Optics: measuring and testing – By dispersed light spectroscopy – Utilizing a spectrometer
Patent
1996-07-03
1997-10-14
Font, Frank G.
Optics: measuring and testing
By dispersed light spectroscopy
Utilizing a spectrometer
356349, 356358, G01B 902
Patent
active
056777680
ABSTRACT:
In the claimed invention for an improved AC type interferometric metrology apparatus, a change in position of an item disposed in a rotating reference frame is measured. The rotating reference frame accumulates a rotation angle over a time period with respect to a fixed reference frame. A quarter wave plate and an interferometer comprising a polarizing beam splitter, a reference path reflector, and a measurement path reflector are all mounted in the rotating reference frame. The measurement path reflector is mounted to item so that changes in its radial position along an axis orthogonal to the axis of rotation of the rotating reference system are measurable. In one preferred embodiment, the components in the fixed reference frame are a two-frequency laser light source, a stationary quarter wave plate, a receiver, for producing a measure signal containing information representing the change in optical path length between the measurement and reference paths of the rotating interferometer, the difference in the two frequencies of the beams from the laser source, and the rotation angle, and a signal processor. The signal processor receives the measure signal, a reference signal representing the difference frequency of the laser light source, and a signal from a rotary encoder containing information proportional to the rotation angle. The signal processor produces a signal representing the measurement of the change in position. In another embodiment, the rotary encoder is replaced by added optical components which automatically produce optical signals that contain information about the rotation angle and the difference in the two frequencies of the beams from the laser source.
REFERENCES:
patent: 4329055 (1982-05-01), Schaefer et al.
patent: 4802765 (1989-02-01), Young et al.
patent: 5457529 (1995-10-01), Tank et al.
patent: 5583638 (1996-12-01), Cutler
Yao Li and George Eichman, "Multipass Counterrotating Wave-Plate Frequency Shifters For Heterodyne Interferometry," Nov. 1986, Optics Letters/vol. 11, No. 11, pp. 718-720.
M. P. Kothiyal and C. Delisle, "Optical Frequency Shifter for Heterodyne Interferometry Using Counterrotating Wave Plates," Aug. 1984, Optics Letters/vol. 9. No. 8, pp. 319-321.
Gary E. Sommargren, "Up/down Frequency Shifter for Optical Heterodyne Interferometry," Aug. 1975, Journal of the Optical Society of America, vol. 65, No. 8, pp. 960-961.
Robert Crane, "Interference Phase Measurement," Applied Optics/vol. 8, No. 3/Mar. 1969, pp. 538-542.
Jae Sun Yoon and Sang Soo Lee, "Multiple-Reflection Laser Doppler Interferometer," Applied Optics/vol. 24, No. 21/1 Nov. 1985, pp. 3429-3431.
R.N. Shagam and J.C. Wyant, "Optical Frequency Shifter for Heterodyne Interferometers Using Multiple Rotating Polarization Retarders," Applied Optics/vol. 17, No. 19/Oct. 1978, pp. 3034-3035.
Font Frank G.
Hewlett--Packard Company
Kim Robert
LandOfFree
Method and interferometric apparatus for measuring changes in di 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 interferometric apparatus for measuring changes in di, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and interferometric apparatus for measuring changes in di will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1558734