Solid-State Imaging Device Dummy Pixel Charge Management
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Solution Overview
Problem
CMOS type solid-state imaging devices with a dummy pixel region between an effective pixel region and an optical black pixel region experience fluctuations in power supply voltage and non-uniform black level output due to abrupt load changes during row scanning, leading to image noise and low image quality.
Innovation Solution
A solid-state imaging device with a pixel array section including an effective pixel region, an optical black pixel region, and a dummy pixel region, where the dummy pixel region's signal output path is interrupted to discharge charges to a power supply, and the row scan section selectively reads only the optical black and effective pixel regions, avoiding the dummy pixel region to prevent charge overflow and maintain uniform black levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a dummy pixel region is provided between the effective pixel region and optical black pixel region to prevent charge overflow, then charge overflow is suppressed, but power supply voltage fluctuates due to abrupt load changes during row scanning
Solution Approach 1:
The light-shielded pixel region is segmented into two distinct parts: an optical black pixel region for generating black level reference signals and a dummy pixel region for absorbing overflow charges. This segmentation allows each region to perform its specific function independently, preventing charge overflow into the optical black pixel region while maintaining stable power supply voltage during row scanning operations.
2Productivity
If the row scan section reads out signals from all pixel regions including dummy pixels, then complete signal readout is achieved, but black level uniformity deteriorates due to load fluctuations
Solution Approach 1:
The dummy pixel region is extracted from the signal readout path by configuring the row scan section to skip this region during row-by-row scanning. This extraction ensures that the dummy pixel region does not contribute to signal readout, thereby preventing load fluctuations from affecting black level uniformity in the optical black pixel region, while the optical black pixel region continues to provide accurate black level references.
3Illumination intensity
If intense light illuminates the effective pixel region near the optical black pixel region, then effective pixel signal generation is enhanced, but charge overflow occurs into the optical black pixel region
Solution Approach 1:
The dummy pixel region acts as an intermediary buffer zone positioned between the effective pixel region and the optical black pixel region. When intense light causes charge overflow in the effective pixel region, the dummy pixel region absorbs these excess charges, preventing them from reaching the optical black pixel region and thereby maintaining the integrity of black level reference signals.
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
Prevents electric charge flow from the optical black pixel region into the effective pixel region, reducing image disturbances and power supply fluctuations, resulting in improved image quality by maintaining uniform black levels and suppressing noise.
Implementation Method 1
each including a photoelectric conversion device and a transistor reading out an electric charge obtained by photoelectric conversion at the photoelectric conversion device
Data Source
AI summary
A solid-state imaging device includes: a pixel array section having an effective pixel region formed by a plurality of pixels which are disposed in the form of a matrix, each of which includes a photoelectric conversion device and a transistor reading out an electric charge obtained by photoelectric conversion at the photoelectric conversion device, and which are illuminated by light and a light-shielded pixel region formed by a plurality of pixels which are shielded from light; a row scan section selecting and controlling each row of pixels of the pixel array section to output a signal from each of the pixels of the selected row of pixels to a column signal line provided in association with the row of pixels; and an A-D conversion section converting the signal output from the signal line into a digital signal.