Fingerprint Photosensor Layout With Microlens and Light Shielding
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Solution Overview
Problem
Conventional fingerprint sensing apparatuses face limitations in imaging quality and photosensitivity due to the design of their light sensing mechanisms, which affect the accuracy and efficiency of fingerprint identification.
Innovation Solution
The proposed photosensitive apparatus incorporates a substrate with an operating circuit, first and second electrodes, dielectric layers, a spacer layer, a light shielding layer, and micro lenses to enhance light transmission and reduce the probability of light entering at large angles, thereby improving imaging quality and photosensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional backlight source is used as the sensor light source, then the structure is simple, but the imaging quality and photosensitivity are limited
Solution Approach 1:
The light receiving area is divided into multiple independent first photosensitive patterns, each capable of receiving light independently. This segmentation increases the total light receiving area while maintaining manageable structural complexity through modular design
Solution Approach 2:
The patent introduces a vertical stacking dimension by placing the light shielding layer, spacer layer, and micro lens above the photosensitive patterns. This three-dimensional arrangement optimizes light path control and enhances photosensitivity without significantly increasing planar footprint
2Reliability
If the light receiving area is increased to improve photosensitivity, then the photosensitivity improves, but the device area increases
Solution Approach 1:
The light shielding layer is positioned within the projection area of the spacer layer, which itself is positioned within the projection area of the micro lens. This nested arrangement ensures that all components are contained within a compact footprint while maximizing the light receiving area of the photosensitive patterns
Solution Approach 2:
By stacking components vertically (light shielding layer, spacer layer, micro lens above the photosensitive patterns), the patent achieves three-dimensional space utilization that increases light receiving area without proportionally increasing the planar device area
3Reliability
If light transmission is increased to improve photosensitivity, then the photosensitivity improves, but light entering at large angles reduces imaging quality
Solution Approach 1:
The light shielding layer acts as an intermediary between the micro lens and the photosensitive patterns, selectively blocking oblique light while allowing perpendicular light to pass through. This mediator structure enables the system to benefit from increased light transmission while maintaining imaging quality by filtering out harmful angled light
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 configuration increases the ratio of light-receiving area to equivalent capacitor, enhancing the photosensitivity and imaging quality of the apparatus, leading to more accurate fingerprint identification.
Implementation Method 1
The light shielding layer is disposed on the spacer layer and has a plurality of light transmission openings corresponding to the first photosensitive patterns. The at least one micro lens is disposed above the light shielding layer and is overlapped with the light transmission openings of the light shielding layer.
Implementation Method 2
Light beams emitted by the backlight source pass through a fingerprint sensor and reaches a finger. Since ridges and valleys of a fingerprint have different reflectivity, light beams reflected by the ridges and valleys of the fingerprint result in multiple photoelectric currents of different sizes on multiple sensor elements located at multiple places in the fingerprint sensor.
Data Source
AI summary
A photosensitive apparatus includes an operating circuit, a first electrode, multiple first photosensitive patterns, a dielectric layer, a second electrode, a spacer layer, a light shielding layer, and at least one micro lens. The first electrode is electrically connected to a first terminal of the operating circuit. The first photosensitive patterns are separated from each other and disposed on the first electrode. Multiple first surfaces of the first photosensitive patterns are electrically connected to the first electrode. The dielectric layer is disposed on the first photosensitive patterns. The second electrode is disposed on the dielectric layer and electrically connected to multiple second surfaces of the first photosensitive patterns through multiple first contact holes of the dielectric layer. The spacer layer is disposed on the second electrode. The light shielding layer is disposed on the spacer layer. The at least one micro lens is disposed above the light shielding layer.