CN-115190979-B - System and method for optical detection and ranging

Abstract

A light detection and ranging system for improving imaging accuracy and measurement range is provided. The light detection and ranging system may include a light source configured to emit a multi-pulse sequence into a three-dimensional environment, wherein the multi-pulse sequence includes a plurality of light pulses having timing characteristics, a photosensitive detector configured to detect light pulses returned from the three-dimensional environment and generate an output signal representative of light energy associated with a subset of the light pulses, one or more processors electrically coupled to the light source and the photosensitive detector, and the one or more processors are configured to generate the timing characteristics based on one or more real-time conditions, and determine one or more parameters for selecting a subset of the light pulses.

Inventors

• PAN ZHENGQING
• XIANG SHAOQING
• LI YIFAN
• SUN KAI

Assignees

• 上海禾赛科技有限公司
• 上海禾赛科技有限公司

Dates

Publication Date

20260421

Application Date

20200121

Priority Date

20200121

Claims (16)

1. 1. A light detection and ranging system comprising: A light source configured to emit a laser pulse sequence according to a timing characteristic; A photosensitive detector configured to detect return pulses of the laser pulse train reflected by objects in a three-dimensional environment and to generate an output signal representative of light energy associated with a subset of the return pulses, the photosensitive detector configured to accumulate the subset of return pulses to form the output signal, and One or more processors electrically coupled to the light source and the photosensitive detector, wherein the one or more processors are configured to: determining one or more parameters for selecting the subset of return pulses, the one or more parameters including a number of light pulses in the subset of return pulses, a parameter representing a combination of immediately adjacent light pulses, and/or a parameter representing a combination of non-immediately adjacent light pulses; Selecting the subset of return pulses based on the one or more parameters includes determining a number of pulses or a selection of pulses accumulated to generate the output signal based on a detection range; wherein the photosensitive detector comprises a SPAD array, the photosensitive detector configured to accumulate a subset of return pulses to form the output signal comprising: Accumulating a selected number of modulation pulses received in an activated region in the SPAD array to generate the output signal; accumulating combinations of selected immediately adjacent light pulses received in activated regions in the SPAD array to generate the output signal, and/or The combination of selected non-immediately adjacent light pulses received in the activated regions in the SPAD array is accumulated to generate the output signal.
2. 2. The light detection and ranging system of claim 1, wherein the one or more processors are further configured to calculate a distance based on a time of flight associated with the subset of return pulses, wherein the time of flight is determined by determining that the sequence of detected light pulses matches the timing characteristic, the timing characteristic comprising one or more selected from the group consisting of an amplitude of each of the plurality of pulses, a duration of each of the plurality of pulses, a time interval between the plurality of pulses, and a number of the plurality of pulses.
3. 3. The light detection and ranging system of claim 2, wherein the one or more parameters for selecting the subset of return pulses are determined based on a distance between the light detection and ranging system and an object located in the three-dimensional environment.
4. 4. The light detection and ranging system of claim 1, wherein the one or more parameters for selecting the subset of return pulses are determined based at least in part on the timing characteristics.
5. 5. The light detection and ranging system of claim 1, wherein the one or more processors are configured to generate the timing characteristic based on one or more real-time conditions obtained based on the detected light pulses.
6. 6. The light detection and ranging system of claim 5, wherein the one or more real-time conditions comprise detecting an object that is within a predetermined distance threshold.
7. 7. The light detection and ranging system of claim 1, wherein the one or more processors are further configured to generate a 3D image based on the output signals.
8. 8. A method of imaging using a light detection and ranging system, comprising: transmitting a laser pulse train into a three-dimensional environment, wherein the laser pulse train comprises a plurality of pulses having a timing characteristic; Detecting a return pulse from the three-dimensional environment, and Generating an output signal representative of optical energy associated with a subset of the return pulses, the generating the output signal comprising accumulating the subset of return pulses to form the output signal; The method further includes determining one or more parameters for selecting the subset of return pulses, the one or more parameters including a number of light pulses in the subset of return pulses, a parameter representing a combination of immediately adjacent light pulses, and/or a parameter representing a combination of non-immediately adjacent light pulses; wherein said accumulating a subset of return pulses to form said output signal comprises: Accumulating a selected number of modulated pulses received in an activated region in a SPAD array of a photosensitive detector to generate the output signal; accumulating combinations of selected immediately adjacent light pulses received in activated regions in the SPAD array to generate the output signal, and/or The combination of selected non-immediately adjacent light pulses received in the activated regions in the SPAD array is accumulated to generate the output signal.
9. 9. The method of claim 8, wherein the one or more parameters for selecting the subset of return pulses are determined based on a distance between the light detection and ranging system and an object located in the three-dimensional environment.
10. 10. The method of claim 8, wherein the one or more parameters for selecting the subset of return pulses are determined based at least in part on the timing characteristics, the timing characteristics including one or more selected from the group consisting of an amplitude of each of a plurality of pulses, a duration of each of the plurality of pulses, a time interval between the plurality of pulses, and a number of the plurality of pulses.
11. 11. The method of claim 8, further comprising calculating a distance based on a time of flight associated with the detected light pulse.
12. 12. The method of claim 11, further comprising determining the time of flight by determining that the detected light pulse sequence matches the timing characteristic.
13. 13. The method of claim 8, further comprising generating the timing characteristic based on one or more real-time conditions, wherein the one or more real-time conditions are obtained based on the detected light pulses.
14. 14. The method of claim 13, wherein the one or more real-time conditions include detecting an object that is within a predetermined distance threshold.
15. 15. The method of claim 8, further comprising generating a 3D image based on the output signal.
16. 16. The method of claim 15, wherein the output signal corresponds to one intensity value of a pixel in the 3D image.

Description

System and method for optical detection and ranging Cross reference The present application is concerned with international PCT application No. PCT/CN2018/119721, filed on 7, 12, 2018, which claims the benefit of chinese application No. 201711303228.8, filed on 8, 12, 2017, each of which is incorporated herein by reference in its entirety. Background Light detection and ranging (Lidar) techniques may be used to obtain three-dimensional information of the environment by measuring distances to objects. The Lidar system may include at least a light source configured to emit light pulses and a detector configured to receive return light pulses. The return light pulse or beam may be referred to as an echo beam. Based on the time interval (i.e. time of flight) between the emission of the light pulse and the detection of the return light pulse, a distance can be obtained. The light pulses may be generated by a laser transmitter and then focused by a lens or lens group. The return light pulse may be received by a detector located near the laser transmitter. The return light pulse may be scattered light from the surface of the object. The light pulses described above may be used to detect obstructions within the field of view. In some cases, the dynamic range of the detector, the signal-to-noise ratio of the detection signal, or the contrast may be limited by stray light. Stray light in Lidar systems may be caused by a variety of sources. For example, the transmitted light may contaminate or interfere with the reception of the return light pulse by the detector. Such contamination or interference may cause difficulty in recognizing the near-field echo. For example, a small portion of the transmitted pulse (stray light) may be received directly by a detector such as an Avalanche Photodiode (APD) within the Lidar system, causing the detection circuitry of the high sensitivity APD to enter a nonlinear saturation region. When the detection circuit is saturated, the magnification of the stray light waveform tail is larger than that of the top pulse, and the pulse width of the stray light pulse in the detection circuit is increased. This may cause the laser pulse echo signal reflected by the near-field obstacle to be annihilated in the trailing waveform tail of the stray light, and the position information of the near-field obstacle cannot be determined, so that a measurement blind area is caused. Summary of The Invention There is a need for an improved optical ranging accuracy and efficiency Lidar system for three-dimensional measurements. More specifically, there is a need for a method and system that can measure near field obstructions and reduce dead zones caused by stray light inside Lidar. The Lidar system proposed in the present application meets the above-mentioned needs by utilizing a laser pulse sequence corresponding to a temporal profile. The laser pulse sequence enables a receiver or receiving device of the Lidar system to have a higher dynamic range. The receiver may include a detector with a high dynamic range, enabling the Lidar system to image with high imaging resolution and a wide measurement range. For example, the receiver may include a pulse detection circuit configured to convert an optical signal into an electrical signal. The pulse detection circuit may be configured to generate the sensor output signal by varying the received photon energy converted into the at least one electrical signal. Or when the electrical signal corresponds to a single light pulse, the pulse detection circuit may generate the sensor output signal by accumulating the electrical signals for generating different combinations of the sensor output signals. In some cases, the pulse detection circuit may generate a sensor output signal representative of optical energy associated with a selected subset of the return optical pulses. The photon energy may be changed by changing the number/count of return light pulses accumulated to generate the output signal and/or changing the selection of a subset of the return light pulses, such that a corresponding total light energy may be selected. In some cases, the detector or photosensor may be configured to accumulate a selected subset of the return modulated pulses received in the activated region of the photosensor to generate the sensor output signal. The sensor output signal may determine the intensity of pixels in the 3D image. The intensity or value of a pixel may be proportional to the light energy of a subset of the light pulses accumulated by the photosensor or pulse detection circuit of the photosensor. In some cases, the intensity or peak power of the output signal (e.g., voltage signal) may be dynamically adjusted on a pixel-by-pixel basis. In some cases, the intensity or peak power of the output signal may be adjusted individually for the activated area of the detector or the entire detector. In one aspect, the present disclosure may enable a detector to accumulate selected li