Photoelectric Conversion Pixel Readout for Row Noise Uniformity
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Solution Overview
Problem
Existing photoelectric conversion devices face issues with noise variation across rows due to differing readout operations, leading to deteriorated image quality and increased readout times.
Innovation Solution
A photoelectric conversion device with a pixel array unit and control circuit that performs synchronized reset and readout operations across rows, ensuring consistent readout periods and noise conditions to minimize noise variation and maintain image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If different readout operations are performed on different rows to enable focus detection, then focus detection capability is improved, but noise levels vary across rows leading to degraded image quality
Solution Approach 1:
The pixel array is divided into two distinct regions: a first region where only the second signal (from all photoelectric conversion elements) is read out, and a second region where both the first signal (from a subset of photoelectric conversion elements) and second signal are read out. This segmentation allows different rows to serve different functions (imaging vs. focus detection) while maintaining uniform noise characteristics across all rows through consistent reset operations.
Solution Approach 2:
Different readout operations are applied to different spatial regions of the pixel array. The first region uses a simplified readout mode optimized for imaging, while the second region uses a dual-signal readout mode for focus detection. This local differentiation enables focus detection capability in specific regions without compromising the image quality in other regions, as each region's readout is optimized for its specific purpose.
2Productivity
If multiple readout operations are performed within the same period, then readout efficiency is improved, but noise variation across rows increases
Solution Approach 1:
A third reset operation is performed on rows that will undergo the second readout operation (dual signal readout) in advance, specifically in the period before their designated readout period. This preliminary reset ensures that these rows are properly initialized and experience the same reset timing as rows in the first region, thereby maintaining uniform noise characteristics across all rows despite the different readout operations.
Solution Approach 2:
The pixel array operates in periodic cycles where each period includes reset operations and readout operations for different regions. The timing of reset operations is carefully synchronized with readout operations across multiple periods, ensuring that all rows experience resets at appropriate intervals regardless of which readout mode they use, thereby maintaining noise consistency while achieving efficient periodic readout of all regions.
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 suppresses noise variation across rows, maintaining image quality while controlling readout times, thereby improving focus detection signal acquisition efficiency.
Implementation Method 1
a pixel array unit in which a plurality of pixels each including a plurality of photoelectric conversion elements are arranged
Data Source
AI summary
A photoelectric conversion device includes pixels each including a plurality of photoelectric conversion elements and arranged in a matrix, and a control circuit that controls the pixels on row-by-row. Each pixel may output a first signal corresponding to charge generated by the first photoelectric conversion element and a second signal corresponding to charge generated by the first and second photoelectric conversion elements. The control circuit performs a first reset operation and a first readout operation for reading out the second signal on pixels in a first row, and performs a second reset operation, a second readout operation for reading out the first signal, and a third readout operation for reading out the second signal on pixels in a second row. The control circuit performs a third reset operation on pixels of any one of rows in a period one before a period during which the second reset operation is performed.