JP5408057B2 - Video display device and head mounted display - Google Patents

Description

  The present invention relates to an image display device that allows an observer to observe an image displayed on a display element as a virtual image, and a head mounted display (hereinafter also referred to as an HMD) including the image display device.

  2. Description of the Related Art Conventionally, various video display apparatuses that use a holographic optical element (hereinafter also referred to as HOE) to allow an observer to observe a video displayed on a display element as a virtual image have been proposed. For example, in the video display apparatus of Patent Document 1, the HOE is formed in a cylindrical shape in a configuration in which video light from the display element is diffracted and reflected by the HOE and guided to the observer's pupil. That is, the HOE is formed on a cylindrical substrate, and the HOE surface is a cylindrical surface having a constant curvature as a whole.

  Here, when the HOE surface is a flat surface, for example, when the observation angle of view increases, the diffraction angle of the image light in the screen changes greatly. That is, the diffraction angle in the HOE (particularly, the difference between the diffraction angle and the regular reflection angle) is larger at the edge of the angle of view than at the center of the angle of view. For this reason, in a configuration in which a light source that emits light having a light emission wavelength width such as an LED is used and the display element modulates the light emitted from the light source and displays an image, a portion with a large diffraction angle (angle of view angle) Part), a large chromatic aberration of magnification occurs due to dispersion caused by diffraction in the HOE, and the resolution is lowered and the image quality is lowered.

  In this respect, in Patent Document 1, by forming the HOE surface as a cylindrical surface, the diffraction angle at the end of the angle of view can be reduced even when the angle of view is wide (can be close to the regular reflection angle). . Therefore, the above-mentioned aberration that occurs when the HOE surface is a flat surface is reduced, and a good virtual image can be observed.

JP-A-11-326824 (see claims 1 to 3, paragraphs [0004] to [0006], [0018], [0019], [0046], etc.)

  However, in the configuration in which the entire HOE surface is a cylindrical surface as in Patent Document 1, in order to make the diffraction angle at the end of the angle of view close to the regular reflection angle in order to cope with the wide angle of view, It is necessary to increase the curvature. When the curvature of the HOE surface increases, the protrusion amount (protrusion amount) to the convex side of the entire HOE surface increases. For this reason, when the observation optical system (eyepiece optical system) including the HOE is arranged in front of the observer's eyes, the thickness of the observation optical system including the HOE (thickness in the direction perpendicular to the plane of the observation pupil) increases. The problem arises.

  The present invention has been made to solve the above-described problems, and its purpose is to reduce lateral chromatic aberration due to dispersion of HOE without increasing the thickness of the observation optical system including HOE even when the angle of view is widened. An object of the present invention is to provide a video display device that can suppress an observer to observe a high-quality video, and an HMD including the video display device.

  An image display device according to the present invention includes a light source having at least one emission peak wavelength and emitting light having a wavelength width including one emission peak wavelength, and modulating the light emitted from the light source to display an image. An image display device comprising: a display element for displaying; and an observation optical system for guiding image light from the display element to an observation pupil and causing an observer to observe a virtual image at the position of the observation pupil, The observation optical system includes a volume phase type reflection type holographic optical element that diffracts and reflects the image light from the display element and guides it to the observation pupil, and the center of the display surface of the display element and the observation When the axis that optically connects the center of the pupil is the optical axis, and the plane that includes the optical axis of the incident light and the optical axis of the reflected light with respect to the holographic optical element is the principal plane, the surface of the holographic optical element is , The main plane and the symmetry plane And has a curvature only in a plane parallel or perpendicular to the main plane, and the radius of curvature decreases in the plane from the position closest to the center of the display surface to the position farthest from the center. The observation pupil side has a concave curved surface.

  In the video display device of the present invention, in the observation optical system, only the surface of the holographic optical element may have optical power.

  In the video display device of the present invention, the surface of the holographic optical element may have a curvature in a wider field angle among two directions having different field angles.

  In the video display device of the present invention, the observation optical system includes a substrate on which the holographic optical element is formed, and the substrate has a plate shape with a constant thickness in a direction perpendicular to the surface of the holographic optical element. It may be a substrate.

  In the video display device of the present invention, the substrate may hold the holographic optical element so that zero-order diffracted light generated by the holographic optical element deviates from an optical path toward the observation pupil.

  In the image display device of the present invention, the observation optical system guides the image light from the display element incident through the incident surface by being totally reflected by at least one total reflection surface, and directs the light to the holographic optical element. You may provide the eyepiece prism which guides.

  In the video display device of the present invention, the observation optical system may further include a correction prism that is joined to the eyepiece prism via the holographic optical element.

  The head mounted display of the present invention may be configured to include the above-described video display device of the present invention and a support member that supports the video display device in front of an observer's eyes.

  According to the present invention, the HOE surface of the observation optical system has a symmetrical shape with the main plane as a symmetric surface, has a curvature only in a plane parallel to or perpendicular to the main plane, and has a display surface within the plane. The radius of curvature decreases with increasing distance from the position closest to the center to the position farthest from the center of the eye. As a result, for example, image light incident on a position close to the center of the display surface by HOE is diffracted at a portion with a large curvature radius (small curvature) of the HOE surface, while reducing the diffraction angle (to the regular reflection angle). The image light incident on the position far from the center of the display surface by the HOE (image light at the end of the angle of view) is diffracted by a portion having a small curvature radius (large curvature) on the HOE surface, and the diffraction angle. Can be reduced (closer to the regular reflection angle).

  Moreover, the curvature of the HOE surface is not constant, but by changing the position according to the position (according to the distance from the center of the display surface), even when the angle of view is widened, compared to a configuration in which the entire HOE surface is a cylindrical surface, The diffraction angle at the edge of the angle of view can be made close to the regular reflection angle while suppressing the amount of protrusion of the entire HOE surface to the side opposite to the observation pupil. Therefore, even when the angle of view is widened, the chromatic aberration of magnification due to the dispersion of the HOE can be suppressed to be small and the observer can observe a high-quality image without increasing the thickness of the observation optical system including the HOE.

1 is a cross-sectional view illustrating a schematic configuration of a video display device according to an embodiment of the present invention. 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 eyepiece optical system of the said video display apparatus. (A) is explanatory drawing which shows the state at the time of exposure of the hologram photosensitive material used when producing flat HOE, (b) is explanatory drawing which shows the state at the time of use of the said HOE. It is explanatory drawing which shows the coordinate axis in the said video display apparatus. It is a graph which shows the cross-sectional shape in the surface parallel to the main plane of the HOE surface of the said video display apparatus. It is a graph which shows the change of the curvature radius in the said surface of the said HOE surface. It is sectional drawing which shows the structure of the outline of the video display apparatus concerning other embodiment of this invention. It is explanatory drawing which shows the coordinate axis in the said video display apparatus. It is a graph which shows the cross-sectional shape in the surface parallel to the main plane of the HOE surface of the said video display apparatus. It is a graph which shows the change of the curvature radius in the said surface of the said HOE surface. It is sectional drawing which shows the structure of the outline of the video display apparatus based on further another embodiment of this invention. It is a perspective view of the eyepiece optical system of the image display device. It is explanatory drawing which shows the coordinate axis in the said video display apparatus. It is explanatory drawing which shows the coordinate axis in the said video display apparatus. It is a graph which shows the cross-sectional shape in the surface perpendicular | vertical to the main plane of the HOE surface of the said video display apparatus. It is a graph which shows the change of the curvature radius in the said surface of the said HOE surface. It is sectional drawing which shows the schematic structure of the exposure optical system which produces HOE of the said video display apparatus. It is sectional drawing which shows the structure of the outline of HUD which concerns on other embodiment of this invention. It is a perspective view which shows the schematic structure of HMD which concerns on said embodiment.

[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 (see FIG. 12), an illumination optical system 12 (see FIG. 12), a display element 13, and an eyepiece optical system 14. In FIG. 1, the light source 11 and the illumination optical system 12 are not shown for convenience. The video display device 1 of the present embodiment is a see-through video display device in which the display element 13 is arranged beside the observer's face, and the HOE 23 described later of the eyepiece optical system 14 is arranged in front of the observer's eyes. The image light traveling in the horizontal direction from the side of the observer's face is diffracted and reflected and guided to the observer's pupil. Each configuration will be described below.

  The light source 11 illuminates the display element 13 and emits light having a wavelength width including at least one emission peak wavelength and including one emission peak wavelength.

  FIG. 2 shows the light emission characteristics of the light source 11 of this embodiment. In the present embodiment, the light source 11 emits light having an emission peak wavelength in three wavelength bands of blue (B), green (G), and red (R). More specifically, the light source 11 has a full width at half maximum with respect to the emission peak wavelength and the intensity peak, and has, for example, three wavelength bands of 462 ± 12 nm (B light), 525 ± 17 nm (G light), and 635 ± 11 nm (R light). It is composed of RGB integrated LEDs that emit light. The light emission intensity in FIG. 2 is shown as a relative value when the maximum light emission intensity of B light is 100.

  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 is composed of, for example, a mirror having a concave reflecting surface. The display element 13 displays video by modulating the light emitted from the light source 11 and incident through the illumination optical system 12 according to image data, and is configured by, for example, a transmissive LCD. The display element 13 is arranged such that the long side direction of the rectangular display screen is a horizontal direction (a direction parallel to the paper surface of FIG. 1), and the short side direction is a 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 observation pupil (optical pupil, exit pupil) P, and causes the observer to observe a virtual image at the position of the observation pupil P. And a substrate 24 on which the HOE 23 is formed.

  The HOE 23 is a volume phase type reflection type holographic optical element that diffracts and reflects the image light from the display element 13 and guides it to the observation pupil P, and transmits the external light to the observation pupil P. It functions as a combiner that can observe the bright outside world at the same time. The HOE 23 is formed on the surface of the substrate 24 opposite to the observation pupil P side, and the shape of the surface of the HOE 23 is defined by the shape of the surface of the substrate 24. Hereinafter, the surface on the substrate 24 side in the HOE 23 is referred to as a HOE surface 23a. Details of the HOE surface 23a will be described later. The HOE 23 has an axially asymmetric (non-rotationally symmetric) positive optical power, and has the same function as an aspherical concave mirror (free-form surface 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.

  FIG. 3 shows the diffraction characteristics of HOE23. As shown in the figure, the HOE 23 is incident light at a specific incident angle, and is, for example, 465 ± 5 nm (B light), 521 ± 5 nm (G light) in the full width at half maximum with respect to the diffraction peak wavelength and the diffraction efficiency peak. , 634 ± 5 nm (R light), and having angle selectivity and wavelength selectivity for diffracting and reflecting light in three wavelength bands.

  The substrate 24 is a plate-like transparent substrate having a constant thickness in the direction perpendicular to the HOE surface 23a, and holds the HOE 23. Note that the thickness of the substrate 24 may be a thickness that does not hinder see-through performance (the observed outside world is not distorted). In particular, the substrate 24 holds the HOE 23 so that all 0th-order diffracted light (regular reflection light) generated by the HOE 23 is out of the optical path toward the observation pupil P.

  In the above configuration, the light emitted from the light source 11 is collected by the illumination optical system 12, is substantially collimated, enters the display element 13, and is modulated there and emitted as video light. Image light from the display element 13 enters the HOE 23 via the substrate 24 of the eyepiece optical system 14.

  The HOE 23 has an optical power equivalent to that of a concave free-form surface, and has diffraction efficiency in a wavelength region corresponding to the emission wavelength region of the light source 11 as shown in FIG. Therefore, only the light in the wavelength region where the diffraction efficiency exists is diffracted and reflected from the image light reaching the HOE 23 and reaches the observation pupil P. Thus, by locating the observer's eye (pupil) E at the position of the observation pupil P, the observer can observe the enlarged virtual image of the image displayed on the display element 13 in front of the eyes. Further, since the HOE 23 functions as a simple transparent film in a wavelength region where there is no diffraction efficiency, the observer can observe the external environment in front of the eye simultaneously with the image.

(Relationship between diffraction angle and chromatic dispersion)
Next, before describing the details of the HOE surface of the present embodiment, the relationship between the diffraction angle and chromatic dispersion in a general flat plate-shaped HOE will be described.

  4A shows a state during exposure of the hologram photosensitive material 101a used when the flat HOE 101 is manufactured, and FIG. 4B shows a state during use (reproduction) of the HOE 101. ing. The incident angles of the two light beams used for exposing the hologram photosensitive material 101a with respect to the hologram photosensitive material 101a are θo (°) and θr (°), respectively, and the exposure wavelength is λr (nm), respectively. In addition, the incident angle and the emission angle of the reproduction beam with respect to the HOE 101 are θc (°) and θv (°), respectively, and the use wavelength (reproduction wavelength) is λc (nm).

  In diffraction in the HOE 101, the diffraction efficiency is maximized when the following Bragg conditional expression is satisfied.

  Equation (1) relates to diffraction by the thin HOE 101. The interval between the interference fringes formed during exposure of the hologram photosensitive material 101a is determined by the incident angle and exposure wavelength of the object light and reference light at the time of exposure, and at the time of reproduction, adjacent fringes (low refractive index portions adjacent to the interference fringes or Since the light intensity of the diffracted light is maximized in the direction in which the light exiting from the adjacent high refractive index portion is shifted by one wavelength, the expression (1) is derived. When two light beams having a wavelength λr are incident on the hologram photosensitive material 101a at incident angles θo and θr, holograms (interference fringes) are recorded by interference of the light beams. When this hologram is irradiated with reproduction light of wavelength λc from an angle θc, diffracted light is generated in the direction of angle θv.

  On the other hand, in the thick HOE 101, since interference fringes are recorded three-dimensionally, the state of interference fringes in the thickness direction must be considered simultaneously with the equation (1). A formula related to diffraction by interference fringes in the thickness direction is formula (2). That is, the expression (2) is obtained when the reproduction light is irradiated from the angle θc onto the hologram formed by the incidence of the two light beams having the incident angles θo and θr and the wavelength λr on the hologram photosensitive material 101a. This is an expression for specifying the wavelength of the light to be reproduced. As the thickness of the HOE 101 increases, the half width at half maximum of the diffraction wavelength range of the equation (2) becomes narrower, and the reproduction conditions become more severe.

  In the volume phase hologram, it is necessary to satisfy the above expressions (1) and (2) at the same time. However, since at least the expression (1) needs to be satisfied, the following can be said.

  From the expression (1), the emission angle θv of the reproduction light is expressed by the expression (3).

  In the formula (3), when the following formula (4) is satisfied, there is no term depending on the wavelength. The direction of the diffracted light at the HOE 101 is constant regardless of the wavelength, and is a direction satisfying sin θv = sin θc, that is, a direction satisfying θv = 180 ° −θc. This means that the diffraction direction at the HOE 101 coincides with the direction of regular reflection at the substrate on which the HOE 101 is formed, and there is no deviation in the diffraction direction due to the deviation between the exposure wavelength and the reproduction wavelength.

  However, in the equation (3), when the following equation (5) is satisfied, there is a term depending on the wavelength, and the direction of the diffracted light in the HOE 101 satisfies the direction satisfying sin θv = sin θc, that is, θv = 180. The direction does not satisfy ° -θc. That is, when the exposure wavelength and the reproduction wavelength are shifted, the diffraction direction by the HOE 101 is shifted from the regular reflection direction on the substrate on which the HOE 101 is formed, and the diffraction angle (exit angle θv) varies depending on the wavelength. Accordingly, when a light source having a wavelength width of the reproduction light is used, the diffraction angle of the reproduction light has a width corresponding to the wavelength width, and image degradation due to chromatic dispersion due to diffraction occurs.

  When the HOE surface is composed of one plane, especially in a direction with a wide angle of view (for example, the horizontal direction), the difference between the diffraction angle and the regular reflection angle at the screen periphery compared to the screen center (incident angle and diffraction angle ), The color dispersion around the screen is remarkably increased, and the image quality is greatly deteriorated.

(Details of HOE surface)
Next, details of the HOE surface of the present embodiment will be described. For convenience of explanation, each direction in the video display device 1 is defined as follows. FIG. 5 is an explanatory diagram showing coordinate axes in the video display device 1. As shown in the figure, the center of the observation pupil P is the origin, the direction perpendicular to the observation pupil plane at the origin, the direction toward the eyepiece optical system 14 is the + Z direction, and the direction upward from the origin is the + X direction. The direction from the origin to the left is the + Y direction. It should be noted that the definition of each direction described above is considered only when the shape of the HOE surface 23a is described in the present embodiment, and it is not different from the definition of the direction in the construction data of the examples described later. .

  Further, an axis optically connecting the center of the display surface of the display element 13 and the center of the observation pupil P formed by the eyepiece optical system 14 is an optical axis, and the optical axis of incident light with respect to the HOE 23 of the eyepiece optical system 14 When a plane including the optical axis of the reflected light is a main plane, in this embodiment, the YZ plane corresponds to the main plane or a plane parallel to the main plane.

FIG. 6 is a graph showing a cross-sectional shape in a plane parallel to the main plane of the HOE surface 23a, and FIG. 7 is a graph showing a change in the radius of curvature of the HOE surface 23a in the plane. As shown in these drawings, the HOE surface 23a is formed of a concave curved surface on the observation pupil P side having a curvature only in a plane parallel to the main plane (only in a direction parallel to the main plane). In addition, the radius of curvature of the HOE surface 23a in the plane decreases from the position b ₁ closest to the center a ₀ of the display surface of the display element 13 toward the position b ₂ farthest in the plane. The HOE surface 23a has a shape that is symmetrical in the vertical direction with the main plane as a symmetry plane.

6 and 7, the cross-sectional shape of the HOE 23a is obtained using a coordinate system (Xhoe, Yhoe, Zhoe) when the reference point Q (X ₀ , Y ₀ , Z ₀ ) of the HOE 23 is the origin of the local coordinates. And the change in curvature respectively. At this time, if the center of the observation pupil P is the global coordinate origin (x, y, z) = (0, 0, 0), the global coordinates of the reference point Q of the HOE 23 are (X ₀ , Y ₀ , Z _0). ) = (0, −0.684, 36.88). However, when the rotation angle of the HOE surface 23a around the X axis is ADE, ADE = −20 °.

By HOE surface 23a is a curved surface as described above, the image light incident at a position close to the center a ₀ of the display surface in HOE23, i.e., a small image of the diffraction angle when HOE surface 23a is a flat surface for light, the radius of curvature of the surface of the HOE 23a larger by diffracting the part (small curvature), while reducing the diffraction angles (while closer to the specular reflection angle), farther from the center a ₀ of the display surface in HOE23 With respect to incident image light, that is, image light having a large diffraction angle when the HOE surface 23a is a flat surface (image light at the end of the angle of view), the HOE surface 23a has a small radius of curvature (large curvature). By diffracting, the diffraction angle can be reduced (close to the regular reflection angle). Note that the maximum curvature radius of the HOE surface 23a may be infinite. That is, the portion having the maximum curvature radius on the HOE surface 23a may be a flat surface.

Moreover, instead of the constant curvature of the surface of the HOE 23a, (depending on the distance from the center a ₀ of the display surface) by position by varying, even when the angle of view, and cylindrical surface the entire surface of the HOE 23a Compared to the configuration, the diffraction angle at the end of the angle of view is made closer to the regular reflection angle while suppressing the protrusion amount (sag amount Zhoe) to the convex side (opposite to the observation pupil P) of the HOE surface 23a. Can do. Therefore, even when the angle of view is widened, the eyepiece optical system 14 including the HOE 23 is not thickened in the Z direction, and the chromatic aberration of magnification due to the dispersion of the HOE 23 can be suppressed to a small level so that an observer can observe a high-quality image. .

  In the present embodiment, since the long side direction of the display surface of the display element 13 is the horizontal direction, the viewing angle of view is wider in the horizontal direction than in the vertical direction. Since the horizontal direction is a direction parallel to the main plane, and the HOE surface 23a has a curvature only in a plane parallel to the main plane, the HOE surface 23a is one of two directions with different viewing angles. It can also be said that it has a curvature in a direction in which the field angle is wider (within a cross section parallel to the direction in which the field angle is wider).

  Thus, since the HOE surface 23a has a curvature in a direction with a wider angle of view, the diffraction angle at the HOE of the image light at the end of the angle of view in the direction of the wider angle of view is changed to that of the HOE surface 23a. The diffraction angle can be reduced by diffracting at a portion having a small radius of curvature (a large curvature) (a deviation from the regular reflection angle can be reduced). Thereby, even when the angle of view is widened in a wider direction, the lateral chromatic aberration due to the dispersion of the HOE 23 can be suppressed to be small over the entire screen.

  In the eyepiece optical system 14, the substrate 24 on which the HOE 23 is formed is a plate-like substrate having a constant thickness in the direction perpendicular to the HOE surface 23a. Therefore, the eyepiece optical system 14 is configured to be thin and lightweight. Thus, a thin video display device 1 can be realized in a direction perpendicular to the plane of the observation pupil P.

  Further, as described above, since the substrate 24 holds the HOE 23 so that all the 0th-order diffracted light generated by the HOE 23 deviates from the optical path toward the observation pupil P, generation of a ghost image due to surface reflection at the HOE 23 is avoided. can do. Further, in order to avoid the generation of a ghost image, when the plate-like substrate 24 holds the HOE 23 as described above, the maximum diffraction angle in a plane parallel to the main plane tends to be large. The configuration of the present embodiment in which the HOE surface 23a has a curvature only in a plane parallel to the plane and changes the curvature is very effective in the configuration using the plate-like substrate 24.

  In this embodiment, the example in which the HOE 23 is formed on the surface of the substrate 24 opposite to the observation pupil P has been described. However, even if the HOE 23 is formed on the surface of the substrate 24 on the observation pupil P side, the above-described book is provided. It is possible to obtain the effects of the embodiment.

  In the present embodiment, the example in which the display element 13 is arranged so that the display surface is horizontally long has been described. However, the display element 13 is arranged so that the display surface is vertically long, and the plane is parallel to the main plane. Alternatively, the HOE surface 23a may have a curvature and the curvature may be changed. In this configuration, the surface on which the HOE surface 23a has a curvature (a surface parallel to the main plane) is a surface parallel to the direction in which the viewing angle of view is narrow (horizontal direction). Even in this case, the above-described HOE surface 23a By changing the curvature, the maximum diffraction angle in a narrow direction of the observation angle of view can be kept small. Therefore, even when the direction of the narrow viewing angle is widened, the observer can observe a high-quality image by reducing the lateral chromatic aberration while suppressing the forward projection of the eyepiece optical system 14.

  Further, since the maximum diffraction angle in the HOE 23 is determined by the observation field angle and the size of the observation pupil P, the size of the observation pupil P is increased in the horizontal direction by suppressing the maximum diffraction angle in a narrow direction of the observation field angle. can do. Since there are individual differences in the eye width (observation pupil position with respect to the frame) of the observer, by forming the size of the observation pupil P large in the horizontal direction, a device that allows more people to observe the image satisfactorily is realized. be able to.

  The HOE 23 is manufactured by exposing a hologram photosensitive material using an exposure optical system. The exposure at this time may be performed after the hologram photosensitive material is attached to the substrate 24, or may be attached to the substrate 24 after the film-shaped hologram photosensitive material is exposed. As the hologram photosensitive material, a photopolymer, a silver salt emulsion, dichromated gelatin or the like is used. Among them, it is desirable to use a photopolymer that can easily produce HOE23 by a dry process.

  It should be noted that when the HOE 23 is manufactured (when the hologram photosensitive material is exposed), it is desirable to apply an antireflection coating or an antireflection film to the surface of the hologram photosensitive material and the surface of the substrate 24. This is because unwanted interference fringes are recorded on the hologram photosensitive material due to the surface reflected light on the hologram photosensitive material at the time of exposure, or the surface reflected light and the back surface reflected light on the substrate 24, thereby causing ghosts and flares in the observed image. This is because the video quality is deteriorated.

[Embodiment 2]
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 the first embodiment are denoted by the same member numbers, and the description thereof is omitted.

  FIG. 8 is a cross-sectional view showing a schematic configuration of the video display device 1 of the present embodiment. In FIG. 8, the light source 11 and the illumination optical system 12 are not shown for convenience. The video display device 1 according to the present embodiment has a display element 13 disposed beside the face of the observer, holds the HOE 23 on one surface of a light guide prism disposed in front of the eyes, and proceeds through the HOE 23 in the horizontal direction. This is a see-through video display device used as a combiner of light and ambient light. Hereinafter, a description will be given centering on differences from the first embodiment.

  The eyepiece optical system 14 of the video display device 1 includes an eyepiece prism 21, a deflection prism 22, and a HOE 23.

  The eyepiece prism 21 is a prism that guides the image light from the display element 13 incident through the surface 21a to the HOE 23 after being totally reflected by the surfaces 21b and 21c at least once. The surfaces 21a, 21b, and 21c are all flat surfaces and do not have optical power.

  The deflecting prism 22 is configured by a substantially U-shaped parallel plate in plan view, and when the deflecting prism 22 is bonded to the eyepiece prism 21 via the HOE 23, the deflection prism 22 is integrated with the eyepiece prism 21 to become a substantially parallel plate. is there.

  The HOE 23 is formed on a surface 21 d that is a joint surface with the deflection prism 22 in the eyepiece prism 21. Therefore, the shape of the HOE surface 23a is defined by the shape of the surface 21d. In the present embodiment, in the eyepiece optical system 14, the surface having optical power is only the HOE surface 23a.

  In the above configuration, the light emitted from the light source 11 is collected by the illumination optical system 12, is substantially collimated, enters the display element 13, and is modulated there and emitted as video light. The image light from the display element 13 enters the inside of the eyepiece prism 21 from the surface 21a, and then is totally reflected by the surfaces 21b and 21c at least once and enters the HOE 23. The image light that has reached the HOE 23 is diffracted and reflected there, and then passes through the surface 21 c and reaches the observation pupil P. Therefore, by locating the observer's eye (pupil) E at the position of the observation pupil P, the observer can observe an enlarged virtual image of the image displayed on the display element 13 in front of the eyes. In addition, the observer can also observe the external environment in front of the eyes through the HOE 23 at the same time.

  Next, the shape of the HOE surface 23a of this embodiment will be described. For convenience of explanation, each direction in the video display device 1 is defined as follows. FIG. 9 is an explanatory diagram showing coordinate axes in the video display device 1 of the present embodiment. As shown in the figure, the center of the observation pupil P is the origin, the direction perpendicular to the observation pupil plane at the origin, the direction toward the eyepiece optical system 14 is the + Z direction, and the direction upward from the origin is the + X direction. The direction from the origin to the left is the + Y direction. Note that the definition of each direction described above is considered only when the shape of the HOE surface 23a is described in the present embodiment, and is different from the definition of the direction in the construction data of the examples described later. deep. In the present embodiment, the YZ plane corresponds to a main plane or a plane parallel to the main plane.

FIG. 10 is a graph showing a cross-sectional shape in a plane parallel to the main plane of the HOE surface 23a, and FIG. 11 is a graph showing a change in the radius of curvature of the HOE surface 23a in the plane. As shown in these drawings, the HOE surface 23a is formed of a concave curved surface on the observation pupil P side having a curvature only in a plane parallel to the main plane (only in a direction parallel to the main plane). In addition, the radius of curvature of the HOE surface 23a in the plane decreases from the position b ₁ closest to the center a ₀ of the display surface of the display element 13 toward the position b ₂ farthest in the plane. The HOE surface 23a has a shape that is symmetrical in the vertical direction with the main plane as a symmetry plane.

10 and 11, the cross-sectional shape of the HOE 23a is obtained using a coordinate system (Xhoe, Yhoe, Zhoe) when the reference point Q (X ₀ , Y ₀ , Z ₀ ) of the HOE 23 is the origin of the local coordinates. And the change in curvature respectively. At this time, if the center of the observation pupil P is the global coordinate origin (x, y, z) = (0, 0, 0), the global coordinates of the reference point Q of the HOE 23 are (X ₀ , Y ₀ , Z _0). ) = (0, 6.6, 19.74). However, when the rotation angle of the HOE surface 23a around the X axis is ADE, ADE = −22 °.

In this embodiment, since the HOE surface 23a is a curved surface as described above, for the image light incident at a position close to the center a ₀ of the display surface in HOE23, large part of the radius of curvature of the surface of the HOE 23a The image light incident at a position far from the center a ₀ of the display surface by the HOE 23 while being diffracted by the diffraction angle close to the regular reflection angle is diffracted at a portion having a small radius of curvature of the HOE surface 23a. Can be made closer to the regular reflection angle. Incidentally, the difference Δθ between the diffraction angles of the 0th-order diffracted light and the 1st-order diffracted light with respect to the light ray (chief ray) connecting the center of the screen and the center of the observation pupil is
Δθ <3 °
The principal ray is diffracted at an angle close to regular reflection on the HOE surface 23a.

  Moreover, even when the angle of view is widened by changing the curvature of the HOE surface 23a depending on the position, the curvature of the HOE surface 23a is more convex toward the convex side of the HOE surface 23a than when the entire HOE surface 23a is a cylindrical surface. The diffraction angle at the field angle edge can be reduced while suppressing the protrusion amount. Therefore, even when the angle of view is widened, the eyepiece optical system 14 including the HOE 23 is not thickened in the Z direction, and the chromatic aberration of magnification due to the dispersion of the HOE 23 can be suppressed to a small level so that an observer can observe a high-quality image. .

  Further, if there are a plurality of surfaces having optical power in the eyepiece optical system 14, the optical power borne by the HOE surface 23a is reduced by sharing the optical power to each surface. Therefore, in this case, the lateral chromatic aberration due to the dispersion of the HOE 23 is originally small. On the other hand, in this embodiment, since only one of the HOE surfaces 23a has optical power in the eyepiece optical system 14, the optical power borne by the HOE surface 23a increases, and the lateral chromatic aberration due to dispersion of the HOE 23 increases. . Therefore, the present invention in which the HOE surface 23a is constituted by the above-described curved surface and the lateral chromatic aberration due to the dispersion of the HOE 23 is reduced is very effective.

  In addition, the eyepiece prism 21 of the eyepiece optical system 14 guides the image light from the display element 13 incident through the surface 21a, which is the incident surface, to be totally reflected by at least one total reflection surface (surfaces 21b and 21c). And lead to HOE23. Thus, by using the eyepiece prism 21 that guides the image light by total reflection, the eyepiece optical system 14 can be configured to be thin, and the compact image display device 1 can be realized.

  In the present embodiment, since the deflection prism 22 is joined to the eyepiece prism 21 via the HOE 23, surface reflection at the HOE 23 can be reduced, and generation of a ghost image due to 0th-order diffracted light can be reduced. it can. Further, in the configuration in which the display image of the display element 13 is superposed on the outside world and observed through, the refraction of the outside light on the surface of the HOE 23 is eliminated by the deflecting prism 22, so that the observer observes the natural outside world without distortion. can do. Therefore, the deflection prism 22 has a function as a correction prism for satisfactorily correcting a visually recognized image and an image of the outside world.

[Embodiment 3]
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 Embodiments 1 and 2 are denoted by the same member numbers, and the description thereof is omitted.

(About video display device)
FIG. 12 is a cross-sectional view showing a schematic configuration of the video display device 1 of the present embodiment. The video display apparatus 1 according to the present embodiment includes a display element 13 disposed above an eyepiece optical system 14 disposed in front of an observer's eye, and holds the HOE 23 on one surface of a light guide prism of the eyepiece optical system 14. Is a see-through video display device used as a combiner of video light traveling in the vertical direction and external light.

  That is, the video display device 1 of the present embodiment is different from the second embodiment in which the light guide direction is the horizontal direction in that the light guide direction of the image light to the observation pupil P is the vertical direction. The point that the image light is guided using total reflection in the prism 21 and the point that the image light is diffracted and reflected by the HOE 23 and guided to the observation pupil P are the same as in the second embodiment. However, the shape of the HOE surface 23a is different from that of the second embodiment. Hereinafter, this point will be described.

  In the image display device 1 of the present embodiment, the image light from the display element 13 is incident on the HOE 23 of the eyepiece optical system 14 from above, and is diffracted and reflected there to be guided to the observation pupil P. The main plane including the optical axis of the incident light and the optical axis of the reflected light is a plane perpendicular to the left-right direction.

  FIG. 13 shows a perspective view of the eyepiece optical system 14. Also in the present embodiment, the HOE 23 is formed on the surface 21d (see FIG. 12) of the eyepiece prism 21, and the shape of the HOE surface 23a is defined by the shape of the surface 21d. In the present embodiment, the HOE surface 23a is composed of a curved surface having a curvature only in the plane perpendicular to the main plane (only in the direction perpendicular to the main plane) and concave on the observation pupil P side. On the other hand, it has a symmetrical shape. Here, the plane perpendicular to the main plane refers to a plane perpendicular to the main plane and perpendicular to the plane of the observation pupil P.

  Here, in this embodiment, each direction in the video display apparatus 1 is defined as follows. 14 and 15 are explanatory diagrams showing coordinate axes in the video display device 1 of the present embodiment. FIG. 14 also serves as a cross-sectional view of the video display device 1 on the YZ plane, and FIG. It also serves as a sectional view of the ZX plane. As shown in these drawings, the center of the observation pupil P is the origin, the direction perpendicular to the observation pupil plane at the origin, the direction toward the eyepiece optical system 14 is the + Z direction, and the direction upward from the origin is + Y. The direction from the origin to the right is the + X direction. In such a coordinate system, the YZ plane corresponds to the main plane or a plane parallel to the main plane, and the ZX plane corresponds to a plane perpendicular to the main plane. The definition of each direction described above is the same as the definition of the direction in the construction data of an embodiment described later.

FIG. 16 is a graph showing a cross-sectional shape in a plane perpendicular to the main plane of the HOE surface 23a, and FIG. 17 is a graph showing a change in the radius of curvature of the HOE surface 23a in the plane. As shown in these drawings, the radius of curvature of the HOE surface 23a in the plane increases from the position b ₁ closest to the center a ₀ of the display surface of the display element 13 toward the position b ₂ farthest in the plane. It is getting smaller.

16 and 17, the cross-sectional shape of the HOE 23a is obtained by using a coordinate system (Xhoe, Yhoe, Zhoe) when the reference point Q (X ₀ , Y ₀ , Z ₀ ) of the HOE 23 is the origin of the local coordinates. And the change in curvature respectively. At this time, if the center of the observation pupil P is the global coordinate origin (x, y, z) = (0, 0, 0), the global coordinates of the reference point Q of the HOE 23 are (X ₀ , Y ₀ , Z _0). ) = (0, 0.164, 17.5).

If the display element 13 is arranged so that the display surface is horizontally long, the HOE surface 23a is a curved surface having a curvature in the long side direction of the screen, that is, in the horizontal direction of the observer. The HOE surface 23a has a left-right symmetric shape in which the radius of curvature is large at the position b ₁ (the center of the HOE surface 23a) closest to the center a ₀ of the display surface of the display element 13, and the radius of curvature decreases toward the left and right ends. It is a curved surface, and the radius of curvature is the smallest at a position b ₂ farthest from the center a _{0 of the} display surface.

  When the HOE surface 23a is constituted by, for example, a flat surface, the left and right ends in the long side direction have a large diffraction angle of the image light, so that the lateral chromatic aberration due to dispersion is large. As in the present embodiment, the HOE surface 23a is configured by a curved surface having a curvature in the left-right direction perpendicular to the main plane and having a smaller radius of curvature toward the left and right ends. The chromatic aberration of magnification caused by diffraction over the entire screen can be suppressed, and a high-quality video display device 1 can be realized.

(About production of HOE)
Next, a manufacturing method (exposure method) of the above-described HOE 23 will be described. FIG. 18 is a cross-sectional view showing a schematic configuration of an exposure optical system for producing the HOE 23. The reflection type HOE 23 separates the laser beam into two luminous fluxes for each of RGB to make the reference beam and the object beam, respectively. The hologram photosensitive material 23p on the substrate (here, the eyepiece prism 21) is moved from the substrate side and the opposite side. It is produced by exposing with two light beams (reference light, object light) and recording interference fringes by these two light beams on the hologram photosensitive material 23p. More specifically, it is as follows. Here, the light on the side where the observer's eyes are arranged is referred to as reference light, and the light from the opposite side is referred to as object light. The emission wavelengths of the RGB lasers are, for example, R: 647 nm, G: 532 nm, and B: 476 nm.

  The hologram photosensitive material 23p is a film-shaped photosensitive material cut into a single rectangular shape, and is attached to the surface 21d of the eyepiece prism 21 as a substrate. At this time, the hologram photosensitive material 23p is cut to a size larger than the exposure area, and the exposure area is defined by the exposure mask 42 disposed between the point light source 41 and the hologram photosensitive material 23p.

  First, for each of RGB, the laser light is separated into two light beams by a beam splitter, and then the respective light beams (reference light and object light) are condensed so as to become divergent light diverging from the point light sources 41 and 51.

  The RGB reference light is a spherical wave emitted from the point light source 41 at the same position, and is incident on the hologram photosensitive material 23 p from the eyepiece prism 21 side through the exposure mask 42. At this time, each of the RGB point light sources 41 is positioned at the center of the observation pupil P of the eyepiece optical system 14 during video observation. In use, the peak of the light source 11 used at the time of use is overlapped so that the light of the RGB peak wavelength from the light source 11 (LED) overlaps with the position of the same (one) point light source 41 when diffracted by the HOE 23. The RGB point light sources 41 may be shifted and arranged on the observation pupil P of the eyepiece optical system 14 in accordance with the amount of deviation between the wavelength and the emission wavelength of the laser used at the time of manufacture.

  On the other hand, the RGB object light is diverging light emitted from the point light source 51 at the same position, shaped into a predetermined wavefront by the free-form surface mirror 52, reflected by the reflection mirror 53, and eyepiece through the color correction prism 54. The light enters the hologram photosensitive material 23 p from the side opposite to the prism 21. At this time, the surface 54a of the color correction prism 54 cancels chromatic aberration caused by refraction of the image light on the surface 21a (see FIG. 12) of the eyepiece prism 21 of the eyepiece optical system 14 used at the time of use. The angle has been determined. The color correction prism 54 is preferably disposed in close contact with the hologram photosensitive material 23p or is disposed via emulsion oil or the like in order to prevent ghosts due to surface reflection.

  By irradiating the hologram photosensitive material 23p with the reference light and the object light as described above, interference fringes due to these two light beams are recorded on the hologram photosensitive material 23p, and the HOE 23 is manufactured.

  When the HOE surface 23a has a curvature only in a plane perpendicular to the main plane as in the present embodiment, the HOE 23 can be manufactured using one continuous hologram photosensitive material 23p as described above. Therefore, the manufacture becomes easy.

  Further, since the exposure mask 42 has a function as a diaphragm for restricting the region where the reference light is irradiated onto the hologram photosensitive material 23p, the effective area of the HOE 23 is an exposure optical system that exposes the hologram photosensitive material 23p. It can be said that it is defined by the diaphragm (exposure mask 42) in the optical path.

  The HOE 23 functions as an effective area having desired optical characteristics only in the area where the interference fringes are formed by exposure. For example, in this embodiment, the effective area of the HOE 23 depends on the outer shape (size) of the hologram photosensitive material 23p. If it is going to prescribe | regulate, flare will generate | occur | produce by the edge of the hologram photosensitive material 23p, and image quality will deteriorate.

  On the other hand, as in the present embodiment, the effective area of the HOE 23 is defined by the diaphragm (exposure mask 42) in the optical path of the exposure optical system, whereby the effective area of the HOE 23 is changed to the formation range of the hologram photosensitive material 23p. Can be formed on the inside. Thereby, since the effective area of the HOE 23 can be prevented from including the edge of the hologram photosensitive material 23p, it is possible to avoid the deterioration of the image quality due to the edge of the hologram photosensitive material 23p.

  Further, by arranging the exposure mask 42 in the optical path, the HOE 23 can be formed by exposure with one exposure optical system, and the manufacturing process can be simplified.

[Embodiment 4]
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 to third embodiments are denoted by the same member numbers, and description thereof is omitted. In the present embodiment, a head-up display (HUD) and a head-mounted display to which the above-described video display device 1 can be applied will be described.

(About HUD)
FIG. 19 is a cross-sectional view showing a schematic configuration of the HUD of this embodiment. In FIG. 19, the light source and the illumination optical system are not shown for convenience. In the HUD of this embodiment, for example, the display element 13 of the video display device 1 is arranged in the dashboard of the vehicle, and the HOE 23 is placed on the thin plate-like substrate 25 arranged in front of the eyes in the user's (driver's) field of view. Is held. Accordingly, the HOE 23 can be used as a combiner that guides the image light from the display element 13 and the external light to the observation pupil P at the same time. In the present embodiment, the HOE 23 and the substrate 25 constitute an observation optical system 26 that guides the image light from the display element 13 to the observation pupil P and causes the observer to observe a virtual image at the position of the observation pupil P. Yes.

  Here, the substrate 25 is a plate-like substrate having a constant thickness in a direction perpendicular to the HOE surface 23a so that the 0th-order diffracted light (regular reflection light) generated by the HOE 23 deviates from the optical path toward the observation pupil P. , And are inclined in a direction parallel to the main plane. In the present embodiment, the image light from the display element 13 travels from the bottom to the top and is diffracted and reflected by the HOE 23 and enters the observation pupil P. Therefore, the main plane is in the horizontal direction (FIG. 19). The HOE 23 is formed symmetrically in the left-right direction with the main plane as a symmetry plane.

The HOE surface 23a has a curvature only in a plane parallel to the main plane, and is configured by a concave curved surface on the observation pupil P side as a whole. In addition, the radius of curvature of the HOE surface 23a in the plane decreases from the position b ₁ closest to the center a ₀ of the display surface of the display element 13 toward the position b ₂ farthest in the plane.

  As in the first embodiment, in this embodiment as well, in order to avoid a ghost image due to the surface reflected light on the HOE 23 and the substrate 25, the substrate 25 is inclined and the 0th-order diffracted light or the like does not reach the observation pupil P. It has become. In such a configuration, since the diffraction angle at the upper end of the field angle is relatively large, lateral chromatic aberration caused by dispersion tends to be relatively large.

  However, as in the present embodiment, by configuring the HOE surface 23a with the above-described curved surface, the diffraction angle (difference between the diffraction angle and the regular reflection angle) at the HOE 23 at the upper end of the angle of view can be kept small. The lateral chromatic aberration due to dispersion at the HOE 23 can be suppressed to a small level.

  Note that if the diffraction angle at the HOE 23 at the upper end of the angle of view is set to be smaller than the regular reflection angle, a ghost image due to regular reflection light may be observed when the observer turns his face downward. is there. In this case, it is possible to avoid the observation of the ghost image by blocking the ghost light with a structural member such as a casing disposed in the middle of the optical path.

(About HMD)
FIG. 20 is a perspective view showing a schematic configuration of the HMD of the present embodiment. The HMD includes the video display device 1 according to the third embodiment and the support member 2 described above.

  The video display device 1 includes a housing 3 that includes a light source 11, an illumination optical system 12, and a display element 13 (see FIG. 12). The housing 3 holds a part of the eyepiece optical system 14. The eyepiece optical system 14 is configured by bonding an eyepiece prism 21 and a deflection prism 22, and has a shape like one lens of a pair of glasses (lens for right eye in FIG. 20) 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. doing.

  The support member 2 is a support mechanism corresponding to a frame of glasses, and supports the image display device 1 so as to be accurately positioned in front of the eyes of the observer (for example, in front of the right eye). The support member 2 includes a temple 5 (right temple 5R, left temple 5L) that contacts the left and right temporal regions of the observer, and a nose pad 6 (right nose pad 6R / left nose pad 6L) that contacts the observer's nose. ) And a nose pad lock unit (not shown) for fixing the nose pad 6 at a predetermined position. The nose pad lock unit holds the nose pad 6 with a spring shaft, and the inclination of the nose pad 6 can be adjusted. Further, the support member 2 also supports a dummy lens 7 disposed in front of the left eye of the observer.

  The observer moves the eyepiece optical system 14 while holding the temple 5 of the support member 2 and adjusts the overall position so that the position of the observation pupil of the eyepiece optical system 14 coincides with the pupil position of the observer. The nose pad 6 is fixed by the nose pad lock unit, and the HMD is mounted on the head. When an image is displayed on the display element 13 in this state, the observer can observe an enlarged virtual image of the display image of the image display device 1 and can observe the outside world through the eyepiece optical system 14 in a see-through manner. it can.

  As described above, the video display device 1 is supported by the support member 2, so that the viewer can observe the video provided from the video display device 1 in a hands-free and stable manner for a long time. Observation can be enjoyed 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.

  Of course, it is possible to configure the video display device 1, and thus the HMD and HUD, by combining the configurations of the above-described embodiments.

〔Example〕
Next, examples of the video display devices 1 according to the above-described first to third embodiments will be described more specifically with reference to construction data and the like as examples 1 to 3. Examples 1 to 3 are numerical examples corresponding to the video display devices 1 of the first to third embodiments.

  In the construction data shown below, Si (i = 1, 2, 3,...) Indicates the i-th surface (observation pupil P is the first surface) counted from the observation pupil P side. ing. Further, in the cover glass (CG) of the display element 13, the surface on the eyepiece optical system 14 side is a CG surface, and the surface on the light source 11 side is an image surface (display surface). In addition, each surface Si becomes clearer with reference to FIG. 5, FIG. 9, and FIG.

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

  The global orthogonal coordinate system (x, y, z) is an absolute coordinate system that matches the local orthogonal coordinate system (X, Y, Z) of the observation pupil plane (S1). That is, the arrangement data of each surface Si is expressed in a global coordinate system with the center of the observation pupil plane as the origin. In the observation pupil plane (S1), the direction from the observation pupil P toward the eyepiece optical system 14 is the + Z direction, the upward direction with respect to the observation pupil P is the + Y direction, and the right direction with respect to the observation pupil P is The + X direction.

  In addition, the manufacturing wavelength (HWL; normalized wavelength) and the used wavelength when the HOE 23 used in each of Examples 1 to 3 is manufactured are 532 nm, and the used order of the diffracted light is the first order. For the HOE surface, the HOE is uniquely defined by defining the two light beams used for fabrication. The definition of the two light beams is performed by determining whether the light source position of each light beam is a convergent beam (VIR) or a diverging beam (REA). The coordinates of the first point light source (HV1) and the second point light source (HV2) are (HX1, HY1, HZ1) and (HX2, HY2, HZ2), respectively.

  In each of the first to third embodiments, complicated wavefront reproduction by HOE is performed. Therefore, in addition to the definition of two light beams, HOE is also defined by a phase function φ. The phase function φ is a generator polynomial based on the position (X, Y) of the HOE, as shown in the following equation (6), and the coefficient is represented by a monomial in ascending order from the first order to the tenth order. In the construction data, the coefficient Cj of the phase function φ is shown.

  The number j of the coefficient Cj is expressed by the following equation (7), where m and n are indices of X and Y.

In the HOE plane, the normal vectors of the emitted light are respectively p ′, q ′, and r ′, the normal vectors of the incident light are respectively p, q, and r, and the wavelength of the reproduced light beam is λ (nm), Assuming that the wavelength of the light beam for producing the HOE is λ ₀ (nm), p ′, q ′, and r ′ are expressed by the following equation (8).

  As described above, in each of the first to third embodiments, the hologram photosensitive material is exposed using a light source that emits light having a wavelength of 532 nm corresponding to G (green), and interference fringes corresponding to the phase function of 532 nm are created. doing. After creating the interference fringes corresponding to the above wavelengths, the hologram photosensitive material is sequentially subjected to multiple exposure using a light source that emits light of other wavelengths R (red) and B (blue), thereby making the eyepiece optical system 14 It can correspond to color display. It is also possible to perform multiple exposure simultaneously for holograms corresponding to RGB.

In the construction data, the surface shape of the polynomial free-form surface is expressed by the following equation (9). Here, Z indicates the sag amount (mm) in the Z-axis direction (optical axis direction) at the position of height h, c indicates the curvature (1 / mm) at the surface apex, and h is the height, that is, Z A distance (mm) from the axis (optical axis) is indicated, k is a conic constant, and c (i, j) is a coefficient (free curved surface coefficient) of x ⁱ y ^j . It should be noted that for all data, the coefficients of the terms not described are all 0, and E−n = × 10 ⁻ⁿ .

Example 1
Surface number Curvature radius Material S1 Pupil surface INFINITY Air
S2 Substrate entrance surface INFINITY PMMA
(XY polynomial surface coefficient)
Y: 3.6866E-02 Y2: -4.1394E-03 Y3: 6.4925E-04
Y4: -4.0291E-05 Y5: -1.6199E-07 Y6: -2.2083E-08
S3 HOE surface (diffractive reflection surface) INFINITY
(XY polynomial surface coefficient)
Y: 3.6866E-02 Y2: -4.1394E-03 Y3: 6.4925E-04
Y4: -4.0291E-05 Y5: -1.6199E-07 Y6: -2.2083E-08
(Definition of two luminous fluxes)
HV1; REA HV2; REA
HX1; 0.000000E + 00 HY1; 0.000000E + 00 HZ1; 0.100000E + 01
HX2; 0.000000E + 00 HY2; 0.000000E + 00 HZ2; 0.100000E + 01
HWL; 532.00
(Phase coefficient)
C2: 9.5525E-02 C3: -4.9889E-03 C5: 3.8435E-03
C7: 1.3277E-05 C9: -1.2231E-03 C10: 2.0391E-08
C12: 2.5675E-07 C14: 8.1069E-05
S4 Substrate exit surface INFINITY Air
(XY polynomial surface coefficient)
Y: 3.6866E-02 Y2: -4.1394E-03 Y3: 6.4925E-04
Y4: -4.0291E-05 Y5: -1.6199E-07 Y6: -2.2083E-08
S5 Image plane INFINITY

Surface number xyz ADE Reference surface number S1 0 0 0 0 (coordinate reference)
S2 0 0 35 -20 S1
S3 0 0 2 0 S2
S4 0 0 0 0 S2
S5 0 76.57 -27.73 -43.48 S1

(Example 2)
Surface number Curvature radius Material S1 Pupil surface INFINITY Air
S2 Injection surface INFINITY PMMA
S3 HOE surface (diffractive reflection surface) INFINITY
(XY polynomial surface coefficient)
Y2: -3.1317E-02 Y3: -8.0485E-03 Y4: -1.1618E-03
Y5: -8.0516E-05 Y6: -2.1900E-06
(Definition of two luminous fluxes)
HV1; REA HV2; REA
HX1; 0.000000E + 00 HY1; 0.000000E + 00 HZ1; 0.000000E + 00
HX2; 0.000000E + 00 HY2; 0.000000E + 00 HZ2; 0.000000E + 00
HWL; 532.00
(Phase coefficient)
C2: 8.9698E-02 C3: -2.5256E-02 C5: 8.1844E-02
C7: -4.4438E-04 C9: 2.4356E-02 C10: -1.2722E-06
C12: -1.4105E-04 C14: 3.4778E-03 C16: -2.6487E-07
C18: -2.0987E-05 C20: 2.4594E-04 C21: -5.9037E-10
C23: -4.3156E-08 C25: -1.5238E-06 C27: 7.2815E-06
C29: 1.8119E-09 C31: -3.3815E-09 C33: -4.2611E-08
C35: 2.9000E-08
S4 Second reflection surface (total reflection surface) INFINITY
S5 First reflection surface (total reflection surface) INFINITY
S6 Incident surface INFINITY
S7 CG side INFINITY BK7
S8 Display screen INFINITY

Surface number xyz ADE Reference surface number S1 0 0 0 0 (coordinate reference)
S2 0 -2 14 0 S1
S3 0 6.6 19.74 -22 S1
S4 0 6 14 0 S1
S5 0 10 18.5 0 S1
S6 0 16.76 15 -85.7 S1
S7 0 20.44 9.28 -48.82 S1
S8 0 0 0.7 0 S7

(Example 3)
Surface number Curvature radius Material S1 Pupil surface INFINITY Air
S2 Injection surface INFINITY PMMA
S3 HOE surface (diffractive reflection surface) INFINITY
(XY polynomial surface coefficient)
X2: -2.4394E-03 X4: -3.0356E-05 X6: -5.3477E-07
X8: -1.2270E-08
(Definition of two luminous fluxes)
HV1; REA HV2; VIR
HX1; 0.000000E + 00 HY1; 0.000000E + 00 HZ1; 0.000000E + 00
HX2; 0.000000E + 00 HY2; 0.000000E + 00 HZ2; 0.000000E + 00
HWL; 532.00
(Phase coefficient)
C2: -9.4030E-02 C3: -1.6930E-02 C5: -1.8831E-02
C7: 2.4887E-04 C9: -1.0513E-04 C10: 9.1556E-05
C12: 1.2468E-05 C14: -1.2551E-04 C16: -3.9056E-06
C18: -8.7326E-06 C20: -8.7201E-06 C21: 9.7327E-07
C23: -9.7672E-07 C25: 5.7536E-07 C27: 7.2400E-06
C29: 1.0168E-08 C31: 1.5354E-07 C33: 6.1819E-07
C35: 1.6951E-06 C36: 3.5887E-08 C38: 3.0111E-08
C40: 9.4827E-09 C42: 6.1225E-08 C44: 1.1060E-07
S4 Third reflection surface (total reflection surface) INFINITY
S5 Second reflection surface (total reflection surface) INFINITY
S6 First reflection surface (total reflection surface) INFINITY
S7 Incident surface INFINITY
S8 CG side INFINITY BK7
S9 Display screen INFINITY

Surface number xyz ADE Reference surface number S1 0 0 0 0 (coordinate reference)
S2 0 -2 14 0 S1
S3 0 -0.164 17.5 -29.94 S1
S4 0 6 14 0 S1
S5 0 10 18.8 0 S1
S6 0 16 14 0 S1
S7 0 18.72 17.49 65.90 S1
S8 0 21.40 19.17 40.37 S1
S9 0 0 0.8 0 S8

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

DESCRIPTION OF SYMBOLS 1 Image display apparatus 2 Support member 11 Light source 13 Display element 14 Eyepiece optical system (observation optical system)
21 eyepiece prism 23 HOE (holographic optical element)
23a HOE surface 24 substrate 25 substrate 26 observation optical system P observation pupil

Claims (8)

A light source that emits light having a wavelength width including at least one emission peak wavelength and including one emission peak wavelength;
A display element for displaying an image by modulating light emitted from the light source;
An image display device comprising an observation optical system for guiding image light from the display element to an observation pupil and causing an observer to observe a virtual image at the position of the observation pupil,
The observation optical system has a volume phase type reflection holographic optical element that diffracts and reflects image light from the display element and guides it to the observation pupil;
An axis optically connecting the center of the display surface of the display element and the center of the observation pupil is an optical axis, and a plane including an optical axis of incident light and an optical axis of reflected light with respect to the holographic optical element is a main plane. Then,
The surface of the holographic optical element is symmetrical with the main plane as a plane of symmetry, has a curvature only in a plane parallel or perpendicular to the main plane, and is centered on the display plane in the plane An image display device comprising a concave curved surface on the side of the observation pupil, wherein the radius of curvature decreases from the closest position to the farthest position.   The video display apparatus according to claim 1, wherein in the observation optical system, only the surface of the holographic optical element has optical power.   3. The video display device according to claim 1, wherein the surface of the holographic optical element has a curvature in a direction having a wider angle of view among two directions having different angles of view. The observation optical system includes a substrate on which the holographic optical element is formed,
4. The video display device according to claim 1, wherein the substrate is a plate-like substrate having a constant thickness in a direction perpendicular to the surface of the holographic optical element.   5. The image display according to claim 4, wherein the substrate holds the holographic optical element so that the zero-order diffracted light generated by the holographic optical element deviates from an optical path toward the observation pupil. apparatus.   The observation optical system includes an eyepiece prism that guides image light from the display element that is incident through an incident surface by being totally reflected by at least one total reflection surface and guides the light to the holographic optical element. The video display device according to claim 1, wherein:   The video display device according to claim 6, wherein the observation optical system further includes a correction prism joined to the eyepiece prism via the holographic optical element. A video display device according to any one of claims 1 to 7,
A head-mounted display, comprising: a support member that supports the video display device in front of an observer's eyes.

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