Abstract: A simple yet versatile non-contact optical inspection instrument and method are described for measuring the height and width of defects and contaminants on a magnetic disk surface. The instrument includes a sensor which produces an illumination beam that is modulated and then focused normally on the disk surface as a spot. The illumination spot is Doppler shifted due to the movement of the disk and the diffusely reflected light is interfered with a reference beam produced by the sensor's illumination optics. The sensor uses two collection optics channels which simultaneously detect both the specular reflected light and the diffuse scattered light produced by the disk surface. The phase shift of the specular reflected light and that of the diffusely scattered light are measured. The output signals from the sensors are processed to estimate the size and type of the defects. Another aspect of the present invention includes a demodulator which increases the frequency of an FM signal.

Abstract: An HGA loader which utilizes sub-ambient air pressure to move a magnetic head of the HGA relative to a test surface. The HGA is mounted to a clamp and located adjacent to a nozzle. The nozzle draws in air through an orifice to create a sub-ambient pressure region below the suspension. Ambient air pressure will flow into the sub-ambient void created by the nozzle located below the suspension beam of tge HGA. The air flow will move the suspension beam away from the disk surface and unload the HGA. The level of the sub-ambient pressure and the separation between the head and disk can be varied by a computer controlled regulator valve. The loader can be used in a flying height tester where calibration is obtained by taking optical data while varying the flying height by changing the sub-ambient pressure. The sub-ambient pressure created by the orifice causes the HGA to bend about its natural pivot point or the bend radius of the suspension or load beam.

Abstract: A spindle motor assembly which utilizes a ionized air bearing to provide a conductive path through the assembly. The spindle motor assembly includes a spindle shaft that is located within a housing and rotated by an internal motor. The assembly also contains an air bearing which allows relative movement between the spindle shaft and the housing. The air bearing is supplied by a source of air that is ionized by an ionizer. The ionized air provides a conductive path between the spindle and the housing. The spindle may be coupled to a clamp that holds a magnetic disk within a disk certifier. The magnetic disk is electrically grounded to the housing through the chuck, the spindle and the ionized air bearing.

Abstract: A method and apparatus for detecting defects on the surface of a data recording medium. In one embodiment the present invention includes a sensor for detecting defects on the surface of a magnetic disk. The sensor generates an analog voltage signal that is representative of a surface anomaly detected on the disk surface. An analog signal processor processes the signal before it is received by a peak detecting circuit. The peak detecting circuit detects and converts a peak of the analog signal into digital data. The digital data is received and manipulated by a digital signal processor where the peak amplitude, average peak amplitude and average peak power of the defect may be calculated.

Abstract: An HGA loader for a flying height tester. The loader includes a clamp that holds a head gimbal assembly (HGA) of a hard disk drive. The clamp is mounted to a pivot assembly that is coupled to a ball screw by a transfer housing. The ball screw is rotated by a belt that is coupled to an electric motor by a pair of pulleys. Rotation of the ball screw moves the transfer housing and clamp between a first position and a second position. The loader has a pair of stops that impede the movement of the transfer housing so that the clamp cannot move beyond the first and second positions. The stops are adjustable so that the first and second positions can be varied. The motor pulley has a clutch that allows the motor to turn even when the clamp reaches the first and second positions. The clutch allows the motor to continue rotation and maintain a proper motor count even when the ball screw and driving belt have stopped moving.

Abstract: A spindle motor assembly which utilizes a reservoir of electrically conductive fluid to provide a conductive path through the assembly. The spindle motor assembly includes a spindle shaft that is located within a housing and rotated by an internal motor. The end of the spindle shaft is located within the reservoir. The reservoir also is electrically coupled to the housing. The electrically conductive fluid provides a conductive path between the spindle and the housing while minimizing the frictional forces on the spindle. The spindle may be coupled to a chuck that holds a magnetic disk within a disk certifier. The magnetic disk is electrically grounded to the housing through the chuck, the spindle and the electrically conductive fluid.

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: A non-contact servo writing system for positioning a transducer on a hard disk drive arm is disclosed. The positioning system includes a master assembly having a master arm. A light source is mounted on the master arm and is reflected off a reflector mounted on the hard drive arm. A sensor mounted on the master arm receives the reflected light and generates a signal proportional to the amount of reflected light received. A servo controller coupled to the sensor controls movement of the hard drive arm in accordance to the signal generated. In one embodiment, the sensor comprises a circuit having a first photosensing element and a second photosensing element. A first signal and a second signal proportional to the amount of reflected light received by the first photosensing element and the second photosensing element respectively are generated by the circuit. The sensor also provides a sensor output signal representative of the difference between the first signal and the second signal.

Abstract: An integrated spring head/gimbal assembly holder is used to precisely load and unload a head/gimbal assembly (HGA) of the type used in magnetic disk drives. The holder includes a fixture base by which the holder is mounted. A first boss extending from the fixture base has a surface in which a recess is formed. The recess receives a second boss on the end of the HGA so that HGA rests on the surface of the first boss. A cantilevered beam extends from the fixture base and serves as a spring which includes a clamping head. Flexure of the cantilevered beam forces the clamping head to drive the second boss firmly against the sidewalls at the edge of the recess and to force the HGA against the surface of the boss. Thus, the HGA is precisely positioned and secured to the holder.

Abstract: A method for calibration and correlation of flying height testers with a calibration slider. The calibration slider has an air bearing surface that contains a flat portion and a sloped portion. To verify accuracy and correlation between flying height testers, the calibration slider is loaded adjacent to a rotating transparent disk of a tester. The slider is separated from the disk by an air film and flies at a zero pitch angle. Zero pitch angle can be attained by adjusting the rotational speed of the disk. The flying height tester includes an optical system which can measure the air film with a light beam that is directed through the disk and reflected from the slider.

Abstract: An apparatus for creating or editing a test program for testing a disk drive by entry command inputs. The apparatus includes an input that allows the user to select the desired test instructions and subsequence of test instructions to create or edit a test program having a sequence of test instructions. The processor executes the test program by generating a plurality of commands that are performed in a predetermined order. The commands may specify that the first circuit performs a glide test or a burnish test or that the second circuit perform a burnish test.

Abstract: The present invention is a clock head assembly that writes reference marks on a magnetic disk of a hard drive. The clock head assembly includes a clock head that is mounted to an arm and coupled to the magnetic disk through a window of the disk drive housing. The arm is pivotally mounted to a housing which has a gasket that seals the window and allows the assembly to operate in a non-clean room environment. The arm is coupled to a cam that is manually actuated by a lever to move the clock head arm assembly between a loaded position and an unloaded position. An alignment plate is also provided for aligning the clock head assembly to the hard drive assembly.

Abstract: An optical sensor which provides a focused elliptical illumination spot. The instrument includes a light source which provides a light beam that is directed through a cylindrical lens. The cylindrical lens focuses the light beam normally on a disk surface as an elliptical illumination spot with a major axis along a tracking direction and a minor axis along a scanning direction. Light scattered by the disk is then detected by a detector and processed to detect defects on the disk surface.

Abstract: A tester which can measure both the air bearing thickness and the dynamic electrical characteristics of a head gimbal assembly (HGA) of a hard disk drive. The tester has a disk that is rotated by a spindle motor. The disk has a transparent portion that is used to measure the air bearing thickness and a magnetic portion that used to measure the electrical characteristics. The HGA is moved adjacent to the transparent and magnetic portions by a loader mechanism. The HGA is separated from the rotating disk by an air bearing. The tester has an optical system which measures the thickness of the air bearing when the HGA is adjacent to the transparent portion of the disk. The tester also has an electrical tester which measures the electrical characteristics when the HGA is adjacent to the magnetic portion. The loader mechanism moves the HGA between the transparent and magnetic portions so that the air bearing thickness and the electrical characteristics of an HGA can be measured in the same tester.

Abstract: An apparatus and method for demodulating an amplitude modulated read signal generated by a magnetic head of a hard disk drive. The apparatus includes a pair of serially connected track and hold circuits that receive the read signal. The track or hold state of each circuit is controlled by a phase lock loop circuit which also receives the read signal. The first track and hold circuit initially tracks the read signal to a peak value. The circuit then switches to a hold state and provides a constant output signal that corresponds to the peak voltage of the read signal. While the first track and hold circuit is in the hold state, the second track and hold circuit is in a tracking state. The second track and hold circuit tracks the output of the first circuit. Because the output of the first circuit is a constant value, the second circuit also provides a constant output signal in the tracking state.

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: A tester for measuring the resistance of magnetoresistive heads as a function of the magnetic field applied to the heads. The tester applies a time varying magnetic field to the magnetoresistive head to be tested and filters the resulting time varying (AC) voltage signal indicative of the resistance of the head with a capacitor to remove the DC component of the signal. The AC component of the signal is then amplified, digitized, and analyzed to obtain the resistance properties of the magnetoresistive head.

Abstract: A tooling fixture that holds a head gimbal assembly (HGA) of a hard disk drive within a piece of test equipment. The tooling fixture includes a plurality of pads that extend from a top surface of a chimney. The HGA has a slider that is mounted to a flexure arm. The flexure arm extends from a base plate of the HGA. The base plate has a swage mount that is inserted into a corresponding aperture of the chimney when an operator loads an HGA into the tester. The pads of the chimney support the base plate and the HGA. The base plate is typically clamped onto the chimney by a spring biased clamp. The HGA is moved adjacent to a rotating disk of the tester. The pads provide a reliable contact surface that improves the repeatability of the HGA positioning which in turn can improve the tester.

Abstract: A rugged spindle for a disk certifier that test the disks of a hard disk drive. The spindle contains a first bearing and a second bearing that are coupled together by a shaft. The first bearing is coupled to a chuck that captures a disk. The second bearing is coupled to the spindle shaft of an electric motor which rotates the disk. The bearings each contain an outer graphite sheath that is separated from a hardened housing by an air bearing. The connecting shaft is bonded to the first and second bearings by an adhesive that is injected through longitudinal passages of the shaft. The bonding adhesive flows along the interface of the connecting shaft and bearings until the adhesive fills an indicator slot of the shaft. Air bearings are created during the bonding process of the second bearing to insure an accurate relationship between the two bearings and the housing.