Solid-State Image Pickup Signal Processing Reference Voltage Adjustment
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Solid-state image pickup apparatuses face challenges in expanding the AD convertible input voltage range due to fluctuations in reset levels among pixels and temperature variations, leading to reduced noise removal efficiency and increased power consumption.
Innovation Solution
A method involving a pixel array with a driving section that reads out signals twice, using the first signal as a reference voltage to adjust the input voltage range for signal processing, ensuring both signals are within the processable range, thereby reducing the impact of pixel dispersion and parasitic capacitance fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the reset level is used as reference voltage for AD conversion, then noise removal efficiency is improved, but the input voltage range becomes insufficient due to pixel dispersion and temperature variations
Solution Approach 1:
The reference voltage is made dynamic by reading it immediately before each signal level from the same pixel, rather than using a fixed predetermined voltage. This allows the reference voltage to adapt to pixel-specific characteristics and temperature variations, ensuring the input voltage range is sufficient for each conversion while maintaining noise removal efficiency through correlation double sampling.
Solution Approach 2:
The reset level is read out in advance immediately before the signal level from the same pixel, preparing the reference voltage beforehand. This preliminary action ensures that the reference voltage is available and appropriate for the subsequent AD conversion, addressing both the noise removal requirement and the input voltage range limitation.
2Device complexity
If a predetermined reference voltage is used for AD conversion, then device complexity is reduced, but power consumption increases due to larger input voltage range margin requirements
Solution Approach 1:
Each pixel serves itself by providing its own reset level as the reference voltage for its subsequent signal conversion. This self-service approach eliminates the need for complex external reference voltage generation circuits while optimizing power consumption by using the actual pixel characteristics rather than requiring larger voltage margins.
3Manufacturing precision
If the reset level fluctuates due to pixel dispersion and temperature variations, then manufacturing precision is maintained, but reliability of AD conversion decreases
Solution Approach 1:
Instead of using a uniform predetermined reference voltage for all pixels, each pixel uses its own locally-specific reset level as the reference voltage. This local quality approach accounts for pixel dispersion and temperature variations in each individual pixel, ensuring reliable AD conversion while maintaining manufacturing precision requirements.
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 eliminates differences in in-plane characteristic fluctuations and offset components, reducing the necessary input voltage range margin and lowering power consumption by ensuring accurate signal processing across varying conditions.
Implementation Method 1
a photodiode 41 as a photoelectric conversion section
Data Source
AI summary
A solid-state imaging device includes a pixel array section that has at least one pixel with a photoelectric conversion unit and a charge detection unit. A driving section is configured to read out a signal of the pixel, a first portion of said signal being based on signal charge, a second portion of said signal being based on a reset potential. A signal processing section is configured to read out the first portion of the signal as a reference voltage, with the reference voltage being adjusted to cause the first and second portions of the signal to be within an input voltage range.