Image Sensor Gain Correction Without Dummy Pixels
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Solution Overview
Problem
Image sensors with divided vertical signal lines face gain differences and temperature fluctuations due to coupling capacitances, leading to noticeable characteristic differences at the border of divided pixel areas, making precise correction challenging, especially when trying to place a dummy pixel area near the border.
Innovation Solution
An image capturing apparatus and method that corrects gain differences between pixel columns at the border of divided areas without using a dummy pixel area, by generating gain data based on predetermined voltages and applying it to output circuits for each divided area, using pixels at the border as reference nodes for correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If vertical signal lines are divided to increase readout speed, then readout speed is improved, but gain differences and characteristic differences occur at the border of divided areas
Solution Approach 1:
The pixel area is divided into multiple divided areas corresponding to the divided vertical signal lines, allowing parallel readout from each area. This segmentation enables high-speed readout while the correction circuit compensates for the resulting gain differences between segments.
Solution Approach 2:
The correction circuit changes the gain parameter of signals from different divided areas by applying correction values. This parameter adjustment compensates for gain differences caused by coupling capacitances at the borders of divided vertical signal lines, restoring signal uniformity.
2Measurement precision
If a dummy pixel area is placed near the border of divided vertical signal lines to detect gain differences, then correction precision is improved, but device complexity and difficulty of placement increase
Solution Approach 1:
Pixels at the border of divided areas serve dual purposes: they are both regular image-sensing pixels and reference pixels for detecting gain differences. This self-service approach eliminates the need for separate dummy pixel areas while maintaining correction precision.
Solution Approach 2:
Border pixels perform multiple functions simultaneously: image signal generation and gain difference detection. This multi-functionality removes the need for dedicated dummy pixels, simplifying the device structure while achieving precise correction.
3Reliability
If dummy pixel area is used for correction, then correction capability is provided, but area occupancy and device complexity increase
Solution Approach 1:
Regular pixels at the border of divided areas perform the correction function without requiring separate dummy pixel structures. This self-service mechanism maintains full correction capability while utilizing existing pixel areas efficiently.
Solution Approach 2:
Border pixels serve both as image-sensing elements and as reference elements for correction, eliminating the need for dedicated dummy pixel areas. This universal usage of pixels maintains reliability while reducing area occupancy.
Data Source
AI summary
In an image capturing apparatus that comprises a pixel area of pixels arranged in a matrix, output circuits 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, a controller performs control to execute first driving for reading out signals corresponding to a predetermined voltage to the output circuits, and second driving for reading out image signals from the pixel area, and a correction circuit generates gain data based on the predetermined voltage for correcting differences between the signals for correction of different columns output for each of the divided areas, and corrects the image signals of the divided areas using the gain data generated for the corresponding divided areas.