Flash Control for Rolling Shutter Image Sensors
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Mobile cellular telephones face challenges in providing sufficient current to both electronic components and flash units due to the flash's high current requirements, leading to potential image artifacts when the flash is disabled due to low battery current during exposure, especially with rolling shutter image sensors.
Innovation Solution
A processor-controlled flash unit that provides varying light intensities throughout the exposure time, prioritizing maximum output during certain portions to balance energy distribution and ensure consistent illumination, synchronizing with other electronic components' energy demands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the flash unit operates at maximum current output, then the light intensity is sufficient for proper exposure, but other electronic components cannot receive adequate current and may malfunction
Solution Approach 1:
The flash unit's current output is made dynamic by varying it across different time periods within the exposure duration. The processor controls the flash to provide different current levels (first current level during first time period, second current level during second time period) rather than maintaining a static maximum output, allowing adaptation to changing power availability conditions
Solution Approach 2:
The flash operation is divided into periodic time segments (first time period and second time period) with different current output characteristics. This periodic modulation of flash intensity allows the system to alternate between higher intensity output and lower intensity output, coordinating with the periodic nature of power availability from the electrical energy storage device
2Reliability
If the flash unit is disabled due to low current availability, then other electronic components can receive sufficient current, but image artifacts appear due to insufficient illumination during exposure
Solution Approach 1:
Instead of a static on/off flash control, the system dynamically adjusts flash current output across multiple time periods. The processor determines when to provide higher current (first current level) versus lower current (second current level) based on power availability, ensuring continuous illumination while adapting to current constraints
Solution Approach 2:
The flash provides partial illumination during the second time period with reduced current output, rather than complete illumination at maximum current throughout. This partial action approach maintains sufficient lighting for acceptable image quality while reducing total power consumption to accommodate other electronic components
3Illumination intensity
If the flash provides continuous maximum intensity throughout exposure, then image quality is maximized, but power consumption is too high for the electrical energy storage device to sustain
Solution Approach 1:
The flash operates in periodic cycles with alternating high-intensity (first current level) and low-intensity (second current level) phases. This periodic action reduces the average power consumption compared to continuous maximum intensity operation, while still providing sufficient illumination during high-intensity phases for acceptable image quality
Solution Approach 2:
The flash provides excessive illumination (higher than minimum required) during the first time period, then reduces to partial illumination during the second time period. This strategy captures sufficient light during high-intensity phases while accepting reduced illumination during low-intensity phases, achieving acceptable overall exposure with reduced total energy consumption
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 enhances the average light intensity and reduces power consumption conflicts, allowing for high-quality images without artifacts, even when other components require high current, by strategically managing the flash unit's energy usage.
Implementation Method 1
a flash unit (28) in an exposure time period of an image sensor array (26)
Data Source
Figure 1
Figure 2
Figure 3
AI summary
An apparatus comprising: at least one processor; and at least one memory including computer program instructions, the at least one memory and the computer program instructions configured to, with the at least one processor, cause the apparatus at least to perform: determining an intensity of ambient light; determining whether the intensity of ambient light is above a threshold light intensity or below said threshold light intensity; if the intensity of ambient light is below said threshold light intensity, controlling the flash unit to provide light only over a time period common to exposure time periods of the plurality of rows of image sensor elements of a rolling shutter image sensor array; and if the intensity of ambient light is above said threshold light intensity, controlling the flash unit to provide light over a time period that is substantially equal to the exposure time of all the sensor elements of the rolling shutter image sensor array; and corresponding device, method and computer program instructions.