WO2020121452A1 - Lidar device - Google Patents

Abstract

This LiDAR device comprises: an optical transmitter that is configured from a first optical phased array and transmits, into a space, diffracted light produced from light output from a plurality of first antenna elements composing the first optical phased array; and an optical receiver that is configured from a second optical phased array and uses a plurality of second antenna elements composing the second optical phased array to receive light arriving from the space. The optical receiver has a plurality of local maximum sensitivity directions each of which is a direction of the arrival of the light from the space in which the light reception sensitivity is at a local maximum. A first angle formed between adjacent directions of diffracted light transmitted into the space by the optical transmitter is different from a second angle formed between adjacent local maximum sensitivity directions of the optical receiver.

Description

Rider device

The present invention generally relates to the field of remote sensing and distance measurement, and more particularly to a lidar (LiDAR, Light Detection and Ranging) for performing three-dimensional spatial mapping, object detection, object tracking, and object identification in an autonomous driving system in real time. Regarding the device.

The lidar device sends the search light to the space, scans the space, receives reflected return light generated by the search light being reflected by an object in the space, and determines the direction and distance of the object in the space. Detect. An optical phased array (OPA, Optical Phased Array) is known as a device constituting such a lidar device. The lidar device using the OPA can be configured at a higher speed and smaller than a lidar device using a mechanical beam scanning device.

As an OPA that can be used for a lidar device, an OPA configured by arranging a plurality of unit cells each including an optical coupler, a phase shifter, and an antenna element has been conventionally known (Patent Document 1). ). However, in this OPA, since each unit cell is composed of many elements such as the above-mentioned optical coupler, the unit cell has a corresponding size. Therefore, there is a limit to reducing the arrangement interval of the unit cells, that is, the arrangement interval of the antenna elements, and the angle range of the beam steering of the search light is narrowed due to the size of the arrangement interval.

Also, as another OPA that can be used for a lidar device, an OPA based on an optical integrated circuit (photonic integrated circuit (PIC)) is conventionally known (Non-patent document 1). This OPA includes a bus waveguide for inputting light, a plurality of branch portions each formed of a thermal phase shifter and an evanescent coupler and provided on the bus waveguide, and the evanescent coupler. And a plurality of grating-based antenna elements for transmitting each of the plurality of lights branched by each to the space. In this OPA, beam steering is performed along the extending direction of the antenna element by changing the wavelength of the input light.

However, in order to secure a practically sufficient beam steering angle range in this OPA, a wavelength tunable laser having an extremely wide wavelength tunable range is required, and the cost of the entire lidar device increases.

U.S. Pat. No. 8,988,754

From the above background, in a lidar device using an optical phased array (OPA), a wider beam steering angle range is realized by overcoming the limitation of the beam steering angle range due to the arrangement pitch of the antenna elements without increasing the cost. Is required to do.

One aspect of the present invention is configured by a first optical phased array, and transmits diffracted light generated by light output from a plurality of first antenna elements forming the first optical phased array to space. And an optical receiver that is configured by a second optical phased array and that receives light coming from the space by a plurality of second antenna elements that configure the second optical phased array. , The optical receiver has a plurality of maximum sensitivity directions with respect to the direction of light coming from the space, the receiving sensitivity of the light being maximum, and the optical transmitter transmits the diffracted light adjacent to the space. In the lidar device, a first angle formed by the directions is different from a second angle formed by the adjacent maximum sensitivity directions in the optical receiver.
According to another aspect of the present invention, a phase shift controller that controls a first phase shifter included in the first optical phased array and a second phase shifter included in the second optical phased array is provided. The phase shift control unit controls the phase shift amount of the first phase shifter to change the sending direction of the main lobe of the diffracted light sent to the space by the optical transmitter, and at the same time, among the maximum sensitivity directions. The phase shift amount of the second phase shifter is controlled so that the maximum sensitivity direction having the maximum sensitivity matches the sending direction of the main lobe.
According to another aspect of the present invention, the array interval of the first antenna elements and the array interval of the second antenna elements are set to different values.
According to another aspect of the present invention, the ratio between the first angle and the second angle is set so as to be expressed as a ratio of natural numbers that are relatively prime.
According to another aspect of the present invention, the ratio of the arrangement interval of the first antenna elements and the arrangement interval of the second antenna elements is set to be represented by a ratio of natural numbers that are mutually prime.
According to another aspect of the present invention, the optical transmitter includes a first optical component that forms an image conversion optical system for the diffracted light generated by the light output from the plurality of first antenna elements. Via the first optical component, the first angle being defined by the angle between adjacent diffracted lights that are delivered to the space via the first optical component.
According to another aspect of the present invention, the first optical component is composed of two convex lenses.
According to another aspect of the present invention, the first optical component includes two prisms forming an anamorphic prism pair.
According to another aspect of the present invention, the optical receiver receives light coming from the space by the plurality of second antenna elements via a second optical component forming an image conversion optical system, The second angle is defined as an angle formed by adjacent maximal sensitivity directions defined in the space with respect to light coming from the space received via the second optical component.

According to the present invention, it is possible to realize a wider beam steering angle range by overcoming the limitation of the beam steering angle range due to the arrangement pitch of the antenna elements in the lidar device using the OPA without increasing the cost. it can.

FIG. 1 is a diagram showing a configuration of a rider device according to a first embodiment of the present invention. FIG. 2 is an explanatory diagram for explaining the operation of the rider device shown in FIG. FIG. 3 is a diagram showing a configuration of a rider device according to a second embodiment of the present invention. FIG. 4 is a diagram showing the configuration of the rider device according to the third embodiment of the present invention. FIG. 5: is a figure which shows the structure of the conventional rider apparatus. FIG. 6 is a diagram showing an example of characteristics of a conventional rider device. FIG. 7 is a diagram showing an example of an optical phased array that can be used in the lidar device. FIG. 8 is a diagram showing a configuration of a unit cell included in the optical phased array shown in FIG. FIG. 9 is a diagram showing another example of the optical phased array that can be used in the lidar device.

Generally, the OPA is provided with an optical branching device for branching the input light into a plurality of lights, a plurality of waveguide lines for propagating each of the plurality of branched lights, and a plurality of waveguide lines provided for the waveguide lines. It is composed of a phase shifter that changes the phase of light propagating in the wave line, and an antenna element that is connected to each waveguide line and outputs the light propagating in the waveguide line. The OPA is generally reciprocal and can be used not only in an optical transmitter that sends out a light beam that is a search light, but also in a receiver that receives the reflected return light of the light beam.

For example, the light received by each of the antenna elements of the OPA is propagated to each waveguide line, the phase is changed by the phase shifter, and the optical branching device is used as an optical coupler (combiner). An optical receiver can be configured by combining the light propagating through the waveguide line into one light and outputting the combined light.

Here, it is assumed that the OPA is used as an optical transmitter and the phase shift amount in the phase shifter is adjusted so that diffracted light is sent out from the antenna element of the OPA toward space. Then, in this state, it is assumed that the OPA is used as an optical receiver and light is received from the antenna element while holding the phase shift amount of the phase shifter. Then, the light arriving from the same direction as the diffracted light transmission direction is received by each of the antenna elements, and then phase-shifted to the same phase by the phase shifter, and the signals are mutually strengthened and output in the optical coupler. The Rukoto. On the contrary, the light arriving from a direction different from the diffracted light transmission direction does not become the same phase even if it undergoes a phase shift by the phase shifter after being received by each of the antenna elements. Will be output without strengthening each other. For this reason, the optical receiver has a maximum reception sensitivity with respect to the light coming from the transmission direction of the diffracted light. Further, the optical receiver has the maximum receiving sensitivity for the light coming from the direction of transmission of the main lobe having the maximum intensity among the diffracted lights.

Hereinafter, in the present specification, an optical transmitter including an OPA functioning as a transmitter for transmitting a beam is referred to as TxOPA, and an optical receiver including an OPA functioning as a receiver for receiving light is referred to as RxOPA. .. Further, in the present specification, for the sake of convenience, the diffracted light, the main lobe, and the side lobes that would be generated by the light sent from the antenna element if the light was sent from the antenna element forming the RxOPA, They are referred to as “diffracted light of RxOPA”, “main lobe of RxOPA”, and “sidelobe of RxOPA”, respectively. Further, in the present specification, the “far-field image of RxOPA” refers to a far-field image of the light transmitted from the antenna element when the light is transmitted from the antenna element forming the RxOPA 104. ..

In addition, in the present specification, the reception sensitivity of RxOPA is the loss received by the light received by the antenna element of the RxOPA before being output from the optical coupler via the phase shifter and the optical coupler of the RxOPA. The reciprocal (that is, the reciprocal of the ratio of the amount of light output from the optical coupler to the total amount of light that reaches the antenna element from the same direction).

A rider device that performs three-dimensional space mapping or the like can be generally realized by the configuration shown in FIG. The rider device 500 shown in FIG. 5 includes TxOPA 502 and RxOPA 504 configured by OPA, and a light source 506. The TxOPA 502 includes a phase shift unit 514 including an optical splitter 510 that splits light from the light source 506, and a plurality of phase shifters 512 that shift the phases of the respective lights split by the optical splitter 510, and a phase shift unit. An antenna unit 518 in which a plurality of antenna elements 516 for emitting each light output from 514 to the space are arranged.

The RxOPA 504 also includes an antenna unit 528 in which antenna elements 526 for receiving light propagating in space are arranged, and a phase shift unit 524 including a plurality of phase shifters 522 for respectively shifting the phases of the light received by each antenna element 526. And an optical coupler 520 for combining and outputting the lights output from the phase shift unit 524.

The lidar device 500 also includes a photodetector 530 that receives the light output from the RxOPA 504, a steering control unit 532 that controls the operation of the phase shift units 514 and 524 of the TxOPA 502 and RxOPA 504, and a light source 506. And a control device 536 that controls the steering control unit 532 and receives the output of the photodetector 530 to perform a data generation process for, for example, spatial mapping.

The light source 506 is, for example, a pulse laser, and the control device 536 measures the distance to an object in space by, for example, the time of flight (TOF) method.

The optical signal from the light source 506 is incident on the TxOPA 502. The steering control unit 532 operates the phase shifter 512 of the phase shift unit 514 to cause the plurality of arranged antenna elements 516 forming the antenna unit 518 of the TxOPA 502 to emit diffracted light toward the space and also to diffract the diffracted light. Beam steering is performed by changing the delivery direction to the space.

Further, the steering control unit 532 controls the phase shifter 522 of the phase shift unit 524 of the RxOPA 504 so that the diffracted light of the RxOPA 504 is directed in the same direction as the diffracted light that the TxOPA 502 is currently sending. To operate. As a result, the RxOPA 504 has the maximum receiving sensitivity for the light coming from the sending direction of the main lobe of the TxOPA 502 and the maximum receiving sensitivity for the light coming from the sending direction of the sidelobe of the TxOPA 502.

Here, in the conventional lidar device 500, in general, about several thousand antenna elements 516 and 526 are required in order to increase the degree of convergence of diffracted light and improve the spatial resolution in object detection. Further, in general, in order to secure the steering angle range of the main lobe used as the search light as wide as possible, the arrangement intervals of the antenna elements 516 and 526 are set so that diffracted light adjacent to the steering angle range of the main lobe does not enter. Both are designed to be as narrow as possible, and as a result, they are designed to have the same arrangement interval p.

As a result, the diffracted lights of TxOPA502 and RxOPA504 both have the same direction. FIG. 6 is a diagram showing exemplary characteristics of the TxOPA 502 and RxOPA 504 shown in FIG. The upper part of FIG. 6 shows the case where the optical phase difference generated in each optical path (each channel) from the optical input end of the optical branching device 510 to each optical output end of the antenna element 516 is zero for the TxOPA502. , Is a far-field image of the light transmitted from the antenna unit 518. Further, in the middle part of FIG. 6, in the RxOPA 504, the optical phase difference generated in each optical path (each channel) from each optical input end of the antenna element 526 to the optical output end of the optical coupler 520 is zero. FIG. 8 is a diagram showing a distribution of reception sensitivity of the RxOPA 504 with respect to the direction of light coming from space at that time. Further, in the lower part of FIG. 6, when the diffracted light having the light intensity distribution shown in the upper part of FIG. 6 is transmitted to the space, and the reflected return light from the space is received by the RxOPA 504 having the receiving sensitivity distribution shown in the middle part of FIG. 6 is a diagram showing a distribution of the total sensitivity of the rider device 500 in each direction in the space viewed from the rider device 500. FIG.

In FIG. 6, the abscissas of the upper, middle, and lower tiers are axes that indicate each direction in the XZ plane (the vertical direction in FIG. 5) by the sine value of the angle θ with respect to the Z axis. .. The vertical axis in the upper part of FIG. 6 is the normalized light intensity obtained by normalizing the intensity of the light transmitted from the TxOPA 502 with the maximum intensity of the main lobe. Further, the vertical axis in the middle of FIG. 6 is the normalized reception sensitivity obtained by normalizing the reception sensitivity of the RxOPA 504 by the maximum reception sensitivity value. Further, the vertical axis in the lower part of FIG. 6 is the normalized total sensitivity obtained by normalizing the total sensitivity of the lidar device 500 with its maximum value.

In the upper part of FIG. 6, the light intensity portion 600 having the maximum intensity at the position of sin θ=0 corresponds to the main lobe of the diffracted light output from the TxOPA 502 (the main maximum beam with the diffraction order of zero), and the maximum light intensity. The light intensity portions 602, 604, 606, 608, 610, 612 other than the portions correspond to side lobes (diffracted light beams having a diffraction order other than zero). Of these, the light intensity portions 602 and 604 correspond to side lobes (diffraction orders are ±1) adjacent to the main lobe, and are generated at positions of sin θ=±λ ₀ /p. Here, λ ₀ is the center wavelength of the light output from the light source 506, and p is the array pitch of the antenna elements 516.

Since the antenna elements 526 of the RxOPA 504 are arranged at the same arrangement pitch p as the antenna elements 516 of the TxOPA 502, the diffracted light of the RxOPA 504 is directed in the same direction as the TxOPA 502. Therefore, the receiving sensitivity of the RxOPA 504 shown in the middle part of FIG. 6 has the maximum portions 620 at the same positions as the light intensity parts 600, 602, 604, 606, 608, 610, 612 corresponding to the diffracted light of the TxOPA 502 in the upper part of FIG. 6, respectively. It has 622, 624, 626, 628, 630, and 632, and has a maximum portion 620 at which the reception sensitivity is maximum at the same position as the light intensity portion 600 corresponding to the main lobe of the TxOPA 502.

Further, the total sensitivity of the lidar device 500 is the light intensity distribution transmitted by the TxOPA 502 (that is, the normalized light intensity value shown in the upper part of FIG. 6) and the reception sensitivity distribution in the RxOPA 504 (that is, the normalized sensitivity shown in the middle part of FIG. 6). It is proportional to the product of (reception sensitivity value). Therefore, the total sensitivity of the lidar device 500 is, as shown in the lower part of FIG. 6, a position (mλ ₀ /p, m=0, ±) where the maximum light intensity of the TxOPA 502 and the maximum reception sensitivity of the RxOPA 504 coincide. 1, ±2, ±3) has maximum portions 640, 642, 644, 646, 648, 650, 652, and shows a maximum portion 640 showing the maximum total sensitivity at the position corresponding to the main lobe (sin θ=0). To have.

In this lidar device 500, when the same phase shift is generated in each channel of the TxOPA 502 and each channel of the RxOPA 504 and the directions of the diffracted light of the TxOPA 502 and the RxOPA 504 are changed in the same manner, the light in the upper stage of FIG. The intensity portion 600 and the like and the maximum portion 620 and the like in the middle of FIG. 6 are shifted in the same direction by the same amount. Further, in response to this, the maximum portions 640 and the like in the lower part of FIG. 6 are also shifted by the same amount in the same direction.

Therefore, for example, when beam steering is performed using the main lobe of the TxOPA 502 as the search light, in the lower part of FIG. 6, the maximum portion 640 of the total sensitivity when the main lobe is used is within the shift range in the horizontal direction in the figure. , The range of the beam steering is limited to the range of Expression (1) so that the maximum portions 642 and 644 of the total sensitivity for the adjacent side lobes do not enter.

That is, if α _max ≡λ ₀ /2p, the allowable range of the steering angle α is −α _max to +α _max , and as a result, the maximum allowable range of the steering angle α is the array pitch of the antenna elements 516 and 526. Limited by the size of p.

Although the beam steering on the XZ plane has been described in the above description, the beam steering on the YZ plane also depends on the array pitch in the Y-axis direction of the antenna elements 516 and 526, similarly to the above. The steering angle range is limited.

On the other hand, as an OPA that can be used for a lidar device, as described above, an OPA configured by arranging a plurality of unit cells each emitting light is known (Patent Document 1). FIG. 7 is a diagram showing a part of the configuration of such an OPA 700, and FIG. 8 is a diagram showing a configuration of a unit cell 710 forming the OPA 700.

Referring to FIG. 7, light input from the optical fiber 702 propagates in the column direction bus waveguide 704. The light propagating through the column-direction bus waveguide 704 is branched by the plurality of evanescent couplers 706 provided in the column-direction bus waveguide 704 at predetermined intervals and propagates through the plurality of row-direction bus waveguides 708. Each unit cell 710 (each of the 16 parts shown by the dotted ellipse in the figure) outputs a part of the light propagating through the row-direction bus waveguide 708 from the adjacent row-direction bus waveguide 708 to the evanescent coupler 800 (described later). A) via. A column direction control wire 712 and a row direction control wire 714, which are current paths, are connected to each unit cell 710, and a phase shifter 806 (described later) included in each unit cell 710 is selectively energized.

Referring to FIG. 8, each unit cell 710 includes an evanescent coupler 800 coupled to the row-direction bus waveguide 708, an antenna element 802, a waveguide 804 connecting the evanescent coupler 800 and the antenna element 802, and the waveguide 804. A phase shifter 806, which is a heater provided in the S-shaped portion, and a column-direction electrode 808 and a row-direction electrode 810, which are two electrodes for energizing the heater, which is the phase shifter 806, are provided. The column direction electrodes 808 and the row direction electrodes 810 are connected to the column direction control wires 712 and the row direction control wires 714, respectively.

The OPA 700 shown in FIG. 7 can generate a controllable linear phase tilt along the row and/or column directions and can operate as an OPA with controllable beam steering in the XZ and YZ planes. ..

However, in the OPA 700 of FIG. 7 according to Patent Document 1, since each unit cell 710 has many additional elements (phase shifter 806, waveguide 804, evanescent coupler 800) in addition to the antenna element 802, its size is sufficient. It cannot be made smaller. As a result, in the OPA 700 of Patent Document 1, the unit cell 710 (specifically, the antenna element 802 included in the unit cell 710) cannot be arranged with a sufficiently small pitch p in both the X direction and the Y direction. ..

For example, the arrangement pitch of the unit cells 710 realized in the OPA 700 is about 9 μm, and when beam steering is performed using light with a center wavelength of 1550 nm, the allowable range of the steering angle α that can be used for the beam steering is From the formula (1), it is limited to ±5°.

As described above, the OPA based on the optical integrated circuit disclosed in Non-Patent Document 1 is known as another OPA that can be used in the lidar device. FIG. 9 is a diagram showing the configuration of the OPA 900 according to Non-Patent Document 1. The OPA 900 includes a bus waveguide 902 for inputting light, and a portion 904 that is provided on the bus waveguide 902 and is composed of thermal phase shifters and evanescent couplers that are alternately cascade-connected. The light branched by the evanescent coupler is connected to the antenna unit 908 in which the antenna elements of the grating base are arranged via the waveguide line unit 906. In this OPA900, the thermal phase shifter controls the phase increment of the light sequentially input to the arrayed antenna elements, and also controls the wavelength of the light input to the bus waveguide 902 to generate a two-dimensional beam. A steering function is provided.

In the TxOPA 502 and the RxOPA 504 shown in FIG. 5, for example, a plurality of grating-based antenna elements forming the antenna unit 908 of the OPA 900 are extended in the Y direction shown in FIG. 5, and the plurality of antenna elements are arranged in the X direction. It can be configured by

However, the plurality of antenna elements forming the antenna unit 908 are configured as waveguides formed on the substrate, and the array pitch of the antenna elements (the array pitch in the X direction) is the waveguides formed as described above. Equal to the array pitch of. The allowable minimum value of the array pitch of the waveguides is limited by the optical confinement strength of the waveguides. If the optical index confinement strength is increased by increasing the refractive index difference between the substrate and the waveguides, the array pitch of the antenna elements is increased. Can be narrowed. However, there is a limit to the difference in refractive index that can be realized depending on the substrate material and the like, and it is difficult to reduce the array pitch from several μm to a large extent. Therefore, in the beam steering of the OPA 900 in the X direction, the steering angle range may be limited to about several degrees, as in the case of the OPA 700 described above.

Further, in order to secure a practically sufficient beam steering range in the Y direction, the OPA900 requires a wavelength tunable laser having an extremely wide wavelength tunable range as shown below, which significantly increases the cost of the entire lidar device. Can be done. Conversely, in the OPA 900, it may be difficult to realize a practical beam steering range in the Y direction without a significant increase in cost.

That is, when the oscillation wavelength of the wavelength tunable laser changes by Δλ with respect to the central wavelength λ ₀ , the steering angle α _{y of the} main lobe emitted from the antenna unit 908 (the deflection angle of the main lobe in the YZ plane with respect to the Z axis) is It is calculated from equation (2).

Here, n _E is the effective refractive index of the waveguide constituting the antenna element, p _g is a grating pitch which is provided to each antenna element. The central wavelength λ ₀ of the wavelength tunable laser is normally set so as to satisfy the formula (3) so that the steering angle α _y becomes zero (α _y =0) when the wavelength shift is zero (Δλ=0). To be selected.

Then, when the maximum wavelength change range of the wavelength tunable laser is λ ₀ ±Δλ _max , the change range of the steering angle α _y in the Y direction that can be realized by the _OPA900 −α _ymax to +α _ymax is _represented by the formula (4). Derived from the relationship.

Here, the grating pitch _pg is usually produced with a value close to the half wavelength λ ₀ /2. If p _g =λ ₀ /2, then equation (4) becomes equation (5).

That is, when the maximum steering angle α _ymax =30°, if the central wavelength λ ₀ is 1550 nm, 2Δλ _max becomes 775 nm, and a wavelength tunable laser capable of controlling the oscillation wavelength over a wide range of 1550±387.5 nm is required. Becomes Then, it is extremely difficult to find a commercially available wavelength tunable laser that satisfies such a condition, or even if it is possible, it is extremely expensive.

Hereinafter, the rider device according to the embodiment of the present invention will be described.
<First Embodiment>
FIG. 1 is a diagram showing a configuration of a rider device according to a first embodiment of the present invention. The lidar device 100 includes a light source 106, a TxOPA 102 that outputs the output light of the light source 106 to the space, and an RxOPA 104 that receives reflected return light that is reflected back from an object in the space among the light sent from the TxOPA 102. , A photodetector 130 that detects the light output from the RxOPA 104. The light source 106 is, for example, a pulse laser.

The TxOPA 102 includes an optical splitter 110 that splits the output light of the light source 106, a phase shift unit 114 that includes a plurality of phase shifters 112 that shift the phases of the lights split by the optical splitter 110, and a phase shift unit. An antenna unit 118 in which a plurality of antenna elements 116 for emitting each light output from 114 to the space are arranged. The antenna elements 116 are two-dimensionally arrayed, for example, along the X-axis and the Y-axis in the drawing so that the mutual intervals have an array pitch (arrangement interval) p _T in the XY plane defined by the X-axis and the Y-axis. Has been done.

The RxOPA 104 includes an antenna unit 128 in which antenna elements 126 that receive the reflected return light are arranged, a phase shift unit 124 that includes a plurality of phase shifters 122 that shift the phase of the light received by each antenna element 126, and a phase shift unit 124. And an optical coupler 120 that combines the lights output from the shift unit 124 into one and outputs the combined light. The antenna elements 126 are two-dimensionally arrayed, for example, along the X-axis and the Y-axis in the drawing so that the mutual intervals have an array pitch (array interval) p _R in the XY plane defined by the X-axis and the Y-axis. Has been done. As a result, in the RxOPA 104, the directions of the plurality of diffracted lights of the RxOPA 104 are the maximum sensitivity directions in which the respective reception sensitivities are maximized. That is, the RxOPA 104 is configured to have a plurality of maximum sensitivity directions with respect to the direction of the light coming from the space, which maximizes the reception sensitivity of the light.

Here, the TxOPA 102 is an optical transmitter including a first optical phased array, and diffraction generated by light output from a plurality of first antenna elements forming the first optical phased array. It corresponds to a light transmitter that sends light to space. The first optical phased array includes an optical splitter 110, a phase shift unit 114 including a phase shifter 112 which is a first phase shifter, an antenna unit 118 including an antenna element 116 which is a first antenna element, It corresponds to the part including.

The RxOPA 104 is an optical receiver including a second optical phased array, and is an optical receiver that receives light coming from a space by a plurality of second antenna elements forming the second optical phased array. It corresponds to a bowl. The second optical phased array includes an optical coupler 120, a phase shift unit 124 including a phase shifter 122 that is a second phase shifter, an antenna unit 128 including an antenna element 126 that is a second antenna element, It corresponds to the part including.

The TxOPA 102 and the RxOPA 104 can be configured using the OPA described in Patent Document 1, for example. That is, the TxOPA 102 is configured such that the antenna elements 802 shown in FIG. 8 as the antenna elements 116 are two-dimensionally arranged in the XY plane at intervals (arrangement pitch) p _T in the X and Y directions shown in FIG. Similarly, the RxOPA 104 is configured such that the antenna elements 802 shown in FIG. 8 as the antenna elements 126 are two-dimensionally arranged in the XY plane at intervals (arrangement pitch) p _R in the X and Y directions shown in FIG.

Further, the phase shifter 112 of the TxOPA 102 is composed of a phase shifter 806 which is a thermal phase shifter including a heater provided on the waveguide 804 as shown in FIG. 8, for example. Similarly, the phase shifter 122 of the RxOPA 104 is composed of a phase shifter 806 including a heater provided on the waveguide 804 as shown in FIG. 8, for example.

Further, the optical branching device 110 of the TxOPA 102 and the optical coupler 120 of the RxOPA 104 are both the column-direction bus waveguide 704 and the row-direction bus waveguide 704 for propagating the light from the light source 106 as shown in FIGS. 708 and evanescent couplers 706 and 800.

However, the configuration of the TxOPA 102 and the RxOPA 104 described above is an example, and the present invention is not limited to this. For example, the antenna units 118 and 128 of the TxOPA 102 and the RxOPA 104 are arbitrary as long as the antenna elements 116 and 126 for transmitting and receiving light are two-dimensionally arrayed in the illustrated XY plane at array pitches p _T and p _R , respectively. It may have a structure of.

The phase shift units 114 and 124 are not limited to the above, and are provided in each optical path that propagates the light branched by the optical branching device 110 and each optical path that propagates the light received by the antenna element 126. It can be configured by a phase shifter having an arbitrary configuration described above. Similarly, the optical branching device 110 and the optical coupler 120 are not limited to the above, and as long as they have the function of branching the input light and the function of multiplexing the input light and combining them into one light, respectively. In, the optical branching device and the optical coupler operating according to any configuration or principle can be used.

The rider device 100 also includes a control device 134 and a steering control unit 132 that is a phase shift control unit. The steering control unit 132 controls the operation of the phase shifters 112 and 122 of the TxOPA 102 and the RxOPA 104 under the control of the control device 134. The control device 134 synchronizes the optical pulse output operation of the light source 106 with the operation of the phase shifter 112 of the TxOPA 102 and the phase shifter 122 of the RxOPA 104, and performs space mapping and the like based on the signal from the photodetector 130. Data generation processing and the like.

That is, with the above-described configuration, the lidar apparatus 100 causes the steering control unit 132 to cause a desired phase shift in the phase shifters 112 and 122 under the control of the control device 134, and the emission direction of the main lobe of the TxOPA 102 and the maximum reception of the RxOPA 104 are received. The beam steering is performed by changing the directions to the X direction and/or the Y direction in the drawing while maintaining the state in which the sensitivity directions are oriented in the same direction. As a result, the lidar device 100 performs beam steering with the main lobe of the TxOPA 102 and receives the reflected return light from the irradiation direction of the main lobe of the TxOPA 102 with the RxOPA 104.

Further, the lidar apparatus 100 measures the time from the light source 106 emitting a light pulse until the reflected return light of the light pulse is received via the RxOPA 104 by the control device 134, thereby irradiating the main lobe of the TxOPA 102. The distance to the object existing in the direction is calculated by the time-of-flight method. Then, the lidar device 100 sequentially detects the reflected return light coming from the emission direction of the main lobe of the TxOPA 102 that sequentially changes according to the beam steering operation, and detects the distance to the object in the sequentially changing direction. , For example, data for space mapping etc. is generated.

In particular, in the rider device 100 according to the present embodiment, the array pitch p _T of the antenna elements 116 of the TxOPA 102 and the array pitch p _R of the antenna elements 126 of the RxOPA 104 have different values, and for example, in Expression (6), It is set to have a relationship. Here, N ₁ /M ₁ is an irreducible function, and M ₁ and N ₁ are relatively prime natural numbers.

As a result, the lidar device 100 has an array pitch of the antenna elements 116 of the TxOPA 102 more than that of a conventional rider device (for example, the rider device 500) configured by using TxOPA and RxOPA in which the array pitch of the antenna elements is the same value p. Beam steering can be performed by changing the steering angle α of the main lobe of the TxOPA 102 in a wider range without reducing p _T with respect to p. This will be described below.

Note that in the following description, for simplicity, the beam steering operation in the X-axis direction will be described as an example. As is apparent to those skilled in the art, the description also applies to the Y-axis direction orthogonal to the X-axis.

As described above, the lidar device 100 according to the present embodiment is configured such that the array pitch p _T of the antenna elements 116 of the TxOPA 102 and the array pitch p _R of the antenna elements 126 of the RxOPA 104 have different values. There is. Therefore, the first angle formed by the directions of the adjacent diffracted light beams transmitted by the TxOPA 102 to each other and the second angle formed by the directions of the adjacent diffracted light beams of the RxOPA 104, that is, the second maximum angle formed by the adjacent maximum sensitivity directions are mutually formed. It is different.

Therefore, if the TxOPA 102 and the RxOPA 104 are controlled so that the directions of the main lobes of the TxOPA 102 and the RxOPA match, the direction of the side lobe adjacent to the main lobe becomes different between the TxOPA 102 and the RxOPA 104. That is, since the reception sensitivity of the RxOPA 104 transmitted from the TxOPA 102 in the direction of the adjacent side lobes does not have a maximum value, reception of light coming from the direction of the adjacent side lobes is suppressed. As a result, the steering angle range of the main lobe of the TxOPA 102 is not limited by the angle between the main lobe and the side lobes adjacent to the main lobe, and a wider steering angle range can be used.

More specifically, the difference Δω _T between the deflection angles (angles with respect to the Z axis) of the adjacent diffracted lights of the TxOPA 102 and the difference Δω _R between the deflection angles of the adjacent diffracted light of the RxOPA 104 are respectively expressed by It is represented by (7) and equation (8).

Further, the equation (9) is established from the equations (6), (7), and (8).

That is, in the lidar device 100, the ratio of the first angle formed by the directions of the adjacent diffracted light beams transmitted by the TxOPA 102 to each other and the second angle formed by the adjacent maximum sensitivity directions of the RxOPA 104 are mutually disjoint. It is set to be expressed as a ratio of natural numbers.

Expression (9) can be expressed as Expression (10).

That is, if the directions of the main lobes of the TxOPA 102 and the RxOPA 104 are the same, the direction of the M _1- th sidelobe counted from the mainlobe of the TxOPA 102 and the direction of the N _1- th sidelobe of the RxOPA 104 counted from the mainlobe. However, it will be the first match. In other words, reception of the reflected light of the 1st to M ₁ −1st side lobes in the TxOPA 102 is suppressed in the RxOPA 104.

As a result, alpha _max allowable variation range -α _max ~ + α _max of the steering angle alpha of the main lobe of TxOPA102 becomes possible determined by equation (11).

That is, as can be seen from the comparison between the equations (1) and (11), the arrangement pitch p _T of the antenna elements 116 of the TxOPA 102 constituting the rider apparatus 100 is set to the arrangement pitch p of the TxOPA 502 of the conventional rider apparatus 500. Even if it does (that is, without setting the array pitch p _T to a value smaller than p), the allowable angle range of the beam steering of the rider apparatus 100 is improved to M times the allowable angle range of the conventional rider apparatus 500.

FIG. 2 is a diagram for explaining the operation of the rider device 100 when N=5 and M=6 in Expression (6). The upper part of FIG. 2 is a diagram showing an example of a far-field image of the light transmitted from the antenna unit 118 of the TxOPA 102, and the middle part of FIG. 2 is a diagram showing the light reception sensitivity distribution in the RxOPA 104. The lower part of FIG. 2 is a diagram showing the distribution of the total sensitivity in the lidar device 100, which is obtained as the product of the light intensity and the receiving sensitivity shown in the upper part and the middle part of FIG. 2, respectively. The horizontal axis in FIG. 2 is the sine value sin θ of the angle θ with respect to the Z-axis direction on the XZ plane. The vertical axis in the upper part of FIG. 2 is the normalized light intensity normalized by the maximum light intensity, the vertical axis in the middle part of FIG. 2 is the normalized reception sensitivity normalized by the maximum reception sensitivity, and the vertical axis in the lower part of FIG. 2 is the total sensitivity. It is the normalized total sensitivity normalized by the maximum value of.

In the light intensity distribution of the TxOPA 102 shown in the upper part of FIG. 2, the sixth side lobes 202 and 204, which are Mth from the main lobe 200 of the TxOPA 102 existing at the position of sin θ=0, and the RxOPA 104 shown in the middle part of FIG. The positions of maximum sensitivity portions 212 and 214 corresponding to the M-th fifth side lobe counted from the maximum intensity portion 210 corresponding to the main lobe of RxOPA 104 existing at the position of sin θ=0 in the reception sensitivity distribution are the same. I am doing it.

Therefore, as shown in the lower part of FIG. 2, the distribution of the total sensitivity in the lidar device 100 is adjacent to the maximum sensitivity portion 220 at the position of sin θ=0 corresponding to the main lobes of the TxOPA 102 and the RxOPA 104. The maximal portions 222 and 224 of the total sensitivity that appear are largely separated and appear at the position of sin θ=±6λ ₀ /p _T (=±5λ ₀ /p _R ). As a result, in the lidar device 100, the arrangement pitch p _T of the antenna element 116 of the TxOPA 102 is reduced by controlling the phase shifters 112 and 122 so that the direction of the main lobe of the TxOPA 102 and the direction of the main lobe of the RxOPA 104 match. Without doing so, as shown in Expression (11), the change range of the beam steering angle α of the main lobe of the TxOPA 102 can be expanded to M times, that is, 6 times, as compared with the conventional lidar device.

Specifically, the rider device 100 according to the present embodiment operates as follows. In the following description, for simplicity, beam steering is performed in the X-axis direction in the figure. However, as will be understood by those skilled in the art, by performing the beam steering operation in the illustrated Y-axis direction similar to the beam steering operation in the X-axis direction in accordance with the beam steering operation in the X-axis direction described below, A dimensional beam steering operation can be performed.

First, the control device 134 of the lidar apparatus 100 controls the light source 106 to generate light pulses at regular time intervals. Further, the control device 134 instructs the steering control unit 132 to change the deflection angle α (steering angle α) in the X direction of the main lobe sent from the TxOPA 102 to the space to perform beam steering. More specifically, the steering control unit 132 makes the phase of the light emitted from each antenna element 116 have a linear phase inclination according to the deflection angle α along the X axis, and the deflection angle α. The phase shifter 112 is controlled so that the time shifts in a predetermined pattern within a predetermined steering angle range. Here, the linear phase inclination according to the deflection angle α is expressed by the equation (12) as the phase shift amount generated in each optical path (each channel) from the optical input end of the optical branching device 110 to the output end of each antenna element 116. ) Can be implemented by setting each phase shifter 122 so that

Here, q is an index attached to each of the antenna elements 116 corresponding to each channel in order from the end along the position of the antenna element 116 on the X axis, and q=−Q,..., −1, 0, 1,..., Q.

The control device 134 also instructs the steering control unit 132 to control the phase shifter 122 so that the main lobe of the RxOPA 104 has the same deflection angle α as the main lobe of the TxOPA 102. Specifically, the steering control unit 132 causes the phase shift amount generated in each optical path (each channel) from the optical receiving end of each antenna element 126 to the optical output end of the optical coupler 120 to follow the equation (13). Each phase shifter 122 is set to.

Here, s is an index which is sequentially attached to each of the antenna elements 126 corresponding to the respective channels from the end along the position of the antenna element 126 on the X axis, and q=−S,..., −1, 0, 1,..., S. From equations (12) and (13), the phases φ _T (u) and φ _R (u) to be generated in each channel corresponding to the antenna elements 116 and 126 having the same index value u are calculated by equation (14). Meet

That is, the phase shift generated in each channel of the RxOPA 104 needs to be p _R /p _T times the phase shift generated in each channel of the TxOPA 102.

The control device 134 further controls the main lobes of the TxOPA 102 and the RxOPA 104 in the same direction as described above, and the optical pulse output from the light source 106 and transmitted from the TxOPA 102 as the main lobe is received from the main lobe direction of the RxOPA 104. The time to reach the object is measured, and the distance to the object existing in the main lobe direction is calculated. Thereby, the control device 134 can generate data for spatial mapping within the beam steering range of the main lobe of the TxOPA 102, for example.

In the present embodiment, the arrangement pitch p _T of the antenna units 118 of the TxOPA 102 and the arrangement pitch p _R of the antenna units 128 of the RxOPA 104 are configured to have the relationship of Expression (6). Not limited to For example, even when the array pitches p _T and p _R simply have different values, the side lobe directions of the TxOPA 102 and the RxOPA 104 are made different, and the allowable range of the steering angle of the main lobe of the TxOPA 102 is the same as above. Can be expanded.

Further, even if the actual arrangement pitch p _T of the antenna units 118 and/or the actual arrangement pitch p _R of the antenna units 128 is not seen in the formula (6), for example, the beam emitting portion of the antenna element 116 of the TxOPA 102 and/or the RxOPA 104. By arranging optical components such as a lens, which form the image conversion optical system, at the beam arrival portion of the antenna element 126, the substantial array pitch p converted from the diffracted light emitted from the TxOPA 102 via these optical components. _{If the} substantial array pitch p _Re calculated from the reception sensitivity of the light received by the RxOPA 104 via _Te and/or these optical components is different from each other (for example, if Expression (6) is satisfied), Similarly, the allowable range of the steering angle of the main lobe of the TxOPA 102 can be expanded.

In other words, the first angle formed by the directions of the adjacent diffracted light beams that the TxOPA 102 sends to the space is, when the diffracted light beams of the TxOPA 102 are sent to the space through the optical components forming the image conversion optical system, It is defined by the angle between adjacent diffracted lights that are sent out into space through the optical component. Further, the second angle formed by the adjacent maximal sensitivity directions in the RxOPA 104 is the same as that before passing through the optical component when the RxOPA 104 receives light from the space via the optical component that constitutes the image conversion optical system. It is defined as an angle formed by adjacent maximal sensitivity directions in the space. Then, similarly to the above, the first angle and the second angle are set to different values (for example, the ratio between the first angle and the second angle is relatively prime). If it is set to be a ratio of natural numbers), the allowable range of the steering angle of the main lobe of the TxOPA 102 can be expanded by the same principle as described above.

<Second Embodiment>
Next, a rider device according to a second embodiment of the present invention will be described.
FIG. 3 is a diagram showing a configuration of a rider device 300 according to the second embodiment of the present invention. In FIG. 3, the same components as those of the rider device 100 according to the first embodiment shown in FIG. 1 are denoted by the same reference symbols as those of FIG. 1, and the description of the rider device 100 described above is cited. And

The lidar device 300 has the same configuration as the lidar device 100, except that an optical unit 346 forming an image conversion optical system is arranged on the light transmission side of the antenna unit 118 of the TxOPA 102. The image conversion optical system configured by the optical unit 346 in the present embodiment is, for example, a two-lens system having an image magnification K ₁ configured of two convex lenses 342 and 344 having focal lengths f ₁ and f ₂ , respectively. It is composed of.

Since the lidar device 300 having the above-described configuration includes the optical unit 346 having the image magnification K ₁ on the light transmission side of the TxOPA 102, the TxOPA 102 is substantially located at the distance f ₂ from the lens 344 to the right side in the drawing. _It functions as an OPA having the antenna elements 316 arranged at a _1- times arrangement pitch K ₁ ·p _T. Therefore, by configuring the optical unit 346, the TxOPA 102, and the RxOPA 104 so that K ₁ ·p _T ≠p _R , the TxOPA 102 sends the light to the space like the lidar device 100 according to the first embodiment. The first angle formed by the adjacent diffracted lights and the second angle formed by the adjacent maximum sensitivity directions in the space in the RxOPA 104 are made different from each other to reduce p _T without reducing the main lobe of the TxOPA 102. The allowable range of the steering angle can be expanded.

For example, in this embodiment, the optical unit 346, the TxOPA 102, and the RxOPA 104 are configured so that the image magnification K ₁ and the array pitches p _T and p _R satisfy the expression (15).

Here, similarly to the equation (6), N ₂ /M ₂ is an irreducible function, and M ₂ and N ₂ are natural numbers that are relatively prime. The image magnification K ₁ is given by the equation (16) using the focal lengths f ₁ and f ₂ of the two lenses 342 and 344 forming the optical unit 346.

At this time, the difference Δω _T2 between the sine values of the deflection angles of the adjacent diffracted lights sent from the TxOPA 102 to the space through the optical unit 346 is given by the equation (17).

Since no lens optical system is arranged in the RxOPA 104, the difference Δω _{R in} the sine values of the deflection angles of the adjacent diffracted lights (that is, the adjacent receiving sensitivity maximum directions) in the RxOPA 104 is expressed by the same formula as in the lidar device 100. It is given in (8).

From the above equations (15), (17), and equation (8), equation (18) is obtained.

That is, of the diffracted light of the TxOPA 102 transmitted from the optical unit 346 to the space, the direction of the M ₂ -th sidelobe counted from the main lobe of the TxOPA 102 and the direction of the N ₂ -th sidelobe counted from the main lobe of the RxOPA 104. You can see that and match.

Accordingly, alpha _max allowable variable range -α _max ~ α _max of the steering angle alpha of the main lobe to be sent from the optical unit 346 to space is given by Equation (19).

That is, in the rider device 300 as well as in the rider device 100, the allowable range of the steering angle of the main lobe output from the TxOPA 102 and transmitted to the space is expanded without reducing the array pitch p _T of the antenna elements 116 of the TxOPA 102. can do. Particularly, in the lidar device 300, the substantial array pitch of the antenna elements 116 of the TxOPA 102 viewed from the light output side of the optical unit 346 is the array pitch p _T of the TxOPA 102 itself and the image magnification K ₁ of the optical unit 346. , K ₁ p _T , the degree of freedom in design can be further improved as compared with the rider device 100.

Specifically, the rider device 300 according to the present embodiment operates as follows. In the following description, for simplicity, beam steering is performed in the X-axis direction in the figure. However, as will be understood by those skilled in the art, by performing the beam steering operation in the illustrated Y-axis direction similar to the beam steering operation in the X-axis direction in accordance with the beam steering operation in the X-axis direction described below, A dimensional beam steering operation can be performed.

The rider device 300 according to the present embodiment operates in the same manner as the rider device 100 described above, but the operation of the steering control unit 332 is slightly different from that of the steering control unit 132. The steering control unit 332 performs beam steering by changing the deflection angle α (steering angle α) of the main lobe sent from the TxOPA 102 to the space in the X direction. More specifically, the steering control unit 332 causes the phase of the light emitted from the virtual antenna element 316 formed by image conversion to have a linear phase inclination according to the deflection angle α along the X axis. In addition, the phase shifter 112 is controlled so that the deflection angle α changes with time in a predetermined pattern within a predetermined steering angle range. Here, the linear phase tilt corresponding to the deflection angle α is expressed by the equation (20) as the phase shift amount generated in each optical path (each channel) from the optical input end of the optical branching device 110 to the output end of each antenna element 116. It is realized by setting each phase shifter 122 so as to comply with (4).

Here, q is an index attached to each of the antenna elements 116 corresponding to each channel in order from the end along the position of the antenna element 116 on the X axis, and q=−Q,..., −1, 0, 1,..., Q.

The phase shift amount generated in each channel of the RxOPA 104 by the phase shifter 122 so that the main lobe of the RxOPA 104 has the same deflection angle α as described above is given by the equation (13) as in the case of the rider device 100. ..

Similar to Expression (14), from Expressions (13) and (20), the phases φ _T2 (u) and φ _R (u) to be generated in each channel corresponding to the antenna elements 116 and 126 having the same index value u, respectively. u) satisfies the equation (21).

That is, the phase shift generated in each channel of the RxOPA 104 needs to be p _R /(K ₁ ·p _T ) times the phase shift generated in each channel of the TxOPA 102.

In the present embodiment, the rider device 300 is configured using the TxOPA 102 and the RxOPA 104 having the array pitches p _T and p _R different from each other, but the present invention is not limited to this. In the rider device 300, the array pitches p _T and p _R may have the same value as long as the expression (15) is satisfied. That is, the lidar device 300 may be configured by using TxOPA and RxOPA in which the antenna elements are arranged at the same interval, instead of the TxOPA 102 and RxOPA104.

<Third Embodiment>
Next, a rider device according to a third embodiment of the present invention will be described.
In the rider device 300 according to the second embodiment described above, the substantial array pitch of the antenna elements 116 of the TxOPA 102 is expanded by the optical unit 346 that is the image conversion optical system configured by the two-lens system. On the other hand, in the third embodiment, an anamorphic prism pair is used as the image conversion optical system to expand the substantial array pitch of the antenna elements 116 in the one-dimensional direction.

FIG. 4 is a diagram showing a configuration of a rider device 400 according to the third embodiment of the present invention. 4, the same components as those of the rider device 100 according to the first embodiment shown in FIG. 1 are assigned the same reference numerals as those shown in FIG. 1, and the description of the rider device 100 described above is cited. And

The lidar device 400 has the same configuration as the lidar device 100, but an optical unit 446 composed of an anamorphic prism pair composed of two prisms 442 and 444 is arranged on the light transmission side of the antenna unit 118 of the TxOPA 102. Is different.

In the present embodiment, the anamorphic prism pair including the two prisms 442 and 444 is configured to magnify the image in the X direction shown in the figure. Therefore, the beam steering of the main lobe of the TxOPA 102 in the Y direction in the drawing is the same as that of the rider device 100 according to the first embodiment shown in FIG.

Since the lidar device 400 having the above configuration is provided with the optical unit 446 having the image magnification K ₂ in the X direction in the drawing on the light transmission side of the TxOPA 102, the TxOPA 102 is substantially the same as the light output side of the prism 444. It functions as an OPA having antenna elements 416 arranged at a distance D from the output surface (right side in the drawing) to the left side in the drawing at an array pitch K ₂ ·p _T of K ₂ times. Therefore, by configuring the optical unit 446, the TxOPA 102, and the RxOPA 104 so that K ₂ ·p _T ≠p _R , in the X direction, similarly to the rider device 100 according to the first embodiment, the first unit. Similar to the lidar device 100 according to the embodiment of the first embodiment, a first angle formed by adjacent diffracted light beams transmitted by the TxOPA 102 to a space and a second angle formed by adjacent maximum sensitivity directions in the space on the RxOPA 104 are formed by a second angle. Can be made different, and the allowable range of the steering angle of the main lobe of the TxOPA 102 can be expanded without reducing p _T. In the Y direction, the rider device 400 operates similarly to the rider device 100, and the allowable range of the steering angle of the main lobe of the TxOPA 102 is expanded without reducing pT as in the rider device 100.

For example, in this embodiment, the optical unit 446, the TxOPA 102, and the RxOPA 104 are configured so that the image magnification K ₂ , the array pitch p _T , and p _R satisfy the expression (22).

Here, as described above, since the optical unit 446 magnifies the image only in the X direction, in the rider apparatus 400, the beam steering of the main lobe of the TxOPA 102 in the Y direction in the drawing is performed in the first embodiment shown in FIG. It is similar to the rider device 100 according to the embodiment. Therefore, the beam steering in the X direction in the figure will be described below.

In the above formula (22), N ₃ /M ₃ is an irreducible function, and M ₃ and N ₃ are natural numbers that are relatively prime. At this time, the difference Δω _T3 between the sine values of the deflection angles of the adjacent diffracted lights sent from the TxOPA 102 to the space through the optical unit 446 is given by the equation (23).

Since the RxOPA 104 is not provided with a lens optical system, Δω _R is the difference between the sine values of the deflection angles of the adjacent diffracted lights (that is, the adjacent receiving sensitivity maximum directions) in the RxOPA 104, and Δω _R is the same as that of the lidar device 100. It is given by equation (8).

From the above equations (22), (23) and equation (8), equation (24) is obtained.

That is, in the diffracted light of the TxOPA 102 transmitted from the optical unit 446 to the space, the direction of the M ₃ sidelobe counted from the main lobe of the TxOPA 102 and the direction of the N _3th sidelobe counted from the main lobe of the RxOPA 104. You can see that and match.

Accordingly, alpha _max allowable variable range -α _max ~ α _max of the steering angle alpha of the main lobe to be sent from the optical unit 446 to space is given by equation (25).

That is, also in the beam steering operation of the rider apparatus 400 in the X direction, similarly to the rider apparatus 100, the main lobe output from the TxOPA 102 and transmitted to the space is output without reducing the array pitch p _T of the antenna elements 116 of the TxOPA 102. The allowable range of the steering angle can be expanded. Particularly in the lidar device 400, the substantial array pitch of the antenna elements 116 of the TxOPA 102 in the X direction viewed from the light output side of the optical unit 446 is the array pitch p _T of the TxOPA 102 itself and the image magnification of the optical unit 446. Since it is given by the product of K ₂ and K ₂ p _T , the degree of freedom in design can be further improved as compared with the rider device 100.

It should be noted that the image magnification K ₂ can be determined from the geometric shape and arrangement of the prisms 442 and 444 forming the anamorphic prism pair in the optical unit 446 according to the conventional technique. Similarly, the distance D that defines the position of the substantial antenna element 416 formed by the presence of the optical unit 446 is determined from the image magnification K ₂ and the distance from the antenna element 116 to the prism 442 according to the related art. obtain.

The rider device 400 according to the present embodiment specifically operates as follows.
The rider device 400 operates in the same manner as the rider device 100 described above, but the operation of the steering control unit 432 is different from that of the steering control unit 132. As with the steering control unit 132, the steering control unit 432 changes the deflection angle α (steering angle α) in the X direction of the main lobe sent from the TxOPA 102 to the space via the optical unit 446 in the same manner as the steering control unit 132. The phase of the light emitted from the antenna element 116 via the optical unit 446 has a linear phase inclination according to the deflection angle α along the X axis, and the deflection angle α is within a predetermined steering angle range. In, the phase shifter 112 is controlled so that it changes with time in a predetermined pattern. Here, the linear phase tilt corresponding to the deflection angle α is expressed by the equation (26) as the phase shift amount generated in each optical path (each channel) from the optical input end of the optical branching device 110 to the output end of each antenna element 116. It is realized by setting each phase shifter 122 so as to comply with (4).

Here, q is an index attached to each antenna element 116 that constitutes the antenna unit 118 in order from the end along the position of the antenna element 116 on the X axis, and q=−Q,..., −1, 0, 1,..., Q.

The linear phase tilt generated by the phase shifter 122 so that the main lobe of the RxOPA 104 has the deflection angle α is given by the equation (13) as in the case of the lidar device 100.

Similar to equation (14), from equations (13) and (26), the phases φ _T3 (u) and φ _R (u) to be generated in each channel corresponding to the antenna elements 116 and 126 having the same index value u, respectively. u) satisfies the equation (27).

That is, the phase shift generated in each channel of the RxOPA 104 needs to be p _R /(K ₂ ·p _T ) times the phase shift generated in each channel of the TxOPA 102.

In the present embodiment, the rider device 400 is configured using the TxOPA 102 and the RxOPA 104 having the array pitches p _T and p _R different from each other, but the present invention is not limited to this. In the rider device 400, the array pitches p _T and p _R may have the same value as long as the expression (22) is satisfied. That is, the lidar device 300 may be configured by using TxOPA and RxOPA in which the antenna elements are arranged at the same interval, instead of the TxOPA 102 and RxOPA104.

The present invention is not limited to the configurations of the above-described embodiments, and can be implemented in various modes without departing from the spirit of the invention.

For example, in each of the above embodiments, the antenna element 116 of the TxOPA 102 and the antenna element 126 of the RxOPA 104 are arranged in the XY plane at the same arrangement pitches p _T and p _R in the X and Y directions. Is not limited. The antenna element 116 of the TxOPA 102 and the antenna element 126 of the RxOPA 104 may be configured to have different array pitches in the X direction and the Y direction.

In this case, in each of the X direction and the Y direction, the first angle formed by the adjacent diffracted lights transmitted by the TxOPA 102 to the space and the second maximum sensitivity direction formed by the adjacent RxOPA 104 in the space are formed by the second angle. By making the angle different, the allowable range of the steering angle in the X direction and the Y direction of the main lobe of the TxOPA 102 can be expanded together without reducing the arrangement pitch in the X direction and the Y direction.

Specifically, the array pitches of the antenna elements of the TxOPA 102 and the RxOPA 104 are different from each other (for example, their ratio is different from each other, taking into consideration the image magnification of the optical components that can be provided in the light emitting portion of the TxOPA 102 and the light receiving portion of the RxOPA 104). Are set so that they are represented by mutually prime natural numbers), the allowable range of the steering angle of the main lobe of the TxOPA 102 can be expanded.

Also, in each of the above embodiments, the TxOPA 102 and the RxOPA 104 are described as being configured using OPA having reciprocity for the sake of simplicity, but the present invention is not limited to this. For example, the RxOPA 104 may be one in which light propagates in one direction from the antenna element 126 to the optical output end of the optical coupler 120. Even in this case, the maximum sensitivity direction is defined for each channel from each antenna element 126 to the optical output end of the optical coupler 120 in consideration of virtual diffracted light when light is virtually propagated in the opposite direction. However, the range of beam steering can be expanded by using the same configuration as each of the above-described embodiments.

Further, in each of the above embodiments, the TxOPA 102 and the RxOPA 104 are configured by using the OPA 700 as disclosed in Patent Document 1, for example, but the present invention is not limited to this. As another example, for example, the TxOPA 102 and the RxOPA 104 can be configured using the OPA 900 disclosed in Non-Patent Document 1. Specifically, for example, the TxOPA 102 and the RxOPA 104 are configured by aligning the extending direction of the antenna elements of the blending base with the Y direction in FIG. 1 so that the antenna elements are arranged in the X direction of FIG. Can be In this case, the arrangement pitch of the antenna elements in the TxOPA 102 and the RxOPA 104 is set to p _T and p _R , respectively, and the beam steering in the X direction is expanded in the allowable angle range of the beam steering by the same configuration as that of each of the above-described embodiments. be able to.

Further, in the second and third embodiments, FIGS. 3 and 4 are drawn assuming that the optical units 346 and 446 forming the image conversion optical system have image magnifications K ₁ and K ₂ that are larger than 1, respectively. However, it is not limited to this. The image magnifications K ₁ and K ₂ may have values smaller than 1. Further, the image conversion optical system can be any optical system as long as it has a function of performing image conversion in at least a one-dimensional direction.

As described above, the lidar device 100 and the like according to the embodiment of the present invention includes the TxOPA 102 that is an optical transmitter configured by an optical phased array. The TxOPA 102 sends the diffracted light generated by the light output from the antenna element 116, which is the plurality of first antenna elements forming the optical phased array, to the space. Further, the lidar device 100 and the like include an RxOPA 104 which is an optical receiver including an optical phased array. The RxOPA 104 receives the light coming from the space by the antenna element 126 which is the plurality of second antenna elements forming the optical phased array. Then, in the lidar device 100 and the like, the RxOPA 104, which is an optical receiver, has a plurality of maximum sensitivity directions in which the reception sensitivity of the light is maximized with respect to the direction of the light coming from the space. In addition, in the lidar device 100 and the like, the first angle formed by the TxOPA 102, which is an optical transmitter, in the direction of adjacent diffracted light that is transmitted to the space, and the adjacent maximum sensitivity direction in the RxOPA 104, which is the optical receiver, form each other. The second angle is different from each other.

According to this configuration, the reflected return light of the side lobe adjacent to the main lobe sent from the TxOPA 102 to the space is suppressed and output in the RxOPA 104. Therefore, the lidar device 100 and the like overcome the limitation of the beam steering angle range due to the angular interval between adjacent diffracted lights determined by the array pitch p _T of the antenna elements 116 of the TxOPA 102 without increasing the cost, A wider beam steering angle range can be realized.

The lidar device 100 and the like include a phase shifter 112 that is a first phase shifter included in the optical phased array that configures the TxOPA 102, and a phase shifter 122 that is a second phase shifter included in the optical phased array that configures the RxOPA 104. A steering control unit 132 or the like, which is a phase shift control unit for controlling Then, the steering control unit 132 or the like which is the phase shift control unit controls the phase shift amount of the phase shifter 112 which is the first phase shifter to control the main lobe of the diffracted light which the TxOPA 102 which is the optical transmitter sends to the space. Change the sending direction. Further, the steering control unit 132 or the like, which is a phase shift control unit, is a second phase shifter so that the maximum sensitivity direction having the maximum sensitivity among the maximum sensitivity directions matches the sending direction of the main lobe of the TxOPA 102. The amount of phase shift of the phase shifter 122 is controlled.

According to this configuration, the receiving sensitivity of the RxOPA 104 with respect to the reflected return light coming from the transmission direction of the main lobe of the TxOPA 102 can be always maintained at the maximum.

Further, in the lidar device 100 and the like, the arrangement interval p _T of the antenna elements 116 that are the first antenna elements and the arrangement interval p _R of the antenna elements 126 that are the second antenna elements are set to different values. .. According to this configuration, the first angle formed by the adjacent diffracted light beams transmitted to the space by the TxOPA 102 and the second angle formed by the adjacent maximum sensitivity directions of the RxOPA 104 are easily different from each other. can do.

In addition, in the rider device 100 and the like, the ratio between the first angle and the second angle is set so as to be represented by a ratio of natural numbers that are relatively prime. According to this configuration, the allowable angle range of the beam steering of the TxOPA 102 can be expanded by the magnification determined by the natural number, as shown in the equation (11), for example.

In addition, in the lidar device 100 and the like, the ratio of the arrangement interval p _T of the antenna elements 116 that are the first antenna elements and the arrangement interval p _R of the antenna elements 126 that is the second antenna element is a ratio of natural numbers that are mutually prime. It is set to be represented. According to this configuration, the ratio between the first angle and the second angle can be easily set so as to be represented by a ratio of natural numbers that are relatively prime.

In the lidar devices 300 and 400, the TxOPA 102, which is an optical transmitter, forms diffracted light generated by the light output from the antenna elements 116, which are the first plurality of antenna elements, in the image conversion optical system. It is sent to the space through the lenses 342 and 344 or the prisms 442 and 444 which are the first optical component. Then, in the lidar devices 300 and 400, the first angle is defined by the angle between adjacent diffracted lights that are sent to the space via the first optical component.

According to this configuration, in addition to the array pitch p _T of the antenna elements 116 of the TxOPA 102 and the array pitch p _R of the antenna elements 126 of the RxOPA 104, the first angle is set using the image magnification of the image conversion optical system. Therefore, the degree of freedom in design is improved.

Further, in the lidar device 300, the first optical component is composed of two convex lenses 342 and 344. With this configuration, the image conversion optical system can be easily configured.

Further, in the lidar device 400, the first optical component is composed of two prisms 442 and 444 which form an anamorphic prism pair. With this configuration, the image conversion optical system can be easily configured.

In addition, in the lidar device 100 and the like, the RxOPA 104, which is an optical receiver, receives the light coming from the space through the second optical component that constitutes the image conversion optical system, and the antenna elements 126 that are the second antenna elements. Can be received by. In this case, the second angle is defined as an angle formed by adjacent maximal sensitivity directions defined in the space with respect to the light received from the space and received through the second optical component. .. With this configuration, the degree of freedom in designing the rider device 100 and the like can be further improved.

100, 300, 400, 500... Rider device, 102, 502... TxOPA, 104, 504... RxOPA, 106, 506... Light source, 110, 510... Optical branching device, 112, 122, 512, 522... Phase shifter, 114, 124, 514, 524... Phase shift unit, 116, 126, 516, 526... Antenna element, 118, 128, 518, 528... Antenna unit, 120, 520... Optical coupler, 130, 530... Photodetector, 132, 532... Steering control unit, 134, 536... Control device, 346, 446... Optical unit, 342, 344... Lens, 442, 444... Prism, 700, 900... OPA.

Claims (9)

1. An optical transmitter configured by a first optical phased array and transmitting to the space diffracted light generated by light output from a plurality of first antenna elements configuring the first optical phased array,
   An optical receiver configured by a second optical phased array and receiving light coming from the space by a plurality of second antenna elements configuring the second optical phased array,
   Equipped with
   The optical receiver has a plurality of maximum sensitivity directions in which the reception sensitivity of the light becomes maximum with respect to the direction of light coming from the space.
   The first angle formed by mutually adjacent directions of the diffracted light emitted by the optical transmitter to the space and the second angle formed by the adjacent maximum sensitivity directions of the optical receiver are different from each other. Is
   Rider device.
2. A phase shift control unit that controls a first phase shifter included in the first optical phased array and a second phase shifter included in the second optical phased array,
   The phase shift control unit controls the phase shift amount of the first phase shifter to change the sending direction of the main lobe of the diffracted light sent to the space by the optical transmitter, and the maximum sensitivity direction among the maximum sensitivity directions. The phase shift amount of the second phase shifter is controlled so that the maximum sensitive direction having sensitivity matches the sending direction of the main lobe.
   The rider device according to claim 1.
3. The array spacing of the first antenna elements and the array spacing of the second antenna elements are set to different values.
   The rider device according to claim 1.
4. The ratio between the first angle and the second angle is set so as to be expressed as a ratio of natural numbers that are relatively prime.
   The rider device according to any one of claims 1 to 3.
5. The ratio of the arrangement interval of the first antenna elements and the arrangement interval of the second antenna elements is set to be expressed by a ratio of natural numbers that are relatively prime.
   The rider device according to claim 4.
6. The optical transmitter sends the diffracted light generated by the light output from the plurality of first antenna elements to the space via a first optical component that constitutes an image conversion optical system,
   The first angle is defined as the angle between adjacent diffracted lights that are delivered to the space via the first optical component,
   The rider device according to any one of claims 1 to 5.
7. The first optical component is composed of two convex lenses,
   The rider device according to claim 6.
8. The first optical component includes two prisms that form an anamorphic prism pair.
   The rider device according to claim 6.
9. The optical receiver receives light coming from the space by the plurality of second antenna elements via a second optical component that constitutes an image conversion optical system,
   The second angle is defined as an angle formed by adjacent maximal sensitivity directions defined in the space with respect to light coming from the space received via the second optical component,
   The rider device according to any one of claims 1 to 8.

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