Laser Radar Scan Mirrors Using Optical Resonator Feedback
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Solution Overview
Problem
Conventional laser radar systems face limitations in beam scan rates and distance calibration, which can drift over time, and are costly, necessitating improved methods for accurate and efficient distance measurement.
Innovation Solution
The implementation of a scanning reflector system with multiple reflective surfaces, a light source, and an optical receiver, utilizing frequency chirped beams and a signal processor to estimate target distances based on the difference frequency between the return and secondary beams, along with a stable optical path length defined by ultralow thermal expansion materials, to enhance measurement accuracy and reduce costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional laser radar systems use encoder-based beam scanning, then distance measurement can be performed, but beam scan rates are limited and distance calibration drifts during use
Solution Approach 1:
The patent replaces the mechanical encoder-based scanning system with an optical resonator system that uses optical feedback to maintain beam pointing stability. The resonator provides a reference optical path that is insensitive to mechanical drift, allowing high-speed scanning without calibration drift. This substitution of mechanical sensing with optical sensing resolves the contradiction between scan speed and calibration stability.
Solution Approach 2:
The patent implements a feedback mechanism using an optical resonator that continuously monitors the beam path and provides corrective feedback to maintain alignment. The resonator's high Q-factor provides stable frequency reference that compensates for drift in real-time, enabling both high scan rates and stable distance calibration without mechanical encoders.
2Reliability
If conventional laser radar systems use traditional optical components, then system functionality is achieved, but system costs are great
Solution Approach 1:
The patent changes the operating parameters of the optical system by using an optical resonator operating at high Q-factor, which allows for relaxed tolerances in other components. This parameter change enables the use of lower-cost optical components while maintaining measurement accuracy, as the resonator's frequency selectivity compensates for component variations.
Solution Approach 2:
The optical resonator serves multiple functions simultaneously: it provides frequency reference, beam pointing stability, and distance measurement calibration. This multi-functionality eliminates the need for separate calibration systems and high-precision mechanical components, reducing overall system cost while maintaining reliability.
3Measurement precision
If laser radar systems increase measurement precision, then distance accuracy improves, but system complexity and cost increase
Solution Approach 1:
The patent merges the frequency reference, beam alignment, and distance measurement functions into a single optical resonator system. This consolidation achieves high measurement precision without requiring separate complex subsystems for each function, thereby reducing overall system complexity while maintaining accuracy.
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 precise and stable distance measurements with reduced costs by using frequency chirped beams and ultralow thermal expansion materials, improving beam scan rates and minimizing calibration drift, thus enhancing the overall performance of laser radar systems.
Implementation Method 1
an optical fiber is configured to receive the measurement beam from the light source and direct to the measurement beam to the scanning reflector from a fiber end surface, and to receive the return beam at the end surface
Implementation Method 2
a corner-cube situated to receive the measurement beam from the end surface of the optical fiber. A beam focusing optic is configured to receive the measurement beam from the corner cube and focus the measurement beam at a target surface
Implementation Method 3
A beam focusing optic is configured to receive the measurement beam from the corner cube and focus the measurement beam at a target surface
Implementation Method 4
the light source is configured so that the optical measurement beam and the secondary optical beam are frequency chirped optical beams
Implementation Method 5
an optical receiver is situated to receive the return optical beam from the scanning reflector
Implementation Method 6
the signal processor is configured to provide an estimated target distance for at least one target location based on the received return optical beam and the secondary beam... based on a difference frequency associated with the received return optical beam and the secondary beam
Data Source
AI summary
Laser radar systems include a pentaprism configured to scan a measurement beam with respect to a target surface. A focusing optical assembly includes a corner cube that is used to adjust measurement beam focus. Target distance is estimated based on heterodyne frequencies between a return beam and a local oscillator beam. The local oscillator beam is configured to propagate to and from the focusing optical assembly before mixing with the return beam. In some examples, heterodyne frequencies are calibrated with respect to target distance using a Fabry-Perot interferometer having mirrors fixed to a lithium aluminosilicate glass-ceramic tube.