Vision system ‘unwraps’ bottle labels for 100% inspection!

Olmec has designed and manufactured a line scan-based vision system for 100% inspection of labels on OTC healthcare product bottles. By rotating the bottle in front of the camera, the label is effectively ‘unwrapped’ to produce an image equivalent to imaging before it was stuck to the bottle. The vision system checks that the information on the label is correct as well as identifying missing or partial print.

The system handles a variety of bottles at a variety of speeds. The bottles are randomly fed into a servo-controlled starwheel which rotates each bottle in turn to the camera position. The ‘unwrap’ process is achieved by using rollers to then rotate the bottle within the pocket of the starwheel in front of a line scan camera which builds up the image of the label line by line. A distortion-free image is produced so there are no false rejects and no possibility of any rogue products getting through. Since the bottles do not need to be oriented before entering the system, speeds up to 120 a minute can be achieved.

The entire inspection cycle from moving the bottle into position, rotating it through 360˚, acquiring an image and making decisions takes just 500 milliseconds. The rotation of the bottle is synchronised with the scanning speed of the camera to eliminate deformations in the image. If the bottle rotates too fast the image is compressed and the pharmacode cannot be read and optical character recognition is also difficult. Similarly, if the bottle rotates too slowly, the image is stretched. In addition, if the bottle is leaning or moving up and down in the starwheel, the image can be skewed or show a ‘corkscrew’ effect. By precisely matching the mechanics of the starwheel with the image acquisition, the system offers a stability that minimises both false rejects and further software processing steps.

Robert Pounder, Technical Director at Olmec, said: “Using line scan technology greatly simplifies the inspection process. The Label Unwrap system design ensures the product is held captive and cannot be released unless it is acceptable; this eliminates the possibility of a product reaching a customer incorrectly coded or without any code at all.”