JP2012113183A - Hologram reproduction device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hologram reproduction device using coherent light such as a laser beam as reproduction illumination light in which speckle noise is effectively made invisible.SOLUTION: A hologram reproduction device of the invention includes a light source unit 4 for temporally changing a projection position of coherent light to form scanning light, a light diffusion element 2 for diffusing the scanning light formed by the light source unit 4 to form diffusion light, and an image reproduction hologram 1 for recording an image using the diffusion light as reference light. The hologram reproduction device reproduces the image recorded on the image reproduction hologram 1 using the diffusion light formed by the light diffusion element 2 as reproduction illumination light.

Description

  The present invention relates to a hologram reproducing apparatus that reproduces an image recorded on a hologram, and more particularly to a hologram reproducing apparatus that uses coherent light such as laser light as a light source for reproduction.

  When reproducing the image recorded on the hologram, if the reproduction wavelength is not a single wavelength, the position of the reproduction image differs depending on the plurality of wavelengths, and therefore the image becomes blurred and a clear image cannot be reproduced. Even when the reproduction angle is deviated from the reference light at the time of hologram production, the position of the reproduction image differs depending on the incident angle, so that a clear reproduction image cannot be obtained. In order to reproduce a reproduced image clearly, it is necessary to enter light having the same wavelength as that at the time of hologram shooting and to make light incident at the same incident angle as that of reference light at the time of hologram recording. In addition, when the reproduced image has a depth, blurring increases as the distance from the surface of the hologram increases depending on the width of the reproduction wavelength and the deviation of the incident angle.

  In a general hologram reproducing method, an image is reproduced using white light as reproduction illumination light in order to improve versatility. In such a reproduction method using white light, a method of narrowing the wavelength region by providing a specific wavelength transmission filter in order to prevent blurring of an image is known (Patent Document 1).

  However, when a specific wavelength transmission filter is used as described in Patent Document 1, light other than the specific wavelength of white light serving as a light source is cut, so that the light use efficiency is low. As a result, power consumption becomes high and precise angle control becomes difficult.

  On the other hand, it is conceivable to use laser light as reproduction illumination light. Since laser light has a single wavelength, it has high light utilization efficiency and low power consumption, and because it has excellent directivity and convergence, it is easy to control the incident angle, and a clear reproduction image can be obtained. Is possible. However, when laser light is used as a light source, speckle noise due to high coherence occurs, which makes it difficult to view an image.

  Speckle noise is speckled image noise that occurs when scattered light from minute irregularities on the surface of an irradiation object interferes when coherent light such as laser light is used as the light source, and this reduces the visibility of the observer It is known to let In order to reduce such speckle noise, various attempts have been made, such as vibrating the diffuser plate through which laser light passes, expanding the wavelength spectrum of the laser spectrum, and vibrating the screen itself that is the target of laser light irradiation. ing. As an attempt to reduce such speckle noise, Patent Document 2 discloses a non-speckle display device that reduces speckle noise by rotating a diffusion element through which coherent light passes.

JP 2007-264300 A Japanese Patent Laid-Open No. 6-208089 JP-A-6-301322

In the configuration disclosed in Patent Document 2, there are problems such as the loss of scattering components due to the use of the scattering plate and the need to secure a space by a large rotating mechanism. There is no description of how much it actually is, and there remains a problem with effectiveness.

  The present invention proposes a new speckle noise reduction method in view of the problem of speckle noise generation during hologram reproduction. Specifically, a method for reducing speckle noise by temporally changing the incident angle of light with respect to a hologram for reproducing an image is employed.

  Therefore, the hologram reproducing apparatus according to the present invention forms a diffused light by diffusing the scan light formed by the light source unit by changing the irradiation position of the coherent light with time and the scan light formed by the light source unit. An image reproducing hologram that records an image using the diffused light as reference light, and records the diffused light formed by the light diffusing element as reproduction illumination light on the image reproducing hologram. The reproduced image is reproduced.

  Furthermore, in the hologram reproducing apparatus according to the present invention, the light source unit includes a scanning device that forms scanning light by temporally deflecting a beam emitted from a coherent light source. Is.

  Furthermore, in the hologram reproducing apparatus according to the present invention, the image reproducing hologram is any one of a transmission hologram and a reflection hologram.

  Furthermore, in the hologram reproducing apparatus according to the present invention, the image reproducing hologram is a transmission hologram, and the light diffusing element is disposed so as not to be overlapped with an image reproduced by the image reproducing hologram. It is characterized by this.

  Furthermore, in the hologram reproducing apparatus according to the present invention, the image reproducing hologram is an image hologram.

  Furthermore, in the hologram reproducing apparatus according to the present invention, the light diffusing element is a diffusing plate.

  Furthermore, in the hologram reproducing apparatus according to the present invention, the light diffusing element is a hologram.

  Furthermore, in the hologram reproducing apparatus according to the present invention, the light diffusing element is a lens array.

  Furthermore, in the hologram reproducing apparatus according to the present invention, the diffused light formed by the light diffusing element is conjugate with the reference light used when recording the image reproducing hologram.

  As described above, according to the hologram reproducing apparatus of the present invention, an image can be obtained by using diffused light whose incident angle changes with time as reproduction illumination light with respect to an image reproducing hologram using diffused light as reference light at the time of recording. By reproducing, the speckle pattern observed together with the reproduced image is temporally changed and averaged, whereby the speckle noise can be made invisible.

The figure which shows the mode of recording of the hologram for image reproduction which concerns on embodiment (Example 1) of this invention. The figure which shows the structure of the hologram reproduction apparatus which concerns on embodiment (Example 1) of this invention. The figure which shows the structure of the light source part which concerns on embodiment of this invention. The figure which shows a mode that the diffused light which injects into the hologram for image reproduction which concerns on embodiment of this invention changes temporally. The figure which shows the mode of recording of the light-diffusion element (hologram) which concerns on embodiment (Example 1) of this invention. The figure which shows the mode of recording of the hologram for image reproduction which concerns on embodiment (Example 2) of this invention. The figure which shows the structure of the hologram reproducing apparatus which concerns on other embodiment (Example 2) of this invention. The figure which shows the mode of recording of the light-diffusion element (hologram) which concerns on embodiment (Example 2) of this invention. The figure which shows the mode of recording of the hologram for image reproduction which concerns on other embodiment (Example 3) of this invention. The figure which shows the structure of the hologram reproducing apparatus which concerns on other embodiment (Example 3) of this invention. The figure which shows the mode of recording of the hologram for image reproduction which concerns on embodiment (Example 4) of this invention. The figure which shows the structure of the hologram reproducing apparatus which concerns on other embodiment (Example 4) of this invention. The figure which shows the mode of recording of the hologram for image reproduction which concerns on embodiment (Example 5) of this invention. The figure which shows the structure of the hologram reproducing apparatus which concerns on other embodiment (Example 5) of this invention.

  Now, the hologram reproducing apparatus according to the present invention will be described by taking some embodiments as examples (examples).

[Example 1]
FIG. 1 is a diagram illustrating a recording state of an image reproducing hologram according to an embodiment of the present invention, and FIG. 2 is a diagram illustrating a configuration of a hologram reproducing apparatus according to an embodiment of the present invention. In this embodiment, a transmission hologram is used as the image reproducing hologram 1, and an image to be reproduced is observed before the image reproducing hologram 1 with respect to the observer. .

  As shown in FIG. 2, the hologram reproducing apparatus according to this embodiment includes an image reproducing hologram 1, a diffusion plate 2 as a light diffusing element, and a light source unit 4 that scans coherent light.

  FIG. 1 shows a method for recording (creating) an image reproducing hologram 1. The image reproducing recording material 11 is simultaneously irradiated with the recording diffused light R from the diffusion plate image reproducing hologram 3a (recording diffusing element) and the object light Ob from the three-dimensional model to be recorded on the same surface. Is done. In the present embodiment, a reflection hologram is used as the diffusion plate image reproduction hologram 3a for forming the recording diffused light R. A method of creating the diffusion plate image reproduction hologram 3a will be described later.

The object light Ob is formed by irradiating the solid model with object illumination light (not shown). In the present embodiment, the same laser beam is branched into two as a light source for forming the recording diffused light R and a light source for forming the object light Ob.

  In the recording material 11 for image reproduction, interference fringes generated by the recording diffused light R (reference light) and the object light Ob that are simultaneously irradiated are recorded. The image reproducing recording material 11 on which the interference fringes are recorded becomes the image reproducing hologram 1 after appropriate post-processing such as development or heating, ultraviolet irradiation or the like. As the image reproducing hologram 1, it is preferable to use a volume hologram. Since the volume hologram generates diffracted light by interference fringes formed therein, it is not necessary to provide unevenness on the surface, and speckle noise that is secondarily generated in the hologram can be suppressed. Furthermore, since the volume hologram can set the diffraction efficiency high and can effectively suppress the 0th-order transmitted light, the image intended by the designer can be reproduced accurately.

  FIG. 2 shows a reproduction configuration of the image reproduction hologram 1 created in FIG. In the present embodiment, the diffusion plate 2 is used to form reproduction diffused light L (reproduction illumination light) for reproducing the image reproduction hologram 1. This diffusing plate 2 has a position where the diffusing plate image 3i is formed at the time of recording, that is, the positional relationship between the diffusing plate image 2 and the image reproducing hologram 1 in terms of the diffusing plate image 3i and the image reproducing recording material in FIG. 11 are arranged in a positional relationship. In the present embodiment, the diffusing plate 2 corresponds to the light diffusing element in the present invention.

  In this embodiment, the diffusion plate 2 is used as the light diffusion element. However, the light diffusion element in the present invention has the same characteristics as the diffusion plate 2, that is, the reproduction diffused light L emitted from the light diffusion element is If the optical element has a characteristic of illuminating the image reproduction hologram 1 to the extent that it can be reproduced (preferably illuminating the entire area of the image reproduction hologram 1), it is configured by arranging fine lenses in an array. A lens array or a normal diffusing plate may be used.

  The diffusing plate 2 is irradiated with the coherent scanning light S formed by the light source unit 4. FIG. 3 shows a configuration example of the light source unit 4. In this example, the light source unit 4 includes a laser light source 41 as a coherent light source and a scanning mirror device 42. The scanning mirror device 42 is a two-dimensional scanner manufactured using MEMS (Micro Electro Mechanical Systems) technology, and corresponds to the scanning device in the present invention. The scanning mirror device 42 resonates and oscillates around the X axis and the Y axis, thereby forming the scanning light S for two-dimensionally scanning the irradiation target surface.

  The light source unit 4 that forms the scanning light S by changing the irradiation position with time is not limited to such a form, and may be composed of two scanning mirror devices, or may have coherent light having a planar shape. Appropriate forms such as one-dimensional scanning can be employed. Further, as the scanning device for forming the scanning light S, in addition to the reflection type device, a refraction type device using a prism, a diffraction grating, or the like may be employed.

  In this embodiment, the diffusing plate 2 is scanned two-dimensionally as a light diffusing element. However, when a hologram is used as the light diffusing element, for example, the reproduction illumination light L from each point of the hologram is It becomes possible to irradiate the entire area of the hologram 1 for image reproduction, and the scanning range of the scanning light S can be freely selected, and the cross section of the scanning light S can be freely shaped. Can be adopted.

At the time of reproduction, first, the scanning light S is irradiated from the light source unit 4 to the diffusion plate 2. The diffusing plate 2 diffuses the scanning light S at each point so as to cover at least the entire area of the image reproducing hologram 1 to form the reproducing diffused light L. The reproduction diffused light L generated by the diffusion plate 2 functions as reproduction illumination light for the image reproduction hologram 1. As shown in FIG. 2, the reproduction diffused light L is conjugate (the same direction and the opposite direction) with the recording diffused light R forming the diffusion plate image 3 i at the time of recording the image reproduction hologram 1. In this embodiment, since a transmission hologram is used for the image reproduction hologram 1, the image reproduction hologram 1 diffracts the reproduction light I on the surface opposite to the surface receiving the reproduction diffused light L, thereby reproducing the image. A reproduced image is formed in front of the hologram 1 for use.

  In the present invention, in particular, by using the scanning light S, as a result, the angle at which the reproduction diffused light L from the light diffusing element (the diffusion plate 2 in this embodiment) enters the image reproduction hologram 1 changes with time. Is done. Therefore, the fixed wavefront information generated in the light diffusing element is temporally changed and averaged in the image reproducing hologram 1, and an image quality equivalent to that obtained when a non-coherent light source is used can be obtained.

  FIG. 4 is a diagram showing the temporal change of the reproduction diffused light L. FIG. Focusing on one point of the image reproduction hologram 1 as shown in the figure, the reproduction diffused light L incident on the image reproduction hologram 1 has an incident angle of t1, t2, t3, t2, t1,. Changes. Since the wavefronts scattered with respect to the incident angles from different angles change with time, the spatial interference patterns of light scattered from a plurality of points also change with time. Accordingly, when the image reproducing hologram 1 is observed, the speckle pattern observed together with the reproduced image also fluctuates with time, and is averaged and invisible. As a result, it is possible to clearly observe an image with reduced speckle noise while reproducing with coherent light.

  FIG. 5 is a diagram showing a recording method of the diffusion plate image reproduction hologram 3a as a recording diffusion element used when recording the image reproduction hologram 1 in FIG. At the time of recording, one of the two laser beams is irradiated from the back surface of the diffusion plate 22, and the diffused light is incident on the front surface of the diffusion plate 22 as object light B from one surface of the recording material 21. One is simultaneously incident as reference light C from the other surface of the recording material 21. Note that the divergence angle of the reference light C is not particularly limited as long as the reproduction illumination light conjugate with the reference light C can be generated during reproduction. Moreover, it is preferable to use the diffusion plate 22 and the diffusion plate 2 used at the time of reproduction having the same or equivalent characteristics.

  Diffused light from the diffusion plate 22 as the object light B and the reference light C are recorded in the recording material 21 by forming interference fringes. The recording material 21 becomes a diffusion plate image reproduction hologram 3a after appropriate post-processing such as development or heating and ultraviolet irradiation. The diffusing plate image reproduction hologram 3a has the same wavelength as the laser light used at the time of recording, and enters the light (conjugate) that travels in the opposite direction to the reference light C at the time of recording as reproducing illuminating light. The diffusion plate image 3i is reproduced at the position where the 22 has been arranged.

[Example 2]
6 and 7 are diagrams for explaining a hologram reproducing apparatus according to another embodiment. FIG. 6 shows a state of recording an image reproducing hologram, and FIG. 7 shows a structure of the hologram reproducing apparatus. FIG. In the second embodiment, a reflection hologram is used as the image reproducing hologram 1, and an image to be reproduced is observed in front of the image reproducing hologram 1 with respect to the observer. .

As shown in FIG. 6, in this embodiment, a transmission hologram is used as the diffusion plate image reproduction hologram 3a (recording diffusion element) for forming the recording diffused light R. The diffusion plate image reproduction hologram 3a emits recording diffused light R so as to reproduce the diffusion plate image 3i. The recording diffused light R is used as reference light for recording an image on the image reproducing recording material 11. The recording method of the diffusion plate image reproduction hologram 3a will be described later. The recording diffused light R (reference light) generated from the diffusion plate image reproducing hologram 3a and the object light Ob from the three-dimensional model are simultaneously irradiated from the opposite surfaces to the image reproducing recording material 11, respectively. Thus, both interference fringes are recorded on the image reproducing recording material 11. The image reproducing recording material 11 on which the interference fringes are recorded becomes the image reproducing hologram 1 after appropriate post-processing such as development or heating, ultraviolet irradiation or the like.

  The image reproducing hologram 1 created in this way is reproduced with the configuration shown in FIG. That is, with respect to the image reproducing hologram 1, the diffusing plate 2 is arranged at a position where the diffusing plate image 3i is reproduced at the time of recording. The light diffusing plate 2 is irradiated with scanning light S having the same wavelength as that during recording from the light source unit 4. The configuration of the light source unit 4 is the same as that of the first embodiment. The diffuser plate 2 uses a diffused diffused light L generated from each point thereof having a diffusion characteristic that illuminates at least the entire area of the image reproducing hologram 1, so that the light source unit 4 can be any of the diffuser plates 2. Even when the point is scanned, a reproduced image is formed at the same position from the image reproducing hologram 1.

  The scanning light S generated by the light source unit 4 is incident from the back surface of the diffusion plate 2, and the reproduction diffused light L is emitted from the front surface of the diffusion plate 2. Thus, in this embodiment, the diffusion plate 2 functions as a light diffusing element, and the reproduction diffused light L from the diffusion plate 2 becomes the reproduction illumination light of the image reproduction hologram 1. Similarly to Example 1, also in this embodiment, the scanning light S from the light source unit 4 enters the diffusion plate 2. Therefore, the reproduction diffused light L incident on the image reproduction hologram 1 changes in incident angle with time as in the first embodiment, and as a result, an image with reduced speckle noise is given to the observer E. It will be observed.

  FIG. 8 is a diagram showing a recording method of the diffusion plate image reproduction hologram 3a as a recording diffusion element used when recording the image reproduction hologram 1 in FIG. At the time of recording, one of the two laser beams is irradiated from the back surface of the diffusion plate 22, the light diffused in front of the diffusion plate 22 is the object light B, and the other is the reference light C. Simultaneous incidence from the same surface. Also in this embodiment, it is not necessary to limit the divergence angle of the reference light C as long as the reproduction illumination light conjugate with the reference light C can be generated during reproduction.

  Diffused light from the diffusion plate 22 as the object light B and the reference light C are recorded in the recording material 21 by forming interference fringes. The recording material 21 becomes a diffusion plate image reproduction hologram 3a after appropriate post-processing such as development or heating and ultraviolet irradiation. The diffusing plate image reproduction hologram 3a has the same wavelength as the laser light used at the time of recording, and enters the light (conjugate) that travels in the opposite direction to the reference light C at the time of recording as reproducing illuminating light. The diffusion plate image 3i is reproduced at the position where the 22 has been arranged.

[Example 3]
9 and 10 are diagrams for explaining a hologram reproducing apparatus according to another embodiment. FIG. 9 shows a state of recording an image reproducing hologram, and FIG. 10 shows a structure of the hologram reproducing apparatus. FIG. In the third embodiment, a transmission hologram is used as the image reproduction hologram 1, and an image to be reproduced is observed with respect to an observer deeper than the image reproduction hologram 1. .

  As shown in FIG. 9, the recording diffused light R (reference light) from the diffusion plate 3b (recording diffusion element) and the object light Ob from the three-dimensional model are applied to the same surface of the image reproducing recording material 11. Are respectively incident. Interference fringes of the recording diffused light R and the object light Ob generated in the image reproducing recording material 11 are recorded. The image reproducing recording material 11 becomes an image reproducing hologram 1 after appropriate post-processing such as development or heating and ultraviolet irradiation.

At the time of reproduction, as shown in FIG. 10, the diffusion plate 2 is arranged with respect to the image reproduction hologram 1 so as to have the same positional relationship as the diffusion plate 3b used at the time of recording. The diffusing plate 2 is arranged so as not to be overlapped with the reproduced image by the image reproducing hologram 1. Specifically, it is realized by shifting the optical axis of the image reproduction hologram 1 and the optical axis of the diffusion plate 2 as shown in the figure. If the diffusing plate 2 is arranged at a position overlapping the reproduced image, speckle noise generated in the diffusing plate 2 is simultaneously observed in the reproduced image, making it difficult to view the reproduced image.

  Scanning light S from the light source unit 4 is incident on the diffusion plate 2, and reproduction diffused light L is emitted from the front surface of the diffusion plate 2. The light source unit 4 in this embodiment is the same as that described above, and forms scanning light by temporally changing the irradiation position of the coherent light. Further, as in the above-described embodiment, the diffuser plate 2 has a diffusion characteristic that the reproduction diffused light L generated from each point illuminates at least the entire area of the image reproduction hologram 1.

  The observer E observes the reproduction image (virtual image) on the back side of the image reproduction hologram 1 by placing the viewpoint on the opposite side of the image reproduction hologram 1 to the side irradiated with the reproduction diffused light L. It becomes possible to do. Also in the third embodiment, since the reproduction diffused light L irradiated to the image reproduction hologram 1 changes in incident angle with time, an image with reduced speckle noise is provided as a result. .

  Also in this embodiment, similarly to the above-described embodiment, the diffusing plate 2 as the light diffusing element is irradiated with the scanning light S that changes its direction with time. Further, as described in the second embodiment, the diffusion plate 2 has a diffusion characteristic in which the reproduction diffused light L generated from each point illuminates at least the entire area of the image reproduction hologram 1. Also in the third embodiment, since the reproduction diffused light L irradiated to the image reproduction hologram 1 changes in incident angle with time, an image with reduced speckle noise is provided as a result. .

[Example 4]
FIGS. 11 and 12 are diagrams for explaining a hologram reproducing apparatus according to another embodiment. FIG. 11 shows a state of recording an image reproducing hologram, and FIG. 12 shows a structure of the hologram reproducing apparatus. FIG. In the fourth embodiment, a reflection hologram is used as the image reproducing hologram 1, and an image to be reproduced is observed to the back of the image reproducing hologram 1 with respect to the observer. .

  As shown in FIG. 11, recording diffused light R (reference light) from the diffusion plate 3b and object light Ob from the three-dimensional model are incident on different surfaces of the image reproducing recording material 11, respectively. Interference fringes of the recording diffused light R and the object light Ob generated in the image reproducing recording material 11 are recorded. The image reproducing recording material 11 becomes an image reproducing hologram 1 after appropriate post-processing such as development or heating and ultraviolet irradiation.

  At the time of reproduction, as shown in FIG. 12, the diffusion plate 2 is arranged with respect to the image reproduction hologram 1 so as to have the same positional relationship as the diffusion plate 3b used at the time of recording. Scanning light S from the light source unit 4 is incident on the diffusion plate 2, and reproduction diffused light L is emitted from the front surface of the diffusion plate 2. The light source unit 4 in this embodiment is the same as that described above, and forms scanning light by temporally changing the irradiation position of the coherent light. Further, as in the above-described embodiment, the diffuser plate 2 has a diffusion characteristic that the reproduction diffused light L generated from each point illuminates at least the entire area of the image reproduction hologram 1. Also in the fourth embodiment, since the reproduction diffused light L irradiated to the image reproduction hologram 1 changes in incident angle with time, an image with reduced speckle noise is provided as a result. .

[Example 5]
FIGS. 13 and 14 are diagrams for explaining a hologram reproducing apparatus according to another embodiment. FIG. 13 shows a state of recording an image reproducing hologram, and FIG. 14 shows a structure of the hologram reproducing apparatus. FIG. In the fifth embodiment, an image hologram is used as the image reproduction hologram 1, and a reproduced image is partially overlapped with the image reproduction hologram 1 or in the vicinity of the image reproduction hologram 1. The embodiment is observed.

  As shown in FIG. 13, during recording, the recording diffused light R from the diffusion plate 3b is used as reference light. On the other hand, since the three-dimensional image to be recorded is located inside or near the image reproducing recording material 11, recording with a three-dimensional model becomes difficult. Therefore, a stereoscopic image is formed inside or in the vicinity of the image reproducing recording material 11 by using the object beam Ob from the recording image reproducing hologram 5. The recorded image reproduction hologram 5 is a transmission hologram in which a stereoscopic image is recorded by a normal recording method, and is recorded by causing the reference light conjugate with the reproduction illumination light L2 to interfere with the object light of the stereoscopic image. It is a thing. In this way, by simultaneously irradiating the recording diffused light R on one surface of the image reproducing recording material 11 and the object light Ob on the other surface, an interference fringe is formed in the image reproducing recording material 11, and the information of the interference fringe To be recorded. The image reproducing recording material 11 becomes an image reproducing hologram 1 after appropriate post-processing such as development or heating and ultraviolet irradiation.

  As shown in FIG. 14, the diffusion plate 2 is installed with respect to the image reproducing hologram 1 so as to have the same positional relationship as the diffusion plate 3 b used at the time of recording. Scanning light S from the light source unit 4 is incident on the diffusion plate 2, and reproduction diffused light L (reproduction illumination light) is irradiated from the front surface of the diffusion plate 2. The light source unit 4 in this embodiment irradiates the diffusing plate 2 as a light diffusing element with scanning light as described above. Also in the fifth embodiment, since the reproduction diffused light L irradiated to the image reproduction hologram 1 changes in incident angle with time, an image with reduced speckle noise is provided as a result. .

  In such an image type hologram, the reproduced image to be formed is located close to the image reproducing hologram 1, so that the influence on the error of the reproduced diffused light L is small. Therefore, it is possible to provide a reproduced image with less blur even if the arrangement position, the arrangement angle, the irradiation characteristic, etc. of the diffusion plate 2 used at the time of reproduction do not exactly match those at the time of recording. It becomes possible to give a degree of freedom to the configuration.

  As described above, in the recording of the first to fifth embodiments, the interference fringes are recorded (interference exposure) by causing the object light Ob and the recording diffused light R to interfere with each other. However, the interference fringes calculated by the computer are used. A so-called computer generated hologram may be employed in which the image is directly recorded on the image reproducing recording material 11.

Table 1 shows speckle contrast under various conditions. (1) and (2) are for comparison, and are measurement results in the case where only a laser parallel light is used and a monochromatic LED is used. (3) and (4) are measurement results according to the embodiment of the present invention, and are measurement results when a volume hologram and a computer generated hologram are used as the light diffusing element, respectively. The speckle contrast is expressed by the following formula (1). For the measurement, a DPSS laser (532 nm) was used as a light source and projected onto a hologram for image reproduction. The volume hologram used in this measurement was prepared so that the diffusion angle, that is, the apex angle of the cone formed by the light beam incident on one point of the image reproduction hologram was 20 °. As a recording material for each hologram, a photopolymer material having sensitivity at 532 nm (the material described in Example 1 of Patent Document 3 cited as the prior art document) is used.
SC = σ / I × 100
= 1 / (Modes) ^0.5 x 100 (1)
SC: speckle contrast σ: standard deviation of luminance I: luminance average value Modes: number of patterns (number of statistically independent speckles)

  Note that the present invention is not limited to these embodiments, and embodiments configured by appropriately combining the configurations of the respective embodiments also fall within the scope of the present invention.

DESCRIPTION OF SYMBOLS 11 ... Image reproduction recording material 1 ... Image reproduction hologram 2 ... Diffusion plate (light diffusion element)
21 ... (for diffusion plate image reproduction) recording material 22 ... diffusion plate 3a ... diffusion plate image reproduction hologram (recording diffusion element)
3b ... Diffusion plate (diffusing element for recording)
3i ... Diffuser image 4 ... Light source 41 ... Laser light source (coherent light source)
42 ... Scanning mirror device (scanning device)
5 ... Hologram for reproducing recorded image

Claims (9)

A light source unit that forms scanning light by temporally changing the irradiation position of the coherent light;
A light diffusing element for diffusing scanning light formed by the light source unit to form diffused light;
An image reproducing hologram for recording an image using diffused light as reference light, and
A hologram reproducing apparatus, which reproduces an image recorded on the image reproducing hologram by using diffused light formed by the light diffusing element as reproduction illumination light. The hologram reproducing apparatus according to claim 1, wherein the light source unit includes a scanning device that forms scanning light by temporally deflecting a beam emitted from a coherent light source. The hologram reproducing apparatus according to claim 1, wherein the image reproducing hologram is any one of a transmission hologram and a reflection hologram. The image reproducing hologram is a transmission hologram,
The hologram reproducing apparatus according to claim 3, wherein the light diffusing element is disposed so as not to be overlapped with an image reproduced by the image reproducing hologram. The hologram reproducing apparatus according to claim 4, wherein the image reproducing hologram is an image hologram. The hologram reproducing apparatus according to claim 1, wherein the light diffusing element is a diffusing plate. The hologram reproducing apparatus according to claim 1, wherein the light diffusing element is a hologram. The hologram reproducing apparatus according to claim 1, wherein the light diffusing element is a lens array. The hologram according to any one of claims 1 to 8, wherein the diffused light formed by the light diffusing element is conjugate with reference light used when recording the image reproducing hologram. Playback device.

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