A white light LED is used to illuminate the source

The light travels via optical fiber to the chromatic optical probe

The chromatic probe focuses light at different colors to different working distances from the probe

The back reflected/scattered light is passed back through the optical fiber to a spectrometer which diffracts the light into a spectrum

The intensity peak in the spectrum corresponds to a precise distance from the chromatic probe

Each measurement is collected at a 4kHz sample rate

Probe can be either single point or line scan (192 point)

For thickness measurement, the spectrum shows two intensity peaks corresponding to the top and bottom surface of the transparent sample