JP6701559B2 - Light guide and virtual image display device - Google Patents

Description

  The present invention relates to a light guide and a virtual image display device using the light guide.

  A virtual image display device using a light guide is known as a device for enlarging a two-dimensional image by a virtual image optical system and displaying the enlarged virtual image so that an observer can observe the enlarged virtual image. In recent years, a head mounted display (hereinafter, referred to as "HMD") has become popular as one form of a light guide used in such a virtual image display device. The HMD is classified into a see-through transparent type and a non-transparent type. The transparent HMD is, for example, Google LTD. (United States) Googleglass (registered trademark).

  Since the transparent HMD is used in combination with an information terminal or for providing AR (Augmented Reality) and the like, it is desired to have a small size and good portability. Since the non-transmissive HMD is used for watching movies, providing games, VR (Virtual Reality), etc., it is desired that the non-transparent HMD has a wide viewing angle that provides an immersive feeling.

  In recent years, even in the transmissive type, from the user's needs, thin-walled, small-sized, and wide viewing angles have been demanded. For example, Patent Documents 1 to 3 are known in consideration of such demands. ing.

  The apparatus of Patent Document 1 has a system in which a number of mirrors coated with a specific reflectance are arranged, and reflection and transmission of light rays are sorted according to the incident angle of light rays to extract image light.

  The device of Patent Document 2 has a structure in which a fine structure and a gap zone are provided on one side surface of a light guide, and a light beam is reflected and propagated at these portions to extract image light.

  The device of Patent Document 3 has a plurality of first element surfaces that have first and second total reflection surfaces that extend to face each other, and that extend obliquely toward the inside of the light guide section, and a first element surface. On the other hand, a method using a light guide plate in which a plurality of second element surfaces extending at an obtuse angle are alternately arranged is used.

  In these types of devices, the light beam taken into the light guide through the collimating optical system spreads and propagates in the vertical visual field direction in the light guide plate. For this reason, if a wide viewing angle is to be achieved, it is difficult to properly extract light due to the plurality of mirrors provided in the light guide or the fine structure on the side surface of the light guide, and there is a problem that a vertical view cannot be secured. It was

  The main object of the present invention is to secure a wide viewing angle of a light guide for a virtual image display device, particularly a vertical viewing angle.

  The present invention is a light guide for a virtual image display device that guides image light from an image display element and emits the image light in order to display a virtual image. A light guide member having a light ray emission portion for emitting the light to the outside, and the light guide member reverses the traveling direction of the image light incident from the light ray incident portion and guided in the light guide member. A retroreflective portion and an image extraction portion that guides and extracts the image light whose traveling direction is reversed in the retroreflective portion to the light ray emission portion, and the retroreflective portion is composed of a number of surfaces. Is the most important feature.

  According to the present invention, a wide viewing angle of a light guide for a virtual image display device is realized, and in particular, a vertical viewing angle is secured.

It is a top view showing an embodiment of a light guide concerning the present invention. FIG. 3 is a partially enlarged plan view for explaining a light ray incident part in the light guide member of the light guide of FIG. 1. FIG. 3 is a partially enlarged plan view for explaining the configuration of an image extraction unit in the light guide member of the light guide of FIG. 1. It is a perspective view of the light guide member of the light guide of FIG. It is a front view of the light guide member of the light guide for explaining the structure of the retroreflective portion. FIG. 3 is a plan view for explaining a virtual image display device using the light guide of FIG. 1. As a reference example, it is a diagram for explaining the spread of image light in a light guide member having no retroreflective portion. It is a figure which shows a mode that the image light radiate|emitted from the corner of an image display element guides in the light guide member of the light guide of FIG. FIG. 9 is a plan view of a light guide member showing how the image light of FIG. 8 is guided. FIG. 6 is a partially enlarged plan view for explaining a disposition state of a boundary surface between an image extraction portion of a light guide member and an optical member. It is a figure explaining the Example of the virtual image display apparatus using the light guide member of FIG. 4, and is a side view for demonstrating the emission state of the image light of a vertical visual field direction. FIG. 12 is a plan view showing the emission state of the image light of FIG. 11 from the horizontal visual field direction. It is a figure explaining the Example of the virtual image display apparatus using the light guide member as a modification, and is a side view for demonstrating the emission state of the image light of a vertical visual field direction. It is a top view which shows the ejection state of the image light of FIG. 13 from a horizontal visual field direction.

  Embodiments to which the present invention is applied will be described below with reference to the drawings. The following embodiments relate to a transmissive light guide and a virtual image display device using the same.

  FIG. 1 shows a light guide 50 of the present embodiment, and FIG. 6 shows the configuration of a virtual image display device in which the light guide 50 is arranged on the optical path of a virtual image display optical system. In FIG. 6, the optical path of the virtual image display optical system in the virtual image display device is shown by a solid line, and the eyes of the user of the device, that is, the virtual image observer are schematically drawn. Hereinafter, regarding the surface of the light guide 50, the surface on the front side (lower side in FIGS. 1 and 6) as viewed from the observer is referred to as “rear surface”, and the surface on the back side (upper side in FIGS. 1 and 6) is referred to as “front surface”. ".

  The light guide 50 is an element that enters and guides image light from the image display element to the inside and emits the image light for displaying a virtual image. In the present embodiment, the light guide member 100 and the optical member 200 are integrally formed. By being provided, the whole has a substantially prismatic shape and has a trapezoidal outer shape which is asymmetric in plan view.

  The light guide member 100 of the light guide 50 has a role of taking in the image light from the image display element inside, guiding the image light, and emitting the image light to the outside for displaying a virtual image. For this reason, the light guide member 100 includes a light ray incident part 101 for injecting the image light into the inside, front and rear surfaces for reflecting the incident image light and guiding it to the inside, and taking out the guided image light to the outside. A light emitting unit 104 for emitting light is provided. Further, the light guide member 100 includes a retroreflector 106 that reverses the traveling direction of image light that is incident from the light beam incident unit 101 and is guided in the light guide member, and image light whose traveling direction is reversed by the retroreflector 106. The image extracting unit 103 is configured to guide the light to the light emitting unit 104 and extract the light.

  In this embodiment, the image extraction unit 103 is provided on the front surface of the light guide member 100, and the light beam emission unit 104 is provided on the rear surface of the light guide member 100. The image extraction unit 103 has a role of reflecting the image light guided inside toward the light emission unit 104, and the light emission unit 104 converts the image light guided from the image extraction unit 103 to a virtual image observer. It has the role of ejecting toward the outside.

  An area of the front surface of the light guide member 100 where the image extracting portion 103 is not provided is a total reflection surface 105 for totally reflecting and advancing the incident image light. In order to improve the see-through property, the total reflection surface 105 and the rear surface of the light guide member 100 are flat surfaces and are formed parallel to each other.

  The image extraction unit 103 has a shape such that the thickness of the member of the light guide member 100 increases toward the retroreflective unit 106, and the detailed configuration will be described later. The retroreflective portion 106 is formed on the end surface on the opposite side to the light ray incident portion 101, and the detailed configuration will be described later.

  The light incident part 101 of the light guide member 100 is shown in an enlarged manner in FIG. The light ray incident portion 101 is continuously provided from the rear surface of the light guide member 100, and has a shape protruding from the front surface of the light guide member 100 in order to secure a wider incident area of image light.

  The image extracting portion 103 of the light guide member 100 is shown in an enlarged manner in FIG. In FIG. 3, the reference plane parallel to the light emitting unit 104 is shown by a dotted line. As shown in FIG. 3, the image extraction unit 103 includes a first surface 103a having an angle of θa with respect to the light beam emitting unit 104 and a second surface 103b having an angle of θb with respect to the light beam emitting unit 104. They are arranged alternately and have a substantially staircase shape.

  The first surface 103 a of the image extracting unit 103 is a surface that plays a role of guiding the image light that enters the light guide member 100 and is reflected by the retroreflecting unit 106 to the light emitting unit 104 and emits the image light from the light emitting unit 104. It is a flat surface that is inclined with respect to the light emitting unit 104. The first surface 103a faces the retroreflective portion 106 by being inclined with respect to the light emitting portion 104 at a predetermined inclination angle.

  The value of the angle θa with which the first surface 103a is inclined with respect to the light emitting portion 104 depends on the refractive index of the material of the light guide member 100, but is preferably set in the range of 20 degrees to 40 degrees.

  On the other hand, the second surface 103b has a role of reflecting the incident image light and guiding it to the retroreflective unit 106, and a role of a reflective surface for reflecting the image light whose traveling direction is reversed by the retroreflective unit 106. And is a plane parallel to the light emitting unit 104. Therefore, the angle θb=0°. Further, the second surface 103b also plays a role as a transmissive surface on which the external light from the front surface and the rear surface of the light guide 50 is incident in order to ensure the see-through property.

  When the second surface 103b is tilted with respect to the light emitting portion 104, that is, when the angle θb≠0° is set, the image light guided in the light guide member 100 has a reflection angle reflected by the second surface 103b. , The reflection angle reflected by the light emitting unit 104 does not match and changes. In this case, the incident angle θin defined by the angle formed by the ray incident from the ray incident portion 101 and the normal line of the ray incident portion 101, and the ray emitted from the ray emitting portion 104 and the normal line of the ray emitting portion 104. The exit angle θout defined by the angle between and does not become the same angle. Further, when the image light is emitted to the outside of the light guide 50 through the first surface 103a and the light ray emission unit 104, it is emitted in different directions, which makes the image unimaginable. Therefore, in the present embodiment, the angle θb is set to 0° and the second surface 103b is formed in parallel with the light beam emitting portion 104.

  As shown in FIG. 3, each second surface 103b preferably has a structure in which the height of the second surface 103b gradually increases as it approaches the retroreflective portion 106. In other words, it is preferable that the distance between the second surface 103b and the light emitting portion 104, that is, the thickness of the member of the light guide member 100 increases as the distance from the retroreflective portion 106 increases.

  According to the light guide member 100 having such a configuration, when viewed from the advancing direction of the image light after the advancing direction of the light rays is inverted by the retroreflecting portion 106, the height of each second surface 103b is gradually decreased, and the image light is reduced. The interval for total reflection is narrowed. Therefore, the number of light rays reflected by the image extraction unit 103 gradually increases, the number of light rays entering the eye from the light ray emission unit 104 increases, and a good virtual image with less brightness unevenness can be observed.

  Next, with reference to the plan view of FIG. 1, the perspective view of FIG. 4, and the front view of FIG. 5, details of the retroreflective section 106 provided in the light guide member 100 will be described.

  As shown in FIG. 1, the retroreflective portion 106 is on a side surface of the light guide member 100 that is a surface perpendicular to the light ray emitting portion 104, specifically, on an end surface on the side opposite to the light ray incident portion 101. It is provided in. The retroreflective portion 106 is composed of a large number of surfaces, as shown in FIGS. 4 and 5. In other words, the end surface on the side opposite to the light incident portion 101 is not a flat surface, but a large number of surfaces as the retroreflective portion 106 are formed.

  As shown in FIG. 5, the retroreflective portion 106 has a first inclined surface 106 a that is inclined at an angle θs with respect to one side surface 107 of the light guide member 100 that is continuous with the light incident portion 101, and a first inclined surface 106 a. On the other hand, the second inclined surface 106b inclined at the angle θp is continuously formed. Then, the first inclined surface 106a and the second inclined surface 106b form one prism. In other words, the retroreflective unit 106 has a configuration in which a plurality of roof-shaped prisms are continuously provided on the end surface on the side opposite to the light incident unit 101. The first inclined surface 106a and the second inclined surface 106b are flat surfaces having substantially the same shape and area.

  In the present embodiment, the angle θs formed by the side surface 107 and the first inclined surface 106a is 135 degrees. The angle θp formed by the first inclined surface 106a and the second inclined surface 106b is the apex angle of the prism, and is 90° in this embodiment. Therefore, the retroreflective portion 106 is composed of a large number of prisms having an apex angle of 90 degrees.

  In order to satisfactorily reflect the image light reaching the retroreflective portion 106, it is preferable to provide the retroreflective portion 106, that is, the first inclined surface 106a and the second inclined surface 106b with a coat having a high reflectance. The reflectance of such a coat is preferably 70% or more.

  In the present embodiment, the retroreflecting portion 106 is formed on one of the side surfaces perpendicular to the light ray emitting portion 104, that is, on the end surface opposite to the light ray incident portion 101.

  Explaining the configuration of the light guide 50 in more detail, the material of the light guide member 100 is preferably a highly transparent material in consideration of the see-through property, and further, in consideration of the above-described processing of the image extracting portion 103, it is molded of resin. Preferably.

  Further, the image extraction unit 103 can be coated with any coating, for example, a mirror coating such as aluminum, silver, or a dielectric coating. In order to prevent as much as possible the loss of the amount of guided image light, it is desirable that the first surface 103a of the image extraction unit 103 be coated with a reflectance of about 100%.

The value of the width w of the second surface 103b of the image extracting unit 103 in the light guide member 100 is
0.5 [mm] <w <3.0 [mm]
It is set to satisfy the condition of. Here, the width w is the length of the second surface 103b in the direction along the longitudinal direction of the light guide member 100, that is, the direction along the traveling direction of the incident image light.

  Hereinafter, the setting condition of the width w of the second surface 103b will be described in detail.

  The width of the visual field that can be confirmed as a virtual image is referred to as an “eye box”, and the distance from the light emitting unit 104 to which the virtual image can be confirmed to the eyeball is referred to as an “eye relief”. Then, assuming that the diameter of the eye box is φ, the eye relief is L, the thickness (wall thickness) of the light guide is tl, and the surface parallel to the light emitting portion 104 of the image extracting portion 103, that is, the number of second surfaces 103b is n. The width w of the second surface 103b is expressed by the following equation.

  Here, the wider the eyebox is, the wider the visible range is. Therefore, it is usually desirable that the eyebox diameter φ be large. On the other hand, when the eyebox diameter φ is increased, the thickness of the light guide becomes thicker, and the difficulty of designing the light guide tends to increase.

  Generally, the diameter of the pupil of the eye is about 5 mm, but since it is necessary to set the proper position of the light guide 50 according to individual differences, it is better to set the eyebox diameter φ larger. Further, in consideration of applying the light guide 50 to a spectacles-type virtual image display device as described later, the eye relief L is generally required to be 15 mm or more.

Therefore, for example, when the eye relief is set to 20 mm and the eye box is set to 5 mm or more and 10 mm or less, the width w of the second surface 103b is 0.5 [mm]<w<3.0 [mm] above.
The condition of must be met.

  When the width w of the second surface 103b of the image extracting unit 103 is less than 0.5 mm, the width of the first surface 103a needs to be shortened, and the diffraction phenomenon of the incident image light is likely to occur, and the manufacturing process is difficult. It is not desirable because it becomes difficult. Further, in order to secure the eye box of 5 mm or more and 10 mm or less at the position of the eye relief 20 mm without shortening the width of the first surface 103a, it is necessary to increase the thickness of the light guide, which is also preferable because the weight becomes large. Absent.

  On the other hand, when the width w of the second surface 103b exceeds 3.0 mm, the density of the light rays emitted from the light ray emitting unit 104 after being reflected by the first surface 103a is reduced due to the incident image light, and the position of the eyes is reduced. This is not desirable because the amount of light at. Therefore, it is desirable that the width w of the second surface 103b of the image extracting unit 103 satisfy the condition of 0.5 [mm]<w<3.0 [mm].

  The width w of the second surface 103b may be different for each second surface 103b. Specifically, since the light ray density of the image light generally decreases as the distance from the light ray incident portion 101 decreases, the width w of the second surface 103b is set to be smaller as the distance from the light ray incident portion 101 decreases. Good to do. With such a setting, the number of arrangements of the first surface 103a per unit length increases as the distance from the light ray incident unit 101 increases, and thus it is possible to reduce unevenness in the light amount.

  Similarly, in order to reduce the unevenness of the light amount, the width of the first surface 103a of the image extraction unit 103 may be different for each first surface 103a. Here, the width of the first surface 103a is the length of the first surface 103a in the direction along the longitudinal direction of the light guide member 100, that is, the direction along the traveling direction of the incident image light. Specifically, it is preferable to set the width of the first surface 103a to be larger as the distance from the light ray incident unit 101 is shorter. With this setting, the area of the first surface 103a increases as the distance from the light ray incident portion 101 increases, and thus unevenness in the light amount can be reduced.

  The thickness of the light guide 50 is preferably in the range of 1 mm to 8 mm. If the thickness of the light guide 50 is less than 1 mm, it becomes difficult to form the shape of the image extracting portion 103 of the light guide member 100. On the other hand, if the thickness of the light guide 50 exceeds 8 mm, it is advantageous to obtain a wide viewing angle, but it is not preferable because the weight of the member increases.

  Next, the configuration of the optical member 200 will be described with reference to FIG. As shown in FIG. 1, the optical member 200 has a tapered outer shape in a plan view. The optical member 200 is provided so as to face the front surface of the light guide member 100, that is, the image extraction unit 103 and the total reflection surface 105, and thus mainly secures the light transmittance, that is, the see-through property of the light emission unit 104 and the image extraction unit 103. Have a role to play.

  The optical member 200 has a front surface 210 positioned parallel to the light emitting portion 104 of the light guide member 100, and a rear surface that is inclined with respect to the front surface 210 as a whole. The rear surface of the optical member 200 is disposed so as to face the image extraction portion 103 of the light guide member 100 and is inclined as a whole with respect to the front surface 210, and the front surface 210 that is disposed so as to face the total reflection surface 105 of the light guide member 100. It has parallel plane portions 205. The inclined portion 203 is configured such that the thickness of the member of the optical member 200 becomes thinner as it approaches the retroreflective portion 106 of the light guide member 100. Details of the inclined portion 203 will be described later.

  Hereinafter, a virtual image display device using the light guide 50 described above will be described with reference to FIG.

  The virtual image display device of this embodiment shown in FIG. 6 includes an image display element 10 that outputs image light of a display image, a collimating optical system 300 that collimates and emits image light from the image display element 10, and the above-described light. The guide 50 is provided as a virtual image display optical system. FIG. 6 shows the optical path of the image light emitted from the center of the image display surface of the image display element 10. In such a virtual image display optical system, the collimating optical system 300 is arranged in the immediate vicinity of the light ray incident part 101 of the light guide member 100, and the image light displayed on the image display element 10, that is, the image information of the display image is angle-converted and guided. It plays a role of making the light incident on the optical member 100.

  The image display element 10 is a device that outputs image light of a display image that is a basis of a virtual image displayed through the light guide 50. The image display device 10 is preferably an organic ELD (Organic Light Emitting Diode) or a liquid crystal display device, but various display systems can be applied. For example, as the image display element 10, a DMD (Digital Micromirror Device) can be applied. Further, as the image display element 10, a TFT (Thin Film Transistor) or an LCOS (Liquid Crystal On Silicon) can be applied. Further, as the image display element 10, a MEMS (Micro Electro Mechanical Systems) can be applied.

  FIG. 6 shows an example in which an LCOS or DMD that requires a light source is used as the image display element 10, and a light source LS for illuminating the image display element 10 is added. Various types of light sources can be applied to the light source LS, and for example, an LED (Light Emitting Diode), a semiconductor laser (Laser Diode: LD), a discharge lamp, or the like can be used.

  The collimating optical system 300 includes a plurality of optical lenses and a diaphragm, and enlarges the image light output from the image display element 10 and emits it as parallel light.

  According to such a virtual image display device, the image light of the image display element 10 illuminated by the light source LS passes through the collimating optical system 300, is enlarged, and enters the light guide 50 as parallel light. That is, the image light, which is the parallel light expanded by the collimating optical system 300, enters from the light ray incident portion 101 of the light guide member 100 in the light guide 50 and is guided inside the light guide member 100. The guided image light travels toward the retroreflective portion 106 while totally reflecting the inside of the light guide member 100, that is, the front surface and the rear surface. When the image light reaches the retroreflector 106, the image light is reflected by a large number of prisms of the above-described first inclined surface 106a and second inclined surface 106b of the retroreflector 106, and travels in the direction of the light ray incident portion 101. Is reversed. When the image light whose traveling direction is reversed reaches the first surface 103a of the image extraction unit 103, the image light is reflected by the first surface 103a and guided to the light ray emission unit 104, and the image is emitted from the light ray emission unit 104 toward both eyes of the user. It is emitted as information. The user can visually recognize the virtual image of the image light by looking forward through the light emitting unit 104 of the light guide member 100 and the optical member 200.

  Next, details of the traveling state of the image light guided in the light guide member 100 will be described with reference to the drawings. FIG. 7 shows a state in which image light is incident on the light guide member 1000 as a reference example in which the retroreflective portion 106 is not provided. The light guide member 1000 as this reference example does not have the retroreflective portion 106, and the first surface 103a of the image extraction portion 103 is formed in the opposite direction, that is, in the direction facing the light ray incident portion 101. The configuration is different from that of the above-described embodiment.

  As shown in the figure, the image light emitted from the image display element 10 is made into collimated light by passing through the collimating optical system 300, and is incident from the light ray incident portion 101 of the light guide member 1000 to be guided. Proceed through 1000. The image light incident from the light ray incident part 101 is totally reflected in the light guide member 1000, and thus becomes divergent light and travels in the light guide member 1000 as shown in FIG. 7. That is, it can be seen that the image light incident from the light ray incident unit 101 diverges as it advances in the light guide member 1000. The degree of divergence of this image light becomes more remarkable as the light becomes wider in the wide-angle direction. Therefore, the image light propagating in the light guide member 1000 spreads and propagates in the vertical visual field direction.

  In this light guide member 1000, when the image light is to be extracted from the first surface 103a of the image extraction unit 103, the image light is extracted as divergent light, and thus the image is emitted from the light beam emission unit 104 and enters the eyes of the observer. The light will diverge in the vertical viewing direction. Therefore, the image light of the peripheral portion of the image having a large divergence angle does not enter the eyes of the observer, and the observed virtual image is lost.

  8 and 9 show how image light is guided in the light guide member 100 of the light guide 50 of the present embodiment. Here, FIG. 8 is a view shown from the front side (front side) of the light guide 50, and FIG. 9 is a view shown from the side side (upper side) of the light guide 50. Further, in FIG. 8 and FIG. 9, only one light ray 400 emitted from the corner of the image display surface of the image display element 10 is extracted and shown for the sake of clarity.

  As shown in the figure, the image light emitted from the corner of the image display element 10 passes through the collimating optical system 300 to be collimated light and enters from the light ray incident part 101 of the light guide member 100 to be guided. It advances in the member 100. The image light incident from the light ray incident part 101 of the light guide member 100 is totally reflected in the light guide member 100, and becomes divergent light to travel in the light guide member 100. That is, the image light incident from the light ray incident unit 101 travels in the light guide member 100 as divergent light until it reaches the retroreflective unit 106, as in the example described above with reference to FIG. 7.

  Subsequently, the image light is reflected by the retroreflective section 106, so that the traveling direction, that is, the light guiding direction is reversed. Here, the image light is reflected by both surfaces of the first inclined surface 106a and the second inclined surface 106b forming the retroreflective portion 106, and the incident light and the emitted light when viewed in the plane direction are parallel and the converged light is And advances in the light guide member 100. Further, the image light is reflected by the first surface 103a of the image extraction unit 103, is emitted from the light beam emission unit 104 as convergent light, and is guided in the direction of the observer's eye. As described above, according to the light guide 50 of the present embodiment, the image light is emitted as convergent light and is provided to the observer's eyes, so that a virtual image display device capable of observing satisfactorily without missing a virtual image even at a wide angle is realized. it can.

(Optical member)
Next, the configuration of the inclined portion 203 of the optical member 200 and the arrangement of the optical member 200 with respect to the light guide member 100 will be described. FIG. 10 shows an enlarged boundary surface between the light guide member 100 and the optical member 200. In FIG. 10, a virtual surface parallel to the front surface 210 of the optical member 200 is indicated by a dotted line.

  As shown in FIG. 10, in the optical member 200, the inclined portion 203 is arranged close to the image extraction portion 103 of the light guide member 100 via an air layer, that is, an air gap 140. In the present embodiment, the edge of the image extraction portion 103 of the light guide member 100 and the edge of the inclined portion 203 of the optical member 200 are bonded using a microball type adhesive. By doing so, it is possible to make the air gap 140 between the take-out portion 103 and the inclined portion 203 even, and to further improve the see-through property.

  The inclined portion 203 of the optical member 200 includes a third surface 203a having an angle of θa′ with respect to the front surface 210, and an angle of θb′ with respect to the front surface 210, at a portion facing the image extracting portion 103 of the light guide member 100. And the fourth surface 203b having the are arranged alternately.

  The front surface 210 is a surface parallel to the light emitting portion 104 of the light guide member 100. The fourth surface 203b is parallel to the front surface 210 and has an angle θb′=0°. Therefore, the fourth surface 203b is parallel to the light emitting portion 104 of the light guide member 100 and the second surface 103b, and θb=θb′=0°. With such a setting, the see-through property of the light guide 50 can be enhanced. If the fourth surface 203b is not a surface parallel to the front surface 210, the light emitting portion 104 of the light guide member 100, or the second surface 103b, the see-through property is deteriorated due to the prism effect, which is not preferable.

  Further, it is preferable that the angle θa′ of the third surface 203a with respect to the front surface 210 is set to the angle θa described above, that is, the angle equal to the angle of the image extraction unit 103 with respect to the light emitting unit 104. In this case, the third surface 203a of the optical member 200 becomes parallel to the first surface 103a of the light guide member 100, and the see-through property of the light guide 50 can be further enhanced.

  In order to obtain the maximum effect on the see-through property of the light guide 50, when the first surface 103a of the light guide member 100 is translated in the normal direction of the light emitting unit 104 (upward direction in FIG. 10), the light guide member 100 faces each other. The misalignment with the third surface 203a that is formed may be eliminated as much as possible. In order to eliminate such a shift, the optical member 200 can be attached with an adjusting mechanism for adjusting the distance between the optical member 200 and the light guide member 100, that is, the air gap 140.

  In order to ensure the see-through property of the light guide 50, the light guide member 100 and the optical member 200 are preferably made of the same material.

  The air gap 140 between the take-out portion 103 and the inclined portion 203 can contain various gases and liquids, but is preferably atmospheric air from the viewpoint of ensuring the see-through property.

  In the embodiments shown in FIGS. 1 to 10 described above, the example in which the light beam incident portion 101 of the light guide member 100 is arranged on the left side of the virtual image observer and the image light is incident from the left side of the virtual image observer has been described. The same effect as described above can be obtained when the arrangement is reversed from right to left, that is, when the light beam incident unit 101 of the light guide member 100 is arranged on the right side of the virtual image observer and the image light is incident from the right side of the virtual image observer. can get.

  Further, although only one eye of the virtual image observer is shown in FIGS. 6 and 9, the light guide 50 can confirm the emitted image with both eyes. On the other hand, the light guide 50 can be made smaller to be a light guide for a single eye.

  In the above-described embodiment, the case where the light guide 50 is applied to the eyeglass-type HMD has been described. The light guide 50 described above can be applied to other types of HMDs, and can also be applied to a head-up display (HUD). The light guide 50 is particularly suitable for displaying a virtual image of an original image formed by a light beam optically modulated by a minute device.

  As described above, according to the above-described embodiment, it is possible to provide a light guide for a virtual image display device that is thin and can secure a wide viewing angle of 40 degrees or more, and particularly can secure a good viewing angle in the vertical direction. it can.

(Example of virtual image display device)
Hereinafter, specific examples of the virtual image display device will be described with reference to FIGS. 11 to 14. 11 and 12 show a virtual image display device manufactured by using the above-described light guide 50 as a first embodiment, and FIGS. 13 and 14 use a light guide 50A as a modified example as a second embodiment. The manufactured virtual image display device is shown.

  In Examples 1 and 2, a collimator lens with a focal length of 7.5 mm was used, and a light guide was made of plastic with a refractive index (Nd)=1.53, and the angle θa of the first surface was 31.5 degrees. Set. Further, the light guide was manufactured so as to satisfy the conditions of the eye relief of 15 mm or more and the eye box of 5 mm or more with respect to the emitted image light.

(Example 1)
In Example 1 shown in FIGS. 11 and 12, the light guide 50 was manufactured by setting the dimensions of the light guide 50 to the following numerical values.
・Thickness of light guide (thickness): thinnest part 1mm, thickest part 1.9mm
・Longitudinal length of light guide: 46mm
・Width of light guide: 33mm

  In Example 1, the horizontal viewing angle of the light guide=50 degrees and the vertical viewing angle=27 degrees were secured.

(Example 2)
The light guide 50A manufactured in Example 2 shown in FIGS. 13 and 14 has a structure in which image light is incident from the rear surface side. Compared with the light guide 50 of the above-described embodiment and Example 1, The configurations are different.

  That is, in the light guide member 100A of the light guide 50A of the second embodiment, as shown in the drawing, the light ray incident portion 101A on which the image light is incident is provided on the same surface as the light ray emission portion 104, that is, on the rear surface. Therefore, in Example 2, the arrangement of the optical paths of the optical system is different, and the collimator lens is provided on the rear surface side of the light guide 50A. Further, the light guide member 100A is provided with a reflection portion 102 for reflecting the image light incident on the light ray incident portion 101A and guiding the image light to the inside of the light guide member 100A. The reflecting portion 102 is a plane that is continuous with the light incident portion 101A and the front surface 105, and is inclined at a predetermined angle with respect to the light incident portion 101A.

  In the second embodiment, the size of the light guide 50A is set to be the same as that of the first embodiment. That is, regarding the thickness (thickness) of the light guide 50A, the thinnest portion was 1 mm, the thickest portion was 1.9 mm, the length in the longitudinal direction was 46 mm, and the width was 33 mm. In Example 2 as well, the horizontal viewing angle of the light guide=50 degrees and the vertical viewing angle=27 degrees were secured.

  As described above, according to the above-described embodiments and examples, it is possible to provide a light guide for a virtual image display device that is thin and can secure a wide viewing angle, and particularly can secure a good viewing angle in the vertical direction. ..

10 image display element 300 collimating optical system LS light source 50, 50A light guide 100, 100A light guide member 101, 101A light incident part 102 reflection part 103 image extraction part 103a first surface 103b second surface 104 light emission part 105 total reflection surface 106 Retroreflective part 106a 1st inclined surface 106b 2nd inclined surface 140 Air layer 200 Optical member 203 Inclined part 205 Flat part 210 Front surface

Patent No. 5698297 Patent No. 5421285 Patent No. 5703875

Claims (8)

A light guide for a virtual image display device, which guides image light from an image display element and emits to display a virtual image,
A light guide member having a light ray incident portion on which the image light is incident and a light ray emission portion for emitting the image light to the outside,
The light guide member includes a retroreflective portion that reverses a traveling direction of image light that is incident from the light beam incident portion and is guided in the light guide member, and image light whose traveling direction is reversed by the retroreflective portion. Equipped with an image extraction part that guides the light to the light emission part
The image extraction unit is configured such that first surfaces that are inclined with respect to the light emitting unit and face the retroreflective unit and second surfaces that are parallel to the light emitting unit are alternately arranged, and Light is guided from one surface to the light emitting part,
The light guide, wherein the retroreflective portion is composed of multiple surfaces. The light guide according to claim 1, wherein the retroreflective portion includes a plurality of prisms having an apex angle of 90 degrees. The light guide according to claim 2, wherein the plurality of prisms are arranged on a surface perpendicular to the light emitting portion. The light guide according to claim 1, wherein the retroreflective portion has a coat having a reflectance of 70% or more. The light guide according to claim 1, wherein the image extraction portion has a shape in which the thickness of the light guide increases from the light incident portion toward the retroreflective portion. The light guide according to any one of claims 1 to 5, wherein a distance between the second surface and the light ray emitting portion increases as the distance from the light ray incident portion to the retroreflective portion increases. Further comprising an optical member integrally provided with the light guide member,
The optical member is joined to the light guide member via an air layer, and a surface opposite to the joined surface is provided with a surface parallel to the light emitting portion of the light guide member. 7. The light guide according to any one of 6 to 6. A light source that emits illumination light,
An image display element that receives the illumination light from the light source and outputs image light of a display image for displaying a virtual image,
A collimating optical system that collimates and emits image light from the image display element,
The light guide according to claim 1, wherein the image light from the collimating optical system is guided and emitted.
Image display device having a virtual image display optical system.