Staring Focal Plane Sensor Dynamic Range Equalization
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Solution Overview
Problem
Staring focal plane sensors face challenges in imaging large dynamic range scenes due to issues like overexposure, underexposure, and poor sensitivity, particularly in regions with varying signal levels, leading to suboptimal image quality and inefficient digitization.
Innovation Solution
The implementation of a focal plane sensor architecture with multiple integration wells and a control circuit that samples sensor pixels at different integration times to equalize signal-to-noise ratios, allowing for digital transformation and unscaling to maintain optimal sensitivity across all pixels, thereby improving image quality and simplifying digitization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single integration time is used for all sensor pixels, then the device complexity is reduced, but the image quality deteriorates due to overexposure or underexposure in different scene regions
Solution Approach 1:
The sensor divides the scene into multiple dynamic range regions using multiple integration wells (first and second integration wells) for each sensor pixel. Each well captures photons during different integration times, segmenting the capture process to handle varying brightness levels across the scene without requiring complex per-pixel control circuitry.
Solution Approach 2:
The sensor dynamically switches between different integration times by alternating between the first and second integration wells. The control circuit selects which well to read out based on the scene's dynamic range requirements, allowing the system to adapt its integration time dynamically while maintaining a relatively simple static architecture.
2Manufacturing precision
If multiple images are captured at different exposures to image high dynamic range scenes, then the image quality improves, but the productivity decreases due to increased time requirements
Solution Approach 1:
The sensor merges multiple exposure captures into a single frame by simultaneously accumulating photons in both the first and second integration wells during the same frame period. The control circuit then selects and combines the appropriate well data to produce a single high dynamic range image, eliminating the need for multiple separate frame captures.
Solution Approach 2:
The dual integration well architecture maintains continuous photon accumulation in both wells simultaneously during each frame period. This allows the sensor to capture both short and long exposure data in parallel without interrupting the imaging process, maintaining high frame rates while achieving high dynamic range coverage.
3Manufacturing precision
If multiple images are combined to achieve high dynamic range imaging, then the image quality improves, but the device complexity increases due to registration requirements
Solution Approach 1:
The sensor segments the high dynamic range capture into distinct spatial regions corresponding to different integration times. By using multiple integration wells that capture different exposure lengths simultaneously, the system naturally separates the dynamic range information by integration time rather than requiring post-capture software registration of multiple frames.
Solution Approach 2:
The sensor creates parallel copies of the same scene capture in different integration wells with different integration times. These copies are then selected and combined by the control circuit based on the scene's dynamic range characteristics, eliminating the need for complex software-based image registration and blending algorithms.
4Ease of operation
If the integration time is adjusted globally to optimize average scene brightness, then the ease of operation is improved, but the measurement precision deteriorates in overexposed or underexposed regions
Solution Approach 1:
The sensor applies different integration times to different spatial regions of the scene by selecting between the first and second integration wells based on local brightness characteristics. The control circuit identifies overexposed and underexposed regions and applies appropriate integration time selections locally, maintaining optimal signal-to-noise ratios across varying scene brightness without complex global adjustments.
Solution Approach 2:
The system dynamically adjusts the effective integration time on a per-pixel or per-region basis by selecting between the two integration wells based on real-time scene analysis. This dynamic adaptation maintains optimal measurement precision across different brightness regions while keeping the control mechanism relatively simple through automated well selection.
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 ensures that all sensor pixels have approximately equalized signal-to-noise ratios, enhancing image quality and simplifying the digitization process, even in scenes with extreme brightness variations, while maintaining efficient operation and frame capture rates.
Implementation Method 1
each sensor pixel includes a photodetector and readout circuit which can be made from the same semiconductor material
Data Source
AI summary
A focal plane staring sensor is provided that includes an M×N sensor, where M is a number of rows of sensor pixels in the sensor and N is a number of columns of sensor pixels in the sensor, where M and N are integers greater than one. A control circuit samples in each sensor pixel value for each sensor pixel of the M×N sensor at a plurality of different integration times corresponding to an amount of time that a photonic charge can be acquired in each sensor pixel of the M×N sensor, wherein the control circuit selects in each sensor pixel one sample from a set of samples to generate a scaled value to facilitate an equalization of a signal to noise ratio between the sensor pixels.