Solid-State Image Sensor Pixel Circuit for Wider Dynamic Range
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Solution Overview
Problem
The dynamic range of pixel signals in solid-state imaging devices using single-slope ADCs is narrowed due to potential differences between the source and drain of transistors, limiting the ability to accurately compare high luminance signals and reducing image quality.
Innovation Solution
A solid-state imaging device with a capacitor that adjusts voltage levels and includes a comparator on the signal line, using a changeable reference signal and a switching element to expand the dynamic range while reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a transistor is connected on the signal line to perform comparison operation, then the comparison function is achieved, but a potential difference is generated between source and drain that narrows the dynamic range of the pixel signal
Solution Approach 1:
A capacitor is introduced as an intermediary element between the photoelectric conversion element and the comparator. This capacitor adjusts the voltage level of the charge-voltage conversion unit, enabling the comparator to accurately compare high luminance signals without being affected by the potential difference inherent in transistor operation, thus expanding the dynamic range while maintaining comparison functionality
2Manufacturing precision
If a capacitor is added to adjust voltage level, then the dynamic range is expanded, but the device complexity increases
Solution Approach 1:
The capacitor is integrated into the existing pixel circuit structure, combining the voltage adjustment function with the charge-voltage conversion unit. This merging approach allows the capacitor to expand the dynamic range without requiring a completely separate circuit architecture, thereby limiting the increase in device complexity
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 enhances the dynamic range and image quality by allowing accurate comparison of high luminance signals with reduced power consumption.
Implementation Method 1
a photoelectric conversion element; charge photoelectrically converted by the photoelectric conversion element
Implementation Method 2
a capacitor that is connected to the charge-voltage conversion unit and adjusts a voltage level of the charge-voltage conversion unit
Data Source
AI summary
[Problem] To expand a dynamic range and output high quality image data with low power consumption. [Solution] A solid-state imaging device includes: a photoelectric conversion element; a charge-voltage conversion unit that converts charge photoelectrically converted by the photoelectric conversion element into a voltage; a capacitor that is connected to the charge-voltage conversion unit and adjusts a voltage level of the charge-voltage conversion unit; a first semiconductor layer in which the photoelectric conversion element and the capacitor are arranged; a signal line that transmits a pixel signal according to the voltage level of the charge-voltage conversion unit; and a comparator that is arranged on the signal line and compares the pixel signal with a predetermined reference signal.