Colorimeter

A colorimeter determines the color difference by comparing the reflection or transmission characteristics of a standard sample and a sample under test for a specific wavelength of light. It usually uses a photodetector to receive light signals and converts them into digital signals for processing and analysis.
Colorimeter generally uses the color space specified by the International Commission on Illumination (CIE), such as CIE Lab, CIE Lch, etc. In these color spaces, color can be expressed by three parameters, namely lightness (L), hue (a, b or h) and saturation (c or s). A colorimeter calculates the color difference by measuring the difference between these three parameters.