| 摘要 |
PROBLEM TO BE SOLVED: To provide a small-sized wavelength-variation measuring instrument having no movable mechanism and facilitating optical axis adjustment, in the case of a wavelength measuring instrument for measuring a variation in the wavelength of a light source oscillating with a single mode. SOLUTION: This instrument is equipped with a lens for converting light incident from an input part into parallel light, and an optical means for generating an optical path difference ofλ0/4 relative to half the surface of a light beam when it goes and comes back one time between first and second reflecting surfaces making up an etalon interferometer into which the parallel light comes from the lens. Further, this instrument is equipped with a reflection prism for separating the parallel light passing through the etalon into two to both sides of an optical axis surface where the optical path difference ofλ0/4 is generated, first and second light receivers for receiving light separated by the reflection prism, and a signal processing means for counting the number of times of variation in the intensity of light from the first and second light receivers to output the amount of variation in wavelength of the incident light.
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