WO2010122854A1

WO2010122854A1 - Image display apparatus, head-mounted display, and head-up display

Info

Publication number: WO2010122854A1
Application number: PCT/JP2010/054207
Authority: WO
Inventors: 佳恵清水; 哲也野田
Original assignee: コニカミノルタオプト株式会社
Priority date: 2009-04-24
Filing date: 2010-03-12
Publication date: 2010-10-28

Abstract

Provided is an image display apparatus wherein a sufficient image brightness is obtained at a small angle of view at which an angle deviation ∆θ of a diffraction angle from a specular reflection angle is small, and at an angle of view at which the angle deviation is large, a lateral chromatic aberration is corrected so that an image which is bright as a whole and which has a high-quality can be observed. To this end, the wavelength range of image light incident upon a center of an optical pupil at an angle of view at which ∆θ is largest, within the wavelength range of at least one of RGB to be emitted is narrower than the wavelength range of the image light incident upon the center of the optical pupil at an angle of view at which ∆θ is smallest.

Description

Video display device, head-mounted display, and head-up display

According to the present invention, image light from a display element is diffracted and reflected by a reflection type volume phase type hologram optical element (hereinafter also referred to as HOE) and guided to an optical pupil, whereby an image is displayed to an observer at the position of the optical pupil. 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 video display device.

Conventionally, various video display devices have been proposed in which video light from the display element and external light are simultaneously guided to the observer's pupil by HOE. Since this HOE is a diffractive optical element, light incident on the HOE is diffracted in different directions depending on the wavelength. For this reason, dispersion (chromatic dispersion) due to wavelength occurs, and there is a concern that the image quality of the observed video is degraded. For example, when an LED is used as the light source for illuminating the display element, the light emission wavelength width of the light source is wide, so that lateral chromatic aberration due to HOE chromatic dispersion occurs, and the image is blurred (resolution is reduced).

Therefore, for example, in Patent Document 1, a wavelength limiting filter is inserted in the optical path to narrow the spectral half-value width for all light beams incident on the HOE. Thereby, the spread of the diffracted light in the HOE is suppressed, and blurring of the image is suppressed.

For example, in Patent Document 2, the HOE color is used at the center of the screen by using the HOE so that the region corresponding to the center of the screen and the HOE (hereinafter also referred to as the center) has an incident / reflection characteristic close to regular reflection. The influence of dispersion is suppressed and lateral chromatic aberration is reduced. In Patent Document 2, in all examples, the viewing angle of view of the video is ± 5 ° in the horizontal direction and ± 6.75 ° in the vertical direction.

JP 2000-267042 A Japanese Patent Laid-Open No. 2003-140079

The reflection type diffractive optical element has a larger dispersion due to the wavelength as the diffraction angle deviates from the regular reflection angle. Therefore, it is necessary to improve the resolution reduction due to dispersion when the angle deviation between the diffraction angle and the specular reflection angle is large. When the angle deviation is small, if the half-value width is limited by the wavelength limiting filter, the video luminance is lowered.

In this respect, in the apparatus of Patent Document 1, the half-value width of the light beam incident on the HOE is uniformly narrowed by the wavelength limiting filter without considering the angle deviation between the diffraction angle and the specular reflection angle at all. The brightness of an image expressed by light diffracted at a diffraction angle with a small angle deviation from the regular reflection angle is lowered.

Further, as in Patent Document 2, when the HOE is used so that the incident / reflection characteristics are close to regular reflection at the center of the HOE, if the HOE has characteristics (optical power) as an optical lens, the center of the screen is obtained. Even if lateral chromatic aberration does not occur, lateral chromatic aberration due to chromatic dispersion of HOE occurs around the screen. Regarding the lateral chromatic aberration around the screen, unless the HOE has an extremely strong optical power, the influence of the chromatic dispersion of the HOE is canceled by the dispersion of the other optical system, and is suppressed to a range where there is no practical problem. it can. However, this is only when the viewing angle of view of the image is small. As the viewing angle of view increases, the angle deviation between the diffraction angle and the specular reflection angle increases, so the influence of the color dispersion of HOE around the screen is affected. It can no longer be ignored. As a result, the image quality of the observed image is degraded due to an increase in lateral chromatic aberration around the screen.

The present invention has been made to solve the above-described problems, and its purpose is to ensure a sufficient image luminance at an angle of view where the angle difference between the diffraction angle and the regular reflection angle is small, and an image with a large angle difference. An object of the present invention is to provide a video display apparatus that can correct lateral chromatic aberration at the corner and observe a bright image with good image quality as a whole, and an HMD and HUD including the video display apparatus.

An image display apparatus according to the present invention includes a light source, a display element that displays an image by modulating light from the light source, and an observation optical system that guides the image light from the display element to an optical pupil. The light emitted from the light source has at least one emission peak wavelength and at least one emission wavelength region including the emission peak wavelength, and the observation optical system corresponds to the emission wavelength region. A reflection type volume phase type hologram optical element that has one diffraction peak wavelength in at least one wavelength region and that diffracts and reflects the image light from the display element in the direction of the optical pupil; The reflection optical power of the hologram optical element is different from the reflection optical power of the substrate surface on which the hologram optical element is formed, and is emitted from the display element to the hologram optical element. When the absolute value of the difference between the diffraction angle when the projected image light beam is diffracted by the hologram optical element and travels toward the center of the optical pupil and the regular reflection angle of the image light beam on the substrate surface is Δθ, In at least one emission wavelength region, an image light having a wavelength width incident on the center of the optical pupil from the angle of view at which Δθ is maximum, and an image of light incident on the center of the optical pupil from an angle of view at which Δθ is minimum It is characterized by being narrower than the wavelength width of the light beam.

In the video display device according to the aspect of the invention, the half-value width of the diffraction wavelength of the hologram optical element may be incident on the light having an angle of view at which Δθ is greater than the region on which the light having an angle of view at which Δθ is minimum It may be narrow in the area.

In the video display device of the present invention, the thickness of the film forming the hologram optical element is such that the light having an angle of view at which Δθ is larger than the region at which the light having an angle of view at which Δθ is minimum is incident. May be thick.

In the video display device of the present invention, the film forming the hologram optical element is formed by exposing a hologram photosensitive material, has a constant film thickness, and has an angle of view that minimizes the Δθ of the display element. At least one of reducing the exposure dose, lowering the heat treatment temperature, or shortening the heat treatment temperature is performed in the region where the light having the angle of view where Δθ is maximum is incident than the region where the light is incident. May be formed.

The video display device of the present invention further includes a wavelength limiting element that limits a wavelength width of light emitted from the light source, and the wavelength limiting element has the Δθ within a region where a light beam is incident on the hologram optical element. You may arrange | position only in the optical path of the peripheral light beam of the light beam which injects into the one part area | region containing the position which becomes the minimum.

The video display device of the present invention further includes a wavelength limiting element that limits a wavelength width of light emitted from the light source, and the wavelength limiting element has the Δθ within a region where a light beam is incident on the hologram optical element. It is arranged across both the optical path of the light beam incident on a part of the region including the minimum position and the optical path of the peripheral light beam, and enters the part of the region including the position where the Δθ is minimum. The wavelength width of the peripheral light beam may be narrower than the wavelength width of the light beam.

In the image display device of the present invention, the wavelength width of the image light incident on the optical pupil center may be gradually reduced from the angle of view at which Δθ is minimized toward the angle of view at which Δθ is maximized. .

In the image display device of the present invention, the wavelength width of the image light incident on the optical pupil center may be continuously narrowed from the angle of view at which Δθ is minimized toward the angle of view at which Δθ is maximized. .

In the image display device of the present invention, in all emission wavelength regions of the light source, among the image light incident on the center of the optical pupil, the wavelength width of the image light from the periphery of the screen of the display element is from the center of the screen. It may be narrower than the wavelength width of the image light.

In the image display device of the present invention, the change in wavelength width of the image light incident on the center of the optical pupil may be symmetric with respect to at least one symmetry axis on the screen.

The video display device of the present invention further includes a luminance adjusting element in which the transmittance of light emitted from the light source is different for each incident region, and in the luminance adjusting element, the region in which the light beam is incident on the hologram optical element, A configuration may be employed in which the transmittance of the light flux in the vicinity thereof is higher than the transmittance of the light flux incident on a part of the region including the position where Δθ is minimized.

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.

In the present invention, in at least one light emission wavelength region (for example, RGB wavelength region), the wavelength width of the image light incident on the center of the optical pupil from the angle of view where Δθ is maximum is from the angle of view where Δθ is minimum. It is narrower than the wavelength width of the image beam incident on the center. That is, the wavelength width of a light beam having a large chromatic dispersion (large Δθ) is narrower than the wavelength width of a light beam having a small chromatic dispersion (small Δθ). For example, the wavelength width of the image light is controlled according to Δθ as described above by using an HOE having a half-value width of the diffraction wavelength depending on the incident region or using a wavelength limiting element having a wavelength width limited by the incident region. It is possible.

As a result, the image light has a wide wavelength width at an angle of view with small chromatic dispersion, so that sufficient image brightness can be ensured, and the wavelength width of the image light is narrowed only at an angle of view with large chromatic dispersion to correct lateral chromatic aberration. can do. Accordingly, it is possible to observe an image that is bright as a whole and has good image quality with reduced blur. In particular, compared to a configuration in which a wavelength limiting element with a uniform limiting wavelength width is inserted in the optical path and the wavelength width of the luminous flux is uniformly limited over the entire screen, the use efficiency of illumination light is increased and power saving is also achieved. Can do.

1 is a cross-sectional view illustrating a schematic configuration of a video display device according to a first embodiment. It is explanatory drawing which expands and shows the principal part of the manufacturing optical system of HOE of the said video display apparatus. It is explanatory drawing which shows the light emission characteristic of the light source of the said video display apparatus. It is explanatory drawing which shows the diffraction characteristic of HOE of the said 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 a hologram photosensitive material, (b) is explanatory drawing which shows the optical path of the principal ray at the time of reproduction | regeneration. It is a top view which shows the structure of the outline of the said HOE. FIG. 7 is an explanatory diagram showing the relationship between the HOE position and film thickness on the A-A ′ line in FIG. 6. FIG. 7 is an explanatory diagram showing the relationship between the position of the HOE on the A-A ′ line in FIG. 6 and the half width of the diffraction wavelength. It is explanatory drawing which shows the relationship between the diffraction angle when an image ray is diffracted by HOE, and goes to the center of an optical pupil, and the regular reflection angle in the board | substrate surface of the said image ray. It is explanatory drawing which shows the relationship between the angle of view of image light and wavelength width in the said video display apparatus. It is a top view which shows the other structure of HOE. It is a top view which shows other structure of HOE. It is a top view which shows the schematic structure of a brightness adjustment filter. FIG. 6 is an aberration diagram showing lateral chromatic aberration in the X direction and the Y direction in the video display apparatus of Example 1. 6 is an aberration diagram illustrating lateral chromatic aberration in the X direction and the Y direction in the video display device of Comparative Example 1. FIG. It is a perspective view which shows the structure of the outline of HMD to which the video display apparatus of Embodiment 1 is applied. 6 is a cross-sectional view illustrating a schematic configuration of a video display device according to a second embodiment. It is explanatory drawing which shows the light emission characteristic of the light source of the said video display apparatus. It is a top view which shows the schematic structure of HOE of the said video display apparatus. FIG. 20 is an explanatory diagram showing the relationship between the HOE position and the film thickness on the B-B ′ line of FIG. 19. FIG. 20 is an explanatory diagram showing the relationship between the position of the HOE on the B-B ′ line of FIG. 19 and the half width of the diffraction wavelength. It is explanatory drawing which shows the relationship between the angle of view of image light and wavelength width in the said video display apparatus. FIG. 6 is an aberration diagram showing lateral chromatic aberration in the X direction and the Y direction in the video display apparatus of Example 2. 10 is an aberration diagram showing lateral chromatic aberration in the X direction and the Y direction in the video display device of Comparative Example 2. FIG. It is sectional drawing which shows the schematic structure of the video display apparatus of Embodiment 3, and HUD provided with the same. It is a top view which shows the schematic structure of the wavelength limiting filter of the said video display apparatus. It is explanatory drawing which shows the relationship between the angle of view of image light and wavelength width in the said video display apparatus. It is a top view which shows the other structure of a wavelength limiting filter. FIG. 10 is an aberration diagram showing lateral chromatic aberration in the X direction and the Y direction in the video display apparatus of Example 3. 10 is an aberration diagram showing lateral chromatic aberration in the X direction and the Y direction in the video display device of Comparative Example 3. FIG.

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

(About video display device)
FIG. 1 is a cross-sectional view showing a schematic configuration of a video display device 1 of the present embodiment. The video display device 1 includes a light source 11, an illumination optical system 12, a display element 13, and an eyepiece optical system 14. In the present embodiment, the observation angle in the horizontal direction is, for example, ± 13 °, and the observation angle in the vertical direction is, for example, ± 7.5 °, so that a so-called wide screen image can be observed. .

The light source 11 illuminates the display element 13, and in the present embodiment, a high color rendering white light that emits light in each wavelength region of blue (B), green (G), and red (R) from the same light emitting surface. It consists of a light source. That is, the light source 11 includes, for example, an LED, which is a semiconductor light emitting element that emits B light, a green phosphor that emits G light when excited by B light, and red fluorescence that emits R light when excited by B light. The BGR light is emitted from the same light emitting surface. The light emission characteristics of the light source 11 will be described later. The light source 11 (particularly the same light emitting surface as described above) is disposed so as to be substantially conjugate with the optical pupil P formed by the eyepiece optical system 14. The light source 11 may be a light source that emits one or two lights of RGB.

The illumination optical system 12 is an optical system that condenses the light from the light source 11 and guides it to the display element 13, and includes, for example, a mirror 21 having a concave reflecting surface. The display element 13 displays an image by modulating light incident from the light source 11 via the illumination optical system 12 in accordance with image data, and is configured by, 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; the same as the left-right direction), and the short side direction is the direction perpendicular thereto.

The eyepiece optical system 14 is an observation 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), and includes an eyepiece prism 31, a deflection prism 32, and a HOE 33. And is configured.

The eyepiece prism 31 totally reflects the image light from the display element 13 and guides it to the optical pupil P through the HOE 33, while transmitting the external light to the optical pupil P. Together with the deflection prism 32, For example, it is made of an acrylic resin. The eyepiece prism 31 is formed in a shape in which a lower end portion of a parallel plate is wedge-shaped. An upper end surface of the eyepiece prism 31 is a surface 31a as an incident surface for image light, and two surfaces positioned in the front-rear direction are

surfaces

31b and 31c parallel to each other.

The deflection prism 32 is formed of a substantially U-shaped parallel plate in plan view (see FIG. 16), and when attached to the lower end portion and both side surface portions (left and right end surfaces) of the eyepiece prism 31, the eyepiece prism. 31 and a substantially parallel flat plate. The deflection prism 32 is provided adjacent to or adhering to the eyepiece prism 31 so as to sandwich the HOE 33 therebetween. Thereby, the refraction when the external light passes through the wedge-shaped lower end of the eyepiece prism 31 can be canceled by the deflecting prism 32, and distortion of the external image observed through the see-through can be prevented.

The HOE 33 diffracts and reflects the image light (BGR light) from the display element 13 in the direction of the optical pupil P, while transmitting the external light and guiding it to the optical pupil P, and a volume phase type reflection hologram. It is an optical element, and is formed on a surface 31 d that is a joint surface with the deflection prism 32 in the eyepiece prism 31. The HOE 33 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. Details of the diffraction characteristics of the HOE 33 will be described later.

In the image display device 1 having the above-described configuration, the light emitted from the light source 11 is reflected and collected by the mirror 21 of the illumination optical system 12 and is substantially collimated and incident on the display element 13 where it is modulated and imaged. It is emitted as light. The image light from the display element 13 enters the inside of the eyepiece prism 31 of the eyepiece optical system 14 from the surface 31a, and then is totally reflected at least once by the

surfaces

31b and 31c and enters the HOE 33.

The HOE 33 has wavelength selectivity that functions as a diffraction element that independently diffracts light in each wavelength region of the BGR emitted from the light source 11 for each wavelength region. It is designed to function as a concave reflecting surface for light. Therefore, the light incident on the HOE 33 is diffracted and reflected there and reaches the optical pupil P. At the same time, external light passes through the HOE 33 and travels toward the optical pupil P. Therefore, by locating the observer's pupil at the position of the optical pupil P, the observer can observe the image displayed on the display element 13 as an enlarged virtual image, and at the same time, observe the outside world image with see-through. Can do. Note that various aberrations (coma aberration, curvature of field, astigmatism, distortion) are corrected in the eyepiece optical system 14 so that the viewer can observe the image displayed on the display element 13 satisfactorily.

Further, since the light emitting surface of the light source 11 and the optical pupil P (observer's pupil) of the eyepiece optical system 14 are substantially conjugate, the light emitted from the light source 11 can be efficiently guided to the optical pupil P. Thus, when the observer's pupil is positioned at the position of the optical pupil P, the light from the light source 11 can be efficiently incident on the pupil (pupil) of the observer, and the observer can obtain a bright high-definition image. Can be observed.

(About manufacturing method of HOE)
Next, a method for manufacturing the above HOE 33 will be described. FIG. 2 is an explanatory view showing, in an enlarged manner, main parts of the manufacturing optical system of the HOE 33. As shown in FIG. The HOE 33 which is a reflection type color hologram is produced by exposing the hologram photosensitive material 33a on the substrate (eyepiece prism 31) using two light beams for each BGR. At this time, one light beam is irradiated to the hologram photosensitive material 33a 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 33a, and this light beam is referred to as reference light. If the exposure wavelengths (reference light and object light) of BGR are λ1 _B , λ1 _G , and λ1 _R , respectively, for example, λ1 _B = 476.5 nm, λ1 _G = 532 nm, and λ1 _R = 647 nm.

In the optical system on the object light generation side, the RGB divergent light from the point light source 41 (object light side light source) is shaped into a predetermined wavefront by a free-form surface mirror 42 which is a reflection surface having optical power, and is planarly reflected. After being reflected by the mirror 43, the hologram photosensitive material 33 a is irradiated through the color correction prism 44. The surface 44a that is the incident surface of the object light in the color correction prism 44 is generated due to the refraction of the image light on the surface 31a of the eyepiece prism 31 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 44 is disposed in close contact with the hologram photosensitive material 33a 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

51R, 51G, and 51B, which are reference light side light sources, is used as reference light on the hologram photosensitive material 33a on the eyepiece prism 31 side. Irradiated from.

In this way, by exposing the hologram photosensitive material 33a with two light beams of object light and reference light for each of RGB, interference fringes are formed in the hologram photosensitive material 33a by interference of the two light beams, and the HOE 33 is manufactured. . At this time, the exposure with two light beams may be performed simultaneously for RGB or sequentially.

In the present embodiment, one of two exposure light sources (object light side light source, reference light side light source) that exposes the reference light side light source, that is, the hologram photosensitive material 33a used when the HOE 33 is manufactured, is an eyepiece during image observation. The optical system 14 is disposed on a surface including the optical pupil P. Thereby, at the time of image observation, the image light from the display element 13 can be efficiently diffracted by the HOE 33 and guided to the optical pupil P. Therefore, by locating the observer's pupil at the position of the optical pupil P, the observer can observe a bright and high-quality image.

Here, the BGR exposure light sources (reference light side light sources) may all be at the same position on the surface of the optical pupil P, or the amount of deviation (exactly between the exposure wavelength and the used wavelength (emission peak wavelength)). May be shifted on the pupil plane in accordance with the deviation of the ratio between the exposure wavelength and the used wavelength between different colors.

In the present embodiment, the point

light sources

51R, 51G, and 51B are used at the time of image observation so that the light of the emission peak wavelength in each wavelength region of the BGR of the light source 11 is diffracted toward the center of the optical pupil P during image observation. It is arranged on the surface of the optical pupil P. That is, as will be described later, with respect to B, since the deviation between the exposure wavelength and the emission peak wavelength is large, only the point light source 51B is shifted from the other point

light sources

51G and 51R on the surface of the optical pupil P. Yes. On the other hand, for G and R, since the difference between the exposure wavelength and the emission peak wavelength is small, the

point light sources

51G and 51R are arranged at the center of the optical pupil P.

In this way, the point

light sources

51R, 51G, and 51B are arranged in consideration of the deviation amount between the exposure wavelength and the emission peak wavelength, and the HOE 33 is manufactured, so that the center of the observer's pupil is centered on the optical pupil P during image observation. When matched, the illumination light is reliably diffracted and reflected by the HOE 33 and reaches the observer's pupil at all angles of view. Therefore, the observer can observe a bright and high-definition image over the entire screen at the center position of the optical pupil P.

(Light emission characteristics of light source)
Next, the light emission characteristics of the light source 11 will be described. FIG. 3 shows the light emission characteristics of the light source 11. The light emitted from the light source 11 emits one light (radiation) in each of the first wavelength region of 400 nm or more and less than 500 nm, the second wavelength region of 500 nm or more and less than 570 nm, and the third wavelength region of 570 nm or more and less than 700 nm. ) It has a peak wavelength and an emission wavelength region including the emission peak wavelength.

The first to third wavelength regions correspond to the BGR wavelength regions. Moreover, as said light emission wavelength area | region, the area | region within each wavelength area | region of BGR and the half value wavelength width of a light emission peak can be considered, for example. Accordingly, for each of the BGRs, there is a relationship of the lower limit wavelength of the wavelength region ≦ the lower limit wavelength of the emission wavelength region, the upper limit wavelength of the wavelength region ≧ the upper limit wavelength of the emission wavelength region. In the following, the terms wavelength region and emission wavelength region are used separately from each other.

In this embodiment, assuming that the emission peak wavelengths in each wavelength region of BGR are λ2 _B , λ2 _G , and λ2 _R , respectively, and the half-value wavelength widths of the emission peaks are Δλ2 _B , Δλ2 _G , and Δλ2 _R , respectively, for example, λ2 _B = 453nm, λ2 _G = 531nm, a _{_{λ2 R = 652nm, Δλ2 B =}} 26nm, Δλ2 G = 100nm, a .DELTA..lambda.2 _R = 120 nm. Therefore, as each emission wavelength region of BGR, here, regions of 440 nm to 466 nm, 500 nm to 570 nm, and 592 nm to 700 nm can be considered.

The amount of deviation between the exposure wavelength and the emission peak wavelength described above is | λ1 _B −λ2 _B | = 23.5 nm for _B , and | λ1 _G −λ2 _G | = 1 nm for _G , R Is | λ1 _R −λ2 _R | = 5 nm. Therefore, since the amount of deviation between the exposure wavelength and the emission peak wavelength for B is larger than the amount of deviation between the exposure wavelength and the emission peak wavelength for G and R, as described above, the point light source 51B is used when the HOE 33 is manufactured. The hologram photosensitive material 33a is exposed by being shifted from the other point

light sources

51G and 51R.

(Diffraction characteristics of HOE)
Next, the diffraction characteristics of the HOE 33 will be described. FIG. 4 shows the diffraction characteristics of the HOE 33 with respect to the screen center chief ray. Note that the screen center principal ray refers to a light ray that is emitted from the center of the display element 13 and enters the center of the optical pupil P via the HOE 33. In each wavelength region of the BGR, the peak wavelengths (diffraction peak wavelengths) of the diffraction efficiency of the HOE 33 with respect to the screen center principal ray are λ3 _B , λ3 _G , and λ3 _R , respectively, and the half-value wavelength widths of the diffraction efficiency peaks are Δλ3 _B and Δλ3, respectively. Assuming _{G 1} and Δλ3 _R , for example, λ3 _B = 453 nm, λ3 _G = 521 nm, and λ3 _R = 634 nm, and Δλ3 _B = Δλ3 _G = Δλ3 _R = 10 nm. That is, in the present embodiment, the HOE 33 has one diffraction peak wavelength and a half width of the diffraction wavelength including the diffraction peak wavelength in the BGR wavelength region corresponding to the light emission wavelength region of the light source 11.

(Supplementary about lateral chromatic aberration)
In the present embodiment, in order to reduce lateral chromatic aberration (magnification chromatic aberration) caused by chromatic dispersion of the HOE 33, the half-width of the diffraction wavelength of the HOE 33 (half-width of the diffraction efficiency peak) of the HOE 33 is controlled, so that the optical pupil is transmitted via the HOE 33. The wavelength width of the image light incident on P is limited. Hereinafter, before explaining this point, a supplementary explanation will be given on the principle of occurrence of the lateral chromatic aberration.

FIG. 5A is an explanatory diagram showing the optical path of the principal ray of the production optical system at the time of exposure of the hologram photosensitive material 33a, and FIG. 5B shows the optical path of the principal ray at the time of reproduction (use state). It is explanatory drawing. Note that the principal ray of the manufacturing optical system includes the point where the principal ray in use (screen center principal ray) intersects with the HOE 33, the point light source for reference light, and the point light source for object light. Let it be a ray of light.

The incident angles of the principal rays of the RGB reference light at the time of exposure are different so as to satisfy the Bragg condition in advance so that the diffraction angles (directions) at the HOE 33 at the emission peak wavelength match in RGB in the usage state. . In the diffraction by the reflective HOE 33, the diffraction intensity of the light diffracted in the Bragg condition, that is, the direction in which the following two expressions are simultaneously satisfied is maximized.
(Sin θ _O −sin θ _R ) / λ _R = (sin θ _I −sin θ _C ) / λ _C
(1)
(Cos θ _O −cos θ _R ) / λ _R = (cos θ _I −cos θ _C ) / λ _C
(2)
here,
λ _R (nm): Manufacturing wavelength (exposure wavelength)
θ _O (°): Object light incident angle (object light angle)
θ _R (°): Reference light incident angle (reference light 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.

When the above equation (1) is modified, the following equation (3) is obtained.
sin θ _I = sin θ _C + (λ _C / λ _R ) × (sin θ _O −sin θ _R )
(3)
In the above equation (3), when sin θ _O −sin θ _R = 0, that is, θ _R = 180 ° −θ _O , there is no wavelength-dependent term, and the direction of the diffracted light at this time is constant regardless of the wavelength. Thus, the direction satisfies sin θ _I = sin θ _C , that is, the direction satisfying θ _C = 180 ° −θ _I. At this time, the diffraction angle at the HOE 33 is equal to the regular reflection angle at the substrate surface (the surface 31d of the eyepiece prism 31) on which the HOE 33 is formed (that is, | θ _C | = | 180 ° −θ _I |).

In the present embodiment, the shape of the surface 31d on which the HOE 33 is formed is, for example, a flat surface. In this case, at one point in the screen (for example, the center of the screen), the incident / reflection characteristics close to regular reflection (| θ _C | = | 180 ° −θ _I | or | θ _C | ≈ | 180 ° −θ _I |), but the difference between | θ _C | and | 180 ° −θ _I | increases toward the periphery of the screen. That is, the wavelength dependence in the diffraction direction increases as it goes toward the periphery of the screen. This is equivalent to the fact that the chromatic dispersion in the refractive optical system suddenly increases toward the periphery of the screen and lateral chromatic aberration increases.

Even when the surface 31d on which the HOE 33 is formed has reflection optical power, if the reflection optical power of the HOE 33 and the reflection optical power of the surface 31d are different, the diffraction angle at the HOE 33 is a regular reflection at the surface 31d. It can be said that the lateral chromatic aberration due to chromatic dispersion during diffraction at the HOE 33 increases as the angle deviation (Δθ) increases, that is, toward the periphery of the screen.

(About wavelength limitation of image light)
In the present embodiment, in order to reduce the lateral chromatic aberration (particularly the periphery of the screen) as described above, the wavelength width of the image light incident on the optical pupil P is limited by using the HOE 33 having the following diffraction characteristics. .

FIG. 6 is a plan view showing a schematic configuration of the HOE 33 of the present embodiment. In FIG. 6, the difference in film thickness for each region is shown by gradation. FIG. 7 is an explanatory diagram showing the relationship between the position (region) of the HOE 33 on the line AA ′ in FIG. 6 and the film thickness. The direction of the line AA ′ corresponds to a direction (horizontal direction of the video display device) perpendicular to a later-described symmetry axis S _{2 in} which the change in film thickness is symmetric.

In the present embodiment, the thickness of HOE33 are from the region R _C corresponding to the center of the screen, towards the region R _E corresponding to the screen around the direction perpendicular to the axis of symmetry S ₂ continuously becomes gradually thicker It has changed. That is, the surface of the HOE33 is a cylindrical surface, the film thickness in the central region R _C including an axis of symmetry S ₂ is the thinnest thickness in the two regions R _E perpendicular direction across the axis of symmetry S ₂ Is the thickest (see FIG. 7). Here, the “continuous change” refers to a change in which the half-value width of the diffraction wavelength is changed in each region and the half-value widths near the boundaries of the plurality of regions are substantially the same. As a result, the FWHM of the diffraction wavelength of HOE33, as shown in FIG. 8, the most widely in the central region R _C, which is narrowest at the two regions R _E both ends.

The region R _C corresponds to a region where image light from the center of the display device 13 is incident, the two regions R _E both ends, the video from the (horizontal) screen periphery of the display device 13 It corresponds to the area where light enters. Therefore, from FIG. 8, the half-value width of the diffraction wavelength of the HOE 33 continuously changes from the region where the image light from the center of the screen is incident to gradually narrowing toward the region where the image light from the periphery of the screen is incident. I can say that.

The hologram photosensitive material (eg, photopolymer) for producing the HOE 33 may be a film-like material or a hologram-sensitive material solution obtained by dissolving a gel-like solid in an organic solvent. The use of the hologram sensitive material liquid is advantageous in that a cylindrical surface can be easily formed.

Here, as shown in FIG. 9, when the image light beam emitted from the display element 13 and incident on the HOE 33 is diffracted by the HOE 33 and travels toward the center of the optical pupil P, the diffraction angle is θ ₁ (°). The regular reflection angle of the light beam on the substrate surface (surface 31d) is θ ₂ (°), and the absolute value | θ ₁ −θ ₂ | of the difference between θ ₁ and θ ₂ is Δθ.

FIG. 10 shows the relationship between the angle of view of the image light (for example, the horizontal direction) and the wavelength width of the image light incident on the center of the optical pupil P via the HOE 33. As shown in FIG. 8, the half-value width of the diffraction wavelength of the HOE 33 is made narrower in the region where the image light from the periphery of the screen is incident than in the region where the image light from the center of the display element 13 is incident. As shown in FIG. 5, the wavelength width of the image light beam that enters the center of the optical pupil P through the HOE 33 from the angle of view where Δθ is maximized (for example, the angle of view at the left end or the right end in the horizontal direction) is the image where Δθ is minimized. It can be made narrower than the wavelength width of the image light incident on the center of the optical pupil P from an angle (for example, a horizontal field angle of 0 °).

As described above, when the reflected optical power of the HOE 33 and the reflected optical power of the surface 31d are different, the lateral chromatic aberration due to chromatic dispersion during diffraction at the HOE 33 increases as Δθ increases. By limiting the wavelength width of the image light having the angle of view at which Δθ is maximized, the wavelength width of the light beam having a large chromatic dispersion (large Δθ) is narrower than the wavelength width of the light beam having a small chromatic dispersion (small Δθ). Therefore, at the angle of view with small chromatic dispersion, the image light has a wide wavelength width, so that sufficient image brightness can be secured, and only at the angle of view with large chromatic dispersion, the wavelength width of the image light is narrowed to correct lateral chromatic aberration. can do. Therefore, it is possible to realize a video display device that is bright overall and has high video quality. In particular, compared to a configuration in which a wavelength limiting element is inserted in the optical path and the wavelength width of the light beam is uniformly limited over the entire screen, the use efficiency of the illumination light is increased and power saving can be realized.

Further, if the wavelength limitation in the HOE 33 is performed for at least one of RGB, the lateral chromatic aberration can be corrected for at least one of RGB. For example, if a photosensitive layer having a photosensitive layer sensitive to any one of RGB is used, and the film thickness of the hologram photosensitive material is gradually increased from a region corresponding to the center of the screen toward a region corresponding to the periphery of the screen. The lateral chromatic aberration can be corrected for any one of RGB by limiting the diffraction wavelength width (wavelength width of image light) of RGB corresponding to the periphery of the screen.

For example, a hologram photosensitive material having sensitivity to three colors of RGB in one photosensitive layer is used, and the film thickness of the hologram photosensitive material is gradually increased from an area corresponding to the center of the screen toward an area corresponding to the periphery of the screen. Alternatively, three photosensitive hologram materials having sensitivity to any one of RGB are used in one photosensitive layer, and for each hologram photosensitive material, gradually from an area corresponding to the center of the screen toward an area corresponding to the periphery of the screen. If the film thickness is increased, all the diffraction wavelength widths of RGB corresponding to the periphery of the screen (wavelength width of image light) can be limited, and lateral chromatic aberration can be corrected for all of RGB. In the former case, it is desirable to optimize the film thickness for G having a high relative visibility. In the latter case, the film thickness may be optimized for each hologram photosensitive material. From the same idea as described above, it is also possible to perform wavelength limitation on the HOE 33 for any two of RGB and correct lateral chromatic aberration for any two of RGB.

From the above, in the present embodiment, in at least one emission wavelength region of RGB, the angle of view of the wavelength of the image light ray that enters the center of the optical pupil P from the angle of view at which Δθ is maximum is the angle of view at which Δθ is minimum. It can be said that it should be narrower than the wavelength width of the image light incident on the center of the optical pupil P.

In addition, due to the wavelength limitation in the HOE 33 described above, in the present embodiment, the wavelength of the image light from the periphery of the screen of the display element 13 among the image light incident on the center of the optical pupil P in all of the RGB emission wavelength regions. The width is narrower than the wavelength width of the image light from the center of the screen. Normally, at the center of the screen, the HOE 33 is used with an incident / reflection characteristic that reduces Δθ in order to reduce lateral chromatic aberration due to chromatic dispersion. At this time, since the lateral chromatic aberration is sufficiently small at the center of the screen where Δθ is small, it is not necessary to limit the wavelength width of the light incident on the optical pupil P. However, since Δθ is large around the screen, lateral chromatic aberration due to chromatic dispersion increases.

As in this embodiment, the wavelength of the image light is narrowed around the screen rather than the center of the screen by the HOE 33, thereby reducing the lateral chromatic aberration around the screen and ensuring sufficient performance (image quality) on the entire screen. However, a bright video display can be realized.

Further, the half-value width of the diffraction wavelength of the HOE 33 is such that the image light from the periphery of the screen is incident (for example, the region R _E ) than the region (for example, the region R _C ) where the image light from the center of the display element 13 is incident. Therefore, the wavelength limitation can be partially performed by the HOE 33 alone without inserting a wavelength limiting element (such as a filter) in the optical path. Further, since the wavelength width of the image light incident on the center of the optical pupil P is wide at the center of the screen, sufficient image brightness can be secured, and the wavelength width of the image light incident on the center of the optical pupil P is narrow around the screen. Therefore, lateral chromatic aberration can be corrected.

In the present embodiment, as shown in FIG. 8, the half-value width of the diffraction wavelength of the HOE 33 is a region where image light from the periphery of the screen enters from a region _RC where image light from the center of the display element 13 enters. since it is narrower R and continuously towards the _E, the wavelength width of the image light rays incident on the center of the diffracted by the optical pupil P at HOE33 is field angle Δθ becomes minimum (e.g., horizontal direction angle of view It can be said that the angle gradually decreases from 0 ° to the angle of view where Δθ is maximized (for example, the angle of view at the left end or the right end in the horizontal direction). In this way, by continuously changing the wavelength width of the image light beam, there is no boundary in the change in the image luminance, so that there is no influence on the image quality of the boundary, and a high-quality image display device can be realized.

Further, as shown in FIG. 6, by a change in thickness of HOE33 is symmetric with respect to the symmetry axis S _2, it is symmetrical with respect to the symmetry axis S ₂ change in the half width of the diffraction wavelength of HOE33 since the change in the wavelength range of the image light rays incident on the center of the optical pupil P from HOE33 also symmetrical with respect to the axis (axis of symmetry) corresponding with the symmetry axis S ₂ and screen. In this case, the lateral chromatic aberration due to the chromatic dispersion of the HOE 33 can be reduced symmetrically with respect to the symmetry axis, and a high-quality video display can be realized.

In the present embodiment, since the horizontal viewing angle of view (for example ± 13 °) is larger than the vertical viewing angle of view (for example ± 7.5 °), image quality degradation due to lateral chromatic aberration in the horizontal direction is caused. large. Therefore, the symmetry of the variation in the thickness of HOE33 to the axis of symmetry S _2, the horizontal direction only, by controlling the half width of the diffraction wavelength of HOE33, to improve the performance (quality) of the periphery of the screen in the horizontal direction be able to.

Incidentally, the HOE 33 may be configured as shown in FIGS. 11 and 12. FIG. 11 is a plan view showing another configuration of the HOE 33. In FIG. 11, regions having different thicknesses and half-value widths of diffraction wavelengths are indicated by different hatchings. This HOE 33 has a plurality of regions R ₁ , R ₂ , R ₃ in a plane and has a rectangular shape as a whole. Region _{R 1} is a rectangular region including the center O of the HOE33, region _{R 2} is rectangular region around the region _{R 1} (the area surrounding the region _{R 1),} region _{R 3} is further region _{R 2} a rectangular region around the (area surrounding the region R _2).

The thickness of HOE33 is thinnest in the region _{R 1,} thickest outermost regions _{R 3,} and has a thickness between them in the region _{R 2.} As a result, the half width of the diffraction wavelength of the HOE 33 is gradually reduced from the region R ₁ corresponding to the center of the screen toward the region R ₃ corresponding to the periphery of the screen (in the order of the regions R ₁ , R ₂ , and R ₃ ). It has become. Here, “stepwise change” refers to a change in which the half-value width of the diffraction wavelength is constant in one region and the half-value width is different among a plurality of regions.

On the other hand, FIG. 12 is a plan view showing still another configuration of the HOE 33. In FIG. 12, the change in the half-value width of the diffraction wavelength is shown by gradation. The HOE 33 has a plurality of regions in the plane. Here, three regions R ₁₁ , R ₁₂ , and R ₁₃ are considered. Region _R 11 is a circular area including the center O of the HOE33, region _{R 12} is a region around the region _{R 11} (the area surrounding at least a portion of the region _{R 11),} area _{R 13} is a further region around the region _{R 12} (the area surrounding at least a portion of the region _{R 12).} The half-value width of the diffraction wavelength of the HOE 33 is continuously narrowed from the region R ₁₁ corresponding to the center of the screen toward the region R ₁₃ corresponding to the periphery of the screen (in the order of the regions R ₁₁ , R ₁₂ , and R ₁₃ ). .

In the HOE 33 in FIG. 12, the film thickness is constant regardless of the region. For example, the production conditions (exposure amount, heat treatment conditions after exposure (heat treatment temperature, heat treatment time)) differ depending on the region. The half-value width of the diffraction wavelength differs depending on the region. For example, in the order of region _R _11, R _{12, R 13,} to reduce the amount of exposure, lowering the heat treatment temperature, shortening the heat treatment time, the area _R _11, R _12, half-width of the order of the diffraction wavelength of the _{R 13} Can be narrowed continuously.

In the configuration of FIG. 11, there are two symmetry axes in which the change in the half-value width of the diffraction wavelength of the HOE 33 is symmetrical (there are two symmetry axes S ₁ and S ₂ perpendicular to each other). On the other hand, in the configuration of FIG. 12, there are innumerable symmetry axes within the plane of the HOE 33 (there are innumerable symmetry axes S passing through the center O) in which the change in the half-value width of the diffraction wavelength of the HOE 33 is symmetric. In these configurations, the change in the wavelength width of the image light beam incident on the center of the optical pupil P changes to the two symmetry axes S ₁ and S ₂ or the myriad symmetry axes S and the axes (symmetry axes) corresponding to the screen. It becomes symmetrical with respect to it.

From the above, if the change in the wavelength width of the image light incident on the center of the optical pupil P is symmetric with respect to at least one symmetry axis on the screen, the lateral chromatic aberration due to the chromatic dispersion of the HOE 33 is taken as the symmetry axis. On the other hand, it can be said that high-definition video display can be realized by reducing symmetrically.

(About brightness adjustment filter)
By the way, when the wavelength limitation by the HOE 33 is performed on the luminous flux around the screen, there is a concern that the video luminance around the screen is lowered. Therefore, for example, the luminance adjustment filter 15 shown in FIG. 13 may be arranged in the optical path between the light source 11 of FIG. 1 and the mirror 21 of the illumination optical system 12.

The brightness adjustment filter 15 is a brightness adjustment element in which the transmittance of light emitted from the light source 11 is different for each incident region. Specifically, the lowest transmittance in the central region T _C of the brightness adjusting filter 15, the highest transmittance in the region T _E at both ends of the horizontal direction, the transmittance continuously in the region between these It has changed. In FIG. 13, the change in transmittance due to the incident region is shown by gradation.

Of the light from the light source 11, light transmitted through the region T _C of the brightness adjusting filter 15, in a region where the light beam is incident on HOE33, part of the region including the position Δθ is minimized (hereinafter, the minimum Δθ called become regions, such as regions R _C of Figure 6. while entering the), light transmitted through the region T _E of the brightness adjusting filter 15, the area of the region (e.g., FIG. 6 Δθ in HOE33 is maximum R _E ). Therefore, the brightness adjustment filter 15 has the lowest transmittance of the light beam (hereinafter also referred to as a main light beam) that enters the region where Δθ is minimum in the HOE 33 and the light beam that enters the region where Δθ is maximum in the HOE 33. It can be said that the transmissivity is the highest and the transmissivity continuously changes between them depending on the incident region. That is, the luminance adjustment filter 15 has a higher transmittance of the peripheral light beam (hereinafter also referred to as the peripheral light beam) than the main light beam.

As described above, the luminance adjustment filter 15 is arranged in the optical path, and the luminance adjustment filter 15 relatively increases the transmittance of the peripheral light beam rather than the main light beam, thereby realizing the video display device 1 with less luminance unevenness on the entire screen. can do.

(Examples and comparative examples)
Next, the result of simulating lateral chromatic aberration in the image display devices of Example 1 and Comparative Example 1 will be described. The video display device of Example 1 corresponds to the video display device 1 of the present embodiment, and is closer to the periphery of the screen than the region (for example, the region _RC ) where the image light from the center of the display element 13 is incident. This is a configuration using the HOE 33 in which the half-value width of the diffraction wavelength is narrow in the region where the image light is incident (for example, the region R _E ). On the other hand, the video display device of Comparative Example 1 has a configuration using a normal HOE in which the half width of the diffraction wavelength is constant regardless of the region. The video display devices of Example 1 and Comparative Example 1 have the same configuration except that the HOE is different (for example, the observation angle of view is the same).

FIG. 14 is an aberration diagram showing lateral chromatic aberration in the X direction and the Y direction on the display surface of the display element 13 in the video display apparatus of Example 1. FIG. FIG. 15 is an aberration diagram showing lateral chromatic aberration in the X direction and the Y direction on the display surface of the display element in the video display apparatus of Comparative Example 1. 14 and 15 respectively show lateral chromatic aberration with respect to a wavelength within a range of ± 5 nm with respect to the center wavelength 532 nm (G light).

In FIG. 14 and FIG. 15, the optical performance is evaluated on the display surface by reverse tracing from the optical pupil P. Therefore, the horizontal axis in FIGS. 14 and 15 corresponds to the position of the optical pupil P in the plane. The vertical axis indicates the amount of lateral chromatic aberration, and the unit is mm.

Note that the X direction is an optical path from the display element 13 toward the optical pupil P, with the axis optically connecting the center of the display surface of the display element 13 and the center of the optical pupil P as the Z axis (optical axis). When unfolded, the direction is perpendicular to the optical axis and parallel to the long side direction of the rectangular display surface, and corresponds to the left-right direction at the pupil position. On the other hand, the Y direction is a direction perpendicular to the optical axis and perpendicular to the X direction, and corresponds to the vertical direction at the pupil position. Note that the coordinates (X, Y) in each aberration diagram indicate local coordinates on the display surface of the display element 13, and “RF” is an abbreviation for a relative field, and the X direction (left-right direction) at the pupil position. And the viewing angle of view in the Y direction (vertical direction). This way of illustration is the same in the examples and comparative examples described later.

In Comparative Example 1, it can be seen from FIG. 15 that the lateral chromatic aberration (magnification chromatic aberration) is abruptly deteriorated due to the chromatic dispersion of the HOE from the center of the screen to the periphery of the screen. In particular, since the viewing angle in the X direction is large, lateral chromatic aberration around the screen in the X direction is large. On the other hand, in Example 1, as shown in FIG. 14, it can be seen that lateral chromatic aberration particularly in the periphery of the screen in the X direction is suppressed. In FIG. 14, due to the wavelength limitation at the HOE 33, light at both ends of the wavelength of 532 ± 5 nm (537 nm, 527 nm) is cut at both ends of the angle of view in the X direction, and lateral chromatic aberration is reduced.

Here, the lateral chromatic aberration for the G light having a center wavelength of 532 nm is shown as an example, but the same tendency is observed for the lateral chromatic aberration of the R light and the B light. That is, for R light and B light, chromatic dispersion increases toward the edge of the screen, and lateral chromatic aberration worsens. However, by controlling the half-value width of the diffraction wavelength for R light and B light with the HOE 33, lateral chromatic aberration for R light and B light around the screen in the X direction can also be suppressed.

(About HMD)
Next, an HMD to which the video display device 1 of the present embodiment is applied will be described. FIG. 16 is a perspective view showing a schematic configuration of the HMD. The HMD includes the above-described video display device 1 and support means 2.

Supplementing the video display device 1, the video display device 1 has a housing 3 that includes at least a light source 11 and a display element 13 (both see 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 31 and a deflection prism 32, and has a shape like one lens of a pair of glasses (lens for right eye in FIG. 16) 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 is a support mechanism corresponding to a spectacle frame (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. The nose pad lock unit 6 holds the nose pad 5 with a spring shaft.

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. 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 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.

Thus, by supporting the video display device 1 by the support means 2, 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 pupil. After the position adjustment, the optical pupil can be fixed at a good position by fixing the position of the nose pad 5 by the nose pad lock unit 6.

From the above, the nose pad 5 and the nose pad lock unit 6 at least have an adjustment mechanism (first adjustment) that adjusts the distance between the eyepiece optical system 14 (or optical pupil) of the video display device 1 and the pupil of the observer. The first adjustment mechanism 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.

[Embodiment 2]
The following will describe still another embodiment of the present invention with reference to the drawings. For convenience of explanation, the same components as those in the first embodiment are denoted by the same member numbers, and the description thereof is omitted.

(About video display device)
FIG. 17 is a cross-sectional view showing a schematic configuration of the video display device 1 of the present embodiment. The video display device 1 of the present embodiment uses the light source 16 as a light source for illuminating the display element 13, and the illumination optical system 12 further includes an aperture stop 22, but the other basic configuration is the embodiment. Same as 1. In the video display device 1 of the present embodiment, the horizontal observation field angle is, for example, ± 6.7 °, and the vertical observation field angle is, for example, ± 5 °. Of course, the video display apparatus 1 of the present embodiment can also be applied to the HMD described in the first embodiment.

The light emitted from the light source 16 passes through the aperture stop 22 of the illumination optical system 12, is reflected and collected by the mirror 21, enters the display element 13 as almost collimated light, and is modulated there as image light. Emitted. Video light from the display element 13 travels to the optical pupil P through the same optical path as in the first embodiment.

The light source 16 of the present embodiment is configured by a white light source (RGB integrated LED (3-chip in 1 package)) in which independent LEDs are combined for each RGB. FIG. 18 shows the light emission characteristics of the light source 16. As shown in the figure, the light source 16 has a characteristic that the half-value width of the emission peak is narrower for all of RGB than the fluorescent type like the light source 11. In particular, for R, since the half-value width of the emission peak is sufficiently narrow compared to the fluorescent type, there is no need to limit the wavelength around the screen. In this embodiment, only B and G are directed toward the screen periphery. The wavelength width of image light is limited. This will be described in detail below.

(About wavelength limitation of image light)
FIG. 19 is a plan view showing a schematic configuration of the HOE 33 of the present embodiment. In FIG. 19, the difference in film thickness for each region is indicated by different hatching. FIG. 20 is an explanatory diagram showing the relationship between the position of the HOE 33 on the line BB ′ of FIG. 19 and the film thickness. The direction of the line B-B 'corresponds to the direction perpendicular (horizontal direction of the image display device) with respect to the symmetry axis S ₂ of the change in thickness is symmetrical.

The HOE 33 of the present embodiment has only one symmetry axis (symmetric axis S ₂ ) in which the change in film thickness is symmetric. HOE33 film thickness is changed stepwise so as to gradually decrease as distance in a direction perpendicular to the axis of symmetry S ₂ from the center of the region R ₁ that includes an axis of symmetry S _2. More specifically, the central region R ₁ has the smallest film thickness, the region R ₃ farthest from the axis of symmetry S _{2 in} the vertical direction has the largest film thickness, and the region R ₁ is between the region R ₃ and the region R _3. It has become therebetween thickness in the region R ₂ (see FIG. 20). As a result, as shown in FIG. 21, the half width of the diffraction wavelength of the HOE 33 is the largest in the center region R ₁ , the narrowest in the two regions R ₃ at both ends, and the half width between them in the region R _2. It has become.

The region R ₁ is a region where image light from the screen center of the display element 13 is incident, and the two regions R _{3 at} both ends are incident with image light from the periphery of the screen (in the horizontal direction) of the display element 13. It is an area to do. Therefore, from FIG. 21, the half width of the diffraction wavelength of the HOE 33 is gradually narrowed from the region R ₁ where the image light from the center of the screen is incident toward the region R ₃ where the image light from the periphery of the screen is incident. It can be said that it is changing gradually.

FIG. 22 shows the relationship between the angle of view of the image light (for example, the horizontal direction) and the wavelength width of the image light incident on the center of the optical pupil P via the HOE 33. As shown in FIG. 21, the half-value width of the diffraction wavelength of the HOE 33 is narrower in the region R ₃ where the image light from the periphery of the screen is incident than in the region R ₁ where the image light from the screen center of the display element 13 is incident. Thus, as shown in FIG. 22, the wavelength width of the image light beam incident on the center of the optical pupil P through the HOE 33 from the angle of view where Δθ is maximum (for example, the angle of view at the left end or the right end in the horizontal direction) is It becomes narrower than the wavelength width of the image light beam incident on the center of the optical pupil P from the angle of view where Δθ is minimized (for example, the angle of view of 0 ° in the horizontal direction). As in the first embodiment, this makes it possible to ensure a sufficient video luminance at the angle of view with small chromatic dispersion since the wavelength width of the image light is wide, and the wavelength of the image light only at the angle of view with large chromatic dispersion. The lateral chromatic aberration can be corrected by narrowing the width.

In particular, in this embodiment, as shown in FIG. 22, the wavelength width of the image light incident on the center of the optical pupil P is gradually increased from the angle of view at which Δθ is minimized toward the angle of view at which Δθ is maximized. It is narrower. For example, three hologram photosensitive materials of a region R ₁ + region R ₂ + region R ₃ , a region R ₂ + region R ₃ , and a region R ₃ are prepared, and these are prepared in each region R _1. , R ₂ , and R ₃ , the thickness of the HOE 33 can be changed step by step for each region. In this way, it is easy to change the thickness of the HOE 33 step by step for each region. Therefore, by changing the half-value width of the diffraction wavelength step by step for each region, Δθ is maximized from the angle of view at which Δθ is minimized. Narrowing the wavelength width of the image light beam stepwise toward the angle of view can be easily realized as compared with the case where the wavelength width is continuously changed as described above, for example. Therefore, the above-described effects can be obtained by controlling the wavelength width of the image light stepwise with a relatively simple configuration of the HOE 33.

(Examples and comparative examples)
Next, the result of simulating lateral chromatic aberration in the image display devices of Example 2 and Comparative Example 2 will be described. The video display device of Example 2 corresponds to the video display device 1 of the present embodiment, and is closer to the periphery of the screen than the region (for example, region R ₁ ) where the image light from the center of the display element 13 is incident. This is a configuration using the HOE 33 in which the half-value width of the diffraction wavelength is narrow in the region where the image light is incident (for example, the region R ₃ ). On the other hand, the video display device of Comparative Example 2 has a configuration using a normal HOE in which the half width of the diffraction wavelength is constant regardless of the region. The video display devices of Example 2 and Comparative Example 2 have the same configuration except that the HOE is different (for example, the observation angle of view is the same).

FIG. 23 is an aberration diagram showing lateral chromatic aberration in the X direction and the Y direction on the display surface of the display element 13 in the video display apparatus of Example 2. FIG. 24 is an aberration diagram showing lateral chromatic aberration in the X direction and Y direction on the display surface of the display element in the video display apparatus of Comparative Example 2. 23 and 24 show lateral chromatic aberration for wavelengths within a range of ± 5 nm with respect to the center wavelength of 532 nm (G light).

In Comparative Example 2, the lateral chromatic aberration around the screen in the X direction is large from FIG. 24, but in Example 2, the lateral chromatic aberration around the screen in the X direction is suppressed as shown in FIG. . In FIG. 23, due to the wavelength limitation at the HOE 33, light at both wavelengths (537 nm, 527 nm) at 532 ± 5 nm is cut at both ends of the angle of view in the X direction, and lateral chromatic aberration is reduced.

Here, the lateral chromatic aberration for the G light having a center wavelength of 532 nm is shown as an example, but the same tendency is observed for the lateral chromatic aberration of the B light. Therefore, the lateral chromatic aberration for the B light around the screen in the X direction can also be suppressed by controlling the half-value width of the diffraction wavelength for the B light by the HOE 33.

[Embodiment 3]
Still another embodiment of the present invention will be described below with reference to the drawings. For convenience of explanation, the same components as those in

Embodiments

1 and 2 are denoted by the same member numbers, and the description thereof is omitted.

(About video display device and HUD)
FIG. 25 is a cross-sectional view illustrating a schematic configuration of the video display device 1 of the present embodiment and a HUD including the same. The video display device 1 of the present embodiment uses a light source 17 as a light source for illuminating the display element 13, uses an illumination lens 23 as the illumination optical system 12, and is in the illumination optical path of the display element 13 (in this embodiment, the illumination lens 23 and A wavelength limiting filter 18 is disposed between the display element 13 and an observation optical system 19 instead of the eyepiece optical system 14. The HUD of the present embodiment includes the video display device 1 having such a configuration, and a configuration in which a later-described HOE 34 of the observation optical system 19 is held by a windshield 35 as a substrate disposed in the field of view of the observer. It is.

The light source 17 is composed of a high-intensity LED that emits monochromatic light (for example, G light having a center wavelength of 532 nm). The wavelength limiting filter 18 is a wavelength limiting element (bandpass filter) that limits the wavelength width of the light emitted from the light source 17, and details thereof will be described later.

The observation optical system 19 includes an HOE 34 and a windshield 35 as a substrate on which the HOE 34 is formed. The HOE 34 is composed of a volume phase type reflection type HOE having a diffraction peak wavelength (for example, 532 nm) only in the G wavelength region, but may have a diffraction peak wavelength also in the B or R wavelength region. Good. In the present embodiment, the half-value width of the diffraction wavelength of the HOE 34 is substantially constant (for example, 10 nm) regardless of the incident region of the image light from the display element 13. The windshield 35 corresponds to a windshield in front of the driver's seat in a transportation means such as a vehicle, a ship, a railroad, and an aircraft.

According to the above configuration, the light emitted from the light source 17 is collected by the illumination lens 23, passes through the wavelength limiting filter 18, and enters the display element 13. Light (video light) modulated in accordance with image data by the display element 13 enters the HOE 34, 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 13 and can observe the outside world through the HOE 34 and the windshield 35.

It should be noted that the HUD may be configured by holding the HOE 34 on a substrate separate from the windshield 35 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.

(About wavelength limitation of image light)
By the way, the HUD is a see-through display that can be observed by superimposing an image on the background (outside) as in the case of the HMD. In the HUD, the above-described HOE 34 is used as a combiner for superimposing image light and external light. However, since the HOE 34 is often arranged almost in parallel with the substrate (windshield 35), the surface reflection of the substrate is taken into consideration. There is a need to. In other words, if the optical system is set so that the light beam at the center of the screen is substantially regularly reflected by the HOE 34, the angle deviation between the light diffracted by the HOE 34 and the light reflected by the surface of the substrate is small, and thus the surface reflection of the substrate. The image by is observed as a ghost.

In order to avoid the observation of such a ghost image, it is necessary to set the diffraction angle at the HOE 34 to deviate from the regular reflection angle with respect to all image heights. In this embodiment, the angle at which the screen center chief ray from the display element 13 is incident on the HOE 34 is 45.5 °, and the exit angle after the screen center chief ray is diffracted by the HOE 34 is 30 °. By setting the angle of view to 5.4 ° and the horizontal observation angle of view to 7.2 °, the light reflected by the surface of the substrate is reflected outside the observation region.

However, as described above, the difference between the incident angle and the diffraction angle at the HOE 34 with respect to the center principal ray of the screen is large, that is, the difference between the regular reflection angle and the diffraction angle is large, and the region corresponding to the bottom edge of the screen and the HOE 34 Since the diffraction angle gradually shifts from the regular reflection angle from the (region where the image light is incident at the lower end of the screen) toward the region corresponding to the upper end of the screen and the HOE 34 (region where the image light is incident at the upper end of the screen), Lateral chromatic aberration increases from the lower end of the screen toward the upper end of the screen.

Therefore, in this embodiment, the lateral chromatic aberration is corrected by inserting the wavelength limiting filter 18 in the optical path. Details of the wavelength limiting filter 18 will be described below.

In the following, since the angle deviation Δθ between the diffraction angle and the regular reflection angle is the smallest in the region corresponding to the lower end of the screen and the HOE 34, the region is also referred to as a region where Δθ is minimized. Further, in the area corresponding to the upper end of the screen and the HOE 34, the angle deviation Δθ between the diffraction angle and the regular reflection angle is the largest, so the area is also referred to as the area where Δθ is the maximum. For convenience of explanation, the direction corresponding to the direction from the lower end of the screen toward the upper end of the screen is defined as the first direction, and the direction perpendicular to the first direction is defined as the second direction.

FIG. 26 is a plan view showing a schematic configuration of the wavelength limiting filter 18. The wavelength limiting filter 18 includes a first region 18a, a second region 18b, a third region 18c, and a fourth region 18d. The first region 18a ~ fourth region 18d are aligned in this order in a first direction, the second direction, shape which is symmetrical with respect to symmetry axis parallel S _W in a first direction It is formed with. The first region 18a, the third region 18c, and the fourth region 18d are all rectangular, and the sizes of the third region 18c and the fourth region 18d are substantially the same. In addition, since the width of the first region 18a in the second direction is slightly narrower than the other regions, the second region 18b has a width in the second direction from the third region 18c and the fourth region 18d. It is the same and is formed in the shape which touches one long side and two short sides of the 1st field 18a. Thereby, the rectangular wavelength limiting filter 18 is formed as a whole.

Further, in the wavelength limiting filter 18, the wavelength width of the transmitted light is varied for each region. For example, the wavelength widths of the transmitted light in the first region 18a, the second region 18b, the third region 18c, and the fourth region 18d are 10 nm (± 5 nm with respect to the center wavelength of 532 nm) and 8 nm (center), respectively. The wavelength is ± 4 nm for the wavelength of 532 nm, 6.5 nm (± 3.25 nm for the center wavelength of 532 nm), and 5 nm (± 2.5 nm for the center wavelength of 532 nm). That is, in this embodiment, the diffraction angle gradually deviates from the regular reflection angle from the region corresponding to the lower end of the screen to the region corresponding to the upper end of the screen and to the region corresponding to HOE 34. In the region corresponding to (for example, the first region 18a), the wavelength width of transmitted light is as wide as 10 nm. In the wavelength limiting filter 18, the region corresponding to the upper end of the screen (for example, the fourth region 18d) has a wavelength width of transmitted light. It is as narrow as 5 nm.

With this configuration of the wavelength limiting filter 18, the light emitted from the light source 17 is incident on the first region 18 a to the fourth region 18 d of the wavelength limiting filter 18. Of these, the light transmitted through the first region 18a is incident on the display element 13 with the widest wavelength width (for example, 10 nm), modulated there, and then incident on the HOE 34 as the main light flux in the region where Δθ is minimized. Then, it is diffracted at a diffraction angle that minimizes Δθ and guided to the optical pupil. On the other hand, the light transmitted through the second region 18b to the fourth region 18d enters the display element 13 as a peripheral light flux with a wavelength width narrower than the above wavelength width (for example, 8 nm, 6.5 nm, 5 nm) in each region. Then, after being modulated there, it is diffracted by the HOE 34 and guided to the optical pupil.

Here, FIG. 27 shows the relationship between the angle of view of the image light (for example, the vertical direction) and the wavelength width of the image light incident on the center of the optical pupil. By inserting the wavelength limiting filter 18 in the optical path, the wavelength width of the image light incident on the optical pupil is limited (narrower) at the upper end of the screen than at the lower end of the screen.

Thus, even when the wavelength limiting filter 18 is used, the wavelength width of the image light ray (for example, the image light beam at the upper end of the screen) incident on the center of the optical pupil from the angle of view where Δθ is maximum is from the angle of view where Δθ is minimum. It becomes narrower than the wavelength width of the image light (for example, the image light at the lower end of the screen) incident on the center of the optical pupil. As a result, the image light has a wide wavelength width at an angle of view with small chromatic dispersion, so that sufficient image brightness can be ensured, and the wavelength width of the image light is narrowed only at an angle of view with large chromatic dispersion to correct lateral chromatic aberration. can do. Therefore, even when the wavelength limiting filter 18 is used, it is possible to realize a video display device that is bright overall and has high video quality.

In addition, since all the light transmitted through the first region 18a to the fourth region 18d of the wavelength limiting filter 18 is incident on the HOE 34 and is diffracted and reflected there, the light is guided to the optical pupil. 18 can be said to be disposed across both the optical path of the main light beam incident on the region where Δθ is minimum in the HOE 34 and the optical path of the peripheral light beam. When the wavelength is limited by the HOE 33 as in the first and second embodiments, it is necessary to control the stable diffraction efficiency or diffraction wavelength width at the time of manufacturing the HOE 33, that is, at the exposure of the hologram photosensitive material, and the exposure process is complicated. become. However, by using the wavelength limiting filter 18 as in the present embodiment and arranging it in the optical paths of both the main light beam and the peripheral light beam, the wavelength width can be easily controlled by the main light beam and the peripheral light beam.

Further, the wavelength limiting filter 18 has different wavelength widths depending on the region through which the light beam passes (the first region 18a to the fourth region 18d). Therefore, the wavelength width control for each region according to Δθ is possible. In particular, the first region 18a to the fourth region 18d are displayed by the main light beam by making the wavelength width of the peripheral light beam narrower than the wavelength width of the main light beam incident on the region where Δθ is minimum in the HOE 34. The lateral chromatic aberration can be corrected for the screen area (for example, the upper end of the screen) displayed by the peripheral luminous flux while ensuring the image brightness for the screen area (for example, the lower end of the screen).

Incidentally, FIG. 28 is a plan view showing another configuration of the wavelength limiting filter 18. As shown in the figure, the wavelength limiting filter 18 may be configured by only the third region 18c and the fourth region 18d. That is, the wavelength limiting filter 18 may be configured not to be disposed in the optical path of the main light flux that enters the region where Δθ is minimum in the HOE 34 but to be disposed only in the optical path of the peripheral light flux. In this case, the wavelength width of the peripheral light beam can be easily and surely narrower than the wavelength width of the main light beam, and the wavelength width of the main light beam is not limited, so that the screen area displayed by the main light beam (for example, the lower end of the screen) It is possible to ensure sufficient video brightness. It is to be noted that the lateral chromatic aberration can be corrected for the screen area (for example, the upper end of the screen) displayed by the peripheral light beam, as in the configuration of FIG.

In the above, the wavelength width of the transmitted light in the wavelength limiting filter 18 is limited stepwise from the first region 18a toward the fourth region 18d, but may be continuously performed. Further, the number of regions for limiting the wavelength width of transmitted light in the wavelength limiting filter 18 is not limited to the above four (see FIG. 26) or two (see FIG. 28).

In the present embodiment, the configuration in which the wavelength width of the monochromatic light (G light) is limited by the wavelength limiting filter 18 has been described. For example, a filter made of a color HOE is arranged in the illumination system, and the wavelength limitation is performed. By using it as an element, it is possible to adopt a configuration in which the wavelength width is limited with respect to a plurality of wavelengths.

(Examples and comparative examples)
Next, the result of simulating lateral chromatic aberration in the image display devices of Example 3 and Comparative Example 3 will be described. The video display apparatus of Example 3 corresponds to the video display apparatus 1 of the present embodiment, and has a configuration using the wavelength limiting filter 18 of FIG. On the other hand, the video display device of Comparative Example 3 has a configuration in which the wavelength limiting filter 18 is removed from the video display device 1 of Example 3. The viewing angle of view is the same in Example 3 and Comparative Example 3.

FIG. 29 is an aberration diagram showing lateral chromatic aberration in the X direction and Y direction on the display surface of the display element 13 in the video display apparatus of Example 3. FIG. 30 is an aberration diagram showing lateral chromatic aberration in the X direction and Y direction on the display surface of the display element in the video display apparatus of Comparative Example 3. 29 and 30 respectively show lateral chromatic aberration with respect to a wavelength within a range of ± 4 nm with respect to the center wavelength of 532 nm (G light).

In Comparative Example 3, it can be seen from FIG. 30 that the lateral chromatic aberration gradually increases from the lower end of the screen toward the upper end of the screen in the vertical direction of the screen, that is, in the Y direction. On the other hand, in Example 3, as shown in FIG. 29, the lateral chromatic aberration at the upper end of the screen in the Y direction is particularly suppressed, and the lateral chromatic aberration around the screen is also suppressed in the X direction. I understand. In FIG. 29, due to the wavelength limitation by the wavelength limiting filter 18, light having wavelengths of 528 to 530 nm and 534 to 536 nm are cut at the angle of view corresponding to the upper end of the screen in the Y direction, and lateral chromatic aberration is reduced. .

[Supplement]
It is desirable that ΔλRmin / ΔλRmax satisfy the following conditional expression, where ΔλRmax (mm) is the maximum value of the half-width of the image wavelength in the observation screen and ΔλRmin (mm) is the minimum value of the half-width of the image wavelength.

0.25 <ΔλRmin / ΔλRmax <0.75
When ΔλRmin / ΔλRmax is large, the difference in half-wave width is small and the difference in the amount of lateral chromatic aberration is also small, so the effect of correcting lateral chromatic aberration is small. On the other hand, if ΔλRmin / ΔλRmax is small, for example, the half-value width of the image light around the screen becomes too narrow, and the image brightness around the screen decreases (the screen periphery becomes dark), resulting in a decrease in image quality. By satisfying the above conditional expression, the occurrence of lateral chromatic aberration can be suppressed without increasing the luminance difference in the screen, and a good image can be obtained. Incidentally, the values of ΔλRmin / ΔλRmax in Examples 1, 2, and 3 are 0.5, 0.7, and 0.3, respectively, which satisfy the above conditional expression.

Of course, the video display device 1, the HMD, and the HUD can be configured by appropriately combining the configurations described in the embodiments.

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

DESCRIPTION OF SYMBOLS 1 Image display apparatus 2 Support means 11, 16, 17 Light source 13 Display element 14 Eyepiece optical system (observation optical system)
15 Brightness adjustment filter (Brightness adjustment element)
18 Wavelength limiting filter (wavelength limiting element)
31d surface (substrate surface)
33, 34 HOE
35 Windshield (substrate)
P Optical pupil

Claims

A light source;
A display element that displays light by modulating light from the light source;
An image display device comprising: an observation optical system that guides image light from the display element to an optical pupil;
The light emitted from the light source has at least one emission peak wavelength and at least one emission wavelength region including the emission peak wavelength;
The observation optical system has one diffraction peak wavelength in at least one wavelength region corresponding to the emission wavelength region, and diffractively reflects image light from the display element in the direction of the optical pupil. And having a volume phase hologram optical element,
The reflection optical power of the hologram optical element is different from the reflection optical power of the substrate surface on which the hologram optical element is formed,
A diffraction angle when an image light beam emitted from the display element and incident on the hologram optical element is diffracted by the hologram optical element toward the center of the optical pupil, and a regular reflection angle of the image light beam on the substrate surface If the absolute value of the difference is Δθ,
In at least one emission wavelength region, an image light having a wavelength width of an image ray incident on the center of the optical pupil from the angle of view at which Δθ is maximum, and an image of light incident on the center of the optical pupil from an angle of view at which Δθ is minimum An image display device characterized by being narrower than the wavelength width of light rays.
The half width of the diffraction wavelength of the hologram optical element is narrower in a region where light having an angle of view where Δθ is maximum is narrower than a region where light having an angle of view where Δθ is minimum is incident. The video display device according to claim 1.
The thickness of the film constituting the hologram optical element is characterized in that a region where light having an angle of view at which Δθ is maximum is thicker than a region where light having an angle of view at which Δθ is minimum. Item 3. The video display device according to Item 2.
The film forming the hologram optical element is formed by exposing a hologram photosensitive material,
A heat treatment that reduces the exposure amount in a region where light having an angle of view at which Δθ is maximum is incident, compared to a region in which light having an angle of view at which Δθ is minimum is incident, with a constant film thickness. The image display device according to claim 2, wherein the image display device is formed by performing at least one of lowering a temperature or shortening a heat treatment temperature.
A wavelength limiting element for limiting the wavelength width of the light emitted from the light source;
The wavelength limiting element is disposed only in an optical path of a peripheral light beam of a light beam incident on a part of the region including a position where Δθ is minimum in a region where the light beam is incident on the hologram optical element. The video display device according to claim 1, wherein
A wavelength limiting element for limiting the wavelength width of the light emitted from the light source;
The wavelength limiting element spans both the optical path of the light beam incident on a part of the region including the position where Δθ is minimum and the optical path of the peripheral light beam in the region where the light beam is incident on the hologram optical element. 2. The image according to claim 1, wherein a wavelength width of the peripheral light beam is made narrower than a wavelength width of a light beam incident on a partial region including a position where the Δθ is minimum. Display device.
7. The wavelength width of the image light beam incident on the center of the optical pupil is gradually reduced from an angle of view at which Δθ is minimized toward an angle of view at which Δθ is maximized. The video display apparatus in any one.
The wavelength width of the image light beam incident on the optical pupil center is continuously narrowed from an angle of view where the Δθ is minimized toward an angle of view where the Δθ is maximized. The video display apparatus in any one.
In all emission wavelength regions of the light source, among the image light incident on the center of the optical pupil, the wavelength width of the image light from the periphery of the screen of the display element is narrower than the wavelength width of the image light from the center of the screen. The video display device according to claim 1, wherein the video display device is a video display device.
10. The image display according to claim 1, wherein the change in the wavelength width of the image light incident on the center of the optical pupil is symmetric with respect to at least one symmetry axis on the screen. apparatus.
Further comprising a luminance adjusting element in which the transmittance of light emitted from the light source is different for each incident region;
In the brightness adjusting element, the transmittance of the light beam in the vicinity thereof is higher than the transmittance of the light beam incident on a part of the region including the position where Δθ is minimum in the region where the light beam is incident on the hologram optical element. The video display device according to claim 1, wherein the video display device is high.
The video display device according to any one of claims 1 to 11,
And a support means for supporting the video display device in front of the observer's eyes.
A video display device according to any one of claims 1 to 11, comprising:
The head-up display, wherein the hologram optical element of the video display device is held on a substrate arranged in the field of view of an observer.