KR102818819B1 - Hologram Recording System - Google Patents

Abstract

A hologram recording system for obtaining an interference pattern formed by self-interference of incident light from a target object, the hologram recording system comprises: a polarizer array including a plurality of polarizers; an image sensor including a plurality of pixels; and an imaging optical system disposed between the polarizer array and the image sensor, wherein the imaging optical system optically corresponds each of the plurality of polarizers to each of the plurality of pixels. According to one aspect of the present disclosure, a hologram recording system capable of obtaining a high-resolution hologram in real time is provided by having an optical structure capable of replacing the use of a polarizing image sensor by utilizing a high-resolution general image sensor.

Description

Hologram Recording System

The present disclosure relates to a holographic recording system, and more particularly, to a holographic recording system that records in real time and has high resolution.

The content described below merely provides background information related to the present embodiment and does not constitute prior art.

Unlike conventional photography, which only records intensity information, holography acquires and records amplitude and phase information of light transmitted from an object.

As of now, there is no sensor that can directly record the amplitude and phase information of visible light, so the relevant information is acquired indirectly through the interference phenomenon of light when acquiring. Interference is a phenomenon that occurs when two light waves called object light and reference light interact, but it is difficult to obtain an interference pattern without using a laser, which is light whose amplitude and phase are artificially aligned. Therefore, lasers have been mainly used in holography technology until recently.

Self-interference holography obtains interference patterns by dividing incident waves emitted or reflected from an object according to space or polarization state in a self-referencing manner. The divided light waves are modulated and propagated into wavefronts with different curvatures by the influence of an interferometer or polarization modulator, forming interference patterns on the image sensor. Since the interference at this time occurs between twin light waves originating from light that started in the same space and time, it is free from light source conditions compared to interference conditions using a laser. Therefore, recording is possible under fluorescent, light bulb, LED, or natural light conditions.

The present disclosure aims to provide a hologram recording system capable of obtaining a high-resolution hologram in real time by having an optical structure that can replace the use of a polarization image sensor by utilizing a high-resolution general image sensor.

The problems to be solved by the present invention are not limited to the problems mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the description below.

According to one aspect of the present disclosure, a hologram recording system for obtaining an interference pattern formed by self-interference of incident light from a target object is provided, the hologram recording system comprising: a polarizer array including a plurality of polarizers; an image sensor including a plurality of pixels; and an imaging optical system disposed between the polarizer array and the image sensor, wherein the imaging optical system optically corresponds each of the plurality of polarizers to each of the plurality of pixels.

According to embodiments of the present disclosure, by obtaining spatially separated and differently phase-shifted interference patterns, it is possible to capture not only static objects but also dynamic objects and holographic videos that change over time.

According to an embodiment of the present disclosure, a high-resolution hologram can be obtained in real time by obtaining individual interference patterns with different phase shifts for each pixel on a high-resolution general image sensor without being constrained by the limited specifications of commercially available polarization image sensors.

The effects of the present disclosure are not limited to the effects mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the description below.

FIG. 1 is a schematic diagram of a hologram recording system according to one embodiment of the present disclosure.
FIG. 2 is a drawing for explaining the characteristics of a geometric phase lens according to embodiments of the present disclosure.
FIG. 3 is an exemplary drawing of a polarizer array according to embodiments of the present disclosure.
FIG. 4 illustrates a part of a holographic recording system according to one embodiment of the present disclosure.
FIG. 5 is a schematic diagram of a hologram recording system according to another embodiment of the present disclosure.

Hereinafter, some embodiments of the present disclosure will be described in detail using exemplary drawings. When adding reference numerals to components of each drawing, it should be noted that the same numerals are used for identical components as much as possible even if they are shown in different drawings. In addition, when describing the present disclosure, if it is determined that a specific description of a related known configuration or function may obscure the gist of the present disclosure, the detailed description thereof will be omitted.

In describing components of embodiments according to the present disclosure, symbols such as first, second, i), ii), a), b), etc. may be used. These symbols are only for distinguishing the components from other components, and the nature or order or sequence of the components is not limited by the symbols. When a part in the specification is said to "include" or "provide" a component, this does not mean that other components are excluded, but rather that other components can be further included, unless explicitly stated otherwise.

The detailed description set forth below, together with the accompanying drawings, is intended to explain exemplary embodiments of the present disclosure and is not intended to represent the only embodiments in which the present disclosure may be practiced.

Embodiments of the present disclosure relate to a self-interference holographic recording system that obtains an interference pattern formed by self-interference of light from a target object under fluorescent, light bulb, LED or natural light conditions.

In order to achieve self-interference, a wavefront modulation device is required to divide the incident light into halves and modulate each separately. There is an example of obtaining a self-interference pattern by spatially separating and modulating the wavefront by borrowing the traditional Michelson interferometer structure and then recombining them. Meanwhile, if a polarization-selective device is utilized, wavefront modulation and interference are possible without dividing the path of the incident light in two. Representative examples include systems that utilize a phase-only SLM (Spacial Light Modulator), a birefringent lens, a liquid crystal lens, or a geometric phase lens. These devices commonly divide the polarization state of the incident light into vertical and horizontal components, or left-circular and right-circular components, and modulate the curvature of one or both of them differently.

Mathematical expression 1 is two light waves traveling in the same direction. class It shows that when interference occurs, three terms are generated. Here, the desired complex hologram is And, Information about the silver light source, represents a twin-image of a hologram.

Mathematical Formula 1

In order to fully utilize the resolution of the image sensor, the propagation directions of the two interfering light waves must be the same, in which case the light source information and the twin image information are superimposed and recorded on the complex hologram to be acquired, as in mathematical expression 1. Since the light source and twin image information act like noise when reproducing the hologram, it has the effect of lowering the quality of the holographic image, and therefore a technology to remove it is necessary.

A representative method for extracting only complex holograms from mathematical expression 1 is phase shift holography. The phase shift method is a method of giving relative phase differences of 0, 90, 180, and 270 degrees to two interfering light waves and then combining them using mathematical expression 2 (only a representative four-step phase shift technique is described).

Mathematical Formula 2

In mathematical expression 2 is a mistake, Is It is an interference pattern with a phase difference of that size. In order to provide a phase difference between two interfering light waves, methods are mainly used to adjust the relative optical path difference, provide a phase delay, or adjust the geometric phase.

The images acquired by the phase shift method can be acquired sequentially over time, but they can also be acquired spatially separated using a polarization image sensor. In this case, the polarization image sensor surface is separated into (mainly) four areas, and the interference pattern with different phase shifts is recorded, and when these are extracted as four different images on a computer and processed as in mathematical equation 2, a complex hologram is obtained. The disadvantage of this method is that it utilizes 1/4 of the resolution of the image sensor, but since one exposure is required to acquire one hologram, it has the advantage of being able to capture not only static objects but also objects that change over time, such as living things, and holographic videos.

FIG. 1 is a schematic diagram of a hologram recording system according to one embodiment of the present disclosure.

Referring to FIG. 1, a hologram recording system according to one embodiment of the present disclosure may include a geometric phase lens (130), a polarizer array (140), an imaging optical system (150), and an image sensor (160), and obtains an interference pattern formed by self-interference of incident light (I) from a target object (not shown). As illustrated, the geometric phase lens (130), the polarizer array (140), the imaging optical system (150), and the image sensor (160) are all aligned with one optical axis (A).

The geometric phase lens (130) is a wavefront modulation device that divides incident light into two light waves having the same propagation direction and changes them into left-handed and right-handed polarizations, respectively. At this time, a polarizing plate (120) may be placed in front of the geometric phase lens (130), and an objective lens (110) may be placed in front of the polarizing plate (120). Here, the forward direction means the reverse direction of the sequential propagation direction in which the incident light enters the hologram recording system and reaches the image sensor.

In embodiments of the present disclosure, the incident light is light from a target object, and the light source may be, for example, a fluorescent light, a light bulb, an LED, or natural light, and the target object may reflect or scatter light from these light sources or may be self-luminous, and the incident light is light reflected, scattered, or self-luminous from the target object and travels into the holographic recording system.

In one embodiment, incident light (I) from a target object sequentially passes through an objective lens (110), a polarizing plate (120), and a geometric phase lens (130). The incident light (I) is collected by the objective lens (110) and changed into linearly polarized light by the polarizing plate (120). The linearly polarized incident light (I) is divided into two light waves of left-circular polarization and right-circular polarization having the same propagation direction by the geometric phase lens (130). An interference pattern is generated by the interference of the left-circular polarization light wave and the right-circular polarization light wave. The interference pattern is generated on an image sensor (160) and acquired by the image sensor (160).

FIG. 2 is a drawing for explaining the characteristics of a geometric phase lens according to embodiments of the present disclosure.

Referring to FIG. 2, the geometric phase lens (130) has both negative and positive foci. In other words, the geometric phase lens has polarization selectivity and changes incident light that is right-handedly polarized into left-handedly polarized light that converges at the positive focal point, and changes incident light that is left-handedly polarized into right-handedly polarized light that diverges from the negative focal point.

For reference, circular polarization means that the direction of vibration of the electric field vector (or magnetic field vector) of a light wave is circular vibration. Circular polarization in which the electric field vector of light rotates clockwise with respect to the observer is called right-handed circular polarization, and circular polarization in which the electric field vector rotates counterclockwise is called left-handed circular polarization.

Geometrical phase lenses are thin film-type passive elements that act as concave or convex lenses depending on the circular polarization of incident light. That is, when light with a linear polarization state enters, it acts as a concave lens for half of the incident light and as a convex lens for the other half, thereby modulating the wavefront. Using this lens, the overall size of a self-interference holographic recording system can be reduced to less than a few centimeters.

As shown in (a) of Fig. 2, the geometric phase lens (130) has a positive focus (f1) for light of right-circular polarization (L2). When parallel light of right-circular polarization (L2) is incident on the geometric phase lens (130), light changed to left-circular polarization (L1) is collected at the positive focus (f1).

Meanwhile, as shown in (b) of Fig. 2, the geometric phase lens (130) has a negative focus (f ₂ ) for light of left-circular polarization (L ₁ ). When parallel light of left-circular polarization (L ₁ ) is incident on the geometric phase lens (130), light changed to right-circular polarization (L ₂ ) is emitted from the negative focus (f ₂ ).

As shown in (c) of Fig. 2, when unpolarized or linearly polarized light (L) is incident on a geometric phase lens (130), some of it is changed into left-circularly polarized light that converges at the positive focus, and the remaining part is changed into right-circularly polarized light that diverges from the negative focus.

In one embodiment, the geometric phase lens (130) forms a condition for self-interference by dividing incident light (I) from a target object into left-circularly polarized light and right-circularly polarized light. The light from the target object is collected as much as possible by the objective lens (110) to form incident light, and the incident light (I) is linearly polarized by the polarizing plate (120). Half of the linearly polarized incident light is modulated into left-circularly polarized light and the other half is modulated into right-circularly polarized light by the geometric phase lens (130). The left-circularly polarized light and the right-circularly polarized light interfere with each other to form an interference pattern having information about the target object.

FIG. 3 is an exemplary drawing of a polarizer array according to embodiments of the present disclosure.

Referring to FIG. 3, the polarizer array (140) includes a plurality of polarizers (141) and spatially divides two light waves that interfere by transmitting through the geometric phase lens to impart different phase differences to each other. That is, the polarizer array (140) imparts a relative phase difference to two interfering light waves in order to extract only a complex hologram as described above as a spatial division phase shifting means.

In the illustrated embodiment, a plurality of polarizers (141) are arranged in a matrix form. In addition, the plurality of polarizers (141) are linear polarizing plates that convert incident light into linearly polarized light, and each has a different polarization axis. The plurality of polarizers have one of four types of polarization axes (0°, 45°, 90°, and 135°) (141a, 141b, 141c, and 141d) that are 45° apart. The micro polarizers having four different types of polarization axes (141a, 141b, 141c, and 141d) all have the same size and are arranged in a 2×2 matrix. In this case, the polarizing plate array (140) includes a plurality of polarizers (141) in which a 2×2 matrix arrangement having four different types of polarization axes (141a, 141b, 141c, and 141d) is repeatedly arranged in a plane.

In another embodiment, the plurality of polarizers have one of three polarization axes (0°, 60°, and 120°) that are spaced apart by 60°. In this case, the plurality of polarizers may have, for example, a hexagonal shape and be arranged in a honeycomb structure.

The polarizer array (140) has a structure in which a plurality of polarizers having different polarization axes are arranged in two dimensions, thereby spatially dividing two interfering light waves according to the plurality of polarizers and imparting different phase differences to them. The polarizer array (140) can be configured to spatially divide two interfering light waves and impart different phase differences to the divided areas. As described above, the polarizer array (140) can include variously modified forms in terms of the arrangement of the plurality of polarizers and the polarization axes, etc., as long as it is configured to allow spatial phase shift.

When using a polarizer array (140), which is a spatial arrangement of a plurality of polarizers having different polarization axes, the holographic recording system of the present disclosure can simultaneously obtain a plurality of interference patterns that are phase-shifted in a spatial division manner, rather than in a manner of changing the phase in a time sequence.

FIG. 4 illustrates a part of a holographic recording system according to one embodiment of the present disclosure.

Referring to FIG. 4, the holographic recording system of the present disclosure includes a polarizer array (140), an imaging optical system (150), and an image sensor (160). A plurality of interference patterns that are phase-shifted in a spatially divided manner by the polarizer array (140) are acquired by the image sensor (160).

In the embodiments, the image sensor (160) is a conventional image sensor formed of a planar array of photodiodes whose current amount changes depending on the intensity of incident light. The photodiodes are expressed as pixels. In addition, the image sensor (160) may include a color filter. The color filter may have a form of an array in which a plurality of color filters are arranged planarly, and the color filter array may be attached to the image sensor.

A polarization image sensor is used to acquire real-time self-interference holograms. A polarization image sensor has the advantage of detecting the brightness of light differently depending on the polarization state of light by attaching polarizing plates with different polarization axes on the pixel array. In order to improve the quality of hologram acquisition, the pixel size must be small (high density) and the number of pixels must be large (high resolution). By acquiring interference patterns more widely and more delicately through a high-density and high-resolution image sensor, the quality of the restored hologram image can be improved. However, commercially available polarization image sensors have limited specifications in terms of the number and size of pixels.

The holographic recording system according to the present disclosure utilizes a high-resolution and high-density general image sensor and has an optical structure that can replace the use of a polarization image sensor. The system of the present disclosure includes a polarizer array (140) and an imaging optical system (150) in front of an image sensor (160). The polarizer array (140), the imaging optical system (150), and the image sensor (160) are sequentially aligned with respect to an optical axis (A) behind a geometric phase lens (130).

As in a city, a plurality of interference patterns that are phase-shifted in a spatially divided manner by the polarizer array (140) are transmitted through the focusing optical system (150) and reach the image sensor (160). At this time, the focusing optical system (150) optically corresponds each of the plurality of polarizers (141) of the polarizer array (140) to each of the plurality of pixels of the image sensor (160). Light from the plurality of polarizers (141) is focused on the plurality of pixels by the focusing optical system (150). The focusing optical system (150) is aligned so that brightness information of light from each of the plurality of polarizers is assigned to one pixel of the image sensor. As a result, the image sensor (160) simultaneously acquires individual interference patterns having different phases for each pixel.

The focusing optical system (150) includes at least one lens, and may be referred to as a reduction optical system when the size of the plurality of pixels is smaller than the size of the plurality of polarizers. In the illustrated embodiment, the size of the plurality of polarizers may be larger than the size of the plurality of pixels for the advantage of manufacturing the polarizing plate array. In this case, the magnification of the focusing optical system corresponds to the ratio of the sizes of the plurality of polarizers and the sizes of the plurality of pixels for an optical one-to-one correspondence between the plurality of polarizers and the plurality of pixels. The focusing optical system may be configured so that the magnification is adjusted according to the sizes of the plurality of polarizers and the plurality of pixels.

FIG. 5 is a schematic diagram of a hologram recording system according to another embodiment of the present disclosure.

Referring to FIG. 5, the polarizer array (240) is a reflective type and includes a plurality of polarizers. The plurality of polarizers have the same optical characteristics as the plurality of polarizers (141) of the polarizer array (140) except that they are reflective. In contrast, in the above-described embodiments, the polarizer array (140) is a transmissive type, and light transmitted through the geometric phase lens (130) transmits through the polarizer array (140), and the light transmitted through the polarizer array (140) propagates in the same direction as the incident light (I) along the optical axis (A). In the present embodiment, the polarizer array (240) is a reflective type, and light incident on the polarizer array (240) is reflected by the polarizer array (240), and the light reflected from the polarizer array (240) propagates in the opposite direction of the incident direction.

In the illustrated embodiment, the holographic recording system further includes an optical element (270) disposed between the polarizer array (240) and the focusing optical system (250). The optical element (270) is configured to reflect incident light (I) transmitted through the geometric phase lens (130) traveling along the optical axis (A’) to the polarizer array (240) and transmit light from the polarizer array (240). In this case, the optical element (270) is a half mirror.

The polarizer array (240), the optical element (270), the focusing optical system (250), and the image sensor (260) are sequentially aligned with respect to the optical axis (A”). In this embodiment, the only differences from the above-described embodiments are that the polarizer array (240) is reflective and that the optical element (270) is added, and the remaining configurations are the same. Therefore, a description of the remaining configurations is omitted in this embodiment.

The embodiments of the present disclosure can be summarized as follows.

A holographic recording system according to one embodiment is a holographic recording system that obtains an interference pattern formed by self-interference of incident light from a target object, the system comprising: a polarizer array including a plurality of polarizers; an image sensor including a plurality of pixels; and an imaging optical system disposed between the polarizer array and the image sensor, wherein the imaging optical system optically corresponds each of the plurality of polarizers to each of the plurality of pixels.

In one embodiment, the magnification of the focusing optical system is a ratio of the sizes of the plurality of polarizers to the sizes of the plurality of pixels.

In one embodiment, the sizes of the plurality of polarizers are larger than the sizes of the plurality of pixels.

In one embodiment, the plurality of polarizers convert incident light into linearly polarized light, wherein the plurality of polarizers have different polarization axes.

In one embodiment, the plurality of polarizers have one of four polarization axes that are 45° apart.

In one embodiment, the plurality of polarizers have one of three polarization axes that are 60° apart.

In one embodiment, the geometric phase lens converts the incident light into left-circular polarization and right-circular polarization.

In one embodiment, the invention further comprises a polarizing plate positioned in front of the geometric phase lens and configured to convert incident light into linearly polarized light.

In one embodiment, the device further includes an objective lens disposed in front of the polarizing plate and focusing the incident light.

In one embodiment, the polarizer array is reflective and further includes an optical element disposed between the polarizer array and the imaging optical system for reflecting incident light to the polarizer array and transmitting light from the polarizer array.

At least some of the components described in the exemplary embodiments of the present disclosure may be implemented as hardware elements including at least one or a combination of a Digital Signal Processor (DSP), a processor, a controller, an Application-Specific IC (ASIC), a programmable logic device (FPGA, etc.), and other electronic devices. In addition, at least some of the functions or processes described in the exemplary embodiments may be implemented as software, and the software may be stored on a recording medium. At least some of the components, functions, and processes described in the exemplary embodiments of the present disclosure may be implemented as a combination of hardware and software.

The method according to exemplary embodiments of the present disclosure can be written as a program executable on a computer, and can also be implemented in various recording media such as a magnetic storage medium, an optical readable medium, a digital storage medium, etc.

The implementations of the various technologies described herein may be implemented as digital electronic circuitry, or as computer hardware, firmware, software, or combinations thereof. The implementations may be implemented as a computer program product, i.e., a computer program tangibly embodied in an information carrier, e.g., a machine-readable storage medium (computer-readable medium) or a radio signal, for processing by the operation of a data processing device, e.g., a programmable processor, a computer, or multiple computers, or for controlling the operation thereof. A computer program, such as the computer program(s) described above, may be written in any form of programming language, including compiled or interpreted languages, and may be deployed in any form, including as a stand-alone program or as a module, component, subroutine, or other unit suitable for use in a computing environment. The computer program may be deployed to be processed on one computer or multiple computers at a single site, or distributed across multiple sites and interconnected by a communications network.

Processors suitable for processing a computer program include, for example, both general-purpose and special-purpose microprocessors, and any one or more processors of any type of digital computer. Typically, the processor will receive instructions and data from a read-only memory or a random access memory or both. Elements of the computer may include at least one processor for executing instructions and one or more memory devices for storing instructions and data. Typically, the computer may include, or be coupled to receive data from, transmit data to, or both, one or more mass storage devices for storing data, such as magnetic, magneto-optical disks, or optical disks. Information carriers suitable for embodying computer program instructions and data include, by way of example, semiconductor memory devices, magnetic media such as hard disks, floppy disks, and magnetic tape, optical media such as CD-ROMs (Compact Disk Read Only Memory) and DVDs (Digital Video Disk), magneto-optical media such as floptical disks, ROMs (Read Only Memory), RAMs (Random Access Memory), flash memory, EPROMs (Erasable Programmable ROM), EEPROMs (Electrically Erasable Programmable ROM), etc. The processor and memory may be supplemented by, or included in, special purpose logic circuitry.

The processor can execute an operating system and software applications running on the operating system. In addition, the processor device can access, store, manipulate, process, and generate data in response to the execution of the software. For ease of understanding, the processor device is sometimes described as being used alone, but those skilled in the art will recognize that the processor device can include multiple processing elements and/or multiple types of processing elements. For example, the processor device can include multiple processors, or one processor and one controller. In addition, other processing configurations, such as parallel processors, are also possible.

Additionally, non-transitory computer-readable media can be any available media that can be accessed by a computer, and can include both computer storage media and transmission media.

While this specification contains details of a number of specific implementations, these should not be construed as limitations on the scope of any invention or what may be claimed, but rather as descriptions of features that may be unique to particular embodiments of particular inventions. Certain features described herein in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, various features described in the context of a single embodiment may also be implemented in multiple embodiments, either individually or in any suitable subcombination. Furthermore, although features may be depicted as operating in a particular combination and initially claimed as such, one or more features from a claimed combination may in some cases be excluded from that combination, and the claimed combination may be modified into a subcombination or variation of a subcombination.

Likewise, although operations are depicted in the drawings in a particular order, this should not be understood to imply that the operations must be performed in the particular order illustrated or in any sequential order to achieve a desirable result, or that all of the illustrated operations must be performed. In certain cases, multitasking and parallel processing may be advantageous. Furthermore, the separation of the various device components of the embodiments described above should not be understood to require such separation in all embodiments, and it should be understood that the program components and devices described may generally be integrated together in a single software product or packaged into multiple software products.

Meanwhile, the embodiments of the present invention disclosed in this specification and drawings are merely specific examples presented to help understanding, and are not intended to limit the scope of the present invention. It will be apparent to those skilled in the art to which the present invention pertains that other modified examples based on the technical idea of the present invention can be implemented in addition to the embodiments disclosed herein.

The scope of protection of this embodiment should be interpreted by the claims below, and all technical ideas within a scope equivalent thereto should be interpreted as being included in the scope of protection of this embodiment.

110 objective lens
120 polarizing plate
130 Geometric phase lens
140 polarizer array
150-degree optical system
160 image sensor

Claims (10)

In a holographic recording system that obtains an interference pattern formed by self-interference of incident light from a target object,
A polarizer array comprising a plurality of polarizers;
A geometric phase lens arranged in front of the polarizer array, which changes the incident light into left-circular polarization and right-circular polarization;
An image sensor comprising a plurality of pixels; and
Including an imaging optical system arranged between the polarizer array and the image sensor,
A holographic recording system in which the above-mentioned focusing optical system optically corresponds each of the plurality of polarizers to each of the plurality of pixels. In the first paragraph,
A holographic recording system, wherein the magnification of the above-mentioned imaging optical system is a ratio of the sizes of the plurality of polarizers to the sizes of the plurality of pixels.
In the first paragraph,
A holographic recording system, wherein the sizes of the plurality of polarizers are larger than the sizes of the plurality of pixels.
In the first paragraph,
The above plurality of polarizers convert incident light into linearly polarized light.
A holographic recording system, wherein the plurality of polarizers have different polarization axes.
In paragraph 4,
A holographic recording system, wherein the plurality of polarizers have one of four types of polarization axes that are 45° apart.
In paragraph 4,
A holographic recording system, wherein the plurality of polarizers have one of three types of polarization axes that differ by 60°.
delete In the first paragraph,
A holographic recording system further comprising a polarizing plate arranged in front of the geometric phase lens and changing the incident light into linearly polarized light. In Article 8,
A holographic recording system further comprising an objective lens disposed in front of the polarizing plate and collecting the incident light.
In the first paragraph,
The above polarizer array is reflective,
A hologram recording system further comprising an optical element disposed between the polarizer array and the focusing optical system, the optical element reflecting the incident light to the polarizer array and transmitting light from the polarizer array.

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