TABLE OF CONTENTS Daniel Malacara
Centro de In ?estigaciones en Optica, A.C.
Le n, Gto, Mexico
| E | electric field strength |
| k | radian wave number |
| r | position |
| t | time |
| ? | wavelength |
| | phase |
| ? | radian frequency |
The requirements for high-quality optical surfaces are more demanding every day. Thus, they should be tested in an easier, faster, and more accurate manner. Optical surfaces usually have a flat or a spherical shape, but they also may be toroidal or generally aspheric. Frequently, an aspherical surface is a conic of revolution. An aspherical surface can only be made as good as it can be tested. Here, the field of optical testing will be reviewed. There are some references that the reader may consult for further details (Malacara, 1991).
Some classical tests will never be obsolete, because they are cheap, simple, and provide almost instantly qualitative results about the shape of the optical surface or wavefront. These are the Foucault or knife-edge test, the Ronchi test, and the Hartmann test. They will be described next.
The Foucault or knife-edge test was invented by Leon Foucault (1852) in France, to evaluate the quality of spherical surfaces. This test detects the presence of transverse aberrations by intercepting the reflected rays deviated from their ideal trajectory, as Fig. 1 shows. The observer is behind the knife, looking at the illuminated optical surface, with the reflected rays entering the eye. The regions corresponding to the intercepted rays will appear dark, as in...
