Patent Application
20160282622
1. Technical Field
The present invention relates to a light guide device suitable for incorporation into a head-mounted display or the like mounted on a head and being used, a head-mounted display, and a method of manufacturing the light guide device.
2. Related Art
In recent years, various head-mounted displays of types that guide image light from a display element to eyes of an observer using a light guide plate have been proposed as head-mounted displays which enable formation and observation of a virtual image.
As the head-mounted display, tor example, a head-mounted display including a light guide plate in which a plurality of glass plates with a reflective layer are laminated and cut into an image extraction portion is known (see, for example, JP-A-2013-076847, JP-A-2010-164988, and JP-A-2010-145859). In this case, a structure in which a dielectric multilayer film or a half mirror is interposed between blocks obtained by cutting the glass plate is obtained.
However, since the light guide plate as described above is obtained by bonding the blocks obtained by cutting the glass plates, a structure in which bonding portions are present side by side at a plurality of places is obtained, and it is not easy to ensure strength. Further, in the case of the light guide plate, it is not easy to cut the light guide plate in a desired outer shape after the light guide plate is formed, and the degree of freedom of the outer shape is low.
An advantage of some aspects of the invention is to provide a light guide device capable of ensuring sufficient strength and increasing the degree of freedom of an outer shape.
Another advantage of some aspects of the invention is to provide a head-mounted display including the light guide device as described above and a method of manufacturing such a light guide device.
A light guide device according to an aspect of the invention includes a light incident portion that takes image light into the inside; a light guide portion that guides the image light taken from the light incident portion through total reflection at first and second light guide surfaces that extend to face each other; a light emission portion that takes the image light passing through the light guide portion to the outside; and a protective layer that is provided in association with at least the light emission portion and suppresses breakage of the light emission portion.
In the light guide device, since the protective layer that suppresses breakage of the light emission portion is provided in association with at least the light emission portion, the light emission portion or the like is protected, and it is possible to prevent the light emission portion from being easily damaged. Accordingly, strength of the light guide device is sufficiently high while the light guide device is thin. As a result, processing after the protective layer is provided is facilitated and the degree of freedom of the shape increases.
In a specific aspect of the invention, the protective layer is in a sheet shape or a plate shape. In this case, the protective layer is relatively thick, and it is possible to improve the strength of the protective layer and the strength of the light emission portion.
In another aspect of the invention, the light emission portion includes a multi-slit-shaped reflective portion in which a plurality of reflective elements reflecting the image light is arranged. In this case, it is easy for breakage to occur at a boundary portion at which the reflective element is arranged, but the protective layer prevents the breakage at the boundary portion.
In still another aspect of the invention, the reflective portion is a flat plate-shaped member formed by arranging the reflective element between a plurality of prism-shape light-transmissive members, and the protective layer is affixed to the flat plate-shaped member. In this case, the protective layer has a role of reinforcing bonding between the light-transmissive members, and it is possible to easily protect the light emission portion or the like.
In still another aspect of the invention, the protective layer is provided on at least one of surfaces on the observer side and the outer side of the light emission portion. For example, when the protective layer is provided on the surface on the outer side, protection of the light emission portion or the like from objects on the outer side becomes reliable, and when the protective layer is provided on the surface on the observation side, protection of eyes or a face becomes reliable.
In still another aspect of the invention, the protective layer is provided in an area other than the light incident portion. In this case, the light guide portion or the like is protected by the protective layer.
In still another aspect of the invention, the protective layer is also provided on an end surface on the light emission portion side. In this case, it is possible to prevent exposure of the end surface and protect the end portion using the protective layer.
In still another aspect of the invention, the protective layer includes a light-transmissive main body, and a surface treatment layer that covers a surface of the main body. In this case, the surface treatment layer can have functions such as strength improvement and anti-reflection.
In still another aspect of the invention, the protective layer is formed of a resin material having adjusted transmittance, and has a uniform thickness. In this case, the protective layer can nave a filtering function.
A head-mounted display according to another aspect of the invention includes the above-described light guide device; and an image forming device that forms image light incident on the light guide device.
In the head-mounted display, since the light guide device is incorporated, it is possible to improve strength or workability in the light emission portion or the like of the light guide device, and it is possible to prevent simple damage of the light guide device to increase a degree of freedom of a shape of the light guide device.
A method of manufacturing a light guide device according to another aspect of the invention is a method of manufacturing a light guide device including a light incident portion that takes image light into the inside, a light guide portion that guides the image light taken from the light incident portion through total reflection at first and second light guide surfaces that extend to face each other, and a light emission portion that takes the image light passing through the light guide portion to the outside, the method of manufacturing a light guide device including: forming a protective layer in a portion including at least the light emission portion. the protective layer, for example can be formed separately from the light emission portion or the like, and then, affixed to the light emission portion or the like.
In the method of manufacturing a light guide device, since the protective layer is formed in the portion including at least the light emission portion, it is possible to protect the light emission portion or the like and suppress damage thereof. Accordingly, strength of the light guide device is sufficiently high while the light guide device being thin. As a result, processing after the protective layer is provided is facilitated and a degree of freedom of the shape increases.
In a specific aspect of the invention, the light emission portion is formed by providing a reflective film on a plurality of glass plates, superposing the plurality of glass plates, and obliquely cutting the glass plates. In this case, it is possible to easily and accurately form a multi-slit-shaped reflective portion or a light emission portion in which a plurality of reflective elements are arranged.
In another specific aspect of the invention, shape processing is performed on the light emission portion having the protective layer provided therein together with the protective layer. In this case, shape processing of the light emission portion can be performed while damage of the light emission portion is prevented, processing of the light emission portion is facilitated, and the degree of freedom of a shape thereof increases.
In still another specific aspect of the invention, the protective layer is provided as a film affixed to a portion including the light emission portion or a plastic plate bonded to the portion including the light emission portion. In this case, the protective layer is formed relatively easily.
In still another specific aspect of the invention, the protective layer is provided through insert molding in which the light emission portion is positioned and is put into a mold, and then a resin is injected into the mold. In this case, the light guide device can have a variety of contours, and an effect of high strength of the light emission portion or the like also becomes reliable.
The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements.
Hereinafter, a light guide device and a head-mounted display according to a first embodiment of the invention will be described in detail with reference to the accompanying drawings.
As illustrated in
An image forming device 80 is fixed to a light incident side of the light guide device 10 through an optical frame (not illustrated). The light guide device 10 and the image forming device 80 form a head-mounted display 100 which is a virtual image display device for one eye that is available individually, and the head-mounted display 100 provides a virtual image as a moving image or a still image to an observer. The head-mounted display 100 is also called a head-mount display.
In the light guide device 10, the main body member 11 is a thin plate shape and is formed using a light-transmissive material, and specifically, glass as a base material. The main body member 11 includes a first main surface 11a on the observer side, a second main surface 11b on the outer side, an upper end portion 11e, a lower end portion 11f, and lateral end portions 11g and 11h. The first main surface 11a and the second main surface 11b are planes parallel to each other and extend along the XY plane. The main body member 11 is an integral member, but functionally includes a light incident portion 20 that takes image light into the inside, a light guide portion 30 that guides the image light from one end to the other end, and a light emission portion 40 that takes the image light to the outside. The main body member 11 takes the image light from the image forming device 80 into the inside through the light incident portion 20, guides the taken image light to the light emission portion 40 through the light guide portion 30, and forms a virtual image so that the image light emitted from the light emission portion 40 is incident on the eye EY of the observer.
The light incident portion 20 is a portion formed integrally with light guide portion 30 so as to extend the light guide portion 30 in a longitudinal direction in the one lateral end portion, 11g of the main body member 11. The light incident portion 20 includes a prism portion 21 formed integrally with the light guide portion 30, and a reflective surface 22 associated with the prism portion 21. The prism portion 21 includes a light incident surface IS and an inclined surface RS as side surfaces. A mirror layer 25 is formed on the inclined surface RS so as to cover the inclined surface RS. Here, the mirror layer 25 cooperates with the inclined surface RS to function as the reflective surface 22 arranged to be inclined with respect to the light incident surface IS. This reflective surface 22 bends the image light incident from the light incident surface IS and directed in a +Z direction as a whole, so that the image light is directed in a −X direction biased in a −Z direction as a whole, thereby coupling the image light to the inside of the light guide portion 30. The light incident surface IS is a portion of the first main surface 11a.
The light guide portion 30 includes a first light guide surface 30a which is a portion of the first main surface 11a, and a second light guide surface 30b which is a portion of the second main surface 11b. The first and second light guide surfaces 30a and 30b are two planes facing each other and extending parallel to the XY plane, and totally reflect image light bent by the reflective surface 22 of the light incident portion 20, respectively. That is, the image light reflected by the reflective surface 22 of the light incident portion 20 is first incident on and totally reflected by the first light guide surface 30a. Then, the image light is incident on and totally reflected by the second light guide surface 30b. Hereinafter, this operation is repeated, and accordingly, the image light is guided to a rear side of the main body member 11, that is, an −X side on which the light emission portion 40 is provided. An effective area EA (see
The light emission portion 40 is a flat plate-shaped member formed integrally with the light guide portion 30 so as to extend the light guide portion 30 to a −X side, that is, an opposite side of the light incident portion 20. The light emission portion (flat plate-shaped member) 40 includes a multi-slit-shaped angle conversion portion, that is, a reflective portion 40r that directs the image light to an observer side while maintaining the angle information of the image light, which includes a large number of half mirror layers 41 inclined with respect to the first and second light guide surfaces 30a and 30b and arranged parallel to each other at equal intervals. The half mirror layer 41 is a reflective element for reflecting the image light and is interposed between a light emission surface ES and an outer surface OS which extend parallel to each other. In the illustrated example, the half mirror layer 41 or the reflective portion 40r is formed only in a central area PA with respect to a vertical direction (see
In the light emission portion (flat plate-shaped member) 40, each half mirror layer (reflective element) 41 is inclined to be close to the light incident portion 20 on the outer side rather than on the observer side of the main body member 11, and is inclined to be close to the light incident portion 20 on the outer surface OS rather than on the light emission surface ES. Specifically, each half mirror layer 41 is arranged to be inclined to the +Z side on the +X side. In other words, each half mirror layer 41 is inclined so that an incident side end (+X side) thereof is rotated clockwise with respect to the main surfaces 11a and 11b or the XY plane using a longitudinal direction (Y-axis direction) as an axis. A rotation angle in this case is set to be suitable for an angular state of the image light propagating through the light guide portion 30. The light emission portion 40 or the reflective portion 40r reflects and bends the image light incident through the first and second light guide surfaces 30a and 30b of the light guide portion 30 at a predetermined angle to emit the image light to the eyes EY side of the observer through, the light emission surface ES. That is, the light emission portion 40 changes the angle of the image light propagating through the light guide portion 30. The light emission surface ES is a portion of the first main surface 11a, and the outer surface OS is a portion of the second main surface 11b.
As illustrated in an enlarged form in
The prism portion 21 of the light incident portion 20, and the light guide portion 30 are formed of the same material as that of the light-transmissive member 44, the light guide prism 144, or the like of the light emission portion 40, and have the same refractive index as that of the light-transmissive member 44, the light guide prism 144, or the like. Therefore, the image light incident on the main body member 11 uniformly propagates between the first main surface 11a and the second main surface 11b.
While the pair of protective layers 12 and 14 are in a plastic plate shape having a certain thickness (that is, a plate shape) in the shown example, the protective layers 12 and 14 may be in a film shape (that is, sheet shape). However, the protective layers 12 and 14 are not thin films which cannot maintain shapes thereof alone and in which presence of a substrate is assumed. The protective layers 12 and 14 are affixed to the first and second main surfaces 11a and 11b so as to cover the first and second main surfaces 11a and 11b of the main body member 11. The protective layers 12 and 14 are provided in a region other than the light incident portion 20. Specifically, the protective layer 12 is fixed to the main body member 11 using an adhesive or the like to cover the first light guide surface 30a, the light emission surface ES, and the like, but to expose the light incident surface IS. The other protective layer 14 is fixed to the main body member 11 using an adhesive or the like to cover the second light guide surface 30b, the outer surface OS, and the like. Both of the protective layers 12 and 14 are members having a uniform thickness, and have light transmission properties, similar to the light incident portion 20. Both of the protective layers 12 and 14 protect the light guide portion 30 and the light emission portion 40 and are affixed to the reflective portion 40r, particularly, such that the reflective portion 40r which is a flat plate-shaped member is interposed therebetween. As a result, both of the protective layers 12 and 14 prevent the light guide portion 30 or the light emission portion 40 from being broken, and increase strength of the light guide device 10 while thinning the light guide device 10.
As illustrated in
Although not described, the protective layer 14 on the outer side has the same structure and function as those of the protective layer 12 on the observer side described above. The protective layer 12 can have a role of protecting the light emission portion 40 or the like from an object on the outer side, and the protective layer 14 can have a role of protecting the eyes EY or a face.
Depending on a manner of usage, any one of the protective layer 12 on the observer side and the protective layer 14 on the outer side can be omitted. That is, the protective layer 12 on the observer side can be omitted and the protective layer 14 can remain. On the contrary, the protective layer 12 can remain and the protective layer 14 can be omitted.
The protective layers 12 and 14 have a high transmittance distribution uniform in a visible region, but can shield an infrared region or an ultraviolet region. That is, the protective layers 12 and 14 may be formed of a resin material having adjusted transmittance, and the surface treatment layer 12b or the main body 12a of the protective layer 12 may function as a wavelength-selective transmissive filter. Further, the protective layers 12 and 14 may have spatial distribution of the transmittance. For example, only a region corresponding to the central area PA of the light emission portion 40 can have a high transmittance. In this case, a phenomenon that external light observed over the central area PA is darker than surroundings can be suppressed.
The image forming device 80 includes an image display device 81 and a projection optical system 82. Among them, the image display device 81 includes an illumination device 81a that emits two-dimensional illumination light, a liquid crystal display device 81b which is a transmissive spatial light modulation device, and a driving control unit 82c that controls operations of the illumination device 81a and the liquid crystal display device 81b.
The illumination device 81a generates illumination light including three colors of red, green, and blue. The liquid crystal display device 81b spatially modulates illumination light from the illumination device 81a to form an image light to be a display target such as a moving image. The driving control unit 82c supplies electric power to the illumination device 81a to emit illumination light with stable luminance, and outputs a driving signal to the liquid crystal display device 81b to form color image light which becomes a base of a moving image or a still image as a transmittance pattern.
The projection optical system 82 is a collimator lens that converts image light emitted from each point on the liquid crystal display device 81b to a light flux in a parallel state. That is, the projection optical system 82 emits the image light that contributes to formation of a virtual image as parallel light that does not form an image.
Hereinafter, an optical path of the image light in the light guide device 10 will be described. Primary components of the respective image light GL1, GL2, and GL3 emitted from the projection optical system 82 are incident from the light incident surface IS of the light guide device 10, and then repeatedly totally reflected at different angles by the first and second main surfaces 11a and 11b.
Specifically, the image light GL1 emitted from a center point of the liquid crystal display device 81b passes through the projection optical system 82, is incident on the light incident surface IS as a parallel light beam, is reflected by the reflective surface 22, is incident on the first main surface 11a of the light guide device 10 at a standard reflection angle γ0, and is totally reflected. Then, the image light GL1 is repeatedly totally reflected by the first and second main surfaces 11a and 11b while maintaining the standard reflection angle γ0, and then, reaches a central portion 40k of the light emission portion 40. The image light GL1 reflected by the central portion 40k is emitted as a parallel light beam in an optical axis AX direction perpendicular to the light emission surface ES or the XY plane from the light emission surface ES. Further, the image light GL2 emitted from one side (+X side) of the liquid crystal display device 81b passes through the projection optical system 82, is incident on the light incident surface IS as a parallel light beam, is reflected by the reflective surface 22, is incident on the first main surface 11a of the light guide device 10 at a maximum reflection angular γ+ (>γ0), and is incident on a surrounding portion 40a on the most entrance side (+X side) of the light emission portion 40 while being repeatedly totally reflected by first and second main surfaces 11a and 11b. The image light GL2 reflected by this surrounding portion 40a is at an obtuse angle with respect to the +X axis to be separated from the light incident portion 20, and is emitted in a direction inclined at an angle θ12 with respect to the optical axis AX. Further, the image light GL3 emitted from the other end side (−X side) of the liquid crystal display device 81b passes through the projection optical system 82, is incident on the light incident surface IS as a parallel light beam, is reflected by the reflective surface 22, is incident on the first main surface 11a of the light guide device 10 at a minimum reflection angle γ− (<γ0), and is incident on a surrounding portion 40b on the rearmost side (−X side) of the light emission portion 40 while being repeatedly totally reflected by the first and second main surfaces 11a and 11b. The image light GL2 reflected by the surrounding portion 40b is at an obtuse angle with respect to the +X axis to be returned to the light incident portion 20 and is emitted in a direction inclined at an angle θ13 with respect to the optical axis AX.
Hereinafter, an example of a method of manufacturing the light guide device 10 will be described. A large number of glass plates that are parallel flat plates of glass are prepared in advance, and a reflective layer that is a metal reflective film or a dielectric multilayer film is formed on one surface of each glass plate to prepare a large number of element plates. Thereafter, the large number of formed element plates are bonded with an adhesive and laminated to be superposed on each other, and all are obliquely cut. Accordingly, a plate-shaped member, that is, a reflective unit having a structure in which the half mirror layer 41 formed of a metal reflective film or a dielectric multilayer film is interposed between the light-transmissive members 44, which are elongated prism pieces obtained by obliquely dividing the parallel flat plates can be obtained. By polishing a pair of facing main surfaces of this reflective unit, the light emission surface ES and the outer surface OS are formed and the light emission portion 40 is obtained. Then, for example, the light guide portion 30 formed of glass is bonded to the light emission portion 40, and the main body member 11 is complete.
In addition, the main body 12a which is a base material of the protective layer 12 is prepared, and the surface treatment layer 12b is formed on one surface of the main body 12a. For the surface treatment layer 12b, for example, the one surface of the main body 12a is sealed and coated by a dip method and cured by heat treatment or the like. Although not described in detail, the protective layer 14 is also prepared in the same manner as the protective layer 12.
Then, a pair of protective layers 12 and 14 are affixed to the first and second main surfaces 11a and 11b of the main body member 11 so as to cover the first and second main surfaces 11a and 11b of the main body member 11. Further, an outer periphery of the main body member 11 is subjected to shape processing into a desired shape together with the protective layers 12 and 14 through cutting or the like, and accordingly, the light guide device 10 is complete. The light guide device 10 is assembled into a frame (not illustrated) together with the image forming device 80.
According to the light guide device 10 in the embodiment, since the protective layers 12 and 14 are provided in association with the light emission portion 40 and the light guide portion 30, the light emission portion 40 and the like are protected and damage thereof can be simply prevented during processing or during use. In particular, an effect of prevention of breakage at the boundary portion at which the half mirror layers 41 are arranged in the reflective portion 40r is significant. Accordingly, the light guide device 10 is thinned and has sufficiently high strength. As a result, processing after the protective layers 12 and 14 are provided is facilitated, and the degree of freedom of the shape is increased.
Hereinafter, a head-mounted display according to a second embodiment will be described. The head-mounted display according to the present embodiment is a modification example of the head-mounted display 100 according to the first embodiment, and is the same as the first head-mounted display 100 unless otherwise mentioned.
As illustrated in
While it is assumed in the second embodiment that a process of cutting an outer periphery of the main body member 11 or the like after the protective layer 112 is formed is not provided, an outer periphery of the obtained light guide device 10 may be cut in a desired shape.
Hereinafter, a head-mounted display according to a third embodiment will be described. The head-mounted display according to the present embodiment is a modification example of the head-mounted display 100 according to the first embodiment, and is the same as the first head-mounted display 100, unless otherwise mentioned.
As illustrated in
An example of a method of manufacturing the light emission portion 40 will be described with reference to
Sizes or spacings of the large number of half mirror layers 41 constituting the reflective portion 40r are not necessarily required to match each other, and may be adjusted according to positions.
Further, in the light guide device 10 illustrated in
In the light guide device 10 illustrated in
Hereinafter, a head-mounted display according to a fourth embodiment will be described. The head-mounted display according to this embodiment is a modification example of the head-mounted display 100 according to the second, embodiment, and is the same as the second head-mounted display 100, unless otherwise mentioned.
As illustrated in
While the invention has been described above based on each embodiment, the invention is not limited to the embodiment and can be implemented in various aspects without departing from the gist of the invention. For example, the following modifications are also possible.
While a transmissive liquid crystal display device 81b or the like is used as the image forming device 80 in the above embodiment, the image forming device 80 is not limited to the transmissive liquid crystal, display device 81b, and various liquid crystal display devices can be used. For example, a configuration using a reflection type liquid crystal display device is also possible, and a digital micromirror device or the like can also be used in place of the liquid crystal display device 81b. Further, a self-luminous element of which representative examples includes an LED array and an organic EL (OLED) can also be used as the image forming device 80.
While the protective layers 12, 14, and 112 do not have a light guide function in the above embodiment, the protective layers 12, 14, and 112 can have the light guide function through adjustment of the refractive index. In this case, surfaces of the protective layers 12, 14, and 112 function as the main surfaces 11a and 11b of the main body member 11 or the light guide surfaces 30a and 30b of the light guide portion 30.
The entire disclosure of Japanese Patent Application No. 2015-059170, filed Mar. 23, 2015 is expressly incorporated by reference herein.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2015-059170 | Mar 2015 | JP | national |
