Time varying gain in an optical detector operating in a lidar system
First Claim
Patent Images
1. A lidar system comprising:
- a light source configured to emit a light pulse; and
a receiver configured to detect light from the light pulse scattered by a remote target, the receiver including;
a photodetector that detects an optical signal corresponding to the light; and
a light pulse-detection circuit configured to convert the optical signal to an electrical signal and to detect whether the converted electrical signal is indicative of the light pulse scattered by the remote target, the light pulse-detection circuit including;
a gain circuit configured to amplify the converted electrical signal by a predetermined amplification amount that varies according to an amount of time that has elapsed since the light pulse has been emitted, wherein within a threshold time period T1 since the light pulse has been emitted the gain circuit operates in a low-gain mode having the predetermined amplification amount below a threshold value, and within a threshold time period T2 after the threshold time period T1 has elapsed, the gain circuit switches to a high-gain mode having the predetermined amplification amount at or above the threshold value, anda comparison circuit configured to compare the amplified electrical signal to a threshold amount to determine whether the amplified electrical signal is indicative of the light pulse scattered by the remote target.
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Abstract
To decrease the likelihood of a false detection when detecting light from light pulses scattered by remote targets in a lidar system, a receiver in the lidar system includes a photodetector and a pulse-detection circuit having a gain circuit with a varying amount of gain over time. The gain circuit operates in a low-gain mode for a time period T1 beginning with time t0 when a light pulse is emitted to prevent the receiver from detecting return light pulses during the threshold time period T1. Upon expiration of the threshold time period T1, the gain circuit operates in a high-gain mode to begin detecting return light pulses until a subsequent light pulse is emitted.
134 Citations
16 Claims
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1. A lidar system comprising:
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a light source configured to emit a light pulse; and a receiver configured to detect light from the light pulse scattered by a remote target, the receiver including; a photodetector that detects an optical signal corresponding to the light; and a light pulse-detection circuit configured to convert the optical signal to an electrical signal and to detect whether the converted electrical signal is indicative of the light pulse scattered by the remote target, the light pulse-detection circuit including; a gain circuit configured to amplify the converted electrical signal by a predetermined amplification amount that varies according to an amount of time that has elapsed since the light pulse has been emitted, wherein within a threshold time period T1 since the light pulse has been emitted the gain circuit operates in a low-gain mode having the predetermined amplification amount below a threshold value, and within a threshold time period T2 after the threshold time period T1 has elapsed, the gain circuit switches to a high-gain mode having the predetermined amplification amount at or above the threshold value, and a comparison circuit configured to compare the amplified electrical signal to a threshold amount to determine whether the amplified electrical signal is indicative of the light pulse scattered by the remote target. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method for dynamically varying gain in a lidar system, the method comprising:
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emitting a light pulse by a light source in a lidar system; detecting, by a receiver in the lidar system, light from the light pulse scattered by a remote target to identify a return light pulse, including detecting an optical signal corresponding to the light; converting, by a light pulse-detection circuit in the lidar system, the optical signal to an electrical signal; amplifying, by the light pulse-detection circuit, the electrical signal by a predetermined amplification amount that varies according to an amount of time that has elapsed since the light pulse has been emitted, wherein within a threshold time period T1 since the light pulse has been emitted, the light pulse-detection circuit operates in a low-gain mode having the predetermined amplification amount below a threshold value, and within a threshold time period T2 after the threshold time period T1 has elapsed, the light pulse-detection circuit switches to a high-gain mode having the predetermined amplification amount at or above the threshold value; and comparing, by the light pulse-detection circuit, the amplified electrical signal to a threshold amount to determine whether the amplified electrical signal is indicative of the light pulse scattered by the remote target. - View Dependent Claims (9, 10, 11, 12, 13)
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14. A controller in a lidar system comprising:
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one or more processors; and a non-transitory computer-readable memory coupled to the one or more processors and storing instructions thereon that, when executed by the one or more processors, cause the controller to; provide a control signal to a light source to emit a light pulse; initialize a clock based on at least one of;
determining the light pulse has been emitted or determining light from the light pulse has been detected; andprovide a control signal to a light pulse-detection circuit indicative of a predetermined amplification amount at which to amplify an electrical signal converted from an optical signal corresponding to light from the light pulse scattered by a remote target, wherein the predetermined amplification amount is based on the amount of time that has elapsed since the light pulse has been emitted, and wherein; within a threshold time period T1 since the light pulse has been emitted, the instructions cause the controller to provide a control signal to the light pulse-detection circuit to operate in a low-gain mode having the predetermined amplification amount below a threshold value; and within a threshold time period T2 after the threshold time period T1 has elapsed, the instructions cause the controller to provide a control signal to the light pulse-detection circuit to switch to a high-gain mode having the predetermined amplification amount at or above the threshold value. - View Dependent Claims (15, 16)
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Specification