Claims
- 1. An apparatus for detecting surface properties of a material, the apparatus comprising:
- a) a light source for producing a beam of light directed along an optical path;
- b) a first spatial filter, positioned along the optical path downstream from the light source, for giving the beam of light a Gaussian intensity profile;
- c) positioning means for positioning the material in the optical path downstream from the first spatial filter;
- d) a second spatial filter, positioned along the optical path downstream from the material, for removing from the beam a Gaussian intensity profile, wherein the second sipatial filter is a spatial inverse of the first spatial filter; and
- e) a detector, positioned along the optical path downstream from the second spatial filter, for detecting the beam.
- 2. The apparatus of claim 1 wherein the first spatial filter comprises a first Fourier lens assembly and a circular aperture positioned in the focal plane of the first Fourier lens assembly.
- 3. The apparatus of claim 1 wherein the second spatial filter comprises a second Fourier lens assembly and an opaque circular disk positioned in the focal plane of the second Fourier lens assembly.
- 4. A method for detecting surface properties of a material, the method comprising the steps of:
- a) producing a beam of light;
- b) spatial filtering the beam of light to produce spatially filtered beam having a Gaussian intensity profile;
- c) causing the spatially filtered beam to interact with the material to produce a distorted beam;
- d) inverse spatial filtering the distorted beam to produce an inverse spatially filtered beam having a Gaussian intensity profile removed, wherein the inverse spatial filtering is a spatial inverse of the spatial filtering; and
- e) detecting the inverse spatially filtered beam.
- 5. The method of claim 4 wherein the spatial filtering comprises passing the beam of light through a circular aperture positioned in the focal plane of a first Fourier lens assembly.
- 6. The method of claim 4 wherein the inverse spatial filtering comprises passing the distorted beam through an opaque circular disk positioned in the focal plane of a second Fourier lens assembly.
- 7. The method of claim 4 wherein causing the spatially filtered beam to interact with the material comprises reflecting the spatially filtered beam from a surface of the material.
- 8. The method of claim 4 wherein causing the spatially filtered beam to interact with the material comprises transmitting the spatially filtered beam through the material.
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims priority from U.S. Provisional Patent Application Ser. No. 60/045,672 filed May 6, 1997, which is incorporated herein by reference.
US Referenced Citations (12)