Photoelectric Conversion Circuits for Expanded Dynamic Range
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Solution Overview
Problem
Existing photoelectric conversion devices face limitations in expanding their dynamic range, particularly in applications with large brightness differences, such as vehicle-mounted and security cameras, where current techniques using multiple photodiodes with different characteristics are insufficient.
Innovation Solution
A photoelectric conversion device is designed with a first and second photoelectric conversion circuit, each with different sensitivities, and a floating diffusion portion, along with transfer and control electrodes, allowing charges to be transferred and potential control between the circuits, enabling improved dynamic range expansion by varying signal output based on illuminance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple photodiodes with different characteristics are combined, then dynamic range is expanded, but device complexity increases
Solution Approach 1:
The photoelectric conversion device is segmented into multiple photoelectric conversion circuits (first, second, and third photodiodes) with different characteristics. Each photodiode has different sensitivity levels, allowing the device to handle various illuminance conditions by selecting appropriate circuits, thereby expanding dynamic range while managing complexity through functional segmentation
Solution Approach 2:
The device dynamically selects which photoelectric conversion circuit to use based on illuminance conditions. The first photodiode is used for low illuminance, the second for intermediate illuminance, and the third for high illuminance. This dynamic selection mechanism allows the device to adapt to varying light conditions, expanding its effective dynamic range
2Measurement precision
If photoelectric conversion circuits with different sensitivities are used, then sensitivity at low illuminance is improved, but signal saturation at high illuminance occurs
Solution Approach 1:
Different photoelectric conversion circuits are designed with different local qualities (sensitivities). The first photodiode has high sensitivity for low illuminance detection, while the second and third photodiodes have lower sensitivity to prevent saturation at high illuminance. Each circuit is optimized for its specific operating range, allowing the device to maintain measurement precision across varying illuminance levels by selecting the appropriate circuit
Solution Approach 2:
The device dynamically switches between photoelectric conversion circuits based on illuminance levels. At low illuminance, the high-sensitivity first photodiode is activated. As illuminance increases, the system transitions to the second and then third photodiodes with progressively lower sensitivity, preventing signal saturation while maintaining accurate measurement across the full dynamic range
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 enhances the dynamic range by improving sensitivity at low illuminance and reducing signal saturation at high illuminance, effectively expanding the range of high sensitivity reading and increasing signal-to-noise ratio.
Implementation Method 1
a first photoelectric conversion circuit, a second photoelectric conversion circuit, a third photoelectric conversion circuit which perform photoelectric conversion
Data Source
AI summary
A photoelectric conversion device includes first and second photoelectric conversion circuits, a floating diffusion portion, first and second transfer electrodes, and a first control electrode. The second photoelectric conversion circuit has sensitivity lower than that of the first photoelectric conversion circuit. Charges generated in the first photoelectric conversion circuit and the second photoelectric conversion circuit are transferred to the floating diffusion portion. The first transfer electrode is configured to transfer charges from the first photoelectric conversion circuit to the floating diffusion portion. The second transfer electrode is configured to transfer charges from the second photoelectric conversion circuit to the floating diffusion portion. The first control electrode is configured to control a potential between the first photoelectric conversion circuit and the second photoelectric conversion circuit so that charges are movable between the first photoelectric conversion circuit and the second photoelectric conversion circuit.