Angled Reflectors for Optical Sensor Height Reduction
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Solution Overview
Problem
Conventional capacitive fingerprint sensors face challenges in detecting fine ridge and valley features through thick layers, such as the cover glass of mobile devices, requiring cutouts that compromise device aesthetics and increase moisture vulnerability, while optical sensors struggle to fit conventional optical elements in small spaces.
Innovation Solution
An optical sensor system with dual-mirror periscope-like arrangements integrated into the display, using an array of imaging cells with reflective surfaces to direct light from the sensing region to detector elements, minimizing thickness and interference with display image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional optical elements are used in optical sensors, then light conditioning can be achieved, but the sensor height becomes too large to fit in small spaces such as display stacks
Solution Approach 1:
The patent transforms the optical path from a vertical arrangement (requiring height) to a lateral arrangement using angled reflectors at 45 degrees. Light travels horizontally through the sensing region and is reflected down to the detector plane, eliminating the need for vertical optical elements and reducing sensor height to fit within display stack constraints.
2Measurement precision
If capacitive sensors are placed close to the sensing array to detect fine ridge and valley features, then detection precision improves, but the cover glass thickness must be reduced or a cutout created
Solution Approach 1:
The patent replaces the mechanical capacitive sensing approach (requiring physical contact through thin cover glass or cutouts) with an optical imaging system. The optical sensor captures light reflected from the fingerprint ridges and valleys, enabling high-resolution imaging through the cover glass without mechanical contact requirements or structural modifications to the device housing.
3Reliability
If cutouts are created in the cover glass for discrete capacitive sensors, then fingerprint detection capability is maintained, but device aesthetics are compromised and moisture ingress risk increases
Solution Approach 1:
The patent integrates the fingerprint sensing function directly into the display structure by embedding the optical sensor and angled reflector assembly within the display stack. This multi-functional integration allows the display to serve both as the user interface and as the housing for the biometric sensor, eliminating the need for separate cutouts while maintaining detection capability and device sealing.
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 reliable biometric imaging, including fingerprint detection, without the need for cutouts, maintaining device aesthetics and preventing moisture ingress, while achieving high resolution and compact design.
Implementation Method 1
a first reflective surface, the first reflective surface positioned to receive light from a first sensing region of the display and to reflect the received light
Implementation Method 2
a second reflective surface, the second reflective surface positioned to receive the reflected light from the first reflective surface, and to further reflect the light in a path that is substantially normal to the detector plane and towards the first detector element
Data Source
AI summary
Systems and methods for optical imaging using an optical sensor in an active area of the display are described. The optical sensor includes a set of detector elements positioned in a detector plane; a transparent layer; and a set of first reflective surfaces in the transparent layer. Each reflective surface in the first set of reflective surfaces is positioned to receive light from a portion of a sensing region of the display and to reflect the received light. The optical sensor further includes a second set of reflective surfaces, each reflective surface in the second set of reflective surfaces is positioned to receive the transmitted light from the first set of reflective surfaces, and to further reflect the received light towards one of the set of detector elements.