JP2012242513A - Electronic holography display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an image from being likely to disconnect in a boundary portion between adjacent spatial light modulators in an electronic holography display device in which a plurality of spatial light modulators with non-display portions in their peripheral portions are arranged.SOLUTION: Disconnection of the image is prevented by arranging an optical system between a surface in which a plurality of display units with the spatial light modulators and magnifying optical systems are laterally arranged and a browser. That is, light beams emitted from the spatial light modulators are magnified for the respective display units by using the magnifying optical systems, light beams from the plurality of display units are connected such that a series of images spread over the entire display surface is obtained. At that time, light from each of the non-display portions is blocked by a shading plate. Next, the series of images is reduced by a reducing optical system. This makes it possible to eliminate the influence of the non-display portions without spoiling display characteristics such as the number of pixels or resolution of each of the spatial light modulators, thus preventing image disconnection in the portions.

Description

  The present invention relates to an electronic holographic display device capable of displaying a large stereoscopic image.

  Display devices using holographic technology are already well known. It is also known that a holographic stereoscopic image can be realized by configuring a hologram on a display device such as a liquid crystal display device using an electronic circuit, and this technique is called electronic holography.

  For example, Non-Patent Document 1 reports on electronic holography with an increased viewing zone angle and display size. This is a laser that is irradiated by a spatial light modulator that shoots a subject under natural light illumination using a method of integral photography (IP), generates hologram image data by computer processing, and displays this image data. This is a real-time color moving image holographic imaging / conversion / display system that modulates light and presents a stereoscopic image. According to this report, a spatial light modulator having a pixel number of 8192 × 4320 and a pixel pitch of 4.8 μm is used, and a display with a viewing angle of 5.6 ° and a diagonal size of 4.2 cm is realized.

  In general, in a display device based on electronic holography, a small stereoscopic image is only obtained due to the small spatial light modulator. Therefore, it can be considered that a plurality of spatial light modulators are arranged to make a substantially large spatial light modulator. However, when a liquid crystal display unit is used as a spatial light modulator, for example, it cannot be displayed in its peripheral circuit part, and its fixed frame is necessary, and further, wiring to each liquid crystal display unit is a light shielding part. Thus, simply arranging the spatial light modulators causes a problem that a space where a hologram cannot be displayed is formed and a stereoscopic image cannot be seen in some places.

  Therefore, Non-Patent Document 2 reports a configuration using a plurality of spatial light modulators and a configuration of FIG. 5 using an expansion optical system. In the configuration of FIG. 5, a plurality of point light sources are used in order to cope with the narrowing of the viewing zone angle caused by the magnifying optical system. According to this report, the resolution obtained was 7680 × 135, the pixel pitch in the horizontal direction was 5.76 μm, and the horizontal viewing zone angle was 6.3 °. However, this configuration has a problem that a pinhole cannot be applied to a collimator for making light from a point light source into parallel light. There is also a problem that vertical parallax is not taken into consideration.

  Further, in Non-Patent Document 3, three spatial light modulators are arranged so as to be contiguous in the viewing zone, and the viewing zone angle is about 15 times three times the viewing zone angle of 5.3 ° in the case of one. The configuration shown in FIG. In this method, the number of images is limited to 3 on the premise of implementation, and in order to expand the viewing zone angle using a larger number of images, it is necessary to improve the arrangement. Incidentally, a color image is displayed in a time-division display with three primary colors.

Sanshina, Senoo, Yamamoto, Oi, Kurita, "Stereoscopic color image reproduction by electronic holography using ultra-high-definition liquid crystal panels", HODIC (Holographic Display Study Group), vol. 30, no. 2, pp. 12 -17 (May, 2010). Y. Takaki and Y. Tanemoto, "Frameless hologram display module managing resolution redistribution optical system," Proc. SPIE, vol.7619, 761902 (2010). T. Senoh, K. Yamamoto, T. Mishina, R. Oi, and T. Kurita, "Wide viewing-zone-angle full-color electronic holography system using very high resolution liquid crystal display panels," Proc. SPIE, vol. 7957, 795709 (2011).

  It is expected that an electronic holographic display device capable of displaying a large stereoscopic image can be realized by arranging a plurality of spatial light modulators, but if they are simply arranged, the boundary of the spatial light modulators There is a problem that the image is interrupted at the portion. This is because, for example, wiring is provided at the end of each spatial light modulator, and this portion becomes a non-display portion, so that it is impossible to display a continuous hologram vertically and horizontally. In the present invention, the non-display portion is not affected.

  Basically, the problem due to the non-display portion is solved by arranging an optical system between a viewer and a surface on which a plurality of spatial light modulators are arranged. For this purpose, the light emitted from the spatial light modulator is expanded by the above optical system for each spatial light modulator, and the light from the plurality of spatial light modulators is connected to spread over the entire display surface. Make an image. At that time, light from the non-display portion is shielded by a light shielding plate. Next, the series of images is reduced by an optical system. As a result, the influence of the non-display portion of the spatial light modulator can be eliminated without impairing display characteristics such as the number of pixels and resolution of the individual spatial light modulator, and the stereoscopic image is not interrupted at that portion. More specifically, it is as follows.

In the electronic holographic display device of the present invention, the spatial light modulator for displaying the hologram, the light irradiation means for irradiating the spatial light modulator with parallel light, and the cross-sectional area of the light emitted from the spatial light modulator are expanded. A plurality of display units comprising a magnifying optical system;
A reduction optical system that receives light from the plurality of display units, and
Is provided.
The optical axes of the plurality of display units are parallel, and the display units are arranged vertically and horizontally as viewed from the viewer of the hologram,
The plurality of display units are expanded so that the light beam from the image display area on each spatial light modulator and the light beam from the image display area on the adjacent spatial light modulator overlap in the adjacent area,
The reduction optical system presents an image obtained by reducing the images of the plurality of display units to a viewer of the hologram.

  The magnifying optical system is provided with a spatial filter for removing transmitted light, higher-order light, or conjugate light between two light collecting systems. Alternatively, the reduction optical system may be a system in which a spatial filter for suppressing transmitted light, high-order light, or conjugate light is provided between two light collecting systems.

  Further, the reflected light from the spatial light modulator is incident on the magnifying optical system.

  Alternatively, the light that has passed through the spatial light modulator may be incident on the magnification optical system.

  The light irradiating means is configured to alternately irradiate the spatial light modulator with light from a plurality of predetermined directions, and performs switching of the irradiation direction in each display unit in a time-sharing manner in synchronization. There may be.

  The light irradiating means is configured to alternately irradiate light having a plurality of predetermined wavelengths to the spatial light modulator, and performs switching of the irradiation wavelength in each display unit in a time-sharing manner in synchronization. There may be.

  The following problem caused by arranging a plurality of spatial light modulators, that is, for example, a wiring is provided at the end of each spatial light modulator and this part becomes a non-display part, so that a gap that cannot display a hologram is created. Thus, it is possible to solve the problem that the stereoscopic image becomes invisible in some places, and to realize an electronic holographic display device capable of displaying a stereoscopic image larger than the conventional one.

It is a figure which shows the example of the electronic holography display device of this invention. In this example, a spatial light modulator for displaying a hologram, in particular, an image display region 2, light irradiation means 3 for irradiating the spatial light modulator with parallel rays, and a cross-sectional area of light emitted from the spatial light modulator A plurality of display units 1 including the expanding optical system 4 to be expanded, and a reduction optical system 10 that receives light from the plurality of display units are provided. The spatial light modulator is controlled by a computer, an image control device, or the like. The optical axes of the plurality of display units are parallel to each other, and the arrangement of the display units as viewed from the viewer 25 is arranged vertically and horizontally. In the plurality of display units 1, the light beam from the image display area 2 of each spatial light modulator and the light beam from the image display area on the adjacent spatial light modulator are substantially in contact with each other or slightly. In an overlapping manner, the reduction optical system 10 presents an image obtained by reducing the images of the plurality of display units to the viewer 25 of the hologram. It is a figure which shows the structure for control of this spatial light modulator and a light source. The spatial light modulator is driven by the display driving unit 12 as illustrated, and the display driving unit 12 is controlled by the control unit 13 according to the display data. The light source 3 is also controlled by the control unit 13. In particular, when performing color display, it is necessary to synchronize the switching of the three primary colors of light emitted from the light source and the display on the spatial light modulator, but the control unit 13 performs this. It is a figure for demonstrating the overlap of said light beam. When the end of the light beam output from each display unit is stepped as shown in (a) and there is a gap between adjacent light beams, the gap is viewed from the viewer. Looks like a black belt. In each figure, the solid lines A and B are the amounts of light beams adjacent to each other, and the dotted line C is the combined light amount. Further, as illustrated in (b), if there is an overlap between adjacent light beams, the amount of light in that portion increases, and it looks like a bright strip. In general, it is known that the sensory brightness is proportional to the logarithm of the light amount, and when the vertical axis is the logarithm of the light amount, the change in (a) of the dotted line C is more than the change in (b). Is also small. However, if the above-mentioned end portion is gradually changed so as to decrease outward as shown in (c), a change in the amount of light with respect to the magnitude of the deviation can be suppressed. In the case (d), the amount of light in the overlapping portion is shifted so as to decrease, and in the case (e), the amount of light in the overlapping portion is shifted so as to increase. It can be seen that the change in the dotted line C is smaller than in the case of b). It is a figure which shows the structural example which detects a viewer's position and changes a visual field automatically. In this configuration example, the liquid crystal shutter 18 is used as the spatial filter F2. The viewer 25 is imaged by the camera 15, the position of the viewer 25 is determined by the position analysis unit 16, and the determined position information is sent to the spatial filter driving unit 17. The spatial filter driving unit 17 transmits light from the liquid crystal shutter 18. The position is controlled. By doing in this way, the substantial viewing area seen from the viewer can be expanded. It is a figure which shows the structure using the expansion optical system of a nonpatent literature 2. FIG. In this configuration, in order to cope with the narrowing of the viewing zone angle by the magnifying optical system, a plurality of point light sources are used, the obtained resolution is 7680 × 135, and the horizontal pixel pitch is 5.76 μm. The horizontal viewing angle was 6.3 °. It is a figure which shows the structure which arrange | positioned three reflection type spatial light modulators of the nonpatent literature 3 so that it might be visible in a viewing zone. The viewing zone angle was able to be about 15 °, which is three times the viewing zone angle of 5.3 °. Incidentally, a color image is displayed in a time-division display with three primary colors.

  Embodiments of the present invention will be described below in detail with reference to the drawings. In the following description, devices having the same function or similar functions are denoted by the same reference numerals unless there is a special reason.

  FIG. 1 shows an example of an electronic holographic display device of the present invention. In this example, a spatial light modulator for displaying a hologram, in particular, an image display region 2, light irradiation means 3 for irradiating the spatial light modulator with parallel rays, and a cross-sectional area of light emitted from the spatial light modulator A plurality of display units 1 including the expanding optical system 4 to be expanded, and a reduction optical system 10 that receives light from the plurality of display units are provided. As shown in FIG. 2, the spatial light modulator is controlled by a computer, an image control device, or the like driven by a display driving unit.

  The optical axes of the plurality of display units are parallel to each other, and the arrangement of the display units as viewed from the viewer 25 is arranged vertically and horizontally. The plurality of display units 1 includes a holographic image of an image displayed in the image display area 2 of each spatial light modulator (SLM), and a holographic image displayed in an image display area on an adjacent spatial light modulator. Are substantially in contact with each other in an adjacent region or slightly overlap each other, and the reduction optical system 10 presents an image obtained by reducing the holographic image to the viewer 25 of the hologram.

  The spatial light modulator has an image display area composed of pixels that are fine enough to display a hologram. For example, the spatial light modulator is a reflective type having 7680 × 4320 pixels described in Non-Patent Document 2. It is a liquid crystal panel.

  As illustrated in FIG. 2, the spatial light modulator is driven by the display driving unit 12, and the display driving unit 12 is controlled by the control unit 13 according to the display data. The light source 3 is also controlled by the control unit 13. In particular, when performing color display, it is necessary to synchronize the switching of the three primary colors of light emitted from the light source and the display on the spatial light modulator, but the control unit 13 performs this.

  The reflection type liquid crystal panel shown in FIG. 1 is irradiated with a linearly polarized laser beam by a polarization beam splitter BS. In this irradiation, it is important for the viewer 25 to prevent the occurrence of unevenness in the brightness of the screen so that the laser beam is branched equally to the plurality of display units. In addition, a control voltage according to image data for displaying an image is applied to each liquid crystal panel. Since the polarization plane of the irradiated light rotates according to this control voltage, when reflected and again passes through the polarization beam splitter BS, the light intensity is modulated according to the rotation angle of the polarization plane. For the user, an image is presented on the liquid crystal panel.

  The image on the liquid crystal panel is enlarged by the enlargement optical system 4. At this time, a circuit for controlling the image display area 2 of the liquid crystal panel is provided in the peripheral portion. In the case where the circuit portion is configured to transmit light, it is necessary to suppress light transmitted through this portion (hereinafter, ambient light). In the example of FIG. 1, for this reason, after condensing the light beam, which is emitted light from the image display region 2, by the condenser lens L1, before passing through or passing through the spatial filter F1 Later, it is absorbed by the light shielding plate to suppress the ambient light. Naturally, the spatial filter F1 has a function of blocking conjugate light, high-order diffracted light, and transmitted light by the hologram. Further, the light transmitted through the spatial filter F1 passes through the first virtual surface 20 again as a parallel light beam or a substantially parallel light beam by the condenser lens L2. At this time, the image display region 2 is enlarged, and it is desirable that the image display region 2 is in contact with or slightly overlaps the light beam that is the light emitted from the adjacent display unit on the first virtual plane 20. However, at this time, since the light beam is brighter and more conspicuous in the portion where the light beam overlaps with the adjacent light beam, it is desirable that the light beam be in contact with almost no gap. By causing the plurality of display units to form an image on the first virtual plane 20, the image without the ambient light is generated.

  Explaining the overlap of the light beams described above, the end of the light beam output from each display unit is stepped as shown in FIG. 3A, and there is a gap between adjacent light beams. The gap looks like a black band when viewed from the viewer. In FIG. 3, solid lines A and B are the light amounts of light beams adjacent to each other, and dotted line C is the combined light amount. Further, as illustrated in FIG. 3B, if there is an overlap between adjacent light beams, the amount of light in that portion increases, and it looks like a bright strip. In general, it is known that the sensory brightness is proportional to the logarithm of the light quantity. When the vertical axis is the logarithm of the light quantity, the change in FIG. ) Is smaller than the change.

However, as shown in FIG. 3 (c), if it is changed gently so as to decrease further outward, a change in the amount of light with respect to the magnitude of the deviation can be suppressed. The case of FIG. 3D is a case where the light amount of the overlapping portion is shifted so as to decrease, and the case of FIG. 3E is a case where the light amount of the overlapping portion is shifted so as to increase. It can be seen that the change in the dotted line C is smaller than in the cases of 3 (a) and (b).
Further, this gentle change is gentle for the viewer, and it is desirable that the change with respect to the distance of the light amount is an exponential function type. This is because the brightness perceived by the viewer is proportional to the logarithm of the light amount as described above. Such end processing can be performed by, for example, the control unit 13 of FIG.

  The image on the first virtual surface 20 is reduced using the reduction optical system 10 and presented to the viewer. At this time, the reduction optical system 10 condenses with the condensing lens L3, suppresses the conjugate light, high-order diffracted light, and transmitted light by the hologram with the spatial filter F2, condenses with the condensing lens L4, and condenses on the virtual surface 21. Project. Here, by making the image on the second virtual surface 21 smaller than the image on the first virtual surface 20, the image seen by the viewer is reduced, but the viewing zone angle can be widened. it can.

  Either one of the spatial filters F1 and F2 can be used, but it is desirable to use both from the viewpoint of image quality viewed from the vicinity of the limit of the viewing zone angle.

  Unlike the case of Non-Patent Document 1, in the present invention, a pinhole is originally unnecessary because parallel light is generated outside the optical system. Vertical parallax is also considered. Furthermore, the center direction of the viewing zone angle can be controlled by making the spatial filter F1 or F2 a spatial filter that transmits light at an arbitrary position using, for example, a liquid crystal shutter. Therefore, this control can be performed according to the position of the viewer, or the viewing zone angle can be substantially enlarged by changing the viewing zone in a time division manner.

  The gap between the light beams of adjacent display units that cause the ambient light or the size of the gap can be dealt with by the same configuration regardless of the size of the gap by changing the focal length of the condenser lens L2. FIG. 1 shows an example in which the size of the spatial light modulator is double the size of the image display area. However, in the case of 3 times or 3.5 times, when the focal length of the condenser lens L1 is f, the focal length of the condenser lens L2 is 3f or 3.5f. Similarly, ambient light can be suppressed.

  FIG. 1 shows the case where the focal lengths of the condenser lenses L2, L3, and L4 are 2f, 2f ', and f', where f is the focal length of the condenser lens L1. If f and f 'are the same, the entire optical system has the same magnification. However, this can be changed. For example, if f ′> f, the image becomes larger but the viewing zone angle becomes narrower.

  In addition, the direction of the reproduced light is changed by switching the pass region of the spatial filter F1 as described above. Thereby, the viewing zone can be enlarged. This switching can be performed mechanically using a mechanical shutter or the like, or electrically using a liquid crystal shutter or the like.

  In addition, the direction of the reproduced light can be changed by switching the pass region of the spatial filter F2. Whether to use the spatial filter F1 or F2 can be determined by ease of manufacturing.

  Also, the aspect ratio of the pixels of the spatial light modulator may be 1 or any other value. It is desirable to change the aspect ratio of the pass region of the spatial filter F1 or F2 according to this aspect ratio. That is, when the passing area is too large, there is a high-order diffracted light and the image quality is slightly deteriorated, and when the passing area is too small, the viewing area tends to be narrowed. It is desirable to comply with the aspect ratio.

  Further, by making the light intensity of the parallel light reaching each spatial light modulator the same in all the spatial light modulators, it is possible to prevent unevenness of the screen. For this purpose, polarizing beam splitters having different reflection and transmission characteristics can be used. As a matter of course, a neutral density filter (ND filter) may be inserted in the middle of the optical path. As the insertion position, for example, a space between the spatial filters F1 and F2 can be considered. By inserting the ND filter, unevenness can be prevented even if the light intensity of the parallel light reaching the spatial light modulator is different.

  In the example of FIG. 1, the spatial light modulator that displays the hologram is of a reflective type, but as described in Non-Patent Document 1, a transmissive spatial light modulator can also be used. When a transmissive spatial light modulator is used, the viewing angle can be expanded by switching light from a plurality of point light sources in a time-sharing manner as described in Non-Patent Document 1. In synchronization with this switching, it is desirable to switch the transmission region of the spatial filter F1 or F2.

  Furthermore, as described in Non-Patent Document 3, a color image can be displayed by sequentially switching a plurality of light sources having different emission wavelengths, for example, three light sources that are three primary colors of light. In synchronization with this switching, the display of the spatial light modulator is switched to an image of each color. This synchronization can be performed, for example, through the control unit 13 in FIG.

  A device that recognizes the position of the viewer's eyes in particular can be realized by a known technique. This technique is applied to the switching of the transmission regions of the spatial filters F1 and F2 in FIG. 1, and the optimal image is presented to the viewer by changing the transmission region position of the spatial filter F1 or F2 according to the viewer's position. be able to. In addition, when there are a plurality of viewers, for example, two viewers, it is wider by switching the transmission region positions of the spatial filters F1 and F2 in a time division manner so that an optimal image can be browsed for each viewer. It can be viewed by multiple viewers under the viewing angle.

  In the example shown in FIG. 4 in which the liquid crystal shutter is used as the spatial filter F2, the viewer 25 is imaged by the camera 15, the position analysis unit 16 determines the position of the viewer 25, and the calculated position information is used as the spatial filter driving unit. The spatial filter drive unit 17 controls the light transmission position of the liquid crystal shutter 18. By doing in this way, the substantial viewing area seen from the viewer can be expanded.

DESCRIPTION OF SYMBOLS 1 Display unit 2 Image display area 3 Light irradiation means 4 Enlargement optical system 10 Reduction optical system 11 Light source 12 Display drive part 13 Control part 15 Camera 16 Position analysis part 17 Spatial filter drive part 18 Liquid crystal shutter 20 1st virtual surface 21 2nd Virtual surface 25 Viewer F1, F2 Spatial filters L1, L2, L3, L4 Condensing lens

Claims (6)

A display unit comprising: a spatial light modulator for displaying a hologram; irradiation means for irradiating the spatial light modulator with a parallel light beam; and an expansion optical system for expanding a cross-sectional area of light emitted from the spatial light modulator. Multiple,
A reduction optical system that receives light from the plurality of display units, and
With
The optical axes of the plurality of display units are parallel, and the display units are arranged vertically and horizontally as viewed from the viewer of the hologram,
In the plurality of display units, the light beam from the image display area on each spatial light modulator and the light beam from the image display area on the adjacent spatial light modulator are overlapped in the adjacent area,
In the reduction optical system, an electronic holographic display device that presents an image obtained by reducing the images of the plurality of display units to a viewer of the hologram.   2. The electronic holographic display device according to claim 1, wherein at least one of the enlargement optical system and the reduction optical system is provided with a spatial filter between two light collection systems.   The electronic holographic display device according to claim 1, wherein reflected light from the spatial light modulator is incident on the magnification optical system.   4. The electronic holographic display device according to claim 1, wherein light that has passed through the spatial light modulator is incident on the magnifying optical system. 5.     The light irradiating means is configured to alternately irradiate the spatial light modulator with light from a plurality of predetermined directions, and performs switching of the irradiation direction in each display unit in a time-sharing manner in synchronization. The electronic holographic display device according to claim 1, wherein the electronic holographic display device is provided.   The light irradiating means is configured to alternately irradiate light having a plurality of predetermined wavelengths to the spatial light modulator, and performs switching of the irradiation wavelength in each display unit in a time-sharing manner in synchronization. The electronic holographic display device according to claim 1, wherein the electronic holographic display device is provided.

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