Overlapping Collimating Elements for Fingerprint Sensor Crosstalk Reduction
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Solution Overview
Problem
Optical identification apparatuses for biological characteristics face challenges in capturing high-quality images due to disorganized light beams from reflected fingerprints, leading to poor identification results and ineffective crosstalk reduction.
Innovation Solution
An image capturing apparatus with a collimator comprising overlapping collimating elements and a light absorbing layer, where the light absorbing layer has light passing openings that expose sensing areas of the sensor, and the collimating elements' transparent substrates are designed to absorb large-angle light beams, addressing the issue of crosstalk by ensuring that 0.3×WS×T1≤T2≤T1, where W is the width of light passing openings, S is the spacing, and T1 and T2 are the thicknesses of the collimating elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional optical identification apparatus uses a light source and sensor to capture fingerprint images, then the basic identification function is achieved, but the captured images have poor quality due to disorganized light beams and crosstalk
Solution Approach 1:
The collimator is divided into multiple collimating elements (first collimating element and second collimating element) with different thicknesses (T1 and T2). Each element segments the light path differently, with the first element having thickness T1 and the second having thickness T2 where 0.3×W×S×T1≤T2≤T1. This segmentation allows different regions of the sensor to receive light from different angular ranges, effectively separating useful light from crosstalk.
Solution Approach 2:
Different regions of the sensor are assigned different functional qualities through the collimating elements. The first collimating element (thickness T1) serves regions more susceptible to crosstalk, while the second collimating element (thickness T2) serves regions requiring different angular filtering. This local differentiation optimizes crosstalk reduction across the entire sensor surface.
2Reliability
If the collimator uses thicker collimating elements to reduce crosstalk, then the identification capability improves, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The invention optimizes the thickness parameters T1 and T2 of the collimating elements within the range 0.3×W×S×T1≤T2≤T1. By carefully selecting these parameters, the system achieves effective crosstalk reduction without requiring excessively thick elements that would complicate the device. The parameter optimization balances performance with manufacturability.
Solution Approach 2:
The collimating elements are constructed as composite structures with transparent substrates and light-absorbing layers. This composite design enables precise control over light transmission and absorption properties, achieving superior crosstalk reduction while maintaining manageable device complexity through well-defined material properties.
3Use of energy by moving object
If the light absorbing layer has larger light passing openings to increase light transmission, then the signal strength improves, but the crosstalk reduction effectiveness decreases
Solution Approach 1:
The invention resolves the contradiction by introducing the angular dimension through collimating elements of different thicknesses. Instead of simply enlarging light passing openings in a single plane, the system uses the thickness dimension (T1 and T2) to control light angles. This allows larger openings to transmit more light while the differential thickness maintains angular discrimination to reduce crosstalk.
Solution Approach 2:
The collimating elements act as intermediaries between the light passing openings and the sensor. They modify the light paths from the openings, allowing larger openings to transmit more light while the collimating elements filter out angled crosstalk rays before they reach the sensor, thus mediating between light transmission and crosstalk reduction requirements.
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
The design effectively reduces crosstalk and enhances the signal-to-noise ratio, improving the identification capability of the image capturing apparatus by absorbing large-angle light beams and ensuring accurate biological characteristic capture.
Implementation Method 1
the light absorbing layer includes a plurality of light passing openings... makes the large-angle light beams reflected several times between the collimating elements and absorbed by the light absorbing layer
Data Source
AI summary
An image capturing apparatus including a cover plate, a sensor, and a collimator is provided. The sensor is located on one side of the cover plate. The collimator is disposed between the cover plate and the sensor, and the collimator includes collimating elements overlapping with each other. Each collimating element includes a transparent substrate and a light absorbing layer disposed on the transparent substrate. The light absorbing layer includes a plurality of light passing openings. The light passing openings expose sensing areas of the sensor. Spacing between the light passing openings is S. A width of each light passing opening is W, and 0.3W<S. A transparent substrate thickness of a first collimating element in the collimating elements is T1. A transparent substrate thickness of a second collimating element in the collimating elements is T2. The image capturing apparatus satisfies:0.3×WS×T1≤T2≤T1.