# US 11,906,626 B2 · Systems and methods for mitigating avalanche photodiode (APD) blinding > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,906,626 B2 - Document ID: US11906626B2 - Status: Granted - Kind: B2 - Application number: 17/017,467 - Filed: 2020-09-10 - Published: 2021-07-29 - Granted: 2024-02-20 - Earliest claimed: 2018-02-15 - Assignees: Velodyne Lidar USA, Inc. - Applicants: Velodyne Lidar USA, Inc. - Inventors: Kiran Kumar Gunnam; Nitinkumar Sagarbhai Barot; Rajesh Ramalingam Varadharajan; Roger Jullian Pinto; Kanke Gao - Web page: https://patentgrep.com/patent/US11906626B2 ## CPC - G01S 17/89: for mapping or imaging - G01S 7/4816: {of receivers alone} - G01S 7/4861: Circuits for detection, sampling, integration or read-out - G01S 7/4863: Detector arrays, e.g. charge-transfer gates - G01S 17/10: using transmission of interrupted, pulse-modulated waves (determination of distance by phase measurements G01S17/32) - G01S 17/42: Simultaneous measurement of distance and other co-ordinates (indirect measurement G01S17/46) - G01S 17/931: of land vehicles - H10F 30/225: the potential barrier working in avalanche mode, e.g. avalanche photodiodes - H10F 55/26: {wherein the radiation-sensitive semiconductor devices have potential barriers} - H10F 77/953: {for devices having potential barriers} - G01S: RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES - H10F: INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION ## Abstract Described herein are systems and methods that that mitigate avalanche photodiode (APD) blinding and allow for improved accuracy in the detection of a multi-return light signal. A blinding spot may occur due to saturation of a primary APD. The systems and methods include the incorporation of a redundant APD and the utilization of time diversity and space diversity. Detection by the APDs is activated by a bias signal. The redundant APD receives a time delayed bias signal compared to the primary APD. Additionally, the redundant APD is positioned off the main focal plane in order to attenuate an output of the redundant APD. With attenuation, the redundant APD may not saturate and may have a successful detection during the blinding spot of the primary APD. Embodiments may include multiple primary APDs and multiple secondary APDs. ## Claims ### Claim 1 A method comprising: receiving a multi-return light signal comprising a plurality of light pulses at a first photodetector and at a second photodetector; in response to receiving the multi-return light signal, generating, by the first and second photodetectors, respective first and second electrical signals, wherein the second electrical signal is attenuated, as compared to the first electrical signal; combining the first and second electrical signals, thereby generating a combined signal; and detecting the plurality of light pulses by decoding the combined signal. ### Claim 2 (depends on 1) The method of claim 1 further comprising: activating, by a first bias signal, the first photodetector; and activating, by a second bias signal, the second photodetector. ### Claim 3 (depends on 2) The method of claim 2, wherein the second bias signal is delayed with respect to the first bias signal. ### Claim 4 (depends on 3) The method of claim 3 further comprising: generating the second bias signal by adding a delay to the first bias signal. ### Claim 5 (depends on 1) The method of claim 1, wherein the first photodetector and second photodetector are structured and arranged in a light detecting and ranging (LIDAR) system. ### Claim 6 (depends on 5) The method of claim 5 further comprising attenuating the second electrical signal by attenuating, using a gain setting of the second photodetector, a first amount of optical power of the multi-return light signal received at the second photodetector relative to a second amount of optical power of the multi-return light signal received at the first photodetector. ### Claim 7 (depends on 1) The method of claim 1, wherein the second electrical signal is attenuated by positioning the second photodetector on a different optical path than the first photodetector. ### Claim 8 (depends on 1) The method of claim 1, wherein the attenuating prevents saturation of the second photodetector under one or more conditions in which the first photodetector saturates. ### Claim 9 (depends on 5) The method of claim 5, wherein the attenuating comprises positioning the second photodetector off a main focal plane of a receiver of the LIDAR system and positioning the first photodetector on a main focal plane of the receiver. ### Claim 10 (depends on 1) The method of claim 1, wherein the second photodetector operates redundantly of the first photodetector. ### Claim 11 (depends on 1) The method of claim 1, wherein the first photodetector comprises a first avalanche photodiode (APD), and the second photodetector comprises a second avalanche photodiode (APD). ### Claim 12 A system comprising: a combiner device structured and arranged to generate a combined signal by combining (1) a first electrical signal generated by a first photodetector in response to the first photodetector receiving a multi-return light signal; and (2) a second electrical signal generated by a second photodetector in response to the second photodetector receiving the multi-return light signal, wherein the multi-return light signal comprises two or more light pulses; a current amplifier, configured to amplify the second electrical signal generated by the second photodetector and coupled to the combiner device; and a receiver device configured to detect the two or more light pulses by decoding the combined signal. ### Claim 13 (depends on 12) The system of claim 12 further comprising the first photodetector and the second photodetector. ### Claim 14 (depends on 12) The system of claim 12 further comprising a gain controller adapted to control the current amplifier based on an output current of the second photodetector and an output current of the first photodetector. ### Claim 15 (depends on 12) The system of claim 12 further comprising a delay component structured and arranged to generate a second bias signal adapted to activate second photodetector by adding a delay to a first bias signal adapted to activate the first photodetector. ### Claim 16 (depends on 15) The system of claim 15 further comprising a range gate control operable to control the delay component. ### Claim 17 (depends on 12) The system of claim 12, wherein the receiver device comprises a trans-impedance amplifier electrically coupled to an output of the combiner device and to an input of a diversity enhanced optical detector. ### Claim 18 (depends on 12) The system of claim 12, wherein the combiner device is structured and arranged to implement MIMO processing with maximum gain ratio combining. ### Claim 19 (depends on 12) The system of claim 12, wherein the first photodetector comprises a first avalanche photodiode (APD), and the second photodetector comprises a second avalanche photodiode (APD). ### Claim 20 A method comprising: activating, by a first bias signal, a first photodetector selected from two or more first photodetectors; activating, by a second bias signal, a second photodetector; receiving, by the selected and activated first photodetector and by the activated second photodetector, a multi-return light signal comprising a plurality of light pulses; amplifying, by a current amplifier, the multi-return light signal of the activated second photodetector; and combining the multi-return light signal of the first photodetector and the second photodetector. ### Claim 21 (depends on 20) The method of claim 20, wherein the first photodetector comprises a first avalanche photodiode (APD), and the second photodetector comprises a second avalanche photodiode (APD). ### Claim 22 (depends on 20) The method of claim 20, wherein the second photodetector is configured to attenuate the multi-return signal.