| 摘要 |
PROBLEM TO BE SOLVED: To allow electromagnetic wave detection with high SN ratio even if an RF signal has a frequency variation &Dgr;ω(t) accompanying frequency variations in a light source.SOLUTION: An electromagnetic wave detection method includes the steps of: branching a beam from one light source into two; branching, into two, a beam from the other light source emitting light of frequency different from that of the one light source; shifting one of the branched four beams by only a frequency of an oscillation signal having a constant frequency; multiplexing respective two beams of the four branched beams including the beam shifted by only a constant frequency, having different light sources to one another to form two pairs of the beams; using the other pair of beams of the two pairs of multiplexed beams, as LO signal; irradiating a measured object with a first RF signal; performing heterodyne detection by mixing the first RF signal penetrating or reflected on the measured object and the LO signal, and outputting a detection signal having as frequency a difference frequency between two beams composing the LO signal and a difference frequency of the frequencies of the first RF signal; and subjecting the detection signal to two-phase lock-in detection by the oscillation signal, and outputting an in-phase component having the same phase as the detection signal and a quadrature component having a quadrature phase to the detection signal. |
