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Colour Recognition with EyeCheck Smart Cameras

POSTED 04/25/2014

Colour is often the only characteristic that can be used to differentiate clearly between two otherwise completely similar objects. Moreover, the eye – the human vision system – is often not as accurate as the digital machine vision. When it comes to the recognition of colour, the human eye can recognise not even 100 grey values and only appox. 7 million different colours. Whereas digital grey scale images contain 256 grey scales and up to 16,7 million different colour shades.

Colour recognition with EyeCheck smart cameras

Typical colour inspection applications
The typical task for a colour sensor camera is to inspect the object according its colour. With a colour sensor such as e.g. the EyeCheck 2000 C, it is possible to solve colour evaluation applications such as the inspection of colour sequence and quality of multi-core cables or the sorting of test tubes in the pharmaceutical industry. The colour sensor detects the aberration to the predefined colour and therefore recognises if by mistake a test tube of the wrong colour appears in the production line. The same is true for the inspection of labels in the beverage industry: wrongly labeled bottles can be rejected along colour characteristics.

Additionally the EyeCheck smart camera offers the advantage, that it can also evaluate other characteristics of the objects. Therefore inspection commands such as e.g. commands for measurements, pattern matching, position adjustments etc. can be applied.

Extended object detection
But it does not always have to be a colour recognition task to use colour sensor. Also when it comes to a simple object detection application, it might be a good idea to use a colour sensor, because it enhances the contrast of an object. Besides, a colour sensor mainly is unaffected by the surrounding environment such as e.g. change of light, daylight deviations or a small change of position of the objects. Therefore the use of a colour sensor offers more security for the object detection.

How the smart camera gets to know the colours
The colour characteristics are parametrized when creating an inspection program with the EyeVision software, same as the other object characteristics. An established colour model is the is the RGB model. For an ordinary grey scale image a single channel for the medium brightness of the cells is sufficient. But for a colour image in the RGB model three channels of the red, green and blue parts of the visible light are used. Important is that this information is always captured with a more or less approximate pattern.

For the colour recognition not the single colour is important, but the specification of a colour area. Because objects will never exactly match a certain colour. This can depend on many reasons, such as e.g. the surface structure or reflexions of the object.

The colour version of the EyeCheck 2000 and 3000 smart camera series opens new applications:
Firstly, compared with grey scale images, the colour sensor the object detection is more accurate. And secondly, EyeCheck sensors can also be used to recognise luminous parts or structured colour surfaces.

The EyeCheck smart camera offers a resolution of up to 5 megapixel in a compact housing. And is equipped with a VGA monitor connection and RS232, USB 2.0 and optionally also Ethernet interfaces.