Werle, P.P.Werle2022-03-082022-03-081997https://publica.fraunhofer.de/handle/publica/303645Using the process according to the invention and the arrangement for absolute interferometry specified for performing the process using radiation generated by diode lasers, relative or absolute distance measurements can be performed without reference interferometers using only one detector and with high precision of the test section measurement. The basic idea of the invention is to modulate radiation generated by a diode laser in such a way that at least a discrete frequency is imposed on the diode laser, said frequency being detected using a known phase-sensitive detection process. As a result of modulating the original radiation of the diode laser, a second laser beam is more or less generated so that a measuring and a reference beam result in a single beam path. The two beams, i.e. the measuring and the reference beam, each have a different frequency, but have parallel wave fronts, travel precisely along the same optical path in the uniform beam path and interfere on the single det ector. The test section is then determined by the above mentioned detection of the phase shift and the detection of the phase shift in the modulation signal. Alternatively, the modulation frequency of the diode laser is changed until a specified phase shift between the original first beam of the diode laser and the second beam generated by modulation is detected by the detector ...de608patent1993-4333423