Machine Vision Use Grows
CI Vision (Aurora, IL) developed the 360 Full View, a wine bottle inspection system that checks the labels after they have been placed on the bottle. The 360 Full View has an aluminum enclosure around a conveyor that features a touch-screen operator interface on a side panel. As a bottle passes through the enclosure, it triggers four cameras to capture images of the bottle simultaneously. The analysis software, based on the Matrox Imaging Library (MIL), performs the routines that calculate the bottle’s coordinates, and determine whether the bottle’s label is the correct one and has been affixed properly.
In addition to the four Basler GigE Scout cameras and MIL, the 360 Full View system also features eight fluorescent tubes mounted in a custom-designed fixture and a custom PC with an Intel motherboard. In the near future, the system will also use the MIL GigE Vision driver.
“The bottle is unoriented when it leaves the labeling machine, so capturing its entire surface was the best way to perform the label verification and bottle localization,” explains Rick Koval, lead software engineer at CI Vision. These two tasks involve several steps, and they all rely on MIL’s image processing functions. A bottle’s presence triggers the cameras, each acquiring a single image. Then MIL’s Measurement module determines the bottle’s location in space.
When the bottle’s position is known, the system’s next task is to detect the locations of the front and back labels; the back label must be directly behind the front in order to pass the inspection. Warping functions and custom LUTs ‘unwrap’ the label image from the bottle, converting it to a 2-D equivalent. With the flat images of the bottle, MIL’s Registration module detects the common areas in those images (the overlapping sections of the images), and locates the edges of the labels with precision, and arranges them into a composite.
The composite image is arranged so that the front label appears first, then the back label, and finally, another portion of the front label; this way the operator can see the entire surface of the wine bottle in a discreet image. The labels’ positions can be verified by their coordinates in the composite image; in other words, if the labels are placed at the correct height, their Y-coordinates are equal. Likewise, if the distance between the labels in the composite is equal, then they are indeed directly opposite from each other. Furthermore, the composite image allows the operator to perform other inspection tasks, such as checking for skewed alignment, and the correct label. If for any reason a bottle fails inspection, it is tracked and diverted through a reject mechanism.
CI Vision has a long history with Matrox Imaging; indeed, all of their systems use Matrox Imaging hardware, software, or both. “We like the Matrox Imaging Library because, frankly, it’s easy to use. Its C interface provides good low-level interaction with our own front-end software. And there’s a strong support team behind MIL that is very proactive and reactive to our needs,” says Koval. Acknowledging that CI Vision’s success is built on MIL’s strength, Director of Marketing Scott Stone adds, “Using MIL allows us to strategically price our products in the market.”
The major challenge Stone and Koval faced was the development of the mathematical model for the ‘unwrapped’ label in conjunction with applying the vision tools that take into account the random nature of consumer products. Glass containers often have slight aberrations and variations in the shape that affect the way the light refracts, or the way the labels are located on the bottle. And though the variability of the bottle’s initial position challenged one aspect, it facilitated another. “Building a system that followed an existing process meant that we could use the existing conveyors, equipment that we were already familiar with,” explains Koval. “Flexibility and usability were key factors for us,” adds Stone. “We had to integrate very complex procedures into a system interface that allowed our customers to make changes very easily.”
The 360 Full View is just one of a suite of products that Kendall Jackson uses on its production lines.