Device for interferometric detection of surface structures

A device for interferometric detection of surface structures, comprising

• at least two laser sources (10-12) for generating at least two laser beams (13-15) of different respective wavelengths,
• a coupler/splitter device (16), coupled to respective outputs of said laser sources, for combining said at least two laser beams into a combined beam and splitting said combined beam into two partial beams,
• means for shifting frequency of one of said two partial beams with respect to the other of said beams, one of the partial beams serving as a reference beam and the other serving as a measuring beam, said measuring beam being guided to a measuring point on an object (26) whose surface is to be measured and reflected there, said referenced beam and said measuring beam being interferometrically superimposed at a photodetector (25),
• and an evaluating device (27) connected to an output of said photodetector device for detecting at least one phase shift,
• wherein
• more than one laser source (10, 11, 12) is provided;
• at least one modulation means (28) is provided, modulating at least one of laser pumping current of each laser source and laser frequency of said laser sources (10, 11, 12);
• the respective outputs of said laser sources are coupled to the input of the coupler/slitter device (16) using optical fibers (13, 14, 15);
• said two partial beams leaving the coupler/splitter device (16) pass through respective optical fibers (17, 18) for at least a portion of a distance to said photodetector (25);
• and said means for shifting frequency includes a lengthening (19) in one (17) of said partial beam optical fibers (17, 18) with respect to the other (18) fiber;
• and wherein
• the laser sources (10-12) operate simultaneously;
• a number of photodetectors (31-33), corresponding to the number of laser sources (10-12), is provided in the photodetector device (30), and
• in front of these photodetectors (31-33), means (34) are provided for splitting the laser beam into its components with different wavelengths and for supplying the individual photodetectors (31-33).