Photosensitive Module With Light Guide Plate for Fingerprint Sensor
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Solution Overview
Problem
The existing fingerprint recognition technologies in electronic devices require cutting the cover plate to accommodate photosensitive elements, leading to increased manufacturing complexity and cost due to the risk of cracking, and reduced accuracy due to the distance between the elements and the finger.
Innovation Solution
A photosensitive module comprising selective light directors and photoelectric converters that use collimated light with a controlled incidence angle, allowing for accurate fingerprint recognition without the need to cut the cover plate, by directing collimated light through optical waveguides and holographic diffraction gratings, and generating electrical signals based on light intensity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the cover plate is cut to accommodate photosensitive elements, then the photosensitive elements can be positioned closer to the finger for improved recognition accuracy, but the manufacturing complexity and cost increase due to the risk of cracking
Solution Approach 1:
The patent introduces a light guide plate as an intermediary component between the cover plate and the photosensitive elements. The light guide plate transmits light from the photosensitive elements (which remain positioned away from the cover plate) to the finger placement area, eliminating the need to cut the cover plate while maintaining recognition accuracy. This mediator resolves the contradiction by decoupling the positional requirements of the photosensitive elements from the cover plate integrity.
2Measurement precision
If the cover plate is cut to accommodate photosensitive elements, then the photosensitive elements can be positioned closer to the finger for improved recognition accuracy, but the manufacturing cost increases due to higher process requirements
Solution Approach 1:
The light guide plate serves as a cost-effective intermediary that eliminates the need for complex cutting processes on the cover plate. By positioning photosensitive elements behind the light guide plate rather than cutting the cover plate, manufacturers avoid the high costs associated with precision cutting, cracking risk management, and post-processing repairs.
Solution Approach 2:
The patent transitions from a two-dimensional solution (cutting the cover plate surface) to a three-dimensional solution (positioning photosensitive elements at a different depth level behind the light guide plate). This dimensional change allows the photosensitive elements to be placed in a region where they can still effectively illuminate and detect the finger without requiring cover plate modifications.
3Device complexity
If the cover plate is not cut, then manufacturing complexity is reduced, but the distance between photosensitive elements and finger increases reducing recognition accuracy
Solution Approach 1:
The light guide plate acts as an optical mediator that bridges the gap created by not cutting the cover plate. It transports light from the photosensitive elements positioned at a safe distance behind the cover plate to the finger placement area on the cover plate surface, effectively eliminating the negative impact of increased distance while maintaining manufacturing simplicity.
Solution Approach 2:
The patent changes the optical parameters of the system by introducing a light guide plate with specific refractive index and optical properties. This parameter change enables efficient light transmission over the increased distance, compensating for the reduced proximity between photosensitive elements and the finger while maintaining recognition accuracy.
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 solution enhances the accuracy of fingerprint recognition by maintaining a consistent distance between the photosensitive cells and the finger, reducing manufacturing complexity and costs, while avoiding the need to cut the cover plate, thus improving the reliability and efficiency of the recognition process.
Implementation Method 1
an optical waveguide plate providing the first surface; a first holographic diffraction grating arranged in the light entry region for coupling the collimated portion of the light into the optical waveguide plate such that the collimated portion of the light propagates within the optical waveguide plate to the light exit region
Implementation Method 2
a first holographic diffraction grating arranged in the light entry region for coupling the collimated portion of the light into the optical waveguide plate
Implementation Method 3
a photoelectric converter arranged in the light exit region and having a light receiving surface facing the light exit region to receive the collimated portion of the light exiting from the selective light director, the photoelectric converter being configured to generate an electrical signal based on an intensity of the received collimated portion of the light
Data Source
AI summary
A photosensitive module includes a plurality of photosensitive cells. Each of the photosensitive cells includes a selective light director having a first surface including a light entry region and a light exit region different from the light entry region, the selective light director being configured to selectively direct a collimated portion of light incident towards the light entry region to the light exit region to exit from the selective light director; and a photoelectric converter arranged in the light exit region and having a light receiving surface facing the light exit region to receive the collimation portion of the light exiting from the selective light director.