JP2017049289A - Light guide device and virtual image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light guide device that has suppressed the occurrence of color irregularity and improved efficiency for light utilization, and a virtual image display device having the same built therein.SOLUTION: A virtual image display device 100 comprises an image forming apparatus 10 and a light guide device 20 as one pair. The light guide device 20 includes an incident part 21 that captures video light, a light guide part 22 for light guide and image formation, and an emission part 23 for drawing out the video light. Since this apparatus forms a virtual image geometrically and optically with respect to a lateral first direction and forms a virtual image to expand the pupil size with first and second hologram elements (diffraction optical elements) 42 and 43 with respect to a vertical second direction, color irregularity can be reduced compared with a case where an image is formed only with a diffraction optical element, such as a hologram element and the image can be displayed with high luminance.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a light guide device used for a head-mounted display or the like used by being mounted on a head, and a virtual image display device incorporating the same.

  In recent years, as a virtual image display device that enables the formation and observation of virtual images like a head-mounted display, the light guide plate guides the image light from the display element to the observer's pupil and enables observation of the external image through the light guide plate Various things have been proposed.

  For example, a first plate-shaped waveguide having an output diffraction grating, a second plate-shaped waveguide having a pair of input / output diffraction gratings, and image light at one end of the first plate-shaped waveguide. A projection display device including an image supply light source device to be supplied is known (see Patent Document 1). In this projection display device, the image light collimated from the image supply light source device enters the first plate-like waveguide, the horizontal exit pupil is enlarged in the waveguide, and the first plate-like waveguide Is incident on the second plate-like waveguide, and the exit pupil in the vertical direction is enlarged in the waveguide. Further, in this projection display device, color display is also possible by providing three layers of channels for three colors in the first plate-like waveguide and the second plate-like waveguide.

  Although there is an advantage that the light guide plate can be made thin by the technique described in Patent Document 1, since a diffraction grating, that is, a diffraction element is used, wavelength selectivity (diffraction efficiency with respect to wavelength) depends on the angle of view of image light. The peak shifts and color spots depending on the position in the screen are generated.

US Pat. No. 8,965,152

  An object of this invention is to provide the light guide device which suppressed generation | occurrence | production of a color spot, and the virtual image display apparatus incorporating this.

  In order to achieve the above-described object, a light guide device according to the present invention includes an incident portion that allows image light to enter, a light guide portion that guides the image light through the incident portion, and image light from the light guide portion to the position of the eye. (Specifically, a position where the eye is scheduled to be placed) and an emitting unit that emits a virtual image with respect to a first direction along a predetermined surface covering the front of the eye, and the first direction along the predetermined surface The pupil size is enlarged by the diffractive optical element in the second direction intersecting with. For the first direction, specifically, a virtual image is formed by, for example, continuous light beam processing that does not involve light beam division.

  According to the above light guide device, the virtual image is formed in the first direction and the pupil size is enlarged by the diffractive optical element in the second direction. Display with brightness is possible. Here, since the diffractive optical element is not used in the first direction, the occurrence of striped spots can be easily avoided. Although the size of the optical element is increased in thickness in order to form a virtual image with respect to the first direction, the size of the optical element in relation to the second direction can be reduced to reduce the thickness of the light guide device. It can be downsized. Further, the pupil size is not enlarged in the first direction, but the pupil size can be enlarged by the diffractive optical element in the second direction.

  In a specific aspect of the present invention, in the light guide device, the light guide unit includes a first part on the incident part side and a second part on the emission part side, and the first part and the first part serve as the first part. A virtual image is geometrically optically formed in one direction, and a virtual image using diffraction is formed in the second direction by the second portion and the emission unit. In this case, since a virtual image using diffraction is formed on the exit side, components on the exit side of the light guide device such as the exit portion and the second portion arranged in front of the eyes can be thinned, and a smart appearance can be easily achieved.

  In another aspect of the present invention, the second part and the emission part are light guide members incorporating a plurality of diffractive optical elements. Taking in image light into the light guide member and taking out image light from the light guide member can be performed using a plurality of diffractive optical elements.

  In still another aspect of the present invention, the light guide member includes a light guide plate, a first hologram element corresponding to a diffractive optical element that is provided on the incident side of the light guide plate and sends image light to the emission side, and emission of the light guide plate. And a second hologram element corresponding to a diffractive optical element that is provided on the side and sends out image light to the eye side. In this case, a hologram element is used to take in and take out the image light from the light guide plate, and it becomes easy to form a color image with high brightness and high accuracy.

  In still another aspect of the invention, the first portion is formed of an optical member having a refractive power in at least the first direction, and an intermediate image is formed therein. Here, the optical member having refractive power means an optical element having a surface that is concavely or convexly curved in the first direction, and has an effect of relatively diverging or converging image light after passing through this surface. . In this case, regarding the geometrical optical virtual image formation, the spread of the image light during the light guide can be reduced, and the first portion of the light guide portion can be extended to reduce the size of the light guide device.

  In still another aspect of the present invention, the first portion is formed of an optical member having no refractive power in the first direction and the second direction. Here, the optical member having no refractive power means an optical element having a plane with respect to the first direction, and does not have an influence of relatively diverging or converging the image light after passing through this plane. In this case, the structure of the first portion of the light guide can be simplified, and image deterioration due to the first portion can be suppressed.

  In still another aspect of the present invention, the first portion emits image light to the second portion by being reflected by the inclined surface with respect to the first direction. The video light is reliably emitted from the light guide unit toward the emission unit, and the coupling efficiency to the emission unit can be increased.

  In yet another aspect of the present invention, the second part is disposed so as to cover the eye, and the first part is disposed on the eyed side with respect to the second part. In this case, it becomes easy to dispose the first portion on the incident side so as not to stand out behind the second portion on the emission side.

  In yet another aspect of the present invention, the second part is disposed so as to cover the eye, and the first part is disposed on the opposite side of the eye across the second part. In this case, since the first portion on the incident side does not interfere with the face, optical design is facilitated.

  In yet another aspect of the invention, the first portion is disposed above the eye and the second portion is disposed in front of the eye. In this case, since the first portion on the incident side is disposed above, the image element that supplies the image light to the incident portion can be disposed in a space in which a space above the corner of the eye is secured. Further, in terms of external appearance, the first portion of the light guide portion acts like a frame, and the second portion of the light guide portion acts like a spectacle lens, which makes it easier to achieve a spectacle-like appearance as the light guide device.

  In still another aspect of the invention, the size of the virtual image screen in the first direction is larger than the size in the second direction. Thus, by relatively increasing the screen size of the virtual image in the first direction in which the virtual image is formed without using the diffractive optical element, color spots can be reduced in the first direction where the size is large. Can be made inconspicuous.

  In still another aspect of the present invention, the first direction corresponds to a horizontal direction at the time of mounting. The horizontal direction at the time of wearing corresponds to the lateral direction in which the eyes are lined up, and it is preferable that the visual field is relatively wide and color spots are not noticeable on the screen.

  In still another aspect of the present invention, the optical system of the emission unit is disposed so as to be substantially orthogonal to the optical axis on the emission side. In this case, optical design of the light guide part and the emission part becomes easy.

  In still another aspect of the present invention, the optical system of the emission unit is arranged to be inclined with respect to the optical axis on the emission side. In this case, the arrangement of the light guide part and the emission part can be arranged along the face, and it becomes easy to achieve a smart appearance.

  In still another aspect of the present invention, the light guide unit includes a first part on the incident part side and a second part on the emission part side, and uses diffraction in the first direction by the incident part and the first part. The virtual image is formed, and the virtual image is formed geometrically and optically in the second direction by the second portion and the emission portion.

  In still another aspect of the present invention, the diffractive optical element is a reflective hologram element or a transmissive hologram element. The reflection type hologram element is used when the image light is introduced into the light guide unit when diffracted in the reflection direction with respect to the incident direction of the image light and introduced into the light guide unit. When light is introduced into the light guide, it is used when the light is diffracted in the transmission direction with respect to the incident direction of the image light and guided to the light guide.

  In order to achieve the above object, a virtual image display device according to the present invention includes a video element that generates video light and the light guide device described above.

  According to the virtual image display device, by using the above-described light guide device, it is possible to prevent color spots in the observed image and to increase the image brightness.

(A) is a rear view which shows the virtual image display apparatus which concerns on 1st Embodiment, (B) is sectional drawing which illustrates one side of a virtual image display apparatus notionally, (C) is a virtual image display apparatus. It is a side view which illustrates one side of this. (A) is a figure explaining an example of the screen of a virtual image, (B) and (C) are figures explaining an example of the display area of a liquid crystal device. It is a figure explaining the image formation by a 1st light guide member or a 1st part. (A) And (B) is a figure explaining the image formation by a 2nd light guide member, (A) is a partial enlarged view of a 1st hologram element periphery especially, (B) is a 1st hologram. It is a figure explaining the function of an element and a 2nd hologram element. It is a perspective view explaining notionally operation of a virtual image display device. It is a figure which illustrates notionally enlargement of the pupil size by a 2nd light guide member. (A)-(C) is a figure explaining generation | occurrence | production and suppression of a color spot. (A) And (B) is the plane sectional view and partial expanded sectional view explaining the modification which incorporates a Fresnel mirror in the 1st light guide member, and performs geometric optical virtual image formation. It is a side view explaining the light guide device concerning a 2nd embodiment. It is a side view explaining the light guide device concerning a 3rd embodiment. It is a plane sectional view explaining the light guide device concerning a 4th embodiment. (A) And (B) is a plane sectional view of the light guide device concerning a 5th embodiment. (A) And (B) is a plane sectional view of the light guide device concerning a 6th embodiment. (A) And (B) is a plane sectional view of the light guide device concerning a 6th embodiment. It is a perspective view explaining the light guide device concerning a 7th embodiment.

[First Embodiment]
Hereinafter, a virtual image display device incorporating the light guide device according to the first embodiment of the present invention will be described.

  A virtual image display device 100 illustrated in FIG. 1A is applied to a head-mounted display, and includes an image forming device 10 and a light guide device 20 as a set. Note that FIG. 1B corresponds to the AA cross section of the virtual image display device 100 illustrated in FIG.

The virtual image display device 100 allows an observer to recognize a color image as a virtual image and allows the observer to observe an external image in a see-through manner. In the virtual image display device 100, the image forming device 10 and the light guide device 20 are normally provided one by one corresponding to the right eye and the left eye of the observer, but the right eye and the left eye are symmetrical. Therefore, only the right eye is shown here, and the illustration for the left eye is omitted.
The virtual image display device 100 as a whole has, for example, an appearance (not shown) like general glasses, and a rim portion 38 or a temple portion that supports the image forming device 10 or the light guide device 20. 39 is provided.

  The image forming apparatus 10 includes a liquid crystal device 11 that is a video element and a projection lens 12 for optical coupling. The liquid crystal device (video element) 11 spatially modulates illumination light from a light source (not shown) to form video light GL to be a moving image or other display target. The projection lens 12 is a lens that temporarily collects the image light GL emitted from each point on the liquid crystal device 11. Note that the projection lens 12 is formed of glass or plastic, and is not limited to one, but may have a plurality of configurations. The projection lens 12 is not limited to a spherical lens, but may be an aspheric lens, a free-form surface lens including an axisymmetric curved surface, or the like.

  The light guide device 20 emits the video light GL formed by the image forming device 10 as virtual image light toward the observer's eye EY, and transmits the external light OL corresponding to the external image substantially as it is. Structurally, the light guide device 20 is orthogonal to the first light guide member 31 that is an optical member that forms a virtual image in the horizontal direction at the time of wearing that is the first direction or the horizontal direction in which the eyes EY are arranged. The second light guide member 32, which is an optical member that forms a virtual image in the longitudinal direction that is the second direction that intersects, is formed. In the case of the present embodiment, the first light guide member (first optical member) 31 is disposed above the eye EY of the observer and in the front direction of the eyebrows, and is a second light guide member (second optical member). 32 is arranged so as to cover the eye EY in the front direction of the eye EY. Here, the first light guide member 31 is on the inner side and is disposed on the side with the eye EY with respect to the second light guide member 32. The first light guide member 31 and the second light guide member 32 are fixed to each other or indirectly fixed via a rim portion 38 or the like.

  Functionally, the light guide device 20 includes an incident portion 21 that takes in image light, a light guide portion 22 for guiding light and forming an image, and an emission portion 23 for taking out image light. The incident portion 21 is provided in the first light guide member 31 in the front direction of the viewer's eyebrow, and the emission portion 23 is configured to cover the eye EY in the front direction of the eye EY in the second light guide member 32. Has been placed.

  In addition, the 1st light guide member 31 consists of the incident part 21 and the 1st part 31a, and the incident part 21 and the 1st part 31a are partially common. In addition, the second light guide member 32 includes a second portion 32a and an emission portion 23, and the second portion 32a and the emission portion 23 are partially in common. The first portion 31 a of the first light guide member 31 and the second portion 32 a of the second light guide member 32 constitute the light guide portion 22 that extends between the incident portion 21 and the emission portion 23. Here, the first portion 31a is disposed above the eye EY, and the second portion 32a is disposed in front of the eye EY so as to cover the eye EY. The first portion 31a is disposed on the side with the eye EY with respect to the second portion 32a. That is, the first portion 31a on the incident side is arranged so as not to stand out behind the second portion 32a on the emission side.

In the case of the light guide device 20 described above, in the first light guide member 31 or the first portion 31a, the incident portion 21 and the first portion 31a form a virtual image geometrically in the lateral first direction, and the second guide A virtual image using diffraction is formed in the vertical second direction by the optical member 32, that is, by the second portion 32 a and the emitting portion 23.
Here, as shown in FIG. 2A, the size of the virtual image screen PW (that is, the projection range PR) observed by the observer in the first direction (specifically, the x direction) is the second size of the screen PW. It is larger than the size in the direction (specifically, the y direction). Thereby, although the reason will be described later, the color spots on the screen PW can be reduced in the first direction having a large size, and the color spots can be made inconspicuous in the entire screen PW. The virtual image formed by the horizontal incident portion 21 and the first portion 31a and the virtual image formed by the vertical second portion 32a and the emission portion 23 may have different imaging magnifications. That is, as shown in FIG. 2B, the display area IA of the liquid crystal device 11 can be made to match the aspect ratio of the virtual image screen PW shown in FIG. As shown in FIG. 2, the display area IA of the liquid crystal device 11 can be different from the aspect ratio of the virtual image screen PW shown in FIG.

Referring back to FIG. 1B and the like, the main body of the first light guide member 31 is an integrated product molded from a resin material having high light transmittance. The first light guide member 31 includes an incident surface IS as the incident portion 21, a first surface S1 having a positive refractive power in the xz plane corresponding to the lateral direction, and a second surface that is a flat surface having no refractive power. It has a surface S2, a third surface S3 which is a flat surface having no refractive power, and a fourth surface S4 which is an inclined surface having a positive refractive power in the xz plane corresponding to the lateral direction. The first surface S1 and the fourth surface S4 are non-transmissive mirrors in which a metal film or the like is formed on a curved surface. The second surface S2 and the third surface S3 are exposed surfaces that are flat surfaces, are total reflection surfaces that reflect the image light GL having an incident angle of a predetermined value or more, and do not particularly contribute to image formation. Among these, in particular, a part of the third surface S3 receives the image light GL that has passed through the first light guide member 31 or the first portion 31a, that is, the image light GL reflected by the fourth surface S4, as the second light guide member. It becomes the 1st coupling part C1 which injects to 32 or the 2nd portion 32a side.
The second and third surfaces S2 and S3 are not limited to those in which the resin molded product of the main body of the first portion 31a is exposed, but may be those in which the resin molded product of the main body is covered with a hard coat layer.

The video light GL introduced into the first light guide member 31 via the incident portion 21 is further converged on the first surface S1 with respect to the xz plane, and once forms an intermediate image at the imaging position P1. Thereafter, the image light GL that has passed through the second and third surfaces S2 and S3 is reflected by the fourth surface S4, which is an inclined surface, to be a parallel light beam, and the light guide direction is greatly changed, so that the third Incident to the first coupling part C1 of the surface S3 at an angle close to perpendicular. The video light GL that has passed through the first coupling portion C1 of the third surface S3 enters the second light guide member 32 described in detail later. Although details will be described later, the first light guide member 31 functions as a collimator in the lateral first direction (in the xz plane) and has a role of ensuring a pupil size of a certain level or more. When the first light guide member 31 has different imaging magnifications in the xz plane and in the y direction, the imaging position P2 in the y direction is different from the imaging position P1 in the xz plane.
In the present embodiment, the first light guide member 31 also functions as a collimator in the vertical second direction (or y direction), but the vertical width of the first light guide member 31 may be narrow. The vertical pupil size is considerably smaller than the horizontal pupil size.

FIG. 3 is a diagram illustrating the video light GL emitted from the first light guide member 31. In this figure, the operation of the second light guide member 32 is excluded for convenience of explanation, and the video light GL exits the first light guide member 31 and goes straight to the opposite side of the original eye.
Of the video light GL that passes through the first coupling portion C1 of the first light guide member 31 and enters the second light guide member 32, the display area IA of the liquid crystal device 11 of the image forming apparatus 10 shown in FIG. Video light GL emitted from each point in FIG. 2A is emitted from the first light guide member 31 in a parallel light beam state. At this time, the angle θ of the image light GL emitted from the first coupling unit C1 with respect to the first coupling unit C1 or the third surface S3 in the xz plane corresponding to the horizontal direction in which the eyes EY are arranged or the horizontal direction at the time of wearing is The horizontal direction D1 on the display area IA (see FIG. 1B) is reflected. That is, the position in the horizontal direction D1 on the display area IA corresponds to the incident angle φ in the xz plane with respect to the optical axis AX of the image light GL incident on the equivalent position of the eye EY (that is, the observation pupil HI). Thus, a virtual image is formed in the lateral direction. Specifically, the image light GL0 from the center of the liquid crystal device 11 shown in FIG. 1B is emitted from the first light guide member 31 (specifically, the second light guide member 32) at an angle θ0 = 0. Injection is performed in a state parallel to the axis AX. In addition, the image light GL1 from the position on the right side (near + x) of the liquid crystal device 11 is emitted from the first light guide member 31 at an angle θ1 with respect to the optical axis AX. Video light GL2 from the position on the left side of the liquid crystal device 11 (closer to −x) is emitted from the first light guide member 31 at an angle θ2 with respect to the optical axis AX. That is, the first light guide member 31 forms a virtual image in the horizontal direction in which the eyes EY are arranged in the first direction. At this time, the distance LE from the first coupling portion C1 to the pupil HI is emitted from the first coupling portion C1 in consideration of the standard light guide distance or optical path length of the video light GL in the second light guide member 32. It is set so that the chief rays of the image light GL thus made intersect. That is, a sufficient pupil size is secured in the lateral direction, and the video light GL is efficiently taken into the eye EY.

  Referring back to FIGS. 1A to 1C, the second light guide member 32 is disposed so as to be orthogonal to the optical axis AX on the exit side or the x axis, and extends in parallel to the xy plane. Here, the optical axis AX on the exit side corresponds to the front direction of the face of the observer when the virtual image display device 100 or the light guide device 20 is mounted, and is parallel to the symmetry axis passing through the center of the rim portion 38. Yes. The second light guide member 32 includes a light guide plate 41 that forms an overall appearance, a first hologram element 42 that is provided on the incident side of the light guide plate 41 and corresponds to a diffractive optical element that sends the video light GL to the emission side, And a second hologram element 43 corresponding to a diffractive optical element that is provided on the exit side of the light guide plate 41 and sends the image light GL to the eye EY side. The second light guide member 32 can be formed to a thickness of about 2 mm.

The light guide plate 41 is disposed in front of the eye EY so as to cover the eye EY. The light guide plate 41 is a parallel plate formed of a resin material having high light transmittance. The light guide plate 41 forms the second portion 32 a of the light guide device 20 in cooperation with the first hologram element 42. The light guide plate 41 has a first surface S21 provided on the inner side with the eye EY, and a second surface S22 provided on the outer side opposite to the eye EY, and the first and second surfaces S21, S22 are Are parallel to each other. The first and second surfaces S21 and S22 are exposed surfaces that are flat surfaces, are total reflection surfaces that reflect the image light GL having an incident angle of a predetermined value or more, and do not particularly contribute to image formation. The video light GL incident on the light guide plate 41 from the first light guide member 31 is propagated downward, that is, in the −y direction as a whole via a first hologram element 42 described later. At this time, since the video light GL is propagated while being totally reflected between the first and second surfaces S21 and S22 parallel to each other, the angle information is maintained, and the parallel rays are propagated as parallel rays.
In addition, a part of the upper side of the first surface S21 of the light guide plate 41 is a second portion for allowing the video light GL emitted from the first coupling portion C1 of the first light guide member 31 to enter the second light guide member 32 side. This is a coupling portion C2 (see FIG. 4A). The first coupling portion C1 and the second coupling portion C2 are not completely in contact with each other and are close to each other. The gap GA between the third surface S3 of the first coupling portion C1 and the first surface S21 of the second coupling portion C2 is desirably secured to the extent that no interference fringes are generated, that is, about 1 μm or several μm.

  The first hologram element 42 is a thin-film or thin-plate member, and is fixed so as to be bonded to the second surface S22 of the light guide plate 41. The first hologram element 42 is a reflective volume hologram in which a three-dimensional interference pattern is formed, and can function as an optical element. The 1st hologram element 42 can be manufactured by the method as described in Unexamined-Japanese-Patent No. 2011-248318 etc., for example. The first hologram element 42 and the light guide plate 41 are in close contact with each other with no gap therebetween or are adhered to each other.

  The second hologram element 43 is a thin-film or thin-plate member, and is fixed so as to be bonded to the second surface S22 of the light guide plate 41. The second hologram element 43 is a reflective volume hologram in which a three-dimensional interference pattern is formed as in the first hologram element 42, and can function as an optical element. The second hologram element 43 and the light guide plate 41 are in close contact with each other with no gap therebetween or are adhered to each other.

  4A is a partially enlarged view of the periphery of the first hologram element 42, and FIG. 4B is a diagram illustrating the functions of the first hologram element 42 and the second hologram element 43. FIG.

  The first hologram element 42 functions like an inclined mirror 142 in the yz plane corresponding to the vertical direction. The image light GL incident on the first hologram element 42 from the first light guide member 31 through the light guide plate 41 has an emission angle ε set to an angle suitable for light guide in the light guide plate 41 by the function of the tilt mirror 142. The light is reflected in the state and returned into the light guide plate 41. At this time, the angle η (η0, η3, η4) of the image light GL emitted from the first light guide member 31 with respect to the second coupling portion C2 or the first surface S21 is on the display area IA provided in the liquid crystal device 11. The vertical direction D2 (see FIG. 1C) is reflected, and the relative angular relationship is maintained even after passing through the first hologram element 42.

  The light guide plate 41 cooperates with the second hologram element 43 while maintaining the angle in the traveling direction of the image light GL, and the width of the light beam, that is, the incident angle in the vertical direction perpendicular to the horizontal direction in which the eyes EY are arranged. It has the role of effectively widening the pupil width.

The second hologram element 43 functions like an inclined mirror 143 in the yz plane corresponding to the vertical direction. The image light GL incident on the second hologram element 43 from the first hologram element 42 through the light guide plate 41 is reflected so as to have an angle suitable for emission from the light guide plate 41 by the function of the inclined mirror 143 of the second hologram element 43. And taken out of the light guide plate 41. At this time, the second hologram element 43 maintains a relative angular relationship between the light beams constituting the video light GL, and the first surface S21 of the video light GL emitted from the second light guide member 32. The angle η (η0, η1, η2) with respect to the angle reflects the vertical direction D2 (see FIG. 1C) on the display area IA provided in the liquid crystal device 11 shown in FIG. . That is, the position in the vertical direction D2 on the display area IA corresponds to the incident angle ζ in the y direction with respect to the optical axis AX of the video light GL incident on the pupil HI, and a virtual image is formed in the vertical direction. Specifically, the image light GL0 from the center of the liquid crystal device 11 shown in FIG. 1C is emitted from the second light guide member 32 in a state parallel to the optical axis AX at an angle η0 = 0. Further, the image lights GL3 and GL4 from the upper and lower (+ y side or −y side) positions of the liquid crystal device 11 are emitted from the second light guide member 32 in a state of forming angles η3 and η4 with respect to the optical axis AX. . That is, the second light guide member 32 forms a virtual image in the vertical direction perpendicular to the eye EY that is the second direction.
The second hologram element 43 is symmetrical with the first hologram element 42, and has a relationship that cancels the wavelength dependence of the angle at which the image light GL is extracted.

  FIG. 5 is a diagram for conceptually explaining the operation of the virtual image display device 100. The video light GL formed by the image forming apparatus 10 first enters the incident portion 21, and is guided to the first portion 31a of the first light guide member 31 having the first surface S1, the fourth surface S4, and the like, and the eye EY. A virtual image is formed in the horizontal direction corresponding to the first direction (see the light L1). The image light GL is changed in the direction of the orthogonal front -z direction and is incident on the second light guide member 32 (see the light L2). The video light GL incident on the second light guide member 32 having the hologram elements 42 and 43 propagates in the vertical direction (specifically, the −y direction) which is the second direction orthogonal to the eye EY and relates to the vertical direction. The pupil size is expanded (see light L3). The video light GL that has reached the emission part 23 of the second light guide member 32 is emitted to the z side where the eye EY is located (see the light L4). At this time, the video light GL indicated by the light L4 is a virtual image having a sufficient viewing angle in the horizontal direction and the vertical direction, and an observer can observe the image formed on the liquid crystal device 11.

  Note that the emission unit 23 is a portion where the second hologram element 43 exists, and can transmit the external light OL although it depends on the diffraction efficiency of the second hologram element 43. Further, the light guide plate 41 that supports the second hologram element 43 can also transmit the external light OL, and as a result, the observer can observe the external environment through the second light guide member 32.

  FIG. 6 is a diagram for conceptually explaining the enlargement of the pupil size by the second light guide member 32. In the second light guide member 32, an action of causing a part of the image light to be emitted to the eye EY side and guiding the rest by the light guide plate 41 at various positions of the second hologram element 43, and the pupil size in the vertical direction is enlarged. Achieved. Specifically, for example, the image light GLa guided by the light guide plate 41 and first diffracted by the second hologram element 43 is an exit observation pupil (or eye) set at a position higher than the position of the eye EY. Ring) Incident on HIa. Further, the image is guided by the light guide plate 41 and hits the second hologram element 43 and is not initially diffracted, but is totally reflected by the first surface S21 of the light guide plate 41 and incident once again on the second hologram element 43 and diffracted. The light GLa is incident on an exit observation pupil (or eye ring) HIb set at a position of the substantially eye EY. Further, the light is guided by the light guide plate 41 and incident twice on the second hologram element 43, but is not diffracted but totally reflected by the first surface S21 of the light guide plate 41 and again incident on the second hologram element 43 and diffracted. The image light GLc is incident on an exit observation pupil (or eye ring) HIc set at a position lower than the position of the eye EY. That is, with respect to the vertical second direction CC, an effective pupil size enlargement is achieved by combining the pupils HIa to HIc.

  According to the light guide device 20 of the embodiment described above, a virtual image is geometrically optically formed in the horizontal first direction, and the first and second hologram elements (diffractive optical elements) 42 and 43 in the vertical second direction. Since the virtual image is formed so as to extend the width of the exit pupil (pupil size), the color spots can be reduced compared to the case where the image is formed only with a diffractive optical element such as a hologram element, and display with high brightness is possible. become. Furthermore, since the first and second hologram elements 42 and 43 are not used in the horizontal first direction, it is possible to easily avoid the occurrence of striped spots. In the light guide device 20 of the embodiment, the first light guide member 31 can be regarded as a relay optical system that does not increase the width (pupil size) of the exit pupil in the first horizontal direction and the second vertical direction. The second light guide member 32 can be regarded as expanding the exit pupil width (pupil size) in the vertical direction without affecting the horizontal direction.

Hereinafter, a virtual image is geometrically optically formed in the lateral direction that is the first direction by the first light guide member 31, and a virtual image that uses diffraction or interference in the longitudinal direction that is the second direction by the second light guide member 32. The reason for forming will be described.
FIG. 7A shows the relationship between the wavelength around the green and the diffraction efficiency regarding the image formation in the vertical direction by the second light guide member 32 in a specific example. FIG. 7B shows the relationship between the wavelength around the green and the diffraction efficiency with respect to the image formation of the comparative example. In each chart, the horizontal axis indicates the wavelength, and the vertical axis indicates the diffraction efficiency. Here, it is assumed that the projection screen by the light guide device 20 is vertical: horizontal = 9: 16, and the horizontal is 1.8 times as long as the vertical. In the case of the embodiment of FIG. 7A, the second light guide member 32 shows a case where a virtual image is formed using a hologram element in a relatively short vertical direction. In the case of the comparative example of FIG. 2 shows a case where a virtual image is formed with a size corresponding to a relatively long lateral direction by a member similar to the light guide member 32. In each chart, the plurality of characteristic curves indicate the characteristics at a plurality of points (including both ends) in the vertical direction on the screen. The larger the variation range of the peak wavelength of the characteristic curve, the longer the vertical direction by the second light guide member 32. This means that the color display tends to be biased with respect to directional image formation.
In the embodiment shown in FIG. 7A where the image forming range is narrow, the variation range of the peak wavelength as a whole is relatively small, about 8 nm. On the other hand, in the comparative example having a wide image forming range shown in FIG. 7B, the variation range of the peak wavelength as a whole exceeds 20 nm and is relatively large. That is, when the projection screen is horizontally long, the second light guide member 32 forms a virtual image using diffraction in the first direction in the vertical direction (the direction in which the screen is relatively narrow), which is the second direction. It can be seen that it is preferable from the viewpoint of color spot suppression rather than forming a virtual image using diffraction in a certain lateral direction.
FIG. 7C is a chromaticity diagram. The points indicated by circles in FIG. 7C correspond to the case of the embodiment shown in FIG. 7A, and show a green variation due to a relatively small hologram element in the vertical direction. A point indicated by a square mark in (C) corresponds to the case of the comparative example shown in FIG. 7B, and shows a green variation due to a relatively large hologram element in the pupil size enlargement direction. As is apparent from the figure, the green variation in the example is significantly smaller than the green variation in the comparative example, and it can be seen that the change in the color gamut indicated by the triangle can be reduced. That is, in the case of the embodiment, it is not necessary to largely adjust the color balance in order to prevent color spots on the projection screen, and a wide color reproduction range can be secured.

  FIGS. 8A and 8B show a modification of the first light guide member 31 shown in FIGS. 1A and 3. Of the first light guide member 31 shown in FIG. 8A, for example, the fourth surface S4 is a Fresnel mirror or a Fresnel lens as shown in an enlarged view in FIG. The first surface S1 can also be a Fresnel mirror. The fourth surface S4 has a positive refracting power at least in the xz plane corresponding to the lateral direction as in the case shown in FIG. 3, but is flat with no undulations because it is a Fresnel mirror. Similarly, the first surface S1 also has a positive refractive power at least in the xz plane corresponding to the lateral direction, but is flat with no undulations because it is a Fresnel mirror.

[Second Embodiment]
Hereinafter, a virtual image display device incorporating a light guide device according to a second embodiment of the present invention will be described. Note that the light guide device according to the second embodiment is a partial modification of the light guide device according to the first embodiment, and description of common portions is omitted.

  As shown in FIG. 9, the light guide device 20 of the present embodiment uses a transmission type volume hologram instead of the reflection type as the first hologram element 42 and the second hologram element 43. In this case, the first hologram element 42 is disposed between the first light guide member 31 and the light guide plate 41. The first hologram element 42 switches the traveling direction of the image light GL passing through the first hologram element 42 to an traveling direction of an angle such that the image light GL propagates while being totally reflected in the light guide plate 41. The second hologram element 43 is affixed on the first surface S21 of the light guide plate 41 on the eye EY side. The second hologram element 43 passes the video light GL propagated through the light guide plate 41 by total reflection out of the light guide plate 41 and sends it out in the direction of the eye EY.

[Third Embodiment]
Hereinafter, a virtual image display device incorporating a light guide device according to a third embodiment of the present invention will be described. Note that the light guide device according to the third embodiment is a partial modification of the light guide device according to the first embodiment, and a description of common portions is omitted.

As shown in FIG. 10, in the light guide device 20 of the present embodiment, the first light guide member 31 is on the outer side and is disposed on the opposite side of the eye EY with the second light guide member 32 interposed therebetween. With such an arrangement, the first light guide member 31 on the incident side and the image forming apparatus 10 do not interfere with the face, so that optical design is facilitated.
In the present embodiment, the first hologram element 42 is a reflection type and is disposed on the eye EY side of the light guide plate 41, and the second hologram element 43 is a reflection type and is disposed on the opposite side of the eye EY of the light guide plate 41.

[Fourth Embodiment]
Hereinafter, a virtual image display device incorporating a light guide device according to a fourth embodiment of the present invention will be described. Note that the light guide device according to the fourth embodiment is a partial modification of the light guide device according to the first embodiment, and a description of common portions is omitted.

  As shown in FIG. 11, in the light guide device 20 of the present embodiment, the first light guide member 31 and the second light guide member 32 are not inclined to the optical axis AX or the x axis on the exit side but are inclined. Has been. In this case, the first and second light guide members 31 and 32 can be arranged along the curve of the face, but the normal line of the second light guide member 32 has an inclination with respect to the optical axis AX. Is omitted, but the characteristics of the optical surface and the hologram element constituting the first light guide member 31 and the like are modified.

[Fifth Embodiment]
Hereinafter, a virtual image display device incorporating a light guide device according to a fifth embodiment of the present invention will be described. Note that the light guide device according to the fifth embodiment is a partial modification of the light guide device according to the first embodiment, and description of common portions is omitted.

As shown in FIG. 12A, the light guide device 20 of this embodiment is a type in which the projection lens 12 is omitted, and the first light guide member 31 is a type that does not form an intermediate image. That is, the video light GL emitted from each point on the liquid crystal device 11 passes through the incident portion 21 having a positive refractive power in the xz plane corresponding to the horizontal direction, and is a first surface that is a flat surface having no refractive power. Reflected by S1 and reflected by the second surface S2 having a positive refractive power in the xz plane corresponding to the lateral direction, it is collimated in the xz plane corresponding to the lateral direction to become a parallel light beam. The image light GL reflected by the second surface S2 that is the inclined surface, collimated, and bent in the optical path passes through the first surface S1 and enters the second light guide member 32.
In this example and the following examples, a surface having a positive refractive power in the xz plane also has a normal refractive power in the direction perpendicular to this, but the description thereof will be omitted hereinafter.

  FIG. 12B shows a modification of the embodiment shown in FIG. In this case, the image light GL emitted from each point on the liquid crystal device 11 passes through the incident portion 21 having positive refractive power in the xz plane corresponding to the horizontal direction, and is a first plane that does not have refractive power. Reflected by the surface S1, reflected by the second surface S2, which is a plane having no refractive power, reflected by the third surface S3 having positive refractive power in the xz plane corresponding to the lateral direction, and corresponding to the lateral direction The collimated light beam is collimated in the xz plane. The image light GL reflected by the third surface S3 that is the inclined surface, collimated, and bent in the optical path passes through the second surface S2 and enters the second light guide member 32.

  In addition, the incident part 21 of the 1st light guide member 31 shown to FIG. 12 (A) and 12 (B) can be made into a Fresnel lens. Further, the second surface S2 of the first light guide member 31 shown in FIG. 12A and the third surface S3 of the first light guide member 31 shown in FIG. 12B can be Fresnel mirrors.

[Sixth embodiment]
Hereinafter, a virtual image display device incorporating a light guide device according to a sixth embodiment of the present invention will be described. Note that the light guide device according to the sixth embodiment is a partial modification of the light guide device according to the first embodiment, and description of common portions is omitted.

  The light guide device 20 shown in FIG. 13A is a type in which the projection lens 12 is omitted and an intermediate image is formed in the first light guide member 31 including the prism portion 131 and the mirror portion. Specifically, the image light GL emitted from each point on the liquid crystal device 11 is sequentially reflected by the first surface S1, the second surface S2, the third surface S3, and the fourth surface S4 via the incident portion 21. Then, it is collimated in the xz plane corresponding to the horizontal direction to become a parallel light flux. The image light GL reflected and collimated by the fourth surface S4 passes through the third surface S3 and enters the second light guide member 32. Here, the first surface S1 is a Fresnel reflection surface, that is, a Fresnel mirror, and the second to fourth surfaces S2 to S4 are free curved surfaces or the like.

  The light guide device 20 shown in FIG. 13B is a type in which the projection lens 12 is omitted and an intermediate image is formed in the first light guide member 31, and the first light guide member 31 has three mirrors. 231a, 231b, 231c. The video light GL emitted from each point on the liquid crystal device 11 is reflected by the first surface S1 as the incident portion 21 provided on the mirror 231a, converged once, and reflected by the second surface S2 provided on the mirror 231b. Finally, the light is reflected by the third surface S3 provided on the mirror 231c and collimated in the xz plane corresponding to the horizontal direction to become a parallel light beam. Here, the first surface S1 and the third surface S3 can be Fresnel mirrors having positive refractive power.

  The light guide device 20 shown in FIG. 14A is not a type that forms an intermediate image in the first light guide member 31, and the first light guide member 31 is composed of one prism 331a and one mirror 331b. Become. Video light GL emitted from each point on the liquid crystal device 11 enters the prism 331a through the incident portion 21, is reflected by the first surface S1, passes through the second surface S2, and is emitted outside the prism 331a. The The video light GL emitted to the outside of the prism 331a is reflected by the third surface S3 provided on the mirror 331b and collimated in the xz plane corresponding to the horizontal direction to become a parallel light bundle. Here, the first to third surfaces S1 to S3 are free-form surfaces.

  The light guide device 20 shown in FIG. 14B is a type that forms an intermediate image in the first light guide member 31. The video light GL emitted from each point on the liquid crystal device 11 and passing through the projection lens 12 enters the first light guide member 31 through the first surface S1 which is the incident portion 21, and the second surface S2 and the first surface S1. The third surface S3, the first surface S1, and the fourth surface S4 are reflected in this order, and are emitted to the outside of the first light guide member 31 through the first surface S1. Here, the first surface S1 and the third surface S3 are flat surfaces, and the second surface S2 and the fourth surface S4 are free-form surfaces.

[Seventh Embodiment]
Hereinafter, a virtual image display device incorporating a light guide device according to a seventh embodiment of the present invention will be described. Note that the light guide device according to the seventh embodiment is a partial modification of the light guide device according to the first embodiment, and a description of common portions will be omitted.

  As shown in FIG. 15, the light guide device 20 of the present embodiment includes a first light guide member 131 and a second light guide member 132, and includes the first light guide member 131 (the incident portion 21 and the first portion 31 a. A virtual image using diffraction (specifically, holography) is formed in the first lateral direction. In addition, a virtual image is geometrically optically formed in the second vertical direction by the second light guide member 132 (including the first portion 32a and the emission unit 23).

Specifically, the video light GL formed by the image forming apparatus 10 is first incident on the incident portion 21 and the first light guide member 131 incorporating a hologram element (not shown) having a diffractive action in the lateral direction. The first portion 31a leads to a virtual image in the horizontal direction (in the xz plane) in which the eyes EY are arranged in the first direction (see the light L1). The image light GL is changed in the direction of the orthogonal front -z direction and is incident on the second light guide member 132 (see the light L2). The image light GL incident on the second light guide member 132 incorporating an optical surface having a refractive power with respect to the vertical direction or other geometrical optical elements is a vertical direction (specifically, the second direction is perpendicular to the eye EY). -Y direction) and a virtual image in the vertical direction (see light L3). The image light GL that has reached the emission part 23 of the second light guide member 132 is emitted to the z side where the eye EY is located (see the light L4). At this time, the video light GL indicated by the light L4 is a virtual image in the horizontal direction and the vertical direction, and an observer can observe the image formed on the liquid crystal device 11.
In the light guide device 20 of the present embodiment, the emission unit 23 is long in the vertical direction that is the ± y direction, and the projection screen is also long in the y direction. For this reason, since the virtual image is formed on the short side by the first light guide member 31 incorporating the hologram element, the occurrence of color spots can be suppressed.

[Others]
Although the present invention has been described with reference to each embodiment, the present invention is not limited to the above-described embodiment, and can be implemented in various modes without departing from the spirit of the present invention. The following modifications are possible.

  The diffractive optical element is not limited to a hologram element, and a diffractive element can be used. When a color image is formed, as described in US Pat. No. 8,965,152, each color is provided in a waveguide. A channel can be provided.

  In the above description, the transmissive liquid crystal device 11 is used as the video element. However, the video element is not limited to the transmissive liquid crystal device, and various devices can be used. For example, a configuration using a reflective liquid crystal panel is possible, and a digital micromirror device or the like can be used instead of the liquid crystal device 11. Moreover, the structure using the self-light-emitting element represented by organic EL, LED array, organic LED, etc. is also possible. Further, a configuration using a laser scanner in which a laser light source and a polygon mirror or other scanner are combined is possible.

  In the above description, the virtual image display device 100 is configured to provide the image forming device 10 and the light guide device 20 one by one corresponding to both the right eye and the left eye, but in either the right eye or the left eye. Only the image forming apparatus 10 and the light guide device 20 may be provided for only one eye.

  In the above description, the virtual image display device 100 of the embodiment is specifically described as a head-mounted display. However, the virtual image display device 100 of the embodiment is applied to a head-up display, a binocular handheld display, and the like. You can also.

In the above description, the image forming apparatus 10 is formed so as to be positioned outside the eyes in the lateral direction.
In the arrangement shown in FIG. 1A, the arrangement of the image forming apparatus 10 and the light guide apparatus 20 can be rotated by 90 ° around the axis of the eye EY (that is, the optical axis AX extending in the z direction). That is, the image forming apparatus 10 can be disposed above the eyes, and the light guide device 20 can be disposed vertically and disposed in front of the eyes EY.

  Although not mentioned above, the upper end surface and the lower end surface of the outer peripheral portion that defines the outer shape of the first light guide member 31 can be a black paint application surface or a sandblasted surface. Furthermore, you may perform black coating application | coating or sandblasting to locations other than an upper end surface and a lower end surface.

  DESCRIPTION OF SYMBOLS 10 ... Image forming apparatus, 11 ... Liquid crystal device, 12 ... Projection lens, 20 ... Light guide device, 21 ... Incident part, 22 ... Light guide part, 23 ... Ejection part, 31, 32, 131, 132 ... Light guide member, 31a ... 1st part, 32a ... 2nd part, 41 ... Light guide plate, 42, 43 ... Hologram element, 100 ... Virtual image display apparatus, AX ... Optical axis, C1 ... 1st coupling part, C2 ... 2nd coupling part, D1 ... Horizontal direction, D2 ... Vertical direction, EY ... Eye, GL ... Video light, GL0, GL1, GL2 ... Video light, GL3, GL4 ... Video light, HI ... Pupil, IA ... Display area, IS ... Incident surface, OL ... External light, PR: Projection range, PW: Screen, S1 to S6: Surface, S21, S22 ... Surface

Claims (17)

An incident part for entering image light;
A light guide that guides image light through the incident portion;
An emission unit that emits image light from the light guide unit to the position of the eye,
A light guide device that forms a virtual image in a first direction along a predetermined surface covering the front of the eye and enlarges a pupil size by a diffractive optical element in a second direction that intersects the first direction along the predetermined surface. The light guide has a first part on the incident part side and a second part on the emission part side,
The virtual part is geometrically optically formed with respect to the first direction by the incident part and the first part, and a virtual image using diffraction is formed by the second part and the emission part with respect to the second direction. The light guide device according to 1.   The light guide device according to claim 2, wherein the second part and the emission unit are light guide members in which a plurality of the diffractive optical elements are incorporated.   The light guide member is provided on a light guide plate, a first hologram element corresponding to the diffractive optical element that is provided on an incident side of the light guide plate and sends image light to an emission side, and provided on an emission side of the light guide plate. The light guide device according to claim 3, further comprising: a second hologram element corresponding to the diffractive optical element that sends image light to the eye side.   5. The light guide device according to claim 2, wherein the first portion is formed of an optical member having a refractive power at least in the first direction, and an intermediate image is formed therein.   5. The light guide device according to claim 2, wherein the first portion is formed of an optical member having no refractive power in the one direction and the second direction.   The light guide device according to any one of claims 5 and 6, wherein the first portion emits image light to the second portion by being reflected by a slope with respect to the first direction.   The guide according to any one of claims 2 to 7, wherein the second portion is disposed so as to cover an eye, and the first portion is disposed on an eyed side with respect to the second portion. Optical device.   The guide according to any one of claims 2 to 7, wherein the second portion is disposed so as to cover the eye, and the first portion is disposed on the opposite side of the eye across the second portion. Optical device.   The light guide device according to any one of claims 2 to 9, wherein the first portion is disposed above the eye, and the second portion is disposed in front of the eye.   The light guide device according to claim 1, wherein a size of the virtual image screen in the first direction is larger than a size in the second direction.   The light guide device according to any one of claims 1 to 11, wherein the first direction corresponds to a horizontal direction at the time of mounting.   The light guide device according to any one of claims 1 to 12, wherein the optical system of the emission unit is disposed so as to be substantially orthogonal to the optical axis on the emission side.   The light guide device according to any one of claims 1 to 12, wherein the optical system of the emission unit is arranged to be inclined with respect to the optical axis on the emission side. The light guide has a first part on the incident part side and a second part on the emission part side,
The virtual image using diffraction in the first direction is formed by the incident portion and the first portion, and the virtual image is geometrically optically formed in the second direction by the second portion and the emission portion. The light guide device according to 1.   The light guide device according to claim 1, wherein the diffractive optical element is a reflective hologram element or a transmissive hologram element.   A virtual image display device comprising: an image element that generates image light; and the light guide device according to claim 1.

Images