Optical Sensor Under Transparent Screen Using Angular Filter
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Solution Overview
Problem
Existing optical sensor integration techniques under partially transparent screens, such as fingerprint sensors in mobile devices, face challenges in achieving optimal performance and efficiency due to limitations in light transmission and sensor calibration.
Innovation Solution
The integration of an angular filter with microlenses or microapertures, an optically transparent low-index layer, and an organic photodiode image sensor, along with a protective stack that includes shielding and shock absorption layers, to create an efficient optical sensor system that is sensitive to visible and near-infrared wavelengths, ensuring effective light transmission and calibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If an optical sensor is integrated under a partially transparent screen, then the screen transparency is maintained, but the light transmission and sensor calibration performance deteriorate
Solution Approach 1:
The patent introduces an angular filter as an intermediary element between the screen and the optical sensor. This angular filter selectively transmits light at specific angles while blocking other angles, thereby improving sensor calibration without compromising screen transparency for the user. The angular filter acts as a mediator that reconciles the conflicting requirements of screen visibility and sensor performance.
Solution Approach 2:
The patent applies different optical properties to different regions and layers of the sensor assembly. The angular filter has specific angular transmission characteristics, the optically transparent layer has optimized refractive index properties, and the photodiode layer is positioned at specific depths. This local optimization of optical properties throughout the stack enables both screen transparency and improved sensor calibration.
2Illumination intensity
If multiple layers are added to optimize optical transmission, then light transmission improves, but device complexity increases
Solution Approach 1:
The angular filter layer serves multiple functions simultaneously: it acts as an angular selector for the optical sensor, provides structural support for the multi-layer stack, and maintains appropriate optical impedance matching. The optically transparent layer with low refractive index also serves dual purposes as both an optical element for light transmission optimization and as a mechanical spacer maintaining layer separation. This multi-functionality reduces the need for additional dedicated components.
3Illumination intensity
If the optical sensor is positioned closer to the screen, then light transmission increases, but structural integrity and protection requirements worsen
Solution Approach 1:
The patent employs thin-film structures for the angular filter and optically transparent layer that provide both optical functionality and mechanical protection. These thin films are designed with appropriate thickness and material properties to protect the underlying photodiode layer while maintaining optimal light transmission characteristics. The layered thin-film structure acts as a protective barrier without significantly impeding optical performance.
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 configuration enhances the optical sensor's ability to detect fingerprints by optimizing light transmission and sensor sensitivity, improving the accuracy and efficiency of fingerprint recognition while maintaining the screen's transparency and structural integrity.
Implementation Method 1
an angular filter with microlenses or microapertures
Implementation Method 2
an optically transparent low-index layer
Implementation Method 3
an organic photodiode image sensor sensitive to visible and near-infrared wavelengths
Implementation Method 4
a protective stack that includes shielding and shock absorption layers
Data Source
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AI summary
The invention relates to a device (30) comprising an at least partially transparent screen, an optical sensor (15) and, between the sensor and the screen, a non-peripheral part which comprises one or more rigid elements (32).