| 摘要 |
<p>A method for measuring with a system, taking into account thermal expansion of an object under test, comprises: providing a maximum allowable discrepancy; providing a coefficient of thermal expansion for an object under test; providing a reference temperature; placing a first reference retroreflector and a second reference retroreflector on the object under test, there being a first distance between the first reference retroreflector and the second reference retroreflector at the reference temperature; measuring a temperature of the object under test; calculating a first temperature difference by subtracting the reference temperature from the measured temperature of the object under test; calculating a scale factor by multiplying the first temperature difference by the coefficient of thermal expansion; measuring the coordinates of the first reference retroreflector and the second reference retroreflector using an absolute distance meter, first angular transducer, and second angular transducer; calculating a second distance between the measured coordinates of the first and second reference retroreflectors; calculating the difference (third distance) between the distance between the retroreflectors at the reference temperature and the measured distance at the measured temperature, by subtracting the first distance from the second distance; calculating the expected difference in distance between the retroreflectors (fourth distance), based on the difference between the measured and reference temperatures, by multiplying the scale factor by the first distance; calculating a discrepancy value by subtracting the third distance from the fourth distance; and taking an action when the discrepancy value exceeds the maximum allowable discrepancy, the action being either issuing an alarm or measuring the three-dimensional coordinates of at least some retroreflector targets from among a collection of retroreflector targets and, from this data, re-establishing a frame of reference for an object under test.</p> |
