Wyko, Inc.

International Business Machines Corporation

Donald K Cohen

Chris P Brophy

Paul J Caber

James D Ayres

Raymond Yardy

Eugene R Cochran

A method of profiling a rough surface of an object includes moving the object along a z axis so that a highest point of the rough surface is optically aligned with and outside of the focus range of a solid-state imaging array. An interferogram of the rough surface then is produced by means of a two beam interferometer. The solid-state imaging array is operated to scan the rough surface along x and y axes to produce intensity data for each pixel of the solid-state imaging array for a plurality of frames each shifted from the other by a preselected phase difference. The modulation for each pixel is computed from the intensity data. The most recently computed modulation of each pixel is compared with a stored prior value of modulation of that pixel. The prior value is replaced with the most recently computed value if the most recently computed value is greater. The object is incrementally moved a selected distance along the z axis, and the foregoing procedure is repeated until maximum values of modulation and corresponding relative height of the rough surface are obtained and stored for each pixel.

Rough surface profiler and method

The relative height variation and the thickness of a film of an object are simultaneously measured. A first interference pattern is produced for a calibration surface at a first wavelength and detected. Intensities of the first interference pattern are measured and used to compute a first group of phase values for each pixel. Intensity values of a point of the calibration samples are measured and used to compute a corresponding phase. A second interference pattern for the calibration surface is produced at a second wavelength and detected. Intensities of the second interference pattern are measured and used to compute a second group of phase values for each pixel. Intensity values of the point of the calibration surface are measured and used to compute a corresponding phase. A value for the surface height change .DELTA.h is computed by obtaining a linear combination of the corresponding phase values of the data groups. A drift value is computer by obtaining the difference between the first and second phase values at the point. A corrected surface height change value is computed for the calibration sample by adding the two. This procedure is repeated for a test surface to obtain its corrected surface height change. A corrected relative surface height change value .thrfore.h' is computed by subtracting the corrected surface height change value of the calibration surface from the corrected surface height change value for the test surface for each pixel. Computed .DELTA.h' values are compared to corresponding values from a mathematical model to obtain a best fit value of film thickness t for each pixel and the height error due to phase change is subtracted.

Apparatus and method for simultaneous measurement of film thickness and

Automatic focusing of an interference microscope is accomplished by directly sensing an interference pattern produced by a white light source with an auxiliary point detector. A beamsplitter intercepts part of the interference beam and directs it to the point detector. A narrow band filter filters light passing through the beam splitter on its way to a main detector array. An objective of the interference microscope is rapidly moved to an initial position between a sample surface and a fringe window by operating a position sensor to sense when the objective is a predetermined safe distance from the sample surface and turning off a motor moving the objective. The objective then moves rapidly from the initial position until the presence of fringes is detected by the point detector. Momentum of the microscope causes the objective to overshoot beyond a fringe window. The microscope objective then is moved more slowly through the interference window until fringes again are detected; the lower speed results in substantially reduced overshoot. Intensity measurements from the detector are sensed and stored as the objective moves through the width of the fringe window. The microscope objective then is yet more slowly moved through the fringe window while sensing the intensities produced by the point detector until the objective reaches a point at which the intensity is equal to a preselected percentage of the maximum stored intensity.

Apparatus and method for automatically focusing an interference

Automatic focusing of an interference microscope is accomplished by directly sensing an interference pattern produced by a white light source with an auxiliary point detector. A beamsplitter intercepts part of the interference beam and directs it to the point detector. A narrow band filter filters light passing through the beam splitter on its way to a main detector array. A memory lock position of the microscope objective is manually selected and stored. Initially, the objective moves rapidly from the memory lock position until the presence of fringes is detected by the point detector. Momentum of the microscope causes the objective to overshoot beyond a fringe window. The microscope objective then is moved more slowly through the interference window until fringes again are detected; the lower speed results in substantially reduced overshoot. Intensity measurements from the point detector are sensed and stored as the objective moves through the width of the fringe window. The microscope objective then is yet more slowly moved through the fringe window while sensing the intensities produced by the point detector until the objective reaches a point at which the intensity is equal to a preselected percentage of the maximum stored intensity.

An optical head for an optical signal recorder includes a nonpolarizing beam combiner for combining the light beams from two like-frequency, sic wavelength, lasers along one light path. The combined beams travel slightly diverging paths so that a first one of the beams can record signals on a disk while a second beam follows the first beam on the disk for direct reading-after-recording. Intermediate the combiner and the disk are a polarization type beam splitter and a focuser. One or more detectors receive reflected light from the disk via the beam splitter for detecting focus, sensed recorded signals and for tracking the beams to tracks of the disk. The combiner and splitter are preferably secured together as a single unit. The combiner uses refraction and internal reflection properties to combine the two like-frequency beams without polarization changes of either beam.

Optical signal recorders employing two lasers and methods therefor

An optical disk recorder focus-error system includes a so-called 'knife-edge' focus detector. The dynamic range of the detector is enlarged by placing an apertured mask intermediate the knife edge and the source of the light beam being focused. The knife-edge mask and the apertured mask can be deposited opaque films on a lens.

Focus detector for optical apparatus

An optical system, preferably used in an optical data recorder, has a laser light source emitting a light beam having an ovate or elliptical cross-section. An astigmatic optical element, such as a hemicylinder or cylindrical lens, disposed at 45 degrees with respect to the major axis, also termed the beam ellipse axis, in front of a focus detector eliminates focus offset errors caused by beam ellipticity.

Optical systems employing ovate light beams

In an optical data storage disk device, focus of the recording and sensing beam is detected by sensing lateral shear (rotational orientation of a light interference pattern) of a beam reflected from the optical data storage disk. An exemplary shear detector includes a quadrant sensor having four quadrants for sensing the rotation of the reflected beam's interference pattern. Electrical analysis circuits illustrate evaluation of the sensed rotated interference pattern.

Optical focus detection employing rotated interference patterns

An optical device, such as an optical digital data recorder, includes a variable optical wedge in the light path. The variable wedge facilitates assembly by a two-step adjustment process; the first step aligns a light receptor portion to receive an input light beam at an angle so as to remove ellipticity from the input beam while the second subsequent step adjusts the wedge assembly to align a transmit and reflected light path for optically coupling the wedge to a record medium. The receptor portion includes a semicircular cross-sectioned lens movable disposed in a mating cavity for adjusting the angle of reception independently of the reflected wave position.

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Tucson, AZ, United States of America

Donald K Cohen