Sparse Focal Plane Array Scanning for Nyquist Sampling
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Solution Overview
Problem
Existing passive millimeter wave camera systems face challenges in generating a complete image without gaps when removing columns of receivers from a fully populated focal plane array, and in reducing noise and improving integration time for image capture.
Innovation Solution
The strategic positioning and staggering of receiver columns in the focal plane array, combined with a scanning reflector that moves the image across the array, allows for Nyquist sampling and cross-calibration, enabling the generation of a complete image even with sparse receiver populations and optimizing integration times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If columns of receivers are removed from a fully populated focal plane array to reduce costs, then the number of receivers is reduced, but gaps appear in the generated image
Solution Approach 1:
The patent introduces temporal dimension by scanning the image across the sparsely populated FPA over time. The scanning reflector moves the image in a scanning pattern, allowing receivers to capture different spatial positions at different time instances. This transforms a 2D spatial sampling problem into a 3D problem (2D space + 1D time), enabling complete image reconstruction from fewer receivers through time-multiplexed sampling.
Solution Approach 2:
The patent performs preliminary positioning of the image relative to the sparse receiver array using the scanning reflector before actual detection. By pre-positioning and scanning the image across the receiver fields of view, the system ensures that all necessary spatial information passes through the limited receiver positions, enabling complete image synthesis during the scanning process.
2Reliability
If a sparsely populated focal plane array is used to reduce noise and improve integration time, then the number of receivers is reduced, but the ability to generate a complete image without gaps is compromised
Solution Approach 1:
The scanning reflector implements periodic scanning motion across the FPA, systematically moving the image through different positions relative to the sparse receiver array. This periodic action ensures that over one complete scan cycle, all spatial regions are sampled by the receivers, enabling reconstruction of a complete image while maintaining the noise reduction benefits of having fewer receivers with longer integration times.
Solution Approach 2:
The patent transforms the static sparse FPA into a dynamic imaging system through the scanning reflector. The relative motion between the image and the sparse receiver array creates temporal variation in the sampling pattern, allowing the system to synthesize a complete image from incomplete spatial samples by exploiting the temporal dynamics of the scanning process.
3Measurement precision
If receivers are staggered and positioned strategically to achieve Nyquist sampling, then image quality is maintained, but the array configuration becomes more complex
Solution Approach 1:
The patent employs asymmetric positioning of receiver columns with different stagger offsets. Specifically, odd-numbered columns are offset by one amount while even-numbered columns are offset by a different amount, creating an asymmetric pattern that achieves Nyquist sampling. This asymmetric configuration is simpler than fully populated arrays while maintaining image quality through the systematic staggered arrangement.
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 allows for the creation of a complete image without gaps, reduces noise through increased integration time, and maintains image quality and resolution while reducing the number of receivers, thereby lowering costs.
Implementation Method 1
a scanning reflector configured to move, thereby moving an image of the scene across the FPA transverse to the receiver columns
Data Source
AI summary
An apparatus includes: a focal plane array (FPA) of receivers for a passive millimeter wave camera, the FPA comprising: receivers configured to sample an image, the image comprising one or more regions, the receivers arranged in an array of dimensions m rows by n columns, and a scanning reflector configured to move, thereby moving an image of the scene across the FPA transverse to the receiver columns.