Multispectral Lidar System Solar Noise Reduction
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Solution Overview
Problem
Lidar systems face challenges in accurately measuring distances and properties of targets due to solar background noise and the need for high signal-to-noise ratio, which can be achieved by using a multispectral approach with a laser emitting a pulse of light at one wavelength and secondary detectors for other wavelengths to enhance measurement accuracy.
Innovation Solution
A multispectral lidar system with a scanner that maintains a fixed spatial relationship between the fields of view of primary and secondary detectors, allowing for distance determination using the primary detector and property measurement using secondary detectors, which can include visible or infrared wavelengths, to modify and enhance the accuracy of measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single-wavelength laser is used for distance measurement, then the system structure is simple, but solar background noise reduces measurement accuracy
Solution Approach 1:
The system segments the detection process by using multiple detectors tuned to different wavelengths. The primary detector measures distance at the laser wavelength while secondary detectors measure other wavelengths to characterize solar background noise, allowing the noise to be subtracted from the primary measurement to improve accuracy.
Solution Approach 2:
Secondary detectors act as intermediaries that measure solar background noise at wavelengths adjacent to the laser wavelength. These measurements serve as a proxy to estimate and remove the noise contribution from the primary distance measurement, thereby improving measurement precision without requiring a fundamentally different measurement approach.
2Measurement precision
If multiple detectors at different wavelengths are used, then signal-to-noise ratio is improved, but device complexity increases
Solution Approach 1:
Multiple detectors serve multiple functions: they simultaneously characterize solar background noise and enable improved distance measurements. The secondary detectors at different wavelengths provide information about the spectral distribution of solar noise, which is then used to correct the primary measurement, making the system more versatile and robust.
Solution Approach 2:
The system changes the wavelength parameter by using detectors tuned to different wavelengths. This allows sampling of the solar spectrum at multiple points, enabling characterization of how solar noise varies with wavelength. This spectral information is then used to optimize the signal-to-noise ratio for the primary measurement wavelength.
3Measurement precision
If solar background noise is present, then detection sensitivity decreases, but adding wavelength diversity increases system complexity
Solution Approach 1:
The system performs preliminary measurements of solar background noise using secondary detectors before or concurrent with the primary distance measurement. By characterizing the noise spectrum in advance, the system can pre-calculate correction factors or noise models that are then applied to improve the sensitivity of the primary detection channel.
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 system improves measurement accuracy by combining signals from different wavelengths, reducing the impact of solar background noise and enhancing the signal-to-noise ratio, leading to more precise distance and property measurements of targets.
Implementation Method 1
a laser configured to emit a pulse of light including a first wavelength
Implementation Method 2
the emitted pulse of light scattered by a remote target
Implementation Method 3
The first detector is configured to detect, over a first angular region defining a first detector field of view (FOV), the emitted pulse of light scattered by a remote target
Implementation Method 4
The second detector is configured to detect, over a second angular region defining a second detector FOV, light scattered or emitted by the remote target and including a second wavelength
Implementation Method 5
determine a distance to the remote target using the light detected by the first detector
Data Source
AI summary
A multispectral lidar system includes a laser configured to emit a pulse of light including a first wavelength, scanner configured to direct the emitted pulse of light in accordance with a scan pattern, a receiver including a first detector and a second detector, and a controller. The first detector is configured to detect the emitted pulse of light scattered by a remote target, and the second detector is configured to detect light scattered or emitted by the remote target and including a second wavelength. The scanner provides, at any point in time, a fixed spatial relationship between the fields of view over which the light with the first wavelength and the second wavelength is received. A controller can determine a distance to the remote target and use this distance to modify a measurement of the property of the remote target based on the light detected by the second detector.