Split-Detector Lidar Photoreceiver for Wide Dynamic Range
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Solution Overview
Problem
Lidar systems face challenges in detecting targets over a wide dynamic range due to saturation issues from strong signal returns from close objects, which can prevent detection of weak signals from distant targets.
Innovation Solution
A split-detector photoreceiver configuration is employed, featuring a primary detector and a secondary detector with distinct recovery times and amplification gains, allowing for simultaneous detection of both strong close-range returns and weak distant returns without saturation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single photoreceiver is used to detect lidar returns, then the system structure is simple, but it cannot simultaneously detect both strong close-range returns and weak distant returns due to saturation from close objects
Solution Approach 1:
The photoreceiver is divided into two separate detectors: a first detector optimized for detecting strong close-range lidar returns and a second detector optimized for detecting weak distant returns. Each detector has its own transimpedance amplifier with independently optimized parameters, allowing simultaneous detection across a wide dynamic range without saturation issues.
2Measurement precision
If the photoreceiver is optimized for high sensitivity to detect weak distant signals, then distant target detection is improved, but the close-range t0 return saturates the detector preventing near target detection
Solution Approach 1:
The detection function is segmented into two parallel channels: one detector optimized for high sensitivity to weak signals (distant targets) and another detector optimized for handling strong signals (close targets). This eliminates the saturation problem by preventing the strong t0 return from overwhelming the high-sensitivity detector.
Solution Approach 2:
Each detector is given locally optimized characteristics: the first detector has parameters optimized for high signal handling capability, while the second detector has parameters optimized for high sensitivity and low noise. This allows each part of the system to excel at its specific function.
3Speed
If the photoreceiver is optimized for fast recovery to detect near targets, then close-range detection is improved, but the system cannot detect distant targets due to insufficient sensitivity
Solution Approach 1:
The recovery time requirement is segmented between two detectors: the first detector has fast recovery time optimized for detecting close-range returns, while the second detector has slower but more sensitive amplification optimized for distant returns. Both detectors operate in parallel, so the fast recovery of the first detector does not compromise the sensitivity of the second.
4Measurement precision
If a single transimpedance amplifier is used, then the circuit is simple, but it cannot provide both high gain for weak signals and fast recovery for strong signals simultaneously
Solution Approach 1:
The amplification function is segmented into two separate transimpedance amplifiers: a first TIA with high gain and optimized parameters for handling strong signals with fast recovery, and a second TIA with high gain and optimized parameters for amplifying weak signals. Each amplifier is independently optimized for its specific signal range.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The split-detector photoreceiver effectively mitigates saturation issues, enabling accurate detection of targets across a wide range of signal strengths from both near and far distances, thereby enhancing the overall performance and reliability of lidar systems.
Implementation Method 1
a photodetector configured to receive a laser return from a target
Data Source
AI summary
Split-detector lidar photoreceivers are described which utilize range-dependent focus to transition from illuminating two detector elements with returns from near targets, within a close-range threshold distance, to illuminating just one detector element for all other returns. In some examples, a split-detector can have or include a “bullseye” (concentric) detector configuration. Because two separate detector elements with separate amplifier chains are used, one channel can be optimized for the strong to and near-target returns, while another channel can be optimized and used for all other returns.