DEVICE FOR DETECTING WAVELENGTH OF LASER BEAM

PURPOSE:To make alignment unnecessary and to enable a title device to be small-sized by providing an optical fiber having one end thereof inserted into the light path of a laser beam and taking out part of the laser beam, and a monitor means for forming an interference fringe of the laser beam guided by the optical fiber and detecting the wavelength of the laser beam from this interference fringe. CONSTITUTION:An optical fiber 17 is inserted into the light path of a laser beam 3 through a light collecting section 15, and the other end is connected to a monitor etalon 19. In the light collecting section 15, a head portion 25 is provided on a magnet stand 21 through a rod 23, and the optical fiber 17 is passing through the rod 23 with its leading end 27 being exposed to the head portion 25. The monitor etalon 19 has a projector portion 29, an etalon 31, a line detector 33 and a power monitor detector 35; the projector portion 29 projects a laser beam to the etalon 31, the etalon 31 transmits only the laser beam of a specified wavelength, and the line detector 33 generates an interference fringe of the laser beam to detect the line width and wavelength of the laser beam.