| 摘要 |
PURPOSE:To eliminate the need to adjust an optical system finely, and to shorten the optical path length of an optical system and reduce the size of a device by varying the tilt angle of an interference filter to the optical axis of laser light and thus adjusting the quantity of the laser light transmitted through the interference filter. CONSTITUTION:An interference filter unit 7 is so constituted so that the tilt angle of the interference filter to the optical axis of the laser light according to a driving signal applied from a subtracter 6; and the tilt angle is controlled by a servo-loop so that the output signal of a photodetector 5 applied to the subtracter 6 becomes equal to a reference voltage. Then, the tilt angle of the interference filter to the optical axis is varied to control the transmissivity of light with one certain wavelength. Wavelength separation and the quantity of transmitted light are therefore stabilized by one interference filter for a light source having plural wavelengths. Consequently, the optical system need not be adjusted to shorten the optical path length of the optical system, and the device is reducible in size.
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