Virtual image display device and optical unit

Abstract

To make an optical element in front of an eye thin.SOLUTION: A virtual image display device 100A and an optical unit 100 comprises: a display 11; a transmissive mirror 23 that deflects image light ML, which is linearly polarized light in a first polarization direction P1 from the display 11, by reflection; and a reflective optical element 25 that acts like a mirror having positive power when reversing the image light ML reflected by the transmissive mirror 23. The reflective optical element 25 includes, in order from the transmissive mirror 23, a first type first lens function member 31 that includes a first polarizing diffraction lens 31b and reverses positive and negative of power by switching the polarization direction with respect to the linearly polarized light to maintain the polarization direction; a first optical element 32 that reflects the linearly polarized light in the first polarization direction P1 while maintaining the polarization direction; a second type second lens function member 33 that includes a second polarizing diffraction lens 33b and reverses the positive and negative of the power by switching the polarization direction with respect to the linearly polarized light to rotate the polarization direction; and a second optical element 34 that selectively transmits the linearly polarized light in the first polarization direction P1.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 head-mounted display device has an image display device that displays an observation image, a partially transmissive reflective surface that partially transmits and partially reflects light from the image display device, and a concave mirror that reflects the light reflected by the partially transmissive reflective surface so that it is directed toward the observer's eyeball, in which the partially transmissive reflective surface is formed by a polarizing beam splitter, and a quarter-wave plate is provided between the polarizing beam splitter and the concave mirror. In this display device, all linearly polarized light components in a predetermined direction from the image display device reach the observer's eye without attenuation, allowing the observer to observe a bright electronic image, i.e., a displayed image, from the image display device (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 06-059217 Summary of the Invention [Problem to be solved by the invention]

[0004] It is desirable for head-mounted display devices to have an appearance similar to that of eyeglasses, but the optical system in Patent Document 1 does not achieve an appearance similar to that of eyeglasses. Specifically, the apex of the concave mirror is positioned approximately 30 mm from the pupil, which is a large deviation from eyeglasses, which are positioned approximately 15 mm from the pupil. [Means for solving the problem]

[0005] A virtual image display device and optical unit according to one aspect of the present invention comprises a display, a transmission mirror that deflects image light, which is linearly polarized in a first polarization direction from the display, by reflection, and a reflective optical element that acts like a mirror with positive power when reversing the image light reflected by the transmission mirror. The reflective optical element comprises, in order from the transmission mirror, a first lens function component that includes a first polarizing diffractive lens and that reverses the positive and negative power by switching the polarization direction, thereby maintaining the polarization direction; a first optical element that reflects linearly polarized light in the first polarization direction while maintaining the polarization direction; a second lens function component that includes a second polarizing diffractive lens and that reverses the positive and negative power by switching the polarization direction, thereby rotating the polarization direction; and a second optical element that selectively transmits linearly polarized light in the first polarization direction. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 2 is a front view of the appearance illustrating the wearing state of the virtual image display device of the first embodiment. [Figure 2] FIG. 2 is a cross-sectional view illustrating the structure of the virtual image display device. [Figure 3] FIG. 2 is a conceptual diagram illustrating the state of light rays in an imaging system. [Figure 4] FIG. 1 is a conceptual perspective view illustrating the function of a polarized diffractive lens. [Figure 5] 4 is a diagram illustrating a modified example of the virtual image display device shown in FIG. 3. FIG. [Figure 6] 4 is a diagram illustrating another modified example of the virtual image display device shown in FIG. 3. FIG. [Figure 7] 4 is a diagram illustrating yet another modified example of the virtual image display device shown in FIG. [Figure 8] FIG. 10 is a side cross-sectional view illustrating a virtual image display device according to a second embodiment. [Figure 9] FIG. 10 is a conceptual diagram illustrating a virtual image display device according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

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

[0008] FIG. 1 is a front view illustrating a state in which a head-mounted display, i.e., a head-mounted display device 200, is worn. The head-mounted display device (hereinafter also referred to as HMD) 200 allows an observer or wearer US wearing it 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 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 right eye, a second virtual image display device 100B for the left eye, a pair of temples 100C supporting the virtual image display devices 100A and 100B, and a user terminal 90 serving as an information terminal. The first virtual image display device 100A includes a first display driver 102a disposed at the top and a first display optical system 103a covering the user's eyes. The second virtual image display device 100B includes a second display driver 102b disposed at the top and a second display optical system 103b covering the user's eyes. The HMD 200, which combines the first virtual image display device 100A and the second virtual image display device 100B, is also a virtual image display device in a broad sense. The pair of temples 100C are mounting members or support devices 106 worn on the head of the wearer US, and support the upper ends of the pair of display optical systems 103a and 103b via display drivers 102a and 102b, which are integrated in appearance. The pair of display drivers 102a and 102b is called a driver 102.

[0010] 2 is a side view illustrating the structure of the imaging system and other components incorporated in the first display driver 102a and the first display optical system 103a. The first display driver 102a includes a display 11, a polarizing filter 12, a lens 14, and a display control device 88. The first display optical system 103a includes a transmission mirror 23 that deflects the image light ML from the display 11 by reflection, and a reflective optical element 25 that acts like a mirror with positive power when reversing the image light ML reflected by the transmission mirror 23. Of these, the combination of the lens 14, the transmission mirror 23, and the reflective optical element 25 is referred to as the imaging optical system 20.

[0011] The display 11 is a self-luminous image light generating device that generates moving or still images on the display surface 11d. The display 11 is, for example, an organic electroluminescence (EL) display that generates monochrome still or moving images, such as green, on the two-dimensional display surface 11d. The display 11 is driven by the display control device 88 to perform display operations. The display 11 is not limited to an EL display, but can be replaced with a display device using an inorganic EL, organic LED, LED array, laser array, quantum dot light-emitting element, or the like. The display 11 is not limited to a self-luminous image light generating device, but may also be configured with an LCD or other light modulation element that forms an image by illuminating the light modulation element with a light source such as a backlight. Instead of an LCD, the display 11 can also use LCOS (Liquid Crystal on Silicon, LCoS is a registered trademark), a digital micromirror device, or the like.

[0012] The polarizing filter 12 polarizes the image light ML emitted from the display 11 in a specific direction. Specifically, the image light ML passes through the polarizing filter 12 and becomes linearly polarized light whose polarization direction is parallel to the Z direction. The image light ML that has passed through the polarizing filter 12 is bent by a transmissive mirror 23 (described later) from the downward -Y direction to the forward +Z direction, and becomes linearly polarized light whose polarization direction is parallel to the Y direction in a first polarization direction.

[0013] The lens 14 is disposed opposite the display surface 11d of the display 11. The lens 14 has positive power. The lens 14 is not limited to being composed of a single lens, but may be composed of multiple lenses. The optical surface 14a on the incident side of the lens 14 is flat, but may also be spherical or aspherical. The optical surface 14b on the exit side of the lens 14 is a convex spherical or aspherical surface.

[0014] The transmission mirror 23 is a flat plate-shaped member facing the lens 14, and is disposed at an angle of 45° with respect to the optical axis AX extending from the display surface 11d of the display 11. More specifically, the normal to the transmission mirror 23 is parallel to the YZ plane extending vertically, and is at an angle of 45° with respect to both the Y and Z directions. The transmission mirror 23 deflects the image light from the display 11 by reflection. The transmission mirror 23 is formed by attaching a transmissive reflective film 23a to one side of a flat substrate, and the transmissive reflective film 23a is formed of a dielectric multilayer film or a metal thin film or multilayer film such as Al. The transmission mirror 23 reflects the image light ML from the display 11 with a reflectance of, for example, about 50%. The transmission mirror 23 also receives external light OL that has entered the reflecting optical element 25 from the outside and passed through the reflecting optical element 25, and transmits the external light OL with a reflectance of, for example, about 50%.

[0015] The reflective optical element 25 is a flat plate-shaped member facing the transmission mirror 23. The reflective optical element 25 has, in order from the transmission mirror 23, a first lens function member 31, a first optical element 32, a second lens function member 33, and a second optical element 34. The reflective optical element 25 is disposed perpendicular to the optical axis AX that intersects with the transmission mirror 23. More specifically, the reflective optical element 25 is disposed so that its normal is parallel to the Z axis extending in the front-to-rear direction. The reflective optical element 25 reverses the image light ML that has been reflected by the transmission mirror 23 and is incident thereon, and acts like a mirror with positive power when reversely propagating the image light ML.

[0016] The second virtual image display device 100B for the left eye is optically identical to the first virtual image display device 100A for the right eye, or is a left-right inverted version of the first virtual image display device 100A, and a detailed description thereof will be omitted.

[0017] In the first virtual image display device 100A, the optical device excluding the display control device 88 is called the optical unit 100. In the second virtual image display device 100B, the optical device excluding the display control device 88 is called the optical unit 100.

[0018] Referring to FIG. 3 , the image light ML reflected by the transmissive mirror 23 enters the first lens function element 31 of the reflective optical element 25 as linearly polarized light in a first polarization direction P1 parallel to the Y direction. The innermost first lens function element 31 is a first-type optical element, including a first polarizing diffractive lens 31b, which reverses the polarity of the power by switching the polarization direction between the first polarization direction P1 and the second polarization direction P2, thereby maintaining the polarization direction. The first optical element 32 reflects the image light ML, which is linearly polarized in the first polarization direction P1 after passing through the first lens function element 31, while maintaining the polarization direction. The first optical element 32 is a reflective polarizing element RP that reflects only the linearly polarized light of interest. The outermost second optical element 34 selectively transmits, from the external light OL, linearly polarized light in the first polarization direction P1, the same as the image light ML entering the reflective optical element 25. The second optical element 34 is an absorptive polarizing element AP that transmits only the linearly polarized light of interest. The external light OL that has passed through the second optical element 34 is incident as linearly polarized light in a first polarization direction P1 on the second lens function member 33 disposed inside the second optical element 34. The second lens function member 33 is a second type of optical member, and includes a second polarizing diffractive lens 33b, which inverts the positive and negative polarities of the power and rotates the polarization direction by switching the polarization direction between the first polarization direction P1 and the second polarization direction P2.

[0019] In the following, for the image light ML passing through the first lens function component 31, the left and right rotation of circularly polarized light is considered from the viewpoint of the rear transmission mirror 23 for the first optical path O1 passing through the first lens function component 31 in the forward direction. Also, the left and right rotation of circularly polarized light is considered from the viewpoint of the outside world side or the second lens function component 33 for the second optical path O2 passing through the first lens function component 31 in the reverse direction. On the other hand, the left and right rotation of circularly polarized light is considered from the viewpoint of the outside world side for the third optical path O3 of outside world light OL passing through the second lens function component 33 or the first lens function component 31 in the reverse direction.

[0020] In the reflecting optical element 25, the first lens function member 31 has, in order from the transmission mirror 23, a first quarter-wave plate 31a, a first polarizing diffraction lens 31b, and a second quarter-wave plate 31c whose fast axis is set in the same direction as the first quarter-wave plate 31a. In addition, in the reflecting optical element 25, the second lens function member 33 has, in order from the transmission mirror 23, a third quarter-wave plate 33a, a second polarizing diffraction lens 33b, and a fourth quarter-wave plate 33c whose fast axis is set in a direction intersecting the third quarter-wave plate 33a.

[0021] The quarter-wave plates 31a and 31c are made of organic or inorganic materials. Specifically, the quarter-wave plates 31a and 31c are made of, for example, a liquid crystal material. The wave plates are fabricated, for example, by applying a photo-crosslinkable polymer liquid crystal material to a flexible transparent resin substrate to form a thin film. The orientation state can be controlled by irradiating this thin film with light whose polarization direction is controlled. This fixes the orientation state in the same direction as the polarization direction. By adjusting the thickness, such a wavelength layer can function as a wave plate for adjusting retardation. Like the quarter-wave plates 31a and 31c, the quarter-wave plates 33a and 33c are also made of organic or inorganic materials, for example, a liquid crystal material.

[0022] Fig. 4 is a diagram illustrating the functions of the first polarized diffractive lens 31b and the second polarized diffractive lens 33b. In Fig. 4, the first region AR1 shows a first operational example of the first-type polarized diffractive lens GP1, and the second region AR2 shows a second operational example of the first-type polarized diffractive lens GP1. In Fig. 4, the third region AR3 shows a first operational example of the second-type polarized diffractive lens GP2, and the fourth region AR4 shows a second operational example of the second-type polarized diffractive lens GP2. The first polarized diffractive lens 31b and the second polarized diffractive lens 33b shown in Fig. 3 are the first-type polarized diffractive lens GP1.

[0023] When collimated right-handed circularly polarized light RCP, such as light ray L1 shown by the solid line, is incident on the polarized diffractive lens GP1 from the left side of the drawing, it converts the right-handed circularly polarized light RCP into left-handed circularly polarized light LCP and converges it to focus or converge at the focal point FP. When collimated left-handed circularly polarized light LCP, such as light ray L1 shown by the solid line, is incident on the polarized diffractive lens GP1, it converts the left-handed circularly polarized light LCP into right-handed circularly polarized light RCP and diverges it. When right-handed circularly polarized light RCP, such as light ray L2 shown by the dashed-dot line, diverging from the focal point FP' on the left side of the drawing, is incident on the polarized diffractive lens GP1, it converts the right-handed circularly polarized light RCP into left-handed circularly polarized light LCP and collimates it. In other words, the polarized diffractive lens GP1 functions like a positive lens with a predetermined focal length for right-handed circularly polarized light RCP, reversing the direction of polarization rotation. The polarized diffractive lens GP1 also functions like a negative lens with the same absolute focal length for left-handed circularly polarized light LCP, reversing the direction of polarization rotation. In other words, the polarized diffractive lens GP1 is an optical element that has a positive power for right-handed circularly polarized light RCP and a negative power for left-handed circularly polarized light LCP.

[0024] When collimated right-handed circularly polarized light RCP, such as light ray L1 shown by a solid line, enters the polarized diffractive lens GP2 from the left side of the drawing, it converts the right-handed circularly polarized light RCP into left-handed circularly polarized light LCP and diverges it. When collimated left-handed circularly polarized light LCP, such as light ray L1 shown by a solid line, enters the polarized diffractive lens GP2 from the left side of the drawing, it converts the left-handed circularly polarized light LCP into right-handed circularly polarized light RCP and converges the light to focus or condense it at a focal point FP. In other words, the polarized diffractive lens GP2 functions like a positive lens with a predetermined focal length for left-handed circularly polarized light LCP, reversing the direction of polarization rotation. Furthermore, the polarized diffractive lens GP2 functions like a negative lens with the same absolute focal length for right-handed circularly polarized light RCP, reversing the direction of polarization rotation. In other words, the polarized diffractive lens GP2 is an optical element that has negative power for right-handed circularly polarized light RCP and positive power for left-handed circularly polarized light LCP.

[0025] The polarized diffractive lenses GP1 and GP2 have a refractive index anisotropy distribution, which is grasped in a plane by a number of annular zones centered on the optical axis AX, and function as a diffractive lens according to the refractive index anisotropy distribution and the polarization state of the incident light. Specifically, when the polarized diffractive lenses GP1 and GP2 have a refractive index anisotropy distribution in which the orientation of the optical axis rotates (actually repeating in the range of 0 to π) with increasing distance from the optical axis AX in two directions that are perpendicular to the central optical axis AX and perpendicular to each other, a geometric phase is formed in the specific circularly polarized light incident thereon, and the circularly polarized light is diffracted at a diffraction angle that reflects the periodic length of the rotation of the optical axis in each direction, and the polarization state is reversed. As a whole, the polarized diffractive lens causes diffraction corresponding to the power formed by the lens shape for specific circularly polarized light, and reverses the state of circular polarization before and after passing through, for example, from right-handed circularly polarized light to left-handed circularly polarized light.

[0026] Although not shown, the polarized diffractive lenses GP1 and GP2 are each formed by forming a thin liquid crystal-containing material layer on a transparent substrate, and are generally thin and plate-like. The liquid crystal-containing material layer contains a predetermined liquid crystal material. The orientation axes of the liquid crystal molecules are aligned parallel to, for example, the X direction in the region near the optical axis AX to form a desired geometric phase. Furthermore, the orientation axes of the liquid crystal molecules gradually rotate within the XY plane as they move away from the optical axis AX, i.e., depending on the distance or radius from the optical axis AX. In other words, the rotation angle of the orientation axes of the liquid crystal molecules increases with the distance from the optical axis AX, and this cycle is repeated periodically. In the liquid crystal compound layer, the orientation axes of the liquid crystal molecules are aligned, for example, with a constant orientation in the Z direction parallel to the optical axis AX. Note that the direction of increasing the rotation angle of the orientation axes of the liquid crystal molecules is reversed between the polarized diffractive lenses GP1 and GP2. The polarized diffractive lenses GP1 and GP2 are manufactured, for example, by coating a substrate with a liquid crystal-containing material film, which is a mixture of a liquid crystal material and a UV-curable organic material layer, and then two-dimensionally scanning the liquid crystal-containing material film with UV laser light of a specific polarization state to adjust the alignment axis of the liquid crystal molecules and cure the organic material layer. This allows the alignment axis of the liquid crystal molecules in the liquid crystal-containing material layer to be controlled and fixed three-dimensionally, resulting in a liquid crystal compound layer in which the rotation angle of the alignment axis increases with distance from the optical axis AX as described above. Such a polarized diffractive lens GP1 itself is a known technology, such as a polarization-dependent liquid crystal Fresnel lens (see, for example, Kohei Noda, et al., Applied Optics, February 10, 2017, Vol. 56, No. 5: 1302).

[0027] The polarized diffraction lens GP1 and the polarized diffraction lens GP2 do not need to be separate entities; simply rotating the polarized diffraction lens GP1 180° around the Y axis and flipping it over will result in the polarized diffraction lens GP2. In other words, by swapping the polarized diffraction lenses GP1 and GP2, they can function as both positive and negative lenses for the same circularly polarized light. This is because, in the polarized diffraction lenses GP1 and GP2, the alignment axes of the liquid crystal molecules are increased so that they rotate in a specific direction depending on the distance from the optical axis AX, as described above. Therefore, the rotation directions relative to the absolute values ​​of the distances in the ±X directions perpendicular to the optical axis AX, for example, are the same. When each of the polarized diffraction lenses GP1 and GP2 is viewed from the back, the rotation directions of the alignment axes are reversed.

[0028] The focal lengths of the polarized diffractive lenses GP1 and GP2 can be increased or decreased depending on the manufacturing method and liquid crystal material. In the liquid crystal compound layer, for example, when increasing the rotation angle of the alignment axis of the liquid crystal molecules with increasing distance from the optical axis AX, the absolute value of the positive or negative power of the polarized diffractive lenses GP1 and GP2 can be increased by increasing the rate of increase in the rotation angle relative to the distance or radius from the optical axis AX, i.e., by reducing the rotation period of the alignment axis. When passing through the polarized diffractive lenses GP1 and GP2, the loss of circularly polarized light L1 is close to zero, and the polarized diffractive lenses GP1 and GP2 exhibit almost 100% transmittance.

[0029] When linearly polarized light is incident on the polarized diffractive lens GP1, the right-handed circularly polarized light (RCP) and the left-handed circularly polarized light (LCP) behave differently. The right-handed circularly polarized light (RCP) component is converged by the polarized diffractive lens GP1, while the left-handed circularly polarized light (LCP) component is diverged by the polarized diffractive lens GP1, and the rotation direction of each polarization is reversed.

[0030] Returning to FIG. 3 , in the reflective optical element 25, the image light ML incident on the first lens function component 31 via the transmissive mirror 23 is linearly polarized light in a first polarization direction P1. The polarization state of this image light ML is changed by the first quarter-wave plate 31a, which is positioned with its fast axis FX tilted 45° counterclockwise, and the image light ML is incident on the first polarizing diffractive lens 31b, which corresponds to the polarizing diffractive lens GP1 shown in FIG. 4, as first circularly polarized light C1 that generates positive power from the forward direction. The image light ML incident on the first polarizing diffractive lens 31b is relatively converged and inverted to become second circularly polarized light C2, which is returned to the first polarization direction P1 by the second quarter-wave plate 31c, which is positioned with its fast axis FX tilted 45° counterclockwise, and then emerges from the first lens function component 31. The image light ML emerging from the first lens function component 31 is linearly polarized light in the first polarization direction P1 and is reflected by the first optical element 32. To explain the polarization state more specifically, when viewed from the -Z side, the first polarized diffractive lens 31b has positive power with respect to the first circularly polarized light C1, i.e., right-handed circularly polarized light RCP, incident from the display 11 side, and converts the transmitted light into the second circularly polarized light C2, i.e., left-handed circularly polarized light LCP.

[0031] The linearly polarized image light ML in the first polarization direction P1 reflected by the first optical element 32 is incident on the first polarizing diffraction lens 31b by the second quarter-wave plate 31c as second circularly polarized light C2, which generates positive power in the reverse direction. The image light ML incident on the first polarizing diffraction lens 31b is relatively further converged and converted into inverted first circularly polarized light C1, and is then emitted from the first lens function member 31 as P1 linearly polarized light in the first polarization direction by the first quarter-wave plate 31a. It passes through the transmission mirror 23 and is incident on the pupil position PP. To explain the polarization state more specifically, from the perspective from the +Z side, the first polarizing diffraction lens 31b has positive power with respect to the second circularly polarized light C2, i.e., left-handed circularly polarized light LCP, which is reflected by the first optical element 32 and incident from the outside, and converts the transmitted light into the first circularly polarized light C1, i.e., right-handed circularly polarized light RCP.

[0032] As described above, the image light ML that has traveled back and forth through the first lens function member 31 is emitted inward from the reflective optical element 25, passes through the transmission mirror 23, and enters the pupil position PP. The first lens function member 31 has a positive power with respect to the image light ML and, like the two nearby positive lenses, has a positive focal length with respect to the image light ML that passes through it twice. When the first lens function member 31 is positioned at a focal length away from the display 11, the reflective optical element 25 functions as a collimator and forms a virtual image that can be viewed at a distance by the eye EY positioned at the pupil position PP. The thickness of the liquid crystal layer of the polarized diffractive lenses 31b and 33b is approximately 10 μm or more, and the reflective optical element 25 can be made extremely thin thanks to the thin-plate polarized diffractive lenses 31b and 33b. This facilitates the achievement of a thin virtual image display device 100A or 100B.

[0033] In the reflective optical element 25, external light OL incident on the second lens functioning member 33 is converted by the second optical element 34 into linearly polarized light in a first polarization direction P1. The polarization state of this external light OL is changed by the fourth quarter-wave plate 33c, which is positioned with its fast axis FX tilted 45° counterclockwise, and the external light OL is incident on the second polarizing diffraction lens 33b, which corresponds to the polarizing diffraction lens GP1 shown in FIG. 4, as second circularly polarized light C2 that generates positive power. The external light OL incident on the second polarizing diffraction lens 33b is converted into first circularly polarized light C1 that is relatively converged and inverted, and is then rotated by the third quarter-wave plate 33a, which is positioned with its fast axis FX tilted 45° clockwise, into linearly polarized light in a second polarization direction P2 that intersects with the first polarization direction P1, and is then emitted from the second lens functioning member 33. The external light OL that has passed through the second lens functioning member 33 is linearly polarized light in the second polarization direction P2 and passes through the first optical element 32. To explain the polarization state more specifically, when viewed from the +Z side, the second polarizing diffraction lens 33b has positive power with respect to the second circularly polarized light C2, i.e., left-handed circularly polarized light LCP, incident from the outside world, and converts the transmitted light into the first circularly polarized light C1, i.e., right-handed circularly polarized light RCP.

[0034] The linearly polarized external light OL in the second polarization direction P2 that passes through the first optical element 32 is incident on the first polarizing diffractive lens 31b by the second quarter-wave plate 31c as first circularly polarized light C1, which generates negative power in the reverse direction. The external light OL that enters the first polarizing diffractive lens 31b is converted into second circularly polarized light C2 that is relatively diverged and inverted, and is emitted from the first lens function member 31 by the first quarter-wave plate 31a as linearly polarized light in the second polarization direction P2, passes through the transmission mirror 23, and is incident on the pupil position PP. Explaining the polarization state more specifically, the first polarizing diffractive lens 31b has negative power with respect to the first circularly polarized light C1, i.e., right-handed circularly polarized light RCP, that passes through the first optical element 32 and enters in the reverse direction from the external side, and maintains the transmitted light as second circularly polarized light C2, i.e., left-handed circularly polarized light LCP.

[0035] As described above, the external light OL passing through the second lens function member 33 and the first lens function member 31 sequentially in opposite directions is relatively converged by passing through the second lens function member 33, and is relatively diverged by passing through the first lens function member 31. In this case, if the two lens function members 31 and 33 are arranged close to each other and the positive power of the second lens function member 33 and the negative power of the first lens function member 31 are equal, the lens actions of the two lens function members 31 and 33 cancel each other out, and the external light OL travels straight through the reflective optical element 25.

[0036] To summarize the above, the image light ML is observed as a virtual image by being reflected so as to be converged by the reflecting optical element 25, and the outside light OL is observed as a direct-view image by being transmitted in a straight line through the reflecting optical element 25. In other words, while observing the real image of the outside light OL through see-through, it is possible to observe a virtual image of the image light ML behind the reflecting optical element 25. In addition, in the virtual image display device 100A shown in FIG. 3, due to losses in the polarizing filter 12 and the transmission mirror 23, the light utilization efficiency of the image light ML is 50%×50%=25%.

[0037] Fig. 5 is a diagram illustrating a modification of the virtual image display devices 100A, 100B or the imaging optical system 20 shown in Fig. 3. In this case, the first optical element 32 is a transmissive mirror HM that has transparency that partially transmits target light.

[0038] The image light ML emitted from the first lens function component 31 is partially reflected by the first optical element 32. The image light ML partially reflected by the first optical element 32 is linearly polarized light in a first polarization direction P1, and has the same polarization state as that shown in FIG. 3. Therefore, the image light ML travels backward through the first lens function component 31 while undergoing the same action as in FIG. 3. The image light ML that has traveled back and forth through the first lens function component 31 is subjected to a converging action, is reflected by the reflecting optical element 25 as a whole so as to be collimated, and is observed as a virtual image. On the other hand, the image light ML that has partially transmitted through the first optical element 32 enters the second lens function component 33 as linearly polarized light in the first polarization direction P1. The image light ML that enters the second lens function component 33 is converted into second circularly polarized light C2 by the third quarter-wave plate 33a, and then converted into first circularly polarized light C1 that is diverged and inverted by the second polarizing diffraction lens 33b, which corresponds to the polarizing diffraction lens GP1. The image light ML emitted from the second lens function member 33 is incident on the second optical element 34 as linearly polarized light in the second polarization direction P2, but is blocked from transmission by the second optical element 34, preventing leakage to the outside. In the virtual image display device 100A shown in FIG. 5, due to losses in the polarizing filter 12, the transmissive mirror 23, and the first optical element 32, the light utilization efficiency of the image light ML is 50%×50%×50%=12.5%.

[0039] 3, the external light OL incident on the reflective optical element 25 from the outside travels backward through the second lens function member 33 and the first lens function member 31. In other words, the external light OL travels straight through the reflective optical element 25 and is observed as a direct-view image.

[0040] FIG. 6 is a diagram illustrating another modified example of the virtual image display devices 100A and 100B or the imaging optical system 20 shown in FIG. 3. In this case, the directions of the fast axes FX of the quarter-wave plates 131a, 131c, 133a, and 133c are inverted across the Y axis compared to the directions of the fast axes FX of the quarter-wave plates 31a, 31c, 33a, and 33c shown in FIG. 3. The polarized diffractive lenses 131b and 133b correspond to the polarized diffractive lenses GP2 shown in FIG. 3. In this case, the function of the polarized diffractive lenses 131b and 133b is the same as that of the polarized diffractive lenses 31b and 33b shown in FIG. 3 as a result of the inversion of the state of the circularly polarized light that acts on them. The image light ML incident on the reflective optical element 25 from the inside is collimated by the convergence action as it travels back and forth through the first lens function member 31, and is observed as a virtual image.

[0041] External light OL incident on the reflective optical element 25 from the outside is subjected to the same action as in Fig. 3 and travels backwards sequentially through the second lens function member 33 and the first lens function member 31. In this case as well, the function of the polarized diffraction lenses 31b, 33b becomes the same as that shown in Fig. 3 as a result of the state of the acting circularly polarized light being reversed, and the external light OL is transmitted through the reflective optical element 25 so as to travel in a straight line, and is observed as a direct-view image.

[0042] 7 is a diagram illustrating another modified example of the virtual image display devices 100A, 100B or the imaging optical system 20 shown in FIG. 3. In this case, the image light ML emitted from the display device 11, reflected by the transmission mirror 23, and incident on the first lens function member 31 is linearly polarized light in the second polarization direction P2. The directions of the fast axes FX of the quarter-wave plates 131a, 131c, 133a, and 133c are inverted across the Y axis compared to the directions of the fast axes FX of the quarter-wave plates 31a, 31c, 33a, and 33c shown in FIG. 3. The first optical element 132 is a reflective polarizing element RP that reflects only linearly polarized light in the second polarization direction P2. In this case, too, the function of the polarized diffractive lenses 31b, 33b is the same as that shown in Figure 3, and the image light ML incident on the reflective optical element 25 from the inside is collimated by the converging action as it travels back and forth through the first lens function member 31, and is observed as a virtual image.

[0043] External light OL incident on the reflective optical element 25 from the outside is subjected to the same action as in the case of Fig. 3 and travels backwards sequentially through the second lens function member 33 and the first lens function member 31. In this case as well, the function of the polarized diffractive lenses 31b and 33b is the same as that shown in Fig. 3, and the external light OL passes through the reflective optical element 25 in a straight line, and is observed as a direct-view image.

[0044] The virtual image display devices 100A, 100B and the optical unit 100 according to the first embodiment described above include, in the example shown in FIG. 3 and other figures, a display 11, a transmission mirror 23 that deflects, by reflection, image light ML that is linearly polarized in a first polarization direction P1 from the display 11, and a reflective optical element 25 that acts like a mirror with positive power when the image light ML reflected by the transmission mirror 23 is propagated backward. The reflective optical element 25 includes, in this order from the transmission mirror 23, a first polarized diffractive lens 31b. The optical element includes a first type first lens function component 31 that reverses the polarity of power and maintains the polarization direction of linearly polarized light by switching the polarization direction; a first optical element 32 that reflects linearly polarized light in the first polarization direction P1 while maintaining the polarization direction; a second type second lens function component 33 that includes a second polarizing diffractive lens 33b that reverses the polarity of power and rotates the polarization direction of linearly polarized light by switching the polarization direction; and a second optical element 34 that selectively transmits linearly polarized light in the first polarization direction P1.

[0045] In the virtual image display device, the image light ML, which is linearly polarized light in the first polarization direction P1 and reflected by the transmission mirror 23, passes through the first lens function member 31, whereby the image light ML can be relatively converged while remaining linearly polarized in the first polarization direction P1, and can be reflected by the first optical element 32. In the virtual image display device, the image light ML, which is linearly polarized light in the first polarization direction P1 and reflected by the first optical element 32, can be relatively converged again while remaining linearly polarized in the first polarization direction P1 by traveling backward through the first lens function member 31. The image light ML that has traveled back and forth through the first lens function member 31 passes through the transmission mirror 23 and is incident on the pupil position PP. Here, the first lens function member 31 has positive power with respect to the image light ML and has a positive focal length with respect to the image light ML that passes through it twice. By arranging the display device 11 at a position a predetermined focal length away, the first lens function member 31 functions as a collimator and forms a virtual image that can be observed by the eye located at the pupil position PP.

[0046] Note that the first polarization direction P1 and the second polarization direction P2 are used for convenience, and their definitions can be interchanged in specific examples. That is, in the example shown in Fig. 7, image light ML that is linearly polarized in the second polarization direction P2 is incident on the reflective optical element 25 and the first optical element 32. In this case, if the second polarization direction P2 is considered to be the first polarization direction and the first polarization direction P1 is considered to be the second polarization direction, the same configuration and function as the example shown in Fig. 3 etc. can be achieved. In other words, the reflective optical element 25 shown in Figure 7 has, in order from the transmissive mirror 23, a first type first lens function component 31 which includes a first polarizing diffractive lens 31b and which inverts the positive and negative power of linearly polarized light by switching the polarization direction, thereby maintaining the polarization direction; a first optical element 132 which reflects linearly polarized light in the first polarization direction (indicated by symbol P2 in the figure) while maintaining the polarization direction; a second type second lens function component 33 which includes a second polarizing diffractive lens 33b and which inverts the positive and negative power of linearly polarized light by switching the polarization direction, thereby rotating the polarization direction; and a second optical element 34 which selectively transmits linearly polarized light in the first polarization direction (indicated by symbol P2 in the figure).

[0047] 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.

[0048] As shown in FIG. 8, the virtual image display devices 100A and 100B of the second embodiment include a display 11, a polarizing filter 12, and lenses 14 and 214 as display driving units 102a and 102b, and include a light-guiding mirror 22 and a reflective optical element 25 as display optical systems 103a and 103b.

[0049] The light-guiding mirror 22 is a flat member overall and includes a first prism 22a and a second prism 22b. A lens 214 is fixed to an incident optical surface 22i of the light-guiding mirror 22. The first prism 22a and the second prism 22b are joined at an inclined surface 22s, and a flat transmission mirror 23 is embedded on the inclined surface 22s. The inner surface 22c and the outer surface 22d of the first prism 22a are parallel to each other and extend perpendicular to the optical axis AX between the pupil position PP. The inner surface 22e and the outer surface 22f of the second prism 22b are parallel to each other. The two inner surfaces 22c and 22e are on the same plane, and the two outer surfaces 22d and 22f are also on the same plane. The image light ML is reflected in the first prism 22a once by the inner surface 22c and once by the outer surface 22d, and is further reflected forward by the transmission mirror 23. In other words, the image light ML is internally reflected twice in the first prism 22a. In this case, the transmission mirror 23 forms an acute angle with the outer surface 22d, specifically an angle of 25° to 32°. Furthermore, the thickness of the light-guiding mirror 22 in the Z direction is 6 mm to 8 mm, which makes it easy to achieve a thin virtual image display device 100A, 100B.

[0050] Third Embodiment The virtual image display device of the third embodiment will be described below. 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 parts common to the virtual image display device of the first embodiment will be omitted.

[0051] 9, virtual image display devices 100A and 100B of the second embodiment include, as display driving units 102a and 102b, a display 11, a polarizing filter 12, and a lens 314, and, as display optical systems 103a and 103b, a transmission mirror 23 and a reflecting optical element 325. The lens 314 functions independently as a collimator, or forms diverging image light ML that has positive power like a magnifying glass.

[0052] The reflective optical element 325 is a flat member facing the transmissive mirror 23. The reflective optical element 325 includes, in order from the transmissive mirror 23, an optical function element 331 and a first optical element 32. The optical function element 331 includes, in order from the transmissive mirror 23, a first quarter-wave plate 31a, a cholesteric liquid crystal plate 338, and a second quarter-wave plate 31c whose fast axis is set in the same direction as the first quarter-wave plate 31a. The cholesteric liquid crystal plate 338 selectively reflects the image light ML, which has passed through the first quarter-wave plate 31a and become the first circularly polarized light C1, i.e., right-handed circularly polarized light RCP, while maintaining the image light ML in the right-handed circularly polarized light RCP state. The first optical element 32 may be a reflective polarizing element RP or an absorptive polarizing element AP.

[0053] The cholesteric liquid crystal plate 338 includes a cholesteric liquid crystal layer. The cholesteric liquid crystal layer has a layered structure of molecules oriented in a certain direction, and the molecular orientation axes are twisted between adjacent layers, resulting in an overall helical orientation around the vertical axis of the layer. The cholesteric liquid crystal plate 338 reflects right-handed circularly polarized RCP light as it is and transmits left-handed circularly polarized LCP light as it is.

[0054] On the other hand, the external light OL that is linearly polarized in the first polarization direction P1 passes through the first optical element 32 and is converted by the second quarter-wave plate 31c into second circularly polarized light C2, i.e., left-handed circularly polarized light LCP, and is incident on the cholesteric liquid crystal plate 338. The external light OL that is left-handed circularly polarized light LCP that has entered the cholesteric liquid crystal plate 338 passes through the cholesteric liquid crystal plate 338 as is, and is caused by the first quarter-wave plate 31a to exit from the first lens function member 31 as linearly polarized light in the second polarization direction P2, passes through the transmission mirror 23, and is incident on the pupil position PP.

[0055] Alternatively, the cholesteric liquid crystal plate 338 may reflect left-handed circularly polarized light LCP as left-handed circularly polarized light LCP and transmit right-handed circularly polarized light RCP as right-handed circularly polarized light RCP. In this case, the cholesteric liquid crystal plate 338 in the reflecting optical element 325 has the function of inverting circularly polarized light, so the optical axes of the quarter-wave plates 31a and 31c shown in FIG. 9 may be arranged in a direction intersecting the illustrated direction. In this case, the image light ML, which is linearly polarized in the first polarization direction P1, passes through the first quarter-wave plate 31a and enters the cholesteric liquid crystal plate 338 as the second circularly polarized light C2, i.e., left-handed circularly polarized light LCP. The cholesteric liquid crystal plate 338 selectively reflects the image light ML while maintaining it in the state of left-handed circularly polarized light LCP, so that the image light ML reflected by the cholesteric liquid crystal plate 338 is returned to linearly polarized light in the first polarization direction P1 when passing through the first quarter-wave plate 31a. On the other hand, the external light OL that is linearly polarized in the first polarization direction P1 passes through the second quarter-wave plate 31c, enters the cholesteric liquid crystal plate 338 as second circularly polarized light C2, i.e., right-handed circularly polarized light RCP, and is transmitted as is through the cholesteric liquid crystal plate 338. The external light OL that has transmitted through the cholesteric liquid crystal plate 338 is converted into linearly polarized light in the second polarization direction P2 when passing through the first quarter-wave plate 31a.

[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, it has been described that the HMD 200 comprises a first virtual image display device 100A and a second virtual image display device 100B, but the HMD 200 may also be configured to support a single first virtual image display device 100A or second display device 100B in front of the eyes by a support device 106.

[0058] In a specific embodiment, the virtual image display device comprises a display, a transmissive mirror that deflects image light, which is linearly polarized in a first polarization direction from the display, by reflection, and a reflective optical element that acts like a mirror with positive power when reversing the image light reflected by the transmissive mirror.The reflective optical element comprises, in order from the transmissive mirror, a first lens function component that includes a first polarizing diffractive lens and that reverses the positive and negative power by switching the polarization direction, thereby maintaining the polarization direction; a first optical element that reflects linearly polarized light in the first polarization direction while maintaining the polarization direction; a second lens function component that includes a second polarizing diffractive lens and that reverses the positive and negative power by switching the polarization direction, thereby rotating the polarization direction; and a second optical element that selectively transmits linearly polarized light in the first polarization direction.

[0059] In the virtual image display device, the linearly polarized image light reflected by the transmission mirror in a first polarization direction can be relatively converged as linearly polarized light in the first polarization direction by passing through the first lens functioning member and then reflected by the first optical element. In the virtual image display device, the linearly polarized image light reflected by the first optical element in a first polarization direction can be relatively converged again as linearly polarized light in the first polarization direction by passing through the first lens functioning member in the opposite direction. The image light that has traveled back and forth through the first lens functioning member passes through the transmission mirror and enters the pupil position. Here, the first lens functioning member has positive power with respect to the image light and has a positive focal length with respect to the image light that passes through it twice. By placing a display device at a predetermined focal length away, the first lens functioning member functions as a collimator and forms a virtual image that can be observed by the eye located at the pupil position.

[0060] In a specific embodiment of the virtual image display device, the first lens functioning component includes, in order from the transmission mirror, a first quarter-wave plate, a first polarizing diffractive lens, and a second quarter-wave plate whose fast axis is set in the same direction as the first quarter-wave plate. Here, the image light incident on the first lens functioning component via the transmission mirror includes linearly polarized light in a first polarization direction. This image light is converted into circularly polarized light that generates positive power from the forward direction by the first quarter-wave plate, whose fast axis is appropriately set. The image light incident on the first polarizing diffractive lens is relatively converged and converted into inverted circularly polarized light, which is then returned to the first polarization direction by the second quarter-wave plate and exits the first lens functioning component. The image light exiting the first lens functioning component is linearly polarized light in the first polarization direction and is reflected by the first optical element. The linearly polarized image light in the first polarization direction reflected by the first optical element is converted by the second quarter-wave plate into circularly polarized light that generates positive power in the reverse direction and is incident on the first polarizing diffractive lens. The image light incident on the first polarizing diffractive lens is relatively further converged and converted into inverted circularly polarized light, and is then emitted by the first quarter-wave plate from the first lens functioning member as linearly polarized light in the first polarization direction, passes through the transmission mirror, and is incident on the pupil position.

[0061] In a specific embodiment of the virtual image display device, the second lens functioning member includes, in order from the transmissive mirror, a third quarter-wave plate, a second polarizing diffractive lens, and a fourth quarter-wave plate whose fast axis is set in a direction intersecting with the third quarter-wave plate. Here, external light incident on the second lens functioning member is linearly polarized in a first polarization direction by the second optical element. This external light is then incident on the second polarizing diffractive lens as circularly polarized light that imparts positive power to the second polarizing diffractive lens by the fourth quarter-wave plate whose fast axis is appropriately set. The external light incident on the second polarizing diffractive lens is relatively converged and inverted into circularly polarized light, which is then rotated by the third quarter-wave plate into linearly polarized light in a second polarization direction intersecting with the first polarization direction, and then exits the second lens functioning member. The external light that passes through the second lens functioning member is linearly polarized in the second polarization direction and passes through the first optical element. The linearly polarized light in the second polarization direction that passes through the first optical element is converted by the second quarter-wave plate into circularly polarized light that generates negative power in the opposite direction and enters the first polarizing diffractive lens. The external light that enters the first polarizing diffractive lens is converted into inverted circularly polarized light while relatively diverging, and is then emitted by the first quarter-wave plate as linearly polarized light in the second polarization direction from the first lens function element, passes through the transmission mirror, and enters the pupil position. As a result, the external light is relatively converged by the second lens function element and relatively diverged by the first lens function element. In other words, if the positive power of the second lens function element and the negative power of the first lens function element are equal, the lens actions of the two lens function elements cancel each other out, and the external light travels straight through the reflective optical element. As a result, the image light is reflected by the reflective optical element so as to be converged, and is observed as a virtual image, while the external light passes through the reflective optical element so as to travel straight, and is observed as a direct-view image. That is, while observing a real image of external light through the see-through, it is possible to observe a virtual image of the image light behind the reflective optical element.

[0062] In a specific aspect of the virtual image display device, the first polarized diffractive lens has positive power for first circularly polarized light incident from the display device side and converts the transmitted light into second circularly polarized light, and has positive power for second circularly polarized light reflected by the first optical element and incident from the outside world side and converts the transmitted light into the first circularly polarized light. Specifically, the first circularly polarized light is right-handed circularly polarized light, and the second circularly polarized light is left-handed circularly polarized light.

[0063] In a specific embodiment of the virtual image display device, the second polarizing diffractive lens has positive power with respect to the second circularly polarized light incident from the outside and converts the transmitted light into the first circularly polarized light, and the first polarizing diffractive lens has negative power with respect to the first circularly polarized light incident from the outside after passing through the first optical element and maintaining the transmitted light as the second circularly polarized light.

[0064] In a specific embodiment of the virtual image display device, the first optical element is a reflective polarizing element that reflects only the target linearly polarized light. In this case, the image light is folded back by reflection at the first optical element. At this time, loss by the reflective polarizing element is small, and a bright virtual image can be formed.

[0065] In a specific embodiment of the virtual image display device, the first optical element is a transmissive mirror, in which case the image light is folded back by reflection at the first optical element.

[0066] In a specific embodiment of the virtual image display device, the second optical element is an absorptive polarizing element that transmits only the target linearly polarized light. In this case, external light can be made to enter the first optical element via the second lens functioning member and transmitted through the first optical element.

[0067] In a specific embodiment of the virtual image display device, a lens having a positive power is disposed between the display and the transmission mirror, thereby reducing the positive power borne by the first lens functioning member and various aberrations including chromatic aberration.

[0068] In a specific embodiment, the optical unit includes a display, a transmission mirror that deflects image light, which is linearly polarized in a first polarization direction from the display, by reflection, and and a reflective optical element that acts like a mirror with positive power when reversing the image light reflected by the transmissive mirror. The reflective optical element has, in order from the transmissive mirror, a first lens function component that includes a first polarizing diffractive lens and that reverses the positive and negative power by switching the polarization direction, thereby maintaining the polarization direction; a first optical element that reflects linearly polarized light in the first polarization direction while maintaining the polarization direction; a second lens function component that includes a second polarizing diffractive lens and that reverses the positive and negative power by switching the polarization direction, thereby rotating the polarization direction; and a second optical element that selectively transmits linearly polarized light in the first polarization direction. [Explanation of symbols]

[0069] 11...display device, 11d...display surface, 12...polarizing filter, 14,214...lens, 14a, 14b...optical surface, 20...imaging optical system, 22...light-guiding mirror, 22c, 22e...inner surface, 22d, 22f...outer surface, 22i...incident optical surface, 22s...inclined surface, 23...transmissive mirror, 23a...transmissive reflective film, 25,325...reflective optical element, 31...first lens function member, 33...second lens function member, 31b...first polarized diffractive lens, 33b...second polarized diffractive lens, 131b, 133b...polarized diffractive lens, 88...display control device, 90...user terminal, 100...optical unit, 100A, 100B...virtual image display device , 100C...Temple, 102...Driver, 102a, 102b...Display driver, 103a, 103b...Display optical system, 106...Support device, 200...Head-mounted display device, 214, 314...Lens, 331...Optical function element, 338...Cholesteric liquid crystal plate, AP...Absorptive polarizing element, RP...Reflective polarizing element, AX...Optical axis, EY...Eye, FP, FP'...Focus, FX...Fast axis, GP1, GP2...Second polarizing diffractive lens, HM...Transmissive mirror, L1, L2...Light beam, LCP...Left circularly polarized light, RCP...Right circularly polarized light, ML...Image light, OL...External light, P1...First polarization direction, P2...Second polarization direction, PP...Pupil position, US...Wearer

Claims

1. A display; a transmission mirror that deflects, by reflection, image light that is linearly polarized in a first polarization direction from the display; a reflective optical element that acts like a mirror having positive power when the image light reflected by the transmission mirror is caused to travel backward, The reflecting optical element has, in order from the transmission mirror, a first lens functioning member including a first polarizing diffractive lens that inverts the positive and negative of power by switching the polarization direction and maintains the polarization direction, a first optical element that reflects linearly polarized light in the first polarization direction while maintaining the polarization direction, a second lens functioning member including a second polarizing diffractive lens that inverts the positive and negative of power by switching the polarization direction and rotates the polarization direction, and a second optical element that selectively transmits linearly polarized light in the first polarization direction. Virtual image display device.

2. the first lens function member includes, in order from the transmission mirror, a first quarter-wave plate, the first polarizing diffraction lens, and a second quarter-wave plate whose fast axis is set in the same direction as that of the first quarter-wave plate; The virtual image display device according to claim 1 .

3. the second lens function member includes, in order from the transmission mirror, a third quarter-wave plate, the second polarizing diffraction lens, and a fourth quarter-wave plate whose fast axis is set in a direction intersecting with the third quarter-wave plate; The virtual image display device according to claim 2 .

4. the first polarized diffractive lens has a positive power with respect to a first circularly polarized light incident from the display device side and converts the transmitted light into a second circularly polarized light, and has a positive power with respect to the second circularly polarized light reflected by the first optical element and incident from the outside world side and converts the transmitted light into the first circularly polarized light; The virtual image display device according to claim 2 .

5. the second polarized diffractive lens has a positive power with respect to second circularly polarized light incident from the outside and converts transmitted light into first circularly polarized light; the first polarized diffractive lens has a negative power with respect to a first circularly polarized light that is transmitted through the first optical element and incident from the outside, and converts the transmitted light into a second circularly polarized light. The virtual image display device according to claim 4 .

6. the first optical element is a reflective polarizing element that reflects only the linearly polarized light of interest; The virtual image display device according to claim 1 .

7. the first optical element is a transmissive mirror; The virtual image display device according to claim 1 .

8. the second optical element is an absorptive polarizing element that transmits only the linearly polarized light of interest; The virtual image display device according to claim 1 .

9. a lens having a positive power is disposed between the display and the transmission mirror; The virtual image display device according to claim 1 .

10. A display; a transmission mirror that deflects, by reflection, image light that is linearly polarized in a first polarization direction from the display; a reflective optical element that acts like a mirror having positive power when the image light reflected by the transmission mirror is caused to travel backward, The reflecting optical element has, in order from the transmission mirror, a first lens functioning member including a first polarizing diffractive lens that inverts the positive and negative of power by switching the polarization direction and maintains the polarization direction, a first optical element that reflects linearly polarized light in the first polarization direction while maintaining the polarization direction, a second lens functioning member including a second polarizing diffractive lens that inverts the positive and negative of power by switching the polarization direction and rotates the polarization direction, and a second optical element that selectively transmits linearly polarized light in the first polarization direction. Optical unit.

Images