A chromatic lens L generates the image of a point source of white light W as a continuum of monochromatic images located on the optical axis ("chromatic coding").
A sample is located within the color-coded segment and its surface scatters the incident light beam.
The backscattered light passes through the chromatic lens L in the opposite direction and arrives at a pinhole P that filters out all but one wavelength, λM.
The collected light is analyzed by an S spectrometer.
The position of the sample (M-point) is directly related to the detected wavelength.