Corning Incorporated

Corning-tropel

Thomas James Dunn

Christopher Alan Lee

Mark Joseph Tronolone

Andrew W Kulawiec

Joseph C Marron

John Weston Frankovich

Joshua Monroe Cobb

Nestor O Farmiga

Robert Dennis Grejda

Paul Francis Michaloski

Paul Gerard Dewa

Yoshihiro Nakamura

Jack Weston Frankovich

Matthew Ronald Millecchia

Alexander Timothy Bean

The methods disclosed herein include recording at near-vertical first and second measurement positions respective first and second interferograms of the photomask surface and defining a difference map as the difference between the first and second interferograms. Respective first and second normal forces on the photomask are also measured at the first and second measurement positions. The change in the normal force is used define a scaling factor, which is applied to the difference map to define a scaled difference map. A compensated flatness measurement with a reduced shape contribution due to gravity is obtained by subtracting the scaled difference map from the first interferogram. An interferometer-based flatness measurement system is also disclosed.

Systems for and methods of measuring photomask flatness with reduced gravity-induced error

A metrology apparatus has an illumination source that directs collimated light to a reference surface and to an optical component having a test surface that is in parallel with the reference surface. A first imaging lens defines a Fourier transform plane for light reflected from the reference surface and the test surface. A spatial filtering element is actuable to a blocking position that blocks specular light at the transform plane. A second imaging lens forms, at an image plane, an image of the test surface. A sensor array generates image data from received light at the image plane.

Edge registration for interferometry

An apparatus for measuring the surface contour of a target area of a substrate has a light source to emit a measurement light beam. A beam splitting element defines a measurement axis and a reference axis. A substrate holder disposes the target area along the measurement axis and tilted away from normal incidence, about a tilt axis that orthogonally intersects the measurement axis, according to a predetermined tilt angle that is a function of the measurement light beam wavelength. An imaging sensor records a fringe pattern generated from the measurement light beam and a reference light beam. A computer extracts frequency profiles from the recorded fringe pattern, each profile taken in a direction that is orthogonal to the direction of the tilt axis, wherein the programmed instructions further compute changes in the contour of the target area surface according to the frequency profiles.

Interferometric roll-off measurement using a static fringe pattern

A grazing-incidence interferometer includes first and second spaced-apart diffractive optical elements with a generally planar object disposed therebetween. The first diffractive optical element forms sheared first-diffracted-order light beams that reflect from opposite first and second surfaces of the object at grazing-incidence angles, while a zero-diffracted-order light beam goes unreflected. The second diffractive optical element combines the unreflected zero-diffracted-order light beam and the sheared reflected beams to form a collimated, combined beam. A 1&#xd7; double-telecentric relay system relays the combined beam to a folding optical system that forms first and second interference images on a diffusing screen located at an image plane. Digital images of the first and second interference images are obtained and processed to characterize the thickness variation of the object.

Grazing-incidence interferometer with dual-side measurement capability using a common image plane

Thickness and group index variations in test strip samples of ultra-low expansion glass are made by extracting the strip samples with front and back faces oriented at an acute skew angle to the axis of the boule. The strip samples are positioned the within an interferometric measurement cavity so that a set of subcavities formed by pairings of each of two reference surfaces together with each of the front and back faces of the strip sample which each subcavity having a different optical path length spacing. The skew angle is sized to avoid diffusion effects of striae present in the boule.

Skewed sectional measurement of striated glass

A frequency-shifting interferometer is arranged for measuring an optical profile of a test object with a continuously tunable light source. A succession of the interference images of the test object are captured together with a measure of the beam frequencies at which interference images are formed. A limited number of the captured interference images of the test object are selected so that the monitored beam frequencies approximately match a predetermined beam frequency spacing pattern. Further processing proceeds based on the selected interference images.

Frequency-shifting interferometer with selective data processing

A Fizeau interferometer incorporates an off-axis paraboloidal reflector that forms virtual images of reference and test surfaces and a camera lens that converts the virtual images into real images on a camera detector surface. The camera detector surface is arranged together with the camera lens to accommodate tilting of the virtual images by the off-axis paraboloidal reflector.

Interferometer with paraboloidal illumination and imaging optic and tilted imaging plane

A wavelength tunable system including a laser having a lasing cavity and an external cavity, the cavities having a common optical axis; a reflective grating fixed in the external cavity; a collimating lens between the lasing cavity and the reflective grating; and an adjustable reflective mirror defining one end of the external cavity and optically coupled to the fixed reflective grating, the adjustable reflective mirror pivots about the fixed reflective grating, and a method of use as defined herein.

Littman configured frequency stepped laser

A wavelength tunable system including: a laser having a lasing cavity and an external cavity; a frequency-adjuster in the external cavity; and an adjustable current source to adjust the laser diode current, and a method of use as defined herein.

Current driven frequency-stepped radiation source and methods thereof

Two common-path interferometers share a measuring cavity for measuring opposite sides of opaque test parts. Interference patterns are formed between one side of the test parts and the reference surface of a first of the two interferometers, between the other side of the test parts and the reference surface of a second of the two interferometers, and between the first and second reference surfaces. The latter measurement between the reference surfaces of the two interferometers enables the measurements of the opposite sides of the test parts to be related to each other.

Overlapping common-path interferometers for two-sided measurement

A mode-monitoring system used in connection with discrete beam frequency tunable laser provides optical feedback that can be used for adjusting the laser or for other processing associated with the use of the laser. For example, the output of a frequency tunable source for a frequency-shifting interferometer can be monitored to support the acquisition or processing of more accurate interference data. A first interferometer for taking desired measurements of optical path length differences traveled by different portions of a measuring beam can be linked to a second interferometer for taking measurements of the measuring beam itself. The additional interference data can be interpreted in accordance with the invention to provide measures of beam frequency and intensity.

Optical feedback from mode-selective tuner

A frequency tuning system for a laser includes mode-matched lasing and feedback cavities. A reflective facet of the feedback cavity is adjustable for retroreflecting different feedback frequencies to the lasing cavity without changing a fixed length of the feedback cavity. A selection among resonant frequencies of the feedback cavity provides for tuning the laser through discrete resonant frequencies of the lasing cavity.

Mode-selective frequency tuning system

A scanning interferometer employs dual interferometer modules at different wavelengths to expand a dynamic range of measurement, a compound probe for measuring multiple surfaces, and a confocal optical system for distinguishing between the surfaces measured by the compound probe. Within the compound probe, miniature optics divide a test beam into two sub-test beams that are focused normal to different test surfaces. Both sub-test beams contain the different wavelengths. A separate interferometer monitors movements of the compound probe for producing absolute measures of the test surfaces.

Growing community of inventors

Penfield, NY, United States of America

Thomas James Dunn