Image Sensor Timing Control for Extended Exposure
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Solution Overview
Problem
Conventional rolling shutter methods in electronic cameras are unable to independently control reset and reading timings, limiting exposure time to less than one frame period, which degrades signal-to-noise (SN) ratio, especially in low-light conditions.
Innovation Solution
An image shooting device with a timing control system that allows for exposure start and reading timings to be set such that the time interval between them is longer than the frame rate, enabling exposure times greater than one frame period, and includes a mode switching mechanism based on photometric values to adjust amplification and timing accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If the reset operation and reading operation are performed on the same row within one frame using conventional rolling shutter method, then the device complexity is reduced and ease of operation is maintained, but the exposure time is limited to less than one frame period and the SN ratio is degraded
Solution Approach 1:
The patent divides the pixel array into multiple row groups and assigns different timing configurations to each group. Specifically, odd-numbered rows and even-numbered rows are processed in separate timing cycles, allowing the exposure time for each row to extend beyond one frame period while maintaining manageable control complexity through systematic segmentation of the pixel array.
Solution Approach 2:
The patent introduces a new timing dimension by decoupling the reset timing and reading timing across different frames. Instead of confining both operations to the same frame, the exposure start timing for a given row is set in one frame while the reading timing is deferred to a subsequent frame, effectively adding a temporal dimension beyond the single-frame constraint.
2Reliability
If the exposure time is extended beyond one frame period, then the SN ratio is improved for dark place shooting, but the timing control becomes more complex and requires different row timing strategies
Solution Approach 1:
The patent segments the pixel rows into odd and even groups, each with dedicated timing control. Odd rows use one timing pattern while even rows use another, allowing independent optimization of exposure timing for each segment. This segmentation enables extended exposure times that improve SN ratio while keeping the control logic organized and manageable through systematic row-group differentiation.
Solution Approach 2:
The patent implements dynamic timing control where the exposure start timing and reading timing are independently adjustable for different row groups. The system dynamically switches between different timing configurations based on the row number, enabling flexible exposure time extension that adapts to different shooting conditions while maintaining operational ease through automated timing management.
3Duration of action of moving object
If different rows are used for exposure start and reading across frames, then exposure time longer than one frame period is achieved, but the reading operation spans multiple frames increasing processing complexity
Solution Approach 1:
The patent segments the pixel array into odd and even row groups that are processed in an interleaved manner. Odd rows are exposed and read in one timing cycle while even rows follow in the next, allowing exposure times to span multiple frames without requiring all pixels to complete their cycle simultaneously. This segmentation maintains frame rate efficiency by ensuring continuous data flow from different row groups.
Solution Approach 2:
The patent implements periodic timing patterns where odd rows and even rows alternate in their exposure and reading cycles. This periodic action creates a rhythmic data flow that maintains productivity by ensuring that while some rows are in extended exposure, other rows are being read out, thereby sustaining the overall frame rate efficiency despite individual rows spanning multiple frames.
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
Enables longer exposure times and improved SN ratio, allowing for higher quality images even in dark environments by independently controlling reset and reading timings and adjusting amplification based on brightness.
Implementation Method 1
a photometry part that measures a brightness of a subject to be shot
Implementation Method 2
converting, after the resetting, the charges accumulated in the photoelectric conversion parts into electric signals and reading them
Data Source
AI summary
There is provided an image shooting device including a pixel part that is formed with a plurality of pixels arranged in a matrix, and a timing control part that provides an exposure start timing and a reading timing after exposure to the pixel part, in which the timing control part controls the exposure start timing and the reading timing such that a time interval between the exposure start timing and the reading timing is longer than the frame rate and that a row that outputs the reading timing is different for each frame when reading a plurality of successive images at a preset frame rate.