Retinal projection device

Abstract

The retina projection device comprises: a switching unit capable of switching the optical path of a light beam; a combiner which converts the light beam into parallel light and irradiates the retina of the user; and a notch filter that reflects circularly polarized light of the second polarity by passing circularly polarized light of the first polarity among the light of the red wavelength, and reflects circularly polarized light of the second polarity by passing circularly polarized light of the green wavelength by passing circularly polarized light of the first polarity. Circularly polarized light of the first polarity in the light of the blue wavelength is made to pass through and circularly polarized light of the second polarity is reflected; and a controller that controls the switching unit in accordance with the position of the pupil of the user, the combiner being provided with: a first holographic diffraction layer that diffracts circularly polarized light of a first polarity in a first wavelength range including a red wavelength; a second holographic diffraction layer that diffracts circularly polarized light of a second polarity in a second wavelength range including a green wavelength; and a third holographic diffraction layer that diffracts circularly polarized light of the first polarity in a third wavelength range including a blue wavelength.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application is based on Japanese Patent Application No. 2023-138960, filed on August 29, 2023, and claims the benefit of priority thereto, the contents of which are incorporated herein by reference in their entirety. Technical Field

[0003] The invention relates to a retinal projection device. Background Art

[0004] A retinal projection device that directly projects an image onto the user's retina is known (for example, refer to U.S. Patent Application Publication No. 2019 / 0361250, Japanese Patent Application Publication No. 2021-5072, and International Publication No. 2019 / 146367). Summary of the invention

[0005] In the retinal projection device described in U.S. Patent Application Publication No. 2019 / 0361250, Japanese Patent Application Publication No. 2021-5072, and International Publication No. 2019 / 146367, the image may not be correctly recognized when the user moves his eyes. For example, when a holographic combiner is used as a combiner, in order to expand the eyebox, it is necessary to expand the allowable range of the incident angle of the light beam incident on the holographic combiner. If a broadband element with a large allowable range of the incident angle is used, the allowable range of the wavelength is expanded, and therefore, stray light caused by chromatic aberration may be generated.

[0006] The present invention describes a retinal projection device capable of reducing stray light caused by chromatic aberration.

[0007] A retinal projection device according to one aspect of the present invention comprises: a projector module including a laser module, a collimating lens and a movable mirror, wherein the laser module emits a laser including a red component having a red wavelength, a green component having a green wavelength and a blue component having a blue wavelength, the collimating lens converts the laser into a parallel light beam, and the movable mirror is used for scanning using the light beam; a switching unit capable of switching the optical path of the light beam; a combiner, which converts the light beam into parallel light and irradiates the light beam to the user's retina; a notch filter, which is arranged between the projector module and the combiner, allows circularly polarized light of a first polarity in light of a red wavelength to pass through and reflects circularly polarized light of a second polarity different from the first polarity, allows circularly polarized light of a second polarity in light of a green wavelength to pass through and reflects the circularly polarized light of the first polarity, and allows circularly polarized light of a first polarity in light of a blue wavelength to pass through and reflects the circularly polarized light of the second polarity; and a controller, which controls the switching unit in a manner that the light beam passes through the pupil according to the position of the user's pupil. The combiner comprises: a first holographic diffraction layer, which diffracts circularly polarized light of a first polarity within a first wavelength range including red wavelengths; a second holographic diffraction layer, which diffracts circularly polarized light of a second polarity within a second wavelength range including green wavelengths; and a third holographic diffraction layer, which diffracts circularly polarized light of a first polarity within a third wavelength range including blue wavelengths.

[0008] In the retinal projection device, circular polarization light of the first polarity is extracted from light of red wavelength, circular polarization light of the second polarity is extracted from light of green wavelength, and circular polarization light of the first polarity is extracted from light of blue wavelength by a notch filter provided between the projector module and the combiner, and circular polarization light of the first polarity having a red wavelength, circular polarization light of the second polarity having a green wavelength, and circular polarization light of the first polarity having a blue wavelength are incident on the combiner. Since the first holographic diffraction layer scatters the circular polarization light of the first polarity, even if the permissible wavelength range of the first holographic diffraction layer is expanded, circular polarization light of the second polarity having a green wavelength close to the red wavelength is not easily scattered. Similarly, since the second holographic diffraction layer scatters the circular polarization light of the second polarity, even if the permissible wavelength range of the second holographic diffraction layer is expanded, circular polarization light of the first polarity having a red wavelength close to the green wavelength and circular polarization light of the first polarity having a blue wavelength close to the green wavelength are not easily scattered. Similarly, since the third holographic diffraction layer scatters the circularly polarized light of the first polarity, even if the permissible wavelength range of the third holographic diffraction layer is expanded, the circularly polarized light of the second polarity having a green wavelength close to the blue wavelength is not easily scattered. As a result, stray light caused by chromatic aberration can be reduced.

[0009] In some embodiments, the first holographic diffraction layer may also be composed of a cholesteric liquid crystal polymer layer having a spiral structure, the spiral structure having a spiral pitch corresponding to a red wavelength and twisted in a twisting direction reflecting circularly polarized light of a first polarity. The second holographic diffraction layer may also be composed of a cholesteric liquid crystal polymer layer having a spiral structure, the spiral structure having a spiral pitch corresponding to a green wavelength and twisted in a twisting direction reflecting circularly polarized light of a second polarity. The third holographic diffraction layer may also be composed of a cholesteric liquid crystal polymer layer having a spiral structure, the spiral structure having a spiral pitch corresponding to a blue wavelength and twisted in a twisting direction reflecting circularly polarized light of a first polarity.

[0010] If the torsion direction of the torsion structure of the electric field vector generated by the rotation of the electric field vector of the circularly polarized light at a certain moment and with the traveling direction of the light as the axis is consistent with the torsion direction of the torsion structure of the orientation direction of the liquid crystal molecules of the cholesteric liquid crystal polymer layer, and the incident light satisfies a certain condition, Bragg reflection is caused and the incident light is diffracted and reflected. On the other hand, if the above-mentioned torsion directions are opposite to each other, Bragg reflection is not caused and the incident light is transmitted. The first holographic diffraction layer is configured to reflect circularly polarized light of the first polarity of the red wavelength, the second holographic diffraction layer is configured to reflect circularly polarized light of the second polarity of the green wavelength, and the third holographic diffraction layer is configured to reflect circularly polarized light of the first polarity of the blue wavelength. Therefore, the above-mentioned function of the combiner can be realized.

[0011] In some embodiments, the notch filter may also include: a first filter, which is composed of a first cholesteric liquid crystal polymer layer having a spiral structure, the spiral structure having a spiral pitch corresponding to the red wavelength and twisted in a twisting direction that reflects the circularly polarized light of the second polarity; a second filter, which is composed of a second cholesteric liquid crystal polymer layer having a spiral structure, the spiral structure having a spiral pitch corresponding to the green wavelength and twisted in a twisting direction that reflects the circularly polarized light of the first polarity; a third filter, which is composed of a third cholesteric liquid crystal polymer layer having a spiral structure, the spiral structure having a spiral pitch corresponding to the blue wavelength and twisted in a twisting direction that reflects the circularly polarized light of the second polarity.

[0012] If the torsion direction of the torsion structure of the electric field vector generated by the rotation of the electric field vector of the circularly polarized light at a certain moment and with the direction of travel of the light as the axis is consistent with the torsion direction of the torsion structure of the orientation direction of the liquid crystal molecules of the cholesteric liquid crystal polymer layer, and the incident light satisfies a certain condition, Bragg reflection is caused and the incident light is diffracted and reflected. On the other hand, if the above-mentioned torsion directions are opposite to each other, Bragg reflection is not caused and the incident light is transmitted. The first filter is configured to reflect circularly polarized light of the second polarity from light of a red wavelength, the second filter is configured to reflect circularly polarized light of the first polarity from light of a green wavelength, and the third filter is configured to reflect circularly polarized light of the second polarity from light of a blue wavelength. Therefore, it is possible to extract circularly polarized light of the first polarity of a red wavelength, circularly polarized light of the second polarity of a green wavelength, and circularly polarized light of the first polarity of a blue wavelength, and to realize the above-mentioned function of the notch filter.

[0013] In some embodiments, the retinal projection device may further include an extinction filter that attenuates the light reflected by the notch filter. In this case, since the light reflected by the notch filter is attenuated by the extinction filter, stray light can be further reduced.

[0014] In some embodiments, the retinal projection device may also include a projection lens that focuses the light beam emitted from the projector module on a focus position. The switching unit may also be configured to overlap with the focus position and include a deflection element that changes the direction of travel of the light beam. In this case, because the deflection element that changes the direction of travel of the light beam is configured near the focus position, the spherical aberration caused by changing the direction of travel (deflection) of the light beam is reduced. Therefore, the quality of the image on the retina is maintained, so the user can correctly recognize the image.

[0015] In some embodiments, the retinal projection device may also include a first wavelength plate, which is arranged between the laser module and the deflection element to convert linear polarized light into circularly polarized light. The deflection element may also include: one or more second wavelength plates, which can switch between a state of preserving the polarization state of circularly polarized light and a state of converting circularly polarized light into circularly polarized light of opposite polarity according to an applied voltage; one or more Pancharatnam-Berry phase optical elements, which convert circularly polarized light into circularly polarized light of opposite polarity and diffract the circularly polarized light along a diffraction direction corresponding to the polarity of the incident circularly polarized light. One or more second wavelength plates and one or more Pancharatnam-Berry phase optical elements may also be arranged alternately one by one.

[0016] According to this structure, by switching the second wavelength plate between a state in which the polarization state of the circularly polarized light is preserved and a state in which the circularly polarized light is converted into a circularly polarized light of opposite polarity, the polarity (polarization state) of the circularly polarized light passing through the second wavelength plate can be switched. The diffraction direction in the Pancharatnam-Berry phase optical element disposed at the rear stage of the second wavelength plate is determined according to the polarity of the circularly polarized light. Therefore, the traveling direction of the light beam can be changed by applying a voltage to the second wavelength plate.

[0017] In several embodiments, one or more Pancharatnam-Berry phase optical elements may also be formed from liquid crystal polymers or metasurfaces. By using liquid crystal polymers or metasurfaces, Pancharatnam-Berry phase optical elements can be easily formed.

[0018] In some embodiments, the second wavelength plate may also include a pair of transparent electrodes and a liquid crystal layer disposed between the pair of transparent electrodes. In this case, by applying a voltage between the pair of transparent electrodes, an electric field is generated in the liquid crystal layer, and the liquid crystal molecules contained in the liquid crystal layer are oriented along the direction of the electric field. Therefore, in a state where a voltage is applied between the pair of transparent electrodes, the second wavelength plate preserves the polarization state of the circularly polarized light passing through the second wavelength plate. In a state where no voltage is applied between the pair of transparent electrodes, the liquid crystal molecules contained in the liquid crystal layer are in an in-plane oriented state. At this time, the second wavelength plate converts the circularly polarized light passing through the second wavelength plate into circularly polarized light of the opposite polarity. In this way, it is possible to switch between a state of preserving the polarization state of the circularly polarized light and a state of converting the circularly polarized light into circularly polarized light of the opposite polarity, depending on the presence or absence of a voltage applied between the pair of transparent electrodes.

[0019] In some embodiments, the retinal projection device may also include a focusing unit, which is arranged between the switching unit and the combiner to focus the light beam. In this case, the switching unit can be arranged at a position separated from the combiner. Therefore, the degree of freedom of the configuration of the switching unit can be increased.

[0020] In some embodiments, the retinal projection device may further include a wavefront correction unit that corrects the aberration of the wavefront of the light beam that passes through the pupil among the light beams constituting the light beam. In this case, the resolution at the center of the field of view can be improved.

[0021] In some embodiments, the wavefront correction unit may be formed by any one of LCOS, a liquid crystal lens, and a variable shape mirror. By using any of these devices, the wavefront correction unit can be easily realized.

[0022] According to various aspects and embodiments of the present invention, stray light caused by chromatic aberration can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a diagram schematically showing the structure of a retinal projection device according to one embodiment.

[0024] Figure 2 It is a rough representation Figure 1 A diagram of the structure of the deflection element is shown.

[0025] Figure 3 It is a rough representation Figure 2 Figure 2 shows the structure of the wave plate.

[0026] Figure 4 It is a rough representation Figure 2 Figure 2 shows the structure of the Pancharatnam-Berry phase optical element.

[0027] Figure 5 It is along Figure 4 Cross-sectional view of the V-V line.

[0028] Figure 6 It is used for Figure 2 A diagram illustrating the operation of the deflection element shown.

[0029] Figure 7 It is used for Figure 2 A diagram illustrating the operation of the deflection element shown.

[0030] Figure 8 It is used for Figure 2 A diagram illustrating the operation of the deflection element shown.

[0031] Fig. 9 It is used for Figure 2 A diagram illustrating the operation of the deflection element shown.

[0032] Fig.10 It is a rough representation Figure 1 Figure 2 shows the structure of the notch filter.

[0033] Fig.11 It is used for Figure 1 The diagram shows the principle of the notch filter.

[0034] Fig.12 It is used for Figure 1 The diagram shows the principle of the notch filter.

[0035] Fig.13 It is used for Figure 1 A diagram illustrating the principle of a reflector shown.

[0036] Fig.14 It is used for Figure 1A diagram illustrating the principle of a reflector shown.

[0037] Fig.15 This is a diagram schematically showing the structure of a retinal projection device according to another embodiment.

[0038] Fig.16 This is a diagram schematically showing the structure of a retinal projection device according to still another embodiment. DETAILED DESCRIPTION

[0039] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, the same elements are marked with the same symbols in the description of the accompanying drawings, and repeated descriptions are omitted. In each figure, an XYZ coordinate system is sometimes shown. The Y-axis direction is a direction that intersects (e.g., is orthogonal to) the X-axis direction and the Z-axis direction. The Z-axis direction is a direction that intersects (e.g., is orthogonal to) the X-axis direction and the Y-axis direction.

[0040] Reference Figure 1 , a retinal projection device according to one embodiment is described. Figure 1 This is a diagram schematically showing the structure of a retinal projection device according to one embodiment. Figure 1 The retinal projection device 1 shown is a device that directly projects (draws) an image onto the user's retina. The retinal projection device 1 is, for example, mounted on a near-eye wearable device. As examples of near-eye wearable devices, smart glasses such as AR (Augmented Reality) glasses, VR (Virtual Reality) glasses, and MR (Mixed Reality) glasses can be cited. The retinal projection device 1 includes a projector module 2, a projection lens 3, an optical unit 4 (switching unit), a combiner 5, a relay lens 6 (focusing unit), a wavefront correction lens 7 (wavefront correction unit), an extraction unit 8, a wavelength plate 9 (first wavelength plate), and a controller 10.

[0041] The projector module 2 is a module that performs scanning using a light beam and includes a laser module 21, a collimator lens 22, a movable mirror 23, and a wavefront correction lens 24 (wavefront correction unit).

[0042] The laser module 21 emits laser light of a color and intensity corresponding to the pixel of the image projected onto the retina. As the laser module 21, for example, a full-color laser module is used. In this case, the laser module 21 includes a red laser diode, a green laser diode, a blue laser diode, and a combiner that combines the laser light emitted from each laser diode into one laser light. As the combiner, for example, a planar lightwave circuit (PLC) is used. The laser module 21 emits a laser light obtained by combining a red laser light having a red wavelength, a green laser light having a green wavelength, and a blue laser light having a blue wavelength. In other words, the laser module 21 emits a laser light including a red component having a red wavelength, a green component having a green wavelength, and a blue component having a blue wavelength.

[0043] The collimator lens 22 is an optical element that converts the laser light emitted from the laser module 21 into a parallel light beam. The movable mirror 23 is a component for performing scanning based on the light beam converted by the collimator lens 22. The movable mirror 23 is provided in the emission direction of the light beam converted by the collimator lens 22. As the movable mirror 23, for example, a MEMS (Micro Electro Mechanical Systems) mirror is used.

[0044] The wavefront correction lens 24 is a lens that corrects the aberration of the wavefront of the light beam that passes through the pupil PP (equivalent to the light beam at the center of the field of view) among the light beams constituting the light beam. The wavefront correction lens 24 corrects the aberration three times or more, for example. The wavefront correction lens 24 is disposed between the collimating lens 22 and the movable mirror 23. The wavefront correction lens 24 is disposed, for example, in front of the movable mirror 23. The wavefront correction lens 24 is composed of a liquid crystal lens.

[0045] In the wavefront correction lens 24, the area through which the light corresponding to the center of the visual field when the pupil PP is located at a certain position passes is close to the area through which the light corresponding to the center of the visual field when the pupil PP is located at another position passes. Therefore, the wavefront correction lens 24 adaptively corrects the aberration of the wavefront according to the position of the pupil PP. Specifically, the controller 10 controls the wavefront correction lens 24 according to the position of the user's pupil PP so that the wavefront error of the light beam constituting the pixels on the line of sight, that is, in the direction of the gaze point, among the light beams passing through the pupil PP is minimized.

[0046] Furthermore, the projector module 2 further includes a laser driver (not shown) that drives the laser module 21 , and a mirror driver (not shown) that drives the movable mirror 23 .

[0047] The projection lens 3 is an optical element that focuses the light beam emitted from the projector module 2 at a focus position P. The focus position P refers to the position where the light beam is focused on a cross section including the central axis of the light beam. When the light beam is focused on one point, the focus position P is an intermediate imaging plane. Here, for the sake of simplicity, the case where the focus position P is an intermediate imaging plane is exemplified.

[0048] The wavelength plate 9 is an optical element that converts linear polarization into circular polarization. Since the laser module 21 generally emits linear polarization, it is necessary to convert the linear polarization into circular polarization until the light reaches the Pancharatnam-Berry phase optical element 44 (described below) in the optical unit 4. Therefore, the wavelength plate 9 is arranged between the laser module 21 and the optical unit 4. The wavelength plate 9 can also be arranged, for example, immediately after the collimating lens 22. In the case where an element based on the action under linear polarization is provided between the laser module 21 and the optical unit 4, the wavelength plate 9 is provided at a later stage than the element based on the action under the linear polarization. As the wavelength plate 9, a true 1 / 4 wavelength plate is used in consideration of wavelength dispersion, etc., but a 1 / 4+N (N is a natural number) wavelength plate can also be used.

[0049] The optical unit 4 is a unit capable of switching the optical path of the light beam. In the present embodiment, the optical unit 4 is a unit for changing the traveling direction of the light beam according to the position of the pupil PP of the user. The position of the pupil PP is the position of the pupil PP in the eyeball E, and can also be expressed as the direction of the pupil PP or the direction of the line of sight. The optical unit 4 is configured to overlap with the focus position P. The optical unit 4 includes a deflection element 41. The deflection element 41 is an optical element that changes the traveling direction of the light beam. The details of the deflection element 41 will be described later.

[0050] The optical unit 4 further includes a field lens 46. The field lens 46 is a lens that changes the traveling direction of the light beam near the focal point of the light beam. The field lens 46 is provided to cover a second end 42b (output end) of the array body 42 described below.

[0051] The combiner 5 is an optical element that converts a light beam into parallel light and irradiates the light beam to the user's retina. The combiner 5 is a holographic combiner. In the present embodiment, the combiner 5 has the following functions: scattering left circularly polarized light (circularly polarized light of the first polarity) in a wavelength range (first wavelength range) including red wavelengths, scattering right circularly polarized light (circularly polarized light of the second polarity) in a wavelength range (second wavelength range) including green wavelengths, and scattering left circularly polarized light in a wavelength range (third wavelength range) including blue wavelengths. The combiner 5 includes a transparent substrate 51 and a reflector 53.

[0052] The transparent substrate 51 is a substrate having visible light transmittance for transmitting visible light. Examples of the constituent material of the transparent substrate 51 include SiO 2, optical glass, and optical plastic. The transparent substrate 51 has a surface 51a facing the eyeball E of the user who wears the near-eye wearable device. The transparent substrate 51 may also be a lens of the near-eye wearable device (smart glasses).

[0053] The reflector 53 is provided on the surface 51a and functions as a semi-transparent concave mirror. The reflector 53 includes a hologram diffraction layer 54 (third hologram diffraction layer), a hologram diffraction layer 55 (second hologram diffraction layer), and a hologram diffraction layer 56 (first hologram diffraction layer).

[0054] The holographic diffraction layer 54 is a reflective diffraction grating layer that scatters (reflects) left circularly polarized light in a wavelength range including a blue wavelength. The holographic diffraction layer 54 does not scatter right circularly polarized light in the above wavelength range. The holographic diffraction layer 54 is composed of a cholesteric liquid crystal polymer layer having a helical structure having a helical pitch corresponding to the blue wavelength and twisted in a twisting direction for reflecting left circularly polarized light.

[0055] The holographic diffraction layer 55 is a reflective diffraction grating layer that scatters (reflects) right circularly polarized light in a wavelength range including a green wavelength. The holographic diffraction layer 55 does not scatter left circularly polarized light in the above wavelength range. The holographic diffraction layer 55 is composed of a cholesteric liquid crystal polymer layer having a helical structure having a helical pitch corresponding to the green wavelength and twisted in a twisting direction for reflecting right circularly polarized light.

[0056] The holographic diffraction layer 56 is a reflective diffraction grating layer that scatters (reflects) left circularly polarized light in a wavelength range including a red wavelength. The holographic diffraction layer 56 does not scatter right circularly polarized light in the above wavelength range. The holographic diffraction layer 56 is composed of a cholesteric liquid crystal polymer layer having a helical structure having a helical pitch corresponding to the red wavelength and twisted in a twisting direction for reflecting left circularly polarized light.

[0057] The holographic diffraction layer 54, the holographic diffraction layer 55, and the holographic diffraction layer 56 are sequentially stacked on the surface 51a. Specifically, the holographic diffraction layer 54 is provided on the surface 51a. The holographic diffraction layer 55 is stacked on the holographic diffraction layer 54. The holographic diffraction layer 56 is stacked on the holographic diffraction layer 55. In addition, the stacking order of the holographic diffraction layer 54, the holographic diffraction layer 55, and the holographic diffraction layer 56 can also be switched arbitrarily.

[0058] The relay lens 6 is a lens that focuses the light beam emitted from the optical unit 4. The relay lens 6 is provided between the optical unit 4 and the combiner 5. The relay lens 6 is composed of a convex lens or a lens group that functions as a convex lens.

[0059] The wavefront correction lens 7 is a lens that mainly corrects the viewing angle dependency of the focus of the light beam, that is, the viewing angle dependency of the visibility in the retina, and the change caused by the switching of the deflection element 41. The wavefront correction lens 7 is arranged between the projection lens 3 and the optical unit 4. The wavefront correction lens 7 is, for example, arranged immediately after the projection lens 3. The wavefront correction lens 7 may also be arranged before the projection lens 3. The wavefront correction lens 7 is composed of, for example, a liquid crystal lens.

[0060] The extraction unit 8 is a unit for extracting desired circularly polarized light components from light of a red wavelength (hereinafter, sometimes referred to as "red light Lr"), light of a green wavelength (hereinafter, sometimes referred to as "green light Lg"), and light of a blue wavelength (hereinafter, sometimes referred to as "blue light Lb"), respectively. The extraction unit 8 includes an extinction filter 81, a wavelength plate 82, and a notch filter 83.

[0061] The extinction filter 81 is a filter for attenuating the light reflected by the notch filter 83. The extinction filter 81 can reduce stray light. The wavelength plate 82 is an optical element that switches the polarization state of the light beam emitted from the optical unit 4 from circular polarization to linear polarization. The wavelength plate 82 is, for example, a 1 / 4 wavelength plate. Instead of the wavelength plate 82, an absorption type linear polarizer can be used.

[0062] The notch filter 83 is a circularly polarized light dependent notch filter, and is a filter for removing unnecessary circularly polarized light components from the red light Lr, the green light Lg, and the blue light Lb, and extracting desired circularly polarized light components. The notch filter 83 has the following functions: passing the left circularly polarized light in the red light Lr and reflecting the right circularly polarized light, passing the right circularly polarized light in the green light Lg and reflecting the left circularly polarized light, and passing the left circularly polarized light in the blue light Lb and reflecting the right circularly polarized light. The details of the notch filter 83 will be described later.

[0063] The controller 10 is a device that performs overall control of the retinal projection device 1. The controller 10 adjusts the traveling direction of the light beam based on the deflection element 41 according to the position of the user's pupil PP. The controller 10 adjusts the traveling direction of the light beam by, for example, changing the voltage applied to the deflection element 41. The retinal projection device 1 may further include a detection unit (not shown) that detects the position of the pupil PP.

[0064] Next, refer to Figure 2 to Figure 5 , the details of the deflection element 41 are described. Figure 2 It is a rough representation Figure 1 A diagram of the structure of the deflection element is shown. Figure 3 It is a rough representation Figure 2 Figure 2 shows the structure of the wave plate. Figure 4 It is a rough representation Figure 2The diagram shows the structure of the Pancharatnam-Berry phase optical element (hereinafter sometimes referred to as "PBOE"). Figure 5 It is along Figure 4 Cross-sectional view of the V-V line.

[0065] like Figure 2 As shown, the deflection element 41 is a transmissive deflection element, and includes one or more wavelength plates 43 (second wavelength plates) and one or more PBOEs 44. The number of wavelength plates 43 included in the deflection element 41 is the same as the number of PBOEs 44 included in the deflection element 41.

[0066] The wavelength plate 43 is an optical element that can switch between a state of preserving (maintaining) the polarization state (polarity) of the circularly polarized light passing through the wavelength plate 43 and a state of converting the circularly polarized light passing through the wavelength plate 43 into circularly polarized light of opposite polarity, according to a voltage applied to the wavelength plate 43. The wavelength plate 43 has, for example, a rectangular plate shape. Figure 3 As shown, the wavelength plate 43 includes a transparent substrate 431 , a transparent substrate 432 , a transparent electrode 433 , a transparent electrode 434 , an alignment layer 435 , an alignment layer 436 , and a liquid crystal layer 437 .

[0067] The transparent substrate 431 and the transparent substrate 432 are each a substrate having visible light transmittance for transmitting visible light. The transparent substrate 431 and the transparent substrate 432 are made of a constituent material with low birefringence. Examples of constituent materials of the transparent substrate 431 and the transparent substrate 432 include SiO 2 , optical glass, and glass substrate for liquid crystal display. Transparent substrate 431 and transparent substrate 432 are separated from each other in the Z-axis direction and are arranged substantially in parallel. Transparent substrate 431 has a surface 431a and a surface 431b that intersect (here, are orthogonal) with the Z-axis direction. Transparent substrate 432 has a surface 432a and a surface 432b that intersect (here, are orthogonal) with the Z-axis direction. Surface 431a and surface 432a are opposite to each other in the Z-axis direction. Surface 431b is a surface on the opposite side of surface 431a. Surface 432b is a surface on the opposite side of surface 432a.

[0068] The transparent electrode 433 and the transparent electrode 434 (a pair of transparent electrodes) are electrodes that are conductive and have visible light transmittance for transmitting visible light. As an example of the constituent material of the transparent electrode 433 and the transparent electrode 434, ITO (Indium Tin Oxide) can be cited. The transparent electrode 433 and the transparent electrode 434 are opposite to each other in the Z-axis direction with the liquid crystal layer 437 interposed therebetween. The transparent electrode 433 is provided on the surface 431a. The transparent electrode 434 is provided on the surface 432a. A voltage is applied to the transparent electrode 433 and the transparent electrode 434.

[0069] The orientation layer 435 and the orientation layer 436 are layers for controlling the arrangement state (orientation) of the liquid crystal molecules Lm1 contained in the liquid crystal layer 437. The constituent materials of the orientation layer 435 and the orientation layer 436 are obtained, for example, by rubbing a polyimide layer in one direction. As the constituent material, a material obtained by coating a material whose molecular orientation changes due to irradiation with polarized light, coating a polymerizable liquid crystal layer thereon in a state where the molecules are arranged by irradiation with polarized light, aligning it, and then polymerizing it, and fixing the orientation of the liquid crystal molecules can be used. As the constituent material, a material obtained by coating a polymerizable material whose molecular orientation changes due to irradiation with polarized light, aligning the molecules by irradiation with polarized light, and then polymerizing it can be used. As for the orientation of the material whose molecular orientation changes due to irradiation with polarized light, after orientation, the orientation gradually deteriorates even at room temperature, and therefore, in most cases, it is necessary to fix the orientation by some method. Generally speaking, most orientation layers have birefringence, and in this case, a layer is added to compensate for it appropriately. The alignment layer 435 is provided on the surface of the transparent electrode 433 that faces the transparent electrode 434 . The alignment layer 436 is provided on the surface of the transparent electrode 434 that faces the transparent electrode 433 .

[0070] The liquid crystal layer 437 is provided between the alignment layer 435 and the alignment layer 436. In other words, the liquid crystal layer 437 is provided between the transparent electrode 433 and the transparent electrode 434. Nematic liquid crystal can be cited as an example of a constituent material of the liquid crystal layer 437. The optical characteristics of the liquid crystal layer 437 change by controlling the alignment of the liquid crystal molecules Lm1 according to the electric field applied to the liquid crystal layer 437.

[0071] In the wavelength plate 43, the light beam is incident on the transparent substrate 431 from the surface 431b, passes through the transparent substrate 431, the transparent electrode 433, the alignment layer 435, the liquid crystal layer 437, the alignment layer 436, the transparent electrode 434, and the transparent substrate 432 in sequence, and is emitted from the surface 432b.

[0072] Since the liquid crystal material is in contact with the alignment layer 435 and the alignment layer 436, the liquid crystal molecule Lm1 is in an in-plane alignment state when no voltage is applied between the transparent electrode 433 and the transparent electrode 434 (voltage non-applied state). That is, the slow axis of the liquid crystal molecule Lm1 is substantially parallel to the plane of the alignment layer 435 and the alignment layer 436 in contact with the liquid crystal layer 437. At this time, the length (thickness) of the liquid crystal layer 437 in the Z-axis direction is adjusted so that the wavelength plate 43 functions as a 1 / 2 wavelength plate (that is, the circularly polarized light passing through the wavelength plate 43 is converted into circularly polarized light of the opposite polarity).

[0073] By applying a voltage between the transparent electrode 433 and the transparent electrode 434, an electric field in the Z-axis direction is generated in the liquid crystal layer 437, and the liquid crystal molecules Lm1 are aligned in the Z-axis direction. That is, the slow axis of the liquid crystal molecule Lm1 is substantially perpendicular to the planes of the alignment layer 435 and the alignment layer 436 in contact with the liquid crystal layer 437. Therefore, in a state where a voltage is applied between the transparent electrode 433 and the transparent electrode 434 (voltage applied state), the wavelength plate 43 retains the polarization state of the circularly polarized light passing through the wavelength plate 43.

[0074] The PBOE 44 is an optical element that converts circularly polarized light passing through the PBOE 44 into circularly polarized light of opposite polarity and diffracts the circularly polarized light in a diffraction direction corresponding to the polarity of the circularly polarized light incident on the PBOE 44. The PBOE 44 has, for example, a rectangular plate shape. Figure 4 and Figure 5 As shown, the PBOE 44 includes a transparent substrate 441, an alignment layer 442, and a liquid crystal layer 443 (liquid crystal polymer).

[0075] The transparent substrate 441 is a substrate having visible light transmittance for transmitting visible light. The transparent substrate 441 is made of a constituent material having low birefringence as well as surface precision. Examples of constituent materials of the transparent substrate 441 include SiO 2 , optical glass, and a glass substrate for a liquid crystal display. The transparent substrate 441 has a surface 441a and a surface 441b that intersect (orthogonally intersect) the Z-axis direction.

[0076] The orientation layer 442 is a layer for controlling the arrangement state (orientation) of the liquid crystal molecules Lm2 contained in the liquid crystal layer 443. The orientation layer 442 is provided on the surface 441a. As an example of the constituent material of the orientation layer 442, there can be cited a material whose molecular orientation changes due to the irradiation of polarized light. As described later, the orientation layer 442 is configured so that the orientation of the liquid crystal molecules Lm2 contained in the liquid crystal layer 443 changes at a constant period. The orientation layer 442 can be obtained, for example, by coating a material whose molecular orientation changes in a direction orthogonal to the vibration direction of the electric field based on the polarized light due to the irradiation of linearly polarized light, and then exposing it to the desired interference electric field of circularly polarized light whose electric fields rotate in opposite directions on the surface.

[0077] The liquid crystal layer 443 is provided on the alignment layer 442. Examples of the constituent material of the liquid crystal layer 443 include nematic liquid crystal and cholesteric liquid crystal. The liquid crystal layer 443 is composed of a liquid crystal polymer obtained by aligning liquid crystal molecules using liquid crystal molecules capable of photopolymerization and then polymerizing them. Details of the manufacturing method of the PBOE 44 will be described later.

[0078] The plurality of liquid crystal molecules Lm2 included in the liquid crystal layer 443 are arranged three-dimensionally in the X-axis direction, the Y-axis direction, and the Z-axis direction. In the X-axis direction, for example, the plurality of liquid crystal molecules Lm2 are arranged in such a manner that the angle (orientation angle) formed by the lag axis of the liquid crystal molecule Lm2 and the X-axis direction gradually increases or decreases. Specifically, in the X-axis direction, within a range equivalent to the period T of the diffraction grating, the plurality of liquid crystal molecules Lm2 are arranged in such a manner that the orientation angle gradually increases from 0 degrees to 180 degrees. In the Y-axis direction and the Z-axis direction, the plurality of liquid crystal molecules Lm2 are arranged in such a manner that the orientation angles of the liquid crystal molecules Lm2 are the same. Since the phase changes by -360 degrees, i.e., 1 wavelength, due to a rotation of the orientation angle of 180 degrees, the rotation of the orientation angle by 180 degrees is equivalent to the amount of 1 period T of the diffraction grating.

[0079] Through the above structure, PBOE44 acts as a diffraction grating that diffracts circularly polarized light at a constant diffraction angle. For example, circularly polarized light is incident on the transparent substrate 441 from the surface 441b, and passes through the transparent substrate 441, the orientation layer 442 and the liquid crystal layer 443 in sequence. At this time, the circularly polarized light gradually changes to the circularly polarized light of the opposite polarity through the birefringence of the liquid crystal molecule Lm2 contained in the liquid crystal layer 443. At this time, the relative phase of the circularly polarized light of the opposite polarity relative to the incident circularly polarized light changes according to the orientation angle of the liquid crystal molecule Lm2, and the amount of change is equal to -2 times the amount of change in the orientation angle of the liquid crystal molecule Lm2 (where the rotation direction of the electric field vector of the incident circularly polarized light is considered to be positive). However, the orientation angle and the phase angle are considered in radians. As a result, the circularly polarized light of the opposite polarity can have a phase difference that depends on the passing position. That is, because the slope of the wavefront can be generated, PBOE44 acts as a diffraction grating. In addition, the diffraction directions of the left circularly polarized light and the right circularly polarized light are opposite to each other. When the deflection element 41 includes a plurality of PBOEs 44 , the diffraction angles of the PBOEs 44 may be different from each other.

[0080] The length (thickness) of the liquid crystal layer 443 in the Z-axis direction is set so that the phase difference based on the birefringence of the liquid crystal becomes 180 degrees. That is, the thickness of the liquid crystal layer 443 is set so that the PBOE44 functions as a 1 / 2 wavelength plate whose lag axis changes in the in-plane direction. As a result, the diffraction efficiency reaches nearly 100%. In this case, zero-order (straight light) is not generated. In the PBOE44, higher-order diffracted light of the second order or higher is not generated.

[0081] The array body 42 is formed by arranging the wavelength plates 43 and the PBOE 44 alternately one by one in the Z-axis direction. The array body 42 has two ends in the Z-axis direction, namely, a first end 42a and a second end 42b. The wavelength plate 43 is arranged at the first end 42a, and the PBOE 44 is arranged at the second end 42b. When the deflection element 41 is arranged near the intermediate imaging plane, the PBOE 44 near the intermediate imaging plane among the PBOE 44 included in the deflection element 41 can also be configured to have the function of a field lens.

[0082] Next, refer to Figure 6 to Figure 9 , the beam steering (beam deflection) performed by the deflection element 41 is described. Figure 6 to Figure 9 It is used for Figure 2 Here, for the sake of convenience, the deflection element 41 includes two wavelength plates 43 and two PBOEs 44, and the left circularly polarized light beam Bin is incident on the deflection element 41. With respect to the incident direction of the light beam Bin, the left side (at Figure 6 to Figure 9 The diffraction angle (in the center is the upper side of the paper) is set to a positive value.

[0083] In the following description, it is assumed that the diffraction angle of PBOE44 does not depend on the incident angle to PBOE44. This assumption is established as a good approximation when the diffraction angle of PBOE44 is small. In fact, in PBOE44, the in-plane direction component of the wave number vector of the incident light due to diffraction changes with the inherent wave number vector of the in-plane direction determined by the orientation pattern of the liquid crystal layer 443 of PBOE44, and this change does not depend on the incident angle. Therefore, the additivity of the diffraction of PBOE44 mentioned above is not strictly about the angle, but actually about the change amount of the in-plane direction component of the wave number vector of the circularly polarized light caused by diffraction.

[0084] exist Figure 6 In the example shown, both wavelength plates 43 are set to a voltage applied state. In this case, if the light beam Bin is incident on the first wavelength plate 43, the left circularly polarized light beam B1 is emitted from the first wavelength plate 43 and is incident on the first PBOE 44. Then, the right circularly polarized light beam B2 is diffracted in the diffraction direction corresponding to the left circularly polarized light (in Figure 6 In the figure, the diffraction angle θ1 (which is on the upper side of the paper) is emitted from the first PBOE 44 and enters the second wavelength plate 43.

[0085] Then, the right circularly polarized light beam B3 is emitted from the second wave plate 43 and enters the second PBOE 44. Then, the left circularly polarized light beam Bout is diffracted in the direction corresponding to the right circularly polarized light (in Figure 6In the example, the diffraction angle θ2 is greater than the diffraction angle θ1.

[0086] exist Figure 7 In the example shown, the first wavelength plate 43 is set to a voltage non-applied state, and the second wavelength plate 43 is set to a voltage applied state. In this case, if the light beam Bin is incident on the first wavelength plate 43, the light beam B1 of right circular polarization is emitted from the first wavelength plate 43 and is incident on the first PBOE 44. Then, the light beam B2 of left circular polarization is diffracted in the diffraction direction corresponding to the right circular polarization (in Figure 7 In the figure, the diffraction angle θ1 (below the paper) is emitted from the first PBOE 44 and enters the second wavelength plate 43.

[0087] Then, the left circularly polarized light beam B3 is emitted from the second wave plate 43 and enters the second PBOE 44. Then, the right circularly polarized light beam Bout is diffracted in the direction corresponding to the left circularly polarized light (in Figure 7 In the figure, the light beam Bout is emitted from the second PBOE 44 at a diffraction angle θ2 (upper side of the paper). Therefore, the light beam Bout is emitted at a diffraction angle (θ2-θ1) relative to the incident direction of the light beam Bin.

[0088] exist Figure 8 In the example shown, the first wavelength plate 43 is set to a voltage applied state, and the second wavelength plate 43 is set to a voltage non-applied state. In this case, if the light beam Bin is incident on the first wavelength plate 43, the left circularly polarized light beam B1 is emitted from the first wavelength plate 43 and is incident on the first PBOE 44. Then, the right circularly polarized light beam B2 is diffracted in the diffraction direction corresponding to the left circularly polarized light (in Figure 8 In the figure, the diffraction angle θ1 (which is on the upper side of the paper) is emitted from the first PBOE 44 and enters the second wavelength plate 43.

[0089] Then, the left circularly polarized light beam B3 is emitted from the second wave plate 43 and is incident on the second PBOE 44. Then, the right circularly polarized light beam Bout is emitted from the second PBOE 44 at a diffraction angle θ2 corresponding to the diffraction direction of the left circularly polarized light. Therefore, the light beam Bout is emitted at a diffraction angle (θ1+θ2) relative to the incident direction of the light beam Bin.

[0090] exist Fig. 9In the example shown, both wavelength plates 43 are set to a voltage non-applied state. In this case, if the light beam Bin is incident on the first wavelength plate 43, the light beam B1 of right circular polarization is emitted from the first wavelength plate 43 and is incident on the first PBOE 44. Then, the light beam B2 of left circular polarization is diffracted in the diffraction direction corresponding to the right circular polarization (in Fig. 9 In the figure, the diffraction angle θ1 (which is on the lower side of the paper) is emitted from the first PBOE 44 and is incident on the second wavelength plate 43.

[0091] Then, the right circularly polarized light beam B3 is emitted from the second wave plate 43 and enters the second PBOE 44. Then, the left circularly polarized light beam Bout is emitted from the second PBOE 44 at a diffraction angle θ2 corresponding to the diffraction direction of the right circularly polarized light. Therefore, the light beam Bout is emitted at a diffraction angle (-θ1-θ2) relative to the incident direction of the light beam Bin.

[0092] In this way, by switching the state of each wavelength plate 43 between the voltage applied state and the voltage non-applied state, the traveling direction of the light beam passing through the deflection element 41 is changed. The traveling direction of the light beam passing through the deflection element 41 can be switched to two or more directions depending on the number n of the sets of wavelength plates 43 and PBOEs 44 included in the optical unit 4. n The direction of travel of the group.

[0093] Next, refer to Fig.10 , details of the notch filter 83 are described. Fig.10 It is a rough representation Figure 1 The structure of the notch filter is shown in FIG. Fig.10 As shown, the notch filter 83 includes a transparent substrate 31, a filter layer 32 (third filter), a filter layer 33 (second filter), and a filter layer 34 (first filter).

[0094] The transparent substrate 31 is a substrate having visible light transmittance for transmitting visible light. The transparent substrate 31 is made of a constituent material with low birefringence. If the transparent substrate 31 is made of a constituent material with high birefringence, the polarization state is affected by the transparent substrate 31. Examples of constituent materials of the transparent substrate 31 include SiO 2 , optical glass, and a glass substrate for a liquid crystal display. The transparent substrate 31 has a surface 31a and a surface 31b. The surface 31b is a surface on the opposite side of the surface 31a.

[0095] The filter layer 32 is a layer that reflects right circularly polarized light from the blue light Lb, removes the right circularly polarized light, and extracts the left circularly polarized light. The filter layer 32 is arranged on the surface 31a. The filter layer 32 includes a cholesteric liquid crystal polymer layer. The cholesteric liquid crystal polymer layer is a polarization-dependent volume diffraction grating (Polarization Volume Grating: PVG). The cholesteric liquid crystal polymer layer of the filter layer 32 has a spiral structure, which has a spiral pitch corresponding to the blue wavelength and is twisted in the twisting direction of the reflected right circularly polarized light. It is expected that the direction of the spiral axis is parallel to the direction of the light beam center that comes to the center of the visual field and the center of the pupil PP when the line of sight is facing the front. In addition, the "direction of the spiral axis" refers to the direction in which the spiral axis extends, and in the following description, it is referred to as the "direction of the spiral axis". The "twisting direction" indicates the direction of the twist in the sense of whether it is a right-hand thread or a left-hand thread.

[0096] The filter layer 33 is a layer that reflects the left circularly polarized light from the green light Lg, removes the left circularly polarized light, and extracts the right circularly polarized light. The filter layer 33 is disposed on the filter layer 32. The filter layer 33 includes a cholesteric liquid crystal polymer layer. The cholesteric liquid crystal polymer layer is PVG. The cholesteric liquid crystal polymer layer of the filter layer 33 has a helical structure having a helical pitch corresponding to the wavelength of green and twisted in the twisting direction of the reflected left circularly polarized light.

[0097] The filter layer 34 is a layer that reflects right circularly polarized light from the red light Lr, removes the right circularly polarized light, and extracts left circularly polarized light. The filter layer 34 is disposed on the filter layer 33. The filter layer 34 includes a cholesteric liquid crystal polymer layer. The cholesteric liquid crystal polymer layer is PVG. The cholesteric liquid crystal polymer layer of the filter layer 34 has a helical structure having a helical pitch corresponding to the wavelength of red and twisted in the twisting direction of the reflected right circularly polarized light.

[0098] In addition, Fig.10 Although not shown in the figure, each cholesteric liquid crystal polymer layer is formed on an alignment layer for controlling the arrangement state of liquid crystal molecules included in the cholesteric liquid crystal polymer layer.

[0099] Here, refer to Fig.11 and Fig.12 , the cholesteric liquid crystal polymer layer in the notch filter 83 is described in detail. Fig.11It is a diagram of Ewald spheres of various colors in the wave number space of light observed on a cross section including the wave number vector in the direction of the helical axis of the cholesteric liquid crystal polymer layer and the wave number vector of the center of the light beam that becomes the center of the field of view in the incident light. Ewald sphere ESr is the Ewald sphere of red light. Ewald sphere ESg is the Ewald sphere of green light. Ewald sphere ESb is the Ewald sphere of blue light. Here, the helical axis direction AX of the cholesteric liquid crystal polymer layer is perpendicular to the film surface.

[0100] By adjusting the composition of each cholesteric liquid crystal polymer layer (the type and amount of the chiral dopant, and the birefringence of the liquid crystal monomer, etc.), the helical pitch of each cholesteric liquid crystal polymer layer and the birefringence of the liquid crystal are appropriately set, thereby, the optical band gap of each cholesteric polymer liquid crystal layer can be set to a desired value. Here, as an example, the wavelength of red light is set to 620nm, the wavelength of green light is set to 520nm, and the wavelength of blue light is set to 450nm for explanation.

[0101] The optical band gap width W is calculated by using the half pitch P / 2 and the extraordinary refractive index n of the liquid crystal of the cholesteric liquid crystal polymer layer. e , ordinary refractive index n o and the effective refractive index n eff , approximated by formula (1). The half pitch P / 2 is the length of the liquid crystal molecule's orientation direction rotated 180 degrees along the helical axis of the cholesteric liquid crystal polymer layer, which is half the helical pitch. The effective refractive index n eff The approximation is made by taking the volume average refractive index of the cholesteric liquid crystal polymer layer. The optical band gap width W is the refractive index n eff The size of the optical band gap in the wavenumber space.

[0102] [Mathematical formula 1]

[0103]

[0104] Using half pitch P / 2, wavelength λ of incident light, and effective refractive index n eff The Bragg condition is expressed by formula (2) where the incident angle θ is the angle between the helical axis and the wave number vector of the incident light. Here, the magnitude of the wave number vector of the incident light in the cholesteric liquid crystal polymer layer is n eff × 2π / λ. The direction of the wave number vector of the incident light is set to the traveling direction of the incident light.

[0105] [Mathematical formula 2]

[0106]

[0107] If the half pitch P of the cholesteric liquid crystal polymer layer is used for red light R / 2, abnormal refractive index n Re , ordinary refractive index n Ro and the effective refractive index n Reff , then the optical band gap width Wr of the optical band gap BGr of the cholesteric liquid crystal polymer layer for red light is expressed by formula (3).

[0108] [Mathematical formula 3]

[0109]

[0110] Similarly, if the half pitch P of the cholesteric liquid crystal polymer layer is used for green light G / 2, abnormal refractive index n Ge , ordinary refractive index n Go and the effective refractive index n Geff , then the optical band gap width Wg of the optical band gap BGg of the cholesteric liquid crystal polymer layer for green light is expressed by formula (4).

[0111] [Formula 4]

[0112]

[0113] Similarly, if the half pitch P of the cholesteric liquid crystal polymer layer used for blue light is B / 2, abnormal refractive index n Be , ordinary refractive index n Bo and the effective refractive index n Beff , then the optical band gap width Wb of the optical band gap BGb of the cholesteric liquid crystal polymer layer for blue light is expressed by formula (5).

[0114] [Formula 5]

[0115]

[0116] When Bragg reflection occurs in each cholesteric liquid crystal polymer layer, the wave number vector of the light changes to the Bragg wave number vector of each cholesteric liquid crystal polymer layer to become outgoing light. For example, the wave number vector Vir of the incident light of red light and the Bragg wave number vector Vwr of the cholesteric liquid crystal polymer layer for red light are synthesized to obtain the wave number vector Vor of the outgoing light of red light.

[0117] The magnitude of the Bragg wave number vector Vwr of the cholesteric liquid crystal polymer layer for red light is 4π / P R , and its direction is parallel to the helical axis direction AX. The magnitude of the Bragg wave number vector Vwg of the cholesteric liquid crystal polymer layer for green light is 4π / P G, and its direction is parallel to the helical axis direction AX. The magnitude of the Bragg wave number vector Vwb of the cholesteric liquid crystal polymer layer for blue light is 4π / P B , whose direction is parallel to the helical axis direction AX. For each combination of wavelength and cholesteric liquid crystal polymer layer, the number of absolute values ​​of the incident angle that satisfies the exact Bragg condition is 1 or 0.

[0118] However, the cholesteric liquid crystal polymer layer has a finite optical band gap width which is not 0. Accordingly, for the combination of incident angle and wavelength that satisfies the Bragg condition, Fig.11 Light in the region of the wave number space with a limited thickness shown in FIG. 8 (which is referred to as "light within the optical band gap") also causes Bragg reflection. On the other hand, according to the principle of wave number uncertainty, even if the material of the cholesteric liquid crystal polymer layer is narrow in the optical band gap width, if the film thickness of the cholesteric liquid crystal polymer layer is reduced, the uncertainty of the wave number can be increased and the region causing Bragg reflection can be expanded. However, in this case, the reflectivity of the Bragg reflection decreases, and the light passing through the cholesteric liquid crystal polymer layer increases. This method cannot be used for the notch filter 83, but can be used for a holographic combiner, etc., and is effective when it is desired to increase the transmittance.

[0119] That is, in the wave number space, incident light in a range where the optical band gap width relaxes the Bragg condition causes Bragg reflection. Fig.11 The reason why Bragg reflection occurs within a certain range of incident angles is shown in FIG. The change amount Dv of the wave number vector at this time is different from the Bragg wave number vector relative to the incident light that does not satisfy the Bragg condition, but is along the spiral axis direction AX when the spiral axis direction AX is perpendicular to the film surface of the cholesteric liquid crystal polymer layer. On the other hand, this is not the case when the spiral axis direction AX is inclined relative to the film surface of the cholesteric liquid crystal polymer layer.

[0120] like Fig.12 As shown, using the magnitude of the Bragg wave number vector 4π / P of the cholesteric liquid crystal polymer layer and the inclination angle α of the helical axis, the magnitude of the in-plane direction component of the Bragg wave number vector is represented by 4π×sinα / P. For example, the in-plane direction component VCr based on the Bragg wave number vector Vwr is represented by 4π×sinα / P R The wave number vector of the emitted light is determined so that the in-plane direction component of the Bragg wave number vector becomes the in-plane direction component of the variation of the wave number vector.

[0121] The effective refractive index n is calculated by the law of conservation of energy and by taking the volume average refractive index value of the cholesteric liquid crystal polymer layer as described above. eff By approximation, it can be approximated to the effective refractive index neff It has nothing to do with the direction of the wave number vector. Therefore, the condition that the end points of the wave number vectors of the incident light and the outgoing light are located on the Ewald sphere can be added, and based on this condition and the condition of the in-plane directional component of the change in the wave number vector, the wave number vector of the outgoing light can be uniquely determined relative to the incident light.

[0122] In terms of the relationship between the wave number vector of the outgoing light and the wave number vector of the incident light, the magnitude of the wave number vector is actually the same as that of the surface relief diffraction grating of 4π×sinα / P. The above relationship is different from the surface relief diffraction grating in that only light within the optical band gap is diffracted, higher-order unnecessary diffraction is not easily generated, and only circularly polarized light of one polarity is diffracted.

[0123] The cholesteric liquid crystal produced for light of a long wavelength causes Bragg reflection with respect to light of a shorter wavelength only within a range of incident angles greater than the assumed long wavelength light. For example, within the incident angle range Rrg, the cholesteric liquid crystal polymer layer for red light causes Bragg reflection of green light. Within the incident angle range Rrb, the cholesteric liquid crystal polymer layer for red light causes Bragg reflection of blue light. Within the incident angle range Rgb, the cholesteric liquid crystal polymer layer for green light causes Bragg reflection of blue light. However, if the incident angle range designed so that the light of a shorter wavelength causes Bragg reflection does not overlap with the incident angle range Rf, it can be seen that there is no problem. The incident angle range Rf is the range of incident angles that acts as a notch filter with respect to all wavelengths of red light, green light, and blue light.

[0124] Here, the estimated incident angle range Rf is the incident angle in the cholesteric liquid crystal polymer layer which always has an effective refractive index of 1 or more, rather than the incident angle from the atmosphere. Light is incident on the cholesteric liquid crystal polymer layer from the atmosphere with refraction caused by the effective refractive index. Therefore, it can be seen that by using a cholesteric liquid crystal polymer having a large effective refractive index, a wider incident angle range from the atmosphere can be obtained.

[0125] In order to obtain a large incident angle range Rf of the notch filter 83, the helical axis direction AX of the cholesteric liquid crystal polymer layer is set so that the helical axis direction AX and the direction of the incident wave number vector when the light (light beam) at the center of the field of view reaches the center of the eye box and the light at the center of the light beam is incident on the notch filter 83 are as parallel as possible. In addition, on the basis of satisfying this condition, the setting angle of the notch filter 83 and the helical axis direction AX may be set so that the helical axis is perpendicular to the film surface.

[0126] Next, refer to Fig.13 and Fig.14 , the cholesteric liquid crystal polymer layer in the reflector 53 is described in detail. Fig.13 It is a diagram of the wave number space of light and the Ewald sphere of blue light and red light observed on a cross section including the wave number vector of the helical axis direction of the cholesteric liquid crystal polymer and the wave number vector of the center of the light beam that becomes the center of the field of view in the incident light. Here, the helical axis direction AX of the cholesteric liquid crystal polymer layer is inclined at an angle α relative to the film surface. In addition, Fig.13 and Fig.14 In the figure, for convenience of explanation, the same reference numerals are given to the elements corresponding to the cholesteric liquid crystal polymer layer of the notch filter 83, and repeated explanations are omitted.

[0127] Since red light and blue light of circularly polarized light of the same polarity are incident on the reflector 53, it is necessary to consider the wave number space of the red light and the blue light in which wavelength selectivity becomes a problem. As described above, the cholesteric liquid crystal produced for light of long wavelength causes Bragg reflection only in the range where the incident angle is larger than the assumed light of the above-mentioned long wavelength with respect to light of shorter wavelength. For example, within the incident angle range Rrb, the cholesteric liquid crystal polymer layer for red light performs Bragg reflection on blue light. However, if it is designed so that the incident angle range Rrb does not overlap with the incident angle range Rg1, it can be seen that there is no problem. The incident angle range Rg1 is the range of the incident angle that functions as a diffraction grating relative to the wavelength of the red light and the blue light.

[0128] Here, the estimated incident angle range Rg1 is the incident angle in the cholesteric liquid crystal polymer layer which always has an effective refractive index of 1 or more, rather than the incident angle from the atmosphere. Light is incident on the cholesteric liquid crystal polymer layer from the atmosphere with refraction caused by the effective refractive index. Therefore, it can be seen that by using a cholesteric liquid crystal polymer having a large effective refractive index, a larger incident angle range from the atmosphere can be obtained.

[0129] Since green light is circularly polarized light of a different polarity than red and blue light, wavelength selectivity is not an issue. Therefore, green light can be considered independently of red and blue light. Fig.14 As shown, the optical band gap width Wg of the cholesteric liquid crystal polymer layer for green light can also be expanded as much as possible.

[0130] In a holographic combiner, in order to realize the function of a concave mirror, it is necessary to change the required inclination α of the spiral axis and the in-plane direction of the inclination according to the location. The inclination α of the spiral axis and the in-plane direction of the inclination can be controlled by the orientation pattern of the optical orientation layer. In order to obtain a larger viewing angle, the spiral pitch can also be changed according to the location. For example, by utilizing the temperature dependence of the spiral pitch of the cholesteric liquid crystal and imparting an in-plane temperature distribution in the state before the cholesteric liquid crystal polymer layer is cured, the spiral pitch can be changed according to the location. It is also possible to use an inkjet method when applying the liquid crystal and change the chiral dopant concentration according to the location, thereby changing the spiral pitch according to the location. The change in the spiral pitch corresponds to the change in the magnitude of the Bragg wave number vector.

[0131] Furthermore, when the liquid crystal is applied by using an inkjet method, the composition of the liquid crystal monomer is changed for each cholesteric liquid crystal polymer layer and depending on the location, thereby controlling the magnitude of the birefringence of the liquid crystal monomer (here, the difference between the inverse of the ordinary refractive index and the inverse of the extraordinary refractive index). Thus, the width of the optical band gap can be controlled for each cholesteric liquid crystal polymer layer and depending on the location. Sometimes, it is necessary to control the optical band gap in conjunction with the control of the helical pitch.

[0132] When the incident angle with respect to the helical axis and the inclination α of the helical axis are substantially equal, light is vertically emitted from the hologram combiner. In this case, the incident angle with respect to the plane is approximately 2α.

[0133] It is desired that the diffraction angles of the three colors of light are consistent and chromatic aberration disappears. When the inclination α of the helical axis of the cholesteric liquid crystal polymer layer for red light constituting the hologram diffraction layer 56 is satisfied, R and the effective refractive index n Reff , the inclination α of the helical axis of the cholesteric liquid crystal polymer layer for green light constituting the holographic diffraction layer 55 G and the effective refractive index n Geff , the inclination α of the helical axis of the cholesteric liquid crystal polymer layer for blue light constituting the holographic diffraction layer 54 B and the effective refractive index n Beff , wavelength of red light λ R 、The wavelength of green light λ G , and the wavelength of blue light λ B In the case of the formula (6), the diffraction angles of the three colors of light are consistent.

[0134] [Mathematical formula 6]

[0135]

[0136] Since the diffraction angle of light when it emerges in the atmosphere is taken as an issue, the effective refractive index does not enter into formula (6). R and spiral pitch P RThe exposure pattern of the photo-alignment layer of the cholesteric liquid crystal polymer layer is directly determined by red light. G and spiral pitch P G The slope α is directly determined by the exposure pattern of the photo-alignment layer of the cholesteric liquid crystal polymer layer for green light. B and spiral pitch P B The exposure pattern of the photo-alignment layer of the cholesteric liquid crystal polymer layer for blue light is directly determined. Therefore, chromatic aberration can be easily eliminated.

[0137] Next, the manufacturing method of the cholesteric liquid crystal polymer layer (PVG) and PBOE is described. As an example of an azo dye used in the alignment layer, brilliant yellow (CASRN: 3051-11-4, product code: B0783 Brilliant Yellow: Brilliant Yellow 3051-11-4, Tokyo Chemical Industry Co., Ltd.) can be cited. A solution obtained by dissolving brilliant yellow (BY) in dimethylformamide (DMF) is uniformly applied to a transparent substrate by spin coating and dried on a flat electric furnace. The brilliant yellow molecules are oriented by exposing the film thus obtained to the interference electric field of the desired circularly polarized light. Thus, an alignment layer is formed.

[0138] In the case of manufacturing PVG, a solution obtained by dissolving a reactive liquid crystal unit containing a chiral dopant and a photopolymerization initiator in a solvent such as toluene is applied to the alignment layer, and then the solvent is evaporated to form a thin film. In the case of manufacturing PBOE, the same as above is performed, but no chiral dopant is added. Thereafter, if the coordination of the liquid crystal is stable, the thin film is cured using UV light. In the case where the thickness of the thin film obtained by applying the solution once is insufficient, the above-mentioned coating and curing are repeated until an appropriate thickness is obtained. In the case of PBOE, the thickness is controlled to function as a half-wavelength plate.

[0139] In the exposure of the orientation layer, for example, an exposure device described in non-patent document 1 (Jianghao Xiong, Shin-Tson Wu, "Planar liquid crystal polarization optics for augmented reality and virtual reality: from fundamentals to applications", eLight1, Article number: 3, 2021) is used. In addition, as an example of a right-handed chiral dopant, R5011 (CAS NO.944537-61-5Chiral Dopant R5011, Daken Chemical Limited) can be cited. As an example of a left-handed chiral dopant, S5011 (CAS NO.693227-30-4Chiral Dopant S5011|Daken Chemical Limited) can be cited. As an example of a reactive liquid crystal unit, reactive liquid crystal unit RM257 (CAS RN: 174063-87-7, product code: B5356, Tokyo Chemical Industry Co., Ltd.) can be cited. By doping with a chiral dopant, a helical structure in a direction perpendicular to the plane can be easily realized. The periodicity can be controlled by adjusting the twisting force and concentration of the helix of the chiral dopant.

[0140] As a method of stacking a plurality of PVGs, there is the following method. After forming one PVG on a transparent substrate, an intermediate layer is coated on the liquid crystal layer of the PVG so that the influence of the orientation of the liquid crystal layer does not affect it. Then, the next PVG is formed on the intermediate layer. As another method of stacking a plurality of PVGs, after forming the PVG on another substrate, the PVGs can be stacked by sequentially repeating transfer based on bonding and peeling on the same transparent substrate.

[0141] Next, the effects of the retinal projection device 1 are described. In order to expand the eye box, it is necessary to expand the permissible range of the incident angle of the light beam incident on the combiner 5. If a broadband element with a large permissible range of the incident angle is used, the permissible range of the wavelength is expanded. However, since the red wavelength and the green wavelength are close, and the green wavelength and the blue wavelength are close, if the permissible range of the wavelength is expanded, stray light caused by chromatic aberration may be generated.

[0142] In contrast, in the retinal projection device 1, the notch filter 83 provided between the projector module 2 and the combiner 5 extracts the left circularly polarized light from the red light Lr, the right circularly polarized light from the green light Lg, and the left circularly polarized light from the blue light Lb, and the left circularly polarized light of the red light Lr, the right circularly polarized light of the green light Lg, and the left circularly polarized light of the blue light Lb enter the combiner 5. Since the hologram diffraction layer 54 reflects (scatters) the left circularly polarized light, even if the permissible wavelength range of the hologram diffraction layer 54 is expanded, the right circularly polarized light of the green light Lg is not easily reflected. Similarly, since the hologram diffraction layer 55 reflects the right circularly polarized light, even if the permissible wavelength range of the hologram diffraction layer 55 is expanded, the left circularly polarized light of the red light Lr and the left circularly polarized light of the blue light Lb are not easily reflected. Similarly, since the hologram diffraction layer 56 reflects left circularly polarized light, even if the permissible wavelength range of the hologram diffraction layer 56 is expanded, the right circularly polarized light of the green light Lg is not easily reflected. Since the red wavelength and the blue wavelength are separated, the hologram diffraction layers 54 and 56 can maintain wavelength selectivity. Therefore, the left circularly polarized light of the red light Lr is not easily reflected by the hologram diffraction layer 54, and the left circularly polarized light of the blue light Lb is not easily reflected by the hologram diffraction layer 56. As a result, stray light caused by chromatic aberration can be reduced.

[0143] If the torsion direction of the torsion structure of the electric field vector generated by the rotation of the electric field vector of the circularly polarized light at a certain moment and with the traveling direction of the light as the axis is consistent with the torsion direction of the torsion structure of the orientation direction of the liquid crystal molecules of the cholesteric liquid crystal polymer layer, and the incident light satisfies a certain condition, Bragg reflection is caused and the incident light is diffracted and reflected. On the other hand, if the above-mentioned torsion directions are opposite to each other, Bragg reflection is not caused and the incident light is transmitted. As described above, by adjusting the helical pitch (to be precise, the product of the helical pitch and the effective refractive index of the cholesteric liquid crystal polymer layer) of the helical structure composed of the liquid crystal molecules of the cholesteric liquid crystal polymer layer, the helical axis direction, the effective refractive index, the torsion direction, the extraordinary refractive index and the ordinary refractive index of each layer obtained by slicing the cholesteric liquid crystal polymer layer with a plane perpendicular to the helical axis, circularly polarized light of a desired polarization state of a desired wavelength is reflected. In the retinal projection device 1, the filter layer 32 is configured to reflect right circularly polarized light from the blue light Lb, the filter layer 33 is configured to reflect left circularly polarized light from the green light Lg, and the filter layer 34 is configured to reflect right circularly polarized light from the red light Lr. Therefore, the left circularly polarized light of the red light Lr, the right circularly polarized light of the green light Lg, and the left circularly polarized light of the blue light Lb can be extracted, and the function of the notch filter 83 can be realized.

[0144] The hologram diffraction layer 54 is configured to reflect the left circularly polarized light of the blue light Lb, the hologram diffraction layer 55 is configured to reflect the right circularly polarized light of the green light Lg, and the hologram diffraction layer 56 is configured to reflect the left circularly polarized light of the red light Lr. Therefore, the function of the reflector 53 can be realized.

[0145] The extinction filter 81 is provided between the notch filter 83 and the relay lens 6. According to this configuration, the light reflected by the notch filter 83 is attenuated by the extinction filter 81, so that stray light can be further reduced.

[0146] If deflection is performed at a position separated from the focal position P, the focusing in the (imaginary) focal point that appears when the deflected light beam is extended forward and backward along the traveling axis is incomplete, resulting in spherical aberration. This is designed in such a way that the light diverging from the focal point of the optical system arranged in the subsequent stage is finally converted into parallel light. If the focusing is incomplete, the conversion to parallel light is also incomplete. Here, it is expressed as "spherical aberration". On the other hand, if deflection is performed at the focal position P, the focus in the above-mentioned focal point is completely maintained, so the spherical aberration is reduced. In the retinal projection device 1, because the deflection element 41 is arranged near the focal position P, the spherical aberration caused by changing the traveling direction (deflection) of the light beam is reduced. Therefore, the quality of the image on the retina is maintained, so the user can correctly recognize the image.

[0147] By switching the wavelength plate 43 between a state in which the polarization state of the circularly polarized light is preserved (voltage non-applied state) and a state in which the circularly polarized light is converted into circularly polarized light of opposite polarity (voltage applied state), the polarity (polarization state) of the circularly polarized light passing through the wavelength plate 43 can be switched. The diffraction direction in the PBOE 44 provided at the subsequent stage of the wavelength plate 43 is determined according to the polarity of the circularly polarized light. Therefore, by applying a voltage to each wavelength plate 43, the traveling direction of the light beam can be selected from the number of traveling directions corresponding to the number n of the sets of the wavelength plates 43 and the PBOE 44 included in the optical unit 4.

[0148] In the wavelength plate 43, a liquid crystal layer 437 is provided between a transparent electrode 433 and a transparent electrode 434. According to this structure, by applying a voltage between the transparent electrode 433 and the transparent electrode 434, an electric field is generated in the liquid crystal layer 437, and the liquid crystal molecules Lm1 included in the liquid crystal layer 437 are oriented in the direction of the electric field. Therefore, in a state where a voltage is applied between the transparent electrode 433 and the transparent electrode 434, the wavelength plate 43 retains the polarization state of the circularly polarized light passing through the wavelength plate 43. In a state where no voltage is applied between the transparent electrode 433 and the transparent electrode 434, the liquid crystal molecules Lm1 included in the liquid crystal layer 437 are in an in-plane oriented state. At this time, the wavelength plate 43 converts the circularly polarized light passing through the wavelength plate 43 into circularly polarized light of the opposite polarity. In this way, the state of retaining the polarization state of the circularly polarized light and the state of converting the circularly polarized light into circularly polarized light of the opposite polarity can be switched according to the presence or absence of the voltage applied between the transparent electrode 433 and the transparent electrode 434.

[0149] The PBOE 44 is made of a liquid crystal polymer. By using a liquid crystal polymer, the PBOE 44 can be easily formed.

[0150] The focus of the combiner 5 is located in front of the combiner 5. Therefore, when the relay lens 6 is not provided, the optical unit 4 needs to be arranged at the focus of the combiner 5. In this case, the optical unit 4 may block the user's field of view. In contrast, in the retinal projection device 1, the relay lens 6 is provided between the optical unit 4 and the combiner 5. With this structure, the optical unit 4 can be arranged at a position separated from the combiner 5. Therefore, the degree of freedom of arrangement of the optical unit 4 can be increased, and the user's field of view can be ensured.

[0151] The wavefront correction lens 7 mainly corrects the change caused by the switch of the deflection element 41 in the visual angle dependence of the focus of the light beam, that is, the visual angle dependence of the visibility in the retina. The function of the wavefront correction lens 7 is to correct the change of the image forming position on the retina (in front of or behind the retina) depending on the incident angle to the pupil PP, which is caused by the change of the aberration of the optical system of the retinal projection device 1 due to the switch of the deflection element 41, or by the aberration of the naked eye. In particular, the wavefront correction lens 7 can cope with the situation that the focus of the naked eye is easily shifted to the back side of the retina at the periphery of the visual field relative to the center of the visual field due to myopia of the type of elongated eye axis. This correction can also be performed using a fixed function lens like a conventional progressive diopter glasses, but if the line of sight moves up, down, left, and right, the correction becomes inappropriate, so the correction effect is not obvious. On the other hand, the wavefront correction lens 7 can be corrected in accordance with the movement of the line of sight by using a variable lens such as a liquid crystal lens.

[0152] A variable wavefront correction lens 24 is provided between the collimating lens 22 and the movable mirror 23. Therefore, the wavefront correction lens 24 can be effectively corrected due to the following Figure 1 The light beam shown in FIG. 1 is incident obliquely on an optical element such as a combiner 5, and generates aberrations of more than three degrees. The aberrations depend on the angle and position of the light beam, but the wavefront correction function of the wavefront correction lens 24 can also be set to make the best correction for the light beam at an angle and position consistent with the line of sight when incident on the pupil PP. In this case, since the resolution is low outside a very narrow range around the line of sight of the naked eye, no practical problems arise. Therefore, the controller 10 detects the position and angle of the pupil PP, controls the light beam to reach the position of the pupil PP through the deflection performed by the optical unit 4, and controls the resolution of the center of the visual field of the naked eye to be kept high through the wavefront correction lens 24.

[0153] The retinal projection device 1 includes a wavefront correction lens 7 and a wavefront correction lens 24, and the wavefront correction lens 7 and the wavefront correction lens 24 share functions. In addition, the controller 10 controls the wavefront correction lens 24 to perform the best correction on the light beam of the pixel at the center of the visual field of the naked eye, that is, forming the focus point on the retina. If the wavefront correction lens 24 can operate at a frequency that can follow the operating frequency of the movable mirror 23, the wavefront correction can be completely performed on all the light beams, and the focus adjustment of each light beam can also be performed. In this case, the wavefront correction lens 24 can also include the function of the wavefront correction lens 7, so the wavefront correction lens 7 can be omitted.

[0154] If the spatial separation of light beams with different viewing angles is well maintained at the position of the wavefront correction lens 7, the wavefront correction lens 7 may be disposed before or after the relay lens 6 at the subsequent stage of the deflection element 41. In this case, an element (wave plate) that converts the circularly polarized light from the deflection element 41 into appropriate linearly polarized light is disposed at the preceding stage. In the case where the wavefront correction lens 7 is disposed at the subsequent stage of the deflection element 41, the wavelength plate 9 may be disposed between the wavefront correction lens 24 and the optical unit 4, or may be disposed immediately after the collimating lens 22.

[0155] Next, refer to Fig.15 , another embodiment of a retinal projection device is described. Fig.15 This is a diagram schematically showing the structure of a retinal projection device according to another embodiment. Fig.15 The retina projection device 1A shown is different from the retina projection device 1 mainly in that it does not include the wavefront correction lens 7 and that the projector module 2 includes a wave plate 26 (first wave plate) instead of the wave plate 9 .

[0156] The wave plate 26 is an optical element that converts linearly polarized light into circularly polarized light and is provided at a subsequent stage of the wavefront correction lens 24 .

[0157] In the retinal projection device 1A, the same effect as that of the retinal projection device 1 is achieved with respect to the common structure with the retinal projection device 1. In the retinal projection device 1A, the wavefront correction lens 7 is not provided, and the projector module 2 includes a wavefront correction lens 24. The wavefront correction lens 24 adaptively corrects the aberration of the wavefront according to the position of the pupil PP, and thus can improve the resolution at the center of the field of view. The wavefront correction lens 24 is composed of a liquid crystal lens. By using a liquid crystal lens, the wavefront correction lens 24 can be easily realized.

[0158] Next, refer to Fig.16 , a retinal projection device according to another embodiment is described. Fig.16 This is a diagram schematically showing the structure of a retinal projection device according to still another embodiment. Fig.16 The retinal projection device 1B shown is different from the retinal projection device 1A mainly in that the projector module 2 includes a reflective wavefront correction element 25 (wavefront correction section) instead of the wavefront correction lens 24 . A wave plate 26 is provided after the wavefront correction element 25 .

[0159] The wavefront correction element 25 is an optical element that corrects the aberration of the wavefront of the light beam that passes through the pupil PP (equivalent to the light beam at the center of the field of view) among the light beams constituting the light beam. The wavefront correction element 25 corrects the aberration three or more times, for example. The wavefront correction element 25 reflects the light beam emitted from the collimating lens 22 and irradiates it to the movable mirror 23. The wavefront correction element 25 is, for example, composed of a variable shape mirror. As examples of variable shape mirrors, a MEMS type variable shape mirror and a piezoelectric element type variable shape mirror can be cited. The wavefront correction element 25 can also be composed of LCOS.

[0160] In the retinal projection device 1B, the same effect as that of the retinal projection device 1A is achieved for the common structure with the retinal projection device 1A. In the retinal projection device 1B, the projector module 2 includes a wavefront correction element 25. The wavefront correction element 25 adaptively corrects the aberration of the wavefront according to the position of the pupil PP, so that the resolution at the center of the field of view can be further improved. The wavefront correction element 25 is composed of a variable shape mirror or LCOS. By using a variable shape mirror or LCOS, the wavefront correction element 25 can be easily realized.

[0161] In addition, the retinal projection device of the present invention is not limited to the above-mentioned embodiment.

[0162] PBOE44 can also be composed of metasurfaces.

[0163] The deflection element 41 can change the direction of travel of the light beam. The deflection element 41 can also be a reflector (mirror), for example. The deflection element 41 can also change the direction of travel of the light beam by controlling the wavefront using a spatial light modulator (SLM). Specifically, the deflection element 41 can also be a variable diffraction grating formed by a liquid crystal SLM.

[0164] The notch filter 83 may also be configured to allow right circularly polarized light in the red light Lr to pass through and reflect left circularly polarized light, allow left circularly polarized light in the green light Lg to pass through and reflect right circularly polarized light, and allow right circularly polarized light in the blue light Lb to pass through and reflect left circularly polarized light. In this case, the combiner 5 is configured to diffract (Bragg reflect) right circularly polarized light in a wavelength range including red wavelengths, diffract (Bragg reflect) left circularly polarized light in a wavelength range including green wavelengths, and diffract (Bragg reflect) right circularly polarized light in a wavelength range including blue wavelengths.

[0165] (Note)

[0166] [Project 1]

[0167] A retinal projection device, wherein:

[0168] have:

[0169] A projector module comprising a laser module, a collimating lens and a movable mirror, wherein the laser module emits a laser light including a red component having a red wavelength, a green component having a green wavelength, and a blue component having a blue wavelength, the collimating lens converts the laser light into a parallel light beam, and the movable mirror is used for scanning using the light beam;

[0170] A switching unit capable of switching the optical path of the light beam;

[0171] a combiner that converts the light beams into parallel light and irradiates the light beams to the user's retina;

[0172] a notch filter disposed between the projector module and the combiner, allowing the circularly polarized light of the first polarity in the red wavelength light to pass through and reflecting the circularly polarized light of the second polarity different from the first polarity, allowing the circularly polarized light of the second polarity in the green wavelength light to pass through and reflecting the circularly polarized light of the first polarity, and allowing the circularly polarized light of the first polarity in the blue wavelength light to pass through and reflecting the circularly polarized light of the second polarity;

[0173] a controller for controlling the switching unit in a manner that the light beam passes through the pupil according to the position of the pupil of the user,

[0174] The above combiner has:

[0175] a first holographic diffraction layer that diffracts the circularly polarized light of the first polarity in the first wavelength range including the red wavelength;

[0176] a second holographic diffraction layer that diffracts the circularly polarized light of the second polarity in a second wavelength range including the green wavelength;

[0177] The third holographic diffraction layer diffracts the circularly polarized light of the first polarity in a third wavelength range including the blue wavelength.

[0178] [Project 2]

[0179] The retinal projection device according to item 1, wherein:

[0180] The first holographic diffraction layer is composed of a cholesteric liquid crystal polymer layer having a helical structure, the helical structure having a helical pitch corresponding to the red wavelength and twisted in a twisting direction for reflecting the circularly polarized light of the first polarity,

[0181] The second holographic diffraction layer is composed of a cholesteric liquid crystal polymer layer having a helical structure, the helical structure having a helical pitch corresponding to the green wavelength and twisted in a twisting direction for reflecting the circularly polarized light of the second polarity,

[0182] The third holographic diffraction layer is composed of a cholesteric liquid crystal polymer layer having a helical structure, the helical structure having a helical pitch corresponding to the blue wavelength and twisted in a twisting direction for reflecting the circularly polarized light of the first polarity.

[0183] [Item 3]

[0184] The retinal projection device according to item 1 or item 2, wherein:

[0185] The above-mentioned notch filter has:

[0186] A first filter, which is composed of a first cholesteric liquid crystal polymer layer having a helical structure, the helical structure having a helical pitch corresponding to the red wavelength and twisted in a twisting direction for reflecting the circularly polarized light of the second polarity;

[0187] a second filter composed of a second cholesteric liquid crystal polymer layer having a helical structure having a helical pitch corresponding to the green wavelength and twisted in a twisting direction for reflecting the circularly polarized light of the first polarity;

[0188] The third filter is composed of a third cholesteric liquid crystal polymer layer having a helical structure having a helical pitch corresponding to the above-mentioned blue wavelength and twisted in a twisting direction for reflecting the above-mentioned circularly polarized light of the second polarity.

[0189] [Item 4]

[0190] The retinal projection device according to any one of items 1 to 3, wherein:

[0191] The device further includes an extinction filter for attenuating the light reflected by the notch filter.

[0192] [Item 5]

[0193] The retinal projection device according to any one of items 1 to 4, wherein:

[0194] further comprising a projection lens for focusing the light beam emitted from the projector module at a focusing position,

[0195] The switching unit is arranged to overlap the focus position and includes a deflection element that changes the traveling direction of the light beam.

[0196] [Item 6]

[0197] The retinal projection device according to item 5, wherein:

[0198] It also includes: a first wave plate, which is disposed between the laser module and the deflection element and converts the linear polarization light into circular polarization light,

[0199] The above-mentioned deflection element has:

[0200] one or more second wavelength plates capable of switching between a state of preserving the polarization state of circularly polarized light and a state of converting the circularly polarized light into circularly polarized light of opposite polarity according to an applied voltage;

[0201] one or more Pancharatnam-Berry phase optical elements that convert circularly polarized light into circularly polarized light of opposite polarity and diffract the circularly polarized light in a diffraction direction corresponding to the polarity of the incident circularly polarized light,

[0202] The one or more second wavelength plates and the one or more Pancharatnam-Berry phase optical elements are arranged alternately one by one.

[0203] [Item 7]

[0204] The retinal projection device according to item 6, wherein:

[0205] The one or more Pancharatnam-Berry phase optical elements are composed of liquid crystal polymers or metasurfaces.

[0206] [Item 8]

[0207] The retinal projection device according to item 6 or item 7, wherein:

[0208] The second wave plate includes a pair of transparent electrodes and a liquid crystal layer provided between the pair of transparent electrodes.

[0209] [Item 9]

[0210] The retinal projection device according to any one of items 5 to 8, wherein:

[0211] The invention further comprises a focusing unit which is provided between the switching unit and the combiner and focuses the light beam.

[0212] [Item 10]

[0213] The retinal projection device according to any one of items 1 to 9, wherein:

[0214] The invention further includes a wavefront correction unit for correcting aberration of a wavefront of light rays that pass through the pupil among the light rays constituting the light beam.

[0215] [Item 11]

[0216] The retinal projection device according to item 10, wherein:

[0217] The wavefront correction unit is composed of any one of LCOS, a liquid crystal lens, and a variable shape mirror.

Claims

1. A retinal projection device, wherein: have: A projector module comprising a laser module, a collimating lens and a movable mirror, wherein the laser module emits a laser light including a red component having a red wavelength, a green component having a green wavelength, and a blue component having a blue wavelength, the collimating lens converts the laser light into a parallel light beam, and the movable mirror is used for scanning using the light beam; a switching unit capable of switching the optical path of the light beam; a combiner that converts the light beams into parallel light and irradiates the light beams to the user's retina; a notch filter disposed between the projector module and the combiner, allowing the circularly polarized light of a first polarity in the red wavelength light to pass through and reflecting the circularly polarized light of a second polarity different from the first polarity, allowing the circularly polarized light of the second polarity in the green wavelength light to pass through and reflecting the circularly polarized light of the first polarity, and allowing the circularly polarized light of the first polarity in the blue wavelength light to pass through and reflecting the circularly polarized light of the second polarity; and a controller for controlling the switching unit in a manner that the light beam passes through the pupil according to the position of the pupil of the user, The combiner has: a first holographic diffraction layer that diffracts the circularly polarized light of the first polarity in a first wavelength range including the red wavelength; a second holographic diffraction layer that diffracts the second polarity circularly polarized light in a second wavelength range including the green wavelength; and A third holographic diffraction layer diffracts the circularly polarized light of the first polarity in a third wavelength range including the blue wavelength.

2. The retinal projection device according to claim 1, wherein: The first holographic diffraction layer is composed of a cholesteric liquid crystal polymer layer having a helical structure, the helical structure having a helical pitch corresponding to the red wavelength and twisted in a twisting direction for reflecting the circularly polarized light of the first polarity, The second holographic diffraction layer is composed of a cholesteric liquid crystal polymer layer having a helical structure, the helical structure having a helical pitch corresponding to the green wavelength and twisted in a twisting direction for reflecting the circularly polarized light of the second polarity, The third holographic diffraction layer is composed of a cholesteric liquid crystal polymer layer having a helical structure, the helical structure having a helical pitch corresponding to the blue wavelength and being twisted in a twisting direction for reflecting the circularly polarized light of the first polarity.

3. The retinal projection device according to claim 1 or 2, wherein: The notch filter has: a first filter composed of a first cholesteric liquid crystal polymer layer having a helical structure having a helical pitch corresponding to the red wavelength and twisted in a twisting direction for reflecting the second polarity circularly polarized light; a second filter composed of a second cholesteric liquid crystal polymer layer having a helical structure having a helical pitch corresponding to the green wavelength and twisted in a twisting direction for reflecting the circularly polarized light of the first polarity; and A third filter is composed of a third cholesteric liquid crystal polymer layer having a helical structure, the helical structure having a helical pitch corresponding to the blue wavelength and twisted in a twisting direction for reflecting the second polarity circularly polarized light.

4. The retinal projection device according to any one of claims 1 to 3, wherein: An extinction filter is further provided for attenuating the light reflected by the notch filter.

5. The retinal projection device according to any one of claims 1 to 4, wherein: further comprising a projection lens for focusing the light beam emitted from the projector module at a focusing position, The switching unit is arranged to overlap with the focus position, and includes a deflection element that changes the traveling direction of the light beam.

6. The retinal projection device according to claim 5, wherein: It also includes: a first wave plate, which is disposed between the laser module and the deflection element and converts the linear polarization light into circular polarization light, The deflection element comprises: one or more second wavelength plates capable of switching between a state of preserving the polarization state of circularly polarized light and a state of converting the circularly polarized light into circularly polarized light of opposite polarity according to an applied voltage; and one or more Pancharatnam-Berry phase optical elements that convert circularly polarized light into circularly polarized light of opposite polarity and diffract the circularly polarized light in a diffraction direction corresponding to the polarity of the incident circularly polarized light, The one or more second wavelength plates and the one or more Pancharatnam-Berry phase optical elements are arranged alternately one by one.

7. The retinal projection device according to claim 6, wherein: The one or more Pancharatnam-Berry phase optical elements are composed of liquid crystal polymers or metasurfaces.

8. A retinal projection device according to claim 6 or 7, wherein: The second wave plate includes a pair of transparent electrodes and a liquid crystal layer provided between the pair of transparent electrodes.

9. The retinal projection device according to any one of claims 5 to 8, wherein: The invention further comprises a focusing unit which is provided between the switching unit and the combiner and focuses the light beam.

10. The retinal projection device according to any one of claims 1 to 9, wherein: The invention further includes a wavefront correction unit that corrects aberration of a wavefront of light that passes through the pupil among the light rays constituting the light beam.

11. The retinal projection device according to claim 10, wherein: The wavefront correction unit is composed of any one of LCOS, a liquid crystal lens, and a variable shape mirror.

Images