Coded Light Pattern Segmentation for Height Measurement
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Solution Overview
Problem
Existing methods for measuring the height or height profile of objects, particularly in package sorting systems, face challenges such as overexposure issues on different surface types and depth of field blurring, leading to incorrect code word recognition and volume calculation errors.
Innovation Solution
A light pattern comprising consecutive coded picture elements with overlapping partial code words, where each picture element group has a specific reference position, allowing for the determination of object height based on the shift of reflected elements, reduces susceptibility to errors by enabling partial code word recognition at any point in the pattern.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a light pattern with coded picture elements is projected onto objects with different surface types, then height measurement is enabled, but overexposure occurs on bright surfaces leading to incorrect code word recognition
Solution Approach 1:
The code word is segmented into multiple picture element groups, where each group can independently serve as a recognition unit. This segmentation allows the system to identify valid code words even when partial overexposure occurs, as long as sufficient picture element groups remain recognizable.
Solution Approach 2:
The system uses more picture element groups than the minimum required for code word definition. This excessive redundancy ensures that even if some groups are overexposed or blurred, enough remaining groups maintain code word recognizability and measurement reliability.
2Measurement precision
If a light pattern is projected onto moving objects on a conveyor belt, then volume measurement is enabled, but depth of field blurring occurs leading to measurement errors
Solution Approach 1:
By dividing the code word into multiple picture element groups distributed across the light pattern, the system ensures that not all groups are equally affected by depth of field blurring. Some groups remain sufficiently sharp for reliable recognition even when others are blurred.
Solution Approach 2:
Different regions of the light pattern exhibit different local qualities regarding focus and sharpness due to depth of field limitations. The system leverages this by designing the code structure to be recognizable from various local regions, ensuring reliable measurement regardless of which specific area remains in focus.
3Device complexity
If conventional light patterns are used for height measurement, then simple implementation is achieved, but error susceptibility increases due to overexposure and blurring
Solution Approach 1:
The code word structure is divided into multiple picture element groups with overlapping sequences. This segmentation creates redundancy that protects against measurement errors without requiring complex additional hardware or processing systems.
Solution Approach 2:
The light pattern incorporates more picture element groups than strictly necessary for basic code word definition. This excessive redundancy provides error protection while maintaining relatively simple implementation, as the additional groups follow the same basic coding structure.
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 enhances accuracy in measuring object height and volume by minimizing errors related to surface type and depth of field issues, ensuring reliable code word recognition and precise volume calculation.
Implementation Method 1
The light source produces a uniquely patterned light sequence across the width of the conveyor system and the moving surface. This light sequence is reflected and captured by the linear image sensor.
Implementation Method 2
Due to the offset arrangement of the linear image sensor, the part of the light sequence reflected by the package is offset in one direction of the longitudinal extent of the light sequence, ie transversely to the transport direction. This offset or shift of the part of the light sequence reflected by the package is proportional to the height of the package
Data Source
Figure 1~2
Figure 3
AI summary
Method for measuring the height or height profile of an object 2, the method comprising the following steps: projecting a light pattern 12 in the form of successive coded image elements 11, 17 onto the object 2 by means of a light source 5, wherein the image elements 11, 17 each have at least one coding feature and together define a codeword 7, 16, wherein groups of image elements from a sequence of a predetermined number of successive image elements 11 each define individual sub-codewords 8, 13, 14, 15 and wherein each group of image elements is assigned to a specific reference position, capturing the light pattern 12 by means of an image sensor 3 which is arranged offset from the light source 5, determining the positions of the groups of image elements and determining the height of the object 2 based on the determined position of the groups of image elements compared to the respective reference position,where immediately adjacent groups of image elements partially comprise the same image elements 11, 17.