Exposure Time Determination for Optical Fingerprint Sensors
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Solution Overview
Problem
In optical fingerprint identification systems, improper exposure times often result in fingerprint images with excessively high or low brightness, leading to unclear images and reduced identification accuracy.
Innovation Solution
An exposure time determination method that adjusts exposure times based on histogram analysis of image brightness signals, involving multiple stages of image sensing and histogram comparison to optimize brightness distribution and pixel counts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If exposure time is increased to improve image brightness, then brightness level improves, but image clarity deteriorates due to overexposure
Solution Approach 1:
The patent applies preliminary action by performing histogram analysis and brightness evaluation before final image capture. The system pre-calculates the optimal exposure time by analyzing brightness distribution in advance, preventing overexposure or underexposure before they occur. This ensures the captured fingerprint image has appropriate brightness and maintains identification accuracy.
Solution Approach 2:
The patent implements feedback through iterative histogram analysis and exposure time adjustment. The system captures a preliminary image, analyzes its brightness histogram, evaluates whether the brightness is appropriate, and adjusts exposure time accordingly. This closed-loop feedback mechanism ensures optimal image brightness while maintaining fingerprint identification accuracy.
2Reliability
If exposure time is decreased to improve image clarity, then image clarity improves, but brightness level deteriorates due to underexposure
Solution Approach 1:
The system performs preliminary histogram analysis and brightness evaluation before final image capture. By pre-calculating the optimal exposure time based on brightness distribution, the system prevents underexposure before it occurs, ensuring the captured image has sufficient brightness while maintaining identification accuracy.
Solution Approach 2:
The patent uses feedback through iterative exposure adjustment. The system captures a test image, analyzes its brightness histogram, evaluates whether brightness is sufficient, and adjusts exposure time accordingly. This closed-loop feedback ensures optimal balance between image brightness and fingerprint identification accuracy.
3Ease of operation
If fixed exposure time is used to simplify operation, then ease of operation improves, but image quality deteriorates due to improper brightness
Solution Approach 1:
The patent applies self-service by enabling the system to automatically determine optimal exposure time through histogram analysis and brightness evaluation. The system autonomously adjusts exposure parameters without requiring manual intervention, ensuring optimal image quality while maintaining operational simplicity. The device serves itself by automatically adapting to different lighting conditions.
4Reliability
If multiple exposure times are tested to optimize image quality, then image quality improves, but operation time increases
Solution Approach 1:
The system performs preliminary histogram analysis on a single test image to determine optimal exposure time, avoiding the need for multiple test captures. By pre-calculating the best exposure time based on brightness distribution analysis, the system reduces time loss while ensuring optimal image quality for fingerprint identification.
Solution Approach 2:
The patent uses efficient feedback by analyzing the histogram of a single test image and calculating optimal exposure time through brightness evaluation. This single-cycle feedback mechanism determines the best exposure time without requiring multiple iterative captures, thus minimizing time loss while ensuring optimal image quality.
Data Source
AI summary
An exposure time determination method for image sensing operation includes: providing a first stage exposure condition which includes a first exposure time; sensing an image according to the first stage exposure condition to generate a first histogram which has a first histogram brightness maximum, a first histogram brightness minimum, and a first histogram width; increasing or decreasing the first exposure time to a second exposure time as a second stage exposure condition, and sensing the image according to the second stage exposure condition to generate a second histogram which has a second histogram brightness maximum, a second histogram brightness minimum, and a second histogram width; comparing the first histogram width with the second histogram width to generate a comparison result, and determining a third exposure time to be a third stage exposure condition according to the comparison result; and sensing the image according to the third stage exposure condition.