Optical Sensor Light Absorption Coating Reduces Cross Talk
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Solution Overview
Problem
Reflective optical sensors face challenges in minimizing cross talk, which affects their performance, with existing methods either requiring complex assembly or being ineffective for analog output and increasing costs.
Innovation Solution
A light absorption coating is applied to the external surface of the optical sensor near the detector to reduce internal reflections and ambient light, minimizing cross talk without increasing sensor size or complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If an opaque barrier is placed between the emitter and detector to minimize cross talk, then cross talk is reduced, but the assembly process becomes complex and sophisticated optics cannot be implemented
Solution Approach 1:
The harmful internal reflections are extracted and absorbed by a separate black coating layer applied to the package walls, rather than using a complex opaque barrier structure. This removes the cross-talk problem while maintaining optical simplicity.
Solution Approach 2:
A black coating layer is introduced as an intermediary element between the optical components and the package walls to absorb stray light. This mediator prevents internal reflections without requiring complex assembly structures.
2Object-affected harmful factors
If a dual photodiode and comparator are used to process light signals differentially, then cross talk is minimized, but the size of the photosensitive area doubles and cost increases
Solution Approach 1:
Instead of trying to detect and differentiate cross-talk signals using additional photodiodes, the invention converts the harmful cross-talk light into a beneficial absorbed energy source by using a black coating that absorbs stray light before it can reach the detector, thereby eliminating cross-talk without additional components.
3Object-affected harmful factors
If a dual photodiode and comparator system is implemented, then cross talk is reduced, but manufacturing cost increases
Solution Approach 1:
The invention uses a simple, inexpensive black coating layer that can be applied through standard manufacturing processes to absorb cross-talk light. This disposable-like coating is much cheaper than implementing a dual photodiode and comparator system, achieving the same cross-talk reduction at lower cost.
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 coating effectively reduces cross talk by 50% to 80% while maintaining sensor reliability and simplicity, enhancing the sensor's performance without significant cost or manufacturing complexity.
Implementation Method 1
The sensors contain a light absorption coating that is placed on a portion of the external surface of the optical sensor near the detector. This absorption coating reduces the amount of cross talk by reducing the amount of light reflected inside a transparent package of the sensor.
Implementation Method 2
These two components are mounted in a side-by-side relationship in the housing of the optical sensor. The LEDs can have a broad angular emission window projected in a large undefined angular range
Implementation Method 3
Reflective optical sensors typically contain a light emitting diode ("LED") as the optical emitter and a photodiode or phototransistor as the optical detector
Data Source
AI summary
Optical sensors containing reduced amounts of cross talk, as well as methods for making and using such sensors are described. The sensors contain a light absorption coating that is placed on a portion of the external surface of the optical sensor near the detector. This absorption coating reduces the amount of cross talk by reducing the amount of light reflected inside a transparent package of the sensor. As well, the coating can also reduce the amount of ambient and/or stray light that enters the sensor. The coating adds little cost or complexity to the manufacturing process for the sensors, yet reduces the cross talk without substantially increasing the size of the sensor or without increasing any reliability risks. Other embodiments are also described.