Two-axis interferometric tracking with cascaded image dividers
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Solution Overview
Problem
Current optical tracking devices, such as those used for determining the position and trajectory of light sources, face limitations in accuracy, particularly when trying to track along two axes simultaneously, as existing solutions either increase device size and weight or fail to adequately account for achromatic effects that affect tracking precision.
Innovation Solution
A two-axis interferometric tracking device is developed, utilizing a cascade of image dividers and pairs of shearing interferometers to split and shear light into orthogonally polarized beams, which are then focused onto focal plane arrays, allowing for precise estimation of a light source's position by processing the relative intensities and phases of the resulting spots, while mitigating achromatic phase shifts through grating period and spacing differences between interferometers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If two single axis interferometric tracking devices are coupled together to achieve two-axis tracking, then tracking accuracy along two axes is improved, but device size and weight more than double
Solution Approach 1:
The patent combines two single-axis tracking functions into a single integrated device by using an optical cascade with multiple image dividers and pairs of shearing interferometers. The first pair of shearing interferometers processes light for tracking along a first axis, while the second pair processes light for tracking along a second axis perpendicular to the first. This merging approach achieves two-axis tracking capability without requiring two separate devices, thereby reducing overall device weight and size while maintaining tracking accuracy.
2Adaptability or versatility
If traditional optical tracking devices are used to track light sources of uncertain color, then tracking is possible, but achromatic effects reduce measurement precision
Solution Approach 1:
The patent addresses achromatic effects by carefully selecting and varying the grating periods and spacing between gratings in the shearing interferometers. By optimizing these parameters, the device compensates for wavelength-dependent phase shifts that occur when tracking light sources of uncertain color or across multiple light bands. This parameter optimization enables accurate angular position determination regardless of the light source's spectral characteristics, maintaining measurement precision across visible, NIR, SWIR, MWIR, and LWIR bands.
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 tracking accuracy by significantly reducing achromatic dispersion, enabling precise angle measurement with high sensitivity and linearity, and allows for effective two-axis tracking with improved performance across various light bands, including visible, NIR, SWIR, MWIR, and LWIR.
Implementation Method 1
utilizing a cascade of image dividers and pairs of shearing interferometers to split and shear light into orthogonally polarized beams
Implementation Method 2
two-axis interferometric tracking device... pairs of shearing interferometers... focused onto focal plane arrays, allowing for precise estimation of a light source's position by processing the relative intensities and phases of the resulting spots
Implementation Method 3
an optical cascade comprising a plurality of image dividers, each of the image dividers splitting incident light into a plurality of non-parallel orthogonally polarized beams
Data Source
AI summary
An interferometric tracking device including: an optical cascade comprising a plurality of image dividers, each of the image dividers splitting incident light into a plurality of non-parallel orthogonally polarized beams, the plurality of image dividers including: an incident image divider receiving light into the optical cascade; one or more intermediary image dividers optically coupled to the incident image divider; and one or more exit image dividers, each exit image divider optically coupled to one of the intermediary image dividers; a plurality of pairs of shearing interferometers, each pair of the shearing interferometers being optically coupled between optically adjacent image dividers in the optical cascade; and one or more focal plane arrays, the orthogonally polarized beams from the one or more exit image dividers being imaged onto the one or more focal plane arrays.