Scanning Lidar Mirror Angle Sensor With Lens-Shift Correction
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Solution Overview
Problem
Conventional lidar systems using magnetic or optical encoders for measuring the angle of a rotatable mirror are susceptible to inaccuracies, leading to misalignment of perceived road orientation, which can cause system faults in autonomous vehicles.
Innovation Solution
An optical system with a light-emitter and detector device optically coupled by a cylindrical lens, receiving primary and secondary reflection light to determine the rotational angle of the rotatable mirror, using a double-bounce path to correct for lens displacement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If magnetic encoders are used to measure the angle of the rotatable mirror, then continuous angle data is provided, but the system becomes susceptible to shifts causing inaccurate point cloud information
Solution Approach 1:
The patent replaces the magnetic encoder (mechanical/electrical system) with an optical measurement system. The optical system uses a light emitter, cylindrical lens, and detector to measure the mirror angle optically, eliminating the susceptibility to magnetic shifts while maintaining continuous angle data provision.
Solution Approach 2:
The patent introduces an optical intermediary system between the mirror and the measurement process. The cylindrical lens acts as an intermediary that creates a reference signal through optical paths (primary and secondary reflections) to accurately determine the mirror angle without direct mechanical contact or magnetic field interaction.
2Measurement precision
If optical encoders are used to measure the angle of the rotatable mirror, then measurement accuracy is improved, but the device complexity increases
Solution Approach 1:
The optical system serves multiple functions: it provides angle measurement, creates reference signals through primary and secondary reflections, and compensates for lens displacement effects. By combining these functions into a single optical measurement system, the patent achieves high precision without proportionally increasing complexity.
Solution Approach 2:
The optical system uses the mirror's own reflective surface and geometry to generate the measurement signal. The primary and secondary reflection paths utilize the mirror's inherent optical properties, eliminating the need for separate encoding markings or complex reference structures that would increase device complexity.
3Measurement precision
If a cylindrical lens is used to optically couple the light-emitter and detector to the rotatable mirror, then lens displacement errors are corrected, but the manufacturing precision requirements increase
Solution Approach 1:
The system uses the secondary reflection path as a feedback mechanism to detect and correct for lens displacement. By comparing the primary and secondary reflection signals, the system can identify and compensate for misalignments, reducing the stringent manufacturing precision requirements for the cylindrical lens.
Solution Approach 2:
The patent employs a composite optical measurement approach combining primary and secondary reflection paths. This composite signal processing method allows the system to tolerate certain manufacturing variations in the cylindrical lens by using the combined information from both optical paths to determine the accurate mirror angle.
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
Provides accurate measurement of the rotatable mirror's orientation, enhancing the precision of point cloud information and aligning the lidar sensor's perception with other sensors in autonomous vehicles.
Implementation Method 1
a light-emitter device configured to emit emission light along an optical axis
Implementation Method 2
The light-emitter device and the detector device are optically coupled to the rotatable mirror by way of the cylindrical lens
Implementation Method 3
The detector device is configured to receive at least a portion of the reflected light and provide a reflected light signal indicative of a rotational angle
Implementation Method 4
the emission light interacts with a reflective surface of the rotatable mirror so as to provide reflected light
Data Source
AI summary
The present disclosure relates to systems and methods that provide an accurate angle measurement of a rotatable mirror. An example method includes receiving, from a detector device, a reflected light signal. The reflected light signal is indicative of primary reflection light and secondary reflection light. The primary reflection light corresponds to a first portion of emission light that reflects directly from the reflective surface of the rotatable mirror toward the detector device. The secondary reflection light corresponds to a second portion of emission light that: 1) reflects from the reflective surface of the rotatable mirror toward a secondary mirror surface; 2) reflects from the secondary mirror surface toward the reflective surface of the rotatable mirror; and 3) reflects from the reflective surface of the rotatable mirror toward the detector device. The method also includes determining, based on the reflected light signal, the rotational angle of the rotatable mirror.