Imaging Control Device Rolling Shutter Brightness Unevenness
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Solution Overview
Problem
In imaging systems using the rolling shutter method, brightness unevenness occurs due to overlapping light emission timing of auxiliary light with exposure start or end timings of pixel rows, leading to inefficiencies in light usage.
Innovation Solution
An imaging control device and method that adjusts the light emission cycle of auxiliary light to be m times the difference in exposure start timings between adjacent pixel rows, where m is an integer greater than or equal to 1, ensuring the light emission cycle is set to avoid overlap with exposure periods and optimize light reception.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the light emission cycle of auxiliary light is set to 1/n of the exposure time, then the auxiliary light can illuminate multiple pixel rows, but brightness unevenness occurs due to overlap with exposure start/end timings
Solution Approach 1:
The patent changes the light emission cycle parameter from the conventional 1/n of exposure time to a value that is not an integer fraction of the exposure time. Specifically, it sets the light emission cycle to be greater than or equal to the sum of the exposure time and the readout time, or sets it to a value that avoids coincidence with exposure start/end timings of all pixel rows. This parameter change eliminates brightness unevenness while maintaining effective illumination coverage.
Solution Approach 2:
The patent determines the light emission timing in advance by calculating the exposure start timings of all pixel rows and selecting a cycle that avoids overlap. The control unit pre-establishes the light emission cycle based on the rolling shutter readout pattern, ensuring that auxiliary light emission does not coincide with any pixel row's exposure start or end timing before actual imaging occurs.
2Productivity
If the difference in exposure start timing between adjacent pixel rows is set to 1/n of exposure time, then the reading process can be optimized, but auxiliary light emission overlaps with exposure periods causing brightness unevenness
Solution Approach 1:
The patent decouples the light emission cycle from the exposure time division ratio. Instead of setting the light emission cycle to 1/n of exposure time to match the rolling shutter pattern, it sets the light emission cycle to a value that is independent of the exposure time division, specifically greater than or equal to exposure time plus readout time, or a value that avoids exposure timing coincidence. This resolves the conflict between reading efficiency and brightness uniformity.
3Illumination intensity
If auxiliary light is emitted frequently to cover all pixel rows, then all pixels receive sufficient light, but light emission overlaps with exposure start/end timings causing noise and brightness unevenness
Solution Approach 1:
The control unit determines the light emission cycle based on feedback about the rolling shutter readout pattern and exposure timings. It calculates when auxiliary light should be emitted by considering the exposure start timings of all pixel rows, ensuring that light emission occurs only during periods when no pixel row is starting or ending exposure. This feedback-based timing control eliminates noise and brightness unevenness while maintaining sufficient illumination.
Solution Approach 2:
The patent implements dynamic timing control where the light emission cycle is adaptively set based on the actual exposure time and readout time of the rolling shutter method. The control unit adjusts the light emission timing dynamically to match the specific imaging conditions, ensuring optimal performance without fixed timing constraints.
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
Prevents brightness unevenness in captured images and enhances the efficiency of auxiliary light usage by ensuring uniform light reception during exposure periods.
Implementation Method 1
an imaging sensor which includes a plurality of pixels each including a photoelectric conversion element
Data Source
AI summary
A digital camera includes an imaging control unit that images a subject by performing driving based on a rolling shutter method on an imaging sensor, and a light emission control unit that emits auxiliary light a plurality of times from a light emission device while the imaging is performed. A difference Δt between start timings of exposure started by the driving in two adjacent pixel rows is a value other than 1/n (n is an integer greater than or equal to 1) of an exposure time in which the exposure is performed. The light emission control unit controls a light emission cycle of the auxiliary light to be a time that is m (m is an integer greater than or equal to 1) times the difference.