Pixel-Wise Dark Current Estimation for Shutterless Uncooled Sensors
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Solution Overview
Problem
Existing methods for estimating dark current patterns in shutterless uncooled cameras are not robust and generic, particularly in applications where temperature cannot be controlled and there is no mechanical shutter, leading to inaccurate image correction.
Innovation Solution
A method that estimates dark current patterns for each pixel of a 2D sensor by characterizing each pixel independently as a function of exposure time and temperature, using a pseudo-empirical model based on regressions and interpolations, specifically employing spline interpolation to predict dark current rates and offsets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a mechanical shutter is used to capture dark reference images, then dark current pattern estimation accuracy is improved, but device complexity and power consumption increase
Solution Approach 1:
The patent extracts the dark current pattern information from the imaging sensor itself by analyzing the relationship between pixel values, exposure time, and temperature. Instead of requiring a separate mechanical shutter system to capture dark reference images, the method extracts dark current characteristics directly from the sensor data through mathematical modeling, thereby eliminating the need for complex mechanical shutter mechanisms.
Solution Approach 2:
The patent replaces the mechanical shutter system with a computational approach. By using regression analysis and mathematical models to estimate dark current patterns based on temperature and exposure time relationships, the invention substitutes physical mechanical components with software-based algorithms, reducing device complexity and power consumption while maintaining estimation accuracy.
2Stability of the object's composition
If temperature control is implemented, then dark current pattern stability is improved, but power consumption and device complexity increase
Solution Approach 1:
The patent performs preliminary characterization of the sensor's dark current behavior across different temperature and exposure time conditions during the manufacturing or calibration phase. This pre-acquired data is stored and used to create predictive models that can estimate dark current patterns under varying conditions without requiring active temperature control during operation, thereby reducing power consumption while maintaining stability.
Solution Approach 2:
The patent changes the approach from controlling temperature physically to modeling the temperature effect mathematically. By using regression models that capture the relationship between temperature, exposure time, and dark current, the system can predict dark current patterns at different temperatures without actually controlling the temperature, thus eliminating the need for power-consuming temperature control mechanisms.
3Measurement precision
If dark reference images are captured just before each image of interest, then dark current estimation accuracy is improved, but acquisition time and productivity decrease
Solution Approach 1:
The patent performs preliminary characterization of dark current behavior across multiple temperature and exposure time combinations during an initial calibration phase. This pre-acquired data is stored in a database or lookup table, allowing the system to quickly retrieve or interpolate dark current patterns during actual imaging operations without requiring time-consuming dark reference captures before each image, thereby maintaining accuracy while improving acquisition speed.
Solution Approach 2:
The patent performs more comprehensive dark current characterization during the initial calibration phase than would be needed for a single imaging operation, collecting data across a wide range of temperatures and exposure times. This excessive preliminary action creates a rich dataset that enables fast interpolation and estimation during operation, trading initial calibration time for significantly faster subsequent image acquisition.
4Ease of manufacture
If existing dark current estimation methods are used, then implementation simplicity is improved, but robustness and generality worsen
Solution Approach 1:
The patent segments the dark current estimation problem into distinct components: temperature-dependent effects, exposure time-dependent effects, and their interaction. By using separate regression models for each factor and combining them systematically, the method achieves both robustness across different conditions and implementation simplicity through modular, standardized calculation steps that can be easily programmed and adapted to different sensor types.
Data Source
AI summary
A dark current pattern estimation method of a 2D sensor for a shutterless uncooled camera is provided. The 2D sensor includes a matrix of pixels (x, y). The dark current pattern is divided into rate and offset. The method includes the steps of setting a new temperature, waiting for the new temperature to stabilize, acquiring averaged images at at least two texp, alternatively and continuously, obtaining from each averaged image a dark current offset and a dark current rate for each pixel, interpolating the dark current offsets obtained for each pixel, interpolating the dark current rate obtained for each pixel, and obtaining the dark current pattern in terms of temperature, exposure time and pixel position.