JP2017067889A - Virtual image optical system, light guide, and virtual image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a virtual image optical system that realizes a compact light guide.SOLUTION: A virtual image optical system comprises an image display element 10, a collimating optical system 300, and a light guide 50 that guides and outputs image light to display a virtual image. The light guide has a light guide member 100 with a light incident section 101 for the image light to enter and a light exit section 104 for the image light to exit, each being formed on a different surface. The collimating optical system has an optical axis at an angle with the light exit section 104. The light guide member 100 has an image extraction section 103 which comprises alternately arranged first surfaces that are at an angle with the light exit section 104 and second surfaces parallel to the light exit section 104 and is configured to guide the image light from the first surfaces to the light exit section 104 in order to extract the image light.SELECTED DRAWING: Figure 3

Description

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

  A virtual image display device using a light guide is known as a device that enlarges a two-dimensional image using a virtual image optical system and displays the enlarged virtual image so that an observer can observe it. In recent years, a head mounted display (hereinafter referred to as “HMD”) is becoming popular as one form of light guide used in such a virtual image display device. The HMD is classified into a see-through transmission type and a non-transmission type. The transmission type HMD is, for example, Google LTD. There is Googleglass (registered trademark) of (USA). Various proposals have also been made by non-transparent HMDs for their immersion.

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

  With regard to the outer shape and size of the HMD, the viewing angle tends to be narrower if emphasis is placed on reducing the size and thickness of the main body. Conversely, when the display area is wide, the main body size increases and becomes thicker. There is a tendency.

  In recent years, the transmissive type has been required to be thin, small, and have a wide viewing angle due to user needs. As a transmissive virtual image display device in consideration of such demand, for example, Patent Document 1 Thru 3 are known.

  The virtual image display device of Patent Document 1 is arranged so that the light incident portion and the light emitting portion of the light guide plate are positioned on the same plane, and the principal ray of the projection lens of the collimating optical system is incident perpendicularly to the light guide plate. Then, two or more main surfaces and edges are provided on the light transmissive substrate. This virtual image display device includes means for imaging light on a light-transmitting substrate by total reflection and one or more partial reflecting surfaces provided on the light-transmitting substrate.

  The virtual image display device of Patent Document 2 has an injection portion for allowing a light beam to enter the optical waveguide in an optical waveguide having two surfaces, and the optical waveguide displays the continuous light reflected by the two surfaces of the optical waveguide. Propagate and emit a light beam. This virtual image display device has a fine structure on a flat surface on one surface of two surfaces of an optical waveguide, and by making the two surfaces of the optical waveguide parallel, a transmitted image and a virtual image can be obtained. Overlapping.

  The virtual image display device of Patent Document 3 uses a light guide plate having a free-form surface, arranges the projection lens so as to be inclined with respect to the light guide plate, and forms an intermediate image in the light guide plate with light emitted from the projection lens. The intermediate image formed in the light guide plate is enlarged by the image extraction unit of the light guide plate to display a virtual image.

  An object of the present invention is to provide a virtual image optical system capable of realizing a light guide in a compact manner.

  A virtual image optical system according to the present invention includes an image display element that outputs image light of a display image, a collimating optical system that collimates and emits image light from the image display element, and image light from the collimating optical system. A light guide that guides and emits light for virtual image display, and the light guide includes a light incident part that receives the image light and a light output part that emits the image light to the outside. A light guide member formed on a different surface, the optical axis of the collimating optical system is inclined with respect to the light emitting part of the light guide, and the light guide member is disposed with respect to the light emitting part. And an image taking-out unit that guides and takes out the image light from the first surface to the light-emitting unit. The first surface is inclined alternately and the second surface is parallel to the light-emitting unit. And

  ADVANTAGE OF THE INVENTION According to this invention, the virtual image optical system which can be implement | achieved compactly of a light guide can be provided.

1 is a plan view schematically showing an embodiment of a virtual image optical system to which the present invention is applied, and shows a positional relationship between an image display element, a collimating optical system, and a light guide. It is a perspective view of the virtual image optical system of FIG. It is an optical path diagram of the virtual image optical system. It is a top view which shows one Embodiment of a light guide. It is a top view which shows other embodiment of a light guide. It is a perspective view of the virtual image optical system by the light guide of FIG. FIG. 5 is a plan view showing various light guides in comparison, where (a) shows the light guide of FIG. 4, (b) shows the light guide of FIG. 5, and (c) shows the light guide of the reference example. It is the elements on larger scale of the light guide member of a light guide, (a) is a figure which expands and shows an image extraction part, (b) is a figure which expands and shows an image extraction part further. It is the elements on larger scale which show one structural example of an optical member, and the arrangement state of a light guide member and an optical member, (a) is a figure which expands and shows an image extraction part, (b) is an image extraction part. It is a figure expanding further. It is the elements on larger scale which show the state which joined the optical member and light guide member of FIG. 9 with the adhesive agent. It is the elements on larger scale which show the state which joined the light guide member of FIG. 9, and the optical member of another structural example with the adhesive agent. It is an optical arrangement | positioning figure which shows an example of the collimating optical system used with a virtual image optical system. It is an optical path diagram explaining the principle of a virtual image optical system. It is the elements on larger scale which explain other embodiment of a light guide member, (a) is a figure which expands and shows an image extraction part, (b) is a figure which expands and shows an image extraction part further. It is the elements on larger scale which show the arrangement state of the light guide member of FIG. 14, and an optical member, (a) is a figure which expands and shows an image extraction part, (b) is a figure which expands and shows an image extraction part further. is there. It is the elements on larger scale which show the state which joined the optical member and light guide member of FIG. 14 with the adhesive agent. It is the elements on larger scale which show the state which joined the light guide member of FIG. 14, and the optical member of another structural example with the adhesive agent. It is a top view which shows the virtual image display apparatus provided with the virtual image optical system of this embodiment. It is a schematic diagram showing the example which applied the light guide of this embodiment to spectacles type HMD, (a) is a case where a light guide is made into a monocular type, (b) And (c) is a monocular for a light guide. The figure shows the case of applying to the left and right eyes and the case of applying to one eye.

  Embodiments to which the present invention is applied will be described below with reference to the drawings. The following embodiments relate to a virtual image optical system and a virtual image display device using a transmissive light guide. First, the configuration of a virtual image optical system for a virtual image display device will be described.

  The virtual image optical system of the present embodiment shown in FIGS. 1 and 2 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 A light guide 50. The light guide 50 guides image light that is enlarged and emitted from the collimating optical system 300 to the inside, and emits the light toward the outside, that is, the eyes of an observer for virtual image display. FIG. 3 schematically shows the eyes of the observer while the optical path of the virtual image optical system is indicated by arrows. Hereinafter, regarding the surface of the light guide 50, the front side (lower side in FIG. 3) viewed from the observer is referred to as a “rear surface”, and the rear side (upper side in FIG. 3) is referred to as a “front surface”.

  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 element 10 is preferably an organic LED (OLED: Organic Light Emitting Diode) or a liquid crystal display element, but various other display methods can be applied. For example, a DMD (Digital Micromirror Device) can be applied as the image display element 10. Further, as the image display element 10, TFT (Thin Film Transistor) or LCOS (Liquid Crystal On Silicon) can be applied. Further, as the image display element 10, MEMS (Micro Electro Mechanical Systems) can be applied.

  The collimating optical system 300 enlarges the above-described image light output from the image display element 10 and emits it as parallel light. As shown in FIG. 3, the collimating optical system 300 is arranged so that the central axis (optical axis) of the emitted light is inclined with respect to a light emitting unit 104 described later of the light guide 50. A configuration example of the collimating optical system 300 will be described later.

(Light guide)
The light guide 50 enters the image light from the collimating optical system 300 and guides it, and emits the light toward the outside, that is, the eyes of the observer, thereby providing the image light to the observer as a virtual image. . As shown in FIG. 4, the light guide 50 is integrated with the light guide member 100 for entering, guiding, and emitting image light, and the light guide member 100 to ensure the see-through property of the light guide 50. The optical member 200 is provided.

(Light guide member)
In this embodiment, the light guide member 100 of the light guide 50 includes a light beam incident part 101 into which image light from the collimating optical system 300 is incident and a light beam emission part 104 that emits image light to the outside. The light incident part 101 and the light emitting part 104 are formed on different surfaces. “Different planes” means that the planes are not the same plane or parallel planes, and the other side is inclined with respect to one side. In this embodiment, the light incident part 101 is inclined at an obtuse angle with respect to the light emitting part 104.

  In the present embodiment, the light incident part 101 and the light emitting part 104 of the light guide member 100 are flat. By making the light incident part 101 and the light emitting part 104 flat, the productivity of the light guide member 100 and the light guide 50 is improved, and the light guide member 100 and the light guide 50 as a whole are made simple. Can do.

  Further, by making the light incident part 101 and the light emitting part 104 different surfaces, it becomes possible to set the angle of the incident light to a more appropriate angle, thereby making the light guide compact, that is, small and thin. It becomes possible to. Also, by making the light incident part 101 and the light emitting part 104 different surfaces, a wide light bundle can be obtained, which is advantageous for making the viewing angle wide.

  In addition, when the light incident part 101 and the light emission part 104 are made into the same surface, although the ease of a processing surface and a management surface exists, the freedom degree of the light incident part 101 and the light emission part 104 reduces. For this reason, if the viewing angle is widened, the light guide becomes larger and thicker. For this reason, in this embodiment, the light incident part 101 and the light emission part 104 are made into different surfaces.

  On the other hand, in order to improve the see-through property, the light guide member 100 has a rear surface on which the light emitting section 104 is provided and a front surface 105 on the back side (upper side in FIG. 4) formed in parallel to each other.

 In the embodiment shown in FIG. 4, the entire rear surface of the light guide member 100 including the light emitting portion 104 is formed as a flat surface. On the other hand, as shown in FIG. 5, the light incident part 101 of the light guide member 100 can be formed in a shape protruding in a triangular shape from the extended surface of the light emitting part 104 in plan view. FIG. 6 shows a perspective view when the virtual image optical system is configured by the light guide shown in FIG. As can be seen by comparing FIG. 2 and FIG. 6, in the embodiment shown in FIG. 5, the area of the light incident portion 101 is relatively large, so that the incident light bundle can be increased, and a wider field of view can be obtained. A corner can be secured. Further, the light guide shown in FIG. 5 can make image light of a wider angle incident by changing the angle of the light ray incident from the collimating optical system 300.

  The light guide member 100 includes an image extraction unit 103 for guiding the image light incident from the light incident unit 101 to the light emission unit 104 and extracting the image light. A specific configuration of the image extraction unit 103 will be described later. The material of the light guide member 100 is preferably a highly permeable material in view of see-through properties, and is preferably molded from a resin in consideration of the processing of the image extraction unit 103 described later.

  The light guide shown in FIG. 4, the light guide shown in FIG. 5, and the light guide having the light incident portion 101 and the light emitting portion 104 as the same surface as reference examples are respectively shown in FIGS. And in comparison with (c). As shown in FIG. 7, the light incident from the collimating optical system 300 travels toward the light emitting section 104 while being totally reflected back and forth in the light guide obliquely. Here, the light guides in FIGS. 7A and 7B in which the light incident portion 101 and the light emitting portion 104 are different surfaces are the same as those in FIG. Compared with the case of c), the number of reflections can be reduced while shortening the length in the longitudinal direction. Thus, the light guide can be made small by making the light incident part 101 and the light emitting part 104 different surfaces.

(Optical member)
Returning to FIG. 4, the outline of the optical member 200 of the light guide 50 will be described. The optical member 50 has a planar taper shape, and is inclined with respect to the front surface 210 as a parallel surface parallel to the light emitting portion 104 of the light guide member 100 and the image extraction portion 103 of the light guide member 100. It has the inclination part 203 arrange | positioned. The inclined portion 203 of the optical member 200 is a portion that is installed in proximity to or joined to the image extraction portion 103 of the light guide member 100, and details of the portion will be described later.

  The light guide 50 is disposed so that the front surface 105 of the light guide member 100 and the front surface 210 of the optical member 200 are flush with each other so that the front surface and the rear surface of the light guide are parallel to each other. It has a shape that keeps up. As a modification of the light guide, the front surface 210 of the optical member 200 may have a shape protruding forward from the position of the front surface 105 of the light guide member 100 or retracted rearward. That is, considering the see-through property, it is desirable that the surface positions of the front surface of the light guide member 100 and the front surface 210 of the optical member 200 coincide with each other. It is good also as a form which shifts. However, it is desirable not to expose the image extraction unit 103 of the light guide member 100 to the outside.

  In the light guide 50, the plane of the light emitting part 104 of the light guide member 100 and the front surface 210 of the optical member 200 are parallel. With this configuration, the see-through property through the light emitting unit 104 is improved. If the surface of the light emitting part 104 of the light guide member 100 and the front surface 210 of the optical member 200 are not parallel, the see-through property is reduced by the prism effect, which is not preferable.

(Image extraction part of light guide member)
Next, the configuration of the image extraction unit 103 of the light guide member 100 will be described with reference to the partially enlarged plan views of FIGS. FIG. 8A shows an enlarged view of each part of the image extracting unit 103 and the light emitting unit 104 of the light guide member 100, and FIG. 8B shows an enlarged view of a part of the image extracting unit 103. Represents. In addition, in FIG. 8B, a virtual plane parallel to the light emitting unit 104 is indicated by a dotted line.

  In the image extraction unit 103, first surfaces 103a having an angle θa with respect to the light emitting unit 104 and second surfaces 103b having an angle θb with respect to the light emitting unit 104 are alternately arranged. It has a substantially stepped shape (see FIG. 8B).

  Here, the first surface 103 a is a surface that plays a role of guiding incident image light to the light emitting unit 104 and emitting it from the light emitting unit 104, and is a plane inclined with respect to the light emitting unit 104. . The angle θa at which the first surface 103a is inclined with respect to the light emitting portion 104 is preferably set in the range of 20 degrees to 30 degrees, although it depends on the refractive index of the material of the light guide member 100.

  On the other hand, the second surface 103 b is a surface serving as a reflecting surface that guides incident image light into the light guide member 100, and is a plane parallel to the light emitting unit 104. Therefore, the angle θb = 0 °. Further, the second surface 103b also serves as a transmission surface for allowing external light from the front and rear surfaces of the light guide 50 to enter in order to ensure see-through performance.

  Here, when the second surface 103b is inclined 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 is reflected by the second surface 103b. The reflection angle and the reflection angle reflected by the light beam emitting unit 104 change without matching. In this case, the incident angle θin defined by the angle formed by the light beam incident from the light beam incident unit 101 and the normal line of the light beam incident unit 101, the light beam emitted from the light beam emitting unit 104, and the normal line of the light beam emitting unit 104 The exit angle θout defined by the angle formed by and is not 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 emitting unit 104, it is emitted in a different direction, which is not a virtual image. Therefore, in the present embodiment, the angle θb = 0 °, and the second surface 103 b is formed in parallel to the light emitting portion 104.

When the width of the second surface 103b of the image extraction unit 103 in the light guide member 100 (the width in the left-right direction in FIG. 8) is w, the value of w is
0.5 [mm] <w <3.0 [mm]
Is set so as to satisfy the following conditions.

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

The width of the field of view that can be confirmed as a virtual image is referred to as “eye box”, and the distance from the light emitting unit 104 that can confirm the virtual image to the eyeball is referred to as “eye relief”. When the diameter of the eye box is φ, the eye relief is L, the thickness of the light guide is t _l , and the number of the surfaces parallel to the light emitting unit 104 included in the image extraction unit 103, that is, the number of the second surfaces 103 b is n, The width w of the surface 103b is expressed by the following equation.

  Here, since the visible range becomes wider as the width of the eye box becomes wider, it is usually desirable that the eye box is wider. On the other hand, when the eye box is widened, the thickness of the light guide increases, and the design difficulty of the light guide tends to increase.

  In general, the diameter of the pupil of the eye is about 5 mm. However, since it is necessary to set an appropriate position of the light guide 50 according to individual differences, it is better to set the eye box diameter φ larger. Further, considering that the light guide 50 is applied to a glasses-type virtual image display device as described later, the eye relief L is preferably set to 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].
It is necessary to satisfy the conditions.

  When the width w of the second surface 103b of the image extraction unit 103 is less than 0.5 mm, the width of the first surface 103a is shortened and diffraction of incident image light is likely to occur, which is not desirable.

  On the other hand, when the width w of the second surface 103b exceeds 3.0 mm, the density of the light beam that is reflected from the first surface 103a and emitted from the light beam emitting unit 104 for the incident image light decreases, and the position of the eye This is not desirable because the amount of light at is reduced. Therefore, it is desirable that the width w of the second surface 103b of the image extraction unit 103 satisfies the condition of 0.5 [mm] <w <3.0 [mm].

  The width w of the second surface 103b may be a different value for each second surface 103b. As a result, it is possible to reduce unevenness in the amount of light.

  The thickness of the light guide 50 is desirably in the range of 1 mm to 8 mm. If the thickness of the light guide 50 is less than 1 mm, it is difficult to form the shape of the image extraction 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 for obtaining a wide viewing angle, but it is not preferable because the weight of the member increases.

(Optical member)
Next, the configuration of the optical member 200 and the arrangement of the optical member 200 with respect to the light guide member 100 will be described. 9 to 11 show an enlarged boundary surface between the light guide member 100 and the optical member 200. FIG. In the example shown in FIGS. 9A and 9B, the optical member 200 is disposed close to the image extraction unit 103 of the light guide member 100 via an air layer, that is, an air gap 140. In other examples shown in FIGS. 10 and 11, the optical member 200 is bonded to the image extraction unit 103 of the light guide member 100 using an adhesive 150.

  First, the configuration shown in FIG. 9 will be described. In addition, in FIG.9 (b), the virtual surface parallel to the front surface 210 is represented by the dotted line. The inclined portion 203 of the optical member 200 includes a third surface 203 a having an angle θa ′ with respect to the front surface 210 and an angle with θb ′ with respect to the front surface 210 at a portion facing the image extracting portion 103 of the light guide member 100. The fourth surfaces 203b having the positions are alternately arranged (see FIG. 9B).

  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 the angle θb ′ = 0 °. Therefore, the fourth surface 203b is parallel to the light emitting portion 104 and the second surface 103b of the light guide member 100, and θb = θb ′ = 0 °. With such setting, the see-through property of the light guide 50 can be enhanced. In addition, when the 4th surface 203b is not a surface parallel to the front surface 210, the light emission part 104 of the light guide member 100, and the 2nd surface 103b, since see-through property falls by a prism effect, it is unpreferable.

  Furthermore, the angle θa ′ of the third surface 203 a with respect to 210 is preferably set to the angle θa described above, that is, an 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 203 of the optical member 200 is 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 improved.

  In order to obtain the maximum effect on the see-through property of the light guide 50, the first surface 103a of the light guide member 100 is opposed when translated in the normal direction (upward direction in FIG. 9) of the light emitting portion 104. This is to minimize the deviation from the third surface 203a. Although some deviation occurs in assembling, as a guide, when the deviation is about 10 μm, the see-through property can be maintained. In order to minimize such a shift, as an example, the optical member 200 can be provided with an adjustment mechanism that adjusts the distance between 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.

  Next, a mode in which the light guide member 100 and the optical member 200 are fixed via an adhesive will be described. FIG. 10 shows an example in which the light guide member 100 and the optical member 200 shown in FIG. 9 are fixed via an adhesive 150. As in the example described with reference to FIG. 9, the positions of the first surface 103a of the light guide member 100 and the opposing third surface 203a coincide with each other in the opposing portions of the light guide member 100 and the optical member 200. Are arranged as follows. With such an arrangement, total reflection at the second surface 103b of the light guide member 100 is maintained, and the see-through property of the light guide 50 can be maintained.

  The refractive index of the adhesive 150 is preferably lower than or equal to the refractive index of the material of the light guide member 100. When the refractive index of the material of the light guide member 100 and the refractive index of the adhesive 150 are made equal, a light guide is provided while ensuring reflection of image light at the interface by applying a coat such as a half mirror to the adhesive interface. 50 see-through performance can be improved. When the refractive index of the adhesive 150 is higher than the refractive index of the material of the light guide member 100, the image light is refracted at the site of the adhesive 150 without being totally reflected, so that a virtual image can be displayed. It becomes difficult.

  FIG. 11 shows a form in which the light guide member 100 and the optical member 200 are fixed via an adhesive 150 as in FIG. 10, but the optical member facing the image extraction unit 103 of the light guide member 100. 10 differs from the example of FIG. 10 in that the inclined portion 203 of 200 is a uniform surface. Also in the example shown in FIG. 11, by setting the refractive index of the adhesive 150 to be equal to or lower than the refractive index of the material of the light guide member 100, high see-through performance can be maintained.

(Configuration of collimating optical system)
Next, a specific configuration of the collimating optical system 300 and a principle of a virtual image optical system using the collimating optical system 300 will be described.

  A collimating optical system 300 shown in FIG. 12 includes an aperture stop, a first lens L1, a second lens L2, a third lens L3, and a fourth lens L4 arranged in this order from the exit side, that is, the light guide 50 side. It has a single lens configuration. In this example, the first lens L1 is a negative meniscus lens having a concave surface with respect to the light guide side, the second lens L2 and the fourth lens L4 are positive lenses having convex surfaces on both sides, and the third lens L3 has concave surfaces on both sides. It is a negative lens. The third lens L3 and the fourth lens L4 are cemented.

  For convenience of explanation, in FIG. 12, the surface of the image display element 10, that is, the image display surface S9 is shown close to the fourth lens L4, but actually, the image display element 10 has a predetermined distance from the fourth lens L4. They are arranged at intervals (see FIG. 3 etc.).

  As shown in FIGS. 12 and 13, the image light output from the image display element 10 is emitted toward the light guide 50 after the position information of the image light is converted into angle information by the collimating optical system 300. . The image light emitted from the collimating optical system 300 is incident on the light incident part 101 of the light guide 50 and is emitted from the light emitting part 104 to the outside. This emission angle is kept at the same angle as the incident angle from the collimating optical system 300.

  When the relationship between the incident angle and the emission angle is not maintained, the image light formed by the display element 10 becomes an image that is not desirable as a virtual image.

  More specifically, as shown in FIGS. 12 and 13, image light A, B, and C are output from the center and both ends of the image display element 10, respectively. The positional information of the image light is converted into angle information θA, θB, and θC through the collimating optical system 300. The image light is emitted from the collimating optical system 300 and is incident on the light incident portion 101 of the light guide 50. At this time, the image light A is incident on the light incident portion 101 at an angle of θA, the image light B is incident at an angle of θB, and the image light C is incident at an angle of θC. For easy understanding, in FIG. 13, for the image lights A, B, and C emitted from the collimator optical system 300, θA is a solid line “-”, and θB is an alternate long and short dash line “-•-”, θC, respectively. Is indicated by a dotted line "...".

  Thus, the image light incident on the light beam incident portion 101 is guided into the light guide 50, and the image lights A, B, and C move inside the light guide 50. Then, when the image lights A, B, and C are emitted from the light emitting portion 104 of the light guide 50, the incident angles of θA, θB, and θC in the image lights are stored as shown in FIG. It is injected in the state.

  Thus, in this embodiment, since the incident angle of each light beam that constitutes the image light emitted from the collimating optical system 300, that is, the angle information is stored, it is emitted from the light beam emitting unit 104 of the light guide 50. A high-quality virtual image can be displayed.

(Example)
Examples of collimating optical systems that can achieve the above-described effects will be described below. Regarding the collimating optical system 300 having the three-group four-lens configuration described above with reference to FIG.
Focal length: 10.0mm
F number: 1.56
Full length: 21.9mm
Injection angle: Maximum 20 degrees.

Also,
Table 1 shows numerical data of examples of the collimating optical system, where R: radius of curvature D: spacing and thickness Nd: refractive index of d-line νd: Abbe number

(Table 1)

  In Table 1, surface numbers S1 to S9 are assigned from the emission side in correspondence with FIG. 12, S1 indicates a diaphragm, and S9 indicates the surface of the display element 10, that is, the image display surface. In Table 1, an asterisk (*) added to the surface number represents an aspherical surface. That is, in this embodiment, the surfaces on both sides of the first lens L1 and the second lens L2 corresponding to the surface numbers S2 to S5 are aspheric surfaces, and the third lens L3 corresponding to the surface numbers S6 and S7 is both spherical surfaces. . The exit side of the fourth lens L4 corresponding to S7 is a spherical surface, and the incident side of the fourth lens L4 corresponding to the surface number S8 is an aspherical surface. Table 2 shows numerical data of such aspheric surfaces.

(Table 2)

  In Table 2, S2, S3, S4, S5 and S8 in the upper column are the surface numbers of the aspheric surfaces described above. K is a conical coefficient, and C4, C6, C8, and C10 are aspherical coefficients.

When an aspheric surface is expressed using the above-mentioned conical coefficient and aspheric coefficient, the following equation is known.
^{X = (H 2 / R)} / [1+ {1-K (H / r) 2} 1/2]
+ C4 · H ⁴ + C6 · H ⁶ + C8 · H ⁸ + C10 · H ¹⁰ + ...

  In this equation, X is “displacement in the optical axis direction at the position of the height H from the optical axis with respect to the surface vertex”, and the aspherical coefficients are C4, C6, C8, C10. expressed.

  In the above-described embodiments, the case where the collimating optical system 300 has a configuration of four lenses in three groups has been described. However, the present invention is not limited to this. The collimating optical system 300 may have other configurations, for example, a configuration with two lenses, or five or more lenses.

  In the embodiment, the position of the stop is located closest to the exit side of the collimating optical system. Considering the combination with the light guide 50, it is desirable that the stop position of the collimating optical system is the most exit side, that is, the light guide 50 side. The image information from the display element 10 is telecentric.

In the embodiment, the F number is 1.56, but the F number can be darkened to nearly 3.0. The F number of the collimating optical system 300 is
1.5 <F number <3.0
It is desirable to satisfy the conditional expression

  If the F number exceeds the lower limit of the conditional expression, the diameter of the collimating optical system 300 needs to be increased and the light guide 50 is increased in size, which is not desirable. On the other hand, if the F number exceeds the upper limit of the conditional expression, it is advantageous for miniaturization, but it is not desirable because the brightness of the virtual image is reduced.

(Example of light guide)
Next, numerical values of specific examples of the light guide will be described.

  In the following Examples 1 and 2, the light guide 50, that is, the light guide member 100 and the optical member 200 are made of a plastic material having a refractive index (Nd) = 1.54. Further, the angle θa of the first surface 103a in the image extraction unit 103 of the light guide member 100 is set to 30 degrees.

Example 1:
The thickness t of the light guide member 100 was set to 1 mm, and the width w of the second surface 103b in the image extraction unit 103 was set to 2.20 mm.

Example 2:
The thickness t of the light guide member 100 was set to 4 mm, and the width w of the second surface 103b in the image extraction unit 103 was set to 0.90 mm.

  Example 1 mainly focuses on weight reduction, and Example 2 mainly pursues light quantity. In each example, the horizontal viewing angle is 40 degrees, and the eye relief is 19 mm and the eye box is 5 mm. it can. In addition, each said angle is an absolute value display.

  In the second embodiment, the width w of the second surface 103b in the image extracting unit 103 is narrower than that in the first embodiment. In the second embodiment, the width of the first surface 103a in the image extraction unit 103 can be reduced by the amount that the width w of the second surface 103b is reduced, and the density of light emitted from the light emitting unit 104 is increased. Thus, it is possible to prevent a decrease in the amount of light at the pupil position.

  As a modification, the embodiment 1 and the embodiment 2 may be combined. Specifically, the thickness t of the light guide member 100 may be set to 1 mm, and the width w of the second surface 103b in the image extraction unit 103 may be set to 0.90 mm. Alternatively, the thickness t of the light guide member 100 can be set to 4 mm, and the width w of the second surface 103b in the image extraction unit 103 can be set to 2.20 mm.

  According to the embodiment described above, the position information of the image light output from the image display element 10 is converted into angle information in the collimating optical system 300 and is incident on the light beam incident portion 101 of the light guide 50. When the image light is emitted from the light emitting unit 104 to the outside, it is emitted in a state where the incident angle from the collimating optical system 300 is preserved, so that a high-quality virtual image can be displayed. In addition, a small light guide 50 having excellent see-through properties and a wide viewing angle of 40 degrees or more can be realized.

(Modification of light guide member)
Another configuration example of the light guide member 100 will be described with reference to FIGS. 14 to 16.

  In the above-described embodiment described with reference to FIG. 8 and the like, the image extraction unit 103 is configured by two planes of the first surface 103a and the second surface 103b. In other words, the image extraction unit 103 has a first surface 103 a having an angle θa with respect to the light emitting unit 104 and a second surface 103 b having an angle θb with respect to the light emitting unit 104. It has a stepped shape.

  On the other hand, in the modification shown in FIG. 14, the image extraction unit 103 is configured by four planes and has a sawtooth shape. Specifically, the image extraction unit 103 includes a first surface 103a having an angle θa with respect to the light emitting unit 104, a second surface 103b having an angle θb, and an inclined surface 103c having an angle θc. A plane 103d having an angle θd has a shape arranged in this order.

  Among the above four surfaces, the functions and optimum ranges of the first surface 103a and the second surface 103b are the same as in the above-described embodiment, and detailed description thereof is omitted.

  The inclined surface 103 c has a role of ensuring a large area of the first surface 103 a and a role of improving the bending strength of the light guide member 100.

  An angle θc of the inclined surface 103c with respect to the light emitting portion 104 is set to a range of greater than 0 ° and 90 °. When the angle θc is 0 °, the inclined surface 103c is the same surface as the second surface 102b, that is, a part of the second surface 102b, and thus has the same configuration as the above-described embodiment. In addition, the angle θc is preferably in the range of 45 ° to 90 ° in consideration of productivity. Furthermore, since the phenomenon such as irregular reflection occurs when the inclined surface 103c is irradiated with the image light from the image display element 10, it is preferable that the inclined surface 103c has an angle range in which the image light from the image display element 10 is not as much as possible.

  The plane 103 d is a part mainly for maintaining see-through property, and it is desirable that the angle θd = 0 ° with respect to the light emitting part 104, that is, parallel to the light emitting part 104. When the angle θd = 0 °, the image light from the image display element 10 can be reflected by the plane 103d as in the second surface 102b.

  Furthermore, as a further modification of the form of FIG. 14, the first surface 103 a and the inclined surface 103 c may be expanded upward in the figure, so that the image extraction unit 103 has a three-plane configuration without the flat surface 103 d. In this case, the image extracting unit 103 includes a first surface 103 a having an angle θa with respect to the light emitting unit 104, a second surface 103 b having an angle θb with respect to the light emitting unit 104, and the light emitting unit 104. On the other hand, an inclined surface 103c having an angle θc is continuously arranged.

  As described above, the image extraction unit 103 has a three-plane configuration or a four-plane configuration, resulting in a complicated shape as compared with the embodiment illustrated in FIG. 8 and the like. The area can be made relatively wide. Accordingly, it is possible to ensure a relatively large amount of image light emitted from the light emitting unit 104. Further, by adopting such a shape, it is possible to improve the bending strength, and it is particularly advantageous when the light guide member 100 is made of resin. That is, when the light guide member 100 is formed of resin, the bending strength is weakened on the tip side where the thickness of the light guide member 100 is reduced, but the bending strength can be improved by adding the inclined surface 103c.

  15 to 17 show an enlarged boundary surface between the light guide member 100 and the optical member 200 when the image extraction unit 103 has a four-plane configuration. In the example shown in FIGS. 15A and 15B, the optical member 200 is disposed close to the image extraction unit 103 of the light guide member 100 via air, that is, an air gap 140. In another example shown in FIGS. 16 and 17, the optical member 200 is bonded to the image extraction unit 103 of the light guide member 100 using an adhesive 150.

  In the example shown in FIGS. 15 and 16, the optical member 200 has the inclined portion 203 having the shape described in FIGS. 9 and 10. That is, in the inclined portion 203 of the optical member 200, the third surface 203a having an angle θa ′ with respect to the front surface 210 and the fourth surface 203b having an angle θb ′ with respect to the front surface 210 are alternately arranged. It has a two-sided structure. The preferred values of the angles θa ′ and θb ′ are the same as described above, and in this example, the angle θa = θa ′ and the angle θb = θb ′. The high see-through property can be maintained by setting the refractive index of the adhesive 150 to be equal to or lower than the refractive index of the material of the light guide member 100 as described above.

  The example shown in FIG. 17 is a case where the inclined portion 203 of the optical member 200 is a uniform surface as in FIG. 11. In this case as well, the refractive index of the adhesive 150 is the refractive index of the material of the light guide member 100. By making it equal or less, high see-through performance can be maintained.

  The modification in which the inclined surface 103c and the plane 103d are added to make the image extraction unit 103 have a three-plane configuration or a four-plane configuration is not limited to the configuration applied to the entire image extraction unit 103, and is applied to a part of the image extraction unit 103. May be. That is, while the first surface 103a and the second surface 103b are alternately arranged, the inclined surface 103c is further formed on a portion where the amount of light is to be secured and the portion where the bending strength is desired to be secured. Can add the plane 103d individually.

  Furthermore, when the image extraction unit 103 has a shape of a three-plane configuration or a four-plane configuration, the inclined portion 203 of the optical member 200 that is opposed to the image extraction unit 103 can have a shape corresponding to the three-plane or four-plane deformation shape. . In this case, as described above, when the first surface 103a of the light guide member 100 is translated in the normal direction of the light emitting portion 104, the deviation from the third surface 203a of the opposing optical member 200 is shifted. By adopting a shape that does not occur, the see-through property of the light guide 50 is improved. In order to eliminate such a deviation, an adjustment mechanism that adjusts the distance between the light guide member 100 and the optical member 200 can be attached.

  As described above, according to the various embodiments described above, a light guide and a virtual image optical system for a virtual image display device that are compact and can realize a wide viewing angle of 40 degrees or more are realized.

(Virtual image display device)
FIG. 18 shows a configuration of a virtual image display device using the light guide 50 and the virtual image optical system described above. In the drawing, the ray path of the image light is indicated by an arrow, and the eyes of the observer, that is, the user are schematically drawn. The virtual image display device shown in FIG. 18 is obtained by adding a light source LS for illuminating the image display element 10 to the virtual image optical system shown in FIG. As the image display element 10, LCOS, DMD, or the like that requires a light source is used. Various light sources LS can be applied. For example, an LED (Light Emitting Diode), a semiconductor laser (Laser Diode: LD), a discharge lamp, or the like can be used.

  According to this virtual image display device, the image light of the image display element 10 illuminated by the light source LS is magnified by the collimating optical system 300 and enters the light guide 50. That is, the image light magnified by the collimating optical system 300 enters from the light beam incident portion 101 of the light guide member 100 in the light guide 50 and is guided into the light guide member 100. The guided image light is reflected by the first surface 103a of the image extraction unit 103 and is emitted from the light emitting unit 104 as image information toward both eyes of the user. The user can visually recognize the virtual image of the image information by looking forward through the light emitting unit 104 and the optical member 200 of the light guide member 100.

  In the embodiment shown in FIGS. 1 to 18 described above, the light incident unit 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. When the arrangement is reversed left and right, that is, when the light beam incident portion 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, the same effect as described above is obtained. can get.

  FIGS. 19A, 19B, and 19C illustrate the case where the above-described light guide 50 is applied to a glasses-type virtual image display device, that is, an HMD.

  The example shown in FIG. 19A is a case where one light guide 50 is applied to an HMD for both eyes, and the light incident portion 101 of the light guide member 100 is arranged on the right side of the virtual image observer, that is, the user. . The light guide 50 is fixed to the frame part 400 that plays a role as a vine hung on the user's ear. In FIG. 19, the frame portion is simplified, but the frame portion 400 may have a shape that covers not only both ends of the light guide 50 but also the upper edge and the lower edge.

  On the other hand, the example shown in FIGS. 19B and 19C is a case where one light guide 50 is downsized and applied to a monocular HMD. The example shown in FIG. 19B is a case where the two light guides 50 and 50 are arranged corresponding to the positions of the left and right eyes of the user, and the light beam incident portions 101 of the respective light guides are arranged on the left and right outer sides. Is done.

  In FIG. 19, the virtual image optical system and the light source are not shown, but these can be attached to the frame unit 400. That is, in the example shown in FIGS. 19A and 19C, the light source L, the image display element 10, and the collimating optical system 300 are arranged in the right eye frame, and in the example shown in FIG. What is necessary is just to attach to a part.

  In the above-described embodiment, the case where the light guide 50 is applied to the eyeglass-type HMD has been described. On the other hand, the above-described light guide 50 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 micro device.

  As described above, according to the above-described embodiments and examples, a transmissive light guide having a small viewing angle of 40 degrees or more is realized, and a virtual image optical system capable of realizing a compact light guide and A virtual image display device can be provided.

DESCRIPTION OF SYMBOLS 10 Image display element 300 Collimating optical system LS Light source 50 Light guide 100 Light guide member 101 Light incident part 103 Image extraction part 103a 1st surface 103b 2nd surface 103c Inclined surface 103d Plane 104 Light emission part 150 Adhesive 200 Optical member 210 Front surface (Parallel plane)
203 Inclined part

Japanese Patent No. 4508655 Japanese Patent No. 5421285 JP 2014-153644 A

Claims (13)

An image display element that outputs image light of a display image, a collimating optical system that collimates and emits image light from the image display element, and guides image light from the collimating optical system to display a virtual image A virtual image optical system comprising a light guide to be emitted,
The light guide has a light guide member in which a light beam incident part on which the image light is incident and a light beam emission part for emitting the image light to the outside are formed on different surfaces, respectively.
The optical axis of the collimating optical system is arranged to be inclined with respect to the light emitting part of the light guide,
In the light guide member, first surfaces inclined with respect to the light emitting portion and second surfaces parallel to the light emitting portion are alternately arranged to guide the image light from the first surface to the light emitting portion. A virtual image optical system comprising an image extracting unit that extracts light. The light guide has an optical member provided integrally with the light guide member,
The virtual image optical system according to claim 1, wherein the optical member includes a parallel plane parallel to the light emitting section, and an inclined section that is inclined with respect to the parallel plane and is disposed to face the image extraction section. The virtual image according to claim 1, wherein the image extraction unit of the light guide member further includes an inclined surface that is provided between the first surface and the second surface and is inclined toward the second surface. Optical system. The virtual image optical system according to any one of claims 1 to 3, wherein the collimating optical system has an F number satisfying the following condition (1).
1.5 <F number <3.0 ... Condition (1)   The virtual image optical system according to claim 1, wherein each of the light incident portion and the light emitting portion of the light guide is a flat surface.   The virtual image optical system according to claim 1, wherein the light incident portion of the light guide protrudes from a surface of the light emitting portion. The virtual image optical system according to claim 2, wherein the inclined portion of the optical member includes a third surface inclined with respect to the parallel surface and a fourth surface parallel to the parallel surface. . The angle at which the third surface of the optical member is inclined with respect to the parallel surface is equal to an angle at which the first surface of the light guide member is inclined with respect to the light emitting portion. Virtual image optical system. 9. The virtual image optical system according to claim 1, wherein a width: w [mm] of the second surface in the image extraction portion of the light guide member satisfies the following condition (2).
0.5 [mm] <w <3.0 [mm] ... Condition (2)   9. The virtual image optical system according to claim 2, wherein the light guide includes the light guide member and the optical member disposed close to each other via an air gap.   The virtual image optical system according to claim 2, wherein the light guide is formed by bonding the light guide member and the optical member with an adhesive.   The virtual image optical system according to claim 2, wherein the optical member is formed of the same material as the light guide member. The virtual image optical system according to any one of claims 1 to 12,
And a light source that illuminates the image display element of the virtual image optical system.