Color sensors operate according to the energetic reflection principle, whereby the partial spectra of red, green and blue are evaluated separately. Either the three colors are emitted sequentially and the quantity of light reflected from the target object is individually registered, or the sensor emits white light that is first split into the RGB partial spectra in the receiver.The RGB intensity values thus determined are compared with previously taught-in reference values. The switching output is activated if the colour values are within the defined tolerance range. Color sensors are ideally suited in sorting packaging or checking different labels, detecting colors and color ranges on packaging and film.
Contrast sensors also operate on the energetic reflection principle and detect gray value differences on matt, glossy or transparent objects and surfaces. Contrast sensors are mostly used in detecting printing marks with the subtlest variations in gray values in the printing and packaging industry, and also checking labels and stickers in the printing industry.