Optical Biometric Imaging Device Adaptive Calibration
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Solution Overview
Problem
Optical fingerprint sensors in user devices face challenges in maintaining image quality due to changes in object distance, such as when a screen protector is applied, making it difficult to calibrate without a dedicated calibration target, especially after the device has left the production facility.
Innovation Solution
A method for determining image reconstruction parameters in optical biometric imaging devices using a microlens array and image sensor, where sub-images captured by the sensor are processed to calculate a demagnification factor based on overlap, allowing for calibration during normal image capture without a specific calibration target, and enabling accurate biometric imaging even with changes in object distance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If calibration is performed using a dedicated calibration target, then manufacturing precision is improved, but device complexity and ease of operation worsen due to requiring special targets and procedures
Solution Approach 1:
The patent uses a virtual calibration target created from captured sub-images instead of a physical calibration target. The system captures images of a virtual target pattern and processes these images to determine calibration parameters, eliminating the need for physical calibration artifacts and simplifying the calibration process.
Solution Approach 2:
The system performs self-calibration by using its own captured images to determine calibration parameters. The calibration process is automated and does not require external calibration targets or manual intervention, allowing the device to calibrate itself using normal imaging operations.
2Adaptability or versatility
If the object distance changes due to screen protector installation, then adaptability improves, but measurement precision deteriorates due to loss of resolution
Solution Approach 1:
The patent implements dynamic calibration parameters that can be adjusted based on the actual object distance. The system determines calibration parameters including demagnification factor and pixel size based on captured images, allowing it to adapt to different object distances caused by screen protectors or other factors, thereby maintaining measurement precision across varying conditions.
3Reliability
If calibration is performed after device deployment, then reliability improves by accounting for wear and tear, but ease of operation worsens due to lack of user knowledge about when calibration is needed
Solution Approach 1:
The system incorporates feedback mechanisms that automatically detect when calibration is needed and perform calibration without user intervention. The system monitors imaging quality and object distance changes, triggering automatic calibration when necessary, thus maintaining reliability while preserving ease of operation.
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 allows for accurate image reconstruction and biometric imaging without the need for a calibration target, simplifying the manufacturing process and enabling adaptive calibration to changes in object distance, such as those caused by screen protectors, thereby maintaining image quality.
Implementation Method 1
an optical biometric imaging device comprising a microlens array and an image sensor arranged to receive light having passed through the microlens array
Implementation Method 2
by the image sensor, capturing a plurality of sub-images together representing an image of a biometric object
Data Source
AI summary
Method for determining image reconstruction parameters in an optical biometric imaging device comprising a plurality of microlenses forming a microlens array and an image sensor arranged to receive light having passed through the microlenses, the method comprising: by the image sensor, capturing a plurality of sub-images together representing an image of a biometric object in contact with a sensing surface of the biometric imaging device, each sub-image corresponding to a respective microlens; and determining a demagnification factor based on at least a subset of the plurality of sub-images.