Optical Filter Film for Fingerprint Recognition Accuracy
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Solution Overview
Problem
Optical fingerprint recognition methods face inaccuracies due to scattered light and ambient light interference, particularly in the long wavelength band above 600 nm, which cannot be effectively filtered by existing through-hole filtering methods.
Innovation Solution
A texture recognition assembly is designed with a filter film layer configured to filter visible light with wavelengths greater than or equal to 600 nm, comprising stacked filter film groups with specific refractive index differences and thicknesses, and a structure that includes a photosensitive sensing layer and a texture contact layer, reducing transmittance of ambient light in the long wavelength band to enhance recognition accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a through-hole filtering method is used to block ambient light, then the structure is simple, but it cannot effectively filter light in the long wavelength band above 600 nm
Solution Approach 1:
The patent employs a composite filter film structure comprising multiple layers with different refractive indices (high refractive index layer and low refractive index layer). This composite structure is designed to selectively reflect long wavelength light (above 600 nm) while allowing shorter wavelengths to pass through, thereby achieving effective ambient light filtering for fingerprint recognition without sacrificing manufacturing feasibility
Solution Approach 2:
The patent utilizes optical parameter changes by controlling the thickness, refractive index, and layer configuration of the filter film. By adjusting these parameters, the filter film achieves wavelength-selective reflection properties, specifically targeting long wavelength ambient light that causes recognition inaccuracies while maintaining transparency for fingerprint imaging wavelengths
2Illumination intensity
If light with wavelength greater than or equal to 600 nm is not filtered, then the photosensitive sensor receives sufficient light for recognition, but scattered light causes image blurring and recognition inaccuracy
Solution Approach 1:
The filter film is designed with spatially varying optical properties through its layered structure. Different layers have different refractive indices and thicknesses, creating localized optical effects that selectively interact with different wavelength components of light. This local quality variation enables the film to reflect long wavelength ambient light while transmitting shorter wavelength light needed for fingerprint recognition
Solution Approach 2:
The patent converts the harmful effect of long wavelength ambient light (which causes scattering and image blurring) into a beneficial reflection. The filter film's optical structure is designed to reflect this specific wavelength range back, preventing it from reaching the photosensitive sensor and causing blur, while allowing beneficial shorter wavelength light to pass through for accurate fingerprint imaging
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 solution effectively filters out ambient light in the long wavelength band, improving the accuracy of fingerprint recognition by reducing scattered light interference and enhancing the distinction between light reflections from ridges and valleys, thereby improving the overall recognition process.
Implementation Method 1
The filter film layer is configured to filter visible light with a wavelength greater than or equal to λ, and a value of λ is greater than or equal to 600 nm
Implementation Method 2
Each of the K filter film groups includes two first films disposed opposite to each other, and a second film disposed between the two first films. A refractive index of the second film is greater than a refractive index of the first film
Data Source
AI summary
A texture recognition assembly, a method of manufacturing the same, and a display apparatus are disclosed. The texture recognition assembly includes a photosensitive sensing layer, a texture contact layer, and a filter film layer disposed at a side of the photosensitive sensing layer proximate to the texture contact layer. The filter film layer is configured to filter visible light with a wavelength greater than or equal to λ. A value of λ is greater than or equal to 600 nm.