Dual Parallax Optical Sensor for Dimensional Measurement
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Solution Overview
Problem
Conventional optical systems for determining object dimensions in environments, such as those used in transportation and logistics, face challenges with noise, sensitivity to reflectivity variations, and errors due to vibrations and shadowing, especially when dealing with untextured or moving objects.
Innovation Solution
A dual 'differential' parallax approach is implemented, using a pair of angled reflectors to produce dual parallax images of a structured light pattern, which reduces errors caused by object texture and parallax angle variations, and mitigates shadowing effects, allowing for accurate dimension measurement even on objects with varying reflectance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single projected laser line and 2D imager are used for parallax-based dimensioning, then the system simplicity and low cost are achieved, but sensitivity to variations in reflectivity on object surfaces increases
Solution Approach 1:
The patent divides the optical system into multiple segments: a first optical system with a first laser line and first imager, and a second optical system with a second laser line and second imager. Each optical system independently measures a portion of the object, and the measurements are combined to determine overall dimensions. This segmentation allows each subsystem to be optimized for specific measurement tasks while reducing overall sensitivity to surface reflectivity variations.
2Device complexity
If conventional parallax approaches are used, then hardware simplicity is maintained, but errors due to vibrations and temperature changes affecting the parallax angle increase
Solution Approach 1:
The patent introduces a conveyor as an intermediary element that provides a stable reference frame for measurements. The conveyor's motion is measured by encoders, and this information is used to compensate for vibrations and temperature changes affecting the parallax angle. The conveyor acts as a mediator between the optical systems and the moving object, enabling stable measurements despite environmental disturbances.
3Device complexity
If laser line position is used for dimensioning, then the system remains compact and simple, but shadowing effects and noise from object features increase measurement errors
Solution Approach 1:
The patent employs periodic scanning of laser lines across the object surface, where multiple laser lines are projected at different positions and times. This periodic action allows the system to build up a complete dimensional measurement over time, averaging out shadowing effects and noise from individual features. The conveyor motion synchronizes with the scanning process to maintain measurement accuracy.
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 approach provides a robust and compact solution that minimizes errors and noise, achieving accurate dimension measurement of moving objects with reduced sensitivity to texture and environmental changes, while maintaining low cost and complexity.
Implementation Method 1
A dual 'differential' parallax approach is implemented, using a pair of angled reflectors to produce dual parallax images of a structured light pattern
Implementation Method 2
the light sensor detects the light reflected from the object in the environment via both the first and the second reflective surfaces
Data Source
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AI summary
First and second reflective portions are angled with respect to one another to produce a parallax image of a structured light pattern (e.g., linear pattern) projected onto a surface of an object to determine at least one dimension (e.g., range, height, width) associated with the object. The reflections may be detected by a light sensor (e.g., a single linear image sensor) as dual "differential" parallax images of the structured light pattern, which advantageously inherently causes errors to cancel out.