Optical Scanning Device

Abstract

To provide an optical scanner of solid-state type, in which the deflection angle is further increased and the scan range is further widened.SOLUTION: An optical scanner 10 comprises a light source 200 and a deflection element 100, the deflection element 100 being provided with a phase modulation control unit 300 including a plurality of pixels 110 arrayed in a mono-dimensional or a two-dimensional shape, constituting a one-cycle diffraction grating by N contiguous elements (N=natural number 2 or greater), and controlling the per-pixel amount of phase modulation, with the length d in array direction of the one-cycle diffraction grating being smaller than a wavelength λ of the light emitted from the light source. Incident light is irradiated by the light source at an incidence angle θi which is oblique to a reflection surface, where the relationship sinθi+(λ / d)>1 or sinθi-(λ / d)>1 applies.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to optical scanning devices. [Background technology]

[0002] In recent years, technological developments toward the realization of autonomous driving of vehicles have been remarkable. Among these, obstacle detection using images, millimeter wave radar, and LiDAR has attracted attention. LiDAR is required to measure distance and angle. However, for angle measurement, mechanical scanning methods equipped with moving parts such as motors are mainstream for LiDAR, but for autonomous driving of vehicles that also generate vibrations while driving, solid-state type optical scanning devices without moving parts are expected.

[0003] Patent Document 1 discloses an element that can be used in a solid-state optical scanning device and functions as a spatial phase modulation element. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] U.S. Patent Application Publication No. 2019 / 0301025 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in solid-state optical scanning devices, there is a demand for a wider scanning range, i.e., it is necessary to increase the deflection angle of the scanned light beam.

[0006] In view of the above, an object of the present disclosure is to provide an optical scanning device having a larger deflection angle and a wider scanning range, even in a solid-state optical scanning device. [Means for solving the problem]

[0007] An optical scanning device according to an embodiment of the present disclosure is an optical scanning device that includes a light source and a deflection element, and deflects light emitted from the light source at a predetermined deflection angle by the deflection element, the deflection element including a plurality of pixels arranged one-dimensionally or two-dimensionally, and each pixel includes a reflective layer portion made of metal provided on a substrate, an insulating layer portion provided on the reflective layer portion, an electrode portion including a pair of metal pillar portions, a first metal pillar portion and a second metal pillar portion, extending perpendicularly from the insulating layer portion, a gap between the first metal pillar portion and the second metal pillar portion spaced apart in the arrangement direction, and a gap between the first metal pillar portion and the second metal pillar portion spaced apart in the arrangement direction. and a dielectric layer section made of a dielectric whose refractive index changes according to an applied voltage, the electrode section and the dielectric layer section being alternately arranged on the reflecting surface of the deflection element to form a diffraction grating of one period consisting of N consecutive pixels (N is a natural number of 2 or more), the length d of the diffraction grating of one period in the arrangement direction being smaller than the wavelength λ of the light emitted from the light source, the phase modulation control section being provided with a phase modulation control section which controls the amount of phase modulation for each pixel by controlling the applied voltage V to be applied to each dielectric layer section, and the incident angle θ at which the light source is obliquely incident on the reflecting surface. i The incident light is irradiated at sinθ i +(λ / d)>1, or sinθ i -(λ / d)>1. Effect of the Invention

[0008] According to the present disclosure, it is possible to provide an optical scanning device with a larger deflection angle and a wider scanning range even in a solid-state optical scanning device. [Brief description of the drawings]

[0009] [Figure 1] 1 is a diagram illustrating a schematic configuration of an optical scanning device according to an embodiment. [Diagram 2] 2 is a diagram showing a reflecting surface of a deflection element of the optical scanning device as viewed from above. [Diagram 3] FIG. 2 is a diagram illustrating a single pixel that constitutes a deflection element. [Figure 4] 1A and 1B are diagrams illustrating a diffraction grating configured by periodically arranging a plurality of pixels. [Diagram 5]1A and 1B are diagrams illustrating a diffraction grating configured by periodically arranging a plurality of pixels. [Figure 6] 1A and 1B are diagrams illustrating recombination of evanescent light in a diffraction grating composed of two pixels. [Figure 7] 1A and 1B are diagrams illustrating recombination of evanescent light in a diffraction grating composed of three or more pixels. [Figure 8] FIG. 13 is a table showing an example of a pixel embodiment. [Figure 9] 11A and 11B are diagrams illustrating analysis results of a magnetic field distribution by a deflection element according to an embodiment. [Figure 10] 11A and 11B are diagrams illustrating analysis results of a magnetic field distribution by a deflection element according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, optical scanning devices according to embodiments of the present disclosure will be described with reference to the drawings.

[0011] FIG. 1 is a diagram showing a schematic configuration of an optical scanning device according to an embodiment of the present disclosure, FIG. 2 is a diagram showing a reflecting surface 100r of a deflection element 100 of the optical scanning device 10 from above, and FIG. 3 is a diagram explaining a single pixel that constitutes the deflection element.

[0012] The optical scanning device 10 is a device that can be used, for example, as an angle measuring device in automatic driving of a vehicle, and is equipped with a light source 200 that irradiates light, a deflection element 100 that deflects the light irradiated from the light source 200 to the reflecting surface 100r of the deflection element 100 at a predetermined angle, and a phase modulation control unit 300 that controls the amount of phase modulation used by the deflection element to modulate the irradiated light.

[0013] The light source 200 is a device that emits coherent parallel light toward the deflection element 100, and is optically arranged so that the light is obliquely incident on the reflecting surface 100r of the deflection element 100. The light source element of the light source 200 may be, for example, a laser element such as a semiconductor laser element. Note that an optical system for guiding light from the light source 200 to the reflecting surface 100r is omitted. In addition, the light output is adjusted by a predetermined power source and a control unit, not shown.

[0014] The wavelength of the light emitted from the light source 200 is suitable for detecting obstacles in an automatic driving of a vehicle, and may be, for example, infrared light having a longer wavelength than visible light, more preferably near infrared light. Specifically, light having a wavelength of 905 nm or a wavelength in the 1.5 μm band, such as 1.55 μm, may be used.

[0015] The polarizer 210 is an optical element for changing the light emitted from the light source 200 into a predetermined polarization state. For example, a wire grid polarizer can be used as the polarizer 210 as a transmission type polarizer. By using such a polarizer 210, the polarization state of the light source can be changed to, for example, TM polarization.

[0016] The deflection element 100 has a plurality of pixels 110 arranged one-dimensionally or two-dimensionally along an array direction AD, and in this figure, a cross section parallel to the array direction and perpendicular to the substrate 103 is shown. The array direction AD is basically parallel to the substrate surface. Among them, the pixel 110 surrounded by the dotted line includes a reflective layer portion 101 provided on the substrate 103 made of, for example, silicon (Si) crystal, an insulating layer portion 102 provided on the reflective layer portion 101, an electrode portion 111 having a pair of metal pillars provided on the insulating layer portion 102, and a dielectric layer portion 112.

[0017] The reflective layer 101 is made of, for example, silver (Ag) and has a thickness of, for example, 100 nm. The insulating layer 102 is made of, for example, silicon oxide (SiO2) and has a thickness of, for example, 300 nm.

[0018] 1 and 2, in a single pixel 110 surrounded by a dotted line, the first metal pillar portion 111A is continuous with the adjacent pixel. Therefore, this single pixel 110 is merely conceptual, and in reality, as shown in Figures 1 and 2, the electrode portion 111 and the dielectric layer portion 112 are alternately and periodically arranged to form a striped pattern.

[0019] The first metal column portions 111A and 111B are made of, for example, silver (Ag). The dielectric material filled in the dielectric layer portion 112 is, for example, a liquid crystal material.

[0020] 2 is a diagram showing a deflection element 100 composed of a plurality of pixels 110 arranged one-dimensionally, viewed from directly above a reflecting surface 100r, in which the area surrounded by a dotted line is a single pixel 110. In such a one-dimensional deflection element 100, the electrodes are shaped like rails.

[0021] 3, the pixel 110 has a first metal column 111A and a second metal column 111B provided as an electrode section 111 consisting of a pair of metal columns on the insulating layer section 102, and the first metal column 111A and the second metal column 111B are spaced apart in the arrangement direction. A dielectric is filled in the gap between the first metal column 111A and the second metal column 111B to form a dielectric layer section 112.

[0022] 3, as in Fig. 1, a cross section parallel to the arrangement direction and perpendicular to the substrate 103 is illustrated. Here, the interval between single pixels 110 in the arrangement direction is defined as pitch p (nm), the height from the insulating layer to the reflective surface 100r is defined as height h (nm), and the width of the gap between the first metal column 111A and the second metal column 111B is defined as the length w (nm) of the gap in the arrangement direction.

[0023] The specifications of the pixel 110, more specifically, the dimensions, can be confirmed by various measuring means. For example, the shape of the surface or cross section can be confirmed by a scanning electron microscope or an atomic force microscope.

[0024] The pixels 110 are so-called plasmonic metamaterials having a nano-sized LC resonant circuit made of metal and dielectric and having a high Q value, and a reflecting surface made of such pixels 110 is also called a metasurface. In particular, the optical scanning device 10 according to the embodiment of the present disclosure is a metascanner using a dynamic metasurface that can control the deflection angle of the beam by controlling the amount of phase modulation of each pixel.

[0025] The phase modulation control unit 300 controls the applied voltage so that a predetermined voltage is applied to each of the pixels 110 individually by the drive circuit 310 electrically connected to the electrode unit 111 of each pixel 110. The phase modulation amount of the incident light incident on the pixel 110 can be changed within a predetermined range by changing the applied voltage V applied to the dielectric filled in the dielectric layer unit 112. For example, a liquid crystal material can be used as the dielectric. When liquid crystal is used as the dielectric, the orientation of the liquid crystal molecules changes according to the applied voltage, and the refractive index changes within a predetermined range, thereby changing the optical path length, and the phase modulation amount of the incident light incident on each pixel 110 can be controlled.

[0026] Furthermore, by configuring the first metal pillar 111A, the second metal pillar 111B, the gap between them, and the dielectric layer 112 of the pixel 110, which function as a metamaterial, in a predetermined manner, the pixel can be made low-profile by utilizing the resonance phenomenon.

[0027] When such a spatial phase modulation element using pixels is used as a scanner (deflector), it is possible to use it as a diffraction grating with a variable period. Fig. 4 is a diagram for explaining a diffraction grating configured by periodically arranging a plurality of pixels 110. In this figure, N pixels 110 are continuously arranged and arrayed to form a diffraction grating with one period. Then, a plurality of such diffraction gratings with one period can be arranged in the arrangement direction.

[0028] The amount of phase modulation by each pixel of the diffraction grating made up of an array of multiple pixels is adjusted by the phase modulation control unit 300 so that the total amount of phase modulation within one period is, for example, 2π (rad). The amount of phase change of each pixel is determined by 2π / N × pixel number, and the phase modulation by each pixel is not continuous but discrete, step-like, or stair-like. In this figure, the height of the steps represents the amount of phase modulation in a schematic manner. In this case, a diffraction grating with a phase modulation amount of a positive slope is shown, and the amount of phase modulation is controlled so that the pixel with a larger pixel number located further back in the direction of incidence has a larger amount of phase modulation.

[0029] The length d of one period of the diffraction grating in the arrangement direction AD is determined by the number of pixels N constituting one period and the pitch p of each pixel in the arrangement direction, and is given by d=N×p.

[0030] Fig. 5 is a diagram for explaining a diffraction grating configured by periodically arranging a plurality of pixels 110 similar to those in Fig. 4, and shows a case where the phase modulation amount is a negative slope. In this diagram, the smaller the pixel number, the larger the phase modulation amount, and the more the incident light can be deflected in the direction from which it was incident. By using the same deflection element 100 and controlling the voltage applied to each pixel by the phase modulation control unit 300, a diffraction grating with a negative slope phase modulation amount can also be realized.

[0031] If the number of all pixels in the array direction of the deflection element 100 is constant, the smaller the period of the diffraction grating is, the larger the deflection (diffraction) angle becomes, but the number of pixels N constituting one period decreases. This reduces the deflection (diffraction) efficiency η to the desired light (for example, 1st or -1st order diffracted light). For example, if the number of pixels N constituting one period is 2 pixels, ±1st order diffracted light will be generated in the case of perpendicular incidence.

[0032] In order to widen the scanning range, it is possible to narrow the pixel pitch or increase the amount of phase modulation. If the amount of phase modulation is large, it means that high-order diffracted light is being used. In a spatial phase modulator made of natural materials that does not use metamaterials, even if the refractive index change caused by voltage application is used, the height h of the pixel electrode becomes high in order to obtain the required amount of phase modulation, for example, 2π. Considering the manufacturing process, such high height and high aspect ratio should be avoided. However, a metascanner using pixels smaller than the wavelength can amplify the equivalent amount of refractive index modulation by utilizing the resonance phenomenon. Because of the high Q value, the optical path length can be increased, and the high aspect ratio of the pixel can be suppressed.

[0033] Next, we will explain how evanescent light is used to generate high-order diffracted light and increase the deflection angle. Figure 6 is a diagram explaining the recombination of evanescent light from a diffraction grating whose period consists of two pixels. In this figure, a single pixel 110 has a pitch p=550 nm, the wavelength of light emitted from the light source is 1.55 μm, and the incident angle is 45°. Since there are two pixels (N=2) in one period, if the total phase modulation amount is 2π, for example, the phase modulation amount of each pixel is 0 and π, as shown in this figure.

[0034] In such a case, the incident angle θ i Incident light A is incident obliquely at in For the reflection angle θ r Consider the reflected light reflected at sinθ r =sin i Considering ±m(λ / d), in such a diffraction grating, when the wavelength λ is 1.55 μm and d = 550 nm × 2, the +1st order diffracted light (m = +1) is sinθ r =sin i +m(λ / d)≒2.12>1. In other words, light that exceeds sinθ=1 is evanescent light. sinθ r =sin iThe diffracted light of +(λ / d)>1 becomes evanescent light and cannot propagate in space. On the other hand, the -1st order diffracted light is sinθ r =sin i -(λ / d)<1. At this time, only -1st order diffracted light is generated, and the +1st order diffracted light, which cannot propagate into space, is coupled to the -1st order diffracted light.

[0035] Similarly, a case where one period of the diffraction grating is composed of three or more pixels will be described. Fig. 7 is a diagram for explaining the recombination of evanescent light of a diffraction grating composed of five pixels in one period. Similarly in this figure, a single pixel 110 has a pitch p=550 nm, the wavelength of light emitted from the light source is 1.55 μm, and the incident angle is 45°. One period is N pixels (N is a natural number of 3 or more in this example), and N=5 in this figure. For example, if the total phase modulation amount is 2π, the phase modulation amount of each pixel with a positive phase slope is 0, 2π / 5, 4π / 5, 6π / 5, and 8π / 5.

[0036] In a diffraction grating that is phase-modulated to generate +1st-order diffracted light because the phase slope is positive, when the wavelength λ is 1.55 μm and d = 550 nm × 5, the +1st-order diffracted light (m = +1) is expressed as sinθ r =sin i +m(λ / d)≒1.27>1. sinθ r =sin i Diffracted light of +(λ / d)>1 becomes evanescent light and cannot propagate in space. On the other hand, for negative order diffracted light, sinθ r =sin i -m(λ / d)<1. At this time, a higher negative order diffracted light is generated. In this example, it is -3rd order diffracted light (m=-3). This -3rd order diffracted light is combined with +1st order diffracted light, which cannot propagate into space.

[0037] In this way, by satisfying certain conditions, evanescent light can be generated, and even if the amount of phase modulation is limited to a certain amount (for example, 2π), the deflection angle can be increased by utilizing higher-order diffracted light.

[0038] In summary, sinθ r =sinθ i Considering diffracted light where ±m(λ / d)>1, at least the +1st order diffracted light, sinθ r =sinθ i By satisfying the condition +(λ / d)>1, evanescent light can be generated and the deflection angle can be increased. This is due to the wavelength λ of the light source and its incident angle θ i This can be achieved by adjusting the length d of one period of the diffraction grating, which is composed of N pixels (N is a natural number of 2 or more), in the arrangement direction. r =sinθ i While evanescent light is generated by satisfying the condition +(λ / d)>1, sinθ r =sinθ i By satisfying -m(λ / d)<1 and generating the -mth order diffracted light that will recombine with the beam, the deflection angle can be improved. Similarly, in a deflector that is phase-modulated to generate -1st order diffracted light, sinθ r =sinθ i While evanescent light is generated when the condition -(λ / d)>1 is satisfied, sinθ r =sinθ i The deflection angle can be improved by satisfying +m(λ / d)<1 and generating m-th order diffracted light that can be recombined.

[0039] In this case, if each pixel of one period of the diffraction grating is given a pixel number n (n is a natural number equal to or less than N), the phase modulation amount of each pixel can be set to a stepped distribution that increases or decreases by TPM / N in the array direction, so that the phase modulation amount in each pixel of pixel number n is TPM×(n-1) / N; (n=1, 2, ... n), assuming that the predetermined total phase modulation amount is TPM (rad). Phase modulation based on this setting can be realized by controlling the voltage applied between each electrode by phase modulation control unit 300.

[0040] In addition, when considering the aspect of a metascanner, at least the length d of one period of the diffraction grating in the arrangement direction must be smaller than the wavelength λ of the light emitted from the light source, and more preferably d<λ / 2. Furthermore, when considering a case where one period of the diffraction grating is composed of N pixels, the pixel pitch p is p<λ / N, and more preferably p<λ / 2N.

[0041] Fig. 8 shows a table of preferred dimensions as an embodiment of the pixel 110. This figure shows pitch p (nm) which is the interval in the arrangement direction of single pixels 110, height h (nm) which is the height from the insulating layer to the reflecting surface 100r, and length w (nm) in the arrangement direction of the gap which is the width of the gap between the first metal pillar 111A and the second metal pillar 111B, which are shown in Fig. 3, and which have been confirmed to improve the deflection angle when used in the deflection element 100 through testing.

[0042] More specifically, the height h of the electrode portion is 600 to 1000 nm, as shown in Fig. 8. If the height of the electrode portion falls within this range, it can be easily manufactured using existing technology.

[0043] The length w of the gap in the arrangement direction is within 100 nm, specifically, 46.5 to 87 nm.

[0044] The pitch p of the individual pixels in the arrangement direction is 310 to 580 nm. In this range of pitch p, the relationship between p and w, p / w, is 0.1 to 0.15.

[0045] The relationship between the length w of the gap in the arrangement direction and the height h of the electrode portion, that is, h / w, is 11.49 to 19.35. In this relationship, the smaller the h / w, the easier the manufacturing process is and the greater the effectiveness is.

[0046] The light source 200 used had a wavelength of 1.55 μm and an incidence angle of 45°. The reflective layer 101 was made of silver (Ag), and the insulating layer 102 was made of silicon oxide (SiO2). A liquid crystal material was used as the dielectric material filled in the dielectric layer 112. Such a pixel 110 can be easily manufactured by applying the existing technology of nanoimprinting or the process of manufacturing a CMOS element.

[0047] An example in which the deflection angle is improved by utilizing the recombination of evanescent light will be described. FIG. 9 shows the analysis results by simulation of the magnetic field distribution phase-modulated by the deflection element 100 described in FIG. 6. The conditions in this analysis are the same as those described in FIG. 6. The left side is a comparative example under conditions in which no evanescent light is generated, and the number of pixels is N=3, in which phase modulation is applied to generate −1st order diffracted light. The deflection angle in this comparative example is −11.6°. In contrast, the right side is an embodiment under conditions in which evanescent light is generated, and the number of pixels is N=2. The deflection angle in this embodiment is improved to −41.0° by utilizing −1st order diffracted light.

[0048] FIG. 10 shows the analysis results of a simulation of the magnetic field distribution phase-modulated by the deflection element 100 described in FIG. 7. The left side is a comparative example under conditions where no evanescent light is generated, with the number of pixels N=3, where phase modulation is applied to generate -1st order diffracted light. The deflection angle in this comparative example is -11.6°. In contrast, the right side is an embodiment under conditions where evanescent light is generated, with the number of pixels N=5, where phase modulation is applied to generate +1st order diffracted light. The deflection angle in this embodiment is improved to -68.3° by utilizing -3rd order diffracted light.

[0049] In this way, by satisfying the conditions for generating evanescent light, high-order diffracted light in the direction opposite to the phase modulation direction can be generated, and the deflection angle can be improved.

[0050] As described above, according to the optical scanning device 10 according to the embodiment of the present disclosure, the optical scanning device 10 includes a light source 200 and a deflection element 100, and deflects light emitted from the light source 200 at a predetermined deflection angle by the deflection element 100. The deflection element 100 includes a plurality of pixels 110 arranged one-dimensionally or two-dimensionally. The pixels each include a reflective layer portion 101 made of a metal provided on a substrate, an insulating layer portion 102 provided on the reflective layer portion, an electrode portion 111 including a pair of metal pillar portions, a first metal pillar portion 111A and a second metal pillar portion 111B, extending perpendicularly from the insulating layer portion, and an electrode portion 111 between the first metal pillar portion and the second metal pillar portion spaced apart in the arrangement direction. a gap, and a dielectric layer portion 112 made of a dielectric material that changes its refractive index in response to an applied voltage, the electrode portions and the dielectric layer portion are alternately arranged on the reflecting surface of the deflection element 100 to form a diffraction grating of one period consisting of N consecutive pixels 110 (N is a natural number of 2 or more), the length d of the diffraction grating of one period in the arrangement direction being smaller than the wavelength λ of light emitted from the light source 200, and a phase modulation control portion 300 is provided for controlling the amount of phase modulation for each pixel by controlling an applied voltage V to be applied to each dielectric layer portion 112, and incident light is irradiated from the light source 200 at an incident angle θi that is oblique incidence on the reflecting surface, and a phase modulation control portion 300 is provided for controlling the amount of phase modulation for each pixel by controlling an incident voltage V to be applied to each dielectric layer portion 112, and the ... sinθ i +(λ / d)>1, or sinθ r =sinθ i Because -(λ / d)>1, even in a solid-state optical scanning device 10 using a metasurface, evanescent light that cannot propagate is coupled to higher-order diffracted light, thereby increasing the deflection angle and widening the scanning range.

[0051] Furthermore, since the length w of the gap in the arrangement direction is 100 nm or less, a high Q value can be obtained even in a solid-state optical scanning device using a metasurface, and the deflection angle can be increased while suppressing the height h of the electrode part, thereby making it possible to widen the scanning range.

[0052] Furthermore, the pitch p of a single pixel in the arrangement direction is 310 to 580 nm, and p / w is 0.1 to 0.15, so that even in a solid-state optical scanning device using a metasurface, it is possible to suppress absorption losses due to the electrodes while maintaining a high Q value, increase the deflection angle, and widen the scanning range.

[0053] Furthermore, since the height h of the electrode portion is 600 to 1000 nm, it can be easily manufactured using existing technology.

[0054] In addition, since the ratio of the length w of the gap in the arrangement direction to the height h of the electrode portion is w:h = 1:11 to 19, the deflection angle can be increased and the scanning range can be made wider, even in a solid-state optical scanning device using a metasurface.

[0055] Furthermore, the phase modulation control unit 300 controls the amount of phase modulation by each pixel constituting one period of the diffraction grating so that the amount of phase modulation increases or decreases by TPM / N in the arrangement direction for a predetermined total phase modulation amount TPM (rad), thereby adjusting the period to a desired one, adjusting the deflection angle, controlling the reflected wavefront, and obtaining a desired diffraction grating.

[0056] Furthermore, since the dielectric material is a liquid crystal material, the refractive index can be changed over a relatively wide range.

[0057] Although the embodiment of the present disclosure has been described, the aspects of the present disclosure are not limited to this embodiment. [Explanation of symbols]

[0058] 10 Optical scanning device 100 deflection element 101 Reflective layer section 102 Insulating layer 103 Substrate 110 pixels 111 Electrode section 111A First metal column 111B Second metal column 112 Dielectric layer 200 light source 210 Deflector 300 Phase modulation control section 310 Drive circuit

Claims

1. An optical scanning device comprising a light source and a deflection element, the optical scanning device reflecting light emitted from the light source by the deflection element and deflecting the light at a predetermined deflection angle, The deflection element includes a plurality of pixels arranged one-dimensionally or two-dimensionally, The pixel is a metal reflective layer provided on a substrate; an insulating layer portion provided on the reflective layer portion; an electrode portion including a pair of metal columns, a first metal column portion and a second metal column portion, extending perpendicularly from the insulating layer portion; a gap between the first metal column and the second metal column spaced apart from the first metal column in the arrangement direction; a dielectric layer portion filled in the gap and made of a dielectric material whose refractive index changes in response to an applied voltage; the electrode portions and the dielectric layer portions are alternately arranged on the reflecting surface of the deflection element to form a diffraction grating having one period including N consecutive pixels (N is a natural number of 2 or more); a length d of the diffraction grating in the arrangement direction of one period is smaller than a wavelength λ of the light emitted from the light source, a phase modulation control unit that controls an amount of phase modulation for each pixel by controlling an applied voltage V applied to each dielectric layer unit, the phase modulation control unit controls a phase modulation amount by each pixel constituting one period of the diffraction grating so as to increase or decrease the phase modulation amount by TPM / N in an array direction for a predetermined total phase modulation amount TPM (rad); The light source irradiates the reflecting surface with light at an incident angle θi such that the light is obliquely incident on the reflecting surface; An optical scanning device in which evanescent light is generated when sin θi+(λ / d)>1 or sin θi−(λ / d)>1 is satisfied.

2. The optical scanning device according to claim 1 , wherein a length w of the gap in the arrangement direction is 100 nm or less.

3. The pitch p of a single pixel in the array direction is 310 to 580 nm; 2. The optical scanning device according to claim 1, wherein p / w is 0.1 to 0.

15.

4. 2. The optical scanning device according to claim 1, wherein the height h of the electrode portion is 600 to 1000 nm.

5. 5. The optical scanning device according to claim 2, wherein a ratio of a length w of the gap in the arrangement direction to a height H of the electrode portion is w:h=1:11-19.

6. An optical scanning device described in any one of claims 1 to 5, wherein the dielectric is a liquid crystal material.

7. A polarizer is disposed between the light source and the deflection element; The optical scanning device according to claim 1 , wherein the light emitted from the light source by the polarizer is incident on the deflection element in a TM polarization state.

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