Virtual image display device and optical unit

Abstract

To reduce the thickness of an imaging optical system to be disposed between an imaging element and an eye while securing resolution.SOLUTION: Virtual image display devices 100A and 100B comprise, in order from the outside: displays 10a and 10b having a pixel area A1 that emits image light of, for example, right circularly polarized light c1, and partially transmitting external light OL; a first optical member 21 having a flat surface on the side of the displays 10a and 10b, and including, in the inside thereof, a semi-transmissive reflective optical surface R1 having power; a wave plate 23, the quarter-wave plate, for converting the polarized state of the image light ML that has passed through the first optical member 21, into vertically polarized light q1, the linearly polarized light; and a second optical member 22 including the polarized light reflective layer R2 for reflecting the image light ML that has passed through the wave plate 23. An imaging optical system IS formed by combining the displays 10a and 10b, the first optical member 21, the wave plate 23 and the second optical element 22, has substantially no power with respect to left circularly polarized light c2, the polarization component of the external light OL that has passed through the light transmission area A2 of the displays 10a and 10b.SELECTED DRAWING: Figure 2

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, and more particularly to a see-through type virtual image display device that enables the viewing of an external image. [Background technology]

[0002] A known virtual image display device includes an image element that displays an image, a first optical unit that is positioned at the image light extraction position, a second optical unit that is positioned closer to the image element than the first optical unit, a Fresnel-type half mirror formed at the junction between the first optical unit and the second optical unit, and a transmission / reflection selection member that is provided on the light exit side of the first optical unit and selectively transmits or reflects light depending on the polarization state of the light (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-24246 Summary of the Invention [Problem to be solved by the invention]

[0004] The above device can eliminate see-through distortion, but when trying to reduce the thickness of the imaging optical system placed between the image sensor and the eye, the Fresnel-type half mirror alone does not have enough power, making it impossible to obtain high resolution and making it more likely that color unevenness will occur around the periphery of the angle of view. [Means for solving the problem]

[0005] The virtual image display device and optical unit of one aspect of the present invention comprise, in order from the outside world, a display having a pixel region that emits circularly polarized image light and that partially transmits outside light; a first optical element that is flat on the display side and has a semi-transmissive reflective optical surface with power inside; a wavelength plate that converts the polarization state of the image light that has passed through the first optical element into linearly polarized light or circularly polarized light; and a second optical element that includes a polarized reflective layer that reflects the image light that has passed through the wavelength plate, and the imaging optical system that combines the display, the first optical element, the wavelength plate, and the second optical element has substantially no power with respect to the polarized component of the outside light that has passed through the light-transmitting region of the display. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 2 is an external perspective view illustrating a wearing state of the virtual image display device of the first embodiment. [Figure 2] FIG. 2 is a conceptual side view illustrating the optical structure of a display optical system. [Figure 3A] 10 is a partially enlarged side view illustrating an example of a specific structure of a first display device. FIG. [Figure 3B] 10 is a partially enlarged rear view illustrating an example of a specific structure of the first display device. FIG. [Figure 3C] 3 is a diagram illustrating a modification of the first display of the device shown in FIG. 2. FIG. [Figure 4] 3 is a conceptual diagram illustrating the polarization state of image light and the like in the device shown in FIG. 2. FIG. [Figure 5] FIG. 3D is a conceptual diagram illustrating a polarization state in the modified example shown in FIG. 3C. [Figure 6] FIG. 10 is a conceptual diagram illustrating a polarization state in another modified example. [Figure 7A] FIG. 4 is a diagram illustrating the optical structure of a virtual image display device according to a second embodiment. [Figure 7B] FIG. 2 is an enlarged view of a central portion of the first display optical system. [Figure 8] FIG. 10 is a conceptual side view illustrating the optical structure of a virtual image display device according to a third embodiment. [Figure 9] 9 is a conceptual diagram illustrating the polarization state of image light and the like in the device shown in FIG. 8. [Figure 10] 9 is a diagram illustrating a modified example of the virtual image display device shown in FIG. 8. FIG. [Figure 11] FIG. 10 is a conceptual diagram illustrating the optical structure of a virtual image display device according to a fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0007] [First embodiment] Hereinafter, a first embodiment of a virtual image display device etc. according to the present invention will be described with reference to FIGS.

[0008] Fig. 1 is a diagram illustrating the wearing state of a head-mounted virtual image display device (hereinafter also referred to as a head-mounted display or HMD) 200, in which the HMD 200 allows an observer or wearer US wearing the device to recognize an image as a virtual image. In Fig. 1 and other figures, X, Y, and Z are Cartesian coordinate systems, with the +X direction corresponding to the lateral direction in which the eyes EY of the observer or wearer US wearing the HMD 200 are aligned, the +Y direction corresponding to the upward direction perpendicular to the lateral direction in which the eyes EY are aligned for the wearer US, and the +Z direction corresponding to the forward 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 right eye and a direct virtual image type, a second virtual image display device 100B for the left eye and a direct virtual image type, a pair of temple-shaped support devices 100C that support the virtual image display devices 100A and 100B, and a user terminal 90 that serves as an information terminal. The first virtual image display device 100A functions independently as an HMD and is composed of a first display driver 102a disposed at the top and a first combiner 103a shaped like a pair of glasses that covers the eyes. The second virtual image display device 100B similarly functions independently as an HMD and is composed of a second display driver 102b disposed at the top and a second combiner 103b shaped like a pair of glasses that covers the eyes. The support device 100C is a mounting member worn on the head of the wearer US and supports the upper ends of the pair of combiners 103a and 103b via the display drivers 102a and 102b, which appear integrated in appearance. The first virtual image display device 100A and the second virtual image display device 100B are optically identical or are left-right reversed versions of each other, and a detailed description of the second virtual image display device 100B will be omitted.

[0010] FIG. 2 is a side cross-sectional view illustrating the internal structure of the first virtual image display device 100A. The first virtual image display device 100A includes a first display 10a, a first display optical system 20a, and a first circuit member 80a. Among these components, the first display 10a emits circularly polarized image light ML. The first display optical system 20a is an imaging optical system IS that directly forms a virtual image without forming an intermediate image. The first display optical system 20a, i.e., the imaging optical system IS, includes a first optical member 21 having a reflective optical surface R1 with power therein, a wavelength plate 23 that converts the polarization state of the image light ML to linearly polarized light or circularly polarized light, and a second optical member 22 that includes a polarizing reflective layer R2. In other words, the first virtual image display device 100A includes, as optical elements, the first display 10a, the first optical member 21, the wavelength plate 23, and the second optical member 22, in that order from the outside. As will be described in detail below, the imaging optical system IS has substantially no power for left-handed circularly polarized light c2, which is a polarization component of the external light OL that has passed through the light transmission area A2 (see FIG. 3(A)) of the display devices 10a and 10b. Here, the imaging optical system IS having substantially no power for a specific polarization component of the external light OL means that the power for the specific polarization component of the external light OL is smaller than the power for the image light ML, and more specifically, means that the focal length of the imaging optical system IS for the specific polarization component of the external light OL is, for example, about 1 to 2 m or more and not more than infinity.

[0011] The first optical member 21 and the second optical member 22 emit the image light ML toward the pupil position PP or the eye EY via a round-trip optical path formed by the reflective optical surface R1 and the polarizing reflective layer R2, and transmit the external light OL directly to make it incident on the pupil position PP. The first optical member 21 is a semi-transmissive reflective optical element, and functions as an optical element with positive power with respect to the image light ML due to the reflective optical surface R1. The wave plate 23 is a quarter-wave plate. The second optical member 22 is a reflective polarizing element, and functions as an optical element with positive or negative power with respect to the image light ML due to the polarizing reflective layer R2.

[0012] Although detailed description will be omitted, the second virtual image display device 100B includes a second display 10b, a second display optical system 20b, and a second circuit member 80b. The second display 10b is similar to the first display 10a, the second display optical system 20b is similar to the first display optical system 20a, and the second circuit member 80b is similar to the first circuit member 80a. The second display optical system 20b includes a first optical member 21, a wave plate 23, and a second optical member 22.

[0013] In the first virtual image display device 100A, the optical device excluding the first circuit member 80a is called the optical unit 100. In the second virtual image display device 100B, the optical device excluding the second circuit member 80b is called the optical unit 100.

[0014] In the first virtual image display device 100A, the first display 10a emits, for example, right-circularly polarized image light ML toward the first display optical system 20a, while partially transmitting external light OL containing a left-circularly polarized component.

[0015] 3A and 3B are a partially enlarged side view and a partially enlarged rear view illustrating an example of the specific structure of the first display 10a. Referring to FIG. 3A, the first display 10a has a structure in which a display panel 11 and a polarizing member 13 are laminated and integrated. Referring to FIG. 3B, the first display 10a has discretely arranged rectangular pixel regions A1 and optically transparent regions A2. The pixel regions A1 correspond to the pixels PX of the first display 10a and are arranged in a matrix along the XY plane. That is, the pixel regions A1 are periodically arranged two-dimensionally in the horizontal X direction and the vertical Y direction.

[0016] The display panel 11 is a self-luminous image light generating device. The display panel 11 includes a light modulation element 11a and a protective glass 11b. The display panel 11 is, for example, an organic EL (organic electroluminescence) display, and forms color still or moving images on a two-dimensional display surface 11d. The display panel 11 emits image light ML toward a polarizing member 13 in units of pixels PX corresponding to pixel regions A1. The pixels PX include sub-pixels Pr, Pg, and Pb corresponding to the three colors RGB. The light modulation element 11a has light-blocking properties in the pixel region A1 to prevent transmission of external light OL, and has light-transmitting properties in the light-transmitting region A2 to allow transmission of the external light OL. By passing through the light-transmitting region A2, the external light OL passes through the imaging optical system IS without being affected by the pixel region A1. The display panel 11 is driven by a first circuit member 80a to perform a display operation.

[0017] The polarizing member 13 has a quarter-wave plate 13a and a rectangular polarizing layer 13b on the display panel 11 side of the quarter-wave plate 13a. Although not shown, the entire polarizing member 13 has a large number of polarizing layers 13b arranged in a matrix along the XY plane in positions in the pixel region A1 facing the pixels PX. The polarizing layer 13b is configured to restrict the transmitted light, i.e., the image light ML, to a predetermined polarization direction, specifically, vertically polarized light P1, which is polarized in a first polarization direction, and to block horizontally polarized light P2, which is polarized in a second polarization direction perpendicular to the first polarization direction. The quarter-wave plate 13a is a plate-shaped member extending along the XY plane, and its fast axis or slow axis is set, for example, midway between the X and Y directions, and converts linearly polarized light that has passed through the polarizing plate 13b into right-handed circularly polarized light c1. Here, when focusing on the vibration of the electric field component or magnetic field component of the image light ML, the vibration direction rotates at the frequency of the image light ML in a plane perpendicular to the light propagation direction, and the amplitude is constant regardless of the direction. Right-handed circularly polarized light is light in which the vibration direction of the electric field component rotates clockwise as seen by an observer standing facing the direction of the light beam, and left-handed circularly polarized light is light in which the vibration direction rotates counterclockwise. However, in this specification, if the image light ML mainly contains right-handed circularly polarized light, even if it also contains linearly polarized light in a specific direction, such image light ML is considered to be right-handed circularly polarized light c1. Similarly, if the image light ML mainly contains left-handed circularly polarized light, such image light ML is considered to be left-handed circularly polarized light c2. In this specification, right-handed circularly polarized light c1 is also referred to as right-handed circularly polarized light c1, and left-handed circularly polarized light c2 is also referred to as left-handed circularly polarized light c2.

[0018] Referring to FIG. 2, the first optical member 21 is a parallel-plate-shaped member overall and has no overall power for transmitted light. In the first optical member 21, a first incident surface 31a on the display panel 11 side and a second exit surface 32b on the wave plate 23 side are parallel to each other and extend parallel to the XY plane. The first optical member 21 has a first lens element 31 and a second lens element 32 bonded together with a reflective optical surface R1 sandwiched therebetween. The first lens element 31 has a first incident surface 31a that is a flat surface and a first exit surface 31b that is a continuously concave curved surface. Specifically, the first exit surface 31b is a concave spherical or aspherical surface. The second lens element 32 has a second incident surface 32a that is a continuously convex curved surface and a second exit surface 32b that is a flat surface. A reflective optical surface R1 made of a single-layer or multi-layer metal film and having transparency is formed by vapor deposition or the like on the second entrance surface 32a of the second lens element 32. The reflective optical surface R1 has the same shape as the second entrance surface 32a. That is, the reflective optical surface R1 is a continuously curved optical surface S1, and is a spherical or aspherical surface concave toward the second exit surface 32b. The reflective optical surface R1 partially transmits the image light ML emitted from the display panel 11 at a predetermined transmittance (specifically, for example, 50%) and partially reflects the image light ML, which is returned light from the wave plate 23 and the second optical member 22, at a corresponding reflectance (specifically, for example, 50%). The first optical member 21 is like a cemented lens with the continuous reflective optical surface R1 embedded therein. The fact that the reflective optical surface R1 is semi-transmissive means that the transmittance can be set appropriately to less than 100%, for example. The transmittance of the reflective optical surface R1 is usually set in the range of 30% to 70%, but is not limited to this.

[0019] The first lens element 31 is formed from a plastic material or glass using a molding method or the like, and the second lens element 32 is also formed from a plastic material or glass using a molding method or the like. The first lens element 31 and the second lens element 32 have the same refractive index and are bonded to each other using, for example, an adhesive having the same refractive index as the first lens element 31. The reflective optical surface R1 may be formed on the first entrance surface 31a, and the second lens element 32 may be a plastic material that is filled and hardened between the second lens element 32 and the wave plate 23.

[0020] The wave plate 23 is a quarter-wave plate. The wave plate 23 is a parallel-plate-shaped member overall and has no overall power with respect to transmitted light. The fast axis or slow axis of the wave plate 23 is set, for example, midway between the X direction and the Y direction perpendicular to the optical axis AX. The wave plate 23 converts the image light ML, which is right-handed circularly polarized light c1 emitted from the display panel 11 and passed through the first optical member 21, into vertically polarized light q1, which is linearly polarized parallel to the vertical Y direction. The wave plate 23 converts the image light ML reflected by the polarizing reflective layer R2 of the second optical member 22 into right-handed circularly polarized light c1 when passing it toward the first optical member 21. The wave plate 23 converts the image light ML, which has been reflected by the polarizing reflective layer R2 of the second optical member 22 and then reflected by the reflective optical surface R1 of the first optical member 21 and converted into left-handed circularly polarized light c2, into horizontally polarized light q2, which is linearly polarized parallel to the X direction when passing it toward the second optical member 22.

[0021] The second optical member 22 is a parallel-plate-like member overall and has no overall power for transmitted light. In the second optical member 22, the third incident surface 33a on the wave plate 23 side and the fourth exit surface 34b on the wave plate 23 side are parallel to each other and extend parallel to the XY plane. The second optical member 22 has a third lens element 33 and a fourth lens element 34 bonded together with a polarizing reflective layer R2 sandwiched therebetween. The third lens element 33 has a flat third incident surface 33a and a continuously curved third exit surface 33b. The third exit surface 33b is specifically aspheric. The fourth lens element 34 has a continuously convexly curved fourth incident surface 34a and a flat fourth exit surface 34b. A wire grid or other reflective polarizer R21 is formed on the third exit surface 33b of the third lens element 33 as the polarizing reflective layer R2 by patterning using vapor deposition, etching, or the like. The polarizing reflective layer R2 is an aspheric surface having the same shape as the third exit surface 33b. The polarizing reflective layer R2 reflects the image light ML that has passed through the reflective optical surface R1 and been converted into vertically polarized light q1 via the wave plate 23, and selectively transmits the image light ML that has been returned from the wave plate 23 and the first optical member 21 and converted into horizontally polarized light q2. The second optical member 22 is like a cemented lens with a continuous polarizing reflective layer R2 embedded inside.

[0022] The third lens element 33 is formed by molding or other techniques from a plastic material or glass, and the fourth lens element 34 is also formed by molding or other techniques from a plastic material or glass. The third lens element 33 and the fourth lens element 34 have the same refractive index and are bonded to each other using, for example, an adhesive having the same refractive index as the third lens element 33. The third lens element 33 may be a plastic material that is filled and hardened between the fourth lens element 34 and the wave plate 23.

[0023] When the polarizing reflective layer R2 is a wire grid type polarizing element, the larger the curvature of the polarizing reflective layer R2, the larger the in-plane distribution of the extinction ratio, so it is desirable to set the radius of curvature to, for example, 40 mm or more.

[0024] With reference to FIG. 4, the polarization state of the image light ML and the like in the first virtual image display device 100A shown in FIG. 2 will be described. The image light ML from the first display 10a is right-handed circularly polarized light c1. It enters the first optical member 21, partially transmits through the reflective optical surface R1, and enters the wave plate 23, which is a quarter-wave plate, in the forward direction. The image light ML that passes through the wave plate 23 is converted into vertically polarized light q1, enters the second optical member 22, is mostly reflected by the polarizing reflective layer R2, and enters the wave plate 23 again. The image light ML that passes through the wave plate 23 in the reverse direction is converted into right-handed circularly polarized light c1, enters the first optical member 21, and is partially reflected by the reflective optical surface R1. The image light ML reflected by the reflective optical surface R1 is converted into left-handed circularly polarized light c2 and enters the wave plate 23, which is a quarter-wave plate, in the forward direction. The image light ML that has passed through the wave plate 23 is converted into horizontally polarized light q2, and is incident on the second optical member 22 and passes through the polarized reflective layer R2. The image light ML that has been emitted from the second optical member 22 is incident on a pupil position PP (see FIG. 2) where the eye EY or pupil of the wearer US is located.

[0025] The external light OL is randomly polarized light, and the external light OL that passes through the light-transmitting region A2 of the first display device 10a contains right-handed circularly polarized light c1 and left-handed circularly polarized light c2. The left-handed circularly polarized light c2 that emerges from the light-transmitting region A2 of the first display device 10a enters the first optical member 21, partially passes through the reflective optical surface R1, and enters the wave plate 23. The external light OL that passes through the wave plate 23 is converted into horizontally polarized light q2, enters the second optical member 22, and passes through the polarized reflective layer R2. In this way, certain components of the external light OL pass through the first display optical system 20a, which is composed of the optical members 21, 22, etc., but the first display optical system 20a does not produce a lens effect on the external light OL.

[0026] In the first virtual image display device 100A shown in FIG. 2, the thickness of the imaging optical system IS, i.e., the distance from the first entrance surface 31a of the first optical member 21 to the second exit surface 32b of the second optical member 22, is 7 mm or less. The FOV (Field of View) of the imaging optical system IS is set to approximately 100° diagonally. By setting the thickness of the imaging optical system IS to 7 mm or less, the virtual image display devices 100A, 100B or the optical unit 100 can be made lighter. In this imaging optical system IS, even though it is 7 mm or less thick, the divergence state of the image light ML is adjusted with high precision by reflection at the reflective optical surface R1 and the polarized reflective layer R2, thereby improving resolution and reducing color unevenness.

[0027] 3C is a diagram illustrating a modification of the first display device 10a shown in FIG. 2. In this case, in the first display device 10a, the display panel 11 has, in order from the outside, a polarizing element 11q, a light modulation element 11a, and a protective glass 11b. The polarizing element 11q restricts polarization in a direction different from that of the polarizing layer 13b of the polarizing member 13. Specifically, the polarizing element 11q is configured to restrict polarization to horizontally polarized light P2, which is polarized in a second polarization direction, and to block vertically polarized light P1, which is polarized in a first polarization direction perpendicular to the second polarization direction.

[0028] As shown in Figure 5, by adding a polarizing element 11q to the display panel 11, the external light OL passing through the first optical member 21 of the first display 10a can be limited to only left-handed circularly polarized light c2, thereby preventing unnecessary external light OL from entering the first display optical system 20a.

[0029] In the above description, the displays 10a and 10b emit the image light ML that is right-handed circularly polarized light c1, but the displays 10a and 10b may emit the image light ML that is left-handed circularly polarized light c2. In this case, the polarizing reflective layer R2 selectively reflects the horizontally polarized light q2.

[0030] 6 illustrates a case in which the first display 10a emits left-handed circularly polarized image light ML. In this case, the left-handed circularly polarized image light ML passes through the reflective optical surface R1 of the first optical member 21. The image light ML passes through the quarter-wave plate 23 in the forward direction, becoming horizontally polarized linearly polarized light q2. The image light ML then passes through the wave plate 23 in the reverse direction, becoming the original left-handed circularly polarized light c2, which is then partially reflected by the reflective optical surface R1. The image light ML reflected by the reflective optical surface R1 becomes right-handed circularly polarized light c1. The image light ML then passes through the wave plate 23 in the forward direction, becoming vertically polarized linearly polarized light q1 in the intersecting direction, which then passes through the polarizing reflective layer R2. Meanwhile, the right-handed circularly polarized light c1 of the external light OL enters the first optical member 21, partially passes through the reflective optical surface R1, and enters the wave plate 23. The external light OL that has passed through the wave plate 23 is converted into vertically polarized light q1, and is incident on the second optical member 22 and passes through the polarized light reflecting layer R2.

[0031] The display panel 11 is not limited to a self-luminous organic EL display, etc., but may also be a light modulation liquid crystal display. When the display panel 11 is a liquid crystal display, for example, a light guide plate may be disposed on the external side of the display panel 11, and illumination light may be supplied from the edge of the light guide plate.

[0032] The display panel 11 may be one that repeats display operations at high speed. In this case, the display panel 11 may be a transmissive device in the pixel region A1, for example, and allows external light OL to pass through during non-display periods between display operations, thereby enabling see-through viewing.

[0033] The virtual image display devices 100A, 100B or the optical unit 100 of the first embodiment described above include, in order from the outside world, displays 10a, 10b having a pixel region A1 that emits, for example, right-circularly polarized image light ML and partially transmits outside light OL, a first optical member 21 that is flat on the display 10a, 10b side and has a semi-transmissive reflective optical surface R1 therein that has power, a wavelength plate 23 that is a quarter-wave plate that converts the polarization state of the image light ML that has passed through the first optical member 21 into vertically polarized light q1 that is linearly polarized, and a second optical member 22 that includes a polarized reflective layer R2 that reflects the image light ML that has passed through the wavelength plate 23, and the imaging optical system IS that combines the displays 10a, 10b, the first optical member 21, the wavelength plate 23, and the second optical member 22 has substantially no power with respect to left-circularly polarized light c2, which is the polarization component of the outside light OL that has passed through the light-transmitting region A2 of the displays 10a, 10b.

[0034] In the virtual image display devices 100A, 100B, etc., the image light ML, for example, right-handed circularly polarized light c1, passes through the reflective optical surface R1 and passes through the quarter-wave plate 23, becoming linearly polarized, vertically polarized light q1, which is reflected by the polarizing reflective layer R2. It then passes through the wave plate 23 again to become the original right-handed circularly polarized light c1, which is then partially reflected by the reflective optical surface R1. The image light ML reflected by the reflective optical surface R1 becomes left-handed circularly polarized light c2, which passes through the wave plate 23 and becomes horizontally polarized light q2, linearly polarized in the intersecting direction, which then passes through the polarizing reflective layer R2. In other words, the divergence state of the image light ML is adjusted in two stages by reflection at the reflective optical surface R1 and the polarizing reflective layer R2, and the image formed on the display surface 11d of the display devices 10a, 10b can be viewed as a highly accurate virtual image. The external light OL contains randomly polarized components, passes through the displays 10a and 10b and the reflective optical surface R1, and becomes horizontally polarized light q2, which is linearly polarized light in an intersecting direction, when passing through the wave plate 23, and then passes through the polarized reflective layer R2. At this time, the external light OL passes through the imaging optical system IS without being subjected to the lens action of the first optical member 21, the wave plate 23, and the second optical member 22. In other words, it is possible to observe a virtual image via the imaging optical system IS while seeing an external image through the see-through view.

[0035] Second Embodiment The virtual image display device of the second embodiment will be described below. 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 parts common to the virtual image display device of the first embodiment will be omitted.

[0036] 7A is a side cross-sectional view illustrating a first display optical system 20a incorporated in a virtual image display device of the second embodiment, and FIG. 7B is a partially enlarged view of the center of the first display optical system 20a. The first display optical system 20a, i.e., the imaging optical system IS, includes a first optical member 21 having a reflective optical surface R1 with power therein, a wave plate 23 that converts the polarization state of the image light ML into linearly polarized light or circularly polarized light, and a second optical member 22 that includes a polarizing reflective layer R2.

[0037] First exit surface 231b provided on first lens element 31 of first optical member 21 and second entrance surface 232a provided on second lens element 32 are Fresnel-type optical surfaces, and are equivalent to first exit surface 31b and second entrance surface 32b of first optical member 21 of the first embodiment. Correspondingly, reflective optical surface R1 built into first optical member 21 is also a Fresnel optical surface S12 having the same shape as second entrance surface 32a, and has the same power as reflective optical surface R1 built into first optical member 21 of the first embodiment.

[0038] The first lens element 31 of the first optical member 21 is obtained by filling and flattening the second entrance surface 232a of the second lens element 32, on which the Fresnel optical surface S12 is formed, with an adhesive or base material having the same refractive index as the second lens element 32. Conversely, the second lens element 32 may be obtained by filling and flattening the first exit surface 231b of the first lens element 31, on which the Fresnel optical surface S12 is formed, with an adhesive or base material having the same refractive index as the first lens element 31.

[0039] In virtual image display devices 100A and 100B of the present embodiment, reflective optical surface R1 is a Fresnel optical surface S12, and first optical member 21 has a first lens element 31 and a second lens element 32 bonded together with reflective optical surface R1 sandwiched therebetween. In this case, first optical member 21 has a parallel plate shape as a whole with Fresnel optical surface S12 embedded therein. Use of Fresnel optical surface S12 allows the imaging optical system IS to be made thinner.

[0040] In this embodiment, the thickness of the imaging optical system IS, that is, the distance from the first entrance surface 31a of the first optical member 21 to the second exit surface 32b of the second optical member 22, is 7 mm or less, and more specifically, about 6.7 mm.

[0041] Third Embodiment The virtual image display device etc. of the third embodiment will be described below. The virtual image display device of the third embodiment is a partial modification of the virtual image display device of the first embodiment.

[0042] 8 is a side cross-sectional view illustrating a first display optical system 20a incorporated in a virtual image display device according to the third embodiment. The first display optical system 20a, i.e., the imaging optical system IS, includes a flat first optical member 21 having an internal reflective optical surface R1 with power, a wavelength plate 323 that converts the polarization state of the image light ML into a different circularly polarized light, and a flat second optical member 22 that includes a planar polarizing reflective layer R2.

[0043] The wave plate 323 is a half wave plate. The wave plate 323 is a parallel plate-like member as a whole, and has no power as a whole with respect to transmitted light.

[0044] In the second optical member 22, a cholesteric liquid crystal layer R22 is formed as a polarizing reflective layer R2 on the third exit surface 33b of the third lens element 33. The external surface of the polarizing reflective layer R2 is a flat surface having the same shape as the third exit surface 33b. The cholesteric liquid crystal layer R22 selectively reflects the image light ML, which has passed through the wave plate 323 and become left-handed circularly polarized light c2, while maintaining the image light ML in the state of left-handed circularly polarized light c2.

[0045] The cholesteric liquid crystal layer R22 has a layered structure of molecules oriented in a certain direction, with the molecular orientation axes twisted between adjacent layers, resulting in an overall helical orientation around the vertical axis of the layer. The cholesteric liquid crystal layer R22 is made of a specific liquid crystal material and has the property of transmitting right-handed circularly polarized light c1 and reflecting left-handed circularly polarized light c2. The cholesteric liquid crystal layer R22 is formed by sandwiching a liquid crystal material containing a liquid crystal material and additives between the third lens element 33 and the fourth lens element 34. With the third lens element 33 and the fourth lens element 34 relatively fixed, the liquid crystal material sandwiched between them is irradiated with UV light or the like, or by removing or evaporating the solvent from the liquid crystal material, or by heating the liquid crystal material sandwiched between them, thereby reducing its fluidity and creating a stable liquid crystal material layer. In other words, the cholesteric liquid crystal layer R22 is formed by stabilizing the liquid crystal material. The cholesteric liquid crystal layer R22 may be solidified on one surface of the third lens element 33 and the fourth lens element 34, for example, and the other of the third lens element 33 and the fourth lens element 34 may be attached and sandwiched therebetween. The cholesteric liquid crystal layer R22 may be fabricated using the methods described in JP-A-2008-501147 and JP-A-2021-532393. By rotating the orientation of the liquid crystal about the optical axis during fabrication, the cholesteric liquid crystal layer R22 can reflect only one type of circularly polarized light and can apply power during reflection. In other words, even if the cholesteric liquid crystal layer R22 itself is flat, it can have a lens effect on the image light ML reflected by it.

[0046] 9, in the virtual image display devices 100A, 100B, etc., the image light ML, for example, right-handed circularly polarized light c1, passes through the reflecting optical surface R1 and passes through the half-wave plate 323, becoming left-handed circularly polarized light c2, which is circularly polarized light, and is reflected by the polarizing reflective layer R2. The image light ML, reflected by the reflecting optical surface R1, becomes the reverse-rotation left-handed circularly polarized light c2, passes through the wave plate 323, becoming the original right-handed circularly polarized light c1, and passes through the polarizing reflective layer R2. In other words, the divergence state of the image light ML is adjusted in two stages by reflection at the reflecting optical surface R1 and the polarizing reflective layer R2, and the image formed on the display surface 11d of the display device 10a, 10b can be viewed as a highly accurate virtual image. The external light OL contains randomly polarized components, and passes through the displays 10a and 10b and the reflective optical surface R1. When passing through the wave plate 323, the left-handed circularly polarized light c2 becomes right-handed circularly polarized light c1, and passes through the polarized reflective layer R2. At this time, the external light passes through the imaging optical system IS without being subjected to the lens action of the first optical member 21, the wave plate 323, and the second optical member 22. In other words, see-through viewing of the external world image becomes possible via the imaging optical system IS.

[0047] Although detailed description will be omitted, similar to the modification of the first embodiment shown in Fig. 3C, a polarizing element 11q can be added to the display panel 11. This allows only left-handed circularly polarized light c2 to enter the first display optical system 20a, i.e., the imaging optical system IS.

[0048] Alternatively, the first display 10a may emit the image light ML of left-handed circularly polarized light c2. In this case, the polarizing reflective layer R2 is a cholesteric liquid crystal layer R22 that transmits the left-handed circularly polarized light c2 and reflects the right-handed circularly polarized light c1.

[0049] 10 is a diagram illustrating a modified example of the first display optical system 20a shown in FIG. 1. In this case, the polarizing reflective layer R2 is not flat but has a curved surface such as an aspherical surface, and the cholesteric liquid crystal layer R22 is provided along this curved surface. Note that the polarizing reflective layer R2 is not limited to the curved surface shown in the example, and various curved surfaces can be used taking aberration correction and power into consideration.

[0050] [Fourth embodiment] The virtual image display device etc. of the fourth embodiment will be described below. The virtual image display device of the fourth embodiment is a partial modification of the virtual image display device of the third embodiment.

[0051] 11 is a side cross-sectional view illustrating a first display optical system 20a incorporated in a virtual image display device of the fourth embodiment. Similar to the third embodiment, the first display optical system 20a, i.e., the imaging optical system IS, includes a first optical member 21 having a reflective optical surface R1 with power therein, a wave plate 323 that converts the polarization state of the image light ML into a different circularly polarized light, and a second optical member 22 that includes a polarizing reflective layer R2.

[0052] First exit surface 231b provided on first lens element 31 of first optical member 21 and second entrance surface 232a provided on first lens element 32 are Fresnel type optical surfaces and are equivalent to first exit surface 31b and second entrance surface 32a of first optical member 21 of the third embodiment. Correspondingly, reflective optical surface R1 built into first optical member 21 is also a Fresnel optical surface S12 having the same shape as second entrance surface 32b, and has the same power as reflective optical surface R1 built into first optical member 21 of the third embodiment.

[0053] In virtual image display devices 100A and 100B of the present embodiment, reflective optical surface R1 is a Fresnel optical surface S12, and first optical member 21 has a first lens element 31 and a second lens element 32 that are bonded together with reflective optical surface R1 in between. In this case, first optical member 21 has a parallel plate shape as a whole, with Fresnel optical surface S12 embedded inside.

[0054] The first lens element 31 of the first optical member 21 is, for example, flattened by filling the second entrance surface 232a of the second lens element 32, on which the Fresnel optical surface S12 is formed, with an adhesive or base material having the same refractive index as the second lens element 32.

[0055] In this embodiment, the thickness of the imaging optical system IS, that is, the distance from the first entrance surface 31a of the first optical member 21 to the second exit surface 32b of the second optical member 22, is 7 mm or less, and specifically, is about 6.3 mm.

[0056] [Variations and Others] The present invention has been described above in accordance with the embodiments, but the present invention is not limited to the above embodiments and can be implemented in various forms without departing from the spirit of the invention, and for example, the following modifications are also possible.

[0057] In the above description, it is assumed that the HMD 200 is used by being worn on the head, but the virtual image display devices 100A and 100B can also be used as handheld displays that are not worn on the head but are peered into like binoculars. In other words, in the present invention, the head-mounted display also includes a handheld display.

[0058] In the above-described embodiment, the layout and size of the pixel region A1 in the displays 10a and 10b can be changed as appropriate within the range in which a sufficient light-transmitting region A2 exists.

[0059] In a specific embodiment, the virtual image display device or optical unit includes, in order from the outside world, a display having a pixel region that emits circularly polarized image light and that partially transmits outside light; a first optical element that is flat on the display side and has a semi-transmissive reflective optical surface with power inside; a wavelength plate that converts the polarization state of the image light that has passed through the first optical element into linearly polarized light or circularly polarized light; and a second optical element that includes a polarized reflective layer that reflects the image light that has passed through the wavelength plate, and the imaging optical system that combines the display, the first optical element, the wavelength plate, and the second optical element has substantially no power with respect to the polarized component of the outside light that has passed through the light-transmitting region of the display.

[0060] In the virtual image display device, circularly polarized image light passing through a reflective optical surface passes through, for example, a quarter-wave plate, becomes linearly polarized, is reflected by the polarizing reflective layer, passes through the wavelength plate again, and is returned to its original circularly polarized state and partially reflected by the reflective optical surface. The image light reflected by the reflective optical surface becomes reverse-circularly polarized light, passes through the quarter-wave plate, becomes linearly polarized in the intersecting direction, and passes through the polarizing reflective layer. In other words, the divergence state of the image light is adjusted in two stages by reflection at the reflective optical surface and the polarizing reflective layer, allowing the image formed on the display surface of the display device to be observed as a highly accurate virtual image. Furthermore, circularly polarized image light passing through a reflective optical surface passes through, for example, a half-wave plate, becomes reverse-circularly polarized light, is reflected by the polarizing reflective layer, passes through the wavelength plate again, and is returned to its original circularly polarized state and is partially reflected by the reflective optical surface. The image light reflected by the reflective optical surface becomes reverse-circularly polarized light, passes through the half-wave plate, and is returned to its original circularly polarized state and passes through the polarizing reflective layer. In other words, the divergence state of the image light is adjusted in two stages by reflection at the reflective optical surface and the polarized reflective layer, allowing the image formed on the display surface of the display to be observed as a highly accurate virtual image. Note that external light contains random polarization components, and when it passes through the display and the reflective optical surface and passes through the wave plate, it becomes linearly polarized light in a cross direction or circularly polarized light in a reverse direction, and then passes through the polarized reflective layer. At this time, the external light passes through the imaging optical system without being substantially subjected to the lens action of the first optical member, the wave plate, and the second optical member. In other words, see-through viewing of the external image is possible via the imaging optical system.

[0061] In a specific embodiment of the virtual image display device, the thickness of the imaging optical system from the first optical member to the second optical member is 7 mm or less. By making the thickness of the imaging optical system 7 mm or less, the virtual image display device or optical unit can be made lighter. In this case, the divergence state is adjusted with high precision by reflection at the reflective optical surface and the polarized reflective layer, thereby improving resolution and reducing color unevenness.

[0062] In a specific embodiment of the virtual image display device, the reflective optical surface is a continuous curved surface, and the first optical member has a first lens element and a second lens element cemented together with the reflective optical surface sandwiched therebetween. In this case, the first optical member is like a cemented lens that is shaped like a parallel plate overall and has the continuous reflective optical surface embedded therein.

[0063] In a specific embodiment of the virtual image display device, the reflective optical surface is a Fresnel optical surface, and the first optical member has a first lens element and a second lens element bonded together with the reflective optical surface sandwiched therebetween. In this case, the first optical member is shaped like a parallel plate overall, with the Fresnel optical surface embedded therein.

[0064] In a specific embodiment of the virtual image display device, the polarizing reflective layer has a continuous curved surface, and the first optical member has a third lens element and a fourth lens element bonded together with the polarizing reflective layer sandwiched therebetween. In this case, the second optical member has a parallel plate shape as a whole and is like a cemented lens with the continuous polarizing reflective layer embedded inside.

[0065] In a specific embodiment of the virtual image display device, the wavelength plate is a quarter-wave plate, and the polarizing reflective layer is a reflective polarizer. That is, circularly polarized image light that passes through the reflective optical surface becomes linearly polarized light by passing through the quarter-wave plate, is reflected by the polarizing reflective layer, and then passes through the wavelength plate again to return to its original circularly polarized state, which is then partially reflected by the reflective optical surface. The image light reflected by the reflective optical surface becomes circularly polarized light in the opposite direction, and passes through the quarter-wave plate to become linearly polarized light in the intersecting direction, which then passes through the polarizing reflective layer.

[0066] In a specific embodiment of the virtual image display device, the wavelength plate is a half-wave plate, and the polarizing reflective layer is a cholesteric liquid crystal layer. That is, circularly polarized image light that passes through the reflective optical surface passes through the half-wave plate, becomes reverse-circularly polarized light, is reflected by the polarizing reflective layer, passes through the wavelength plate again, and returns to its original circularly polarized state, which is then partially reflected by the reflective optical surface. The image light reflected by the reflective optical surface becomes reverse-circularly polarized light, passes through the half-wave plate, and returns to its original circularly polarized state, passing through the polarizing reflective layer.

[0067] In a specific embodiment of the virtual image display device, the cholesteric liquid crystal layer is formed on a plane.

[0068] In a specific embodiment of the virtual image display device, the cholesteric liquid crystal layer is formed by stabilizing a liquid crystal material.

[0069] In a specific embodiment of the virtual image display device, the display has pixel regions that block the transmission of external light and light-transmitting regions that are optically transparent to the external light, respectively. The external light passes through the light-transmitting regions without being affected by the pixel regions, enters the imaging optical system, and also passes through the imaging optical system. [Explanation of symbols]

[0070] 10a, 10b... display, 11... display panel, 11a... light modulation element, 11b... protective glass, 11b... polarizing plate, 11d... display surface, 11q... polarizing element, 13... polarizing member, 13a... 1 / 4 wavelength plate, 13b... polarizing layer, 21, 22... optical member, 23... wavelength plate (1 / 4 wavelength plate), 323... wavelength plate (1 / 2 wavelength plate), 90... user terminal, 100... optical unit, 100A, 100B... virtual image display device, 100C... support device, 102a, 102b... display drive unit, 103a, 103b... combiner, A1... pixel region, A2... light transmission region, AX... optical axis, EY... eye, IS... imaging optical system, ML... image light, OL... external light, P1... vertically polarized light, P2... horizontally polarized light, PP... pupil position, PX... pixel, Pr, Pg, Pb... sub-pixel, R1... reflective optical surface, R2... polarized reflective layer, R21... polarizer, R22... cholesteric liquid crystal layer, S1... optical surface, S12... Fresnel optical surface, US... wearer, c1... right-handed circularly polarized light, c2... left-handed circularly polarized light, q1... vertically polarized light, q2... horizontally polarized light

Claims

1. In order from the outside world, a display having a pixel region that emits circularly polarized image light and that partially transmits external light; a first optical member having a flat surface on the display device side and a semi-transmissive reflective optical surface having power therein; a wave plate that converts the polarization state of the image light that has passed through the first optical member into linearly polarized light or circularly polarized light; a second optical member including a polarizing reflective layer that reflects the image light that has passed through the wave plate; Equipped with an imaging optical system that combines the display, the first optical member, the wave plate, and the second optical member has substantially no power with respect to the polarized component of external light that has passed through the light transmission region of the display; Virtual image display device.

2. a thickness of the imaging optical system from the first optical member to the second optical member is 7 mm or less; The virtual image display device according to claim 1 .

3. the reflective optical surface is a continuously curved surface; the first optical member has a first lens element and a second lens element cemented together with the reflecting optical surface interposed therebetween; The virtual image display device according to claim 1 .

4. the reflective optical surface is a Fresnel optical surface, the first optical member has a first lens element and a second lens element cemented together with the reflecting optical surface interposed therebetween; The virtual image display device according to claim 1 .

5. the polarizing reflective layer is a continuous curved surface, the first optical member has a third lens element and a fourth lens element bonded together with the polarizing reflective layer interposed therebetween; The virtual image display device according to claim 1 .

6. the wave plate is a quarter wave plate, The polarizing reflective layer is a reflective polarizer. The virtual image display device according to claim 1 .

7. the wave plate is a half wave plate, the polarized reflective layer is a cholesteric liquid crystal layer; The virtual image display device according to claim 1 .

8. The cholesteric liquid crystal layer is formed on a plane. The virtual image display device according to claim 7 .

9. The cholesteric liquid crystal layer is formed by stabilizing a liquid crystal material. The virtual image display device according to claim 7 .

10. the display device has the pixel region that blocks transmission of the external light and the light-transmitting region that is optically transparent to the external light, The virtual image display device according to claim 1 .

11. In order from the outside world, a display having a pixel region that emits circularly polarized image light and that partially transmits external light; a first optical member having a flat surface on the display device side and a semi-transmissive reflective optical surface having power therein; a wave plate that converts the polarization state of the image light that has passed through the first optical member into linearly polarized light or circularly polarized light; a second optical member including a polarizing reflective layer that reflects the image light that has passed through the wave plate; Equipped with an imaging optical system that combines the display, the first optical member, the wave plate, and the second optical member has substantially no power with respect to the polarized component of external light that has passed through the light transmission region of the display; Optical unit.

Images