Image Sensor Optical Black Array Signal Correction
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Solution Overview
Problem
Image sensors face challenges in correcting output signals to reduce vertical shading and error values such as dark currents and light leakages, which affect image quality.
Innovation Solution
Incorporating an optical black sample array adjacent to the active array, and optionally a dummy array, to compare and correct signal values, thereby subtracting storage-diode leakage currents and light leakages from the active array signals, using a circuit that generates and processes control signals to adjust pixel outputs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an optical black sample array is added adjacent to the active array for signal correction, then vertical shading and dark current errors are reduced, but device complexity and manufacturing cost increase
Solution Approach 1:
The pixel array is segmented into distinct functional regions: the active array for image capture and the optical black sample array for error measurement. This segmentation allows independent optimization of each region's function while maintaining overall system integration, enabling accurate dark current and vertical shading correction without compromising the active imaging area.
Solution Approach 2:
The optical black sample array serves as an intermediary element between the active array and the correction processing circuitry. It captures only dark current and leakage signals without optical input, providing a reference measurement that mediates the correction process. This intermediary structure enables precise error characterization that can be subtracted from active array outputs.
2Measurement precision
If signal correction processing is performed using the optical black sample array, then image quality improves, but processing time and computational resources increase
Solution Approach 1:
The optical black sample array performs preliminary measurement of dark current and leakage signals during the same exposure period as the active array. By capturing error signals in advance and simultaneously with the image data, the correction process eliminates the need for separate measurement steps, reducing overall processing time while maintaining accurate correction.
Solution Approach 2:
The correction system implements feedback by continuously comparing active array outputs with optical black sample array outputs and dynamically adjusting corrected values. This feedback mechanism enables real-time correction of vertical shading and dark current variations, improving image quality without requiring extensive post-processing computational resources.
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 effectively reduces vertical shading and error values in image sensor outputs, enhancing image quality by compensating for signal components that are not related to optical signals.
Implementation Method 1
Each of the pixels in the active array and the optical black sample array may include a photodiode
Data Source
AI summary
A pixel array includes an array of pixels to receive light, a first pixel to be blocked from receiving the light, and a circuit to adjust signals output from pixels in the array based on a signal from the first pixel. The signals output from the pixels in the array include a first error value. The circuit reduces the first error value in the signals from the pixels in the array based on the signal from the first pixel. The circuit may also reduce a second error value in the signals output from the pixels in the array based on a signal from a second pixel. The first and second pixels may be outside of the pixel array. The first and second error values may be storage diode leakage value and a dark current value.