CN115656974B - Detection method for laser radar integrated double APDs - Google Patents
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- CN115656974B CN115656974B CN202211576016.8A CN202211576016A CN115656974B CN 115656974 B CN115656974 B CN 115656974B CN 202211576016 A CN202211576016 A CN 202211576016A CN 115656974 B CN115656974 B CN 115656974B
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Abstract
The invention discloses a detection method of laser radar integrated double APDs, which is applied TO laser radar, wherein the laser radar comprises a laser transmitter, a scanning system, an APD detector and a processor, the APD detector adopts a TO packaging structure, a main APD and an auxiliary APD are arranged on a substrate of the APD detector, lenses of the main APD and the APD detector are coaxial, the auxiliary APD and the main APD are arranged at intervals according TO a preset distance, the main APD and the auxiliary APD adopt chips with the same breakdown voltage and share the same power supply, the current detected by the processor is set as I Detection And set its upper limit to I max . When the processor detects I Detection ≥I max At this time, the bias voltage of the main APD is selected to be set to be 0, and the signals received by the auxiliary APD are used as the first selection of distance measurement calculation to play a role in protecting the main APD; when the processor detects I Detection ＜I max At this time, signals received by the main APD and the auxiliary APD are selected to be used as the first selection of ranging calculation, so that noise of the laser radar influenced by ambient light and temperature can be removed, and the signal-to-noise ratio of the laser radar is improved.
Description
Technical Field
The invention relates to the technical field of laser radar ranging, in particular to a detection method of laser radar integrated double APDs.
Background
Lidar is widely used in various technical scenes, and particularly in the field of automobiles, vehicle-mounted lidar is the most important 'eye'. The mainstream technical scheme of the laser radar is time of flight (TOF), namely, a transmitting end laser emits pulsed light, the pulsed light is reflected after meeting an object, a receiving end detector receives the pulsed light, and the optical path time is calculated to obtain the distance.
At present, a single APD detector is often adopted as a receiving end detector of a laser radar, and the single APD detector has the following three problems:
1. an outer layer lens of the laser radar can filter out a part of sunlight and other environment light, but a considerable part of environment light enters the APD detector to form noise, so that the detection performance of the APD detector is influenced;
2. the noise of the APD detector is mainly influenced by dark current, the temperature range of the laser radar is-40 to 85 ℃, the high temperature of the vehicle-mounted laser radar even reaches 105 ℃, the breakdown voltage of the APD detector is in a linear relation with the temperature, when the temperature rises, the breakdown voltage is increased, in order to keep the gain of the APD detector stable, the working voltage of the APD detector needs to be increased, meanwhile, the dark current is also increased, the noise is increased, and the detection performance of the APD detector is directly influenced;
3. under the condition of overlarge detection light intensity, the single APD detector enters a saturated state, and the phenomena of expansion, ghost and the like can occur in a point cloud picture of the laser radar. For example, for a vehicle-mounted laser radar, the reflectivity of an object can directly affect the parameter settings of a transmitting end laser and a receiving end detector, and in a theoretical model, the reflectivity of the object is 10%, but in an actual driving scene, many high-reflectivity objects can exist, including signs, cone barrels, license plates and the like. The high-reflectivity object can not only saturate the detector at the receiving end to influence the point cloud picture data, but also cause physical damage to the detector at the receiving end in severe cases.
Disclosure of Invention
The invention aims to provide a detection method of a laser radar integrated double APD (avalanche photo diode), which plays a role in protecting a main APD (avalanche photo diode) in different application scenes, can remove noise of the laser radar influenced by ambient light and temperature, and improves the signal-to-noise ratio of the laser radar.
In order to achieve the purpose, the invention adopts the following technical scheme:
a detection method of laser radar integrated double APDs is applied to laser radars, wherein each laser radar comprises a laser transmitter, a scanning system, an APD detector and a processor;
the APD detector adopts a TO packaging structure, a main APD and an auxiliary APD are arranged on a substrate of the TO packaging structure, lenses of the main APD and the APD detector are coaxial, the auxiliary APD and the main APD are arranged at intervals according TO a preset distance, and the main APD and the auxiliary APD are chips with the same breakdown voltage and share the same power supply;
the detection method comprises the following steps: setting the current detected by the processor to I Detection And set its upper limit to I max The laser emitter emits laser to the target object, the laser is reflected by the target object and then received by the APD detector through the scanning system, the APD detector transmits the received signal to the processor, and when the processor detects I Detection ≥I max When the processor detects I, the processor sends out an instruction to set the bias voltage of the main APD to be 0, the auxiliary APD normally works, the processor carries out distance measurement calculation according to signals received by the auxiliary APD Detection ＜I max And in time, the main APD and the auxiliary APD work normally, and the processor carries out distance measurement calculation according to signals received by the main APD and the auxiliary APD.
Further, the saturation current of the main APD is I Saturation of Upper limit of current detected by processor I max Not more than I Saturation of 。
Further, the processor detects an upper limit I of the current max To 95% of I Saturation of 。
Further, the diameters of the main APD and the auxiliary APD are both 200um, and the main APD and the auxiliary APD are arranged at intervals of 600-800um according to a preset distance on a substrate of the APD detector.
Furthermore, a TEC semiconductor refrigerator is arranged in the APD detector, a substrate of the APD detector is arranged on the TEC semiconductor refrigerator, and a thermistor connected with the TEC semiconductor refrigerator is further arranged on the substrate of the APD detector and used for monitoring the temperatures of the main APD and the sub APD in real time.
The beneficial effects of the invention are as follows:
in the practical application scenario, when the processor detects I Probing ≥I max At this time, the bias voltage of the main APD is selected to be set to be 0, and the signals received by the auxiliary APD are used as the first selection of distance measurement calculation to play a role in protecting the main APD; when the processor detects I Detection ＜I max When the signals received by the primary APD and the secondary APD are selected together as the first choice for the distance measurement calculation, the method can be usedThe noise of the laser radar influenced by ambient light and temperature is removed, and the signal-to-noise ratio of the laser radar is improved.
Drawings
FIG. 1 is a schematic diagram of the structure of an APD detector of the present invention;
FIG. 2 is a schematic diagram of a substrate structure of an APD detector according to the present invention.
Description of the labeling: 1. target object, 2, scanning system, 3, lens, 4, substrate, 5, main APD,6, auxiliary APD,7, thermistor, 8, TEC semiconductor refrigerator.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific examples described herein are intended to be illustrative only and are not intended to be limiting.
Referring to fig. 1-2, a method for detecting a laser radar integrated with dual APDs is disclosed, which is applied to a laser radar, where the laser radar includes a laser transmitter, a scanning system 2 (only schematically shown in the drawings, the structure of the scanning system is not completely shown), an APD detector, and a processor.
The APD detector adopts a TO packaging structure, a main APD5 and an auxiliary APD6 are arranged on a substrate 4 of the APD detector, the main APD5 is coaxial with a lens 3 of the APD detector, the auxiliary APD6 and the main APD5 are arranged at intervals according TO a preset distance, the main APD5 and the auxiliary APD6 adopt chips with the same breakdown voltage, and the main APD5 and the auxiliary APD6 share the same power supply.
In this embodiment, the diameters of the main APD5 and the sub APD6 are both 200um, and on the substrate 4 of the APD detector, the main APD5 and the sub APD6 are arranged at intervals of 600-800um according to a preset distance.
When the reflected light of the target object 1 enters the APD detector through the lens 3, the incident light of the APD detector has a certain divergence angle, the main APD5 and the sub APD6 receive the incident light at the same time, the main APD5 receives the light of the main optical path, and the sub APD6 receives the diverged light.
A TEC semiconductor refrigerator 8 is arranged in the APD detector, a substrate 4 of the APD detector is arranged on the TEC semiconductor refrigerator 8, and a thermistor 7 connected with the TEC semiconductor refrigerator 8 is further arranged on the substrate 4 of the APD detector and used for monitoring the temperatures of the main APD5 and the auxiliary APD6 in real time. The thermistor 7 monitors the temperature of the main APD5 and the auxiliary APD6 in real time, and feeds temperature signals back to the TEC semiconductor refrigerator 8, and the TEC semiconductor refrigerator 8 heats when the temperature signals are lower than the preset values and refrigerates when the temperature signals are higher than the preset values, so that the working temperature of each device is maintained.
In the APD detector, the pins are positioned as APD +, APD-, TEC +, TEC-, thermistor and thermistor.
The detection method comprises the following steps:
setting the current detected by the processor as I Probing And set its upper limit to I max . At the receiving end of the lidar, the saturation optical power of the main APD5 is known, while at the bias voltage V apd Under certain conditions, the saturation current I of the main APD5 Saturation of Can be determined. Thus, if the saturation current of main APD5 is I Saturation of Upper limit of current detected by processor I max Should not be greater than I Saturation of 。
Preferably, the upper limit I of the current detected by the processor max To 95% of I Saturation of 。
The laser emitter emits laser to the target object 1, the laser is reflected by the target object 1 and then received by the APD detector through the scanning system 2, the APD detector transmits the received signal to the processor, and the following operations are executed:
when the processor detects I Detection ≥I max When the signal is received by the auxiliary APD6, the processor carries out distance measurement calculation according to the signal received by the auxiliary APD 6;
when the processor detects I Detection ＜I max In the process, the main APD5 and the auxiliary APD6 work normally, and the processor carries out distance measurement calculation according to signals received by the main APD5 and the auxiliary APD 6.
It should be noted that the processor and the distance measurement calculation performed by the processor are well known in the art, and therefore are not described herein again.
According to the method, the practical application scenes of the laser radar are divided into the following two types:
1. when the laser radar meets high-reflection objects, namely, the received light power is too high.
When the processor detects I Detection ≥I max At this time, the bias voltage of main APD5 is selected to be 0, and the signal received by sub APD6 is selected as the first choice of the distance measurement calculation, thereby protecting main APD 5.
2. When the laser radar does not encounter high-reflection objects, namely in a normal working state.
When the processor detects I Probing ＜I max At this time, signals received by the main APD5 and the auxiliary APD6 are selected to be used as the first selection of distance measurement calculation, so that noise of the laser radar influenced by ambient light and temperature can be removed, and the signal-to-noise ratio of the laser radar can be improved.
Specifically, the primary APD5 and the secondary APD6 are in the same environment and are affected by the environment uniformly, and the environmental noises received by the two are also uniform under the same power supply. Meanwhile, as the breakdown voltages of the main APD5 and the sub APD6 are consistent, the dark current is consistent, and under the same power supply, when the temperature change is influenced, the change of the dark current is consistent, that is, the noise influence is also the same.
An anti-impedance amplifier is added behind the circuits of the main APD5 and the auxiliary APD6, the signals detected by the two are amplified, and then the signals are compared, so that the noise of the laser radar influenced by ambient light and temperature can be removed, and the signal-to-noise ratio of the laser radar can be improved.
The present invention is not limited to the above embodiments, and those skilled in the art can implement the present invention in other various embodiments according to the disclosure of the present invention, so that all designs and concepts of the present invention can be changed or modified without departing from the scope of the present invention.
Claims (5)
1. A detection method of laser radar integrated double APDs is applied to laser radars, the laser radars comprise a laser transmitter, a scanning system, an APD detector and a processor, and the detection method is characterized in that:
the APD detector adopts a TO packaging structure, a main APD and an auxiliary APD are arranged on a substrate of the APD detector, lenses of the main APD and the APD detector are coaxial, the auxiliary APD and the main APD are arranged at intervals of 600-800 mu m according TO a preset distance, the main APD and the auxiliary APD are chips with the same breakdown voltage, and the main APD and the auxiliary APD share the same power supply;
the detection method comprises the following steps: setting the current detected by the processor to I Probing And set its upper limit to I max The laser emitter emits laser to the target object, the laser is reflected by the target object and then received by the APD detector through the scanning system, the APD detector transmits the received signal to the processor, and when the processor detects I Probing ≥I max When the processor detects I, the processor sends out an instruction to set the bias voltage of the main APD to be 0, the auxiliary APD normally works, the processor carries out distance measurement calculation according to signals received by the auxiliary APD Probing ＜I max And when the APDs are in normal operation, the processor performs distance measurement calculation according to signals received by the main APDs and the auxiliary APDs.
2. The method for detecting the lidar integrated dual APD according to claim 1, wherein: the saturation current of the main APD is I Saturation of Upper limit of current detected by processor I max Not more than I Saturation of 。
3. The method of claim 2, wherein the method comprises the following steps: upper limit I of current detected by the processor max To 95% of I Saturation of 。
4. The method of claim 1, wherein the method comprises the following steps: the diameters of the main APD and the auxiliary APD are both 200um.
5. The method of claim 1, wherein the method comprises the following steps: the APD detector is internally provided with a TEC semiconductor refrigerator, a substrate of the APD detector is arranged on the TEC semiconductor refrigerator, and a thermistor connected with the TEC semiconductor refrigerator is further arranged on the substrate of the APD detector and used for monitoring the temperature of the main APD and the auxiliary APD in real time.
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| US10775486B2 (en) * | 2018-02-15 | 2020-09-15 | Velodyne Lidar, Inc. | Systems and methods for mitigating avalanche photodiode (APD) blinding |
| US11789132B2 (en) * | 2018-04-09 | 2023-10-17 | Innovusion, Inc. | Compensation circuitry for lidar receiver systems and method of use thereof |
| CN113156404B (en) * | 2020-01-21 | 2023-03-24 | 苏州一径科技有限公司 | Reverse bias voltage adjusting device and method and laser radar |
| CN113820689B (en) * | 2020-06-18 | 2024-05-17 | 华为技术有限公司 | Receiver, laser ranging equipment and point cloud image generation method |
| CN114137548A (en) * | 2020-08-12 | 2022-03-04 | 上海禾赛科技有限公司 | Photoelectric detection device, laser radar comprising same and detection method using same |
| CN114167431A (en) * | 2020-08-21 | 2022-03-11 | 上海禾赛科技有限公司 | Method for detection by means of a lidar and lidar |
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| CN112068150B (en) * | 2020-08-28 | 2023-12-26 | 上海禾赛科技有限公司 | Laser radar and ranging method |
| CN216670268U (en) * | 2021-10-27 | 2022-06-03 | 北醒（北京）光子科技有限公司 | Photoelectric receiving circuit and laser ranging device with same |
| CN114859369A (en) * | 2022-05-03 | 2022-08-05 | 浙江大学湖州研究院 | Laser detector sensitivity adjusting device and method |
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| CN108318132A (en) * | 2018-04-03 | 2018-07-24 | 福建海创光电有限公司 | A kind of device expanding APD linear probing ranges |
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