Interferometer with a wavelength-tuned diode laser for surface profilometry

An interference profilometer has been developed which uses a diode laser as a non-expensive, compact and wavelength tunable light source. The profilometer works like an optical stylus and can be realized at relatively low expense. Two different methods of interference signal processing have been worked out. Both methods take advantage of the wavelength tunability of the diode laser. In connection with the development of the profilometer the spectral properties of different types of diode laser in the wavelength range from 780 nm down to 633 nm have been measured. The performance of the profilometer was proved by comparison measurements with a HeNe laser interferometer and by the measurement of well known surfaces. A measurement range of up to 100 mu m and a measurement uncertainty of better than 10 nm can be achieved.