Retina projection device

Abstract

To reduce chromatic aberrations.SOLUTION: A retina projection device 10 is mounted to a near-eye wearable device, and comprises: a light source unit 11 for emitting a laser beam including at least one of red light, green light and blue light; a movable mirror 13 for performing a scan by the laser light; a reflector 15 for reflecting the laser light coming by way of the movable mirror 13 and irradiating the retina RE of a user wearing the near-eye wearable device with reflected light, thereby projecting an image to the retina RE; and an adjustment unit 14 provided between the movable mirror 13 and the reflector 15, for injecting red light, green light, and blue light corresponding to one pixel into the reflector 15 at mutually different angles so that the red light, green light, and blue light corresponding to one pixel included in the image are reflected in the same direction by the reflector 15.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a retinal projection device.

Background Art

[0002] Near-eye wearable devices such as smart glasses are known. For example, Patent Document 1 discloses a near-eye display assembly including an image source and a combiner including a nanostructured surface optically coupled to the image source, wherein image information is formed on the nanostructured surface of the combiner to convey the image information within the user's field of view.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the near-eye display assembly described in Patent Document 1, the nanostructured surface functions as a reflective surface. In reflectors such as mirrors (metaoptical mirrors) and diffractive mirrors composed of such nanostructures, the reflection angle of light may change depending on the wavelength of the light. Therefore, when an image is projected onto the user's retina, chromatic aberration may occur.

[0005] The present disclosure describes a retinal projection device capable of reducing chromatic aberration.

Means for Solving the Problems

[0006] The retinal projection device according to one aspect of the present disclosure is a device mounted on a near-eye wearable device. This retinal projection device includes a light source that emits laser light including at least one of red light, green light, and blue light, a movable mirror that performs scanning with the laser light, and reflects the laser light passing through the movable mirror to irradiate the retina of a user wearing the near-eye wearable device with reflected light, thereby projecting an image onto the retina. A reflector, and an adjustment unit provided between the movable mirror and the reflector, so that red light, green light, and blue light corresponding to one pixel included in the image are reflected in the same direction by the reflector. The red light, green light, and blue light corresponding to one pixel are incident on the reflector at different incident angles.

[0007] In this retinal projection device, the adjustment unit causes the red light, green light, and blue light corresponding to one pixel included in the image to be incident on the reflector at different incident angles so that the red light, green light, and blue light are reflected in the same direction by the reflector. Therefore, the red light, green light, and blue light corresponding to one pixel can be reflected in the same direction, so that chromatic aberration can be reduced.

[0008] In some embodiments, the adjustment unit may be a first spectroscopic device and a second spectroscopic device arranged in order along the optical path of the laser light, and the first spectroscopic device and the second spectroscopic device whose refraction angle changes depending on the wavelength of the laser light. The first spectroscopic device may receive the laser light passing through the movable mirror. The second spectroscopic device may emit the red light, green light, and blue light corresponding to one pixel toward the same position of the reflector. In this case, when the laser light including red light, green light, and blue light is incident on the first spectroscopic device, the traveling directions of the red light, green light, and blue light are changed for each wavelength. Therefore, since the red light, green light, and blue light are incident on different positions of the second spectroscopic device, the red light, green light, and blue light are emitted toward the same position of the reflector by the second spectroscopic device, so that the incident angles of the red light, green light, and blue light on the reflector can be made different from each other.

[0009] In some embodiments, each of the first spectroscopic device and the second spectroscopic device may be a metalens including a plurality of nanostructures provided along the surface on which the laser light is incident. By using the metalens, the first spectroscopic device and the second spectroscopic device can be easily realized.

[0010] In some embodiments, each of the first spectroscopic device and the second spectroscopic device may be a diffractive lens. By using the diffractive lens, the first spectroscopic device and the second spectroscopic device can be easily realized.

[0011] In some embodiments, each of the first spectroscopic device and the second spectroscopic device may be a prism. By using the prism, the first spectroscopic device and the second spectroscopic device can be easily realized.

[0012] In some embodiments, the adjustment unit may be a mirror provided between the first spectroscopic device and the second spectroscopic device, and may further include a mirror that reflects the laser light in a regular reflection manner. In this case, the incident angle at which the laser light is incident on the mirror is equal to the reflection angle at which the laser light is reflected by the mirror. Therefore, the traveling direction of the laser light can be changed without being affected by the wavelength of the laser light. Accordingly, the degree of freedom in arranging the first spectroscopic device and the second spectroscopic device can be increased.

[0013] In some embodiments, the adjustment unit may be a third spectroscopic device provided between the first spectroscopic device and the second spectroscopic device, and may further include a third spectroscopic device whose refraction angle changes depending on the wavelength of the laser light. In this case, it becomes easier to adjust the incident angles of the red light, green light, and blue light corresponding to one pixel.

[0014] In some embodiments, the retinal projection device may further include a collimator provided between the light source and the movable mirror to convert the laser light into parallel light. In this case, since the diffusion of the laser light is suppressed, the adjustment unit can more reliably adjust the incident angles of the red light, green light, and blue light.

[0015] In some embodiments, the reflector may be a meta-mirror including a plurality of nanostructures provided along the surface of the lens of the near-eye wearable device facing the user's eyeball. Even when a meta-mirror in which the reflection angle of light changes depending on the wavelength of light is used as the reflector, chromatic aberration can be reduced.

Advantages of the Invention

[0016] According to each aspect and each embodiment of the present disclosure, chromatic aberration can be reduced.

Brief Description of the Drawings

[0017]

Figure 1

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Figure 13

DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the description of the drawings, the same reference numerals are assigned to the same elements, and redundant descriptions are omitted. In each figure, an XYZ coordinate system and a UVW coordinate system may be shown. The Y-axis direction intersects (for example, is orthogonal to) the X-axis direction and the Z-axis direction. The Z-axis direction intersects (for example, is orthogonal to) the X-axis direction and the Y-axis direction. The V-axis direction intersects (for example, is orthogonal to) the U-axis direction and the W-axis direction. The W-axis direction intersects (for example, is orthogonal to) the U-axis direction and the V-axis direction.

[0019] Referring to FIG. 1, a near-eye wearable device including a retinal projection device according to an embodiment will be described. FIG. 1 is a perspective view showing the appearance of a near-eye wearable device including a retinal projection device according to an embodiment. The near-eye wearable device 1 shown in FIG. 1 is a device that superimposes an image on the field of view of the real world. The near-eye wearable device 1 is, for example, a head-mounted device (head-mounted display), and can take forms such as glasses type, goggle type, hat type, and helmet type. Examples of the near-eye wearable device 1 include smart glasses such as AR (Augmented Reality) glasses and MR (Mixed Reality) glasses. The near-eye wearable device 1 includes a frame 2, a lens 3, and a retinal projection device 10.

[0020] Frame 2 includes a pair of rims 2a, a bridge 2b, and a pair of temples 2c. The rim 2a is a part for holding the lens 3. The bridge 2b is a part for connecting the pair of rims 2a. The temple 2c extends from the rim 2a and is a part that is placed on the user's ear. The frame 2 may be a rimless frame. The lens 3 has an inner surface 3a (see FIG. 2) facing the eyeball E (see FIG. 2) of the user wearing the near-eye wearable device 1.

[0021] In the present embodiment, the retinal projection device 10 is a device that directly projects (draws) an image onto the retina RE (see FIG. 2) of the user wearing the near-eye wearable device 1. The retinal projection device 10 is mounted on the near-eye wearable device 1. In the present embodiment, the near-eye wearable device 1 includes two retinal projection devices 10 in order to project an image onto both the left and right retinas RE, but it may include only one of the retinal projection devices 10.

[0022] Next, the retinal projection device 10 will be described in detail with reference to FIG. 2. FIG. 2 is a configuration diagram schematically showing the retinal projection device shown in FIG. 1. As shown in FIG. 2, the retinal projection device 10 includes a light source unit 11 (light source), a collimator lens 12 (collimator), a movable mirror 13, an adjustment unit 14, and a reflector 15.

[0023] The light source unit 11 emits laser light. As the light source unit 11, for example, a full-color laser module is used. The light source unit 11 includes a red laser diode, a green laser diode, a blue laser diode, and a multiplexer that multiplexes the laser light emitted from each laser diode into one laser light. The light source unit 11 emits the multiplexed laser light. The multiplexed laser light includes at least one of light having a red wavelength (red light Lr), light having a green wavelength (green light Lg), and light having a blue wavelength (blue light Lb). In the following description, the red light Lr, the green light Lg, and the blue light Lb may be referred to as "visible light", and the red light Lr, the green light Lg, and the blue light Lb may be collectively referred to as "laser light Ls". The light source unit 11 emits laser light having a color and intensity corresponding to the pixels of the image projected onto the retina RE.

[0024] The collimator lens 12 is an optical component that converts the laser light emitted from the light source unit 11 into parallel light. The collimator lens 12 is provided between the light source unit 11 and the movable mirror 13.

[0025] The movable mirror 13 is an optical component for performing scanning with the laser light Ls. The movable mirror 13 is provided in the emission direction of the laser light converted into parallel light by the collimator lens 12. The movable mirror 13 is configured to be swingable, for example, about an axis extending in the lateral direction (X-axis direction) of the lens 3 and about an axis extending in the longitudinal direction (Y-axis direction) of the lens 3, and reflects the laser light by changing the angle in the X-axis direction and the Y-axis direction. As the movable mirror 13, for example, a MEMS (Micro Electro Mechanical Systems) mirror is used.

[0026] The adjustment unit 14 is a device that causes red light Lr, green light Lg, and blue light Lb corresponding to one pixel included in an image to be incident on the reflector 15 at different incident angles so that the red light Lr, green light Lg, and blue light Lb corresponding to the pixel are reflected by the reflector 15 in the same direction. The adjustment unit 14 is provided between the movable mirror 13 and the reflector 15. Details of the adjustment unit 14 will be described later.

[0027] The reflector 15 is an optical component that reflects the laser light Ls that has passed through the movable mirror 13 and irradiates the retina of the user wearing the near-eye wearable device 1 with the reflected light Lref, thereby projecting an image onto the retina RE. An image is not displayed on the reflector 15. The reflector 15 is provided on the inner surface 3a of the lens 3. The reflector 15 is a meta-mirror including a plurality of nanostructures provided along the inner surface 3a. The meta-mirror is also referred to as a meta-optics mirror. Details of the reflector 15 will be described later.

[0028] Although not shown in the drawings, the retinal projection device 10 further includes a laser driver that drives the light source unit 11, a mirror driver that drives the movable mirror 13, and a controller that controls the laser driver and the mirror driver.

[0029] Next, the adjustment unit 14 will be described in detail with reference to FIGS. 3 to 7. FIG. 3 is a configuration diagram schematically showing the adjustment unit shown in FIG. 2. FIG. 4 is a plan view showing an enlarged unit region of the spectroscopic device shown in FIG. 3. FIG. 5 is a perspective view schematically showing the nanostructure shown in FIG. 4. FIG. 6 is a diagram showing the relationship between the diameter of the columnar body and the amount of phase change of the transmitted light. FIG. 7 is a diagram showing the relationship between the position in the U-axis direction of the spectroscopic device shown in FIG. 4 and the amount of phase change of the transmitted light.

[0030] As shown in FIG. 3, the adjustment unit 14 includes a spectroscopic device SP1 (first spectroscopic device), a spectroscopic device SP2 (third spectroscopic device), a spectroscopic device SP3 (second spectroscopic device), and a mirror M. The spectroscopic device SP1, the spectroscopic device SP2, the mirror M, and the spectroscopic device SP3 are arranged in that order along the optical path of the laser beam Ls.

[0031] The mirror M is an optical device that specularly reflects (mirror-reflects) each visible light included in the laser beam Ls. The mirror M is, for example, a total reflection mirror. The mirror M is provided between the spectroscopic device SP2 and the spectroscopic device SP3 in the optical path of the laser beam Ls.

[0032] Each of the spectroscopic devices SP1, SP2, and SP3 is an optical device whose refraction angle changes depending on the wavelength of the laser beam Ls (visible light). In the present embodiment, each of the spectroscopic devices SP1, SP2, and SP3 is a metalens. A metalens is also referred to as a metasurface lens. The laser beam Ls that has passed through the movable mirror 13 is incident on the spectroscopic device SP1. The spectroscopic device SP3 emits the red light Lr, the green light Lg, and the blue light Lb corresponding to one pixel toward the same position of the reflector 15. The spectroscopic devices SP1, SP2, and SP3 are arranged such that the normal lines of the incident surfaces of the spectroscopic device SP1, the spectroscopic device SP2, and the spectroscopic device SP3 intersect each other. The incident surface is the surface on which the laser beam Ls (visible light) is incident.

[0033] As shown in FIG. 4, each spectroscopic device includes a plurality of unit regions 40. The plurality of unit regions 40 are provided in a two-dimensional array along the incident surface of the spectroscopic device. Two adjacent unit regions 40 are arranged with a predetermined interval Dr therebetween. The UVW coordinate system shown in FIGS. 4 and 5 is set for each spectroscopic device and is a coordinate system that is valid only within the corresponding spectroscopic device.

[0034] As shown in FIGS. 4 and 5, each spectroscopic device includes a substrate 61 and a plurality of columnar bodies 62. The substrate 61 is a substrate having visible light transmissibility that transmits visible light. That is, the substrate 61 is a transparent substrate. As a constituent material of the substrate 61, a material having visible light translucency and a refractive index greater than 1 is used. Examples of such constituent materials include silicon oxide (for example, SiO2), titanium oxide (for example, TiO2), silicon nitride (for example, SiN), and titanium nitride (for example, TiN). The substrate 61 has a surface 61a and a surface 61b. The surface 61a and the surface 61b are main surfaces that intersect the incident direction of the laser light Ls. The thickness of the substrate 61 (the distance between the surface 61a and the surface 61b) is, for example, 0.1 mm to 5 mm.

[0035] Each columnar body 62 is a columnar member having visible light transmissibility that transmits visible light. Each columnar body 62 has, for example, a cylindrical shape. The shape of each columnar body 62 is not limited to a cylinder, and may be a prism, or may be a frustum of a cone or a frustum of a pyramid with a tapered tip. As a constituent material of the columnar body 62, a material having visible light translucency and a refractive index greater than 1 is used, similar to the substrate 61. The refractive index of the columnar body 62 is greater than 1.

[0036] Each columnar body 62 is provided standing on the surface 61a. The length (height Hp) of the columnar body 62 in the direction intersecting (orthogonal to) the surface 61a is, for example, 0.1 μm to 10 μm. The diameter Dp of the columnar body 62 is, for example, 100 nm to 250 nm. The height Hp and the diameter Dp of the columnar body 62 are determined so as to obtain a desired refraction angle for each visible light. The method for determining the height Hp and the diameter Dp of the columnar body 62 will be described later.

[0037] A plurality of columnar bodies 62 are provided for each unit region 40, and the plurality of columnar bodies 62 included in one unit region 40 are arranged in one direction (U-axis direction). The central axes of the plurality of columnar bodies 62 included in one unit region 40 are substantially aligned on a straight line. The interval Da between two adjacent central axes is substantially constant. No columnar body 62 is provided in the region other than the unit region 40.

[0038] Each unit area 40 is divided into a plurality of nanostructures 60 arranged in the U-axis direction. Each nanostructure 60 includes one columnar body 62 and a base 63. The base 63 is a part of the substrate 61 and is a rectangular parallelepiped-shaped portion having an outer shape of a rectangle (square) with a side length Ln centered on the central axis of the columnar body 62 in plan view. When visible light passes through the nanostructure 60, a phase delay corresponding to the height Hp and diameter Dp of the columnar body 62 occurs. In the present embodiment, the height Hp of all the columnar bodies 62 included in the spectroscopic device is set to the same height, and the phase delay is adjusted by the diameter Dp.

[0039] For example, when silicon dioxide (SiO2) is used as the constituent material of the columnar body 62 and the base 63, and the length Ln is 250 nm and the height Hp is 1.5 μm, the amount of phase change φ A (phase delay amount) in a single nanostructure 60 including columnar bodies 62 having different diameters Dp is obtained, and the relationship shown in FIG. 6 is obtained. The horizontal axis in FIG. 6 indicates the diameter Dp (unit: μm), and the vertical axis in FIG. 6 indicates the amount of phase change φ A (unit: radian).

[0040] The amount of phase change φ A is the amount of change in the phase of the transmitted light when the diameter Dp of the columnar body 62 is changed, with the phase of the transmitted light in the nanostructure 60 including the columnar body 62 having a certain diameter Dp as a reference. In the example shown in FIG. 6, with the phase of the transmitted light in the nanostructure 60 including the columnar body 62 having a diameter Dp of 0.1 μm being 0 radians, the amount of phase change φ A of the transmitted light when the diameter Dp is changed is shown. As shown in FIG. 6, as the diameter Dp increases, the amount of phase change φ A of the transmitted light after passing through the nanostructure 60 increases.

[0041] As shown in FIG. 7, the diameters Dp of the plurality of columnar bodies 62 included in one unit area 40 are such that, from one end 40a to the other end 40b in the U-axis direction of the unit area 40, the amount of phase change φ AIt is set to increase or decrease linearly. The horizontal axis in FIG. 7 indicates the position u (unit: μm) in the U-axis direction, and the vertical axis in FIG. 7 indicates the amount of phase change φ A (unit: radian). Further, in one unit region 40, the amount of phase change φ of the transmitted light from one end 40a to the other end 40b A is configured to change substantially 360° (2π radians).

[0042] In other words, the phase gradient dφ A which is the gradient of φ at the position u A / du becomes a desired value, and the condition that the amount of phase change φ of the transmitted light changes substantially 360° (2π radians) from one end 40a to the other end 40b is satisfied, and the diameters Dp of the plurality of columnar bodies 62 included in one unit region 40 are set. A For example, in order to obtain a phase gradient dφ

[0043] / du of 4.93 radians / μm, two adjacent unit regions 40 are arranged at an interval Dr of 273 nm. In each unit region 40, columnar bodies 62 having a diameter Dp of 100 nm, columnar bodies 62 having a diameter Dp of 160 nm, columnar bodies 62 having a diameter Dp of 206 nm, and columnar bodies 62 having a diameter Dp of 235 nm are arranged in order at an interval Da of 250 nm from one end 40a to the other end 40b. A The method for determining the phase gradient dφ / du will be described later. A

[0044] Next, with reference to FIGS. 8 to 12, the configuration of the reflector 15 will be described. FIG. 8 is an enlarged view showing the reflector shown in FIG. 2. FIG. 9 is a plan view schematically showing an example of the unit region shown in FIG. 8. FIG. 10 is a cross-sectional view taken along the line X-X of FIG. 9. FIG. 11 is a diagram showing the relationship between the length of the metal body and the amount of phase change of the reflected light. FIG. 12 is a diagram showing the relationship between the position in the X-axis direction of the reflector shown in FIG. 8 and the amount of phase change of the reflected light.

[0045] ​As shown in FIG. 8, the reflector 15 is divided into a plurality of unit regions 50. The plurality of unit regions 50 are provided along the inner surface 3a of the lens 3. The plurality of unit regions 50 are arranged in a two-dimensional array in the lateral direction (X-axis direction) and the longitudinal direction (Y-axis direction) of the lens 3. Each unit region 50 is configured to reflect the laser light Ls at a reflection angle θ corresponding to the position where the unit region 50 is provided when the laser light Ls is incident on the unit region 50. r It is a nanostructure configured to reflect the laser light Ls at the reflection angle θ. The reflection angle θ of each unit region 50 is set so that the laser light Ls (reflected light Lref) reflected by each unit region 50 passes through the center of the pupil PP. r is set.

[0046] As shown in FIGS. 9 and 10, the reflector 15 includes a metal layer 51, a dielectric layer 52, and a metal layer 53 in this order in the Z-axis direction.

[0047] The metal layer 51 is a base layer. The metal layer 51 is provided on the inner surface 3a of the lens 3. The metal layer 51 is made of a metal having high reflection characteristics in the visible light region. The metal layer 51 is composed of, for example, a metal containing at least one element selected from the group consisting of gold (Au), copper (Cu), silver (Ag), iridium (Ir), ruthenium (Ru), rhodium (Rh), titanium (Ti), tantalum (Ta), tungsten (W), cobalt (Co), iron (Fe), and nickel (Ni). The length (thickness d1) of the metal layer 51 in the Z-axis direction may be a length that allows the metal layer 51 to pass a resonance current and reflect light, and is, for example, 1 nm to 1000 nm. Hereinafter, the length in the Z-axis direction may be referred to as "thickness" in some cases.

[0048] The dielectric layer 52 is a layer that functions as a spacer. The dielectric layer 52 is provided between the metal layer 51 and the metal layer 53 in the Z-axis direction. In the present embodiment, the dielectric layer 52 is provided on the metal layer 51. The dielectric layer 52 has a dielectric constant such that it does not inhibit the electromagnetic action between the metal layer 51 and the metal layer 53. The dielectric layer 52 is composed of a material that is transparent in the visible light region. The dielectric layer 52 may be composed of a material having a high dielectric constant in order to realize high reflection characteristics. The dielectric layer 52 is composed of, for example, one compound selected from the group consisting of silicon oxide (e.g., SiO2), titanium oxide (e.g., TiO2), magnesium oxide (e.g., MgO), and aluminum oxide (e.g., Al2O3). The thickness d2 of the dielectric layer 52 is, for example, 1 nm to 1000 nm.

[0049] The metal layer 53 is a layer that excites electromagnetic resonance together with the metal layer 51. The metal layer 51 and the metal layer 53 are laminated in the Z-axis direction with the dielectric layer 52 interposed therebetween. In the present embodiment, the metal layer 53 is provided on the dielectric layer 52. The metal layer 53 is composed of a metal having high reflection characteristics in the visible light region. Similar to the metal layer 51, the metal layer 53 is composed of, for example, a metal containing at least one element selected from the group consisting of gold (Au), copper (Cu), silver (Ag), iridium (Ir), ruthenium (Ru), rhodium (Rh), titanium (Ti), tantalum (Ta), tungsten (W), cobalt (Co), iron (Fe), and nickel (Ni).

[0050] The metal layer 53 includes a plurality of metal bodies 54 arranged in the X-axis direction. The thickness d3 of each metal body 54 is, for example, 1 nm to 1000 nm. The length (width Wm) of each metal body 54 in the X-axis direction is about 100 nm. The length Lm of each metal body 54 in the Y-axis direction is the reflection angle θ rIt is determined according to [specific conditions]. The interval Ds between two metal bodies 54 adjacent to each other in the X-axis direction is set so that the wavefront of the reflected light is continuous. The interval Ds only needs to be of a size such that the two metal bodies 54 do not contact each other, and for example, it is set to be half or less of the wavelength of the incident light (laser light Ls). The interval Ds is, for example, about 20 nm. The plurality of metal bodies 54 are formed, for example, by photolithography.

[0051] When visible light is reflected by the metal body 54, a phase delay corresponding to the width Wm and length Lm of the metal body 54 occurs. In this embodiment, the widths Wm of all the metal bodies 54 included in the reflector 15 are set to the same width, and the phase delay is adjusted by the length Lm. For example, when gold (Au) is used as the constituent material of the metal layer 51 and the metal body 54, and silicon dioxide (SiO2) is used as the constituent material of the dielectric layer 52, with a thickness d1 of 200 nm, a thickness d2 of 50 nm, a thickness d3 of 40 nm, and a width Wm of 100 nm, the phase change amount φ B (phase delay amount) of a single metal body 54 having different lengths Lm is obtained, and the relationship shown in FIG. 11 is obtained. The horizontal axis in FIG. 11 indicates the length Lm (unit: nm), and the vertical axis in FIG. 11 indicates the phase change amount φ B (unit: °).

[0052] The phase change amount φ B is the change amount of the phase of the reflected light Lref when the length Lm is changed, with the phase of the reflected light Lref of the metal body 54 having a certain length Lm as the reference. In the example shown in FIG. 11, with the phase of the reflected light Lref of the metal body 54 having a length Lm of 40 nm as 0°, the phase change amount φ B of the reflected light Lref when the length Lm is changed is shown. As shown in FIG. 11, as the length Lm increases, the phase change amount φ B of the reflected light Lref increases.

[0053] For example, in the metal body 54 having a length Lm of 40 nm (hereinafter referred to as "metal body 54A"), the phase change amount φ B is 0°, and in the metal body 54 having a length Lm of 100 nm (hereinafter referred to as "metal body 54B"), the phase change amount φB is 50°, and for the metal body 54 (hereinafter referred to as "metal body 54C") having a length Lm of 130 nm, the phase change amount φ B is 140°, and for the metal body 54 (hereinafter referred to as "metal body 54D") having a length Lm of 150 nm, the phase change amount φ B is 200°, and for the metal body 54 (hereinafter referred to as "metal body 54E") having a length Lm of 250 nm, the phase change amount φ B is 300°.

[0054] As shown in FIG. 12, the lengths Lm of the plurality of metal bodies 54 included in one unit region 50 are such that, from one end 50a to the other end 50b of the unit region 50, the phase change amount φ of the reflected light Lref by the metal body 54 B is set to increase or decrease linearly. The horizontal axis in FIG. 12 indicates the position x (unit: nm) in the X-axis direction, and the vertical axis in FIG. 12 indicates the phase change amount φ B (unit: °). Further, in one unit region 50, from one end 50a to the other end 50b, the phase change amount φ of the reflected light Lref B substantially changes by 360° (2π radians).

[0055] In other words, in the unit region 50 having a desired length Lx, from one end 50a to the other end 50b, the phase change amount φ of the reflected light Lref by the metal body 54 B increases or decreases linearly, and the phase change amount φ of the reflected light Lref from one end 50a to the other end 50b B substantially changes by 360° (2π radians). The lengths Lm of the plurality of metal bodies 54 included in one unit region 50 are set so that this condition is satisfied.

[0056] In order to satisfy the above conditions, some of the metal bodies 54 may be selected from the metal bodies 54 according to the length Lx, and the number and length Lm of the metal bodies 54 included in the unit region 50 may be determined by arranging the selected metal bodies 54 in the X-axis direction. Two metal bodies 54 having the same length Lm may be grouped, and a plurality of groups may be arranged in the X-axis direction. For example, as shown in FIG. 12, when the length Lx is 1200 nm, in the X-axis direction, from one end 50a to the other end 50b, the metal bodies 54A, the metal bodies 54A, the metal bodies 54B, the metal bodies 54B, the metal bodies 54C, the metal bodies 54C, the metal bodies 54D, the metal bodies 54D, the metal bodies 54E, and the metal bodies 54E are arranged in order at an interval Ds of 20 nm. The method for determining the length Lx will be described later.

[0057] Next, with reference to FIG. 13, the method for determining the phase gradient dφ A / du and the length Lx will be described. FIG. 13 is a diagram for explaining the incident angle and the refraction angle in each spectroscopic device and the incident angle and the reflection angle in the reflector. In FIG. 13, the adjustment unit 14 is generalized, and the case where the adjustment unit 14 includes N spectroscopic devices SP k (k is an integer from 1 to N) will be described for the method of determining the phase gradient dφ A / du and the length Lx. Note that FIG. 3 shows an example where N = 3.

[0058] First, the operating principle of each spectroscopic device will be described. In the k-th spectroscopic device SP k (hereinafter simply referred to as "spectroscopic device SP k "), the laser beam Ls passes through with a different phase change amount φ Ak depending on the position u in the U-axis direction, so that a wavefront is formed by the interference between the transmitted lights. That is, a plane wave having the phase gradient dφ Ak / du as the wave vector is generated. Here, according to the generalized Snell's law, Equation (1) holds.

Equation

[0059] As shown in FIG. 13, the incident angle θik is the angle formed by the normal to the incident surface of the spectroscopic device SP k and the incident direction of the laser beam Ls. The refraction angle θ tk is the angle formed by the normal to the incident surface of the spectroscopic device SP k and the emission direction of the transmitted light. Here, the incident angle θ ik and the refraction angle θ tk shall be represented with the counterclockwise direction from the normal as a positive value and the clockwise direction from the normal as a negative value. The refractive index n i is the refractive index of the surrounding medium on the incident side of the spectroscopic device SP k The refractive index n t is the refractive index of the surrounding medium on the transmission side of the spectroscopic device SP. For simplicity of explanation, it is assumed that the phase gradient dφ k / du does not depend on the wavelength λ. The refractive index n Ak and the refractive index n i are assumed to be 1, and Equation (2) is obtained from Equation (1). t

Equation

[0060] The wavelength λ of the red light Lr red , the wavelength λ of the green light Lg green and the wavelength λ of the blue light Lb blue are different from each other, and in the spectroscopic device SP k the positions where the red light Lr, the green light Lg, and the blue light Lb are incident may be different. Therefore, by substituting the wavelength λ red and the phase gradient dφ k / du at the position where the red light Lr is incident in the spectroscopic device SP Ak_red into Equation (2), Equation (3) representing the relationship between the incident angle θ k and the refraction angle θ ik_red of the red light Lr in the spectroscopic device SP tk_red is obtained.

Equation

[0061] The wavelength λ​green and the spectroscopic device SP k the phase gradient dφ at the position where the green light Lg is incident Ak_green / du is substituted into Equation (2), and the incident angle θ k of the green light Lg in the spectroscopic device SP ik_green and the refraction angle θ tk_green The equation (4) representing the relationship between them is obtained. [Number]

[0062] Wavelength λ blue and the spectroscopic device SP k the phase gradient dφ at the position where the blue light Lb is incident Ak_blue / du is substituted into Equation (2), and the incident angle θ k of the blue light Lb in the spectroscopic device SP ik_blue and the refraction angle θ tk_blue The equation (5) representing the relationship between them is obtained. [Number]

[0063] The spectroscopic device SP k The incident angle of each color of light in is the angle obtained by subtracting the angle α k-1 (hereinafter simply referred to as "the spectroscopic device SP k-1 ") from the refraction angle θ tk-1 of the (k - 1)-th spectroscopic device SP k The angle α k is the angle formed by the normal of the incident surface of the spectroscopic device SP k-1 and the normal of the incident surface of the spectroscopic device SP k Here, the angle α k is represented with the counterclockwise direction from the normal of the incident surface of the spectroscopic device SP k-1 as a positive value and the clockwise direction from the normal of the incident surface of the spectroscopic device SP k-1 as a negative value. Therefore, by expressing the incident angle θ ik_red in Equation (3) using the refraction angle θ tk-1_red and the angle α k Equation (6) is obtained.

Mathematics

[0064] The incident angle θ in Equation (4) ik_green is represented by the refraction angle θ tk-1_green and the angle α k to obtain Equation (7).

Mathematics

[0065] The incident angle θ in Equation (5) ik_blue is represented by the refraction angle θ tk-1_blue and the angle α k to obtain Equation (8).

Mathematics

[0066] Note that the refraction angle θ t0_red is the incident angle θ i1_red and the refraction angle θ t0_green is the incident angle θ i1_green and the refraction angle θ t0_blue is the incident angle θ i1_blue The angle α1 is 0°.

[0067] Since the laser beam Ls in which the red light Lr, the green light Lg, and the blue light Lb are combined is incident on the first spectroscopic device SP1, as shown in Equation (9), the incident angle θ i1_red , the incident angle θ i1_green , and the incident angle θ i1_blue are equal to each other, and as shown in Equation (10), the phase gradient dφ A1_red / du, the phase gradient dφ A1_green / du, and the phase gradient dφ A1_blue / du are equal to each other.

Mathematics

Mathematics

[0068] Next, the operating principle of the reflector 15 will be described. In the reflector 15, the amount of phase change φ varies depending on the position x in the X-axis direction. B Thus, the laser beam Ls (visible light) is reflected, and an interference of the reflected lights forms a wavefront. That is, a plane wave having a wave number vector Φ of dφ / dx is generated. Here, as shown in FIG. 10, according to the generalized Snell's law, Equation (11) holds. B / dx is the wave number vector Φ of the plane wave generated. Here, as shown in FIG. 10, according to the generalized Snell's law, Equation (11) holds.

Equation

[0069] The incident angle θ i is the angle formed by the normal to the reflecting surface of the reflector 15 and the incident direction of the laser beam Ls. The reflection angle θ r is the angle formed by the normal to the reflecting surface of the reflector 15 and the emission direction of the reflected light Lref. In the plane including the laser beam Ls and the reflected light Lref, when the reflected light Lref is emitted on the side opposite to the incident light (laser beam Ls) with the normal as a boundary, the reflection angle θ r is represented by a positive value, and when the reflected light Lref is emitted on the same side as the incident light (laser beam Ls) with the normal as a boundary, the reflection angle θ r is represented by a negative value.

[0070] The wave number vector k0 is expressed as 2π / λ using the wavelength λ of the laser beam Ls. The wave number vector Φ is expressed as 2π / Lx using the length Lx in the X-axis direction of the unit region 50. By transforming Equation (11) using these relationships, Equation (12) is obtained.

Equation

[0071] The red light Lr, green light Lg, and blue light Lb that constitute the same pixel are incident on the same position of the reflector 15 at different incident angles and are reflected at the same reflection angle. The incident angle θ of the red light Lr in the reflector 15 i_red and the reflection angle θr_red The relationship with the wavelength λ red and the length Lx is expressed by Equation (13).

Number

[0072] The incident angle θ of the green light Lg on the reflector 15 i_green and the reflection angle θ r_green The relationship with the wavelength λ green and the length Lx is expressed by Equation (14).

Number

[0073] The incident angle θ of the blue light Lb on the reflector 15 i_blue and the reflection angle θ r_blue The relationship with the wavelength λ blue and the length Lx is expressed by Equation (15).

Number

[0074] The incident angle of each color light on the reflector 15 is the angle obtained by adding the refraction angle in the Nth spectroscopic device SP N The angle β is the angle formed by the normal line of the incident surface of the Nth spectroscopic device SP N and the normal line of the reflection surface of the reflector 15. Therefore, Equations (13) to (15) are respectively transformed into Equations (16) to (18).

Number

Number

Number

[0075] As described above, the reflection angle θ r_red the reflection angle θr_green and the reflection angle θ r_blue are equal reflection angles θ to each other r , and the reflection angle θ r is predetermined according to the position where the unit region 50 is provided, so the formula (19) holds. [Number]

[0076] Under the conditions of formula (9) and formula (10), so that formula (19) is satisfied, the angle α k , the angle β, the phase gradient dφ Ak_red / du, the phase gradient dφ Ak_green / du, the phase gradient dφ Ak_blue / du, and the length Lx are determined. Note that the number of the spectroscopic devices SP k may be adjusted so that a solution satisfying the above conditions can be obtained, and one or more mirrors M may be provided in the optical path as necessary.

[0077] For example, when a mirror M is provided between the spectroscopic device SP k-1 and the spectroscopic device SP k , the incident angle θ ik is the angle obtained by subtracting the angle obtained by subtracting the refraction angle θ tk-1 from the angle γ1 from the angle obtained by subtracting it from the angle γ2. The angle γ1 is the angle formed by the normal of the incident surface of the spectroscopic device SP k-1 and the normal of the reflection surface of the mirror M. The angle γ2 is the angle formed by the normal of the incident surface of the spectroscopic device SP k and the normal of the reflection surface of the mirror M.

[0078] In the example shown in FIG. 3, the angle α1 is set to 20°, the angle γ1 is set to 39°, the angle γ2 is set to 61°, and the angle β is set to 0°. Assuming that the incident angle θ i1 of the laser beam Ls corresponding to the rightmost pixel is -10°, the incident angle θ i1 of the laser beam Ls corresponding to the central pixel is 0°, and the incident angle θ i1 of the laser beam Ls corresponding to the leftmost pixel is +10°, when each parameter is set to the value described in Table 1, the reflection angle θ r_red , the reflection angle θr_green and the reflection angle θ r_blue are equal to each other. The wavelength λ red is 650 nm, the wavelength λ green is 550 nm, the wavelength λ blue is set to 450 nm, and each parameter is calculated.

Table 1

[0079] In the retinal projection device 10 described above, the red light Lr, green light Lg, and blue light Lb corresponding to one pixel included in the image are incident on the reflector 15 at different incident angles so that they are reflected in the same direction by the reflector 15 by the adjustment unit 14. Therefore, since the red light Lr, green light Lg, and blue light Lb corresponding to one pixel can be reflected in the same direction by the reflector 15, chromatic aberration can be reduced.

[0080] In the adjustment unit 14, the spectroscopic device SP1, spectroscopic device SP2, and spectroscopic device SP3 are arranged in order along the optical path of the laser light Ls. When the laser light Ls including the red light Lr, green light Lg, and blue light Lb is incident on the spectroscopic device SP1, the traveling directions of the red light Lr, green light Lg, and blue light Lb are changed for each wavelength, and further, the traveling directions of each visible light are finely adjusted by the spectroscopic device SP2. Therefore, since the red light Lr, green light Lg, and blue light Lb are incident on different positions of the spectroscopic device SP3, the red light Lr, green light Lg, and blue light Lb are emitted toward the same position of the reflector 15 by the spectroscopic device SP3, so that the incident angles at which the red light Lr, green light Lg, and blue light Lb are incident on the reflector 15 can be made different from each other.

[0081] By providing the spectroscopic device SP2 between the spectroscopic device SP1 and the spectroscopic device SP3, it becomes easier to adjust the incident angles of the red light Lr, green light Lg, and blue light Lb.

[0082] In the adjustment unit 14, a mirror M is provided between the spectroscopic device SP2 and the spectroscopic device SP3. The incident angle at which the laser beam Ls (visible light) is incident on the mirror M is equal to the reflection angle at which the laser beam Ls (visible light) is reflected by the mirror M. Therefore, the traveling direction of the laser beam Ls (visible light) can be changed without being affected by the wavelength of the laser beam Ls (visible light). Accordingly, the degree of freedom in arranging the spectroscopic device SP1, the spectroscopic device SP2, and the spectroscopic device SP3 can be increased.

[0083] Each spectroscopic device is a metalens including a plurality of nanostructures 60 provided along the incident surface of the spectroscopic device. By using the metalens, the spectroscopic device can be easily realized.

[0084] A collimator lens 12 is provided between the light source unit 11 and the movable mirror 13. For this reason, the divergence of the laser beam Ls is suppressed, so that the adjustment of the incident angles of the red light Lr, the green light Lg, and the blue light Lb by the adjustment unit 14 can be performed more reliably.

[0085] Since the reflector 15 is a metasurface mirror, the reflection angle of light changes depending on the wavelength of the light. According to the retinal projection device 10, even when the metasurface mirror is used as the reflector 15, chromatic aberration can be reduced.

[0086] Note that the retinal projection device according to the present disclosure is not limited to the above embodiment.

[0087] The retinal projection device 10 may not include the collimator lens 12.

[0088] The adjustment unit 14 only needs to include two or more spectroscopic devices SP k and may not include the mirror M.

[0089] Each spectroscopic device SP k may be a diffractive lens. By using the diffractive lens, the spectroscopic device SP k can be easily realized.

[0090] Each spectroscopic device SP k may be a prism. By using a prism, the spectroscopic device SP k can be easily realized.

[0091] The reflector 15 may be any reflector whose reflection angle of light changes depending on the wavelength of the light, and is not limited to a meta-mirror.

[0092] (Appendix) [Clause 1] A retinal projection device mounted on a near-eye wearable device, a light source that emits laser light including at least one of red light, green light, and blue light, a movable mirror that performs scanning with the laser light, a reflector that reflects the laser light that has passed through the movable mirror and irradiates the retina of a user wearing the near-eye wearable device with the reflected light to project an image onto the retina, an adjustment unit provided between the movable mirror and the reflector, and causing the red light, the green light, and the blue light corresponding to one pixel included in the image to be incident on the reflector at different incident angles so that the red light, the green light, and the blue light corresponding to the one pixel are reflected in the same direction by the reflector, A retinal projection device comprising:

[0093] [Clause 2] The adjustment unit is a first spectroscopic device and a second spectroscopic device arranged in order along the optical path of the laser light, and includes the first spectroscopic device and the second spectroscopic device whose refraction angle changes depending on the wavelength of the laser light, the laser light that has passed through the movable mirror is incident on the first spectroscopic device, The second spectroscopic device emits the red light, the green light, and the blue light corresponding to the one pixel toward the same position of the reflector. The retinal projection device according to Clause 1.

[0094] [Clause 3] The retinal projection device according to clause 2, wherein each of the first spectroscopic device and the second spectroscopic device is a metalens including a plurality of nanostructures provided along the surface on which the laser light is incident.

[0095] [Clause 4] The retinal projection device according to clause 2, wherein each of the first spectroscopic device and the second spectroscopic device is a diffractive lens.

[0096] [Clause 5] The retinal projection device according to clause 2, wherein each of the first spectroscopic device and the second spectroscopic device is a prism.

[0097] [Clause 6] The retinal projection device according to any one of clauses 2 to 5, wherein the adjustment unit is a mirror provided between the first spectroscopic device and the second spectroscopic device, and further includes the mirror that reflects the laser light in a regular reflection manner.

[0098] [Clause 7] The retinal projection device according to any one of clauses 2 to 6, wherein the adjustment unit is a third spectroscopic device provided between the first spectroscopic device and the second spectroscopic device, and further includes the third spectroscopic device whose refraction angle changes depending on the wavelength of the laser light.

[0099] [Clause 8] The retinal projection device according to any one of clauses 1 to 7, further including a collimator provided between the light source and the movable mirror, and converting the laser light into parallel light.

[0100] [Clause 9] The retinal projection device according to any one of clauses 1 to 8, wherein the reflector is a metamirror including a plurality of nanostructures provided along the surface of the lens of the near-eye wearable device facing the user's eyeball.

Description of Reference Numerals

[0101] 1... Near-eye wearable device, 3... Lens, 3a... Inner surface, 10... Retinal projection device, 11... Light source unit (light source), 12... Collimator lens (collimator), 13... Movable mirror, 14... Adjustment unit, 15... Reflector, M... Mirror, RE... Retina, SP1... Spectroscopic device (first spectroscopic device), SP2... Spectroscopic device (third spectroscopic device), SP3... Spectroscopic device (second spectroscopic device).

Claims

1. A retinal projection device mounted on a near-eye wearable device, comprising: a light source that emits a laser beam including at least one of red light, green light, and blue light; a movable mirror that performs scanning with the laser beam; a reflector that reflects the laser beam that has passed through the movable mirror and irradiates the retina of a user wearing the near-eye wearable device with the reflected light, thereby projecting an image onto the retina; an adjustment unit provided between the movable mirror and the reflector, the adjustment unit being configured to cause the red light, the green light, and the blue light corresponding to one pixel included in the image to be incident on the reflector at different incident angles so that the red light, the green light, and the blue light are reflected in the same direction by the reflector; A retinal projection device comprising the above components.

2. The adjustment unit is a first spectroscopic device and a second spectroscopic device that are arranged in order along the optical path of the laser beam, and the adjustment unit includes the first spectroscopic device and the second spectroscopic device whose refraction angle changes depending on the wavelength of the laser beam. The laser beam that has passed through the movable mirror is incident on the first spectroscopic device. The second spectroscopic device emits the red light, the green light, and the blue light corresponding to the one pixel toward the same position of the reflector. The retinal projection device according to claim 1.

3. Each of the first spectroscopic device and the second spectroscopic device is a metalens including a plurality of nanostructures provided along the surface on which the laser beam is incident. The retinal projection device according to claim 2.

4. Each of the first spectroscopic device and the second spectroscopic device is a diffractive lens. The retinal projection device according to claim 2.

5. Each of the first spectroscopic device and the second spectroscopic device is a prism. The retinal projection device according to claim 2.

6. The adjustment unit is a mirror provided between the first spectroscopic device and the second spectroscopic device, and the retinal projection device according to any one of claims 2 to 5 further includes the mirror that reflects the laser beam specularly.

7. The adjustment unit is a third spectroscopic device provided between the first spectroscopic device and the second spectroscopic device, and the retinal projection device according to any one of claims 2 to 5 further includes the third spectroscopic device whose refraction angle changes depending on the wavelength of the laser beam.

8. The retinal projection device according to any one of claims 1 to 5, further comprising a collimator provided between the light source and the movable mirror for converting the laser light into parallel light.

9. The reflector is a meta-mirror including a plurality of nanostructures provided along a surface of the lens of the near-eye wearable device facing the user's eyeball, according to any one of claims 1 to 5. Retinal projection device described.

Images