Solid-State Imaging Device Variable Voltage Charge Accumulation
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Solution Overview
Problem
Existing solid-state imaging devices face challenges in expanding dynamic range without deteriorating image quality, as increasing the number of divisions in time-division or spatial-division systems leads to artifact generation and resolution reduction, and intra-pixel memory systems are limited by charge capacity.
Innovation Solution
A solid-state imaging device with a pixel array and drive portion that includes a first and second photoelectric conversion portion, an electric charge accumulating portion connected to a variable voltage power source, and transfer gates to manage charge transfer and potential coupling, allowing for reduced voltage during charge accumulation and readout, thereby expanding dynamic range without degrading image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the number of divisions is increased in time-division or spatial-division systems, then the dynamic range is expanded, but artifact generation and resolution reduction occur
Solution Approach 1:
The pixel is divided into multiple photoelectric conversion portions (first, second, third, fourth) with different sensitivity characteristics. Each portion captures light differently, allowing synthesis of a wider dynamic range image while maintaining quality through selective use of each portion's strengths
Solution Approach 2:
Different regions within the pixel (different photoelectric conversion portions) are given different sensitivity characteristics and functions. The first photoelectric conversion portion has higher sensitivity for low-light conditions, while the second has lower sensitivity for high-light conditions, allowing each region to optimize for its specific function
2Quantity of substance
If the number of divisions is increased in time-division or spatial-division systems, then the dynamic range is expanded, but resolution is reduced
Solution Approach 1:
The pixel is segmented into multiple photoelectric conversion portions that simultaneously capture different light intensity ranges. By synthesizing data from all portions, the system achieves both extended dynamic range and maintained resolution without the trade-off present in conventional division systems
Solution Approach 2:
The patent merges the output signals from multiple photoelectric conversion portions with different sensitivities. The signal processing unit combines these signals to produce a final image that benefits from both the extended dynamic range coverage and the preserved spatial resolution of all portions
3Quantity of substance
If intra-pixel memory capacity is increased, then the dynamic range is expanded, but the device complexity increases
Solution Approach 1:
The patent changes the sensitivity parameter of different photoelectric conversion portions rather than increasing memory capacity. By creating portions with different sensitivity characteristics that naturally capture different dynamic range segments, the system achieves extended dynamic range without requiring large memory expansions
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 expands the dynamic range of the solid-state imaging device without compromising image quality, suppressing artifacts and resolution loss associated with increased divisions in other systems.
Implementation Method 1
a first photoelectric conversion portion, a second photoelectric conversion portion a sensitivity of which is lower than that of the first photoelectric conversion portion
Data Source
AI summary
A solid-state imaging device is provided that includes a pixel array with unit pixels. Each unit pixel includes, among other things, first and second photoelectric conversion portions; an electric charge accumulating portion that accumulates charges produced by the second photoelectric conversion portion, a counter electrode of the electric charge accumulating portion being connected to a variable voltage power source; and a charge-to-voltage conversion portion. For at least a part of a time period for which charges produced by the second photoelectric conversion portion are accumulated in the electric charge accumulating portion, a drive portion that controls an operation of the unit pixel causes a voltage of the variable voltage power source to be lower than that when a signal based on the charges accumulated in the electric charge accumulating portion is read out.