Virtual image display device and optical unit

Abstract

To reduce the thickness of an imaging system of a virtual image display device.SOLUTION: A virtual image display device 100A, 100B or an optical unit 100 comprises: a display unit 40 that emits video light ML; a first polarization diffraction lens 51 that is arranged opposite to the display unit 40, and has a positive power for the video light ML being circularly polarized light; and a second polarization diffraction lens 52 that is arranged opposite to the display unit 40 with the first polarization diffraction lens 51 therebetween, and has a positive power for the video light ML being circularly polarized light passing through the first polarization diffraction lens 51.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 virtual image display device that uses a polarized diffractive lens. [Background technology]

[0002] A known virtual image display device includes a liquid crystal panel having an image display area and a transparent display area surrounding the image display area, and a light guide plate that guides backlight incident on an edge of the panel from a light source, the light guide plate having a light-emitting area that irradiates the image display area of ​​the liquid crystal panel with the backlight and a light-transmitting area that transmits ambient light (see Patent Document 1). This virtual image display device enables a see-through display in which image light and ambient light are superimposed. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2016 / 056298 Summary of the Invention [Problem to be solved by the invention]

[0004] In the virtual image display device, when the liquid crystal panel is placed close to the eyes, an imaging system is required to observe the image formed in the image display area. For example, by using an optical system that incorporates a lens with a half mirror on one side and folds the optical path twice as the imaging system, the virtual image display device including the imaging system can be made thinner.

[0005] However, imaging systems that fold the optical path twice have a section where light travels backward and incorporate lenses, so there is a limit to how much the thickness of the imaging system can be reduced, and it is not easy to meet the demand for further thinning. Also, imaging systems that fold the optical path twice usually act on ambient light, so additional measures are required to allow ambient light to pass through. [Means for solving the problem]

[0006] A virtual image display device according to one aspect of the present invention comprises a display that emits image light, a first polarizing diffractive lens that is disposed opposite the display and has positive power for circularly polarized image light, and a second polarizing diffractive lens that is disposed opposite the display across the first polarizing diffractive lens and has positive power for circularly polarized image light that has passed through the first polarizing diffractive lens. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 2 is an external front view illustrating a wearing state of the virtual image display device of the first embodiment. [Figure 2] FIG. 1 is a conceptual perspective view illustrating a structure of a virtual image display device. [Figure 3] FIG. 2 is an enlarged side cross-sectional view illustrating a display device. [Figure 4] FIG. 10 is a diagram illustrating the state of light passing through the display. [Figure 5] FIG. 2 is a side cross-sectional view illustrating an imaging system of the virtual image display device. [Figure 6] 1A and 1B are a perspective view and a rear view illustrating the state of light rays in an imaging system. [Figure 7] FIG. 1 is a conceptual perspective view illustrating the function of a polarized diffractive lens. [Figure 8] 10 is a chart illustrating the operation of the virtual image display device. [Figure 9] FIG. 10 is a side cross-sectional view illustrating a virtual image display device according to a modified example. [Figure 10] FIG. 10 is a side cross-sectional view illustrating a virtual image display device according to a second embodiment. [Figure 11] FIG. 10 is a side cross-sectional view illustrating a virtual image display device according to a third embodiment. [Figure 12] FIG. 10 is a side cross-sectional view illustrating a virtual image display device according to a modified example. [Figure 13] FIG. 10 is a side cross-sectional view illustrating a virtual image display device according to a fourth embodiment. [Figure 14] FIG. 14 is a perspective view of the optical unit shown in FIG. [Figure 15] FIG. 14 is a side cross-sectional view illustrating a modified example of the virtual image display device shown in FIG. [Figure 16] FIG. 16 is a perspective view of the optical unit shown in FIG. [Figure 17] FIG. 10 is a side cross-sectional view illustrating a virtual image display device according to a fifth embodiment. [Figure 18] FIG. 18 is a perspective view of the optical unit shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0008] [First embodiment] Hereinafter, a virtual image display device according to a first embodiment of the present invention will be described with reference to FIGS.

[0009] 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.

[0010] 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.

[0011] 2 is a perspective view illustrating the structure of the first display optical system 103a. The first display optical system 103a includes a plate-like display 40 that forms a two-dimensional image and emits corresponding image light ML, and a plate-like imaging system 50 that functions as a lens for the image light ML emitted from the display 40 to form a virtual image.

[0012] The display 40 includes a light source 10 that generates three colors of light as illumination light in a time-division manner and a composite display member 20 that forms and emits image light ML. The light source 10 is also part of the first display drive unit 102a shown in FIG. 1 and is disposed above and adjacent to the upper edge of the light-guiding member 21 (described later) of the composite display member 20 so as to supply illumination light from the upper edge to the light-guiding member 21. The display 40 is driven and operated by a drive circuit 81 of a control device 80 incorporated in the first display drive unit 102a or the drive device 102. The composite display member 20 of the display 40 is disposed close to the eye EY with the imaging system 50 sandwiched therebetween, enabling observation of a virtual image formed by the image light ML and a see-through view of the outside world. In the first display optical system 103a, the distance between the eye EY and the imaging system 50 in the direction of the optical axis AX is, for example, approximately 10 mm to 20 mm. The distance between the transmissive liquid crystal panel 22 of the display 40 and the imaging system 50 in the direction of the optical axis AX is, for example, about 5 mm to 25 mm.

[0013] The light source 10 includes one or more R light-emitting elements 10r that emit red light, one or more B light-emitting elements 10b that emit blue light, and one or more G light-emitting elements 10g that emit green light. The R light-emitting elements 10r, B light-emitting elements 10b, and G light-emitting elements 10g are self-emitting elements, such as organic light-emitting diodes (OLEDs), but may also be light-emitting diodes such as micro light-emitting diodes (μLEDs) made of inorganic materials. A multiplexer / demultiplexer including a beam splitter can be incorporated between the light source 10 and the light-guiding member 21 of the composite display member 20 to help diffuse the illumination light.

[0014] The composite display member 20 is a plate-like member extending along the XY plane perpendicular to the optical axis AX, and includes, in order from the outside, a light-guiding member 21, a transmissive liquid crystal panel 22, and a quarter-wave plate 23. The composite display member 20 has a structure in which the light-guiding member 21, the transmissive liquid crystal panel 22, and the quarter-wave plate 23 are laminated together and integrated by a frame (not shown). The light-guiding member 21 and the transmissive liquid crystal panel 22 are disposed adjacent to each other with a predetermined distance or less between them. The transmissive liquid crystal panel 22 is an imager 2a that forms image light. The transmissive liquid crystal panel 22 includes a plurality of pixels PX (see FIG. 3) arranged in a matrix along the XY plane.

[0015] The imaging system 50 is disposed on the face side, i.e., the -Z side, of the display 40 or the composite display member 20, and covers the eyes. The imaging system 50 is a plate-shaped member extending along the XY plane and includes, in order from the outside, a first polarizing diffractive lens 51, a switching half-wave plate 55, and a second polarizing diffractive lens 52. The composite display member 20 has a structure in which its constituent optical elements, namely the first polarizing diffractive lens 51, the switching half-wave plate 55, and the second polarizing diffractive lens 52, are arranged parallel to one another and adjacent to one another, and are integrated by a frame (not shown). This integration stabilizes the optical performance of the imaging system 50 and enables the imaging system 50 to be made thinner. Note that, including cases in which other optical elements are disposed between the first polarizing diffractive lens 51 and the second polarizing diffractive lens 52 in addition to the switching half-wave plate 55, these can be integrated by directly fixing them with an adhesive, or by closely contacting each other and fixing them at their peripheries. Furthermore, the distance between the first polarizing diffractive lens 51 and the second polarizing diffractive lens 52 can be adjusted before they are integrated. The imaging system 50 is a dynamic optical element whose function changes depending on the state of the switching half-wave plate 55. The imaging system 50 functions as a lens for the image light ML emitted from the composite display member 20. In other words, the imaging system 50 comprehensively forms an image of the multiple pixels that make up the transmissive liquid crystal panel 22, making it possible to observe the image formed on the transmissive liquid crystal panel 22 as a virtual image. On the other hand, the imaging system 50 functions as a parallel plate for the external light OL that passes through the composite display member 20. In other words, the external light OL is observed as a direct-view image by passing through the composite display member 20 in a straight line.

[0016] The second display optical system 103b is optically identical to the first display optical system 103a, or is a left-right inversion of the first display optical system 103a, and a detailed description thereof will be omitted.

[0017] In the first virtual image display device 100A, the optical device excluding the control device 80 is called the optical unit 100. In the second virtual image display device 100B, the optical device excluding the control device 80 is called the optical unit 100.

[0018] Fig. 3 is a conceptual enlarged cross-sectional view illustrating the structure of the display 40, and Fig. 4 is a diagram illustrating the state of light in the display 40. In Fig. 4, a first region AR1 indicates a case where the first display optical system 103a is in an image observation period and the display 40 is in a display state, and a second region AR2 indicates a case where the first display optical system 103a is in an ambient light observation period and the display 40 is in a non-display state.

[0019] 3, the light source 10 generates three colored illumination lights ILr, ILg, and ILb as the illumination light IL, and supplies the three colored illumination lights ILr, ILg, and ILb to the light guide member 21 of the composite display member 20. As shown in FIG.

[0020] The light-guiding member 21 is a light-guiding plate 11 to which a ferroelectric liquid crystal plate 12 is fixed. Illumination light ILr, ILg, ILb from the light source 10 is coupled into the light-guiding plate 11 from the upper end of the light-guiding plate 11. The light-guiding plate 11 propagates the illumination light ILr, ILg, ILb incident from the light source 10 downward.

[0021] The ferroelectric liquid crystal panel 12 is a device that performs switching operations in response to a drive signal from a drive circuit 81. It can be switched between a scattering state (ON state) that allows illumination light IL (ILr, ILg, ILb) to exit the light guide plate 11 and a transparent state (OFF state) that transmits external light OL and allows it to pass through. The ferroelectric liquid crystal panel 12 includes a ferroelectric liquid crystal layer 12a sandwiched between a pair of substrates 12b and 12c via a transparent electrode layer (not shown). The ferroelectric liquid crystal layer 12a is, for example, a reverse-mode polymer-dispersed liquid crystal that is in a transmissive state when no electric field is applied and in a scattering state when an electric field is applied (see, for example, Japanese Patent Application Laid-Open No. 6-308543). The ferroelectric liquid crystal panel 12 can be switched ON and OFF not in units of pixels PX but across the entire surface. The ferroelectric liquid crystal layer 12a may be in a transmissive state when an electric field is applied and in a scattering state when an electric field is not applied.

[0022] The transmissive liquid crystal panel 22 includes a liquid crystal modulation member 14 and a pair of polarizing plates 15 and 16 sandwiching the liquid crystal modulation member 14. In this case, the transmissive liquid crystal panel 22 is, for example, an IPS (in-plane switching) type liquid crystal modulation element, and includes three types of sub-pixels PXs that constitute the pixel PX: PXs(R), PXs(G), and PXs(B). Although not shown, these sub-pixels PXs(R), PXs(G), and PXs(B) are arranged in a stripe or Bayer pattern to constitute the pixel PX. In the sub-pixel PXs(R) for red display, a red color filter 41r is disposed near the first polarizing plate 15. In the sub-pixel PXs(G) for green display, a green color filter 41g is disposed near the first polarizing plate 15. In the sub-pixel PXs(B) for blue display, a blue color filter 41b is disposed near the first polarizing plate 15. The liquid crystal modulation member 14 does not rotate the polarization direction of incident light when an electric field is not applied, but rotates the polarization direction of incident light when an electric field is applied. In this case, the pair of polarizers 15, 16 are absorptive polarizing elements and are arranged so that their polarization directions intersect, more specifically, are perpendicular to each other. The transmissive liquid crystal panel 22 can switch ON and OFF for each subpixel PXs in response to a drive signal from the drive circuit 81, allowing incident light to partially pass through at any intermediate gradation between ON and OFF. For this reason, the liquid crystal modulation member 14 includes not only a liquid crystal layer 31, a common electrode 32, pixel electrodes 33, and a black matrix 35, but also scanning lines, signal lines, switching elements, and the like (not shown).

[0023] The transmissive liquid crystal panel 22 or the liquid crystal modulation member 14 may rotate the polarization direction of incident light when no electric field is applied, but not when an electric field is applied. In this case, the pair of polarizing plates 15 and 16 are arranged so that the polarization directions are parallel to each other.

[0024] The quarter-wave plate 23 has a principal axis, for example, midway between the X and Y directions, and converts the image light ML and the external light OL (see FIG. 2 ) from linearly polarized light to circularly polarized light. 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 in which the light beam propagates, 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, then such image light ML is considered to be right-handed circularly polarized light RCP. Similarly, if the image light ML mainly contains left-handed circularly polarized light, then such image light ML is considered to be left-handed circularly polarized light LCP. In this specification, right-handed circularly polarized RCP is also referred to as right-handed circularly polarized RCP, and left-handed circularly polarized LCP is also referred to as left-handed circularly polarized LCP.

[0025] 4, when the display 40 is in a display state during an image observation period, the light-emitting elements 10r, 10g, and 10b of the light source 10 emit light, and illumination light ILr, ILg, and ILb are supplied to the light-guiding member 21. At this timing, when the ferroelectric liquid crystal plate 12 is switched to the ON state and enters a scattering state, the illumination light ILr, ILg, and ILb passes through the first polarizer 15 of the transmissive liquid crystal panel 22 and illuminates the liquid crystal modulation member 14 as second polarized light P2, which is horizontally polarized light or horizontally polarized light. In other words, the colorless sub-pixels PXs(R), PXs(G), and PXs(B) constituting the transmissive liquid crystal panel 22 are illuminated. The image light ML(R), ML(G), and ML(B) that passes through the liquid crystal modulation member 14 are illumination light ILr, ILg, and ILb whose polarization planes are rotated in response to a drive signal. Only the first polarized light P1, which is vertically polarized light or vertically polarized light, is emitted through the second polarizer 16. The image light ML(R), ML(G), and ML(B) emitted from each sub-pixel PXs of the transmissive liquid crystal panel 22 passes through the quarter-wave plate 23 and is converted from the first polarized light P1 into right-handed circularly polarized light RCP.

[0026] On the other hand, when the display 40 is in a non-display state during the ambient light observation period, the light source 10 is set to a non-emitting state, i.e., an extinguished state, and the supply of the illumination light IL to the light-guiding member 21 is stopped. At this timing, the ferroelectric liquid crystal plate 12 is switched to the OFF state and becomes a transmissive state. The ambient light OL (OL(R), OL(G), OL(B)) travels straight across the light-guiding member 21 and enters the transmissive liquid crystal panel 22. At this time, each sub-pixel PXs of the transmissive liquid crystal panel 22 operates, for example, in a normally-off mode and is set to a maximum transmittance state by a drive signal. The second polarized light P2 of the ambient light OL that enters each sub-pixel PXs(R), PXs(G), PXs(B) of the transmissive liquid crystal panel 22 travels straight through the transmissive liquid crystal panel 22, i.e., the pixel PX, and is converted into the first polarized light P1. The ambient light OL emitted from each sub-pixel PXs of the transmissive liquid crystal panel 22 passes through the quarter-wave plate 23 and is converted from the first polarized light P1 to right-handed circularly polarized light RCP.

[0027] Fig. 5 is a side cross-sectional view showing the optical unit 100 of the display optical systems 103a and 103b, and Fig. 6 is a view of the optical unit 100 seen from another direction. In Fig. 6, the first region BR1 is a perspective view of the optical unit 100, and the second region BR2 is a rear view of the optical unit 100.

[0028] The optical unit 100 comprises a display 40 that emits image light ML and transmits external light OL, an imaging system 50 that functions as a positive lens or collimator with positive power for the image light ML, and a support member 101 that fixes these relative to one another.

[0029] In imaging system 50, first polarizing diffractive lens 51 functions alone as a positive lens when predetermined circularly polarized light is incident, and second polarizing diffractive lens 52 also functions alone as a positive lens when predetermined circularly polarized light is incident. Switching half-wave plate 55 can be switched between an ON state and an OFF state, and when switching half-wave plate 55 is in the ON state, it causes polarizing diffractive lenses 51 and 52 to both function as positive lenses, and when switching half-wave plate 55 is in the OFF state, it cancels out the powers of polarizing diffractive lenses 51 and 52 and causes them to function like parallel flat plate glass.

[0030] FIG. 7 is a diagram illustrating the functions of the first polarized diffractive lens 51 and the second polarized diffractive lens 52. In FIG. 7, the first region CR1 shows a first operational example of the first type of polarized diffractive lens GP1, and the second region CR2 shows a second operational example of the first type of polarized diffractive lens GP1. In FIG. 7, the third region CR3 shows a first operational example of the second type of polarized diffractive lens GP2, and the fourth region CR4 shows a second operational example of the second type of polarized diffractive lens GP2. The first polarized diffractive lens 51 and the second polarized diffractive lens 52 shown in FIG. 5 are the first type of polarized diffractive lens GP1.

[0031] 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 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 diverging from the focal point FP' on the left side of the drawing, such as light ray L2 shown by the dashed-dot line, 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.

[0032] 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 at the 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.

[0033] 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.

[0034] 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).

[0035] 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.

[0036] 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.

[0037] 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 focused after passing through the polarized diffractive lens GP1, while the left-handed circularly polarized light (LCP) component is diverged after passing through the polarized diffractive lens GP1, and the rotation direction of each polarization is reversed.

[0038] 5 , the switching half-wave plate 55 is a device that performs a switching operation in response to a drive signal from the drive circuit 81. Depending on the orientation direction of the liquid crystal, the switching half-wave plate 55 switches the polarization state of incident light from right-handed circularly polarized light (RCP) to left-handed circularly polarized light (LCP) and passes the light, or passes the light as right-handed circularly polarized light (LCP). That is, the switching half-wave plate 55 switches between an ON state, which is a first state in which the image light ML that has passed through the first polarizing diffractive lens 51 is converted from left-handed circularly polarized light (LCP), which is the second circularly polarized light, back to right-handed circularly polarized light (RCP), which is the first circularly polarized light, and an OFF state, which is a second state in which the image light ML that has passed through the first polarizing diffractive lens 51 is passed as left-handed circularly polarized light (LCP), which is the second circularly polarized light. The switching half-wave plate 55 includes a liquid crystal layer 55a sandwiched between a pair of substrates 55b and 55c with a transparent electrode layer (not shown) interposed therebetween. Liquid crystal layer 55a is, for example, an IPS (in-plane switching) type liquid crystal, which, when an electric field is applied, causes switching half-wave plate 55 to function as an optical element equivalent to a half-wave plate with its major axis or fast axis set in a specific direction (for example, halfway between the X and Y directions), and causes switching half-wave plate 55 to function as an isotropic parallel plate when no electric field is applied. Switching half-wave plate 55 switches between the ON and OFF states over the entire surface, rather than on a pixel-by-pixel basis.

[0039] 7, when the image light ML and external light OL incident from the display 40 are right-handed circularly polarized light RCP, the first polarizing diffractive lens 51 functions as an optical element having positive power with respect to the image light ML and external light OL, reducing the divergence of the image light ML and external light OL while reversing the direction of polarization rotation to convert them to left-handed circularly polarized light LCP. The image light ML and external light OL that have passed through the first polarizing diffractive lens 51 are incident on the switching half-wave plate 55 in the state of left-handed circularly polarized light LCP.

[0040] The switching half-wave plate 55 is in the ON state during the image observation period, that is, when the image light ML is incident, and is in the OFF state during the ambient light observation period, that is, when the ambient light OL is incident.

[0041] During the image observation period, the switching half-wave plate 55, in its ON state, converts the incident image light ML from left-handed circularly polarized light (LCP) to right-handed circularly polarized light (RCP). However, unlike a parallel plate, the image light ML passes through without substantially converging, and is incident on the second polarizing diffractive lens 52. The second polarizing diffractive lens 52 is the polarizing diffractive lens GP1 shown in FIG. 7. When the image light ML passing through the switching half-wave plate 55 is right-handed circularly polarized light (RCP), the second polarizing diffractive lens 52 functions as an optical element with positive power for the image light ML, reducing the divergence of the image light ML and reversing the direction of polarization rotation to convert it to left-handed circularly polarized light (LCP). In this case, the absolute values ​​of the powers of the first polarizing diffractive lens 51 and the second polarizing diffractive lens 52 are set to be equal, and the composite focal length of the polarizing diffractive lenses 51 and 52 is approximately equivalent to the composite focal length of two adjacently arranged thin convex lenses. When the combined focal length of both polarizing diffractive lenses 51, 52 is equal to the distance from the midpoint between both polarizing diffractive lenses 51, 52 to display surface 11d of display device 40, imaging system 50 functions as a collimator, collimating and focusing image light ML at pupil position PP. Although Fig. 6 shows only the chief ray of image light ML from display surface 11d, it can be seen that image light ML from a diagonal position on display surface 11d passes through pupil position PP.

[0042] On the other hand, during the external light observation period, the switching half-wave plate 55 in the OFF state maintains the external light OL incident thereon as left-handed circularly polarized light (LCP) and causes it to enter the second polarizing diffractive lens 52. The second polarizing diffractive lens 52 is the polarizing diffractive lens GP1 shown in FIG. 7. When the external light OL passing through the switching half-wave plate 55 is left-handed circularly polarized light (LCP), the second polarizing diffractive lens 52 functions as an optical element with negative power with respect to the external light OL, reducing the convergence of the external light OL while reversing the direction of polarization rotation to convert it to right-handed circularly polarized light (RCP). In this case, the two polarizing diffractive lenses 51 and 52 are positioned close to each other and are set so that the absolute values ​​of their powers are equal, and the composite focal length of the two polarizing diffractive lenses 51 and 52 is infinity. When the combined focal length of the polarized diffraction lenses 51, 52 is infinity, the imaging system 50 functions as equivalent to a parallel plate, which is an optical system with approximately zero power, and causes the external light OL to travel in a substantially straight line without exerting any imaging effect such as focusing, thereby enabling the external light OL to be observed with the naked eye.

[0043] As described above, during the image observation period, the imaging system 50 has positive power due to the switching half-wave plate 55 in the ON state, making it possible to observe the image light ML, and during the external light observation period, the imaging system 50 has substantially zero power due to the switching half-wave plate 55 in the OFF state, making it possible to observe the external light OL. In other words, the virtual image display devices 100A, 100B or the display optical systems 103a, 103b that perform such display enable a see-through display in which the image light ML and the external light OL are superimposed in a time-division manner.

[0044] 8 is a timing chart illustrating the display operation of the display optical systems 103a and 103b. The horizontal axis represents time, and from top to bottom, the diagram shows a blinking signal SS1 for the R light-emitting element 10r, an R drive signal SM1 for red display applied to the liquid crystal modulation element 14, a blinking signal SS2 for the G light-emitting element 10g, a G drive signal SM2 for green display applied to the liquid crystal modulation element 14, a blinking signal SS3 for the B light-emitting element 10b, a B drive signal SM3 for blue display applied to the liquid crystal modulation element 14, an on / off signal SD for the ferroelectric liquid crystal plate (FLC) 12, and an on / off signal SW for the switching half-wave plate (½λ) 55. The operation of the first virtual image display device 100A includes, in each frame, a first subframe Z1 for video observation and a second subframe Z2 for ambient light observation.

[0045] In this case, when the first virtual image display device 100A is in the image observation period and the transmissive liquid crystal panel 22 is in the display state, three colors of image light ML(R), ML(G), and ML(B) are displayed simultaneously in parallel, and when the first virtual image display device 100A is in the external light observation period and the transmissive liquid crystal panel 22 is in the non-display state, the external light OL is transmitted through the sub-pixels PXs(R), PXs(G), and PXs(B) of the transmissive liquid crystal panel 22 in a balanced manner, making it possible to observe an external image without coloration.

[0046] Fig. 9 is a diagram illustrating modified first display optical systems 103a and 103b, and corresponds to Fig. 5. In this case, in the first stage of time division, image light ML of left-handed circularly polarized LCP is emitted from the display device 40, and in the second stage of time division, outside light OL of left-handed circularly polarized LCP is transmitted by the display device 40.

[0047] In the imaging system 50, the first polarized diffractive lens 151 and the second polarized diffractive lens 152 are the polarized diffractive lenses GP2 shown in FIG. 7, and when the image light ML and external light OL incident from the display 40 are left-handed circularly polarized light LCP, they function as optical elements with positive power with respect to the image light ML and external light OL, reducing the divergence of the image light ML and external light OL while reversing the direction of rotation of the polarization to convert them to right-handed circularly polarized light RCP.

[0048] During the image observation period, image light ML that has passed through first polarizing diffractive lens 151 is incident on switching half-wave plate 55, converted back into left-handed circularly polarized light LCP, and then incident on second polarizing diffractive lens 152. As a result, first polarizing diffractive lens 151 and second polarizing diffractive lens 152 relatively converge the image light ML passing through from the display device 40 side, and change the first circularly polarized light, left-handed circularly polarized light LCP, into the second circularly polarized light, right-handed circularly polarized light RCP. In this case, because imaging system 50 has positive power, it becomes possible to observe the image light ML.

[0049] On the other hand, during the external light observation period, external light OL that has passed through first polarizing diffractive lens 151 is incident on switching half-wave plate 55, where it is maintained as right-handed circularly polarized light RCP, and then incident on second polarizing diffractive lens 152. As a result, first polarizing diffractive lens 151 and second polarizing diffractive lens 152 cause external light OL passing through from the display device 40 side to travel in a substantially straight line, and maintain it as left-handed circularly polarized light LCP, which is the first circularly polarized light. In this case, since imaging system 50 has no power, it becomes possible to observe external light OL.

[0050] In the above description, a display 40 incorporating a transmissive liquid crystal panel 22 was used, but other types of imager 2a, such as an organic EL (organic electroluminescence) display, can also be used instead of the transmissive liquid crystal panel 22. However, it is desirable that the imager 2a of the organic EL display blocks external light OL while an image is being displayed and transmits external light OL while the image display is stopped. In this case, it is desirable to place a polarizing plate 16 (see FIG. 3) on the light emission side of the organic EL display serving as the imager 2a.

[0051] In the above explanation, the transmissive liquid crystal panel 22 has been described as having three color sub-pixels PXs(R), PXs(G), and PXs(B), but if the chromatic aberration of the imaging system 50 is large, the imager 2a or the transmissive liquid crystal panel 22 can be made up of only single-color pixels. Note that if the lateral chromatic aberration of the imaging system 50 is large, the lateral chromatic aberration can be canceled out by adjusting the magnification of the image formed on the sub-pixels PXs(R), PXs(G), and PXs(B), etc.

[0052] The virtual image display device 100A, 100B or optical unit 100 of the first embodiment described above comprises a display 40 that emits image light ML, a first polarized diffractive lens 51 that is arranged opposite the display 40 and has positive power for circularly polarized image light ML, and a second polarized diffractive lens 52 that is arranged opposite the display 40 across the first polarized diffractive lens 51 and has positive power for circularly polarized image light ML that has passed through the first polarized diffractive lens 51.

[0053] In the virtual image display devices 100A and 100B, the first polarizing diffractive lens 51 has a positive power with respect to the circularly polarized image light ML from the display device 40, and the second polarizing diffractive lens 52 has a positive power with respect to the circularly polarized image light ML that has passed through the first polarizing diffractive lens 51. Therefore, even when the display device 40 is placed in front of the eyes, the image formed on the display surface 11d of the display device 40 can be observed by the imaging system 50, which includes the pair of polarizing diffractive lenses 51 and 52 and is thin but has a short focal length. In other words, the virtual image display devices 100A and 100B, including the imaging system 50, can be made thinner.

[0054] The virtual image display devices 100A and 100B of the present embodiment further include a switching half-wave plate 55 disposed between the first polarizing diffractive lens 51 and the second polarizing diffractive lens 52. The switching half-wave plate 55 converts image light ML, which has passed through the first polarizing diffractive lens 51 from right-circularly polarized light (RCP) to left-circularly polarized light (LCP), a second circularly polarized light, back to the first circularly polarized light, i.e., right-circularly polarized light (RCP). The switching half-wave plate 55 switches between an ON state, which is a first state in which the image light ML, which has passed through the first polarizing diffractive lens 51, is converted from left-circularly polarized light (LCP) to right-circularly polarized light (RCP), a second circularly polarized light, and an OFF state, which is a second state in which the image light ML, which has passed through the first polarizing diffractive lens 51, passes through as left-circularly polarized light (LCP), a second circularly polarized light. The display 40 emits the image light ML, which is the first circularly polarized light, when the switching half-wave plate 55 is in the first state, and transmits external light OL when the switching half-wave plate 55 is in the second state. In this case, when the switching half-wave plate 55 is in the first state, the image formed on the display surface 11d of the display device 40 can be observed as a virtual image due to the lens effect of the polarizing diffraction lenses 51 and 52, and when the switching half-wave plate 55 is in the second state, the outside world can be observed with direct vision due to the flat plate effect of the polarizing diffraction lenses 51 and 52. Such virtual image display devices 100A and 100B enable a see-through display in which the image light ML and the outside world light OL are superimposed.

[0055] 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.

[0056] In the virtual image display device 100A, 100B or the optical unit 100 shown in FIG. 10, an external light blocking type light guide member 221 is incorporated into the composite display member 220 of the display device 40. The light guide member 221 has a light blocking film 21c formed on its outer surface 21a, and the transmissive liquid crystal panel 22 does not transmit external light OL. In other words, the second sub-frame Z2, which is the sub-frame for external light observation in FIG. 8, is omitted. As a result, only image light ML is incident on the imaging system 50.

[0057] 5, a non-dynamic half-wave plate 255 that is kept in a constant state is disposed in the imaging system 50, and converts the image light ML that has passed through the first polarizing diffractive lens 51 and become left-handed circularly polarized light LCP into right-handed circularly polarized light RCP. The first polarizing diffractive lens 51 and the second polarizing diffractive lens 52 are polarizing diffractive lenses GP1.

[0058] In this embodiment, the display 40 does not transmit external light OL, so the virtual image display devices 100A and 100B do not perform see-through display, but display only the virtual image formed by the display 40.

[0059] 7 can also be used as the first polarizing diffractive lens 51 and the second polarizing diffractive lens 52 in the imaging system 50. In this case, the polarization state of the image light ML is reversed to that shown in FIG. 10, but it is possible to make the image light ML of collimated right-handed circularly polarized light RCP incident on the pupil position PP.

[0060] In the virtual image display devices 100A and 100B of the present embodiment, the half-wave plate 255 is disposed between the first polarizing diffractive lens 51 and the second polarizing diffractive lens 52, and converts the image light ML, which has passed through the first polarizing diffractive lens 51 from the first circularly polarized light (right circularly polarized RCP) to the second circularly polarized light (left circularly polarized LCP), back to the first circularly polarized light, i.e., right circularly polarized RCP. In this case, the half-wave plate 255 allows the first circularly polarized light, i.e., right circularly polarized RCP, to be incident on the second polarizing diffractive lens 52, and therefore, assuming that the first polarizing diffractive lens 51 and the second polarizing diffractive lens 52 are of the same type that exhibit similar power characteristics for the right circularly polarized RCP, these lenses can be made to function like positive lenses despite their plate shape.

[0061] 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.

[0062] 11, imaging system 50 includes first polarizing diffractive lens 51, second polarizing diffractive lens 352, and switching half-wave plate 55. Polarizing diffractive lens GP1 shown in FIG. 7 is used as first polarizing diffractive lens 51, and polarizing diffractive lens GP2 shown in FIG. 7 is used as second polarizing diffractive lens 352.

[0063] In the imaging system 50, when the image light ML or external light OL incident from the display 40 is right-handed circularly polarized RCP, the first polarizing diffractive lens 51 functions as an optical element having positive power for the image light ML or external light OL, reversing the direction of rotation of the polarization to convert it to left-handed circularly polarized LCP. When the incident image light ML or external light OL is right-handed circularly polarized RCP, the second polarizing diffractive lens 352 functions as an optical element having positive power for the image light ML or external light OL, reversing the direction of rotation of the polarization to convert it to left-handed circularly polarized LCP.

[0064] During the image observation period, the image light ML that has passed through the first polarizing diffractive lens 51 enters the switching half-wave plate 55, which is in the OFF state, is retained as left-handed circularly polarized light (LCP), and then enters the second polarizing diffractive lens 352. The second polarizing diffractive lens 352 functions as an optical element with positive power for the image light ML that has passed through the switching half-wave plate 55 and is left-handed circularly polarized light (LCP), and while converging the image light ML, it reverses the direction of polarization rotation to convert it into right-handed circularly polarized light (RCP). In other words, the imaging system 50 as a whole uses its positive power to converge the image light ML passing through from the display 40 side, maintaining the first circularly polarized light (right-handed circularly polarized light) as the first circularly polarized light (RCP). In this case, since the imaging system 50 has positive power, it is possible to observe the image light ML.

[0065] During the external light observation period, external light OL that has passed through the first polarizing diffractive lens 51 enters the switching half-wave plate 55 in the ON state, is converted from left-handed circularly polarized light LCP to right-handed circularly polarized light RCP, and then enters the second polarizing diffractive lens 352. The second polarizing diffractive lens 352 functions as an optical element having negative power with respect to the right-handed circularly polarized image light ML that has passed through the switching half-wave plate 55. That is, the first polarizing diffractive lens 51 applies a converging action to the external light OL passing through from the display 40 side by using its positive power, converting the first circularly polarized light, right-handed circularly polarized light RCP, into the second circularly polarized light, left-handed circularly polarized light LCP. The second polarizing diffractive lens 352 also converts the first circularly polarized light, right-handed circularly polarized light RCP, into the second circularly polarized light, left-handed circularly polarized light LCP, by using its negative power to offset the convergence of the external light OL that has been emitted from the first polarizing diffractive lens 51, passed through the switching half-wave plate 55, and returned to right-handed circularly polarized light RCP. That is, the imaging system 50 allows the external light OL to travel substantially straight without exerting any imaging action such as focusing on the external light OL, thereby realizing a state in which the external light OL can be observed with the naked eye.

[0066] Fig. 12 is a diagram illustrating modified virtual image display devices 100A and 100B. In this case, in the illustrated display device 40, an external light-blocking type light-guiding member 221 is incorporated into a composite display member 220, as in Fig. 10. Also, in the imaging system 50, the switching half-wave plate 55 shown in Fig. 5 is omitted. Here, the imaging system 50 includes a polarizing diffractive lens GP1 as the first polarizing diffractive lens 51 and a polarizing diffractive lens GP2 as the second polarizing diffractive lens 352. However, when left-handed circularly polarized LCP image light ML is output from the display device 40, the first polarizing diffractive lens 51 is the polarizing diffractive lens GP2, and the second polarizing diffractive lens 352 is the polarizing diffractive lens GP1.

[0067] In this embodiment, the display 40 does not transmit external light OL, so the virtual image display devices 100A and 100B do not perform see-through display, but display only the virtual image formed by the display 40.

[0068] In this embodiment, the imaging system 50 does not have a half-wave plate and is composed only of polarizing diffractive lenses 51 and 352. Here, the distance between the first polarizing diffractive lens 51 and the second polarizing diffractive lens 352 is adjustable, and they can also be placed in close contact.

[0069] [Fourth embodiment] The virtual image display device of the fourth embodiment will be described below. Note that the virtual image display device of the fourth embodiment is a partial modification of the virtual image display device of the second embodiment, and a description of parts common to the virtual image display device of the second embodiment will be omitted.

[0070] FIG. 13 is a side cross-sectional view illustrating virtual image display devices 100A, 100B or optical unit 100 according to a fourth embodiment, and FIG. 14 is a perspective view of optical unit 100. In this embodiment, a third polarizing diffractive lens 53 is disposed in imaging system 50 instead of switching half-wave plate 55 shown in FIGS. 5 and 11. In imaging system 50, polarizing diffractive lens GP1 shown in FIG. 7 is used as first polarizing diffractive lens 51, polarizing diffractive lens GP1 shown in FIG. 7 is used as second polarizing diffractive lens 52, and polarizing diffractive lens GP1 shown in FIG. 7 is used as third polarizing diffractive lens 53. First polarizing diffractive lens 51, third polarizing diffractive lens 53, and second polarizing diffractive lens 52 are disposed separated from one another at a predetermined interval.

[0071] In the imaging system 50, when the image light ML incident from the display 40 is right-handed circularly polarized light RCP, the first polarizing diffractive lens 51 functions as an optical element with positive power for the image light ML, converging the image light ML while reversing the direction of polarization rotation to convert it to left-handed circularly polarized light LCP. Because the image light ML passing through the first polarizing diffractive lens 51 is left-handed circularly polarized light LCP, the third polarizing diffractive lens 53 functions as an optical element with negative power for the image light ML, diverging the image light ML while reversing the direction of polarization rotation to convert it to right-handed circularly polarized light RCP. Because the image light ML passing through the third polarizing diffractive lens 53 is right-handed circularly polarized light RCP, the second polarizing diffractive lens 52 converging the image light ML while reversing the direction of polarization rotation to convert it to left-handed circularly polarized light LCP. In this case, the imaging system 50 functions similarly to a lens system with a negative lens sandwiched between two positive lenses. Here, the power of each of the polarizing diffractive lenses 51, 52, and 53 can be set arbitrarily as long as the combined power of the imaging system 50 is positive.

[0072] Although not shown, when left-handed circularly polarized LCP image light ML is emitted from the display 40, the polarized diffractive lens GP1 shown in Figure 7 can be used as the first polarized diffractive lens 51, the second polarized diffractive lens 52, and the third polarized diffractive lens 53.

[0073] Fig. 15 is a side cross-sectional view illustrating a modified example of the virtual image display devices 100A, 100B or the optical unit 100 shown in Fig. 13, and Fig. 16 is a perspective view of the optical unit 100. In this case, the first polarizing diffractive lens 51, the third polarizing diffractive lens 53, and the second polarizing diffractive lens 52 are bonded together and arranged in close contact with each other.

[0074] Fifth Embodiment Hereinafter, a virtual image display device etc. of the fifth embodiment will be described. Note that the virtual image display device of the fifth embodiment is a partially modified version of the virtual image display device of the fourth embodiment, and a description of parts common to the virtual image display device of the fourth embodiment will be omitted.

[0075] FIG. 17 is a side cross-sectional view illustrating a virtual image display device 100A, 100B or an optical unit 100 according to a fifth embodiment, and FIG. 18 is a perspective view of the optical unit 100. In this embodiment, the imaging system 50 is composed of a first polarizing diffractive lens 51, a third polarizing diffractive lens 53, and a second polarizing diffractive lens 52. The power and distribution of the polarizing diffractive lens 51, the lenses 52, and 53 are appropriately adjusted, so that the chief ray of the image light ML emitted from the display device 40 extends approximately perpendicular to the display surface 11d of the display device 40. In other words, the imaging system 50 is telecentric on the display device 40 side. If the imaging system 50 is telecentric on the display device 40 side, the efficiency of capturing the image light ML from the display device 40 is increased, and color unevenness occurring in the virtual image can be reduced. In other words, the imaging system 50 can display a good virtual image with reduced aberrations.

[0076] [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.

[0077] The display device 40 and the composite display member 20 incorporated therein are not limited to those exemplified in FIG. 3 and the like, and various types of display panels can be used.

[0078] In the virtual image display devices 100A and 100B of FIG. 17, the imaging system 50 is configured with three polarizing diffractive lenses 51 and lenses 52 and 53, but the imaging system 50 can be configured with four or more polarizing diffractive lenses 51.

[0079] 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.

[0080] In a specific embodiment, the virtual image display device comprises a display that emits image light, a first polarized diffractive lens that is arranged opposite the display and has positive power for circularly polarized image light, and a second polarized diffractive lens that is arranged opposite the display across the first polarized diffractive lens and has positive power for circularly polarized image light that enters through the first polarized diffractive lens.

[0081] In the virtual image display device, the first polarizing diffractive lens has a positive power for circularly polarized image light from the display, and the second polarizing diffractive lens has a positive power for circularly polarized image light that has passed through the first polarizing diffractive lens and is incident thereon, so even if the display is placed in front of the eyes, the image formed on the display surface of the display can be observed by an imaging system that includes a pair of polarizing diffractive lenses and is thin but has a short focal length. In other words, the virtual image display device, including the imaging system, can be made thinner.

[0082] In the virtual image display device, the first polarizing diffractive lens and the second polarizing diffractive lens have a refractive index anisotropy distribution formed in a plane, and generate a geometric phase corresponding to the lens shape for predetermined circularly polarized light.

[0083] In a specific aspect, the virtual image display device further includes a wave plate disposed between the first polarizing diffractive lens and the second polarizing diffractive lens, which converts the image light that has passed through the first polarizing diffractive lens from the first circularly polarized light to the second circularly polarized light, back to the first circularly polarized light. In this case, the wave plate allows the first circularly polarized light to be incident on the second polarizing diffractive lens, and therefore, on the assumption that the first polarizing diffractive lens and the second polarizing diffractive lens are of the same type that exhibit similar power characteristics for circularly polarized light, these lenses can be made to function like positive lenses, despite their plate shape.

[0084] In a specific aspect of the virtual image display device, the first polarizing diffractive lens and the second polarizing diffractive lens convert the image light passing through from the display side from right-handed circularly polarized light, which is the first circular polarization, to left-handed circularly polarized light, which is the second circular polarization. In other words, the first polarizing diffractive lens and the second polarizing diffractive lens convert the incident right-handed circularly polarized light into left-handed circularly polarized light and emit it in a relatively converged state.

[0085] In a specific embodiment of the virtual image display device, the first polarizing diffractive lens and the second polarizing diffractive lens convert the image light passing through from the display side from the first circularly polarized light (left-handed circularly polarized light) to the second circularly polarized light (right-handed circularly polarized light). In other words, the first polarizing diffractive lens and the second polarizing diffractive lens convert the incident left-handed circularly polarized light into right-handed circularly polarized light and emit it in a relatively converged state.

[0086] In a specific embodiment of the virtual image display device, the wave plate is a switching half-wave plate that switches between a first state in which the image light that has passed through the first polarizing diffractive lens is converted from the second circularly polarized light back to the first circularly polarized light and a second state in which the image light that has passed through the first polarizing diffractive lens passes through as the second circularly polarized light. The display device outputs the image light that is the first circularly polarized light when the switching half-wave plate is in the first state and transmits external light when the switching half-wave plate is in the second state. In this case, when the switching half-wave plate is in the first state, an image formed on the display surface of the display device can be observed as a virtual image, and when the switching half-wave plate is in the second state, the external world can be observed with direct vision. Such a virtual image display device enables a see-through display in which the image light and external world light are superimposed.

[0087] In a specific aspect of the virtual image display device, the first polarizing diffractive lens converts the image light passing through from the display device side from first circularly polarized light to second circularly polarized light, and the second polarizing diffractive lens converts the image light passing through from the first polarizing diffractive lens side from second circularly polarized light to first circularly polarized light. In this case, assuming that the first polarizing diffractive lens and the second polarizing diffractive lens are of the reverse type that exhibit inverted power characteristics for circularly polarized light, these can be made to function like positive lenses despite their plate shapes.

[0088] In a specific aspect of the virtual image display device, the first polarizing diffractive lens converts the image light passing through from the display device side from right-handed circularly polarized light, which is a first circular polarization, to left-handed circularly polarized light, which is a second circular polarization, and the second polarizing diffractive lens converts the image light passing through from the first polarizing diffractive lens side from left-handed circularly polarized light, which is a second circular polarization, to right-handed circularly polarized light, which is a second circular polarization. In other words, the first polarizing diffractive lens converts incident right-handed circularly polarized light into left-handed circularly polarized light and emits it in a relatively converged state. The second polarizing diffractive lens converts incident left-handed circularly polarized light into right-handed circularly polarized light and emits it in a relatively converged state.

[0089] In a specific embodiment of the virtual image display device, the first polarizing diffractive lens converts the image light passing through from the display side from left circularly polarized light, which is the first circular polarization, to right circularly polarized light, which is the second circular polarization, and the second polarizing diffractive lens converts the image light passing through from the first polarizing diffractive lens side from right circularly polarized light, which is the second circular polarization, to left circularly polarized light, which is the first circular polarization.

[0090] In a specific embodiment of the virtual image display device, the display includes an imager that forms image light, a polarizing plate that converts the image light emitted from the imager into predetermined linearly polarized light, and a quarter-wave plate that converts the predetermined linearly polarized light into predetermined circularly polarized light. In this case, the image light emitted from the display can be circularly polarized.

[0091] In a specific aspect, the virtual image display device further includes a third polarizing diffractive lens that is disposed between the first polarizing diffractive lens and the second polarizing diffractive lens and has negative power with respect to the image light that has passed through the first polarizing diffractive lens and become the second circularly polarized light and then changed from the second circularly polarized light to the first circularly polarized light. In this case, an image formed on the display surface of the display can be observed by an imaging system with a desired focal length achieved by combining the first polarizing diffractive lens, the third polarizing diffractive lens, and the second polarizing diffractive lens.

[0092] In a specific embodiment of the virtual image display device, the chief ray of the image light emitted from the display is perpendicular to the display surface of the display, and in this case, the imaging system can display a good virtual image with reduced aberrations.

[0093] In a specific embodiment of the virtual image display device, the optical elements included in the first polarizing diffractive lens and the second polarizing diffractive lens are integrated together, which stabilizes the optical performance of the imaging system and enables the imaging system to be made thinner.

[0094] In a specific embodiment, the optical unit comprises a display that emits image light, a first polarized diffractive lens that is arranged opposite the display and has positive power for circularly polarized image light, and a second polarized diffractive lens that is arranged opposite the display across the first polarized diffractive lens and has positive power for circularly polarized image light that enters through the first polarized diffractive lens. [Explanation of symbols]

[0095] 2a...imager, 10...light source, 11...light guide plate, 11d...display surface, 12...ferroelectric liquid crystal plate, 14...liquid crystal modulation member, 15, 16...first polarizing plate, 20, 220...composite display member, 21, 221...light guide member, 22...transmissive liquid crystal panel, 23...quarter wave plate, 31...liquid crystal layer, 40...display, 50...imaging system, 51, 151...first polarizing diffractive lens, 52, 152, 352...second polarizing diffractive lens, 53...third polarizing diffractive lens, 55...switching half wave plate, 2 55...half-wave plate, 55a...liquid crystal layer, 55b, 55c...substrate, 81...drive circuit, 90...user terminal, 100...optical unit, 100A, 100B...virtual image display device, 100C...temple, 102a, 102b...display drive unit, 103a, 103b...display optical system, AX...optical axis, EY...eye, GP1, GP2...polarized diffractive lens, IL...illumination light, LCP...left circularly polarized light, RCP...right circularly polarized light, ML...image light, OL...external light, PP...pupil position, PX...pixel, US...wearer

Claims

1. a display that emits image light; a first polarizing diffractive lens disposed opposite the display and having a positive power with respect to the circularly polarized image light; a second polarizing diffractive lens that is disposed opposite the display device across the first polarizing diffractive lens and has a positive power with respect to the circularly polarized image light that is incident through the first polarizing diffractive lens; A virtual image display device comprising:

2. the first polarized diffractive lens and the second polarized diffractive lens have a refractive index anisotropy distribution formed in a plane, and generate a geometric phase corresponding to the lens shape for predetermined circularly polarized light; The virtual image display device according to claim 1 .

3. further comprising a wave plate disposed between the first polarizing diffractive lens and the second polarizing diffractive lens, which converts the image light, which has passed through the first polarizing diffractive lens from a first circularly polarized light to a second circularly polarized light, back to the first circularly polarized light; The virtual image display device according to claim 1 .

4. the first polarized diffractive lens and the second polarized diffractive lens convert the image light passing through from the display device side from the first circularly polarized light, which is right-handed circularly polarized light, to the second circularly polarized light, which is left-handed circularly polarized light. The virtual image display device according to claim 3 .

5. the first polarized diffractive lens and the second polarized diffractive lens convert the image light passing through from the display device side from the first circularly polarized light, which is left-handed circularly polarized light, to the second circularly polarized light, which is right-handed circularly polarized light. The virtual image display device according to claim 3 .

6. the wave plate is a switching half-wave plate that is switched between a first state in which the image light that has passed through the first polarizing diffractive lens is converted from the second circularly polarized light back to the first circularly polarized light, and a second state in which the image light that has passed through the first polarizing diffractive lens is passed as the second circularly polarized light, the display emits the image light that is the first circularly polarized light when the switching half-wave plate is in the first state, and transmits external light when the switching half-wave plate is in the second state; The virtual image display device according to claim 3 .

7. the first polarized diffractive lens converts the image light passing through from the display device side from a first circularly polarized light into a second circularly polarized light; the second polarizing diffractive lens converts the image light passing through from the first polarizing diffractive lens side from the second circularly polarized light to the first circularly polarized light; The virtual image display device according to claim 1 .

8. the first polarized diffractive lens converts the image light passing through from the display device side from the first circularly polarized light, which is right-handed circularly polarized light, to the second circularly polarized light, which is left-handed circularly polarized light; the second polarizing diffractive lens converts the image light passing through from the first polarizing diffractive lens side from the second circularly polarized light (left circularly polarized light) to the first circularly polarized light (right circularly polarized light), The virtual image display device according to claim 7 .

9. the first polarized diffractive lens converts the image light passing through from the display device side from the first circularly polarized light, which is left-handed circularly polarized light, to the second circularly polarized light, which is right-handed circularly polarized light; the second polarizing diffractive lens converts the image light passing through from the first polarizing diffractive lens side from the second circularly polarized light, which is right-handed circularly polarized light, to the first circularly polarized light, which is left-handed circularly polarized light. The virtual image display device according to claim 7 .

10. The display device includes an imager that forms the image light, a polarizing plate that converts the image light emitted from the imager into predetermined linearly polarized light, and a quarter-wave plate that converts the predetermined linearly polarized light into predetermined circularly polarized light. The virtual image display device according to claim 1 .

11. further comprising a third polarizing diffractive lens disposed between the first polarizing diffractive lens and the second polarizing diffractive lens, the third polarizing diffractive lens having a negative power with respect to the image light that has passed through the first polarizing diffractive lens and become the second circularly polarized light and has been changed from the second circularly polarized light to the first circularly polarized light; The virtual image display device according to claim 1 .

12. The virtual image display device according to claim 11 , wherein a chief ray of the image light emitted from the display is perpendicular to a display surface of the display.

13. The optical elements included in the first polarized diffractive lens to the second polarized diffractive lens are integrated. The virtual image display device according to claim 1 .

14. a display that emits image light; a first polarizing diffractive lens disposed opposite the display and having a positive power with respect to the circularly polarized image light; a second polarizing diffractive lens that is disposed opposite the display device across the first polarizing diffractive lens and has a positive power with respect to the circularly polarized image light that is incident through the first polarizing diffractive lens; An optical unit comprising:

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