Optical Interferometer Emitter Layout for Path Length Compensation
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Solution Overview
Problem
The conventional optical interferometer systems in LIDAR systems suffer from errors in velocity measurements due to differing path lengths of reflected and reference optical signals caused by the tilted surfaces of the Fabry-Perot etalon, leading to inaccurate velocity projections.
Innovation Solution
The implementation of a ferrule with pairs of optical emitters, where each reflected signal emitter is paired with a reference signal emitter, positioned symmetrically around an axis to minimize path length differences and reduce errors, and the use of symmetrical cross-sections to avoid overlap of interference patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the Fabry-Perot etalon uses tilted input and output surfaces to diminish undesired optical effects, then optical quality is improved, but path length differences between reflected and reference signals cause measurement errors
Solution Approach 1:
The patent introduces asymmetrical path length compensation by positioning the reference signal emitter at a different location than the reflected signal emitter. The reference signal travels a longer path through the Fabry-Perot etalon to compensate for the shorter path of the reflected signal, thereby equalizing the optical paths and eliminating measurement errors while maintaining the beneficial tilted surfaces for optical quality.
Solution Approach 2:
The patent changes the positional parameter of the reference signal emitter within the ferrule to adjust the reference signal's path length. By varying the emitter's location, the system compensates for path length differences caused by the tilted etalon surfaces, maintaining velocity measurement accuracy without altering the etalon's optimized optical geometry.
2Adaptability or versatility
If multiple optical signals are emitted from different locations on the ferrule, then velocity vector determination is enabled, but path length differences cause erroneous velocity projections
Solution Approach 1:
The patent applies local quality by assigning different positional characteristics to different emitters within the ferrule. Each emitter is strategically positioned to achieve the desired path length for its specific function (reference vs. reflected signals), allowing multi-directional velocity measurement while maintaining accuracy through localized path optimization.
3Loss of information
If the reference optical signal and reflected optical signal are projected from different locations on the ferrule, then separate interference patterns are generated, but path length differences lead to calculation errors
Solution Approach 1:
The patent uses the reference signal as an optical copy that replicates the properties of the reflected signal but with a compensated path length. By creating this reference copy from a strategically positioned emitter, the system can compare the two signals to determine velocity while correcting for path length differences introduced by the tilted etalon surfaces.
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 reduces errors in velocity measurements by ensuring consistent path lengths for reflected and reference signals, thereby enhancing the accuracy of LIDAR system velocity calculations.
Implementation Method 1
the Fabry-Perot etalon output optical signal generates a desired interference pattern which is emitted as the output optical signal
Implementation Method 2
a Fabry-Perot etalon which includes first and second optically clear components which are separated, e.g., by free space
Data Source
AI summary
Techniques are provided for symmetrically locating optical emitters in a surface of a ferrule. Such symmetrical displacement of each pair of optical emitters diminishes differences in path lengths through which optical signals propagate in an optical interferometer with tilted input and/or output surfaces.