Optical Proximity Sensor Multilayer Mask Crosstalk Reduction
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Solution Overview
Problem
Optical proximity sensors face significant challenges with optical crosstalk due to Fresnel reflections from glass or plastic covers in devices like smartphones and tablets, which affect signal-to-noise ratio and accuracy despite attempts to control it with air gaps, rubber boots, and specially designed apertures.
Innovation Solution
The implementation of a multilayer mask with elongated light blocking slats in an optical proximity sensor arrangement, which blocks specularly reflected light while allowing light from other angles to reach the light sensitive component, improving signal-to-noise ratio and accuracy by precisely controlling optical paths and reducing crosstalk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a glass or plastic cover is used to protect the sensor, then the sensor is protected from environmental damage, but optical crosstalk increases due to Fresnel reflections
Solution Approach 1:
The patent introduces a light barrier as an intermediary component positioned between the light emitting component and the light sensitive component. This light barrier selectively blocks specularly reflected light (crosstalk) while allowing directly reflected light from the target object to reach the sensor, thus resolving the contradiction between sensor protection and optical crosstalk reduction
Solution Approach 2:
The patent applies different optical properties to different regions of the optical path. The light barrier is designed with specific geometric features (such as angled surfaces or selective transparency) that create local variations in light transmission, allowing it to block harmful reflected light in certain directions while permitting useful light from the target to pass through
2Object-affected harmful factors
If traditional crosstalk control methods (air gaps, rubber boots, apertures) are used, then some crosstalk is reduced, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent merges the light barrier function directly into the sensor assembly structure, integrating crosstalk control within the existing device architecture rather than adding separate external components. This integration approach reduces overall device complexity while maintaining effective crosstalk suppression
Solution Approach 2:
The patent modifies optical parameters (such as light path geometry, barrier positioning, and angular characteristics) to achieve crosstalk reduction through optical design rather than mechanical structures. By changing the angular parameters of light blocking and the spatial parameters of the barrier, the solution achieves simplicity while maintaining effectiveness
3Use of energy by moving object
If larger apertures are used to improve light gathering, then light gathering efficiency increases, but optical crosstalk from reflected light increases
Solution Approach 1:
The patent addresses the aperture-crosstalk tradeoff by introducing a spatial dimension through the light barrier. The barrier is positioned at a specific distance and angle in the optical path, creating a three-dimensional solution that allows large apertures to gather more light while the barrier selectively blocks reflected light paths that would otherwise enter the sensor
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 effectively reduces optical crosstalk, enhances light gathering efficiency, and improves the accuracy of optical proximity detection by specifically targeting and blocking offending rays, leading to improved system performance and larger apertures that were previously restricted.
Implementation Method 1
Fresnel reflection or specular reflection denotes mirror-like reflection of light, or of other kinds of electromagnetic waves, from a surface, in which light from a single incoming direction is reflected into a single outgoing direction
Implementation Method 2
The sensor typically is a semiconductor device such as a photodiode, which generates a current when light energy strikes it
Implementation Method 3
The light source may be a semiconductor device that emits light when activated, for example, a light emitting diode
Data Source
AI summary
An optical proximity sensor arrangement comprises a semiconductor substrate (100) with a main surface (101). A first integrated circuit (200) comprises at least one light sensitive component (201). The first integrated circuit is arranged on the substrate at or near the main surface. A second integrated circuit (300) comprises at least one light emitting component (301), and is arranged on the substrate at or near the main surface. A light barrier (400) is arranged between the first and second integrated circuits. The light barrier being designed to block light to be emitted by the at least one light emitting component from directly reaching the at least one light sensitive component. A multilayer mask (500) is arranged on or near the first integrated circuit and comprising a stack (501) of a first layer (502) of first elongated light blocking slats (503) and at least one second layer (504) of second elongated light blocking slats (505). The light blocking slats are arranged in the mask to block light, incident on the mask from a first region of incidence (701), and to pass light, incident on the mask from a second region of incidence (702), from reaching the at least one light sensitive component.