Asymmetric Optical Element for Proximity Sensor Signal Accuracy
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Solution Overview
Problem
Proximity sensors in electronic devices, such as cellular telephones, face challenges in accurately detecting user proximity due to low reflected infrared light signals from dark hair, leading to inadequate deactivation of touch screen functions.
Innovation Solution
The implementation of optical structures, including a convex lens to collimate light and a prism structure to deflect light, is used in conjunction with an infrared-transparent ink window, ensuring strong reflected signals without introducing noise from the display cover layer reflections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional proximity sensor is used without optical structures, then the device complexity is low, but the measurement precision is insufficient due to weak reflected signals from dark hair
Solution Approach 1:
The optical structure is divided into two distinct portions: a first portion (convex lens) for collimating light to reduce noise, and a second portion (prism structure) for deflecting light to enhance signal strength. This segmentation allows each portion to perform its specific function optimally, resolving the contradiction between measurement precision and device complexity by breaking down the complex optical system into manageable functional segments.
Solution Approach 2:
Different regions of the optical structure have different optical properties: the first portion has collimating capability while the second portion has light-deflecting capability. This local differentiation of optical quality enables the system to simultaneously achieve noise reduction and signal enhancement, improving proximity detection accuracy without requiring a uniformly complex optical design throughout the entire structure.
2Object-generated harmful factors
If collimated light is used to reduce noise from display cover layer reflections, then the noise signal is minimized, but the reflected signal strength from external objects may be reduced
Solution Approach 1:
The optical structure segments the light beam into two paths: collimated light that passes through the display cover layer with minimal noise, and uncollimated light that is deflected at angles to illuminate external objects more effectively. This segmentation resolves the contradiction by allowing both noise reduction and signal enhancement to occur simultaneously through different portions of the segmented optical system.
Solution Approach 2:
The asymmetric optical structure acts as an intermediary that mediates between the conflicting requirements of noise reduction and signal enhancement. By introducing this intermediate optical element with asymmetric properties, the system can transform the light beam in a way that simultaneously achieves both goals, resolving the contradiction that cannot be solved by simple collimation alone.
3Measurement precision
If an asymmetric optical structure is implemented, then proximity detection accuracy is improved, but the manufacturing precision requirements increase
Solution Approach 1:
Dividing the optical structure into two separate portions allows each to be manufactured and tested independently, reducing the cumulative tolerance stacking that would occur in a monolithic asymmetric structure. This segmentation lowers manufacturing precision requirements while maintaining the asymmetric optical properties needed for improved proximity detection 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 configuration enhances the accuracy of proximity detection by increasing the strength of reflected signals while minimizing noise, effectively deactivating touch screen functions when a user's head is in close proximity.
Implementation Method 1
a first portion such as a convex lens that is configured to collimate light from the light source. The collimated light may propagate along a vertical axis that serves as a surface normal to the display cover layer.
Implementation Method 2
a second portion such as a prism structure or other light reflecting structure for deflecting light away from the propagation axis of the collimated light.
Implementation Method 3
An opening in the opaque masking layer may be filled with a material such as an infrared-transparent ink to form a window for a light-based proximity sensor.
Implementation Method 4
a detector that is configured to detect reflections of emitted light from the light-emitting diode that have reflected off of nearby external objects such as the head of a user.
Data Source
AI summary
A proximity sensor may be mounted below a display cover layer in an electronic device. The proximity sensor may have a light source that emits light and a detector configured to detect reflections of the emitted light from nearby external objects. Optical structures may be interposed between the proximity sensor and the window in the display cover layer. The optical structures may include a first portion such as a convex lens that is configured to collimate light from the light source so that the light propagates along a surface normal to the display cover layer. The optical structures may also include a second portion such as a prism structure for deflecting uncollimated light away from the propagation axis of the collimated light.