Coded Aperture Mask for Optical Fingerprint Sensor Integration
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Solution Overview
Problem
Existing optical fingerprint sensors face challenges in achieving high resolution due to the complexity and sensitivity of manufacturing small microlenses, and are prone to spatial differences in transmissivity, making them difficult to integrate with display panels effectively.
Innovation Solution
The implementation of a coded aperture imaging principle in an optical fingerprint sensor, where a transmission mask with a repeating pattern of coded aperture elements forms multiple coded images on the image sensor, reducing computational complexity and allowing for a smaller sensor size, integrated with a display panel without refractive elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If microlenses are made small to achieve high resolution, then image resolution is improved, but manufacturing complexity and sensitivity to variations increase
Solution Approach 1:
The patent removes microlenses and other refractive elements from the optical fingerprint sensor, replacing them with a coded aperture mask that directly modulates light. This extraction of refractive elements eliminates the manufacturing complexity associated with making and positioning small microlenses while maintaining high resolution through computational reconstruction of the fingerprint image from the coded aperture patterns.
2Measurement precision
If microlenses are made small to achieve high resolution, then image resolution is improved, but sensitivity to spatial differences in transmissivity increases
Solution Approach 1:
The patent eliminates microlenses that are sensitive to spatial variations in transmissivity by replacing them with a coded aperture mask. The coded aperture approach uses direct light modulation followed by computational reconstruction, which is inherently more robust to variations in the optical path and eliminates the reliability issues associated with small microlens arrays.
3Strength
If refractive elements are used to focus light, then light focusing capability is improved, but integration with display panel becomes difficult
Solution Approach 1:
The patent removes all refractive elements (microlenses, collimators) from the sensor structure and replaces them with a coded aperture mask that can be directly integrated into the display panel stack. This flat, non-refractive design allows for easier manufacturing and integration with display technologies while achieving comparable or superior performance through computational imaging.
4Area of moving object
If sensor size is reduced for compact integration, then device compactness is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent replaces the mechanical/optical focusing system (microlenses requiring precise positioning) with a coded aperture mask and computational reconstruction system. This substitution allows for relaxed manufacturing tolerances while achieving high resolution, as the coded aperture patterns can be manufactured with standard precision and the high-resolution image is recovered through computational algorithms rather than purely optical means.
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 enables a more compact and robust optical fingerprint sensor with improved resolution, easier integration with display devices, and reduced manufacturing complexity, while maintaining high image reconstruction accuracy.
Implementation Method 1
coded aperture imaging is based on the principle of blocking the incoming light in a known pattern so that a coded shadow is cast upon the image sensor
Implementation Method 2
an image sensor configured to capture an image corresponding to the coded image projected thereonto by the coded aperture
Data Source
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Figure 3A~3B
Figure 4A~4D
AI summary
The invention relates to an optical biometric imaging device (102) configured to capture an image of an object (104) in contact with an outer surface (106) of the biometric imaging device, the biometric imaging device comprising: an image sensor (200) comprising a photodetector pixel array (202); a transparent substrate (204) arranged to cover the image sensor; a transmission mask (206, 302) arranged to cover the transparent substrate, wherein the transmission mask comprises a plurality of openings (208), the openings forming a coded aperture configured to project a coded image of an object in contact with the outer surface of the imaging device onto the image sensor; and image sensor circuitry (210) configured to capture an image corresponding to the coded image projected onto the image sensor.