Editing Sample Thickness Measurement via Multi-wavelength Laser Interferometry (section)

===Experimental Setups===
The experimental optical setup consists of three main subsystems: three laser sources with different wavelengths, a beam-conditioning module, and an interferometer.

The light sources are selected as follows: a red laser with wavelength <math>\lambda_1 = 650\,\mathrm{nm}</math>, a yellow laser with wavelength <math>\lambda_2 = 594\,\mathrm{nm}</math> and a violet laser with wavelength <math>\lambda_3 = 405\,\mathrm{nm}</math>.

To improve the contrast and signal-to-noise ratio of the interference fringes, the beam first passes through a spatial filter composed of a microscope objective and a pinhole. This stage reshapes the wavefront by removing higher-order transverse modes and speckle noise. The filtered beam is then collimated into a parallel beam using an achromatic lens.
Next, the beam is directed through a beam splitter (BS) and normally incident onto both the standard sample surface and the reference mirror in optical contact with it. The reflected beams recombine at the beam splitter and interfere on the target plane of a CCD camera.
Since the sensitive area of the CCD is much smaller than the actual interference pattern, a beam-converging (imaging) system is incorporated into the optical path to ensure that the interference pattern can be captured more completely.

[[File:EXP_SETUP.jpeg|1000px|center]]