Abstract: The invention provides a technique for eliminating "ripple" or ghost fringes from a wavefront transmitted by an optical window with a very small wedge angle, distortions in the wavefront being measured by an interferometer. A collimated beam produced by the interferometer is transmitted through the optical window, which is tilted so as to prevent direct reflections from entering a detector of the interferometer. The beam transmitted through the window is reflected by a return flat back through the window and transmitted to the detector. The return flat is tilted slightly in the direction of or opposite to the direction of tilt of the window, causing the re-incident angle of the returned ray to be different from the original incident angle of the collimated beam. This causes the multiple reflections within the window to be different and to be out of phase. The ghost fringes are cancelled by appropriately tilting the return flat.

Abstract: 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.

Abstract: A method and system are described for performing phase unwrapping integrations in a phase-shifting interferometric profiling operation. The disclosed technique uses one characteristic of modulation or slope distributions to segment the modulation or slope histogram into a plurality of sections. The principal phase values are divided into a plurality of groups in accordance with corresponding modulation or slope histogram sections. The phase unwrapping integrations are performed in such an order that the areas with a high probability of containing a 2.pi. discontinuity are contained in the last group integrated. Thus, inaccuracies due to 2.pi. discontinuities do not "propagate" to earlier-computed phase values computed by the phase unwrapping algorithm.

Abstract: A scanning probe microscope achieves increased resolution and speed in profiling a surface of a sample by producing an error signal representing a difference between a probe signal and a desired value of the probe signal. The error signal is compensated for delay in response of a position translator. The position translator moves in response to the compensated error signal to produce a change in the probe signal dependent upon how closely the probe moves along the sample surface. A signal representing height of the sample surface is produced by filtering and scaling the probe signal and summing the resulting signal with the compensated error signal. Both high frequency components of the probe signal and low frequency components of the compensated error signal are included in the sample surface height-representing signal, resulting in very high image resolution without sacrificing scanning speed.

Abstract: 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.

Abstract: A scanning probe microscope includes a base, an inner piezoelectric tube, and an outer PMN translator arrangement including three PMN posts, with first ends of the PMN posts connected to the base. A first end of the inner piezoelectric tube is rigidly connected to second ends of the PMN posts. Inner quadrant conductors are disposed on the inner surfaces of the inner piezoelectric tube, and outer quadrant conductors are disposed on the outer surfaces of the inner piezoelectric tube. Separate x and y scan control voltage signals are applied to corresponding opposed quadrant conductors of the inner piezoelectric tube to control scanning of the free end of the inner tube in the x and y directions. A z scan control voltage is produced by a servo control circuit in response to a probe signal and applied to the PMN posts, which have negligible hysteresis. The servo control circuit refers to a look-up table to correct non-linearities of the PMN posts.

Abstract: A scanning probe microscope includes a probe support carrying a scanning probe, a piezoelectric transducer having a free end connected to a stage on which the sample is supported, probe sensing circuitry connected to sense a signal indicating interaction between the tip of the probe and a point of the sample surface and producing in response thereto a Z control voltage so as to optimize the interaction and produce a Z coordinate representing the height of a presently scanned point of the sample surface. Optical sensing circuitry includes a light source connected in fixed relation to the sample stage, a position sensitive photodetector, and optics focusing lens for focusing a portion of the light onto a position sensitive detector to cause it to produce X and Y position signals. The light source includes a retroreflector attached to the piezoelectric transducer receiving a beam from a stationary laser and focused by a stationary lens onto the position sensitive detector.

Abstract: A computerized phase shifting interferometer operates interactively with a user to correct surface profile data of a sample containing a film of material which is optically dissimilar to the material of a substrate. Profile data is measured, and optically dissimilar areas of the sample are identified by differences in measured height. The user is prompted to enter optical parameters for each identified area into the computer. Then the user is prompted to enter a best guess of the film thickness. A Newton approximation technique is performed by the computer to produce subsequent guesses of the film thickness until a computed thickness increment is below a predetermined value.

Abstract: A scanning probe microscope includes a base, an inner piezoelectric tube, and an outer piezoelectric tube, with a first end of the outer piezoelectric tube connected to the base. A first end of the inner piezoelectric tube is rigidly connected to a second end of the outer piezoelectric tube. Thin inner conductors are disposed on the inner surfaces of the inner piezoelectric tube and the outer piezoelectric tube, and quadrant conductors are disposed on the outer surfaces of the inner piezoelectric tube and the outer piezoelectric tube. Separate x, y, and z scan control voltage signals are applied to various quadrant conductors of the inner and outer piezoelectric tubes to control scanning of the free end of the inner tube in the x, y, and z directions, respectively.

Abstract: A scanning probe microscope includes a probe support carrying a scanning probe, a piezoelectric transducer having a free end connected to a stage on which the sample is supported, probe sensing circuitry connected to sense a signal indicating interaction between the tip of the probe and a point of the sample surface and producing in response thereto a Z control voltage so as to optimize the interaction and produce a Z coordinate representing the height of a presently scanned point of the sample surface. Optical sensing circuitry includes a light source connected in fixed relation to the sample stage, a position sensitive photodetector, and optics focusing lens for focusing a portion of the light onto a position sensitive detector to cause it to produce X and Y position signals. The light source includes a retroreflector attached to the piezoelectric transducer receiving a beam from a stationary laser and focused by a stationary lens onto the position sensitive detector.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: A thin, flexible, reflecting diffuse material is placed or formed on an anterior surface of a cornea. The material has properties that precisely conform to changes in shape of the cornea. This allows remote sensing of the shape of the cornea by projected fringe contouring.

Abstract: A scanning probe microscope includes a base, an inner piezoelectric tube, and an outer piezoelectric tube, with a first end of the outer piezoelectric tube connected to the base. A first end of the inner piezoelectric tube is rigidly connected to a second end of the outer piezoelectric tube. Thin inner conductors are disposed on the inner surfaces of the inner piezoelectric tube and the other piezoelectric tube, and quadrant conductors are disposed on the outer surfaces of the inner piezoelectric tube and the outer piezoelectric tube. Variable voltages are applied to the quadrant conductors of the outer piezoelectric tube and the inner piezoelectric tube and varied to cause lateral and axial movement of the second end of the outer piezoelectric tube and also to cause lateral and perpendicular movement of the second end of the inner piezoelectric tube relative to its first end.

Abstract: A method and apparatus is disclosed for aligning a reflective surface with an alignment axis in a representative environment of an interferometer. An image of the reflective surface is focused onto a diffuse screen to form a spot image thereon. Rays of the spot image emanating from the diffuse screen are collimated. Some of the collimated rays are focused onto a detector to form a non-inverted image spot. A portion of the collimated rays are intercepted and inverted by means of an image inverter aligned with the alignment axis. The inverted rays are focused onto the detector to form an inverted image spot. The reflecting surface is moved so as to cause the inverted image spot and the non-inverted image spot to coincide, at which point the reflecting surface is aligned with the alignment axis.

Abstract: A system for aligning a test beam of an infrared interferometer with a reference beam thereof includes a phosphor screen positioned in a common path of the interferometer at a focal point of a lens in the path. The phosphor screen is illuminated with ultraviolet light to stimulate an area of the phosphor screen to emit visible light. Infrared laser light from the test beam is focused onto a spot of the phosphor screen. The infrared laser light acts on the spot to prevent the phosphor screen from emitting visible light from the spot and hence the position where the laser beam strikes the phosphor screen appears dark. Visible light emitted by the phosphor screen is focused into a visible light camera, and an image of visible light emitted by the phosphor screen is produced on a video monitor. The dark spot on the phosphor screen appears as an image spot on the video monitor. The test beam is adjusted to move the image spot to a predetermined location of the video monitor representing an aligned condition.

Abstract: A phase shifting projector includes an incandescent lamp, a heat-absorbing filter filtering infrared light from the incandescent lamp, a condensing lens receiving light from the filter, a transparent slide having a sinusoidal grating thereon, a projecting lens, a rotatable transparent plate disposed between the slide and the projecting lens, a test surface on which the grating is projected, and a stepper motor connected to the transparent plate for rotating it about an axis generally parallel to a line of the grating to modulate the phase of the grating image projected on the test surface.

Abstract: An interferometer includes a thin, absorbing pellicle in the path of a test beam to attenuate the test beam so that its intensity is approximately equal to the intensity of a reference beam. The pellicle reflects less than about six percent of the test beam, thereby avoiding spurious reflections that produce spurious fringes.

Abstract: 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.