Photoelectric Conversion Device Parallel AD Conversion
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Solution Overview
Problem
Existing photoelectric conversion devices face challenges in speeding up signal processing due to the need for separate analog-to-digital (AD) conversion for each photodiode, resulting in prolonged operation times and increased complexity.
Innovation Solution
A photoelectric conversion device with a cell array and clamping units that allow simultaneous AD conversion of signals from multiple photodiodes by clamping one signal at a reference level, enabling faster processing through intra-cell amplification and column AD conversion units.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If separate AD conversion is performed for each photodiode, then measurement precision is maintained, but operation time increases and productivity decreases
Solution Approach 1:
The pixel array is divided into multiple pixel units, each containing multiple photodiodes that share a common amplification transistor. This segmentation allows signals from multiple photodiodes to be processed through a shared AD conversion path, reducing the total number of AD conversions needed while maintaining signal integrity through the amplification stage.
Solution Approach 2:
Multiple photodiodes within a pixel unit are merged to share a common amplification MOS transistor and common AD conversion circuitry. This merging reduces the number of separate conversion operations required, directly improving operation speed while the amplification stage ensures measurement precision is maintained for each individual photodiode signal.
2Measurement precision
If AD converter is provided at each vertical signal line, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The amplification MOS transistor serves multiple functions: it amplifies signals from multiple different photodiodes within a pixel unit and prepares them for AD conversion. This multi-functionality reduces the need for separate dedicated circuits for each photodiode, thereby reducing device complexity while maintaining the precision benefits of having an amplifier at each conversion point.
Solution Approach 2:
Multiple photodiodes share common amplification and AD conversion resources, merging what would otherwise be separate dedicated circuits. This sharing approach reduces the overall number of components and circuit complexity while ensuring that each photodiode signal receives proper amplification and accurate conversion.
3Measurement precision
If separate amplification circuits are provided for each photodiode, then signal amplification quality is improved, but device complexity and area increase
Solution Approach 1:
The pixel array is segmented into pixel units with a specific hierarchy: multiple photodiodes share one amplification transistor, and multiple pixel units share one AD converter. This hierarchical segmentation provides amplification quality close to dedicated circuits while avoiding the full complexity and area cost of completely separate amplification circuits for each photodiode.
Solution Approach 2:
The amplification MOS transistor is designed as a universal component that can handle and amplify signals from multiple photodiodes within its pixel unit. This multi-functional design maintains high signal amplification quality while reducing the total number of amplification circuits needed, thereby reducing device complexity and area.
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 reduces the time required for AD conversion and simplifies the operation of the device, allowing for faster signal processing and improved efficiency by performing AD conversion in parallel for multiple photodiodes.
Implementation Method 1
a first photoelectric conversion unit; a second photoelectric conversion unit
Data Source
AI summary
An AD conversion unit AD-converts a first analog signal output from a clamping unit and generated based on a signal generated at a first photoelectric conversion unit. Then, while the first analog signal is clamped at a reference level, signals generated based on the signals generated at the first and second photoelectric conversion units are applied to the clamping unit, whereby the AD conversion unit AD-converts a second analog signal output from the clamping unit.