JP2017049511A - Light guide device and virtual image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light guide device in which unevenness of video light and external light is hardly generated and a ghost is hardly formed, and a virtual image display device incorporating the light guide device.SOLUTION: A light guide device 20 comprises: a parallel light guide body 22; an incidence section 21; and an emission section 23. In this case, arrangement intervals SP of a plurality of half mirrors 31 vary from an incidence side close to the incidence section 21 toward a counter incidence side based on an eye point EP or a line of sight EL such that the plurality of half mirrors 31 is substantially continuously connected to one another. Accordingly, the plurality of half mirrors 31 constituting a reflection unit 30 is substantially uniformly arranged so as not to overlap with one another ahead of the eye point EP or the line of sight EL. Thus, stripe-shaped unevenness extending along the half mirrors 31 can be prevented from being observed when external light OL is observed.SELECTED DRAWING: Figure 2

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.

  2. Description of the Related Art In recent years, various types of virtual image display devices that enable formation and observation of virtual images, such as a head-mounted display, have been proposed that guide video light from a display element to an observer's pupil using a light guide plate.

For example, as a device for introducing a collimated image or the like into the observer's field of view, a number of half mirrors (hereinafter also referred to as “HM”) are arranged in a parallel plane light guide plate, and this HM reflects image light. And what is shown to an observer is publicly known (refer to patent documents 1-6).
In the apparatus of Patent Document 1, the image light introduced from one end side of the light guide plate is reflected while passing through a plurality of HMs crossing the light guide plate obliquely and reaches the observer. In the apparatus of Patent Document 2, the image light introduced into the light guide plate propagates while being totally reflected in the light guide plate, is reflected by the outer surface, and then is reflected by a plurality of HMs obliquely crossing the light guide plate. And head to the observer. In the devices of Patent Documents 3 and 4, the image light introduced into the light guide plate propagates while totally reflected in the light guide plate, and is reflected by the surface on the viewer side, and then crosses the light guide plate diagonally. Reflected by the HM and heads toward the observer. At this time, for example, in order to increase efficiency, the reflectance of the light incident on the HM with a large incident angle (50 degrees to 70 degrees) is almost zero, and the light with a small angle (40 degrees or less) is It is set to have a predetermined reflectance. In the apparatus shown in FIG. 1 of Patent Document 5, the image light introduced into the light guide plate propagates through the light guide plate while being totally reflected, is reflected by the surface on the outside world side, is reflected by the HM, and is observed by the observer. Head for. Here, the region where the HM is provided has the same thickness as the light guide plate, and is characterized in that the reflectance of the HM sequentially increases as the distance from the display increases. In the device of Patent Document 6, the image light introduced into the light guide plate propagates while being totally reflected in the light guide plate, is reflected by the surface on the viewer side, and then is reflected by a plurality of HMs to the viewer. Head. Here, the thickness of the region or layer provided with the HM is set to be thinner than the light guide plate, and the image light can be observed without transmitting the HM.

  As another display device, there is one in which a thin micromirror array is attached to one side of a parallel plate-shaped light guide plate (see Patent Document 7). In this apparatus, a scanning beam image source is used to form an image, and the pupil is enlarged in the vertical direction. The scanning light introduced into the light guide plate propagates through the light guide plate and the half mirror array, is reflected by the surface on the outside world side, is reflected by the HM of the half mirror array on the viewer side, and travels toward the viewer.

In the devices described in Patent Documents 1 to 5, since the luminance decreases every time the image light passes through the HM, unevenness occurs in the field of view, and it is not easy to eliminate or suppress this. In order to eliminate such luminance unevenness, for example, when the reflectance of the HM on the back side or the counter-light source side is sequentially increased, the transmittance of the HM decreases correspondingly, and unevenness occurs in outside light (see-through light). End up. Although Patent Document 4 discloses a method for avoiding gaps and overlap between HMs (see FIG. 15 and the like), these methods are also caused by video light passing through the HM several other times. It can be said that it is meaningful to solve serious problems such as uneven brightness of image light and unevenness of external light.
In the apparatus described in Patent Document 6, since the thickness of the reflection unit formed by arranging the HMs is thinner than the light guide, the light reaches the HM on the back side without passing through other HMs. There is no unevenness in the amount of light. However, in the reflection unit, an HM unit having two small surfaces as a set is arranged, and the image light is reflected twice by the HM, so that the reflection efficiency tends to decrease.
Even in the apparatus described in Patent Document 7, the beam bundle is divided by HM in order to widen the width of the beam bundle. As the image light propagates to the back side, the luminance decreases and unevenness occurs in the field of view. It is not easy to eliminate or suppress this.

Japanese Patent Laid-Open No. 3-15815 JP 2013-210633 A JP 2010-164988 A US Pat. No. 7,724,443 International Publication No. WO2007 / 062098 JP 2012-88588 A International Publication WO2009 / 009268

  The present invention has been made in view of the above-described background art, and provides a light guide device that hardly causes unevenness in image light and external light while ensuring the luminance of the image light, and a virtual image display device incorporating the light guide device. Objective.

  In order to achieve the above object, a light guide device according to the present invention is provided on one end side of a light guide body having a pair of faces that are opposed to and extend substantially parallel to the observer side and the outside world side. And a light emitting part provided on the other end side of the light guide. The light emitting part is directed toward the observer side by reflecting the image light reflected on the external side of the light guide. A plurality of mirrors are arranged to have a reflecting unit, and the plurality of mirrors are inclined toward the incident part side toward the outside, and the arrangement interval of the plurality of mirrors is from the incident side close to the incident part to the non-incident side. From this point, the mirror changes so that the plurality of mirrors are connected substantially continuously with the eye point as a reference. Here, the eye point means the position of the exit pupil set in the light guide device, and the exit pupil is assumed to be an observer's eye, and image light with various angles of view emitted from the exit unit. Means the place where When the eye point has a spread, the center of the eye point may be used as a reference.

According to the above light guide device, the arrangement interval of the plurality of mirrors changes from the incident side to the non-incident side so that the plurality of mirrors are connected substantially continuously with the eye point as a reference. The mirrors are arranged substantially uniformly in front of the eye point in a substantially unbroken state. That is, when the observer's eyes are arranged at the eye point, the plurality of mirrors constituting the reflection unit are arranged substantially uniformly in a state where there is almost no break in front of the line of sight. Thereby, when observing external light etc., it can prevent that the stripe-shaped nonuniformity extended along a mirror is observed.
In the light guide device, since the image light reflected on the external side of the light guide is set so that the image light incident on the reflection unit is directed to the viewer side, the image light is However, it is possible to adopt a configuration in which only the mirror incident at or near the position where the light enters the emission part without being reflected by the boundary surface between the light guide and the reflection unit can be used. As a result, the number of times that the image light to be observed passes through the mirror can be reduced to prevent uneven brightness and dimming, and on the other hand, unintentional emission of image light can be prevented and generation of ghost light can be suppressed. .

  In a specific aspect of the present invention, in the light guide device, the arrangement interval of the reflection units gradually increases from the incident side close to the incident portion to the non-incident side. When a plurality of mirrors are uniformly inclined toward the incident side toward the outside, the line of sight extending from the eye point with respect to the mirror or the incident angle to the mirror of the backward light path is relatively on the non-incident side Therefore, by increasing the arrangement interval on the non-incident side, it is possible to ensure a state in which a plurality of mirrors are continuously connected.

  In another aspect of the present invention, the incident part is disposed on the ear side of the observer, and the emission part is disposed on the nose side of the observer. In this case, the image light supply source can be arranged in the portion from the corner of the eye to the ear or in the vicinity thereof, and the virtual image display device incorporating the light guide device can be easily designed to fit the face.

  In still another aspect of the present invention, the plurality of mirrors are arranged without gaps with the eye point as a reference. The influence of the external light on the unevenness is suppressed when the mirrors have the same degree of overlap rather than a slight gap in the mirrors. From this point of view, it is desirable to arrange a plurality of mirrors with no gap based on the eye point.

  In still another aspect of the present invention, the image light of all angles of view is reflected the same number of times inside the light guide and then reflected by a plurality of mirrors to reach the eye point.

  In still another aspect of the present invention, the incident portion has at least one of a curved incident surface and reflecting surface.

  In still another aspect of the present invention, the plurality of mirrors are arranged in parallel. In this case, the angle information is maintained regardless of the incident position on the reflection unit, the formation of the image light is facilitated, and a highly accurate image can be displayed.

  In still another aspect of the present invention, the plurality of mirrors are arranged at an interval or pitch of 0.5 mm to 2.0 mm. By arranging multiple mirrors at the intervals as described above, wavelength dispersion due to image light interference when the interval between the mirrors is relatively narrow, and difference in light transmission when the mirror width is relatively wide This has the effect of suppressing the occurrence of black streaks.

  In still another aspect of the present invention, the angle at which the light used for image formation of the image light is incident on the mirror of the reflection unit gradually decreases from the incident side to the non-incident side. In other words, the angle at which the observed image light is incident on the mirror increases on the incident side or entrance side near the image light source, and the observed image light is incident on the mirror on the side opposite to the image light source or on the far side. The angle to do becomes smaller. In other words, the incident angle to the mirror of the line of sight extending from the eye point to the mirror (corresponding to the actual line of sight of the observer properly wearing the light guide device) gradually decreases from the incident side to the non-incident side. .

  In still another aspect of the present invention, the light beam used for image formation is reflected by a predetermined surface region on the outer side of the light guide and is incident on the reflection unit. In the cross section including the optical axis, The width is reduced by one of the straight optical paths before and after being reflected. In this case, since the light beam used for image formation is once narrowed around the predetermined surface area, it is easy to make the viewing angle relatively wide. In addition, with respect to the cross-sectional direction including the optical axis, the light guide can be thinned to reduce the incident portion, and the projection lens that allows the image light to enter the light guide can be reduced in size, making the projection lens easier to manufacture. be able to.

  In yet another aspect of the present invention, in the cross section including the optical axis, the incident width at which the light bundle used for image formation enters the reflection unit is the incident width at which the light bundle used for image formation enters the predetermined surface area. Wider than. In this way, by making the incident light flux used for image formation incident on the predetermined surface area relatively narrow, the image light is not reflected at the boundary surface between the light guide and the reflection unit, and is directly reflected on the reflection unit. Therefore, it becomes easy to take out the image light from the incident position.

  In still another aspect of the present invention, the plurality of mirrors are constituted by half mirrors. In this case, the see-through view can be facilitated by increasing the transparency of external light.

  In still another aspect of the present invention, the reflection unit is arranged along a surface provided on the observer side of the light guide. In this case, it becomes easy to reflect the image light reflected by the surface of the light guide on the outside side by the plurality of mirrors.

In yet another aspect of the present invention, the arrangement interval of the reflection units is SP, the mirror occupation width is MW, the mirror interval adjustment amount is g, the reflection unit thickness is TI, and the light guide and the reflection unit When the inclination angle is σ, the angle with respect to the optical axis of the optical path extending from the eye point to any point of interest of the reflection unit is ε, and the refractive index of the reflection unit is n, the following relationship is obtained: SP = MW + g
g≈TI × {sin (σ−ε) / √ [n ² −sin ² (σ−ε)]}
Meet. In this case, the arrangement interval of the reflection units can be appropriately set according to the mirror tilt angle and arrangement.

  In yet another aspect of the present invention, the reflection unit is disposed so as to be inclined such that the portion on the non-incident side is relatively closer to the outside than the portion on the incident side. In this case, it becomes easy to reflect the image light reflected by the external surface side of the light guide to the viewer side by the plurality of mirrors.

  In still another aspect of the present invention, the light guide has first and second total reflection surfaces that extend in parallel as a pair of opposing surfaces, and the first and second image lights captured from the incident portion. It is guided by total reflection at the total reflection surface.

  In still another aspect of the present invention, the surface present in the incident portion is a non-axisymmetric curved surface. By using a non-axisymmetric curved surface in this way, the degree of freedom in design increases and good optical performance can be realized.

  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 unevenness of an observed image and external light and to observe a high-quality image.

(A) is sectional drawing which shows the virtual image display apparatus which concerns on 1st Embodiment, (B) is a reverse view of a light guide device. It is a figure explaining the optical path of the image light in a light guide device etc. in the section containing an optical axis. It is the elements on larger scale explaining the arrangement | positioning of the mirror in a reflection unit, or the change of an optical path, and respond | corresponds to the front direction of eyes. It is the elements on larger scale explaining the arrangement | positioning of the mirror in a reflection unit, and the change of an optical path, and respond | corresponds to a near direction with respect to the front of eyes. It is a figure explaining the example of 1 production of a reflection unit. It is sectional drawing explaining the modification in the emission side of the optical path of image light. (A) is sectional drawing explaining another modification in the emission side of the optical path of image light, (B) is explanatory drawing to which a part of (A) was expanded. It is a figure explaining the virtual image display apparatus which concerns on 2nd 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.

[1A. Structure of light guide device and virtual image display device]
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. 1A corresponds to the AA cross section of the light guide device 20 illustrated in FIG.

  The virtual image display device 100 allows an observer to recognize a video 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 left eye is shown here, and the illustration for the right eye is omitted. The virtual image display device 100 as a whole has, for example, an appearance (not shown) like general glasses.

  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 the light source 14 to form video light GL to be a moving image or other display target. The projection lens 12 functions as a collimating lens that makes the image light GL emitted from each point on the liquid crystal device 11 in the vertical y direction substantially parallel, and cooperates with a part of the light guide device 20 in the horizontal xz cross section. Works as a collimating lens. 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 has a flat portion, emits the image light GL formed by the image forming device 10 as virtual image light toward the observer's eye EY, and outputs the external light OL corresponding to the external image. Permeate substantially as it is. The light guide device 20 includes an incident portion 21 that captures image light, a parallel light guide 22 for guiding light, and an emission portion 23 that extracts image light. In the case of this embodiment, the incident part 21 is arrange | positioned at an observer's ear | edge side, and the injection | emission part 23 is arrange | positioned at an observer's nose side. The parallel light guide 22 and the main body of the incident portion 21 are an integrated product molded from a resin material having high light transmittance. In the case of the first embodiment, the optical path of the video light GL that passes through the light guide device 20 is composed of one type of optical path that is reflected the same number of times, and is not a type that combines a plurality of types of optical paths.
The parallel light guide 22 is disposed to be inclined with respect to the optical axis AX with respect to the eye EY of the observer, and the normal direction Z is inclined by an angle σ with respect to the optical axis AX. . In this case, the parallel light guide 22 can be arranged along the face curve, but the normal line of the parallel light guide 22 has an inclination with respect to the optical axis AX. As described above, when the normal line of the parallel light guide 22 is inclined by the angle σ with respect to the x direction parallel to the optical axis AX, the image light GL0 on and near the optical axis AX emitted from the reflection unit 30 is light The angle σ is formed with respect to the normal line of the exit surface OS.

The incident portion 21 includes a light incident surface IS that captures the video light GL from the image forming apparatus 10 and a reflective surface RS that reflects and guides the captured video light GL into the parallel light guide 22. The light incident surface IS is formed of a concave curved surface 21b on the projection lens 12 side, and the curved surface 21b also has a function of totally reflecting the image light GL reflected by the reflecting surface RS on the inner surface side. The reflecting surface RS is formed from a concave curved surface 21a on the projection lens 12 side. That is, the reflective surface RS is formed by forming a film such as aluminum vapor deposition on the curved surface 21a, reflects the video light GL incident from the light incident surface IS, bends the optical path in a predetermined direction, and the curved surface 21b The image light GL reflected by the RS is totally reflected on the inner side, and the optical path is bent in a predetermined direction. That is, the incident part 21 reliably couples the video light GL into the parallel light guide 22 by bending the video light GL incident from the light incident surface IS by two reflections.
Note that the curved surface 21b and the curved surface 21a are not limited to spherical surfaces or aspheric surfaces, and may be non-axisymmetric curved surfaces. Thereby, the optical performance of the light guide device 20 can be improved.

The parallel light guide 22 is a flat plate portion that is parallel to the y axis and inclined with respect to the z axis, and is also referred to as a light guide. The parallel light guide (light guide) 22 is formed of a light transmissive resin material or the like, and has a pair of parallel planes 22a and 22b. Since both the planes 22a and 22b are parallel planes, no enlargement or focus shift occurs with respect to the external image. Further, the one flat surface 22a on the + z side or the Z side functions as a total reflection surface that totally reflects the image light from the incident portion 21, and has a role of guiding the image light to the emission portion 23 with a small loss. The + z side plane 22a is disposed on the outside side of the parallel light guide 22 and functions as a first total reflection surface, and is also referred to as an outside side surface in this specification. In addition, the −z side plane 22b is also referred to as an observer side surface in the present specification. The back plane (observer side face) 22 b extends to one end of the emitting portion 23. Here, an extended plane of the back side plane 22 b is a boundary surface IF between the parallel light guide 22 and the emitting portion 23.
In the parallel light guide 22, the image light GL reflected on the inner side of the reflection surface RS or the light incident surface IS of the incident portion 21 is incident on the plane 22 a which is a total reflection surface, and is totally reflected here, and is guided by the light guide device. It is led to the back side of 20, that is, the + x side or the X side where the injection portion 23 is provided.
The parallel light guide 22 has a termination surface ES as a side surface that defines an end surface on the + x side or the X side in the outer shape of the light guide device 20. Further, the parallel light guide 22 has an upper end surface TP and a lower end surface BP as upper and lower surfaces that define an end surface on the ± y side.

  As shown in FIG. 2, the emission portion 23 is formed in a layered manner on the extension along the back plane 22 b on the back side (+ X side) of the parallel light guide 22, or along the boundary surface IF. It is formed in layers. The emission unit 23 reflects the incident video light GL at a predetermined angle when passing the video light GL totally reflected by the predetermined surface region FR on the external surface side (total reflection surface) 22a of the parallel light guide 22. And bent to the light exit surface OS side. Here, the image light GL that first enters the emission unit 23 without passing through the emission unit 23 so far is an extraction target as virtual image light. That is, even if there is light reflected by the inner surface of the light exit surface OS or the boundary surface IF in the light emitting portion 23, this is not used as image light. The emitting unit 23 includes a reflection unit 30 in which a plurality of transmissive mirrors (that is, a plurality of half mirrors) are arranged. The detailed structure thereof will be described in detail later with reference to FIG.

Since the light guide device 20 has the above-described structure, the image light GL emitted from the image forming device 10 and incident on the light guide device 20 from the light incident surface IS is bent by the incident portion 21 by a plurality of reflections. The light is totally reflected in the predetermined surface region FR of the flat surface 22a of the parallel light guide 22 and travels substantially along the optical axis AX. The video light GL reflected by the predetermined surface region FR of the flat surface 22a on the + z side or the + Z side is incident on the emission unit 23. At this time, the width in the longitudinal direction of the predetermined surface region FR is narrower than the width in the longitudinal direction of the injection portion 23 in the XY plane. That is, the incident width at which the light beam of the video light GL is incident on the emitting portion 23 (or the reflection unit 30) is wider than the incident width at which the light beam of the video light GL is incident on the predetermined surface region FR. Thus, by relatively narrowing the incident width at which the light bundle of the image light GL enters the predetermined surface region FR, interference of the optical path is less likely to occur, and the boundary surface IF is not used for light guiding (that is, It is easy to directly enter the image light GL from the predetermined surface area FR into the emission unit 23 or the reflection unit 30 without reflecting the image light GL at the boundary surface IF. The image light GL incident on the emission part 23 is in a state where it can be taken out by being bent at an appropriate angle in the emission part 23 or the reflection unit 30, and finally emitted from the light emission surface OS. The image light GL emitted from the light exit surface OS enters the observer's eye EY as virtual image light. The virtual image light forms an image on the retina of the observer, so that the observer can recognize the video light GL based on the virtual image.
Here, the angle at which the video light GL used for image formation is incident on the emitting portion 23 increases as the distance from the incident portion 21 on the light source side increases. In other words, the video light GL having a large inclination with respect to the Z direction or the optical axis AX parallel to the outer surface side plane 22a is incident on the back side of the emission unit 23 and is bent at a relatively large angle. On the front side, image light GL having a small inclination with respect to the Z direction or the optical axis AX is incident and bent at a relatively small angle.

[1B. (Optical path of image light)
Hereinafter, the optical path of the image light will be described in detail. As shown in FIG. 2, among the image lights respectively emitted from the emission surface 11a of the liquid crystal device 11, a component emitted from the central portion of the emission surface 11a indicated by a broken line is defined as image light GL0, and is indicated by a one-dot chain line in the drawing. The component emitted from the left side (−x side near + z) of the periphery of the emission surface 11a shown is the image light GL1, and the right side (near −z side) of the periphery of the emission surface 11a shown by the two-dot chain line in the figure. The component emitted from the (+ x side) is defined as video light GL2. Among these, the optical path of the image light GL0 extends along the optical axis AX.

The main components of the image lights GL0, GL1, and GL2 that have passed through the projection lens 12 are incident from the light incident surface IS of the light guide device 20, and then pass through the parallel light guide 22 through the incident portion 21 and are emitted. 23.
Specifically, out of the image lights GL0, GL1, and GL2, the image light GL0 emitted from the central portion of the emission surface 11a is bent at the incident portion 21 and coupled into the parallel light guide 22 and then standardized. The incident light enters the predetermined surface area FR of the one plane 22a at the reflection angle θ0, is totally reflected, passes through this without being reflected by the boundary surface IF between the parallel light guide 22 and the emitting portion 23 (or the reflection unit 30), The light directly enters the central portion 23 k of the emission part 23. The image light GL0 is reflected at a predetermined angle at the portion 23k, and is parallel to the optical axis AX direction (the direction of the angle σ with respect to the Z direction) inclined from the light exit surface OS to the XY plane including the light exit surface OS. It is emitted as a light beam.
Further, the image light GL1 emitted from one end side (−x side) of the emission surface 11a is bent by the incident portion 21 and coupled into the parallel light guide 22, and then the one plane 22a at the maximum reflection angle θ1. Is incident on the predetermined surface area FR and is totally reflected, passes through the parallel light guide 22 and the emission part 23 (or the reflection unit 30) without being reflected by the boundary surface IF, and the back side of the emission part 23 ( The light is reflected at a predetermined angle at the portion 23h on the + X side) and is emitted as a parallel light flux from the light exit surface OS toward the predetermined angle direction. The exit angle at this time (corresponding to the angle γ1 when the optical axis AX is used as a reference) is relatively large to be returned to the incident portion 21 side.
On the other hand, the image light GL2 emitted from the other end side (+ x side) of the emission surface 11a is bent at the incident portion 21 and coupled into the parallel light guide 22, and then one plane 22a with the minimum reflection angle θ2. Is incident on the predetermined surface region FR and is totally reflected, passes through the parallel light guide 22 and the exit portion 23 (or the reflection unit 30) without being reflected by the boundary surface IF, and enters the entrance portion ( -X side) portion 23m is reflected at a predetermined angle, and is emitted as a parallel light flux from the light exit surface OS toward the predetermined angle direction. The exit angle at this time (corresponding to the angle γ2 with the optical axis AX as a reference) is relatively small to the extent that it is returned to the incident portion 21 side.
That is, the image lights GL0, GL1, and GL2 having various angles of view gather at the eye point EP assuming the observer's eye EY. The eye point EP means the position of the exit pupil set in the light guide device 20, and if the eye EY is placed here, a bright and clear image can be obtained.
Note that the video lights GL0, GL1, and GL2 have been described on behalf of part of the entire light beam of the video light GL, but the light beam components that make up the other video light GL are similar to the video light GL0 and the like. Since these are guided and emitted from the light exit surface OS, illustration and description thereof are omitted.

Here, as an example of the value of the refractive index n of the transparent resin material used for the incident portion 21 and the parallel light guide 22, when n = 1.4, the value of the critical angle θc is θc≈45.6 °. Become. The minimum reflection angle θ2 among the reflection angles θ0, θ1, and θ2 of the image lights GL0, GL1, and GL2 is set to a value larger than the critical angle θc, so that the necessary image light can be obtained within the parallel light guide 22. The total reflection condition on the plane 22a can be satisfied.
The image light GL0 for the center is incident on the portion 23k of the emission unit 23 at the elevation angle φ0 (= 90 ° −θ0), and the image light GL1 for the periphery is emitted at the elevation angle φ1 (= 90 ° −θ1). The image light GL2 for the periphery is incident on the portion 23m of the emission part 23 at an elevation angle φ2 (= 90 ° −θ2). Here, a relationship of φ2>φ0> φ1 is established between the elevation angles φ0, φ1, and φ2, reflecting the magnitude relationship of the reflection angles θ0, θ1, and θ2. That is, the incident angle ι (see FIGS. 3 and 4) of the reflection unit 30 to the half mirror 31 is gradually increased in the order of the portion 23m corresponding to the elevation angle φ2, the portion 23k corresponding to the elevation angle φ0, and the portion 23h corresponding to the elevation angle φ1. Becomes smaller. In other words, the incident angle ι to the half mirror 31 or the reflection angle at the half mirror 31 (which is also the incident angle of the line of sight when considering the backward light path) decreases as the distance from the incident portion 21 increases.

The overall behavior of the light bundle of the image light GL that is reflected by the external plane 22a of the parallel light guide 22 and travels toward the exit portion 23 will be described. In the cross section including the optical axis AX, the width of the light bundle of the image light GL is narrowed by any one of the front and rear straight light paths P1 and P2 reflected by the predetermined surface region FR on the outside of the parallel light guide 22. Specifically, the light beam of the image light GL is located at a position in the XZ cross section including the optical axis AX, in the vicinity of the predetermined plane region FR, that is, in the vicinity of the boundary between the straight light paths P1 and P2 and over both the straight light paths P1 and P2. As a whole, the width is narrowed and the beam width is narrowed. As a result, the beam bundle of the image light GL is narrowed in front of the emission unit 23, and it becomes easy to make the viewing angle in the horizontal direction relatively wide.
In the example shown in the figure, the beam width is narrowed and the beam width is narrowed at a position where the light beam of the image light GL straddles both the straight light paths P1 and P2, but only one side of the straight light paths P1 and P2 is used. The width may be narrowed to narrow the beam width.

[1C. (Structure of the emission part and bending of the optical path by the emission part)
Hereinafter, the structure of the emission unit 23 and the bending of the optical path of the image light by the emission unit 23 will be described in detail with reference to FIGS. 3 is an enlarged view of the emission part 23 in the front direction of the eye EY, and FIG. 4 is an enlarged view of the emission part 23 in a direction inclined closer to the ear than the front of the eye EY.

  First, the structure of the injection unit 23 will be described. The emission unit 23 includes a reflection unit 30 in which a plurality of half mirrors 31 that respectively reflect the image light GL are arranged. The reflection unit 30 is a rectangular plate-like member extending along an XY plane inclined by an angle σ with respect to the optical axis AX, and has a structure in which a large number of thin strip-like half mirrors 31 are embedded so as to form a stripe pattern. That is, the reflection unit 30 is configured by arranging a large number of elongated half mirrors 31 extending in the y direction or the Y direction in the direction in which the parallel light guide 22 extends, that is, in the X direction. More specifically, the half mirror 31 has upper and lower portions in a direction extending parallel to the planes 22a and 22b of the parallel light guide 22 shown in FIG. 2 and perpendicular to the X direction in which the half mirrors 31 are arranged. It extends linearly with the y direction or the Y direction as the longitudinal direction. Further, the half mirror 31 is inclined toward the incident portion 21 side toward the outside from the observer side of the parallel light guide 22. More specifically, the half mirror 31 is inclined so that the upper end (+ Z side) rotates counterclockwise with the longitudinal direction (Y direction) as an axis and the YZ plane orthogonal to the planes 22a and 22b as a reference. ing. That is, each half mirror 31 extends in the direction between the −X direction and the + Z direction as viewed in the XZ section. Further, all the half mirrors 31 are precisely arranged parallel to each other.

  The reflection unit 30 has a structure in which a large number of block members 32 are joined, and the half mirror 31 has a thin film shape sandwiched between a pair of adjacent block members 32. Here, the refractive index of the block member 32 is substantially equal to the refractive index of the parallel light guide 22, but the refractive indexes of the two can be made different. In order to make the refractive indexes of the two different, it is necessary to adjust or correct the angle δ at which the half mirror 31 is inclined. The reflectance of the half mirror 31 with respect to the image light GL is set to be 10% or more and 50% or less in the assumed incident angle range of the image light GL from the viewpoint of facilitating observation of the external light OL by see-through. The reflectivity for the video light GL of the half mirror 31 of the specific embodiment is set to 20%, for example, and the transmittance for the video light GL is set to 80%, for example.

  Here, the thickness TI of the reflection unit 30 (that is, the width of the half mirror 31 in the Z-axis direction) is set to about 0.7 mm to 3.0 mm. In addition, the thickness of the parallel light guide 22 that supports the reflection unit 30 is, for example, about several mm to 10 mm, and preferably about 4 mm to 6 mm. If the thickness of the parallel light guide 22 is sufficiently larger than the thickness of the reflection unit 30, it is easy to reduce the incident angle of the image light GL to the reflection unit 30 or the boundary surface IF, and the image light GL is taken into the eye EY. It is easy to suppress the reflection at the half mirror 31 at a position that is not present. On the other hand, when the thickness of the parallel light guide 22 is relatively thin, the parallel light guide 22 and the light guide device 20 can be easily reduced in weight.

  The half mirrors 31 are all set to the same inclination, and can form an inclination angle δ of, for example, about 48 ° to 70 ° clockwise with respect to the plane 22b on the viewer side of the parallel light guide 22. Has an inclination angle δ of 60 °, for example. Here, it is assumed that the elevation angle φ0 of the video light GL0 is set to, for example, 30 °, the elevation angle φ1 of the video light GL1 is set to, for example, 22 °, and the elevation angle φ2 of the video light GL2 is set to, for example, 38 °. In this case, the image light GL1 and the image light GL2 enter the observer's eye EY at an angle γ1 = γ2≈12.5 ° with the optical axis AX as a reference.

  As a result, a component having a relatively large total reflection angle (image light GL1) in the image light GL is mainly incident on the + X side portion 23h side of the reflection unit 30, which is the non-incident side, and the total reflection angle is compared. Angle when the image light GL is collected on the observer's eye EY as a whole when a relatively small component (image light GL2) is mainly incident on the −X side portion 23m side of the exit portion 23. It becomes possible to take out efficiently in a state. Since the video light GL is taken out with such an angle relationship, the light guide device 20 can pass the video light GL in the reflection unit 30 only once, as a rule, without passing it multiple times. Can be extracted as virtual image light with little loss.

  Note that the unused light that passes through the half mirror 31 of the reflection unit 30 may be incident again on the external surface side plane 22a. 23h or further on the heel side and can enter the outside of the effective area, and the possibility of entering the eye EY is reduced.

  In addition, in the central side and back side portions 23k and 23h of the reflection unit 30, a part of the image light GL passes through the half mirror 31 a plurality of times (specifically, one reflection and one or more transmissions). Pass through). In this case, the number of times of passing through the half mirror 31 is plural, but since the reflected light from the plural half mirrors 31 respectively enters the observer's eye EY as the image light GL, the loss of light quantity does not become so large.

Hereinafter, with reference to FIGS. 3 and 4 and the like, the arrangement interval of the plurality of half mirrors 31 constituting the reflection unit 30 will be described.
The arrangement interval SP in the arrangement direction of the plurality of half mirrors 31 or the Z direction in which the reflection unit 30 extends is set on the assumption that the eye EY of the observer is observed from the incident side close to the incident portion 21 to the counter incident side close to the end surface ES. The plurality of half mirrors 31 are changed so as to be connected substantially continuously with reference to the line of sight EL extending from the center EPa of the eye point EP (see FIG. 2) to an arbitrary point of interest. As a result, the arrangement interval SP of the plurality of half mirrors 31 in the reflection unit 30 gradually increases from the incident side close to the incident portion 21 to the non-incident side. Specifically, as shown in FIG. 3, the arrangement interval SP at the front position where the line of sight EL extends in the front direction (center portion 23k of the reflection unit 30) is in a direction inclined toward the ear as shown in FIG. It is relatively wider than the array interval SP at the incident side position where the line of sight EL extends (the entrance side portion 23m of the reflection unit 30). The specific arrangement interval SP of the half mirrors 31 is within a range of about 0.5 mm to 2.0 mm in each part, although there is a difference in size within the reflection unit 30.
The line-of-sight EL described above corresponds to the actual line of sight of the observer wearing the virtual image display device 100, but it goes without saying that it is a kind of virtual that does not require an actual observer. . Further, the eye point EP has a spread that is larger than the diameter of the pupil of the eye EY in the direction perpendicular to the optical axis AX in practice, but when the eye point EP has such a spread, the center EPa of the eye point EP is used as a reference. That's fine. That is, the line of sight EL is a line (an optical path obtained by reversing the video light GL) extending from the center EPa of the eye point EP toward a point on the arbitrary half mirror 31 (a point of interest).

The arrangement interval SP of the half mirrors 31 will be considered in detail with reference to FIG. As described above, when the thickness of the reflection unit 30 is TI and the inclination angle of the reflection unit 30 is σ, the angle with respect to the optical axis AX of the optical path extending from the eye point EP to an arbitrary point of interest in the reflection unit 30 (that is, The angle of view line EL) is ε, the occupied width of the half mirror 31 is MW, the distance adjustment amount of the half mirror 31 is g, and the refractive index of the reflection unit 30 is n. Here, the angle ε of the line of sight EL is the same as the angle of the line of sight EL with respect to the optical axis direction line AX ′ parallel to the optical axis AX, and the eye EY is closer to the ear than the front direction and the point of interest is the optical axis. If it is on the -x side of AX, it is a positive value (in the case of illustration), and if the eye EY is closer to the nose than the front direction and the point of interest is on the + x side of the optical axis AX, it is a negative value. . The occupied width of the half mirror 31 is MW, which means the width of the half mirror 31 when the half mirror 31 is viewed from the normal direction of the reflection unit 30. In addition, when the line of sight EL is inclined with respect to the normal direction of the reflection unit 30, the distance adjustment amount g of the half mirror 31 is the half mirror 31 focused on the observer end e <b> 2 of the half mirror 31 adjacent to the incident side. This is a value for matching with the outside world edge e1. That is, the arrangement interval SP of the half mirrors 31 is expressed by the following relational expression (1).
SP = MW + g (1)
Given in. As shown in FIG. 4, when the line of sight EL moves slightly toward the nose relative to the normal direction of the reflection unit 30 as a reference (front), the interval adjustment amount g is a positive value. Although detailed illustration is omitted, in the central portion 23k (corresponding to FIG. 3) of the reflection unit 30, the interval adjustment amount g is a relatively large positive value, and in the rear portion 23h of the reflection unit 30, The interval adjustment amount g becomes a larger positive value.

ここで、幾何的な関係からｇ＝ＴＩ×ｔａｎ（ν２）なる関係が成り立っており、間隔調整量ｇは、以下の関係式（２）
ｇ＝ＴＩ×ｔａｎ（ν２） … （２）
で与えられ、以下の関係式（２）'に置き換えることができる。
ｇ＝ＴＩ×｛ｓｉｎ（σ−ε）／√［ｎ^２−ｓｉｎ^２（σ−ε）］｝
… （２）' Considering the optical path based on the eye EY, when the line of sight EL passes through the external edge e1 of the half mirror 31 of interest and the observer end e2 of the half mirror 31 adjacent to the incident side, both the half mirrors 31 are continuous. Looks like they are connected. If the angle of incidence of the line of sight EL from the observation side to the light exit surface OS is ν1, and the angle of incidence of the line of sight EL from the light exit surface OS to the outside is ν2, both angles ν1 and ν2 are normal to the light exit surface OS. Is the angle formed by the line of sight EL. The incident angle ν1 is represented by a difference σ−ε between the inclination angle σ of the reflection unit 30 and the inclination angle ε of the line of sight EL. The exit angle ν2 is given by n × sin (ν2) = sin (ν1) using the incident angle ν1 according to Snell's law. That is, the angle ν2 can be expressed as follows.

Here, the relationship g = TI × tan (ν2) is established from the geometric relationship, and the interval adjustment amount g is expressed by the following relational expression (2).
g = TI × tan (ν2) (2)
And can be replaced by the following relational expression (2) ′.
g = TI × {sin (σ−ε) / √ [n ² −sin ² (σ−ε)]}
(2) '

The above is the case where the plurality of half mirrors 31 constituting the reflection unit 30 have no overlap or break with respect to the line of sight EL in the X direction, that is, the plurality of half mirrors 31 have no overlap or gap with respect to the line of sight EL. Although the case where it arrange | positions is demonstrated, if it is slight overlap and a clearance gap in the range which is not conspicuous, it can be said that the some half mirror 31 is connected substantially continuously. That is, the following relational expression (3)
g≈TI × {sin (σ−ε) / √ [n ² −sin ² (σ−ε)]}
(3)
Or the following relational expression (4)
SP ≒ MW + TI x tan (ν2)
MW + TI × {sin (σ−ε) / √ [n ² −sin ² (σ−ε)]}
(4)
If it is satisfied, it is enough. In particular, even if there is an overlap between the adjacent half mirrors 31 with respect to the direction of the line of sight EL, if there is no gap, unevenness observed with respect to the external light OL can be suppressed to a relatively small amount. On the other hand, when there is a gap between the adjacent half mirrors 31 with reference to the direction of the line of sight EL, it is desirable to make this gap as narrow as possible from the viewpoint of preventing occurrence of unevenness.

  With reference to FIG. 5, an example of the manufacturing method of the reflection unit 30 is demonstrated. A large number of glass plates 91 that are parallel flat plates made of glass are prepared in advance. The thickness of each glass plate 91 takes into consideration the arrangement interval SP of the half mirrors 31. The thickness of the glass plate 91 corresponding to the central portion 23 k of the reflection unit 30 is used as the standard, and the incident side or the entrance. The glass plate 91 corresponding to the side portion 23m is relatively thin, and the glass plate 91 corresponding to the counter-incident side or back side portion 23h is relatively thick. In the case of FIG. 5, the lower glass plate 91 is thin and the upper glass plate 91 is thick. After that, a large number of element plates 90 are prepared by forming a reflective film 92 that is a metal reflective film or a dielectric multilayer film on one surface of a large number of prepared glass plates 91. Thereafter, the formed many element plates 90 are stacked while being bonded with an adhesive in order of thickness, and the whole is cut obliquely along the cutting lines C1 and C2. Thus, the reflection unit 30 has a structure in which a half mirror 31 made of a metal reflection film or a dielectric multilayer film is sandwiched between block members 32 that are elongated prism pieces obtained by obliquely dividing a parallel plate, and is half-finished on one end side. It is possible to obtain a mirror in which the arrangement interval of the mirror 31 is narrow and the arrangement interval of the half mirror 31 is wide on the other end side. The reflection unit 30 is attached to an appropriate position on the viewer side of the parallel light guide 22 via an adhesive, and is fixed by curing the adhesive.

[1D. Summary of First Embodiment]
According to the light guide device 20 of the first embodiment described above, the arrangement interval SP of the plurality of half mirrors 31 is a plurality of half mirrors on the basis of the eye point EP from the incident side close to the incident part 21 to the counter incident side. Since 31 are changed so as to be connected substantially continuously, the plurality of half mirrors 31 constituting the reflection unit 30 are arranged substantially uniformly in front of the eye point EP without any breaks or overlaps. That is, when the eye EY of the observer is arranged at the eye point EP, the plurality of half mirrors 31 are arranged substantially uniformly in a state where there is no cut or overlap in front of the line of sight EL. Thereby, when observing the external light OL, streaky unevenness extending along the half mirror 31 can be prevented from being observed.
In the light guide device 20 of the present embodiment, the image light GL incident on the reflection unit 30 is reflected by reflecting the image light GL reflected by the external surface side plane 22a of the parallel light guide 22 to the observer's eyes EY. Since the image light GL is not reflected by the boundary surface IF between the parallel light guide 22 and the reflection unit 30, the position where the image light GL enters the emission unit 23 or the reflection unit 30 or the position thereof is set. It only passes through the nearby half mirror 31. In other words, in the light guide device 20 of the present embodiment, the reflection unit 30 is thinner than about half of the parallel light guide 22 in the optical axis AX direction, and the half mirror 31 constituting the reflection unit 30 is a parallel light guide. In addition to being inclined so as to be closer to the incident portion 21 on the outside side than the viewer side of 22, at least a portion close to the incident portion 21 of the reflection unit 30 is disposed on the observer side of the parallel light guide 22. As a result, the inclination of the image light GL to be observed with respect to the optical axis AX is relatively increased on the far side away from the incident portion 21 in the reflection unit 30, and the image light GL from the incident portion 21 is reflected by the reflection unit 30. It is easy to directly enter the target location. As a result, the number of times that the image light GL to be observed passes through the half mirror 31 can be reduced to prevent luminance unevenness and dimming. On the other hand, unintentional emission of the image light GL can be prevented and ghost light can be generated. Can be suppressed.

FIG. 6 is a diagram for explaining a modification example regarding the structure and the like of the emission unit 23 in the light guide device 20 according to the first embodiment. In this case, the thickness of the reflection unit 30 is thick on the incident side close to the incident portion 21 and thin on the non-incident side far from the incident portion 21. On the side far from the incident portion 21, the elevation angle φ ₂ of the video light GL ₂ is small. By making the reflection unit 30 thin, it is possible to suppress an increase in the number of times of passing through the half mirror 31. Here, it is desirable that the observation-side light exit surface OS of the reflection unit 30 and the external light-side plane 22 a of the parallel light guide 22 are parallel to each other. That is, the part adjacent to the reflection unit 30 among the parallel light guides 22 has a slight wedge angle in principle.
Even when the thickness of the reflection unit 30 varies depending on the position in the X direction as described above, the relational expression (2) of the interval adjustment amount g for the half mirror 31 and the relational expression (4) of the arrangement interval SP for the half mirror 31. The same applies. That is, the thickness TI of the reflection unit 30 in the relational expressions (2) to (4) may be treated as a variable that increases linearly according to the position X, for example.

FIG. 7A is a diagram for explaining another modified example regarding the structure and the like of the emission unit 23 in the light guide device 20 according to the first embodiment. In this case, the reflection unit 30 provided in the emission part 23 is incorporated in an inclined state. Specifically, the reflection unit 30 is inclined so that the far side portion 23 h far from the incident portion 21 is closer to the outside than the front portion 23 m close to the incident portion 21. That is, the entrance surface 30a and the exit surface 30b of the reflection unit 30 are appropriately inclined counterclockwise by less than 90 ° with respect to the plane 22b of the parallel light guide 22.
Note that the emission unit 23 includes a prism member 23f having a wedge-shaped cross section joined to the emission surface 30b of the reflection unit 30 on the opposite side of the parallel light guide 22 with the reflection unit 30 interposed therebetween. As a result, the plane 22a on the outside side of the parallel light guide 22 and the light exit surface OS facing the plane 22a are parallel to enable natural observation of the outside light OL. Even if the reflection unit 30 is arranged in an inclined state, if the angle condition is the same as in the example shown in FIGS. 2 to 4, a plurality of video light GLs reflected by the plane 22 a on the external side of the parallel light guide 22 are provided. Can be reflected by the half mirror 31 and pass through the light exit surface OS on the observation side, and a virtual image can be formed as in the case of FIG.

この角ν２を利用すれば、間隔調整量ｇは、既述の関係式（２）
ｇ＝ＴＩ×ｔａｎ（ν２） … （２）
で与えられる。 FIG. 7B is an enlarged view of a part shown in FIG. In this case, since the reflection unit 30 is arranged to be inclined with respect to the parallel light guide 22, the angular relationship is changed, and the arrangement interval SP of the half mirrors 31 is a modification of the case shown in FIGS. It is necessary to. Here, assuming that the thickness of the reflection unit 30 is TI, the inclination angle of the parallel light guide 22 is σ, and the wedge angle of the prism member 23f is ρ, the optical axis AX of the optical path extending from the eye point EP to an arbitrary point of interest An angle with respect to (that is, an angle of the line of sight EL) is ε, an occupied width of the half mirror 31 is MW, and an interval adjustment amount of the half mirror 31 is g. Further, the refractive index of the reflection unit 30 is n, and the refractive index of the prism member 23f is n1. In this case, the arrangement interval SP of the half mirrors 31 is the same relational expression (1) as that when the reflection unit 30 is not inclined.
SP = MW + g (1)
Given in. When the incident angle of the line of sight EL across the light exit surface OS is ν3 and the exit angle is ν4, and the incident angle of the line of sight EL across the exit surface 30b is ν1 and the exit angle is ν2, the angles ν3 and ν4 Snell's law holds between the angle and the angles ν1 and ν2. That is, the angle ν2 can be expressed as follows, although detailed description is omitted.

If this angle ν2 is used, the interval adjustment amount g can be expressed by the relational expression (2) described above.
g = TI × tan (ν2) (2)
Given in.

The above is the case where the plurality of half mirrors 31 constituting the reflection unit 30 have no overlap and no break with respect to the X direction with respect to the eye point EP or the line of sight EL, that is, the plurality of half mirrors 31 are based on the eye point EP or the line of sight EL. However, a slight overlap or gap within an inconspicuous range is allowed. That is, the following relational expression (4) ′
SP≈MW + TI × tan (ν2) (4) ′
It is enough if is satisfied.

In the first embodiment described above and the modifications thereof, the incident portion 21 is configured by the curved surfaces 21a and 21b, but one or both of them may be configured by a plane. In this case, the portion corresponding to the curved surface 21b can be a plane obtained by extending the plane 22b of the parallel light guide 22.
In addition, the incident portion 21 may be configured such that the image light GL incident from the light incident surface IS is directly coupled to the parallel light guide 22 without being reflected by the inner surface.
Furthermore, the parallel light guide 22 is not limited to a perfect parallel flat plate, and can have a slight curve and a wedge angle. That is, the flat surfaces 22a and 22b of the parallel light guide 22 can be aspherical surfaces or other curved surfaces, or can be formed with an inclination angle with each other. However, when the planes 22a and 22b are curved, diopter and magnification changes occur. In addition, when an inclination is provided between the planes 22a and 22b, chromatic dispersion occurs, so it is desirable that the inclination angle is small.
The manufacturing method of the reflection unit 30 is not limited to what is illustrated in FIG. A resin substrate having a sawtooth-shaped cross section having a plurality of slopes extending in parallel corresponding to the slope of the sawtooth is prepared, half mirrors 31 are formed on the slopes, and the slope of the resin substrate is formed. The optical structure shown in FIG. 3 or the like can also be obtained by filling the groove containing the resin with a curable liquid or solid resin.

[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. 8, the light guide device 20 of the present embodiment includes an incident portion 21 that takes in image light, a parallel light guide 22 for guiding light, and an emission portion 23 that takes out image light. Thus, it has basically the same structure as the light guide device 20 of the first embodiment. However, in the case of the second embodiment, the optical path of the video light GL passing through the light guide device 20 includes a plurality of types of optical paths having different numbers of reflections, and is a type that combines these types of optical paths. Further, in the case of the second embodiment, the parallel light guide 22 is arranged in parallel to the xy plane without being inclined.

  In addition, although detailed description is abbreviate | omitted for the reflection unit 30 which comprises the injection | emission part 23, it has the structure similar to the case of 1st Embodiment, has the structure which joined many block members 32, The half mirror 31 is a thin film sandwiched between a pair of adjacent block members 32. The arrangement interval SP of the plurality of half mirrors 31 is substantially the same as that of the plurality of half mirrors 31 on the basis of the observer's eye point EP or line of sight EL from the incident side close to the incident portion 21 to the counter incident side close to the end surface ES. It changes so that it may be connected continuously. As a result, the arrangement interval SP of the plurality of half mirrors 31 in the reflection unit 30 gradually increases from the incident side close to the incident portion 21 to the non-incident side.

  Hereinafter, the optical path of the image light will be described. Of the image light respectively emitted from the emission surface 11a of the liquid crystal device 11, the component emitted from the central portion of the emission surface 11a indicated by the broken line is defined as the image light GL0, and the periphery of the emission surface 11a indicated by the alternate long and short dash line in the figure. Of these, the component emitted from the left side (−x side) of the paper surface is the video light GL1, and the component emitted from the right side (+ x side) of the light emission surface 11a indicated by the two-dot chain line in the drawing is the video light GL2. .

The main components of the video lights GL0, GL1, and GL2 that have passed through the projection lens 12 are respectively incident from the light incident surface IS of the light guide device 20, and then reflected by the reflecting surface RS facing the first and second components. Total reflection is repeated at different angles on the planes 22a and 22b corresponding to the total reflection surface.
Specifically, among the image lights GL0, GL1, and GL2, the image light GL0 emitted from the central portion of the emission surface 11a is reflected by the reflection surface RS of the incident portion 21 as a parallel light flux, and then the standard reflection angle θ0. The light enters the plane 22b on the viewer side of the parallel light guide 22 and is totally reflected. Thereafter, the image light GL0 repeats total reflection on the pair of flat surfaces 22a and 22b while maintaining the standard reflection angle θ0. The video light GL0 is totally reflected even times on the planes 22a and 22b, passes through it without being reflected by the boundary surface IF between the parallel light guide 22 and the emitting unit 23 or the reflecting unit 30, and is a central portion of the emitting unit 23. Incident at 23k. The image light GL0 is reflected at a predetermined angle at the portion 23k, and is emitted as a parallel light flux from the light exit surface OS in the optical axis AX direction perpendicular to the xy plane including the light exit surface OS.
Further, the image light GL1 emitted from one end side (−x side) of the emission surface 11a is reflected by the reflection surface RS of the incident portion 21 as a parallel light beam, and then observed by the parallel light guide 22 at the maximum reflection angle θ1. The light enters the person-side plane 22b and is totally reflected. The image light GL1 is totally reflected a plurality of times on the planes 22a and 22b, passes through the boundary surface IF between the parallel light guide 22 and the emitting unit 23 or the reflecting unit 30, and passes through the inner side of the emitting unit 23. The light is reflected at a predetermined angle at the (+ x side) portion 23h and is emitted as a parallel light flux from the light exit surface OS toward the predetermined angle direction. The exit angle γ1 at this time is such that it is returned to the incident portion 21 side and becomes an acute ray with respect to the + x axis.
On the other hand, the image light GL2 emitted from the other end side (+ x side) of the emission surface 11a is reflected by the reflection surface RS of the incident portion 21 as a parallel light beam, and then observed by the parallel light guide 22 at the minimum reflection angle θ2. The light enters the person-side plane 22b and is totally reflected. The image light GL2 is totally reflected a plurality of times on the planes 22a and 22b, passes through the boundary surface IF between the parallel light guide 22 and the emitting portion 23 or the reflecting unit 30, and passes through the entrance portion of the emitting portion 23. The light is reflected at a predetermined angle at the (−x side) portion 23m, and is emitted as a parallel light flux from the light exit surface OS toward the predetermined angle direction. The exit angle γ2 at this time is such that it is away from the incident portion 21 side, and becomes an obtuse angle ray with respect to the + x axis.
In the above, the total number of reflections until the image lights GL0, GL1, and GL2 reach the emission unit 23 does not necessarily match. In other words, in the illustrated example, the total number of reflections with the image light GL2 is one or more times greater than the total reflection number with the image light GL1, and the total reflection number with respect to the image light GL0 is the total reflection number of both the image lights GL1 and GL2. Including the case where it matches the number of reflections. However, since the light reflection efficiency due to total reflection on the planes 22a and 22b is very high, even if the number of reflections differs between the image lights GL0, GL1 and GL2 as described above, this causes uneven brightness. It rarely occurs. The video lights GL0, GL1, and GL2 are described on behalf of a part of the whole light beam of the video light GL. However, the light beam components constituting the other video light GL are similar to the video light GL0 and the like. Since these are guided and emitted from the light exit surface OS, illustration and description thereof are omitted.

  The image light GL0 for the center is incident on the portion 23k of the emission part 23 at an elevation angle φ0 (= 90 ° −θ0), and the image light GL1 for the periphery is emitted at an elevation angle φ1 (= 90 ° −θ1). The image light GL2 for the periphery is incident on the portion 23m of the emission part 23 at an elevation angle φ2 (= 90 ° −θ2). Here, a relationship of φ2> φ0> φ1 is established between the elevation angles φ0, φ1, and φ2, reflecting the magnitude relationship of the reflection angles θ0, θ1, and θ2. That is, the incident angle of the reflection unit 30 to the half mirror 31 gradually decreases in the order of the portion 23m corresponding to the elevation angle φ2, the portion 23k corresponding to the elevation angle φ0, and the portion 23h corresponding to the elevation angle φ1. In other words, the incident angle to the half mirror 31 or the reflection angle at the half mirror 31 decreases as the distance from the incident portion 21 increases.

  The overall behavior of the light bundle of the image light GL that is reflected by the external plane 22a of the parallel light guide 22 and travels toward the exit portion 23 will be described. In the cross section including the optical axis AX, the width of the light bundle of the image light GL is narrowed by any one of the front and rear straight light paths P1 and P2 reflected by the predetermined surface region FR on the outside of the parallel light guide 22. Specifically, the beam bundle of the image light GL is narrowed as a whole in the straight light path P2 after reflection at the predetermined surface region FR in a cross section including the optical axis AX, and the beam width becomes narrow. As a result, the beam bundle of the image light GL is narrowed in front of the emission unit 23, and it becomes easy to make the viewing angle in the horizontal direction relatively wide.

[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 reflectivities of a large number of half mirrors 31 provided in the reflection unit 30 are matched in principle. However, the reflectivities of these half mirrors 31 can be gradually changed from the incident side close to the incident part 21 to the non-incident side.

  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 plane light 22a, 22b or the curved surface 21b of the parallel light guide 22 is assumed to guide the image light by being totally reflected by the interface with the air without applying a mirror or a half mirror on the surface. The total reflection in the present invention includes reflection formed by forming a mirror coat or a half mirror film on the whole or a part of the planes 22a and 22b. For example, a case where the incident angle of the image light GL satisfies the total reflection condition and a mirror coat or the like is applied to a part of the planes 22a and 22b to reflect substantially all the image light is included.

  In the above description, the parallel light guide 22 is horizontally long in the X direction or the x direction, and the light incident surface IS is positioned on the outer side in the lateral direction of the eye. However, the position of the light incident surface IS is not limited to this. For example, the light incident surface IS may be provided on the upper end surface TP or the lower end surface BP above and below the light guide device 20. In this case, the reflection unit 30 is rotated by 90 ° around the optical axis AX in front of the eyes.

  Although not mentioned above, the upper end surface TP, the lower end surface BP, and the like of the outer peripheral portion that defines the outer shape of the parallel light guide 22 can be used as a black paint application surface or a sandblasted surface. Furthermore, you may perform black coating application | coating or sandblasting to locations other than upper end surface TP and lower end surface BP. Only a part of the upper end surface TP, the lower end surface BP, or the like may be subjected to black coating or sandblasting.

  Moreover, as the half mirror 31 which comprises the reflection unit 30, it is not restricted to what reduces a reflectance suitably, A hologram mirror can be used. The hologram mirror at this time can be a multi-layer type that collectively processes RGB colors, but can also be a single layer film for each color.

  DESCRIPTION OF SYMBOLS 10 ... Image forming apparatus, 11 ... Liquid crystal device, 11a ... Ejection surface, 12 ... Projection lens, 14 ... Light source, 20 ... Light guide device, 21 ... Incident part, 22 ... Parallel light guide, 22a, 22b ... Plane (all Reflective surface), 23 ... Ejecting part, 23h, 23k, 23m ... part, 30 ... Reflecting unit, 31 ... Half mirror, 32 ... Block member, 100 ... Virtual image display device, AX ... Optical axis, EY ... Eye, GL ... Video Light, GL0, GL1, GL2 ... Video light, IS ... Light incident surface, OS ... Light exit surface, RS ... Reflecting surface, IF ... Boundary surface, FR ... Predetermined surface area

Claims (18)

A light guide having a pair of faces facing and extending substantially parallel to the observer side and the external side;
An incident portion provided on one end side of the light guide;
An emission part provided on the other end side of the light guide,
The emission unit includes a reflection unit in which a plurality of mirrors are arranged to be directed toward the observer side by reflecting video light reflected on the outside of the light guide,
The plurality of mirrors are inclined toward the incident part toward the outside,
The light guide device, wherein an array interval of the plurality of mirrors changes from an incident side close to the incident portion to a non-incident side so that the plurality of mirrors are connected substantially continuously with an eye point as a reference.   The light guide device according to claim 1, wherein the arrangement interval of the reflection units gradually increases from an incident side close to the incident portion to a non-incident side.   The light guide device according to claim 2, wherein the incident unit is disposed on an ear side of the observer, and the emitting unit is disposed on a nose side of the observer.   The light guide device according to any one of claims 1 to 3, wherein the plurality of mirrors are arranged without a gap with respect to the eye point.   5. The image light of all angles of view is reflected by the plurality of mirrors after being reflected the same number of times within the light guide, and reaches the eye point. 6. Light guide device.   The light guide device according to claim 5, wherein the incident portion has at least one of a curved incident surface and a reflecting surface.   The light guide device according to any one of claims 1 to 6, wherein the plurality of mirrors are arranged in parallel.   The light guide device according to any one of claims 1 to 7, wherein the plurality of mirrors are arranged at intervals of 0.5 mm to 2.0 mm.   9. The guide according to claim 1, wherein an angle at which light used for image formation of the image light is incident on the mirror of the reflection unit gradually decreases from an incident side to a counter incident side. Optical device.   A light beam used for image formation is reflected by a predetermined surface area on the outside of the light guide and is incident on the reflection unit, and in a cross section including the optical axis, a straight optical path before and after being reflected by the predetermined surface area The light guide device according to any one of claims 1 to 9, wherein the width is narrowed by any of the above.   The cross section including the optical axis has an incident width at which a light beam used for image formation is incident on the reflection unit is wider than an incident width at which the light beam used for image formation is incident on the predetermined surface region. The light guide device described.   The light guide device according to any one of claims 1 to 11, wherein the plurality of mirrors are configured by half mirrors.   The light guide device according to claim 1, wherein the reflection unit is disposed along a surface provided on an observer side of the light guide. The arrangement interval of the reflection units is SP, the mirror occupation width is MW, the mirror interval adjustment amount is g, the thickness of the reflection unit is TI, and the inclination angle of the light guide and the reflection unit is σ. When the angle with respect to the optical axis of the optical path extending from the eye point to an arbitrary point of interest of the reflection unit is ε and the refractive index of the reflection unit is n, the following relationship is obtained: SP = MW + g
g≈TI × {sin (σ−ε) / √ [n ² −sin ² (σ−ε)]}
The light guide device according to claim 13, wherein:   The light guide device according to any one of claims 1 to 12, wherein the reflection unit is disposed so as to be inclined such that a portion on the anti-incident side is relatively closer to the outside than a portion on the incident side.   The light guide has first and second total reflection surfaces extending in parallel as the pair of opposing surfaces, and image light taken from the incident portion is reflected by the first and second total reflection surfaces. The light guide device according to claim 1, wherein the light guide device is guided by total reflection.   The light guide device according to claim 1, wherein a surface of the incident portion is a non-axisymmetric curved surface.   A virtual image display device comprising: an image element that generates image light; and the light guide device according to claim 1.

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