FMCW LIDAR Dispersion Compensation via Micro-Structured Oscillator
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Solution Overview
Problem
In frequency-modulated continuous-wave (FMCW) LIDAR systems, the changing wavelength of the FMCW beam due to the continuous scanning motion of the MEMS mirror causes dispersion, resulting in all wavelengths not being directed at the same point on a target, disrupting the measurement principle.
Innovation Solution
An oscillator system with a transmitter that transmits a frequency-modulated continuous wave light beam and an oscillator structure that oscillates based on a deflection angle, combined with a dispersive element to compensate for the propagation direction disturbance, ensuring each wavelength is directed at the same point by synchronizing the wavelength with the deflection angle and using a micro-structured reflective surface to align wavelengths correctly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If continuous scanning motion of the MEMS mirror is used to illuminate the scene, then the field of view can be continuously scanned and objects can be detected, but the changing wavelength of the FMCW beam causes dispersion and propagation direction disturbance, resulting in all wavelengths not being directed at the same point on the target
Solution Approach 1:
The patent applies preliminary action by synchronizing the wavelength modulation of the FMCW beam with the deflection angle of the MEMS mirror before the light reaches the target. The controller pre-coordinates the wavelength ramps with the mirror oscillation, ensuring that each wavelength is directed at the correct point on the target despite the continuous scanning motion. This preemptive synchronization prevents dispersion and maintains measurement accuracy throughout the scanning process.
2Measurement precision
If the wavelength of the FMCW beam continuously varies over time, then frequency modulation can be implemented for distance measurement, but the propagation direction becomes wavelength-dependent, disrupting the FMCW measurement principle
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the relationship between wavelength and deflection angle through synchronized modulation. The controller modifies the wavelength parameter of the FMCW beam in coordination with the mechanical deflection angle parameter of the MEMS mirror. This coordinated parameter change ensures that the propagation direction remains consistent across different wavelengths, maintaining the integrity of the FMCW measurement principle while enabling continuous frequency modulation for distance measurement.
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 effectively compensates for the dispersion effect, allowing all wavelengths of the FMCW light beam to be directed at the same point, thereby maintaining the integrity of the FMCW measurement principle and enabling accurate distance and depth mapping.
Implementation Method 1
a dispersive element arranged in the transmission path and configured to receive the FMCW light beam and output a compensated FMCW light beam along the transmission path, wherein the dispersive element is configured to compensate for a propagation direction disturbance caused by an oscillation of the oscillator structure
Implementation Method 2
the reflective surface is a micro-structured surface configured to compensate for a propagation direction disturbance caused by an oscillation of the oscillator structure such that each wavelength of a corresponding wavelength ramp of the FMCW light beam is reflected by the reflective surface in a same direction along transmission path
Data Source
AI summary
An oscillator system includes a transmitter configured to transmit a frequency modulated continuous wave (FMCW) light beam along a transmission path, where the FMCW light beam comprises a plurality of wavelength ramps and a wavelength of the FMCW light beam continuously varies over time; and an oscillator structure configured to oscillate about a scanning axis based on a deflection angle of the oscillator structure that continuously varies over time. The oscillator structure is arranged in the transmission path and is configured to receive the FMCW light beam at a reflective surface. The reflective surface is a micro-structured surface configured to compensate for a propagation direction disturbance caused by an oscillation of the oscillator structure such that each wavelength of a corresponding wavelength ramp of the FMCW light beam is reflected by the reflective surface in a same direction along transmission path.