| 摘要 |
PURPOSE:To achieve a higher sensitivity by using an optical heterodyne interferometer for the measurement of a phase change in a fluid generated by a photothermal effect. CONSTITUTION:A linearly polarized light with a frequency nu emitted from a light source He-Ne laser Ia.HN is divided into two beams with a beam splitter PBs to be incident on two acoustic optical elements (AOM1 and AOM2) respectively. Beams nu1 and nu2 are emitted from the AOM1 and AOM2 to be incident into a fiber. An interference beat between the lights nu1 and nu2 is detected on a detector PD1. Likewise, an interference beat is detected with a detector PD2. A light source Ia.C for excitation uses a continuous light beam matched with an absorption line of particles used being pulsated with chopper. In the case of measuring a density, a phase change caused by a photothermal effect is detected with a heterodyne interference probe set overlapped at a point involved to determine it from an initial value thereof. A speed is determined by a analyzing a change of a curve of the phase change thus obtained. |
