A point-diffraction interferometer with vibration-desensitizing capability

Kihm, Hagyong; Park, Jungjae; Kwon, Tae-Young; You, Joon Ho; Kim, Seung-Woo

doi:10.1117/12.678691

Cited by 3 publications

(2 citation statements)

References 19 publications

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“…Instantaneous phase-shifting techniques use polarisation components [7] or holographic elements [3], [6], splitting the beams in multiple paths and phase-shifted interferograms are simultaneously recorded. In conclusion, the already available phase-shifting interferometric configurations, that handle the presence of vibrations, are very complex and expensive systems.…”

Section: Vibration Tolerant Methodsmentioning

confidence: 99%

Phase-shift Fizeau interferometer in presence of vibration

2008

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In the context of this article we demonstrate a novel Fizeau interferometric system that copes with the presence of vibrations. Besides the conventional high spatial, but low temporal resolution detector system (the CCD camera) used in phase shifting interferometry, an additional high temporal, but low spatial resolution detector system was integrated, in order to measure the random phase shifts that are induced under the influence of the vibrations. The additional sensor consists of three photodiodes. The acquired analog signals enable the measurement of the occurring phase shifts at three non-collinear locations on the test surface. The resulting phase shifts at the three individual locations enable the determination of the random phase shifts over the entire image aperture. To avoid the smear phenomenon at very short exposure time, a beam shutter was integrated. Another alternative is to integrate a pulsed laser diode, for this purpose the concept of a wavelength meter is proposed. While the random oscillations of the test object are continuously measured, the CCD camera acquires several interferograms. In consequence, a phase shifting algorithm for random phase shifts was applied. In order to proof the validity of the new interferometer, a test surface of known topography was measured. The results of the measurements in presence of vibrations show very good concordance with the surface data given by the supplier. The analysis of the root mean square (RMS) over ten different measurement show a measurement repeatability of about 0.004 waves (approximately 2.5 nm for 632.8 nm laser wavelength).

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Section: Vibration Tolerant Methodsmentioning

confidence: 99%

Phase-shift Fizeau interferometer in presence of vibration

2008

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“…A combination of beam splitters, polarising filters and retardation plates can be built up in a way that four phase-shifted interferograms are imaged as a 2x2 array on a single image sensor [7], [8] . Using this approach there is no problem of synchronising several cameras.…”

Section: Four Interferograms On One Image Sensormentioning

confidence: 99%

Random-phase-shift Fizeau interferometer

Doloca

Tutsch

2008

SPIE Proceedings

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In the context of this article we demonstrate a novel Fizeau interferometric system that copes with the presence of vibrations. Besides the conventional high spatial, but low temporal resolution detector system (the CCD camera) used in phase shifting interferometry, an additional high temporal, but low spatial resolution detector system was integrated, in order to measure the random phase shifts that are induced under the influence of the vibrations. The additional sensor consists of three photodiodes. The acquired analog signals enable the measurement of the occurring phase shifts at three non-collinear locations on the test surface. Under the assumption of the rigid body shifts and tilts of the test object, the resulting phase shifts at the three individual locations enable the determination of the random phase shifts over the entire image aperture. While the random oscillations of the test object are continuously measured, the CCD camera acquires several interferograms. In consequence, a phase shifting algorithm for random phase shifts was applied. In order to prove the validity of the new interferometer, a test surface of known topography was measured. The results of the measurements in presence of vibrations show very good concordance with the surface data given by the supplier. The analysis of the root mean square (RMS) over ten different measurements shows a measurement repeatability of about 0.004 waves (approximately 2.5 nm for 632.8 nm laser wavelength).

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Random-phase-shift Fizeau interferometer

et al. 2011

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A new and potentially cost efficient kind of vibration-tolerant surface measurement interferometer based on the Fizeau-principle is demonstrated. The crucial novelty of this approach is the combination of two optoelectronic sensors: an image sensor with high spatial resolution and an arrangement of photodiodes with high temporal resolution. The photodiodes continuously measure the random-phase-shifts caused by environmental vibrations in three noncollinear points of the test surface. The high spatial resolution sensor takes several "frozen" images of the test surface by using short exposure times. Under the assumption of rigid body movement the continuously measured phase shifts of the three surface points enable the calculation of a virtual plane that is representative for the position and orientation of the whole test surface. For this purpose a new random-phase-shift algorithm had to be developed. The whole system was tested on an optical table without vibration isolation under the influence of random vibrations. The analysis of the root-mean-square (RMS) over ten different measurements shows a measurement repeatability of about 0.004 wave (approximately 2.5 nm for 632.8 nm laser wavelength).

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A point-diffraction interferometer with vibration-desensitizing capability

Cited by 3 publications

References 19 publications

Phase-shift Fizeau interferometer in presence of vibration

Phase-shift Fizeau interferometer in presence of vibration

Random-phase-shift Fizeau interferometer

Random-phase-shift Fizeau interferometer

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