JP2017207686A - Virtual image display device and virtual image display method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a virtual image display device in which a gap or luminance unevenness in an observed virtual image can be decreased while maintaining a wide viewing angle of a light guide.SOLUTION: The virtual image display device includes each one pair of image display elements 10 that output image light of displayed images for virtual display, collimation optical systems 300 that collimate the image light from the image display elements 10 and emit the light, and light guides 50 having light guide members 100 that guide the image light from the collimation optical systems 300 and emit the light. Each light guide member 100 has a ray entrance part 101 for receiving the light from the image display element 10 via the collimation optical system 300, a ray emitting part 104 for emitting the image light to the outside, and an image extracting part 103 for guiding and extracting the image light to the ray emitting part 104. Each image display element 10 outputs image light of a partial image produced by dividing the whole image to be visually recognized by both eyes.SELECTED DRAWING: Figure 1

Description

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

  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).

  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).

  In recent years, the transmission type has been required to have a thin wall, a small size, and a wide viewing angle because of user needs, and those described in the following patent documents are known in consideration of such a demand. It has been.

  The apparatus of Patent Document 1 employs a system in which a number of mirrors coated with a specific reflectivity are arranged, and image light is extracted by sorting light reflection and transmission according to the incident angle of the light.

  The apparatus of Patent Document 2 employs a method of taking out image light by providing a fine structure and a gap zone on one side of a light guide and reflecting and propagating light rays at these portions.

  The device of Patent Document 3 has first and second total reflection surfaces extending opposite to each other, and includes a plurality of first element surfaces extending obliquely toward the inside of the light guide unit, and first element surfaces. On the other hand, a light guide plate formed by alternately arranging a plurality of second element surfaces extending at an obtuse angle is used.

  In these types of devices, the light rays taken into the light guide via the collimating optical system spread and propagate in the direction of the vertical visual field in the light guide plate, and thus have the following problems.

  That is, when the image light spreads and propagates in the light guide plate, it is difficult for the light to hit a plurality of mirrors provided in the light guide for extracting the image light or the periodic fine structure on the side surface of the light guide, and a wide viewing angle. The more light becomes, the more efficiently light cannot be extracted. For this reason, a gap occurs in the observed virtual image, or luminance unevenness occurs.

  Further, in order to efficiently extract image light from the light guide, a configuration in which the arrangement position of the plurality of mirrors or the period of the fine structure is changed may be considered. However, with such a configuration, the efficiency of extracting image light can be optimized at a specific eye position, but if the eye position is changed, a virtual image gap or luminance unevenness occurs.

  Furthermore, since the light beam propagating at a large reflection angle in the light guide is reflected by total reflection at the fine structure portion at the time of image extraction, there is no energy loss. On the other hand, of the light emitted from the image display element, the light beam propagating at a small reflection angle in the light guide is reflected as image light by the reflective coating applied to the fine structure portion, and therefore reflection loss is reduced. Arise. Therefore, luminance unevenness occurs in the observed virtual image.

  Patent Document 4 discloses an image display element for the left eye and an image display element for the right eye. When the temperature of one image display element exceeds a specified value, the image display element is completely hidden and the temperature is normal. A method of displaying a virtual image only with the other image display element within the range is disclosed. In Patent Document 4, one image display element is completely hidden, and the other image display element is completely displayed.

  The main object of the present invention is to provide a virtual image display apparatus and method that can reduce gaps and luminance unevenness of observed virtual images while ensuring a wide viewing angle of the light guide.

  A virtual image display device according to the present invention includes an image display element that outputs image light of a display image for virtual image display, a collimating optical system that collimates and emits image light from the image display element, and the collimating optical system A pair of light guides each having a light guide member that guides and emits image light from each of the light guide members, and each of the light guide members receives light from the image display element via the collimating optical system. A light incident portion for emitting the image light to the outside, and an image extracting portion for guiding the image light to the light emitting portion for extraction. The element is characterized by outputting image light of a partial image obtained by dividing the entire image visually recognized by both eyes.

  ADVANTAGE OF THE INVENTION According to this invention, the virtual image display apparatus and method which can reduce the clearance gap and brightness nonuniformity of a virtual image observed while ensuring the wide viewing angle of a light guide can be provided.

It is a top view which shows embodiment of the virtual image display apparatus which concerns on this invention. FIG. 2 is a partially enlarged plan view for explaining a light ray incident portion and a reflection portion in a light guide member of the light guide of FIG. 1. It is a partial enlarged plan view for demonstrating the image extraction part and image injection | emission part in the said light guide member. It is a perspective view which shows an example of the virtual image display apparatus which concerns on this invention. It is a figure for demonstrating the image light and virtual image inject | emitted with the virtual image display apparatus of this embodiment, and is a figure which shows the state of a virtual image when the emitted image light is observed with both eyes. It is a figure explaining the modification of the virtual image display apparatus of FIG. 1, and is a top view which shows typically the example which cut | disconnected some optical components which comprise a collimating optical system. It is a top view of the virtual image display apparatus for demonstrating a mode that two light inject | emitted from the both ends in the longitudinal direction of the display surface of each image display element for left eyes and right eyes propagates in a light guide member. It is a top view which shows the example which added the light source which illuminates an image display element in a virtual image display apparatus. It is a figure explaining 2nd Embodiment of a light guide member, and is a perspective view which shows the example which provided the retroreflection part in the side surface. FIG. 10 is a partially enlarged plan view for explaining a light incident portion of the light guide member in FIG. 9. FIG. 10 is a partially enlarged plan view for explaining an image extraction unit and an image emission unit of the light guide member in FIG. 9. It is a front view which shows a mode that the image light inject | emitted from the corner of the image display element within the light guide member of FIG. It is a top view which shows a mode that the image light inject | emitted from the corner of the image display element within the light guide member of FIG. In the virtual image display device shown in FIG. 12 and FIG. 13, it is a diagram for explaining a case where image light is displayed in all display areas of the left and right image display elements, where (а) is viewed with the left eye, and (b) is The state of the luminance distribution of the virtual image when viewed with the right eye is shown. In the virtual image display device shown in FIG. 12 and FIG. 13, a state in which two lights emitted from both ends in the longitudinal direction of the display surface of each of the left-eye and right-eye image display elements propagates in the light guide member will be described. FIG. 15 shows a virtual image distribution when image light is output only from the display area portion on the side where the reflection angle of light when propagating in the light guide member is reduced, and (а) is when viewed with the left eye , (B) are data of the luminance distribution of the virtual image when viewed with the right eye. It is a figure which shows the luminance distribution of a virtual image when the luminance distribution of each right and left virtual image in FIG. 15 is observed with both eyes.

  Embodiments to which the present invention is applied will be described below with reference to the drawings. Each embodiment described below relates to a virtual image display device using a transmissive light guide, and more specifically to a head mounted display (HMD) including a pair of left and right virtual image optical systems.

(First embodiment)
FIG. 1 shows a configuration of a virtual image display device 1 as an HMD according to the first embodiment, and modifications thereof are shown in FIGS. In FIGS. 1, 6 to 8, the optical path of the virtual image display optical system in the virtual image display apparatus is indicated by a solid line, and the eyes of the user of the apparatus, that is, the virtual image observer are schematically illustrated.

  As shown in FIG. 1, the virtual image display device 1 has a pair of left and right virtual image optical systems, and each virtual image optical system includes an image display element 10 (10L, 10R) and a collimating optical system 300 (300L, 300R) and the light guide 50 (50L, 50R). The virtual image display device 1 has a casing such as a casing or a headband for storing these optical elements. Hereinafter, the configuration of the left-eye (L side) virtual image optical system will be described unless otherwise specified. Further, regarding the surface of the light guide 50, the front side (lower side in FIG. 1) viewed from the observer is referred to as “rear surface”, and the rear side (upper side in FIG. 1) is referred to as “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 ELD (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.

  In the present embodiment, the image display element 10 is configured to output image light of display images that are different from each other between the image display element 10L for the left eye and the image display element 10R for the right eye, and details of the configuration will be described later. To do.

  In the present embodiment, each of the image display elements 10 (10L, 10R) has a rectangular display surface that is long in the horizontal (horizontal direction), and does not output image light from all areas of the display surface. The image light is output from a part of the area.

  Specifically, the display surface of the image display element 10 (10L, 10R) is divided into an output region 10d that outputs image light and a non-output region 10n that does not output image light in the longitudinal direction. . In the present embodiment, output regions 10d are formed on the right side of the display surface of the image display element 10L for the left eye and on the left side of the display surface of the image display element 10R for the right eye, respectively. In this example, the output region 10d has a half area of the display surface of the image display element 10, in other words, the area ratio of the output region 10d and the non-output region 10n on the display surface is 1: 1. The area ratio between the output region 10d and the non-output region 10n on the display surface can be variously changed.

  Although the collimating optical system 300 is schematically illustrated in FIG. 1, the collimating optical system 300 is actually composed of a plurality of optical lenses, diaphragms, and the like (see FIG. 4), and enlarges the image light output from the image display element 10 in parallel. Ejected as light.

  The light guide 50 is an element that enters and guides image light emitted from the image display element 10 and emits the light for virtual image display. In the present embodiment, the light guide 50 has a substantially prismatic shape and a pentagonal shape in plan view. The light guide member 100 has an outer shape.

  The light guide member 100 of the light guide 50 has a role of taking the image light from the image display element 10 and guiding it, and emitting it outside for virtual image display. For this reason, the light guide member 100 includes a light beam incident portion 101 for entering image light therein, a reflection portion 102 for reflecting incident image light, a front surface and a rear surface for guiding image light inside, and a guided image. A light emitting unit 104 is provided for extracting light and emitting it to the outside. In addition, the light guide member 100 includes an image extracting unit 103 that guides and extracts image light to the light emitting unit 104.

  In the present embodiment, the image extraction unit 103 is provided on the front surface of the light guide member 100, and the light emitting 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 to the inside of the light guide member 100 toward the light emission unit 104, and the light emission unit 104 is an image light guided from the image extraction unit 103. Is emitted outside toward the eyes of the virtual image observer.

  A region where the image extraction unit 103 is not provided in the front surface of the light guide member 100 is a total reflection surface 105 for causing the incident image light to be totally reflected and proceed. 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 in parallel to each other.

  In FIG. 1, the front surface of the light guide member 100, that is, the total reflection surface 105 and the image extraction unit 103 are in a straight line, but in the present embodiment, the image extraction unit 103 has a stepped configuration (see FIG. 3), and the detailed configuration Will be described later. The image extraction unit 103 has a shape such that the thickness of the light guide member 100 increases toward the light incident unit 101.

In FIG. 2, the light incident part 101 and the reflective part 102 of the light guide member 100 are shown in an enlarged manner, and the extension lines of the light incident part 101 and the reflective part 102 are indicated by dotted lines. As shown in FIG. 2, the reflecting part 102 is inclined at an angle θ ₀ with respect to the light incident part 101. The light incident part 101 is provided on the rear surface of the light guide member 100, and the reflection part 102 is provided at a predetermined angle (180−θ ₀ degrees) with respect to the front surface of the light guide member 100. In the present embodiment, a notch surface 100 a is provided between the light incident part 101 and the reflecting part 102. As another form, it is good also as a structure which does not have the notch surface 100a, ie, the structure in which the light-incidence part 101 and the reflection part 102 continue in planar triangle shape.

  The reflective portion 102 can be coated with an arbitrary coating material. In order to guide the image information to the inside of the light guide 50, it is desirable that the reflecting portion 102 is provided with a mirror coating having a high reflectance such as aluminum, silver, or a dielectric coating.

  The image extraction unit 103 of the light guide member 100 is shown in an enlarged manner in FIG. In FIG. 3, a reference plane parallel to the light emitting unit 104 is represented by a dotted line. As shown in FIG. 3, the image extraction unit 103 includes 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 substantially stepped shape. In FIG. 3, a virtual plane parallel to the light emitting section 104 is represented by a dotted line, and the width of the second surface 103b is represented by w.

  The first surface 103 a of the image extraction unit 103 is a surface that plays a role of guiding the image light incident inside the light guide member 100 to the light emitting unit 104 and emitting it from the light emitting unit 104. The plane is inclined at an angle θa. Here, the inclination direction of the first surface 103 a with respect to the light emitting part 104 is opposite to the inclination direction of the reflecting part 102 with respect to the light incident part 101.

  The value of the angle θa at which the first surface 103a is inclined with respect to the light emitting section 104 is preferably set in the range of 20 degrees to 40 degrees, although it depends on the refractive index of the material of the light guide member 100. Further, it is more preferable to set the value of the angle θa to be the same as the value of the inclination angle θ0 of the reflecting unit 102 with respect to the light beam incident unit 101 described above. Becomes easier.

  On the other hand, the second surface 103 b is a surface that serves as a reflecting surface that reflects incident image light, 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.

  An arbitrary coating can be applied to the image extraction unit 103, that is, the first surface 103a and the second surface 103b. Here, in consideration of providing the light guide 50 with see-through properties, it is desirable to apply a coating such as a half mirror that ensures a certain degree of transmittance to the image extraction unit 103.

  When the second surface 103b is tilted with respect to the light emitting section 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 angle of reflection reflected by the light emitting section 104 changes 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.

  As shown in FIG. 3, each second surface 103 b preferably has a structure in which the height of the surface gradually decreases as the distance from the light incident portion 101 increases. In other words, it is preferable that the distance between the second surface 103 b and the light emitting part 104, that is, the thickness of the light guide member 100 becomes thinner as the distance from the light incident part 101 increases.

The value of the width w of the second surface 103b of the image extraction unit 103 in the light guide member 100 is
0.5 [mm] <w <3.0 [mm]
Is set so as to satisfy the following conditions. 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 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 (thickness) of the light guide is tl, and the number of the surfaces parallel to the light emitting unit 104 of the image extracting unit 103, that is, the number of the second surfaces 103b is n. The width w of the second surface 103b is expressed by the following equation.

  Here, the wider the eyebox width, the wider the visible range, so it is usually desirable that the eyebox diameter φ is larger. On the other hand, when the eyebox diameter φ is increased, 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 will be 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].
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, it is necessary to shorten the width of the first surface 103a. Undesirable because it becomes difficult. Further, in order to ensure the eye box 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 desirable because the weight increases. Absent.

  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. Specifically, since the light beam density of image light decreases as the distance from the reflection unit 102 increases, it is preferable to set the width w of the second surface 103b to be smaller as the distance from the reflection unit 102 increases. . With this setting, the number of arrangements per unit length of the first surface 103a increases as the distance from the reflecting portion 102 increases, so that unevenness in the amount of light can be reduced.

  Similarly, in order to reduce unevenness in the amount of light, 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, the width of the first surface 103a may be set to increase as the distance from the reflecting portion 102 increases. With this setting, the area of the first surface 103a increases as the distance from the reflecting portion 102 increases, and thus the amount of light unevenness can be reduced.

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

  According to the light guide member 100 having such a configuration, when viewed from the traveling direction of the image light incident from the light incident portion 101, the height of each second surface 103b is sequentially decreased, and the interval at which the image light is totally reflected is narrowed. . For this reason, the light rays reflected by the image extraction unit 103 gradually increase, the light rays entering the eyes from the light emission unit 104 increase, and a good virtual image with little luminance unevenness can be observed.

  FIG. 4 is a perspective view of the virtual image display device 1 from the rear surface side of the light guide member 100. According to the virtual image display device 1 of the present embodiment including such a virtual image optical system, the image light emitted from the image display element 10 passes through the collimating optical system 300 and is enlarged and is incident on the light guide 50 as parallel light. Incident. That is, image light that is parallel light expanded by the collimating optical system 300 is incident from the light beam incident portion 101 of the light guide member 100 in the light guide 50 and guided to the inside of the light guide member 100. The guided image light travels inside the light guide member 100 while being totally reflected by the front and rear surfaces. When the image light reaches the image extracting unit 103 described above, the image light is reflected by the first surface 103a described above, guided to the light emitting unit 104, and emitted from the light emitting unit 104 toward the user's eyes as image 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. Specifically, the user can visually recognize the virtual image of the image light by looking through the light emitting unit 104 of the light guide member 100L with the left eye and looking through the light emitting unit 104 of the light guide member 100R with the right eye. it can.

  FIG. 5 shows an example of an image, that is, a virtual image obtained by displaying different areas on the image display elements 10 for the left eye and the right eye in the virtual image display device of the present embodiment and observing with both eyes. Yes. In FIG. 5, the image IR shown on the left side is a virtual image visually recognized by the right eye, and the image IL shown on the right side is a virtual image visually recognized by the left eye. In other words, in FIG. 5, the virtual image IR shown on the left side is a virtual image based on the partial image displayed by the image display element 10R for the right eye, and the virtual image IL shown on the right side is a part displayed by the image display element 10L for the left eye. It is a virtual image based on an image.

  As described above, in the present embodiment, the image display element 10L and the image display element 10R emit different images. That is, each of the image display elements 10L and 10R outputs image light of one partial image among the partial images obtained by dividing the entire image that is simultaneously viewed with both eyes into left and right. More specifically, regarding the entire image (virtual image) visually recognized by both eyes of the user, the image display element 10L for the left eye displays a partial image on the right half of the entire image, and the image display element 10R for the right eye as a whole. Displays the partial image in the left half of the image.

  In order to display such a partial image, as described above with reference to FIG. 1, the right half of the display surface of the image display element 10L for the left eye and the left half of the display surface of the image display element 10R for the right eye are output regions 10d. It is said. Further, the left half of the display surface of the image display element 10L and the right half of the display surface of the image display element 10R are set as a non-output region 10n.

  In order to divide the display surface of the image display element 10 into the output area 10d and the non-output area 10n, for example, the right half of the image display element 10R and the left half of the image display element 10L are covered. be able to. With this configuration, the covered region functions as the non-output region 10n, and the output of image light from the region is physically blocked.

  On the other hand, in order to divide the display surface of the image display element 10 into an output region 10d and a non-output region 10n, an output from a region (such as a pixel) corresponding to the non-output region 10n is prohibited by electrical processing. You can also With this configuration, the output prohibited area functions as the non-output area 10n, and the output of image light from the area is prohibited by electrical processing.

  Thus, by outputting different partial images from the image display element 10R and the image display element 10L, the virtual images of the partial images emitted from the respective light guides (50A, 50B) are observed with both eyes. At this time, the virtual image seen by the left eye and the virtual image seen by the right eye complement each other, thereby confirming the virtual image of the entire image.

(Modification)
A modification of this embodiment is shown in FIG. FIG. 6 is a plan view showing a case where a part of the optical components constituting the collimating optical system 300 is cut out. Although schematically illustrated in FIG. 6, actually, the collimating optical system 300 includes a plurality of optical lenses, a diaphragm, and the like (see FIG. 4). Each of these optical components has a shape in which a portion corresponding to the non-output region 10n of the corresponding image display element 10 (10L or 10R) is cut out.

  As can be seen from comparison with FIG. 1, in the modification shown in FIG. 6, the left-eye side of the optical lens constituting the optical system of the collimating optical system 300L for the left eye is cut off. Similarly, in the collimating optical system 300R for the right eye, the right half side of the optical lens constituting the optical system is cut off. With such a configuration, the collimating optical system 300 can be realized in a light weight and a small size.

  FIG. 7 is a plan view illustrating a state in which the image light emitted from the image display element 10 propagates in the light guide member 100. In FIG. 7, it is assumed that image light is output not only from the entire display area of the image display element 10 (10L, 10R), that is, from the output area 10d but also from the non-output area 10n. In FIG. 7, the reference plane 11 that defines the horizontal (horizontal) direction, that is, the center in the longitudinal direction, of the display surface of each image display element 10 (10L, 10R) is indicated by a broken line.

  As shown in FIG. 7, regarding the light guide member 100L for the left side, that is, the left eye, the light indicated by the solid line emitted from the left side of the display area of the image display element 10L is more than the light indicated by the dotted line emitted from the right side. It can also be seen that the angle of reflection within the light guide member 100L increases. On the other hand, the opposite is true for the right-side light guide member 100R. That is, it can be seen that the light indicated by the dotted line emitted from the left side of the display area of the image display element 10R has a smaller reflection angle in the light guide member 100 than the light indicated by the solid line emitted from the right side.

  The light propagating in the light guide member 100 is more likely to be extracted as image light because the smaller the reflection angle in the light guide member 100, the higher the frequency of hitting the first surface 103 a of the image extraction unit 103. Conversely, light propagating at a large reflection angle in the light guide member 100 is less likely to hit the first surface 103a of the image extraction unit 103, so that it is difficult to extract it as image light, and less light reaches the eyes. Therefore, a region in the display surface of the image display element 10 that emits light having a large reflection angle in the light guide member 100 is a portion where a gap between virtual images or luminance unevenness easily occurs.

  Therefore, in the present embodiment, as shown in FIG. 7, in each of the left and right image display elements 10, a region where the reflection angle when image light output from the image display elements propagates in the light guide member 100 is small. Only the output region 10d is provided. In other words, the position of the reference surface 11 that partitions the output region 10d and the non-output region 10n defines a region where the reflection angle when the image light output from the image display element propagates in the light guide member 100 is small. Can be set or adjusted to With this configuration, gaps and luminance unevenness in the left and right virtual images (partial images) are reduced, and a good virtual image (entire image) is obtained when observed with both eyes.

Here, when the light emitted from the center of the display surface of the image display element 10 propagates in the light guide member 100 is θ,
Reflection angle θ = 2 × θ ₀
It becomes.

  Therefore, when the light emitted from the image display element 10 propagates in the light guide member 100, the output region 10d is provided so that the reflection angle is equal to or less than θ, and the image light is emitted. In this case, the reflection angle when propagating in the light guide member 100 is reduced, and a good virtual image in which gaps and luminance unevenness are suppressed as much as possible can be obtained.

  FIG. 8 shows a case where an image display element 10 that requires a light source such as liquid crystal or DMD is used. In the example of FIG. 8, the light source 400 is used to illuminate only the display portion of the image light in the display areas of the left and right image display elements 10. With such a configuration, the light from the light source 400 can be efficiently collected in a part of the display area of the image display element 10 (half in this example), thus saving energy.

(Second embodiment of light guide member)
With reference to FIG. 9 thru | or FIG. 13, 2nd Embodiment of a light guide member is described. FIG. 9 is a diagram showing a light guide member 100A suitable for constituting a virtual image display device having a wide viewing angle of 40 degrees or more. Parts having the same functions as those in the first embodiment are denoted by the same reference numerals. I will explain.

  As shown in FIG. 9, the entire light guide member 100 </ b> A has a substantially prismatic shape and a wedge-shaped outer shape in plan view. The light guide member 100A has a light beam incident portion 101 for entering image light therein, a front surface and a rear surface for reflecting the incident image light and guiding it to the inside, and taking out the guided image light and emitting it to the outside. The light emission part 104 is provided. Further, the light guide member 100 includes a retroreflecting unit 106 that reverses the traveling direction of the image light that is incident from the light incident unit 101 and guides the light in the light guiding member, and the image light whose traveling direction is reversed by the retroreflecting unit 106. The image extracting unit 103 includes a light emitting unit 104 that guides and extracts the light.

  The light guide member 100A is provided with an image extraction unit 103 on the front surface and a light emitting unit 104 on the rear surface. The image extraction unit 103 has a role of reflecting the image light guided inside toward the light beam emission unit 104, and the light beam emission unit 104 converts the image light guided from the image extraction unit 103 to the virtual image observer. It has a role of injecting outside towards the eyes.

  A region where the image extraction unit 103 is not provided in the front surface of the light guide member 100 </ b> A is a total reflection surface 105 for allowing incident image light to be totally reflected and proceed. 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 in parallel to each other.

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

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

  The image extraction unit 103 of the light guide member 100A is enlarged and shown in FIG. In FIG. 11, a reference plane parallel to the light emitting unit 104 is represented by a dotted line. As illustrated in FIG. 11, the image extraction unit 103 includes an inclined surface (hereinafter, referred to as a “third surface”) 103 c that is inclined with respect to the light emitting unit 104 at an angle θc; A fourth surface 103d having an angle θd with respect to the light emitting portion 104. In the image extraction unit 103, the third surface 103c and the fourth surface 103d are alternately arranged and have a substantially stepped shape.

  The third surface 103 c of the image extracting unit 103 is a surface that plays a role of guiding the image light incident on the inside of the light guide member 100 and reflected by the retroreflecting unit 106 to the light emitting unit 104 and emitting it from the light emitting unit 104. There is a plane that is inclined with respect to the light emitting portion 104. The third surface 103 c is opposed to the retroreflective portion 106 by being inclined at a predetermined inclination angle with respect to the light emitting portion 104.

  The value of the angle θc at which the third surface 103c is inclined with respect to the light emitting section 104 is preferably set in the range of 20 degrees to 40 degrees, although it depends on the refractive index of the material of the light guide member 100.

  On the other hand, the fourth surface 103d serves to reflect incident image light and guide it to the retroreflective unit 106, and to serve as a reflective surface to reflect image light whose traveling direction is reversed by the retroreflective unit 106. It is a plane parallel to the light emitting part 104. Therefore, the angle θd = 0 °. Further, the fourth surface 103d also plays a role as a transmission surface on which external light from the front and rear surfaces of the light guide 50 is incident in order to ensure see-through performance.

  When the fourth surface 103d is inclined with respect to the light emitting portion 104, that is, when the angle θd ≠ 0 ° is set, the image light guided in the light guide member 100 has a reflection angle reflected by the fourth surface 103d. The angle of reflection reflected by the light emitting section 104 changes 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 fourth surface 103d and the light beam emitting unit 104, the image light is emitted in different directions, which is not a virtual image. Therefore, in the present embodiment, the angle θd = 0 °, and the fourth surface 103 d is formed in parallel to the light emitting unit 104.

  As shown in FIG. 11, it is preferable that each fourth surface 103 d has a structure in which the height of the surface sequentially increases as it approaches the retroreflective portion 106. In other words, it is preferable that the distance between the fourth surface 103d and the light emitting portion 104, that is, the thickness of the light guide member 100 increases as the retroreflective portion 106 is approached.

  According to the light guide member 100A having such a configuration, when viewed from the traveling direction of the image light after the traveling direction of the light beam is reversed by the retroreflecting unit 106, the height of each fourth surface 103d is sequentially decreased, and the image light is transmitted. The interval of total reflection is reduced. For this reason, the light rays reflected by the image extraction unit 103 gradually increase, the light rays entering the eyes from the light emission unit 104 increase, and a good virtual image with little luminance unevenness can be observed.

  Next, with reference to the front view of FIG. 12 and the plan view of FIG. 13, the details of the retroreflective portion 106 provided in the light guide member 100A will be described.

  As shown in FIG. 12, the retroreflective portion 106 is on one side surface of the light guide member 100 </ b> A that is a surface perpendicular to the light emitting portion 104, specifically, on the end surface opposite to the light incident portion 101. Is provided. The retroreflective portion 106 is composed of a number of surfaces. In other words, the end surface 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. 12, the retroreflective unit 106 includes 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 unit 101, and a first inclined surface 106 a. On the other hand, the second inclined surface 106b inclined at an angle θp is formed continuously. The first inclined surface 106a and the second inclined surface 106b constitute one prism. In other words, the retroreflective portion 106 has a configuration in which a plurality of roof-shaped prisms are continuously provided on the end surface opposite to the light incident portion 101. The first inclined surface 106a and the second inclined surface 106b are planes having substantially the same shape and area.

  In the present embodiment, the angle θs formed between the side surface 107 and the first inclined surface 106a is 135 degrees. Further, 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 formed at 90 degrees in this embodiment. Therefore, the retroreflective unit 106 is configured by a large number of prisms having an apex angle of 90 degrees.

  In order to satisfactorily reflect the image light that has reached the retroreflective portion 106, it is preferable to provide a highly reflective coat on the retroreflective portion 106, that is, the first inclined surface 106a and the second inclined surface 106b. The reflectance of such a coat is desirably 70% or more.

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

  The material of the light guide member 100A is preferably a highly transmissive 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 above.

  In addition, the image extraction unit 103 can be applied with an arbitrary coat, and for example, a mirror coat such as aluminum, silver, or a dielectric coat can be applied. In order to prevent the loss of the light amount of the guided image light as much as possible, it is desirable to coat the third surface 103c of the image extraction unit 103 with a reflectance of approximately 100%.

The value of the width _{w 2} of the fourth surface 103d of the image pickup section 103 in the light guide member 100A is
_{0.5 [mm] <w 2 <} 3.0 [mm]
Is set so as to satisfy the following conditions. Here, the width w ₂ is the length of the fourth surface 103 d 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.

The setting conditions of the width _{w 2} of the fourth surface 103d, from the same viewpoint as the width w of the second surface 103b as described above,
It is desirable to satisfy the condition of 0.5 [mm] <w ₂ <3.0 [mm].

If the width _{w 2} of the fourth surface 103d image pickup section 103 is less than 0.5 mm, it is necessary to shorten the width of the third surface 103c, tends to occur diffraction of the incident image light, also produced Is not desirable because it becomes difficult. Further, in order to secure the eye box 5 mm or more and 10 mm or less at the position of the eye relief 20 mm without shortening the width of the third surface 103 c, it is necessary to increase the thickness of the light guide, which is desirable because the weight increases. Absent.

On the other hand, when the width _{w 2} of the fourth surface 103d exceeds 3.0 mm, per incident image light, the density of light emitted from the beam emitter 104 reflects the third surface 103c is decreased, eye This is not desirable because the amount of light at the position is reduced. Therefore, it is desirable that the width w ₂ of the fourth surface 103 d of the image extraction unit 103 satisfies the condition of 0.5 [mm] <w ₂ <3.0 [mm].

Width _{w 2} of the fourth surface 103d may be different values in each of the fourth surface 103d. Specifically, since the light beam density of the image light decreases as the distance from the light beam incident portion 101 becomes shorter, the width w of the fourth surface 103d is set to decrease as the distance from the light beam incident portion 101 decreases. Good. With this setting, the number of arrangements per unit length of the third surface 103c increases as the distance from the light incident part 101 increases, so that unevenness in the amount of light can be reduced.

  Similarly, in order to reduce unevenness in the amount of light, the width of the third surface 103c of the image extraction unit 103 may be different for each third surface 103c. Here, the width of the third surface 103 c is the length of the third surface 103 c 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, the width of the third surface 103c may be set to increase as the distance from the light incident portion 101 becomes shorter. With this setting, the area of the third surface 103c increases as the distance from the light incident portion 101 increases, so that unevenness in the amount of light can be reduced.

  The thickness of the light guide member 100A is desirably in the range of 1 mm to 8 mm. If the thickness of the light guide member 100A 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, when the thickness of the light guide member 100A exceeds 8 mm, it is advantageous to obtain a wide viewing angle, but it is not preferable because the weight of the member increases.

  The operation of the virtual image display device using the light guide member 100A having such a configuration will be described with reference to FIGS. Here, FIG. 12 is a diagram showing the light guide 50 from the front side (front), and FIG. 13 is a diagram showing the light guide 50 from the side (upper) side. 12 and 13, only one light beam 400 emitted from the corner of the display surface of the image display element 10 is extracted and shown for easy understanding.

  As shown in the figure, the image light of the partial image emitted from the corner of the image display element 10 enters the collimated light through the collimating optical system 300 and enters from the light incident part 101 of the light guide member 100A. The light guide member 100A advances. The image light that has entered from the light beam incident portion 101 of the light guide member 100A is totally reflected in the light guide member 100A, and becomes divergent light and travels in the light guide member 100A. That is, the image light of the partial image incident from the light incident part 101 travels in the light guide member 100 as divergent light until reaching the retroreflective part 106.

  Subsequently, the image light is reflected by the retroreflecting unit 106, so that the traveling direction, that is, the light guiding direction is reversed. Here, the image light is reflected on both the first inclined surface 106a and the second inclined surface 106b constituting the retroreflecting unit 106, and the incident light and the outgoing light viewed from the plane direction become parallel and convergent light. Then, the light guide member 100A travels. Further, the image light is reflected by the third surface 103 c of the image extraction unit 103, is emitted from the light emitting unit 104 as convergent light, and is guided toward the observer's eyes. As described above, according to the virtual image display device using the light guide member 100A, the image light is emitted as convergent light and provided to the observer's eyes, so that the virtual image display can be satisfactorily observed without missing the virtual image even at a wide angle. A device can be realized.

  On the other hand, if the image extraction unit 103 attempts to extract an image without providing the retroreflective unit 106, the light hitting the image extraction unit 103 becomes divergent light, and light does not enter the eye in the case of a wide viewing angle, and a virtual image is formed. It will be lacking. Therefore, the light guide member 100A has a configuration in which the retroreflective portion 106 is provided as shown in FIG. 9. With this configuration, the direction of the image light traveling inside is inverted by the retroreflective portion 106 and becomes convergent light. A good virtual image can be observed even at a wide viewing angle.

  FIG. 14 is a diagram illustrating a case where image light is displayed in all display areas of the left and right image display elements 10 (10L, 10R) in the configuration shown in FIGS. 12 and 13, and (а) is the left eye. When viewed, (b) shows the brightness distribution of the virtual image when viewed with the right eye.

  The right-eye light guide 50R and the collimating optical system 300R are obtained by rotating the left-eye light guide 50L and the collimating optical system 300L by 180 degrees with respect to the center of the left and right eyes. ), The luminance distribution is also symmetrical.

  Further, as shown in FIG. 14A, when the image light emitted from the image display element 10L for the left eye is viewed with the left eye, the low-luminance portion can be formed on the left side, and the gap between the virtual images is on the right side. I can do it. The virtual image when viewed with the right eye is the opposite. That is, as shown in FIG. 14B, when the image light emitted from the image display element 10R for the right eye is viewed with the right eye, the low-luminance portion can be formed on the right side, and the gap between the virtual images is on the left side. I can do it.

  When such two image lights are viewed with both eyes, the two virtual images are superimposed, so that a gap between the other images overlaps a portion where the luminance of one image is low. In this case, a gap may be seen depending on the brightness of the virtual image, resulting in degradation of image quality.

  FIG. 15 is a diagram corresponding to FIG. 7, and is a plan view showing a state in which the image light emitted from the image display element 10 propagates in the light guide member 100 </ b> A in the configuration described above with reference to FIGS. 12 and 13. . FIG. 15 also illustrates the case where image light is output not only from the entire display area of the image display element 10 (10L, 10R), that is, from the output area 10d but also from the non-output area 10n. In FIG. 15, the reference plane 11 that defines the horizontal direction, that is, the center in the longitudinal direction, of the display surface of each image display element 10 (10L, 10R) is indicated by a solid line. In FIG. 15, in each of the left and right light guide members 100 </ b> A (L, R), light rays propagating at a small reflection angle are indicated by dotted lines, and light rays propagating at a large reflection angle are indicated by solid lines.

  As shown in FIG. 15, regarding the light guide member 100A (L) for the left side, that is, the left eye, the light indicated by the solid line emitted from the left side of the display area of the image display element 10L is more than the light indicated by the dotted line emitted from the right side. Also, it can be seen that the reflection angle in the light guide member 100A (L) increases. On the other hand, the opposite is true for the right-hand or right-eye light guide member 100A (R). That is, it is understood that the light indicated by the dotted line emitted from the left side of the display area of the image display element 10R has a smaller reflection angle in the light guide member 100A (R) than the light indicated by the solid line emitted from the right side. .

  16 shows an image only from the portion of the display area on the light ray side of the dotted line from the reference plane 11 of the image display element 10 (10L, 10R) in FIG. 15, that is, the side where the angle when propagating in the light guide member 100 becomes smaller. The luminance distribution of a virtual image visually recognized when light is output is shown. Here, FIG. 16A shows data of the luminance distribution of the virtual image when viewed with the left eye, and FIG. 16B shows data of the luminance distribution of the virtual image when viewed with the right eye.

As can be seen from FIG. 16 (a), the virtual image distribution when viewed with the left eye is displayed on the left side of the figure, and the right side with the virtual image gap shown in FIG. 14 (a) is not displayed. Further, as can be seen from FIG. 16B, the luminance distribution of the virtual image when viewed with the right eye is displayed on the right side in the figure, and the left side with the virtual image gap shown in FIG. 14B is displayed. It has not been.

  FIG. 17 shows data obtained by synthesizing the luminance distribution of the virtual image shown in FIGS. 16A and 16B. The luminance distribution of the virtual image visually recognized by both eyes is shown on the left side, and the luminance distribution scale of the virtual image visually recognized by both eyes is shown. Shown on the right. As apparent from the comparison with FIG. 14, it can be seen that there is no gap in the periphery of the virtual image. Therefore, when a virtual image is viewed with both eyes, a good image can be observed.

  In the embodiment described above, the right half of the display surface of the image display element 10L for the left eye and the left half of the display surface of the image display element 10R for the right eye are used as the output region 10d, and the left half of the display surface of the image display element 10L and The right half of the display surface of the image display element 10R is defined as a non-output area 10n. That is, the output area 10d in the image display elements 10L and 10R has a bilaterally symmetric configuration with respect to the center of the display area.

On the other hand, the arrangement of the output area 10d in the display area is not limited to this, and various modifications can be made.

For example, the output regions 10d of the image display elements 10L and 10R can be arranged so that a part of the images overlap so that a gap between the left and right virtual images is not overlapped. Then, by adjusting the arrangement of the output areas 10d of the image display elements 10L and 10R in such overlapping portions, it is possible to create a good image in which the boundary when the images for the left eye and the right eye are overlapped is not noticeable. With such a configuration, for example, it is possible to eliminate a gap at the boundary between the virtual images IR and IL shown in FIG.

In general, when the image light output from the image display element 10L for the left eye and the image light output from the image display element 10R for the right eye are combined, the entire display area of each of the image display elements 10L and 10R is obtained. It is only necessary that the image is equivalent to the image when it is ejected.

(Example)
Hereinafter, specific examples of the virtual image display device will be described. This embodiment is a virtual image display device manufactured using the light guide member 100A described in FIG. 12 and the like, using a collimator lens with a focal length of 7.5 mm, and a plastic having a refractive index (Nd) = 1.53. The light guide member 100A was manufactured and the angle θc of the third surface was set to 31.5 degrees. Further, the light guide member 100A was manufactured by setting the dimensions to the following numerical values.
-Thickness (thickness) of light guide member 100A: thinnest part 1mm, thickest part 1.9mm
-Length in the longitudinal direction of the light guide member 100A: 46 mm
-The width of the light guide member 100A: 33 mm
In addition, a 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.

  In this example, the horizontal viewing angle of the light guide was ensured to be 50 degrees or more.

  As described above, according to the above-described embodiments and examples, a virtual image display device and a virtual image display method capable of reducing gaps and luminance unevenness of observed virtual images while ensuring a wide viewing angle of the light guide. Can be provided.

DESCRIPTION OF SYMBOLS 1 Virtual image display apparatus 300 (300L, 300R) Collimating optical system 400 (400L, 400R) Light source 10 (10L, 10R) Image display element 10d Output area 10n Non-output area 50 (50L, 50R) Light guide 100, 100A Light guide member 101, 101A Light incident part 102 Reflecting part 103 Image extracting part 104 Light emitting part 105, 105A Total reflection surface 106 Retroreflective part

Patent No. 5698297 Japanese Patent No.54212285 Japanese Patent No. 5703875 Patent 5742270

Claims (9)

An image display element that outputs image light of a display image for virtual image display;
A collimating optical system for collimating and emitting image light from the image display element;
A light guide having a light guide member that guides and emits image light from the collimating optical system;
Each with a pair,
Each of the light guide members includes a light incident portion for entering light from the image display element via the collimating optical system, a light emitting portion for emitting the image light to the outside, and the image light. An image take-out part that guides the light to the light-emitting part and takes it out,
Each said image display element outputs the image light of the partial image which divided | segmented the whole image visually recognized with both eyes. The virtual image display apparatus characterized by the above-mentioned. The virtual image display device according to claim 1, wherein the pair of image display elements is divided into an output region that outputs image light and a non-output region that does not output image light with respect to the longitudinal direction of each display surface. The pair of collimating optical systems each include one or more optical components, and each optical component has a shape in which a portion corresponding to the non-output region of the corresponding image display element is cut out. Virtual image display device. The output areas of the pair of image display elements are image lights output from the image display elements among the two areas divided by a reference plane that divides the longitudinal center of the image display elements. The virtual image display device according to claim 1, wherein the virtual image display device is a region on a side where an angle when propagating in the guide is reduced. The virtual image display device according to claim 2, further comprising a light source that illuminates the output region of the image display element. Each of the image display elements is
The virtual image display device according to claim 1, wherein the image light of the partial image is output so that a part of the image overlaps the entire image visually recognized by both eyes. An image display element that outputs image light of a display image for virtual image display, a collimating optical system that collimates and emits image light from the image display element, and guides image light from the collimating optical system A light guide having a light guide member to be emitted, and a virtual image display method in a virtual image optical system each comprising a pair,
Each said image display element outputs the image light of the partial image which divided | segmented the whole image visually recognized with both eyes. The virtual image display method characterized by the above-mentioned. In the pair of image display elements, image light output from the image display element propagates in the light guide among two regions separated by a reference plane that divides the longitudinal center of the image display element. The virtual image display method according to claim 7, wherein the image light of the partial image is output from a region on a side where the angle when the image is reduced. The virtual image display method according to claim 7, wherein each of the image display elements outputs image light of a partial image so that a part of the image overlaps with respect to the entire image visually recognized by both eyes.