JP2016042136A - Light guide device and virtual image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light guide device that prevents unevenness of video light and external light and formation of ghost, and a virtual image display device having the same built therein.SOLUTION: A light guide device 20 includes a parallel light guide body 22, an incident part 21, and an emission part 23. Since the light guide device 20 is set such that video light GL reflected on a plane (first total reflection surface) 22a on the outside side of the parallel light guide body 22 is reflected on a plurality of half mirrors 31 to be directed to an observer side, the inclination of the video light GL to be observed can be relatively increased on the depth side of a reflection unit 30 distant from the incident part 21. This setting can reduce the number of times the video light GL to be observed passes the half mirrors 31 to prevent unevenness in brightness and extinction, and also suppresses the occurrence of ghost light.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 1-4).
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 apparatus of Patent Document 3, the image light introduced into the light guide plate propagates while being totally reflected in the light guide plate, and is reflected by the surface on the viewer side, and then a plurality of HMs crossing the light guide plate diagonally. Reflected toward the observer. At this time, in order to increase the efficiency, the light having a large incident angle (50 degrees to 70 degrees) among the light incident on the HM is set to almost zero reflectance, and the light having a small angle (40 degrees or less) is predetermined. It is set so as to be the reflectance. In the apparatus of Patent Document 4, 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.

In the devices described in Patent Documents 1 to 3, since the luminance decreases every time video light passes through 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.
In the apparatus described in Patent Document 4, since the thickness of the reflection unit formed by arranging HM is thinner than the light guide, the light reaches the HM on the back side without passing through the other HM. 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.

Japanese Patent Laid-Open No. 3-15815 JP 2013-210633 A JP 2010-164988 A JP 2012-88588 A

  The present invention has been made in view of the above-described background art, and an object thereof is to provide a light guide device in which unevenness in image light and external light is less likely to occur and in which a ghost is hardly formed, and a virtual image display device incorporating the same. To do.

  In order to achieve the above object, a light guide device according to the present invention is provided on a parallel light guide having a pair of opposed planes corresponding to an observer side and an external side, and one end of the parallel light guide. An incident portion and an emission portion provided on the other end side of the parallel light guide, and the emission portion includes a reflection unit in which a plurality of mirrors that reflect video light are arranged. The mirror is inclined so that it approaches the incident part on the outside side of the parallel light guide from the observer side, and the image light reflected by the plane on the outside side of the parallel light guide is reflected by the angle of the plurality of mirrors. Reflected by multiple mirrors and directed toward the viewer. Here, the parallel light guide means a member having a light guide region sandwiched between a pair of planes. Note that the parallel light guide may be formed integrally with one or both of the incident portion and the emission portion. In this case, even if a portion obtained by extending a pair of planes is provided at the incidence portion or the emission portion. Good.

  According to the above light guide device, since the image light reflected by the external light plane of the parallel light guide is set to be reflected by the plurality of mirrors and directed to the viewer side, the incident portion of the reflection unit The inclination angle of the image light to be observed (corresponding to the incident angle when the image light to be observed is reflected by the light guide plane) is relatively increased on the far side away from it can. 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 the generation of ghost light can also be suppressed.

  In a specific aspect of the present invention, in the light guide device, the thickness of the reflection unit is thinner than the thickness of the parallel light guide. In this case, it is possible to reduce the number of times the image light reflected by the external light-side surface of the parallel light guide and enters the reflection unit can pass through the mirror, and the image light can be extracted to the viewer side with little loss.

  In 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 a variable pitch. In this case, generation of diffraction unevenness and moire can be suppressed.

  In still another aspect of the present invention, the plurality of mirrors are arranged at a random pitch. In this case, the occurrence of uneven diffraction and moire can be reliably suppressed.

  In still another aspect of the present invention, the plurality of mirrors are arranged at a pitch of 0.5 mm to 2.0 mm. By arranging a plurality of mirrors at the pitches described above, the color shift due to the difference in the way of image light interference when the mirror pitch is relatively narrow, and the light when the mirror width is relatively wide This has the effect of suppressing the occurrence of black streaks due to the difference in transmission amount.

  In still another aspect of the present invention, the angle at which light used for image formation in the image light is incident on the mirror of the reflection unit becomes smaller as the distance from the incident portion increases. In other words, the angle at which the observed image light enters the mirror is increased on the entrance side near the image light source, and the angle at which the observed image light is incident on the mirror is decreased on the far side away from the image light source.

  In another aspect of the present invention, the plurality of mirrors are composed of half mirrors. In this case, the see-through view can be facilitated by increasing the transparency of external light. Further, it becomes easy to narrow the interval between the plurality of mirrors, and the utilization efficiency of the image light can be improved.

  In another aspect of the present invention, the reflection unit is disposed along a plane obtained by extending the plane on the viewer side of the parallel light guide. In this case, it becomes easy to reflect the image light reflected on the external light plane of the parallel light guide by the plurality of mirrors.

  In yet another aspect of the present invention, the reflecting unit is disposed so as to be inclined so that a portion near the incident portion is closer to the outside than a portion far from the incident portion. In this case, the image light reflected by the external light plane of the parallel light guide can be reflected to the viewer by the plurality of mirrors.

  In still another aspect of the present invention, the parallel light guide has first and second total reflection surfaces extending opposite to each other, and image light taken from the incident portion is input to the first and second total reflection surfaces. Guided by total internal reflection.

  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 a projection optical system in which video light from the video element is made into a substantially parallel light flux and incident on the light guide device described above. With.

  According to the virtual image display device, by using the above-described light guide device, it is possible to prevent luminance unevenness and dimming of an observed image and to suppress generation of ghost light, and to observe a high-quality image. Can be.

(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 an enlarged view for demonstrating the optical path of the image light in a light guide apparatus. It is the elements on larger scale explaining the change of the optical path in a reflection unit. (A) And (B) is a figure explaining the preparation examples of a reflection unit. It is sectional drawing explaining the modification regarding introduction of the optical path of image light. It is sectional drawing explaining the modification in the emission side of the optical path of image light. (A) shows an arrangement modification of the reflection unit, and (B) shows a structural modification of the reflection unit. It is sectional drawing which shows the virtual image display apparatus which concerns on 2nd Embodiment. It is the elements on larger scale explaining the change of the optical path in a reflection unit. (A) And (B) is a figure explaining the modification regarding the incident part of a light guide device.

[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. 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. Note that FIG. 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 an image element and a collimating 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 collimating lens 12 converts the image light GL emitted from each point on the liquid crystal device 11 into parallel rays. The collimating lens 12 is made of glass or plastic, and is not limited to a single lens, and may have a plurality of configurations.

  The light guide device 20 is a flat plate extending in parallel with the XY plane in the figure, emits the image light GL formed by the image forming device 10 as virtual image light toward the observer's eye EY, and corresponds to an external image. The external light EL is substantially transmitted 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 addition, 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.

  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 reflection surface RS is formed by depositing aluminum vapor deposition or the like on the inclined surface 21a, reflects the incident video light GL, and bends the optical path in a predetermined direction close to the orthogonal direction. In other words, the reflection surface RS bends the image light GL that is incident from the light incident surface IS and travels in the + Z direction as a whole so as to be directed in the −X direction as a whole, so that the video light GL enters the parallel light guide 22. Make sure to join. The incident portion 21 has a triangular prism shape protruding in the Z direction in order to secure the size of the reflecting surface RS. The width in the Z direction of the reflecting surface RS is larger than the width or thickness in the parallel light guide 22 + Z direction, and the video light GL can be coupled to the parallel light guide 22 without loss.

The parallel light guide 22 is a flat plate extending parallel to the XY plane in the drawing. The parallel light guide 22 is formed of a light transmissive resin material or the like, and has a pair of flat surfaces 22a and 22b parallel to the XY plane. Since both the planes 22a and 22b are parallel planes, no enlargement or focus shift occurs with respect to the external image. Moreover, both planes 22a and 22b function as a total reflection surface that totally reflects the image light bent by the reflection surface RS of the incident portion 21, and have a role of guiding the image light to the emission portion 23 with a small loss. Here, the flat surface 22a on the + Z side is disposed on the external field side of the parallel light guide 22 and functions as a first total reflection surface, and is also referred to as an external field side surface in this specification. Further, the -Z side plane 22b is disposed on the viewer side of the parallel light guide 22 and functions as a second total reflection surface, and is also referred to as a viewer side surface in this specification. A part of the back surface (observer side surface) 22b close to the image forming apparatus 10 is common to the light incident surface IS. That is, a part of the observer side surface 22b also functions as the light incident surface IS. Further, the plane 20b obtained by extending the back side plane (outside surface side) 22b to a position close to the observer's eye EY includes the light emission surface OS of the emission unit 23 in part.
In the parallel light guide 22, the video light GL reflected by the reflection surface RS of the incident portion 21 first enters the plane 22 b that is the second total reflection surface and is totally reflected. Next, the video light GL enters the plane 22a which is the first total reflection surface and is totally reflected. The pair of total reflections as described above are repeated once or a plurality of times, and the video light GL is guided to the back side of the light guide device 20, that is, the −Z side where the emission unit 23 is provided.
The parallel light guide 22 has a termination surface ES as a side surface defining an end surface on 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.

  The emission portion 23 is formed in a layered manner along the back side plane (second total reflection surface) 22b on the back side (−Z side) of the parallel light guide 22. The emission unit 23 passes the video light GL that is propagated while being totally reflected by the plane (first total reflection surface) 22a on the outside world among the pair of planes 22a and 22b of the parallel light guide 22. The incident video light GL is reflected at a predetermined angle and bent toward the light exit surface OS. Here, it is assumed that the video light GL that first enters the emission unit 23 is an extraction target as virtual 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. In addition, the emission part 23 or the reflection unit 30 is arrange | positioned so that it may adjoin and adjoin the plane 20b which extended the plane 22a by the side of the observer of the parallel light guide 22. FIG. That is, the exit part 23 or the reflection unit 30 is arranged not only at a part close to the incident part 21 but also at a part away from the incident part 21 on the observer side of the parallel light guide 22.

Since the light guide device 20 has the above-described structure, the video light GL emitted from the image forming device 10 and incident on the light guide device 20 from the light incident surface IS is uniformly reflected by the incident portion 21 and bent. Then, the light is repeatedly totally reflected on the pair of flat surfaces 22a and 22b of the parallel light guide 22 and travels substantially along the optical axis OA. Of the image light GL reflected by the + Z side plane 22 a, a specific one enters the emission unit 23. 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 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. That is, the image light GL having a large inclination with respect to the Z direction is incident on the back side of the emission unit 23 and is bent at a relatively small angle, and the inclination on the front side of the emission unit 23 is small with respect to the Z direction. The image light GL enters and is bent at a relatively large angle.

[B. (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) of the drawing surface 11a shown in the drawing is the video light GL1, and the component emitted from the right side (+ Z side) of the drawing surface 11a shown by the two-dot chain line in the drawing. Is image light GL2.

Main components of the video lights GL0, GL1, and GL2 that have passed through the collimating lens 12 are incident on the light incident surface IS of the light guide device 20 and then on the planes 22a and 22b corresponding to the first and second total reflection surfaces, respectively. Total reflection is repeated at different angles.
More specifically, among the image light GL0, GL1, GL2, image light GL0 emitted from the central portion of the exit surface 11a is reflected at the incident portion 21 as parallel light beams, parallel guide with a standard reflection angle theta ₀ The light 22 is incident on the viewer-side plane 22b and is totally reflected. Then, image light GL0 repeats while maintaining the standard reflection angle theta _0, a pair of plane 22a, a total reflection at 22b. The image light GL0 is totally reflected even times on the planes 22a and 22b, and enters the central portion 23k of the emitting portion 23. The image light GL1 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 direction of the optical axis AX 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 exit surface 11a is reflected at the incident portion 21 as parallel light beams, the plane of the viewer side of the parallel light guide body 22 at the maximum reflection angle theta ₁ It enters 22b and is totally reflected. The image light GL1 is totally reflected a plurality of times on the planes 22a and 22b, reflected at a predetermined angle on the back side (−X side) portion 23h of the emission unit 23, and directed from the light emission surface OS toward a predetermined angle direction. And emitted as a parallel light flux. The exit angle γ _{1 at} this time is such that it is returned to the incident portion 21 side, and is an acute angle with respect to the + X axis.
On the other hand, the image light GL2 emitted from the other end (-X side) of the exit surface 11a is reflected at the incident portion 21 as parallel light beams, the observer side of the parallel light guide body 22 at a minimum angle of reflection theta ₂ And is totally reflected. The image light GL2 is totally reflected a plurality of times on the planes 22a and 22b, reflected at a predetermined angle at the entrance side (+ X side) portion 23m of the emitting portion 23, and directed from the light exit surface OS toward a predetermined angular direction. It is emitted as a parallel beam. The exit angle γ _{2 at} this time is such that it is away from the incident portion 21 side, and becomes an obtuse angle with respect to the + X axis.
Note that the total number of reflections until the image lights GL0, GL1, and GL2 reach the emission unit 23 does not necessarily match. 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.

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. Each image light GL0, GL1, reflection angle theta ₀ of _GL2, θ _1, the reflection angle theta ₂ which is the minimum of the theta ₂ by a value larger than the critical angle .theta.c, parallel light guide for the required image light 22 to satisfy the total reflection condition.
The image light GL0 for the center is incident on the portion 23k of the emission unit 23 at an elevation angle φ ₀ (= 90 ° −θ ₀ ), and the image light GL1 for the periphery is an elevation angle φ ₁ (= 90 ° −θ ₁ ). The incident image light GL2 is incident on the portion 23m of the emission portion 23 at an elevation angle φ ₂ (= 90 ° −θ ₂ ). Here, a relationship of φ ₂ > φ ₀ > φ ₁ is established between the elevation angles φ ₀ , φ ₁ , φ ₂ reflecting the magnitude relationship of the reflection angles θ ₀ , θ ₁ , θ ₂ . In other words, the angle of incidence on the half mirror 31 of the reflecting unit 30 iota (see FIG. 3), the portion corresponding to the elevation angle phi ₂ 23m, portions corresponding to elevation phi ₀ 23k, in order of portions 23n corresponding to the elevation angle phi ₁ Gradually get smaller. In other words, the incident angle ι to the half mirror 31 or the reflection angle at the half mirror 31 decreases as the distance from the incident portion 21 increases.

[C. (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.

  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 and has a structure in which a large number of thin strip-like half mirrors 31 are embedded in 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 in the direction in which the parallel light guides 22 extend, that is, in the X direction, at a predetermined pitch PT. 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 as the longitudinal direction. Further, the half mirror 31 is inclined so as to be closer to the incident portion 21 on the outside side than the observer side of the parallel light guide 22. More specifically, the half mirror 31 is tilted so that the upper end (+ Z side) rotates counterclockwise with the longitudinal direction (Y-axis direction) as an axis and the YZ plane orthogonal to the planes 22a and 22b as a reference. doing. That is, each half mirror 31 extends in a 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 EL 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.

  An example of the manufacturing method of the reflection unit 30 will be described. A number of element plates are prepared in advance by forming a metal reflective film or a dielectric multilayer film on one surface of a parallel flat plate having light transmittance. Thereafter, the formed many element plates are laminated while being bonded with an adhesive, and the whole is cut obliquely. As a result, it is possible to obtain a reflection unit 30 having a structure in which a half mirror 31 made of a metal reflection film or a dielectric multilayer film is sandwiched between elongated block members 32 of parallel flat plates. The reflection unit 30 is fitted so as to be embedded in a recess formed at a proper position on the viewer side of the parallel light guide 22 and fixed by curing the adhesive filled in the gap.

The reflection unit 30 is not limited to being manufactured separately from the parallel light guide 22, and may be formed integrally with the parallel light guide 22.
For example, as shown in FIG. 4A, a base material 22i to be a parallel light guide 22 is prepared, and a sawtooth cross section having a large number of triangular sections 22j arranged at positions where the reflection unit 30 is to be formed. A three-dimensional structure portion 22k is formed. A reflective layer 22n to be the half mirror 31 is formed on the inclined surface 22m of the structure portion 22k, and liquid resin is poured into the groove of the structure portion 22k. As a result, as shown in FIG. 4B, a large number of triangular sections 22p filled with liquid resin are formed in the grooves constituting the structural portion 22k, and the layered injection portion 23, that is, the reflection unit 30 is completed. .
In FIG. 4A and the like, the reflection unit 30 is formed on the base material 22i that becomes the parallel light guide 22, but the base material formed separately from the parallel light guide 22 is shown in FIG. 4A and the like. The reflection unit 30 can be formed by a technique, and the reflection unit 30 thus formed can be joined to the parallel light guide 22.

  In addition, the pitch PT of the half mirror 31 in the reflection unit 30 is set to about 0.5 mm to 2.0 mm. By arranging the plurality of half mirrors 31 at the above pitch, the effect of suppressing color misregistration due to the difference in the way of interference of the image light when the pitch of the half mirror 31 is narrowed, and the pitch of the half mirror 31 are widened. This has the effect of suppressing black streaks due to the difference in the amount of transmitted light.

  Strictly speaking, the pitch PT of the half mirrors 31 is arranged at a variable pitch, not at regular intervals. More specifically, the pitch PT of the half mirrors 31 in the reflection unit 30 is a random pitch that increases or decreases randomly around the reference interval. Thus, by arranging the half mirrors 31 in the reflection unit 30 at a random pitch, it is possible to reliably suppress the occurrence of diffraction unevenness and moire. In addition, not only a random pitch but the predetermined pitch pattern containing the pitch which increases / decreases in multiple steps, for example may be repeated.

  Here, the thickness of the reflection unit 30, that is, the thickness TI 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, the incident angle of the image light GL to the reflection unit 30 or the flat surface 20b can be easily reduced, and the image light GL is not taken into the eye EY. It is easy to suppress reflection by the half mirror 31 at the position. 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.

In the specific examples shown in FIGS. 2, 3 and the like, all the half mirrors 31 have an inclination angle δ of, for example, about 48 ° to 65 ° in the clockwise direction with respect to the observer side surface 22b of the parallel light guide 22. Specifically, for example, the inclination angle δ is 54 °. Here, set to the elevation angle phi ₀ of the image light GL0, for example 18 °, it is set to the elevation angle phi ₁ of the image light GL1, for example 11 °, which is set to the elevation angle phi ₂ of the image light GL2 is, for example, 25 ° And In this case, the image light GL0 that has entered the center of the reflection unit 30 is emitted in the −Z direction perpendicular to the plane 22b and enters the eye EY of the observer. In addition, the image light GL1 that has entered the rear portion 23h away from the incident portion 21 of the reflection unit 30 enters the observer's eye EY at an angle γ ₁ = 10.5 ° with respect to the image light GL0. . Further, the image light GL1 incident on the front portion 23m near the incident portion 21 of the reflection unit 30 enters the observer's eye EY at an angle γ ₂ = 10.5 ° with respect to the image light GL0.

  As a result, the component having the relatively large total reflection angle (image light GL1) in the image light GL is incident on the −X side portion 23h side of the reflection unit 30, and the component having the relatively small total reflection angle (image light). When GL2) is incident on the + X side portion 23m side of the emitting portion 23, the image light GL can be efficiently extracted in an angle state where the image light GL is collected on the observer's eye EY as a whole. Since the video light GL is extracted in such an angular relationship, the light guide device 20 can pass the video light GL through the reflection unit 30 a plurality of times without passing through the reflection unit 30 only once, and the video light GL is reduced. It can be extracted as virtual image light with loss.

Note that the video light GL passes through the half mirror 31 a plurality of times in the central side and the back side portions 23k and 23h of the reflection unit 30 and the like. In this case, the number of times the half mirror 31 passes is plural. However, since the reflected light from the plurality of 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.
Further, in the central side and back side portions 23k and 23h of the reflection unit 30, there is a possibility that a component of the image light GL reflected on the back side of the parallel light guide 22 or on the plane 22b side on the viewer side may also occur. is there. However, such image light GL is guided out of the optical path as non-use light GX (see FIG. 3), and is prevented from entering the observer's eye EY.

[D. Summary of First Embodiment]
According to the light guide device 20 of the first embodiment described above, the half mirror 31 constituting the reflection unit 30 is inclined so as to be closer to the incident portion 21 on the outside side than the observer side of the parallel light guide 22. In addition, at least a portion of the reflecting unit 30 that is close to the incident portion 21 is disposed on the viewer side of the parallel light guide 22 and is reflected by a plane (first total reflection surface) 22a on the outside of the parallel light guide 22. Since the image light GL is reflected by the plurality of half mirrors 31 and directed toward the viewer side, the image light GL to be observed on the far side away from the incident part 21 in the reflection unit 30 is set. it can be relatively large inclination angle theta _1. 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 uneven brightness and light reduction, thereby suppressing the generation of ghost light.

The number of total reflections of the video light GL in the parallel light guide 22 is not limited to that illustrated in FIG. That is, the number of total reflections of the video light GL from the incident part 21 to the emission part 23 can be appropriately changed according to the thickness in the Z direction and the length in the X direction of the parallel light guide 22.
FIG. 5 is a diagram for explaining an example in which the arrangement or the like of the incident portion 21 of the light guide device 20 is changed, and corresponds to FIG. In this case, by changing the length of the parallel light guide 22 or the like, the video light GL reaches the emission unit 23 with the total number of reflections different from that illustrated in FIG. As a result, the image taken out from the emitting unit 23 is basically obtained from the video light GL having the same total number of reflections.

FIG. 6 is a diagram illustrating an example in which the structure and the like of the emission unit 23 of the light guide device 20 are changed. In this case, the thickness of the reflection unit 30 is thicker on the side closer to the incident part 21 and thinner on the side farther from the incident part 21. The side farther from the entrance portion 21, the elevation angle phi ₂ of the image light GL2 are smaller, by reducing the reflection unit 30, it is possible to suppress the number of passes through the half mirror 31 is increased.

  FIG. 7A is a diagram for explaining an example in which the arrangement of the emission unit 23 is changed, and is a cross-sectional view in which a part of the light guide device 20 shown in FIG. 2 is enlarged. In this case, the parallel light guide 22 and the reflection unit 30 are separate from each other, and the reflection unit 30 is attached to the observer side surface 22 b provided on the back side of the parallel light guide 22.

  FIG. 7B is a diagram for explaining an example in which the structure of the emission unit 23 or the reflection unit 30 is changed, and corresponds to FIG. In this case, the pitch of the half mirror 31 is slightly wide, and a part of the external light EL can be directly passed. That is, there is a gap through which the external light EL passes between a pair of adjacent half mirrors 31 when viewed from the front of the parallel light guide 22, and a part of the external light EL is formed between the multiple half mirrors 31. It passes through many gaps and enters the observer's eye EY with relatively little loss. When the pitch of the half mirrors 31 is wide as described above, the external light EL can be seen through the reflection unit 30 even if a simple mirror that does not have optical transparency is used instead of the half mirror 31.

[Second Embodiment]
Hereinafter, the light guide device and the virtual image display device according to the second embodiment will be described with reference to FIGS. Note that the light guide device and the virtual image display device according to the present embodiment are modifications of the first embodiment shown in FIG. 1A and the like, and description of common matters is omitted.

  As shown in FIGS. 8 and 9, in the light guide device 20 according to the present embodiment, the reflection unit 30 provided in the emission unit 23 is incorporated in an inclined state. That is, the reflection unit 30 is inclined so that the back 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.

  As shown in FIG. 9, even if the reflection unit 30 is arranged in an inclined state, the angle condition is the same as that of the first embodiment (see FIG. 3), so the plane 22 a on the outside side of the parallel light guide 22. The image light GL reflected by the light beam can be reflected by the plurality of half mirrors 31 and can pass through the plane 22b on the observation side. The video lights GL0, GL1, and GL2 emitted from the emission unit 23 form virtual images as in the case of FIG.

  In addition, in the said 1st Embodiment, the edge part 23p of the back | inner side far from the incident part 21 of the reflection unit 30 does not need to be connected with the plane 22a on the outside world side, and the structure where the edge part 23p is separated from the plane 22a. You can also Further, the reflection unit 30 does not need to extend on a straight line, and can be formed in, for example, a concave shape on the + Z side as viewed in the cross section of FIG. 8, and further can be formed of a plurality of line segments. It needs to be in shape.

[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, but the reflectivities of these half mirrors 31 can be gradually increased from the incident part 21 to the emission part 23.

  In the above description, the image light GL is reflected by the incident portion 21 and is incident on one plane 22b of the parallel light guide 22. However, the shape of the incident portion 21 (the inclination of the reflection surface RS or the light incident surface IS, The image light GL can be made incident on the other flat surface 22a of the parallel light guide 22 by changing the interval or the like.

Further, the light incident surface IS of the incident portion 21 does not need to be a common surface with any of the pair of flat surfaces 22a and 22b constituting the parallel light guide 22, and can be different from these.
For example, as shown in FIG. 10A, the incident portion 121 provided on the light incident side of the parallel light guide 22 can be projected from the flat surface 22b on the back side. In this case, the light incident surface IS is observed. Although it is provided separately from the person side surface 22 b, it becomes easy to make the image light GL incident obliquely on the parallel light guide 22.
Furthermore, as shown in FIG. 10B, when the incident portion 121 that protrudes from the observer side surface 22b is provided, a structure in which the incident surface 121 is reflected once by the inclined surface 21f can also be formed. The degree of freedom of design can be increased.

  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 see-through type virtual image display device has been described. However, the emission unit 23 can be applied to a virtual image display device other than the see-through type. When it is not necessary to observe an external image, the light reflectance of the flat surface 22a and the like can be made approximately 100%.

  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, in the planes 22a and 22b of the parallel light guide 22, the image light is totally reflected and guided by the interface with air without applying a mirror or a half mirror on the surface. The total reflection includes the 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, the case where the incident angle of the image light GL satisfies the total reflection condition and the whole or a part of the planes 22a and 22b is mirror-coated to reflect substantially all the image light.

  In the above description, the parallel light guide 22 is horizontally long in the X direction, and the light incident surface IS is formed so as to be positioned on the left and right outer sides of the eye on a plane parallel to the XY plane, but the image light GL is guided. The position of the light incident surface IS is not limited to this as long as it can be appropriately guided into the optical device 20, and for example, it can be provided on a part of the upper end surface TP or the lower end surface BP above and below the light guide device 20. is there.

  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.

  DESCRIPTION OF SYMBOLS 10 ... Image forming apparatus, 11 ... Liquid crystal device, 11a ... Ejection surface, 12 ... Collimating 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, GX ... Unused light, IS ... Light incident surface, OS ... Light exit surface, RS ... Reflective surface

Claims (12)

A parallel light guide having a pair of opposing planes corresponding to the observer side and the outside world side;
An incident portion provided on one end of the parallel light guide;
An emission part provided on the other end side of the parallel light guide,
The emission unit has a reflection unit formed by arranging a plurality of mirrors that reflect image light,
In the reflection unit, the plurality of mirrors are inclined so as to approach the incident portion on the outside side of the parallel light guide from the observer side, and the outside of the parallel light guide is determined according to the angle of the plurality of mirrors. A light guide device that reflects video light reflected by a flat surface on the side toward the observer side by the plurality of mirrors.   The light guide device according to claim 1, wherein a thickness of the reflection unit is thinner than a thickness of the parallel light guide.   The light guide device according to claim 1, wherein the plurality of mirrors are arranged in parallel.   The light guide device according to any one of claims 1 to 3, wherein the plurality of mirrors are arranged at a variable pitch.   The light guide device according to claim 4, wherein the plurality of mirrors are arranged at a random pitch.   The light guide device according to any one of claims 1 to 5, wherein the plurality of mirrors are arranged at a pitch of 0.5 mm to 2.0 mm.   The light guide according to any one of claims 1 to 6, wherein an angle at which light used for image formation out of image light is incident on the mirror of the reflection unit decreases as the distance from the incident portion decreases. apparatus.   The light guide device according to any one of claims 1 to 7, 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 plane obtained by extending a plane on the viewer side of the parallel light guide.   The light guide device according to any one of claims 1 to 8, wherein the reflection unit is disposed so as to be inclined so that a portion far from the incident portion is closer to the outside than a portion close to the reflection portion.   The parallel light guide has first and second total reflection surfaces extending opposite to each other, and guides the image light taken in from the incident portion by total reflection on the first and second total reflection surfaces. The light guide device according to any one of claims 1 to 10. An image element for generating image light;
A virtual image display device comprising: a projection optical system that makes the image light substantially parallel light flux and enters the light guide device according to any one of claims 1 to 11.

Images