Polarization Camera Inspection of Transparent Packaging
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Solution Overview
Problem
Machine vision systems struggle to effectively analyze transparent or translucent surfaces, such as packing tape, end seals, and shrink wrap, in the logistics industry due to low contrast and reflective conditions.
Innovation Solution
The implementation of a vision system with a polarization camera and polarizer array on the imager chip, combined with polarized illumination, allows for enhanced contrast and glare reduction, enabling accurate inspection of transparent or translucent features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional illumination techniques are used, then the system is simple and easy to operate, but the contrast is insufficient for detecting transparent or translucent materials
Solution Approach 1:
The patent changes the polarization state parameter of light to enable detection of transparent materials. By using polarized illumination and a polarization camera with polarizer array, the system creates measurable contrast differences in the polarization domain that are invisible in standard intensity images, thereby detecting transparent/translucent packaging materials without significantly increasing system complexity.
Solution Approach 2:
The patent introduces polarization state as an intermediary parameter between the transparent material and the detector. The polarized light interacts with the transparent material, and the polarization camera measures the modified polarization state, creating an intermediate representation that reveals the presence and properties of transparent packaging that would otherwise be invisible.
2Measurement precision
If traditional cameras are used, then the device complexity is low, but the ability to detect transparent or translucent features is insufficient
Solution Approach 1:
The patent transforms the detection parameter from standard light intensity to polarization state. The polarization camera with polarizer array captures images in multiple polarization channels, enabling detection of transparent materials through their effect on polarization rather than through intensity contrast, thereby achieving superior detection capability.
Solution Approach 2:
The patent adds the polarization dimension to the traditional intensity-based imaging. By measuring light properties in the polarization domain in addition to intensity, the system creates a multi-dimensional representation of the scene that reveals transparent materials through their polarization characteristics rather than relying solely on intensity contrast.
3Measurement precision
If standard imaging is used, then the system is simple to operate, but glare from reflective surfaces prevents accurate inspection
Solution Approach 1:
The patent changes the measurement parameter from intensity to polarization state to eliminate glare problems. Since polarized light and polarized cameras measure the polarization angle and degree, they can distinguish between specular reflections (which preserve or modify polarization in predictable ways) and diffuse reflections, thereby eliminating glare interference from reflective packaging surfaces.
Solution Approach 2:
The patent converts the harmful effect of reflective surfaces into a useful signal. By measuring polarization state, the system can actually detect and characterize reflective surfaces through their polarization properties, turning the glare problem into a source of information about surface orientation and material properties that can be used for accurate inspection.
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 enables robust inspection of transparent or translucent surfaces, improving the detection of defects and ensuring proper packaging, even under challenging illumination conditions.
Implementation Method 1
A vision system camera having a first image sensor can provide image data to a vision system processor, the sensor receiving light from a first field of view that can include the object through a first light-polarizing filter assembly
Implementation Method 2
An illumination source can project polarized light onto the substrate within the field of view
Data Source
AI summary
This invention provides a system and method inspecting transparent or translucent features on a substrate of an object. A vision system camera, having an image sensor that provides image data to a vision system processor, receives light from a field of view that includes the object through a light-polarizing filter assembly. An illumination source projects polarized light onto the substrate within the field of view. A vision system process locates and registers the substrate, and locates thereon, based upon registration, the transparent or translucent features. A vision system process then performs inspection on the features using predetermined thresholds. The substrate can be a shipping box on a conveyor, having flaps sealed at a seam by transparent tape. Alternatively, a plurality of illuminators or cameras can project and receive polarized light oriented in a plurality of polarization angles, which generates a plurality of images that are combined into a result image.