PURPOSE:To make the wavelengths of green and yellow colors selectable with a Cu-vapor laser device by providing at least one convex lens and pinhole plate between resonators of an oscillator so that the intensity distribution of the laser beam of the device can be made to a circular form instead of an annular form and the spreading angle of the beam can be made narrower. CONSTITUTION:When only green laser light of 510.6nm in wavelength is to be oscillated, a fine-movement stage 6a is adjusted so that the interval between convex lenses 5 and 6 can become equal to the sum of the focal distances of the lenses 5 and 6 against green light and another fine-movement stage 7d is adjusted so that the distance between the lens 5 and pinhole plate 7 can become 598.7 mm (equal to the focal distance of the lens 5). As a result, the green laser light emitted from a laser tube 2 is focused on the pinhole of the plate 7 after passing through the lens 5 and becomes parallel rays after passing through the lens 6. The parallel rays oscillate while they make reciprocal movement between an output mirror 3 and totally reflecting mirror 4 and are emitted from the mirror 3 after oscillation. Only yellow light of 578nm can also be made to oscillate in the same way.
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