Optics: measuring and testing – By dispersed light spectroscopy – Utilizing a spectrometer
Patent
1998-01-26
1999-12-07
Turner, Samuel A.
Optics: measuring and testing
By dispersed light spectroscopy
Utilizing a spectrometer
382108, G01B 902
Patent
active
059992638
ABSTRACT:
Interference data is acquired as a sequence of pairs of adjacent acquisition intervals in relative quadrature separated by non-acquisition intervals of known, typically constant, phase. The interval pairs in quadrature straddle interline transfer events of the imaging device, such that the two intervals of a given pair are separated only by the very short time interval of an interline transfer event. As a result, the two intervals are acquired serially but almost simultaneously. Preferably four quadpairs are acquired in a measurement, with the phase separation between the pairs being nominally an odd multiple of .pi./2. Because the intervals of each pair are acquired nearly simultaneously and in quadrature, the interference data exhibits similar favorable characteristics exhibited by simultaneous phase quadrature interference data. Namely, when phase calculations are performed using the interference data, ripple error associated with vibrational disturbances tends to cancel out. Advantageously, however, the system is much easier to implement than a true simultaneous phase quadrature system, and there is no requirement to separately measure the DC term of the interference pattern by performing an integration over 2 .pi..
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de Groot Peter
Deck Leslie L.
Turner Samuel A.
Zygo Corporation
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