Veeco Instruments Inc.

Wyko, Inc.

Molecular Devices Corporation

Veeco Corporation

David J Aziz

Bryan W Guenther

Robert E Knowlden

Martin D Andrews

Paul R Unruh

Matthew P Abbene

Andrey Klishin

Richard W Swinford

A light source with multiple parallel beams is combined with a pair of opposing mirrors mounted on a rotating fixture and with a fixed aperture to produce a single output beam. Through the motion of the rotating fixture, the pair of mirrors shifts the location of the output of each input beam passing through the device so as to sequentially channel each beam into the optical path defined by the aperture. Thus, the input source corresponding to the output beam may be quickly switched by rotating the pair of mirrors to the position that produces the appropriate shift of the beam selected from the light source. In another embodiment of the invention, the pair of opposing mirrors is replaced by a transparent block similarly mounted on a rotating fixture.

Achromatic beam switch

A pulsed light source in used conjunction with a ramping scanning mechanism for phase-shift and vertical-scanning interferometry. The pulse length and the scanning velocity are selected such that a minimal change in OPD occurs during the pulse. As long as the duration of the pulse is shorter than the detector's integration time, the effective integration time and the corresponding phase shift are determined by the length of the pulse, rather than the detector's characteristics. The resulting minimal phase shift produces negligible loss of fringe modulation, thereby greatly improving signal utilization during phase-shifting and vertical-scanning interferometry.

Pulsed source scanning interferometer

Average fringe contrast is determined by PSI measurements at each step of relatively large translations of the reference optics and mirror of a white-light Linnik interference objective and the resulting data are used to minimize the OPD between the reference and test beam paths of the instrument. Utilizing the same algorithms used in the art to perform conventional vertical scanning interferometry, the position of minimum OPD is determined by finding the position of maximum average fringe contrast. Furthermore, by automating the system with a precise translation mechanism, operator-to-operator variations are completely eliminated and the precision of the process of OPD minimization is greatly improved. In another embodiment of the invention, the optimal focal position of the reference mirror is found at the same time by calculating the average lateral variation of fringe contrast as a function of OPD and focal position. The optimal OPD and focal position correspond to the maximum average lateral variation of fringe contrast in the resulting three-dimensional space.

Automated minimization of optical path difference and reference mirror focus in white-light interference microscope objective

A laser interferometer is embedded into an interference microscope to precisely determine the in-focus position of the microscope objective's reference mirror. A collimated laser beam is introduced into the microscope system and split into two beams directed toward a calibration reference surface and the interference objective. The light reflected from the calibration reference surface is returned to the camera. The light into the interference objective is focused onto the reference mirror and returned to the camera. For the purpose of calibration, the two beams are combined at the camera to produce interference fringes. When the reference mirror is in focus, the returned beam is collimated; if the mirror is on either side of focus, the beam is either converging or diverging. Accordingly, the interferogram produced at the camera reflects the in-focus or out-of-focus condition of the reference mirror. The curvature of the wavefront returned from the reference mirror is determined electronically by analyzing the interference fringes produced with the beam returned from the calibration reference surface. By minimizing the curvature of the reference-mirror wavefront as the mirror is translated along the optical path, the reference mirror can be focused with an accuracy greater than possible by visual observation. Furthermore, by automating the focusing system with a precise translation mechanism driven by closed-loop control, operator-to-operator variations are completely eliminated.

Embedded interferometer for reference-mirror calibration of interferometric microscope

A crash protection mechanism for a microscope objective includes a tapered, self-centering combination of sleeves interposed between the objective and its housing in an interferometric profiler. A three-lobed, tapered inner sleeve is affixed to the objective, while a matingly tapered outer sleeve is attached to the objective housing. A spring-loaded mechanism urges the objective outward toward the sample surface, so that it can move inward axially under crash conditions and then return to its original axial position. The mating tapered sleeves create an outward seated position that provides a high degree of repeatability when the objective is returned to its position after a crash.

Self-centering crash protection mechanism for interference microscope objective

Structural components are added to an interferometric objective to offset the effects of temperature variations. The components are mounted between the sleeve housing the optics of the objective and the collar housing the optics of the interferometer. Each component is coupled sequentially, such that the thermal response of the assembly is substantially the linear combination of the response of each component and is designed to cause a shift in the opposite direction to the shift produced by a temperature change in the unmodified device. The thermal characteristics and dimensions of the components are chosen empirically to provide a minimum shift between the reference mirror and focal point in the interferometric objective as a function of temperature.

Method and apparatus for correcting shifts between a reference focal

A low-magnification interference microscope objective is rendered parfocal with a high-magnification objective by folding the light beam to the side of the optical axis of the objective, thereby maintaining the original optical path length while shortening the mechanical length of the objective. The beam is reflected by a mirror, causing it to travel some distance out to the side, and then it is reflected back toward the beamsplitter by an additional pair of mirrors. After a final reflection within the beamsplitter, the resulting beam is coaxial with the original optical axis, while the physical length of the objective has been substantially reduced. This approach makes it possible to obtain a desired distance from the mounting shoulder of the objective to the focal point.

Folded low-power interference microscope objective

A broad-bandwidth interferometric device is adapted for longitudinal insertion into a cylinder cavity to produce irradiance signals at multiple vertical-scanning positions as a function of optical path differences between a reference mirror incorporated in the probe and the cylinder-wall surface. The light-source beam is passed through an objective lens placed longitudinally in the cylinder and then divided by a beam splitter disposed in fixed relation to the cylinder wall to produce a test beam directed radially to the wall and a reference beam directed axially to a reference mirror disposed in fixed relation to the lens. During scanning, the objective lens and reference mirror are translated together, while the beam splitter remains stationary with respect to the cylinder wall, thereby varying the position of the focal point of the test beam and providing the vertical-scanning effect required to produce interference fringes and a corresponding map of the tested cylinder surface. In order to reduce the length of the instrument, the reference beam may be folded to the side by a reflective surface and the reference mirror may be positioned perpendicularly to the main axis of the instrument. In that case, the lens, fold mirror and reference mirror are all translated together, while the beam splitter remains stationary and fixed with the test surface.

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Tucson, AZ, United States of America

David J Aziz