Temperature Feedback in Solid-State Imaging for Dark Current Control
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Solution Overview
Problem
Image sensors using materials with narrower band gap energy than silicon, such as InGaAs, have higher sensitivity to temperature fluctuations, leading to increased dark current and decreased image quality at higher temperatures.
Innovation Solution
A solid-state imaging apparatus is designed with a photoelectric conversion unit using a material with a smaller band gap energy than silicon, and a circuit board incorporating a thermometer circuit to monitor and control temperature, thereby reducing dark current and maintaining image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a material with narrower band gap energy than silicon (such as InGaAs) is used for the photoelectric conversion film, then sensitivity to long-wavelength light (infrared light) is improved, but sensitivity to temperature fluctuations increases and dark current generation increases at higher temperatures
Solution Approach 1:
The patent implements a feedback control system where a thermometer circuit continuously monitors the temperature of the circuit board, and this temperature information is fed back to a temperature control circuit that adjusts the operation of the photoelectric conversion unit accordingly. This closed-loop feedback mechanism enables dynamic compensation for temperature-induced dark current variations, maintaining optimal performance across varying temperature conditions while preserving the high infrared sensitivity of narrow band gap materials like InGaAs.
2Temperature
If temperature is increased to improve operational conditions, then image quality decreases due to increased dark current generation
Solution Approach 1:
The thermometer circuit provides continuous temperature monitoring that feeds back to the temperature control circuit, which dynamically adjusts photoelectric conversion parameters to compensate for temperature-induced dark current increases. This feedback mechanism allows the system to maintain reliable image quality across a wide temperature range by automatically correcting for thermal effects without requiring active cooling or temperature restriction.
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 proposed solution effectively suppresses the decrease in image quality by accurately monitoring and controlling temperature, thereby reducing dark current and ensuring high image quality even at higher temperatures.
Implementation Method 1
a photoelectric conversion unit including a material having a smaller band gap energy than silicon
Implementation Method 2
a thermometer circuit that detects a temperature of the circuit board
Data Source
AI summary
A decrease in image quality is suppressed. A solid-state imaging apparatus according to an embodiment includes: a photoelectric conversion unit (PD) including a material having a smaller band gap energy than silicon; and a circuit board joined to the photoelectric conversion unit, the circuit board including: a pixel signal generation circuit that generates a pixel signal having a voltage value corresponding to a charge generated in the photoelectric conversion unit; and a thermometer circuit that detects a temperature of the circuit board.