Imaging Device Avalanche Photoelectric Conversion Dark Current Shielding
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Solution Overview
Problem
Current imaging devices face challenges in achieving high-definition imaging under low illuminance conditions due to reduced light-receiving areas, leading to increased dark current and decreased imaging quality, while also requiring low power consumption and high-speed operation.
Innovation Solution
The proposed imaging device incorporates a circuit configuration with oxide semiconductors and selenium-based photoelectric conversion elements, utilizing avalanche charge multiplication for enhanced sensitivity and incorporating a shielding mechanism to reduce dark current, allowing for high-speed and low-power operation across a wide temperature range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the light-receiving area of the photoelectric conversion element is reduced to highly integrate pixels, then the integration degree is improved, but the sensitivity to light deteriorates making it difficult to perform imaging under low illuminance condition
Solution Approach 1:
The patent changes the material parameter of the photoelectric conversion element from conventional materials to avalanche photoelectric conversion elements, which have inherently higher sensitivity. This material parameter change enables the element to achieve sufficient sensitivity even with a reduced light-receiving area, thus resolving the contradiction between high integration degree and maintained sensitivity under low illuminance conditions.
2Reliability
If avalanche photoelectric conversion elements are used to improve sensitivity under low illuminance condition, then the sensitivity is improved, but the dark current increases causing deterioration in imaging quality
Solution Approach 1:
The patent extracts and removes the source of dark current by carefully controlling the connection of the avalanche photoelectric conversion element to exclude it from the pixel circuit's signal path. The element is connected such that its dark current does not flow into the pixel circuit, thereby eliminating the harmful effect while preserving the high sensitivity benefit.
Solution Approach 2:
The patent applies different connection configurations to different parts of the imaging device. Specifically, the avalanche photoelectric conversion elements are selectively connected to utilize their high sensitivity in low illuminance regions while their dark current is isolated from the main pixel circuit through specific wiring arrangements, creating localized optimization without compromising overall image quality.
3Measurement precision
If the area per pixel is reduced to achieve high-definition imaging, then the resolution is improved, but the light-receiving area decreases leading to increased dark current and decreased imaging quality
Solution Approach 1:
The patent changes the photoelectric conversion mechanism parameter by adopting avalanche photoelectric conversion elements, which provide higher gain and sensitivity. This enables the system to maintain adequate signal levels even with the smaller photoelectric conversion area resulting from high-resolution pixel integration, thereby preventing dark current from becoming the dominant noise source.
Solution Approach 2:
The patent converts the potentially harmful dark current effect into a manageable parameter by using the avalanche multiplication effect to amplify the useful signal so strongly that the dark current becomes relatively insignificant. The high gain from avalanche multiplication compensates for the reduced light-receiving area, turning the limitation into an opportunity to achieve both high resolution and acceptable image quality.
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 configuration enables high-definition imaging with improved dynamic range and reliability under low illuminance conditions, while maintaining low power consumption and supporting high-speed operation across a broad temperature range.
Implementation Method 1
a first photoelectric conversion element... a second photoelectric conversion element
Implementation Method 2
a photoelectric conversion element utilizing avalanche charge multiplication
Data Source
AI summary
An imaging device with excellent imaging performance is provided. The imaging device has a first circuit including a first photoelectric conversion element and a second circuit including a second photoelectric conversion element. The second circuit is shielded from light. In the imaging device, a current mirror circuit in which a transistor connected to the second photoelectric conversion element serves as an input transistor and a transistor connected to the first photoelectric conversion element serves as an output transistor is formed. With such a configuration, the amount of photocurrent in the first circuit from which the contribution of the dark current of the first photoelectric conversion element has been excluded can be detected.