Abstract: A laser based inspection tool (LIT) for inspecting planar surfaces is described. In a preferred embodiment the LIT can simultaneously inspect both planar surfaces of disks for use in disk drives. In one embodiment of the invention, the incident beam is directed onto the surface to be inspected at an angle slightly offset from perpendicular so that the reflected beam is physically separated from the incident beam. The reflected beam is routed to a detector which converts the intensity of the reflected into an analog signal. The analog signal is sampled and digitized to generate pixel data stored in a buffer. Various analyses are performed on the data including calculating a rate of change in the pixel data. If the rate of change in the pixel data exceeds a selected threshold that indicates a possible defect if it occurs in the data area of the disk.

Abstract: A laser based inspection tool (LIT) for inspecting planar surfaces is described. In a preferred embodiment the LIT can simultaneously inspect both planar surfaces of disks for use in disk drives. In an embodiment of the invention, light reflected from the surface at an angle slightly offset from perpendicular is routed through a telecentric lens to a detector which converts the intensity of the reflected beam into an analog signal. The analog signal is sampled and digitized to generate pixel data. A data acquisition system sequentially stores the pixel data in a buffer. A median filter and derivative analysis can be applied to the pixel data to detect deviations indicating defects. An optional calibration system periodically reflects the scanning beam back to a detector to form a reference signal for use in absolute reflectivity measurements.

Abstract: A method of making a calibration disk for a laser based inspection tool (LIT) for inspecting planar surfaces is described. The calibration disk has a plurality of overlapping bumps forming a circular ring with a width of one bump. The circular ring of bumps forms a feature of a known width and position on a disk which can be used to adjust one or more LIT's to yield calibrated results. The ring of overlapping bumps is preferably formed by rotating a disk substrate under a stationary pulsing laser beam.

Abstract: A laser based inspection tool (LIT) for inspecting planar surfaces is described. In a preferred embodiment the LIT can simultaneously inspect both planar surfaces of disks for use in disk drives. In an embodiment of the invention, the incident beam is directed onto the surface to be inspected at an angle slightly offset from perpendicular so that the reflected beam is physically separated from the incident beam. Although slightly offset the reflected beam is routed back through the telecentric lens and scanner which are used for the incident beam. Preferably an aperture mask is placed in the path of the reflected beam and the incident beam to limit the cone of scattered light. Since the incident and reflected beams are physically separated, there may be an aperture for each beam, but the two masks may be physically connected. The aperture masks may also be used for alignment adjustments of the beams.

Abstract: A laser-based inspection tool (LIT) for disks that allows simultaneous inspection of disk surfaces for defects and curvature. The laser beam is directed by a rotating scanner, such as a rotating polygon mirror, to the input of a telecentric lens assembly that provides an output beam parallel to its optical axis as the beam is being scanned. The output beam from the telecentric lens strikes the disk surface substantially perpendicularly. The beam is then reflected from the disk surface and passes back through a collection lens to the sensing surface of an optical detector. The detector outputs analog signals that represent the X and Y positions on the sensing surface where the reflected light beam is incident, which thus correspond to the slope of the disk surface at the point where the laser beam was incident. A mechanical disk lifter moves the disk in a plane parallel to the disk surface so that different scan lines can be generated on the disk surface.

Abstract: A laser based inspection tool (LIT) for inspecting planar surfaces is described. In a preferred embodiment the LIT can simultaneously inspect both planar surfaces of disks for use in disk drives. In one embodiment of the invention, a disk is moved into an inspection subcompartment between a pair of air knives which blow partially ionized air onto the planar sides of the disk to remove loose particles adhering thereto. After the disk moves through the air knife streams, the two laser beams scan the two sides of the disk. Preferably the scan occurs after the air knives have been turned off and as the disk moves out of the inspection subcompartment. The subcompartment may optionally have an air source which forces air to flow out of the subcompartment to aid in maintaining a clean environment for inspection.

Abstract: A glass disk substrate inspection tool uses a polarized laser beam that is directed to the first surface of the disk substrate at Brewster's angle and is then transmitted through the disk substrate to a light detector that generates a signal representative of the intensity of the light received. Because the light polarized parallel to the plane of incidence, i.e., the plane formed by the line of the incident beam and a line perpendicular to the surface of the disk substrate, is completely transmitted, there is no surface reflection at either the first or second surfaces of the disk substrate. The polarized beam is directed by a first rotating scanner to the input of a telecentric lens assembly that provides an output beam parallel to its optical axis as the beam is being scanned. The beam is then directed by a first fixed mirror to strike the first surface of the disk substrate at Brewster's angle as the beam is scanned along a line across the first disk surface.

Abstract: A laser based inspection tool (LIT) for inspecting planar surfaces is described. In a preferred embodiment the LIT can simultaneously inspect both planar surfaces of disks for use in disk drives. The choice of a polygon scanner is preferred, but other scanning means such as a galvonometer mirror could be used. A separate polygon scanner is used for each side of the disk. The polygons are arranged in a common plane, but rotate in opposite directions to reduce the inteference which might otherwise result when the beams pass through the central hole in the disk and impinge on the detection channel for the other side. Preferably the rotation of the polygons is synchonized and angularly offset so that the two beams are synchonized and offset.

Abstract: A laser based inspection tool (LIT) for inspecting planar surfaces is described. In a preferred embodiment the LIT can simultaneously inspect both planar surfaces of disks for use in disk drives. The LIT uses a mechanical lifter which moves the disk through the laser scan lines (i.e. perpendicular to the scan lines) to allow the entire surface on each side of the disk to be scanned. The light reflected from the surface is routed to a detector which converts the intensity of the reflected beam into an analog signal. The analog signal is sampled and digitized to generate pixel data. A data acquisition system sequentially stores the pixel data in a buffer. The edges of the planar surface in the pixel data are determined for each scan line while data acquisition is in progress. A mask is applied to direct the defect detection only to meaningful areas of the disk while data acquisition is in progress. A median filter and derivative analysis can be applied to the pixel data to detect deviations indicating defects.

Abstract: A laser based inspection tool (LIT) for inspecting planar surfaces is described. In a preferred embodiment the LIT can simultaneously inspect both planar surfaces of disks for use in disk drives. The LIT uses a mechanical lifter which moves the disk through the laser scan lines (i.e. perpendicular to the scan lines) to allow the entire surface on each side of the disk to be scanned. The light reflected from the surface is routed to a detector which converts the intensity of the reflected beam into an analog signal. The analog signal is sampled and digitized to generate pixel data. A data acquisition system sequentially stores the pixel data in a buffer. The edges of the planar surface in the pixel data are determined for each scan line while data acquisition is in progress. A mask is applied to direct the defect detection only to meaningful areas of the disk while data acquisition is in progress. A median filter and derivative analysis can be applied to the pixel data to detect deviations indicating defects.

Abstract: A calibration disk for a laser based inspection tool (LIT) for inspecting planar surfaces is described. The calibration disk has a plurality of overlapping bumps forming a circular ring with a width of one bump. The circular ring of bumps forms a feature of a known width and position on a disk which can be used to adjust one or more LIT's to yield calibrated results.

Abstract: An optical disk recorder employs laser drive signals having diverse current or power levels. A scaling digital-analog-converter (DAC) supplies a scaled reference signal to a plurality of scaled DACs. The scaled DACs supply the diverse laser drive signals. Calibrating the scaling DAC calibrates the scaled DACs. A base array of DACs include not only the scaling DAC but a plurality of base array DACs. Such base array DACs control reading operations as well as supplying a threshold current. The threshold current is that laser drive signal current level below which laser 25 does not emit a laser beam. During writing, the CUT current is added to the laser drive currents supplied by the scaled DACs. A desired CUT current is determined by calculating a slope of the laser drive current to emission of radiation. Then the slope is extrapolated to a zero emission point below which no coherent emission of radiation occurs.

Abstract: A method for optically measuring at least one characteristic of a thin film on a reflecting substrate. A p-polarized beam of collimated light of known intensity is directed through an integrating sphere onto the film at substantially the Brewster's angle of the film. All the light is reflected into the sphere, including all diffusely reflected light as well as the light specularly reflected at a region inside the sphere where the specularly reflected light is incident. A reflective surface is provided for determining the thickness of the film as a function of the total intensity of light sensed within the sphere. An absorptive surface is provided at said region for absorbing the specularly reflected light for determining the porosity or surface roughness of the film based on the intensity of the diffused light sensed within the sphere not reflected from the substrate.

Abstract: An apparatus and process for determining focus correction for a lithographic tool are provided. A periodic surface relief structure containing focus information is illuminated so that diffraction beams are generated. An object is translated orthogonally to the periodic structure to cause a change in the intensity of the diffracted beams. Focus correction is determined based upon the changes in the intensity of the diffracted beams.

Abstract: A flat panel display device comprising a matrix of X and Y drive lines and a plurality of selecting field effect transistors (FETs) is described. Each FET is selectively operable by applying a potential across a unique pair of X and Y drive lines for controlling activation of a corresponding optical transducer. A high value resistance is interposed in series between the gate electrode of each selecting FET and associated drive line to minimize the effect a short circuit caused by a defective gate electrode establishing an electrical connection between X and Y drive lines. The resistance is preferably provided by a segment of undoped polysilicon on a polysilicon circuit line connecting each gate electrode with the associated X drive line.

Abstract: A drop-on-demand ink jet printer in which the print head includes a cavity having a nozzle portion at one end and a transducer mounted to contract a wall portion of the cavity when energized by a suitable voltage drive pulse. The drive pulses are produced at a predetermined rate but at a selectively controlled amplitude in response to the print data. In cases where no drop is required to print the data, the drive pulse is at a lower amplitude than the threshold voltage level, and for the first drop to be formed following a time at which no drop was formed, the amplitude of the drive pulse is greater than the threshold voltage level. At steady state operation of producing drops in sequence, the amplitude of the drive pulses equals the threshold voltage level.