Design of an optical probe for surface profile measurement

We propose a novel optical probe for surface profile mea- surement of optical surfaces. This probe uses a laser beam to measure local slopes of a surface and obtains the surface profile through numeri- cal integration of the measured slopes. Slope measurement is based on a new angle measurement method, namely, angle measurement based on the internal-reflection effect (AMIRE). The probe is a high-resolution (0.1-arcsec), compact (80360340 mm) device with a simple measure- ment principle. For surface profile measurement, the probe is installed on a coordinate measuring machine (CMM), which provides the neces- sary scanning motion. A commercial laser interferometer is used to mea- sure the rotational error of the CMM in real time. The result is subtracted from the slope data collected by the probe for error compensation. Mea- surement results of a spherical mirror are presented that show a nanometer-order resolution in surface profile measurement.