Optoelectronic Sensor Screen Placement for Reflection Avoidance
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Solution Overview
Problem
Optoelectronic sensors, such as light barriers, face challenges in detecting objects due to reflections from nearby surfaces, particularly in applications like door access systems, where reflections can prevent the detection of objects, leading to reduced availability and increased alignment difficulties.
Innovation Solution
The use of strategically positioned screens or apertures, separate from the sensor housing, to limit light beams and prevent reflections, allowing for reliable object detection without reducing the system's range or increasing alignment requirements, with the screens' placement calculated based on the distance between the optical axis and the reflecting surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the transmission and reception cone angles are reduced to avoid reflections, then reflection risk is lowered, but alignment difficulty increases
Solution Approach 1:
A screen is introduced as an intermediary element between the light transmitter and receiver. The screen limits the light beams to prevent reflections from reaching the receiver, while being positioned at a calculated distance to maintain ease of alignment. The screen acts as a mediator that solves the reflection problem without requiring restrictive cone angles.
Solution Approach 2:
The light beam path is segmented by introducing a screen that physically divides the space between transmitter and receiver. This segmentation allows the light to be confined to a specific path, preventing reflections while maintaining larger cone angles for easier alignment.
2Reliability
If screens are positioned close to the sensor to prevent reflections, then reflection prevention improves, but alignment tolerance decreases
Solution Approach 1:
Instead of positioning the screen in the immediate vicinity of the sensor (one-dimensional approach), the screen is positioned at a calculated distance along the light path (extending into the spatial dimension). This dimensional change allows sufficient reflection prevention while maintaining adequate alignment tolerance.
3Device complexity
If a single sensor is used to monitor multiple doors, then device complexity is reduced, but detection reliability decreases due to reflections
Solution Approach 1:
A single sensor system is designed to perform multiple functions by monitoring several doors simultaneously. The screen enables this multi-functionality by preventing reflections that would otherwise compromise detection accuracy, allowing one sensor to reliably monitor multiple door positions.
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 ensures reliable object detection across multiple doors with a single sensor, maintaining system availability and simplifying alignment, while preventing reflections and maintaining radiant intensity consistency.
Implementation Method 1
an optoelectronic converter emits light, which is bundled onto the corresponding receiving unit by the optical functional element
Implementation Method 2
The receiving unit has a corresponding optical functional element, which collects the light on an optoelectronic converter
Implementation Method 3
a noticeable part of the currently active light beam of a light transmitter/light receiver pair around an object, which should actually be recognized by interrupting the light beam, reaches the receiver through reflection
Data Source
AI summary
The sensor has a transmitter (2) transmitting light rays. The transmitter and a sensor optics are arranged in a sensor housing (8). A receiver (10) receives the rays. The receiver and another sensor optics are arranged in another sensor housing (12). A diaphragm (16) is arranged between the housings and spaced at a distance from the housings for limiting the rays. A distance of the diaphragm from the optics is calculated according to a formula involving a distance of an optical axis (46) to a reflecting surface, a half opening of the optics, and a half opening angle of the sensor.