Light beam deflecting device and light projecting and receiving device

Abstract

To achieve a light beam deflecting device that does not need to perform individual optical alignment for each of a plurality of observation visual fields.SOLUTION: A light beam deflecting device comprises: a planar optical waveguide circuit 3 that branches light emitted from a light source 1 into a first number of light beams, the first number being the same as the number of divided areas in a first direction in a target space, and emits the branched light beams from a predetermined emission position in the first direction so that the light beams are simultaneously radiated to the position of one pixel in a corresponding area; a first optical system 4 that converts the first number of light beams emitted from the planar optical waveguide circuit 3 into parallel light beams and emits the light beams at an emission angle corresponding to the predetermined emission position; and a second optical system 5 that reflects the first number of light beams emitted from the first optical system and radiates the reflected light beams to the target space.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a light beam deflector that irradiates a target space with light and performs beam scanning in horizontal and vertical directions, and to a light projecting and receiving device that integrates a light beam deflector and a light receiving device. [Background technology]

[0002] LiDAR (Light Detection and Ranging) is a technology that uses laser light to measure the distance to an object and its shape based on the information from the reflected light. In LiDAR, the light beam that is irradiated onto the object must be deflected to obtain a 3D image of the object. MEMS (Micro Electro Mechanical Systems) mirrors are used as beam deflection devices for automotive LiDAR because they are small, inexpensive, and highly reliable.

[0003] When applying MEMS mirrors to automotive LiDAR, (1) the optical deflection angle of the MEMS mirror is small compared to the required field of view, and (2) it is necessary to achieve both the required frame period and spatial resolution. Therefore, the observation field of view is divided into multiple fields of view, and measurements are taken simultaneously in each of the divided fields of view.

[0004] For example, Non-Patent Document 1 proposes a LiDAR device that divides the horizontal field of view into three parts by using three transmitting laser diodes, as shown in FIG.

[0005] The LiDAR device shown in Non-Patent Document 1 employs a dTOF (direct Time of Flight) method, in which pulsed light is emitted from a light source, the light reflected by the target is received by a sensor, and the distance to the target is measured by detecting the time of flight of the light from when it is emitted until it is received by the sensor.

[0006] The dTOF method can be realized with a relatively simple configuration, and has been integrated into single chips and modularized, leading to its widespread use in automobiles, platform gates, industrial robots, etc. However, the dTOF method requires a filter to remove the effects of sunlight, etc., and cannot distinguish whether the received pulse is its own or that of another source, which poses the problem of interference with other LiDAR devices.

[0007] One method proposed for measuring the distance to an object is the frequency-modulated continuous wave (FMCW) method, which continuously emits laser light while changing its frequency and measures the frequency shift of the light returned from the object to measure the distance to the object. The FMCW method has limited practical application due to its complex configuration, but it is attracting attention as a high-precision LiDAR for autonomous driving because it is not affected by sunlight or other LiDARs and does not require filters. [Prior art documents] [Non-patent literature]

[0008] [Non-Patent Document 1] C.Niclass et al.,OPTICS EXPRESS 21 May 2012 Vol.20 ,No.11,11863 Summary of the Invention [Problem to be solved by the invention]

[0009] In the FMCW method, in addition to the round-trip propagation time of light, frequency-modulated light must be sent back and forth, which increases the measurement time. In addition, the observation field must be divided to cover the long measurement time, which requires multiple transmitter / receiver modules, and these multiple individual transmitter / receiver modules must be implemented with precision.

[0010] The conventional device described above is configured to implement multiple individual transmitter / receiver modules, and in order to accurately set the observation field of view covered by each transmitter / receiver module, it was necessary to perform optical alignment individually for each of the multiple observation fields.

[0011] The present invention has been made to solve the above-mentioned problems, and aims to provide a light beam deflector that can easily and accurately set an observation field of view without having to perform optical alignment individually for each of multiple observation fields. [Means for solving the problem]

[0012] In order to solve the above problem, the light beam deflection device of the present invention includes a light source; a planar optical waveguide circuit that branches light emitted from the light source into a first number of light beams equal to the number of divided areas in a first direction of a target space and emits the branched light beams from predetermined emission positions in the first direction so that each of the light beams is simultaneously irradiated onto a pixel position in a corresponding area; a first optical system that converts each of the first number of light beams emitted from the planar optical waveguide circuit into parallel light beams and emits the parallel light beams at an emission angle corresponding to the predetermined emission position; and a second optical system that reflects each of the first number of light beams emitted from the first optical system and irradiates each reflected light beam onto the target space.

[0013] In addition, one configuration example of the light beam deflection device of the present invention further includes a control circuit that controls the deflection angle of the reflected light in the second optical system, and the control circuit is configured to perform drive control in the first direction to simultaneously deflect the first number of light beams irradiated from the second optical system to the target space in the first direction, and drive control in the second direction to simultaneously deflect the first number of light beams irradiated from the second optical system to the target space in the second direction by changing the deflection angle of the reflected light in a second direction perpendicular to the first direction.

[0014] In addition, in one configuration example of the light beam deflection device of the present invention, the second optical system is a MEMS mirror, the drive control in the first direction is resonant drive control on a resonant drive axis of the MEMS mirror, and the drive control in the second direction is linear drive control on a linear drive axis of the MEMS mirror.

[0015] In one configuration example of the optical beam deflector of the present invention, the planar optical waveguide circuit includes a splitter that splits the light emitted from the light source into the first number of light beams, and the splitting ratio of the light energy in the splitter is set to increase at a predetermined rate with increasing distance from the emission position at the center of the planar optical waveguide circuit.

[0016] In order to solve the above-mentioned problems, a light projecting and receiving device of the present invention includes the above-mentioned optical beam deflector, the first number of first photodetectors that convert incident light into an electric signal, the first number of second photodetectors that convert incident light into an electric signal, and the first number of transimpedance amplifiers that calculate a difference between output signals of the first and second photodetectors, and the planar lightwave circuit includes a first optical waveguide, a first optical splitter that splits the light guided in the optical waveguide into two lights at a predetermined splitting ratio, a second optical waveguide and a third optical waveguide that guide the light output from the optical splitter, a second optical splitter that splits the light from the first optical waveguide into the first number of lights, a third optical splitter that splits the light from the second optical waveguide into the first number of lights, and a third optical amplifier that splits the light output from the second optical splitter into the first number of lights. the first number of fourth optical waveguides that guide the light output from the third optical splitter; the first number of fifth optical waveguides that guide the light output from the third optical splitter; the first number of fourth optical splitters that split into two each of the first number of return lights that are reflected by an object present in the target space and enter the fourth optical waveguides; and the first number of first couplers that combine the light output from the fourth optical splitter and the light guided in the fifth optical waveguides in equal proportions and output the split light in half, wherein the first photodetector converts the light output from a first port of the first coupler into an electrical signal, the second photodetector converts the light output from a second port of the first coupler into an electrical signal, and the transimpedance amplifier calculates the difference between the output signal from the first photodetector and the output signal from the second photodetector. [Effects of the Invention]

[0017] According to the present invention, it is possible to realize a light beam deflector that can easily and accurately set a plurality of observation fields without individually performing optical alignment for each of the observation fields. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a diagram illustrating the configuration of a light beam deflector according to a first embodiment of the present invention. [Figure 2A] FIG. 2A is a diagram illustrating a detailed configuration of the light beam deflector according to the first embodiment of the present invention. [Figure 2B] FIG. 2B is a diagram illustrating a detailed configuration of the light beam deflector according to the first embodiment of the present invention. [Figure 2C] FIG. 2C is a diagram for explaining a detailed configuration of the light beam deflector according to the first embodiment of the present invention. [Figure 3] FIG. 3 is a diagram for explaining the observation field and beam scanning according to the first embodiment of the present invention. [Figure 4A] FIG. 4A is a diagram for explaining driving of the MEMS mirror according to the first embodiment of the present invention. [Figure 4B] FIG. 4B is a diagram for explaining driving of the MEMS mirror according to the first embodiment of the present invention. [Figure 5] FIG. 5 is a diagram showing the configuration of a light projecting and receiving device according to a third embodiment of the present invention. [Figure 6] FIG. 6 is a block diagram showing an example of the configuration of a computer of a control circuit that controls a MEMS mirror according to an embodiment of the present invention. [Figure 7] FIG. 7 is a diagram showing the configuration of a conventional light beam deflector. DETAILED DESCRIPTION OF THE INVENTION

[0019] <Configuration of the optical beam deflector> Hereinafter, embodiments of the present invention will be described with reference to the drawings. Fig. 1 is a diagram showing the configuration of a light beam deflector according to a first embodiment of the present invention. In the following description, a case will be described in which the observation area of ​​the target space is divided in the horizontal direction (X-axis direction), but the observation area of ​​the target space may also be configured to be divided in the vertical direction (Y-axis direction). In this case, the direction in which the observation area is divided may be described as a first direction, and the direction perpendicular to the first direction may be described as a second direction.

[0020] The optical beam deflector includes a semiconductor laser 1, an optical amplifier 2 that amplifies the light emitted from the semiconductor laser 1, a planar optical waveguide circuit 3 that branches the light amplified by the optical amplifier 2 into a first number of light beams equal to the number of areas divided in the horizontal direction (first direction) of a target space and emits the branched light beams from predetermined horizontal emission positions so that each of the light beams is simultaneously irradiated onto a pixel position in the corresponding area, a focal plane lens 4 (first optical system) that converts each of the first number of light beams emitted from the planar optical waveguide circuit 3 into parallel light beams and emits each of the parallel light beams at an emission angle corresponding to the predetermined emission position, a MEMS mirror 5 (second optical system) that reflects each of the first number of light beams emitted from the focal plane lens 4 and irradiates the reflected light beams onto the target space, and a control circuit 6 that drives and controls the MEMS mirror 5 to control the deflection angle of the light reflected by the MEMS mirror 5. Reference numeral 200 in FIG. 1 denotes a screen onto which light from the optical beam deflector is irradiated.

[0021] Laser light emitted from semiconductor laser 1 is amplified by optical amplifier 2 and then incident on planar optical waveguide circuit 3. A semiconductor laser is suitable as light source 1 when beam scanning is performed using a MEMS mirror as in this embodiment. The wavelength of the laser light emitted from semiconductor laser 1 can be selected appropriately according to the mirror size of the MEMS mirror used, etc. The laser light is amplified in optical amplifier 2 as needed. An EDFA (Erbium-Doped Fiber Amplifier) ​​can be used as the optical amplifier 2.

[0022] <Planar optical waveguide circuit> The planar optical waveguide circuit 3 includes an optical waveguide 30 that guides the light amplified by the optical amplifier 2, a 1×16 optical splitter 31 that splits the light from the optical waveguide 30 into a first number (16) of light beams, and 16 optical waveguides 36 that guide each of the light beams split by the optical splitter 31. The light beams split by the optical splitter 31 are emitted from predetermined emission positions in the horizontal direction of the planar optical waveguide circuit 3.

[0023] <Focal plane lens> The focal plane lens 4 converts each of the first number of light beams output from the planar optical waveguide circuit 3 into parallel light beams, and outputs each of the parallel light beams at an output angle corresponding to a predetermined output position in the horizontal direction of the planar optical waveguide circuit 3, and deflects the light beams so that they pass through the focal point on the target space side of the focal plane lens 4. This makes it possible to make the first number of light beams output from the planar optical waveguide circuit 3 incident on the MEMS mirror with a beam size corresponding to the mirror size of the MEMS mirror.

[0024] <MEMSミラー> The MEMS mirror 5 reflects each of the first number of light beams emitted from the focal plane lens 4 and irradiates the reflected light beams toward an observation area in the target space. Since the light beams emitted from the focal plane lens 4 are emitted at emission angles corresponding to predetermined emission positions in the horizontal direction of the planar optical waveguide circuit 3, the light beams reflected by the MEMS mirror 5 are also reflected at different angles. This makes it possible to simultaneously irradiate light onto a plurality of areas obtained by dividing the target space into the first number of areas, and simultaneously measure a plurality of observation areas obtained by dividing the observation field of view.

[0025] In this embodiment, the operating modes of the MEMS mirror are as follows: when driving the MEMS mirror in the horizontal direction (X-axis direction in FIG. 1), the MEMS mirror is controlled by resonant drive control (non-linear mode) on a resonant drive axis capable of high-speed driving; and when driving the MEMS mirror in the vertical direction (Y-axis direction in FIG. 1), the MEMS mirror is controlled by linear drive control (linear mode) on a linear drive axis capable of high-precision driving.

[0026] Fig. 2A is a configuration example of the beam deflection device of Fig. 1 as viewed from the Y-axis direction. As shown in Fig. 2A, the light branched by the planar optical waveguide circuit 3 is emitted from a predetermined emission position in the horizontal direction (X-axis direction) of the planar optical waveguide circuit 3, converted into parallel light by the focal plane lens 4, emitted at an emission angle corresponding to the predetermined emission position in the horizontal direction (X-axis direction) of the planar optical waveguide circuit 3, and deflected so as to pass through the focal point of the focal plane lens 4 on the target space side.

[0027] With this configuration, the light emitted by the focal plane lens 4 can be incident on the MEMS mirror 5 with a beam size corresponding to the mirror size of the MEMS mirror 5. The light reflected by the MEMS mirror 5 is reflected at different angles corresponding to the angle of incidence on the MEMS mirror 5, and the light can be simultaneously irradiated onto the first number of divided areas of the target space.

[0028] The light split into the first number of beams is simultaneously deflected in each of the first number of areas by resonant driving in the horizontal direction (X-axis direction) of the MEMS mirror 5. This allows the light to be deflected so as to cover the interval between the split beams in FIG. 2A.

[0029] Figure 2B is a configuration example of the beam deflection device of Figure 1 viewed from the X-axis direction. As shown in Figure 2B, light emitted from the planar optical waveguide circuit 3 is incident on the MEMS mirror 5 without changing its angle in the vertical direction (Y-axis direction) of the planar optical waveguide circuit 3, and is deflected by linear driving of the MEMS mirror 5 in the vertical direction (Y-axis direction), so that the light can be deflected to cover the vertical direction of the observation area.

[0030] Fig. 2C shows another example of the configuration of the beam deflector of Fig. 1 as viewed from the X-axis direction. As shown in Fig. 2C, a fixed mirror 7 and a relay lens 8 may be installed between the focal plane lens 4 and the MEMS mirror 5. This is an effective configuration when the light incident on the MEMS mirror cannot be narrowed down to a beam size corresponding to the mirror size of the MEMS mirror due to restrictions on the distance between the focal plane lens 4 and the MEMS mirror 5 or the focal length of the focal plane lens 4.

[0031] <Target specifications for automotive LiDAR> The target specifications of the vehicle-mounted LiDAR to which the present invention is applied will be explained. Table 1 shows an example of the target specifications of the vehicle-mounted LiDAR.

[0032] [Table 1]

[0033] The specifications for automotive LiDAR require a horizontal resolution of 512 pixels, a vertical resolution of 128 pixels, and a frame rate of approximately 15 to 20 Hz. The time required to allocate to one pixel (the time required to process each pixel sequentially) is determined by the frame rate and spatial resolution. For example, if a total of 65,536 pixels, 512 pixels horizontally and 128 pixels vertically, are measured at a frame rate of 20 Hz (a period of 50 ms), the time allocated to one pixel is 0.76 μs, as shown in Table 1.

[0034] As shown in Table 1, if the maximum measuring distance is 300 m, the round-trip time of light reflected back from 300 m away is 2 μs, which is longer than the 0.76 μs assigned to one pixel. Therefore, to achieve a frame rate of 20 Hz, it is necessary to divide the target space into areas and process each area simultaneously. In an actual device, it is necessary to design device parameters such as the number of divided areas, taking into account the round-trip propagation delay time of light as well as the time required for transmitting and receiving optical signals for measurement.

[0035] In this embodiment, the target space is divided into 16 observation areas for beam scanning. Table 2 shows an example of parameter design for the focal plane lens 4 and the planar optical waveguide circuit 3. Table 3 shows an example of specifications for the MEMS mirror 5.

[0036] [Table 2]

[0037] [Table 3]

[0038] The focal length of the focal plane lens is designed so that the beam diameter at 300 m meets a specified value when the maximum measuring distance is 300 m, and so that the beam diameter matches the mirror size of MEMS mirror 5. When using light with a wavelength of 1550 nm and a focal plane lens with a focal length of 12 mm, the beam diameter is 2.37 mm, as shown in Table 2, which meets the MEMS mirror size (3.6 × 4.0 mm) in Table 3.

[0039] If the number of light branches in the planar optical waveguide circuit 3 is 16, and the horizontal viewing angle is 120°, the beam deflection angle due to the optical splitter and focal plane lens is 112.5°, and the array length required to obtain this beam deflection angle is 35.92 mm. In this case, the array spacing at the output end of the planar optical waveguide circuit 3 is 2394.57 μm, as shown in Table 2, which is a fully feasible array spacing.

[0040] 3 is a diagram illustrating the observation field and beam scanning according to the first embodiment of the present invention. In this embodiment, the observation area is divided into 16 areas in the horizontal direction, and high-speed resonant driving is performed simultaneously in each of the 16 divided areas, while linear driving capable of high-precision driving is performed in the vertical direction.

[0041] According to the specifications of the MEMS mirror 5 shown in Table 3, drive in the horizontal direction (X-axis direction in Figure 1) is performed by resonant drive with a drive frequency of 1100 Hz, and drive in the vertical direction (Y-axis direction in Figure 1) is performed by linear drive with a drive frequency of up to 100 Hz.

[0042] Table 4 shows an example of design of drive parameters for the MEMS mirror 5 when the MEMS mirror 5 in Table 3 is used. [Table 4]

[0043] When FMCW is used as the distance measurement method, if the FMCW up-chirp period and down-chirp period are each 5 μs and the maximum distance measurement distance is 300 m, the processing time per pixel will be approximately 12 μs. When the horizontal drive frequency of the MEMS mirror is 1100 Hz, the horizontal scan time is approximately 454 μs, as shown in Table 4. The number of pixels that can be allocated to this 454 μs exceeds 32 pixels, and by setting the number of area divisions to 16, it is possible to meet the horizontal resolution target value of 512 pixels in Table 1.

[0044] 4A is a diagram for explaining the driving of the MEMS mirror according to the first embodiment of the present invention. When horizontal driving is repeated for the same number of pixels in the vertical direction, the time required for horizontal beam scanning is 454 × 128 ≈ 58 ms.

[0045] Furthermore, as shown in Table 4, when the vertical drive frequency is 100 Hz, the time required for vertical beam scanning is 5 ms. In this case, the total time required to measure the target space is the sum of the time required for horizontal beam scanning, which is 58 + 5 ≒ 63 ms, and the achievable frame rate is 15.83 Hz, as shown in Table 4. From the above, it can be seen that by using the design parameters listed in Tables 2 to 4, the target frame rate for automotive LiDAR shown in Table 1 can be met.

[0046] 4B is a diagram for explaining the driving of the MEMS mirror according to the first embodiment of the present invention. In FIG. 4A, after the beam scanning in the vertical direction is completed, the beam scanning is performed by returning to the initial pixel position. As shown in FIG. 4B, after the beam scanning in the vertical direction is completed, the beam scanning may be performed in the opposite direction instead of returning to the initial pixel position in the vertical direction as in FIG. 4A. By performing the beam scanning as shown in FIG. 4B, the frame rate can be improved.

[0047] As described above, the optical system of the light beam deflector according to the embodiment of the present invention is configured to include a planar optical waveguide circuit, a focal plane lens, and an MEMS mirror, split light emitted from a single light source, and irradiate each of the split light onto a plurality of divided observation areas. This configuration allows for simultaneous horizontal beam scanning in the plurality of observation areas, thereby realizing a light beam deflector that does not require individual optical alignment in each of the plurality of observation areas. It has been confirmed that this embodiment can realize a light beam deflector that meets the target specifications of the automotive LiDAR to which the present invention is applied.

[0048] [Second embodiment] The 16 light beams emitted from the PLC (Planar Lightwave Circuit) splitter 31 and the focal plane lens 4 are incident on the MEMS mirror 5 with a spread of 112°, so the diameter of the MEMS mirror as seen from the light beams incident obliquely on the surface of the MEMS mirror 5 is smaller than that of the light beams incident perpendicularly.

[0049] For example, the diameter (minor diameter) of the MEMS mirror as seen by a light beam incident at an angle θ from the vertical plane is cosθ, and if θ = 60°, then cos = 0.5, and the ratio of the minor diameter to the major diameter is 1:2.

[0050] For this reason, the MEMS mirror cannot receive the beam spread at the base of the Gaussian beam on the major axis side, and the transmitted optical power of an optical beam that is obliquely incident on the MEMS mirror 5 is lower than that of an optical beam that is perpendicularly incident.

[0051] To solve this problem, it is possible to correct the decrease in transmission optical power at the periphery of the PLC splitter, which is far from the center, by gradually changing the branching ratio of the optical power from the output ports (#8, #9) located at the center of the PLC splitter 31 to the output ports (#1, #16) located at the periphery. Specifically, by configuring the branching ratio of the optical energy in the splitter to increase at a predetermined rate with increasing distance from the output position at the center of the planar optical waveguide circuit 3, it is possible to correct the decrease in transmission optical power at the output ports located at the periphery of the PLC splitter.

[0052] The rate at which the branching ratio of the PLC splitter 31 is increased may be set according to the divergence angle of the light beam emitted from the focal plane lens 4. When the divergence angle is 112°, the branching ratio of the peripheral output ports (#1, #16) may be increased by about 1 to 2 dB compared to the output ports (#8, #9) located at the center of the PLC splitter, and the branching ratio of the output ports between the center and the periphery (#2 to #7, #10 to #15) may be set to increase at a constant rate from the central output ports (#8, #9).

[0053] [Third embodiment] In the first embodiment, a light beam deflector applied to a LiDAR is described, but in a LiDAR, it is necessary to receive light returning from a target space. In the third embodiment, a configuration of a light projecting and receiving device in which a light beam deflector and a light receiving device are integrated will be described.

[0054] Fig. 5 shows an example of the configuration of a light projecting and receiving device that integrates a light beam deflector and a light receiving device. The light projecting and receiving device is configured by adding 16 photodetectors 9-1 to 9-16, 16 photodetectors 10-1 to 10-16, and 16 transimpedance amplifiers (TIA) 11-1 to 11-16 to a planar optical waveguide circuit 3. The configuration after the focal plane lens 4 is the same as that of the first embodiment, and is therefore omitted from Fig. 5.

[0055] The planar optical waveguide circuit 3 in the third embodiment includes an optical waveguide 30 (first optical waveguide), a 10:1 optical splitter 32 (first optical splitter) that splits light into two lights at a splitting ratio of 10:1, optical waveguides (33-1, 33-2) (second optical waveguide, third optical waveguide), 1×16 optical splitters (34-1, 34-2) (second optical splitter, third optical splitter) that split the light from the optical waveguides (33-1, 33-2) into 16 lights, respectively, and optical waveguides (36-1 to 36-16) (fourth optical waveguide) that guide the light output from the 1×16 optical splitter (34-1). The optical waveguide (36-17 to 36-32) (fifth optical waveguide) guides the light output from the 1x16 optical splitter (34-2), 3dB splitters (35-1 to 35-16) (fourth optical splitter) split the light reflected by an object present in the target space and entering the optical waveguides (36-1 to 36-16) into two, and 16 3dB couplers (37-1 to 37-16) (first couplers) combine the light output from the 3dB splitters (35-1 to 35-16) and the light guided by the optical waveguides (36-17 to 36-32) in equal proportions, divide the light into two, and output the combined light.

[0056] The light (probe light) split by the 10:1 optical splitter 32 and then split by the 1×16 optical splitter (34-1) is guided by the optical waveguides (36-1 to 36-16) and emitted from the output end of the planar optical waveguide circuit 3. The probe light emitted from the planar optical waveguide circuit 3 passes through the focal plane lens 4, is reflected by the MEMS mirror 5, and is emitted into the target space.

[0057] On the other hand, the light (reference light) split by the 10:1 optical splitter 32 and then split by the 1×16 optical splitter (34-2) is guided by optical waveguides (36-17 to 36-32) and input to the input ports of the 3 dB couplers (37-1 to 37-16).

[0058] The return light reflected by an object present in the target space and returning from the target space travels the opposite path to the probe light, i.e., is reflected by the MEMS mirror 5, passes through the focal plane lens 4, and enters the exit end of the same optical waveguide (36-1 to 36-16) of the planar optical waveguide circuit 3 as the source of the probe light.

[0059] The returned light is guided through the optical waveguides (36-1 to 36-16), split by the 3dB splitters (35-1 to 35-16), and merged with the light (reference light) guided through the optical waveguides (36-17 to 36-32) in an equal ratio in the 3dB couplers (37-1 to 37-16), split into two equal parts, and output from two ports.

[0060] The light output from the ports (first ports) of the 3 dB couplers (37-1 to 37-16) is guided by the optical waveguides (38-1 to 38-16), and the light output from the other ports (second ports) of the 3 dB couplers (37-1 to 37-16) is guided by the optical waveguides (39-1 to 39-16).

[0061] The photodetectors (9-1 to 9-16, 10-1 to 10-16) (first photodetector, second photodetector) convert the light guided in the optical waveguides (38-1 to 38-16) and the light guided in the optical waveguides (39-1 to 39-16) into electrical signals.

[0062] Transimpedance amplifiers (TIA) (11-1 to 11-16) calculate and amplify the differences between the output signals from the photodetectors (9-1 to 9-16, 10-1 to 10-16), thereby obtaining received signals.

[0063] In the first embodiment, it is assumed that the light beam deflector and the light receiving device are provided separately. On the other hand, in the third embodiment, the light beam deflector and the light receiving device are integrated, but the total time required to measure the target space is the same as in the first embodiment, and this embodiment also satisfies the specifications of the automotive LiDAR shown in Table 1.

[0064] Note that the configuration subsequent to the TIAs (11-1 to 11-16) is not an essential component in the present invention, and is therefore omitted from Fig. 5. An example of the use of the received signals obtained by the TIAs (11-1 to 11-16) is LiDAR, but the application of the present invention is not limited to LiDAR.

[0065] The control circuit 6 described in the first embodiment is a control circuit that controls the drive current of the MEMS mirror 5. The control circuit 6 can be realized by a computer equipped with a CPU (Central Processing Unit), a storage device, and an interface, and a program that controls these hardware resources. An example configuration of this computer is shown in FIG.

[0066] The computer includes a CPU 200, a storage device 201, and an interface device (I / F) 202. The I / F 202 is connected to a circuit that supplies a control signal for driving the MEMS mirror, etc. In such a computer, a program for implementing the method of the present invention is stored in the storage device 201. The CPU 200 executes the processing described in the first embodiment in accordance with the program stored in the storage device 201. [Industrial Applicability]

[0067] The present invention can be applied to light deflection technology required for LiDAR and the like. [Explanation of symbols]

[0068] 1...semiconductor laser, 2...optical amplifier, 3...planar optical waveguide circuit, 4...focal plane lens, 5...MEMS mirror, 6...control circuit.

Claims

1. A light source and a planar optical waveguide circuit that splits light emitted from the light source into a first number of light beams equal to the number of areas divided in a first direction of a target space, and outputs the split light beams from predetermined output positions in the first direction so that each of the light beams is simultaneously irradiated onto a pixel position in a corresponding area; a first optical system that converts each of the first number of light beams output from the planar optical waveguide into parallel light beams and outputs the parallel light beams at an output angle corresponding to the predetermined output position; a second optical system that reflects each of the first number of light beams emitted from the first optical system and irradiates each reflected light beam onto the target space; An optical beam deflection device comprising:

2. a control circuit for controlling a deflection angle of the reflected light in the second optical system; The control circuit drive control in the first direction to simultaneously deflect the first number of light beams irradiated from the second optical system to the target space in the first direction; and a drive control in the second direction to simultaneously deflect the first number of light beams irradiated from the second optical system to the target space in the second direction by changing a deflection angle of the reflected light in a second direction perpendicular to the first direction.

2. The optical beam deflector according to claim 1.

3. the second optical system is a MEMS mirror; The drive control in the first direction is a resonant drive control on a resonant drive axis of the MEMS mirror, and the drive control in the second direction is a linear drive control on a linear drive axis of the MEMS mirror.

3. The optical beam deflector according to claim 2.

4. the planar optical waveguide circuit includes a splitter that splits the light emitted from the light source into the first number of light beams; The splitting ratio of the optical energy in the splitter is set to increase at a predetermined rate as the distance from the center of the planar optical waveguide increases.

2. The optical beam deflector according to claim 1.

5. a light beam deflector according to claim 1; the first number of first photodetectors that convert incident light into an electrical signal; the first number of second photodetectors for converting incident light into an electrical signal; the first number of transimpedance amplifiers for determining a difference between output signals of the first and second photodetectors; The planar optical waveguide circuit comprises: a first optical waveguide; a first optical splitter that splits the light guided through the optical waveguide into two lights at a predetermined splitting ratio; a second optical waveguide and a third optical waveguide for guiding the light output from the optical splitter; a second optical splitter that splits the light from the first optical waveguide into a first number of light beams; a third optical splitter that splits the light from the second optical waveguide into the first number of light beams; a first number of fourth optical waveguides that guide the light output from the second optical splitter; and a first number of fifth optical waveguides that guide the light output from the third optical splitter. a first number of fourth optical splitters each splitting a first number of return beams that are reflected by an object present in the target space and enter the fourth optical waveguide into two beams; the first number of first couplers that combine the light output from the fourth optical splitter and the light guided by the fifth optical waveguide in equal proportions, divide the light into two equal parts, and output the combined light, the first photodetector converts the light emitted from the first port of the first coupler into an electrical signal; the second photodetector converts the light emitted from the second port of the first coupler into an electrical signal; The transimpedance amplifier determines the difference between the output signal from the first photodetector and the output signal from the second photodetector. A light projecting and receiving device characterized by:

Images