Ultrahigh accuracy 3-D profilometer

An ultrahigh accuracy 3-D profilometer using a laser heterodyne interferometer has been developed. The profiles of aspheric lenses and their molds have been measured. It can measure not only the rectangular coordinates but also the polar coordinates of the surface profile. The measuring accuracy of each of the three axes is 0.01-0.05 microm if the inclination of the investigated surface is less than +/-25 degrees . The accuracy of the polar coordinate measurement is also better than 0.05 microm when the inclination of the aspheric surface is less than +/-55 degrees . The dynamic range of the X-Y-Z measurement is 40 x 40 x 20 (mm).