| 摘要 |
PURPOSE:To measure photoabsorptivity of a thin film on a liquid surface accurately and sensitively, by making an excitation beam irradiate a measuring part of a sample intermittently while several probe beams irradiate it to detect deflection of the probe beam. CONSTITUTION:An excitation beam 5 emitted from an excitation light source 6 is modulated 7 into a light intermittent or varying in the intensity to irradiate a measuring part of a thin film 1 developed on a liquid surface 2 of a liquid tank 4, which causes an intermittent change in the refractive index of the thin film 1 near the beam. On the other hand, probe beams 8a and 8b are made incident into the liquid tank 4 and totally reflected at the irradiation part of the excitation beam 5 on the liquid surface 2 to leave the liquid tank 4. With such an arrangement, the beams 8a and 8b pass through the measuring part at which the refractive index varies intermittently by the irradiation with the beam 5. The optical paths of the beams 8a and 8b are deflected according to the distribution of refractive index thus changed. When the beams 8a and 8b are both made to pass through an area with the refractive index distribution symmetrical with respect to the center of the excitation beam irradiation area, the vector sum of deflection of the probe beam due to variations in the liquid surface is down to zero, thereby enabling the detecting 10 of deflection according to the refractive index. |
