Virtual image display device and optical unit
Patent Information
- Application Number
- JP2023139665
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2023-08-30
- Publication Date
- 2025-03-13
Smart Images
Figure 2025033732000001_ABST
Abstract
Description
[Technical field]
[0001] The present invention relates to a virtual image display device and an optical unit that enable the observation of a virtual image. [Background technology]
[0002] A diffractive display element incorporated in a virtual image display device is known that includes a waveguide, an in-coupling region, an out-coupling region, and an exit pupil expander region, the exit pupil expander region including a number of diffractive zones and a number of non-diffractive zones arranged two-dimensionally (Patent Document 1). In this diffractive display element, the distribution of the two types of zones that make up the exit pupil expander region is adjusted to improve the uniformity of the image over the entire field angle within the eyebox. [Prior art documents] [Patent documents]
[0003] [Patent Document 1] Special Publication No. 2021-517265 Summary of the Invention [Problem to be solved by the invention]
[0004] In the display device shown in Patent Document 1, the uniformity within the beam when it is irradiated onto the in-coupling region is not eliminated during subsequent propagation, and becomes a factor that reduces spatial uniformity when it reaches the eyebox. [Means for solving the problem]
[0005] A virtual image display device and optical unit in one aspect of the present invention includes a display panel that emits image light, a projection optical system that collimates the image light from the display panel, a light guide plate that guides the image light, and a light guide member having an input diffractive optical element that causes the image light to enter the light guide plate, and an output diffractive optical element that emits the image light from the light guide plate, wherein the input diffractive optical element has a distribution of diffraction efficiency that tends to cancel out unevenness in the image light incident on the input diffractive optical element. [Brief description of the drawings]
[0006] [Figure 1] FIG. 1 is a plan view illustrating a state in which an HMD according to a first embodiment is worn. [Diagram 2] FIG. 2 is a side view illustrating the arrangement of an optical system that constitutes the virtual image display device. [Diagram 3] FIG. 2 is a plan view for explaining the arrangement of an optical system that constitutes the virtual image display device. [Figure 4] FIG. 4 is a rear view illustrating a light-guiding optical system or a light-guiding member. [Diagram 5] 4 is a plan view illustrating the optical system of the first display driving section. FIG. [Figure 6] FIG. 4 is an enlarged rear view illustrating an input diffractive optical element. [Figure 7] 4 is a conceptual diagram showing a beam profile of light incident on an input diffractive optical element. FIG. [Figure 8] 7A to 7C are diagrams illustrating modified examples of the input diffractive optical element shown in FIG. [Figure 9] 4A to 4C are diagrams specifically illustrating a diffractive structure formed on an input diffractive optical element. [Figure 10] 10A and 10B are diagrams illustrating modified examples of the input diffractive optical element shown in FIG. [Figure 11] 11A and 11B are diagrams illustrating optical characteristics of an optical system upstream of a light guiding member. [Figure 12] 1A and 1B are diagrams illustrating a specific example of an input diffractive optical element. [Figure 13] 13A and 13B are diagrams illustrating an input diffractive optical element in the second embodiment. [Figure 14] 14 is a diagram illustrating a modified example of the input diffractive optical element shown in FIG. 13. [Figure 15] 1A and 1B are diagrams illustrating a specific example of an input diffractive optical element. [Figure 16] 13A to 13C are diagrams illustrating an input diffractive optical element in the third embodiment. [Figure 17] 1A and 1B are diagrams illustrating a specific example of an input diffractive optical element. [Figure 18] FIG. 13 is a diagram illustrating a virtual image display device according to a fourth embodiment. [Figure 19] 13A and 13B are diagrams illustrating modified examples of the input diffractive optical element. [Figure 20] 13A and 13B are diagrams illustrating another modified example of the input diffractive optical element. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0007] [First embodiment] Hereinafter, a first embodiment of a virtual image display device according to the present invention will be described with reference to FIGS.
[0008] Fig. 1 is a diagram for explaining the wearing state of a head mounted display device (hereinafter also referred to as a head mounted display or HMD) 200, in which the observer or wearer US wearing the HMD 200 recognizes an image as a virtual image. In Fig. 1 etc., X, Y, and Z are an orthogonal coordinate system, the +X direction corresponds to the lateral direction in which the eyes EY of the observer or wearer US wearing the HMD 200 are aligned, the +Y direction corresponds to the upward direction perpendicular to the lateral direction in which the eyes EY are aligned for the wearer US, and the +Z direction corresponds to the forward direction or front direction for the wearer US. The ±Y directions are parallel to the vertical axis or vertical direction.
[0009] The HMD 200 includes a first virtual image display device 100A for the left eye, a second virtual image display device 100B for the right eye, a pair of temple-shaped support devices 100C for supporting the virtual image display devices 100A and 100B, and a user terminal 90 that is an information terminal. The first virtual image display device 100A functions as an HMD by itself, and is composed of a first display drive unit 102a arranged at the top, and a first light guide optical system 103a that is shaped like a pair of glasses and covers the front of the eyes. The second virtual image display device 100B also functions as an HMD by itself, and is composed of a second display drive unit 102b arranged at the top, and a second light guide optical system 103b that is shaped like a pair of glasses and covers the front of the eyes. The support device 100C is a mounting member that is mounted on the head of the wearer US, and supports the upper end sides of the pair of light guide optical systems 103a and 103b via the display drive units 102a and 102b that are integrated in appearance. The first virtual image display device 100A and the second virtual image display device 100B are optically reversed from left to right, and a detailed description of the second virtual image display device 100B will be omitted.
[0010] Fig. 2 is a side view specifically explaining the first display driving unit 102a and the first light guiding optical system 103a of the first virtual image display device 100A. Fig. 3 is a plan view specifically explaining the first display driving unit 102a and the first light guiding optical system 103a. Fig. 4 is a rear view mainly explaining the first light guiding optical system 103a.
[0011] 2 and 3, the first display driving unit 102a includes an image light generating device 10, a projection optical system 20, and a driving circuit member 88. The image light generating device 10 is an optical engine including a display panel 11a. The projection optical system 20 is a collimator including a plurality of lens elements 21. The image light ML generated by the image light generating device 10 is collimated by the projection optical system 20 and coupled to the first light guiding optical system 103a, which is the light guiding member 50. The driving circuit member 88 causes the display panel 11a to perform a display operation. In the first virtual image display device 100A, an optical device excluding the driving circuit member 88 is called an optical unit 100. The first virtual image display device 100A guides the image light ML to the eye EY of the wearer US, thereby allowing the wearer US to view a virtual image.
[0012] 4, the first light guiding optical system 103a is a light guiding member 50 that enables color display and extends approximately parallel to the XY plane. The first light guiding optical system 103a has a light guiding plate 51a, an incident diffraction layer 51b, a pupil enlargement grating layer 51e, and an exit diffraction layer 51c. The incident diffraction layer 51b, the exit diffraction layer 51c, and the pupil enlargement grating layer 51e diffract light in accordance with the wavelength of the image light ML. The incident diffraction layer 51b guides the collimated image light ML from the first display driving unit 102a into the light guide plate 51a and propagates it laterally, the pupil enlargement lattice layer 51e propagates the image light ML propagating laterally within the light guide plate 51a downward while expanding the pupil size of the image light ML, and the exit diffraction layer 51c exits the image light ML toward a pupil position PP (see Figure 2) set inside where the eye EY (see Figure 2) is located, while expanding the pupil size of the image light ML propagating downward within the light guide plate 51a.
[0013] FIG. 5 is a diagram for explaining the optical system of the first display driving unit 102a. In the first display driving unit 102a, the image light generating device 10 includes only one display panel 11a. That is, the display panel 11a includes pixels of three colors, RGB, and the pixels of each color are two-dimensionally arranged in the display panel 11a. The projection optical system 20 includes a plurality of lens elements 21. The display panel 11a and the projection optical system 20 are fixed in a state in which they are positioned relative to each other by a lens barrel 30. The lens barrel 30 is supported together with the drive circuit member 88 by a holder 71 (see FIG. 2) that also serves as a cover in a state in which they are positioned relative to each other, and is fixed to the first light guiding optical system 103a.
[0014] The display panel 11a is a display element or display device that emits image light ML to form an image corresponding to a virtual image. Specifically, the display panel 11a is a display of various light-emitting element arrays such as OLED (Organic Light Emitting Diode), organic EL (Organic Electro-Luminescence), inorganic EL, and LED, and forms still images or moving images on a two-dimensional display surface parallel to the XY plane. The display panel 11a has a light-emitting element 14a. The light-emitting element 14a is a multiplicity of pixels two-dimensionally arranged on a substrate along the XY plane. When the display panel 11a is an OLED display, each pixel constituting the light-emitting element 14a includes, in order from the substrate side, a cathode, an electron transport layer, a light-emitting layer, a hole transport layer, and a transparent electrode layer.
[0015] The display panel 11a is not limited to a self-luminous image light generating device, but may be composed of an LCD or other light modulation element, and may form an image by illuminating the light modulation element with a light source such as a background. Instead of an LCD, LCOS (Liquid crystal on silicon, LCoS is a registered trademark), a digital micromirror device, or the like may be used as the display panel 11a.
[0016] The projection optical system 20 includes a first lens 21a and a second lens 21b as lens elements 21 that collimate, i.e., parallelize, the incident light. The projection optical system 20 has a function substantially equivalent to that of a single lens 20i, and collimates the image light ML emitted from the display surface 11d of the display panel 11a to a state having a predetermined light beam width, and emits the image light ML toward the incident diffraction layer 51b provided on the light guide member 50 in an inclination angle state according to the pixel position. The projection optical system 20 may include an optical element such as a reflecting mirror in addition to one or more lens elements made of resin or glass. The optical surface of the optical element or lens element 21 that constitutes the projection optical system 20 may be any of a spherical surface, an aspherical surface, and a free-form surface.
[0017] Returning to Fig. 4, in the first light guiding optical system 103a or the light guiding member 50, the incident diffraction layer 51b is an input diffractive optical element DI, and is formed with a diffraction pattern that extends linearly in the vertical Y direction and repeats periodically in the horizontal X direction. The exit diffraction layer 51c is an output diffractive optical element DO, and is formed with a diffraction pattern that extends linearly in the horizontal X direction and repeats periodically in the vertical Y direction. The pupil enlargement grating layer 51e is a pupil enlargement diffractive optical element DE, and is provided on the -X side of the incident diffraction layer 51b to bend the optical path of the image light ML that is guided into the light guiding plate 51a and travels in the -X direction as a whole, so that it travels in the -Y direction as a whole.
[0018] Light guide plate 51a is a member formed from a parallel plate, and has first total reflection surface 51i and second total reflection surface 51o, which are a pair of flat surfaces extending parallel to the XY plane (see FIG. 2).
[0019] The entrance diffraction layer 51b, the exit diffraction layer 51c, and the pupil enlargement grating layer 51e are formed on a first total reflection surface 51i of the light guide plate 51a.
[0020] The incident diffraction layer 51b, the exit diffraction layer 51c, and the pupil enlargement grating layer 51e diffract light in accordance with the wavelength of the image light ML, and are formed, for example, of a surface relief type diffraction element. The surface relief type diffraction element is formed by nanoimprinting, but is not limited to this, and can also be formed by etching the surface of the light guide plate 51a, or a diffraction element may be attached.
[0021] The pupil enlargement grating layer 51e does not substantially impair the angular information of the image light ML in the left-right X direction or the vertical Y direction while switching the diffraction direction. The pupil enlargement grating layer 51e, i.e., the pupil enlargement diffractive optical element DE, guides the image light ML guided into the light guide plate 51a from the input diffractive optical element DI, which is the incident diffraction layer 51b, to the output diffractive optical element DO, which is the exit diffraction layer 51c, while enlarging the pupil of the exit diffraction layer 51c. More specifically, the pupil enlargement grating layer 51e is interposed between the incident diffraction layer 51b and the exit diffraction layer 51c, and divides the light beam while guiding the image light ML in a direction (-Y direction) intersecting the diffraction direction (-X direction) of the incident diffraction layer 51b, and has a role of expanding the light beam width in the horizontal direction. The pupil enlargement grating layer 51e is formed by a diffraction pattern that extends linearly in the oblique DS2 direction parallel to the XY plane and is periodically repeated in the DS1 direction parallel to the XY plane and perpendicular to the DS2 direction. The DS1 direction is rotated 45° clockwise with respect to the +Y direction, and is an intermediate direction between the -X direction and the +Y direction. The grating period or pitch in the X direction and the Y direction of the pattern formed on the pupil enlargement grating layer 51e is consistent with the grating period in the X direction of the pattern formed on the entrance diffraction layer 51b, and is consistent with the grating period in the Y direction of the pattern formed on the exit diffraction layer 51c. The exit diffraction layer 51c divides the light beam while guiding the image light ML in the -Y direction, and has a role of expanding the light beam width in the vertical direction. As a result, the light beam width in the X direction and the Y direction of the image light ML incident on the pupil position PP shown in FIG. 2 has a spread corresponding to the exit diffraction layer 51c, and the pupil size in the vertical direction and the horizontal direction increases through the pupil enlargement grating layer 51e, the exit diffraction layer 51c, etc. From the exit diffraction layer 51c, the image light ML collimated around the exit optical axis OX (see FIG. 2) perpendicular to the light guide plate 51a is emitted. The image light ML emitted from the emission diffractive layer 51c is approximately ±25° with respect to the emission optical axis OX. In other words, the angle of view of the first virtual image display device 100A is approximately 50°.
[0022] 6 is an enlarged view illustrating the incident diffraction layer 51b. The diffraction efficiency of the incident diffraction layer 51b has a concentric symmetrical distribution. Specifically, the incident diffraction layer 51b shown in the figure has a first zone 61, a second zone 62, and a third zone 63 that are divided into ring-shaped zones in terms of diffraction characteristics. The first zone 61 is located at the very center and has the lowest diffraction efficiency for the image light ML incident thereon. The third zone 63 is located at the very outside and has the highest diffraction efficiency for the image light ML incident thereon.
[0023] FIG. 7 is a conceptual diagram for explaining the beam profile of the image light ML incident on the incident diffraction layer 51b. The upper chart shows the beam profile P0 of the image light ML incident on the incident diffraction layer 51b, and the lower chart shows the beam profile P1 of the image light ML diffracted by the incident diffraction layer 51b and passing through the incident diffraction layer 51b. Here, the horizontal axis indicates the position in the X direction on the incident diffraction layer 51b, and the vertical axis indicates the light intensity. On the horizontal axis, the symbol O corresponds to the center of the incident diffraction layer 51b and the point through which the optical axis AX passes. The reason will be described later, but in the beam profile P1, the spatial non-uniformity of the beam profile P0, that is, the unevenness NU of the image light ML incident on the incident diffraction layer 51b, is almost canceled out and the unevenness NU is substantially eliminated.
[0024] In this case, the image light ML from each pixel constituting the light emitting element 14a of the display panel 11a is incident on the incident diffraction layer 51b in a superimposed state, but the individual beam profiles of the image light ML incident on the incident diffraction layer 51b from each pixel of the light emitting element 14a and the beam profile P0 of the image light ML obtained by superimposing these maintain a proportional relationship and have a similar distribution. Although not specifically shown in the drawings, the light distribution characteristic corresponding to the relationship between the divergence angle and light intensity of the image light ML emitted from each pixel of the light emitting element 14a shows a pattern substantially similar to that of the beam profile P0.
[0025] In the upper chart, the dashed-dotted line illustrates the diffraction efficiency of the incident diffraction layer 51b. Region Z1 shows the diffraction efficiency of the first zone 61, region Z2 shows the diffraction efficiency of the second zone 62, and region Z3 shows the diffraction efficiency of the third zone 63. Here, when the diffraction efficiency of the first zone 61 is DE1, the diffraction efficiency of the second zone 62 is DE2, and the diffraction efficiency of the third zone 63 is DE3, DE1 < DE2 < DE3. As a result, as shown in the lower chart, the beam profile P1 of the video light ML diffracted after passing through the incident diffraction layer 51b has almost no relative light intensity difference between the zones 61, 62, and 63.
[0026] The beam profile P1 of the video light ML diffracted after passing through the incident diffraction layer 51b may be a predetermined degree higher in the central zone 61 than in the peripheral zone 63, or conversely, may be a predetermined degree higher in the peripheral zone 63 than in the central zone 61. Further, the beam profile P1 of the video light ML that has passed through the incident diffraction layer 51b may be a predetermined degree higher in the intermediate zone 62 than in the zones 61 and 63 sandwiching it, or conversely, may be a predetermined degree lower in the intermediate zone 62 than in the zones 61 and 63 sandwiching it. Specifically, for example, if the difference between the illuminance after passing through the central zone 61 and the illuminance after passing through the peripheral zone 63 is about ±40% or less based on the larger illuminance, it can be said that the input diffractive optical element DI has a distribution of diffraction efficiency that tends to cancel out the non-uniformity NU of the video light ML incident on the input diffractive optical element DI. However, it is more desirable that the difference between the illuminance after passing through the central zone 61 and the illuminance after passing through the peripheral zone 63 is about ±25% or less based on the larger illuminance.
[0027] In the above description, the incident diffraction layer 51b is composed of three zones 61, 62, and 63 with different diffraction efficiencies. However, if the number of zones is increased, the beam profile P1 of the image light ML diffracted through the incident diffraction layer 51b will have flatter characteristics than that shown in the figure. Furthermore, if the diffraction efficiency of the incident diffraction layer 51b changes continuously according to the distance from the optical axis AX, the beam profile P1 of the image light ML can be made uniform and flat. Specifically, the exit angle of the image light ML is θ, the position of the image light ML incident on the incident diffraction layer 51b is x, and the relational expression between the exit angle θ determined by the characteristics of the projection optical system 20 and the position x is x=f(θ). In this case, in consideration of the light distribution characteristics of the image light ML emitted from the light emitting element 14a, if the function of the light intensity distribution or illuminance distribution immediately before incidence on the incident diffraction layer 51b is set as g(x)=g(f(θ)), the diffraction efficiency E(x) or diffraction efficiency E(θ) to be set on the incident diffraction layer 51b will have a distribution that cancels the light intensity distribution, and the diffraction efficiency E(x),E(θ)∝1 / g(x)=1 / g(f(θ)). The original beam profile P0 of the image light ML is, for example, a Lambertian light distribution (light intensity∝COSθ), but by setting the diffraction efficiency E(x) or diffraction efficiency E(θ) as described above, the non-uniformity of the beam profile P0 that causes unevenness in the beam after being coupled to the light guide plate 51a is eliminated.
[0028] FIG. 8 is a diagram for explaining a modified example of the incident diffraction layer 51b shown in FIG. 6. In this case, it includes 3×3 block areas 60aa, 60ab, 60ac, 60ba, 60bb, 60bc, 60ca, 60cb, and 60cc arranged in a matrix. Here, the block area 60bb corresponds to the central first zone 61, and the remaining block areas 60aa, 60ab, 60ac, 60ba, 60bc, 60ca, 60cb, and 60cc can be regarded as corresponding to the peripheral second zone 62. When the diffraction efficiency of the first zone 61 composed of the block area 60bb is DE1 and the diffraction efficiency of the second zone 62 composed of the block areas 60aa, etc. is DE2, DE1 < DE2. That is, the attenuation of the video light ML in the peripheral second zone 62 is less than the attenuation of the video light ML in the central first zone 61, and the beam profile of the video light ML diffracted through the incident diffraction layer 51b has less difference between the center and the periphery and is uniformized.
[0029] In the above description, it is assumed that the incident diffraction layer 51b includes 3×3 block areas, but the incident diffraction layer 51b may include n×n (n is a natural number) block areas. When n is increased, it becomes easier to flatten the beam profile of the video light ML diffracted through the incident diffraction layer 51b. The block area does not have to be square and may be rectangular. However, it is desirable that each zone divided by the block area is formed in a rotationally symmetric annular shape.
[0030] FIG. 9 is a diagram specifically explaining the diffraction structure formed in the incident diffraction layer 51b which is the input diffractive optical element DI. The incident diffraction layer 51b is a slanted type diffractive optical element and is formed with a pattern PT having periodicity in the horizontal X direction. The pattern PT includes a number of convex portions 51e and grooves 51t protruding in the -Z direction from the underlying layer 51f and extending in the vertical Y direction. The grating period of this pattern PT is set so that the reflection angle or incident angle in the light guide plate 51a is greater than the critical angle determined by the refractive index of the light guide plate 51a in order to propagate the video light ML by total reflection in the light guide plate 51a.
[0031] The cross-sectional shape of the convex portion 51e in the first zone 61 at the center is different from that of the convex portion 51e in the third zone 63 at the periphery. The cross-sectional shape of the convex portion 51e is based on a cross section of a parallelogram along the XZ plane with a basic inclination of an inclination angle SA0 rotated clockwise with respect to the -Z direction as a reference, and the inclination of the side surface S1 on the -X side is changed according to the position. In the convex portion 51e formed in the first zone 61 at the center, if the inclination angle of the side surface S1 is SA1(+), and in the convex portion 51e formed in the third zone 63 at the periphery, if the inclination angle of the side surface S1 is SA1(-), the inclination angle SA1(+) of the first zone 61 is made larger than the inclination angle SA1(-) of the third zone 63. However, all the convex portions 51e have the same depth D of the pattern PT and the duty ratio W0 / P0. In this way, by making the inclination angle SA1(+) of the side surface S1 in the first zone 61 relatively large, the diffraction efficiency in the central first zone 61 can be made lower than the diffraction efficiency in the peripheral third zone 63. Although the above describes adjusting the diffraction efficiency in two stages, the distribution of the diffraction efficiency of the incident diffraction layer 51b can be adjusted in three or more stages by using annular zones.
[0032] FIG. 10 is a diagram for explaining the diffraction structure of a modified example of the incident diffraction layer 51b shown in FIG. 9. In the case of the incident diffraction layer 51b shown in the figure, the cross-sectional shape of the convex portion 51e is based on a cross section of a parallelogram along the XZ plane with a basic inclination of an inclination angle SA0 rotated clockwise with respect to the -Z direction as a reference, and the inclination of the side surface S2 on the +X side is changed according to the position. In the convex portion 51e formed in the first zone 61 at the center, the inclination angle of the side surface S2 is SA2(-), and in the convex portion 51e formed in the third zone 63 at the periphery, the inclination angle of the side surface S2 is SA2(+), the inclination angle SA2(-) of the first zone 61 is made smaller than the inclination angle SA1(+) of the third zone 63. However, all the convex portions 51e have the same depth D of the pattern PT and the duty ratio W0 / P0. In this way, by making the inclination angle SA2(-) of the side surface S2 in the first zone 61 relatively small, the diffraction efficiency in the central first zone 61 can be made lower than the diffraction efficiency in the peripheral third zone 63. Although the above describes adjusting the diffraction efficiency in two stages, the distribution of the diffraction efficiency of the incident diffraction layer 51b can be adjusted in three or more stages by using annular zones.
[0033] FIG. 11 is a diagram for explaining the optical characteristics of the optical system in the stage before the light guide member 50. In FIG. 11, an area AR1 shows a specific example of the orientation characteristics of the display panel 11a, and an area AR2 shows the beam profile of the image light ML that has passed through the projection optical system 20. In the orientation characteristics, the horizontal axis is the exit angle of the image light ML, and the vertical axis is the normalized luminance or illuminance. In the beam profile, the horizontal axis indicates a position that passes through the center of the incident diffraction layer 51b and is parallel to the X direction. The display panel 11a is specifically a micro display of an organic light emitting diode. In the micro OLED display, it is said that light up to ±24° of the image light ML emitted from the micro OLED display is swallowed by the projection optical system 20 and collimated with an exit pupil diameter of 3 mm. The orientation characteristics and beam profile of the image light ML are close to a Gaussian distribution. Even if the display panel 11a is a micro LED display, the orientation characteristics of the image light ML are highly directional as described above, and the beam profile has a tendency to be highly luminous at the center of the front.
[0034] FIG. 12 is a diagram for explaining a specific example of the incident diffraction layer 51b. In FIG. 12, the region BR1 is a chart for explaining the pattern PT of the incident diffraction layer 51b shown in FIG. 9, and the region BR2 shows the beam profile of the image light ML immediately after passing through the incident diffraction layer 51b shown in FIG. 9. In addition, in FIG. 12, the region CR1 is a chart for explaining the pattern PT of the incident diffraction layer 51b shown in FIG. 10, and the region CR2 shows the beam profile of the image light ML immediately after passing through the incident diffraction layer 51b shown in FIG. 10. In the above, the refractive index of the glass material forming the light guide plate 51a is 1.9, and the refractive index of the material forming the incident diffraction layer 51b is 2.0. In addition, the depth D0 of the pattern PT is 300 nm, the pitch P0 is 380 nm, and the width W0 is 190 nm. Furthermore, the inclination angle SA0=40°. The depth D0, the width W0, the pitch P0, the inclination angles SA0, SA1, SA2, etc. are design parameters.
[0035] In the example shown in the region BR1 of FIG. 12 (corresponding to FIG. 9), the inclination angle SA1 of the side surface S1 of the convex portion 51e constituting the pattern PT changes discontinuously and nonlinearly according to the position in the X direction of the incident diffraction layer 51b. The inclination angle SA1 of the side surface S1 tends to be largest at the position of x=0 where the optical axis AX passes, and smallest in the periphery (x=approximately ±3 mm). The inclination angle SA1 is also expressed as Angle Left, assuming that it is viewed from the +Z side. As shown in the region BR2 of FIG. 12, the beam profile after passing through the inclined incident diffraction layer 51b is adjusted to be approximately uniform regardless of the position in the X direction. That is, the design parameters of the incident diffraction layer 51b are set to uniformize the beam profile of the image light incident on the incident diffraction layer 51b from the projection optical system 20. The beam profile before passing through the incident diffraction layer 51b is shown by a dotted line. It can be seen that the beam profile after passing through the inclined incident diffraction layer 51b is spatially more uniform than before.
[0036] In the example shown in the region CR1 of FIG. 12 (corresponding to FIG. 10), the inclination angle SA2 of the side surface S2 of the convex portion 51e constituting the pattern PT varies discontinuously and nonlinearly depending on the position in the X direction of the incident diffraction layer 51b. The inclination angle SA2 of the side surface S2 tends to be smallest at the position of x=0 where the optical axis AX passes, and largest around it (x=approximately ±3 mm). The inclination angle SA2 is also expressed as Angle Right, assuming that it is viewed from the +Z side. As shown in the region CR2 of FIG. 12, the beam profile after passing through the inclined type incident diffraction layer 51b is adjusted to be approximately uniform regardless of the position in the X direction.
[0037] The virtual image display devices 100A, 100B of the first embodiment described above include a display panel 11a that emits image light ML, a projection optical system 20 that collimates the image light ML from the display panel 11a, a light guide plate 51a that guides the image light ML, and a light guide member 50 that includes an input diffractive optical element DI that causes the image light ML to enter the light guide plate 51a, and an output diffractive optical element DO that emits the image light ML from the light guide plate 51a, and the input diffractive optical element DI has a distribution of diffraction efficiency that tends to cancel out unevenness NU in the image light ML incident on the input diffractive optical element DI.
[0038] In the above-mentioned virtual image display devices 100A and 100B, the input diffractive optical element DI has a distribution of diffraction efficiency that tends to cancel out unevenness NU in the image light ML incident thereon. Therefore, even if unevenness NU in the image light ML is formed on the input diffractive optical element DI due to the light distribution characteristics of the display panel 11a, the distribution can be suppressed and the light can be guided into the light guide plate 51a, thereby suppressing display unevenness such as fluctuations in pixel brightness due to movement of the line of sight.
[0039] Second Embodiment Hereinafter, a virtual image display device according to a second embodiment of the present invention will be described. Note that the virtual image display device of the second embodiment is a partial modification of the virtual image display device of the first embodiment, and a description of the common parts will be omitted.
[0040] 13 is a diagram specifically illustrating the diffraction structure formed in the incident diffraction layer 51b of the light guide member 50 in the virtual image display device according to the second embodiment. The incident diffraction layer 51b, which is the input diffractive optical element DI, is a binary type diffractive optical element that includes a large number of convex portions 51e and grooves 51t extending in the vertical Y direction and is formed in a pattern PT having periodicity in the horizontal X direction.
[0041] The cross-sectional shape of the convex portion 51e in the first zone 61 at the center is different from that of the convex portion 51e in the third zone 63 at the periphery. The cross-sectional shape of the convex portion 51e is such that the depth, which is the vertical dimension, is changed according to the position. If the depth of the convex portion 51e formed in the first zone 61 at the center is D(-) and the depth of the convex portion 51e formed in the third zone 63 at the periphery is D(+), the depth D(-) of the first zone 61 is made smaller than the depth D(+) of the third zone 63. However, all the convex portions 51e do not have an inclination, and there is no difference in the duty ratio W0 / P0 of the pattern PT. In this way, by relatively reducing the depth D(-) of the convex portion 51e in the first zone 61, the diffraction efficiency in the first zone 61 at the center can be made lower than the diffraction efficiency in the third zone 63 at the periphery. Although the diffraction efficiency is adjusted in two stages as described above, the distribution of the diffraction efficiency of the incident diffraction layer 51b can be adjusted in three or more stages by using ring-shaped zones.
[0042] FIG. 14 is a diagram for explaining the diffraction structure of a modified example of the incident diffraction layer 51b shown in FIG. 13. In the case of the incident diffraction layer 51b shown in the figure, the cross-sectional shape of the convex portion 51e is such that the duty ratio, which is the occupancy rate with respect to the whole, that is, the ratio of the width W0 to the pitch P0, is changed according to the position. If the duty ratio of the convex portion 51e formed in the first zone 61 in the center is W(-) / P0 and the duty ratio of the convex portion 51e formed in the third zone 63 in the periphery is W(+) / P0, the duty ratio W(-) / P0 of the first zone 61 is made smaller than the duty ratio W(+) / P0 of the third zone 63. However, all the convex portions 51e do not have an inclination, and there is no difference in the depth D of the pattern PT. In this way, by relatively reducing the duty ratio W(-) / P0 of the convex portion 51e in the first zone 61, the diffraction efficiency in the first zone 61 in the center can be made lower than the diffraction efficiency in the third zone 63 in the periphery. Although the diffraction efficiency is adjusted in two stages as described above, the distribution of the diffraction efficiency of the incident diffraction layer 51b can be adjusted in three or more stages by using ring-shaped zones.
[0043] FIG. 15 is a diagram for explaining a specific example of the incident diffraction layer 51b. In FIG. 15, the region DR1 is a chart for explaining the pattern PT of the incident diffraction layer 51b shown in FIG. 13, and the region DR2 shows the beam profile of the image light ML immediately after passing through the incident diffraction layer 51b shown in FIG. 13. In addition, in FIG. 15, the region ER1 is a chart for explaining the pattern PT of the incident diffraction layer 51b shown in FIG. 14, and the region ER2 shows the beam profile of the image light ML immediately after passing through the incident diffraction layer 51b shown in FIG. 14. In the above, the refractive index of the glass material forming the light guide plate 51a is 1.9, and the refractive index of the material forming the incident diffraction layer 51b is 2.0. In addition, the depth D0 of the pattern PT is 300 nm, the pitch P0 is 380 nm, and the width W0 is 190 nm. The depth D0, D, the width W0, W, the pitch P0, and the like are design parameters.
[0044] In the example shown in the region DR1 of FIG. 15 (corresponding to FIG. 13), the groove depth D of the convex portion 51e constituting the pattern PT changes discontinuously and nonlinearly depending on the position in the X direction of the incident diffraction layer 51b. The groove depth D tends to be smallest at the position of x=0 where the optical axis AX passes, and largest around it (x=approximately ±3 mm). As shown in the region DR2 of FIG. 15, the beam profile after passing through the binary type incident diffraction layer 51b is adjusted to be approximately uniform regardless of the position in the X direction. It can be seen that the beam profile after passing through the binary type incident diffraction layer 51b is more spatially uniform than before.
[0045] In the example shown in the region ER1 of FIG. 15 (corresponding to FIG. 14), the duty ratio W / P0 of the convex portion 51e constituting the pattern PT changes discontinuously and nonlinearly according to the position in the X direction of the incident diffraction layer 51b. The duty ratio W / P0 tends to be largest at the position of x=0 where the optical axis AX passes, and smallest around it (x=approximately ±3 mm). As shown in the region ER2 of FIG. 15, the beam profile after passing through the binary type incident diffraction layer 51b is adjusted to be approximately uniform regardless of the position in the X direction. That is, the design parameters of the incident diffraction layer 51b are set to uniformize the beam profile of the image light incident on the incident diffraction layer 51b from the projection optical system 20.
[0046] Third Embodiment Hereinafter, a virtual image display device according to a third embodiment of the present invention will be described. Note that the virtual image display device of the third embodiment is a partial modification of the virtual image display device of the first embodiment, and a description of the common parts will be omitted.
[0047] 16 is a diagram specifically illustrating the diffraction structure formed in the incident diffraction layer 51b of the light guide member 50 in the virtual image display device according to the third embodiment. The incident diffraction layer 51b, which is the input diffractive optical element DI, is a blazed type diffractive optical element that includes a large number of convex portions 51e extending in the vertical Y direction and is formed in a pattern PT having periodicity in the horizontal X direction.
[0048] The triangular cross-sectional shape of the convex portion 51e in the first zone 61 at the center is different from the triangular cross-sectional shape of the convex portion 51e in the third zone 63 at the periphery. The cross-sectional shape of the convex portion 51e is such that the depth, which is the vertical dimension, is changed according to the position. If the depth of the convex portion 51e formed in the first zone 61 at the center is D(-) and the depth of the convex portion 51e formed in the third zone 63 at the periphery is D(+), the depth D(-) of the first zone 61 is smaller than the depth D(+) of the third zone 63. However, all the convex portions 51e have the same width or pitch P0 of the pattern PT. In this way, by making the depth D(-) of the convex portion 51e in the first zone 61 relatively small, the diffraction efficiency in the first zone 61 at the center can be made lower than the diffraction efficiency in the third zone 63 at the periphery. Although the diffraction efficiency is adjusted in two stages as described above, the distribution of the diffraction efficiency of the incident diffraction layer 51b can be adjusted in three or more stages by using ring-shaped zones.
[0049] FIG. 17 is a diagram for explaining a specific example of the incident diffraction layer 51b. In FIG. 17, the region FR1 is a chart for explaining the pattern PT of the incident diffraction layer 51b shown in FIG. 16, and the region FR2 shows the beam profile of the image light ML immediately after passing through the incident diffraction layer 51b shown in FIG. 16. In the above, the refractive index of the glass material forming the light guide plate 51a is 1.9, and the refractive index of the material forming the incident diffraction layer 51b is 2.0. In addition, the pitch P0 of the pattern PT is 380 nm.
[0050] In the example shown in the region FR1 of FIG. 17, the depth D of the convex portion 51e constituting the pattern PT changes discontinuously and nonlinearly depending on the position in the X direction of the incident diffraction layer 51b. The depth D tends to be smallest at the position of x=0 where the optical axis AX passes, and largest around it (x=approximately ±3 mm). As shown in the region FR2 of FIG. 17, the beam profile after passing through the blazed type incident diffraction layer 51b is adjusted to be approximately uniform regardless of the position in the X direction. It can be seen that the beam profile after passing through the blazed type incident diffraction layer 51b is more spatially uniform than before.
[0051] [Fourth embodiment] Hereinafter, a virtual image display device according to a fourth embodiment of the present invention will be described. Note that the virtual image display device of the fourth embodiment is a partial modification of the virtual image display device of the first embodiment, and a description of the common parts will be omitted.
[0052] 18 is a diagram illustrating the optical system of the first display driver 102a. In the first display driver 102a, the image light generation device 10 includes three display panels 11r, 11b, and 11g, and a cross dichroic prism 18. The projection optical system 20 is a collimator including a plurality of lenses 21a and 21b.
[0053] The red display panel 11r is a first display panel, and emits red image light MLr, which is a first image light. The display panel 11r is, for example, an organic light emitting diode display, and forms a still image or a moving image on a two-dimensional display surface parallel to the YZ plane, and emits red image light MLr.
[0054] The blue display panel 11b is a second display panel, and emits blue image light MLb, which is the second image light. The display panel 11b is, for example, an organic light-emitting diode display, like the red display panel 11r, and forms a still image or a moving image on a two-dimensional display surface parallel to the YZ plane, and emits blue image light MLb. The light-emitting element 14a incorporated in the blue display panel 11b has a different emission wavelength from the light-emitting element 14a of the red display panel 11r. In other words, the blue image light MLb, which is the second image light, and the red image light MLr, which is the first image light, have different wavelength ranges.
[0055] The green display panel 11g is a third display panel and emits green image light MLg, which is the third image light. The display panel 11g is, for example, an organic light-emitting diode display, similar to the red display panel 11r, and forms a still image or a moving image on a two-dimensional display surface parallel to the XY plane, and emits green image light MLg. The light-emitting element 14a incorporated in the green display panel 11g has a different emission wavelength from the light-emitting element 14a of the red and blue display panels 11r and 11b. That is, the red image light MLr, which is the first image light, and the blue image light MLb, which is the second image light, have different wavelength ranges. That is, the green image light MLg, which is the third image light, and the red image light MLr, which is the first image light, and the blue image light MLb, which is the second image light, have different wavelength ranges.
[0056] The light emitting element 14a incorporated in the display panels 11r, 11b, and 11g is an organic light emitting diode display with a first-order resonant cavity. Therefore, the orientation characteristics of the display panels 11r, 11b, and 11g are such that the light intensity is high in the front direction parallel to the optical axis AX, and the light intensity drops rapidly in a direction slightly tilted from the front direction. The angle at which the light intensity is half-maximum is defined as the radiation angle, and the radiation angle from the pixel of the red image light MLr, the radiation angle from the pixel of the blue image light MLb, and the radiation angle from the pixel of the green image light MLg are within about 20°. Based on these radiation angles of the image lights MLr, MLb, and MLg, the dichroic mirrors 18r and 18b of the cross dichroic prism 18 described later are designed.
[0057] The primary resonance type cavity provided in the light emitting element 14a is formed by a reflective electrode disposed below the light emitting layer and a transparent and reflective counter electrode disposed above the light emitting layer in an organic light emitting diode device or an organic EL device (for a specific structure of the cavity, see, for example, JP 2016-170936 A). The cavity is expressed by the resonance equation: 2D-Φ=mλ(m=0,1,2,3…) D: Optical distance from the reflecting electrode to the counter electrode (half mirror) (=Σ(refractive index × film thickness)) Φ: Total phase shift (= phase shift φU at the counter electrode + phase shift φL at the reflective electrode) m: resonance order That is, for a first-order resonant cavity, m=1.
[0058] The organic light-emitting diode display is not limited to one provided with a first-order resonant cavity, but may be one provided with a zero-order resonant cavity where m = 0, or one provided with a second-order or higher resonant cavity where m = 2.... In general, compared to a zero-order resonant cavity, a first-order resonant cavity has higher luminance but has a relatively higher peak in the light distribution characteristics, resulting in lower beam uniformity.
[0059] The red display panel 11r is fixed so as to be attached to the first light incident surface 18ib of the cross dichroic prism 18. The first red display panel 11r causes red image light MLr, which is the first image light, to enter the cross dichroic prism 18 from the first light incident surface 18ib. The blue display panel 11b is fixed so as to be attached to the second light incident surface 18ic of the cross dichroic prism 18. The second blue display panel 11b causes blue image light MLb, which is the second image light, to enter the cross dichroic prism 18 from the second light incident surface 18ic. The green display panel 11g is fixed so as to be attached to the third light incident surface 18ia of the cross dichroic prism 18. The third green display panel 11g causes green image light MLg, which is the third image light, to enter the cross dichroic prism 18 from the third light incident surface 18ia.
[0060] The cross dichroic prism 18 is formed by joining four right-angled triangular prisms made of glass or the like so that the edges of the right angles coincide with each other, and has a structure in which two dichroic mirrors 18r, 18b perpendicular to the joining portion are embedded. One dichroic mirror 18r is disposed at an angle of 45° with the first entrance surface 18ib. The dichroic mirror 18r forms a surface that connects the diagonal corners of the square outline when viewed from the direction of the cross axis CX of the cross dichroic prism 18. The other dichroic mirror 18b is disposed at an angle of 45° with the second entrance surface 18ic. The dichroic mirror 18b forms a surface that connects the diagonal corners of the square outline when viewed from the direction of the cross axis CX of the cross dichroic prism 18.
[0061] The red image light MLr incident on the first entrance surface 18ib of the cross dichroic prism 18 from the first display panel 11r for red is reflected by the dichroic mirror 18r and bent toward the exit side, i.e., the projection optical system 20, and is emitted from the light exit surface 18o in the +Z direction to the outside. The blue image light MLb incident on the second entrance surface 18ic of the cross dichroic prism 18 from the second display panel 11b for blue is reflected by the dichroic mirror 18b and bent toward the exit side, i.e., the projection optical system 20, and is emitted from the light exit surface 18o in the +X direction to the outside. The green image light MLg incident on the third entrance surface 18ia of the cross dichroic prism 18 from the third display panel 11g for green passes through the dichroic mirrors 18r and 18b toward the projection optical system 20 without being reflected, and is emitted from the light exit surface 18o in the +Z direction to the outside. That is, the cross dichroic prism 18 transmits the green image light MLg. As a result, the cross dichroic prism 18 synthesizes an image in which the red image light MLr, the green image light MLg, and the blue image light MLb are superimposed, and the image light is emitted as image light ML and can be incident on the projection optical system 20.
[0062] In the cross dichroic prism 18, the cross axis CX extends along the intersection line between the two dichroic mirrors 18r, 18b and is parallel to the Y direction. The optical axis AX passing through the light exit surface 18o of the cross dichroic prism 18 extends in the horizontal direction perpendicular to the light guide plate 51a, that is, in the Z direction.
[0063] The projection optical system 20 is an optical system that is approximately telecentric with respect to the display panels 11r, 11b, and 11g, which are the object side. That is, the main rays of the image light MLg, MLr, and MLb emitted from each part of the light emitting element 14a, which is the display surface of each display panel 11b, 11r, and 11g, pass through the light entrance surfaces 18ib, 18ic, and 18ia of the cross dichroic prism 18 in a state approximately parallel to the optical axis AX, thereby entering the cross dichroic prism 18 and being emitted from the cross dichroic prism 18 approximately parallel to the optical axis AX. As a result, the red image light MLr, the green image light MLg, and the blue image light MLb within a predetermined angle range are incident on the dichroic mirrors 18r and 18b, and light loss due to the dichroic mirrors 18r and 18b can be suppressed.
[0064] In this case, the input diffraction layer 51b, which is the input diffraction optical element DI, is an inclined, binary, or blazed type diffraction element, and has a distribution of diffraction efficiency that tends to cancel out the unevenness NU of the image light ML incident on the input diffraction optical element DI.
[0065] [Other matters] The above-described structure is merely an example, and various modifications can be made within the scope of achieving the same function.
[0066] 19, the input diffraction layer 51b or the input diffractive optical element DI is not limited to a circle, but may be an ellipse. When the light distribution characteristic of the display panel 11a is biased in the horizontal X direction and has high luminance, the zones 61, 62, and 63 provided in the input diffractive optical element DI may also be an ellipse. In this case, too, the distribution of the diffraction efficiency in the input diffractive optical element DI tends to cancel out the unevenness NU of the image light ML incident on the input diffractive optical element DI according to the light distribution characteristic of the display panel 11a.
[0067] When the aspect ratio of the display panel 11a shown in FIG. 5 is longer in the horizontal X direction than in the vertical Y direction, as shown in FIG. 20, the incident diffraction layer 51b or the input diffractive optical element DI may include block areas 60a, 60b, 60c divided only in the horizontal X direction. When the diffraction efficiency of the first zone 61 composed of the block area 60b is DE1 and the diffraction efficiency of the second zone 62 composed of the block areas 60a and 60c is DE2, DE1 < DE2. In this case, on the premise that the unevenness of the video light ML is large in the horizontal direction and small in the vertical direction, the diffraction efficiency is adjusted only in the horizontal direction.
[0068] The light guide member 50 is not limited to including the incident diffraction layer 51b, the emission diffraction layer 51c, and the pupil expansion grating layer 51e. For example, the pupil expansion grating layer 51e can be omitted. In this case, the incident diffraction layer 51b guides the collimated video light ML into the light guide plate 51a and propagates it in the horizontal direction, and the emission diffraction layer 51c emits it toward the pupil position PP inside the video light ML propagating in the horizontal direction in the light guide plate 51a.
[0069] In the light guide member 50, the incident diffraction layer 51b, the emission diffraction layer 51c, and the pupil expansion grating layer 51e may be disposed on the second total reflection surface 51o on the outer side of the light guide plate 51a, that is, the +Z side. In this case, the incident diffraction layer 51b, the emission diffraction layer 51c, and the pupil expansion grating layer 51e are designed to function as reflective diffraction elements that partially transmit external light.
[0070] The incident diffraction layer 51b, the emission diffraction layer 51c, and the pupil expansion grating layer 51e may be formed from a volume hologram. In this case, the distribution of the diffraction efficiency of the incident diffraction layer 51b is performed by adjusting the modulation degree of the refractive index difference. The incident diffraction layer 51b, the emission diffraction layer 51c, and the pupil expansion grating layer 51e are not limited to being composed of a single layer, and may be a laminate of a plurality of functional layers adapted to the wavelength and the angular direction of the video light ML.
[0071] The exit diffraction layer 51c and the pupil enlargement grating layer 51e may have a spatial distribution of diffraction efficiency so as to reduce macroscopic display unevenness or image unevenness.
[0072] The light guide member 50 may be a stack of multiple light guides in parallel. In this case, each of the light guides may correspond to, for example, three colors, R, G, and G. Each light guide includes a light guide plate 51a, an entrance diffraction layer 51b, an exit diffraction layer 51c, and a pupil enlargement grating layer 51e.
[0073] In the above, the virtual image display devices 100A, 100B can be used as HMDs, but the present invention is not limited to this and can be applied to various optical devices. For example, the present invention can be applied to a head-up display (HUD).
[0074] In a specific embodiment, the virtual image display device includes a display panel that emits image light, a projection optical system that collimates the image light from the display panel, a light guide plate that guides the image light, and a light guide member having an input diffractive optical element that causes the image light to enter the light guide plate, and an output diffractive optical element that emits the image light from the light guide plate, and the input diffractive optical element has a distribution of diffraction efficiency that tends to cancel out unevenness in the image light incident on the input diffractive optical element.
[0075] In the above-mentioned virtual image display device, the input diffractive optical element has a distribution of diffraction efficiency that tends to cancel out unevenness in the image light incident on the input diffractive optical element. Therefore, even if unevenness in the image light is formed on the input diffractive optical element due to the light distribution characteristics of the display panel, the distribution can be suppressed and the light can be guided into the light guide plate, thereby suppressing display unevenness such as fluctuations in pixel brightness due to movement of the line of sight.
[0076] In a specific embodiment of the virtual image display device, the design parameters of the input diffractive optical element are set to homogenize the beam profile of the image light incident on the input diffractive optical element from the projection optical system, thereby homogenizing the luminance distribution of the image light incident on the input diffractive optical element.
[0077] In a specific embodiment of the virtual image display device, the input diffractive optical element is any one of a tilted type, a binary type, and a blazed type.
[0078] In a virtual image display device according to a specific embodiment, the inclination angle, depth, and duty ratio of the diffractive structure in the input diffractive optical element are changed in accordance with the beam profile of the image light.
[0079] In a specific embodiment of the virtual image display device, the diffraction efficiency of the input diffractive optical element is relatively higher at the periphery than at the center. This corresponds to a case where the light distribution characteristic of the display panel is strong in the direction of the principal ray and becomes weaker as the angle with respect to the principal ray increases, and the diffraction efficiency of the input diffractive optical element is such that such orientation characteristic is cancelled out, thereby suppressing display unevenness.
[0080] In a virtual image display device according to a specific embodiment, the diffraction efficiency of the input diffractive optical element has a concentric symmetrical distribution, whereby display unevenness can be suppressed in all directions.
[0081] In a specific embodiment of the virtual image display device, the diffraction efficiency of the input diffractive optical element changes in the direction in which the aspect ratio of the display panel is large. In this case, display unevenness can be suppressed in the direction in which the influence is large.
[0082] In a specific embodiment of the virtual image display device, the display panel is a first order resonant cavity provided organic light emitting diode display.
[0083] In a virtual image display device according to a specific embodiment, the light-guiding member has a magnifying diffractive optical element that guides the image light guided from the input diffractive optical element into the light-guiding plate to the output diffractive optical element while enlarging the pupil of the output diffractive optical element.
[0084] In a specific embodiment, the virtual image display device includes a first display panel that is a display panel and emits a first image light corresponding to the image light, a second display panel that emits a second image light having a wavelength range different from that of the first image light, a third display panel that emits a third image light having a wavelength range different from that of the first image light and the second image light, and a cross dichroic prism that combines the first image light, the second image light, and the third image light. In this manner, by combining the first display panel, the second display panel, and the third display panel, a high-luminance virtual image can be displayed.
[0085] In a specific embodiment, the optical unit includes a display panel that emits image light, a projection optical system that collimates the image light from the display panel, a light guide plate that guides the image light, an input diffractive optical element that causes the image light to enter the light guide plate, and a light guide member having an output diffractive optical element that emits the image light from the light guide plate, and the input diffractive optical element has a distribution of diffraction efficiency that tends to cancel out unevenness in the image light incident on the input diffractive optical element. [Explanation of symbols]
[0086] 10...image light generating device, 11a...display panel, 11d...display surface, 11r, 11b, 11g...display panel, 14a...light emitting element, 18...cross dichroic prism, 18b, 18r...dichroic mirror, 18ib, 18ic, 18ia...light entrance surface, 18o...light exit surface, 20...projection optical system, 20i...lens, 21...lens element, 21a, 21b...lens, 30...lens barrel, 50...light guiding member, 51a...light guiding plate, 51b...entrance diffraction layer, 51c...exit diffraction layer, 51e...pupil enlargement grating layer, 51e...convex portion, 51f...undercoat layer, 51t...groove, 60a, 60b, 60c...block area, 60aa, 60ab, 60ac, 60ba, 60bb, 60bc , 60ca, 60cb, 60cc...block area, 61, 62, 63...zone, 71...holder, 88...drive circuit member, 90...user terminal, 100...optical unit, 100A, 100B...virtual image display device, 100C...support device, 102a, 102b...display drive unit, 103a, 103b...light guiding optical system, AX...optical axis, CX...cross axis, DE...pupil expansion diffractive optical element, DI...input diffractive optical element, DO...output diffractive optical element, EY...eye, ML...image light, MLb...blue image light, MLg...green image light, MLr...red image light, NU...unevenness, OX...exiting optical axis, P0, P1...beam profile, PP...pupil position, PT...pattern, S1, S2...side, US...wearer
Claims
1. A display panel that emits image light; a projection optical system that collimates the image light from the display panel; a light guide member including a light guide plate that guides the image light, an input diffractive optical element that causes the image light to enter the light guide plate, and an output diffractive optical element that causes the image light to exit from the light guide plate; Equipped with the input diffractive optical element has a distribution of diffraction efficiency that tends to cancel out unevenness in the image light incident on the input diffractive optical element. Virtual image display device.
2. the design parameters of the input diffractive optical element are set to uniformize the beam profile of the image light incident on the input diffractive optical element from the projection optical system; The virtual image display device according to claim 1 .
3. The input diffractive optical element is any one of a tilted type, a binary type, and a blazed type. The virtual image display device according to claim 1 .
4. In the input diffractive optical element, an inclination angle, a depth, and a duty ratio of a diffractive structure are changed according to the beam profile of the image light. The virtual image display device according to claim 3 .
5. The diffraction efficiency of the input diffractive optical element is relatively higher at the periphery than at the center. The virtual image display device according to claim 1 .
6. The diffraction efficiency of the input diffractive optical element has a concentric symmetric distribution. The virtual image display device according to claim 5 .
7. the diffraction efficiency of the input diffractive optical element varies with respect to the large aspect ratio direction of the display panel; The virtual image display device according to claim 1 .
8. The display panel is a first-order resonant cavity-equipped organic light-emitting diode display. The virtual image display device according to claim 1 .
9. the light guiding member has a magnifying diffractive optical element that guides the image light, which has been guided from the input diffractive optical element into the light guiding plate, to the output diffractive optical element while enlarging the pupil of the output diffractive optical element; The virtual image display device according to claim 1 .
10. a first display panel which is the display panel and emits a first image light corresponding to the image light; a second display panel that emits second image light having a wavelength range different from that of the first image light; a third display panel that emits third image light having a wavelength range different from those of the first image light and the second image light; a cross dichroic prism that combines the first image light, the second image light, and the third image light, The virtual image display device according to claim 1 .
11. A display panel that emits image light; a projection optical system that collimates the image light from the display panel; a light guide member including a light guide plate that guides the image light, an input diffractive optical element that causes the image light to enter the light guide plate, and an output diffractive optical element that causes the image light to exit from the light guide plate; Equipped with the input diffractive optical element has a distribution of diffraction efficiency that tends to cancel out unevenness in the image light incident on the input diffractive optical element. Optical unit.
Citation Information
Patent Citations
Exit pupil expander
JP2021517265A