JP2010169916A - Video display device and head-mount display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To brightly observe a periphery of a screen and observe a video with much presence when gazing a center of the screen, and brightly observe a gazing point when gazing the periphery of the screen in constitution of a wide viewing angle using an HOE 23 manufactured so that a position of a reference light source is deviated from an optical pupil. <P>SOLUTION: In the constitution of the wide viewing angle where an observation angle of a video is 15° or more, when wavelength having maximum diffraction efficiency in a light beam M<SB>1</SB>passing through a center of the optical pupil P out of light beams of a prescribed wavelength region emitted from a center of a display surface of the display element is defined as λ<SB>0</SB>, wavelength having maximum diffraction efficiency in a light beam M<SB>2</SB>passing through the center of the optical pupil P out of light beams of the prescribed wavelength region emitted from a periphery part of the display surface of the display element is defined as λy, and a half viewing angle of the observation viewing angle is defined as θ, the HOE 23 satisfying 0.08<¾((λy/λ<SB>0</SB>)-1)/sinθ¾<0.2 is used. When the HOE satisfies the conditional expression, the reference light source R during exposure is located in a prescribed range between a turning center C and an iris I during video observation. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention provides a video display device with a wide viewing angle so that the observer's eyeball rotates when observing the periphery of the screen, and a head-mounted display (hereinafter also referred to as an HMD) including the video display device. It is about.

  A see-through type image display device using a reflection type hologram optical element (hereinafter also referred to as HOE) as a combiner that simultaneously guides image light from the display element and external light to the optical pupil has been proposed. For example, in Patent Document 1, in an image display device whose observation angle of view in the vertical direction is as narrow as 10 degrees (± 5 degrees), even if the observer's pupil (iris) moves within the optical pupil plane of the eyepiece optical system, A configuration capable of observing a good image has been proposed.

  More specifically, the reflection type HOE is manufactured by exposing a hologram photosensitive material with two light beams (reference light and object light) and recording interference fringes. A light source) is disposed on the opposite side of the optical pupil position, for example, from the hologram photosensitive material, and the hologram photosensitive material is exposed to produce an HOE. When the HOE produced in this way is used as a combiner, even if the position of the observer's pupil (iris) is shifted in the optical pupil plane during image observation, depending on the observation direction, the hologram photosensitive material during exposure is used. Since there are those approaching the incident direction of the exposure light beam or those in the same direction as the incident direction, luminance unevenness due to the shift of the pupil position can be reduced.

JP 2004-61731 A

  However, in the configuration of Patent Document 1, even in the best state where the observer's pupil (iris) is located at the center of the optical pupil, the diffraction efficiency of light from the periphery of the screen toward the center of the optical pupil is low. The image becomes darker from the center of the screen toward the periphery of the screen. In the configuration of Patent Document 1, since the viewing angle of view is narrow, even though the degradation of the video quality of the entire screen due to the darkness of the screen periphery is small, the viewing angle of view of the video is, for example, 15 ° or more. Then, since the periphery of the screen is darkened suddenly, the video quality of the entire screen is greatly reduced.

  In general, when the viewing angle of view of the video is wide, when observing the periphery of the screen, the observer rotates the eyeball and moves the point of sight to observe. At this time, if the position of the reference light source at the time of exposure is not properly set (if the diffraction characteristics of the HOE are not set appropriately), a realistic image cannot be observed when the center of the screen is watched, and the eyeball is rotated. When the periphery of the screen is watched, the image of the gazing point (the periphery of the screen) cannot be observed brightly. Hereinafter, this problem will be further described with reference to the drawings.

FIGS. 12A and 12B show a case where an image is observed using the HOE 101 produced by aligning the position of the reference light source R during exposure with the position of the observer's pupil (iris I) during image observation. It is explanatory drawing which shows typically the light beam which injects into an observer's pupil. Note that the position of the iris I coincides with the position of the optical pupil P of the eyepiece optical system. In addition, a ₁ , a ₂ , and a ₃ in the figure are light rays that have the highest diffraction efficiency at the HOE 101 among light rays that travel from the display element to the center of the optical pupil P via the HOE 101, respectively. Shows the top ray, the center ray, and the bottom ray. Further, b ₁ , b ₂ , and b ₃ in the drawing respectively indicate light distribution ranges (light fluxes) having relatively high intensities centered on the light beams a ₁ , a ₂ , and a ₃ having the maximum diffraction efficiency. Note that C in the figure indicates the center of rotation of the eyeball of the observer during video observation.

When observing an image using the HOE 101 manufactured by aligning the position of the reference light source R at the time of exposure with the position of the iris I at the time of image observation, the center of the screen is not rotated without rotating the eyeball as shown in FIG. When gazing, it is possible to observe not only the center of the screen but also the periphery of the screen brightly. This can be easily understood from the fact that the light beams b ₁ , b ₂ and b ₃ are incident on the pupil (pupil) without vignetting in the iris I. However, as shown in FIG. 5B, when the observer rotates the eyeball and watches the upper end of the screen, for example, the light efficiently diffracted by the HOE 101 (for example, the light beam a having the maximum diffraction efficiency included in the light beam b _{1). 1} ) is vignetted by Iris I, so the upper edge of the screen becomes darker.

On the other hand, FIGS. 13A and 13B show the observer's pupil when observing an image using the HOE 102 produced by aligning the position of the reference light source R during exposure with the rotation center C during image observation. It is explanatory drawing which shows typically the light beam which injects into. When observing an image using the HOE 102, when the observer turns the eyeball and looks at the upper end of the screen, for example, as shown in FIG. This can be easily understood from the fact that the light beam b ₁ is incident on the pupil without vignetting in the iris I. However, as shown in FIG. 4B, when the observer gazes at the center of the screen, the observation direction to the periphery of the screen (for example, the direction of the solid line c ₁ ) and the exposure direction of the reference light (the direction of the light beam a ₁ ) Since the angle difference is large, the periphery of the screen becomes dark, and only the vicinity of the gazing point (screen center) can be observed brightly.

  In order for the observer to observe a realistic or immersive image, not only the vicinity of the gazing point but also the surrounding image light must enter the observer's pupil to some extent (at this time the surrounding image Is not required until resolution). Accordingly, if the periphery of the screen is dark when the center of the screen is watched as described above, the observer cannot observe a realistic image.

  The present invention has been made to solve the above-described problems, and has as its purpose a wide angle of view that involves the rotation of the eyeball when observing the periphery of the screen, and the position of the reference light source deviates from the optical pupil. In the configuration using the HOE produced in this way, when looking at the center of the screen, the periphery of the screen can be observed brightly, so that a realistic image can be observed and the deterioration of the image quality of the entire screen can be avoided, while the periphery of the screen is closely watched. Sometimes, it is to provide a video display device capable of brightly observing a video image of a gazing point and a head mounted display including the video display device.

An image display device of the present invention includes a display element that displays an image, and an eyepiece optical system that guides image light from the display element to an optical pupil, and the eyepiece optical system optically transmits image light from the display element. While diffracting and reflecting in the pupil direction, and having a volume phase type reflection hologram optical element that transmits external light and guides it to the optical pupil, the observer's pupil is positioned at the position of the optical pupil. Simultaneously observing the outside world, the image display device having an observation angle of 15 ° or more for the image, in a light ray passing through the center of the optical pupil among light rays of a predetermined wavelength region emitted from the center of the display surface of the display element. The wavelength of maximum diffraction efficiency is λ _0, and the wavelength of maximum diffraction efficiency in the light passing through the center of the optical pupil among the light in the predetermined wavelength region emitted from the periphery of the display surface of the display element is λy, and the viewing angle of view The half angle of view is θ When
0.08 <| ((λy / λ ₀ ) −1) / sin θ | <0.2
It is characterized by satisfying.

In the image display device of the present invention, the image light from the display element has at least one intensity peak wavelength λpeak, and when the full width at half maximum of the intensity peak including the intensity peak wavelength λpeak is FWHM, In all of the wavelength regions corresponding to at least one intensity peak wavelength λpeak,
| Λpeak−λ ₀ | / FWHM <0.4
It is desirable to satisfy

The video display device of the present invention has a wavelength region of 500 nm <λ ₀ <600 nm.
| Λpeak−λ ₀ | / FWHM <0.2
It is further desirable to satisfy

The image display device of the present invention has an observation angle of view of 20 ° or more, and passes through the center of the optical pupil among rays in a predetermined wavelength region emitted from a position corresponding to a half angle of view of 10 ° on the display surface of the display element. when the wavelength of the diffraction efficiency up in light and with lambda _10, in all the wavelength region corresponding to at least one intensity peak wavelength Ramudapeak,
| Λ ₁₀ −λ ₀ | / FWHM <0.9
It is desirable to satisfy

The video display device of the present invention has a wavelength region of 500 nm <λ ₀ <600 nm.
| Λ ₁₀ −λ ₀ | / FWHM <0.4
It is further desirable to satisfy

  The video display device of the present invention may further include a light source that illuminates the display element, and the light source may be arranged substantially conjugate with the optical pupil.

  The head-mounted display of the present invention includes the above-described video display device of the present invention and support means for supporting the video display device in front of an observer's eyes.

  In the head-mounted display of the present invention, the support means may include an adjustment mechanism that adjusts the distance between the eyepiece optical system of the video display device and the pupil of the observer.

  In the head mounted display of the present invention, it is preferable that the display element of the video display device displays an index for adjusting the position of the optical pupil when the distance is adjusted by the adjusting mechanism.

  In a wide-angle video display device with an observation angle of view of 15 ° or more, the observer's eyeball is rotated when the periphery of the screen is observed. In such a wide field angle configuration, a predetermined conditional expression is satisfied, that is, a HOE manufactured by positioning a reference light source at the time of exposure in a predetermined range between the rotation center and the iris position at the time of image observation is used. As a result, when the center of the screen is watched, not only the center of the screen but also the periphery of the screen can be observed brightly. As a result, it is possible to observe a realistic video, and to avoid a reduction in the video quality of the entire screen. Further, by satisfying the predetermined conditional expression, even when the eyeball is rotated and the periphery of the screen is watched, the image of the gazing point (the periphery of the screen) can be observed as a bright and high-quality image.

It is sectional drawing which shows the structure of the outline of the video display apparatus of this invention. It is explanatory drawing which shows the spectral intensity characteristic of the light source of the said video display apparatus. It is explanatory drawing which expands and shows the principal part of the optical system which manufactures HOE of the said video display apparatus. It is sectional drawing which shows the schematic structure of the other video display apparatus of this invention. It is explanatory drawing which expands and shows the principal part of the optical system which manufactures HOE of the said video display apparatus. It is explanatory drawing which shows the position of the reference light source at the time of exposure for producing HOE of each video display apparatus. (A) is explanatory drawing which shows the optical path of the principal ray of the manufacturing optical system at the time of exposure of the hologram photosensitive material for producing HOE, (b) is explanatory drawing which shows the optical path of the principal ray at the time of reproduction | regeneration is there. (A) is explanatory drawing which shows the positional relationship of the iris and image light beam in an iris cross section when a reference light source is located in the rotation center, (b) is between an iris and a rotation center. It is explanatory drawing which shows the positional relationship of the iris and image light flux in an iris cross section when located in FIG. (A) is explanatory drawing which shows the positional relationship in the iris cross section of the image light beam of a 10 degree angle of view, and an iris, when the position of a reference light source corresponds with an optical pupil, (b) It is explanatory drawing which shows the positional relationship of the said image light beam and iris in an iris cross section when a reference light source is located between an iris and a rotation center. 1 is a perspective view showing a schematic configuration of an HMD to which a video display device is applied. It is explanatory drawing which shows the example of a display screen of the display element of the said video display apparatus. (A) shows a case where an HOE produced by matching the position of the reference light source at the time of exposure with the position of the observer's pupil at the time of image observation is used as the observer's pupil when gazing at the center of the screen. It is explanatory drawing which shows typically the incident light beam, (b) is explanatory drawing which shows typically the light beam which injects into an observer's pupil when rotating the eyeball and gazing at the upper end of a screen. (A) shows the observer's pupil when using the HOE produced by aligning the position of the reference light source at the time of exposure with the center of rotation at the time of video observation and gazing at the upper end of the screen by rotating the eyeball. FIG. 5B is an explanatory diagram schematically showing a light beam incident on the observer's pupil when gazing at the center of the screen.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[About the first video display device]
FIG. 1 is a cross-sectional view showing a schematic configuration of a first video display device 1a according to an embodiment of the present invention. The observation angle of view of the image in the image display device 1a is, for example, 26.3 ° in the horizontal direction, 15 ° in the vertical direction, and 30.1 ° in the diagonal direction, and has a wide angle of view of 15 ° or more in any direction. ing. Therefore, when the periphery of the screen is observed, rotation of the eyeball E of the observer naturally occurs around the rotation center C. The video display device 1 a includes a light source 11, an illumination optical system 12, a display element 13, and an eyepiece optical system 14.

  The light source 11 illuminates the display element 13 and is an RGB-integrated type having three light emitting units that emit light having wavelengths corresponding to the three primary colors of red (R), green (G), and blue (B). It consists of LEDs.

Here, FIG. 2 is an explanatory diagram showing the spectral intensity characteristics of the light source 11, that is, the relationship between the wavelength λ1 of the emitted light and the light intensity (light emission intensity). Assuming that the central wavelengths (intensity peak wavelength, use wavelength) of the BGR light emitted from the light source 11 are λ1 _B , λ1 _G , and λ1 _R , respectively, for example, λ1 _B = 457 nm, λ1 _G = 516 nm, and λ1 _R = 636 nm. is there. If the full width at half maximum of the intensity peak of the emitted light from the light source 11 is FWHM (Full Width at Half Maximum), each FWHM of BGR is, for example, 28.6 nm (± 14.3 nm), 44.6 nm (± 22.3 nm) and 21.0 nm (± 10.5 nm). Note that the light intensity on the vertical axis in FIG. 2 indicates the relative value of the light intensity of the B light and the G light with respect to the maximum light intensity of the R light. The light source 11 may be configured to emit at least one of BGR light, and may be configured to emit only monochromatic G light, for example.

  The light source 11 (light emitting surface) is disposed so as to be substantially conjugate with the optical pupil P formed by the eyepiece optical system 14. As a result, the light from the light source 11 is efficiently guided to the optical pupil P. Therefore, when the observer's pupil is positioned at the position of the optical pupil P (for example, the center of the optical pupil P coincides with the center of the iris I). The viewer can observe a bright image. If the light emission area of the light source 11 is too small at the conjugate optical pupil position (iris position), a diffusion plate may be inserted on the light emission surface to increase the light emission area in a pseudo manner.

  The illumination optical system 12 condenses the light emitted from the light source 11 and guides it to the display element 13, and is composed of, for example, a single mirror having a concave reflecting surface. The display element 13 modulates the light from the light source according to the image data and displays an image, and is composed of, for example, a transmissive LCD. The display element 13 is arranged so that the long side direction of the rectangular display screen is the horizontal direction (direction perpendicular to the paper surface of FIG. 1) and the short side direction is the direction perpendicular thereto.

  The eyepiece optical system 14 is an optical system that guides the image light from the display element 13 to the optical pupil P (or the observer's pupil at the position of the optical pupil P). The eyepiece prism 21, the deflection prism 22, the HOE 23, and the like. It is comprised.

  The eyepiece prism 21 totally reflects the image light from the display element 13 and guides it to the optical pupil P through the HOE 23, while transmitting the external light to the optical pupil P. Together with the deflection prism 22, For example, it is made of an acrylic resin. The eyepiece prism 21 has a shape in which the lower end portion of the parallel plate is wedge-shaped. The upper end surface of the eyepiece prism 21 is a surface 21a as an incident surface for image light, and the two surfaces positioned in the front-rear direction are surfaces 21b and 21c parallel to each other.

  The deflecting prism 22 is configured by a substantially U-shaped parallel plate in plan view (see FIG. 10), and when the deflecting prism 22 is bonded to the lower end portion and both side surface portions (left and right end surfaces) of the eyepiece prism 21, the eyepiece prism. 21 is a substantially parallel flat plate. The deflection prism 22 is provided adjacent to or attached to the eyepiece prism 21 so as to sandwich the HOE 23. Thereby, distortion can be prevented from occurring in the external image observed by the observer through the eyepiece prism 21.

  That is, for example, when the deflecting prism 22 is not provided, external light is refracted when passing through the wedge-shaped lower end portion of the eyepiece prism 21, so that the external image observed through the eyepiece prism 21 is distorted. However, the deflection prism 22 is joined to the eyepiece prism 21 to form an integral substantially parallel flat plate, so that the deflection when the external light passes through the wedge-shaped lower end of the eyepiece prism 21 is canceled by the deflection prism 22. Can do. As a result, it is possible to prevent distortion in the external image observed through the see-through.

  The HOE 23 is a volume phase type reflection hologram optical element that diffracts and reflects the image light (BGR light) from the display element 13 in the direction of the optical pupil P and transmits the external light to the optical pupil P. The eyepiece prism 21 is provided on the joint surface with the deflecting prism 22. The HOE 23 has an axially asymmetric positive optical power, and has the same function as an aspherical concave mirror having a positive optical power. Thereby, the degree of freedom of arrangement of each optical member constituting the apparatus can be increased, and the apparatus can be easily reduced in size, and an image with good aberration correction can be provided to the observer.

  In the video display device 1a having the above configuration, the light emitted from the light source 11 is converted into substantially collimated light by the illumination optical system 12 and enters the display element 13, where it is modulated and emitted as video light. The image light from the display element 13 enters the inside of the eyepiece prism 21 of the eyepiece optical system 14 from the surface 21a, and then is totally reflected by the surfaces 21b and 21c at least once and enters the HOE 23. The HOE 23 has an optical function equivalent to that of the concave mirror for the front and rear wavelength ranges including the emission peak wavelengths of RGB of the light source 11, and does not have such an optical function for the other wavelength ranges. Acts as a combiner. Therefore, the light incident on the HOE 23 is diffracted and reflected there and reaches the optical pupil P. At the same time, external light passes through the HOE 23 and travels toward the optical pupil P. Therefore, by locating the observer's pupil (iris I) at the position of the optical pupil P, the observer can observe the outside world see-through simultaneously with the image (enlarged virtual image) displayed on the display element 11.

Next, a method for manufacturing the above HOE 23 will be described. FIG. 3 is an explanatory view showing, in an enlarged manner, main parts of the manufacturing optical system of the HOE 23. As shown in FIG. The HOE 23, which is a reflection type color hologram, is manufactured by exposing the hologram photosensitive material 23a on the substrate (eyepiece prism 21) using two light beams and recording interference fringes due to the interference of the two light beams for each BGR. The At this time, one light beam is irradiated to the hologram photosensitive material 23a from the side opposite to the substrate, and this light beam is referred to as object light. The other light beam is irradiated from the substrate side to the hologram photosensitive material 23a. This light beam is referred to as reference light. Assuming that the exposure wavelengths (reference light and object light) of BGR are λ2 _B , λ2 _G , and λ2 _R , respectively, for example, λ2 _B = 476.5 nm, λ2 _G = 532 nm, λ2 as shown in FIG. _R = 647 nm.

  In the optical system on the object light generation side, RGB divergent light from the point light source 31 is shaped into a predetermined wavefront by a free-form surface mirror 32 which is a reflection surface having optical power, and is reflected by the plane reflection mirror 33. Thereafter, the hologram photosensitive material 23 a is irradiated through the color correction prism 34. The surface 34a that is the incident surface of the object light in the color correction prism 34 is generated due to the refraction of the image light on the surface 21a of the eyepiece prism 21 of the eyepiece optical system 14 that is used during reproduction (image observation). The angle is determined so as to cancel the chromatic aberration. At this time, it is desirable that the color correction prism 34 is disposed in close contact with the hologram photosensitive material 23a in order to prevent a ghost due to surface reflection, or is disposed via emulsion oil or the like.

  On the other hand, in the optical system on the reference light generation side, divergent light (for example, spherical waves) from the RGB point light sources 41R, 41G, and 41B, which are reference light sources, is irradiated from the eyepiece prism 21 side to the hologram photosensitive material 23a as reference light. Is done. In the present embodiment, the point light sources 41R, 41G, and 41B are positioned farther from the eyepiece prism 21 than the position of the optical pupil P at the time of reproduction, that is, on the side opposite to the hologram optical element 23 with respect to the optical pupil P. And is in the same position on a plane substantially parallel to the optical pupil plane. In addition, the reference light source at the time of exposure is located in a predetermined range between the rotation center C of the eyeball E of the observer at the time of video observation and the pupil (iris I) of the observer arranged on the optical pupil P. The details will be described later.

  As described above, by exposing the hologram photosensitive material 23a with two light beams of object light and reference light for each of RGB, interference fringes are formed in the hologram photosensitive material 23a by interference of the two light beams, and the HOE 23 is manufactured. . At this time, the exposure with two light beams may be performed simultaneously for RGB or sequentially.

  In this embodiment, when designing the manufacturing optical system, one color (for example, RGB) is used in order to make the wavefront generation optical system on one side (object light generation side) of the manufacturing optical system common to the three colors RGB. Among them, the phase function of the HOE 23 is optimized and set for G) where the wavelength is in the middle. Here, the phase function is a function representing the phase shift of the wavefront between the incident light and the diffracted light, and is one of the methods for optically defining the HOE 23.

[About the second video display device]
FIG. 4 is a cross-sectional view showing a schematic configuration of a second video display device 1b according to another embodiment of the present invention. The observation angle of view of the image in the image display device 1b is, for example, 41.5 ° in the horizontal direction, 33 ° in the vertical direction, and 50 ° in the diagonal direction, and has a wide angle of view of 20 ° or more in any direction. . Therefore, in the second video display device 1b, as in the case of the first video display device 1a, the rotation of the eyeball E of the observer naturally occurs around the rotation center C when observing the periphery of the screen. Become. The video display device 1b is significantly different from the video display device 1a in the configuration of the illumination optical system 12.

  The illumination optical system 12 includes, from the light source 11 side, a first group 12A having a positive power and a second group 12B having a positive power. The first group 12A includes a collimator lens 51, a first Fresnel lens 52, and a reflection mirror 53 from the light source 11 side. On the other hand, the second group 12B has a second Fresnel lens 54.

  By making the illumination optical system 12 into a positive and positive two-group configuration, the length of the illumination optical system 12 is shortened in the direction in which the light travels, compared to the case where the illumination optical system 12 is configured with one optical element. However, a large NA can be secured. In addition, since the first group 12A has at least one reflecting surface (reflecting mirror 53), the optical path of the illumination optical system 12 is folded so that the illumination optical system 12 does not jump back and forth. Can do. That is, the illumination optical system 12 that is small and compact and has a high NA can be realized. Therefore, even when a large display element 13 is used, the illumination optical system 12 can be used to realize a small, compact, and wide-angle video display device 1b.

  In the image display device 1b, the image light from the display element 13 is incident on the inside of the eyepiece prism 21 of the eyepiece optical system 14 from the surface 21a, and then totally reflected once by the surfaces 21b and 21c to the HOE 23. Incident. In other words, the total number of reflections of the image light inside the eyepiece prism 21 is one less than that of the image display device 1a. This is because the number of reflections is optimized in order to reduce the overall size in consideration of the thickness of the optical system.

  FIG. 5 is an explanatory diagram showing an enlarged main part of the manufacturing optical system of the HOE 23 of the video display device 1b, but is basically the same as the manufacturing optical system shown in FIG. However, the RGB point light sources 41R, 41G, and 41B as the reference light sources are used in such a manner that the diffraction angle at the HOE 23 of the light having the intensity peak wavelength (use wavelength) λ1 of the light source 11 in use is matched with BGR. The positions are shifted on a plane substantially parallel to the optical pupil plane in accordance with the shift between λ1 and exposure wavelength λ2. As a result, it is possible to suppress the occurrence of color unevenness in the image observed through the HOE 23 during reproduction due to the difference between the use wavelength λ1 and the exposure wavelength λ2. The method for exposing the hologram photosensitive material 23a is the same as that in the case of FIG.

[Regular expressions]
Next, various conditional expressions will be described. FIG. 6 is an explanatory diagram showing the position of the reference light source R at the time of exposure for producing the HOE 23 of the video display devices 1a and 1b. The video display devices 1a and 1b described above have a configuration in which the viewing angle of view of the video is 15 ° or more, and the light beams passing through the center of the optical pupil P among the light beams in a predetermined wavelength region emitted from the center of the display surface of the display element 13. The maximum wavelength of diffraction efficiency at M ₁ is λ ₀ (nm), and the light ray M ₂ (M ₃₎ that passes through the center of the optical pupil P among the light rays in the predetermined wavelength region emitted from the peripheral portion of the display surface of the display element 13. ) When the maximum wavelength of diffraction efficiency is λy (nm) and the half angle of view is θ (°),
0.08 <| ((λy / λ ₀ ) −1) / sin θ | <0.2 (1)
Is satisfied.

  In the video display devices 1a and 1b having a wide angle of view with an observation angle of view of 15 ° or more, as described above, the observer's eyeball E is rotated when the periphery of the screen is observed. Conditional expression (1) defines an appropriate range (diffractive characteristics of the HOE 23) of the position of the reference light source R in a predetermined wavelength region during exposure between the rotation center C and the iris I during image observation. For example, at least one of the wavelength regions of RGB can be considered as the predetermined wavelength region.

  When the value of conditional expression (1) is less than or equal to the lower limit value, the position of the reference light source R during exposure is too close to the position of the iris I during image observation. In this case, when the image is observed using the HOE 23 produced by the exposure, when gazing at the center of the screen, not only the center of the screen but also the periphery of the screen can be observed brightly. When gazing at, the light efficiently diffracted by the HOE 23 is vignetted by the iris I, so the periphery of the screen suddenly becomes dark (see FIGS. 12A and 12B).

  On the other hand, when the value of conditional expression (1) is equal to or greater than the upper limit value, the position of the reference light source R during exposure is too close to the rotation center C during image observation. In this case, when an image is observed using the HOE 23 produced by the exposure, when the eyeball E is rotated and the periphery of the screen is observed, the vicinity of the gazing point (the periphery of the screen) can be observed brightly, but the center of the screen is observed. When gazing, the angle difference between the observation direction to the periphery of the screen and the exposure direction of the reference light is large, so that the periphery of the screen becomes dark (see FIGS. 13A and 13B).

  Therefore, in a configuration with a wide field angle of 15 ° or more, if the conditional expression (1) is satisfied, that is, the reference light source R during exposure is between the rotation center C and the iris I during image observation. With the configuration using the HOE 23 manufactured in a predetermined range, not only the screen center but also the screen periphery can be observed brightly when gazing at the screen center, thereby observing a realistic image. be able to. Further, even when the eyeball E is rotated and the periphery of the screen is watched, the image of the gazing point (the periphery of the screen) can be observed as a bright and high-quality image.

Note that, when the center of the screen is observed, the periphery of the screen can be observed brightly. In FIG. 6, the exposure direction (the direction of the light beam having the maximum diffraction efficiency) indicated by the thick broken line and the direction of the light beam M ₂ (M ₃ ) having the wavelength λy It can be easily understood from the small angle difference. Further, the fact that the image of the gazing point can be observed brightly when gazing at the periphery of the screen is that the rays I _U and I _D when the light beam having the maximum diffraction efficiency shown by the thick broken line or the thick solid line in FIG. It can be easily understood from the fact that it is incident on the pupil (pupil) without vignetting. Note that N ₁ , N ₂ , and N ₃ in the figure respectively indicate light beams that enter the observer's pupil when the center of the screen is watched.

Further, in order to condition (1) is satisfied, at least, the need for a λy ≠ λ _0. This also shows that the position of the reference light source R at the time of exposure is shifted (not coincident) with the position of the iris I (the position of the optical pupil P) at the time of image observation. Therefore, by satisfying conditional expression (1), the above-mentioned effect that the periphery of the screen can be observed brightly when the center of the screen is watched is obtained, and the position of the reference light source R at the time of exposure is the position of the iris I (optical) It can be said that it can be obtained with a configuration using the HOE 23 manufactured off the position of the pupil P) and with a wide angle of view. Therefore, in such a configuration, it is possible to avoid a reduction in the video quality of the entire screen due to darkening of the periphery of the screen when the center of the screen is watched.

  In addition, since the above-described effects can be obtained without forming the optical pupil P with a wide angle of view, it is possible to avoid an increase in the size of the eyepiece optical system 14, and in particular, an image display device such as an HMD. It is possible to avoid an increase in the burden on the user in the configuration in which the head is mounted on the head.

When the image light from the display element 13 has at least one intensity peak wavelength λpeak (nm), the full width at half maximum of the intensity peak including the intensity peak wavelength λpeak is FWHM (nm). In all of the wavelength regions corresponding to at least one intensity peak wavelength λpeak,
| Λpeak−λ ₀ | / FWHM <0.4 (2)
It is desirable to satisfy

Conditional expression (2), in all of the at least one wavelength region (e.g., RGB wavelength range), the appropriate range of the deviation of the diffraction efficiency wavelength maximum lambda ₀ of the intensity peak wavelength λpeak and the screen central principal ray of the image light Is stipulated. In all wavelength ranges, by satisfying the conditional expression (2), since the deviation between λpeak and lambda ₀ is small, it is possible to diffract image light by efficiently HOE23, when watching the screen center It is possible to observe bright images. If the light source 11 illuminates the display element 13 to display an image as described above, λpeak corresponds to the intensity peak wavelength (λ1 _R , λ1 _G , λ1 _B ) of the light source 11, and the intensity peak wavelength. And λ ₀ are small, so that it is possible to realize power-saving video display devices 1a and 1b that efficiently use illumination light.

At this time, in the wavelength region of 500 nm <λ ₀ <600 nm,
| Λpeak−λ ₀ | / FWHM <0.2 (2 ′)
It is further desirable to satisfy By satisfying conditional expression (2 '), the amount of deviation between λpeak and lambda ₀ in the wavelength region of G is very small, to obtain a more effective the above effect in the wavelength region of high the luminosity G be able to. In other words, the observer can recognize the image brighter when the user focuses on the center of the screen.

In addition, in the configuration in which the observation angle of view is 20 ° or more as in the video display device 1b, the optical component of the light in the predetermined wavelength region emitted from the position corresponding to the half angle of view 10 ° on the display surface of the display element 13 is used. When the maximum wavelength of the diffraction efficiency in the light beam passing through the center of the pupil P is λ ₁₀ (nm), in all the wavelength regions corresponding to at least one intensity peak wavelength λ peak,
| Λ ₁₀ −λ ₀ | / FWHM <0.9 (3)
It is desirable to satisfy

Conditional expression (3) indicates that in all at least one wavelength region (for example, RGB wavelength region), the diffraction efficiency maximum wavelength λ ₁₀ corresponding to the half angle of view of 10 ° and the diffraction efficiency maximum wavelength of the screen center principal ray An appropriate range of deviation from λ ₀ is specified. Note that the half angle of view of 10 ° corresponds to the limit of the angle of view at which the observer can resolve the image around the point of sight (center of the screen) when the center of the screen is watched. By satisfying conditional expression (3), the amount of deviation between λ ₁₀ and λ ₀ is small, so that the brightness of the screen area that can be resolved by the observer when the screen center is watched can be secured, Easier to resolve video.

At this time, in the wavelength region of 500 nm <λ ₀ <600 nm,
| Λ ₁₀ −λ ₀ | / FWHM <0.4 (3 ′)
It is further desirable to satisfy By satisfying conditional expression (3 ′), the amount of deviation between λ ₁₀ and λ ₀ is very small in the G wavelength region, so that the above effect can be more effectively achieved in the G wavelength region with high visibility. Obtainable. In other words, the brightness of the screen area that can be resolved by the observer when the screen center is watched can be ensured, and the resolution of the video is further facilitated.

〔Example〕
Hereinafter, examples of the video display devices 1a and 1b will be described in more detail with reference to construction data and the like as Examples 1 and 2. Examples 1 and 2 are numerical examples corresponding to the video display devices 1a and 1b, respectively. Optical configuration diagrams (FIGS. 1 and 4) representing the video display devices 1a and 1b are the corresponding examples 1 and 2. The same applies to.

  In the construction data shown below, Si (i = 1, 2, 3,...) Indicates the i-th surface (the optical pupil P is the first surface) counted from the optical pupil P side. ing. Further, in the cover glass (CG) of the display element 13, the surface on the eyepiece optical system 14 side is a CG surface, and the surface on the light source 11 side is an image surface (display surface).

  The arrangement of each surface Si is specified by each surface data of surface vertex coordinates (x, y, z) and rotation angle (ADE). The surface vertex coordinates of the surface Si are the local orthogonal coordinate system (X, Y, z) in the global orthogonal coordinate system (x, y, z) with the surface vertex as the origin of the local orthogonal coordinate system (X, Y, Z). , Z) is represented by the coordinates (x, y, z) of the origin (unit: mm). Further, the inclination of the surface Si is represented by a rotation angle around the X axis (X rotation) with the surface vertex as the center. The unit of the rotation angle is °, and the counterclockwise direction when viewed from the positive direction of the X axis is the positive direction of the rotation angle of the X rotation.

  The global orthogonal coordinate system (x, y, z) is an absolute coordinate system that matches the local orthogonal coordinate system (X, Y, Z) of the optical pupil plane (S1). In other words, the arrangement data of each surface Si is expressed in a global coordinate system with the center of the optical pupil plane as the origin. In the optical pupil plane (S1), the direction from the optical pupil P toward the eyepiece optical system 14 is the + Z direction, the upward direction with respect to the optical pupil P is the + Y direction, and the direction is perpendicular to the YZ plane. 1 (FIG. 4), the direction from the back to the front (the direction from left to right when the HMD is attached) is the + X direction.

  In addition, the manufacturing wavelength (HWL; standardized wavelength) and the working wavelength when producing the HOE 23 used in each of Examples 1 and 2 are both 532 nm, and the use order of the diffracted light is the first order. For the HOE surface, the HOE is uniquely defined by defining the two light beams used for fabrication. The definition of the two light beams is performed by determining whether the light source position of each light beam is the convergent beam (VIA) or the divergent beam (REA). The coordinates of the first point light source (HV1) and the second point light source (HV2) are (HX1, HY1, HZ1) and (HX2, HY2, HZ2), respectively.

  In each of the first and second embodiments, complicated wavefront reproduction by HOE is performed. Therefore, in addition to the definition of the two light beams, the HOE is also defined by the phase function φ. The phase function φ is a generator polynomial based on the position (X, Y) of the HOE, as shown in the following formula 1, and the coefficient is expressed by a monomial in ascending order from the first order to the tenth order. In the construction data, the coefficient Cj of the phase function φ is shown.

  Note that the number j of the coefficient Cj is expressed by the following equation 2 where m and n are indices of X and Y.

In the HOE plane, the normal vectors of the emitted light are respectively p ′, q ′, and r ′, the normal vectors of the incident light are respectively p, q, and r, and the wavelength of the reproduced light beam is λ (nm), Assuming that the wavelength of the light beam for producing the HOE is λ ₀ (nm), p ′, q ′, and r ′ are expressed by the following equation (3).

  As described above, in each of Examples 1 and 2, the hologram photosensitive material is exposed using a light source that emits light having a wavelength of 532 nm, and the phase function φ of the HOE corresponding to the wavelength of 532 nm is created. After the phase function φ corresponding to the wavelength is created, the eyepiece optical system 14 can be adapted to color display by multiple exposure of the hologram photosensitive material using a light source that emits light of other wavelengths. It is also possible to simultaneously perform multiple exposure of holograms corresponding to RGB.

In the construction data, the surface shape of the rotationally symmetric aspheric surface is expressed by the following equation (4). Here, Z indicates the sag amount (mm) in the Z-axis direction (optical axis direction) at the position of height h, c indicates the curvature (1 / mm) at the surface apex, and h is the height, that is, Z A distance (mm) from the axis (optical axis) is indicated, k is a conic constant, and A, B, C, D, E, F, and G are 4th order, 6th order, 8th order, 10th order, 12th, respectively. Next, 14th and 16th order coefficients (aspherical coefficients) are shown. It should be noted that for all data, the coefficients of the terms not described are all 0, and E−n = × 10 ⁻ⁿ .

  Further, the surface shape of the anamorphic aspheric surface is expressed by the following equation (5). Here, Z represents the sag amount (mm) in the Z-axis direction, CUX represents the curvature in the X direction (1 / mm), that is, the reciprocal of the curvature radius RX in the X direction, and CUY represents the curvature in the Y direction (1 / mm ), That is, the reciprocal of the radius of curvature RY in the Y direction. KX and KY denote conic constants in the X direction and the Y direction, respectively. Furthermore, AR, BR, CR, and DR indicate rotationally symmetric components of the fourth-order, sixth-order, eighth-order, and tenth-order aspheric coefficients, respectively. AP, BP, CP, and DP are fourth-order, sixth-order, The non-rotationally symmetric components of the 8th and 10th order aspheric coefficients are shown.

  In Example 2, the maximum sag amount of each zone of the Fresnel lens (the first Fresnel lens 52 and the second Fresnel lens 54) was set to 0.1 mm.

Example 1
Surface number Curvature radius S1 Pupil surface INFINITY
S2 Prism exit surface INFINITY
S3 HOE surface (spherical surface) -298.9958
Definition of two luminous fluxes
HV1; REA HV2; VIR
HX1; 0.000000E + 00 HY1; -5.881204E + 00 HZ1; -1.668113E + 01
HX2; 0.000000E + 00 HY2; 2.485100E + 08 HZ2; -6.062901E + 09
HWL; 532
Phase coefficient
C2; 2.8590E-01 C3; 1.2283E-02 C5; 1.3066E-02
C7; -2.9177E-04 C9; -2.2883E-04 C10; -2.7068E-05
C12; -4.4477E-05 C14; -3.8149E-05 C16; 6.7067E-08
C18; -6.8171E-06 C20; -9.4960E-06 C21; 2.8217E-07
C23; -1.4597E-07 C25; 1.2215E-06 C27; 2.7292E-06
C29; -3.8156E-08 C31; 7.2240E-08 C33; 2.1242E-07
C35; 2.5148E-07 C36; -5.6472E-09 C38; 5.5861E-09
C40; 2.4856E-09 C42; -5.0000E-08 C44; -9.0279E-08
C46; 0.0000E + 00 C48; 0.0000E + 00 C50; 0.0000E + 00
C52; 0.0000E + 00 C54; 0.0000E + 00 C55; 0.0000E + 00
C57; 0.0000E + 00 C59; 0.0000E + 00 C61; 0.0000E + 00
C63; 0.0000E + 00 C65; 0.0000E + 00
S4 Reflective surface INFINITY
S5 Reflective surface INFINITY
S6 Reflective surface INFINITY
S7 Prism entrance surface -127.8262934
(Aspherical)
k; 0 A; 1.30052E-04 B; -5.79585E-06
C; 1.17700E-07 D; -7.88409E-10
S8 CG side INFINITY
S9 Display screen INFINITY

Surface number xyz ADE Nd νd
S1 0 0 0 0 Pupil diameter 3mm
S2 0 -2.000 17.000 0.000 1.4914 59.93
S3 0 -2.000 19.350 -31.000 1.4914 59.93
S4 0 1.500 17.000 0 1.4914 59.93
S5 0 9.000 21.700 0 1.4914 59.93
S6 0 17.000 17.000 0 1.4914 59.93
S7 0 21.916 22.000 73.275
S8 0 28.729 26.765 44.970 1.5168 65.26
S9 0 29.294 27.331 44.970

(Example 2)
Surface number Curvature radius S1 Pupil surface INFINITY
S2 Prism exit surface INFINITY
S3 HOE surface RX; -120
(Cylindrical surface)
Definition of two luminous fluxes
HV1; REA HV2; VIR
HX1; 0.000000E + 00 HY1; -1.000000E + 01 HZ1; -2.000000E + 01
HX2; 0.000000E + 00 HY2; 1.000000E + 05 HZ2; 1.000000E + 07
HWL; 532
Phase coefficient
C2; 3.1811E-01 C3; -3.3433E-03 C5; 1.0001E-01
C7; -3.3369E-03 C9; 4.5312E-03 C10; 1.1062E-04
C12; -1.9324E-04 C14; 9.3845E-05 C16; 1.9016E-05
C18; -3.9148E-06 C20; -4.6293E-07 C21; 6.3647E-07
C23; 9.2264E-07 C25; 1.2446E-08 C27; -7.1215E-08
C29; 2.9856E-08 C31; 1.8793E-08 C33; 1.3940E-09
C35; -1.4538E-09 C36; -1.0259E-10 C38; 3.9337E-10
C40; 2.1328E-10 C42; -1.6236E-11 C44; -1.0251E-11
C46; 1.1740E-10 C48; -1.9255E-11 C50; 3.9689E-12
C52; -1.2523E-12 C54; 1.0166E-14 C55; 4.1204E-12
C57; 2.1960E-12 C59; -4.6175E-13 C61; 5.6801E-14
C63; -1.4087E-14 C65; 2.6281E-16
S4 Reflective surface INFINITY
S5 Reflective surface INFINITY
S6 Prism entrance surface 292.0530513
(Aspherical)
k; 0 A; -1.55846E-04 B; 3.10103E-06
C; -3.32367E-08 D; 1.22114E-10 E; 0.00000E + 00
F; 0.00000E + 00 G; 0.00000E + 00
S7 CG side INFINITY
S8 Display screen INFINITY

Surface number xyz ADE Nd νd
S1 0 0 0 0 Pupil diameter 3mm
S2 0 0 21.5 0 1.4914 59.93
S3 0 18.0125 41.5525 -29.7994 1.4914 59.93
S4 0 1.5 21.5 0 1.4914 59.93
S5 0 6.5 31 0 1.4914 59.93
S6 0 15.1485 25.1107 -51.5372
S7 0 22.4032 25.601 -35.7442 1.5168 65.26
S8 0 22.8705 24.9517 -35.7442

  The values of the conditional expressions (1) to (3) described above are as shown in Tables 1 to 3 below. From these tables, it can be seen that the video display devices 1a and 1b of Examples 1 and 2 satisfy all the conditional expressions (1) to (3). From Tables 2 and 3, it can be seen that the conditional expressions (2 ') and (3') are further satisfied in the G wavelength region.

[Method for calculating the λy · λ _10]
The above-described conditional expression (1) λy and conditional expression (3) λ ₁₀ can be calculated based on Bragg diffraction conditions. Hereinafter, this point will be described.

  FIG. 7A is an explanatory view showing the optical path of the principal ray of the production optical system at the time of exposure of the hologram photosensitive material 23a, and FIG. 7B shows the optical path of the principal ray at the time of reproduction (use state). It is explanatory drawing. The principal ray of the manufacturing optical system is a ray connecting the point where the principal ray in the use state shown in FIG. 4B intersects with the HOE 23, the point light source of the reference light, and the point light source of the object light. On the other hand, the principal ray in the use state is a light ray that is emitted from the center of the display surface of the display element 13 (see FIG. 1) and goes toward the center of the optical pupil P in the use state.

The incident angle of the principal ray of the manufacturing optical system, that is, the principal ray of the RGB reference light is preliminarily set so that the diffraction angle (direction) at the HOE 23 at the wavelength at which the diffraction efficiency reaches a peak in the use state matches with RGB. Different to meet Bragg's requirements. Diffraction by the reflection type HOE 23 has a maximum diffraction intensity of light diffracted in the Bragg condition, that is, in a direction in which the following two expressions are simultaneously satisfied.
(Sin θ _O −sin θ _R ) / λ _R = (sin θ _I −sin θ _C ) / λ _C
(Cos θ _O −cos θ _R ) / λ _R = (cos θ _I −cos θ _C ) / λ _C
here,
λ _R (nm): Manufacturing wavelength (exposure wavelength)
θ _O (°): Object light incident angle (object light angle)
θ _R (°): Reference beam incident angle (reference beam angle)
λ _C (nm): wavelength used (diffraction wavelength)
θ _I (°): Image chief ray incident angle (image light angle)
θ _C (°): Image chief ray emission angle (line-of-sight angle)
It is. Note that θ _O , θ _R , θ _I , and θ _C are all angles in the prism medium.

Tables 4 to 6 show the simulation results of the diffraction wavelength λ _C that satisfies the Bragg condition when the line-of-sight angle θ _C is set to 30 ° ± Δθ. It is a calculation result at 5 °, 16.5 ° in Example 2, and 10 °. Note that Δθ corresponds to the half field angle of the observation field angle. That is, Δθ = 1.2 ° corresponds to a half field angle of 7.5 °, Δθ = 4.8 ° corresponds to a half field angle of 16.5 °, and Δθ = 2.96 ° corresponds to a half field angle. It corresponds to an angle of view of 10 °.

Although Table 4 to Table 6 do not consider the shrinkage of the hologram photosensitive material at the time of manufacturing the HOE, in actuality, it is necessary to design and perform exposure in consideration of such shrinkage. In the first and second embodiments, the shrinkage (2%) of the hologram photosensitive material is taken into consideration, and in the second embodiment, the diffraction efficiency peak wavelength of the screen center chief ray is matched with the intensity peak wavelength of the light source. . As a result, when the exposure wavelength of BGR was 476.5 nm, 532.0 nm, and 647.0 nm, respectively, as shown in Tables 1 to 3, λ ₀ of BGR was 467.0 nm in Example 1, respectively. 521.4 nm and 634.1 nm, and in Example 2, they are 457.0 nm, 516.0 nm, and 636.0 nm, respectively.

On the other hand, the value of [lambda] y / lambda ₀ is the diffraction peak wavelength is shifted from the exposure wavelength, it takes a constant value according to the observation angle (half angle). For example, in B of Table 4 (Example 1) in which the shrinkage of the hologram photosensitive material is not taken into account, if the diffraction wavelength at a viewing angle of 30 ° is λ ₀ (476.5 nm), Δθ = 1.2 ° ( (Line-of-sight angle 28.8 °) corresponds to half angle of view 7.5 °, the diffraction wavelength (482.2 nm) when the line-of-sight angle is 28.8 ° is λy, and the value of λy / λ ₀ is 1.012. It becomes. Therefore, λy when considering the shrinkage of the hologram photosensitive material is 467.0 × 1.012 = 472.6 nm. Other colors (G and R) and λy of Example 2 can be obtained in the same manner as described above.

Similarly, λ ₁₀ can be obtained based on Table 6 that does not consider the shrinkage of the hologram photosensitive material. That is, for example, in Table 6 (Example 2) B, if the diffraction wavelength at a line-of-sight angle of 30 ° is λ ₀ (476.5 nm), Δθ = 2.96 ° (line-of-sight angle 27.04 °) is half. Since it corresponds to an angle of view of 10 °, the diffraction wavelength (490.1 nm) when the viewing angle is 27.04 ° is λ ₁₀ , and the value of λ ₁₀ / λ ₀ is 1.0285. Therefore, λy when considering the shrinkage of the hologram photosensitive material is 457.0 × 1.0285 = 470.0 nm. Other colors (G and R) can be obtained in the same manner as described above.

[Relationship between θ and L]
By the way, when the half field angle of the observation field angle is θ (°) and the distance (shift amount) from the optical pupil P (iris I) of the reference light source R is L (mm), the above-mentioned various conditional expressions are satisfied. The parameters are calculated based on Bragg diffraction conditions within a range that satisfies the following relational expression.
When 7.5 ≦ θ <12.8, 2.5 <L ≦ 11
When θ ≧ 12.8, 2.5 <L <2.5 / tan θ

  Here, the upper limit value (11 mm) of L when 7.5 ≦ θ <12.8 corresponds to the average distance between the rotation center C of the human eyeball and the iris I. On the other hand, the upper limit value of L (2.5 / tan θ) when θ ≧ 12.8 is based on the condition for the peripheral luminous flux of the gazing point to enter the iris I (pupil) when the center of the screen is watched. It is set. Further, the lower limit value of L (2.5 mm) is set based on the condition that the periphery of the gazing point can be brightly observed even at a half angle of view of 10 ° or more accompanied by eyeball rotation. A method for setting the upper limit value (2.5 / tan θ) and the lower limit value (2.5 mm) of L will be described below.

(About the upper limit of L)
FIG. 8A shows an iris I and an image light beam (an optical pupil in consideration of diffraction efficiency) A _{1 to} A _{3 in} the iris section (optical pupil section) when the reference light source R is located at the rotation center C. It is explanatory drawing which shows the positional relationship with these. From FIG. 5A, when the center of the screen is observed, the image light flux A _{3 with} θ> 12.8 ° does not overlap with the iris I in the iris cross section, and therefore does not enter the pupil (pupil). It turns out that the image cannot be observed. Incidentally, the image light fluxes A ₁ and A ₂ are θ = 12.8 ° and θ = −12.8 °, respectively, when gazing at the center of the screen, and the overlapping amount Δ (mm with the iris I in the iris cross section. ) Are light fluxes where Δ≈0. Therefore, when the reference light source R is located at the rotation center C, an image within the range of | θ | ≦ 12.8 ° can be observed.

On the other hand, FIG. 8B shows the iris I in the iris cross section when the reference light source R is located at a distance L from the iris I between the iris I (optical pupil P) and the rotation center C. It is explanatory drawing which shows the positional relationship of an image light beam. When the reference light source R is located at a distance L from the iris I, the direction in which the diffraction efficiency for the image light beam A ₃ is maximized is shifted from the state shown in FIG. Become. In this case, the overlap of the image light beam A ₃ and the iris I in the iris cross section can be considered as the overlap of the image light beam A ₁ and the iris I whose direction of maximum diffraction efficiency is equal to the image light beam A ₃ (image). It can be considered that the cross section of the light beam A ₃ is shifted to the iris cross section along the direction of maximum diffraction efficiency). Accordingly, when the center of the screen is watched, a part of the image light flux A ₃ overlaps with the iris I, so that an image around the screen (image represented by the light flux A ₃ ) can be observed.

Here, the diameter of the human iris I is said to be about 3 mm on average. If the diameter of the image light fluxes A _{1 to} A ₃ (the diameter of the optical pupil P) in the overlapping direction with the iris I is 2 mm, for example, L can be obtained by the following calculation from FIG.
L = {(half the diameter of the iris I) + (half the diameter of the image light beam)} / tan θ
= (1 + 1.5) / tan θ
= 2.5 / tan θ

Therefore, in order for a part of the image light flux A ₃ with θ> 12.8 ° to enter the pupil, that is, Δ> 0, L <2.5 / tan θ is sufficient. Therefore, when θ> 12.8 °, the upper limit value of L is 2.5 / tan θ.

(About the lower limit of L)
FIG. 9A shows an image light beam B ₁ (diffraction efficiency of 10 ° field angle) when the eyeball of the observer rotates 10 ° when the position of the reference light source R coincides with the optical pupil P. It is explanatory drawing which shows the positional relationship in the iris cross section (optical pupil cross section) of the optical pupil) and the iris I when it considers. On the other hand, FIG. 9B shows the image light flux B ₁ at the iris cross section when the reference light source R is located at a distance L from the iris I between the iris I (optical pupil P) and the rotation center C. It is explanatory drawing which shows the positional relationship with the iris I.

In the state of FIG. 5A, when the eyeball is rotated by 10 °, the overlap amount Δ in the iris cross section between the image light beam B ₁ having an angle of view of 10 ° and the iris I is, for example, 0.4 mm. When the position of the reference light source R is shifted from the optical pupil P by a distance L as shown in FIG. 5B, the direction in which the diffraction efficiency in the image light beam B ₁ is maximized (the direction of the broken line in the figure) is also the rotation center C. since shifting parallel to the direction, in the iris section, the overlap of the image beam B ₁ and the iris I of the angle of view of 10 °, would increase than in FIG. (a) (image beam B ₁ Can be considered by shifting the cross-section to the iris cross-section along the direction of maximum diffraction efficiency).

Here, for example, if L = 2.5 mm, the overlapping amount Δ of the image light beam B ₁ having an angle of view of 10 ° and the iris I in the iris cross section is 1.0 mm, and the periphery of the gazing point is observed brightly. be able to. Therefore, at a half angle of view of 10 ° or more, if the lower limit value of L is set to 2.5 mm, it can be said that the periphery of the gazing point can be brightly observed even when the eyeball is rotated.

  Eye rotation occurs when the observation angle of view is 15 ° or more, that is, when the half angle of view is 7.5 ° or more. If the lower limit of L is set to 2.5 mm, the eyeball rotates. The amount of overlap Δ between the image light flux in the field angle direction and the iris I can be secured to 1.0 mm or more, and the periphery of the gazing point can be observed more brightly. From the above, the lower limit value of L when θ ≧ 7.5 ° is set to 2.5 mm.

  Note that L described above is not determined depending only on θ, but varies within the above range depending on how much overlap Δ between the image light flux and the iris I in the iris cross section is secured.

[About HMD]
The video display devices 1a and 1b having the above-described configuration can be applied to the HMD. Hereinafter, the HMD will be described.

  FIG. 10 is a perspective view showing a schematic configuration of the HMD. The HMD includes a video display device 1 and support means 2. The video display device 1 corresponds to the video display devices 1a and 1b described above.

  The video display device 1 has a housing 3 that includes at least a light source 11 and a display element 13 (both refer to FIG. 1). The housing 3 holds a part of the eyepiece optical system 14. The eyepiece optical system 14 is configured by bonding an eyepiece prism 21 and a deflection prism 22 and has a shape like one lens of a pair of glasses (lens for right eye in FIG. 10) as a whole. In addition, the video display device 1 has a circuit board (not shown) for supplying at least driving power and a video signal to the light source 11 and the display element 13 via a cable 4 provided through the housing 3. is doing.

  The support means 2 corresponds to a frame of a spectacle (including a bridge and a temple), and supports the video display device 1 in front of the observer's eyes (for example, in front of the right eye). Further, the support means 2 includes a nose pad 5 (right nose pad 5R / left nose pad 5L) that contacts the observer's nose, and a nose pad lock unit 6 that fixes the nose pad 5 at a predetermined position. Yes.

  When the observer wears the HMD on the head and displays an image on the display element 13, the image light is guided to the optical pupil via the eyepiece optical system 14. Accordingly, by aligning the observer's pupil (iris) with the position of the optical pupil, the observer can observe an enlarged virtual image of the display image of the image display device 1. At the same time, the observer can observe the outside world image through the eyepiece optical system 14 in a see-through manner.

  As described above, the video display device 1 is supported by the support unit 2, so that the observer can observe the video provided from the video display device 1 in a hands-free and stable manner for a long time. In addition, you may enable it to observe an image | video with both eyes using two image display apparatuses 1. FIG. In this case, it is necessary to provide an adjustment mechanism (not shown) for adjusting the distance (eye width distance) between both eyepiece optical systems.

  Further, by freely moving the above-described nose pad 5, the position of the image display device 1 can be adjusted relative to the observer in the front and rear, left and right, and up and down directions. The position of the optical pupil of the system 14 can be placed at the position of the observer's iris. After the position adjustment, the position of the nose pad 5 is fixed by the nose pad lock unit 6, so that the observer's pupil can be fixed at a good position. Therefore, the nose pad 5 and the nose pad lock unit 6 constitute at least an adjustment mechanism (first adjustment mechanism) that adjusts the distance between the eyepiece optical system 14 (optical pupil) of the video display device 1 and the pupil of the observer. I can say that.

  In this way, by adjusting the distance between the eyepiece optical system 14 and the observer's pupil by the first adjustment mechanism, when the observer's pupil is positioned at the position of the optical pupil, it is inevitably necessary at the time of exposure. The position of the reference light source is located in a predetermined range between the rotation center and the iris at the time of video observation. That is, by the above adjustment, it is possible to realize an HOE arrangement that can achieve the above-described effects of the present invention.

  Note that the first adjustment mechanism described above may be configured independently of the second adjustment mechanism for adjusting the vertical and horizontal positions of the video display device 1. In this case, each position adjustment becomes easier.

  FIG. 11 shows a display screen example of the display element 13 of the video display device 1. As shown in the figure, the display element 13 may display an index 61 for adjusting the position of the optical pupil during distance adjustment by the first adjustment mechanism. The index 61 is composed of a total of seven marks, one at the center of the screen, four at the periphery thereof, and one at the upper and lower ends of the screen outside. However, the marks other than the mark at the upper and lower ends of the screen are circular, and the mark at the upper and lower ends of the screen is semicircular. Note that the shape, number, and position of the marks constituting the index 61 are not limited to the above.

  When the distance between the eyepiece optical system 14 and the observer's pupil is adjusted, the display element 13 displays the index 61 for position adjustment, so that the observer operates the first adjustment mechanism while viewing the index 61 to perform the optical operation. The pupil position and the observer's pupil position can be matched. In addition, since the display element 13 that normally displays an image is also used for position adjustment for displaying the index 61, it is not necessary to separately provide a dedicated optical system for projecting the index for position adjustment, and the size and weight are reduced. Effective for HMD.

  In addition, although the example which applied the video display apparatus to HMD was demonstrated above, the video display apparatus of this invention is applicable also to other apparatuses, such as a head up display (HUD), for example.

  The video display device of the present invention can be used for, for example, an HMD and a HUD.

DESCRIPTION OF SYMBOLS 1 Video display apparatus 1a Video display apparatus 1b Video display apparatus 2 Support means 5 Nose pad (adjustment mechanism)
5R nose pad (adjustment mechanism)
5L nose pad (adjustment mechanism)
6 Nose pad lock unit (adjustment mechanism)
DESCRIPTION OF SYMBOLS 11 Light source 13 Display element 14 Eyepiece optical system 23 HOE (hologram optical element)
61 Index C Rotation center E Eyeball I Iris M ₁ ray M ₂ ray M ₃ ray P Optical pupil

Claims (9)

A display element for displaying an image;
An eyepiece optical system for guiding the image light from the display element to an optical pupil,
The eyepiece optical system has a volume phase type reflection hologram optical element that diffracts and reflects the image light from the display element in the direction of the optical pupil, and transmits external light to the optical pupil,
An image display device having an observation angle of view of 15 ° or more for observing the outside world simultaneously with the image by positioning an observer's pupil at the position of the optical pupil,
The wavelength of the maximum diffraction efficiency in a light ray passing through the center of the optical pupil among light rays in a predetermined wavelength region emitted from the center of the display surface of the display element is λ _0, and the light emitted from the peripheral portion of the display surface of the display element When the diffraction efficiency maximum wavelength in the light beam passing through the optical pupil center among the light beams in the predetermined wavelength region is λy, and the half field angle of the observation field angle is θ,
0.08 <| ((λy / λ ₀ ) −1) / sin θ | <0.2
An image display device characterized by satisfying The image light from the display element has at least one intensity peak wavelength λpeak,
When the full width at half maximum of the intensity peak including the intensity peak wavelength λpeak is FWHM, in all the wavelength regions corresponding to at least one intensity peak wavelength λpeak,
| Λpeak−λ ₀ | / FWHM <0.4
The video display device according to claim 1, wherein: In the wavelength region of 500 nm <λ ₀ <600 nm,
| Λpeak−λ ₀ | / FWHM <0.2
The video display device according to claim 2, wherein: The observation angle of view is 20 ° or more,
At least one intensity when the wavelength of maximum diffraction efficiency in a light beam passing through the center of the optical pupil among light beams in a predetermined wavelength region emitted from a position corresponding to a half field angle of 10 ° on the display surface of the display element is λ _10. In all of the wavelength region corresponding to the peak wavelength λpeak,
| Λ ₁₀ −λ ₀ | / FWHM <0.9
The video display device according to claim 2, wherein: In the wavelength region of 500 nm <λ ₀ <600 nm,
| Λ ₁₀ −λ ₀ | / FWHM <0.4
The video display device according to claim 4, wherein: A light source for illuminating the display element;
6. The video display device according to claim 1, wherein the light source is disposed substantially conjugate with the optical pupil. The video display device according to any one of claims 1 to 6,
A head-mounted display comprising support means for supporting the video display device in front of an observer's eyes.   8. The head mounted display according to claim 7, wherein the support means includes an adjustment mechanism for adjusting a distance between the eyepiece optical system of the video display device and the pupil of the observer.   9. The head mounted display according to claim 8, wherein the display element of the video display device displays an index for adjusting the position of the optical pupil when the distance is adjusted by the adjusting mechanism.

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