“ Before writing to disk, data is encoded in the "8 in 14" standard and stored in the form of land and pits. In the embossed plates, the recesses are 1/4 wavelength deep in the material of the reading laser plate (about 125 nm), as a result of the interference of light reflected from the environment and the recesses, the wave is extinguished. The pits are 500 nm wide and the track spacing is 1.6 mm. The differences in light reflection are used by the lens servo to guide the beam along the path and focus it. ”