Dual SMI Sensor Measurement for 3D Object Length and Speed
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Solution Overview
Problem
Existing SMI sensor technologies struggle to accurately measure the length of three-dimensional objects, such as parallelepipeds, without requiring additional sensors or markings, and fail to distinguish between the object and the transport medium, leading to inaccurate length and speed measurements.
Innovation Solution
A device with a sensor arrangement of two SMI sensors emitting measurement light beams at opposite angles to the movement axis, allowing for the detection of characteristic changes in reflected light intensity to determine object length and speed without additional sensors or markings, using a control and evaluation unit to process signals from these sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single SMI sensor is used to measure object speed, then the radial speed of scanned object points can be determined, but the length determination of three-dimensional objects and distinction between object and transport medium is not possible
Solution Approach 1:
The measurement task is segmented into two independent measurement directions by using two SMI sensors with different measurement axis orientations. Each sensor measures radial speed along its own axis, and the combination of these segmented measurements enables length determination of three-dimensional objects while maintaining manageable device complexity
Solution Approach 2:
The solution transitions from single-axis radial speed measurement to multi-dimensional speed measurement by orienting two SMI sensors at different angles relative to the movement axis. This dimensional expansion allows the system to distinguish between object and transport medium movements and to calculate object length along the movement direction
2Measurement precision
If SMI sensors are used to measure object speed, then radial speed can be determined, but the speed measurement remains the same whether scanning the object or the transport medium, making object recognition impossible
Solution Approach 1:
The two SMI sensors are configured with asymmetric measurement axis orientations relative to the movement axis. This asymmetric arrangement creates different measurement characteristics when scanning the object versus the transport medium, enabling the evaluation unit to distinguish between the two and detect object presence
Solution Approach 2:
The evaluation unit acts as an intermediary that processes the measured speed signals from both SMI sensors. By comparing and analyzing the speed measurements from the two differently oriented sensors, the evaluation unit can identify when an object is present on the transport medium based on the differential measurement results
3Measurement precision
If code markings are added to objects for position determination, then absolute position can be determined, but the objects require additional markings which increases manufacturing complexity
Solution Approach 1:
The SMI sensor system performs position and length determination using only the object's natural reflective properties and its movement through the measurement space. No external markings, codes, or modifications to the object are required - the object serves itself as the measurement target, simplifying manufacturing while maintaining measurement precision
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
Enables contactless measurement of three-dimensional object lengths and speeds by analyzing intensity changes in reflected light, providing accurate length determination even at variable speeds and distinguishing objects from transport media.
Implementation Method 1
Self-mixing interference results between the transmitted light and the light reflected back in the laser resonator, whereby a periodic oscillation of the intensity of the laser is produced
Implementation Method 2
a portion of the transmitted light is diffusely reflected at the surface of the moving object and so returns to the laser, with this diffusely reflected portion of the transmitted light undergoing a phase offset with respect to the transmitted light due to the Doppler effect caused by the movement of the object
Implementation Method 3
this diffusely reflected portion of the transmitted light undergoing a phase offset with respect to the transmitted light due to the Doppler effect caused by the movement of the object
Data Source
AI summary
The invention relates to a device and to a method for measuring an object that moves in a direction of movement along a movement axis, wherein the device has a first sensor arrangement having a first SMI sensor and a second SMI sensor, wherein the SMI sensors irradiate measurement light beams in opposite directions along a movement axis. A control and evaluation unit is configured to receive first and second measured signals, to determine a speed of the object along the movement axis from at least one of the measured signals, to detect a first characteristic change of the second measured signal, a first characteristic change of the first measured signal, and a second characteristic change of the first measured signal, and to determine an object length of the object along the movement axis.