CMOS Image Sensor Readout Circuit Compensation for Pixel Signal Deviations
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Solution Overview
Problem
Image sensing devices, particularly CMOS image sensors, face deterioration in characteristics due to readout deviations among pixel signals, which affect the accuracy and reliability of image capture.
Innovation Solution
The implementation of readout circuits with compensators that apply predetermined resistance values in readout lines to directly or inversely compensate for readout deviations, utilizing non-salicide poly resistors or metal resistors to adjust resistance values based on the distance from power source supplying circuits, thereby reducing or increasing readout deviations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If pixel signals are read out from the pixel array, then image capture is enabled, but readout deviations occur among pixel signals causing deterioration in characteristics
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing compensation values for each readout line in a compensation value storage unit. These compensation values are determined in advance based on the characteristics of each readout line, so that when pixel signals are read out, the appropriate compensation can be immediately applied to correct readout deviations without affecting the image capture process.
Solution Approach 2:
The patent employs parameter changes by adjusting the compensation values stored for each readout line based on varying conditions such as temperature, voltage, and process variations. The compensation values are not fixed but are modified according to the actual operating conditions to optimally correct readout deviations under different scenarios, thereby maintaining high reliability during image capture.
2Reliability
If compensation values are stored for each readout line, then readout deviations are corrected, but device complexity increases
Solution Approach 1:
The patent applies local quality by assigning specific compensation values to each individual readout line based on its unique characteristics. Rather than using a uniform compensation approach for all readout lines, the system tailors the compensation values to the specific needs of each line, which improves correction effectiveness while allowing the complexity to be distributed and managed locally for each readout line.
3Measurement precision
If resistance values are adjusted to compensate for readout deviations, then accuracy is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent applies preliminary action by pre-determining and storing compensation values that account for manufacturing variations. Instead of requiring precise resistance control during manufacturing, the system measures and stores compensation values in advance that capture the actual characteristics of each readout line, thereby compensating for manufacturing imprecisions during operation rather than during fabrication.
Solution Approach 2:
The patent employs self-service by having the system automatically measure, store, and apply compensation values without requiring external calibration or adjustment. The image sensing device itself performs the compensation by using its internal compensation value storage unit to automatically correct readout deviations, eliminating the need for external precision adjustment mechanisms.
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 alleviates readout deviations among pixel signals, improving the operational reliability and accuracy of image sensing devices by fine-tuning resistance values under control signals, and compensating for variations in process, voltage, and temperature.
Implementation Method 1
a plurality of compensators coupled to the plurality of readout lines, and suitable for applying respective predetermined resistance values in the plurality of readout lines
Data Source
AI summary
An image sensing device includes a pixel array including a plurality of pixels arranged in rows and columns, and suitable for outputting a plurality of pixel signals, and a plurality of readout circuits coupled to the pixel array, and suitable for compensating for readout deviations among the plurality of pixel signals when reading out the plurality of pixel signals.