Filter Collimator With Interference And Absorption Films
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Solution Overview
Problem
Conventional optical fingerprint identifiers suffer from crosstalk due to the inefficiencies in collimators, which compromises their reliability.
Innovation Solution
A filter collimator is designed with a substrate, a photodiode, an interference-type filter film, and an absorption-type filter film, where the interference-type filter film has high transmittance at specific angles and wavebands, and the absorption-type filter film has high transmittance in non-overlapping wavebands, reducing crosstalk by allowing significant light signals only within a specific angle range to the photodiode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional collimators are used in optical fingerprint identifiers, then the system can be constructed with standard optical elements, but crosstalk occurs which compromises reliability
Solution Approach 1:
The filter collimator is divided into multiple functional layers: an interference-type filter film layer and an absorption-type filter film layer, each segment performing specific wavelength filtering functions. This segmentation allows precise control of light transmission at different wavelengths and angles, eliminating crosstalk while maintaining reliability
Solution Approach 2:
Different regions of the filter collimator have different optical properties tailored to specific functions. The interference-type filter film provides angle-dependent wavelength filtering, while the absorption-type filter film provides angle-independent wavelength filtering. This local quality differentiation enables precise control of light signals from different directions, eliminating crosstalk
2Reliability
If filter films with angle-dependent transmittance are used, then crosstalk is reduced by filtering light at specific angles, but the device complexity increases
Solution Approach 1:
The patent combines two filter films with different filtering mechanisms into a single integrated filter collimator structure. The interference-type filter film and absorption-type filter film work together in one device, achieving both angle-dependent and angle-independent filtering without requiring separate components, thus reducing overall system complexity while improving reliability
Solution Approach 2:
The filter collimator performs multiple functions simultaneously: wavelength filtering, angle-dependent signal separation, and crosstalk elimination. By integrating these functions into a single component with multiple filter layers, the device achieves high reliability without proportionally increasing complexity
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 filter collimator effectively minimizes crosstalk by allowing significant light signals only within a specific angle range to the photodiode, enhancing the reliability of fingerprint identification systems.
Implementation Method 1
an interference-type filter film disposed between the substrate and the first light-shielding layer. When a first light is incident at a first angle relative to the normal of the top surface of the substrate, the interference-type filter film has a transmittance greater than 50% in a first waveband
Implementation Method 2
the absorption-type filter film has a transmittance greater than 50% in a third waveband
Data Source
AI summary
A filter collimator is provided. The filter collimator includes a substrate having a photodiode. The filter collimator also includes an interference-type and an absorption-type filter film disposed over the substrate. When a first light is incident at a first angle relative to the normal of the top surface of the substrate, the interference-type filter film has a transmittance greater than 50% in a first waveband, and when a second light is incident at a second angle relative to the normal of the top surface of the substrate, the interference-type filter film has a transmittance greater than 50% in a second waveband, the absorption-type filter film has a transmittance greater than 50% in a third waveband, and wherein the first waveband partially overlaps the third waveband, the second waveband does not overlap the third waveband, and the second angle is greater than the first angle.