| 摘要 |
A mechanism for providing thermal compensation when measuring surface topography at an elevated temperature using a non-contact vibration transducer, such as a laser Doppler vibrometer (LDV). Thermal compensation is provided to a detector output signal to correct for thermal diffraction of a reflected portion of a beam of radiant energy directed at a surface of a test object. The thermal compensation is based on a calculated deviation between the detector output signal r2 at an elevated temperature and the detector output signal r1 at approximately room temperature. In one embodiment, the thermal compensation mechanism calculates a stationary signal r3 (t) which represents the detector output signal without noise and corrected for thermal diffraction at the elevated temperature according to the following equation: r 3  ( t ) = lim T → ∞  1 / T  ∫ - t / 2 + t / 2  r 2 *  ( t ) * r 2 *  ( t + &Dgr;   t )    t , wherein T represents the total number of spectrums measured at the elevated temperature at multiple times upon which the compensation is based, and wherein r2*=r2−r2 (baseline). |
