Sony Patent | Image display device and display device

Patent: Image display device and display device

Drawings: Click to check drawins

Publication Number: 20210011293

Publication Date: 20210114

Applicant: Sony

Assignee: Sony Semiconductor Solutions Corporation

Abstract

An image display device 10 includes an optical splitter 11 to which an image emitted from an image forming device 21 placed in an outside (outside of the image display device 10) is injected and that is configured to divide the image into a plurality of images, and a light collecting element 12 configured to collect, on a pupil 32 of a viewer 31, a plurality of images divided by the optical splitter 11 and emitted from the optical splitter 11, and if a focal distance of the light collecting element 12 is denoted by F.sub.0 (unit: mm) and an optical distance from the optical splitter 11 to the light collecting element 12 is by L.sub.0 (unit: mm), L.sub.0=F.sub.0.+-.10 is satisfied.

Claims

1. An image display device comprising: an optical splitter to which an image emitted from an image forming device placed in an outside is injected and that is configured to divide the image into a plurality of images; and a light collecting element configured to collect, on a pupil of a viewer, a plurality of images divided by the optical splitter and emitted from the optical splitter, wherein, if a focal distance of the light collecting element is denoted by F.sub.0 (unit: mm) and an optical distance from the optical splitter to the light collecting element is by L.sub.0 (unit: mm), L.sub.0=F.sub.0.+-.10 is satisfied.

2. An image display device comprising: an optical splitter to which an image emitted from an image forming device placed in an outside is injected and that is configured to divide the image into a plurality of images; and a light collecting element configured to collect, on a pupil of a viewer, a plurality of images divided by the optical splitter and emitted from the optical splitter, wherein, if an extension line of a center line of the pupil is taken as a Z-axis, a straight line connecting turning centers of left and right eyeballs is as an X-axis, and an axis orthogonal to the X-axis and the Z-axis and is as a Y-axis, the optical splitter and the light collecting element are provided in an imaginary plane parallel to an XY plane.

3. An image display device comprising: an optical splitter to which an image emitted from an image forming device placed in an outside is injected and that is configured to divide the image into a plurality of images; and a light collecting element configured to collect, on a pupil of a viewer, a plurality of images divided by the optical splitter and emitted from the optical splitter, wherein the optical splitter is provided on an ear side of the viewer, and the light collecting element is provided on a nose side of the viewer.

4. The image display device according to claim 1, wherein a light beam included in an image incident on the optical splitter is parallel light, and also a light beam included in each of a plurality of images emitted from the optical splitter is parallel light.

5. The image display device according to claim 1, wherein a plurality of images divided by the optical splitter and formed on a retina of the viewer is a same image.

6. The image display device according to claim 1, wherein a plurality of images divided by the optical splitter is directly incident on the light collecting element.

7. The image display device according to claim 6, wherein the optical splitter includes a reflective diffraction grating or a reflective hologram diffraction grating, or a transmission diffraction grating or a transmission hologram diffraction grating, and the light collecting element includes a hologram lens.

8. The image display device according to claim 1, wherein a plurality of images divided by the optical splitter is reflected once or more, and is incident on the light collecting element.

9. The image display device according to claim 8, wherein the optical splitter includes a transmission diffraction grating or a transmission hologram diffraction grating, or a reflective diffraction grating or a reflective hologram diffraction grating, the light collecting element includes a hologram lens, and a light reflection member configured to reflect, toward the light collecting element, light emitted from the optical splitter is further provided.

10. The image display device according to claim 1, wherein an amount of displacement on the pupil of the viewer between a plurality of images divided by the optical splitter is not less than 2 mm and not more than 7 mm.

11. The image display device according to claim 1, wherein division is made into at least two images by the optical splitter.

12. The image display device according to claim 1, wherein the light collecting element includes a hologram lens.

13. The image display device according to claim 1, wherein the optical splitter includes a diffraction grating or a volume hologram diffraction grating.

14. The image display device according to claim 1, wherein a position display means is installed.

15. The image display device according to claim 14, wherein the position display means includes a retroreflection marker.

16. The image display device according to claim 1, wherein the image forming device is placed more on a front side than the viewer.

17. The image display device according to claim 1, configured to be mounted on a head of the viewer.

18. A display device comprising: an image forming device; and an image display device, wherein the image display device includes the image display device according to claim 1.

19. The display device according to claim 18, wherein a position display means is installed in the image display device, a position detection means configured to detect a position of the position display means is provided in the image forming device, and a position of an image emitted from the image forming device is controlled on a basis of a result of detection of the position of the position display means by the position detection means.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to an image display device, and a display device including the image display device.

BACKGROUND ART

[0002] A retinal projection display based on the Maxwellian view in which an image (a light flux) is directly projected on the retina of a viewer and thereby the image is displayed, specifically, a retinal projection head-mounted display (hereinafter, occasionally abbreviated as a “retinal projection HMD”) is widely known. Meanwhile, in such a retinal projection HMD, it is necessary that a point of light convergence be caused to be located on the pupil; however, the diameter of the pupil of a human being is 2 mm in a bright environment and 7 mm in a dark environment, and the range is very narrow. Therefore, it is necessary to strictly control the position of the image so that the image (the light flux) is incident on the pupil of the human being. Further, there is also a problem that, due to the movement of the eyeball, the mounting misalignment of the retinal projection HMD, etc., the image (the light flux) deviates from the pupil of the viewer and the image cannot continue to be viewed correctly.

[0003] There is disclosed a technology in which, in a retinal projection HMD, an optical splitter that splits light is provided on the optical path between an image forming device and an eyepiece that causes an image to converge on the pupil (for example, U.S. Pat. No. 5,701,132). In this technology, the problem mentioned above is solved by causing a plurality of images to converge on the pupil of a viewer by means of split fluxes of light.

CITATION LIST

Patent Document

[0004] Patent Document 1: U.S. Pat. No. 5,701,132

SUMMARY OF THE INVENTION

Problems to be Solved by the Invention

[0005] Meanwhile, it is difficult to provide an optical splitter between an image forming device and an eyepiece in a case of envisaging a retinal projection HMD of a style in which the technology disclosed in the published US patent document mentioned above is applied and the image forming device and the eyepiece are separated, that is, of a style in which the image forming device is placed in a place far away from the eyepiece (specifically, for example, in a case where a viewer wears the image forming device on the hand or in a case where the image forming device is provided in a facility in the outside and a viewer wears the eyepiece as an eyeglass). That is, in a case where the optical splitter is provided on the image forming device side, there is a problem that the distance between the optical splitter and the eyepiece is long; further, in a case where the optical splitter is provided on the eyepiece side, since the optical splitter needs to be provided outside the eyeglasses, there is a problem that it is difficult to reduce the size and weight of the retinal projection head-mounted display.

[0006] Thus, an object of the present disclosure is to provide a display device, such as a retinal projection HMD, having a configuration and a structure capable of achieving size and weight reduction, and an image display device to be included in a relevant display device.

Solutions to Problems

[0007] In order to achieve the issues described above, according to a first aspect of the present disclosure, there is provided an image display device including:

[0008] an optical splitter to which an image emitted from an image forming device placed in an outside (outside of the image display device) is injected and that is configured to divide the image into a plurality of images; and

[0009] a light collecting element configured to collect, on a pupil of a viewer, a plurality of images divided by the optical splitter and emitted from the optical splitter,

[0010] in which, if a focal distance of the light collecting element is denoted by F.sub.0 (unit: mm) and an optical distance from the optical splitter to the light collecting element is by L.sub.0 (unit: mm),

L.sub.0=F.sub.0.+-.10

[0011] is satisfied.

[0012] In order to achieve the issues described above, according to a second aspect of the present disclosure, there is provided an image display device including:

[0013] an optical splitter to which an image emitted from an image forming device placed in an outside is injected and that is configured to divide the image into a plurality of images; and

[0014] a light collecting element configured to collect, on a pupil of a viewer, a plurality of images divided by the optical splitter and emitted from the optical splitter,

[0015] in which, if an extension line of a center line of the pupil is taken as a Z-axis, a straight line connecting turning centers of left and right eyeballs is as an X-axis, and an axis orthogonal to the X-axis and the Z-axis and is as a Y-axis, the optical splitter and the light collecting element are provided in an imaginary plane parallel to an XY plane.

[0016] In order to achieve the issues described above, according to a third aspect of the present disclosure, there is provided an image display device including:

[0017] an optical splitter to which an image emitted from an image forming device placed in an outside is injected and that is configured to divide the image into a plurality of images; and

[0018] a light collecting element configured to collect, on a pupil of a viewer, a plurality of images divided by the optical splitter and emitted from the optical splitter,

[0019] in which the optical splitter is provided on an ear side of the viewer, and the light collecting element is provided on a nose side of the viewer.

[0020] A display device of the present disclosure for achieving the object mentioned above includes an image forming device and an image display device, and the image display device includes the image display device according to any of the first aspect to the third aspect of the present disclosure.

BRIEF DESCRIPTION OF DRAWINGS

[0021] FIG. 1A and FIG. 1B are a conceptual diagram of an image display device and a display device of Example 1 and a schematic cross-sectional view of the image display device of Example 1, respectively.

[0022] FIG. 2A, FIG. 2B, and FIG. 2C are conceptual diagrams of the image display device and the display device of Example 1.

[0023] FIG. 3A and FIG. 3B are schematic cross-sectional views of modification examples of the image display device of Example 1.

[0024] FIG. 4A and FIG. 4B are schematic cross-sectional views of an image display device of Example 2 and a modification example thereof, respectively.

[0025] FIG. 5A and FIG. 5B are schematic cross-sectional views of other modification examples of the image display device of Example 2.

[0026] FIG. 6A and FIG. 6B are a schematic diagram of the image display device of Example 1 as seen from the front side and a schematic cross-sectional view of the image display device of Example 1 taken in an XZ plane, respectively.

[0027] FIG. 7A and FIG. 7B are conceptual diagrams of an image forming device of a first configuration and an image forming device of a second configuration, respectively.

[0028] FIG. 8 is a schematic diagram of a frame, etc. including the image display device of Example 1 as seen from the front side.

[0029] FIG. 9A and FIG. 9B are schematic diagrams of a state where a display device of Example 1 is being used in a room and a state where an image forming device is provided on the back surface of the back of each of seats, respectively.

[0030] FIG. 10A and FIG. 10B are schematic diagrams of a state where a display device of Example 3 is being used in a room and a schematic cross-sectional view of the image display device of Example 3 taken in an XZ plane, respectively.

[0031] FIG. 11 is a diagram for describing a method for fabricating a reflective volume hologram diffraction grating.

[0032] FIG. 12A is an enlarged schematic cross-sectional view showing part of a reflective volume hologram diffraction grating, and FIG. 12B and FIG. 12C are schematic partial cross-sectional views of a reflective blazed diffraction grating and a reflective blazed diffraction grating having step shapes, respectively (however, hatching lines are omitted).

MODE FOR CARRYING OUT THE INVENTION

[0033] Hereinafter, the present disclosure will be described on the basis of examples, with reference to the drawings, but the present disclosure is not limited to the examples, and various numerical values or materials in the examples are merely an example. Furthermore, the present disclosure will be described in the following order.

[0034] 1. Overall description of image display devices according to first aspect to third aspect of present disclosure and display device of present disclosure

[0035] 2. Example 1 (an image display devices according to the first aspect to the third aspect of the present disclosure and a display device of the present disclosure)

[0036] 3. Example 2 (modification of Example 1)

[0037] 4. Example 3 (modification of Example 1 and Example 2)

[0038] 5. Others

OVERALL DESCRIPTION OF IMAGE DISPLAY DEVICES ACCORDING TO FIRST ASPECT TO THIRD ASPECT OF PRESENT DISCLOSURE AND DISPLAY DEVICE OF PRESENT DISCLOSURE

[0039] In the image display devices according to the first aspect to the third aspect of the present disclosure and the image display devices according to the first aspect to the third aspect of the present disclosure included in the display device of the present disclosure, the light collecting element causes a plurality of images divided by the optical splitter and emitted from the optical splitter to be collected on the pupil of the viewer; in a state where it is assumed that the position of the light collecting element and the position of the pupil of the viewer are relatively fixed, there is a case where all of the plurality of images is collected on the pupil of the viewer and there is also a case where part of the plurality of images is collected on the pupil of the viewer. However, if the light collecting element and the pupil of the viewer relatively move along an XY plane, the light collecting element can cause all of the plurality of images to be collected on the pupil of the viewer.

[0040] Further, in the image display device according to the first aspect of the present disclosure and the image display device according to the first aspect of the present disclosure included in the display device of the present disclosure, in a case where, for example, the optical splitter includes a diffraction grating, L.sub.0 is defined as the optical distance from the optical splitter to the light collecting element (specifically, the optical distance between the facing surfaces of the optical splitter and the light collecting element) along the course of light that is emitted from the center of the image forming device, is incident on the optical splitter, is emitted as the 0-th order diffracted light from the optical splitter, and is incident on the light collecting element (for the sake of convenience, referred to as a “center light course”). The optical distance refers to the actual length of the optical path in a medium multiplied by the refractive index of the medium. It is preferable that the pupil of the viewer be located at the focus of the light collecting element; however, if no problem occurs in actual use, the pupil of the viewer may be located in a position slightly shifted from the focus of the light collecting element.

[0041] Further, in the image display device according to the second aspect of the present disclosure and the image display device according to the second aspect of the present disclosure included in the display device of the present disclosure, the center line of the pupil (the center line of the pupil of the eyeball of the viewer (a line-of-sight front-side light beam)) is a straight line that is parallel to the perpendicular bisector of a straight line (an X-axis) connecting the turning centers of the left and right eyeballs and that passes through the turning center of each eyeball. Alternatively, the center line of the pupil (a pupillary axis) is defined by a straight line that passes through the center of the entrance pupil of the eyeball and that is perpendicular to the surface of the cornea. Although the optical splitter and the light collecting element are provided in an imaginary plane parallel to an XY plane, the optical splitter and the light collecting element may not be provided in an imaginary plane parallel to a strictly identical XY plane. That is, also in a case where the optical splitter is provided in a first XY plane and the light collecting element is provided in a second XY plane, and the distance between the first XY plane and the second XY plane is, for example, not more than 30 mm, the optical splitter and the light collecting element are regarded as being provided in an imaginary plane parallel to the XY plane. Further, also in a case where the optical splitter is provided in a first XY plane and the light collecting element is provided in a second XY plane, and the first XY plane is inclined with respect to the second XY plane, the optical splitter and the light collecting element are regarded as being provided in an imaginary plane parallel to the XY plane.

[0042] In the display device of the present disclosure, it is possible to employ a form in which

[0043] a position display means is installed in the image display device,

[0044] a position detection means that detects the position of the position display means is provided in the image forming device, and

[0045] the position of an image emitted from the image forming device is controlled on the basis of the result of detection of the position of the position display means by the position detection means. Here, specifically, a retroreflection marker may be given as the position display means, and a light emitting diode that emits infrared rays and an infrared sensor or an infrared camera that detects infrared rays returning from the retroreflection marker may be given as the position detection means. It is preferable that a filter (an infrared transmission filter) that transmits infrared rays and blocks visible light be placed on the infrared incident side of the infrared sensor or the infrared camera. Then, if the position of the retroreflection marker and further the position of the image display device are detected by the position detection means and the position of an image emitted from the image forming device is controlled on the basis of the detection result, the image emitted from the image forming device can be surely caused to arrive at the optical splitter. Examples of the method for controlling the position of an image emitted from the image forming device include a method in which a movable mirror that an image emitted from the image forming device is incident on is placed and an image reflected by the movable mirror is caused to be incident on the optical splitter; however, the method is not limited to such a method.

[0046] In the image display devices according to the first aspect to the third aspect of the present disclosure, or the image display devices according to the first aspect to the third aspect of the present disclosure included in the display device of the present disclosure including the preferred forms mentioned above (hereinafter, these are collectively referred to as “the image display device, etc. of the present disclosure”), it is possible to employ a form in which a light beam included in an image incident on the optical splitter is substantially parallel light and also a light beam included in each of a plurality of images emitted from the optical splitter is substantially parallel light.

[0047] In the image display device, etc. of the present disclosure including the preferred forms mentioned above, it is possible to employ a form in which a plurality of images divided by the optical splitter and formed as images on the retina of the viewer is the same image.

[0048] Then, in the image display device, etc. of the present disclosure including the various preferred forms described hereinabove, it is possible to employ a configuration in which a plurality of images divided by the optical splitter is directly incident on the light collecting element. The space located between the optical splitter and the light collecting element may be occupied by air, or may be occupied by a base material (for example, a plastic material or glass). In a case of the former, it is sufficient that the optical splitter and the light collecting element be installed on an appropriate support member; in a case of the latter, it is sufficient that the optical splitter and the light collecting element be installed on the base material. Then, in such a configuration, it is possible to employ a configuration in which the optical splitter includes a reflective diffraction grating or a reflective hologram diffraction grating (specifically, a reflective volume hologram diffraction grating), or a transmission diffraction grating or a transmission hologram diffraction grating (specifically, a transmission volume hologram diffraction grating), and the light collecting element includes a hologram lens.

[0049] Alternatively, in the image display device, etc. of the present disclosure including the various preferred forms described hereinabove, it is possible to employ a configuration in which a plurality of images divided by the optical splitter is reflected once or more and is incident on the light collecting element. Then, in this case, it is possible to employ a configuration in which the optical splitter includes a transmission diffraction grating or a transmission hologram diffraction grating (specifically, a transmission volume hologram diffraction grating), or a reflective diffraction grating or a reflective hologram diffraction grating (specifically, a reflective volume hologram diffraction grating), the light collecting element includes a hologram lens, and a light reflection member that reflects, toward the light collecting element, light emitted from the optical splitter is further provided. A reflective diffraction grating member may be given as the light reflection member. Then, in this case, the space located between the optical splitter, the light reflection member, and the light collecting element may be occupied by air, or may be occupied by a base material (for example, a plastic material or glass). In a case of the former, it is sufficient that the optical splitter, the light reflection member, and the light collecting element be installed on an appropriate support member; in a case of the latter, it is sufficient that the optical splitter, the light reflection member, and the light collecting element be installed on the base material. Alternatively, it is also possible to employ a configuration in which a base material serves also as the light reflection member. Specifically, it is sufficient that the optical splitter and the light collecting element be installed on a base material, and a plurality of images divided by the optical splitter and propagating through the base material be caused to be totally reflected in the base material once or more and be caused to be incident on the light collecting element. Note that the term of “total reflection” means total internal reflection or total reflection in the base material.

[0050] Furthermore, in the image display device, etc. of the present disclosure including the various preferred forms and configurations described hereinabove, it is possible to employ a form in which the amount of displacement on the pupil of the viewer between a plurality of images divided by the optical splitter is not less than 2 mm and not more than 7 mm. Alternatively, it is preferable that

(mm).ltoreq.F.sub.0tan(.theta.).ltoreq.7 (mm)

[0051] be satisfied. Here, the angle between the light flux (referred to as “center light flux-A”) located at the center of, among the images divided by the optical splitter, the image located most on the inside (for the sake of convenience, referred to as “image-A”) and the light flux (referred to as “center light flux-B”) located at the center of the image located most on the inside symmetrically to image-A with the center light course as a symmetry axis (for the sake of convenience, referred to as “image-B”) is set to 2 .theta..

[0052] Furthermore, in the image display device, etc. of the present disclosure including the various preferred forms and configurations described hereinabove, it is possible to employ a form in which division is made into at least two images by the optical splitter. If a horizontal direction (an X-axis direction) and a vertical direction (a Y-axis direction) are set with the viewer as a standard, specific examples include a form in which division is made into three images in the horizontal direction by the optical splitter, a form in which division is made into three images in the vertical direction, a form in which an image is divided into three images in the horizontal direction and into three images in the vertical direction in a cross form (since one image including the center light course overlaps, this is a form in which division is made into a total of five images), a form in which an image is divided into two images in the horizontal direction and into two images in the vertical direction, i.e., 2.times.2=4, and a form in which an image is divided into three images in the horizontal direction and into three images in the vertical direction, i.e., 3.times.3=9, for example.

[0053] Furthermore, in the image display device, etc. of the present disclosure including the various preferred forms and configurations described hereinabove, it is possible to employ a form in which the light collecting element includes a hologram lens, as described above. The hologram lens may have a configuration and a structure that are widely known. The hologram lens may be formed on a surface of a base material. By the light collecting element including a hologram lens, the image display device can be made a semi-transmission (see-through) type, and thereby the exterior can be seen via the light collecting element. In a case where it is not necessary that the image display device be a semi-transmission (see-through) type, the light collecting element may include, for example, an ordinary lens.

[0054] Furthermore, in the image display device, etc. of the present disclosure including the various preferred forms and configurations described hereinabove, it is possible to employ a form in which the optical splitter includes a diffraction grating (a reflective diffraction grating or a transmission diffraction grating). The diffraction grating may have a configuration and a structure that are widely known; examples include a reflective blazed diffraction grating (see FIG. 12B) and a reflective blazed diffraction grating having step shapes (see FIG. 12C), for example; however, the form is not limited to these diffraction gratings. A plurality of images is obtained on the basis of the k-th order diffracted light (provided that k=0, .+-.1, .+-.2, … ) emitted from the diffraction grating. The diffraction grating is an optical element that creates a diffraction phenomenon by means of a lattice-like pattern; in the lattice pattern, for example, straight-lined concavities and convexities are arranged parallel with a period of a micrometer size; the period, the pattern thickness (the thickness difference between concavity and convexity), etc. of the lattice pattern are selected on the basis of the wavelength region of light emitted from the image forming device, as appropriate. The diffraction grating may be formed on a surface of a base material. Further, a light reflection film including a dielectric multiple-layer film or a metal film may be formed on the light incident surface of the reflective diffraction grating. The diffraction grating may be fabricated by a widely known method.

[0055] Alternatively, the optical splitter may include a hologram diffraction grating. That is, the optical splitter may include a transmission volume hologram diffraction grating, or may include a reflective volume hologram diffraction grating.

[0056] FIG. 12A illustrates a schematic partial cross-sectional view in which the reflective volume hologram diffraction grating is enlarged. An interference fringe having an inclined angle (a slant angle) .phi. is formed on the reflective volume hologram diffraction grating. Here, the inclined angle .phi. indicates an angle between a front surface of the reflective volume hologram diffraction grating and the interference fringe. The interference fringe is formed over a front surface of the reflective volume hologram diffraction grating from the inside thereof. The interference fringe satisfies a Bragg’s condition. Here, the Bragg’s condition indicates a condition of satisfying Expression (A) described below. In Expression (A), m represents a positive integer, .lamda. represents a wavelength, d represents a pitch of a grating surface (an interval of a virtual flat surface including the interference fringe in a normal line direction), .THETA. represents a complementary angle of the angle incident on the interference fringe. In addition, a relationship of .THETA. in a case where light enters the reflective volume hologram diffraction grating at an incident angle .psi., the inclined angle .phi., and the incident angle .psi. is represented by Expression (B).

m.lamda.=2dsin(.THETA.) (A)

.THETA.=90.degree.-(.phi.+.psi.) (B)

[0057] If the angle of incidence .psi. of light included in an image is fixed, it is necessary to variously change the value of .THETA. in order to obtain a plurality of images divided by the optical splitter and emitted from the optical splitter. To change the value of .THETA., it is sufficient that the value of the angle of inclination .phi. be changed from Formula (B), and further it is sufficient that the value of the pitch d of the grating surface be changed from Formula (A). In other words, by appropriately selecting the value of the angle of inclination .phi. and the value of the pitch d of the grating surface, an image incident on the optical splitter including a volume hologram diffraction grating can be divided by the optical splitter, and a plurality of images can be caused to be emitted from the optical splitter. Note that, if an image including parallel light is incident on the optical splitter, also a light beam included in each of images emitted from the optical splitter is parallel light.

[0058] It is possible to employ a form in which also a reflective diffraction grating member included in the light reflection member includes a hologram diffraction grating, more specifically, a volume hologram diffraction grating.

[0059] A photopolymer material may be given as a constituent material of the volume hologram diffraction grating. It is sufficient that the constituent material and the basic structure of the volume hologram diffraction grating be the same as the constituent material and the structure of a conventional volume hologram diffraction grating. On the volume hologram diffraction grating, interference fringes are formed from the interior to the surface; it is sufficient that the method for forming relevant interference fringes themselves be the same as a conventional formation method. Specifically, it is sufficient that, as shown in FIG. 11, for example, a member (for example, a photopolymer material) included in the volume hologram diffraction grating be irradiated with object light from a first prescribed direction on one side and simultaneously the member included in the volume hologram diffraction grating be irradiated with reference light from a second prescribed direction on another side, and interference fringes formed by the object light and the reference light be recorded in the volume hologram diffraction grating. In the example shown in FIG. 11, a mirror that applies reference light to the photopolymer material is tilted 60 degrees and (60.+-.6 degrees), and reference light is applied to the photopolymer material three times in total. In the volume hologram diffraction grating thus obtained, the injected image can be divided into three images. A desired pitch of interference fringes on the surface of the volume hologram diffraction grating and a desired angle of inclination (angle of slanting) of interference fringes can be obtained by appropriately selecting the first prescribed direction, the second prescribed direction, and the wavelengths of object light and reference light. The angle of inclination of interference fringes means the angle between the surface of the volume hologram diffraction grating and the interference fringes. In a case where the volume hologram diffraction grating includes a stacked structure of P volume hologram diffraction grating layers, it is sufficient that the stacking of such volume hologram diffraction grating layers be performed by a method in which P volume hologram diffraction grating layers are separately fabricated and then the P volume hologram diffraction grating layers are stacked (adhered) using, for example, an ultraviolet curable adhesive. Further, P volume hologram diffraction grating layers may be fabricated by a method in which one volume hologram diffraction grating layer is fabricated using a photopolymer material having tackiness and then photopolymer materials having tackiness are sequentially stuck thereon to fabricate volume hologram diffraction grating layers. Such a volume hologram diffraction grating is a refractive index modulation type. As necessary, monomers in the photopolymer materials that are not polymerized but left during the irradiation of the fabricated volume hologram diffraction grating layers with object light and reference light may be polymerized and fixated by irradiating the volume hologram diffraction grating layers with energy rays. Further, heat treatment may be performed for stabilization, as necessary.

[0060] Furthermore, in the image display device of the present disclosure including the various preferred forms and configurations described hereinabove, it is possible to employ a form in which a position display means is installed; in this case, it is possible to employ a form in which the position display means includes a retroreflection marker.

[0061] Furthermore, in the image display device of the present disclosure including the various preferred forms and configurations described hereinabove, it is possible to employ a form in which the image forming device is placed more on the front side than the viewer. Note that, as long as the image forming device is placed more on the front side than the viewer, the image forming device may be located in a place higher than the head of the viewer, may be located at the same level as the head of the viewer, may be located in a place lower than the head of the viewer, may be located facing the viewer, or may be located obliquely with respect to the viewer, depending on the specifications of the optical splitter and the light collecting element.

[0062] Furthermore, it is possible to employ a form in which any of the image display device, etc. of the present disclosure including the various preferred forms and configurations described hereinabove is mounted on the head of the viewer. That is, it is possible to employ a form in which each of the image display device, etc. of the present disclosure is a head-mounted display (HMD), more specifically, a retinal projection HMD based on the Maxwellian view.

[0063] In a case of forming the base material with transparent plastic materials, examples of plastic materials include polyethylene terephthalate, polyethylene naphthalate, polycarbonate, cellulose esters such as cellulose acetate, fluoropolymers such as a copolymer of polyvinylidene fluoride or polytetrafluoroethylene and hexafluoropropylene, polyethers such as polyoxymethylene, polyolefins such as polyacetal, polystyrene, polyethylene, polypropylene, and a methylpentene polymer, polyimides such as polyamide-imide and polyetherimide, polyamide, polyethersulfone, polyphenylene sulfide, polyvinylidene fluoride, tetraacetyl cellulose, brominated phenoxy, polyarylate, polysulfone, and the like. In a case of forming the base material with glass, examples of glass include transparent glass, such as soda-lime glass or white sheet glass. A hard coat layer including an organic/inorganic mixed layer and/or an antireflection film containing a fluorine-based resin may be formed on the outer surface of the base material. The support member may include a framework-like member containing a metal, an alloy, or a plastic material, and may include a frame described later.

[0064] In the image display device of the present disclosure having various preferred aspects and configurations described hereinabove, it is possible to set an aspect in which the image forming device includes a plurality of pixels arranged in a two-dimensional matrix. Such a configuration of the image forming device, for convenience, will be referred to as an “image forming device of a first configuration”.

[0065] For example, examples of the image forming device of the first configuration are capable of including an image forming device configured of a reflective spatial light modulation device and a light source; an image forming device configured of a transmissive spatial light modulation device and a light source; and an image forming device configured of a light emitting element such as an organic electro luminescence (EL), an inorganic EL, a light emitting diode (LED), and a semiconductor laser element, and among them, the image forming device configured of the organic EL light-emitting element (organic EL display device), or the image forming device configured of the reflective spatial light modulation device and the light source is preferable. Examples of the spatial light modulation device are capable of including a light valve, for example, a transmissive or reflective liquid crystal display device such as liquid crystal on silicon (LCOS), and a digital micro mirror device (DMD), and examples of the light source are capable of including a light emitting element. Further, it is possible to set a configuration in which the reflective spatial light modulation device includes a polarization beam splitter which reflects a part of light from the liquid crystal display device and the light source and guides the light to the liquid crystal display device, allows a part of light reflected by the liquid crystal display device to pass therethrough, and guides the light to an optical splitter. Examples of the light emitting element configuring the light source are capable of including a red light emitting element, a green light emitting element, a blue light emitting element, and a white light emitting element. Alternatively, red light, green light, and blue light exiting from the red light emitting element, the green light emitting element, and the blue light emitting element are mixed or subjected to brightness homogenization by using a light pipe, and thus, white light may be obtained. For example, a semiconductor laser element, a solid laser, or an LED can be exemplified as the light emitting element. It is sufficient that the number of pixels be determined on the basis of the specification to be required in the image display device, and 320.times.240, 432.times.240, 640.times.480, 1024.times.768, 1920.times.1080, and the like can be exemplified as a specific value of the number of pixels. In the image forming device of the first configuration, it is possible to employ a form in which a diaphragm is placed in a position of the front focus (the focus on the image forming device side) of a lens system (described later); the diaphragm falls under an image emission section from which an image is emitted from the image forming device.

[0066] Alternatively, in the image display device of the display device according to the present disclosure having preferred aspects and configurations described hereinabove, it is possible to set an aspect in which the image forming device includes the light source, and a scanning means scanning light exiting from the light source to form an image. Such an image forming device, for convenience, will be referred to as an “image forming device of a second configuration”.

[0067] Examples of the light source in the image forming device of the second configuration are capable of including a light emitting element, and specifically, are capable of including a red light emitting element, a green light emitting element, a blue light emitting element, and a white light emitting element, or red light, green light, and blue light exiting from the red light emitting element, the green light emitting element, and the blue light emitting element are mixed or subjected to brightness homogenization by using a light pipe, and thus, white light may be obtained. For example, a semiconductor laser element, a solid laser, or an LED can be exemplified as the light emitting element. It is sufficient that the number of pixels (virtual pixels) in the image forming device of the second configuration be determined on the basis of the specification to be required in the image display device, and 320.times.240, 432.times.240, 640.times.480, 1024.times.768, 1920.times.1080, and the like can be exemplified as a specific value of the number of pixels (virtual pixels). In addition, in a case where color image display is performed, and the light source is configured of the red light emitting element, the green light emitting element, and the blue light emitting element, for example, it is preferable to perform color synthesis by using a cross prism. Examples of the scanning means are capable of including a micro electro mechanical systems (MEMS) mirror including a micro mirror which is capable of performing horizontal scanning and perpendicular scanning with respect to light exiting from the light source, for example, rotating the light in a two-dimensional direction, or a Galvano mirror. In the image forming device of the second configuration, it is possible to employ a form in which a MEMS mirror or a galvanometer mirror is placed in a position of the front focus (the focus on the image forming device side) of a lens system (described later); the MEMS mirror and the galvanometer mirror fall under an image emission section from which an image is emitted from the image forming device.

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