Electronic Imaging Dark Floor Correction
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Solution Overview
Problem
Existing methods for removing dark signal noise from electronic imaging systems either introduce additional noise or fail to account for regional temperature variations and defective pixels, leading to suboptimal image processing.
Innovation Solution
A method that combines a contemporaneously captured dark frame with a calibrated dark floor, using a defective pixel map to adjust and refine the dark floor, allowing for improved noise reduction and pixel correction, and dynamically updating the defective pixel map based on new data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a contemporary dark frame is captured and subtracted to remove dark signal, then the base level dark signal is removed, but noise in the dark frame adds to the noise in the final processed image
Solution Approach 1:
The patent combines a contemporary dark frame (captured at the same time as the image) with a pre-acquired dark frame (captured under similar conditions but at a different time) to create an adjusted dark frame. This merged approach leverages the temporal proximity of the contemporary dark frame for accuracy while using the pre-acquired dark frame to average out noise, thereby removing dark signal without significantly increasing noise in the final image.
2Measurement precision
If a contemporary dark frame is captured with the same exposure time as the actual image, then accurate dark signal removal is achieved, but the total capture time is doubled
Solution Approach 1:
The patent performs preliminary acquisition of a dark frame under representative conditions before actual image capture. This pre-acquired dark frame is then combined with a brief contemporary dark frame (which requires minimal exposure time) to create an adjusted dark frame. This approach achieves accurate dark signal removal without requiring a full-length contemporary dark frame capture, thereby significantly reducing the total capture time.
3Loss of time
If a baseline dark floor is used from calibration, then noise is reduced and capture time is shortened, but regional temperature variations and defective pixels are not accounted for
Solution Approach 1:
The patent uses the contemporary dark frame (captured at the same time as the image) to provide feedback about current environmental conditions such as temperature and defective pixel states. This feedback is used to adjust the pre-acquired baseline dark floor, creating an adjusted dark frame that reflects current conditions. This feedback mechanism allows the system to maintain the time efficiency of using a pre-acquired baseline while improving accuracy by accounting for regional temperature variations and defective pixels.
Data Source
AI summary
An electronic imaging system includes a method for calibrating an image sensor having a array of pixels each used in capturing an image, the method comprising the steps of capturing first dark floor values at a first time from substantially all of the pixels in the array, storing the first dark floor values, capturing second dark floor values at a second time from substantially all of the pixels in the array, using the first and second dark floor values to compute third dark floor values, using the third dark floor values when processing the captured image.