JP5982993B2 - Hologram manufacturing apparatus and hologram manufacturing method - Google Patents

Description

  The present invention relates to a hologram production apparatus and a hologram production method for producing a hologram.

  In an optical projection device (projector), it is important to uniformly illuminate a screen with light emitted from a light source. As a method for realizing uniform illumination of the screen, a three-liquid crystal type using a fly-eye lens, an integrator rod type for DMD (Digital Micromirror Device), and the like have been proposed.

  However, with these methods, there is a large limitation on the optical arrangement determined by the focal length of the constituent lenses when performing rectangular illumination according to the shape of the liquid crystal display, and the degree of design freedom is low and the number of parts is also large. There is.

  In the integrator rod system, if dust or scratches are present on the rod end surface, an image is formed on the micro display as an image, so it is necessary to keep the end surface clean.

  On the other hand, optical projectors generally illuminate a spatial light modulator such as a liquid crystal display using an illumination device consisting of a white light source such as a high-pressure mercury lamp, and enlarge and project the resulting modulated image on a screen with a lens. Adopted. However, a high-intensity discharge lamp such as a high-pressure mercury lamp has a relatively short life, and when used in an optical projector or the like, it is necessary to frequently replace the lamp.

  Thus, a method using a coherent light source such as a laser has been proposed. For example, semiconductor lasers widely used in the industry have a much longer lifetime than high-intensity discharge lamps such as high-pressure mercury lamps. Further, since it is a light source capable of generating light of a single wavelength, there is an advantage that a spectroscopic device such as a dichroic mirror becomes unnecessary, and the entire device can be downsized.

  However, a method using a coherent light source such as a laser beam has a new problem such as generation of speckle. A speckle is a speckled pattern that appears when a scattering surface is irradiated with coherent light such as laser light. When speckle is generated on a screen, it is observed as a spotted brightness unevenness and observed. It becomes a factor having a physiological adverse effect on the person. The reason why speckles occur when coherent light is used is that coherent light reflected by each part of a scattering reflection surface such as a screen interferes with each other because of its extremely high coherence. . For example, in the following Non-Patent Document 1, detailed theoretical considerations regarding the generation of speckle are made. Further, in Patent Document 3 below, the speckle is reduced by irradiating the scattering plate with laser light, guiding the scattered light obtained therefrom to the spatial light modulator, and rotating the scattering plate with a motor. Technology is disclosed.

  As described above, in the system using the coherent light source, a problem inherent to the generation of speckles occurs, and thus a technique for suppressing the generation of speckles has been proposed. For example, in Patent Document 3 below, the speckle is reduced by irradiating a scattering plate with laser light, guiding the scattered light obtained therefrom to a spatial light modulator, and rotating the scattering plate with a motor. Technology is disclosed.

  Based on the above points, the inventors of the present invention have made extensive research and constructed an irradiation device using a coherent light source and a hologram recording medium. The light modulator is illuminated by the irradiation device and is generated by the light modulator. The inventors have invented a projection device that projects a modulated image.

  In this projection apparatus, when the hologram recording medium is irradiated with coherent light, it is desirable to diffuse the coherent light with a uniform amount of light from the entire area of the hologram recording medium. If it is not uniform, an area where brightness protrudes and becomes brighter in the illumination area, and brightness unevenness occurs in the illumination area.

  Patent Document 4 below discloses a technique for adjusting a light intensity distribution by arranging a phase mask on an object surface that emits object light used when forming interference fringes on a hologram recording medium.

JP 2009-282083 A JP 2008-224760 A Japanese Patent Laid-Open No. 6-208089 Japanese Patent No. 4138164

Speckle Phenomena in Optics, Joseph W. Goodman, Roberts & Co., 2006

  The illuminance on the recording target surface of the interference fringe when recording the interference fringe on the hologram recording material decreases as the distance between the object surface irradiated with object light and the recording target surface increases. This is because light is diffused in areas other than the recording target surface. Therefore, when the distance between the object surface and the recording target surface is increased, the balance between the object light and the reference light is lost, and high-quality interference fringes are not formed, and a desired diffraction efficiency cannot be obtained.

  Further, depending on the hologram recording material, there is a possibility that good quality interference fringes cannot be formed due to insufficient light quantity.

  Furthermore, if the amount of object light is increased to obtain sufficient diffraction efficiency, the amount of reference light must be increased, and the overall amount of light when recording interference fringes increases.

  In addition, the illuminance is improved by changing the object light irradiated from the object surface to a light beam with high directivity, but the light beam does not spread, so that the area where the interference fringes are formed is reduced.

In Patent Document 4 described above, the illuminance distribution is adjusted by providing a phase mask on the Fourier transform plane corresponding to the object plane. To achieve this, a phase mask such as an SLM that is a spatial light modulator is used. This is necessary, and the configuration of the hologram production apparatus becomes complicated.
The present invention has been made in order to solve the above-described problems of the prior art, and generates high-quality interference with a hologram recording material by generating reproduction light having a uniform intensity distribution while increasing the use efficiency of object light. A hologram manufacturing apparatus and a hologram manufacturing method capable of forming stripes are provided.

In order to solve the above problems, in one aspect of the present invention, an object surface that diffuses object light related to object information recorded on a hologram recording material;
A mapping optical system for mapping the object plane onto a predetermined image plane;
An aperture that allows a portion of the object light that has passed through the mapping optical system to pass therethrough, and a diaphragm member that allows rays from the entire area of the aperture to reach each point on the image plane,
The hologram recording material is disposed in the vicinity of an image plane of the mapping optical system so that interference fringes are formed by interference between the reference light and the object light that has passed through the aperture of the diaphragm member. A hologram production apparatus is provided.

  According to the present invention, it is possible to generate reproduction light having a uniform intensity distribution while improving the utilization efficiency of object light, and form high-quality interference fringes on the hologram recording material.

The block diagram which shows the whole structure of the hologram production apparatus which concerns on one Embodiment of this invention. FIG. 2 is a diagram schematically illustrating a passage path of a light beam on the object light side when forming interference fringes in the hologram manufacturing apparatus 10 of FIG. The figure which shows the simulation result of illumination intensity distribution. The figure which shows illuminance distribution when a diffusion angle is 20 degree | times. The figure which shows the illumination intensity distribution at the time of making a diffusion angle into 15 degree | times. FIG. 3 is a diagram for explaining a method for generating a reproduced image using interference fringes recorded on a hologram recording medium 55 manufactured by the hologram manufacturing apparatus 10 of FIG. 1. The block diagram which shows an example of the projection apparatus comprised using the hologram recording medium 55 produced with the hologram production apparatus 10 of FIG. The figure explaining the scanning path | route of the scanning device 65. FIG. The figure which shows the example which rotates the mirror device 66 to a biaxial direction.

  Hereinafter, embodiments of the present invention will be described in detail. FIG. 1 is a block diagram showing the overall configuration of a hologram manufacturing apparatus according to an embodiment of the present invention. 1 includes a coherent light source 11, a beam splitter 12, an object optical system 13, a diffuser plate 14, a mapping optical system 15, a diaphragm member 16, a reference optical system 17, and a reflection mirror 18. , 19.

  The coherent light source 11 emits coherent light. An example of the coherent light source 11 is a laser light source. When the monochromatic hologram recording medium 55 is formed, only one coherent light source 11 is required. However, when the color hologram recording medium 55 is formed, a plurality of coherent light sources 11 having emission wavelengths corresponding to the respective colors are used. Is required. In the present specification, the recording surface 55a having interference fringes recorded thereon is called a hologram recording medium 55, and before the interference fringes are recorded is called a hologram recording material 58, and the interference fringes of the hologram recording material 58 are recorded. The target surface is referred to as a recording target surface 58a.

  For example, when a red interference fringe, a green interference fringe, and a blue interference fringe are formed along the surface direction of the recording target surface 58a of the hologram recording material 58, a coherent light having a red emission wavelength is formed. It is necessary to provide a light source 11, a coherent light source 11 having a green emission wavelength, and a coherent light source 11 having a blue emission wavelength.

  The plurality of color interference fringes are not necessarily formed along the surface direction of the recording surface 55a, and may be formed as separate layers in the depth direction of the recording surface 55a.

  The beam splitter 12 branches the coherent light from the coherent light source 11 into two coherent lights (first coherent light and second coherent light). The first coherent light is used for generating object light, and the second coherent light is used for generating reference light.

  The object optical system 13 converts the first coherent light into a parallel light beam according to the size of the object surface 14 a on the diffusion plate 14. This parallel light beam is incident on the diffusion plate 14.

  The diffuser plate 14 generates diffused light obtained by diffusing the parallel light flux from the object optical system 13, and the diffused light is incident on the mapping optical system 15. The diffusion surface of the diffusion plate 14 corresponds to the object surface 14a, and the diffused light diffused from the diffusion plate 14 corresponds to the object light.

  The mapping optical system 15 includes a first lens group 15a and a second lens group 15b arranged on the optical axis. The object plane 14a is arranged at the position of the focal length of the first lens group 15a. The first lens group 15a receives object light diffused from the object surface 14a (diffusion surface) and converts it into parallel light. The second lens group 15b maps the object light that has passed through the first lens group 15a to a predetermined image plane position. Here, the predetermined image plane position is a focal position of the second lens group 15b, and the hologram recording material 58 is disposed in the vicinity of the focal position. Each of the first lens group 15a and the second lens group 15b is composed of one or more lenses. The object plane 14a is disposed at the front focal position of the first lens group 15a, and the second lens group 15b is disposed at the rear focal position of the first lens group 15a. The first lens group 15a and the second lens group 15b may be optical members that have a positive refractive power and focus, and may be, for example, a concave mirror.

  The diaphragm member 16 allows part of the object light that has passed through the mapping optical system 15 to pass therethrough. The object light that has passed through the opening of the diaphragm member 16 is incident on the recording target surface 58 a of the hologram recording material 58. The aperture member 16 is arranged so that the light rays from the entire area of the aperture reach each point on the image plane described above.

  The reference optical system 17 converts the second coherent light into reference light of a parallel light beam according to the size of the recording target surface 58a of the hologram recording material 58 and makes it incident on the recording target surface 58a.

  Thereby, on the recording target surface 58 a of the hologram recording material 58, the object light that has passed through the opening of the aperture member 16 interferes with the reference light generated by the reference optical system 17 to form interference fringes.

  Here, the contrast of the interference fringes is determined by the ratio of the light amount of the object light and the reference light. When the amount of object light is lower than the amount of reference light, the contrast of interference fringes is reduced. The object light is light diffused by the diffusing plate 14, and it is difficult to control the amount of diffused light so that it is uniform over the entire diffusion region. Therefore, when the object light diffused by the diffusing plate 14 is directly incident on the hologram recording material 58 to form an interference fringe, the amount of the object light is not uniform depending on the location, so that the contrast of the interference fringe is lowered. .

  On the other hand, in the present embodiment, only the object light that has passed through the opening of the diaphragm member 16 out of the object light diffused by the diffusion plate 14 is incident on the hologram recording material 58, so that the recording of the hologram recording material 58 is performed. The amount of object light on the target surface 58a can be made uniform, and the interference fringe contrast is improved.

  The central portion of the aperture of the diaphragm member 16 is provided on the optical axis of the mapping optical system 15, and the object light passing through the aperture of the diaphragm member 16 is in the entire area of the object light that has passed through the mapping optical system 15. Thus, the light flux has a high uniformity of light quantity. That is, by providing the diaphragm member 16, it is possible to remove a light beam having a low light quantity on the peripheral edge side from the object light. Therefore, object light having a high uniformity in the amount of light is incident on the recording target surface 58 a of the hologram recording material 58.

  In the present embodiment, the mapping optical system 15 is disposed between the diffusion plate 14 and the diaphragm member 16. This mapping optical system 15 plays a role of converging the object light diffused by the diffusion plate 14 to some extent and guiding it in the direction of the diaphragm member 16. Therefore, by providing the mapping optical system 15, it is possible to increase the amount of object light passing through the opening of the diaphragm member 16 and improve the quality of interference fringes formed on the hologram recording medium 55. More specifically, the object light is converged by the mapping optical system 15 and passes through the opening of the diaphragm member 16. Light rays from the entire area of the aperture reach each point on the image plane of the mapping optical system 15. The diffusion plate 14 itself used in the present embodiment only needs to have a small diffusion region, and compared with the case where the light diffused by the diffusion plate 14 is directly used as the recording light of the hologram recording material 58, the light use efficiency is lost. Less.

  The mapping optical system 15 includes a first lens group 15a and a second lens group 15b. Depending on the focal length of the first lens group 15a and the second lens group 15b, a recording target surface 58a of the hologram recording material 58 is provided. The amount of object light incident thereon and the size of the object light optical image change. Ideally, it is desirable that the focal length f1 of the first lens group 15a be less than or equal to the focal length f2 of the second lens group 15b. When the focal length f1 of the first lens group 15a is long, the distance between the diffusing surface (object surface 14a) of the diffusing plate 14 and the first lens group 15a increases, and the object light diffused by the diffusing plate 14 Among them, the proportion of the object light not incident on the first lens group 15a increases, and as a result, the amount of the object light incident on the hologram recording material 58 decreases. If the focal length f2 of the second lens group 15b is short, the proportion of the object light that does not pass through the opening of the diaphragm member 16 increases, and the amount of the object light incident on the hologram recording material 58 is also reduced. Therefore, from such a viewpoint, f1 ≦ f2 is the best.

  FIG. 1 shows an example in which the focal length f1 of the first lens group 15a is 100 mm and the focal length f2 of the second lens group 15b is 150 mm. In this case, the focal length ratio (f2 / f1) is 1.5. For this reason, the light flux region incident on the recording target surface 58a of the hologram recording material 58 is 1.5 times as large as the light flux region passing through the object surface 14a on the diffusion plate 14.

  Even if f1> f2, it is possible to form high-quality interference fringes on the hologram recording medium 55. In this case, the size of the object light incident area on the hologram recording material 58 is smaller than the size of the object light diffusion area on the diffusion plate 14.

  FIG. 2 is a diagram schematically showing the passage path of the light beam on the object light side when the interference fringes are formed by the hologram manufacturing apparatus 10 of FIG. In FIG. 2, the first lens group 15a in the mapping optical system 15 is composed of a combination lens composed of two lenses, the second lens group 15b is composed of one lens, and the focal length of the first lens group 15a. An example is shown in which f1 is 110 mm and the focal length f2 of the second lens group 15b is 150 mm.

  In FIG. 2, only the rays of the object light that contribute to the formation of interference fringes are shown. That is, FIG. 2 shows that the object light diffused from the object surface 14a on the diffusion plate 14 passes through the first lens group 15a and the second lens group 15b, and further passes through the opening of the aperture member 16. Only light rays incident on the recording target surface 58a are shown. As can be seen from FIG. 2, the size of the light beam region on the recording target surface 58a of the hologram recording material 58 is 150/110 = 1.36 times larger than the size of the light beam region on the object surface 14a of the diffusion plate 14. Has been expanded to a degree.

  FIG. 3 is a diagram showing a simulation result of the illuminance distribution on the recording target surface 58a of the hologram recording material 58 in the hologram production apparatus 10 of FIG. FIG. 3A is a diagram showing the illuminance distribution of the recording target surface 58a by changing the type of hatching for each illuminance, and FIG. 3B is a graph showing the illuminance distribution in the XX direction of FIG. FIG. 3C is a graph showing the illuminance distribution in the Y-Y direction of FIG.

  4 and 5 show the illuminance on the recording target surface 58a of the hologram recording material 58 when the mapping optical system 15 is removed from FIG. 1 and the object light from the diffusion plate 14 is directly incident on the diaphragm member 16. It is a figure which shows the simulation result of distribution. 4 and 5 show the illuminance distribution when the diffusion angle of the diffusion plate 14 is 20 degrees, and FIG. 5 shows the illuminance distribution when the diffusion angle is 15 degrees.

  As can be seen from a comparison of FIGS. 3 to 5, the provision of the mapping optical system 15 increases the amount of object light incident on the diaphragm member 16 and increases the illuminance of the recording target surface 58 a as a whole. 3 to 5, since the interference fringes are formed on the recording target surface 58a using the object light that has passed through the opening of the diaphragm member 16, the amount of the object light on the recording target surface 58a is uniform. And there is no large variation in the illuminance distribution across the entire recording target surface 58a.

  Thus, in the present embodiment, among the object light diffused from the object surface 14a on the diffusion plate 14, only the object light that has passed through the opening of the aperture member 16 via the mapping optical system 15 is used as the hologram recording material 58. Since the interference fringes are formed by being incident on the upper recording target surface 58a, there is no variation in the amount of light of the object light incident on the recording target surface 58a, and interference fringes with high uniformity in the amount of light can be formed.

  In the present embodiment, the object light diffused by the object surface 14 a on the diffusion plate 14 or the object light that has passed through the mapping optical system 15 is not directly incident on the recording target surface 58 a on the hologram recording material 58. Since only the object light that has passed through the aperture of the aperture member 16 is incident, even if the object surface 14a or the mapping optical system 15 on the diffusion plate 14 is dusty or scratched, it is less likely to be affected by the interference fringes. Can improve the quality.

  From another viewpoint, the interference fringes formed on the hologram recording medium 55 are recorded information on the object light that has passed through the opening of the diaphragm member 16, that is, information on the opening of the diaphragm member 16. As described above, the interference fringes are less susceptible to dust and scratches on the object surface 14a on the diffusion plate 14 and the mapping optical system 15.

  Further, in the present embodiment, the mapping optical system 15 is disposed between the diffusing plate 14 and the diaphragm member 16, and the object light diffused from the diffusing plate 14 is converged to some extent by the mapping optical system 15. Since the aperture of the aperture member 16 is passed through, the amount of object light passing through the aperture of the aperture member 16 can be increased as compared with the configuration without the mapping optical system 15, and as a result, the light is incident on the hologram recording material 58. As a result, the amount of object light increases, and high-quality interference fringes can be formed.

  FIG. 6 is a diagram for explaining a method for generating a reproduced image using interference fringes recorded on the hologram recording medium 55 manufactured by the hologram manufacturing apparatus 10 of FIG. Reproduction illumination light composed of parallel light beams is incident on the hologram recording medium 55 from a direction opposite to the incident direction of the reference light shown in FIG. The reproduction illumination light is diffused by interference fringes on the hologram recording medium 55 to form a reproduction image at the position where the diaphragm member 16 was present. Regardless of the location on the recording surface 55a on the hologram recording medium 55, the reproduction illumination light forms a reproduction image at the position shown in FIG.

  FIG. 7 is a block diagram showing an example of a projection apparatus configured using the hologram recording medium 55 produced by the hologram production apparatus 10 of FIG.

  The projection apparatus 20 of FIG. 7 includes a hologram recording medium 55, an irradiation apparatus 60, an optical modulator 30, and a projection optical system 80. A configuration in which the hologram recording medium 55 and the irradiation device 60 are combined corresponds to the illumination device 40. Therefore, when it is desired to manufacture the illumination device 40, the light modulator 30 and the projection optical system 80 may be removed from FIG.

  The irradiation device 60 irradiates the hologram recording medium 55 with coherent light so that the coherent light scans the surface of the hologram recording medium 55. The irradiation device 60 scans the surface of the hologram recording medium 55 with a plurality of laser light sources 61 (61r, 61g, 61b) that irradiate coherent light composed of parallel light beams and the coherent light emitted from each laser light source 61. Device 65.

  The scanning device 65 varies the reflection angle of the incident coherent light so that the reflected coherent light scans on the hologram recording medium 55. The reason why the coherent light is scanned on the hologram recording medium 55 is to prevent the speckle from being visually recognized, as will be described later.

  The coherent light incident on the hologram recording medium 55 is diffused by the interference fringes on the hologram recording medium 55 to form a reproduced image at the position where the diaphragm member 16 was located, as shown in FIG. This position is the illuminated area LZ. In FIG. 7, the light modulator 30 is arranged at this position. As a result, the light modulator 30 arranged so as to overlap the illuminated area LZ is illuminated by the reproduced image. The reproduced image includes information of the object light diffused by the diffusion plate 14. In this embodiment, the hologram recording is performed so that all the points of the hologram recording medium 55 uniformly irradiate all the openings of the diaphragm member 16. Since the medium 55 is manufactured, the reproduced image also becomes uniform light with no unevenness in the amount of light.

  The shape of the illuminated region LZ on the light modulator 30 illuminated by the illumination device 40 is similar to the shape of the diaphragm member 16 shown in FIG.

  As the optical modulator 30, for example, a reflective microdisplay made of a micro electro mechanical systems (MEMS) element such as a DMD (digital micromirror device) can be used. The DMD is also used as the optical modulator 30 in the apparatus disclosed in Patent Document 2 described above.

  In addition, a transmissive liquid crystal panel can be used as the optical modulator 30, but the coherent light passing through the imaging optical system 70 has various optical path lengths in the liquid crystal panel, not parallel light. Because of the difference, the contrast may decrease depending on the light incident angle on the liquid crystal panel. From this point of view, it is desirable to use a reflective microdisplay such as DMD as the optical modulator 30 of the present embodiment.

  It is preferable that the incident surface of the light modulator 30 has the same position and the same shape and size as the illuminated region LZ where the illumination device 40 emits coherent light. In this case, it is because the coherent light from the illuminating device 40 can be utilized with high utilization efficiency for displaying the image on the diffusion screen 15.

  The projection optical system 80 that projects the modulated image generated by the light modulator 30 onto the diffusing screen 15 includes a projection lens 81 composed of a plurality of lens groups, for example, and the modulated image generated by the light modulator 30. Is refracted by the projection lens 81 and projects a modulated image on the diffusing screen 15. The size of the modulated image projected on the diffusion screen 15 can be adjusted by the diameter of the projection lens 81, the distance between the projection lens 81 and the light modulator 30, and the distance between the projection lens 81 and the diffusion screen 15. The diffusing screen 15 in FIG. 7 is a transmissive type, and diffuses the projected modulated image light. The diffusing screen 15 may be a reflective type.

  Although omitted in FIG. 7, the modulated image diffused by the diffusion screen 15 is incident on a half mirror (not shown), and a part of the modulated image light diffused by the diffusion screen 15 is reflected by this half mirror. Thus, a virtual image of the modulated image may be formed, and this virtual image may be viewed by an observer through a half mirror together with external light. Thereby, a head-up display device can be realized. In this case, for example, the front windshield of the vehicle can be used as the half mirror, and the observer can view the virtual image while viewing the scenery outside the vehicle through the windshield by sitting in the driver's seat and facing forward. Alternatively, a hologram recording medium 55 or a prism may be used instead of the half mirror.

  The optical modulator 30 can generate various modulated images. The modulated image is generated by the optical modulator 30, and the modulated image is illuminated by the illuminated region LZ, so that the various modulated images are displayed on the diffusion screen. Can be projected.

  The hologram recording medium 55 used in the present embodiment is a reflective volume hologram using, for example, a photopolymer.

  Next, the configuration of the irradiation device 60 that irradiates the hologram recording medium 55 on which interference fringes are formed with the configuration as shown in FIG. 2 with coherent light will be described. In the example shown in FIGS. 1 to 6, the irradiation device 60 includes a laser light source 61 that generates coherent light, and a scanning device 65 that changes the traveling direction of the coherent light from the laser light source 61.

  The laser light source 61 may be a monochromatic laser light source or a plurality of laser light sources having different emission wavelengths. For example, a plurality of red, green, and blue laser light sources may be used. When a plurality of laser light sources 61 are used, the laser light from each laser light source 61 is made to be a parallel light flux as shown in FIG. Alternatively, the laser light from each laser light source 61 may be irradiated to the same point on the scanning device 65, and the reflected light from the scanning device 65 may be incident on the hologram recording medium 55 as a parallel light beam using a lens. .

  By using a plurality of laser light sources 61 having different emission wavelengths, the hologram recording medium 55 is illuminated with reproduction illumination light in which the illumination colors of the laser light sources 61 are mixed. In this case, the coherent light from each laser light source is reflected at a reflection angle corresponding to the incident angle of the scanning device 65, is incident on the hologram recording medium 55, is diffracted separately from the hologram recording medium 55, and is illuminated. Overlapping on the region LZ becomes a composite color. For example, when a plurality of red, green, and blue laser light sources are used, the color becomes white. Alternatively, a separate scanning device 65 may be provided for each laser light source.

  For example, when illuminating in white, it may be possible to reproduce a color closer to white by separately providing a laser light source that emits light other than red, green, and blue, for example, a laser light source that emits yellow light. Accordingly, the type and number of laser light sources provided in the irradiation device 60 are not particularly limited.

  In the case of forming a color modulated image with the light modulator 30, various realization methods can be considered. When the light modulator 30 is composed of LCOS or the like and has a color filter for each pixel, the modulated image generated by the light modulator 30 is colored by making the illuminated area LZ white light. can do.

  Alternatively, for example, an optical modulator 30 that generates a red modulated image, an optical modulator 30 that generates a green modulated image, and an optical modulator 30 that generates a blue modulated image are arranged close to each other. The three illuminated areas LZ that illuminate each of the optical modulators 30 may be sequentially illuminated with diffused light from the hologram recording medium 55. As a result, the three color modulation images generated by the three light modulators 30 are combined to generate a color modulation image. Instead of such time-division driving, three color modulation images generated simultaneously by the three optical modulators 30 may be combined using a prism or the like to generate a color modulation image.

  The projection optical system 80 described above is provided mainly for projecting the modulated image of the light modulator 30 onto the diffusing screen 15. By providing the diffusion screen 15, speckles are overlapped and averaged, and as a result, speckles are not noticeable.

  The scanning device 65 changes the traveling direction of the coherent light with time, and directs it in various directions so that the traveling direction of the coherent light is not constant. As a result, the coherent light whose traveling direction is changed by the scanning device 65 scans on the incident surface of the hologram recording medium 55.

  FIG. 8 is a diagram for explaining the scanning path of the scanning device 65.

  The scanning device 65 according to the present embodiment includes a reflecting device 66 having a reflecting surface 66a that can be rotated about one axis RA1. The reflection device 66 includes a mirror device having a mirror as a reflection surface 66a that can be rotated about one axis RA1. This mirror device 66 changes the traveling direction of coherent light from the laser light source 61 by changing the orientation of the mirror 66a. At this time, as shown in FIG. 6, the mirror device 66 generally receives coherent light from the laser light source 61 at the reference point SP.

  The coherent light whose traveling direction is finally adjusted by the mirror device 66 can be incident on the hologram recording medium 55 as reproduction illumination light La (see FIG. 6) that can form one light beam diverging from the reference point SP. As a result, the coherent light from the irradiation device 60 scans on the hologram recording medium 55, and the image of the scattering plate 6 in which the coherent light incident on each position on the hologram recording medium 55 has the same contour. 5 is reproduced at the same position (illuminated area LZ).

  As shown in FIG. 8, the reflection device 66 is configured to rotate the mirror 66a along one axis RA1. In the example shown in FIG. 8, the rotation axis RA1 of the mirror 66a has an XY coordinate system defined on the plate surface of the hologram recording medium 55 (that is, the XY plane is parallel to the plate surface of the hologram recording medium 55). It extends parallel to the Y axis of the (XY coordinate system). Then, since the mirror 66a rotates around an axis line RA1 parallel to the Y axis of the XY coordinate system defined on the plate surface of the hologram recording medium 55, the coherent light from the irradiation device 60 is transferred to the hologram recording medium 55. The incident point IP reciprocates in a direction parallel to the X axis of the XY coordinate system defined on the plate surface of the hologram recording medium 55. That is, in the example shown in FIG. 8, the irradiation device 60 irradiates the hologram recording medium 55 with the coherent light so that the coherent light scans on the hologram recording medium 55 along a linear path.

  As described above, the scanning device 65 configured by the mirror device 66 or the like is a member that can rotate at least around the axis line RA1, and is configured by using, for example, MEMS. The scanning device 65 periodically rotates, but in applications such as a liquid crystal display device that is directly observed by humans, it is 1/30 seconds per cycle, which is more coherent at a higher speed depending on the type of screen to be displayed. If it can scan with light, there will be no restriction | limiting in particular in the rotation frequency.

  As a practical problem, the hologram recording material 58 may shrink when the hologram recording medium 55 is produced. In such a case, it is preferable to adjust the incident / exit angle of the coherent light irradiated from the irradiation device 60 to the hologram recording medium 55 in consideration of the shrinkage of the hologram recording material 58. Therefore, the wavelength of the coherent light generated by the coherent light source 61 does not need to be exactly the same as the wavelength of the light used in the exposure process of FIG. 2, and may be substantially the same.

  For the same reason, the traveling direction of the light incident on the hologram recording medium 55 is imaged in the illuminated region LZ even if it does not take the exact same path as the one light beam included in the divergent light beam from the reference point SP. 5 can be reproduced. Actually, in the example shown in FIG. 8, the mirror (reflection surface) 66a of the mirror device 66 constituting the scanning device 65 is inevitably deviated from the rotation axis RA1. Therefore, when the mirror 66a is rotated around the rotation axis RA1 that does not pass through the reference point SP, the light incident on the hologram recording medium 55 may not be a single light beam that forms a divergent light beam from the reference point SP. is there. However, in practice, the image 5 can be substantially reproduced by being superimposed on the illuminated region LZ by coherent light from the irradiation device 60 having the illustrated configuration.

  By the way, the scanning device 65 does not necessarily have to be a member that reflects the coherent light. Instead of reflecting, the scanning device 65 may cause the coherent light to be refracted or diffracted to scan the hologram recording medium 55. .

(Operational effect of this embodiment)
Next, the operation and effect of the projection apparatus 20 having the above configuration will be described.

  In the present embodiment, since a modulated image is generated using the scanning device 65, the hologram recording medium 55, and the optical modulator 30, for example, compared with a case where a modulated image is generated using a normal liquid crystal display device. The hardware configuration up to the generation of can be greatly reduced. In the present embodiment, the scanning device 65 scans the hologram recording medium 55 with coherent light and projects a modulated image onto the diffusion screen 15, so that speckle is not conspicuous while using coherent light. Thus, the projection device 20 capable of displaying a high-quality image can be realized. In addition, by providing the diffusion screen 15, the viewing angle can be widened.

  The scanning device 65 makes each position on the hologram recording medium 55 incident coherent light of a corresponding specific wavelength at an incident angle that satisfies the Bragg condition at the position. As a result, the coherent light incident on each position illuminates the entire illuminated area LZ by diffracting by the interference fringes recorded on the hologram recording medium 55. That is, the coherent light that has entered the hologram recording medium 55 from the irradiation device 60 is diffused (expanded) by the hologram recording medium 55 and enters the entire illuminated area LZ.

  In this way, the irradiation device 60 illuminates the illuminated area LZ with coherent light. For example, when the laser light source 61 includes a plurality of laser light sources 61 that emit light of different colors, information on the light of each color that has passed through the diaphragm member 16 is reproduced in the illuminated region LZ. Therefore, when these laser light sources 61 emit light at the same time, the illuminated area LZ is illuminated with white in which three colors are mixed.

  In the present embodiment, as described below, a light image can be formed on the illuminated area LZ without conspicuous speckles.

  The irradiation device 60 described above irradiates the hologram recording medium 55 with coherent light so that the coherent light scans on the hologram recording medium 55. Further, the coherent light incident on the arbitrary position in the hologram recording medium 55 from the irradiation device 60 illuminates the entire illuminated area LZ, but the illumination directions of the coherent light illuminating the illuminated area LZ are different from each other. Since the position on the hologram recording medium 55 where the coherent light enters changes with time, the incident direction of the coherent light to the illuminated region LZ also changes with time.

  As described above, in this embodiment, coherent light continuously scans on the hologram recording medium 55. Along with this, the incident direction of coherent light incident on the illuminated area LZ from the irradiation device 60 via the hologram recording medium 55 also changes continuously. Here, if the incident direction of the coherent light from the hologram recording medium 55 to the illuminated area LZ changes only slightly (for example, several degrees), the pattern of speckles generated on the illuminated area LZ also changes greatly. Correlated speckle patterns are superimposed. In addition, the frequency of scanning devices 65 such as MEMS mirrors and polygon mirrors that are commercially available is usually several hundred Hz or higher, and scanning devices 65 that reach tens of thousands of Hz are not uncommon.

  From the above, according to the present embodiment, the incident direction of coherent light changes temporally at each position of the illuminated region LZ, and this change is a speed that cannot be resolved by the human eye. It is. Accordingly, if a screen is arranged in the illuminated area LZ, speckles generated corresponding to each incident angle are overlapped and averaged and observed by the observer, so that the image displayed on the screen Speckle can be made very inconspicuous for an observer who observes the above. In the case of the present embodiment, the light modulator 30 is arranged so as to overlap the position of the illuminated region LZ, and the light modulator 30 projects onto the diffusion screen 15 via the projection optical system 80. Similarly, since speckles generated on the diffusion screen 15 are overlapped and averaged, the speckles generated on the diffusion screen 15 become inconspicuous.

  As described above, in the embodiment of the present invention, the scanning device 65 is used to scan the coherent light on the hologram recording medium 55, and the coherent light diffracted by the hologram recording medium 55 is incident on the entire illuminated area LZ. The lighting device 40 can be realized with a very simple configuration.

(Other features of this embodiment)
Non-Patent Document 1 mentioned above proposes a method using a numerical value called speckle contrast (unit%) as a parameter indicating the degree of speckle generated on the screen. This speckle contrast is defined as a value obtained by dividing the standard deviation of the actual luminance variation on the screen divided by the average luminance value when displaying a test pattern image that should have a uniform luminance distribution. Amount. The larger the speckle contrast value is, the larger the speckle occurrence level on the screen is, which indicates that the spot-like luminance unevenness pattern is more prominently presented to the observer.

  In addition, according to the above-described embodiment, the following advantages can be obtained.

  According to this embodiment described above, the hologram recording medium 55 for making speckles inconspicuous can also function as an optical member for shaping and adjusting the beam form of coherent light emitted from the irradiation device 60. . Therefore, the optical system can be reduced in size and simplified.

  Further, according to the present embodiment described above, coherent light incident on a specific position of the hologram recording medium 55 generates information on the light of each color that has passed through the diaphragm member 16 in the entire illuminated area LZ. For this reason, all the light diffracted by the hologram recording medium 55 can be used for illumination, and the use efficiency of the light from the laser light source 61 is excellent.

(Avoiding zero-order light)
A part of the coherent light from the irradiation device 60 passes through the hologram recording medium 55 without being diffracted by the hologram recording medium 55. Such light is called zero order light. When the zero-order light enters the illuminated area LZ, abnormal areas such as point-like areas, linear areas, and planar areas whose brightness (luminance) increases sharply compared to the surroundings are illuminated area LZ. Will occur within.

  When the volume hologram recording medium 55 (hereinafter referred to as volume reflection type holo) is used, especially in the case of a volume reflection type hologram, the illuminated region LZ is not arranged in the direction in which the zero order light travels, and therefore the zero order light is compared. Can be easily avoided. In the case of using a volume transmission type hologram recording medium 55 (hereinafter referred to as volume transmission type holo), the zero-order light can be separated by selecting a recording angle so that incident light and outgoing light do not interfere with each other. When the optical path of the 0th-order light and the optical path of the 1st-order light cannot be separated due to an arrangement problem, it is desirable to increase the diffraction efficiency as much as possible and suppress the influence of the 0th-order light as much as possible.

(Reflective and transmissive hologram recording medium 55)
The reflection type holo has higher wavelength selectivity than the transmission type holo. That is, the reflection type holo can diffract coherent light having a desired wavelength only by a desired layer even if interference fringes corresponding to different wavelengths are laminated. The reflection type holo is also excellent in that it is easy to remove the influence of zero-order light.

  On the other hand, the transmission type holo has a wide diffractable spectrum and a wide tolerance of the laser light source 61. However, when interference fringes corresponding to different wavelengths are laminated, coherent light of a desired wavelength is generated even in layers other than the desired layer. It will be diffracted. Therefore, in general, it is difficult to make the transmission type holo a laminated structure.

(Irradiation device 60)
In the above-described embodiment, the example in which the irradiation device 60 includes the laser light source 61 and the scanning device 65 has been described. Although the scanning device 65 is an example of the uniaxial rotation type mirror device 66 that changes the traveling direction of the coherent light by reflection, the scanning device 65 is not limited thereto. As shown in FIG. 9, the scanning device 65 has a second rotation in which the mirror (reflection surface 66a) of the mirror device 66 intersects not only the first rotation axis RA1 but also the first rotation axis RA1. It may be rotatable about the axis RA2. In the example shown in FIG. 9, the second rotation axis RA2 of the mirror 66a is a first rotation axis RA1 extending in parallel with the Y axis of the XY coordinate system defined on the plate surface of the hologram recording medium 55. Are orthogonal. Since the mirror 66a can be rotated about both the first axis RA1 and the second axis RA2, the incident point IP of the coherent light from the irradiation device 60 to the hologram recording medium 55 is equal to that of the hologram recording medium 55. It can move in a two-dimensional direction on the plate surface. For this reason, as shown in FIG. 9 as an example, the incident point IP of the coherent light to the hologram recording medium 55 can be moved on the circumference.

  Further, the scanning device 65 may include two or more mirror devices 66. In this case, even if the mirror 66a of the mirror device 66 is rotatable only about a single axis, the incident point IP of the coherent light from the irradiation device 60 to the hologram recording medium 55 is changed to the hologram recording medium 55. Can be moved in a two-dimensional direction on the plate surface.

  Specific examples of the mirror device 66a included in the scanning device 65 include a MEMS mirror, a polygon mirror, and a galvano scanner.

  The scanning device 65 may include a reflection device that changes the traveling direction of coherent light by reflection, that is, a device other than the mirror device 66 described above as an example in the present embodiment. For example, the scanning device 65 may include a refractive prism, a lens, and the like.

  In the first place, the scanning device 65 is not essential, and the light source 61 of the irradiation device 60 is configured to be displaceable (moving, swinging, rotating) with respect to the hologram recording medium 55, and by the displacement of the light source 61 with respect to the hologram recording medium 55, The coherent light emitted from the light source 61 may scan the hologram recording medium 55.

  Furthermore, although the light source 61 of the irradiation apparatus 60 has been described on the assumption that the laser light shaped as a linear light beam is oscillated, the present invention is not limited to this. In particular, in the embodiment described above, the coherent light irradiated to each position of the hologram recording medium 55 is shaped by the hologram recording medium 55 into a light beam that enters the entire illuminated area LZ. Therefore, inconvenience does not occur even if the coherent light irradiated to the hologram recording medium 55 from the light source 61 of the irradiation device 60 is not accurately shaped. For this reason, the coherent light generated from the light source 61 may be diverging light. Further, the cross-sectional shape of the coherent light generated from the light source 61 may not be a circle but an ellipse or the like. Furthermore, the transverse mode of the coherent light generated from the light source 61 may be a multimode.

  When the light source 61 generates a divergent light beam, the coherent light is incident on a region having a certain area instead of a point when entering the hologram recording medium 55. In this case, the light diffracted by the hologram recording medium 55 and incident on each position of the illuminated area LZ is multiplexed in angle. In other words, at each moment, coherent light is incident on each position of the illuminated area LZ from a certain angle range. Speckle can be made more inconspicuous by such multiplexing of angles.

  Further, FIG. 1 shows an example in which the coherent light reflected by the scanning device 65 is directly incident on the hologram recording medium 55. However, a condensing lens is provided between the scanning device 65 and the hologram recording medium 55. The coherent light may be converted into a parallel light flux by the condenser lens and incident on the hologram recording medium 55. In such an example, a parallel light beam is used as the reference light Lr instead of the above-described convergent light beam in the exposure process when the hologram recording medium 55 is manufactured. Such a hologram recording medium 55 can be produced and duplicated more easily.

(Hologram recording medium 55)
In the above-described embodiment, an example in which the reflective volume hologram 55 using a photopolymer is used has been described, but the present invention is not limited thereto. Further, the hologram recording medium 55 may include a volume hologram of a type for recording using a photosensitive medium containing a silver salt material. Furthermore, the hologram recording medium 55 may include a transmissive volume hologram recording medium 55 or a relief (embossed) hologram recording medium 55.

  However, in the relief (embossed) hologram, hologram interference fringes are recorded by the concavo-convex structure on the surface. However, in the case of this relief-type hologram, scattering due to the uneven structure on the surface may cause a loss of light amount and may cause a new unintended speckle generation. In this respect, the volume-type hologram is preferable. . In the volume hologram, since the hologram interference fringe is recorded as a refractive index modulation pattern (refractive index distribution) inside the medium, it is not affected by scattering due to the uneven structure on the surface.

  However, even volume holograms that are recorded using a photosensitive medium containing silver salt material may cause light loss due to scattering by silver salt particles, and may cause unintended new speckle generation. There is sex. In this respect, the hologram recording medium 55 is preferably a volume hologram using a photopolymer.

  In addition, in the recording process shown in FIG. 2, a so-called Fresnel type hologram recording medium 55 is produced, and a Fourier transform type hologram recording medium 55 obtained by performing recording using a lens is produced. It doesn't matter. However, when the Fourier transform type hologram recording medium 55 is used, a lens may also be used during image reproduction.

  Further, the striped pattern to be formed on the hologram recording medium 55, for example, the refractive index modulation pattern or the uneven pattern, does not use the actual object light Lo and the reference light Lr, but the planned wavelength and incident direction of the reproduction illumination light La. In addition, it may be designed using a computer based on the shape and position of the image to be reproduced. The hologram recording medium 55 obtained in this way is also called a computer-generated hologram. When a plurality of coherent lights having different wavelength ranges are irradiated from the irradiation device 60 as in the above-described modification, the hologram recording medium 55 as a computer-generated hologram corresponds to each coherent light in each wavelength range. The coherent light in each wavelength region may be diffracted in the corresponding region to reproduce an image.

(Lighting method)
In the above-described embodiment, the irradiation device 60 is configured to be able to scan the coherent light on the hologram recording medium 55 in a one-dimensional direction, and the coherent light irradiated on each position of the hologram recording medium 55 in the two-dimensional direction. In this example, the illuminating device 40 illuminates the two-dimensional illuminated area LZ. However, as described above, the present invention is not limited to such an example. For example, the irradiation device 60 is configured to be able to scan the coherent light in the two-dimensional direction on the hologram recording medium 55, and The hologram recording medium 55 is configured to diffuse the coherent light irradiated to each position in a two-dimensional direction, whereby the illuminating device 40 creates a two-dimensional illuminated area LZ as shown in FIG. It may be illuminated.

  Further, as already mentioned, the irradiation device 60 is configured to be able to scan the holographic recording medium 55 with coherent light in a one-dimensional direction, and the holographic recording medium 55 is irradiated to each position. The light may be configured to diffuse in a one-dimensional direction, so that the illumination device 40 may illuminate the one-dimensional illuminated area LZ. In this aspect, the scanning direction of the coherent light by the irradiation device 60 and the diffusion direction of the hologram recording medium 55 may be parallel.

  Further, the irradiation device 60 is configured to be able to scan the coherent light on the hologram recording medium 55 in a one-dimensional direction or a two-dimensional direction, and the coherent light irradiated to each position on the hologram recording medium 55 is one-dimensional. It may be configured to diffuse in the direction. In this embodiment, the illumination device 40 illuminates a two-dimensional area by sequentially illuminating the illuminated areas LZ corresponding to the hologram recording media 55. Also good. At this time, each illuminated area LZ may be sequentially illuminated at a speed as if it were illuminated simultaneously by the human eye, or it can be recognized that the illuminated area LZ is also illuminated sequentially by the human eye. It may be illuminated sequentially at such a slow speed.

  The aspect of the present invention is not limited to the individual embodiments described above, and includes various modifications that can be conceived by those skilled in the art, and the effects of the present invention are not limited to the contents described above. That is, various additions, modifications, and partial deletions can be made without departing from the concept and spirit of the present invention derived from the contents defined in the claims and equivalents thereof.

  DESCRIPTION OF SYMBOLS 10 Hologram production apparatus, 11 Coherent light source, 12 Beam splitter, 13 Object optical system, 14 Diffuser plate, 14a Object surface, 15 Mapping optical system, 16 Diaphragm member, 17 Reference optical system, 18, 19 Reflection mirror, 20 Projection apparatus, 55 hologram recording medium, 55a recording surface, 58 hologram recording material, 58a recording target surface, 60 irradiation device, 61 light source, 65 scanning device, 66 mirror device (reflection device), 66a mirror (reflection surface), 70 imaging optical system , 80 Projection optical system, 81 Projection lens, LZ Illuminated area

Claims (4)

An object surface that diffuses object light related to object information recorded on the hologram recording material;
A mapping optical system for mapping the object plane onto a predetermined image plane;
An aperture that allows a portion of the object light that has passed through the mapping optical system to pass therethrough, and a diaphragm member that allows rays from the entire area of the aperture to reach each point on the image plane,
The hologram recording material is disposed in the vicinity of the image plane of the mapping optical system so that interference fringes are formed by interference between the reference light and the object light that has passed through the aperture of the diaphragm member ,
The mapping optical system is
A first lens group for entering the object light diffused from the object surface;
A second lens group that maps the object light that has passed through the first lens group onto the predetermined image plane;
The hologram production apparatus, wherein the object plane is disposed at a front focal position of the first lens group, and the second lens group is disposed at a rear focal position of the first lens group . The focal length of the first lens group, the hologram manufacturing apparatus according to claim 1, wherein at the focal length following the second lens group. Opening of the diaphragm member is a hologram manufacturing apparatus according to claim 1 or 2, characterized in that it is arranged on the optical axis of the mapping optical system. A hologram manufacturing method for recording interference fringes by causing object light and reference light generated by branching coherent light emitted from the same light source to enter a hologram recording material,
At least part of the object light diffused from the object surface is incident on the mapping optical system;
Passing a part of the object light that has passed through the mapping optical system through the aperture of the aperture member;
The diaphragm member is arranged so that light rays from the entire area of the opening reach each point on the image plane of the mapping optical system,
The object light that has passed through the aperture of the diaphragm member is incident on the recording target surface of the hologram recording material disposed near the image plane of the mapping optical system, and the reference light is incident on the recording surface. Forming the interference fringes ;
The mapping optical system is
Disposing the object plane at a front focal position of a first lens group for entering the object light diffused from the object plane;
A hologram manufacturing method , wherein a second lens group that maps the object light that has passed through the first lens group onto the predetermined image plane is disposed at a back focal position of the first lens group .