| 摘要 |
PROBLEM TO BE SOLVED: To provide an electromagnetic wave spectroscopic measurement system of a homodyne detection type having high SNR by reducing cyclic noise of a frequency identical to that of a target wave.SOLUTION: By increasing a period of "sawtooth" control voltage Vcnt by (n+1) times, a frequency of cyclic noise caused by electrooptical crystal, which is a main constituent of an optical phase modulator, becomes 1/(1+n) times, or moves toward a lower side of a target wave frequency. A frequency spectrum for n=3 is shown here as a specific example. The target wave frequency fis 20 kHz, and the frequency of a fundamental wave of the cyclic noise caused by the electrooptical crystal is a quarter thereof, or 5 kHz. |
