Low-noise large-angle optical phased array laser radar structure and detection method

Abstract

The invention discloses a low-noise and large-angle optical phased array laser radar structure and a detection method, relates to the technical field of laser radar structures, and aims to solve the problems that in the existing general non-uniform design, the bottom noise is remarkably increased, the side mode suppression ratio is also reduced, and the detection efficiency is low while the symmetry of an array is broken and the formation of a high-order grating lobe is suppressed. According to the key points of the technical scheme, the laser radar comprises a laser radar chip, and the interior of the laser radar chip comprises an end face coupler, a light beam splitting array, a phase shifter array, an optical switch array, an auxiliary waveguide array and a grating antenna array. And n paths of the light beam splitting arrays, the phase shifter arrays, the optical switch arrays, the auxiliary waveguide arrays and the grating antenna arrays are correspondingly arranged. And the effect of realizing a low-noise and large-angle scanning detection system is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of laser radar structures, and in particular to a low-noise, large-angle optical phased array laser radar structure and a detection method. Background Art

[0002] LiDAR is an important equipment for high-tech civilian and military technologies such as intelligent driving and intelligent robots. Light detection and ranging (LiDAR) based on optical phased array (OPA) is a system that achieves two-dimensional light beam steering through phase and wavelength control. It can achieve the same functions as traditional radar on a chip and has the advantages of flexible steering and integration. Silicon-based LiDAR is considered to be an alternative solution to traditional LiDAR due to its low power consumption and compatibility with CMOS technology.

[0003] A laser radar array receiver front-end readout integrated circuit with application number CN201710482621.1 adopts a planar array photoelectric converter module to receive and process optical signals in parallel, does not require a scanning mechanism, has a wide detection range, can receive pulse echo signals at any four adjacent positions, and the receiver readout integrated circuit outputs four analog voltages. The receiver is compatible with traditional 4-quadrant or 8-quadrant laser radar receivers and has good adaptability.

[0004] The above-mentioned existing technical solutions have the following defects: At present, the detection of optical phased array laser radar has the following limitations: 1. Scanning angle limitation: The limitation brought by the principle of optical phased array. The far-field spot is formed by interference. The uniform array has inherent secondary peaks and higher-order peaks. When it is turned beyond a certain angle, the main peak and the secondary peak will be indistinguishable, thus limiting further turning. The existing technology breaks the symmetry of the array through algorithm optimization, which can break the formation of high-order grating lobes. In theory, it can achieve a full range of 180° scanning, but this non-uniform array will significantly increase the noise; 2. Noise limitation: The side mode suppression ratio will affect the distinguishability of the main lobe in long-distance detection. The larger the side mode suppression ratio, the longer the detection distance. In the usual non-uniform design, by breaking the symmetry of the array and suppressing the formation of high-order grating lobes, the background noise increases significantly and the side mode suppression ratio decreases, making it impossible to achieve long-distance detection. Summary of the invention

[0005] The purpose of the present invention is to provide an optical phased array lidar structure and detection method that can realize two non-uniform array detections with different distribution modes by controlling the input of the optical switch array twice. The two signals are added to reduce the noise increase caused by the non-uniform array. The invention can simultaneously realize low-noise and large-angle silicon-based lidar transmission and reception.

[0006] To achieve the above object, the present invention provides the following technical solutions: A low-noise, large-angle optical phased array laser radar structure comprises a laser radar chip, wherein the laser radar chip internally comprises an end coupler, an optical beam splitter array, a phase shifter array, an optical switch array, an auxiliary waveguide array and a grating antenna array, wherein the optical beam splitter array, the phase shifter array, the optical switch array, the auxiliary waveguide array and the grating antenna array are each correspondingly provided with n paths.

[0007] Furthermore, when the input light passes through the end face coupler, the optical beam splitter array and the phase shifter array in sequence, all n channels have input power.

[0008] Furthermore, the optical beam splitting array is a log2n-level beam splitter array structure, and the log2n-level optical beam splitting array is used to equally split the input light into n paths, and the specific structure of the optical beam splitting array includes a 1×2-path MMI or Y-branch coupler.

[0009] Furthermore, the optical switch array is used to realize non-uniform opening of m channels in n-channel gratings, complete far-field non-uniform array interference, and the power of a certain channel that is turned off is released through the auxiliary evanescent waveguide.

[0010] Furthermore, the state of each device in the optical switch array is optimized by an algorithm, and a control voltage is input through a digital-to-electrical converter.

[0011] A detection method for a low-noise, large-angle optical phased array laser radar structure is as follows: S1: two or more non-uniform opening matrices m1 and m2 based on n-way uniformly spaced OPA arrays are obtained by algorithm; S2: The optical switch array of the laser radar chip is turned on by the digital-to-electrical conversion module to realize the matrix m1 grating. The input light is transmitted through the structure of the laser radar chip, and the received signal is obtained and recorded. A1: The specific operation of the laser radar chip is that the input light enters the chip through the end face coupling method, and then enters the optical beam splitter array. The input power is equally divided into n paths through the log2n-level cascade optical beam splitter array and transmitted backward to the phase shift area. The phase shifter array is controlled by an external digital-to-electrical conversion module to realize the scanning function of the laser radar. It is then connected to the optical switch array, which is also controlled by an external digital-to-electrical conversion module. The turned-on switch transmits the power of this path to the grating antenna array for transmission, and the turned-off switch transmits the power to the auxiliary evanescent waveguide. S3: The optical switch unit of the chip laser radar chip is turned on by the digital-to-electrical conversion module to realize the matrix m2-way grating opening. The input light is transmitted through the structure shown in the laser radar chip, and the received signal is obtained and recorded. S4: Add two or more received signals to obtain a final received signal. The received signal at this time reduces the relative power of noise while maintaining the large-angle scanning of the non-uniform array.

[0012] Furthermore, the two or more opened arrays in S1 are all non-uniform arrays and are different.

[0013] Furthermore, the received signal spectrograms obtained by transmitting twice or more times in S4 are accumulated.

[0014] In summary, the beneficial technical effects of the present invention are: 1. The present invention allows input light to enter the chip through end-face coupling, and then enters the optical beam splitter array. Through the log2n-level cascaded optical beam splitter array, the input power is equally divided into n paths and transmitted backward to the phase shift region. The phase shifter is controlled by an external digital-to-electrical conversion module to realize the scanning function of the laser radar; 2. The present invention is connected to an optical switch array and is also controlled by an external digital-to-electrical conversion module. The turned-on switch transmits the power of the local path to the grating antenna array for transmission, and the turned-off switch transmits the power to the auxiliary evanescent waveguide. 3. The present invention realizes low-noise and large-angle operation through a matching detection method. On the basis of the manufactured uniform array, a genetic algorithm or other algorithms are used to optimize the parameters of the on and off of each optical path to obtain two or more groups of open arrays. The open arrays are sequentially applied to the optical phased array structure described in this application to obtain two or more groups of received data. Finally, the data are added to realize a low-noise and large-angle scanning detection system. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of the work flow structure of the present invention; Figure 2 This is a schematic diagram of the structure of the laser radar chip of the present invention.

[0016] In the figure, 1. LiDAR chip; 2. End coupler; 3. Optical beam splitter array; 4. Phase shifter array; 5. Optical switch array; 6. Auxiliary waveguide array; 7. Grating antenna array. DETAILED DESCRIPTION

[0017] The present invention is further described in detail below in conjunction with the accompanying drawings.

[0018] Reference Figure 1 and Figure 2A low-noise, large-angle optical phased array laser radar structure includes a laser radar chip 1. The laser radar chip 1 includes an end coupler 2, an optical beam splitter array 3, a phase shifter array 4, an optical switch array 5, an auxiliary waveguide array 6 and a grating antenna array 7. The optical beam splitter array 3, the phase shifter array 4, the optical switch array 5, the auxiliary waveguide array 6 and the grating antenna array 7 are each correspondingly provided with n paths.

[0019] Reference Figure 1 When the input light passes through the end coupler 2, the optical beam splitter array 3 and the phase shifter array 4 in sequence, N channels all have input power. The optical beam splitter array 3 is a log2n-level beam splitter array structure. The log2n-level optical beam splitter array 3 is used to divide the input light into n channels, and the specific structure of the optical beam splitter array 3 includes a 1×2-channel MMI or Y-branch coupler. The optical switch array 5 is used to realize the non-uniform opening of m channels in the n-channel grating and complete the far-field non-uniform array interference. The power of a certain channel that is turned off is released through the auxiliary evanescent waveguide. The state of each device in the optical switch array 5 is optimized by the algorithm, and the control voltage input is performed through the digital-to-electrical converter.

[0020] The invention comprises an optical phased array laser radar array structure and a matching detection method. The structure comprises an end coupler 2 at the input end, an optical beam splitter array 3, a phase shifter array 4, an optical switch array 5, an auxiliary waveguide array 6 and a grating antenna array 7. The input light enters the chip through the end coupling method and then enters the optical beam splitter array. The input power is equally divided into n paths and transmitted backward to the phase shift region through the optical beam splitter array 3 cascaded in log2n stages. The phase shifter is controlled by an external digital-to-electrical conversion module to realize the scanning function of the laser radar. The optical switch array 5 is connected to the chip and is also connected to the external The digital-to-electrical conversion module controls the on-switch to transmit the power of the local path to the grating antenna array for emission, and the off-switch transmits the power to the auxiliary evanescent waveguide. The present application realizes low-noise and large-angle operation through a matching detection method. On the basis of the manufactured uniform array, a genetic algorithm or other algorithms are used to optimize the parameters of the on and off of each optical path to obtain two or more groups of open arrays, which are sequentially applied to the optical phased array array structure described in the present application to obtain two or more groups of received data, and finally the data are added to realize a low-noise and large-angle scanning detection system.

[0021] Working principle: two or more non-uniform opening matrices m1 and m2 based on n-way evenly spaced OPA arrays are obtained through the algorithm. The two or more opening arrays are non-uniform arrays and are different; then the optical switch array 5 of the laser radar chip 1 is turned on by the digital-to-electrical converter to realize the matrix m1-way grating opening. The input light is emitted through the structure of the laser radar chip 1, and the received signal is obtained and recorded. The laser radar chip 1 is operated specifically. The input light enters the chip through the end face coupling method, and then enters the optical beam splitter array 3. Through the log2n-level cascade optical beam splitter array, the input power is equally divided into n paths and transmitted backward to the phase shift area. The phase shifter array 4 is realized by an external digital-to-electrical conversion module. Control is performed to realize the scanning function of the laser radar, and then the optical switch array 5 is connected, which is also controlled by an external digital-to-electrical conversion module. The turned-on switch transmits the local power to the grating antenna array for transmission, and the turned-off switch transmits the power to the auxiliary evanescent waveguide. The optical switch unit of the chip laser radar chip is turned on by the digital-to-electrical converter to realize the opening of the matrix m2 grating, and the input light is transmitted through the structure shown in the laser radar chip 1 to obtain and record the received signal; two or more received signals are added to obtain the final received signal. At this time, the received signal reduces the relative power of the noise while maintaining the large-angle scanning of the non-uniform array, and the received signal spectrum diagram obtained by two or more transmissions is accumulated.

[0022] The embodiments of this specific implementation method are all preferred embodiments of the present invention, and are not intended to limit the protection scope of the present invention. Therefore, any equivalent changes made based on the structure, shape, and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A low-noise, large-angle optical phased array laser radar structure, comprising a laser radar chip (1), characterized in that: The laser radar chip (1) comprises an end face coupler (2), an optical beam splitter array (3), a phase shifter array (4), an optical switch array (5), an auxiliary waveguide array (6) and a grating antenna array (7), wherein the optical beam splitter array (3), the phase shifter array (4), the optical switch array (5), the auxiliary waveguide array (6) and the grating antenna array (7) are each provided with n paths.

2. The low-noise, large-angle optical phased array laser radar structure according to claim 1, characterized in that: When the input light passes through the end face coupler (2), the light beam splitting array (3) and the phase shifter array (4) in sequence, N channels all have input power.

3. The low-noise, large-angle optical phased array laser radar structure according to claim 2, characterized in that: The optical beam splitting array (3) is a log2n-level beam splitter array structure, and the log2n-level optical beam splitting array (3) is used to equally split input light into n paths, and the specific structure of the optical beam splitting array (3) includes a 1×2-path MMI or Y-branch coupler.

4. The low-noise, large-angle optical phased array laser radar structure according to claim 3, characterized in that: The optical switch array (5) is used to realize the non-uniform opening of m paths in the n-path grating, complete the far-field non-uniform array interference, and the power of a certain path that is turned off is released through the auxiliary evanescent waveguide.

5. The low-noise, large-angle optical phased array laser radar structure according to claim 4, characterized in that: The state of each device in the optical switch array (5) is optimized by an algorithm, and a control voltage input is performed through a digital-to-electrical converter.

6. A detection method for a low-noise, large-angle optical phased array laser radar structure as claimed in claim 5, characterized in that: The method is as follows: S1: two or more non-uniform opening matrices m1 and m2 based on n-way uniformly spaced OPA arrays are obtained by algorithm; S2: The optical switch array (5) of the laser radar chip (1) is turned on by means of a digital-to-electrical conversion module to realize the opening of the matrix m1-path grating, and the input light is emitted through the structure of the laser radar chip (1), and a received signal is obtained and recorded; A1: The specific operation of the laser radar chip (1) is that the input light enters the chip through the end face coupling method, and then enters the optical beam splitter array (3). The input power is equally divided into n paths through the log2n-level cascade optical beam splitter array and transmitted backward to the phase shift area. The phase shifter array (4) is controlled by an external digital-to-electrical conversion module to realize the scanning function of the laser radar. It is then connected to the optical switch array (5), which is also controlled by an external digital-to-electrical conversion module. The turned-on switch transmits the power of this path to the grating antenna array for transmission, and the turned-off switch transmits the power to the auxiliary evanescent waveguide. S3: The optical switch unit of the chip laser radar chip is turned on by the digital-to-electrical conversion module to realize the matrix m2 grating. The input light is transmitted through the structure shown in the laser radar chip (1), and the received signal is obtained and recorded. S4: Add two or more received signals to obtain a final received signal. The received signal at this time reduces the relative power of noise while maintaining the large-angle scanning of the non-uniform array.

7. The detection method of a low-noise, large-angle optical phased array laser radar structure according to claim 6, characterized in that: The two or more opened arrays in S1 are all non-uniform arrays and are different.

8. The detection method of a low-noise, large-angle optical phased array laser radar structure according to claim 6, characterized in that: The received signal spectrograms obtained by two or more transmissions in S4 are accumulated.

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