14 | 2021-11-22 | Filtre angulaire optique |
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US (1) | US20240045125A1 (fr) |
EP (1) | EP4260104A1 (fr) |
JP (1) | JP2024500393A (fr) |
CN (1) | CN116685881A (fr) |
FR (1) | FR3117615B1 (fr) |
WO (1) | WO2022128337A1 (fr) |
Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR2013151A1 (fr) | 1968-07-17 | 1970-03-27 | Gen Electric | |
EP3575845A1 (fr) * | 2018-05-30 | 2019-12-04 | Depixus | Dispositif d'imagerie en gros plan multicanal |
EP3593342A1 (fr) * | 2017-03-06 | 2020-01-15 | Isorg | Systeme d'acquisition d'images |
US20200327296A1 (en) * | 2019-04-10 | 2020-10-15 | Shenzhen GOODIX Technology Co., Ltd. | Optical fingerprint identification apparatus and electronic device |
-
2020
- 2020-12-14 FR FR2013151A patent/FR3117615B1/fr active Active
-
2021
- 2021-11-22 US US18/266,547 patent/US20240045125A1/en active Pending
- 2021-11-22 WO PCT/EP2021/082404 patent/WO2022128337A1/fr active Application Filing
- 2021-11-22 JP JP2023536173A patent/JP2024500393A/ja active Pending
- 2021-11-22 CN CN202180084152.2A patent/CN116685881A/zh active Pending
- 2021-11-22 EP EP21815506.7A patent/EP4260104A1/fr active Pending
Patent Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR2013151A1 (fr) | 1968-07-17 | 1970-03-27 | Gen Electric | |
EP3593342A1 (fr) * | 2017-03-06 | 2020-01-15 | Isorg | Systeme d'acquisition d'images |
EP3575845A1 (fr) * | 2018-05-30 | 2019-12-04 | Depixus | Dispositif d'imagerie en gros plan multicanal |
US20200327296A1 (en) * | 2019-04-10 | 2020-10-15 | Shenzhen GOODIX Technology Co., Ltd. | Optical fingerprint identification apparatus and electronic device |
Also Published As
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US20240045125A1 (en) | 2024-02-08 |
FR3117615B1 (fr) | 2023-08-04 |
CN116685881A (zh) | 2023-09-01 |
EP4260104A1 (fr) | 2023-10-18 |
FR3117615A1 (fr) | 2022-06-17 |
JP2024500393A (ja) | 2024-01-09 |
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