Abstract: A method for measuring and determining a rotation angle of a rotating object in which a clock track corresponding to a desired angular resolution is applied on a magnetic, optical or optomagnetic storage medium. The storage medium is then rotated synchronously with the rotating object, and during the operation a pulse sequence corresponding to the clock track is read from said storage medium. The read pulse sequence is then supplied for further processing to following electronics in which the actual rotation angle is firstly stored in a FIFO memory and secondly directly available for further uses. Furthermore, the invention provides an apparatus for measuring and determining a path difference in Michelson interferometers in which path difference are generated via a rotary movement, for example of a rotating retroreflector.

Abstract: A semiconductor laser HL has an external resonator including a reflector R which reflects the emitted laser beam back into the front facet of the laser. The light emitted from the rear facet of the laser falls on a photodiode PD which generates a signal s which is evaluated by an evaluation unit AE. By differentiation or other processing of the shapes of pulses in the signal s, it is possible to determine the direction of change of any of several operating parameters of the laser system, such as the length L between laser HL and reflector R, the tilt angle of reflector R with respect to the optical axis of the laser or the refractive index n of the medium in the space N defined between the laser and the reflector. For example, one can detect when gas G is fed into space N to change the medium from ordinary air to carbon dioxide, or the reverse.