Sony Patent | Video projection system, video projection device, video display light diffraction optical element, and video projection method

Patent: Video projection system, video projection device, video display light diffraction optical element, and video projection method

Drawings: Click to check drawins

Publication Number: 20210397003

Publication Date: 20211223

Applicant: Sony

Abstract

The present technology provides a video projection system (100) including: a video projection device (101) equipped with a projection optical system (110) configured to project video display light onto an eyeball (130); and an optical element (120) configured to cause the video display light to be collected near a pupil and then to reach a retina. The video projection system (100) is used in a state where a positional relationship between the optical element (120) and the eyeball (130) is fixed. Furthermore, the present technology also provides a video projection method including: a projection step of projecting video display light from a video projection device toward an eyeball; and a light collecting step of causing video display light projected in the projection step to be collected near a pupil with an optical element (120) and then to reach a retina. The projection step and the light collecting step are performed in a state where a positional relationship between the optical element (120) and the eyeball (130) is fixed.

Claims

1. A video projection system comprising: a video projection device equipped with a projection optical system configured to project video display light onto an eyeball; and an optical element configured to cause the video display light to be collected near a pupil and then to reach a retina, wherein the video projection system is used in a state where a positional relationship between the optical element and the eyeball is fixed.

2. The video projection system according to claim 1, wherein a main light beam of the video display light incident on the optical element is substantially parallel to an optical axis.

3. The video projection system according to claim 1, wherein the optical element is used in contact with a surface of the eyeball.

4. The video projection system according to claim 3, wherein the video projection system is used in a state where a positional relationship between the optical element and a pupil is fixed.

5. The video projection system according to claim 1, wherein the optical element is used without contacting a surface of the eyeball.

6. The video projection system according to claim 1, wherein the optical element has a curved surface, and a curvature center of the curved surface and a curvature center of a curved surface of the surface of the eyeball are substantially concentric.

7. The video projection system according to claim 1, wherein the optical element is a holographic optical element.

8. The video projection system according to claim 1, wherein the projection optical system includes a two-dimensional array display element, and the two-dimensional array display element forms the video display light.

9. The video projection system according to claim 1, wherein the projection optical system includes a scanning mirror, and the scanning mirror forms the video display light.

10. The video projection system according to claim 1, wherein the projection optical system includes a partial multiplexing member, and the partial multiplexing member reflects or diffracts the video display light to reach the optical element.

11. The video projection system according to claim 1, wherein the optical element has a holographic optical element layer, and the holographic optical element layer diffracts the video display light incident on the optical element to be collected near a pupil.

12. The video projection system according to claim 11, wherein the optical element further has a 0th-order light reflecting layer, the optical element has a lamination in an order of the holographic optical element layer and the 0th-order light reflecting layer from an outside world side, and the 0th-order light reflecting layer reflects 0th-order light having passed through the holographic optical element layer to advance in a direction other than an eyeball.

13. The video projection system according to claim 11, wherein the holographic optical element layer includes a plurality of layers, and the plurality of layers diffracts light having a different wavelength from one another.

14. The video projection system according to claim 1, wherein the optical element has a first holographic optical element layer and a second holographic optical element layer, the optical element has a lamination in an order of the first holographic optical element layer and the second holographic optical element layer from an outside world side, the first holographic optical element layer transmits the video display light, the second holographic optical element layer reflects the transmitted video display light, and the first holographic optical element layer diffracts the reflected video display light to be collected near a pupil.

15. The video projection system according to claim 14, wherein the optical element further has a 0th-order light reflecting layer, the optical element has a lamination in an order of the first holographic optical element layer, the second holographic optical element layer, and the 0th-order light reflecting layer from an outside world side, and the 0th-order light reflecting layer reflects 0th-order light having passed through the first and second holographic optical element layers to advance in a direction other than an eyeball.

16. The video projection system according to claim 14, wherein the first and/or second holographic optical element layer includes a plurality of layers, and the plurality of layers diffracts light having a different wavelength from one another.

17. The video projection system according to claim 1, wherein the projection optical system includes a light discrimination element, and the light discrimination element separates and removes an unnecessary wavelength component from the video display light.

18. The video projection system according to claim 1, wherein the optical element has a holographic optical element layer, and the holographic optical element layer diffracts the video display light incident on the optical element to be collected on a front side or a back side of a pupil.

19. The video projection system according to claim 18, further comprising: an eyeball position detection device configured to detect a position of the eyeball with respect to the optical element; and a control unit configured to specify a light beam group that reaches a retina on a basis of a detection result of the eyeball position detection device, the control unit being configured to control the projection optical system to form the video display light with the light beam group.

20. A video projection device comprising: a projection optical system configured to project video display light onto an eyeball, wherein the video projection device is used in combination with an optical element configured to cause the video display light to be collected near a pupil and then to reach a retina, and a positional relationship between the optical element and the eyeball is fixed in use of the combination.

21. A video display light diffraction optical element that is used in combination with a video projection device equipped with a projection optical system configured to project video display light onto an eyeball, wherein a positional relationship with the eyeball is fixed in use in the combination, and the video display light is collected near a pupil and reaches a retina.

22. A video projection method comprising: a projection step of projecting video display light from a video projection device toward an eyeball; and a light collecting step of causing video display light projected in the projection step to be collected near a pupil with an optical element and then to reach a retina, wherein the projection step and the light collecting step are performed in a state where a positional relationship between the optical element and the eyeball is fixed.

Description

TECHNICAL FIELD

[0001] The present technology relates to a video projection system, a video projection device, a video display light diffraction optical element, and a video projection method. More specifically, the present technology relates to: a video projection system equipped with a projection optical system configured to project video display light onto an eyeball, and with an optical element configured to cause the video display light to be collected near a pupil and then to reach a retina; each element included in the video projection system; and a video projection method in the video projection system.

BACKGROUND ART

[0002] In recent years, attention has been focused on technology of superimposing an image on a scene of an outside world. The present technology is also called augmented reality (AR) technology. One of products using this technology is a head-mounted display. The head-mounted display is used by being mounted on the head of a user. In an image display method using the head-mounted display, for example, when light from the head-mounted display reaches the user’s eyes in addition to light from an outside world, the user recognizes an image of the light from the display as if being superimposed on an image of the outside world.

[0003] Regarding the AR technology, a video presentation method using a contact lens as an optical element has also been proposed. For example, Patent Document 1 below discloses a beam scanned type display device for displaying an image by scanning a user’s retina with a beam. The beam scanned type display device includes: a chassis that mounts a light source for outputting a beam to draw each pixel configuring an image and a scan unit for performing a scan with the beam from the light source in two-dimensional direction; and a contact lens that includes a deflection unit for deflecting the beam with which the scan unit performs the scan in direction to the eye retina of the user wearing the chassis and is independent from the chassis.

CITATION LIST

Patent Document

[0004] Patent Document 1: International Publication No. 2009/066446

SUMMARY OF THE INVENTION

Problems to be Solved by the Invention

[0005] A head-mounted display that projects a video image directly onto a retina causes video display light to be collected near a pupil and to reach the retina. Therefore, when an eyeball is rotated by a user changing a visual line or the like, the video display light may not pass through the pupil and may not reach the retina. Therefore, a main object of the present technology is to provide a technique for recognizing a video image without being affected by a position of a pupil.

Solutions to Problems

[0006] The present technology provides a video projection system including: a video projection device equipped with a projection optical system configured to project video display light onto an eyeball; and an optical element configured to cause the video display light to be collected near a pupil and then to reach a retina. The video projection system is used in a state where a positional relationship between the optical element and the eyeball is fixed.

[0007] According to one implementation aspect of the present technology, a main light beam of the video display light incident on the optical element may be substantially parallel to an optical axis.

[0008] According to one implementation aspect of the present technology, the optical element may be used in contact with a surface of the eyeball.

[0009] According to one implementation aspect of the present technology, the video projection system may be used in a state where a positional relationship between the optical element and the pupil is fixed.

[0010] According to one implementation aspect of the present technology, the optical element may be used without contacting a surface of the eyeball.

[0011] According to one implementation aspect of the present technology, the optical element may have a curved surface, and a curvature center of the curved surface and a curvature center of a curved surface of the surface of the eyeball may be substantially concentric.

[0012] According to one implementation aspect of the present technology, the optical element may be a holographic optical element.

[0013] According to one implementation aspect of the present technology, the projection optical system may include a two-dimensional array display element, and the two-dimensional array display element may form the video display light.

[0014] According to one implementation aspect of the present technology, the projection optical system may include a scanning mirror, and the scanning mirror may form the video display light.

[0015] According to one implementation aspect of the present technology, the projection optical system may include a partial multiplexing member, and the partial multiplexing member may reflect or diffract the video display light to reach the optical element.

[0016] According to one implementation aspect of the present technology, the optical element may have a holographic optical element layer, and the holographic optical element layer may diffract the video display light incident on the optical element to be collected near the pupil.

[0017] According to one implementation aspect of the present technology, the optical element may further have a 0th-order light reflecting layer, the optical element may have a lamination in an order of the holographic optical element layer and the 0th-order light reflecting layer from an outside world side, and the 0th-order light reflecting layer may reflect 0th-order light having passed through the holographic optical element layer to advance in a direction other than the eyeball.

[0018] According to one implementation aspect of the present technology, the holographic optical element layer may include a plurality of layers, and the plurality of layers may diffract light having a different wavelength from one another.

[0019] According to one implementation aspect of the present technology, the optical element may have a first holographic optical element layer and a second holographic optical element layer, the optical element may have a lamination in an order of the first holographic optical element layer and the second holographic optical element layer from an outside world side, the first holographic optical element layer may transmit the video display light, the second holographic optical element layer may reflect the transmitted video display light, and the first holographic optical element layer may diffract the reflected video display light to be collected near the pupil.

[0020] According to one implementation aspect of the present technology, the optical element may further have a 0th-order light reflecting layer, the optical element may have a lamination in an order of the first holographic optical element layer, the second holographic optical element layer, and the 0th-order light reflecting layer from an outside world side, and the 0th-order light reflecting layer may reflect the 0th-order light having passed through the first and second holographic optical element layers to advance in a direction other than the eyeball.

[0021] According to one implementation aspect of the present technology, the first and/or second holographic optical element layer may include a plurality of layers, and the plurality of layers may diffract light having a different wavelength from one another.

[0022] According to one implementation aspect of the present technology, the projection optical system may include a light discrimination element, and the light discrimination element may separate and remove an unnecessary wavelength component from the video display light.

[0023] According to one implementation aspect of the present technology, the optical element may have a holographic optical element layer, and the holographic optical element layer may diffract the video display light incident on the optical element to be collected on a front side or a back side of the pupil.

[0024] According to one implementation aspect of the present technology, there may be further provided: an eyeball position detection device configured to detect a position of the eyeball with respect to the optical element; and a control unit configured to specify a light beam group that reaches a retina on the basis of a detection result of the eyeball position detection device, and control the projection optical system to form the video display light with the light beam group.

[0025] Furthermore, the present technology also provides a video projection device including a projection optical system configured to project video display light onto an eyeball. The video projection device is used in combination with an optical element configured to cause the video display light to be collected near a pupil and then to reach a retina, and a positional relationship between the optical element and the eyeball is fixed in use in the combination.

[0026] Furthermore, the present technology also provides a video display light diffraction optical element that is used in combination with a video projection device equipped with a projection optical system configured to project video display light onto an eyeball, and a positional relationship with the eyeball is fixed in use in the combination. The video display light diffraction optical element causes the video display light to be collected near a pupil and then to reach a retina.

[0027] Furthermore, the present technology also provides a video projection method including: a projection step of projecting video display light from a video projection device toward an eyeball; and a light collecting step of causing video display light projected in the projection step to be collected near a pupil with an optical element and then to reach a retina. In the video projection method, the projection step and the light collecting step are performed in a state where a positional relationship between the optical element and the eyeball is fixed.

BRIEF DESCRIPTION OF DRAWINGS

[0028] FIG. 1 is a view showing an example of a video projection system according to the present technology.

[0029] FIG. 2 is a view showing a relationship between a video display light diffraction optical element and video display light according to the present technology.

[0030] FIG. 3 is a view showing an example of the video projection system according to the present technology.

[0031] FIG. 4 is a view showing an example of the video projection system according to the present technology.

[0032] FIG. 5 is a view showing an example of the video projection system according to the present technology.

[0033] FIG. 6 is a view showing an example of the video projection system according to the present technology.

[0034] FIG. 7 is a view showing an example of the video projection system according to the present technology.

[0035] FIG. 8 is a view showing an example of a video projection device according to the present technology.

[0036] FIG. 9 is a view showing an example of the video projection device according to the present technology.

[0037] FIG. 10 is a view showing an example of the video projection device according to the present technology.

[0038] FIG. 11 is a view showing an example of the video projection device according to the present technology.

[0039] FIG. 12 is a view showing an example of the video projection device according to the present technology.

[0040] FIG. 13 is a view showing an example of the video projection device according to the present technology.

[0041] FIG. 14 is a view showing an example of the video projection device according to the present technology.

[0042] FIG. 15 is a view showing an example of the video projection device according to the present technology.

[0043] FIG. 16 is a view showing an example of the video display light diffraction optical element according to the present technology.

[0044] FIG. 17 is a view showing an example of the video display light diffraction optical element according to the present technology.

[0045] FIG. 18 is a view showing an experimental example of the video projection system according to the present technology.

[0046] FIG. 19 is a view showing an experimental example of the video projection system according to the present technology.

[0047] FIG. 20 is a view showing an experimental example of the video projection system according to the present technology.

[0048] FIG. 21 is a view showing an experimental example of the video projection system according to the present technology.

[0049] FIG. 22 is a view showing an experimental example of the video projection system according to the present technology.

[0050] FIG. 23 is a view showing an example of the video display light diffraction optical element according to the present technology.

[0051] FIG. 24 is a view showing an example of the video display light diffraction optical element according to the present technology.

[0052] FIG. 25 is a view showing an example of the video display light diffraction optical element according to the present technology.

[0053] FIG. 26 is a view showing an example of the video display light diffraction optical element according to the present technology.

[0054] FIG. 27 is a view showing an example of the video display light diffraction optical element according to the present technology.

[0055] FIG. 28 is a view showing an example of diffraction efficiency of the video projection system according to the present technology.

[0056] FIG. 29 is a view showing an example of diffraction efficiency of the video projection system according to the present technology.

[0057] FIG. 30 is a view showing an example of the video projection system according to the present technology.

[0058] FIG. 31 is a view showing an example of diffraction efficiency of the video projection system according to the present technology.

[0059] FIG. 32 is a view showing an example of diffraction efficiency of the video projection system according to the present technology.

[0060] FIG. 33 is a view showing a video projection system of Modified Example 1 according to the present technology.

[0061] FIG. 34 is a view showing the video projection system of Modified Example 1 according to the present technology.

[0062] FIG. 35 is a view showing the video projection system of Modified Example 1 according to the present technology.

[0063] FIG. 36 is a view showing a video projection system of Modified Example 2 according to the present technology.

[0064] FIG. 37 is a view showing the video projection system of Modified Example 2 according to the present technology.

[0065] FIG. 38 is a view showing the video projection system of Modified Example 2 according to the present technology.

[0066] FIG. 39 is a block diagram showing functions of the video projection systems of Modified Examples 1 and 2 according to the present technology.

MODE FOR CARRYING OUT THE INVENTION

[0067] Hereinafter, a preferred mode for implementing the present technology will be described. Note that the embodiments described below show representative embodiments of the present technology, and do not limit the scope of the present technology. Note that the present technology will be described in the following order.

[0068] 1. First embodiment (video projection system)

[0069] (1) Description of first embodiment

[0070] (2) First example of first embodiment (video projection system)

[0071] (3) Second example of first embodiment (video projection system)

[0072] (4) Third example of first embodiment (configuration example of video projection device)

[0073] (5) Fourth example of first embodiment (configuration example of optical element)

[0074] (6) Fifth example of first embodiment (configuration example of optical element)

[0075] (7) Sixth example of first embodiment (configuration example of video projection device)

[0076] 2. Second embodiment (video projection device)

[0077] 3. Third embodiment (video display light diffraction optical element)

[0078] 4. Fourth embodiment (video projection method)

[0079] 5. Modified example (video projection system)

1. First Embodiment (Video Projection System)

(1) Description of First Embodiment

[0080] A video projection system according to the present technology includes: a video projection device equipped with a projection optical system; and an optical element. The projection optical system projects video display light toward the optical element provided in front of an eyeball. Since the optical element of the present technology is used in a state where a positional relationship with the eyeball is fixed, the video display light can be collected near a pupil even if a position of the eyeball with respect to the projection optical system moves, and a field of view that can be displayed is widened.

[0081] According to one implementation aspect of the present technology, the projection optical system may include a two-dimensional array display element. The two-dimensional array display element may form the video display light from illumination light emitted from a light source. The two-dimensional array display element may be, for example, an LCD, an LCOS, or an OLED.

[0082] According to another implementation aspect of the present technology, the projection optical system may include a scanning mirror. The scanning mirror may scan a laser beam emitted from the light source to cause the laser beam to reach the optical element. As a result of the scanning, a video image may be formed. The scanning mirror may be, for example, a MEMS mirror.

[0083] According to one implementation aspect of the present technology, the optical element may be used in contact with a surface of the eyeball. For example, the optical element may be used in a state where a positional relationship with a pupil is fixed. In the present implementation aspect, the optical element may be, for example, a contact-lens-shaped optical element having a material similar to that of a contact lens, and more particularly a contact lens-shaped holographic optical element. Since the optical element is the contact-lens-shaped optical element, it is possible to enlarge a field of view in which a video image by video display light can be recognized, for example, to 60 degrees or more. Furthermore, since the optical element is the contact-lens-shaped optical element, it is possible to easily enlarge an eye box (that is, a spatial area around the eyeball, in which a video image by video display light can be recognized).

[0084] According to another implementation aspect of the present technology, the optical element may be used without contacting a surface of the eyeball. In the present implementation aspect, the optical element may have, for example, a distance of 20 mm or less between a surface of the eyeball and an eyeball-side surface of the optical element. The distance may be 12 mm or more, for example, to prevent user’s eyelashes from coming into contact with the optical element when mounted.

(2) First Example of First Embodiment (Video Projection System)

[0085] According to one implementation aspect of the present technology, the projection optical system includes a two-dimensional array display element. An example of a video projection system according to the present implementation aspect will be described with reference to FIGS. 1 to 4.

[0086] FIG. 1(a) is a schematic view showing an example of a video projection system 100 according to the present technology. Furthermore, FIG. 1(b) is an enlarged view of an area A of FIG. 1(a). Note that FIG. 1 schematically shows a main light beam and a peripheral light beam emitted from a projection optical system 110.

[0087] As shown in FIG. 1(a), the video projection system 100 includes a video projection device 101 and an optical element 120. Since the video projection system 100 is used in a state where a positional relationship between the optical element 120 and an eyeball 130 is fixed, a distance between the optical element 120 and a rotation center of the eyeball 130 does not change even if the eyeball 130 rotates. Therefore, it is not necessary to adjust video display light in accordance with movement of the eyeball, and it is not necessary to provide an eye tracking device.

[0088] The video projection device 101 includes the projection optical system 110, and the projection optical system 110 includes a two-dimensional array display element 111, a first lens 112, and a second lens 113.

[0089] The two-dimensional array display element 111 forms video display light from, for example, illumination light emitted from a light source (not shown). For example, on an optical path between the light source and the two-dimensional array display element 111, an imaging system and a color separation synthesis system may be provided. An arrangement of these components may be appropriately designed by those skilled in the art. The two-dimensional array display element 111 may be, for example, an LCD, an LCOS, or an OLED.

[0090] Emission of the video display light by the two-dimensional array display element 111 may be controlled by, for example, a control unit (not shown). That is, the video projection device 101 may include a control unit (not shown) configured to control emission of the video display light by the two-dimensional array display element 111. The control unit may include, for example, a central processing unit (CPU) and a RAM. As the CPU, any processor may be used. The RAM may include, for example, a cache memory and a main memory, and temporarily store a program used by the CPU. The video projection device 101 may further include, for example, various components used for controlling a video display element, such as a disk, a communication device, and a drive. The disk may store, for example, various image data and various programs such as a program for realizing emission of video display light by the two-dimensional array display element 111. The communication device may acquire image data and/or a program for controlling the video display element, from a network, for example. The drive may read out a program and/or image data recorded on, for example, a recording medium such as a microSD memory card and an SD memory card, and output to the RAM.

[0091] In a video presentation method (also called image presentation by Maxwellian view) in which video display light is collected near a pupil and reaches the retina, conventionally, a scanning mirror has often been used. In a case of using a scanning mirror, it is required to use a laser beam as a light source.

[0092] In the video projection system of the present technology, since the two-dimensional array display element can be used as described above, a range of selection of the light source is widened. Furthermore, in a case of scanning the laser beam with a scanning mirror, it is difficult to widen a display field angle, and a display time per pixel may become shorter and display driving may be difficult when the number of pixels is to be increased. However, the two-dimensional array display element makes it possible to easily increase the number of pixels by increasing the number of pixels of the display element even in a case of a wide viewing angle.

[0093] The first lens 112 and the second lens 113 are provided between the two-dimensional array display element 111 and the optical element 120. As shown in FIG. 1(a), the video display light projected from the two-dimensional array display element 111 is refracted by the first lens 112 and further refracted by the second lens 113 to be incident on the optical element 120.

[0094] As shown in FIG. 1(b), the video projection system 100 is configured such that video display light refracted by the second lens 113 has a focal point at P1 to P3 immediately before the optical element 120. Since the video display light has the focal point immediately before the optical element 120, peripheral light beams are prevented from being dismissed by the pupil, and peripheral light beams can be sufficiently incident on the pupil. Therefore, when the optical element 120 causes peripheral light beams to be collected near the pupil, a bright image can be projected onto a retina 132. A distance between the focal point and the optical element 120 may be set in accordance with an amount of peripheral light beams desired to be incident on the pupil.

[0095] In the present embodiment, a main light beam of video display light incident on the optical element 120 may preferably have a direction such that the video display light may be collected near the pupil after being incident on the optical element 120, and more preferably, may be substantially parallel to an optical axis. That is, in the present embodiment, it is preferable that the main light beam of the video display light reaches the optical element 120 as a telecentric light beam. The projection optical system 110 may be configured such that video display light whose main light beam is substantially parallel to the optical axis is incident on the optical element 120.

[0096] As shown in FIG. 2, since the main light beam of the video display light is substantially parallel to the optical axis, the video display light can be collected near the pupil even if a position of the optical element 120 and the eyeball 130 changes. Specifically, for example, even if the optical element 120 and the eyeball 130 move to a position shown in FIG. 2(b) or 2(c) from a position shown in FIG. 2(a), the video display light can be collected near the pupil and guided to the retina 132.

[0097] Furthermore, when the main light beam of the video display light is substantially parallel to the optical axis, an angle and a position of the main light beam of the video display light incident on the optical element 120 are always unchanged, even if a position of the optical element 120 and the eyeball 130 changes. Therefore, according to the present embodiment, it is possible to prevent a change of resolution of a central portion of a field of view recognized by the user, even if the eyeball 130 is moved.

[0098] In the present embodiment, the projection optical system 110 may be configured such that the video display light is collected near the pupil and reaches the retina 132. That is, the video display light may be projected onto the retina 132 by so-called Maxwellian view. For example, as shown in FIG. 1(a), the video display light projected from the projection optical system 110 is diffracted by the optical element 120. The diffracted video display light is collected near the pupil and then reaches the retina 132.

[0099] In the Maxwellian view optical system, since one dot (a minimum display unit) in a displayed video image passes through one point on a crystalline lens 131, the one-dot image on the retina is less susceptible to a state of the crystalline lens 131. Therefore, even a user having, for example, myopia, hyperopia, astigmatism, or the like can clearly recognize the video image. Furthermore, a virtual image that appears to float in a space is focus-free, and the virtual image comes into focus at any distance from the eye.

[0100] In the present technology, the video display light may be collected near the pupil, and, for example, may be collected on the pupil or may be shifted from the pupil by several mm to a dozen mm (for example, 1 mm to 20 mm, particularly 2 mm to 15 mm) in an optical axis direction. As in the latter case, Maxwellian view can be realized even if the focal point is not on the pupil. Shifting the focal point in the optical axis direction can make it difficult for the user to lose a video image even if the video image is shifted. More specifically, the video display light may be collected on the pupil, in the crystalline lens 131, or between a cornea surface and the pupil.

[0101] In the present embodiment, a main light beam of video display light may diverge or converge on condition that the video display light is collected near the pupil. The main light beam diverging or converging in this way is included in the main light beam that is “substantially parallel” in the present technology. For example, a main light beam that is slightly diverging or converging due to a manufacturing tolerance is included in the main light beam that is “substantially parallel”.

[0102] For example, the video display light refracted by the second lens 113 may diverge as shown in FIG. 3 or may converge as shown in FIG. 4. When the main light beam diverges, a difference .theta..sub.1 between a maximum angle and a minimum angle with respect to an optical axis is preferably 5 degrees or less, 4 degrees or less, 3 degrees or less, 2 degrees or less, or 1 degree or less. There are no particular restrictions in a case where the main light beam converges, but a difference .theta.2 between a maximum angle and a minimum angle with respect to an optical axis is more preferably 5 degrees or less, 4 degrees or less, 3 degrees or less, 2 degrees or less, or 1 degree or less.

[0103] The optical element 120 causes the video display light to be collected near the pupil and to reach the retina 132.

[0104] In the present technology, the optical element 120 is used in a state where a positional relationship with the eyeball 130 is fixed. Preferably, as shown in FIG. 1, the optical element 120 may be provided in contact with the eyeball 130, for example, and may be used in a state where the positional relationship between the optical element 120 and the pupil is fixed. Furthermore, the optical element 120 may have a curved surface, and a curvature center of the curved surface and a rotation center of the eyeball 130 may be concentric. By fixing the positional relationship between the optical element 120 and the pupil, the video display light refracted by the lens 113 can be collected near the pupil even if the eyeball 130 rotates to change a position of the pupil.

[0105] In the present technology, the optical element 120 is, for example, a contact-lens-shaped optical element, and may preferably be a contact-lens-shaped holographic optical element. Since the optical element 120 is the contact-lens-shaped optical element, it is possible to enlarge a field of view in which a video image by video display light can be recognized, for example, to 60 degrees or more, and more particularly 100 degrees or more. Furthermore, since the optical element 120 is the contact-lens-shaped optical element, it is possible to easily enlarge an eye box (that is, a spatial area around the eyeball, in which a video image by video display light can be recognized).

[0106] Such a holographic optical element layer may be manufactured by a technique known in the technical field, or may be given with a desired optical characteristic by a technique known in the technical field. For example, it is possible to use, as it is as the optical element 120, a holographic optical element manufactured so as to collect video display light projected from the projection optical system 110 near the pupil, or it is possible to form one or two or more of the holographic optical element layers inside a protective layer having a material generally used as a contact lens material, and use as the optical element 120.

Alternatively, it is also possible to form a photopolymer layer on a surface of a commercially available contact lens or inside a protective layer having a material generally used as contact lens material, and form a hologram, in the photopolymer layer, so that video display light projected from the projection optical system 110 is collected near the pupil, to use as the optical element 120. Furthermore, a diffraction optical element of a relief-type generally called DOE may be used as the optical element 120. Alternatively, it is also possible to use, as the optical element 120, an emboss-type hologram obtained by creating, with use of an imprint method or the like, an uneven surface on a surface of a commercially available contact lens or inside a protective layer having a material generally used as contact lens material, and forming an interference fringe so that video display light projected from the projection optical system 110 is collected near the pupil. The optical element 120 may have a function as a contact lens (for example, a visual acuity correction function), or may not have such a function.

(3) Second Example of First Embodiment (Video Projection System)

[0107] According to another implementation aspect of the present technology, the projection optical system includes a scanning mirror. An example of the video projection system in the present implementation aspect will be described with reference to FIGS. 5 to 7. Note that, since the description (2) described above applies to an optical element, the description will be omitted in the following.

[0108] FIG. 5 is a schematic view showing an example of a video projection system 200 according to the present technology.

[0109] As shown in FIG. 5, the video projection system 200 includes a video projection device 201 and an optical element 220. The video projection device 201 includes a projection optical system 210, and the projection optical system 210 includes a light source 211, a scanning mirror 212, and a lens 213.

[0110] The light source 211 emits a light beam toward the scanning mirror 212. As the light source 211, for example, an LED or an LD may be used. The light source 211 may be outputted as a single luminous flux including, for example, red, green, and blue laser beams.

[0111] The scanning mirror 212 may two-dimensionally scan a laser beam emitted from the light source 211 to cause the laser beam to reach the optical element 220. As the scanning mirror 212, for example, a MEMS mirror may be used. The scanning mirror 212 may move a direction of the laser beam at a high speed so that a video image is formed on a retina 232.

[0112] Emission of video display light from the light source 211 may be controlled by, for example, a control unit (not shown). That is, the video projection device 201 may include a control unit (not shown) configured to control emission of the video display light by the light source 211. Furthermore, the control unit may control driving of the scanning mirror 212. For example, the control unit may change a scanning swing angle of the scanning mirror 212. The control unit may include, for example, a central processing unit (CPU) and a RAM. As the CPU, any processor may be used. The RAM may include, for example, a cache memory and a main memory, and temporarily store a program used by the CPU. The video projection device 201 may further include, for example, various components used for controlling a video display element, such as a disk, a communication device, and a drive. The disk may store, for example, various image data and various programs such as a program for realizing emission of video display light by the light source 211. The communication device may acquire image data and/or a program for controlling the video display element, from a network, for example. The drive may read out a program and/or image data recorded on, for example, a recording medium such as a microSD memory card and an SD memory card, and output to the RAM.

[0113] The lens 213 is provided between the light source 211 and the optical element 220. As shown in FIG. 5, the video display light projected from the light source 211 is refracted by the lens 213 and incident on the optical element 220.
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