Optical Fingerprint Sensor Collimator Filter Aperture Design
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Solution Overview
Problem
Conventional optical fingerprint sensors are too bulky for integration in mobile devices, and capacitive sensors face challenges in detecting fine ridge and valley features through thick layers like cover glass, requiring cutouts and mechanical buttons that compromise device design and user experience.
Innovation Solution
An optical fingerprint sensor system utilizing a collimator filter layer with an array of apertures between an illumination layer and an image sensor array, allowing only specific reflected light to reach the sensor elements, preventing blurring and enabling detection through thick cover layers without the need for cutouts or mechanical buttons.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional optical fingerprint sensors are used, then high-resolution fingerprint imaging is achieved, but the sensor becomes too bulky for mobile devices
Solution Approach 1:
The optical path is segmented into distinct functional layers: illumination layer, collimator layer with apertures, cover layer, and image sensor array. This segmentation allows each component to be optimized independently, enabling high-resolution imaging while reducing overall sensor volume for mobile device integration.
Solution Approach 2:
The patent transitions from conventional lateral light blocking to vertical light filtering by positioning the collimator layer between the illumination source and the sensor array. This dimensional reorganization allows light path control in the vertical dimension, reducing the horizontal footprint and enabling compact mobile device integration while maintaining imaging resolution.
2Volume of moving object
If capacitive sensors are used to reduce size, then the sensor becomes compact for mobile devices, but the ability to detect fine ridge and valley features through thick cover glass deteriorates
Solution Approach 1:
The collimator layer with apertures acts as an intermediary optical element between the illumination source and the image sensor array. It conditions the reflected light from the fingerprint, allowing fine ridge and valley features to be detected through thick cover glass while maintaining a compact sensor design suitable for mobile devices.
3Volume of moving object
If a pinhole camera approach is used to create a compact optical sensor, then device size is reduced, but image quality deteriorates due to light blocking and inversion
Solution Approach 1:
The patent extracts and eliminates the light-blocking layer inherent in pinhole camera designs. By using a collimator layer with apertures positioned strategically in the optical path, the system allows sufficient light transmission while maintaining compact size, and the image sensor array captures non-inverted images, thereby improving image quality compared to traditional pinhole approaches.
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
Enables a lower-profile, sensitive, and high-resolution optical fingerprint sensor suitable for mobile devices, maintaining image quality and user experience by filtering light effectively through various thicknesses of cover layers.
Implementation Method 1
a collimator filter layer disposed above the image sensor array, the collimator filter layer having an array of apertures
Implementation Method 2
transmitting light in an illumination region such that at least a portion of light reflects from a sensing region
Implementation Method 3
an image sensor array; a collimator filter layer disposed above the image sensor array
Data Source
AI summary
Fingerprint sensors include a plurality of optical sensor elements, a collimator filter disposed above the plurality of optical sensor elements, and a display disposed above the collimator filter, wherein the display is a fingerprint imaging light source. The collimator filter has a plurality of apertures, and the plurality of optical sensor elements is configured to receive light transmitted through one aperture of the plurality of apertures.