Head-mounted display

Abstract

To provide a head-mounted display with high display quality.SOLUTION: A head-mounted display 100 according to this embodiment includes: aspherical combiners 121L and 121R disposed in front of a user and reflecting display light PL11 and PL12 forming a display image in a direction of the user; and beam splitters 122L and 122R disposed between the combiners 121L and 121R and the user, and reflecting display light PL11 and PR 11 to the combiners 121L and 121R and transmitting display light PL12 and PR12 reflected by a concave mirror. In an optical system, a distortion aberration is equal to or less than a predetermined value in an inner range than an effective viewing angle, and in an outer range, the distortion aberration increases as one moves toward the outside of the field of view. An image height characteristic is substantially linear in the inner range than the effective viewing angle, and a slope of the image height characteristic in the outer range is smaller than a slope of the image height characteristic in the inner range.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a head mounted display. [Background technology]

[0002] Patent Document 1 discloses a head-mounted display device having a concave mirror. The concave mirror of the device is an aspheric mirror. Specifically, it is a 4th, 6th, 8th, or 10th order aspheric mirror. If the surface coefficients are A, B, C, and D, then in Examples 1 to 5, C=0 and D=0. . [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2000-352692 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-mentioned head mounted displays, it is desirable to improve the display quality. For example, a wide viewing angle is desirable.

[0005] The present disclosure has been made in consideration of the above points, and provides a head mounted display with high display quality. The purpose is to provide a lei. [Means for solving the problem]

[0006] The head mounted display according to the present embodiment is disposed in front of the user and displays a display image. an aspheric concave mirror that reflects display light forming an image toward the user; The display light is reflected by the concave mirror. a beam splitter for transmitting the display light projected from the optical system to the eye of the user. This corresponds to the effective visual field, which is the horizontal visual angle within the range in which high visual acuity can be obtained with eye movement of In a range inside the effective viewing angle, the distortion aberration is equal to or smaller than a predetermined value, In the range outside of the viewing angle, the distortion increases toward the outside of the field of view. The image height characteristic showing the relationship with the image height is substantially linear in the range inside the effective viewing angle. A, and the gradient of the image height characteristic in a range outside the effective viewing angle is This is smaller than the inclination of the image height characteristic in the range inside the corner. Effect of the Invention

[0007] According to the present disclosure, an object is to provide a head mounted display with high display quality. do. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram showing a configuration of a portion of a head mounted display according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a diagram showing functional blocks of the head mounted display according to the present embodiment. [Diagram 3] 2 is a diagram for explaining display light and external light in an optical system of a head mounted display. FIG. [Figure 4] FIG. 2 is a schematic diagram showing a simplified optical system. [Diagram 5] FIG. 2 is a ray diagram of display light in an optical system. [Figure 6] 1 is a diagram for explaining the relationship between image height (display element size) and viewing angle (half angle of view). [Figure 7] 5 is a graph showing a simulation result of image height characteristics in the optical system of the first embodiment. [Figure 8] FIG. 8 is an enlarged view of a part of FIG. [Figure 9] 1 is a table showing aspheric coefficients according to the first embodiment. [Figure 10] 13 is a graph showing a simulation result of image height characteristics in the optical system of Comparative Example 3. FIG. [Figure 11] FIG. 2 is a diagram illustrating distortion of an optical system. [Figure 12] FIG. 2 is a diagram showing distortion of an optical system. [Figure 13] 13A and 13B are diagrams showing a display image corrected in accordance with distortion aberration of the optical system. [Figure 14] 11 is a table showing aspheric coefficients of Examples 2 and 3. [Figure 15] 13 is a graph showing a simulation result of image height characteristics in the second embodiment. [Figure 16] FIG. 16 is an enlarged view of a part of FIG. [Figure 17] 1 is a graph showing the relationship between viewing angle and distortion. [Figure 18] FIG. 11 is a diagram showing an example of an aspheric coefficient in the optical system of the second embodiment. [Figure 19] 13 is a graph showing aspheric coefficients when R=-100, -150, and -200. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, specific embodiments to which the present invention is applied will be described in detail with reference to the drawings. However, the present disclosure is not limited to the following embodiments. Therefore, the following description and drawings have been simplified appropriately. Embodiment 1 The head mounted display and the display method thereof according to the present embodiment are shown in the drawings. 1 is a schematic diagram showing a configuration of a part of a head mounted display 100. FIG. 2 is a perspective view showing some functional blocks of the head mounted display 100. 1 and 2 are diagrams mainly showing the image display of the head mounted display 100. FIG. 1 shows the internal configuration of the head mounted display 100. In reality, each of the components shown in FIG. 1 may be covered with a cover or the like.

[0010] The head mounted display 100 is suitable for gaming, entertainment, industrial, It can be used for various purposes such as medical use and flight simulators. The display 100 is, for example, a VR (Virtual Reality) head-mounted display. displays and AR (Augmented Reality) head-mounted displays and MR (Mixed Reality) head-mounted displays. In the embodiment, the head mounted display 100 is an optical device used for AR or MR. It is a see-through type head mounted display, but it is a non-transparent head It may be a mounted display.

[0011] For the sake of clarity, the following explanation will be given using the XYZ three-dimensional Cartesian coordinate system. As a guideline, the front-to-back direction (depth direction) is the Z direction, the left-to-right direction (horizontal direction) is the X direction, and the up-down direction ( The vertical direction is the Y direction. The forward direction is the +Z direction, the backward direction is the -Z direction, and the right direction is the +X direction. The left direction is the -X direction, the upward direction is the +Y direction, and the downward direction is the -Y direction.

[0012] A user (not shown) wears a head-mounted display 100. The front display 100 includes a display element unit 101, a frame 102, and a left-eye optical system 10. The optical system for the right eye 103R includes a control unit 105. 105L and a control unit 105R.

[0013] The frame 102 has a goggle or eyeglass shape and is attached to a headband or the like (not shown). The frame 102 is fitted to the head of the user. The optical system 103L, the optical system for the right eye 103R, the control unit 105L, and the control unit 105R are attached. In addition, a binocular head mounted display 100 is illustrated in FIG. , or a non-immersive head-mounted display having a glasses shape.

[0014] The display element unit 101 includes a left eye display element 101L and a right eye display element 101R. The left eye display element 101L generates a display image for the left eye. The right eye display element 101R , a display image for the right eye is generated. are flat panels such as LCD monitors and organic EL (Electro-Luminescence) monitors, respectively. The left eye display element 101L and the right eye display element 101R are curved. The left eye display element 101L and the right eye display element 101 R each has a plurality of pixels arranged in an array. The display element 101L for the left eye may be arranged not only in a two-dimensional manner but also in a pen-tile arrangement. is disposed on the left side (−X side) of the right-eye display element 101R.

[0015] A control unit 105 is provided above (on the +Y side of) the display element unit 101. 5 receives video signals, control signals, and power from an external device. For example, (registered trademark), or via a wired connection such as WiFi (registered trademark) or Bluetooth (registered trademark). A video signal and the like are input to the control unit 105 via a wireless connection such as a head mounted display. The player 100 may include a video generating unit (not shown) for generating a video signal, and a control The unit 105 may receive as input a video signal generated by a video generation unit.

[0016] The control unit 105L and the control unit 105R are CPUs (Central Processing It has hardware resources such as a computer unit (CPU) and memory, and the computer The control unit 105L and the control unit 105R operate according to a computer program. Each of the display units includes a display driver circuit, etc. The control unit 105L receives a video signal, a control A display signal for a left eye image is generated based on the signal and output to the left eye display element 101L. As a result, the left eye display element 101L outputs display light for displaying an image for the left eye. The control unit 105R generates a display signal for the right eye image based on the video signal, the control signal, etc. The right eye display element 101R then outputs the resulting signal to the right eye display element 101R. In other words, the control unit 105 outputs a display light for displaying a display image for the right eye. is output to the display element unit 101.

[0017] The display element unit 101 includes a left eye display element 101L and a right eye display element 101R. The display device is not limited to the above-mentioned configuration, and may be configured as a single display device. The display element unit may generate a display image for the left eye and a display image for the right eye. 101 generates an image for the left eye using a portion of one side of the display area of ​​the display, and A portion of the image is used to generate the image for the right eye.

[0018] A part or the whole of the display element unit 101, the control unit 105, etc. are fixed to a frame 102. The structure is not limited to a structure in which the sensor 101 is fixed to the frame 102, and the sensor 101 may be provided detachably to the frame 102. By attaching a smartphone, tablet computer, or the like to the frame 102, In this case, the display element unit 101, the control unit 105, etc. may be realized in a smartphone or the like. An application program that generates images to be displayed on a head-mounted display (application You just need to install the above beforehand.

[0019] The left-eye optical system 103L converts the display light output from the left-eye display element 101L into a left-eye image. The right eye optical system 103R guides the right eye display element 101R to the left eye EL of the user. The left-eye optical system 103L guides the reflected display light to the right eye ER of the user as a right-eye image. The left-eye optical system 103L is disposed to the left (−X side) of the right-eye optical system 103R. The right-eye optical system 103R is disposed in front of the left eye EL of the user (in the +Z direction). The display element unit 101 is disposed in front of the eye ER (in the +Z direction). The virtual image of the displayed image can be viewed directly ahead (in the +Z direction).

[0020] As described above, the head mounted display 100 according to the present embodiment is a semi-transmissive or This can be applied to any head-mounted display, including non-transparent head-mounted displays. The head-mounted display 100 is a semi-transmissive head-mounted display. Therefore, the left eye optical system 103L and the right eye optical system 103R are In the semi-transmissive head mounted display 100, a display element unit The display light from 101 and external light are incident on the left eye EL and the right eye ER. The user can visually recognize a superimposed image in which the display image is superimposed on the scenery in the forward direction (+Z direction).

[0021] Hereinafter, the left eye optical system 103L and the right eye optical system 103R (hereinafter collectively referred to as the optical system) FIG. 3 is a side view showing a schematic diagram of the optical system. The right-eye optical system 103L and the right-eye optical system 103R have the same configuration, so in FIG. Here, the left-eye optical system 103L will be mainly described.

[0022] The left-eye optical system 103L includes a combiner 121L, a beam splitter 122L, and a light shielding The combiner 121L, the beam splitter 122L, and the shielding portion 150L are provided. The optical section 150L is fixed to the frame 102 shown in FIG.

[0023] The combiner 121L is a concave mirror, and the beam splitter 122L is a plane mirror. The combiner 121L and the beam splitter 122L are formed by using a beam splitter such as a half mirror. The combiner 121L is a splitter that reflects part of the incoming light and transmits part of it. If the ratios of reflected light and transmitted light are equal, the combiner 121L will receive approximately half of the incident light. The beam splitter 122L transmits half of the light and reflects the other half. Similarly, the reflection ratio of the beam splitter 122L is If the ratio of the incident light to the reflected light is equal, the beam splitter 122L will receive approximately half the light. The combiner 121L and the beam splitter 122L transmit half of the light and reflect the other half. You can increase the reflection ratio and decrease the transmission ratio, or you can decrease the reflection ratio and increase the transmission ratio. You may increase the number of

[0024] The combiner 121L and the beam splitter 122L are positioned in front of the left eye EL of the user ( The combiner 121L is arranged in the +Z direction. It is located in front of (+Z direction).

[0025] A left-eye display element 101L is disposed above the beam splitter 122L (in the +Y direction). The left-eye display element 101L emits display light PL11 for forming a display image. That is, the left eye display element 101L is disposed diagonally above and in front of the left eye EL.

[0026] The light blocking portion 150L is disposed below (in the -Y direction) the beam splitter 122L. In other words, the light shielding portion 150L is disposed diagonally below and in front of the left eye EL. The light-shielding portion 150L is made of a black material that absorbs light. Instead of the light-shielding part 150L, ​​the lower part is made of a material that allows the user to see diagonally downward in front. A window may be provided.

[0027] The display light PL11 from the left-eye display element 101L will be described. The display surface of the left eye display element 1L faces vertically downward (in the -Y direction). The display light PL11 from the left eye display element 101L is emitted in the -Y direction. For example, a liquid crystal monitor has a liquid crystal display panel. By controlling the polarization state of the light, the light is spatially modulated.

[0028] Below the left-eye display element 101L (in the -Y direction), a beam splitter 122L is inclined. The display light PL11 from the left-eye display element 101L is directed through a beam splitter The light PL11 is incident on the beam splitter 122L. The beam splitter 122L reflects a part of the display light PL11. The remaining display light PL11 transmitted through the beam splitter 122L is reflected by the light shielding portion 150L. It is absorbed.

[0029] The display light PL11 reflected by the beam splitter 122L is reflected forward (in the +Z direction). The display light PL11 reflected by the beam splitter 122L is then reflected by the combiner 121. The combiner 121L reflects a part of the display light PL11 backward (in the −Z direction). The display light PL11 reflected by the combiner 121L is set as the display light PL12. The combiner 121L is a concave mirror and is configured to condense the display light PL12 toward the left eye EL. The display light PL12 reflected by the combiner 121L is The beam splitter 122L splits one of the display light beams PL12 into The part is transparent.

[0030] The display light PL12 transmitted through the beam splitter 122L is incident on the left eye EL. In this way, the left-eye optical system 103L reflects the display light PL11 from the left-eye display element 101L to the The optical system displays a virtual image in front of the user (in the +Z direction). In addition, because a concave mirror is used as the combiner 121L, the displayed image is enlarged. It will be displayed as follows.

[0031] Next, the external light PL21 from the front (+Z direction) of the user will be described. A part of the external light PL21 transmitted through the combiner 121L. The external light PL21 enters the beam splitter 122L. The external light PL21 that passes through the beam splitter 122L enters the left eye EL. Shoot.

[0032] Since the head mounted display 100 is a semi-transmissive type, the combiner 121L is The external light PL21 from the +Z direction and the display light PL12 from the left eye display element 101L are combined. By providing the combiner 121L in front of the user (in the +Z direction), The display 100 can be an optical see-through type. In other words, the user can see the scenery with the display image superimposed on it. It can be seen.

[0033] The right-eye optical system 103R, like the left-eye optical system 103L, includes a combiner 121R, a beam splitter 122R, and a beam splitter 123R. The right eye display element 10 has a splitter 122R and a light blocking portion 150R. The display light PR11 from the beam splitter 122R is reflected by the beam splitter 122R and is input to the combiner 12 The combiner 121R combines the external light PR21 from the front (+Z direction) with the right-eye light PR1R. The display light PR12 from the display element 101R is synthesized. The ophthalmic optical system 103L will be collectively described as an optical system.

[0034] The combiners 121L and 121R are aspheric concave mirrors. 21L and 121R are aspheric mirrors. The focal length of combiners 121L and 121R is f. FIG. 4 is a schematic diagram showing a simplified optical system. In the following description, the beam splitters 122L and 122R are omitted. The following explanation will omit 22L and 122R.

[0035] The left eye display element 101L and the right eye display element 101R are respectively connected to a combiner 121L and The left eye display element 101R is disposed at a distance f from the left eye display element 101L. The distance between the combiner 121L and the right eye display element 10 is approximately equal to the focal length f. The distance between 1R and combiner 121R is approximately equal to the focal length f.

[0036] As shown in FIG. 5, the left eye display element 101L and the right eye display element 101R emit light at one point. The reflected display lights PL11 and PR11 are incident on combiners 121L and 121R while spreading. The display lights PL12 and PR12 reflected by the combiners 121L and 121R are The display light PL11 emitted from one point of the left eye display element 101L is converted into a parallel light beam. The light is reflected by the light source 121L to become a parallel light beam and enter the left eye EL. The display light PR11 emitted from a point on 101R is reflected by the combiner 121R. The light beam becomes parallel and enters the right eye ER. Note that FIG. 5 shows the viewing angle of 0° in the vertical direction (Y direction). , ray diagrams showing the simulation results at 5°, 10°, 15°, 20°, and 27°. Here, the viewing angle refers to the angle that spreads radially from the left eye EL and the right eye ER. At each viewing angle, the display light PL reflected by the combiners 121L and 121R is 12 and PR12 are essentially parallel light beams.

[0037] The image formation by the left eye EL and the right eye ER allows the user to see the left eye display element 101L and the right eye display element 101R. The image displayed on the 01R can be seen. Figure 6 shows the relationship between the object (object surface) and the image height. FIG. 6 shows an imaging optical system with a convex lens having a focal length f. In this case, the relationship between the image height y on the image plane and the angle of view θ is expressed by the following formula (1). y = f × tan θ (1) When the above relationship is applied to the optical systems in Figures 3 and 4, the focal length f of the lens is the same as that of a concave mirror ( The image height y corresponds to the focal length f of the combiners 121L and 121R. 1L corresponds to the distance from the center of the right eye display element 101R (the optical axis of the optical system). This corresponds to the viewing angle.

[0038] From equation (1), equation (2) is obtained. θ = arctan(y / f) (2) By increasing the image height y, the viewing angle θ can be increased. y is the display element size (panel size) of the left eye display element 101L and the right eye display element 101R ) and it is difficult to increase it beyond a certain level. In the case where the display element 101R for use is a display element having a large aspect ratio in the left-right direction (X direction), In this case, the image height y is the horizontal direction (X direction) of the left eye display element 101L and the right eye display element 101R. Determined by the display element size (panel size).

[0039] Moreover, by reducing the focal length f of the concave mirror, the viewing angle θ can be increased. However, if the focal length f of the concave mirror is reduced, the overall optical system becomes smaller. For example, In order to shorten the optical distance between the left-eye display element 101L and the combiner 121L, The left eye display element 101L needs to be lowered downward (in the -Z direction). If L is lowered too much, the display light PL12 reflected by the combiner 121L will be significantly reduced in the +Y direction. The component with a small viewing angle interferes with the left eye display element 101L. Therefore, the upper end (+Y end) of the virtual image cannot be seen. In this embodiment, in order to widen the viewing angle, the effective field of view is Outside of this range, distortion is increased.

[0040] The human visual field is approximately 200° left and right and 135° up and down, but high visual acuity can be obtained with the eyes stationary. The visual field that can be discriminated is about several degrees. Approximately 15° to the left and right, approximately 8° up, and approximately 12° down. When looking outside the effective visual field, it is natural Therefore, in this embodiment, the range within the effective field of view is set to high quality. The image quality is reduced outside the effective field of view, achieving high image quality and reducing costs and size. It is compatible with typification.

[0041] Generally, the effective visual field is within approximately 15° to the left and right, approximately 8° above, and approximately 12° below. Here, the effective field of view is adjusted to the larger horizontal field of view angle compared to the vertical field of view. In this case, the viewing angle corresponding to the effective field of view is assumed to be 15°. The effective field of view is within a range of 15° in the direction. The viewing angle that corresponds to the effective field of view is called the effective viewing angle. The effective viewing angle corresponds to the maximum angle of the effective viewing field in the left-right direction. In the embodiment, the effective viewing angle is described as 15°, but the effective viewing angle is not limited to this value. Also, the combiner 121L and the combiner 121R are the left eye EL and the right eye EL, respectively. It is located from inside the ER's field of view to outside the field of view. In other words, the combiner 121L The part of the combiner 121R close to the optical axis is within the effective field of view, and the combiner 121L and The part of the combiner 121R far from the optical axis is outside the effective field of view. For example, the combiner 121L, Only the center of 121R is within the effective field of view, and the peripheral parts of the combiners 121L and 121R are visible. It may be outside the effective field of view.

[0042] In the optical system, within the range inside the effective viewing angle corresponding to the effective viewing field of the user's eye, Distortion is below a certain value. For example, the certain value is the limit at which the image can be seen without discomfort. On the other hand, in the range outside the effective viewing angle, At viewing angles less than the effective viewing angle, it is difficult for people with good eyesight to see the displayed image or Since the scenery can be seen, distortion is reduced. When viewing a scene in the sky, the user must rotate his / her head to obtain a high level of visual acuity. The user rotates his / her head so that the scenery he / she wants to see is within the effective field of view. Even if the distortion aberration is large, the deterioration of the display quality can be suppressed.

[0043] FIG. 7 is a graph showing the results of a simulation of image height characteristics, showing the relationship between the viewing angle and the image height. FIG. 8 is an enlarged view of a part of FIG. 7. The horizontal axis represents the viewing angle, and the vertical axis represents the image height. The image height characteristic is a characteristic that indicates the change in image height with respect to the viewing angle.

[0044] The image height is measured in the left and right directions ( For example, if an optical system is designed with the optical axis at the center of the panel, the image The height is in the left-right direction from the center of the panel of the left-eye display element 101L or the right-eye display element 101R. (X direction) distance. A viewing angle of 0° corresponds to an image height of 0 mm, i.e., the center of the panel. A viewing angle of 15° corresponds to a distance of about 23 mm from the center of the panel. The size of the display panel in the left-right direction (X direction) of the right-eye display element 101L or the right-eye display element 101R is To make it 66mm, the half width is 33mm. The size from the center of the panel to the left or right edge In other words, the maximum image height is 33 mm. The viewing angle corresponding to 33 mm is This is the maximum viewing angle (maximum display angle) in the X direction.

[0045] 7 and 8 show the simulation results of Example 1 and Comparative Examples 1 and 2. Comparative Example 1 is a spherical mirror with a radius of curvature R = -180 mm, i.e., f = 90 mm, which is not an aspherical mirror. In Comparative Example 2, the image height characteristic is shown for y=f in formula (1) when f=90 mm. * Image height characteristics of tan θ. Comparative Example 2 is an image height characteristic of an ideal optical system without distortion. The image height in Comparative Example 2 is taken as the ideal image height.

[0046] In Comparative Examples 1 and 2, the image height characteristics are substantially linear. In Comparative Example 2, the slope of the graph of the image height characteristics is almost constant. Therefore, the slope of the graph for Comparative Example 1 is smaller than that for Comparative Example 2. Since the maximum viewing angle is mm, the maximum viewing angle of Comparative Example 1 is 22°, and the maximum viewing angle of Comparative Example 2 is The angle is 21°.

[0047] In the first embodiment, the relationship between the viewing angle and the image height is substantially linear up to the vicinity of the effective viewing angle. However, when the viewing angle becomes larger than the effective viewing angle, in the first embodiment, The relationship between the viewing angle and image height is no longer linear. In Example 1, the slope of the graph is smaller than in Comparative Examples 1 and 2. Furthermore, the viewing angle is larger. The tilt gradually decreases as the effective viewing angle approaches 15°. The graph gradually begins to curve, and as the viewing angle increases, the image height characteristics (logical) of Comparative Example 2 become In this way, as the viewing angle becomes larger, the effective viewing angle increases. As a result, distortion gradually increases.

[0048] In this embodiment, when the viewing angle becomes larger than the effective viewing angle, the image quality is improved. Furthermore, as the viewing angle increases, the slope of the graph of the image height characteristics becomes smaller. In this way, the maximum viewing angle can be increased. In Example 1, the maximum viewing angle corresponding to an image height of 33 mm is approximately 27°. In comparison with Comparative Example 1, which is a spherical mirror, the viewing angle is about 5° wider in Example 1 than in Comparative Example 1. The viewing angle can be increased by about 23%. The image height characteristics of Example 1 are almost the same as those of Comparative Examples 1 and 2. We have explained the image height characteristics of the sub-unit 101 in the left-right direction (X direction), but the image height characteristics in the up-down direction are also In other words, the viewing angle is the same in the vertical direction of the display element unit 101 as well. When the field angle becomes larger than this, the increase in image height relative to the increase in the field angle becomes smaller. However, Since the panel size of the display element unit 101 has a large aspect ratio in the left-right direction (X direction), The maximum viewing angle in the vertical direction is smaller than the maximum viewing angle in the horizontal direction (X direction), which is 27°. .

[0049] The shape of the reflecting surface of the concave mirror will be explained below. The sag amount of the concave mirror is Z. The sag amount Z is , the profile shape of the reflecting surface of the aspheric mirror. r is the optical axis in a plane perpendicular to the optical axis. The sag Z is the radial distance from the apex of the aspheric mirror to the reflecting surface. Specifically, the sag amount Z is expressed as a function of r as shown in the following formula (3). can be.

[0050]

number

[0051] where c is the curvature (the inverse of the radius of curvature R), k is the conic constant, and αn is the aspheric coefficient. α1 is the quadratic α1 is the aspheric coefficient of the fourth order, α2 is the aspheric coefficient of the sixth order, and α4 is the aspheric coefficient of the eighth order. The coefficient, α5, is the 10th order aspheric coefficient. Using c, k, and α1 to α5, the aspheric concave mirror Thus, the amount of sag Z changes according to r.

[0052] In Example 1, the curvature c, the conic constant k, and the aspheric coefficients α1 to α5 are set to the values ​​shown in the table of FIG. The curvature c is the inverse of R=-180. The first to third order aspheric coefficients α1 to α3 are , is 0. The conic constant k is also 0.

[0053] By setting the aspheric coefficient as shown in Figure 9, the radius of curvature of only the outer part of the concave mirror is made small. As shown in Figures 7 and 8, the lens can be bent so that it is only outside the effective field of view. This is because the inside of the effective field of view is almost the base distortion. The lens has a spherical shape with a radius of curvature R = -180 mm, and becomes aspherical around the effective viewing angle. In other words, the wire is bent so that the radius of curvature becomes smaller.

[0054] By using the conic constant k or low-order (e.g. 2nd to 6th order) aspheric coefficients, the spherical shape can be created from the inside. In this case, the radius of curvature may become smaller as shown in Figs. If distortion becomes large inside the effective field of view, it becomes difficult to obtain satisfactory image height characteristics. Therefore, in the first embodiment, the conic constant k is set to 0, and the second to sixth order aspheric lenses are used. The surface coefficients α1 to α3 are set to 0.

[0055] Next, the shape of the image height characteristic will be described. In this case, it is possible to use Comparative Example 3 shown in FIG. The effective viewing angle is changed linearly from the effective viewing angle. Above the effective viewing angle, the spherical shape has a smaller radius of curvature. Below this, the radius of curvature is R = -180, and above the effective viewing angle, the radius of curvature is Ro = R x 0.5 5 (=-180×0.55). In FIG. 10, Comparative Examples 1 and 2 are the same as those in FIG. and FIG. 8.

[0056] However, in Comparative Example 3, the change in the curved surface shape was discontinuous before and after the effective viewing angle, In other words, the image displayed near the boundary of the effective field of view may appear unnatural. Therefore, in the present embodiment, the change in image height before and after the effective viewing angle is Specifically, it is preferable to make the curve on the outside of the effective viewing angle smooth. In other words, it is preferable to use a so-called relaxation curve in the range outside the effective viewing angle. The image height characteristics are in the form of a transition curve. However, here we will simplify it by gradually reducing the amount of change inside the effective viewing angle by a certain coefficient. The amount of change is calculated based on the amount of change in the curve. By using such a curve, The change in the curved shape of the concave mirror around the effective viewing angle becomes smooth. The connection of the displayed images can be made more natural. This helps prevent deterioration of the display quality. It is possible.

[0057] The spot position on the display panel in the optical system designed in this way is shown in Figure 11. In the concave mirror of Example 1, the positions of the spots in the left and right directions (X direction) are shown at intervals of 2.5°. The results of a simulation performed in the viewing angle range of 0° to 25° are shown here. At effective viewing angles of 15° or less, the spots are arranged at nearly equal intervals. When the spot interval exceeds 100°, the spot interval gradually becomes shorter. In Figure 11, the panel size is 58 mm long and 66 mm wide.

[0058] FIG. 12 is a diagram showing the distortion aberration characteristics on a display panel. As shown in FIG. The difference creates what is known as a barrel shape, i.e. it appears to bulge outwards from the center.

[0059] The display image formed by the left eye display element 101L or the right eye display element 101R is It is preferable that the correction is performed according to the distortion characteristics. The control unit 105 forms the display image so that the display image is distorted according to the difference. 05 uses software or hardware to realize the formation of distorted display images FIG. 13 is a diagram showing an example of the left and right display images that have been corrected according to the distortion aberration. 3. The left and right display images were corrected according to the distortion aberration of the optical system and viewed without going through the optical system. A display image is shown.

[0060] As shown in FIG. 13, the control unit 105 forms a display image that bulges outward from the center. The display element unit 101 displays an image having a distortion equivalent to the distortion aberration of the optical system. That is, the display element unit 101 forms a display image distorted according to the distortion aberration of the optical system. The control unit 105 corrects the displayed image so that the user can see the distorted displayed image through the optical system. By viewing the image, the appropriate display image can be visually recognized. This improves the display quality. It is possible.

[0061] According to the above configuration, the display quality can be improved. Even when using a lens, the effective field of view is free of chromatic aberration and provides extremely high image quality. In addition, by gradually increasing the distortion outside the effective field of view, Furthermore, it is possible to obtain a wider viewing angle than the above. It can be connected to nature.

[0062] Embodiment 2 In the second embodiment, the shapes of the reflecting surfaces of combiners 121L and 121R are different. Specifically, in the second embodiment, the fourth-order and sixth-order aspheric coefficients α2 and α The basic configuration of the head mounted display 100 is Since this is similar to the first embodiment, the explanation will be omitted.

[0063] The results of a simulation performed by changing the radius of curvature R will be described below. In Example 2, the radius of curvature R is -180 mm, and in Example 3, the radius of curvature R is -150 mm. In the optical systems of Examples 2 and 3, the conic constant k and the aspheric coefficients α2 to α5 are The values ​​are shown in Table 14. Note that k = 0 and α1 = 0. c is the It is the inverse of the radius of curvature.

[0064] FIG. 15 shows the image height characteristics in the optical system according to the second embodiment. FIG. 16 shows a part of FIG. 15 and 16 are graphs showing Examples 1 and 2 and Comparative Examples 1 and 2. 15 and 16, Example 1 and Comparative Examples 1 and 2 are the same as those in FIGS. As in the first embodiment, the effective viewing angle is 15° and the maximum image height is 33 m. m.

[0065] In the second embodiment, the image height characteristic is almost linear below the effective viewing angle, and above the effective viewing angle In other words, in the range outside the effective viewing angle, The image height characteristics are in the shape of a relaxation curve. Distortion gradually increases beyond the effective viewing angle. That is, in the same manner as in the first embodiment, the viewing angle becomes smaller in the range outside the effective viewing angle. As the lens moves toward the outside, the distortion becomes gradually larger. The same effect can be obtained.

[0066] In Comparative Example 2, y=f*tanθ, so y in Comparative Example 2 is the ideal height. The difference is defined as the amount of deviation between the ideal image height and the actual image height. Let A be the actual image height by the optical system. Then, the distortion aberration (%) is expressed as 100×(yA) / A. 17 is a graph showing the relationship between the aberration (%) and the aberration (%) in Comparative Example 1 and Examples 1 to 3. The simulation results are shown.

[0067] Figure 17 shows the results of a simulation in which the viewing angle is changed in increments of 2.5°. In the simulation, the distortion (%) was calculated at 2.5° intervals. FIG. 17 is a graph showing the simulation results of Examples 1 to 3 and Comparative Example 1. be.

[0068] In Examples 1 to 3, the distortion is 5% or less at angles equal to or less than the effective viewing angle. In Examples 1 to 3, the distortion aberration exceeds 5% over the entire range of the viewing angle of 20° or more. On the other hand, in Comparative Example 1, the distortion is 5% or less when the viewing angle is 20° or less. In this way, by increasing the distortion aberration at or above the effective viewing angle corresponding to the effective field of view, In this way, it is preferable to keep the distortion within the range inside the effective viewing angle to 5% or less. This makes it possible to widen the angle of view (viewing angle).

[0069] FIG. 18 is a table showing an example of aspheric coefficients in the optical system of the present embodiment. 1 shows an example of an aspheric coefficient that exhibits good distortion characteristics obtained from a simulation. In Figure 18, R = -100mm, -120mm, -150mm, -180mm, - This shows an example of the aspheric coefficient at 200 mm. In the following, the case of R=-100 mm is shown as R -100, R=-120mm is R-120, R=-150mm is R-150 , when R = -180 mm, it is written as R-180, and when R = -200 mm, it is written as R-200. FIG. 18 shows a table of aspheric coefficients and absolute values ​​of the aspheric coefficients. By using the aspheric coefficients shown in the table, a good optical system can be obtained. , k=0.

[0070] FIG. 19 is a graph showing the absolute values ​​of the aspheric coefficients in the table of FIG. 18. 19 is a graph showing the relationship between the absolute value of the aspheric coefficient and the aspheric order of the fourth and sixth orders. , 8th and 10th order aspheric coefficients, i.e., α2, α3, α4, and α5. indicates the aspheric coefficients α2, α3, α4, and α5 when R=-100, -150, and -200. The reason why the absolute value is shown is that if the Z direction, i.e. the direction of the curved surface of the concave mirror, is reversed, the curvature This is because the sign of the refractive index radius R and the sign of the aspherical coefficients are both reversed.

[0071] The absolute value of the fourth-order aspheric coefficient α2 and the absolute value of the sixth-order aspheric coefficient α3 are relatively small. By setting the value to a small value, it is possible to easily obtain the desired distortion characteristics. For example, The absolute value of the surface coefficient α2 is 1.735×10 -7 For example, the sixth degree The absolute value of the aspheric coefficient α3 is 2.151×10 -10 It is preferable that the number of Simulation results showed that good characteristics could be obtained by setting the aspheric coefficients in the above range. It was.

[0072] The absolute value of the fourth-order aspheric coefficient α2 is 8.049×10 -8 Greater than or equal to 1.735 x 1 0 -7 The absolute value of the sixth-order aspheric coefficient α3 is preferably 9.832×10 -11 Greater than or equal to 2.151×10 -10 It is preferable that the aspheric coefficient is 8 or less. The absolute value of the number α4 is 1.181 × 10 -13 Greater than or equal to 2.432×10 -13 Below It is preferable that the absolute value of the 10th-order aspheric coefficient α5 is 2.687×10 -17 End , 5.656×10 -17 It is preferable that the following is true: As a result, good characteristics were obtained by setting the aspheric coefficient within the above range.

[0073] In addition, the head mounted display 100 is an optical see-through type head mounted display. However, the head mounted display 100 is a non-transparent head mounted display. In the case of a non-transparent head-mounted display, In this case, a reflecting mirror may be provided instead of the combiners 121L and 121R. In other words, the concave mirrors arranged in front of the beam splitters 122L and 122R are half mirrors. The concave mirror reflects the display light to the The light is reflected back towards the laser.

[0074] The present invention has been described above in detail based on the embodiments. The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit and scope of the present invention. Needless to say, two or more of the above embodiments may be combined as appropriate. It is Noh. [Explanation of symbols]

[0075] EL left eye ER right eye 100 Head Mounted Display 101 Display element section 101L Display element for left eye 101R Display element for right eye 102 Frames 103L Optical system for left eye 103R Optical system for right eye 121L Combiner 121R Combiner 122L Beam Splitter 122R Beam Splitter PL11, PL12, PR11, PR12 display light PL21, PR21 External light

Claims

1. an aspheric concave mirror disposed in front of a user and configured to reflect display light forming a display image toward the user; a beam splitter disposed between the concave mirror and the user, for reflecting the display light to the concave mirror and transmitting the display light reflected by the concave mirror; In the optical system, a distortion aberration is 5% or less in a range inside an effective field of view that corresponds to an effective field of view, which is a field of view in the left-right direction within a range in which high visual acuity can be obtained by eye movement of the user's eyes; In the range outside the effective viewing angle, the distortion becomes larger toward the outside of the field of view, A head mounted display, in which an image height characteristic indicating the relationship between a viewing angle and an image height is linear in a range inside the effective viewing angle, and a slope of the image height characteristic in a range outside the effective viewing angle is smaller than a slope of the image height characteristic in a range inside the effective viewing angle.

2. The head mounted display according to claim 1 , wherein the image height characteristics are not linear in a range outside the effective viewing angle.

3. The head mounted display according to claim 1 , wherein the image height characteristic is linear in a range outside the effective viewing angle.

4. 3. The head mounted display according to claim 1, wherein in a range outside the effective viewing angle, an image height characteristic indicating the relationship between the viewing angle and the image height has a transition curve shape.

5. a control unit that generates a display signal for displaying the display image, 5. The head mounted display according to claim 1, wherein the control unit corrects the displayed image in accordance with a characteristic of distortion aberration of the optical system.

Images