Abstract: An apparatus that can measure a space between a first surface and a second surface such as the air bearing between a slider and a disk. The apparatus may include a light source that can reflect a light beam from the slider and the disk. By way of example, the light beam can be reflected off of an Al2O3 cap of a slider. A birefringent element such as a Savart plate may split the reflected light beam into an ordinary beam and an extraordinary beam. The ordinary and extraordinary beams may combine to form an interference pattern that is detected by a photodetector. A controller receives data from the photodetector. The apparatus may have a mechanism which can vary a phase between the ordinary and extraordinary beams so that the controller can calculate a phase value &phgr;. The controller then computes the space from the phase value &phgr;. The variation in phase between the beams may be created by tilting the birefringent element, or moving the reflected light beam directed into the birefringent element.

Abstract: A simple yet versatile noncontact optical inspection instrument and method are described for the inspection of magnetic disk surfaces for surface defects. This instrument is capable of inspecting the disk surface at any point in the disk manufacturing process. Surface defects such as bumps, pits and scratches can be measured. Surface contaminants such as particles and stains can also be measured. The instrument is also capable of discriminating between surface defects and surface contaminants. The instrument is comprised of two identical optical sensors which are located on opposite sides of the disk. A carriage supports and translates these sensors along the disk radius while a spindle rotates the disk. Both surfaces of the disk are therefore simultaneously scanned in a spiral fashion. The sensor's illumination optics produce a monochromatic focused spot of light which is normally incident upon the disk surface.

Abstract: A calibration medium that is used to calibrate a flying height tester which measures the gap of an air bearing formed between a magnetic recording head and a substrate. The medium contains a first ridge and a second ridge that extend from an underlying substrate. The ridges may be coated with a reflective material. A flying height tester can be calibrated by measuring light reflected from each ridge. The ridges have varying thicknesses so that the calibration medium will produce multiple data points.

Abstract: An apparatus and method for measuring the space between a transparent member such as a substrate, and reflective member such as a slider. The apparatus includes a first optical system which detects a first light beam that is reflected from the substrate and the slider. The reflected light is separated into four separate beams. The intensities of the beams are detected and utilized to determine a first stokes parameter, a second stokes parameter, a third stokes parameter and a fourth stokes parameter of the reflected light. The stokes parameters are used to compute the real index of refraction n, extinction coefficient k and the thickness of the space. The four stokes parameters account for any depolarized light that is reflected from the slider. The first optical system may have a photodetector which detects an image of the slider. The image provides multiple data points that can be used to calculate n, k and the thickness of the air gap without a retract routine.

Abstract: An apparatus and method for optically measuring the air gap between a transparent glass disk and an air bearing slider without separately measuring the real index of refraction n and extinction coefficient k of the slider using an external ellipsometer. The phase offset required to compute the air gap is computed from a measurement of the air slider reflectivity and from an empirically derived equation that correlates the index of refraction with the reflectance of the slider. The apparatus includes a light source for directing a light beam through the transparent member and air gap, and onto the reflective slider. The light reflects off of the slider and the transparent member to create an interference pattern. The reflected light is detected by a photodetector that is coupled to a computer. The slider reflectivity r is found from the reflected light. An empirically derived linear equation which correlates the real part (n) of the slider refractive index to reflectivity (r) is next used to estimate n from r.

Abstract: An apparatus and method for measuring the topographic profile of a reflective member having an index of refraction. The apparatus comprises a first optical system that reflects a light beam from the reflective member and detects the reflected light beam. A second optical system directs the light beam to interfere with the reflected light beam and detects the resulting interference pattern. A processor coupled to the first optical system and the second optical system computes the index of refraction of the reflective member from the detected reflected light beam and provides the topographic profile of the reflective member from the index of refraction and the interference pattern.

Abstract: An electrostatic discharge device for a flying height tester which measures the air gap of a recording head. The tester includes a transparent disk that is rotated by a spindle motor. The spindle motor is mounted to a spin stand. The tester has a manifold that is mounted to the spin stand and directs a flow of ionized fluid to a bottom surface of the disk. The manifold is also electrically grounded. The ionized fluid and electrically grounded manifold provide an electrical path that discharge electrostatic charge located on the bottom surface of the disk. The manifold extends from an inner disk diameter to an outer disk diameter so that ionized fluid is introduced to the entire bottom surface of the rotating disk. Additionally, the manifold location is such that the ionized fluid provides an electrical path from the disk to the manifold that is relatively constant across the surface of the disk.

Abstract: An apparatus and method for measuring the space between a transparent member such as a disk, and reflective member such as a slider, by detecting a change of polarization of a reflected light beam. The apparatus includes a light source that emits a light beam. The light beam is circularly polarized and directed onto the disk and reflected off of the interface between the disk and the slider. The reflected light beam is split into four separately polarized beams by a beam splitter/polarizer assembly. The four light beams have varying intensities that are measured by photodetectors. Stokes parameters are computed from electrical signals that are generated by the photodetectors. The Stokes parameters correlate to the change in polarization of the reflected light beam. Ellipsometric parameters delta and psi are computed from the Stokes parameters.

Abstract: Projectors and cameras disposed about an object under test obtain digital moire information of overlapping aspects (views) of the object. The system is calibrated using a calibration pattern of straight lines on a flat reference surface and a projected pattern of lines which are perpendicular to the lines of the calibration pattern and contain marker fringes between predetermined lines. Each aspect is calibrated individually by stepping the calibration pattern along the axis of each camera so as to obtain a plurality of tables which relate phase information to distance in each of a plurality of planes spaced successively closer to the camera. The calibration tables define a calibrated volume in space between the cameras and projectors. When the object under test is located in this volume, the video signals from the camera are converted into digital moire information.

Abstract: An optical projection camera alignment system and method particularly adapted for a solid state image sensor array type cameras such that a high intensity light source is directed onto the image sensor array to effectively project the image of the image sensor array out of the camera, through its lens systems, onto an object plane. The focus and angular orientation of the camera is then adjusted to accurately focus and align the image of the camera's image sensor array with respect to the object plane. In multiple camera installations the overlap and relative alignment of neighboring camera's fields-of-view can be set at desired levels. In a preferred apparatus embodiment of the invention, a pair of fiber optic bundles each having a right angle prism affixed to one end is inserted into the camera body and the cavity between the lens system and the image sensor array.