LiDAR Single-Photon Detector Sub-Gating for Solar Noise
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Solution Overview
Problem
Current LiDAR systems face challenges in achieving a large field of view, high resolution, and high update rates while operating within eye safety limits and accommodating varying ambient light conditions, particularly in automotive applications, due to limitations in laser power and solar background noise.
Innovation Solution
A LiDAR system operating at a wavelength range of 1350 nm to 1390 nm with a single-photon detector gated at 3.3 MHz, using a 'range-gated' mode with sub-gate periods to reduce solar-background-induced noise and employing statistical analysis and digital thresholding to enhance signal-to-noise ratio and mitigate noise photons.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high laser power is used to achieve high-resolution performance, then measurement precision is improved, but eye safety is compromised
Solution Approach 1:
The patent changes the operating wavelength parameter from conventional 905 nm to 1550 nm. This parameter change enables higher permissible laser power (several orders of magnitude higher MPE) while maintaining eye safety, thereby achieving high-resolution performance without compromising safety. The 1550 nm wavelength is specifically chosen because it falls in a region where the human eye is less sensitive and maximum permissible energy levels are much higher.
Solution Approach 2:
The patent employs pulsed laser operation with nanosecond-range pulse durations repeated at high repetition rates. This periodic action concentrates the total energy into short bursts, allowing high peak power for sufficient return signal while keeping average power within safety limits. The pulsed mode enables time-gated detection that further improves signal-to-noise ratio by rejecting ambient light.
2Measurement precision
If 1550 nm wavelength is used to operate at higher power, then measurement precision is improved, but solar background noise increases
Solution Approach 1:
The patent uses time-gated detection synchronized with the pulsed laser transmission. The detector is activated only during specific time windows corresponding to expected return signal arrival times. This periodic gating rejects continuous solar background noise while capturing the pulsed return signal, thereby improving signal-to-noise ratio despite operating at 1550 nm where solar background is higher.
Solution Approach 2:
The patent replaces conventional continuous-wave or long-pulse operation with ultrashort nanosecond pulsed operation combined with time-gated detection. This substitution in the temporal domain allows discrimination between the short-duration laser return signal and the continuous solar background, effectively filtering out solar noise while maintaining sensitivity to weak return signals.
3Measurement precision
If FOV is restricted to mitigate solar background effects, then measurement precision is improved, but productivity decreases
Solution Approach 1:
The patent uses high-repetition-rate pulsed operation combined with time-gated detection to achieve high update rates while maintaining large FOV. The periodic pulsing allows parallel detection across multiple directions without being limited by solar background, as the time gating rejects continuous ambient light. This enables rapid scanning and high productivity while maintaining measurement precision across a wide field of view.
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
This approach enables high-resolution, high-signal-to-noise operation over a 500-meter field of view, reducing the impact of solar background noise and avoiding the need for restricted fields of view or costly wavelength filters, thus providing a cost-effective and high-performance LiDAR system suitable for vehicular applications.
Implementation Method 1
detecting a reflection of the pulse
Implementation Method 2
the single-photon detector is gated at a frequency of approximately 3.3 MHz, yielding a series of 0.3 microsecond detection frames
Data Source
AI summary
A method for developing a map of objects in a region surrounding a location is disclosed. The method includes interrogating the region along a detection axis with a series of optical pulses and detecting reflections of the optical pulses that originate at objects located along the detection axis. A multi-dimensional map of the region is developed by scanning the detection axis about the location in at least one dimension. The reflections are detected via a single-photon detector that is armed using a sub-gating scheme such that the single-photon detector selectively detects photons of reflections that originate only within each of a plurality of zones that collectively define the detection field. In some embodiments, the optical pulses have a wavelength within the range of 1350 nm to 1390 nm, which is a spectral range having a relatively high eye-safety threshold and a relatively low solar background.