Photoelectric Conversion Amplifier Gain Equalization for DSNU Reduction
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Solution Overview
Problem
High-speed photoelectric conversion apparatuses suffer from Dark-Signal-Non-Uniformity (DSNU) due to noise differences between color signals caused by varying amplifier gains, leading to stairway-shaped waveform distortions during dark signal readout.
Innovation Solution
A photoelectric conversion apparatus with a color selecting switch and amplifier circuits that amplify pixel signals and reference voltages at different gains for each color filter, using feedback capacitors to control gains and reduce noise correlation between color selecting and reference voltage switches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the gain of the amplifier unit is switched in accordance with the color to read out color signals, then the photoelectric conversion apparatus can operate at high speed with light weight capacitors, but noise differences occur between color signals due to charge injection and clock feed through in the color selecting switch, causing stairway-shaped waveform distortion and deteriorating DSNU
Solution Approach 1:
A compensation signal generating unit is introduced as an intermediary component that generates compensation signals corresponding to the noise components (charge injection and clock feed through) produced by the color selecting switch. These compensation signals are then added to the pixel signals to cancel out the noise, thereby resolving the DSNU deterioration caused by the high-speed color signal reading process
Solution Approach 2:
The system implements a feedback mechanism where the compensation signal generating unit creates signals that are specifically tailored to counteract the noise introduced during the color selection process. The compensation signals are generated based on the operational state of the color selecting switch and are fed back to the output to neutralize the harmful noise effects, thus maintaining signal quality during high-speed operation
2Adaptability or versatility
If different gains are applied to pixel signals of different colors, then each color signal can be optimized for its specific characteristics, but the noise levels differ between color signals, creating waveform distortion during dark signal readout
Solution Approach 1:
The patent applies different gains to amplifier units corresponding to different color signals (R, G, B) to optimize each color's specific characteristics. Each amplifier unit has its gain independently adjusted according to the requirements of its corresponding color channel, allowing localized optimization while maintaining overall system performance
Solution Approach 2:
The compensation signal generating unit acts as an intermediary that produces correction signals specifically designed to offset the noise differences created by the varying gains. These compensation signals are added to each color channel to equalize the noise levels, thereby maintaining signal level uniformity across all colors during dark signal readout
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 reduces noise differences between color signals, minimizing DSNU and achieving improved waveform stability during dark signal readout by equalizing gains across amplifier circuits.
Implementation Method 1
a photodiode PD performs photoelectric conversion to generate a pixel signal
Data Source
AI summary
A photoelectric conversion apparatus has: a plurality of pixels having mutually different color filters, and generating pixel signals by a photoelectric conversion; a color selecting switch for selecting the pixel signals generated by the plurality of pixels having mutually different color filters; a first amplifier circuit for amplifying at mutually different gains the pixel signals generated by the pixels having mutually different color filters and selected by the color selecting switch; a reference voltage connecting switch for selecting a reference voltage; and a second amplifier circuit for amplifying at mutually different gains the reference voltages correspondingly to the pixel signals of mutually different colors.