JP2013195801A - Holographic stereogram recording device and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a holographic stereogram recording device capable of recording an element hologram under an exposure condition that is not influenced by darkness of an image to be displayed.SOLUTION: A holographic stereogram recording device includes: a spatial light modulation unit that creates object light by performing spatial light modulation of light; an object light optical system that condenses the object light in a recording medium; and a reference light optical system that irradiates a condensed portion of the object light in the recording medium with reference light interfering with the object light, and an element hologram is recorded in the condensed portion where the reference light and the object light are intersected. The spatial light modulation unit includes a spatial light modulator having a signal light region that is arranged on an optical axis of the object light optical system and that creates signal light in response to image information, and a dimming region that is arranged outside the signal light region and that creates auxiliary light without including the image information.

Description

  The present invention relates to a holographic stereogram recording apparatus and method for recording a holographic stereogram on a recording medium.

  A holographic stereogram is a multi-viewpoint element image that is a collection of small planar images of a part of an object, such as a parallax image obtained by photographing the object corresponding to the viewpoint position of the left and right eyes of a human, for example. It is known as a technique for recording a three-dimensional image that can be observed with the naked eye by synthesizing on a recording medium. A holographic stereogram recording medium is a recording medium in which a plurality of two-dimensional images taken from a large number of viewpoints (observation positions) are recorded on a photosensitive sheet of a photosensitive recording material so as to be laid out as minute element holograms in the form of dots or strips. is there. Actual holographic stereogram recording is performed by sequentially arranging and recording a plurality of element holograms on a recording medium using an object light optical system and a reference light optical system (see Patent Document 1).

JP 2001-350395 A

  In holographic stereogram recording, as shown in FIG. 1, object light modulated by a spatial light modulator of an object light optical system is condensed on a recording medium by an objective lens, and is placed at the same position of the condensing point. When the reference light is irradiated by the reference light optical system, an element hologram is formed at one point of the recording medium. Here, the pattern displayed at the position A on the spatial light modulator is irradiated onto the recording medium obliquely from above by the objective lens. Similarly, the pattern displayed at the position B is irradiated on the recording medium from the horizontal direction, and the pattern displayed at the position C is irradiated obliquely downward.

  When the recorded recording medium is illuminated with the same wavelength component as the reference light, as shown in FIG. 2, the pattern light A in the horizontal direction extends from the recorded element hologram diagonally downward of the recording medium. B pattern light is reproduced, and C pattern light is reproduced obliquely upward. At this time, an image obtained by viewing a certain portion of the object from a diagonally downward θ angle at an A position on the spatial light modulator, an image viewed from the front at a B position, and an obliquely upward image at a C position. If an image viewed from the angle θ is displayed, an image as if an actual object was viewed from that angle can be observed according to the viewing angle.

  The recorded element hologram represents information on a part of the object. By sequentially arranging the element holograms on the recording medium, a holographic stereogram of the entire object is completed, and one object image is synthesized on the recording medium. The As described above, since all element holograms display images according to viewing angles, as shown in FIG. 3, when viewed with both eyes, images with different viewpoints are provided for the right eye and the left eye. It will be recognized as a stereoscopic image.

  The above is a method for recording and reproducing a holographic stereogram on the premise that an ideal hologram is recorded. As described in Patent Document 1, unless hologram recording itself is performed correctly, the object light at the time of recording cannot be reproduced, so that a correct image cannot be reproduced. In order to record the hologram correctly, it is necessary to appropriately set the exposure amounts of the reference beam and the object beam to the recording medium. In addition to the total exposure amount, the light quantity ratio between the reference light and the object light is also an important parameter. In other words, from the standpoint of hologram recording alone, it is ideal that the light amounts of the reference light and object light are equal in recording of all element holograms. Although the reference light can always have a constant exposure amount, the object light has a display pattern on the spatial light modulator that is determined according to the object to be recorded. Is impossible. In particular, the amount of light becomes a problem when recording with dark object light. For example, when recording an object placed in front of a black background, recording of an element hologram in the background portion may result in a black image, that is, a dark image when viewed from any direction. In the recording of the dark portion, most of the display area of the spatial light modulator is not displayed (black), so that the amount of object light is extremely small. There is a problem that a correct element hologram cannot be recorded as it is. Actually, Patent Document 1 does not mention recording of element holograms in dark portions.

  Therefore, an object of the present invention is to provide a holographic stereogram recording apparatus and method capable of recording an element hologram under an exposure condition that does not depend on the darkness of an image to be displayed.

A holographic stereogram recording apparatus according to the present invention includes a spatial light modulator that spatially modulates coherent light according to image information to generate object light, and an object light optical system that focuses the object light on a recording medium. A reference light optical system for irradiating the condensing portion of the object light on the recording medium with reference light that interferes with the object light, and an element hologram at the condensing portion where the reference light and the object light intersect A holographic stereogram recording device for recording
The spatial light modulation unit is disposed on the optical axis of the object light optical system and generates a signal light according to the image information, and is disposed outside the signal light region and includes the image information. And a spatial light modulator having a dimming region for generating no auxiliary light.

Further, the holographic stereogram recording method according to the present invention includes a spatial light modulator that spatially modulates coherent light according to image information to generate object light, and object light optics that focuses the object light on a recording medium. System and a reference light optical system that irradiates the object light condensing portion of the recording medium with reference light that interferes with the object light, at the condensing portion where the reference light and the object light intersect A holographic stereogram recording method for recording an element hologram,
Forming a signal light region for generating signal light according to the image information on the optical axis of the object light optical system of the spatial light modulator;
Forming a dimming region for generating auxiliary light not including the image information outside the signal light region of the spatial light modulator.

  According to the configuration of the present invention described above, element holograms can be recorded under exposure conditions that are not affected by the darkness of the image to be displayed.

It is a schematic diagram which shows the conventional holographic stereogram recording. It is a schematic diagram which shows the conventional holographic stereogram reproduction | regeneration. It is a schematic diagram which shows the conventional holographic stereogram reproduction | regeneration. It is a schematic diagram which shows the structure of the holographic stereogram recording device of embodiment of this invention. It is a schematic diagram which shows the optical path of the reference light in the holographic stereogram recording device of embodiment of this invention. It is a schematic diagram which shows the optical path of the object light in the holographic stereogram recording device of embodiment of this invention. It is a schematic perspective view which shows the relationship between the spatial light modulator, the objective lens, a recording medium, reference light, and object light in the holographic stereogram recording device of embodiment of this invention. It is a schematic diagram which shows the holographic stereogram recording of embodiment of this invention. It is a schematic diagram which shows the holographic stereogram reproduction | regeneration of embodiment of this invention. It is a flowchart for demonstrating the recording operation | movement of the holographic stereogram recording device of embodiment of this invention. It is a front view which shows the image information of the display pattern of the signal light area | region displayed on the spatial light modulator in the holographic stereogram recording device of embodiment of this invention. It is a front view which shows the display pattern of the light control area | region unrelated to the image information displayed on the spatial light modulator in the holographic stereogram recording device of embodiment of this invention. It is a front view which shows the display pattern of the light control area | region unrelated to the image information displayed on the spatial light modulator in the holographic stereogram recording device of further embodiment of this invention. It is a schematic perspective view which shows the relationship between the spatial light modulator, the objective lens, a recording medium, reference light, and object light in the holographic stereogram recording device of other embodiment of this invention. It is a schematic perspective view which shows the relationship between the spatial light modulator, the objective lens, a recording medium, reference light, and object light in the holographic stereogram recording device of further another embodiment of this invention. It is a schematic diagram which shows the structure of the holographic stereogram recording device of other embodiment of this invention.

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

  FIG. 4 is a schematic diagram illustrating the overall structure of the holographic stereogram recording apparatus according to the embodiment of the present invention. FIG. 5 is a schematic diagram illustrating the optical path of the reference light. FIG. 6 illustrates the optical path of the object light. It is a schematic diagram to explain. FIG. 7 is a schematic perspective view showing the relationship between a recording medium, reference light, and object light in such a holographic stereogram recording apparatus.

  As shown in FIG. 4, the holographic stereogram recording apparatus includes a laser light source 21, a collimator lens 22, a shutter 23, a half-wave plate 24, a polarizing beam splitter 25, an aperture 26, a reduction optical system 27, a mirror 28, Mirror 29, recording medium 33, medium moving mechanism 35, medium position controller 36, main controller 51, exposure controller 52, shutter opening / closing mechanism 53, image generator IS, dimming area generator DRS, display driver DD, mirror 61, a beam diffusion plate 62, a spatial light modulator 64, relay lenses 65 and 66, a Nyquist filter 67, and an objective lens 68.

  The main controller 51 is connected to the exposure controller 52 for driving the shutter 23, the medium position controller 36 for driving the medium moving mechanism 35, and the image generator IS for driving the spatial light modulator 64. ing.

  The reference light optical system that generates reference light from the coherent light of the light source 21 includes a polarization beam splitter 25, an aperture 26, a reduction optical system 27, a mirror 28, and a mirror 29. An object light optical system that generates object light obtained by modulating coherent light from the coherent light of the light source 21 according to image information includes a polarization beam splitter 25, a mirror 61, a beam diffusion plate 62, a spatial light modulator 64, a relay lens 65, 66, a Nyquist filter 67 and an objective lens 68.

  The medium moving mechanism 35 is included in a support unit that supports a predetermined position of the recording medium 33 at a recording position where the optical paths of the reference light and the object light intersect.

  Next, as shown in FIG. 5, the light path of the reference light in the holographic stereogram recording apparatus will be described by blocking the laser light by placing a light shielding plate between the polarizing beam splitter 25 and the mirror 61. Laser light emitted from the light source 21 is converted into parallel light by the collimator lens 22 and passes through the opening of the shutter 23 and the half-wave plate 24. The polarization beam splitter 25 branches the transmitted laser light beam into a reference light beam. The light beam for reference light is supplied to the reduction optical system 27 via a rectangular aperture 26 having an appropriate size. The reduction optical system 27 converts the light into parallel light (reference light) having a thin rectangular beam cross section. Thereafter, the reference light is irradiated from the side opposite to the incident surface of the object light to the object light condensing point (recording position) of the recording medium 33 through the mirror 28 and the mirror 29. The spot of the reference light is made to have the same size as the spot of the object light on the photosensitive sheet surface of the recording medium 33 by the aperture.

  Next, as shown in FIG. 6, the light path of the object light in the holographic stereogram recording apparatus will be described by blocking the laser light by placing a light shielding plate between the polarizing beam splitter 25 and the aperture 26. FIG. The polarization beam splitter 25 divides the laser light emitted from the light source 21 and converted into parallel light by the collimator lens 22 and transmitted through the opening of the shutter 23 and the half-wave plate 24 into a light beam for object light. Here, the beam light for object light may be converted into an appropriate parallel beam diameter using an expander lens (not shown). The mirror 61 causes the object light beam, which has been converted into parallel light, to enter the spatial light modulator 64 via the beam diffusion plate 62 from the normal direction of the principal surfaces thereof.

  Usually, the element hologram has a square shape with a side length of about several hundred microns, and it is preferable to uniformly expose the inside of the element hologram. However, the size of the beam spot collected by the objective lens is much smaller than the element hologram size. For example, if the wavelength of the laser beam is 0.532 microns and the NA of the objective lens 68 is 0.5, the diameter of the beam spot at the focal point is about 1.3 microns. A beam diffusing plate 62 is arranged on the display surface of the spatial light modulator 64 in order to avoid the concentration of power only at a minute condensing point.

  The spatial light modulator 64 typically consists of a region or two-dimensional array of addressable pixels (pixels) that can selectively transmit incident light. The spatial light modulator 64 is controlled by the main controller 51. Under the control of the main controller 51, the image generation unit IS, the dimming region generation unit DRS, and the display driver DD cause the spatial light modulator 64 to display an image pattern based on the parallax image synthesis calculated in advance. The main controller 51, the image generation unit IS, the dimming region generation unit DRS, and the display driver DD are included in the spatial light modulation unit. 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 unit of the spatial light modulator based on the image pattern signal. The spatial light modulator 64 includes, for example, an active matrix driving circuit and includes a transmissive liquid crystal device. For example, the spatial light modulator 64 has a predetermined number of pixels, for example, a VGA type (640 × 480 pixels) or an XGA type (1024 × 768 pixels). It has a pixel arrangement.

  As shown in FIG. 6, the spatial light modulator 64 spatially modulates the transmitted light according to the displayed image pattern to generate object light, and the object light is relay lens 65, Nyquist filter 67, and relay lens 66. Is made incident on the objective lens 68 through the imaging optical system. The objective lens 68 condenses the object light as a spherical wave at a predetermined position on the main surface of 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 between the two relay lenses 65 and 66 removes unnecessary diffracted light by the spatial light modulator 64 and limits the size of the element hologram to be recorded. To do. That is, the Nyquist filter is positioned at a position conjugate with the surface of the recording medium 33 in order to limit the shape of the beam spot at the condensing point in the lateral direction and restrict the beam from being excessively expanded in the lateral direction. 67 is arranged. The size (area) of the spot on the surface of the recording medium 33 by the object light in the vicinity of the display surface of the spatial light modulator 64 is the optical magnification determined by the focal length ratio of the relay lens 66 and the objective lens 68, and the size of the Nyquist filter 67 is set. Since it becomes the multiplied size, the size of the Nyquist filter 67 is determined so as to have an appropriate element hologram size. By the action of the beam diffusing plate 62 and the Nyquist filter 67, the object light has the size of the element hologram accurately on the surface of the recording medium 33, and can be a beam spot having a uniform intensity distribution. The beam diffusing plate 62 is desirably disposed on the display surface of the spatial light modulator 64 or its imaging surface (PL1 surface), but is disposed in another place in the optical path of the object light. It doesn't matter.

  The display pattern of the spatial light modulator 64 is once imaged on the imaging plane PL1 immediately before the objective lens 68 by the imaging optical system. The objective lens 68 is arranged so that the position of the image plane PL1 is equal to the focal length fo of the objective lens 68. The recording medium 33 is disposed at a position equal to the focal length fo of the objective lens 68 on the opposite side.

  For example, the recording medium 33 has a structure in which a photosensitive sheet made of a photosensitive material is sandwiched between a glass substrate and a PET film (not shown). The object light is incident from the glass substrate side and is condensed near the interface of the photosensitive sheet. The reference light is incident from the PET film side. Since the laser light passes through the beam diffusion plate 62 before entering the spatial light modulator 64, the beam profile on the interface of the photosensitive sheet has a shape in which the peak intensity is reduced and the width is expanded in the lateral direction. 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.

  The lateral spread at the condensing point of the recording medium 33 is limited by the Nyquist filter 67 (FIG. 4), and as shown in FIG. 7, object light is irradiated only to a rectangular area having a predetermined size. become. Element holograms are recorded in the recording medium region where the optical paths of the reference beam and the object beam intersect.

  As shown in FIG. 7, a plurality of element holograms are recorded by repeated raster scanning in the plane direction of the recording medium. In order to align a plurality of element holograms without gaps, recording is performed by moving the recording position at which the optical paths of the reference beam and the object beam intersect on the recording medium 33 relative to the length of one side of the element hologram in the XY axis direction. To do. When the movement of the recording medium is completed and the vibration of the recording medium is settled, the next element hologram is recorded. By repeating this operation, an element hologram matrix is formed on the recording medium. You may record so that element holograms may overlap and there may be a gap between element holograms. In this way, a holographic stereogram in which one three-dimensional image is reproduced as a whole is obtained by repeatedly performing raster scan recording of a plurality of element holograms in the XY plane direction of the recording medium.

  Ideally, the light amounts of the reference light and object light are equal in recording of all element holograms. The reference light branched first can always have a constant exposure amount, but the object light has a display pattern on the spatial light modulator determined according to the object to be recorded. It is impossible to control the amount of light. Therefore, in the holographic stereogram recording method of the present embodiment, in the object light optical system, the signal light that has been subjected to spatial light modulation according to the display image, and the spatial light that is on the outer peripheral side and is not related to the display image. Both modulated auxiliary lights are used as object lights.

  For example, in the holographic stereogram recording apparatus, as shown in FIG. 7, the spatial light modulator 64 is arranged on the optical axis of the object light optical system, displays image information, and signal light corresponding to the image information. And a dimming region DR that generates auxiliary light that is disposed outside the signal light region and does not include image information. In this embodiment, as shown in FIG. 7, a dimming region DR is provided outside the signal light region IR on the spatial light modulator 64, and the light is modulated by the signal light modulated by the signal light region IR and the dimming region DR. Both of the auxiliary light thus used are used as object light.

  As shown in FIG. 8, the object light (signal light and auxiliary light) modulated by the spatial light modulator 64 of the object light optical system is condensed on the recording medium 33 by the objective lens 68, and at the same time, its condensing point. Are irradiated with reference light by the reference light optical system, and an element hologram is formed at the same point. Here, the pattern displayed in the dimming region DR of the spatial light modulator 64 is irradiated from the objective lens 68 to the recording medium 33 obliquely in the vertical direction and the horizontal direction. The image pattern displayed in the central signal light region IR is applied to the recording medium 33 at a position including the optical axis.

  In this case, as shown in FIG. 9, when the recorded recording medium is illuminated with the same wavelength component as the reference light, the recorded element hologram is adjusted in the diagonally up and down direction and the left and right direction of the recording medium 33. The image pattern light (signal light) displayed in the signal light region IR in the center of the spatial light modulator is reproduced in the horizontal direction which is the optical axis of the pattern light (auxiliary light) displayed in the light region DR. At this time, as shown in FIG. 9, only the image recorded in the signal light region IR is observed in the viewing area of the observer, and the pattern displayed in the light control region DR cannot be confirmed. Conversely, only the pattern displayed in the light control area DR is observed from outside the viewing area (non-viewing area), and the pattern image in the signal light area cannot be confirmed. Speaking only when viewing an image within the range of the viewing zone, the pattern displayed in the light control region DR has no effect on the reproduced image.

  By using the signal light and the auxiliary light (signal light region IR and dimming region DR) in this embodiment, for example, if the sum of the light amount of the auxiliary light and the light amount of the signal light is controlled to be substantially constant, the display Since the amount of the signal light is compensated by the presence of the auxiliary light without affecting the image to be displayed, the element hologram can be recorded under the exposure condition that is not affected by the darkness of the image to be displayed.

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

  First, prior to the start of recording, the half-wave plate 24 shown in FIG. 4 is adjusted to an appropriate angle to set the light quantity ratio between the object light and the reference light. This light quantity ratio is calculated in advance from the characteristics of the photosensitive sheet, the transmittance of the beam diffusing plate, the efficiency of the spatial light modulator, the transmittance of the optical component, and the like.

  The image generation unit IS moves the recording medium to a predetermined position, for example, the first element hologram writing position, and the image generation unit IS records an element hologram image pattern to be recorded first in a predetermined order, for example, in accordance with a command from the main controller 51 shown in FIG. Generate (step S1). The image pattern generation 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 is sequentially calculated or stored in the storage unit of the main controller 51 or the like in advance. This is done using image data. Then, the dimming area generation unit DRS generates a dimming area pattern corresponding to the display pattern in accordance with the command of the image generation unit IS. The image generation unit IS and the dimming region generation unit DRS transfer the display pattern data and the dimming region pattern data to the display driver DD, thereby causing the spatial light modulator 64 to receive a two-dimensional pattern (signal light region IR and The dimming area DR) is displayed (step S2).

  Next, an element hologram writing operation is performed by the exposure control unit 52 in response to a command from the main controller 51 shown in FIG. The display of the spatial light modulator 64 and the opening and closing of the shutter are controlled by the main controller 51, and processing is performed so that the timings of both are appropriately synchronized. Here, exposure is performed for a predetermined time by the main controller 51 instructing the shutter opening / closing mechanism 53 to appropriately open / close the shutter 23 so that the exposure energy amount, exposure time, and exposure pattern necessary for exposure recording are obtained. Here, by opening the shutter 23 (step S3), a signal light region forming step for forming a signal light region IR for generating signal light and a control light for generating auxiliary light not including image information outside the signal light region IR. The dimming region forming step for forming the light region DR is performed simultaneously. If the shutter 23 is a normally closed shutter, the exposure control unit 52 sends a command to continue applying voltage.

  Next, the main controller 51 determines whether or not the exposure time is a specified value (step S4). If not, the process returns to step S3, and if satisfied, the shutter is closed (step S5).

  Next, when the exposure of each element hologram is completed, the main controller 51 determines whether or not the number of exposures is a specified value (step S6). If not, the process returns to step S2, and if satisfied, the spatial light modulator 64. The recording pattern display is stopped (step S7).

  Next, when the exposure of one element hologram is completed, the main controller 51 sends a command to move the recording medium to the next recording position. Usually, the element holograms are moved by the same length as one side of the element holograms so that the element holograms are aligned with no gaps. 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 the exposure operation of the element hologram, an element hologram row is formed on the recording medium, and a holographic stereogram is completed.

  Next, the main controller 51 determines whether or not the element hologram is at the final recording position (step S8), and if not, sends a command to move the recording medium to the next recording position (step S9), and returns to step S1. In response to the command, the image generation unit IS generates an image pattern of the second element hologram to be recorded next. The main controller 51 repeatedly executes steps S1 to S8 and ends the operation if it is satisfied that the final recording position has been reached.

  According to the use of the signal light and the auxiliary light (the signal light region IR and the light control region DR) in this embodiment, the exposure condition is not affected by the darkness of the image to be displayed without affecting the displayed image. Element holograms can be recorded at A specific setting example of the signal light region IR and the light control region DR will be described. For example, consider the case where the display patterns (image information) of the three types of signal light regions IR shown in FIG. 11 are displayed on the spatial light modulator. Here, a spatial light modulator of 12 × 12 pixels is assumed, 8 × 8 pixels are used for the central signal light region IR, and an annular shape having a width of 2 pixels is given to the outer light control region DR. The light transmission state of the pixel (simply referred to as white) is shown in white, and the light blocking state of the pixel (simply referred to as black) is shown in black. Further, the percentage of the number of light transmission state pixels with respect to the total number of pixels is called a white ratio. Note that the number of pixels of the spatial light modulator is not limited to 12 × 12 pixels. FIG. 11A shows an extremely white pattern, FIG. 11B shows a pattern in which white and black are almost half, and FIG. 11C shows an extremely black pattern. When hologram recording is performed using these image information patterns as object light, there is a concern that the pattern recording of FIG. Further, depending on the characteristics of the recording medium, there may be a case where either FIG. 11A or FIG. These phenomena are caused by the fact that the amount of object light is greatly changed with respect to a constant amount of reference light.

  Therefore, the dimming areas shown in FIGS. 12 (a ′), (b ′) and (c ′) are provided outside the image information patterns in FIGS. 11 (a), (b) and (c) of the signal light area IR. Each DR is added. FIG. 11 (a) shows the pattern of FIG. 12 (a ′) with a lot of black, FIG. 11 (b) shows the pattern of FIG. 12 (b ′) with the same number of white and black, and FIG. 11 (c). Uses the pattern shown in FIG. By adding the pattern of FIG. 12 complementary to the light amount to the image information of FIG. 11, the total light amount (object light) of the signal light and the auxiliary light becomes substantially uniform at the focal point, and is uniform for any pattern. Recording conditions can be achieved.

  There are various methods for combining the patterns of the light control region DR. Three examples are given below.

  The first combination example is a method in which the number of whites in the signal light region IR and the dimming region DR is the same. For example, if the number of whites in the signal light region IR is 20, the number of whites in the light control region DR is 80. If the number of whites in the signal light region IR is 50, the number of whites in the light control region DR is 50. If the number of whites in the signal light region IR is 90, the total number of whites in the signal light region IR and the light control region DR is constant, for example, the number of whites in the light control region DR is ten. The pattern of the light control region DR is determined so as to be a number (100 in this example).

  The second combination example is a method of using the dimming region DR having a corresponding white ratio when the white ratio of the signal light region IR is within a predetermined range. For example, when the range is divided into three and the white ratio of the signal light region IR is 0 to 25%, a pattern having a white ratio of 80% is used as the dimming region DR, and the white ratio of the signal light region IR is 25. When the white ratio is ˜75%, a pattern with a white ratio of 50% is used as the light control region DR. Used as region DR. Note that the number of divisions of the white ratio range of the signal light region IR is not limited to three.

  The third combination example is a method of using a corresponding dimming region DR pattern when the white ratio of the signal light region IR is within a predetermined range. For example, when the white ratio of the signal light region IR is 0 to 25%, the pattern shown in FIG. 12 (a ′) is used as the dimming region DR, and when the white ratio of the signal light region IR is 25 to 75%, The pattern shown in FIG. 12B ′ is used as the light control region DR, and when the white ratio of the signal light region IR is 75 to 100%, the pattern shown in FIG. 12C ′ is used as the light control region DR. Note that the number of divisions of the white ratio range of the signal light region IR is not limited to three.

  In the above embodiment, the light amount of the auxiliary light is changed according to the light amount of the signal light. However, in a further embodiment, the light amount of the auxiliary light is made substantially uniform regardless of the light amount of the signal light. May be.

  For example, the image information patterns shown in FIGS. 11A, 11B, and 11C in the signal light region IR are shown in FIGS. 13A ″, 13B ″, and 13C ″. As described above, this can be realized by always using a pattern with a substantially uniform white ratio (67/80 = 84%) for the light control region DR. The same effect can be obtained by making all the light control regions DR have the same pattern (for example, all white).

  Of the various exposure conditions that can be assumed, the greatest concern is that the amount of object light becomes zero (or a state close to zero). Hologram recording is performed by causing the object light and the reference light to interfere with each other, and it is a situation that the light quantity of the object light must be avoided. In a further embodiment, it is possible to avoid a situation in which the object light becomes 0 light quantity, and a certain effect can be expected.

  In the embodiment up to FIG. 12, it is necessary to calculate the pattern of the light control region DR according to the light amount of the signal light. However, in the further embodiment shown in FIG. 13, a specific pattern is used regardless of the light amount of the signal light. (Constant amount of light) may be added, and the load of calculation processing can be reduced.

  In another embodiment, as shown in FIG. 14, the dimming region DR2 for generating auxiliary light is formed of a member different from the spatial light modulator 64 and a light-transmitting material such as transparent resin or glass that transmits laser light. You can also. The dimming region DR2 is formed integrally with the spatial light modulator, but the dimming region DR2 may be provided around the spatial light modulator 64. In the embodiment shown in FIG. 14, the area of the dimming region DR2 (constant light amount) may be set regardless of the light amount of the signal light, and there is an effect that the load of calculation processing can be reduced.

  Further, in the above embodiment, the dimming region for generating auxiliary light is formed as an annular shape surrounding the signal light region IR along the periphery thereof, but is not limited to this, and in still other embodiments. As shown in FIG. 15, the signal light region IR of the spatial light modulator 64 may be provided in the horizontal direction (Y direction), and the dimming region DR3 for generating auxiliary light may be provided so as to sandwich the signal light region IR. . By setting the light control region DR3, it is possible to reduce the arrival of the pattern by the light control region DR3 in the left and right eyes of the observer.

  In the above embodiment, the signal light region IR and the light control region DR are both rectangular regions, but of course other shapes such as a circle may be used. Further, it is not necessary to provide the light control region DR just outside the signal light region IR, a buffer region that displays nothing may be provided outside the signal light region IR, and the light control region DR may be provided outside the buffer region. .

  In the above embodiment, the spatial light modulator uses a transmissive spatial light modulator that performs spatial light modulation on the transmitted light like liquid crystal, but of course, DMD (Digital Mirror Device) or LCOS (Liquid A reflective spatial light modulator that performs spatial light modulation on the reflected light, such as Crystal on Silicon, may be used.

  In the above embodiment, the reference light is irradiated from the side opposite to the main surface of the recording medium on which the object light is incident as shown in FIGS. 4 to 7, but the object light is incident as shown in FIG. The arrangement of the mirrors 28 and 29 of the reference light optical system shown in FIG. 4 may be changed so that the reference light is irradiated from the same side as the main surface of the recording medium 33. A hologram recorded with reference light and object light facing a recording medium as shown in FIG. 4 is called a reflection hologram, and the reference light and object light are irradiated from the same surface side as shown in FIG. The recorded hologram is called a transmission hologram. In any case, the reference light has the same magnitude as the signal light on the photosensitive sheet surface. Thus, the element hologram is recorded on the surface of the recording medium by simultaneously irradiating the same minute area with the object light and the reference light.

  As in the present embodiment, in the optical system of the holographic stereogram, there is no conventional example in which a kind of dimming region is provided on the spatial light modulator of object light. In hologram recording, it is indispensable to control the ratio of object light and reference light within an appropriate range, and it is a well-known fact that correct recording cannot be performed when the object light is extremely small. is there. However, this is not a problem in holographic memory. This is because in the reproduction of a hologram in the holographic memory, the recorded information is reproduced by decoding the reproduction light. In other words, by using an appropriate modulation method for recording any information, it is easy to limit the amount of object light within a certain range and never deviate from appropriate exposure conditions. On the other hand, holographic stereograms are recorded for the purpose of viewing the reproduced light directly. Although the exposure conditions are ensured, information cannot be added to the object light. That is, the problem of enabling arbitrary information to be recorded while ensuring the exposure conditions can be said to be a problem unique to the holographic stereogram.

  In this embodiment, a dimming area irrelevant to the display of the object in the signal light area is provided, and auxiliary light that passes through or reflects the dimming area is also used as the object light. It is possible to control the light amount of the object light within an appropriate range by performing appropriate display in the light control region of the present embodiment. Furthermore, according to the present embodiment, the multi-viewpoint element image may be an extremely dark image or a complete all-black image depending on the image to be recorded. Correct hologram recording can be achieved.

DESCRIPTION OF SYMBOLS 21 Light source 22 Collimator lens 23 Shutter 24 1/2 wavelength plate 25 Polarizing beam splitter 26 Aperture 27 Reduction optical system 33 Recording medium 35 Medium moving mechanism 36 Medium position control part 51 Main controller 62 Beam diffuser plate 64 Spatial light modulator 65,66 Relay lens 67 Nyquist filter 68 Objective lens

Claims (11)

A spatial light modulator that spatially modulates coherent light according to image information to generate object light; an object light optical system that focuses the object light on a recording medium; and reference light that interferes with the object light. A holographic stereogram recording apparatus for recording an element hologram at the light converging portion where the reference light and the object light intersect with each other. And
The spatial light modulation unit is disposed on the optical axis of the object light optical system and generates a signal light according to the image information, and is disposed outside the signal light region and includes the image information. A holographic stereogram recording device comprising a spatial light modulator having a dimming region for generating no auxiliary light.   2. The holographic stereogram recording apparatus according to claim 1, wherein the dimming area is arranged along a periphery of the signal light area.   3. The holographic stereogram recording apparatus according to claim 2, wherein the light control area is arranged in an annular shape surrounding the signal light area.   2. The spatial light modulation unit includes a dimming region generation unit that controls the spatial light modulator so that a sum of a light amount of the auxiliary light and a light amount of the signal light is substantially constant. 4. The holographic stereogram recording device according to any one of items 1 to 3.   The said spatial light modulation part contains the light control area | region production | generation part which controls the light quantity of the said auxiliary light so that it may become a fixed light quantity irrespective of the light quantity of the said signal light, The any one of Claim 1 thru | or 3 characterized by the above-mentioned. 2. A holographic stereogram recording device according to claim 1.   2. The spatial light modulator, wherein the light control region is formed of a light-transmitting material so that the light amount of the auxiliary light is constant regardless of the light amount of the signal light. 4. The holographic stereogram recording device according to any one of 3 above. A spatial light modulator that spatially modulates coherent light in accordance with image information to generate object light, an object light optical system that focuses the object light on a recording medium, and reference light that interferes with the object light. A holographic stereogram recording method for recording an element hologram at a condensing portion where the reference light and the object light intersect using a reference light optical system that irradiates the condensing portion of the object light on a recording medium. And
Forming a signal light region for generating signal light according to the image information on the optical axis of the object light optical system of the spatial light modulator;
A holographic stereogram recording method comprising: forming a dimming area for generating auxiliary light not including the image information outside the signal light area of the spatial light modulator.   8. The holographic stereogram recording method according to claim 7, wherein the dimming area is arranged along a periphery of the signal light area.   9. The holographic stereogram recording method according to claim 8, wherein the dimming area is arranged in an annular shape surrounding the signal light area.   The holographic stereogram recording according to any one of claims 7 to 9, wherein the spatial light modulator is controlled so that a total amount of the auxiliary light and the signal light is substantially constant. Method.   The holographic stereo according to any one of claims 7 to 9, wherein the spatial light modulator is controlled so that a light amount of the auxiliary light becomes a constant light amount regardless of a light amount of the signal light. Gram recording method.

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