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Colour cameras

Single chip colour cameras, Three-chip colour camera, Multilayered colour imaging sensor technology

As most people see the world in colour and watch colour television, there is often an expectation that any image shown on a screen should be in full colour, and monochrome images seem somehow inferior.

However, in vision applications there is often no benefit in including colour information, as the algorithms used are frequently only affected by contrast. There can even be disadvantages in using a colour camera, as spatial resolution can be decreased whilst transmission bandwidth, CPU overhead, and costs can increase.

Even where colour information is crucial, such as in the printing industry, it may be better to use a suitably coloured filter or a monochrome illumination to get a stable solution. But of course there are many applications where colours need to be accurately measured or differentiated and in these situations it is important to understand the methods that the camera uses to generate the colour information.

Single chip colour cameras

The most common type of colour cameras used in vision have a single CCD or CMOS sensor overlaid with coloured filters that cover each of the pixels. These are usually red, green and blue, arranged in the pattern shown below, called a Bayer filter array. There are twice as many green pixels compared to red or blue which mimics the resolving power and greater sensitivity to green light of the human eye.