Fingerprint Sensor Spacer Layer for High Contrast Imaging
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing fingerprint recording technologies face challenges in achieving uniform contrast over a large placement surface without compromising brightness or brilliance, particularly due to limitations in the distance between the sensor and placement surface, leading to low contrast between skin ridges and valleys.
Innovation Solution
A direct optical recording apparatus with a series of layers, including a cover layer, sensor layer, spacer layer, and substrate, where the spacer layer limits light incident angles to enhance contrast by using spacer structures and a diode aperture layer to control the angular spectrum of illumination, preventing ambient and scatter light from reaching the sensor at large angles, and utilizing an air layer between the illumination and sensor layers for directed illumination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the distance between the sensor layer and placement surface is increased, then the field of view and coverage area are improved, but the contrast between skin ridges and valleys deteriorates due to inclusion of ambient and scatter light at large angles
Solution Approach 1:
The sensor layer is divided into multiple sensor pixels arranged in a two-dimensional grid, where each sensor pixel independently detects light from specific angular directions. This segmentation allows the system to cover a larger placement surface area while maintaining contrast precision for each individual sensing point.
Solution Approach 2:
Each sensor pixel is equipped with a light-sensitive element that has specific angular sensitivity characteristics, making different parts of the sensor layer responsive to different angular ranges. This local differentiation enables the system to maintain high contrast measurement precision across the entire large placement surface by selectively detecting light within specific angular cones at each location.
2Measurement precision
If aperture openings are arranged off-center to prevent direct back-reflection, then contrast is improved, but device complexity increases due to additional aperture structures
Solution Approach 1:
The patent combines the light-sensitive element with the aperture structure into an integrated sensor pixel unit. The aperture opening is directly formed as part of the light-sensitive element structure, eliminating the need for separate aperture components and reducing overall device complexity while maintaining the contrast improvement benefits of angularly selective light detection.
Solution Approach 2:
The light-sensitive element serves multiple functions simultaneously: it acts as both the photosensitive detection element and the aperture structure for angular light filtering. This multi-functionality reduces the number of separate components needed in the system, simplifying the overall device structure while maintaining effective contrast enhancement.
3Measurement precision
If microlenses are added to limit incident angles, then contrast is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent extracts the angular filtering function from separate optical elements like microlenses and integrates it directly into the light-sensitive element structure through aperture openings. This extraction eliminates the need for complex microlens fabrication processes while achieving the same incident angle limitation effect, thereby simplifying manufacturing.
Solution Approach 2:
The aperture opening structure formed as part of the light-sensitive element can be created using standard semiconductor fabrication processes that are already widely available and cost-effective. This approach replaces expensive and complex microlens manufacturing with more economical planar processing techniques, making the solution more manufacturable and cost-effective.
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 allows for improved contrast in the recording of security-related objects by limiting the incident angles of light, increasing the participation of direct back-reflection and scatter light in imaging, thereby enhancing the visibility of skin ridges and valleys without affecting the brightness or brilliance of the imaging process.
Implementation Method 1
the spacer layer with spacer structures in order to limit light incident from the placement surface to small incident angles on the sensor layer
Implementation Method 2
light coming from the illumination elements is partially reflected at an interface from placement surface to air, i.e., in a skin valley, due to the large difference in the refractive index
Implementation Method 3
an illumination layer for emitting illumination light which is arranged below a plane of the entrance apertures of the light-sensitive elements of the sensor layer considered from direction of the placement surface
Data Source
AI summary
An apparatus for direct optical recording of security-related objects with a series of layers comprising a cover layer with an object placement surface, a sensor layer, a spacer layer with spacer structures for limiting light incident from the placement surface to small incident angles on the sensor layer, and a substrate as carrier of the series of layers. To capture security-related objects with good contrast over a large surface, the sensor pixels have a light-sensitive element and a passage region, and the spacer layer is produced by spacer structures provided on the sensor layer or by spacer structures formed from existing raised-shaped function elements, and the spacer layer comprises cutouts in the region of the entrance aperture of every light-sensitive element, each cutout filled with a medium having a refractive index lower than that of the sensor layer and a layer adjoining in a direction of the placement surface.