Top-Hat Tunable Optical Filter for Wide-Angle LiDAR Sensing
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Solution Overview
Problem
Existing tunable optical filters for LiDAR systems face limitations in acceptance angle, aperture shape, and temperature range, leading to reduced signal-to-noise ratio and maximum range due to angular shifts and temperature-induced wavelength variations.
Innovation Solution
A tunable optical filter with a top-hat pass band shape is developed, utilizing a set of stacked dielectric mirrors with actuation electrodes to maintain equal spacing between movable mirrors, providing a large area rectangular shape and high reliability over a wide temperature range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If single cavity Fabry-Perot filters are used, then large area for MEMS filters is achieved, but angular range is very limited
Solution Approach 1:
The single cavity filter is segmented into multiple cavities (first cavity between first and second mirrors, second cavity between second and third mirrors) with different optical path lengths. This segmentation allows each cavity to contribute differently to the overall spectral response, enabling both large area coverage and extended angular range through the combined effect of multiple cavities with varying characteristics.
2Manufacturing precision
If equally spaced cavities are used, then tuning on desired pass band range is obtained, but temperature drift compensation is insufficient
Solution Approach 1:
The cavities are designed with different optical path lengths rather than equal spacing, creating local variations in spectral characteristics. The first cavity has a different optical path length than the second cavity, allowing each to respond differently to temperature changes and angular variations. This local differentiation enables better temperature drift compensation while maintaining pass band tuning capability.
3Area of stationary object
If circular membrane with annular ring actuation is used, then large area is achieved, but aperture shape does not match rectangular sensor arrays
Solution Approach 1:
The membrane is designed with rectangular geometry to dynamically match the sensor array aperture shape. The actuation mechanism uses interdigitated electrodes arranged in a rectangular pattern that applies electrostatic forces across the rectangular membrane surface. This dynamic alignment between the rectangular filter aperture and rectangular sensor array ensures optimal light coupling and eliminates wasted aperture area, while the electrostatic actuation provides precise control over the membrane position.
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
The filter achieves reduced dependency on angle of incidence, stable spectral shape, high wavelength accuracy, and increased transmission, enabling precise control of plate distance and compensation for plate parallelism, thus enhancing signal-to-noise ratio and range.
Implementation Method 1
The upper mirror and the lower mirror movements are activated by means of actuation electrodes which are configured to ensure equal distancing between the upper mirror and the intermediate mirror and between the intermediate mirror and the lower mirror
Implementation Method 2
A tunable optical filter with a top-hat pass band shape is developed, utilizing a set of stacked dielectric mirrors
Implementation Method 3
a set of at least three stacked dielectric mirrors parallelly adjacent to the plane of installation of the sensor
Implementation Method 4
The suggested interferometer arrangement has both an electrically tunable interferometer and a reference interferometer on the same substrate
Data Source
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AI summary
The present application describes a tunable optical filter with a top-hat pass band shape. The proposed tunable optical filter is adapted to be installed over a top surface of a sensor, and comprises a set of at least three stacked dielectric mirrors parallelly adjacent to the plane of installation of the sensor, the at least three stacked dielectric mirrors comprise an upper mirror, an intermediate mirror and a lower mirror, wherein the set of at least three stacked mirrors is spaced within a variable distance to create at least two independent and adjacently equal volumetry cavities between the upper mirror and the intermediate mirror and between the intermediate mirror and the lower mirror.