The present invention relates to an optical element, a light source device, an optical scanning device, and an irradiation device.

Abstract

To provide an optical element with which a small-sized and highly functional light source device is easily produced.SOLUTION: The optical element includes a substrate and a plurality of meta-atoms provided on the substrate, and power generated by the plurality of meta-atoms is different between a first cross section and a second cross section orthogonal to the first cross section.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an optical element, a light source device, an optical scanning device, and an irradiation device. [Background technology]

[0002] Patent Document 1 discloses a light source device in which an aspherical lens is integrally provided with a cover glass for protecting the light source. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 2682641 Summary of the Invention [Problem to be solved by the invention]

[0004] However, it is very difficult to manufacture a cover glass integrally formed with an aspherical lens, as in Patent Document 1. In particular, it is difficult to process an aspherical surface using glass materials, making it difficult to form a surface shape that is advantageous for miniaturization.

[0005] An object of the present invention is to provide an optical element that is easy to manufacture and yet small in size. [Means for solving the problem]

[0006] An optical element according to one aspect of the present invention comprises a substrate and a plurality of meta-atoms provided on the substrate, and is characterized in that the power generated by the plurality of meta-atoms is different between a first cross section and a second cross section perpendicular to the first cross section. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide an optical element that makes it easy to fabricate a small, highly functional light source device. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a cross-sectional view of an optical element according to a first embodiment. [Figure 2] 1 is a schematic diagram of a light source device according to a first embodiment. [Figure 3] 1 is a schematic diagram of a laser beam in Example 1. FIG. [Figure 4] 1 is a schematic diagram of a surface of an optical element according to a first embodiment. [Figure 5] FIG. 1 is a perspective view of a meta-atom structure according to Example 1. [Figure 6] FIG. 1 shows multiple meta-atom structures of Example 1. [Figure 7] FIG. 2 is a cross-sectional view of the structure of Example 1 in the meridional direction of the first surface. [Figure 8] FIG. 2 is a cross-sectional view of the structure of the first surface in the sagittal direction of the first embodiment. [Figure 9] FIG. 10 is a schematic diagram of a light source device according to a second embodiment. [Figure 10] FIG. 10 is a schematic diagram of the surface of the optical element of Example 2. [Figure 11] FIG. 10 is a cross-sectional view of a light source module according to a second embodiment. [Figure 12] FIG. 10 is a schematic diagram of an optical scanning device according to a second embodiment. [Figure 13] FIG. 10 is a cross-sectional view of the structure of Example 2 in the meridional direction of the first surface. [Figure 14] FIG. 10 is a cross-sectional view of the structure of the second surface of the second embodiment in the sagittal direction. [Figure 15] FIG. 10 is a schematic diagram of a face authentication system according to a third embodiment. [Figure 16] FIG. 10 is a schematic diagram of a face authentication system according to a fourth embodiment. [Figure 17] FIG. 10 is a cross-sectional view of the optical system of Example 5 when focused at infinity. DETAILED DESCRIPTION OF THE INVENTION

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings, the same reference numerals are used to designate the same components, and redundant explanations will be omitted. [Example]

[0010] Figure 1 shows cross-sectional views of the optical element (metasurface element) of this example, where Figure 1(a) and Figure 1(b) are meridional and sagittal cross-sectional views, respectively.

[0011] The optical element includes a substrate 2 and a plurality of meta-atoms provided on the substrate 2. An emission point 1 emits a light beam 10. The substrate 2 is a transmissive substrate including a meta-atom structure and a metasurface with anamorphic power. The substrate 2 has a linear expansion coefficient of 5×10 -5 [K -1 In this embodiment, the substrate 2 is made of the following materials: -7The substrate 2 is made of quartz glass. The substrate 2 has a first surface (R1 surface, incident surface) 3 onto which the light beam 10 is incident and a second surface (R2 surface, exit surface) 4 configured so that the light beam passing through the first surface 3 is irradiated (incident) onto a downstream optical system (not shown), a liquid crystal panel, or the like with a desired intensity distribution. The optical axis 20 is set to pass through the light-emitting point 1 and the coordinate origin of the first surface 3 and the second surface 4. In this embodiment, the first surface 3 and the second surface 4 are flat, and the thickness of the substrate 2 is 0.775 mm. This configuration reduces optical performance degradation due to temperature-induced expansion of the substrate 2. Therefore, the optical element with anamorphic power of this embodiment can be placed near a light source that generates a large amount of heat. Furthermore, unlike a refractive lens with a curvature on its surface, its thickness is constant, so curvature changes due to temperature rise are less likely to occur. The meta-atom structure includes structures with shapes smaller than the wavelength of the incident light. The structure is arranged so that a phase delay profile (phase difference) set according to position is satisfied in a desired wavelength band to achieve desired optical performance. The metasurface is configured so that the power generated by the multiple meta-atoms differs between a first cross section and a second cross section perpendicular to the first cross section. In this embodiment, one of the first and second cross sections is a cross section in the meridional direction, and the other is a cross section in the sagittal direction. High functionality can be achieved by adjusting the intensity distribution and angle of the output light beam in the two orthogonal directions to desired values. The metasurface is formed on at least one of the first surface 3 and the second surface 4.

[0012] In FIG. 1(a), the first surface 3 has negative power and converts the light beam 10 into a diverging light beam 11. The second surface 4 has positive power and converts the diverging light beam 11 into a parallel light beam, the output light beam 12. The metasurface is configured so that the width of the output light beam 12 is wider than when the metasurface is not provided, and the light beam density of the output light beam 12 is approximately uniform and parallel. The light beam density is defined by the light rays obtained by dividing the light beam 10 at equal angles, and is determined so that when the metasurface is not provided, the light beam density is sparser off-axis (periphery) than on-axis (center).

[0013] In Fig. 1(b), the metasurface is configured so that the beam width of the emitted beam 12 is equivalent to that when the metasurface is not provided. In addition, the metasurface is configured so that the beam density of the emitted beam 12 becomes denser and more parallel as it moves from the optical axis 20 toward the periphery.

[0014] Table 1 shows the optical parameters of the optical element of this example.

[0015] [Table 1]

[0016] In this embodiment, a diffractive metasurface with anamorphic power is formed on both the first surface 3 and the second surface 4. The metasurface may also be a dispersion-controlled diffractive surface for the purpose of correcting chromatic aberration, etc. The phase function φ, which determines the power of the metasurface, is expressed by the following equation.

[0017]

number

[0018] Here, m is the diffraction order, and c3, c5, c10, c14, c21, and c27 are phase coefficients. The terms related to c3, c10, and c21 represent the power in the sagittal direction. Table 2 shows the phase coefficients of this embodiment.

[0019] [Table 2]

[0020] In this embodiment, the phase is determined with a design wavelength λ of 520 nm and a diffraction order m of 1. In this embodiment, second, fourth, and sixth order coefficients are set in the meridional and sagittal sections. The first surface 3 has positive phase coefficients c3 and c5, giving it negative power on the optical axis (including near the axis). This allows the beam width near the axis to be widened. Furthermore, by setting negative power, the effects of wavelength dispersion can be canceled out by the second surface 4, reducing the effects of wavelength fluctuations and the like. (Explanation of laser element) FIG. 2 is a schematic diagram of a semiconductor laser 350, which is an example of a light source device according to this embodiment. A laser chip (laser crystal) 303 and a monitoring photodiode 308 are encapsulated in a package 304 containing an optical element 300 with a metasurface, with the laser chip 303 abutting a reference portion (not shown), using a sealing material 302. The laser chip 303 is attached to a heat sink 306 via a submount 305. The photodiode 308 is disposed on the rear side of the laser chip 303 and is irradiated with a laser beam (laser light, emitted light) from the rear side of the laser chip 303. The electrodes of the laser chip 303 and the photodiode 308 are connected to corresponding terminals 309. A laser beam 301 output from the front side of the laser chip 303 is radiated to the outside through the optical element 300.

[0021] 3 is a schematic diagram of a laser beam 301 emitted from a laser chip 303. In the laser chip 303, the laser beam 301 is emitted from a rectangular near-field pattern (NFP) 501 serving as a light-emitting point, and is incident on an optical element 300. Reference numeral 510 denotes an elliptical far-field pattern (FFP), and the minor axis direction of the NFP 501 is a major axis 502, and the major axis direction of the NFP 501 is a minor axis 503.

[0022] FIG. 4 is a schematic diagram of the surface of the optical element 300. The optical element 300 is composed of a circular planar substrate (transmitting substrate) with a diameter of 2.0 mm. The holding portion (reference portion) 602 is a mechanical attachment portion that abuts against a holder or the like. The meta-atom structures 603 are virtual regions obtained by dividing the planar substrate into rectangular regions at regular intervals, and are configured with the same length in the meridional direction 610 and the sagittal direction 611. The meta-atom structures 603 are uniformly and tightly arranged within ranges of diameters of 0.7 mm and 1.6 mm on the first surface 3 and the second surface 4, respectively.

[0023] FIG. 5 is a perspective view of the meta-atom structure 603. The meridional length 610 and sagittal length 611 of the meta-atom structure 603 are 350 nm. A cylindrical structure 650 with a height of 1200 nm is formed on top of the meta-atom structure 603. The structure 650 is made of silicon nitride (Si3N4). The height 654 is constant throughout, and the length (maximum diameter) 652 in the meridional and sagittal directions varies depending on the position. The length 652 may be approximately the same as the design wavelength, for example, 500 nm or less. In this embodiment, the structure 650 is cylindrical, but the present invention is not limited thereto. The structure 650 may be, for example, a square prism or a triangular prism. Furthermore, multiple structures 605 may be arranged in a combination of different shapes, such as a square prism and a square prism.

[0024] 6 is a diagram showing three adjacent meta-atom structures 603. In this example, the meridional length 610 is set to 350 nm, and the phase is continuously changed by changing the meridional lengths 701, 702, and 702 of the structures 650 within the effective range. In other words, the structure spacing 710 is changed depending on the position to create a phase difference. In this example, the changes in the lengths of the multiple structures from the center to the periphery in the meridional and sagittal directions are different from each other.

[0025] FIG. 7 is a cross-sectional view of the structures on the first surface 3 in the meridional direction. FIG. 8 is a cross-sectional view of the structures on the first surface 3 in the sagittal direction. In this embodiment, anamorphic power can be obtained by varying the change in length of the structures from on-axis to off-axis in two cross sections perpendicular to each other in the meridional and sagittal directions. The number of structures on the first surface 3 is approximately 4 million. In this embodiment, the minimum length of the structures is 45 nm, and the minimum structure spacing is 45 nm, and the optical element 300 can be fabricated by lithography.

[0026] When the power having the larger absolute value of the powers at the first and second cross sections is P1 and the power having the smaller absolute value is P2, it is preferable that the optical element 300 satisfies at least one of the following conditional expressions (1) and (2):

[0027] 0.1<|P1| (1) 0.20<|P2 / P1|<0.95 (2) By satisfying at least one of the conditional expressions (1) and (2), it is possible to achieve both miniaturization of the optical element 300 and ease of manufacturing, which is preferable.

[0028] In this embodiment, as described above, one of the first and second cross sections is a cross section in the meridional direction, and the other is a cross section in the sagittal direction. In this embodiment, the power of the cross section in the meridional direction is 0.434, and the power of the cross section in the sagittal direction is 0.204, so the powers P1 and P2 are 0.434 and 0.204, respectively. Therefore, |P2 / P1| is 0.469. Therefore, conditional expressions (1) and (2) are satisfied.

[0029] It is preferable that the numerical ranges of conditional expressions (1) and (2) be set to the numerical ranges of the following conditional expressions (1a) and (2a). In particular, it is more preferable to satisfy conditional expression (2a), since this can reduce performance degradation due to assembly performance.

[0030] 0.2<|P1|<10000.0 (1a) 0.30<|P2 / P1|<0.90 (2a) It is more preferable that the numerical ranges of the conditional expressions (1) and (2) are the numerical ranges of the following conditional expressions (1b) and (2b).

[0031] 0.3<|P1|<10000.0 (1b) 0.35<|P2 / P1|<0.85 (2b) As described above, according to the configuration of this embodiment, it is possible to realize an optical element that makes it easy to fabricate a small, highly functional light source device.

[0032] The optical element of this embodiment may be mounted on, for example, an optical scanning device, a light source of an optical pickup, a laser projector, AR glasses, and an irradiation device for face authentication. [Example]

[0033] 9 is a schematic diagram of a VCSEL package, which is an example of a light source device according to this embodiment. The VCSEL package includes a mounting substrate 210, a VCSEL (light-emitting element) 200, and an optical element 230. The mounting substrate 210 is configured to have the same external dimensions as the optical element 230. The VCSEL 200 is mounted on the mounting substrate 210 via a submount substrate 220 and a die-bonding material (bonding layer) 240. An electrode on the top surface of the VCSEL 200 is connected by a wire 250 to wiring formed on the mounting substrate 210. The optical element 230 is adhesively fixed to a support 270 via an adhesive (not shown). This makes it possible to prevent dust from entering the VCSEL package.

[0034] FIG. 10 is a schematic diagram of the surface of the optical element 230. The optical element 230 is composed of a 5 mm square planar substrate. The optical element 230 has a holding portion 702 and a meta-atom structure 703. The meta-atom structure 703 has a meridional length 710 and a sagittal length 711, both equal to 400 nm, and a cylindrical structure with a height of 700 nm is formed on top of it. The planar substrate is made of S-bsl7 (OHARA), and its height is constant throughout, while its lengths in the two directions vary depending on the position. In this embodiment, the optical element 230 is fabricated in a rectangular shape and is mounted based on a plane parallel to the meridional and sagittal directions. This reduces rotational errors around the optical axis during mounting, thereby reducing degradation of optical performance due to rotational errors around the optical axis, which are inherent to anamorphic elements.

[0035] In this embodiment, the first surface 3 of the optical element 230 is a rotationally symmetric surface, and the second surface 4 is an optical surface having anamorphic power, and the intensity distribution and angle of the emitted light beam are set to desired values, thereby achieving high performance.

[0036] Table 3 shows the optical parameters of the optical element of this example.

[0037] [Table 3]

[0038] In this embodiment, a diffractive metasurface with anamorphic power is formed on both the first surface 3 and the second surface 4. The phase function φ that determines the power of the metasurface is expressed by the following equation.

[0039]

number

[0040] Here, m is the diffraction order, and c3, c5, c10, c14, c21, and c27 are phase coefficients. The terms related to c3, c10, and c21 represent the power in the sagittal direction. Table 4 shows the phase coefficients of this embodiment.

[0041] [Table 4]

[0042] In this embodiment, the phase is determined with a design wavelength λ of 790 nm and a diffraction order m of 1. Also, in this embodiment, second- and fourth-order coefficients are set in the meridional and sagittal sections. The first surface 3 is a rotationally symmetric surface with convex power near the axis, with phase coefficients c3 and c5 equal to phase coefficients c10 and c14. The second surface 4 has power only in the sagittal direction, and is configured so that the light beam emitted from the second surface 4 becomes convergent light in the sagittal direction.

[0043] In this embodiment, the length of the structure changes from the center to the periphery. In addition, since the structure has anamorphic power, the length is set to be different between the meridional section and the sagittal section.

[0044] FIG. 11 is a cross-sectional view of the light source module (laser light source module) of this embodiment. FIGS. 11(a) and 11(b) are meridional and sagittal cross-sectional views, respectively. The light source 260 is composed of a VCSEL and emits a light beam. The substrate 261 includes a meta-atom structure and is provided with a metasurface having anamorphic power, which converts the light beam emitted from the light source 260 into a parallel light beam in the meridional direction and into a convergent light beam in the sagittal direction. In this embodiment, the substrate 261 has a linear expansion coefficient of 72×10 -7The metasurface is constructed from a material that is resistant to light. This allows an optical element with anamorphic power to be placed near a light source that generates a large amount of heat. Furthermore, unlike refractive lenses with a curvature on the surface, the thickness is constant, so the curvature is less likely to change with temperature rise. The aperture (slit member) 262 determines the beam width. The phase function of the metasurface and the distance from the light source 260 to the metasurface are determined so that the light is focused at focusing position A, which is 45.3 mm away from the light source 260 in the sagittal direction.

[0045] FIG. 12 is a schematic diagram of an optical scanning device using the light source module of this embodiment. The substrate 261 converts the light beam emitted from the light source 260 into a flat light beam in the main scanning direction and a convergent light beam in the sub-scanning direction, and forms a substantially linear image on the deflection surface (deflective reflection surface) of the optical deflector 263 in the sub-scanning cross section. The first cross section is the main scanning cross section, and the second cross section is the sub-scanning cross section. The diaphragm 262 limits the light beam passing through the substrate 261. The optical deflector 263 is an optical deflector with multiple deflection surfaces and a rotating polygon mirror rotated by a driving means (not shown), such as a motor. The optical deflector 263 deflects the light beam from the light source 260 to scan the scanned surface 265 in the main scanning direction. The fθ lens 264 forms a spot on the scanned surface 265 using the deflected light beam from the optical deflector 263. The deflecting surface and the scanned surface 265 are set in a substantially conjugate relationship in the sub-scanning cross section, which reduces the deviation of the imaging position due to the tilt of the deflecting surface (plane tilt). By using the light source module, the distance from the light source 260 to the optical deflector 263 can be shortened.

[0046] FIG. 13 is a cross-sectional view of the structures on the first surface 3 in the meridional direction. FIG. 14 is a cross-sectional view of the structures on the second surface 4 in the sagittal direction. In this embodiment, the first surface 3 has a rotationally symmetric shape, and the second surface 4 has power only in the sagittal direction. This allows the changes in the lengths of the structures from on-axis to off-axis to be different in two cross sections perpendicular to each other in the meridional and sagittal directions, thereby achieving anamorphic power. The number of structures on the first surface 3 is approximately 10,000 within a 2 mm square area. The minimum structure length is 52 nm, and the minimum structure spacing is 52 nm, making it possible to fabricate optical elements using lithography.

[0047] When the power of the first or second cross section having the larger absolute value is P1 and the power of the second cross section having the smaller absolute value is P2, the optical element preferably satisfies at least one of the above-mentioned conditional expressions (1) and (2).

[0048] In this embodiment, the power of the cross section in the meridional direction is 0.200, and the power of the cross section in the sagittal direction is 0.224, so the powers P1 and P2 are 0.224 and 0.200, respectively. Therefore, |P2 / P1| is 0.894. Therefore, conditional expressions (1) and (2) are satisfied.

[0049] As described above, according to the configuration of this embodiment, it is possible to realize an optical element that makes it easy to fabricate a small, highly functional light source device. [Example]

[0050] In recent years, the demand for improved security has led to an increasing demand for facial recognition. Generally, facial recognition is a technology that detects human facial regions from digital images and identifies individuals, but there are also known technologies that can distinguish between flat and three-dimensional objects. Even with the conventional square pattern projection method, it is possible to identify faces in dark places using a flood illuminator. However, because the illumination range is wide, the light intensity of each dot is low, which reduces detection accuracy, and increasing the light intensity increases power consumption.

[0051] FIG. 15 is a schematic diagram of a face authentication system using the anamorphic light source device of this embodiment. A highly functional mobile phone (smartphone) 960 has a light projector (laser dot projector) 961 and a camera 962 on its top. 950 is an infrared laser dot as invisible light. The anamorphic light source device installed in the highly functional mobile phone 960 passes a light beam from a VCSEL light source having multiple light-emitting points (not shown) through an optical element, which is an anamorphic metasurface element, and emits it from the light projector 961. The dot pattern 951 emitted from the light projector 961 is projected onto a rectangular illumination area. In this embodiment, it is projected horizontally onto a subject 952 such as a face. In this embodiment, the longitudinal cross section of the illumination area is the first cross section, and the lateral cross section of the illumination area is the second cross section. The position of the dot pattern 951 can be photographed by the camera 962, calculated, and compared to provide information for identifying an individual, along with a planar image.

[0052] In this embodiment, by using an anamorphic light source device, it is possible to provide a face recognition system that uses laser dots only in the range necessary for face recognition without changing the number or arrangement of light emitting points of the light source, and that has high utilization efficiency of the laser light amount. In the anamorphic light source device of this embodiment, the height of the optical element is set so that the second surface 4 of Example 1 generates high-order diffracted light.

[0053] In this embodiment, the meta-atomic structure of the first surface 3 and / or the second surface 4 is changed to emit higher-order diffracted light, but the same effect can be obtained by providing a separate diffraction element.

[0054] In facial recognition technology, the dot position generated by the anamorphic light source device may be determined using AI (artificial intelligence) and deep learning (one of the deep learning or machine learning techniques).

[0055] As described above, according to the configuration of this embodiment, it is possible to realize an optical element that makes it easy to fabricate a small, highly functional light source device. [Example]

[0056] 16 is a schematic diagram of a face authentication system using the anamorphic light source device of this embodiment. In this embodiment, only the configuration different from that of embodiment 3 will be described, and a description of the same configuration will be omitted.

[0057] This embodiment differs from embodiment 3 in that the dot pattern is made vertically long. In this embodiment, the vertical concavities and convexities of the face are used as features, and recognition is performed using data that is asymmetric in the longitudinal direction, thereby improving recognition accuracy compared to the configuration of embodiment 3. In this embodiment, a vertically long dot pattern is used, but a similar effect can be obtained by using a cross pattern or the like. [Example]

[0058] FIG. 17 is a cross-sectional view of the optical system 100 when focused at infinity. The optical element described in Example 1 may be used in part of the optical system 100. The optical system 100 has, arranged in order from the object side to the image side, an open aperture stop (aperture stop) SP, a first positive lens (first lens) 101, and a second negative lens (second lens) 102. The optical system 100 also has, arranged in order from the object side to the image side, a third lens 103 having a first transmissive-reflective surface HM1 and a second transmissive-reflective surface HM2, and a member G such as a glass block such as a prism and a sensor protective glass. The third lens 103 has a quarter-wave plate QWP on the image side of the first transmissive-reflective surface HM1.

[0059] A focusing group f is composed of a first positive lens 101, a second negative lens 102, and a third lens 103. Focusing is performed by integrally moving each lens that composes the focusing group f in the optical axis direction. Ry1 is an axial ray, and Ry2 is the most off-axis ray. The optical system 100 is configured to guide the axial ray Ry1 to an image plane IM.

[0060] As described above, according to the configuration of this embodiment, it is possible to realize an optical element that makes it easy to fabricate a small, highly functional light source device.

[0061] The disclosure of this embodiment includes the following configuration. (Configuration 1) a substrate and a plurality of meta-atoms disposed on the substrate; An optical element, wherein the power generated by the plurality of meta-atoms is different between a first cross section and a second cross section perpendicular to the first cross section. (Configuration 2) The substrate has a linear expansion coefficient of 1×10 -5 [K -1 ] The optical element according to configuration 1, characterized in that it is made of the following materials: (Configuration 3) When the power at the first and second cross sections, whichever has a larger absolute value, is designated as P1 and the power at the second cross section, which has a smaller absolute value, is designated as P2, 0.20<|P2 / P1|<0.95 3. The optical element according to configuration 1 or 2, wherein the following condition is satisfied: (Configuration 4) When the power at the first cross section and the power at the second cross section, whichever has a larger absolute value, is designated as P1, 0.1<|P1| 4. The optical element according to any one of configurations 1 to 3, wherein the following condition is satisfied: (Configuration 5) 5. The optical element according to any one of configurations 1 to 4, wherein the linear expansion coefficient of the meta-atom is smaller than the linear expansion coefficient of the substrate. (Configuration 6) The optical element of configuration 5, wherein the substrate is made of quartz glass and the meta-atom is made of silicon nitride. (Configuration 7) 7. The optical element according to any one of configurations 1 to 6, wherein the plurality of meta-atoms include a plurality of meta-atoms having mutually different maximum diameters. (Configuration 8) 8. The optical element of claim 7, wherein the maximum diameter of each of the meta-atoms is 500 nm or less. (Configuration 9) 9. The optical element according to any one of configurations 1 to 8, wherein the power generated by the plurality of meta-atoms has a negative power on the optical axis. (Configuration 10) 10. The optical element according to any one of configurations 1 to 9, wherein the surface on which the plurality of meta-atoms are provided is a dispersion-controlled diffractive surface. (Configuration 11) An optical element according to any one of configurations 1 to 10; a light source that emits a light beam. (Configuration 12) 12. The light source device according to claim 11, wherein the optical element and the light source are integrally configured as one module. (Configuration 13) 13. The light source device according to configuration 11 or 12, wherein the light beam emitted from the light source device is a parallel light beam. (Configuration 14) A light source device according to any one of configurations 11 to 13; a deflector that deflects the light beam from the light source device to scan the surface to be scanned in the main scanning direction, 10. An optical scanning device, wherein the first cross section is a main scanning cross section, and the second cross section is a sub-scanning cross section. (Configuration 15) A light source device according to any one of configurations 11 to 13; a light projection unit that projects a dot pattern onto a rectangular illumination area using a light beam from the light source device, An irradiation device, wherein the first cross section is a cross section in the longitudinal direction of the irradiation area, and the second cross section is a cross section in the lateral direction of the irradiation area.

[0062] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and changes are possible within the scope of the gist of the present invention. [Explanation of symbols]

[0063] 2 Substrate (transparent substrate) 300 Optical Elements

Claims

1. a substrate and a plurality of meta-atoms disposed on the substrate; An optical element, wherein the power generated by the plurality of meta-atoms is different between a first cross section and a second cross section perpendicular to the first cross section.

2. The substrate has a linear expansion coefficient of 1×10 －５ [K －１ 2. The optical element according to claim 1, wherein the optical element is made of the following material:

3. When the power at the first and second cross sections, whichever has a larger absolute value, is designated as P1 and the power at the second cross section, which has a smaller absolute value, is designated as P2, 0.20<|P2 / P1|<0.95 3. The optical element according to claim 1, wherein the following condition is satisfied:

4. When the power at the first cross section and the power at the second cross section, whichever has a larger absolute value, is designated as P1, 0.1<|P1| 3. The optical element according to claim 1, wherein the following condition is satisfied:

5. 3. The optical element according to claim 1, wherein the linear expansion coefficient of the meta-atom is smaller than the linear expansion coefficient of the substrate.

6. The optical element of claim 5 , wherein the substrate is made of quartz glass and the meta-atom is made of silicon nitride.

7. 3. The optical element according to claim 1, wherein the plurality of meta-atoms include a plurality of meta-atoms having mutually different maximum diameters.

8. 8. The optical element according to claim 7, wherein each of the plurality of meta-atoms has a maximum diameter of 500 nm or less.

9. 3. The optical element according to claim 1, wherein the power generated by the plurality of meta-atoms has a negative power on the optical axis.

10. 3. The optical element according to claim 1, wherein the surface on which the plurality of meta-atoms are provided is a dispersion-controlled diffractive surface.

11. The optical element according to claim 1 or 2; a light source that emits a light beam.

12. 12. The light source device according to claim 11, wherein the optical element and the light source are integrally configured as one module.

13. 12. The light source device according to claim 11, wherein the light beam emitted from the light source device is a parallel light beam.

14. The light source device according to claim 11; a deflector that deflects the light beam from the light source device to scan the surface to be scanned in the main scanning direction, 10. An optical scanning device, wherein the first cross section is a main scanning cross section, and the second cross section is a sub-scanning cross section.

15. The light source device according to claim 11; a light projection unit that projects a dot pattern onto a rectangular illumination area using a light beam from the light source device, An irradiation device, characterized in that the first cross section is a cross section in the longitudinal direction of the irradiation area, and the second cross section is a cross section in the lateral direction of the irradiation area.

Images