Patent ID: 7124635

Claim:
An evaluation method for a coefficient of thermal expansion of an ultra-low-expansion glass material, including: (a) a step of measuring, in the used ultrasonic frequency range, the longitudinal velocity and attenuation coefficient, the shear velocity and attenuation coefficient, and the density, of a standard specimen of the ultra-low-expansion glass material; (b) a step of calculating a first leaky acoustic wave characteristic with respect to said standard specimen, from said acoustic velocities, attenuation coefficients, and density; (c) a step of obtaining, by measuring the leaky acoustic wave interference signal curve V(z) with respect to said standard specimen, a second leaky acoustic wave characteristic from that V(z) curve; (d) a step of obtaining, as a calibration coefficient, the ratio of said first leaky acoustic wave characteristic calculated in said Step (b) and said second leaky acoustic wave characteristic obtained from said V(z) curve in Step (c); (e) a step of measuring a V(z) curve with respect to the measured specimen of the ultra-low-expansion glass material and obtaining from that V(z) curve a third leaky acoustic wave characteristic; (f) a step of calibrating, with said calibration coefficient, said third leaky acoustic wave characteristic obtained for said measured specimen; (g) a step of obtaining the relationship between the coefficient of thermal expansion of said ultra-low-expansion glass material and said third leaky acoustic wave characteristic, absolutely calibrated; and (h) a step of measuring a fourth leaky acoustic wave characteristic with respect to the ultra-low-expansion glass specimen under evaluation, and, based on said relationship, evaluating the coefficient of thermal expansion.