CMOS Image Sensor Low Power Control via Frame Difference Detection
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Solution Overview
Problem
CMOS image sensors face challenges in reducing power consumption, especially when capturing images of static objects where many pixels have no change in output data between frames, leading to inefficiencies in A/D conversion and column selection operations.
Innovation Solution
An imaging device with a circuit that determines differences between frames, using oxide semiconductor transistors to enable low-power operation by selectively powering A/D converters and column selection circuits based on frame differences, allowing for high-speed, high-resolution imaging under low illuminance and varying temperatures with a high aperture ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If A/D converter and column selection circuit operate continuously to maintain high-speed imaging capability, then imaging speed is improved, but power consumption increases
Solution Approach 1:
The patent implements dynamic operation of the A/D converter and column selection circuit based on frame difference detection. When no significant changes are detected between frames, these circuits are stopped to save power. When changes are detected, the circuits are activated to maintain imaging speed, thus dynamically adapting operation state to actual needs.
Solution Approach 2:
The imaging device uses its own frame difference detection capability to control its power consumption. The system automatically determines when to activate or deactivate processing circuits based on whether image content has changed, making the power management self-regulating without external control.
2Productivity
If A/D converter is provided in every column for parallel processing, then processing speed is improved, but device complexity increases
Solution Approach 1:
The patent makes the A/D converter and column selection circuit universal by providing them shared across multiple columns rather than dedicating separate instances to each column. This multi-functional approach maintains parallel processing capability when needed while reducing overall circuit complexity and component count.
Solution Approach 2:
The shared A/D converter and column selection circuit are dynamically activated only for columns that contain significant frame differences, rather than operating continuously for all columns. This dynamic activation maintains productivity when needed while reducing device complexity in terms of active component requirements.
3Reliability
If all pixels continuously output data for every frame, then imaging completeness is improved, but power consumption increases
Solution Approach 1:
The patent extracts only the pixels that contain significant changes between frames and outputs data only from those pixels. By taking out and processing only the relevant subset of pixel data rather than all pixel data, the system maintains imaging completeness for changed regions while reducing power consumption from unnecessary processing of unchanged regions.
Solution Approach 2:
Instead of processing all pixel data for every frame, the patent applies partial action by processing only the portion of pixel data that contains significant changes. This selective processing maintains the necessary imaging completeness while avoiding the excessive power consumption that would result from processing all pixels regardless of whether their data has changed.
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 reduces power consumption by selectively powering components only when frame differences are detected, enabling efficient high-speed, high-resolution imaging under low illuminance and a wide temperature range with improved reliability.
Implementation Method 1
Each of the first and the second pixel circuit includes a photoelectric conversion element
Data Source
AI summary
An imaging device with low power consumption is provided. It includes a pixel capable of outputting difference data between two different frames, a circuit determining the significance of the difference data, a circuit controlling power supply, an A/D converter, and the like; obtains image data and then obtains difference data; and shuts off power supply to the A/D converter and the like in the case where it is determined that there is no difference, and continues or restarts the power supply to the A/D converter and the like when it is determined that there is a difference. Determining the significance of the difference data can be performed row by row in a pixel array or at nearly the same time in all the pixels included in the pixel array.