Diffractive Optical Element Lidar Backscan Correction
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Solution Overview
Problem
Lidar systems face challenges in detecting return light pulses during bi-directional scanning due to misalignment of the light source and detector fields of view, leading to inefficiencies in signal detection and increased noise levels, particularly from solar background noise.
Innovation Solution
Incorporating a diffractive optical element that deflects light pulses of different wavelengths by specific angles to ensure alignment of the light source and detector fields of view during forward and reverse scanning directions, allowing for precise detection of scattered light pulses within the detector's field of view.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If bi-directional scanning is implemented to increase scanning coverage and speed, then productivity is improved, but measurement precision deteriorates due to misalignment of light source and detector fields of view
Solution Approach 1:
The patent applies local quality by using different wavelengths for forward and reverse scanning light pulses. The diffractive optical element creates wavelength-dependent deflection angles, allowing the system to maintain proper field of view alignment for each scanning direction independently. This local differentiation in wavelength selection enables precise detection in both directions without compromising measurement accuracy.
Solution Approach 2:
The patent changes the wavelength parameter of light pulses based on scanning direction. By selecting a first wavelength for forward scanning and a second wavelength for reverse scanning, the system utilizes the diffractive optical element's wavelength-dependent properties to achieve proper angular deflection and field of view alignment for each direction, thereby maintaining measurement precision while enabling bi-directional scanning.
2Measurement precision
If diffractive optical element is used to correct field of view alignment, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The diffractive optical element serves multiple functions simultaneously: it deflects light pulses by wavelength-dependent angles to correct field of view misalignment, enables bi-directional scanning operation, and maintains proper alignment for both forward and reverse scanning directions. This multi-functionality reduces the need for separate alignment mechanisms for each scanning direction, thereby managing device complexity while achieving precise alignment.
3Measurement precision
If different wavelengths are used for forward and reverse scanning, then measurement precision is improved through better alignment, but loss of information increases due to wavelength separation requirements
Solution Approach 1:
The system performs preliminary wavelength selection based on the anticipated scanning direction. By pre-determining which wavelength to use (first wavelength for forward scanning, second wavelength for reverse scanning), the diffractive optical element can pre-deflect the light pulses into the correct field of view alignment before detection occurs. This preliminary action ensures proper alignment is established in advance, minimizing information loss during the detection process.
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 solution enhances the signal-to-noise ratio by ensuring optimal alignment and detection efficiency during bi-directional scanning, reducing the impact of solar noise and improving the accuracy of distance measurements in lidar systems.
Implementation Method 1
a diffractive optical element that deflects the first and second light pulses at different angles according to the respective first and second wavelengths
Data Source
AI summary
To detect return light pulses in a lidar system when scanning in the forward-scanning and reverse-scanning directions, a light source may transmit first light pulses having a first wavelength when scanning in the forward-scanning direction and may transmit second light pulses having a second wavelength when scanning in the reverse-scanning direction. A diffractive optical element (DOE) is configured to deflect the two wavelengths in opposite directions, so that light pulses are transmitted ahead of the field of view of the detector in the scanning direction of the lidar system. A controller may determine the scanning direction of a scanner in the lidar system and transmit a control signal to a light source indicative of a wavelength that corresponds to the scanning direction. The light source may then transmit light pulses at the requested wavelength.