Dual Integration Capacitor Circuit for High Dynamic Range Imaging
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Solution Overview
Problem
Image capture devices are typically optimized for either bright or low ambient light conditions, leading to suboptimal performance in varying light environments due to competing capacitance requirements, resulting in either insufficient sensitivity or image saturation.
Innovation Solution
A high dynamic range direct injection circuit with two integration capacitors of different capacitance values, where a smaller capacitor with high gain handles low-level signals and a larger capacitor with a threshold switch diverts excess charge from the smaller capacitor under bright conditions, allowing for increased dynamic range and optimal performance in both low and high ambient light scenarios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single integration capacitor is used in the image sensor, then the device can be optimized for either bright or low ambient light conditions, but it cannot simultaneously maintain high sensitivity and prevent image saturation in varying light conditions
Solution Approach 1:
The integration capacitor is segmented into two distinct capacitors: a first integration capacitor with smaller capacitance for high sensitivity in low light conditions, and a second integration capacitor with larger capacitance for preventing saturation in bright light conditions. This segmentation allows each capacitor to be optimized for specific light conditions, resolving the contradiction between sensitivity and adaptability.
Solution Approach 2:
The circuit dynamically switches between the two integration capacitors based on ambient light conditions. A control mechanism monitors light intensity and selects the appropriate capacitor, enabling the system to adapt its capacitance value in real-time. This dynamic adaptation allows the device to maintain optimal performance across varying light conditions.
2Adaptability or versatility
If a larger integration capacitor is used to prevent image saturation in bright light, then dynamic range increases, but sensitivity to low-level signals decreases
Solution Approach 1:
Different regions of the circuit have different capacitance properties tailored to their specific functions. The first integration capacitor provides high sensitivity for low-level signals, while the second integration capacitor provides high capacity for bright light conditions. This local differentiation of quality allows the system to maintain both high dynamic range and high sensitivity simultaneously.
Solution Approach 2:
The integration function is segmented across two capacitors with different capacitance values. The smaller first capacitor handles low-level signals with high gain, while the larger second capacitor handles bright light conditions. This segmentation resolves the contradiction by allowing each capacitor to operate in its optimal range.
3Measurement precision
If a smaller integration capacitor is used to maintain high sensitivity in low light conditions, then signal amplification is improved, but image saturation occurs easily in bright light conditions
Solution Approach 1:
The integration capacitor is segmented into two distinct capacitors: a first integration capacitor with smaller capacitance for high sensitivity in low light conditions, and a second integration capacitor with larger capacitance for preventing saturation in bright light conditions. This segmentation allows each capacitor to be optimized for specific light conditions, resolving the contradiction between sensitivity and adaptability.
Solution Approach 2:
A control mechanism acts as an intermediary between the photodetector and the two integration capacitors, routing signals to the appropriate capacitor based on light intensity. This intermediary prevents direct connection to the wrong capacitor, avoiding both saturation in bright light and insufficient capacity in low light conditions.
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 enables image capture devices to maintain high sensitivity and dynamic range across varying light conditions, effectively preventing image saturation and ensuring accurate light intensity representation, thereby enhancing image quality.
Implementation Method 1
a photodetector configured to generate a photo-current in response to receiving light
Implementation Method 2
a first integration capacitor coupled to the photodetector and configured to accumulate charge corresponding to the photo-current, a second integration capacitor configured to accumulate charge corresponding to the photo-current
Data Source
AI summary
According to one aspect, embodiments herein provide a unit cell circuit comprising a photodetector configured to generate a photo-current in response to receiving light, a first integration capacitor configured to accumulate charge corresponding to the photo-current, a second integration capacitor configured to accumulate charge corresponding to the photo-current, a charge diverting switch coupled to the photodetector and configured to selectively couple the first integration capacitor to the second integration capacitor and divert the photo-current to the second integration capacitor in response to a voltage across the first integration capacitor exceeding a threshold level, and read-out circuitry coupled to the first integration capacitor and the charge diverting switch and configured to read-out a first voltage sample from the first integration capacitor corresponding to charge accumulated on the first integration capacitor and to read-out a second voltage sample from the second integration capacitor corresponding to charge accumulated on the second integration capacitor.