| 摘要 |
PURPOSE:To limit variation in temperature given to a sample to a narrow range and to accurately measure the expansion coefficient of the sample almost at the temperature where the method and device are used by detecting resonance wavelength which varies owing to the expansion of a spacer made of a body to be measured with laser light. CONSTITUTION:A Fabri-Perot interferometer which uses the body to be measured as the spacer 1 is put in a thermostat 4 and held at temperature T1 and the transmission peak wavelength lambda1 of a Fabri-Perot band-pass filter 14 and the peak wavelength of a laser spectrum 16 are adjusted to the same value. Then the refractive index n1 of a medium to light in a cavity and the length d1 of the spacer 1 at this time are found. Then the temperature in the thermostat 4 is varied to T2 and while the laser light is monitored by a photodetecting means 11, the transmission peak wavelength lambda2 of a Fabri-Perot band-pass filter 15 and the peak wavelength of the laser spectrum 17 are made equal to each other. Then when the refractive index of the medium is denoted as n2 and the length of the spacer is denoted as d2, the expansion coefficient is calculated from those values.
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