JP2011257445A - Holographic stereogram creation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a holographic stereogram creation device capable of accurately achieving effects of double refraction of a recording medium in creating a holographic stereogram and capable of being miniaturized.SOLUTION: A holographic stereogram creation device comprises: a reference light generating unit for generating reference light from coherent light emitted from a light source; an object light generating unit for generating object light obtained by modulating the coherent light in accordance with recording information from the coherent light; an exposure optical system for spatially separating optical paths of the reference light and the object light from each other and for crossing the optical paths of the reference light and the object light and making the optical paths interfere with each other; a supporting unit for supplying and supporting a recording medium at a recording position at which the optical paths of the reference light and the object light cross; a polarization state detecting unit for detecting a polarization state of the reference light transmitted through the recording medium; and a polarization state varying unit for changing the polarization state of the reference light in accordance with the polarization state of the reference light.

Description

  The present invention relates to a hologram recording apparatus that records a holographic stereogram image or a hologram image on a recording medium, and more particularly to a holographic stereogram creation apparatus.

  In general, a hologram divides laser light (coherent light) into two parts, irradiates one of the objects on the object and irradiates the diffuse reflected light (object light) on the photosensitive sheet, and simultaneously applies the other light at a predetermined angle. In this method, the entire photosensitive sheet is directly irradiated as reference light, and optical interference fringes due to interference between the two lights are recorded on the photosensitive sheet. By illuminating the hologram with reference light during recording at a predetermined angle, object light having the same intensity and direction as during recording is reproduced, and a three-dimensional image of the subject is obtained.

  The holographic stereogram applies a stereogram to a hologram (one that enables stereoscopic viewing by viewing a set of planar images (parallax images) obtained by photographing an object corresponding to the viewpoint position of the left and right eyes of a human). It is a thing. The holographic stereogram is obtained by recording a plurality of two-dimensional images taken from a large number of viewpoints (observation positions) on a photosensitive sheet so as to be spread as dot-shaped (or strip-shaped) small holograms (element holograms). Therefore, since a set of many parallax images is reproduced in the holographic stereogram, motion parallax can also be used, and a change in the viewpoint of the observer and a three-dimensional image corresponding to many observers can be reproduced.

  In the holographic stereogram, a parallax image obtained by viewing an object from various angles is synthesized on a photosensitive sheet during reproduction, so that a three-dimensional image can be observed with the naked eye. In actual exposure recording, element holograms are sequentially arranged and recorded on a recording medium, so that a large holographic stereogram can be recorded even with a small optical system.

  A photosensitive sheet used for producing a holographic stereogram or a hologram is generally known as a recording medium protected by a base film and a cover film sandwiching the photosensitive sheet. A base film and a cover film, for example, a PET film, sandwiching a photosensitive sheet have birefringence. Such birefringence has an adverse effect on the interference of laser light applied to the recording medium when creating a holographic stereogram or hologram.

  Therefore, a reverse correction system is applied to the hologram recording device so that a bright hologram image is reproduced while avoiding a decrease in coherence between the object beam and the reference beam due to transmission through a recording medium having birefringence. It has been proposed (see Patent Document 1).

JP 2003-015509 A

  In the reverse correction system of such a conventional hologram recording apparatus, the polarization plane of the reference light is rotated by the half-wave plate, the reference light is incident on the recording medium, and the polarized light out of the reference light transmitted through a partial region of the recording medium. The intensity of the reference light transmitted through the plate is detected by a photodetector, and the rotation angle of the half-wave plate is determined so that the detected reference light intensity is minimized or maximized.

  In such a conventional hologram recording apparatus, the polarization plane of the reference light is tilted and the polarization state after passing through the recording medium is detected so as to make the polarization state on the recording medium appropriate. There is difficulty in arranging the system, in particular, a polarizing plate and a photodetector for detecting reference light. That is, as shown in FIG. 1, in the conventional hologram recording apparatus, a mask having a strip-shaped opening is disposed close to the object light input side of the recording medium supported by the recording medium feeding mechanism. Is exposed to the recording medium, the reference light is exposed to the recording medium from the mask opposite side (recording medium feeding mechanism side), and the polarizing plate and the photodetector are sandwiched between the mask and the recording medium feeding mechanism. The reference light leaking from the peripheral edge must be detected, and there is a problem that a sufficient amount of light cannot be obtained. Even if the reference light is obtained from the peripheral edge, there is a problem that the detection result does not accurately represent the influence of the original birefringence because it is the reference light that has been multiple-reflected inside a relatively thin recording medium.

  Furthermore, in the situation where an objective lens with a large numerical aperture is used to expand the visible range of the reproduced image during hologram reproduction, the objective lens is placed very close to the recording medium. It is not realistic to arrange the reference light detection system (polarizing plate or photodetector) in the form of an apparatus.

  Therefore, an object of the present invention is to provide a holographic stereogram creation apparatus that can more accurately acquire the influence of birefringence of a recording medium when creating a holographic stereogram and that can be miniaturized.

  A holographic stereogram creation device according to the present invention includes a reference light generation unit that generates reference light from coherent light emitted from a light source, and modulates coherent light from the coherent light according to recording information. An object light generating unit that generates object light, an exposure optical system that spatially separates the optical paths of the reference light and the object light, crosses the optical paths of the reference light and the object light, and interferes, and the reference light and the object light. A support unit that supplies and supports the recording medium at a recording position where the optical paths intersect, a polarization state detection unit that detects a polarization state of the reference light transmitted through the recording medium, and a polarization state of the reference light according to the polarization state of the reference light A holographic stereogram creation device that creates a holographic stereogram that preserves the optical interference fringes of the reference light and the object light. A reflection-type spatial light phase modulator that generates a reflected light as object light by performing spatial light phase modulation on the emitted light according to recording information, and at least one that separates a modulation component of light from the reflection-type spatial light phase modulator Two polarization beam splitters, the polarization state detection unit includes a polarization beam splitter and a light detection unit that detects the amount of light incident through the polarization beam splitter, and the exposure optical system includes: An optical path for guiding the reference light transmitted through the recording medium to the light detection unit via the polarization beam splitter along the optical path of the object light is provided.

  According to the configuration of the present invention described above, the phase modulation component and the non-phase modulation component are generated by the reflective spatial light phase modulator, the modulation component is separated by the polarization beam splitter, and is guided to the recording medium as object light. Since the splitter is also used as a polarizing plate for detecting the polarization state, it is possible to provide a holographic stereogram creation device that can more accurately acquire the influence of birefringence of the recording medium when creating the holographic stereogram and can be miniaturized. The photosensitive sheet used for recording is often coated on a resin base material such as a PET film, and birefringence due to the resin base material is a problem when recording holograms. The birefringence problem can be solved by adjusting the angle of the wave plate disposed in the optical path of the reference light, which is the polarization state variable section, so that the polarization state of the reference light that has passed through the light beam coincides with the polarization state of the object light. In addition, by using a reflective spatial light phase modulator to guide the reference light to the optical path of the object light, the polarization beam splitter can also serve as a function for detecting the polarization state of the reference light. In addition to being able to reduce, it is possible to arrange a realistic polarization state detector.

It is a schematic diagram which shows an example of exposure recording of the object beam and the reference beam in the conventional hologram recording apparatus. It is a schematic diagram for demonstrating the structure of the holographic stereogram preparation apparatus of embodiment by this invention. It is a schematic diagram for demonstrating the optical path of the object light in the structure of the holographic stereogram production apparatus of embodiment by this invention. It is a schematic diagram for demonstrating the optical path of the reference light in the structure of the holographic stereogram production apparatus of embodiment by this invention. It is a schematic sectional drawing for demonstrating the spatial light modulation apparatus which consists of a polarization beam splitter for modulation | alteration component separation in the embodiment by this invention, and a reflection type spatial light phase modulator. It is a schematic sectional drawing for demonstrating the relationship between the recording medium, reference light, and object light in the holographic stereogram production apparatus of embodiment by this invention. It is a schematic perspective view for demonstrating the relationship between the recording medium, reference light, and object light in the holographic stereogram production apparatus of embodiment by this invention. It is a flowchart for demonstrating the recording preparation operation | movement of the holographic stereogram production apparatus of embodiment by this invention. It is a flowchart for demonstrating the recording operation | movement of the holographic stereogram creation apparatus of embodiment by this invention. It is a schematic sectional drawing for demonstrating the holographic stereogram obtained by the holographic stereogram creation apparatus of embodiment by this invention. It is a schematic diagram for demonstrating the structure of the holographic stereogram preparation apparatus of other embodiment by this invention. It is a schematic diagram for demonstrating the structure of the holographic stereogram preparation apparatus of other embodiment by this invention. It is a schematic diagram for demonstrating the structure of the holographic stereogram preparation apparatus of other embodiment by this invention. It is a schematic diagram for demonstrating the structure of the holographic stereogram preparation apparatus of other embodiment by this invention. It is a schematic diagram for demonstrating the structure of the holographic stereogram preparation apparatus of other embodiment by this invention.

  Hereinafter, an example of a holographic stereogram creating apparatus that creates a holographic stereogram by sequentially recording minute element hologram rows on a recording medium will be described with reference to the drawings.

  FIG. 2 is a schematic diagram showing the overall structure of such a holographic stereogram creating apparatus, FIG. 3 is a diagram for explaining the optical path of object light, and FIG. 4 is a diagram for explaining the optical path of reference light. As shown in FIGS. 2 to 4, the holographic stereogram creating apparatus includes a laser light source 21 that emits coherent light, a collimator lens 22, a first shutter 23, a ratio setting half-wave plate 24, and an exposure tool. Polarization beam splitter 25, aperture 26, reduction optical system 27, mirror 28, light quantity adjusting half-wave plate 29, light quantity adjusting half-wave plate rotating mechanism 29a, light quantity adjusting quarter-wave plate 30, light quantity adjustment 1/4 wavelength plate rotating mechanism 30a, mirror 31, recording medium 33, stage 35, biaxial stepping motor 41, main controller 51, second shutter 61, diffuser plate 62, polarization beam splitter 63 for separating the modulation component, reflection type A spatial light phase modulator 64, relay lenses 65 and 66, a Nyquist filter 67, an objective lens 68, and a light detection unit 71, and a recording medium 3. Except for the stage 35 and the two-axis stepping motor 41, these elements constitute an exposure optical system that spatially separates the optical paths of the reference light and the object light from each other, and crosses and interferes with the optical paths of the reference light and the object light. is doing.

  The main controller 51 includes a first shutter 23, a second shutter 61, a biaxial stepping motor 41 that drives the stage 35, and a light amount adjusting half-wave plate rotating mechanism that rotates the light amount adjusting half-wave plate 29. 29a is connected to a light amount adjusting quarter-wave plate rotating mechanism 30a for rotating and driving the light amount adjusting quarter-wave plate 30 and the light detection unit 71. When the second shutter 61 is closed by the signal from the main controller 51, only the reference light is irradiated to the recording medium 33. Further, when the first shutter 23 and the second shutter 61 are opened, the reference light and the object light are recorded on the recording medium. 33 is irradiated. In response to the detection signal from the light detector 71, the main controller 51 passes through the light amount adjusting half-wave plate rotating mechanism 29a and the light amount adjusting quarter-wave plate rotating mechanism 30a to adjust the light amount. 29 and the rotation angle of the light quantity adjusting quarter-wave plate 30 are adjusted.

  The exposure polarization beam splitter 25 is included in a reference light generation unit that generates reference light from coherent light from the light source 21.

  The exposure polarization beam splitter 25, the second shutter 61, the diffusion plate 62, the modulation component separation polarization beam splitter 63, and the reflective spatial light phase modulator 64 are coherent according to the recording information from the coherent light of the light source 21. Included in an object light generation unit that generates object light obtained by modulating the characteristic light.

  The stage 35 and the biaxial stepping motor 41 are included in a support unit that supplies and supports the recording medium 33 at a recording position where the optical paths of the reference light and the object light intersect.

  The optical path of the object light in the holographic stereogram creation device will be described with reference to FIG. The laser light emitted from the light source 21 with good coherence is converted into parallel light by the collimator lens 22, then transmitted through the first shutter 23 and the ratio setting half-wave plate 24, and then by the exposure polarization beam splitter 25. The laser beam is divided into a reference beam and an object beam. Here, the beam light for object light may be converted into an appropriate parallel light beam diameter by an expander lens (not shown) or the like. The collimated laser beam for object light is incident on the reflective spatial light phase modulator 64 through the second shutter 61, the diffusion plate 62, and the polarization beam splitter 63 for separating the modulation component. The modulation component separating polarization beam splitter 63 and the reflective spatial light phase modulator 64 function as a spatial light modulator.

  The reflective spatial light phase modulator 64 changes the phase of light reflected on the on pixel electrode and off pixel electrode within the beam diameter. The reflective spatial light phase modulator 64 is a device that modulates incident light into a spatial pattern and reflects an image corresponding to an electrical input or an optical input. A reflective spatial light phase modulator typically consists of a region or a two-dimensional array of addressable pixels that can reflect incident light. The image pattern signal for controlling the pixels from the main controller 51 is first processed by an accompanying control circuit and then loaded into the pixel matrix array one frame at a time. The image pattern here is synthesized from a plurality of parallax images, and the image cannot be recognized even if it is displayed on the display based on the image pattern signal.

  For example, a liquid crystal reflective spatial light modulator (LCOS-SLM) is known as a reflective spatial light phase modulator. In this phase modulator, a reflective layer is disposed adjacent to the liquid crystal layer, and incident light is transmitted through the liquid crystal layer and reflected back by the reflective layer. The reflective spatial light phase modulator 64 is an electrical address type liquid crystal spatial light phase modulator, and is address-driven by an image pattern signal input from the main controller 51.

  The reflective spatial light phase modulator 64 is, for example, a plurality of pixel electrodes (pixel matrix array) driven by an active matrix driving circuit on a silicon substrate on which an active matrix driving circuit is formed, and a dielectric multilayer covering them. Although it has a basic configuration in which transparent substrates such as a reflective layer, a liquid crystal layer, a transparent conductive film, and glass are sequentially laminated, necessary alignment layers, light shielding layers, and the like are also included. The pixel matrix array has a predetermined number of pixels, for example, a VGA type (640 × 480 pixels) or XGA type (1024 × 768 pixels) pixel array.

  The active matrix drive circuit controls the voltage applied to each pixel electrode in accordance with the image pattern signal input from the main controller 51. Since the active matrix driving circuit controls the applied voltage of each pixel row and pixel column arranged in the XY axis direction, a predetermined voltage is applied to the pixel electrode with an image pattern designated by the main controller 51.

  The birefringence of the liquid crystal layer changes due to the rotation of the liquid crystal molecules at the application site in accordance with the change in the voltage applied to the liquid crystal layer via each pixel electrode. The light incident on the liquid crystal layer from the transparent substrate side according to the change distribution of the birefringence is phase-modulated when propagating through the liquid crystal layer. The phase-modulated light is reflected by the reflection layer, propagates again through the liquid crystal layer, is further phase-modulated, and then is emitted as phase-modulated light. The reflective spatial light phase modulator 64 phase-modulates the incident light from the modulation component separating polarization beam splitter 63 to the liquid crystal layer, and outputs phase-modulated light having a phase distribution (for example, π in a round trip) of the image pattern signal. reflect.

  Therefore, the reflective spatial light phase modulator 64 is used as a spatial light modulator in combination with the polarization beam splitter 63 for separating the modulation component as shown in FIG. The incident light as linearly polarized light that is transmitted through the modulation component separating polarization beam splitter 63 is only the partial light reflected on the ON pixel electrode, and its polarization direction is bent by 90 degrees. Reflected by the polarizing film. By such an operation, spatial modulation is given to the incident light. Since the object light is based on the parallel light transmitted through the exposure polarizing beam splitter 25, it is linearly polarized light (P-polarized light) parallel to the paper surface at this transmission time, but is reflected by the reflective spatial light phase modulator 64. After the modulation, the polarization direction is bent by 90 degrees, so that the linearly polarized light (S-polarized light) perpendicular to the paper surface is formed on the photosensitive sheet surface. The LCOS type reflective spatial light phase modulator 64 uses a ferroelectric liquid crystal that responds two to three orders of magnitude faster than a nematic liquid crystal, and there are some that can perform display switching at a very high speed. . In order to record a holographic stereogram, it is necessary to sequentially record a large number of element holograms, and it takes a lot of time to record. Therefore, it is preferable to use a high-speed type reflective spatial light phase modulator 64. is there. The polarization beam splitter 63 for separating the modulation component is combined with the reflective spatial light phase modulator 64 to separate only the modulation component from the emitted light.

  As shown in FIG. 3, the object light that has undergone phase modulation in accordance with the image pattern and is reflected by the polarization beam splitter 63 for separating the modulation component passes through the imaging optical system (relay lens 65, Nyquist filter 67, relay lens 66). Then, the light enters the objective lens 68. The objective lens 68 condenses the object light as a spherical wave at a predetermined position on the recording medium 33. As the imaging optical system, a 4f optical system using two relay lenses 65 and 66 is used. The Nyquist filter 67 having a rectangular opening disposed at the confocal position of the two relay lenses 65 and 66 removes unnecessary diffracted light by the reflective spatial light phase modulator 64 and records elements. It also limits the size of the hologram. An image pattern based on the parallax image synthesis calculated in advance by a computer or the like is displayed on the reflective spatial light phase modulator 64 by a control signal from the main controller 51, and the display pattern is displayed immediately before the objective lens 68 by the imaging optical system. Then, the light is focused on the photosensitive sheet surface of the recording medium 33.

  As shown in FIG. 6, the recording medium 33 has a structure in which a photosensitive sheet 33a is sandwiched between a glass substrate 33b and a PET base material 33c. The object light enters from the glass substrate side and is condensed on the interface of the photosensitive sheet 33a. Since the object light passes through the diffuser plate 62 before entering the reflective spatial light phase modulator 64, the beam profile on the interface of the photosensitive sheet 33a has a shape in which the peak intensity is reduced and the width is expanded in the lateral direction. Become. By reducing the peak intensity, uniform recording can be performed within one element hologram, and the sensitivity of the photosensitive sheet can be effectively utilized. Further, the lateral spread at the condensing point is limited by the Nyquist filter 67, and as shown in FIG. 7, only the rectangular region having a predetermined size is irradiated with object light. The recording medium 33 includes at least a photosensitive sheet and a resin base layer, and object light is incident from the photosensitive sheet side and reference light is incident from the resin base layer side.

  Next, the optical path of the reference light in the holographic stereogram creation device will be described with reference to FIG. The reference light of the laser parallel light transmitted from the light source 21 through the first shutter 23 and the ratio setting half-wave plate 24 and separated from the object light by the exposure polarization beam splitter 25 has an appropriate size. After being converted into parallel light having a thin rectangular light beam cross section by a rectangular aperture 26 having a rectangular shape, a reduction optical system 27, etc., a mirror 28, a light quantity adjusting half-wave plate 29, and a light quantity adjusting quarter-wave plate The object light condensing point (recording position) on the photosensitive sheet of the recording medium 33 is irradiated from the surface opposite to the incident surface of the object light through the mirror 30 and the mirror 31. At this time, the spot of the reference light has the same size as the spot of the object light on the photosensitive sheet surface. As described above, the exposure optical system includes a reduction optical system that generates a partial reference light beam having a smaller cross-sectional area from the reference light beam, and sequentially records minute element hologram rows on the recording medium 33. A holographic stereogram is created. This facilitates raster scan recording.

  In this embodiment, the exposure optical system has an optical path that guides the reference light transmitted through the recording medium to the light detection unit via the polarization beam splitter along the optical path of the object light, that is, as shown in FIG. The reference light that has passed through 33 is guided to the light detector 71 through the imaging optical system (relay lens 65, Nyquist filter 67, relay lens 66) in the optical path of the object light, and via the modulation component separating polarization beam splitter 63. As a configuration. Therefore, as shown in FIG. 6, when the numerical aperture of the objective lens is NA = sin θ, the inclination of the reference light with respect to the optical axis of the objective lens on the recording medium is set to θ or less. That is, the reference light reflected by the mirror 31 and transmitting the reference light is incident on the condensing point (recording position) at an angle within the numerical aperture NA of the objective lens 68 (within the opening angle θ). In addition, it is necessary to arrange the photosensitive sheet surface in the vicinity of the condensing surface (Fourier surface) of the object light. In such a reflection hologram, it is common to irradiate reference light (illumination light) from an oblique direction in order to improve the visibility of the image, but the angular range thereof is the numerical aperture NA of the objective lens 68 for object light. Constrained by In FIG. 6, the reference light transmitted through the recording medium 33 is incident on the objective lens at the aperture angle of the objective lens 68. As a result, even if the reference light returns to the objective lens 68 again and interferes with the reference light, the reproduced light of the recorded reference light appears in accordance with the irradiation direction of the subsequent illumination light. The influence on the observation of the reproduced stereoscopic image is reduced.

  As shown in FIG. 4, the object light is condensed toward the recording position by the objective lens 68 from one surface side of the recording medium 33, and the reference light is recorded from the other surface side within the opening angle θ of the objective lens. The reference light transmitted to the medium recording position and transmitted is made incident on the polarization beam splitter 63 for separating the modulation component. In other words, the reference light transmitted through the recording medium 33 is guided to the light detection unit 71 via the polarization beam splitter 63 along the optical path of the object light. Then, the light detection unit 71 detects the amount of light incident through the polarization beam splitter 63 and outputs it to the main controller 51.

  The main controller 51 refers to the light amount adjusting half-wave plate 29 and the light amount adjusting quarter-wave plate 30 respectively so that the light amount is minimized according to the light amount value output detected by the light detection unit 71. The optical path of light is rotated around the rotation axis, and the respective rotation angles are set. The calculation of an appropriate angle is performed by the main controller 51, and the rotation angles of the light amount adjusting half-wave plate 29 and the light amount adjusting quarter-wave plate 30 are set to the respective light amount adjusting half-wave plate rotating mechanisms 29a and 29a. It transfers to the quarter wave plate rotating mechanism 30a for light quantity adjustment. Since the reference light is reflected by the exposure polarizing beam splitter 25, the reference light is linearly polarized light (S-polarized light) perpendicular to the paper surface at this point. Since there is a PET base material having birefringence in front of the photosensitive sheet on the reference light incident side, it is not known how the polarization state changes on the photosensitive sheet surface. If there is no refraction, the polarization state of the reference light passing through the recording medium 33 is the same as the polarization state on the photosensitive sheet. That is, by monitoring the polarization state of the reference light that has passed through the recording medium 33 with the light detection unit 71, the polarization state of the reference light before entering the recording medium is controlled to obtain a desired polarization state on the photosensitive sheet surface. Is possible. The fact that the reference light that has passed through the recording medium 33 is not guided to the light detection unit 71 means that the polarization state is reflected by the polarization beam splitter 63 for separating the modulation component, that is, linearly polarized light (S-polarized light) perpendicular to the paper surface. Therefore, the same polarization state as that of the object light is guaranteed on the photosensitive sheet surface.

  As described above, in the present embodiment, the light amount adjusting half-wave plate 29 and the light amount adjusting quarter-wave plate 30 arranged in the reference light path between the mirrors 28 and 31 correspond to the polarization state of the reference light. A polarization state variable unit that changes the polarization state of the reference light, and the objective lens 68, the polarization beam splitter 63 for modulating component separation, and the light detection unit 71 detect the polarization state of the reference light transmitted through the recording medium 33. It is a state detection unit. Further, the portion of the modulation beam separating polarization beam splitter 63 of the spatial light modulator comprising the modulation beam separating polarization beam splitter 63 and the reflective spatial light phase modulator 64 detects the polarization state of the reference light that has passed through the recording medium. It also serves as a function.

  Next, the operation of the holographic stereogram creating apparatus and the recording preparation operation will be described based on the flowchart shown in FIG.

  Prior to the start of recording, recording preparation is performed as follows. First, the ratio setting half-wave plate 24 shown in FIG. 4 is adjusted to an appropriate rotation angle to set the light quantity ratio between the object light and the reference light (step S1). The half-wave plate 24 is rotated about the optical path of the laser beam as a rotation axis, and the rotation angle of the optical axis of the half-wave plate 24 is adjusted. This light quantity ratio is calculated in advance from the characteristics of the photosensitive sheet, the transmittance of the diffusion plate, the efficiency of the reflective spatial light phase modulator 64, the transmittance of the optical component, and the like.

  The photosensitive sheet of the recording medium is provided with a polarization adjustment region for adjusting the polarization state from the transmitted light state separately from the normal region for recording a three-dimensional image, and the reference light passes through the polarization adjustment region. The recording medium is moved as possible (step S2). The polarization adjustment region is provided in a peripheral portion that does not interfere with the recording of the element hologram, and the position thereof is recorded in advance in a memory or the like. As shown in FIG. The recording medium is moved by transferring it to the moving mechanism (the biaxial stepping motor 41 of the stage 35).

  Next, in response to a command from the main controller 51, a command is transferred to the shutter opening / closing mechanism (not shown) so as to open the first shutter 23 and close the second shutter 61 shown in FIG. Irradiate the medium (step S3). The shutter opening / closing operation here is not necessarily controlled by the main controller 51, and may be manually opened / closed. As shown in FIG. 4, when only the reference light is irradiated onto the recording medium 33, the reference light enters the light detection unit 71 via the recording medium 33, the objective lens 68, and the modulation component separating polarization beam splitter 63. To do.

  In accordance with the light quantity value output detected by the light detection unit 71 shown in FIG. 4, the main controller 51 makes the light quantity adjustment half-wave plate 29 and the light quantity adjustment quarter-wave plate 30 so that the light quantity is minimized. Each is rotated about the optical path of the reference light as a rotation axis, and the respective rotation angles are set (step S4). The angle adjustment of the light amount adjusting half-wave plate 29 and the light amount adjusting quarter-wave plate 30 is not necessarily performed automatically by the main controller 51, and is manually performed so that the light amount in the light detection unit 71 is minimized. You may adjust with.

  Next, the first shutter 23 shown in FIG. 4 is closed (step S5), the recording medium is moved to the first element hologram writing position (step S6), and the preparation for automatic writing is completed.

  Further, the operation of the holographic stereogram creating apparatus and the element hologram writing / recording operation will be described based on the flowchart shown in FIG.

  First, the image pattern of the element hologram to be recorded first is generated by the image generation unit of the main controller 51 shown in FIG. 2 (step S7), and the first shutter 23 and the second shutter 61 are opened by the control from the main controller 51. (Step S8). This represents a minute parallax image to be displayed at the target element hologram position from the parallax image of the original three-dimensional image, and uses a sequential calculation or a pre-calculated and stored in a storage device or the like. . By transferring this image data to the drive circuit in the XY-axis direction of the reflective spatial light phase modulator 64, a two-dimensional image pattern is displayed on the reflective spatial light phase modulator 64, that is, exposure recording is performed for a predetermined time. (Step S9).

  Next, it is determined whether or not the exposure time is a specified value (step S10). If not, the process returns to step S9, and if satisfied, both shutters are closed (step S11). Here, exposure is performed by instructing an appropriate shutter opening / closing timing to the shutter opening / closing mechanism by the main controller 51 so that the exposure energy amount, exposure time, and exposure pattern necessary for exposure recording are obtained. The display of the reflective spatial light phase modulator 64 and the opening and closing of the shutter are controlled by the main controller 51, and processing is performed so that the timing of both is appropriately synchronized.

  Next, when the exposure of each element hologram is completed, it is determined whether or not the number of exposures is a specified value (step S12). If not, the process returns to step S8, and if satisfied, the reflection type spatial light phase modulator 64 is returned. The display of the two-dimensional recording pattern is stopped (step S13).

  Next, it is determined whether or not the element hologram is at the final recording position (step S14). If not, the recording medium is transferred to the next recording position (step S15), and then the process returns to step S7 to be satisfied. If it ends, it will end.

  Here, in general, the element hologram shown in FIG. 7 is repeatedly raster-scanned and recorded in the plane direction of the recording medium so that the element holograms are aligned without gap so that the reference beam is in the XY axis direction as long as one side of the element hologram. And the recording position where the optical path of the object light intersects (the area where the optical path of the reference light and the object light intersect) moves, but even if the element holograms overlap each other or there is a gap between the element holograms good. When the movement of the recording medium is completed and the vibration of the recording medium is settled, the next element hologram is recorded. Thereafter, by repeating this operation, an element hologram row is formed on the recording medium, and a holographic stereogram is created. That is, the element hologram recorded on the recording medium is a part of the hologram on which the three-dimensional image is reproduced by irradiation with the reproduction reference light, and the element hologram is repeatedly raster-scan recorded in the plane direction of the recording medium. Thus, a hologram on which one three-dimensional image is reproduced as a whole is recorded.

  As shown in FIG. 10, the completed holographic stereogram is illuminated with white light from the same angle as the reference light, so that a three-dimensional image can be observed on the illuminated surface side.

  Since the image pattern displayed on the reflective spatial light phase modulator 64 is synthesized in advance from a plurality of parallax images and stored in the main controller, the object light obtained by being modulated by the reflective spatial light phase modulator 64 is The three-dimensional partial image is calculated from the three-dimensional image to be reproduced, and the image information calculated therefrom is carried.

<< Other Embodiments >>
11 to 15 are schematic views showing a holographic stereogram creating apparatus according to another embodiment. The same components shown in FIG. 2 are denoted by the same reference numerals, and detailed description thereof is omitted.

  In other embodiments, as shown in the embodiments of FIGS. 11 and 12, in addition to the polarization beam splitter 63 for separating the modulation components for separating the components modulated by the reflective spatial light phase modulator 64, One or more polarization beam splitters 63a may be added. Normally, a polarization beam splitter cannot completely separate two polarization states, and another polarization component leaks within a certain extinction ratio range. By disposing the second polarization beam splitter in the optical path of the object light and separating the non-modulation component leaked by the first modulation component separating polarization beam splitter 63, the non-modulation component on the recording medium is separated. Can be further reduced. In this case, the second and third polarization beam splitters can also separate the modulation component. Polarization detection of the reference light can also be performed by the second and third modulation component separating polarization beam splitters.

  Unlike the holographic stereogram creation device shown in FIG. 11, the reference light detection unit is not provided on the first modulation component separating polarization beam splitter 63 side, and the relay lens 66 and the objective lens 68 of the object light optical path are provided. A polarization plane rotating half-wave plate λ / 2 and a second modulation component separating polarizing beam splitter 63a are arranged between the non-modulated components leaked by the first modulating component separating polarizing beam splitter 63. In addition to separation, a light detection unit 71 is provided in the vicinity of the second polarization component separating polarization beam splitter 63 a to detect reference light from the recording medium 33 via the objective lens 68. Also in this example, the polarization state of the reference light is adjusted by the light amount adjusting half-wave plate 29 and the light amount adjusting quarter-wave plate 30 so that the light amount in the light detection unit 71 is minimized.

  12 is an example in which the second polarization beam splitter 63a is used as a mirror as in the holographic stereogram creation device shown in FIG. 12, and the second polarization beam is provided between the relay lens 66 and the objective lens 68 in the object light path. The splitter 63a is arranged as a mirror, and a light detector 71 is provided in the vicinity of the second polarizing beam splitter 63a to detect the reference light from the recording medium 33 through the objective lens 68. Also in this example, the polarization state of the reference light is adjusted by the light amount adjusting half-wave plate 29 and the light amount adjusting quarter-wave plate 30 so that the light amount in the light detection unit 71 is minimized.

  The holographic stereogram creating apparatus of the embodiment shown in FIG. 13 is an example in the case where object light and reference light are both circularly polarized and interfered and recorded on the photosensitive sheet surface of the recording medium.

  Although an example in the case of exposure recording in which both object light and reference light are linearly polarized light (S-polarized light) has been described, it is also possible to record circularly polarized light as shown in FIG. In this case, it is necessary to match the rotation direction (clockwise and counterclockwise) of circularly polarized light between the object light and the reference light. In order to obtain circular polarization, a quarter-wave plate λ / 4 may be added between the relay lens 66 and the objective lens 68 in the object light optical path in the object light optical path. The polarization state in the following optical arrangement will be described. As shown in FIG. 13, the modulation component of the object light modulated by the reflective spatial light phase modulator 64 and reflected by the polarization beam splitter 63 for separating the modulation component is linearly polarized light (S-polarized light) perpendicular to the paper surface. The quarter-wave plate λ / 4 is arranged with its crystal axis direction inclined by 45 degrees with respect to this polarization direction, and becomes circularly polarized when object light passes through. Here, it is assumed that the circularly polarized light is clockwise. It is sufficient that the polarization state of the reference light after passing through the recording medium 33 is clockwise circularly polarized light. At that time, the reference light that has passed through the quarter-wave plate λ / 4 becomes linearly polarized light (P-polarized light) parallel to the paper surface, that is, linearly polarized light that is 90 degrees different from the original object light. Since this is the polarization direction passing through the polarization beam splitter 63 for separating the modulation component, the polarization state of the original reference light is adjusted so that the amount of light received by the light detection unit 71 is maximized. It is guaranteed that the polarization state at is the same clockwise circular polarization as the object light. As shown in FIG. 13, one half-wave plate 29 and one quarter-wave plate 30 are inserted in the optical path of the reference light, and polarization after passing through the recording medium is adjusted by adjusting these wave plates. It is possible to make the state circularly polarized.

  FIG. 14 shows an example in which the second polarizing beam splitter 63a is used as a mirror, and the second polarizing beam splitter 63a and the quarter wavelength plate λ / 4 are provided between the relay lens 66 and the objective lens 68 in the object light optical path. Is provided in the vicinity of the second polarizing beam splitter 63a, on the side opposite to the quarter-wave plate λ / 4, and a light detector 71 is provided to detect reference light from the recording medium 33 via the objective lens 68. It is an example. In this case, since a quarter wavelength plate λ / 4 is added between the polarizing beam splitter 63a closest to the recording medium and the recording medium 33, the reference light after passing through the recording medium is the same clockwise circle as the object light. When polarized light passes through the quarter-wave plate λ / 4, it becomes linearly polarized light that is 90 ° different from the original object light, so that the amount of light received by the light detection unit 71 is maximized. Preparation is done.

  One advantage in recording these circularly polarized lights is that the reference light is not guided to the reflective spatial light phase modulator 64 in the optimum polarization state. In linearly polarized recording, the state in which the reference light after passing through the recording medium is guided to the reflective spatial light phase modulator 64 is the best polarization state. Since the surface of the reflective spatial light phase modulator 64 has a high reflectance, the reference light guided onto the reflective spatial light phase modulator 64 is reflected and travels the same optical path again to reach the recording medium. Here, interference occurs with the original reference light, and a hologram resulting from the interference between the reference lights is recorded on the recording medium, so that the sensitivity of the recording medium is wasted. In circularly polarized recording, the state in which light is not guided to the reflective spatial light phase modulator 64 is the optimum state, and the reflected light from the reflective spatial light phase modulator 64 does not return to the recording medium.

  The use of a plurality of polarization beam splitters makes it possible to more effectively remove the non-modulated component of the object light, and by using a polarization beam splitter instead of the optical path folding mirror, the polarization beam splitter can The function of removing the modulation component and detecting the polarization of the reference light can be provided.

  When the circularly polarized light is recorded, the reference light is not guided to the reflective spatial light phase modulator 64, so that it is possible to avoid recording interference fringes between the reference lights.

  In addition, although the example in the case of exposure recording in which the object beam and the reference beam are both S-polarized linearly polarized light has been described, the configuration shown in the holographic stereogram creating apparatus in FIG. Exposure recording of object light and reference light can also be performed.

21 light source 22 collimator lens 23 first shutter 24 ratio setting half-wave plate 25 exposure polarizing beam splitter 26 aperture 27 reduction optical system 28 mirror 29 light amount adjustment half-wave plate 30 light amount adjustment quarter-wave plate 31 mirror 35 stage 33 recording medium 412 axis stepping motor 51 main controller 61 second shutter 62 diffuser plate 63 modulation component separating polarization beam splitter 64 reflective spatial light phase modulator 65, 66 relay lens 67 Nyquist filter 68 objective lens 71 light Detection unit

Claims (10)

A reference light generation unit that generates reference light from coherent light emitted from a light source, and object light generation that generates object light obtained by modulating the coherent light according to recording information from the coherent light And an exposure optical system that spatially separates the optical paths of the reference light and the object light from each other so as to intersect and interfere with the optical paths of the reference light and the object light, and an intersection of the optical paths of the reference light and the object light A support unit that supplies and supports a recording medium at a recording position to be detected, a polarization state detection unit that detects a polarization state of the reference light transmitted through the recording medium, and polarization of the reference light according to the polarization state of the reference light A holographic stereogram creation device for creating a holographic stereogram for storing optical interference fringes of the reference light and the object light, comprising a polarization state variable unit that changes a state,
The object light generation unit includes a reflection-type spatial light phase modulator that generates and reflects the incident light as spatial light phase-modulated according to the recording information, and the reflection-type spatial light phase modulator. At least one polarizing beam splitter that separates the modulated component of the light of
The polarization state detection unit includes the polarization beam splitter, and a light detection unit that detects the amount of light incident through the polarization beam splitter.
The exposure optical system includes an optical path that guides the reference light transmitted through the recording medium to the light detection unit via the polarization beam splitter along the optical path of the object light;
Holographic stereogram creation device characterized by   The exposure optical system irradiates the object light from one surface side of the recording medium toward the recording position and the reference light as parallel light from the other surface side of the recording medium. The holographic stereogram creation device according to claim 1, further comprising: a reference light optical system that makes the reference light transmitted through the recording medium incident on the objective lens within an aperture angle of the objective lens.   The holographic stereogram creation apparatus according to claim 2, wherein the reference light transmitted through the recording medium is incident on the objective lens at an aperture angle of the objective lens.   The polarization state varying unit is disposed in an optical path of the reference light, and includes a quarter wavelength plate and a half wavelength plate that transmit the reference light. The holographic stereogram creation device described.   The ¼ wavelength plate and the ½ wavelength plate are respectively adjusted by rotating the optical path of the reference light as a rotation axis so that an output value from the light detection unit becomes maximum or minimum. The holographic stereogram creation device according to claim 4.   6. The holographic stereogram creation according to claim 1, wherein the exposure optical system includes a quarter-wave plate that is disposed in an optical path of the object light and transmits the object light. apparatus.   The rotation angle of each of the half-wave plate and the quarter-wave plate is set according to the output of the light amount of the reference light incident through the polarization beam splitter detected by the light detection unit. 7. The holographic stereogram creation device according to claim 5, further comprising a controller. The element hologram recorded on the recording medium is a part of a hologram in which a three-dimensional image is reproduced by irradiation with reproduction reference light,
The holographic stereogram creation according to claim 7, wherein a hologram that reproduces one three-dimensional image as a whole is recorded by repeatedly performing raster scan recording of the element hologram in a plane direction of a recording medium. apparatus.   9. The holographic stereogram recording according to claim 7, wherein the object light carries a calculated three-dimensional image from a reproduced three-dimensional image and carries image information calculated therefrom. Equipment   10. The recording medium according to claim 1, wherein the recording medium includes at least a photosensitive sheet and a resin base layer, the object light is incident from the photosensitive sheet side, and the reference light is incident from the resin base layer side. The holographic stereogram creation device according to any one of the above.

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