Rolling-Shutter Illumination Timing for Biometric Image Contrast
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Traditional biometric identification systems face issues such as susceptibility to presentation attacks, lack of speed, inaccuracy, and operational limitations, including interference from simultaneous illumination of light sources at different positions that degrade image quality and increase power consumption.
Innovation Solution
A time delayed coordinated illumination system is implemented with spatially separated banks of light sources operated in sequence with a rolling shutter camera to improve image contrast and uniformity, reducing interference and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If multiple light sources are operated simultaneously to illuminate the field of view, then the illumination coverage is improved, but the image contrast deteriorates due to phase shift interference
Solution Approach 1:
The patent applies periodic action by operating multiple light sources in sequential time intervals rather than simultaneously. Each light source is activated for a specific duration corresponding to the rolling shutter exposure time, creating a time-delayed illumination sequence that eliminates phase shift interference while maintaining comprehensive illumination coverage across the field of view.
Solution Approach 2:
The patent implements preliminary action by pre-coordinating the activation timing of each light source with the rolling shutter's row-by-row exposure sequence. The illumination timing is calculated and set in advance based on the shutter speed and field of view dimensions, ensuring that each light source activates precisely when needed for its corresponding spatial region without causing interference.
2Illumination intensity
If multiple banks of light sources are operated simultaneously to provide comprehensive illumination, then the illumination uniformity is improved, but the power consumption increases
Solution Approach 1:
The patent reduces power consumption by activating only one bank of light sources at a time in a periodic sequence that matches the rolling shutter's exposure timeline. This time-multiplexed illumination approach ensures that the entire field of view receives adequate illumination over the exposure duration while minimizing the number of simultaneously active light sources, thereby reducing overall power consumption.
Solution Approach 2:
The patent implements dynamic illumination control by adjusting the activation sequence and timing of light sources based on the rolling shutter's exposure parameters and the spatial requirements of the field of view. This dynamic coordination allows the system to provide uniform illumination coverage while adapting the power consumption profile to the actual imaging needs rather than maintaining constant high-power operation.
3Measurement precision
If the illumination duration is extended to improve image quality, then the image contrast is improved, but the temporal resolution deteriorates
Solution Approach 1:
The patent applies segmentation by dividing the illumination task across multiple light sources that operate in sequential time intervals corresponding to different spatial regions of the field of view. Each light source illuminates a specific portion of the scene during its designated time window, allowing the rolling shutter to capture high-contrast images of different regions at different times without requiring extended total illumination duration, thus preserving temporal resolution.
Data Source
AI summary
An input device uses banks of spatially separated light sources to selectively illuminate a field of view to acquire input image data used for biometric identification. In one implementation a plurality of banks of light sources are arranged from a first end to a second end of a device. Each bank may comprise light sources that are arranged on both sides of a device centerline. A camera with a rolling shutter acquires rows of image data beginning at the first end and scanning to the second end. While the camera is operating, banks of lights are progressively activated in coordination with the rolling shutter to illuminate a portion of a field of view and an object within, such as a hand, being imaged. This results in high-contrast input image data that is well illuminated, while reducing overall power requirements. The input image data may then be processed for identification.