Biometric Module Light Guide Uniform Illumination
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Solution Overview
Problem
Fingerprint recognition systems using optical fingerprint recognition techniques face issues with hot spots due to overly concentrated light distribution, compromising recognition functionality, especially in devices with full-size screens where space for the fingerprint recognition device is limited.
Innovation Solution
A biometric identification module that includes a light source, a cover plate with optical film layers, and an image-capture device, where the light beam is guided to disperse uniformly through total internal reflection in the cover plate or light guide layer, reducing hot spots and improving fingerprint image clarity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the light-emitting device is disposed below the display screen and adjusted to high intensity, then sufficient light intensity can be transmitted to the finger, but hot spots readily occur to the fingerprint image obtained by the image-capture device
Solution Approach 1:
A light guide layer is introduced as an intermediary component between the light-emitting device and the finger. This light guide layer receives light from the light-emitting device and guides it to uniformly illuminate the finger, preventing direct concentrated light from causing hot spots in the fingerprint image while maintaining sufficient illumination intensity for recognition.
Solution Approach 2:
The light guide layer has different functional regions: a first region that receives light from the light-emitting device and a second region that illuminates the finger. This local differentiation allows the system to concentrate light reception in one area while distributing light emission uniformly across the finger surface, resolving the contradiction between intensity and hot spot formation.
2Reliability
If the light distribution is overly-concentrated, then the light beam can be intense enough for recognition, but hot spots occur that compromise fingerprint recognition function
Solution Approach 1:
The light guide layer serves as a mediator that decouples the light concentration function from the light emission function. It receives concentrated light from the light-emitting device in the first region and redistributes it uniformly in the second region where it contacts the finger, thereby maintaining recognition reliability while eliminating hot spots.
Solution Approach 2:
The light guide layer extends the light path from a direct vertical arrangement to a distributed planar structure. By spreading the light interaction across the extended surface of the light guide layer rather than concentrating it at a single point below the display, the system maintains sufficient total light intensity while distributing it uniformly to prevent hot spots.
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 alleviates the issue of hot spots, ensuring uniform light distribution and enhancing the quality of fingerprint recognition, even in devices with limited space for the fingerprint recognition device.
Implementation Method 1
the light beam emitted by the light source passes through the first optical film layer to be sequentially transmitted in the first region and the second region of the cover plate
Data Source
AI summary
A biometric identification module including a light source, a cover plate, a display device, an image-capture device, and a first optical film layer is provided. The display device is disposed between the cover plate and the image-capture device. A first optical film layer is disposed on a first region of the cover plate and located between the first region and the light source, wherein the light beam emitted by the light source passes through the first optical film layer to be sequentially transmitted in the first region and a second region of the cover plate, and a finger disposed on the second region of the cover plate reflects the light beam from the second region of the cover plate. The light beam reflected by the finger sequentially passes through the second region of the cover plate and the display device to be received by the image-capture device.