Optical Fingerprint Sensor Light Guide Reducing Adhesive Cost
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Solution Overview
Problem
Conventional optical fingerprint identification systems require a large amount of high-cost optical adhesives, making them costly and inefficient for image capturing apparatuses.
Innovation Solution
The use of a light guide device with a refractive index between 1.4 and 1.6, such as glass, is inserted between the transparent device and the image capturing device to reduce the need for optical adhesives, and a light absorbing layer is applied to the sidewall to improve image quality by absorbing stray light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a large amount of optical adhesives is used to connect the transparent device and the image capturing device, then the connection reliability is improved, but the material cost increases significantly
Solution Approach 1:
The patent changes the refractive index parameter of the light guide device to be between 1.4 and 1.6, which creates optimal total internal reflection conditions at the interface with the environment medium. This parameter change enables the light guide device to replace optical adhesives in certain connection areas, reducing adhesive usage while maintaining optical performance and connection reliability.
Solution Approach 2:
The patent extracts the optical adhesive from specific regions by introducing a light guide device with appropriate refractive index. The light guide device is inserted between the transparent device and the image capturing device, eliminating the need for optical adhesives in areas where total internal reflection occurs, thereby reducing the quantity of optical adhesive required.
2Strength
If optical adhesives are used to connect components, then the connection strength is improved, but the manufacturing cost increases
Solution Approach 1:
The patent replaces the mechanical bonding method (optical adhesive) with an optical principle-based solution (total internal reflection). By designing the light guide device with specific refractive index, the connection relies on optical reflection rather than adhesive bonding, reducing material costs while maintaining sufficient connection strength for the application.
Solution Approach 2:
The patent utilizes the refractive index parameter of the light guide device (1.4-1.6) to create optimal optical conditions. This parameter change enables the system to achieve both connection functionality and cost reduction by eliminating the need for expensive optical adhesives in certain regions.
3Quantity of substance
If the light guide device with refractive index between 1.4 and 1.6 is inserted between the transparent device and the image capturing device, then the cost of optical adhesives is reduced, but the device complexity increases
Solution Approach 1:
The light guide device serves multiple functions simultaneously: it guides light from the light source, creates total internal reflection at its interface with the environment medium, and replaces the need for optical adhesives in connection areas. This multi-functionality justifies the added structural element while reducing overall material usage.
Solution Approach 2:
The light guide device acts as an intermediary component between the transparent device and the image capturing device. By positioning it strategically, it enables total internal reflection and reduces optical adhesive requirements, balancing the trade-off between increased device complexity and reduced material usage.
4Measurement precision
If a light absorbing layer is applied to the sidewall of the light guide device, then stray light interference is reduced and image quality is improved, but the manufacturing complexity increases
Solution Approach 1:
The patent converts the potentially harmful effect of stray light reflecting from the sidewall into a beneficial outcome by applying a light-absorbing coating. This coating absorbs unwanted stray light that would otherwise create noise in the captured image, thereby improving image quality at the cost of additional manufacturing steps.
Solution Approach 2:
The light-absorbing layer is applied specifically to the sidewall region of the light guide device where stray light generation is most problematic. This localized treatment addresses the specific issue of sidewall reflections without requiring modifications to the entire device structure, balancing manufacturing complexity with image quality improvement.
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 decreases the usage and cost of optical adhesives while enhancing image capturing quality by reducing light loss and stray light interference.
Implementation Method 1
The light beam passed through the light guide device is transmitted toward the transparent device, and is totally reflected by an interface between the transparent device and the environment medium
Implementation Method 2
The light absorbing layer covers the sidewall of the light guide device. The light beam passed through the light guide device is transmitted toward the transparent device, and is totally reflected by an interface between the transparent device and the environment medium
Data Source
AI summary
An image capturing apparatus including a light guide device having a first surface and a second surface opposite to each other, a transparent device disposed on the first surface, an image capturing device disposed on the second surface, a first optical adhesive, a second optical adhesive and a light source is provided. The first optical adhesive is disposed between the transparent device and the first surface. The transparent device is connected to the first surface through the first optical adhesive. The second optical adhesive is disposed between the second surface and the image capturing device. The image capturing device is connected to the second surface through the second optical adhesive. The light source is adapted to emit a light beam. The light beam passed through the light guide device is transmitted toward the transparent device and totally reflected by an interface between the transparent device and an environment medium.