Laser Radar Remote Local Oscillator Thermal Stability
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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, an optical receiver, and a signal processor to estimate target distance using frequency chirped optical beams and a corner-cube configuration, along with a Fabry-Perot resonator for precise calibration, utilizing ultralow thermal expansion materials to minimize thermal drift.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional laser radar systems use traditional scanning mechanisms, then distance measurement can be achieved, but beam scan rates are limited and distance calibration drifts over time
Solution Approach 1:
The patent employs dynamic scanning mirrors that can rapidly change orientation to deflect laser beams across the target surface. The mirrors are mounted on rotational stages that enable high-speed scanning motions, allowing the system to achieve high beam scan rates while maintaining measurement accuracy through active stabilization of the optical path.
Solution Approach 2:
The system uses ultralow thermal expansion materials for the optical bench and mounting structures to minimize thermal expansion effects. By selecting materials with near-zero thermal expansion coefficients, the patent compensates for temperature variations that would otherwise cause distance calibration drift, maintaining measurement precision over time.
2Reliability
If conventional laser radar systems use standard optical components, then the system can function, but costs are great
Solution Approach 1:
The patent specifies using ultralow thermal expansion materials such as Zerodur or fused quartz for the optical bench and structural components. These materials cost more than standard aluminum or steel, but they provide superior dimensional stability that eliminates the need for expensive active thermal compensation systems or frequent recalibration, ultimately reducing total system cost while maintaining high measurement accuracy.
Solution Approach 2:
The system replaces mechanical encoder-based position sensing with optical interferometric measurement methods. This substitution eliminates the need for expensive high-precision mechanical encoders and their associated calibration systems, while providing more accurate and drift-free position measurements through non-contact optical sensing.
3Measurement precision
If the optical path is not stabilized against thermal effects, then the system is simpler, but distance calibration drifts during use
Solution Approach 1:
The patent implements passive thermal stabilization by constructing the optical path support structure from ultralow thermal expansion materials. This approach changes the thermal parameter of the support structure itself, allowing the optical path to remain stable without requiring active temperature control systems, thermal compensation mechanisms, or complex real-time calibration routines.
Solution Approach 2:
The patent describes nesting the laser source, scanning mirrors, and optical components within a thermally isolated enclosure or vacuum chamber. This nested configuration protects the sensitive optical path from external thermal fluctuations and environmental disturbances, maintaining measurement precision without requiring complex active stabilization systems.
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 enhances the accuracy and reliability of distance measurements by stabilizing the optical path and reducing thermal expansion effects, leading to improved beam focusing and precise target distance estimation.
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
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 estimated target distance for the at least one target location is 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.