Touch Panel Light Path Limiting Structure for Fingerprint Crosstalk
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Solution Overview
Problem
In existing fingerprint recognition technologies for display devices, crosstalk between infrared light-emitting sub-pixels and photosensitive elements hinders accurate recognition of fingerprint valleys and ridges due to widespread light reception, leading to inaccurate information verification.
Innovation Solution
A touch panel design featuring a light path limiting structure with a central area of higher refractive index and a peripheral area of lower refractive index, which directs and totally reflects light emitted from light-emitting elements, minimizing crosstalk by concentrating light emission and reception within a small angle range, thereby enhancing fingerprint recognition accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If infrared light-emitting sub-pixels are added to original pixels for fingerprint recognition, then fingerprint recognition function is achieved, but light crosstalk occurs between adjacent photosensitive elements
Solution Approach 1:
The patent divides the light path into distinct segments by introducing light path limiting structures (light shielding layers and light reflecting layers) between adjacent light-emitting sub-pixels and photosensitive elements. This segmentation prevents light from one sub-pixel from reaching adjacent photosensitive elements, thereby eliminating crosstalk while maintaining the fingerprint recognition function.
Solution Approach 2:
The patent extracts and removes the harmful light crosstalk by introducing light path limiting structures that specifically block stray light paths. The light shielding layers and light reflecting layers are strategically placed to extract only the unwanted light paths while allowing the useful light to reach the intended photosensitive elements.
2Measurement precision
If light path limiting structure with refractive index difference is used, then light crosstalk is reduced, but device structure becomes more complex
Solution Approach 1:
The patent applies local quality by creating regions with different refractive indices at specific locations where light crosstalk occurs. The light path limiting structures are selectively positioned only where needed to block crosstalk paths, rather than uniformly across the entire device, thereby reducing overall structural complexity while maintaining light reception accuracy.
Solution Approach 2:
The patent introduces intermediary light path limiting structures (light shielding layers and light reflecting layers) that mediate between the light-emitting sub-pixels and photosensitive elements. These intermediary structures control light propagation without requiring fundamental changes to the core fingerprint recognition functionality, thus managing complexity while improving precision.
3Area of stationary object
If light is emitted in wide range, then light coverage is improved, but crosstalk between photosensitive elements increases
Solution Approach 1:
The patent inverts the conventional approach by instead of trying to control the light emission pattern, it blocks the harmful light paths after emission using light path limiting structures. The light-emitting sub-pixels can emit light in a wide range as before, but the light shielding layers and light reflecting layers strategically positioned in the light path block the crosstalk before it reaches adjacent photosensitive elements.
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 reduces crosstalk between fingerprint recognizing units, allowing for precise recognition of fingerprints by ensuring that most light is incident on the corresponding photosensitive elements, improving the accuracy of fingerprint verification.
Implementation Method 1
the refractive index of the peripheral area is less than the refractive index of the central area; and the light path limiting structure is configured to enable light emitted from the light-emitting element to be reflected in the central area to the peripheral area
Implementation Method 2
to be totally reflected in the peripheral area, and then exit the side of the light path limiting structure away from the light-emitting element
Data Source
AI summary
A touch panel, a display panel, a display device, and a method for recognizing a fingerprint are disclosed. The touch panel includes: an underlying substrate, a plurality of fingerprint recognizing units located on the underlying substrate, an encapsulation layer covering the plurality of fingerprint recognizing units, where each of the fingerprint recognizing units includes a light-emitting element and a photosensitive element; and a light path limiting structure arranged above the light-emitting element, where the light path limiting structure is arranged above the light-emitting element to enable light emitted from the light-emitting element to be totally reflected to thereby be transmitted in the light path limiting structure, and to exit the light path limiting structure by being concentrated in a small angle range.