Gesture Sensor Module Optical Isolation Design
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Solution Overview
Problem
Gesture sensor modules face performance degradation due to light pollution and cross-talk issues caused by the close proximity of optical emitters and sensors, which complicates miniaturization efforts.
Innovation Solution
The design incorporates separate cavities for the optical emitter and sensor dies with an optical barrier in between, along with a conical opening and reflective coating to minimize light reflection and enhance optical isolation, allowing for reduced cross-talk and improved sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the optical emitter and optical sensor are arranged closely together for miniaturization, then the device size is reduced, but cross-talk between the emitter and sensor increases
Solution Approach 1:
The package is divided into separate cavities - a first cavity housing the optical emitter and a second cavity housing the optical sensor. This segmentation physically separates the light source and detector, preventing direct optical coupling while maintaining compact overall dimensions.
Solution Approach 2:
A reflective coating is applied to the cavity wall between the emitter and sensor to redirect stray light away from the sensor. This intermediary surface modifies the optical path, converting harmful reflected light into useful light that exits through the optical opening.
2Device complexity
If the optical emitter and optical sensor are arranged closely together, then the device complexity is reduced, but light pollution increases
Solution Approach 1:
The cavity is designed with a conical opening whose width increases with distance from the emitter surface. This three-dimensional geometric feature redirects light in specific angular directions, allowing light to exit the package while preventing it from reflecting back to the sensor.
Solution Approach 2:
The reflective coating is applied selectively to specific cavity surfaces where it will most effectively redirect stray light away from the sensor. This localized application optimizes light management while minimizing material usage and manufacturing complexity.
3Object-affected harmful factors
If the sensor surface is positioned higher than the emitter surface, then cross-talk is reduced, but the manufacturing precision requirements increase
Solution Approach 1:
The package structure is designed with pre-formed cavities at different heights during manufacturing. The first cavity for the emitter and second cavity for the sensor are created with predetermined height differences, eliminating the need for post-assembly height adjustment and reducing manufacturing precision requirements.
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 reduces cross-talk to less than 5% and increases the sensitivity of the optical sensor, while maintaining a compact package height suitable for integration into electronic devices like mobile computing and touch screens.
Implementation Method 1
an optical barrier positioned laterally between the optical emitter die and the optical sensor die
Implementation Method 2
the surface of the opening can be reflective. In some embodiments, the surface of the opening can be coated with a reflective metal layer
Data Source
AI summary
An integrated gesture sensor module includes an optical sensor die, an application-specific integrated circuit (ASIC) die, and an optical emitter die disposed in a single package. The optical sensor die and ASIC die can be disposed in a first cavity of the package, and the optical emitter die can be disposed in a second cavity of the package. The second cavity can be conical or step-shaped so that the opening defining the cavity increases with distance from the upper surface of the optical emitter die. The upper surface of the optical emitter die may be higher than the upper surface of the optical sensor die. An optical barrier positioned between the first and second cavities can include a portion of a pre-molded, laminate, or ceramic package, molding compound, and/or metallized vias.