The CVS 2 Colour Vision Sensor: the far-sighted 2-D colour sorter
Waldkirch, April 2005 – 2-D colour detection over operating distances of up to 270 mm, sorting of up to 15 colours, differentiation of objects with two colours, and the possibility of transferring product- or batch-based device parameters from a control system or PC are the highlights of the new CVS 2 Colour Vision Sensor. The sensor can be used wherever materials or objects have to be identified, sorted and controlled on the basis of their colour, but where point-oriented colour sensors fail because they cannot detect all the colour information or their scanning distance is insufficient.
The CVS 2 is no optoelectronic scanner but a camera sensor with a CMOS chip for image acquisition. This converts an object’s light information into electrical charges and collects them in image points, so-called pixels. During colour detection, a minimum pixel sum process is used to check whether a colour tone is present in the viewing field of the CVS 2 in at least the pre-programmed amount. The output switches as soon as a sufficient number of pixels of the taught-in colour(s) is detected in the viewing field. In this way the sensor can, for example, detect and differentiate between any designs on labels, something that was almost impossible with point-oriented sensors.
High sorting performance and long range
The CVS 2 is specially designed for high sorting performance and flexibility. The sensor, illumination and control system are accommodated in an IP67 sensor housing roughly the size of a photoelectric switch.
A total of 15 different target colours can be taught-in and stored in the device. Up to three colours can be sorted via the two digital switching outputs, and up to 15 colours via the serial interface. The CVS 2 can also distinguish between objects with two colours. Depending on the task, the response time of the camera sensor is between 5 and 40 ms, allowing rapid sorting processes. Many users also need ranges that cannot be achieved with classical colour sensors employing LED light sources. Here the CVS 2 offers three alternatives with wide depth-of-field ranges: 50 - 100 mm,
90 - 150 mm, and 210 - 270 mm.
Flexibility for colour sorting
In addition to its sorting power and long ranges, the CVS 2’s parameterisation and user-friendly operation ensure flexible use. Parameter value setting takes place interactively with menu guidance, by means of five buttons on the device itself. The digital video pictures supplied by the CMOS chip are displayed directly on the colour monitor of the CVS 2. Together with teach-in programming of the colours to be detected this makes commissioning particularly easy. A separate monitor and control panel that can be directly connected to the camera sensor is available for installation locations where the TFT display is not visible, or the buttons are difficult to reach. The parameter sets generated during teach-in can be transferred to a controller or PC via the serial interface. These values can be automatically transferred back to the CVS 2 with a download if, for example, the packaging material is changed – thus offering highly flexible machine use.
Versatile use, in the food industry too
The CVS 2 offers versatile use in many areas, including checking the browning of meatballs, checking bottle tops and seals, detecting logos, checking the design of labels, checking that boxes or carrier systems are complete, checking the presence of instruction leaflets, differentiating between objects according to colour, or checking filling levels in transparent containers. The fact that the sensor has no glass components is an advantage that also allows the solution of colour detection and sorting tasks in the food industry.