Image Sensor Border Shading Correction via Segmented Signal Readout
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Solution Overview
Problem
Image sensors with divided vertical signal lines face challenges in high-precision correction of dark shading at the border areas due to the difficulty in placing optical black pixel regions, leading to errors from temperature distribution and offset differences.
Innovation Solution
An image capturing apparatus and method that includes a pixel area divided into columns, with output circuits and a controller for reading out signals to obtain correction data from border rows, and correction circuits to correct image signals using this data, ensuring high-precision correction of dark shading differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If optical black pixel regions are placed near AD conversion circuits for correction, then correction data can be obtained, but error from temperature distribution and offset level differences is added to correction data
Solution Approach 1:
The pixel area is divided into multiple divided areas corresponding to divided vertical signal lines. Optical black pixel regions are placed at borders between these divided areas, segmenting the correction approach to focus specifically on border region characteristics rather than using distant pixels that are affected by temperature gradients.
Solution Approach 2:
The invention applies local quality by placing optical black pixel regions specifically at border locations between divided areas rather than uniformly distributing them. This localized placement ensures that correction data is obtained from pixels that are spatially close to the border, thereby minimizing the influence of temperature distribution and offset level differences while maintaining high correction precision.
2Speed
If vertical signal lines are divided to reduce parasitic resistance and capacitance, then settling time is shortened and readout speed increases, but characteristic differences emerge at the border between divided signal lines
Solution Approach 1:
The invention performs preliminary action by obtaining correction data from optical black pixel regions at borders before actual image capture. This pre-correction approach allows the system to compensate for characteristic differences at borders in advance, ensuring uniformity across the entire image while maintaining the high readout speed enabled by divided vertical signal lines.
Solution Approach 2:
The invention implements feedback by using correction data obtained from border pixels to adjust and compensate for characteristic differences at the borders between divided vertical signal lines. This feedback mechanism ensures that while divided signal lines provide high-speed readout, the resulting characteristic differences are corrected to maintain signal uniformity across the image.
3Device complexity
If optical black pixel regions are placed far from border pixels to avoid interference, then border correction is simpler, but error from temperature distribution and offset differences is added to correction data
Solution Approach 1:
The invention segments the pixel area into divided areas with optical black pixel regions positioned at the borders. This segmentation allows correction to be performed locally at each border region using nearby pixels, simplifying the correction process while maintaining high accuracy by minimizing the distance between correction pixels and target pixels.
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 enables high-precision correction of dark shading differences at the border of divided areas, reducing errors and improving image quality by accurately accounting for column-to-column variations.
Implementation Method 1
a photodiode PD that performs photoelectric conversion on light formed by the imaging optical system 10
Data Source
AI summary
An image capturing apparatus comprises a pixel area having a plurality of pixels arranged in a matrix; output circuits that apply preset processing to signals read out in parallel from divided areas obtained by dividing the pixel area in a column direction and output the processed signals in parallel; a controller that performs control to execute first driving for reading out signals for obtaining correction data from the divided areas to the output circuits, and second driving for reading out image signals from the divided areas to the output circuits; and a correction circuit that obtains the correction data from the signals read out through the first driving and corrects the image signals using the correction data. The controller executes the first driving with respect to pixels in a part of rows that includes a row at a border of the divided areas.