Global Shutter Sensor Parasitic Light Compensation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional CMOS sensors suffer from parasitic light sensitivity, leading to brightness nonuniformity in images due to the light sensitivity of floating diffusion, where charges are stored for varying times across pixel rows, causing gradient issues in images.
Innovation Solution
A global shutter sensor calculates parasitic light sensitivity using time-based or spatial-based methods to determine gains and exposure periods for different pixel regions, adjusting these parameters to compensate for brightness nonuniformity by acquiring image frames with varying exposure periods and processing pixel data to calculate compensation values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If charges are stored at the floating diffusion for varying times across pixel rows, then the global shutter function is achieved, but brightness nonuniformity and gradient issues occur due to parasitic light sensitivity
Solution Approach 1:
The patent applies local quality by dividing the pixel array into multiple pixel groups (e.g., first pixel group, second pixel group) with different storage times. Each pixel group is assigned a specific storage time based on its position, creating localized variations in exposure characteristics. This allows the system to maintain global shutter functionality while compensating for parasitic light sensitivity effects in different regions of the sensor.
2Productivity
If different storage times are used for different pixel rows, then readout sequentiality is improved, but parasitic light sensitivity causes gradient artifacts in the image
Solution Approach 1:
The patent implements parameter changes by systematically varying the storage time parameter across different pixel groups. The processor determines specific storage times for each pixel group based on their positional characteristics, creating a controlled parameter variation scheme. This allows optimization of readout efficiency while preventing the harmful gradient artifacts that would result from uniform storage time assignment.
Solution Approach 2:
The patent employs feedback mechanisms where the processor analyzes the relationship between pixel group positions and parasitic light sensitivity effects, then uses this information to determine optimal storage times for each group. This feedback loop enables the system to adapt storage time assignments to minimize gradient artifacts while maintaining efficient readout performance.
3Device complexity
If uniform exposure periods are used across all pixels, then simplicity is maintained, but brightness nonuniformity cannot be compensated
Solution Approach 1:
The patent applies segmentation by dividing the pixel array into distinct pixel groups, where each group can be assigned different exposure periods. This segmentation strategy allows the system to move from a simple uniform exposure approach to a differentiated exposure scheme that compensates for brightness nonuniformity. The processor manages these segmented groups efficiently, maintaining reasonable system complexity while achieving improved image quality.
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
The solution effectively compensates for parasitic light sensitivity, achieving uniform image brightness across pixel regions by adjusting gains and exposure periods, thereby improving image uniformity.
Implementation Method 1
The pixel array has a first pixel region and a second pixel region. The pixel array acquires a first image frame and a second image frame respectively using a first exposure period and a second exposure period
Data Source
AI summary
There is provided a global shutter sensor including a pixel array and a processor. The pixel array acquires first pixel data corresponding to a first exposure period and second pixel data corresponding to a second exposure period of different pixel regions using time division or spatial division, wherein the first exposure period is shorter than the second exposure period. The processor calculates a difference between (the second exposure period/the first exposure period)×the first pixel data and the second pixel data to obtain parasitic light sensitivity of the different pixel regions, and determines gains and/or exposure periods corresponding to the different pixel regions to compensate the parasitic light sensitivity.