Optical Barrier Layout for Dark-Object Proximity Sensing
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Solution Overview
Problem
Optical proximity sensors in cell phones struggle to detect dark objects, such as black hair or objects with dense opaque materials, due to absorption or obstruction of infrared light, leading to false battery-saving screen activations, and existing designs face challenges in minimizing optical crosstalk while maintaining detection capabilities.
Innovation Solution
A proximity sensor arrangement featuring a narrow optical barrier between the light emitting device and photo-detector, designed to block specular reflections while allowing diffusively scattered light to reach the detector, reducing optical crosstalk and improving detection of dark objects by adjusting the barrier's geometry to intersect the emission cone and cover surfaces effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the optical barrier is made narrow to block specular reflections, then optical crosstalk is reduced, but detection of dark objects placed close against the cover becomes difficult
Solution Approach 1:
The patent positions the optical barrier at a specific distance from the cover surface, creating a three-dimensional spatial arrangement. The barrier extends partially toward the cover but maintains a gap, utilizing the z-dimension (depth) to block specular reflection paths while leaving diffuse reflection paths open. This dimensional positioning resolves the contradiction by selectively blocking harmful direct reflections while preserving detection paths for dark objects.
Solution Approach 2:
The optical barrier is designed with non-uniform geometry, extending only partially toward the cover rather than spanning the entire space. This local presence is sufficient to block specular reflections from specific angles while leaving other regions open for diffuse light paths. The barrier's selective positioning creates different optical properties in different spatial zones, resolving the contradiction between blocking and detecting.
2Measurement precision
If the critical point is placed just outside the glass outer surface to detect black hair, then detection of dark objects is improved, but optical crosstalk increases significantly
Solution Approach 1:
The patent extracts the optical barrier function from the cover glass itself and implements it as a separate, dedicated component positioned at a controlled distance from the cover. This separation allows the barrier to be optimized specifically for blocking specular reflections without compromising the cover's optical properties. The barrier is 'taken out' from the problematic configuration (critical point at cover surface) and repositioned to resolve the contradiction.
Solution Approach 2:
The optical barrier acts as an intermediary element between the light source/detector assembly and the cover glass. It mediates the optical paths by selectively blocking harmful specular reflections while allowing useful diffuse reflections to reach the detector. This intermediary position at a controlled distance from the cover enables the barrier to manage the contradiction between crosstalk reduction and dark object detection.
3Ease of manufacture
If variations in sensor to glass spacing or LED divergence angle occur, then manufacturing tolerances are relaxed, but the critical point may lie inside the glass causing yield losses
Solution Approach 1:
The patent designs the optical barrier with sufficient extension distance from the detector to accommodate expected variations in spacing and LED divergence. This extra margin 'cushions' against manufacturing tolerances, ensuring that even with variations, the barrier remains effective at blocking specular reflections and the critical point stays in the correct position. This beforehand cushioning prevents yield losses without requiring tight manufacturing tolerances.
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 enhances the detection of dark objects and passes the black card test by reducing optical crosstalk, ensuring accurate proximity detection without unnecessary battery consumption, while maintaining mechanical robustness and ease of production.
Implementation Method 1
block specular reflections that would occur if a light transmissive cover plate were placed over the optical sensor device
Implementation Method 2
pass light emitted from the light emitting device to the photo-detector via the cover and scattered on or above a first surface of the cover
Implementation Method 3
The sensor detects the amount of IR light that is reflected from the proximity target
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 3A~3B
AI summary
A proximity sensor arrangement comprises an optical barrier (1) being placed between a light emitting device (2) and a photo-detector (3). The light emitting device (2), the photo-detector (3) and the optical barrier (1) are covered by a cover (4). The optical barrier (1) is being designed to block light (21) emitted from the light emitting device (2) to the photo-detector (3) and reflected (22) by the cover (4) by means of specular reflection. Furthermore, the optical barrier (1) is being designed to pass the light (22) emitted from the light emitting device (2) to the photo-detector (3) via the cover (4) and scattered (23) on or above a first surface (41) of the cover facing away from the light emitting device (2) and the photo-detector (3).