Optical Sensor Folded Collimator for Thick Cover Glass Fingerprint Imaging
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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 smartphone cover glass, requiring cutouts that compromise device aesthetics and integrity, while optical sensors struggle to fit within small display stacks due to the size constraints.
Innovation Solution
An optical sensor design incorporating a transparent layer with apertures and reflective surfaces that restrict light angles, acting as a folded collimator, allowing for thin detector configurations that avoid image blurring and maintain display quality, enabling fingerprint detection without the need for cutouts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional capacitive fingerprint sensors are used to detect fingerprints through thick cover glass, then the sensor can be integrated into the display, but the sensor cannot reliably detect fine ridge and valley features through thick layers
Solution Approach 1:
The patent replaces capacitive sensing (electrical field-based) with optical sensing (light-based). The optical sensor uses light sources to illuminate the fingerprint and detectors to capture reflected light patterns, enabling reliable fingerprint detection through thick cover glass without the limitations of capacitive sensing. This substitution of the sensing mechanism allows the sensor to penetrate thicker materials while maintaining detection reliability.
Solution Approach 2:
The patent introduces optical elements (lenses, mirrors, light guides) as intermediaries between the light source and the fingerprint, and between the fingerprint and the detectors. These optical elements condition and direct the light to ensure sufficient light reaches the fingerprint and returns to the detectors, enabling reliable sensing through the cover glass thickness.
2Manufacturing precision
If optical fingerprint sensors are used with conventional optical elements to condition light, then light can be properly conditioned before reaching sensor elements, but the optical elements cannot fit within the limited height of the display stack
Solution Approach 1:
The patent transitions from a conventional vertical stacking arrangement of optical elements to a lateral or folded optical path configuration. By changing the dimensional arrangement of optical components (using side-mounted lenses, folded light paths, or integrating optics into the cover glass plane), the sensor achieves proper light conditioning while maintaining a thin profile that fits within the display stack height constraints.
Solution Approach 2:
The patent integrates multiple functions into fewer components. For example, the cover glass itself may serve as both a protective element and an optical element (light guide or lens). Detectors may be positioned to serve both display and sensing functions. This multi-functionality reduces the number of separate optical elements needed, thereby reducing overall sensor thickness while maintaining image quality.
3Reliability
If cutouts are formed in the cover glass for discrete capacitive fingerprint sensors, then the sensors can detect fingerprints without sensing through thick cover glass, but the device aesthetics and integrity are compromised
Solution Approach 1:
The patent merges the fingerprint sensor with the display structure itself. The optical sensor components (light sources, detectors, and optical elements) are integrated into the display stack or cover glass, allowing the sensor to be flush with the device surface. This integration eliminates the need for separate cutouts while maintaining both device aesthetics and fingerprint detection capability.
Solution Approach 2:
The patent replaces the mechanical cutout approach with an optical sensing system that can penetrate the cover glass. By using light-based sensing instead of direct contact capacitive sensing, the system maintains the integrity of the cover glass surface while achieving reliable fingerprint detection, thus preserving device aesthetics and structural integrity.
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 solution allows for reliable fingerprint imaging through thick cover layers without compromising device aesthetics or integrity, achieving high-resolution fingerprint capture while minimizing the sensor's thickness and maintaining image quality.
Implementation Method 1
a first set of reflective surfaces disposed below the second side of the transparent layer configured to receive light transmitted through the first set of apertures and to reflect the received light
Implementation Method 2
An optical sensor design incorporating a transparent layer with apertures and reflective surfaces that restrict light angles, acting as a folded collimator, allowing for thin detector configurations that avoid image blurring and maintain display quality
Data Source
AI summary
Systems and methods for optical imaging are disclosed. An optical sensor for imaging a biometric input object on a sensing region includes a transparent layer having a first side and a second side opposite the first side; a set of apertures disposed above the first side of the transparent layer; a first set of reflective surfaces disposed below the second side of the transparent layer configured to receive light transmitted through the first set of apertures and to reflect the received light; a second set of reflective surfaces disposed above the first side of the transparent layer configured to receive the light reflected from the first set of reflective surfaces and to further reflect the light; and a plurality of detector elements positioned to receive the further reflected light from the second set of reflective surfaces.