Colour measurement is required in many industry sectors, enabling companies to select, monitor, differentiate, grade and sort various types of coloured objects involved in manufacturing, automated handling and other production processes. Measured objects can take the form of solids, powders or liquids and it is also possible to measure the colours of transparent or translucent surfaces such as coatings, labels and plastics, as well as LEDs and glass objects.
In order to fully understand which colour measurement technology your sensor requires for a specific application, it is important to consider the following factors.
Industrial colour measurement
When defining a colour of an object, the term ‘colour space’ is often used. In industrial non-contact colour measurement applications, there are three main types of colour space that colour sensor technology use: Greyscale colour space, the CIE RGB colour space and the CIE XYZ colour space. Although the sensor supplier’s datasheet may state that the sensor you are purchasing is a ‘true colour’ sensor, it is important to ask which colour space the sensor chip technology is based on, as this can have dramatic effects on sensor performance.
Greyscale Colour Space
This is defined as a colorimetric (or more specifically photometric) grayscale image that has a defined grayscale color space. This maps the stored numeric sample values to the achromatic channel of a standard color space, and is based on measured properties of human vision. These sensors are using greyscale references against RGB colour space to define the colour rather than ‘true colour measurement’.
RGB colour space
The CIE RGB colour space is an additive colour model in which red (R), green (G) and blue (B) light are combined in various ways to reproduce a broad array of colours. All three colours are displayed as one result in the colour white. Black colour is produced when R/G/B = 0/0/0.
