Optical beam deflection device and optical transceiver

Abstract

Achieve a larger number of horizontal and vertical resolution points and a higher frame rate than before. 【Solution means】The optical beam deflection device includes a wavelength-variable semiconductor laser 1, a planar optical waveguide circuit 3 that branches the light emitted from the wavelength-variable semiconductor laser 1 into the same first number of lights as the number of divided areas in the first direction of the target space, and selects and emits the emission positions in the first direction of the branched lights so that these lights are simultaneously irradiated to the positions of one pixel in each corresponding area, a dispersion element 5 that deflects the first number of lights emitted from the planar optical waveguide circuit 3 at an angle corresponding to the wavelength of the light in a plane parallel to the second direction orthogonal to the first direction, an optical system 6 that converts the first number of lights emitted from the dispersion element 5 to be parallel to the axis of the optical system, and an optical system 7 that deflects the first number of lights emitted from the optical system 6 and irradiates the target space.

Description

Technical Field

[0001] The present invention relates to an optical beam deflection device that irradiates light onto a target space to perform beam scanning in the horizontal and vertical directions, and a light transmitting and receiving device that integrates the optical beam deflection device and a light receiving device.

Background Art

[0002] As a technique for irradiating laser light and measuring the distance to a target object and the shape of the target object based on the information of the reflected light, LiDAR (Light Detection And Ranging) is known. As such a LiDAR method, there are a dTOF (direct Time of Flight) method for measuring the round-trip time of an optical pulse, and an FMCW (Frequency Modulated Continuous Wave) method for continuously irradiating while changing the frequency of the laser light and measuring the frequency shift of the light returned from the target object.

[0003] Since dTOF has a relatively simple configuration, chip integration and modularization have advanced, and it has been widely put into practical use in automobiles, home doors, industrial robots, etc. However, in dTOF, a filter for removing the influence of sunlight and the like is required, and since it is impossible to distinguish whether the received pulse is transmitted by itself or transmitted from another source, there has been a problem of interference with other LiDARs.

[0004] On the other hand, although FMCW has a limited practical application due to its complex configuration, it is attracting attention as a high-precision LiDAR for autonomous driving, for example, because it is not affected by sunlight or other LiDARs and does not require a filter.

[0005] In LiDAR, in order to acquire a 3D image of an object, deflection of a light beam irradiated onto the object is necessary (see Patent Document 1, Patent Document 2, and Non-Patent Document 1). FIG. 8 is a diagram showing the configuration of a light beam deflection device disclosed in Patent Document 1. This light beam deflection device includes a dispersion element 1000 arranged to direct light from a wavelength-variable laser (not shown) in one of the first directions (for example, along the x-axis in FIG. 8), and dispersion elements 1001-1, 1001-2, ···, 1001-M arranged to direct the light received from the dispersion element 1000 in one of the second directions according to the position where the light is incident. Reference numeral 1002 in FIG. 8 is a screen irradiated with the light from the dispersion elements 1001-1 to 1001-M.

[0006] Each of the first directions corresponds to a possible optical path of the light 1003 emitted from the dispersion element 1000 and then corresponds to a wavelength channel. For example, as shown in FIG. 8, the optical path 1003a corresponds to the wavelength channel λ1, and the optical path 1003b corresponds to the wavelength channel λ N . The dispersion element 1000 is composed of, for example, one or more diffraction gratings. The angular spread of the light 1003 depends on the range of the wavelength channel and the dispersion characteristics of the dispersion element 1000. In one example, the dispersion element 1000 has a grating period of 1000 to 1100 lines / mm and realizes a deflection of 5 to 10°.

[0007] The M dispersion elements 1001-1, 1001-2, ···, 1001-M corresponding to M wavelength bands each consist of a variable pitch diffraction grating whose grating period continuously changes from the first end to the second end. As shown in FIG. 8, the second directions are aligned along planes based on the respective wavelength bands. For example, the light in the wavelength channels {λ1, λ2, ···, λ k} incident on the dispersion element 1001-1 is deflected by the dispersion element 1001-1 in a direction arranged along the leftmost plane 1004-1 corresponding to the first one of the M wavelength bands. Similarly, although not shown, the light in the wavelength channels {λ k+1 , λ k+2 , ···, λ 2kThe light in} is deflected by the dispersion element 1001-2 in a direction aligned along the plane corresponding to the second of the M wavelength bands. The light in the wavelength channels {λ N-k+1 ,λ N-k+2 ,···,λ N} incident on the dispersion element 1001-M is deflected by the dispersion element 1001-M in a direction aligned along the rightmost plane 1004-M corresponding to the M-th of the M wavelength bands.

[0008] FIG. 9 is a diagram showing the configuration of an optical beam deflector disclosed in Patent Document 2. This optical beam deflector includes a wavelength-variable laser 2000 that outputs one selected light from among N wavelength channels grouped into M non-adjacent wavelength channel groups, an optical interleaver 2001 for routing the light from the wavelength-variable laser 2000 from the first port 2002 to one of the second ports 2003-1, 2003-2, ···, 2003-M, and a dispersion element array 2004-1, 2004-2, ···, 2004-M arranged to receive the light routed from one of the second ports 2003-1, 2003-2, ···, 2003-M, respectively. 2005 in FIG. 9 is a screen irradiated with the light from the dispersion element array 2004-1, 2004-2, ···, 2004-M.

[0009] The N wavelength channels are each represented by a center wavelength λ1, λ2, ···, λ Ν , and the M groups of interleaved wavelength channels are {λ1, λ Μ+1 , ···, λ Ν-Μ+1}, {λ2, λ Μ+2 , ···, λ Ν-Μ+2}, ···, {λ Μ , λ 2Μ , ···, λ Ν} That is. The wavelength-variable laser 2000 can have a wavelength tuning range of 100 nm, such as from approximately 1527 nm to approximately 1567 nm (or approximately 5000 GHz at 1550 nm), which can be adjusted stepwise from 0.0004 nm to 0.008 nm (or stepwise from approximately 50 MHz to 1 GHz at 1550 nm). For example, when the wavelength-variable laser 2000 can be wavelength-tuned over 40 nm, there are a total of approximately 5000 steps (i.e., N = 5000).

[0010] The optical interleaver 2001 is composed of one or more Mach-Zehnder interferometers (MZIs) or one or more arrayed waveguide gratings (AWGs). The free spectral range (FSR) of the optical interleaver 2001 is designed to be 10 GHz or less in one use case. In another use case, the FSR is designed to be 5 GHz or less. In yet another use case, the FSR is designed to be 1 GHz or less.

[0011] The above optical beam deflection devices are all related to two-dimensional optical beam deflection technology for LiDAR using a wavelength-variable laser. Each optical beam deflection device provides two-dimensional optical beam deflection technology in the horizontal and vertical directions using a wavelength-variable laser developed for optical communication, with a wavelength tuning range of approximately 30 to 40 nm. Table 1 shows an example of the target specifications for in-vehicle LiDAR.

[0012]

Table 1

[0013] As specifications for in-vehicle LiDAR, a horizontal resolution of 512 pixels, a vertical resolution of 128 pixels, and a frame rate of about 10 to 20 Hz are required. From the frame rate and spatial resolution, the required time allocated to one pixel (the time required when processing each pixel sequentially) is determined. When measuring a total of 65,536 pixels with 512 pixels horizontally and 128 pixels vertically at a frame rate of 20 Hz (period 50 ms), the time allocated to one pixel is 0.76 μs as shown in Table 1.

[0014] However, as shown in Table 1, when the maximum measurement distance is 300 m, the round-trip propagation time (round-trip time) of the light returning from 300 m away is 2 μs, which is longer than the 0.76 μs allocated to one pixel. Therefore, in order to achieve a frame rate of 20 Hz, it is necessary to divide the target space into areas and process each area simultaneously. In practice, in addition to the round-trip propagation delay time of the light, the transmission time and reception time of the optical signal for measurement are also required.

[0015] For example, when using the FMCW method as the LiDAR method, a case where 5 μs is required for each of the transmission and reception of the optical signal is shown in Fig. 10. In Fig. 10, 800 is the transmission signal, 801 is the reception signal, 802 is the up-chirp period during which the optical frequency of the transmission signal increases, 803 is the down-chirp period during which the optical frequency of the transmission signal decreases, and 804 is the optical frequency chirp width. From the comparison of the total value of the FMCW sweep time and the round-trip propagation delay time of the light (5 μs × 2 + 2 μs = 12 μs) with the time allocated to one pixel of 0.76 μs (12 / 0.76 ≈ 15.8), at least 16 areas need to be measured simultaneously in this setting.

[0016] That is, in the wavelength variable range of about 30 to 40 nm shown in the prior art, the above-described resolution points and frame rate cannot be achieved, and an extremely wide wavelength variable range is required for realization. However, it is impossible to realize such a wavelength variable semiconductor laser with a wide wavelength variable range using a single small and low-cost semiconductor laser chip suitable for in-vehicle use. Non-Patent Document 1 experimentally shows a form of two-dimensional beam steering using the wavelength variable means disclosed in Patent Document 2. However, in the wavelength variable range of 100 nm using a measuring instrument, the resolution points are only 69 pixels horizontally and 47 pixels vertically.

Prior Art Documents

Patent Documents

[0017]

Patent Document 1

Patent Document 2

Non-Patent Documents

[0018]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0019] The present invention has been made to solve the above problems, and an object thereof is to provide an optical beam deflection device and a light transmitting and receiving device capable of realizing a larger number of horizontal and vertical resolution points and a higher frame rate than in the prior art.

Means for Solving the Problems

[0020] The optical beam deflector of the present invention includes a wavelength-variable light source, a planar optical waveguide circuit that branches the light emitted from the wavelength-variable light source into the same first number of lights as the number of divided areas in the first direction of the target space, and selects and emits the emission positions of the branched lights in the first direction so that these lights are simultaneously irradiated to the positions of one pixel in the corresponding areas, a dispersion element that deflects the first number of lights emitted from the planar optical waveguide circuit at an angle corresponding to the wavelength of the light in a plane parallel to the second direction orthogonal to the first direction, a first optical system that converts and emits the first number of lights emitted from the dispersion element so as to be parallel to the axis of the optical system, and a second optical system that deflects the first number of lights emitted from the first optical system and irradiates the target space.

[0021] Also, one configuration example of the optical beam deflector of the present invention further includes a control unit that controls the wavelength variation by the wavelength-variable light source and the selection of the emission position by the planar optical waveguide circuit. The control unit changes the wavelength of the light emitted from the wavelength-variable light source to change the deflection angle of the light in the plane parallel to the second direction, thereby simultaneously moving the first number of lights irradiated from the second optical system to the target space in the second direction, which is the scanning in the second direction. After the scanning of the line in the second direction is completed, the control unit changes the emission position of the light emitted from the planar optical waveguide circuit to change the deflection angle of the light in the plane parallel to the first direction, thereby simultaneously moving the first number of lights irradiated to the target space in the first direction, which is the scanning in the first direction, and repeats this process.Also, in one configuration example of the optical beam deflection device of the present invention, the planar optical waveguide circuit includes an optical splitter that splits the light emitted from the wavelength-variable light source into the first number of lights, and the same second number of output ports as the number of pixels in the first direction in each divided area of the target space, and the first number of optical switches that selectively output the light split by the optical splitter to any one of the second number of output ports, and an optical waveguide arranged in the first direction in the number obtained by multiplying the first number by the second number so as to guide the light output from each output port of the first number of optical switches and emit it from the end face of the planar optical waveguide circuit. It is characterized by comprising these components.

[0022] Also, one configuration example of the optical beam deflection device of the present invention further includes a focal plane lens inserted between the planar optical waveguide circuit and the dispersion element. The focal plane lens is characterized by converting each of the first number of lights emitted from the planar optical waveguide circuit into parallel light and at the same time deflecting these parallel lights so as to pass through the focal points on the target space side of the focal plane lens. Also, in one configuration example of the optical beam deflection device of the present invention, the dispersion element is characterized by comprising a plurality of diffraction gratings arranged along the traveling direction of light. Also, in one configuration example of the optical beam deflection device of the present invention, the first optical system is characterized by comprising a telecentric fθ lens. Also, in one configuration example of the optical beam deflection device of the present invention, the second optical system is characterized by comprising a convex lens.

[0023] Further, the light transmitting and receiving device of the present invention includes the light beam deflecting device, the first number of first photodetectors that convert incident light into an electrical signal, the first number of second photodetectors that convert incident light into an electrical signal, and the first number of transimpedance amplifiers that obtain the difference between the output signals of the first and second photodetectors. The planar optical waveguide circuit includes a first optical splitter that splits the light emitted from the wavelength-variable light source into the first number of lights, the first number of second optical splitters that each split the light split by the first optical splitter into two, the first number of first couplers that output one of the lights split by the second optical splitter from a first port to a second port and output the light input to the second port to a third port, a second number of output ports equal to the number of pixels in the first direction in each divided area of the target space, the first number of optical switches that selectively output the light output from the second port of the first coupler to any one of the second number of output ports, a first number of optical waveguides arranged along the first direction in the number obtained by multiplying the first number by the second number so as to waveguide the light output from each output port of the first number of optical switches and emit it from the first end face of the planar optical waveguide circuit, the first number of second couplers that combine the light output from the third port of the first coupler and the other light split by the second optical splitter, divide the combined light into two equal parts, and output the divided light, the first number of second optical waveguides that waveguide the light output from one output port of the second coupler and emit it from the second end face of the planar optical waveguide circuit, and the first number of third optical waveguides that waveguide the light output from the other output port of the second coupler and emit it from the second end face of the planar optical waveguide circuit. The first number of return lights returned from the target space enter the emission end of the first optical waveguide of the planar optical waveguide circuit through the second optical system, the first optical system, and the dispersion element. The first coupler outputs the return light output from the input port of the optical switch and input to the second port to the third port. The first photodetector converts the light emitted from the second optical waveguide into an electrical signal, and the second photodetector converts the light emitted from the third optical waveguide into an electrical signal.The transimpedance amplifier is characterized by obtaining the difference between output signals from the first and second photodetectors that receive the emitted light of the second and third optical waveguides connected to the same second coupler.

Advantages of the Invention

[0024] According to the present invention, by providing a wavelength-variable light source, a planar optical waveguide circuit, a dispersion element, and first and second optical systems, it is possible to simultaneously perform scanning in the second direction of each area divided in the first direction of the target space. As a result, the present invention can achieve a larger number of horizontal and vertical resolution points and a higher frame rate than in the prior art, and can satisfy, for example, the specifications of the horizontal and vertical resolution points and the frame rate required for in-vehicle LiDAR.

Brief Description of the Drawings

[0025]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

DETAILED DESCRIPTION OF THE INVENTION

[0026] [First Embodiment] Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing the configuration of an optical beam deflection device according to the first embodiment of the present invention. The optical beam deflection device includes a wavelength tunable semiconductor laser 1 (wavelength tunable light source), an optical amplifier 2 that amplifies the light emitted from the wavelength tunable semiconductor laser 1, and the light amplified by the optical amplifier 2 is branched into a first number of lights equal to the number of areas divided in the vertical direction (Y direction in FIG. 1) of the target space, and the vertical emission positions of the branched lights are selected so that these lights are simultaneously irradiated to the positions of one pixel in each corresponding area and then emitted. A planar optical waveguide circuit 3, a focal plane lens 4 that converts the first number of lights emitted from the planar optical waveguide circuit 3 into parallel lights and deflects them at the same time, a dispersion element 5 that deflects the first number of lights emitted from the focal plane lens 4 at an angle corresponding to the wavelength of the light in the horizontal plane, an optical system 6 that converts the first number of lights emitted from the dispersion element 5 so as to be parallel to the axis of the optical system and then emits them, an optical system 7 that deflects the first number of lights emitted from the optical system 6 and irradiates the target space, and a control unit 8 that controls the wavelength tuning by the wavelength tunable semiconductor laser 1 and the selection of the emission position by the planar optical waveguide circuit 3. Reference numeral 12 in FIG. 1 is a screen irradiated with light from the optical beam deflection device.

[0027] FIG. 2 is a diagram showing the detailed configuration of the optical beam deflection device of FIG. 1. The wavelength tunable semiconductor laser 1 has a wavelength tuning range of 30 to 40 nm. As the wavelength tunable semiconductor laser 1, for example, there is an RTF (Reflection-type Transversal Filter)-LD (Laser Diode). Since the RTF-LD can control the wavelength by voltage, it can switch the wavelength at a higher speed compared to other wavelength tunable lasers.

[0028] The optical amplifier 2 amplifies the laser light emitted from the wavelength tunable semiconductor laser 1. Examples of the optical amplifier 2 include, for example, a polarization maintaining EDFA (Erbium-Doped Fiber Amplifer).

[0029] As shown in FIG. 2, 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 16 lights (the first number), 16 optical waveguides 32-1 to 32-16 that respectively guide the lights split by the optical splitter 31, and the same second number (8 in this embodiment) as the number of vertical pixels in each divided area of the target space. It has output ports, and 16 1×8 optical switches 33-1 to 33-16 that selectively output the light split by the 1×16 optical splitter 31 to any one of the 8 output ports, and 128 optical waveguides 34-1 to 34-128 that respectively guide the lights output from the output ports of the 1×8 optical switches 33-1 to 33-16.

[0030] The optical waveguides 34-1 to 34-128 are arranged along the vertical direction in the number obtained by multiplying the first number (16 in this embodiment) by the second number (8 in this embodiment) so as to guide the light output from each output port of the 1×8 optical switches 33-1 to 33-16 and emit it from the end face of the planar optical waveguide circuit 3. The interval between the optical waveguides 34-1 to 34-128 at the end face of the planar optical waveguide circuit 3 is, for example, 10 to 20 μm.

[0031] With the above configuration, the planar optical waveguide circuit 3 branches the light amplified by the optical amplifier 2 into a first number of lights, and selects and emits the vertical emission positions of the branched lights so that these lights are simultaneously irradiated to the positions of one pixel in each corresponding area. In this embodiment, since it is assumed that the vertical resolution of 128 pixels is divided into 16 areas, the first number is 16, and the number of branches of the 1×16 optical splitter 31, the number of the optical waveguides 32-1 to 32-16, and the number of the 1×8 optical switches 33-1 to 33-16 are all 16. Further, since the number of pixels in the vertical direction in each divided area of the target space is 8, the second number is 8, and the number of output ports of the 1×8 optical switches 33-1 to 33-16 is 8. As an example of the 1×8 optical switches 33-1 to 33-16, there is, for example, a Mach-Zehnder interferometric optical switch.

[0032] The focal plane lens (focal plano collimating lens) 4 converts each of the first number of lights emitted from the planar optical waveguide circuit 3 into parallel light, and at the same time deflects these parallel lights so that they pass through the focal points on the target space side of the focal plane lens 4.

[0033] The dispersion element 5 deflects each of the first number of lights emitted from the focal plane lens 4 at an angle corresponding to the wavelength of the light in the horizontal plane. As an example of the dispersion element 5, there is, for example, a diffraction grating. Further, in this embodiment, a plurality of transmissive diffraction gratings are arranged along the traveling direction of the light.

[0034] The optical system 6 converts and emits the first number of lights emitted from the dispersion element 5 so as to be parallel to the axis of the optical system 6. Due to the wavelength variation by the wavelength-variable semiconductor laser 1, the switching of the emission position by the planar optical waveguide circuit 3, the deflection by the focal plane lens 4, and the deflection by the dispersion element 5, the angle of the light incident on the optical system 6 changes, but the light incident on the optical system 6 is emitted in a direction parallel to the axis of the optical system 6. As an example of the optical system 6, there is, for example, a telecentric fθ lens. The telecentric fθ lens is a combination of a plurality of lenses precisely processed.

[0035] The optical system 7 irradiates the target space by deflecting a first number of lights incident parallel to the axes of the optical systems 6 and 7 so as to pass through the focal point on the target space side of the optical system 7. By using this optical system 7, the deflection angle of the light can be enlarged. As an example of the optical system 7, there is a convex lens formed by precisely processing and combining a plurality of lenses.

[0036] The main design parameters of the light beam deflection device will be described. Fig. 3(A) is a cross-sectional view of the light beam deflection device cut in the horizontal plane, and Fig. 3(B) is a cross-sectional view of the light beam deflection device cut in the vertical plane. In Fig. 3(A), θ1 is the angle at which the outgoing light of the dispersion element 5 spreads in the horizontal plane, θ2 is the angle at which the outgoing light of the optical system 7 spreads in the horizontal plane, f0 is the focal length of the focal plane lens 4, f1 is the focal length of the optical system 6, f2 is the focal length of the optical system 7, h1 is the maximum image height in the horizontal direction (the X direction in Fig. 1) of the outgoing light of the optical system 6 (the distance from the position of the outermost light beam among the outgoing lights of the optical system 6 to the optical axis of the optical system 6), and h2 is the maximum image height in the vertical direction of the outgoing light of the optical system 6.

[0037] In Fig. 3(A) and Fig. 3(B), 60 indicates the rightmost light (for example, the light of the shortest wavelength) in the horizontal direction among the outgoing lights of the optical system 6, 61 indicates the leftmost light (for example, the light of the longest wavelength) in the horizontal direction among the outgoing lights of the optical system 6, 62 indicates the uppermost light (for example, the light emitted from the optical waveguide 34 - 128) in the vertical direction among the outgoing lights of the optical system 6, and 63 indicates the lowermost light (for example, the light emitted from the optical waveguide 34 - 1) in the vertical direction among the outgoing lights of the optical system 6.

[0038] The horizontal positions of the output ends of the optical waveguides 34 - 1 to 34 - 128 of the planar optical waveguide circuit 3 coincide with the horizontal positions of the axis (L in Fig. 3(A) and Fig. 3(B)) of the lens system (the focal plane lens 4, the dispersion element 5, and the optical systems 6 and 7). The vertical intervals between the output ends of the optical waveguides 34 - 1 to 34 - 128 are set such that the ratio of the maximum image height h1 in the horizontal direction and the maximum image height h2 in the vertical direction of the outgoing light of the optical system 6 becomes a desired value (in this embodiment, h1:h2 = 512:128).

[0039] As described above, the dispersion element 5 is composed of a plurality of transmissive diffraction gratings arranged along the traveling direction of light. The grooves of each diffraction grating are formed along the vertical direction. Thereby, the dispersion element 5 deflects the incident light in the horizontal plane at an angle corresponding to its wavelength. The dispersion element 5 is arranged such that the position on the axis L of the exit surface of the last-stage diffraction grating coincides with the position on the axis L of the focal point on the object space side of the lens 4. Note that when the diffraction gratings are multi-staged, since the exit position of the light shifts simultaneously with the angle of the light for each wavelength of the light, an optical design taking into account the position shift is required.

[0040] The relationship among the maximum image height h1 in the horizontal direction of the exit light of the optical system 6, the focal length f1 of the optical system 6, and the angle θ1 by which the exit light of the dispersion element 5 spreads in the horizontal plane is as shown in Equation (1).

[0041]

Number

[0042] The relationship among the maximum image height h1, the focal length f2 of the optical system 7, and the angle θ2 by which the exit light of the optical system 7 spreads in the horizontal plane is as shown in Equation (2).

[0043]

Number

[0044] Equation (3) is obtained from Equation (1) and Equation (2).

[0045]

Number

[0046] FIG. 4 is a flowchart for explaining the operation of the optical beam deflection device. The control unit 8 sets the 1×8 optical switches 33-1 to 33-16 by outputting control signals thereto respectively (step S100 in FIG. 4). In the beam scanning of the first line, the 1×8 optical switches 33-1 to 33-16 are set so that the optical beam is irradiated to the position of the uppermost pixel in each of the vertically divided 16 areas. In the example of FIGS. 2 and 3(B), the 1×8 optical switches 33-1 to 33-16 are set so that light is emitted from the optical waveguides 34-1, 34-9, 34-17, ···, 34-121.

[0047] Next, the control unit 8 changes the wavelength of the laser light emitted from the wavelength-variable semiconductor laser 1 by changing the voltage supplied to the wavelength-variable semiconductor laser 1 (step S101 in FIG. 4). FIG. 5 shows a virtual screen 12 for showing the spatial distribution of the beam irradiated to the target space. As described above, in this embodiment, the 128 pixels of the vertical resolution points in the target space are divided into 16 areas A1 to A16. The number of pixels in the vertical direction in each of the areas A1 to A16 is 8. In FIG. 5, the pixels with the horizontal number x (x is 1 to 512), the vertical number y (y is 1 to 8) in each of the areas A1 to A16, and the area number n (n is 1 to 16) are represented by P(x, y, n).

[0048] The 16 optical beams emitted from the optical waveguides 34-1, 34-9, 34-17, ···, 34-121 pass through the focal plane lens 4, the dispersion element 5, and the optical systems 6 and 7 and are irradiated to the position of the uppermost pixel (the pixel with the number y being 1) in each of the areas A1 to A16 of the target space. Further, since the control unit 8 continuously changes the wavelength of the laser light from the shortest wavelength to the longest wavelength, the deflection angle of the light in the horizontal plane changes by the dispersion element 5, so that the irradiation position of the optical beam moves from the position of the rightmost pixel (the pixel with the number x being 1) in the horizontal direction to the position of the leftmost pixel (the pixel with the number x being 512), and the beam scanning of one line is performed.

[0049] After the beam scanning of the first line is completed, the control unit 8 switches the output ports selected by the 1×8 optical switches 33-1 to 33-16, thereby switching the optical waveguides 34 (34-1 to 34-128) from which the light of the planar optical waveguide circuit 3 exits (step S102 in FIG. 4). In the beam scanning of the second line, the 1×8 optical switches 33-1 to 33-16 are set so that the light beam is irradiated on the position of the second pixel from the top (the pixel with number y = 2) in each area A1 to A16 of the target space. Although not shown in FIG. 2, the 1×8 optical switches 33-1 to 33-16 are set so that light exits from the optical waveguides 34-2, 34-10, 34-18, ···, 34-122. The control unit 8 performs the beam scanning of the second line by the process of step S101.

[0050] After the beam scanning of the second line is completed, the control unit 8 switches the output ports selected by the 1×8 optical switches 33-1 to 33-16 (step S102). In the beam scanning of the third line, the 1×8 optical switches 33-1 to 33-16 are set so that the light beam is irradiated on the position of the third pixel from the top (the pixel with number y = 3) in each area A1 to A16 of the target space. Although not shown in FIG. 2, the 1×8 optical switches 33-1 to 33-16 are set so that light exits from the optical waveguides 34-3, 34-11, 34-19, ···, 34-123. The control unit 8 performs the beam scanning of the third line by the process of step S101.

[0051] Subsequently, beam scanning of the fourth to seventh lines is sequentially performed in the same manner. After the beam scanning of the seventh line is completed, the control unit 8 switches the output ports selected by the 1×8 optical switches 33-1 to 33-16 (step S102). In the beam scanning of the eighth line, the 1×8 optical switches 33-1 to 33-16 are set so that the optical beam is irradiated at the position of the lowermost pixel (the pixel with number y = 8) in each of the areas A1 to A16 of the target space. In the example of FIGS. 2 and 3(B), the 1×8 optical switches 33-1 to 33-16 are set so that light is emitted from the optical waveguides 34-8, 34-16, 34-24, ···, 34-128. The control unit 8 performs the beam scanning of the eighth line by the process of step S101.

[0052] When the beam scanning of the eighth line is completed, the scanning of all areas is completed (YES in step S103 of FIG. 4). As described above, in this embodiment, by simultaneously performing the horizontal beam scanning of each area divided in the vertical direction, simultaneous measurement of 16 areas is possible, and the horizontal and vertical resolution points and frame rate required for in-vehicle LiDAR can be realized. When this embodiment is applied to an in-vehicle LiDAR, since continuous measurement is required, the process of FIG. 4 may be repeatedly performed. Also, in this embodiment, while using different deflection means for the horizontal beam deflection and the vertical beam deflection, the optical systems for the horizontal and vertical deflections can be integrated into one.

[0053] Table 2 shows specific numerical examples when the FMCW method is used as the LiDAR method.

[0054]

Table 2

[0055] Here, the wavelength switching time of the wavelength-variable semiconductor laser 1 is set to 1 μs, and the switching times of the 1×8 optical switches 33-1 to 33-16 are set to 100 μs. As described above, the horizontal beam deflection that requires high-speed scanning is performed by wavelength variation, and the vertical beam deflection is performed by switching the 1×8 optical switches 33-1 to 33-16. In the vertical direction, the space where the light beam is irradiated is divided into 16 parts, and horizontal beam scanning is simultaneously performed for each of the 16 divided areas. The number of lines in one area is 8.

[0056] The up-chirp period and down-chirp period of FMCW are each set to 5 μs. Assuming the maximum ranging distance is 300 m, the round-trip time of the light returning from 300 m away is 2 μs. Since a total of 13 μs, which is the sum of the FMCW sweep time (5 μs × 2), the round-trip time of 2 μs, and the wavelength switching time of 1 μs, is used for 1 pixel, the time required for the beam scanning of 1 horizontal line with 512 pixels is 6656.7 μs. The time required for the beam scanning in the vertical direction is 100 μs × 8 = 800 μs. Therefore, the total time required for measuring the target space is 6656.7 × 8 + 800 = 54048 μs ≒ 54 ms, and the achievable frame rate is 18.5 Hz. From the above, it can be seen that using the configuration of this embodiment can satisfy the specifications of the in-vehicle LiDAR shown in Table 1.

[0057] [Second Embodiment] In the first embodiment, for example, the optical beam deflection device applied to LiDAR was described. However, in LiDAR, it is necessary to receive the light returning from the target space. In this embodiment, the configuration of a light transmitting and receiving device in which the optical beam deflection device and the light receiving device are integrated is shown in FIG. 6.

[0058] The light transmitting and receiving device uses a planar optical waveguide circuit 3a instead of the planar optical waveguide circuit 3 of the first embodiment, and adds 16 photodetectors 9-1 to 9-16, 16 photodetectors 10-1 to 10-16, and 16 transimpedance amplifiers (TIAs) 11-1 to 11-16. Since the configuration after the focal plane lens 4 is the same as that of the first embodiment, it is omitted in FIG. 6.

[0059] The planar optical waveguide circuit 3a includes an optical waveguide 30, a 1×16 optical splitter 31, optical waveguides 32-1 to 32-16, 1×8 optical switches 33-1 to 33-16, optical waveguides 34-1 to 34-128, 16 10:1 optical splitters 35-1 to 35-16 that branch the light from the optical waveguides 32-1 to 32-16 into two lights with a branching ratio of 10:1 respectively, 16 3dB couplers 36-1 to 36-16 that output the light input to the first port from the 10:1 optical splitters 35-1 to 35-16 to the second port and output the light input to the second port to the third port, 16 3dB couplers 37-1 to 37-16 that combine the light output from the third port of the 3dB couplers 36-1 to 36-16 and the light output from the second output port of the 10:1 optical splitters 35-1 to 35-16 in an equal ratio, divide them into two equal parts and output, 16 optical waveguides 38-1 to 38-16 that connect the first output port of the 10:1 optical splitters 35-1 to 35-16 and the first port of the 3dB couplers 36-1 to 36-16, 16 optical waveguides 39-1 to 39-16 that connect the second output port of the 10:1 optical splitters 35-1 to 35-16 and the second port of the 3dB couplers 37-1 to 37-16, 16 optical waveguides 40-1 to 40-16 that connect the second port of the 3dB couplers 36-1 to 36-16 and the input ports of the 1×8 optical switches 33-1 to 33-16, 16 optical waveguides 41-1 to 41-16 that connect the third port of the 3dB couplers 36-1 to 36-16 and the first port of the 3dB couplers 37-1 to 37-16, 16 optical waveguides 42-1 to 42-16 that guide the light output from the third port of the 3dB couplers 37-1 to 37-16, and 16 optical waveguides 43-1 to 43-16 that guide the light output from the fourth port of the 3dB couplers 37-1 to 37-16.

[0060] The light (probe light) branched by the 1×16 optical splitter 31 and guided by the optical waveguides 32-1 to 32-16 is branched into two by the 10:1 optical splitters 35-1 to 35-16 at a branching ratio of the output light intensity 1 of the second port to the output light intensity 10 of the first port. The probe light output from the first ports of the 10:1 optical splitters 35-1 to 35-16 is guided by the optical waveguides 38-1 to 38-16, input to the first ports of the 3dB couplers 36-1 to 36-16, and output from the second ports of the 3dB couplers 36-1 to 36-16. On the other hand, the light (reference light) output from the second ports of the 10:1 optical splitters 35-1 to 35-16 is guided by the optical waveguides 39-1 to 39-16 and input to the second ports of the 3dB couplers 37-1 to 37-16.

[0061] The probe light output from the second ports of the 3dB couplers 36-1 to 36-16 is guided by the optical waveguides 40-1 to 40-16 and input to the 1×8 optical switches 33-1 to 33-16. Thereafter, the probe light is irradiated onto the target space by the configuration after the focal plane lens 4 described in the first embodiment.

[0062] On the other hand, the return light reflected by the object existing in the target space and returning from the target space enters the output end of the same optical waveguide as the emission source of the probe light among the optical waveguides 34-1 to 34-128 of the planar optical waveguide circuit 3 through the reverse path of the probe light, that is, through the optical system 7, the optical system 6, the dispersion element 5, and the focal plane lens 4.

[0063] It is a prerequisite for this embodiment to maintain the selection of the 1×8 optical switches 33-1 to 33-16 until the return light returns to the optical waveguide 34 (34-1 to 34-128) that emitted the probe light. However, in the numerical example shown in Table 2, considering 2 μs as the round-trip time of light, the required time for each pixel is calculated. Therefore, even if the control unit 8 maintains the selection of the 1×8 optical switches 33-1 to 33-16 until the return light returns to the optical waveguide 34 (34-1 to 34-128) that emitted the probe light, the total time required for measuring the target space is the same as that in the first embodiment.

[0064] The return light is input from the optical waveguides 34-1 to 34-128 into the 1×8 optical switches 33-1 to 33-16, and is output from the input ports of the 1×8 optical switches 33-1 to 33-16. Then, the return light is guided by the optical waveguides 40-1 to 40-16, input into the second ports of the 3dB couplers 36-1 to 36-16, and output from the third ports of the 3dB couplers 36-1 to 36-16.

[0065] The 3dB couplers 37-1 to 37-16 combine the return light guided by the optical waveguides 41-1 to 41-16 and input into the first ports and the reference light guided by the optical waveguides 39-1 to 39-16 and input into the second ports at an equal ratio, split them into two equal parts, and output them to the third port and the fourth port. The light output from the third ports of the 3dB couplers 37-1 to 37-16 is guided by the optical waveguides 42-1 to 42-16, and the light output from the fourth ports of the 3dB couplers 37-1 to 37-16 is guided by the optical waveguides 43-1 to 43-16.

[0066] The photodetectors 9-1 to 9-16 convert the light emitted from the optical waveguides 42-1 to 42-16 into electrical signals. The photodetectors 10-1 to 10-16 convert the light emitted from the optical waveguides 43-1 to 43-16 into electrical signals. The TIAs 11-1 to 11-16 amplify the difference between the output signals from the photodetectors 9-1 to 9-16 and 10-1 to 10-16 that receive the light emitted from the optical waveguides 42-1 to 42-16 and 43-1 to 43-16 connected to the same 3dB couplers 37-1 to 37-16. In this way, the received signal can be obtained.

[0067] In the first embodiment, it is assumed that the optical beam deflection device and the light receiving device are provided separately. On the other hand, in this embodiment, although the optical beam deflection device and the light receiving device are integrated, the total time required for measuring the target space is the same as that in the first embodiment, and in this embodiment as well, the specifications of the in-vehicle LiDAR shown in Table 1 can be satisfied.

[0068] Note that since the configuration after TIA11-1 to 11-16 is not an essential component in the present invention, it is omitted in FIG. 6. As an example of the utilization of the received signal obtained by TIA11-1 to 11-16, for example, there is LiDAR, but the application target of the present invention is not limited to LiDAR.

[0069] Also, in the first and second embodiments, the vertical direction is set as the first direction and the horizontal direction orthogonal to the vertical direction is set as the second direction, but the vertical direction and the horizontal direction may be interchanged. That is, the beam deflection in the vertical direction may be performed by wavelength variation, and the beam deflection in the horizontal direction may be performed by switching the 1×8 optical switches 33-1 to 33-16.

[0070] The control unit 8 described in the first and second embodiments can be realized by a computer including a CPU (Central Processing Unit), a storage device, and an interface, and a program for controlling these hardware resources. A configuration example of this computer is shown in FIG. 7.

[0071] The computer includes a CPU 200, a storage device 201, and an interface device (I / F) 202. Circuits for supplying voltage to the wavelength-variable semiconductor laser 1 and circuits for supplying control signals to the 1×8 optical switches 33-1 to 33-16 are connected to the I / F 202. In such a computer, a program for realizing the method of the present invention is stored in the storage device 201. The CPU 200 executes the processes described in the first and second embodiments according to the program stored in the storage device 201.

Industrial Applicability

[0072] The present invention can be applied to the optical deflection technology required for LiDAR and the like.

Explanation of Reference Numerals

[0073] 1…Wavelength tunable semiconductor laser, 2…Optical amplifier, 3, 3a…Planar optical waveguide circuit, 4…Focus plane lens, 5…Dispersion element, 6, 7…Optical system, 8…Control unit, 9-1 to 9-16, 10-1 to 10-16…Photodetector, 11-1 to 11-16…TIA, 30, 32-1 to 32-16, 34-1 to 34-128, 38-1 to 38-16, 39-1 to 39-16, 40-1 to 40-16, 41-1 to 41-16, 42-1 to 42-16, 43-1 to 43-16…Optical waveguide, 31…1×16 optical splitter, 33-1 to 33-16…1×8 optical switch, 35-1 to 35-16…10:1 optical splitter 35-1 to 35-16, 36-1 to 36-16, 37-1 to 37-16…3dB coupler.

Claims

1. A wavelength-variable light source, a planar optical waveguide circuit that branches the light emitted from the wavelength-variable light source into a first number of lights equal to the number of divided areas in a first direction of a target space, and selects and emits the emission positions in the first direction of the branched lights so that these lights are simultaneously irradiated to the positions of one pixel in each corresponding area, a dispersion element that deflects each of the first number of lights emitted from the planar optical waveguide circuit at an angle corresponding to the wavelength of the light in a plane parallel to a second direction orthogonal to the first direction, a first optical system that converts and emits the first number of lights emitted from the dispersion element so as to be parallel to the axis of the optical system, and a second optical system that deflects each of the first number of lights emitted from the first optical system and irradiates the target space. A light beam deflection device characterized by comprising:

2. In the light beam deflection device according to Claim 1, further comprising a control unit that controls the wavelength variation by the wavelength-variable light source and the selection of the emission position by the planar optical waveguide circuit, the control unit changes the wavelength of the light emitted from the wavelength-variable light source to change the deflection angle of the light in a plane parallel to the second direction, thereby simultaneously moving the first number of lights irradiated from the second optical system to the target space in the second direction for the scanning in the second direction, and after the scanning of the line in the second direction is completed, changes the emission position of the light emitted from the planar optical waveguide circuit to change the deflection angle of the light in a plane parallel to the first direction, thereby simultaneously moving the first number of lights irradiated to the target space in the first direction for the scanning in the first direction, and repeats this. A light beam deflection device characterized by this.

3. In the light beam deflection device according to Claim 1, the planar optical waveguide circuit, an optical splitter that branches the light emitted from the wavelength-variable light source into the first number of lights, comprises a second number of output ports equal to the number of pixels in the first direction in each of the divided areas of the target space, and the first number of optical switches that selectively output the light branched by the optical splitter to any one of the second number of output ports, An optical beam deflector, comprising: an optical waveguide arranged in the first direction in a number obtained by multiplying the first number by the second number so as to waveguide light output from each output port of the first number of optical switches and emit the light from an end face of a planar optical waveguide circuit.

4. In the optical beam deflector according to claim 1, further comprising a focal plane lens inserted between the planar optical waveguide circuit and the dispersion element, wherein the focal plane lens converts the first number of lights emitted from the planar optical waveguide circuit into parallel lights respectively, and at the same time deflects these parallel lights so as to pass through a focal point on the object space side of the focal plane lens.

5. In the optical beam deflector according to claim 1, the dispersion element comprises a plurality of diffraction gratings arranged along a traveling direction of light.

6. In the optical beam deflector according to claim 1, the first optical system comprises a telecentric fθ lens.

7. In the optical beam deflector according to claim 1, the second optical system comprises a convex lens.

8. The optical beam deflector according to claim 1, the first number of first photodetectors for converting incident light into an electrical signal, the first number of second photodetectors for converting incident light into an electrical signal, and the first number of transimpedance amplifiers for obtaining a difference between output signals of the first and second photodetectors, wherein the planar optical waveguide circuit comprises a first optical splitter for branching light emitted from the wavelength tunable light source into the first number of lights, the first number of second optical splitters for branching the lights branched by the first optical splitter into two respectively, the first number of first couplers for outputting one of the lights branched by the second optical splitter from a first port to a second port and outputting the light input to the second port to a third port, and the first number of optical switches each having the second number of output ports equal to a number of pixels in the first direction in each divided area of the object space, and selectively outputting the light output from the second port of the first coupler to any one of the second number of output ports. A first optical waveguide arranged in the first direction and having a number obtained by multiplying the first number by the second number so as to guide light output from each output port of the first number of optical switches and emit the light from a first end face of the planar optical waveguide circuit. A first number of second couplers that combine the light output from the third port of the first coupler and the other light branched by the second optical splitter, divide the combined light into two equal parts, and output the divided light. A first number of second optical waveguides that guide the light output from one output port of the second coupler and emit the light from a second end face of the planar optical waveguide circuit. A first number of third optical waveguides that guide the light output from the other output port of the second coupler and emit the light from a second end face of the planar optical waveguide circuit. The first number of return lights returned from the target space enter the emission end of the first optical waveguide of the planar optical waveguide circuit through the second optical system, the first optical system, and the dispersion element. The first coupler outputs the return light output from the input port of the optical switch and input to the second port to the third port. The first photodetector converts the light emitted from the second optical waveguide into an electrical signal. The second photodetector converts the light emitted from the third optical waveguide into an electrical signal. The transimpedance amplifier is characterized by obtaining a difference between output signals from the first and second photodetectors that receive the emitted light from the second and third optical waveguides connected to the same second coupler. The light transmitting and receiving device.

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