A newly developed interferometer for characterization of aspheric surfaces is presented. The interferometer is based on
the Fizeau configuration and uses a sub-Nyquist CCD camera as a detector. Due to the camera design, the instrument is
capable of recording very dense fringe patterns of up to 4 fringes/pixel. This enables processing of interferograms with
hundreds of fringes in the field of view. Thus, the interferometer can be used to measure many types of aspheric surfaces
using a standard transmission sphere as a reference. However, the main obstacle associated with this kind of
interferometer is caused by the presence of so called "re-trace" errors, which can be significant. Such errors occur from
un-equal optical paths the reference and test beams travel through in the optical system of the interferometer. A ray
tracing procedure has been developed to subtract the influence of the optical system of the interferometer on the
measurement. This method of error compensation results in reducing measurement errors to λ/5 PV (peak to valley) for
the full range of fringe densities with the low order aberrations not exceeding λ/10. We present measurements of test
surfaces illustrating the effectiveness of the error compensation procedures as well as preliminary measurements of
multiple aspheric surfaces.
OMNISCATR 1000 is a second generation of a new generation of high resolution three dimensional scatterometers. The instrument can acquire 200,000 three dimensional scatter data points with a dynamic range of 108. A description of OMNISCATR 1000 and its capabilities is presented. Data is also presented showing that the instrument's high speed data acquisition system has a measurement repeatability of 2.5%.
With OMNISCATR's high resolution and three-dimensional light scatter measurement capabilities, a new method is now available for analyzing surface and material properties such as tooling or etching patterns, contamination, and bulk defects. Scatter data from patterned wafers, sub-micron grit particles, and defective interocular lenses is presented.
A new instrument has been developed that takes hundreds of thousands of points of scattered light data at 0.1 degree(s) resolution over a three dimensional segment of the hemisphere. The data can be acquired and displayed in 0.5 to 20 seconds depending on the amount of data desired. The instrument is the size of a 'shoe box' and provides solid state operation. With the instrument's high resolution three dimensional capability, well-defined three dimensional interference patterns, speckle, and diffraction can be seen in near-real-time. Much of these patterns are out of the plane of incidence and sometimes add significantly to the scatter, and may allow a scattering surface to be characterized through methods not available before. The high speed capability makes this instrument ideal for scattered light measurements to be used for high resolution surface defect quality control on high volume assembly lines.