| 摘要 |
PROBLEM TO BE SOLVED: To provide a two-beam spectrophotometer that can obtain a large S/N ratio regardless of the number of revolutions, power-supply frequency, or power-supply voltage of a sector mirror. SOLUTION: A counter 21 measures a synchronizing signal from a photo- interrupter 4, and a microcomputer 22 calculates the number of revolutions of the sector mirror 21. The microcomputer 22 also calculates the frequency at which the amplitude of noise becomes the maximum from the number of revolutions of the selector mirror 1, and sets the notch frequency of a notch filter to the calculated frequency. The notch filter is a digital filter and is realized by the numerical operation by means of the microprocessor 22. Since the notch filter is the digital filter, in addition, the notch frequency of the filter can be changed easily and can always be set to the optimum value. Consequently, the notch filter can damp the noise frequency components of signals obtained from a detector, and can pass the other aimed frequency components.
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