Optical Sensor Triangulation for Conveyor Detection
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Solution Overview
Problem
Existing optical sensors using the triangulation principle struggle to reliably detect objects against backgrounds with inhomogeneous optical properties, such as conveyor belts, especially when objects have shiny or reflective surfaces, leading to false detections due to multiple reflections and scattered light effects.
Innovation Solution
An optical sensor with multiple transmitters arranged in a line parallel to the spatially resolving receiver, using a switching signal generated from analog-digital converter output signals within predetermined limits, and employing a convex hull in a two-dimensional vector space to distinguish objects from background, with adjustable switching hysteresis and energy deviations to enhance detection reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple transmitters are used to increase detection sensitivity, then detection sensitivity is improved, but false detections increase due to multiple reflections and scattered light effects
Solution Approach 1:
The evaluation unit segments the detection space by comparing distances measured by different transmitters. Each transmitter creates a triangulation button with the receiver, and the system divides the measurement space into regions where objects should and should not be detected based on geometric relationships between multiple transmitter measurements
Solution Approach 2:
The patent introduces an intermediary evaluation mechanism that processes distance measurements from multiple transmitters before making detection decisions. The evaluation unit acts as a mediator that reconciles potentially conflicting measurements by checking geometric consistency across all transmitter-receiver pairs
2Measurement precision
If multiple transmitters are activated cyclically to form triangulation buttons, then detection sensitivity increases, but device complexity increases
Solution Approach 1:
The patent merges the functions of multiple transmitters and the evaluation unit into a coordinated system. The control unit integrates the operation of multiple transmitters cyclically, and the evaluation unit combines distance measurements from all triangulation buttons into a unified detection decision, reducing overall system complexity through functional integration
3Length of stationary object
If the transmitter and receiver are arranged at a distance for triangulation measurement, then measurement range is improved, but measurement precision deteriorates due to signal attenuation and scattering
Solution Approach 1:
The patent applies local quality by having each transmitter-receiver pair operate with optimized local geometry. Each triangulation button is formed with specific transmitter-receiver spacing suited to its measurement task, allowing different parts of the sensor system to have different optimal characteristics for their specific measurement zones
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 significantly increases the detection reliability of objects against inhomogeneous backgrounds, reducing false positives and improving reproducibility by accounting for signal offsets and energy deviations, even for shiny or reflective objects.
Implementation Method 1
a spatially resolving receiver, which can be formed by a PSD (position sensitive device) element... receiving received light beams
Implementation Method 2
at least one transmitter that emits light beams... receiving received light beams... multiple reflections of incident light rays
Data Source
Figure 1
Figure 2~3
AI summary
The invention relates to an optical sensor 1 with several light-beam emitting transmitters 3a-3c, each of which is individually activated cyclically, and with a position-resolving receiver 4, which has two terminals, each of which can output an analog signal. Each transmitter 3a-3c forms a triangulation probe with the position-resolving receiver 4. An evaluation unit of the receiver 4 is provided in which a switching signal is generated depending on the output signals of the position-resolving receiver 4, the switching states of which indicate whether an object 8 is present against a background or not. The transmitters 3a-3c are arranged along a straight line parallel to the longitudinal axis of the position-resolving receiver 4. The components of the optical sensor 1 are integrated in a housing 2. The receiver 4 is preferably a PSD element (Position Sensitive Detector).Preferably, the transmitters 3a to 3c are arranged close together along the longitudinal axis of the PSD element. The transmitters 3a to 3c and the position-resolving receiver 4 are arranged on a printed circuit board 5. A transmitting optic 6 is associated with the transmitter arrangement, and a receiving optic 7 is associated with the position-resolving receiver 4. The sensor 1 detects an object 8, which is arranged on a conveyor belt 9 forming a background. The transmitters 3a to 3c, which can emit light of the same or different wavelengths, are operated in pulsed mode, so that they emit light beams 10 in the form of transmitted light pulses. If a transmitter is activated for a time interval, it can emit a single transmitted light pulse or a sequence of transmitted light pulses.Through cyclic individual activation, object 8 is detected with the transmitted light pulses of all transmitters 3a to 3c, so that distance information is available for all three triangulation buttons for object detection.