WO2011001787A1 - Video display device, hmd, and hud - Google Patents

Abstract

Provided is a video display device which allows bright video to be observed with excellent image quality by reducing the color unevenness on a screen, taking spectral luminous efficiency into account, without reducing light use efficiency. To achieve this, the ratios of maximum diffraction efficiency of blue, green, and red (B, G, and R) components in an HOE are made different depending on the area. More specifically, at the direction of the angle of view in which the diffraction peak wavelength of the red component is shifted (where the long wavelength side is the positive direction of the angle of view), if the maximum diffraction efficiencies η of R and C components (where C is a color different from R) at the angles of view θ, -θ, and 0 are ηR_θ, ηR_-θ, ηR₀, ηC_θ, ηC_-θ, ηC₀, and the spectral luminous efficiencies N at the diffraction peak wavelengths Rλ and Cλ of R and C at the angles of view θ, -θ, and 0 in photopic vision are NRλ_θ, NRλ_-θ, NRλ₀, NCλ_θ, NCλ_-θ, and NCλ₀, the video display device satisfies P > (ηR_θ/ηC_θ) > (ηR₀/ηC₀) > (ηR_-θ/ηC_-θ) > Q, where P = {(NCλ_θ/NCλ₀)•(NRλ₀/NRλ_θ)}² and Q = {(NCλ_-θ/NCλ₀)•(NRλ₀/NRλ_-θ)}².

Description

[Name of invention determined by ISA based on Rule 37.2] Video display device, HMD and HUD

The present invention relates to an image display device that allows an observer to observe an image, and a head-mounted display (hereinafter also referred to as HMD) and a head-up display (hereinafter also referred to as HUD) provided with the image display device.

2. Description of the Related Art Conventionally, there has been known an image display apparatus that allows an observer to observe an image using a volume phase type reflection type hologram optical element (hereinafter also referred to as HOE). In this image display device, the image light from the display element is diffracted and reflected by the HOE and guided to the optical pupil, and at the same time, the external light is transmitted and guided to the optical pupil, so that the image and the external environment are transmitted at the position of the optical pupil. Superimposing can be observed. In such a conventional see-through video display device, the diffraction efficiency of the HOE is constant regardless of the region.

By the way, the volume phase type reflection type HOE has high wavelength selectivity and angle selectivity. Therefore, the incident angle of the light beam on the HOE during reproduction (image observation) is the incident angle of the light beam during manufacturing (exposure). The wavelength of light diffracted and reflected by the HOE changes. As a result, color unevenness occurs when the observer's pupil position deviates from the optical pupil center, or color unevenness occurs in the viewing angle direction within the observation screen.

Here, focus on the latter color unevenness, that is, color unevenness in the screen. For example, Patent Documents 1 and 2 disclose methods for reducing color unevenness in a screen. Specifically, in Patent Document 1, the correction circuit corrects R (red), G (green), and B (blue) video signals to correct the display color balance of the display element, or transmits the display element. By correcting the color balance of light with a correction filter, color unevenness in the screen is reduced. Further, in Patent Document 2, the color unevenness in the screen is reduced by correcting the luminance signal of each color when the pixel of the display element is driven by a correction circuit.

Japanese Patent Laying-Open No. 2005-241825 (see claims 1, 2, 4, paragraph [0023], etc.) JP 2009-36955 A (see claims 1 and 8, paragraphs [0012] and [0013], etc.)

However, any of the methods disclosed in Patent Documents 1 and 2 can be corrected only in a direction that suppresses a color with strong color unevenness. For example, when the R color unevenness is strong, the correction circuit lowers the level (pixel value) of the R video signal or luminance signal, or the correction filter reduces the R transmitted light amount. This means that the amount of image light is reduced, and the light use efficiency is reduced.

In addition, since humans perceive brightness differently for each wavelength, it is necessary to consider relative visibility when correcting color unevenness in the screen. In other words, unless the color unevenness in the screen is corrected in consideration of the relative visibility, when a person actually sees the image with his eyes, a good image with reduced color unevenness cannot be felt.

The present invention has been made to solve the above-described problems, and its object is to reduce color unevenness in a screen in consideration of specific visibility and without reducing light utilization efficiency. Accordingly, it is an object of the present invention to provide a video display device capable of observing a bright video with good image quality, and an HMD and a HUD including the video display device.

The image display device of the present invention includes a light source, a display element that modulates light from the light source and displays an image, and a volume phase reflection type that diffracts and reflects the image light from the display element and guides it to an optical pupil. And an observation optical system having two hologram optical elements, wherein the hologram optical element includes two colors including an R wavelength range among RGB wavelength ranges corresponding to red, green, and blue. The light of the above wavelength range is diffracted and reflected and guided to the optical pupil, and the ratio of the maximum diffraction efficiency of each color of the hologram optical element differs depending on the area, and the center of the display surface of the display element and the center of the optical pupil Is the optical axis, the angle of view at the center of the observation screen is 0, and two in the observation screen in the plane including the optical axis of the incident light and the optical axis of the reflected light with respect to the hologram optical element. Of the maximum field angle, the diffraction peak wavelength of R The larger one is θ, the smaller one is −θ, and the light in the wavelength range of two or more colors diffracted and reflected by the hologram optical element has a wavelength region different from R and in the photopic diopter sensitivity curve. The maximum diffraction efficiency η of R and C at the angles of view θ, −θ, 0, respectively, is represented by ηR _θ , ηR ₋ , where C is the color in the wavelength region shorter than the wavelength with the highest relative visibility. _θ , ηR ₀ , ηC _θ , ηC _−θ , and ηC _0, and the relative luminous sensitivities N in the bright places of the diffraction peak wavelengths Rλ and Cλ of the R and C at the angles of view θ, −θ, 0 are respectively represented by NRλ _θ , NRλ _−θ , NRλ ₀ , NCλ _θ , NCλ _−θ and NCλ ₀ , the following conditional expression (1),
P> (ηR _θ / ηC _θ )> (ηR ₀ / ηC ₀ )> (ηR _−θ / ηC _−θ )> Q
... (1)
However,
P = {(NCλ _θ / NCλ ₀ ) · (NRλ ₀ / NRλ _θ )} ²
Q = {(NCλ _−θ / NCλ ₀ ) · (NRλ ₀ / NRλ _−θ )} ²
It is characterized by satisfying.

The video display device of the present invention may satisfy the conditional expression (1) in the R wavelength region and the B or G wavelength region.

The image display device of the present invention may satisfy the conditional expression (1) in both the R wavelength range and the B wavelength range, and the R wavelength range and the G wavelength range.

The video display device of the present invention includes the following conditional expression (2),
ηR _θ > ηR _−θ (2)
It is desirable to satisfy

The video display device of the present invention includes the following conditional expression (3):
ηC _θ <ηC _−θ (3)
It is desirable to satisfy

The video display device of the present invention includes the following conditional expression (4),
(ΗR _θ / ηC _θ ) ≧ 1.5 × (ηR _−θ / ηC _−θ ) (4)
It is desirable to satisfy

The video display device of the present invention includes the following conditional expression (5),
P ′> (ηG _θ / ηB _θ )> (ηG ₀ / ηB ₀ )
> (ΗG _−θ / ηB _−θ )> Q ′ (5)
However,
P ′ = {(NBλ _θ / NBλ ₀ ) · (NGλ ₀ / NGλ _θ )} ²
Q ′ = {(NBλ _−θ / NBλ ₀ ) · (NGλ ₀ / NGλ _−θ )} ²
It is desirable to satisfy

In the video display device of the present invention, it is desirable that the hologram optical element is formed by multiple recording of interference fringes corresponding to two or more different colors of RGB in one layer.

The head-mounted display of the present invention may be configured to include the above-described video display device of the present invention and support means for supporting the video display device in front of the observer's eyes.

The head-up display of the present invention includes the above-described video display device of the present invention, and the hologram optical element of the video display device may be held on a substrate arranged in the field of view of the observer. Good.

Of conditional expression (1), (ηR _θ / ηC _θ )> (ηR ₀ / ηC ₀ )> (ηR _−θ / ηC _−θ ) is referred to as conditional expression D. By varying the maximum diffraction efficiency ratio of each color of the HOE depending on the region so as to satisfy the conditional expression D, in the HOE, in the direction in which the field angles θ and −θ are stretched (hereinafter also referred to as the field angle direction), the maximum R The change in diffraction efficiency is larger than the change in the maximum diffraction efficiency of C.

In the viewing angle direction in the observation screen, as for R, the relative luminous sensitivity (relative relative luminous sensitivity) changes with respect to the center of the viewing angle as compared with C (for example, B or G), and color unevenness in the screen The impact on is great. Therefore, by making the change in the maximum diffraction efficiency for such R larger than that for C, compared to the case where the maximum diffraction efficiency ratio of each color in HOE is constant regardless of the region, The amount of change in (relative specific luminous sensitivity) × (diffraction efficiency) can be suppressed, and color unevenness in the screen can be reduced. In this way, it is possible to reduce the color unevenness in the screen in consideration of the relative visual sensitivity, so that the observer observes an image with good image quality in which the color unevenness in the screen is reduced during actual image observation. Can do (feel).

Further, by setting (ηR _θ / ηC _θ ) in conditional expression D to be smaller than the upper limit P and setting (ηR _−θ / ηC _−θ ) to be larger than the lower limit Q, (ηR _θ / ηC _θ ) is When the value becomes too large or (ηR _−θ / ηC _−θ ) becomes too small, a phenomenon in which the color unevenness in the screen is reversed can be avoided, and the effect of reducing the color unevenness by the conditional expression D can be avoided. You can get it properly.

In addition, by making the maximum diffraction efficiency ratio of each color of the HOE different depending on the region as described above, it becomes possible to increase the diffraction efficiency of a necessary color for each HOE region (for each angle of view). Thereby, the light use efficiency of a required color can be improved compared with the structure which reduces the color nonuniformity in a screen using a correction circuit and a correction filter conventionally. As a result, the observer can brightly observe an image with reduced color unevenness.

4 is a graph illustrating an example of a relationship between a position of an HOE in an X direction and a maximum diffraction efficiency of each color of RGB in the video display device according to the embodiment of the present invention. It is sectional drawing which shows the schematic structure of the said video display apparatus. (A) is explanatory drawing which shows the exposure light beam when producing the said HOE, (b) is explanatory drawing which shows the reproduction | regeneration light beam at the time of image observation. It is explanatory drawing which shows a photopic visual acuity sensitivity curve. It is the graph which normalized and showed the relative visibility in each view angle on the basis of the screen center (view angle 0 degree). It is a top view of the HOE. FIG. 3 is a graph showing a change in (relative relative luminous sensitivity) × (diffraction efficiency) with respect to a change in field angle, normalized with respect to an angle of view of 0 °, for each color of RGB in the setting of FIG. 1. (A) BGR diffraction efficiency distribution at an angle of view of 6 °, (b) BGR diffraction efficiency distribution at an angle of view of 0 °, and (c) BGR diffraction efficiency distribution at an angle of view of −6 °. It is a graph which shows distribution. It is a graph which shows the other example of the relationship between the position of the X direction of HOE, and the maximum diffraction efficiency of each color of RGB. FIG. 10 is a graph showing a change in (relative relative luminous sensitivity) × (diffraction efficiency) with respect to a change in field angle, normalized with respect to an angle of view of 0 °, for each color of RGB in the setting of FIG. 9. It is explanatory drawing which shows the schematic structure of the exposure optical system which produces the said HOE. (A) is explanatory drawing which shows the exposure light beam when producing HOE of other embodiment of this invention, (b) is explanatory drawing which shows the reproduction | regeneration light beam at the time of image observation. It is the graph which normalized and showed the relative visibility in each view angle on the basis of the screen center (view angle 0 degree). It is a top view of the HOE. It is a graph which shows the relationship between the position of the Y direction of the said HOE, and the maximum diffraction efficiency of RGB. 16 is a graph showing a change in (relative relative luminous sensitivity) × (diffraction efficiency) with respect to a change in field angle, normalized with respect to a field angle of 0 °, for each color of RGB in the setting of FIG. 15. It is sectional drawing which shows the structure of the outline of the video display apparatus of further another embodiment of this invention. It is a perspective view which shows the structure of outline of HMD. It is sectional drawing which shows the structure of the outline of HUD.

[Embodiment 1]
An embodiment of the present invention will be described below with reference to the drawings.

<About video display device>
FIG. 2 is a cross-sectional view showing a schematic configuration of the video display device 1 of the present embodiment. The video display device 1 includes a light source 11, a display element 12, an eyepiece optical system 13, and a light guide unit 14. Note that the video display device 1 of the present embodiment is a horizontal insertion type, that is, the display element 12 is arranged at one end portion in the eye width direction (left-right direction, horizontal direction) of the observer, and the video light is generated in the light guide unit 14. Is of a type that guides light horizontally. The eyepiece optical system 13 and the light guide unit 14 constitute an observation optical system.

The light source 11 is composed of an LED that emits light in each of the R, G, and B wavelength ranges corresponding to, for example, red, green, and blue. The display element 12 is a light modulation element that displays light by modulating light from the light source 11 according to image data, and is configured by an LCD, for example. The eyepiece optical system 13 converts the image light from the display element 12 into parallel light and guides it to the light guide means 14.

The light guide means 14 has a light guide member 21 and HOEs 22 and 23. The light guide member 21 is a transparent substrate that guides video light from the display element 12 inside, and has parallel surfaces 21 a and 21 b that face each other. The surface 21a is a surface on the display element 12 side, and the surface 21b is a surface opposite to the display element 12 with respect to the surface 21a. The surfaces 21a and 21b are located substantially parallel to the display surface of the display element 12.

The HOE 22 (first HOE) is a volume phase type reflection type diffractive optical element, and is produced by exposing a hologram photosensitive material (for example, photopolymer), which is a constituent material thereof, with two light beams. The HOE 22 is held on the surface 21 b of the light guide member 21, and diffracts and reflects video light incident on the light guide member 21 through the surface 21 a so as to be totally reflected in the light guide member 21.

The HOE 23 (second HOE) is a volume phase type reflection type diffractive optical element, and is manufactured by exposing a hologram photosensitive material (for example, photopolymer), which is a constituent material thereof, with two light beams. The HOE 23 is also held on the surface 21b of the light guide member 21, and diffracts the image light that is diffracted and reflected by the HOE 22 and is totally reflected inside the light guide member 21 in the direction of the optical pupil E. Reflect.

In the present embodiment, the HOEs 22 and 23 diffract and reflect light in all the RGB wavelength ranges, but it is only necessary to diffract and reflect light in two or more wavelength ranges including the R wavelength range. . Note that the ratio of the maximum diffraction efficiency of each color of the HOE 22 is constant regardless of the region. On the other hand, the ratio of the maximum diffraction efficiency of each color of the HOE 23 differs depending on the region, and this is a major feature of the present invention, which will be described later. The HOEs 22 and 23 are manufactured so as to reflect incident parallel light with parallel light.

According to the above configuration, the light from the light source 11 is modulated by the display element 12 and is incident on the eyepiece optical system 13 as image light, and is enlarged and collimated into the light guide member 21 in the surface 21a. Incident from the side. This image light is diffracted and reflected by the HOE 22 and guided to the HOE 23 while repeating total reflection between the surfaces 21a and 21b. In the HOE 23, the incident image light is diffracted and reflected and guided to the optical pupil E through the surface 21a. Therefore, at the position of the optical pupil E, the observer can observe an enlarged virtual image of the image displayed on the display element 12. Further, the HOE 23 has high wavelength selectivity of diffracted and reflected light, and transmits almost all the external light, so that the observer can observe the external world see-through while observing the virtual image of the display image.

<Color unevenness in the screen when the diffraction efficiency is constant>
Next, before explaining the method for reducing color unevenness in the screen of the present invention, color unevenness in the screen when the diffraction efficiency of the HOE 23 is constant regardless of the region will be described.

For convenience of explanation below, an axis that optically connects the center of the display surface of the display element 12 and the center of the optical pupil E is defined as an optical axis, and the optical axis direction is defined as a Z direction. Of the two directions perpendicular to the Z direction, the eye width direction (left-right direction) is the X direction, and the vertical direction is the Y direction. In addition, the angle of view at the center of the observation screen is set to 0 (°), and the two maximum values in the observation screen in the plane including the optical axis of the incident light and the optical axis of the reflected light with respect to the HOE 23 (in the ZX plane in FIG. 2). Of the angles of view, the larger R diffraction peak wavelength is defined as + θ (°), and the smaller one is defined as −θ (°). That is, in the X direction (view angle direction), the direction in which the R diffraction peak wavelength shifts to the long wavelength side is the positive view angle direction (view angle plus side), and conversely, the R diffraction peak wavelength is short. The direction shifted to the wavelength side is defined as the negative direction of the angle of view (view angle minus side).

FIG. 3A shows exposure rays (1) and (2) when the HOE 23 is manufactured (when the hologram photosensitive material 23a is exposed), and FIG. 3B shows reproduction rays during video observation. Show. The HOE 23 is manufactured by exposing the hologram photosensitive material 23a with two light beams (exposure light beams (1) and (2)) parallel to the optical axis, and recording interference fringes on the hologram photosensitive material 23a as a refractive index distribution. In the present embodiment, the HOE 23 is manufactured with the incident angles of the exposure light beams (1) and (2) to the hologram photosensitive material 23a being 0 ° and 60 °, respectively, and the exposure wavelengths of the BGR being 476.5 nm, 532 nm, and 647 nm. did. A prism 31 is disposed in close contact with the surface 21a of the light guide member 21, and the exposure light beam (2) is applied to the hologram photosensitive material 23a through the prism 31. Thereby, at the time of image observation, the image light can be totally reflected by the surface 21 a of the light guide member 21 and can be incident on the HOE 23.

Here, it is assumed that the maximum field angle at the time of image observation is ± 6 °, and the hologram photosensitive material 23a undergoes 2% polymerization shrinkage in the film thickness direction during exposure. At the center of the observation screen at the time of image observation (view angle θ = 0 °), the observation direction of the image and the direction of the exposure light beam (1) are the same, so the wavelength at the time of exposure × 0.98 (2% polymerization shrinkage) The diffraction efficiency is maximized for image light having a wavelength of However, if the observation angle of view is different in the X direction within the plane including the optical axis in the observation screen, the observation direction of the image and the direction of the exposure light beam (1) are shifted, so that the diffraction peak wavelength reaching the optical pupil E Varies according to Bragg's conditional expression. Table 1 shows the relationship between the observation angle of view and the diffraction peak wavelength of each BGR in the present embodiment.

Thus, the diffraction peak wavelength of BGR changes depending on the viewing angle of view. Conventionally, focusing on the diffraction peak wavelength difference (color difference, luminance difference) in the field angle direction, in order to correct color unevenness in the screen, a filter is inserted to change the transmittance or to electrically Although the intensity of each color is changed by performing signal processing, both methods are methods in which the amount of light decreases, and the light utilization efficiency decreases.

On the other hand, FIG. 4 shows a photopic luminosity curve (hereinafter also simply referred to as a luminosity curve). As shown in the figure, the relative visibility is highest near the wavelength of 555 nm, and decreases from the wavelength toward the long wavelength side and the short wavelength side. Even if video light having the same energy (intensity) exists at each wavelength of BGR, the relative visibility differs depending on the wavelength, and the brightness (luminance) perceived by humans differs.

Here, from Table 1, the wavelength range of the image light of each BGR varies depending on the angle of view, and is B: 455 to 476 nm, G: 509 to 532 nm, and R: 618 to 647 nm (hatched hatched wavelengths in FIG. 4). Area reference). At this time, when the relative visibility at each angle of view is normalized with respect to the screen center (angle of view 0 °), it is as shown in FIG. Hereinafter, the normalized relative luminous efficiency is also referred to as relative specific luminous efficiency.

From FIG. 5, for B and G, the change in relative relative luminous sensitivity with respect to the change in angle of view shows almost the same behavior, while for R, the change in relative relative luminous sensitivity is completely different from B and G. Behave differently. That is, for B and G, the relative relative luminous sensitivity increases monotonously as the angle of view increases toward the plus side, whereas the relative relative luminous sensitivity monotonously decreases for R. In addition, the amount of change in relative relative luminous sensitivity is much larger in R than B and G.

Here, the luminance of the image actually observed at the position of the optical pupil is assumed that the image light having the same energy amount at each wavelength reaches the HOE 23.
(Relative specific luminous efficiency) x (Diffraction efficiency)
It is represented by At this time, when the diffraction efficiency of the HOE 23 is constant regardless of the region, the change in (relative relative luminous sensitivity) × (diffraction efficiency) for each angle of view is substantially the same as the change in relative relative luminous sensitivity in FIG. It becomes the behavior of. Therefore, in this case, the luminance of the observed image varies depending on the angle of view, and B and G are brighter on the plus side of the angle of view, and conversely, R is brighter on the minus side of the angle of view. That is, in B, G, and R, the direction in which the video brightness is brightened is reversed (between the view angle plus side and the view angle minus side), and in principle, color unevenness occurs in the screen.

<About the method for reducing color unevenness in the screen of the present invention>
Next, a method for reducing color unevenness in the screen of the present invention will be described. In the present invention, the color unevenness in the screen caused by the reverse of the gradient of the relative visibility curve depending on the angle of view between B, G, and R is improved by devising the HOE 23. Specifically, it is as follows.

Here, it is assumed that a color having a wavelength region different from R is C in the light of any two or three wavelength regions of RGB that the HOE 23 diffracts and reflects. That is, the wavelength range of C is the wavelength range of B or G that is on the shorter wavelength side than the wavelength (555 nm) with the highest specific visibility in the specific visibility curve shown in FIG. In the HOE 23, the maximum diffraction efficiencies η of R and C at angles of view θ °, −θ °, and 0 ° are ηR _θ , ηR _−θ , ηR ₀ , ηC _θ , ηC _−θ , and ηC ₀ , respectively. . Further, the relative luminous sensitivities N in the bright places of the diffraction peak wavelengths Rλ (nm) and Cλ (nm) of R and C at angles of view θ °, −θ °, and 0 ° are respectively represented as NRλ _θ , NRλ _−θ , NRλ ₀ , NCλ _θ , NCλ _−θ , and NCλ _{0 are} assumed.

FIG. 6 is a plan view of the HOE 23. Assuming that the position of the region corresponding to the angle of view 0 ° in the X direction of the HOE 23 is a reference (0 mm), the position of the region corresponding to the angle of view θ ° and −θ ° is 2.5 mm from the reference position, respectively. -2.5 mm position.

FIG. 1 shows the relationship between the position of the HOE 23 in the X direction and the maximum diffraction efficiency for each color of RGB. As shown in the figure, in the present embodiment, the ratio of the maximum diffraction efficiency of each color of RGB is varied depending on the region in the HOE 23 so as to satisfy the following conditional expression (1). That is,
P> (ηR _θ / ηC _θ )> (ηR ₀ / ηC ₀ )> (ηR _−θ / ηC _−θ )> Q
... (1)
However,
P = {(NCλ _θ / NCλ ₀ ) · (NRλ ₀ / NRλ _θ )} ²
Q = {(NCλ _−θ / NCλ ₀ ) · (NRλ ₀ / NRλ _−θ )} ²
It is.

Of conditional expression (1), (ηR _θ / ηC _θ )> (ηR ₀ / ηC ₀ )> (ηR _−θ / ηC _−θ ) is referred to as conditional expression D. By varying the maximum diffraction efficiency ratio (for example, ηR / ηB, ηR / ηG) of each color of the HOE 23 depending on the region so as to satisfy the conditional expression D, in the HOE 23, the direction in which the angles of view θ and −θ are stretched (X direction) , The change in the maximum diffraction efficiency of R is larger than the change in the maximum diffraction efficiency of C.

As shown in FIG. 5, in the X direction, the change in relative relative luminous sensitivity is larger in R than in C (B or G). By making the change in maximum diffraction efficiency larger than C for large R, it becomes possible to reduce color unevenness in the screen.

That is, at the angle of view θ where the diffraction peak wavelength of R is larger, the relative visibility of R is lower (see FIG. 4). Therefore, in the region corresponding to the angle of view θ and the HOE 23, the region corresponding to the center of the angle of view and the HOE 23 Rather than the maximum diffraction efficiency ratio of R and C (that is, (ηR _θ / ηC _θ )> (ηR ₀ / ηC ₀ )). On the other hand, at the angle of view −θ where the diffraction peak wavelength of R is smaller, the relative visibility of R is higher (see FIG. 4), so in the region corresponding to the angle of view −θ and HOE 23, the center of view angle corresponds to HOE 23. The maximum diffraction efficiency ratio of R and C is made lower than that in the region to be (that is, (ηR ₀ / ηC ₀ )> (ηR _−θ / ηC _−θ )).

FIG. 7 shows the change of (relative relative luminous sensitivity) × (diffraction efficiency) with respect to the change of the angle of view for each color of RGB, normalized based on the angle of view of 0 °. By making the maximum diffraction efficiency ratio of R and C different depending on the region of HOE 23 as described above, the relative specific luminous efficiency changes most as compared with the case where the maximum diffraction efficiency ratio is constant regardless of the HOE region. For large R, the amount of change in (relative relative luminous sensitivity) × (diffraction efficiency) with respect to the change in the angle of view can be suppressed, and color unevenness in the screen can be reduced. In the example of FIG. 7, for all of RGB, (relative relative luminous sensitivity) × (diffraction efficiency) = 0.7 to 1.3, and the amount of change is suppressed to 30% or less. Recognize. As described above, since the color unevenness in the screen can be reduced in consideration of the relative visibility, the observer can perceive an image with good image quality during actual image observation.

Further, by satisfying the conditional expression D, the maximum diffraction efficiency of R and C in the HOE 23 can be changed monotonously (including almost monotone) in the X direction. Since the change in relative relative luminous sensitivity in the X direction is monotonic as shown in FIG. 5, the maximum diffraction efficiency of R and C changes monotonously in the X direction in accordance with such monotonous change in relative relative visual sensitivity. By doing so, color unevenness in the screen can be reduced with a simple configuration of the HOE 23 (without complicated setting of diffraction efficiency).

P corresponds to the upper limit of (ηR _θ / ηC _θ ) in conditional expression D, and Q corresponds to the lower limit of (ηR _−θ / ηC _−θ ) in conditional expression D. If (ηR _θ / ηC _θ ) becomes too large or (ηR _−θ / ηC _−θ ) becomes too small, color unevenness in the screen may be reversed. Therefore, by setting (ηR _θ / ηC _θ ) to be smaller than the upper limit P and setting (ηR _−θ / ηC _−θ ) to be larger than the lower limit Q, a phenomenon in which color unevenness in the screen is reversed and generated. Can be avoided, and the effect of reducing color unevenness by conditional expression D can be obtained appropriately.

8A shows the distribution of diffraction efficiency of BGR at an angle of view of 6 °, FIG. 8B shows an angle of view of 0 °, and FIG. 8C shows an angle of view of −6 °. As described above, by making the maximum diffraction efficiency ratio of each color of the HOE 23 different depending on the region, as shown in FIG. 8A, at the angle of view 6 °, the maximum diffraction efficiency of R is larger than the angle of view 0 °, As shown in FIG. 8C, when the angle of view is -6 °, the maximum diffraction efficiency of B and G is larger than that of the angle of view of 0 °. It becomes possible to increase the diffraction efficiency. Therefore, compared to the conventional configuration in which the color unevenness in the screen is reduced using the correction circuit and the correction filter, the light use efficiency of the necessary color can be increased, and the observer can reduce the color unevenness. The image can be observed brightly.

By the way, since C is in the wavelength range of B or G, conditional expression (1) is satisfied when C is replaced with B, or conditional expression (1) is satisfied when C is replaced with G. As described above, the ratio of the maximum diffraction efficiency of each color may be varied depending on the region of the HOE 23. That is, the conditional expression (1) may be satisfied in the R wavelength region and the B or G wavelength region. In this case, even when the HOE 23 is fabricated so as to diffract and reflect light in the two color wavelength ranges, it is possible to reduce color unevenness in the screen in consideration of the relative visibility of the two colors. .

Further, the ratio of the maximum diffraction efficiency of each color may be varied depending on the region of the HOE 23 so as to satisfy the conditional expression (1) for both the case where C is replaced with B and the case where G is replaced. That is, the conditional expression (1) may be satisfied in both the R wavelength range and the B wavelength range, and the R wavelength range and the G wavelength range. In this case, even when the HOE 23 is fabricated so as to diffract and reflect light in the three wavelength bands of RGB, it is possible to reduce color unevenness in the screen in consideration of all the relative luminous sensitivities of the three colors of RGB. It becomes possible. Therefore, for example, when a white image is displayed on the display element 12, the observer can observe (feel) a white image or an image close thereto at any angle of view in the observation screen.

Further, the video display device 1 of the present embodiment has the following conditional expression (2),
ηR _θ > ηR _−θ (2)
It is desirable to satisfy

From FIG. 4, it can be seen that the relative visual sensitivity of R is lower at an angle of view θ where the diffraction peak wavelength of R is larger, and that the relative visual sensitivity of R is higher at an angle of view −θ where the diffraction peak wavelength of R is smaller. As described above. By satisfying the conditional expression (2), the maximum diffraction efficiency of R becomes higher at the angle of view θ where the relative luminous sensitivity of R is lower, and the angle of view −θ where the relative luminance of R is higher is higher. Then, the maximum diffraction efficiency of R becomes lower.

That is, in the X direction, the change in the relative relative luminous sensitivity of R and the change in the maximum diffraction efficiency of R are reversed (the straight line between two points on the curve indicating the change in relative relative luminous sensitivity in FIG. 5). The slope is positive, and the slope of a straight line between two points on the curve indicating the change in the maximum diffraction efficiency of R in FIG. 1 is negative). In this case, in the X direction, the maximum relative diffraction efficiency of R and the maximum diffraction efficiency of R are changed in the same direction (when the inclination is both positive), the maximum diffraction efficiency of R with respect to the angle of view. It can be said that the change will be greater. As described above, the effect of reducing color unevenness in the screen can be reliably obtained by greatly changing the maximum diffraction efficiency of R for R having a large change in relative relative luminous sensitivity.

Further, by satisfying conditional expression (2), R relative relative luminous sensitivity and R maximum diffraction efficiency are changed in the same direction in the X direction, compared to Rη (θR _θ <ηR _−θ ). It is also possible to reduce the luminance difference and reduce luminance unevenness. That is, even if the relative relative luminous sensitivity of R and the maximum diffraction efficiency of R are changed in the same direction in the X direction, an effect of reducing color unevenness in the screen can be obtained as long as the conditional expression (1) is satisfied. However, in this case, for R, the value of (relative relative luminous sensitivity) × (diffraction efficiency) is larger on the minus angle of view and smaller on the plus side of the angle of view. This means that an R luminance difference occurs at both ends of the field angle.

When the conditional expression (2) is satisfied, the angle of view of R is smaller than the case of ηR _θ <ηR _−θ because the difference between the values of (relative relative luminous sensitivity) × (diffraction efficiency) is smaller than ηR _θ <ηR _−θ. The luminance difference of R at both ends is reduced. Therefore, by satisfying conditional expression (2), it is possible to reduce both color unevenness and luminance unevenness in the screen.

In addition, the video display device 1 of the present embodiment has the following conditional expression (3):
ηC _θ <ηC _−θ (3)
It is desirable to satisfy

Regardless of whether the wavelength range of C is the wavelength range of B or the wavelength range of G, the change in relative relative luminous sensitivity in the wavelength range of C is the change in relative relative luminous sensitivity in the wavelength range of R. Since the opposite is true, the relative specific luminous efficiency of C is higher on the positive angle of view and lower on the negative angle of view. By satisfying the conditional expression (3), the maximum diffraction efficiency of C is lower at the angle of view θ where the relative relative luminous sensitivity of C is higher, and at the angle of view −θ where the relative relative visibility of C is lower, The maximum diffraction efficiency of C becomes higher.

Thus, in the X direction, the change in the relative relative luminous sensitivity of C and the change in the maximum diffraction efficiency of C have opposite behaviors. Can be definitely obtained. In particular, when conditional expressions (2) and (3) are satisfied at the same time, for both R and C, the amount of change in (relative relative luminous sensitivity) × (diffraction efficiency) relative to the change in the angle of view can be suppressed. The highest effect of reducing color unevenness in the screen can be obtained.

Further, the video display device 1 of the present embodiment has the following conditional expression (4),
(ΗR _θ / ηC _θ ) ≧ 1.5 × (ηR _−θ / ηC _−θ ) (4)
It is desirable to satisfy

Conditional expression (4) indicates a level for effectively reducing color unevenness in the screen. By satisfying conditional expression (4), it is possible to reliably change the maximum diffraction efficiency of R, which has a large change in relative specific luminous efficiency, to be larger than the maximum diffraction efficiency of C in the X direction. Thereby, the effect of reducing color unevenness in the screen can be obtained with certainty.

In addition, the video display device 1 of the present embodiment has the following conditional expression (5),
P ′> (ηG _θ / ηB _θ )> (ηG ₀ / ηB ₀ )> (ηG _−θ / ηB _−θ )
> Q '(5)
However,
P ′ = {(NBλ _θ / NBλ ₀ ) · (NGλ ₀ / NGλ _θ )} ²
Q ′ = {(NBλ _−θ / NBλ ₀ ) · (NGλ ₀ / NGλ _−θ )} ²
It is desirable to satisfy

In the B wavelength region and the G wavelength region, the change in relative relative luminous sensitivity with respect to the wavelength tends to be the same and color unevenness hardly occurs. However, by satisfying conditional expression (5), the color caused by B and G Unevenness can be further improved.

P ′ corresponds to the upper limit of (ηG _θ / ηB _θ ) in conditional expression (5), and Q ′ corresponds to the lower limit of (ηG _−θ / ηB _−θ ) in conditional expression (5). If (ηG _θ / ηB _θ ) becomes too large or (ηG _−θ / ηB _−θ ) becomes too small, color unevenness in the screen may be reversed. Therefore, by setting (ηG _θ / ηB _θ ) to be smaller than the upper limit P ′ and setting (ηG _−θ / ηB _−θ ) to be larger than the lower limit Q ′, color unevenness in the screen is reversed and generated. Can be avoided, and color unevenness caused by B and G can be improved.

<Confirmation of conditional expression>
Next, it is confirmed that the video display device 1 of the present embodiment satisfies the conditional expressions (1) to (5) described above.

(Regarding conditional expression (1))
Between R and B, from FIG.
(ΗR _θ / ηB _θ ) = 0.9 / 0.55 = 1.64
(ΗR ₀ / ηB ₀ ) = 0.65 / 0.7 = 0.93
(ΗR _−θ / ηB _−θ ) = 0.4 / 0.85 = 0.47
It is. Therefore, the video display apparatus 1 according to the present embodiment has a conditional expression D between R and B, that is,
(ΗR _θ / ηB _θ )> (ηR ₀ / ηB ₀ )> (ηR _−θ / ηB _−θ )
Is satisfied.

From FIG.
P = {(NBλ _θ / NBλ ₀ ) · (NRλ ₀ / NRλ _θ )} ²
= {(0.12 / 0.08). (0.23 / 0.13)} ²
= 7.04
And
Q = {(NBλ _−θ / NBλ ₀ ) · (NRλ ₀ / NRλ _−θ )} ²
= {(0.05 / 0.08) · (0.23 / 0.39)} ²
= 0.14
It is. Therefore, the video display apparatus 1 according to the present embodiment has conditional expression (1) between R and B, that is,
P> (ηR _θ / ηB _θ )> (ηR ₀ / ηB ₀ )> (ηR _−θ / ηB _−θ )> Q
Is satisfied.

Also, between R and G, from FIG.
(ΗR _θ / ηG _θ ) = 0.9 / 0.65 = 1.38
(ΗR ₀ / ηG ₀ ) = 0.65 / 0.75 = 0.87
(ΗR _−θ / ηG _−θ ) = 0.4 / 0.85 = 0.47
It is. Therefore, the video display device 1 according to the present embodiment also satisfies the conditional expression D between R and G, that is,
(ΗR _θ / ηG _θ )> (ηR ₀ / ηG ₀ )> (ηR _−θ / ηG _−θ )
Is satisfied.

From FIG.
P = {(NGλ _θ / NGλ ₀ ) · (NRλ ₀ / NRλ _θ )} ²
= {(0.88 / 0.73) · (0.23 / 0.13)} ²
= 4.55
And
Q = {(NGλ _−θ / NGλ ₀ ) · (NRλ ₀ / NRλ _−θ )} ²
= {(0.48 / 0.73) · (0.23 / 0.39)} ²
= 0.15
It is. Therefore, the video display device 1 according to the present embodiment also satisfies the conditional expression (1) between R and G, that is,
P> (ηR _θ / ηG _θ )> (ηR ₀ / ηG ₀ )> (ηR _−θ / ηG _−θ )> Q
Is satisfied.

(Regarding conditional expression (2))
From FIG. 1, since ηR _θ = 0.9 and ηR _−θ = 0.4, the video display device 1 of the present embodiment has the conditional expression (2), that is,
ηR _θ > ηR _−θ
Is satisfied.

(Regarding conditional expression (3))
From FIG. 1, since ηB _θ = 0.55 and ηB _−θ = 0.85, the video display apparatus 1 of the present embodiment has conditional expression (3) for B, that is,
ηB _θ <ηB _−θ
Is satisfied.

Similarly, from FIG. 1, since ηG _θ = 0.65 and ηG _−θ = 0.85, the video display device 1 of the present embodiment also applies conditional expression (3) for G, that is,
ηG _θ <ηG _−θ
Is satisfied.

(Regarding conditional expression (4))
Between R and B, from FIG.
(ΗR _θ / ηB _θ ) = 0.9 / 0.55 = 1.64
(ΗR _−θ / ηB _−θ ) = 0.4 / 0.85 = 0.47
So
(ΗR _θ / ηB _θ ) ≧ 3.47 × (ηR _−θ / ηB _−θ )
It is. Therefore, the video display device 1 according to the present embodiment has conditional expression (4) between R and B, that is,
(ΗR _θ / ηB _θ ) ≧ 1.5 × (ηR _−θ / ηB _−θ )
Is satisfied.

Also, between R and G, from FIG.
(ΗR _θ / ηG _θ ) = 0.9 / 0.65 = 1.38
(ΗR _−θ / ηG _−θ ) = 0.4 / 0.85 = 0.47
So
(ΗR _θ / ηG _θ ) ≧ 2.94 × (ηR _−θ / ηG _−θ )
It is. Therefore, the video display device 1 according to the present embodiment also satisfies the conditional expression (4) between R and G, that is,
(ΗR _θ / ηG _θ ) ≧ 1.5 × (ηR _−θ / ηG _−θ )
Is satisfied.

(Regarding conditional expression (5))
Between G and B, from FIG.
(ΗG _θ / ηB _θ ) = 0.65 / 0.55 = 1.18
(ΗG ₀ / ηB ₀ ) = 0.75 / 0.7 = 1.07
(ΗG _−θ / ηB _−θ ) = 0.85 / 0.85 = 1
It is. Therefore, the video display device 1 according to the present embodiment is also between G and B.
(ΗG _θ / ηB _θ )> (ηG ₀ / ηB ₀ )> (ηG _−θ / ηB _−θ )
Is satisfied.

From FIG.
P ′ = {(NBλ _θ / NBλ ₀ ) · (NGλ ₀ / NGλ _θ )} ²
= {(0.12 / 0.08). (0.73 / 0.88)} ²
= 1.55
And
Q ′ = {(NBλ _−θ / NBλ ₀ ) · (NGλ ₀ / NGλ _−θ )} ²
= {(0.05 / 0.08) · (0.73 / 0.48)} ²
= 0.90
It is. Therefore, the video display device 1 according to the present embodiment also satisfies the conditional expression (5) between G and B, that is,
P ′> (ηG _θ / ηB _θ )> (ηG ₀ / ηB ₀ )> (ηG _−θ / ηB _−θ )
> Q '
Is satisfied.

<Other diffraction efficiency settings>
By the way, even if the maximum diffraction efficiency of B and G is made constant in the X direction of the HOE 23 and only the maximum diffraction efficiency of R is varied depending on the region, the ratio of the maximum diffraction efficiency of each color can be varied depending on the region. Conditional expression (1) can be satisfied.

9 shows another example of the relationship between the position of the HOE 23 in the X direction and the maximum diffraction efficiency for each color of RGB. FIG. 10 shows the maximum diffraction efficiency of RGB in the HOE 23 as shown in FIG. The change of (relative relative luminous sensitivity) × (diffraction efficiency) with respect to the change in the angle of view for each color of RGB when set is standardized with an angle of view of 0 ° as a standard.

As shown in FIG. 9, the change in the maximum diffraction efficiency of G is shown in FIG. 5, with the maximum diffraction efficiency of B being constant and the effectiveness being low (the change in relative relative luminous sensitivity is small) in the X direction of the HOE 23. Even if the behavior in the same direction as the change of the relative relative luminous sensitivity of G (even if the maximum diffraction efficiency of G is changed in the direction of increasing the color unevenness of G), the change (slope) of the maximum diffraction efficiency of G is R. If it is smaller than the change (slope) of the maximum diffraction efficiency, the conditional expression (1) can be satisfied. As a result, color unevenness in the screen can be reduced as shown in FIG. 10 compared to a configuration in which the maximum diffraction efficiency ratio of each color of the HOE is constant regardless of the region. Therefore, in order to reduce the color unevenness in the screen, it can be said that it is most important to change the maximum diffraction efficiency depending on the region for R that has the greatest influence on the color unevenness. In order to further enhance the effect of reducing color unevenness, it is desirable that B and G have a diffraction efficiency distribution having an inclination opposite to R in HOE 23 as shown in FIG.

The video display device using the HOE 23 set as shown in FIG. 9 further satisfies the conditional expressions (2), (4), and (5) in addition to the conditional expression (1) described above. This point will be confirmed below.

(Regarding conditional expression (1))
From FIG. 9 between R and B,
(ΗR _θ / ηB _θ ) = 0.9 / 0.65 = 1.38
(ΗR ₀ / ηB ₀ ) = 0.65 / 0.65 = 1
(ΗR _−θ / ηB _−θ ) = 0.4 / 0.65 = 0.62
It is. Therefore, the video display device has a conditional expression D between R and B, that is,
(ΗR _θ / ηB _θ )> (ηR ₀ / ηB ₀ )> (ηR _−θ / ηB _−θ )
Is satisfied.

From FIG.
P = {(NBλ _θ / NBλ ₀ ) · (NRλ ₀ / NRλ _θ )} ²
= 7.04
And
Q = {(NBλ _−θ / NBλ ₀ ) · (NRλ ₀ / NRλ _−θ )} ²
= 0.14
And the video display device has a conditional expression (1) between R and B, that is,
P> (ηR _θ / ηB _θ )> (ηR ₀ / ηB ₀ )> (ηR _−θ / ηB _−θ )> Q
Is satisfied.

From FIG. 9 between R and G,
(ΗR _θ / ηG _θ ) = 0.9 / 0.85 = 1.06
(ΗR ₀ / ηG ₀ ) = 0.65 / 0.75 = 0.87
(ΗR _−θ / ηG _−θ ) = 0.4 / 0.65 = 0.62
It is. Therefore, the above video display device can satisfy the conditional expression D between R and G, that is,
(ΗR _θ / ηG _θ )> (ηR ₀ / ηG ₀ )> (ηR _−θ / ηG _−θ )
Is satisfied.

From FIG.
P = {(NGλ _θ / NGλ ₀ ) · (NRλ ₀ / NRλ _θ )} ²
= 4.55
And
Q = {(NGλ _−θ / NGλ ₀ ) · (NRλ ₀ / NRλ _−θ )} ²
= 0.15
In the video display device, the conditional expression (1) between R and G, that is,
P> (ηR _θ / ηG _θ )> (ηR ₀ / ηG ₀ )> (ηR _−θ / ηG _−θ )> Q
Is satisfied.

(Regarding conditional expression (2))
From FIG. 9, ηR _θ = 0.9 and ηR _−θ = 0.4. Therefore, the video display device has the conditional expression (2), that is,
ηR _θ > ηR _−θ
Is satisfied.

(Regarding conditional expression (4))
From FIG. 9 between R and B,
(ΗR _θ / ηB _θ ) = 0.9 / 0.65 = 1.38
(ΗR _−θ / ηB _−θ ) = 0.4 / 0.65 = 0.62
So
(ΗR _θ / ηB _θ ) ≧ 2.25 × (ηR _−θ / ηB _−θ )
It is. Therefore, the video display device has conditional expression (4) between R and B, that is,
(ΗR _θ / ηB _θ ) ≧ 1.5 × (ηR _−θ / ηB _−θ )
Is satisfied.

Moreover, between R and G, from FIG.
(ΗR _θ / ηG _θ ) = 0.9 / 0.85 = 1.06
(ΗR _−θ / ηG _−θ ) = 0.4 / 0.65 = 0.62
So
(ΗR _θ / ηG _θ ) ≧ 1.72 × (ηR _−θ / ηG _−θ )
It is. Therefore, the above video display apparatus can satisfy the conditional expression (4) between R and G, that is,
(ΗR _θ / ηG _θ ) ≧ 1.5 × (ηR _−θ / ηG _−θ )
Is satisfied.

(Regarding conditional expression (5))
From FIG. 9 between G and B,
(ΗG _θ / ηB _θ ) = 0.85 / 0.65 = 1.31
(ΗG ₀ / ηB ₀ ) = 0.75 / 0.65 = 1.15
(ΗG _−θ / ηB _−θ ) = 0.65 / 0.65 = 1
It is. Therefore, the video display device can be used between G and B.
(ΗG _θ / ηB _θ )> (ηG ₀ / ηB ₀ )> (ηG _−θ / ηB _−θ )
Is satisfied.

From FIG.
P ′ = {(NBλ _θ / NBλ ₀ ) · (NGλ ₀ / NGλ _θ )} ²
= {(0.12 / 0.08). (0.73 / 0.88)} ²
= 1.55
And
Q ′ = {(NBλ _−θ / NBλ ₀ ) · (NGλ ₀ / NGλ _−θ )} ²
= {(0.05 / 0.08) · (0.73 / 0.48)} ²
= 0.90
It is. Therefore, the above video display apparatus can satisfy the conditional expression (5) between G and B, that is,
P ′> (ηG _θ / ηB _θ )> (ηG ₀ / ηB ₀ )> (ηG _−θ / ηB _−θ )
> Q '
Is satisfied.

<About single-layer HOE>
By the way, in this embodiment, HOE23 is produced using the hologram photosensitive material which has a sensitivity in two or more different colors among BGR in one photosensitive layer. That is, the HOE 23 is a single layer HOE in which interference fringes corresponding to two or more colors of BGR are recorded in a single layer. A method for manufacturing the HOE 23 will be described later.

As described above, in the HOE 23, when the interference fringes corresponding to each color are recorded in multiple layers in one layer, the interference fringes are recorded so as to overlap each other, so that the refractive index modulation Δn is increased for each interference fringe. It is difficult to increase the diffraction efficiency of each color at the same time. That is, the diffraction efficiency of each color has a trade-off relationship. For example, if the HOE is manufactured so that the maximum diffraction efficiency ratio of each color is the same in all regions, the distribution of diffraction efficiency similar to that in FIG. 8B in all regions, that is, the maximum diffraction efficiency of BGR in all regions is approximately both. It only rises to about 70%.

On the other hand, in the HOE 23 as in the present invention, by varying the ratio of the maximum diffraction efficiency of each color depending on the area, as described above, the maximum diffraction efficiency of 90% can be realized at an angle of view of 6 °. (See Fig. 8 (a)), it is possible to achieve a maximum diffraction efficiency of 85% for B and G at an angle of view of -6 ° (see Fig. 8 (c)). Compared with the case where HOE is used, it is possible to increase the diffraction efficiency of a color with low specific visibility according to the angle of view. That is, in the present invention, since the diffraction efficiency of each color is not increased at the same time, on the contrary, it is possible to adopt a configuration using a single layer HOE in which it is difficult to simultaneously increase the diffraction efficiency of each color. In other words, the present invention can be easily realized with a configuration using a single layer HOE, and the present invention becomes effective.

In addition, when color unevenness is improved by image processing or filters as in the past, the light utilization efficiency when using the HOE with the maximum diffraction efficiency ratio of each color in the entire region is further reduced by the light amount reduction due to image processing or the like. The utilization efficiency will be further reduced. In the present invention, since the ratio of the maximum diffraction efficiency of each color is changed depending on the region using a single layer HOE, the diffraction efficiency of a necessary color can be increased depending on the angle of view without performing image processing or the like. It can be said that the configuration using HOE is highly effective in terms of improving the light utilization efficiency.

<Method for producing HOE>
Next, a method for manufacturing the above-described HOE 23 will be described. FIG. 11 shows a schematic configuration of an exposure optical system for manufacturing the HOE 23. The RGB three laser beams emitted from the laser light sources 41R, 41G, and 41B are adjusted in optical axis by a pair of mirrors 42R, 42G, and 42B, and transmitted through the shutters 43R, 43G, and 43B. The beam diameter is enlarged by the pandas 44R, 44G, and 44B, and the light passes through the transmittance changing filters 45R, 45G, and 45B. At this time, the exposure time is adjusted by turning on / off the shutters 43R, 43G, and 43B.

The G laser beam that has passed through the transmittance changing filter 45G is reflected by the mirror 46, and is optically combined by the dichroic mirror 47 with the B laser beam that has passed through the transmittance changing filter 45B. The G and B laser beams are optically combined by the dichroic mirror 48 with the R laser beam transmitted through the transmittance changing filter 45R.

Thereafter, the RGB laser light is incident on the mirror 49 through one optical path, reflected there, and then split into two light beams by the beam splitter 50. One of the branched light beams is irradiated onto the hologram photosensitive material 23a via the mirror 51 and an arbitrary optical system 52, and the other light beam is irradiated onto the hologram photosensitive material 23a via the mirror 53, the arbitrary optical system 54 and the prism 31. Is irradiated at a predetermined incident angle. In this way, the desired HOE 23 is produced by causing the two light beams to interfere with each other in the hologram photosensitive material 23a.

Here, the transmittance changing filters 45R, 45G, and 45B are gradation filters whose transmittance changes sequentially depending on the region. In FIG. 11, the change in transmittance in the transmittance changing filters 45R, 45G, and 45B is shown by gradation, and the portion where the gradation is dark shows that the transmittance is low and the light portion shows that the transmittance is high. By irradiating the hologram photosensitive material 23a with RGB laser light through such transmittance changing filters 45R, 45G, and 45B, the necessary intensity distribution (exposure amount distribution) can be provided in the exposure beam cross section. .

At this time, there is a correlation between the exposure intensity (exposure amount) and the diffraction efficiency of the HOE. The higher the exposure amount, the higher the diffraction efficiency, and the lower the exposure amount, the lower the diffraction efficiency. Accordingly, the exposure intensity of each region that can obtain a desired diffraction efficiency in each region of the HOE 23 is obtained for each RGB, and an arbitrary transmittance changing filter 45R that changes the transmittance to correspond to the exposure intensity of each region. By using 45G and 45B, a desired HOE 23 in which the ratio of the maximum diffraction efficiency of RGB varies depending on the region can be produced.

In addition, the following can be used as three laser beams of RGB. For example, as the R laser light, a krypton ion laser or a helium neon laser can be used. As the G laser light, a solid-state laser such as Nd: YAG (SHG) or Nd: YVO ₄ (SHG) or a dye laser can be used. As the B laser beam, a solid-state laser such as an argon ion laser or sapphire can be used.

The shutters 43R, 43G, and 43B are arranged independently on the three RGB laser light paths. However, a RGB common shutter is provided on the optical path after the dichroic mirror 48 bundles the RGB laser lights into one. One may be provided. The beam expanders 44R, 44G, and 44B are also arranged independently in the RGB three laser light paths. However, the RGB common beams are arranged in the optical path after the dichroic mirror 48 bundles the RGB laser lights into one. Only one expander may be provided. However, it is more preferable to provide one beam expander corresponding to each RGB color before bundling them into one, because the beam diameter of each RGB can be expanded to a required size.

As the beam splitter 50, a transmission / reflection mirror (half mirror) coated with chromium or a multilayer film, a polarization beam splitter, or the like can be used, but the light amounts of the two light beams on the exposure surface are substantially equal. It is desirable to set the branching ratio appropriately. At this time, it is desirable to split the laser beams having a plurality of wavelengths at substantially the same branching ratio. For this purpose, it is easy to use a transmission / reflection mirror coated with chromium or a multilayer film having a desired reflection / transmission ratio. .

It should be noted that the polarization direction of the laser light may be horizontal or vertical with respect to the optical table on which the laser light sources 41R, 41G, and 41B are installed, because the polarization direction does not rotate due to reflection by a mirror or the like. In practice, it is most desirable to set the polarization direction of the laser light so that it is incident on the hologram photosensitive material as S-polarized light.

[Embodiment 2]
The following will describe another embodiment of the present invention with reference to the drawings.

The image display apparatus of the present embodiment is a vertical insertion type, that is, a display element is arranged above the HOE, and image light from above is diffracted and reflected by the HOE to guide the optical pupil, and the position of the optical pupil HOE is used for observing an image, and diffracting and reflecting incident parallel light into convergent light. Hereinafter, an example in which the maximum diffraction efficiency ratio of each color of the HOE is varied depending on the region will be described.

FIG. 12A shows exposure light beams (1) and (2) when the HOE 61 of the present embodiment is manufactured (when the hologram photosensitive material 61a is exposed), and FIG. The reproduction beam is shown. The exposure light beam (1) is parallel light having an incident angle of 30 ° with respect to the hologram photosensitive material 61a. The exposure light beam (2) is diverging light from a point light source located at a distance of 30 mm in the optical axis direction from the center of the hologram photosensitive material 61a, and the incident angle of the central light beam on the hologram photosensitive material 61a is 30 °. The HOE 61 is produced by exposing the hologram photosensitive material 61a with such exposure light beams (1) and (2).

In this embodiment, similarly to the first embodiment, the exposure wavelengths of the BGR are set to 476.5 nm, 532 nm, and 647 nm, but it is assumed that there is no polymerization shrinkage of the hologram photosensitive material 61a at the time of exposure.

When observing the image, the image is observed at a distance of 15 mm from the center of the HOE 61 in the optical axis direction. The observation angle of view at this time is ± 7 ° in the vertical direction (Y direction).

Also in this embodiment, the angle of view at the center of the observation screen is set to 0 (°), and two in the Y direction in the observation screen in the plane including the optical axis of the incident light and the optical axis of the reflected light with respect to the HOE 61 are displayed. Of the maximum angle of view, the larger diffraction peak wavelength of R is defined as + θ (°), and the smaller one is defined as −θ (°). Therefore, in this embodiment, the downward direction with respect to the center of the angle of view is the positive direction of the angle of view (view angle plus side), and the upward direction is the negative direction of the angle of view (view angle minus side). Table 2 shows the relationship between the observation angle of view of each BGR and the diffraction peak wavelength in this embodiment.

From Table 2, the wavelength range of the image light of each BGR varies depending on the angle of view, and is B: 470 to 483 nm, G: 526 to 539 nm, and R: 639 to 656 nm. The specific visibility in the wavelength range corresponding to the observation angle of view is extracted from the specific visibility curve shown in FIG. 4, and the relative visibility of BGR at each extracted angle of view is based on the screen center (0 ° angle of view). When normalized, the result is as shown in FIG. From the figure, the gradient direction of relative relative luminous sensitivity is reversed between B and R and between G and R, and in principle, color unevenness occurs in the screen. That is, assuming that the energy (intensity) of the image light is the same at each wavelength, in this embodiment, the upper side of the angle of view (the minus angle of view) is observed in red, and the lower side of the angle of view (plus angle of view) is bluish It becomes easier to observe.

FIG. 14 is a plan view of the HOE 61. In the Y direction of the HOE 61, assuming that the position of the region corresponding to the angle of view of 0 ° is the reference (0 mm), the position corresponding to the upper end of the angle of view is the position −3 mm from the reference position and corresponds to the lower end of the angle of view. The position is 3 mm from the reference position.

FIG. 15 shows the relationship between the position of the HOE 61 in the Y direction and the RGB maximum diffraction efficiency in this embodiment, and FIG. 16 shows (relative relative luminous sensitivity) with respect to changes in the field angle for each color of RGB. The change in (diffraction efficiency) is shown normalized with an angle of view of 0 ° as a reference. Also in this embodiment, the ratio of the maximum diffraction efficiency of each color of RGB in the HOE 61 is varied depending on the region so as to satisfy the conditional expressions (1) to (5) described above (see FIG. 15). As a result, as shown in FIG. 16, the amount of change in (relative relative luminous sensitivity) × (diffraction efficiency) with respect to the change in the angle of view can be suppressed for R having the largest change in relative specific luminous efficiency. In the example of FIG. 16, for all of RGB, (relative relative luminous sensitivity) × (diffraction efficiency) = 0.7 to 1.2, and the amount of change is suppressed to 30% or less. Recognize. Therefore, also in the configuration of the present embodiment, the color unevenness in the screen can be reduced in consideration of the relative visibility, and an image with good image quality can be observed during actual image observation. The effect of can be obtained.

In the present embodiment, the diffraction efficiency distribution of each color reflects the Gaussian intensity distribution of the exposure light beam so that the vicinity of the maximum diffraction efficiency is maximized as shown in FIG. Distribution. However, overall, as in the first embodiment, it can be considered that the maximum diffraction efficiency of each color changes monotonously (increases / decreases) in accordance with the slope of the relative visibility curve.

Next, it is confirmed that the video display device of this embodiment satisfies the conditional expressions (1) to (5).

(Regarding conditional expression (1))
Between R and B, from FIG.
(ΗR _θ / ηB _θ ) = 0.78 / 0.55 = 1.42
(ΗR ₀ / ηB ₀ ) = 0.65 / 0.7 = 0.93
(ΗR _−θ / ηB _−θ ) = 0.45 / 0.73 = 0.62
It is. Therefore, the video display apparatus according to the present embodiment has a conditional expression D between R and B, that is,
(ΗR _θ / ηB _θ )> (ηR ₀ / ηB ₀ )> (ηR _−θ / ηB _−θ )
Is satisfied.

From FIG.
P = {(NBλ _θ / NBλ ₀ ) · (NRλ ₀ / NRλ _θ )} ²
= {(0.16 / 0.12) · (0.13 / 0.08)} ²
= 4.69
And
Q = {(NBλ _−θ / NBλ ₀ ) · (NRλ ₀ / NRλ _−θ )} ²
= {(0.09 / 0.12) · (0.13 / 0.18)} ²
= 0.29
It is. Therefore, the video display device according to the present embodiment has conditional expression (1) between R and B, that is,
P> (ηR _θ / ηB _θ )> (ηR ₀ / ηB ₀ )> (ηR _−θ / ηB _−θ )> Q
Is satisfied.

Also, between R and G, from FIG.
(ΗR _θ / ηG _θ ) = 0.78 / 0.75 = 1.04
(ΗR ₀ / ηG ₀ ) = 0.65 / 0.8 = 0.81
(ΗR _−θ / ηG _−θ ) = 0.45 / 0.82 = 0.55
It is. Therefore, the video display apparatus according to the present embodiment can satisfy the conditional expression D between R and G, that is,
(ΗR _θ / ηG _θ )> (ηR ₀ / ηG ₀ )> (ηR _−θ / ηG _−θ )
Is satisfied.

From FIG.
P = {(NGλ _θ / NGλ ₀ ) · (NRλ ₀ / NRλ _θ )} ²
= {(0.95 / 0.88). (0.13 / 0.08)} ²
= 3.08
And
Q = {(NGλ _−θ / NGλ ₀ ) · (NRλ ₀ / NRλ _−θ )} ²
= {(0.81 / 0.88). (0.13 / 0.18)} ²
= 0.44
It is. Therefore, the video display apparatus according to the present embodiment can satisfy the conditional expression (1) between R and G, that is,
P> (ηR _θ / ηG _θ )> (ηR ₀ / ηG ₀ )> (ηR _−θ / ηG _−θ )> Q
Is satisfied.

(Regarding conditional expression (2))
From FIG. 15, since ηR _θ = 0.78 and ηR _−θ = 0.45, the video display apparatus of the present embodiment has the conditional expression (2), that is,
ηR _θ > ηR _−θ
Is satisfied.

(Regarding conditional expression (3))
From FIG. 15, since ηB _θ = 0.55 and ηB _−θ = 0.73, the video display apparatus of the present embodiment has conditional expression (3) for B, that is,
ηB _θ <ηB _−θ
Is satisfied.

Similarly, from FIG. 15, since ηG _θ = 0.75 and ηG _−θ = 0.82, the video display apparatus of this embodiment also applies conditional expression (3) for G, that is,
ηG _θ <ηG _−θ
Is satisfied.

(Regarding conditional expression (4))
Between R and B, from FIG.
(ΗR _θ / ηB _θ ) = 0.78 / 0.55 = 1.42
(ΗR _−θ / ηB _−θ ) = 0.45 / 0.73 = 0.62
So
(ΗR _θ / ηB _θ ) ≧ 2.3 × (ηR _−θ / ηB _−θ )
It is. Therefore, the video display device according to the present embodiment has conditional expression (4) between R and B, that is,
(ΗR _θ / ηB _θ ) ≧ 1.5 × (ηR _−θ / ηB _−θ )
Is satisfied.

Also, between R and G, from FIG.
(ΗR _θ / ηG _θ ) = 0.78 / 0.75 = 1.04
(ΗR _−θ / ηG _−θ ) = 0.45 / 0.82 = 0.55
So
(ΗR _θ / ηG _θ ) ≧ 1.89 × (ηR _−θ / ηG _−θ )
It is. Therefore, the video display apparatus according to the present embodiment can satisfy the conditional expression (4) between R and G, that is,
(ΗR _θ / ηG _θ ) ≧ 1.5 × (ηR _−θ / ηG _−θ )
Is satisfied.

(Regarding conditional expression (5))
Between G and B, from FIG.
(ΗG _θ / ηB _θ ) = 0.75 / 0.55 = 1.36
(ΗG ₀ / ηB ₀ ) = 0.8 / 0.7 = 1.14
(ΗG _−θ / ηB _−θ ) = 0.82 / 0.73 = 1.12
It is. Therefore, the video display device of the present embodiment is also between G and B.
(ΗG _θ / ηB _θ )> (ηG ₀ / ηB ₀ )> (ηG _−θ / ηB _−θ )
Is satisfied.

From FIG.
P ′ = {(NBλ _θ / NBλ ₀ ) · (NGλ ₀ / NGλ _θ )} ²
= {(0.16 / 0.12) · (0.83 / 0.95)} ²
= 1.52
And
Q ′ = {(NBλ _−θ / NBλ ₀ ) · (NGλ ₀ / NGλ _−θ )} ²
= {(0.09 / 0.12) · (0.88 / 0.81)} ²
= 0.66
It is. Therefore, the video display apparatus according to the present embodiment can satisfy the conditional expression (5) between G and B, that is,
P ′> (ηG _θ / ηB _θ )> (ηG ₀ / ηB ₀ )> (ηG _−θ / ηB _−θ )
> Q '
Is satisfied.

Next, a method for manufacturing the HOE 61 will be described.

The HOE 61 of the present embodiment can be manufactured by exposing the hologram photosensitive material 61a with two light beams using the same exposure optical system as in FIG. 11, but in this embodiment, the transmittance changing filter 45R • 45G and 45B are omitted, and an arbitrary optical system is inserted so that the light beam applied to the hologram photosensitive material from the optical pupil side becomes divergent light from a point light source.

At this time, since the laser light generally has a Gaussian intensity distribution, the following (A), (B), and (C) are adjusted by using the intensity distribution, and the laser beam of this embodiment is adjusted. The HOE 61 can be easily manufactured.

(A) The optical paths of the RGB laser beams are adjusted by a pair of mirrors for adjusting the optical path so that the center of the intensity of the exposure light beams of RGB is irradiated on the portion of the HOE surface where the diffraction efficiency is to be maximized. In the example of the present embodiment, the RGB lasers are set so that the intensity centers of the RGB colors are R: Y = 2.3 mm, G: Y = −2.3 mm, and B: Y = −2.1 mm. Adjust the light path.

(B) The amount of intensity decrease from the intensity center toward the periphery is adjusted by arbitrarily changing the expansion ratio of the beam diameter in the beam expander for each color. If the enlargement ratio is increased, the strength reduction amount is small, and if the expansion ratio is small, the strength reduction amount is large.

(C) According to the above (A) and (B), the beam shape is adjusted, and finally the laser intensity of each color is adjusted so that each color has the required maximum diffraction efficiency ratio.

As described above, the first and second embodiments have been described based on the assumption that the energy of the image light is the same at each wavelength. However, in reality, the image light has the wavelength characteristics of the intensity distribution of the light source light, and the display element. Since it is affected by the wavelength characteristics of the transmittance of the color filter, it is more desirable to set the maximum diffraction efficiency ratio of each region in consideration of these characteristics.

However, the relative visibility curve with respect to the wavelength is always constant, and the gradient direction of relative relative visibility in the screen is reversed between B, G, and R, so that in principle, color unevenness occurs. Therefore, the present invention in which the diffraction efficiency is set for each HOE region in consideration of the relative visibility with respect to the wavelength region desired to be used in the video display device is effective as a method for reducing the color unevenness while improving the light utilization efficiency. is there.

In the above, an LED is assumed as the light source of the video display device, but the light source may be a fluorescent tube. Since the fluorescent tube has a flat intensity characteristic with respect to the wavelength, it is easy to make the energy of the image light close to the same at each wavelength. Therefore, the configuration of the present invention described on the premise that the energy of the image light is the same at each wavelength becomes more effective, and the present invention can reliably reduce the color unevenness in the screen.

[Embodiment 3]
The following will describe still another embodiment of the present invention with reference to the drawings. In the present embodiment, a video display device, HMD, and HUD to which the HOE 61 of the second embodiment can be applied will be described.

<About video display device>
FIG. 17 is a cross-sectional view showing a schematic configuration of the video display device 71 of the present embodiment. The video display device 71 includes a light source 81, an illumination optical system 82, a display element 83, and an eyepiece optical system 84.

The light source 81 illuminates the display element 83 and is composed of, for example, an LED. The light source 81 is disposed so as to be substantially conjugate with the optical pupil E formed by the eyepiece optical system 84. The illumination optical system 82 is an optical system that condenses light from the light source 81 and guides it to the display element 83, and includes, for example, a mirror 82a having a concave reflecting surface. The display element 83 displays light by modulating light incident from the light source 81 via the illumination optical system 82 according to image data, and is configured by, for example, a transmissive LCD. The display element 83 is arranged such that the long side direction of the rectangular display screen is the horizontal direction (direction perpendicular to the paper surface of FIG. 17; the same as the left-right direction), and the short side direction is the direction perpendicular thereto.

The eyepiece optical system 84 is an observation optical system that guides the image light from the display element 83 to the optical pupil E (or the pupil of the observer at the position of the optical pupil E), and includes an eyepiece prism 91, a deflection prism 92, and a HOE 93. And is configured. The HOE 93 corresponds to the HOE 61 of the second embodiment.

The eyepiece prism 91 totally reflects the image light from the display element 83 and guides it to the optical pupil E through the HOE 93 while transmitting the external light to the optical pupil E. For example, it is made of an acrylic resin. The eyepiece prism 91 has a shape in which a lower end portion of a parallel plate is wedge-shaped. The upper end surface of the eyepiece prism 91 is a surface 91a as an incident surface for image light, and the two surfaces positioned in the front-rear direction are surfaces 91b and 91c parallel to each other.

The deflection prism 92 is configured by a substantially U-shaped parallel plate in plan view, and is integrated with the eyepiece prism 91 when bonded to the lower end portion and both side surface portions (left and right end surfaces) of the eyepiece prism 91. It becomes a substantially parallel plate. The deflection prism 92 is provided adjacent to or adhering to the eyepiece prism 91 so as to sandwich the HOE 93 therebetween. Thereby, the refraction when the external light passes through the wedge-shaped lower end of the eyepiece prism 91 can be canceled by the deflecting prism 92, and distortion of the external image observed through the see-through can be prevented.

The HOE 93 diffracts and reflects the image light (RGB light) from the display element 83 in the direction of the optical pupil E, while transmitting a volume of external light and guiding it to the optical pupil E as a volume phase type reflection hologram. It is an optical element and is formed on a surface 91 d that is a joint surface with the deflecting prism 92 in the eyepiece prism 91. The HOE 93 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 image display device 71 having the above-described configuration, the light emitted from the light source 81 is reflected and collected by the mirror 82a of the illumination optical system 82, and enters the display element 83 as almost collimated light, where it is modulated and imaged. It is emitted as light. Image light from the display element 83 enters the inside of the eyepiece prism 91 of the eyepiece optical system 84 from the surface 91a, and then is totally reflected at least once by the surfaces 91b and 91c and enters the HOE 93.

The HOE 93 has wavelength selectivity that functions as a diffraction element that independently diffracts light in each of the RGB wavelength regions emitted from the light source 81 for each wavelength region. It is designed to function as a concave reflecting surface for light. Therefore, the light incident on the HOE 93 is diffracted and reflected there to reach the optical pupil E, and at the same time, external light passes through the HOE 93 and travels toward the optical pupil E. Therefore, by locating the observer's pupil at the position of the optical pupil E, the observer can observe the image displayed on the display element 83 as an enlarged virtual image, and at the same time, can observe the outside world in a see-through manner. it can. Note that various aberrations (coma aberration, curvature of field, astigmatism, distortion) are corrected in the eyepiece optical system 84 so that the viewer can observe the image displayed on the display element 83 satisfactorily.

Further, since the light source 81 and the optical pupil E of the eyepiece optical system 84 are substantially conjugate, the light emitted from the light source 81 can be efficiently guided to the optical pupil E. Accordingly, when the observer's pupil is positioned at the position of the optical pupil E, the light from the light source 81 can be efficiently incident on the observer's pupil (pupil), and the observer can obtain a bright high-definition image. Can be observed.

<About HMD>
FIG. 18 is a perspective view showing a schematic configuration of the HMD. The HMD includes the above-described video display device 71 and support means 72.

Supplementing the video display device 71, the video display device 71 further includes a housing 73 that includes at least a light source 81 and a display element 83 (both see FIG. 17). The housing 73 holds a part of the eyepiece optical system 84. The eyepiece optical system 84 is configured by bonding the eyepiece prism 91 and the deflecting prism 92 as described above, and has a shape like one lens of a pair of glasses (lens for right eye in FIG. 18) as a whole. . Further, the video display device 71 has a circuit board (not shown) for supplying at least driving power and a video signal to the light source 81 and the display element 83 via a cable 74 provided through the housing 73. is doing.

The support means 72 is a support mechanism corresponding to a spectacle frame (including a bridge and a temple), and supports the image display device 71 in front of the observer's eyes (for example, in front of the right eye). Further, the support means 72 includes a nose pad 75 (right nose pad 75R / left nose pad 75L) that comes into contact with the observer's nose, and a nose pad lock unit 76 that fixes the nose pad 75 at a predetermined position. Yes. The nose pad lock unit 76 holds the nose pad 75 with a spring shaft.

When the observer wears the HMD on the head and displays an image on the display element 83, the image light is guided to the optical pupil via the eyepiece optical system 84. Therefore, by aligning the observer's pupil with the position of the optical pupil, the observer can observe an enlarged virtual image of the display image on the image display device 71. At the same time, the observer can observe the outside world through the eyepiece optical system 84 in a see-through manner.

Thus, by supporting the video display device 71 by the support means 72, the observer can observe the video provided from the video display device 71 in a hands-free and stable manner for a long time. Note that two video display devices 71 may be used so that video can be observed with both eyes. In this case, it is necessary to provide an adjustment mechanism (not shown) for adjusting the distance (eye distance) between the two observation optical systems.

<About HUD>
FIG. 19 is a cross-sectional view showing a schematic configuration of the HUD. The video display device 71 applied to the HUD uses an illumination lens 82 b as the illumination optical system 82 and uses an observation optical system 85 instead of the eyepiece optical system 84.

The observation optical system 85 includes a HOE 93 corresponding to the HOE 61 of the second embodiment and a substrate 94 that holds the HOE 93. The substrate 94 can be formed of a transparent windshield corresponding to the windshield in front of the driver's seat in a vehicle, ship, railroad, aircraft, or the like, for example, at least a part of which is within the observer's field of view. Placed in.

According to the above configuration, the light emitted from the light source 81 is collected by the illumination lens 82 b and enters the display element 83. The light (video light) modulated by the display element 83 according to the image data is incident on the HOE 93 where it is diffracted and reflected and guided to the optical pupil. At the position of the optical pupil, the observer can observe the magnified virtual image of the image displayed on the display element 83 and at the same time observe the outside world through the HOE 93 and the substrate 94.

It should be noted that the HUD may be configured by holding the HOE 93 on a substrate separate from the windshield and placing the substrate in the field of view of the observer. In this case, the HUD can function as a document display device such as a prompter. Therefore, it can be said that the HUD of the present embodiment only needs to be configured by including the video display device 71 and the HOE 93 of the video display device 71 being held on a substrate disposed in the field of view of the observer.

In the configuration of FIG. 19, since the image light from the display element 83 is incident on the HOE 93 from the lower side, the side where the diffraction peak wavelength of R becomes longer is shown in the both ends of the vertical field angle. 17 and the configuration of FIG. Therefore, when the conditional expressions (1) to (5) are applied to the video display device 71 applied to the HUD, the upward direction with respect to the center of the angle of view is the positive direction of the angle of view (the angle of view plus side), and The direction is the negative direction of the angle of view (the angle of view minus side).

Of course, the HOE can be manufactured by appropriately combining the configurations and methods described in the embodiments, and the video display device, the HMD, and the HUD can be configured. For example, the method for manufacturing the HOE of Embodiment 2 can be applied to Embodiment 1, and conversely, the method for manufacturing HOE of Embodiment 1 can also be applied to Embodiment 2. Of course, the video display device according to the first embodiment that guides the video light in the horizontal direction can be applied to the HMD or HUD according to the third embodiment.

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

DESCRIPTION OF SYMBOLS 1 Image display apparatus 11 Light source 12 Display element 13 Eyepiece optical system (observation optical system)
14 Light guiding means (observation optical system)
23 HOE
61 HOE
Reference Signs List 71 Video display device 72 Support means 81 Light source 83 Display element 84 Eyepiece optical system (observation optical system)
85 Observation optical system 93 HOE
94 Substrate E Optical pupil

Claims (10)

1. A light source;
   A display element that displays light by modulating light from the light source;
   An observation optical system having a volume phase type reflection type hologram optical element that diffracts and reflects the image light from the display element and guides it to the optical pupil, and an image display device comprising:
   The hologram optical element diffracts and reflects light of two or more wavelength ranges including the R wavelength range among the RGB wavelength ranges corresponding to red, green, and blue to guide the optical pupil,
   The ratio of the maximum diffraction efficiency of each color of the hologram optical element differs depending on the region,
   The optical axis is an axis that optically connects the center of the display surface of the display element and the center of the optical pupil,
   The angle of view at the center of the observation screen is 0, and the diffraction peak wavelength of R out of the two maximum angles of view in the observation screen in a plane including the optical axis of incident light and the optical axis of reflected light with respect to the hologram optical element. The larger of is θ, the smaller is -θ,
   Among the light of two or more wavelength ranges diffracted and reflected by the hologram optical element, the wavelength is different from R and shorter than the wavelength having the highest relative visibility in the photopic luminosity curve. When the area color is C,
   The maximum diffraction efficiencies η of R and C at angles of view θ, −θ, 0 are ηR _θ , ηR _−θ , ηR ₀ , ηC _θ , ηC _−θ , and ηC ₀ , respectively.
   R and C diffraction peak wavelengths Rλ and Cλ at various angles of view _θ , λλ, _θ , λλ ₀ , NRλ ₀ , NCλ _θ , NCλ _−θ , NCλ respectively. _{If 0} ,
   An image display apparatus satisfying the following conditional expression (1):
   P> (ηR _θ / ηC _θ )> (ηR ₀ / ηC ₀ )
   > (ΗR _−θ / ηC _−θ )> Q (1)
   However,
   P = {(NCλ _θ / NCλ ₀ ) · (NRλ ₀ / NRλ _θ )} ²
   Q = {(NCλ _−θ / NCλ ₀ ) · (NRλ ₀ / NRλ _−θ )} ²
2. 2. The video display device according to claim 1, wherein the conditional expression (1) is satisfied in an R wavelength region and a B or G wavelength region.
3. 2. The video display device according to claim 1, wherein the conditional expression (1) is satisfied in both of an R wavelength region and a B wavelength region, and an R wavelength region and a G wavelength region.
4. The video display apparatus according to claim 1, wherein the following conditional expression (2) is satisfied.
   ηR _θ > ηR _−θ (2)
5. The video display device according to claim 1, wherein the following conditional expression (3) is satisfied.
   ηC _θ <ηC _−θ (3)
6. The video display device according to claim 1, wherein the following conditional expression (4) is satisfied.
   (ΗR _θ / ηC _θ ) ≧ 1.5 × (ηR _−θ / ηC _−θ ) (4)
7. The video display device according to claim 1, wherein the following conditional expression (5) is satisfied.
   P ′> (ηG _θ / ηB _θ )> (ηG ₀ / ηB ₀ )
   > (ΗG _−θ / ηB _−θ )> Q ′ (5)
   However,
   P ′ = {(NBλ _θ / NBλ ₀ ) · (NGλ ₀ / NGλ _θ )} ²
   Q ′ = {(NBλ _−θ / NBλ ₀ ) · (NGλ ₀ / NGλ _−θ )} ²
8. The image display device according to any one of claims 1 to 7, wherein the hologram optical element is formed by multiple recording of interference fringes corresponding to two or more different colors of RGB in one layer.
9. The video display device according to any one of claims 1 to 8,
   And a support means for supporting the video display device in front of the observer's eyes.
10. 9. The image display device according to claim 1, wherein the hologram optical element of the image display device is held on a substrate disposed in the field of view of an observer. Head-up display.

Images