Colour vision sensors keep watchful eye on defects
Dean Palmer takes a look at how colour vision sensors are helping to check for production line defects, particularly in automotive and food and beverage application
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Process and manufacturing engineers now have a powerful tool in their battle to enhance quality and reduce defect rates while ensuring that production systems still run to their optimal capacity and speed.
Sick's CVS1 colour vision sensor - with its large field of view of up to 100 x 115mm - can be positioned up to 270mm away from the target object, which ensures easier installation and eliminates the need for accurate guidance and positioning of target objects.
For engineers, this means that applications which require products to be differentiated and sorted by their colour, even over long distances and without the need for consistent presentation, can now be achieved.
The CVS1 colour vision sensor does not normally require any extra accessories. Features include internal lighting, a keypad for programming and a colour monitor, enabling users to view the target object through the 'tech-in' process. All this is integrated into a compact (95 x 42 x 34mm) IP67-rated plastic housing.
The basic teach-in procedure is a simple push button action, but it is also possible to edit each single parameter after teaching. All this makes it ideal for many industrial environments, but it is particularly suited to the food and beverage industry and automotive applications.
According to Sick, using pixel sum evaluation, even coloured objects with uneven surfaces or of inconsistent colour can be reliably detected. The CVS compares the pixel sum count of every object with those stored in its memory and provides an NPN or PNP switched output as required.
The CVS2 goes even further. This sensor allows users to detect two-coloured objects, enabling the detection of defined colour combinations. At the same time, its serial interface allows sorting and detection of up to 15 colours with further sorting of a maximum of three colours, made possible using its two digital outputs. The serial interface can also be used to upload and download the parameter settings to or from a number of other sensing units.
Other options are available from Sick, including an external lighting ring, an external monitor/keypad and a selection of extension cords depending on the model being used.
Another Sick vision product, the ICR890 CCD camera for bar code reading, offers high-end shipping and sorting markets a flexible, rapid and reliable identification system for use within logistical processes.
The camera's modular design includes fully integrated illumination, focus control and a high performance decoder. And, depending on the application, proprietary products, such as the firm's VMS400 (Volume Measurement System) or an MLG (Modular Light Grid) can be integrated into a single system solution, using CAN connectivity in combination with Sick's MSC800 system controller.
The ICR890's omni-directional system offers advantages when processes regularly see small bar codes that have to be read at high speeds, dirty or weakly contrasting codes, and bar codes with highly fluctuating module widths. The unit's reading field covers all common conveyor belt widths up to 1m and travel speeds of up to 4.8m/s. The depth of field is between 1,100mm (with a minimum resolution of 0.2mm) and 1,400mm (with a minimum resolution of =0.3mm.
A high speed image output with 2 Gbit Ethernet channels can be used for video coding or OCR applications. The integrated JPEG encoder can display real time compressed pictures - a feature that leads to significant reduction of the data rate to the host system.
