Photoelectric Conversion Layer Shutter Switching for Distortion-Free Imaging
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Solution Overview
Problem
Conventional CMOS image sensors using the rolling shutter method face issues with image distortion when capturing moving objects and inconsistent brightness, particularly when using flash, as each pixel array row has different exposure start and end times, necessitating a global shutter function where all pixels start and end exposure simultaneously.
Innovation Solution
An imaging device is designed to perform global shutter operations while minimizing circuit complexity within pixels by using a voltage supply circuit that applies different voltages between exposure and non-exposure periods, with a photoelectric conversion layer having specific photocurrent characteristics and a reset transistor to manage charge accumulation, allowing all pixels to start and end exposure simultaneously.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a global shutter function is implemented using conventional methods (transfer transistor and charge storage unit per pixel), then all pixels can start and end exposure simultaneously, but circuit complexity within pixels increases
Solution Approach 1:
The charge storage function is extracted from individual pixels and relocated to a memory region outside the pixel array. This removes the need for transfer transistors and charge storage units within each pixel, thereby reducing in-pixel circuit complexity while maintaining global shutter capability.
Solution Approach 2:
The patent merges the charge storage function with the memory structure by utilizing a shared memory region that serves both as temporary storage for signal charges from all pixels and as part of the readout circuitry. This consolidation eliminates redundant components and simplifies the overall system architecture.
2Device complexity
If rolling shutter method is used, then circuit complexity is reduced, but image distortion occurs when capturing moving objects
Solution Approach 1:
The patent implements preliminary action by having all pixels simultaneously complete their exposure and transfer charges to the memory region before sequential readout begins. This pre-synchronization of charge transfer ensures that all pixels capture the same temporal moment, eliminating rolling shutter distortion while keeping pixel circuits simple.
3Device complexity
If rolling shutter method is used, then circuit structure is simplified, but brightness inconsistency occurs when using flash
Solution Approach 1:
By extracting the charge storage function from individual pixels to a shared memory region, the patent enables synchronized exposure termination across all pixels. This allows the flash to illuminate all pixels uniformly during their exposure period, eliminating brightness inconsistency while keeping the pixel circuit structure simple.
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 solution enables the realization of global shutter functions without increasing circuit complexity, suppressing parasitic sensitivity and maintaining image quality by ensuring all pixels start and end exposure uniformly, thus reducing image distortion and brightness inconsistencies.
Implementation Method 1
pixels each including a photoelectric converter that converts light into a signal charge
Data Source
AI summary
An imaging device including pixels each including a photoelectric converter that converts light into a signal charge; and controller, where the controller causes the pixels to perform global shutter operation in a first frame period and causes the pixels to perform rolling shatter operation in a second frame period different from the first frame period.