Optical Proximity Sensor Light Guides for Compact High-Fidelity Sensing
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Solution Overview
Problem
Consumer electronic devices face challenges in maximizing the display area while minimizing the space dedicated to user-facing sensors, such as proximity sensors, and achieving high sensing fidelity.
Innovation Solution
The optical proximity sensor employs a housing with first and second chimneys, each containing a light guide made of dielectric materials, configured to direct light towards a target location and an optical detector, with features like tapered shafts, flanges, and reflective coatings to enhance sensing accuracy and reduce crosstalk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If the sensor footprint is reduced to maximize display area, then the display area increases, but the sensing fidelity deteriorates
Solution Approach 1:
The light guide is nested within the housing structure, with the emitter and detector positioned in recesses. The light guide shaft extends through the housing to reach the target, allowing the sensor components to be compactly arranged while maintaining sufficient optical path length for accurate sensing.
Solution Approach 2:
The light guide shaft extends in the depth dimension (z-axis) rather than requiring lateral expansion. By utilizing the vertical dimension for light propagation, the sensor achieves adequate sensing distance without increasing the lateral footprint, thus preserving display area while maintaining sensing fidelity.
2Area of stationary object
If the sensor aperture is reduced to minimize footprint, then the footprint decreases, but the light collection capability deteriorates
Solution Approach 1:
The light guide shaft features a tapered geometry with varying cross-sectional area along its length. The shaft has a smaller aperture at the housing end and a larger aperture at the target end, optimizing light collection at each location. This local variation in geometry allows compact aperture at the sensor while maintaining adequate light gathering area at the target.
Solution Approach 2:
The light guide is made of dielectric material with specific optical properties that enable efficient light transmission through the tapered shaft. The material composition is optimized to minimize absorption and maximize light guidance from the smaller aperture at the housing to the larger effective aperture at the target.
3Length of moving object
If the emitter and detector are positioned closer to reduce device size, then the device size decreases, but the crosstalk between emitter and detector increases
Solution Approach 1:
The light guide shaft acts as an intermediary optical element between the emitter and detector. It guides the emitted light along a controlled path to the target and directs the reflected light back to the detector, preventing direct optical coupling between the emitter and detector that would cause crosstalk, even when they are positioned close together.
Solution Approach 2:
The optical path is segmented into distinct sections: the emitter chamber, the light guide shaft, and the detector chamber. This segmentation through the housing structure with recesses and the light guide shaft creates optical isolation between the emitter and detector, reducing crosstalk while allowing compact positioning.
4Area of stationary object
If the light guide shaft aperture is reduced to minimize sensor footprint, then the footprint decreases, but the light propagation capability deteriorates
Solution Approach 1:
The light guide shaft features a tapered geometry with varying cross-sectional area along its length. The shaft has a smaller aperture at the housing end and a larger aperture at the target end, optimizing light collection at each location. This local variation in geometry allows compact aperture at the sensor while maintaining adequate light gathering area at the target.
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 design allows for a smaller sensor footprint while maintaining high sensing fidelity, reducing the need for multiple apertures and improving detection accuracy by minimizing crosstalk and blind spots.
Implementation Method 1
The first light guide is configured to direct light emitted from the optical emitter through the first chimney
Implementation Method 2
The second light guide is configured to direct a returned portion of the light emitted from the optical emitter though the second chimney towards the optical detector
Implementation Method 3
The shaft has a taper that increases a cross-sectional area of the shaft as it extends away from the light input end of the second light guide
Data Source
AI summary
An optical proximity sensor includes a housing, an optical emitter, and an optical detector. A first light guide disposed in a first chimney of the housing is configured to direct light from the optical emitter through the first chimney towards a target location. A second light guide disposed in a second chimney of the housing is configured to direct a returned portion of the light emitted from the optical emitter through the second chimney towards the optical detector.