Abstract: The present invention relates to a three-dimensional micropattern using a hologram which can not be counterfeited with color copying machines or diffraction grating image forming devices. The three-dimensional micropattern comprises a hologram composed of a three-dimensional aggregation of a large number of very small micro-letters A-Z or geometric micro-figures. The micro-letters or geometric micro-figures are three-dimensionally aggregated to constitute a three-dimensional object (conical object) to allow reconstruction of a three-dimensional image of the specific three-dimensional object.

Abstract: A holographic optical element comprising at least two sets of regions, the regions of each set being different from the regions of the other set(s) and being interleaved or overlapping with the regions of the other set(s) and being constructed such that light incident on each set of regions is directed to a respective one of a plurality of viewing zones. The holographic optical element is typically incorporated in a display device such as a stereoscopic display device.

Abstract: In a system in which images having parallax data, and which are made up of plural images containing the parallax information, are processed with viewing point conversion, and the resulting new images having parallax data are used, as in a system of generating a holographic stereogram, a unit for generating the images having parallax data is to be independent from other unit or units. To this end, the information necessary to perform viewing point conversion processing of converting the viewing point for an object is attached to images having parallax data when the images having parallax data have been produced. When the images having parallax data is exchanged between the unit for generating the images having parallax data and other unit or units, the exchanged images having parallax data need to be those to which the information has been attached.

Abstract: A surface microstructure is superimposed on the surface of a replication mould such as an injection moulding tool insert by laser interference exposure of a mask pattern and etching or electroplating the additional microstructure. The technique enables the post-processing of planar and non-planar replication moulds with additional microstructure to improve the functionality and value of the moulded components. A major area of application is an anti-reflection surface for injection moulded polymer optical components, achieved by the superposition of submicrometer anti-reflection grating structure onto injection moulding tool inserts.

Abstract: Large format, highly selective display screens can be formed from a plurality of holographic optical elements. In accordance with the teachings of the present invention, systems and methods are described to provide a holographic screen for display of static and/or dynamic projected conventional two-dimensional images, two-dimensional stereograms, and holographic stereograms. One aspect of the present invention includes presenting live-image three-dimensional displays using an array of two-dimensional data projectors. Another aspect includes projecting and enlarging static or dynamic source three-dimensional images (real objects, holograms, or other autostereoscopic images).

Abstract: The present invention concerns methods and devices for creating and printing variable size and variable resolution holographic stereograms and holographic optical elements using computer rendered images of three-dimensional computer models or using computer processed images. The present invention is an apparatus and method for printing one-step, full-color, full-parallax holographic stereograms utilizing a reference beam-steering system that allows a reference beam to expose a holographic recording material from different angles. More particularly, a coherent beam is split into object and reference beams. The object beam passes through an object beam unit in which a rendered image is displayed, while the reference beam passes through the reference beam-steering system. The object and reference beams interfere with each other at an elemental hologram on a holographic recording material.

Abstract: A single photographic subsystem 2 photographs an original image for a hologram and provides an image information file Fp. In addition, this subsystem provides a management information file Fm for storing management information about the image information file Fp. An image processing section 4 generates a composite image file Fs by applying specified image processing to the image information file Fp and the management information about the management information file Fm provided from the single photographic subsystem 2 via a transmission system 3a. A hologram printer 5 receives the composite image file Fs generated in the image processing section 4 and prints a holographic stereogram based on this composite image file Fs.

Abstract: The current invention comprises the recording of full parallax, one-step, full color holographic stereograms so as to properly display the resultant imagery when the hologram is mounted on a curved substrate after recording. It also comprises mounting the hologram on a substrate that can be curved in one or two dimensions, thereby producing any arbitrary shape. The hologram is scalable, making it possible to create curved holograms of unlimited size. The hologram can be generated for application to one of a variety of curved substrates, including hemi-cylindrical substrates with opaque backing to allow up to 180 degrees of horizontal view zone, and full cylinders with transparent backing to allow viewing through 360 degrees horizontally. It also includes adaptation to conical, spherical, and other curved geometric and irregular topographies.

Abstract: An image exposure recorder for exposure-recording a holographic stereogram image or a hologram image on a recording medium for hologram. The recorder has an inverse correction system for rotating the polarization plane of a reference light (R) by means of a half-wave plate (11), directing the reference light (R) to a hologram recording medium (3), and measuring the intensity of a part of the reference light (R) transmitted through a polarizer (12) out of the reference light (R) transmitted through a part of the area of the hologram recording medium by means of a photodetector (13). In the inverse correction system, the angle of rotation of the half-wave plate is so determined that the intensity of the reference light (R) determined by the photodetector may be minimum or maximum.

Abstract: A bright holographic stereograin having a high diffraction efficiency can be prepared by restricting vibrations. The apparatus comprises: an optical system 15 for letting an objective laser L2 beam subjected to image-modulation based on each image of a parallax image sequence and a reference laser L3 beam having coherence with respect to the objective laser beam L2 enter into a recording medium 3 and for recording interference fringes generated by the objective laser beam L2 and the reference laser beam L3, as a hologram element, onto the recording medium 3; an anti-vibration support means 19 for supporting the optical system 15 on a casing 20 while preventing vibrations; and cooling means 48 to 52 for cooling the optical system 15.

Abstract: A system and method for creating and displaying representations of holographic images comprises a display device, digital image data, a simulation module configured to create a representation of a holographic image and display the representation on the display device, and a processor configured to control the simulation module. The digital image data may include a sequence of images selected by a user by utilizing a selection module. An inspection module inspects the sequence of images for errors. An image sizing module manipulates the digital image data to conform to a size of a final stereogram, and a color module manipulates the digital image data to conform to a color of the final stereogram. A sequence repair module fills any gaps in the sequence of images. When the user determines that the representation is satisfactory, an image data formatter configures the digital image data to conform to requirements of a service provider.

Abstract: In generating a parallax image string used for generating a holographic stereogram, the image quality of a stereoscopic image generated from the parallax image string is to be maintained as the time needed in imaging the parallax image string is shortened. To this end, an optimum number of image frames of each of plural parallax image strings are photographed in agreement with the localized position of the reproduced image of a generated holographic stereogram. The image processing is executed for equating the numbers of frame images of the parallax image strings. The parallax image strings having the equal number of the frame images of the parallax image strings are synthesized by, for example, chroma key synthesis to generate a new parallax image string.

Abstract: A single photographic subsystem 2 photographs an original image for a hologram and provides an image information file Fp. In addition, this subsystem provides a management information file Fm for storing management information about the image information file Fp. An image processing section 4 generates a composite image file Fs by applying specified image processing to the image information file Fp and the management information about the management information file Fm provided from the single photographic subsystem 2 via a transmission system 3a. A hologram printer 5 receives the composite image file Fs generated in the image processing section 4 and prints a holographic stereogram based on this composite image file Fs.

Abstract: A holographic stereogram printing system to print holographic stereograms with good efficiency and no drop in the operating rate of the imaging system and holographic printer. An imaging system control section of an imaging system comprises an operating section that along with controlling the operation of the camera according to the desired selection of the user such as imaging method, image size selection or image layout, also creates an information management file for the base image based on the control information. A holographic stereogram printer prints out a holographic stereogram according to the information management file provided along a transmission path.

Abstract: An image recording apparatus and an image recording method can be suitably used for preparing a large number of edge-lit type holograms or holographic stereograms in a simple manner by copying. A hologram recording medium 11 is applied onto a principal surface 10a of a light-introducing block for copying 10 and held in contact with a master 15. Then, reference light L equivalent to reproducing light for reproducing the image of the master 15 is introduced into the light-introducing block for copying 10 through an end face thereof 10b.

Abstract: A system for the production of a second three-dimensional image magnified from a first three-dimensional image in substantially the same proportions, including a first active optical system for creating from the three-dimensional image, a first two-dimensional array. The array is comprised of two-dimensional elemental images. The first active optical system has a number of elements which is equal to the number of elemental images in the array. The configuration of the elements of the first active optical system corresponds to the configuration of the elemental images in the array. The first array is magnified equally in all directions to create a second two-dimensional array comprised also of two-dimensional elemental images. A second active optical system reconstructs a second three-dimensional image that is a magnification of the first three-dimensional image. The second active optical system has an F-number equal to the F-number of the first active optical system.

Abstract: A holographic optical element comprising at least two sets of regions, the regions of each set being different from the regions of the other set(s) and being interleaved or overlapping with the regions of the other set(s) and being constructed such that light incident on each set of regions is directed to a respective one of a plurality of viewing zones. The holographic optical element is typically incorporated in a display device such as a stereoscopic display device.

Abstract: Method and apparatus are disclosed for optical packet decoding, waveform generation and wavelength multiplexing/demultiplexing using a programmed holographic structure. A configurable programmed holographic structure is disclosed. A configurable programmed holographic structure may be dynamically re-configured through the application of control mechanisms which alter operative holographic structures.

Abstract: The present invention provides a holographic stereogram creating apparatus and method capable of obtaining a more preferable reproduction of image, by arranging on an optical path of a reference light, a mask having an opening corresponding to an element hologram.

Abstract: A holographic optical element comprising at least two sets of regions, the regions of each set being different from the regions of the other set(s) and being interleaved or overlapping with the regions of the other set(s) and being constructed such that light incident on each set of regions is directed to a respective one of a plurality of viewing zones.

Abstract: A holographic stereogram printing system to print holographic stereograms with good efficiency and no drop in the operating rate of the imaging system and holographic printer. An imaging system control section of an imaging system comprises an operating section that along with controlling the operation of the camera according to the desired selection of the user such as imaging method, image size selection or image layout, also creates an information management file for the base image based on the control information. A holographic stereogram printer prints out a holographic stereogram according to the information management file provided along a transmission path.

Abstract: A system and method are disclosed to replace complex fast cylindrical lens (FCL) systems used for producing one-step horizontal parallax only holographic sterograms. A substantially monochromatic fast cylindrical lens is combined with chromatic corrector optics and image scaling performed in conjunction with spatial light modulators (SLMs) in order to avoid the use of an anchromatic FCL.

Abstract: A printed material production apparatus comprises: a picture image input section for inputting a picture image string; a picture image conversion section for converting an inputted picture image string inputted into a panoramic picture image; a picture image processing section for generating a viewing point converted picture image string including a plurality of viewing point converted picture images in accordance with the panoramic picture image generated; and a printing section for producing printed material in accordance with the viewing point converted picture image string generated.

Abstract: An image reproducing apparatus having a small size and which is highly portable reproduces an image contained within a hologram or holographic stereogram. In one embodiment, when a movable section movably attached to an apparatus body is moved from a first position, in which the movable section abuts the apparatus body, to a second position in which the movable section and apparatus body are separated, illumination light from a light source is irradiated at a predetermined incidence angle onto a hologram or holographic stereogram attached to a hologram attach section. In other embodiments, light from a light source is reflected from an edge portion of a light transmitting member, or from a separately provided mirror, to be irradiated at a predetermined angle onto the hologram or holographic stereogram.

Abstract: An image recording apparatus having a small size and which is highly portable reproduces an image contained within a hologram or holographic stereogram. In one embodiment, when a movable section movably attached to an apparatus body is moved from a first position, in which the mavable sections abuts the apparatus body, to a second position in which the movable section and apparatus body are separated, illumination light from a light source is irradiated at a perdetermined incidence angle onto a hologram or holographic stereogram attached to a hologram attach section. In other embodiments, light from a light source is reflected from an edge portion of a light transmitting member, or from a separately provided mirror, to be irradiated at a perdetermined angle onto the hologram or holographic stereogram.

Abstract: A method for displaying computer generated holograms of a display object is performed by computing fringe patterns produced by light interference from the display object. The steps are summarized as follows: three-dimensional data of the display object are converted into computational data for fringe pattern generation; a sampling rule for sampling computational data is selected; computational data are sampled according to a selected sampling rule; wavefronts generated by light illumination are computed by assuming that each sampled position has a light source; fringe patterns generated by computed wavefronts and a reference beam are computed; fringe patterns are stored as hologram images; sampling and a wavefront generation are repeated for all data; and a series of hologram images thus generated are displayed successively.

Abstract: A method and apparatus for making holograms includes a technique for exposing a film substrate or other light-sensitive medium to consecutive two dimensional images, together representative of a physical three-dimensional system, to generate a three dimensional hologram of the physical system. Low beam ratios are employed to superimpose multiple (20-300) images on the substrate. Each image is relatively weak, but the combination of the series of weak images ultimately appears as a single clearly defined hologram.

Abstract: A system for stereoscopic image display includes a projection device (2) with modulators (21, 22) and a polarization splitter prism (3) for the projection of images with differing perspectives each with differing polarization directions. A holographic screen (1) has a grid structure that corresponds to a hologram recording of actual screens with differing polarization directions. The incident light beams (A, B) have the effect that two differently polarized images are generated on the holographic screen (1), where said images can be perceived separately by the left and the right eye by using eyeglasses (5) with polarization filters.

Abstract: The imaging device reads out a first time spatial parameter required for image capturing of an object from various time spatial parameters stored in the storage server and/or recorded on the recording medium, captures the images of the object and produces the captured image data on the basis of this time spatial parameter. The imaging device causes the captured image data and the time spatial parameter corresponding thereto to be stored in the storage server, and/or to be recorded on the recording medium. These captured image data and the time spatial parameter corresponding thereto are supplied to the image data processing unit in the holographic stereogram producing device, in which this supplied time spatial parameter is used as a second time spatial parameter which is required at the time of producing a holographic stereogram.

Abstract: A method of rendering image data for full parallax autostereoscopic displays. The method is based on a double frustrum camera technique, where two cameras provide image data from opposing sides of an image plane. The near clipping plane is located on the image plane. The distance between the near clipping plane and the eyepoint of the camera frustra is adjusted to minimize or avoid clipping.

Abstract: A slit head 76A is provided prior to intermittent feed rollers 73A and 73B. The slit head 76A is made of a rigid body such as magnetic iron and is used as a contact member. The slit head 76A is provided with a slit 78 on the side of a reference light L4 in the vicinity of an exposure position P1. The reference light L4 is transmitted through the slit 78 of the slit head 76A. In addition to magnetic iron, stainless steel and the like are used for the contact member 76A. On the side of an object light L3 at the exposure position P1, there is provided a presser plate member 76B for pressing the holographic recording medium 10 against the slit head 76A. The presser plate member 76B is also provided with a slit 82 and is arranged corresponding to an incident position of the object light L3. A magnetic member is used for the presser plate member 76B.

Abstract: The present invention concerns methods and devices for creating and printing variable size and variable resolution holographic stereograms and holographic optical elements using computer rendered images of three-dimensional computer models or using computer processed images. The present invention is an apparatus and method for printing one-step, full-color, full-parallax holographic stereograms utilizing a reference beam-steering system that allows a reference beam to expose a holographic recording material from different angles. More particularly, a coherent beam is split into object and reference beams. The object beam passes through an object beam unit in which a rendered image is displayed, while the reference beam passes through the reference beam-steering system. The object and reference beams interfere with each other at an elemental hologram on a holographic recording material.

Abstract: A system for producing a white-light interference hologram includes a camera adapted for recording a first and a second bitmap image of a scene from separate vantage points, and the separation distance of the vantage points, a computing engine adapted to compute three-dimensional x, y, and z characteristics of an interference hologram topology for the scene from the bitmap image and separation data, wherein x and y are two dimensional locations of bits in a bitmap of the topology and z is a depth dimension for each x,y bit, and a printer adapted to print in color the x,y bitmap, and to create the depth dimension z at each x,y bit location, providing thereby a three-dimensional interference hologram topology for the scene. In a preferred embodiment the depth dimension is created by electrophoresis, using a medium having an electrophoretic gel layer, with the ink applied to the gel in a bit-mapped pattern being ionic in nature, and capable of being migrated in the gel layer by electrophoresis.

Abstract: In a system in which images having parallax data, and which are made up of plural images containing the parallax information are processed with viewing point conversion, and the resulting new images having parallax data are used, as in a system of generating a holographic stereogram, a unit for generating the images having parallax data is to be independent from other unit or units. To this end, the information necessary to perform viewing point conversion processing of converting the viewing point for an object is attached to images having parallax data when the images having parallax data have been produced. When the images having parallax data is exchanged between the unit for generating the images having parallax data and other unit or units, the exchanged images having parallax data need to be those to which the information has been attached.

Abstract: The present invention concerns methods and devices for creating and printing variable size and variable resolution holographic stereograms and holographic optical elements using computer rendered images of three-dimensional computer models or using computer processed images. The present invention is an apparatus and method for printing one-step, full-color, full-parallax holographic stereograms utilizing a reference beam-steering system that allows a reference beam to expose a holographic recording material from different angles. More particularly, a coherent beam is split into object and reference beams. The object beam passes through an object beam unit in which a rendered image is displayed, while the reference beam passes through the reference beam-steering system. The object and reference beams interfere with each other at an elemental hologram on a holographic recording material.

Abstract: An image data generating method for generating image data corresponding to a planar holographic stereogram is provided. First, an object of imaging device is rotated, while the distance between the object and the imaging device is kept substantially constant, for shooting plural images of different viewing angles by the imaging device. The image data of plural images is then corrected for keystone distortion. The image data corrected for keystone distortion is then processed with viewing point conversion processing for converting the viewing point for generating image data of images recorded on the holographic stereogram. In addition, image data including the information for plural images is compressed for storage in the internal storage device of the computer.

Abstract: The invention makes it possible to form a hologram for reproducing a three-dimensional image easily free of limitations placed by the size of the three-dimensional image to be reproduced, the size of the hologram and reference light for reproduction. A controller calculates a three-dimensional interference pattern for generating reproduction light associated with a desired three-dimensional image when a recording medium (1) is illuminated with reference light for reproduction, divides the three-dimensional interference pattern into partial interference patterns and calculates reference light and information light for recording for each of the partial interference patterns. A final hologram is formed by illuminating the recording medium (1) with reference light and information light for recording using a head (10) while changing the relative positional relationship between the recording medium (1) and the head (10) by moving the head (10) with a VCM (13) while transporting the recording medium (1).

Abstract: A method of rendering image data for full parallax autostereoscopic displays. The method is based on a double frustrum camera technique, where two cameras provide image data from opposing sides of an image plane. The near clipping plane is located on the image plane. The distance between the near clipping plane and the eyepoint of the camera frustra is adjusted to minimize or avoid clipping.

Abstract: An electro-optical display system for visually displaying a polarized spatially multiplexed image (SMI) of a 3-D object for use in stereoscopic viewing thereof with high image quality and resolution. The electro-optical display system comprises a liquid crystal display device and a micropolarization panel of electrically-passive construction, laminated thereto. The liquid crystal display device visually displays a composite pixel pattern representative of a spatially multiplexed image composed of first and second spatially modulated perspective images of the object. The polarized light passing through first and second optically transparent patterns in the micropolarization panel form a polarized SMI which can be used to stereoscopically view the 3-D object with high image quality and resolution, by viewing the same through an electrically-passive pair of polarizing eyeglasses.

Abstract: A single photographic subsystem 2 photographs an original image for a hologram and provides an image information file Fp. In addition, this subsystem provides a management information file Fm for storing management information about the image information file Fp. An image processing section 4 generates a composite image file Fs by applying specified image processing to the image information file Fp and the management information about the management information file Fm provided from the single photographic subsystem 2 via a transmission system 3a. A hologram printer 5 receives the composite image file Fs generated in the image processing section 4 and prints a holographic stereogram based on this composite image file Fs.

Abstract: An optical member 7 is bonded, at its rear side 7b, to a holographic stereogram 6. The front side 7a of the optical member 7 consists of parallel triangular prisms. Illumination light 9 is applied to the front surface 7a of the optical member 7 at a predetermined angle of, for example, 60°. The optical member 7 is made of, for example, optical glass or transparent plastic. Each triangular prism has an incidence surface 8, to which the illumination light is applied at right angles. The illumination light is applied to the interface 22 between the optical member 7 and the holographic stereogram 6, at an incidence angle &thgr; of, for example, 60°, thereby to suppress surface reflection of the illumination light 9 at the interface 22.

Abstract: A slit head 76A is provided prior to intermittent feed rollers 73A and 73B. The slit head 76A is made of a rigid body such as magnetic iron and is used as a contact member. The slit head 76A is provided with a slit 78 on the side of a reference light L4 in the vicinity of an exposure position P1. The reference light L4 is transmitted through the slit 78 of the slit head 76A. In addition to magnetic iron, stainless steel and the like are used for the contact member 76A. On the side of an object light L3 at the exposure position P1, there is provided a presser plate member 76B for pressing the holographic recording medium 10 against the slit head 76A. The presser plate member 76B is also provided with a slit 82 and is arranged corresponding to an incident position of the object light L3. A magnetic member is used for the presser plate member 76B.

Abstract: An illuminating optical system 36 evenly spreads an object beam L3 split from a beam splitter 34. When a control computer sends a number of images in the parallax direction, a spatial light modulation section (liquid crystal) 38 displays these images in that number of divisions under control of the control computer. A superposed projection optical system 39 superposes and projects light beams passing through the spatial light modulation section 38. A beam-condensing projection optical system 41 condenses a projected image's beam from the superposed projection optical system 39 in the parallax direction and forms this image in the non-parallax direction on the surface of a hologram recording medium 42.

Abstract: A holographic stereogram printing system to print holographic stereograms with good efficiency and no drop in the operating rate of the imaging system and holographic printer. An imaging system control section of an imaging system comprises an operating section that along with controlling the operation of the camera according to the desired selection of the user such as imaging method, image size selection or image layout, also creates an information management file for the base image based on the control information. A holographic stereogram printer prints out a holographic stereogram according to the information management file provided along a transmission path.

Abstract: The present invention concerns methods and devices for creating and printing variable size and variable resolution holographic stereograms and holographic optical elements using computer rendered images of three-dimensional computer models or using computer processed images. The present invention is an apparatus and method for printing one-step, full-color, full-parallax holographic stereograms utilizing a reference beam-steering system that allows a reference beam to expose a holographic recording material from different angles. More particularly, a coherent beam is split into object and reference beams. The object beam passes through an object beam unit in which a rendered image is displayed, while the reference beam passes through the reference beam-steering system. The object and reference beams interfere with each other at an elemental hologram on a holographic recording material.

Abstract: The present invention is an apparatus and method for displaying large, continuous, autostereoscopic images. The present invention overcomes the size limitation of typical aulostereoscopic images by recording a continuous, autostereoscopic image onto separate sheets or segments of recording material, mounting the recorded segments to separate tiles, and then displaying the tiles to display a continuous, autostereoscopic image. Although the autostereoscopic image display of the present invention is comprised of separate segments, the present invention offers viewers of the display a unitary visual impression of a large, autostereoscopic image without apparent discontinuities. In one broad aspect, the present invention provides a system for easily displaying segments of recording material to form a large, continuous, autostereoscopic image. The display can be disassembled into components that are light, compact, easily transportable, and easily storable.

Abstract: An apparatus and method are disclosed for replicating a hologram. The apparatus comprises an assembly operable to position a hologram in proximity to holographic recording material. The apparatus further comprises a beam steering unit operable to direct a beam at component portions of the hologram to replicate the component portions onto a holographic recording material. The beam steering unit is further operable to enable independently variable angles of incidence at which the beam strikes each component portion.

Abstract: A hologram-image recording method and apparatus are provided which prevents or attenuates vibrations so as to produce a bright holographic stereogram having high diffraction efficiency. Such apparatus may includes an exposing recording portion for sequentially exposing and recording interference fringes generated by an object laser beam modulated in accordance with each element image of parallax images and a reference laser beam having coherency with the object laser beam on a recording medium as an elemental hologram, wherein the object laser beam is incident on a surface of the recording medium and the reference laser beam is incident on one of said surface and an opposite surface of the recording medium. The apparatus may further include a moving device for moving the recording medium in a predetermined direction and a braking device for applying a load to the recording medium which resists the movement thereof.

Abstract: A method is proposed, how to produce a holographic screen for projection of the three-dimensional color images, where a narrow and elongate slit-shaped diffuser is recorded on a hologram as an object to ensure the well defined viewing zone forming in the course of the image projection. Further to the back side of the holographic screen a mirror is attached to transform it into reflection mode of operation. Further, the holographic screen is rotated under a control of an eye-tracking system to provide viewing zone movement together with a viewer's eye. Also, a diffuser with vertical light scattering is attached to a surface of the holographic screen to increase a vertical size of a viewing zone of the holographic screen. In addition, two or more holographic screens manufactured by this method are combined in a mosaic manner to form a big size holographic screen.

Abstract: An image recording method and apparatus for recording an image on a holographic stereogram in such a manner as to generate an optimum reproduced image, and an image reproducing method and apparatus capable of generating an optimum reproduced image from the holographic stereogram. A parallax image string is recorded as a series of strip- or dot-shaped hologram elements by having an object light beam and a reference light beam fall on one and the other surfaces of a recording medium for hologram 130. On the reference light incident side, a light inlet block 52 is arranged for having contact with the recording medium for hologram 130 so that no significant change in the refractive index will be produced on an interface with the recording medium for hologram 130. The reference light beam is illuminated via this light inlet block 52 on the recording medium for hologram.