CN115308976A - Liquid crystal polarization camera system based on micro-lens array - Google Patents

Liquid crystal polarization camera system based on micro-lens array Download PDF

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CN115308976A
CN115308976A CN202210779418.1A CN202210779418A CN115308976A CN 115308976 A CN115308976 A CN 115308976A CN 202210779418 A CN202210779418 A CN 202210779418A CN 115308976 A CN115308976 A CN 115308976A
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liquid crystal
polarization
polarizing film
micro
image sensor
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寿乾龙
孟志
秦鑫伟
黄文彬
陈林森
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Suzhou University
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Suzhou University
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    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03B—APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
    • G03B17/00—Details of cameras or camera bodies; Accessories therefor
    • G03B17/02—Bodies
    • G03B17/12—Bodies with means for supporting objectives, supplementary lenses, filters, masks, or turrets
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B3/00—Simple or compound lenses
    • G02B3/0006—Arrays
    • G02B3/0037—Arrays characterized by the distribution or form of lenses
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/30—Polarising elements
    • G02B5/3016—Polarising elements involving passive liquid crystal elements

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  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Chemical & Material Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Liquid Crystal (AREA)

Abstract

The application discloses a liquid crystal polarization camera system based on a micro-lens array. The system comprises: the micro-lens array is arranged in parallel relative to the liquid crystal polarizing film and comprises a plurality of micro-lens units which are regularly arranged, each micro-lens unit corresponds to each focal plane unit on the liquid crystal polarizing film, light is split into a plurality of beams after being incident to the micro-lens array, the beams penetrate through the liquid crystal polarizing film and are respectively focused on the image sensor, the beams penetrate through the micro-lens array to be split and focused on the corresponding liquid crystal polarizing film, the liquid crystal polarizing film is filtered in four-angle polarization directions, the four-angle polarization units serve as a macro-polarization unit and are sequentially distributed on the whole liquid crystal polarizing film, the linearly polarized light after being filtered is received by a camera image sensing device, and the collected light field information is reconstructed to obtain a polarization image. The integrated circuit has the advantages of simple structure, high integration level, small volume, low cost and the like.

Description

Liquid crystal polarization camera system based on micro-lens array
Technical Field
The application belongs to the technical field of optical imaging, and particularly relates to a liquid crystal polarization camera system based on a micro-lens array.
Background
The polarization imaging technology can acquire polarization state information of light beams besides three types of information of light intensity, light spectrum and space of object reflected light beams, and can improve the information dimension of images, so that more detailed information of the objects can be embodied on the images. At present, a polarization camera mainly adopts a polarization element to be integrated with an image sensing device, and has the problems of large volume, low integration level and high cost.
Disclosure of Invention
In order to solve the above-mentioned problems of large volume and low integration level of the polarization camera, the present application provides a liquid crystal polarization camera system based on a microlens array. The system can also effectively reduce the cost.
In order to achieve the purpose, the following technical scheme is adopted in the application:
a liquid crystal polarization camera system based on a microlens array, comprising:
a micro lens array, a liquid crystal polarizing film and an image sensor, wherein the micro lens array and the liquid crystal polarizing film are arranged in parallel,
the micro lens array comprises a plurality of micro lens units which are regularly arranged, each micro lens unit corresponds to each focal plane unit on the liquid crystal polarizing film,
the light is split into a plurality of beams after being incident to the micro lens array, passes through the liquid crystal polarizing film and is respectively focused on the image sensor.
Preferably, the liquid crystal polarizing film is bonded to the image sensor (seamless bonding). The liquid crystal polarizing film and the image sensor are in a fit state, so that the crosstalk condition of the filtering light beams in the process of transmitting to the image sensor can be reduced, and the possibility of acquiring error information by the image sensor can be reduced.
Preferably, the microlens unit is a plano-convex lens. The structure can focus the light beam, and meanwhile, the processing is relatively labor-saving, and the thickness is thinner.
Preferably, the image sensor is arranged at the focal length of the microlens array. This can reduce the overall volume of the polarization camera.
Preferably, the liquid crystal polarizing film comprises a plurality of polarizing pixel elements which are in one-to-one matching correspondence with the micro lens units,
when the micro lens array splits the incident light, the incident light is focused to the corresponding pixel units respectively, so that the light distribution is uniform.
Preferably, the focal length of the microlens unit satisfies the formula condition
Figure BDA0003727110340000021
Wherein f is the focal length of the micro-lens, N is the refractive index of the micro-lens, and R is the curvature radius of the micro-lens.
Preferably, the liquid crystal polarizing film comprises a liquid crystal polarizing film spliced by four sequentially ordered polarization angle focusing surfaces, and the image sensor receives the light field information subjected to beam splitting and polarization filtering of the liquid crystal polarizing film for image reconstruction.
Preferably, in the liquid crystal polarization camera system based on the microlens array, the polarization unit on each focusing surface corresponds to the pixel unit on the image sensor one by one, so that each pixel unit can only obtain polarization information in one direction.
Preferably, in the liquid crystal polarization camera system based on the microlens array, the light beam after polarization filtering is transmitted to the pixel unit of the image sensor, and the image sensor acquires single polarization information and spectrum information and reconstructs the acquired light field information.
Preferably, the microlens array comprises a transparent substrate, and a plurality of regularly arranged microlens units are arranged on the side of the substrate far away from the image sensor.
Advantageous effects
Compared with the prior art, the liquid crystal polarization camera system based on the micro lens array integrates the micro lens array, the liquid crystal polarization film and the camera image sensing device, light beams penetrate through the micro lens array to be split and focused onto the corresponding liquid crystal polarization film, filtering is carried out on the liquid crystal polarization film in the polarization directions of four angles, the polarization units of the four angles are used as a macro-polarization unit, the whole liquid crystal polarization film is sequentially arranged, the linearly polarized light after filtering is received by the image sensor system of the camera, and the collected light field information is reconstructed to obtain a polarization image. The integrated circuit has the advantages of simple structure, high integration level, small volume, low cost and the like. The defects of high cost, low integration level and the like of the original polarization camera are avoided.
Drawings
The accompanying drawings are included to provide an understanding of the disclosed embodiments and are incorporated in and constitute a part of this specification, illustrate embodiments of the disclosure and together with the example serve to explain the principles of the disclosure and not to limit the disclosure. The shapes and sizes of the various elements in the drawings are not to scale and are merely illustrative of the present application.
FIG. 1: the liquid crystal polarization camera system based on the micro-lens array is schematic;
FIG. 2 shows a schematic view of a microlens array according to an embodiment of the present application, and b is a schematic view of a microlens unit according to an embodiment of the present application;
FIG. 3: a partial schematic diagram of a four-angle polarizing element;
FIG. 4 is a schematic view of: an assembly schematic diagram of a micro lens array, a liquid crystal polarizing film and an image sensor;
wherein: 301 is a natural light source, 302 is a microlens array, 303 is a liquid crystal polarizing film, 304 is an image sensor, 305 is a microlens unit, and 306 is a four-angle linear polarization unit.
Detailed Description
The above-described scheme is further illustrated below with reference to specific examples. It should be understood that these examples are for illustrative purposes and are not intended to limit the scope of the present application. The conditions employed in the examples may be further adjusted as determined by the particular manufacturer, and the conditions not specified are generally those used in routine experimentation.
Unless otherwise defined, technical or scientific terms used in the embodiments of the present disclosure should have the ordinary meaning as understood by those having ordinary skill in the art to which the present application belongs. The use of "first," "second," and similar terms in the embodiments of the disclosure is not intended to indicate any order, quantity, or importance, but rather to distinguish one element from another. The word "comprising" or "comprises", and the like, means that the element or item preceding the word comprises the element or item listed after the word and its equivalent, but does not exclude other elements or items. The terms "connected" or "coupled" and the like are not restricted to physical or mechanical connections, but may include electrical connections, whether direct or indirect. In this context, "electrically connected" includes the case where constituent elements are connected together by an element having some kind of electrical action. The "element having a certain electric function" is not particularly limited as long as it can transmit and receive an electric signal between connected components. "upper", "lower", "left", "right", and the like are used merely to indicate relative positional relationships, and when the absolute position of the object being described is changed, the relative positional relationships may also be changed accordingly.
In the present application, the terms "upper", "lower", "inside", "middle", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings. These terms are used primarily to better describe the present application and its embodiments, and are not used to limit the indicated devices, elements or components to a particular orientation or to be constructed and operated in a particular orientation.
The application provides a liquid crystal polarization camera system based on microlens array, includes: the liquid crystal display device comprises a micro lens array, a liquid crystal polarizing film and an image sensor;
the micro lens units in the micro lens array are plano-convex lenses, and each lens corresponds to each focal plane unit on the polarizing element. The natural light is incident to the micro lens array and then split into a plurality of beams of light, and the beams of light are focused on the image sensor. The liquid crystal polarizing film adopts liquid crystal and dichroic dye, is a four-polarization-angle focusing-plane polarizing film, and is in seamless joint with the image sensor. And the image sensor receives the light field information subjected to beam splitting and polarization filtering to perform image reconstruction, and is arranged at the focal length of the micro lens array. The working mechanism of the system is as follows: the micro lens array, the liquid crystal polarizing film and the image sensor are arranged in parallel, the liquid crystal polarizing film is attached to the image sensor, and the integrated module of the liquid crystal polarizing film and the image sensor is arranged at the focal length of the micro lens array. When external natural light enters and passes through the micro-lens array, the natural light is divided into a plurality of beams which are respectively transmitted to each pixel of the image sensor, a liquid crystal polarizing film corresponding to the front of the image sensor filters the beams to obtain single polarization information, the single polarization information is transmitted to the image sensor to be received, and finally the collected light field information is reconstructed to obtain an image. In this embodiment, the microlens array, the liquid crystal polarizing film, and the image sensor are integrated, so that the integration level of the polarization camera can be improved, and the size and cost of the polarization camera can be reduced. The camera imaging system adopts a CMOS camera which has the characteristics of low power consumption, high integration level, high response speed and the like, and each electric element can be integrated on one chip and is controlled by a plurality of charge-voltage converters and row-column switches, so that the reading speed is high. An imaging device such as a CCD may be used according to actual needs.
A microlens array module: the micro lens array not only has the functions of focusing, imaging and the like of the traditional lens, but also has the characteristics of small unit size and high integration level, and can build different optical systems to realize the functions which are difficult to realize by the traditional optical device. The micro-lens can adjust the incident light so that it is focused on a single pixel, which can reduce crosstalk between light rays. The structure of the micro lens unit adopts a plano-convex structure, the micro lens arrays correspond to the polarization pixels on the liquid crystal polarizing film one by one, and when the micro lens arrays split incident light beams, the incident light beams are respectively focused to the corresponding units, so that the light beams can be uniformly distributed. Wherein the focal length of the micro lens satisfies the formula condition
Figure BDA0003727110340000051
Where f is the focal length of the microlens, and N is the microlensAnd the refractive index, R is the curvature radius of the micro-lens. The micro lens array can adopt a plano-convex structure, the structure can focus light beams, meanwhile, the processing is relatively labor-saving, and the thickness is thinner.
A liquid crystal polarizing film module: the liquid crystal polarizing film is made of liquid crystal, dichroic dye and photo-alignment agent. Wherein it is patterned with four different polarization angle sub-foci. The polarization units on the focusing surface correspond to the pixels on the image sensor one by one, and each pixel can only obtain polarization information in one direction. The liquid crystal polarizing film and the image sensor are in a fit state, so that the crosstalk condition of the filtering light beams in the process of transmitting to the image sensor can be reduced, and the possibility of acquiring error information by the image sensor can be reduced. The photo-alignment agent for preparing the liquid crystal polarizing film uses SD1 molecules. SD1 has the characteristic of repeated flash, can improve the fault tolerance rate of preparation, and has low orientation exposure energy and good orientation effect.
An image sensor module: the light beams after polarization filtering are transmitted to pixel units of an image sensor, and the image sensor acquires single polarization information and spectrum information and reconstructs the acquired light field information. The image sensor is placed at the focal length of the microlens array, which is small, which can reduce the overall volume of the polarization camera. The camera imaging system adopts a CMOS camera which has the characteristics of low power consumption, high integration level, high response speed and the like, and each electric element can be integrated on one chip and is controlled by a plurality of charge-voltage converters and row-column switches, so that the reading speed is high. An imaging device such as a CCD may be used according to actual needs.
The liquid crystal polarization camera system based on the microlens array proposed by the present application is described next with reference to fig. 1 to 4.
The liquid crystal polarization camera system based on the micro lens array comprises a natural light source 301, a micro lens array 302, a liquid crystal polarization film 303, an image sensor 304, a micro lens unit 305 and a four-angle linear polarization unit 306. The light beams split and focused by the natural light source 301 incident on the microlens array 302 are filtered by the liquid crystal polarizing film 303 and transmitted to the image sensor 304 to acquire information.
The three interfaces of the microlens array 302, the liquid crystal polarizing film 303 and the image sensor 304 are parallel, wherein the image sensor 304 is placed at the focal length f of the microlens array 302, and the liquid crystal polarizing film 303 and the image sensor 304 are attached.
The microlens array 302 includes a plurality of microlens units 305, and the structure thereof is a plano-convex structure.
The macro-pixel unit of the liquid crystal polarizing film 302 is a four-angle linear polarizing unit 306, which adopts 4 different angles. In this example, a CMOS type camera is used, wherein the resolution of the camera is 2448 × 2048 and the pixel cell size is 3.45 μm × 3.45 μm. The polarizing units of the liquid crystal polarizing film 303 are in one-to-one correspondence with the pixel units, so the size is also 3.45 μm × 3.45 μm, and the number of the polarizing units is 2448 × 2048. Four polarizing pixel units adjacent to the liquid crystal polarizing film in the vertical, horizontal and vertical directions are a macro pixel unit, namely the number of the macro pixel units is 1224 multiplied by 1024, wherein the polarizing directions are respectively four kinds of 0 degrees, 45 degrees, 90 degrees and 135 degrees. The microlens units 305 (see b diagram in fig. 2) of the microlens array 302 (see a diagram in fig. 2) need to be focused to the corresponding polarization units, the size is also set to be 3.45 μm × 3.45 μm, and the number of the microlens units 305 is 2448 × 2048, the refractive index of the microlens units is 1.49, the focal length f thereof is 1.02mm, that is, the distance between the microlens array 302 and the image sensor is 1.02mm.
In the present embodiment, the liquid crystal polarizing film 303 is prepared by conducting alignment of liquid crystal and dichroic dye by SD1 spin-coating exposure, followed by spin-coating of liquid crystal and dichroic dye solution. When the light beam passes through the microlens array 302, an adjusted light beam can be obtained, and the light beam can pass through the single polarization pixel unit without being incident on other pixel units, thereby avoiding crosstalk of light. The adjusted light beam can obtain linearly polarized light with a single polarization direction after passing through the liquid crystal polarizing film 303, light field information is acquired in pixel units which are transmitted to the image sensor 304 through the RGB filter, and a polarization image is obtained after internal data processing and image reconstruction.
The above embodiments are merely illustrative of the technical concepts and features of the present application, and the purpose of the present invention is to enable those skilled in the art to understand the content of the present application and implement the present application, and not to limit the protection scope of the present application. All equivalent changes and modifications made according to the spirit of the present application are intended to be covered by the scope of the present application.

Claims (10)

1. A liquid crystal polarization camera system based on a microlens array, comprising:
a micro lens array, a liquid crystal polarizing film and an image sensor, wherein the micro lens array and the liquid crystal polarizing film are arranged in parallel,
the micro lens array comprises a plurality of micro lens units which are regularly arranged, each micro lens unit corresponds to each focal plane unit on the liquid crystal polarizing film,
the light is split into a plurality of beams after being incident to the micro lens array, passes through the liquid crystal polarizing film and is respectively focused on the image sensor.
2. The microlens array based liquid crystal polarization camera system of claim 1, wherein the liquid crystal polarizing film is attached to an image sensor.
3. The microlens array based liquid crystal polarization camera system of claim 1, wherein the microlens elements are plano-convex lenses.
4. The microlens array based liquid crystal polarization camera system of claim 1, wherein the image sensor is configured at a focal length of the microlens array.
5. The microlens array based liquid crystal polarization camera system of claim 1, wherein the liquid crystal polarizing film comprises a plurality of polarization picture elements in one-to-one matching correspondence with the microlens cells,
when the micro lens array splits the incident light, the incident light is focused to the corresponding pixel units respectively, so that the light distribution is uniform.
6. The microlens array based liquid crystal polarization camera system of claim 1, wherein the focal length of the microlens unit satisfies a formula condition
Figure FDA0003727110330000011
Wherein f is the focal length of the micro-lens, N is the refractive index of the micro-lens, and R is the curvature radius of the micro-lens.
7. The microlens array-based liquid crystal polarization camera system of any one of claims 1 to 6, wherein
The liquid crystal polarizing film comprises four liquid crystal polarizing films which are sequentially arranged and spliced by polarization angle focusing surfaces, and the image sensor receives light field information which is subjected to beam splitting and polarization filtering of the liquid crystal polarizing films for image reconstruction.
8. The microlens array based liquid crystal polarization camera system of claim 7,
and the polarization units on each focusing surface correspond to the pixel units on the image sensor one by one, so that each pixel unit can only obtain polarization information in one direction.
9. The microlens array based liquid crystal polarization camera system of claim 8,
the light beams after polarization filtering are transmitted to pixel units of an image sensor, and the image sensor acquires single polarization information and spectrum information and reconstructs the acquired light field information.
10. The microlens array based liquid crystal polarization camera system of claim 1,
the microlens array comprises a transparent substrate, and a plurality of regularly arranged microlens units are arranged on the side, far away from the image sensor, of the substrate.
CN202210779418.1A 2022-07-02 2022-07-02 Liquid crystal polarization camera system based on micro-lens array Pending CN115308976A (en)

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