Optics: measuring and testing – By dispersed light spectroscopy – Utilizing a spectrometer
Patent
1996-12-19
1998-07-07
Nelms, David C.
Optics: measuring and testing
By dispersed light spectroscopy
Utilizing a spectrometer
356345, G01B 902
Patent
active
057777411
ABSTRACT:
A method and system for providing interferometric measurements having reduced sensitivity to vibrations. An interference pattern from an interferometer (35) is amplitude split into first and second interferograms and imaged onto first and second detectors (10, 11), respectively, such as CCD cameras (10, 11). The two cameras (10, 11) have different data acquisition rates. The frame integration period of the slow detector is distinctly shorter than that of the fast detector. The detectors (10,11) are disposed such that the image fields substantially overlap and are synchronized with each other for enhancing vibration insensitivity. The shorter the integration period of the slow detector with respect to the fast detector, the greater the vibration insensitivity. During data acquisition a phase shifter (45) changes the phase difference between the beams in the interferometer (35) while data from both cameras (10, 11) is taken by a frame grabber (15) and saved in a computer (25). During data analysis, the phase at each image point on each frame of the fast data set is calculated by the computer (25), with the phase difference between interferograms in the slow data set being determined from the phases derived from the fast data set and with the slow data set then being analyzed for phase at each image point using the measured phase increments.
REFERENCES:
patent: 4594003 (1986-06-01), Sommargren
patent: 4624569 (1986-11-01), Kwon
patent: 4653921 (1987-03-01), Kwon
patent: 5410405 (1995-04-01), Schultz et al.
de Groot, Peter J., "Vibration in phase-shifting interferometry", pp. 354-365, J.Opt.Soc.Am. A/vol. 12, No. 2 (Feb. 1995).
Farrell, C.T., et al., "Phase-step insensitive algorithms for phase-shifting interferometry", pp. 648-652, Meas. Sci. Technol. 5 (1994).
Greivenkamp, J.E., et al., "Phase Shifting Interferometry", pp. 501-598, Chapter 14, Optical Shop Testing, Second Edition (John Wiley & Sons, Inc., 1992).
Greivenkamp, J.E., "Generalized data reduction for heterodyne interferometry", pp. 350-352, Optical Engineering, vol. 23, No. 4 (Jul./Aug. 1984).
Kinnstaetter, K., et al., "Accuracy of phase shifting interferometry", pp. 5082-5089, Applied Optics, vol. 27, No. 24 (Dec. 15, 1988).
Kong, In-Bok, et al., "General algorithm of phase-shifting interferometry by iterative least-squares fitting", pp. 183-188, Optical Engineering, vol. 34, No. 1 (Jan. 1995).
Meiling, John A., "Interferometric Metrology of Surface Finish Below 1 Angstrom RMS", pp. 7-10, Tucson, Arizona, USA.
Schwider, J., et al., "Digital wave-front measuring interferometry: some systematic error sources", pp. 3421-3432, Applied Optics, vol. 22, No. 21 (Nov. 1983).
Seligson, J.L., et al., "Stability of a lateral-shearing heterodyne Twyman-Green interferometer", pp. 353-356, Optical Engineering, vol. 23, No. 4(Jul./Aug. 1984).
Smythe, R., et al., "Precision Surface Metrology", pp. 16-21, Proceedings of SPIE--The International Society for Optical Engineering, San Diego, California (Aug. 1983).
van Wingerden, Johannes, et al., "Linear approximation for measurement errors in phase shifting interferometry", pp. 2718-2729, Applied Optics, vol. 30, No. 19 (Jul. 1, 1991).
Wizinowich, Peter L., "Phase shifting interferometry in the presence of vibration: a new algorithm and system", pp. 3271-3279, Applied Optics, vol. 29, No. 22 (Aug. 1990).
Kim Robert
Nelms David C.
Zygo Corporation
LandOfFree
Method and apparatus for optical interferometric measurements wi does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for optical interferometric measurements wi, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for optical interferometric measurements wi will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1211959