Solid-State Imaging Device Incomplete Charge Transfer
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Solution Overview
Problem
Current solid-state imaging devices face challenges in achieving high signal-to-noise ratio (S/N) and expanding dynamic range, especially in low luminance scenes, where electronic shutter methods struggle to secure sufficient exposure time and are prone to noise accumulation, and logarithmic response introduces fixed pattern noise.
Innovation Solution
A solid-state imaging device with a pixel array and transfer gate system that performs incomplete transfers, adding remaining charges to new charges generated after the transfer, allowing for improved S/N and dynamic range expansion without narrowing the normal saturation level.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the electronic shutter is released at high speed to expand dynamic range, then the dynamic range is improved, but the exposure time in dark areas becomes insufficient causing S/N deterioration
Solution Approach 1:
The patent segments the charge transfer process into multiple stages: a first incomplete transfer that retains some charges, followed by a second transfer that completes the readout. This segmentation allows the system to maintain high S/N ratio by ensuring sufficient exposure time while still achieving expanded dynamic range through the controlled incomplete transfer mechanism.
Solution Approach 2:
The patent introduces dynamic control of the transfer gate timing, where the first transfer occurs before the charge storage period ends, creating an incomplete transfer state. This dynamic approach allows flexible adjustment between exposure time and dynamic range requirements, resolving the contradiction between maintaining S/N ratio and expanding dynamic range.
2Adaptability or versatility
If logarithmic response characteristic is used to expand dynamic range, then the dynamic range is improved, but fixed pattern noise becomes prominent in low luminance areas
Solution Approach 1:
The patent changes the operational parameters of the transfer gate by controlling its timing and transfer completeness. By adjusting when the transfer occurs and how complete it is, the system achieves dynamic range expansion without relying on logarithmic response, thereby avoiding the fixed pattern noise that plagues logarithmic methods in low luminance areas.
3Measurement precision
If exposure time is extended to improve S/N ratio in low luminance scenes, then the S/N ratio is improved, but saturation occurs in high luminance areas reducing dynamic range
Solution Approach 1:
The patent performs a preliminary incomplete transfer before the charge storage period ends. This preliminary action removes excess charges that would otherwise cause saturation in high luminance areas, while leaving sufficient charges to maintain high S/N ratio in low luminance areas. This resolves the contradiction by preventing saturation before it occurs.
Solution Approach 2:
The patent applies partial transfer action by intentionally leaving some charges in the photoelectric conversion element after the first transfer. This partial approach allows the system to avoid complete saturation in bright areas while maintaining sufficient signal levels in dark areas, achieving both high S/N ratio and expanded dynamic range simultaneously.
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 approach enables high S/N acquisition in low luminance conditions and expands the dynamic range while maintaining good S/N in high luminance scenarios, avoiding saturation and reducing fixed pattern noise.
Implementation Method 1
a photoelectric conversion part configured to receive incident light and generate signal charges
Data Source
AI summary
A solid-state imaging device includes a pixel array area in which an unit pixel including a photoelectric conversion element converting optical signals to signal charges and a transfer gate transferring the signal charges which have been photoelectrically converted in the photoelectric conversion element is two-dimensionally arranged in a matrix form, a supply voltage control means for supplying plural first control voltages sequentially to a control electrode of the transfer gate, and a driving means for performing driving of reading out signal charges transferred by the transfer gate when the plural first control voltages are sequentially applied twice and more.