Abstract: A system for predicting the failure of a storage unit, such as a disk drive. In a most general sense, the inventive system includes a first mechanism (20, 22, 24) for moving an element (16) over a surface (12) which is moving relative to the element (16). The first mechanism includes an arm (18, 20) for supporting the element (16) over the surface (12) and a motor (24) connected to the arm (18, 20). A position error detector (42) is included for detecting a change in torque applied to the motor (24) due to friction between the element (16) and the surface (12). The position error detector (42) provides a signal in response to changes in torque which is processed to predict a head disk interaction or failure of the storage system. In a particular embodiment, the position error detector (42) senses a change in a lateral force applied to the element (12) in response to a change in friction between the surface and the element.

Abstract: A method for increasing data storage on a hard disk drive is disclosed herein, the method including determining a capacity goal for the disk drive, partitioning the usable disk surface on the disk drive into regions, and calculating a transfer rate based on the capacity goal and the usable disk space. The rate at which data may be transferred is then increased by a first selected quantity and/or decreased by a second selected quantity to establish a higher and/or lower transfer rate. For multiple data heads used in an individual disk drive unit, a first group of heads is partitioned from the remaining heads based on a particular selection criteria, and the remaining heads are arranged into a second group. The first group of data heads then operates at a higher transfer rate than the second group of data heads, and an algorithm for reading and writing data at the different rates is created.

Abstract: In a disk drive, the tendency of a flying head to physically engage a constant-speed data recording disk when the drive is operated at an altitude higher than the altitude at which the drive was manufactured is tested by. During manufacture of the drive, the constant disk speed is reduced to a lower speed that is a function of a mathematical relationship between the manufacturing altitude to the higher altitude. The invention then determines if the head in fact physically engages the disk at this lower speed. In an embodiment, this lower speed is calculated as a function of the ratio of the manufacturing altitude to the higher altitude. An embodiment of the invention provides a rotatable rigid magnetic recording disk and a magneto-resistive (MR) head that is generally stationary relative to the rotating disk.

Abstract: In a method of the present invention, all the information is erased from a magnetic disk in a single revolution, and testing is conducted, for every track, to determine whether or not a defect is present on the magnetic disk. The apparatus includes a magnet for erasing information from the magnetic disk when the magnet is made to face the disk for a predetermined time. Subsequent to erasure the apparatus tests every disk track for defects. Test data is written onto disk tracks using a read/write head. The head is then used to obtain read signals from the data. Thresholds calculated from the read signals are used to determine if defects are present in any of the tracks.

Abstract: Magnetic tape storage apparatus including a drive unit for writing/reading information on and from a magnetic tape using a rotary head (RH) by the helical scan method and a storage control unit for controlling the drive unit.

Abstract: A method is shown for testing a magnetic disk to be used in a disk drive. The method includes the steps of measuring a height profile of an outer radial edge of the disk, using the profile to determine a slope value for each of a pair of radial segments of the disk, calculating a difference value between the slope values of the pair, comparing the difference value to a preselected threshold difference value and indicating when the difference value is equal to or less than the threshold difference value. The threshold value indicates an outer most diameter of the disk where fly height operation for a head is still stable.

Abstract: A positioning device for magnetic head and disk tester comprises a base plate (100) which supports a rotary spindle (170), for rotating a magnetic disk (168) with a medium to be tested or to be used for testing, and a rotary platform (150) which may slide in one direction (A) along guide shafts (106 and 108) attached to the base plate (100). The rotary platform rotatingly supports a tool support (208) which supports a mechanical arm (218). The latter supports a pair of head holders (220 and 222) with respective read-write heads (228 and 222) to be tested or to be used for testing the disk. The positioning device of this type makes it possible to replace the heads in a convenient position unobstructed by other parts. This is achieved by unlocking the tool support (208) from the rotatable platform (150) by pushing down a lock finger (234) and turning the tool support with the head away from the working position.

Abstract: In a magnetic recording system, a loop-back test circuit provides a technique to test a magnetic recording head, a read circuit, and a write circuit to a read-write head, is sensed through the voltage generated at the head by the test current, such that a small voltage portion of the test signal is transferred through a resistor toga read circuit. The voltage portion is then filtered through a capacitor to form detectable peaks such that the read signal is generated with pulses corresponding to the peaks.

Abstract: An offset amount measuring apparatus for measuring an offset amount resulting from an offset produced when a disk, which is provided with a plurality of clock mark signals recorded around each circular data track at physically regular intervals, is mounted by chucking on a disk apparatus, reading the clock mark signals from the circular data track with a head, is disclosed.

Abstract: An apparatus and method for detecting defects in the magnetic medium of a disk drive system includes sampling the output signal of the read channel of the system to provide a sampled output signal. In one embodiment, the sampled output signals from the read channel is squared. A delayed sampled output signal is also provided. The squared sampled output signal is summed with the delayed squared output signal. The square of the expected value of the sum of the squared sampled output signal and the delayed squared output signal is subtracted from the sum to provide a difference output signal. A threshold detector determines when the difference output signal of the subtraction means exceeds a predetermined threshold to provide an output signal indicative of a defect in the medium. One threshold detector determines when the absolute value of the difference output signal exceeds a predetermined threshold value.

Abstract: A differentiating qualifier channel in a hard disk drive. The analog signal read off a magnetic disk by the transducer is amplified and filtered, then immediately differentiated. This differentiated waveform is used to both qualify and to detect the peaks of the analog read signal. Data pulses are qualified by noting that the differentiated waveform always changes polarity after the zero-crossing of a valid peak. Positive and negative peak signals are generated whenever the differentiated waveform exceeds established positive and negative thresholds. From this, a polarity signal is constructed. The pulses indicating where the polarity signal changes states are used to enable a latch. The latch is clocked by a zero-crossings signal which has been delayed such that the zero-crossings occur after the change in polarity. The output from this latch gives the valid qualified data pulses.

Abstract: The invention produces and maintains clearance and glide test results for a disk file, stores these results, and monitors head clearance and disk asperities over the useful life of the file using native disk file electronics. The disk file includes a predictive failure analysis component which utilizes clearance and glide test results to predict impending failure of a disk in the disk file.

Abstract: A method of loading a negative pressure type magnetic head with respect to a magnetic recording medium. For loading the magnetic head is brought close to the medium to float above a surface of the medium so as to satisfy the following conditions when reaching a region of air flow occurring due to rotation of said magnetic recording medium.+0.1.degree..ltoreq..theta..sub.P .ltoreq.+1.8.degree.-1.2.degree..ltoreq..theta..sub.R .ltoreq.+1.2.degree.VL.ltoreq.100 [mm/sec]where .theta..sub.P represents a pitching angle of the magnetic head, .theta..sub.R designates a rolling angle of said magnetic head, and VL denotes a speed of the magnetic head taken when being brought close to the medium.

Abstract: At the wafer level, a conventional write signal is applied to a pre-selected thin film head. Thereafter, first and second constant amplitude, differing frequency sine wave signals are applied to the head along with a DC bias signal whose magnitude is varied. The level of frequency mixing in the output signal of the head is detected at each level of magnitude of the DC bias signal and this data is utilized in predicting the level of noise in the read-back signal of the thin film head during normal read and write operations in connection with a rotating storage disk.

Abstract: A method for analyzing the relative spatial alignment of the erase head pole tips relative to the record head pole tips on a recording of a magnetic tape to be partially overwritten by providing, through first and second erase heads, successive momentary erase pulses of a predetermined time duration in a predetermined phase relation on a non-overlapping basis, wherein each erase head thereby erases recorded information while leaving portions of information therebetween on adjacent track pairs, and then reading or playing back the results of the erasure for analysis of the RF envelope of the erasing pattern by a waveform monitor or ferrofluidic techniques. The duration of the erasures and playback is such that the RF envelope includes at least one erasure from the first erase head and at least one erasure from the second erase head.

Abstract: A hard disk inspection apparatus has a fixed magnetic head for magnetically recording data on and reproducing data from an outside recording area of the back surface of a hard disk and a fine-adjustment magnetic head with a micrometer mechanism for magnetically recording data on and reproducing data from an outside recording area of the front surface of the hard disk. Both heads are mounted on a carriage. A fixed magnetic head for magnetically recording data on and reproducing data from an inside recording area of the back surface of the hard disk and a fine-adjustment magnetic head with another micrometer mechanism for magnetically recording data on and reproducing data from an inside recording area of the front surface of the hard disk are both mounted on another carriage. This arrangement enables easy and accurate alignment between the magnetic heads and improves the inspection efficiency.

Abstract: A method and apparatus are disclosed for measuring the magnetic properties of magnetic materials by generating flux lines through a balanced magnetic core and through a magnetic sample placed adjacent to the core. Increased sensitivity is accomplished through a modulation of the flux in the magnetic core which is measured and subsequently demodulated to yield an electrical signal corresponding to the magnetic properties of the material being tested.

Abstract: An apparatus for detecting defects in a processing track on a hard disc uses an average or mean average level value as a reference value, in which an arithmetic means computes the average or mean average level value based on an average level value (Track Average Amplitude or TAA) for a plurality of tracks prior to the processing track which is stored in a memory means. The apparatus enables obtaining the reference value with less dispersion, which gives even and stable detected results of any defect in each track on the hard disc, and enables improvement in the efficiency of the throughput.

Abstract: The present invention discloses a method of measuring magnetic fields on magnetically recorded media. The method entails replacing the metal tip typically used with a scanning tunneling microscope with a flexible thin-film nickel of iron magnetic probe. The present invention describes a mathematical equation that relates probe position to magnetic field strength. In order to establish a tunneling current between the magnetic probe and the magnetically recorded media, any protective layer on the magnetically recorded media is removed. The magnetic probe and the magnetically recorded media may be coated with at least three-hundred angstroms of gold in order to reduce spurious probe deflections due to oxide growths on either the magnetic probe or the magnetically recorded media. The scanning tunneling microscope is designed to maintain a constant tunneling current between the probe and the item being scanned.

Abstract: A magnetic disk inspection apparatus for recording and reproducing inspection signals onto and from each track on a magnetic disk, in which the inspection signals are recorded and reproduced automatically without a manual operation onto and from the magnetic disk, the maximum value is detected from the reproduction signals on the basis of the sampling signal, the average value of the maximum values is calculated for each sector, the difference between the average values in the same sector number of the adjacent tracks is determined, the change ratio based on this difference is calculated and quality of the magnetic disk is judged on the basis of this change ratio.

Abstract: A positioning device includes a base platform (100) which bears linear slide mechanisms (102 and 104). Stationary shafts (106 and 108) of the slide mechanisms are rigidly attached to the base platform. Sliding bushings (110 and 112) are mounted into a movable housing (124) whose motion is governed by a first stepper motor (136). The translation range of the housing is limited by a stop post (148) mounted onto the base platform. The housing supports a ball bearing (130), which comprises an outer race (132) and an inner race (134). The inner race is rigidly attached to the housing. The outer race supports a rotatable platform (150). The rotational motion of the outer race of the bearing is governed by a second stepper motor (154). The rotatable platform bears a mechanical arm (172) which holds a transducing head (180) centrally disposed with respect to the bearing.

Abstract: An improved data recording system incorporates a detection circuit directly into the data read channel circuitry of the recording system to provide the capability of automatic self-testing and mapping of media flaws. The flaw detection circuit outputs an error signal in response to distortions in the readback signal caused by a defect on the medium. Firmware code is utilized for controlling the scanning of the medium by the flaw detection circuit and for recording the locations of the defects on the medium in response to the error signal. The detection circuit itself comprises a phase-splitter for splitting the readback signal into in-phase and quadrature-phase components. These components are then squared and summed to generate a phase independent flaw signal having an amplitude modulated in relation to the locations of the defects.

Abstract: A flaw identification circuit receives digitized read data and provides an error output representative of defects in a magnetic storage medium. A uniform data pattern is written on the magnetic storage medium. The flaw identification circuitry uses a precision delay circuit and a linear ramp circuit. The linear ramp circuit generates a linear ramp using the charging of a capacitor with a constant current source. This provides an accurate time base reference. The output of the linear ramp circuit is applied to a flash analog-to-digital converter. The flash analog-to-digital converter is directly triggered by the digitized read data signal. The output of the flash analog-to-digital converter is applied to a maximum comparator and a minimum comparator. If the output value of the analog-to-digital converter falls outside of the maximum and minimum value range, an error is signalled. The error is representative of shifts in the location of edges of data pulses in the digitized read data signal.

Abstract: A pulse qualification apparatus and method provides for qualifying signal pulses from a raw data signal by comparison to a variable qualification level. Pulse qualification is done on a read signal developed by moving a magnetic transducer relative to addressable portions of a magnetic disk. A qualification level generator circuit generates a qualification level signal which varies in value depending upon the addressed portion of the magnetic disk. A threshold detector is used in qualifying pulses from a transducer read signal by comparision to the qualification level signal to generate an encoded pulse signal representing occurrences of qualifying pulses. Error recovery is accomplished by increasing or decreasing the qualification level of the address portion of the magnetic disk where the error occurs. This process is repeated until qualifcation channel requirements are met.

Abstract: A magnetic head tester has a popcorn noise detector for discriminating internally generated popcorn noise events from externally generated noise events. The popcorn noise detector includes a discriminator which receives the magnetic head output signal from the head and generates a comparator pulse for each popcorn noise event detected. A counter counts the number of pulses output from the detector. The discriminator includes a retriggerable noise detection gate circuit for producing a noise detection gate signal when triggered by a comparator pulse. The discriminator responds to a single comparator pulse during the gate period by indicating a popcorn noise event at the output of the discriminator. The discriminator responds to a plurality of comparator pulses during the gate period by indicating that no popcorn noise event has occurred.

Abstract: A method and circuitry are described for sensing the clearance between a magnetic transducer and a moving magnetic recording medium in a magnetic disk or tape storage system or alternatively sensing the degree of magnetic instability of a magnetic transducer in such a system. Magnetic transitions prewritten on a preselected area of the medium are read to obtain a readback signal. The width of said signal is sensed at a predetermined amplitude level which is a preselected percentage of its base-to-peak amplitude to provide a voltage corresponding to the width of said signal at said level. The voltage is proportional to the width of the readback signal divided by the time period between successive transitions of identical polarity, so as to provide a measurement of clearance of degree of magnetic instability that is independent of the relative velocity between said transducer and medium.The voltage is digitized and compared to a prestored digital reference value.

Abstract: A media flaw detection apparatus having a sensitivity which is independent of the location of the flaw relative to the written test signal. The apparatus is equally sensitive to missing or extra bit defects. According to the invention, in-phase and quadrature-phase signals are heterodyned against the analog playback input signal. The resulting signals are squared and summed to produce a signal analogous to the effect of the flaw.

Abstract: An open head detection circuit for detecting an open-circuit condition in a magnetic head connected to head contacts. The detector circuit includes a threshold source which generates a threshold voltage that is between a head contact voltage representative of a connected head and a head contact voltage representative of an open head. A comparator, coupled to receive head voltage signals from the head contacts and coupled to the threshold source, compares the head voltage signals to the threshold voltage and generates comparator signals representative of the comparison. Sampling circuitry, coupled to the comparator and coupled to receive write data signals, samples the comparator signals after detection of the write data signals and before the write data signals affect the comparator signals.

Abstract: A circuit board guide and interfitting device to eliminate floating cables. The device involves a mounting system for removably mounting the test printed circuit board or a multiplicity of such boards in a manner by which the test printed circuit boards can be plugged into an interface printed circuit board which in turn is plugged into the computer peripheral equipment to be tested such as disk drives, tape drives, floppy drives, optical drives, etc. The invention further involves a system wherein the specialized mounting member for removably mounting the test printed circuit board is combined with an interface board and a bracket for retaining an edge connector which in turn enables the test printed circuit board to be directly plugged into the interface printed circuit board which in turn can be directly plugged into the piece of equipment to be tested, all through the elimination of flexible interconnecting cables.

Abstract: A system for testing a helical recording tape using linear heads thereby enabling the tape to be run at high speed and shortening the test time uses a multiplexing system to interrogate sequentially short portions of each recorded track the portions being re-assembled in a suitable memory to provide continuous recordings from each track.

Abstract: A method and an apparatus are disclosed for determining or defining a magnetic information carrier (TAMB) which includes a plurality of tracks P each having a synchronization index (IND). In the method, (1) the synchronization index (IND) is located, which makes it possible to initialize (pulse I.sub.N) the sequence (SEQ.sub.1, SEQ.sub.2, . . . ) of the following successive operations, which are repeatable p times; (2) the entire surface of the track is first erased; (3) next, on this same surface, a succession of magnetic domains (A.sub.i, A.sub.i+1, A.sub.i+2, . . . ) is written; (4) at predetermined sampling times (t.sub.n, t.sub.n+1. . . ), with a predetermined sampling period T.sub.E, a signal S is read, which is a function of the magnetization inside each of the domains read at these times; and (5) the values of the current I and signal S are memorized.

Abstract: An environmentally controlled media defect detection system for Winchester disk drives includes a testing cabinet which is divided into two sections. The first section is maintained at an environmentally controlled elevated temperature for testing Winchester disk drives at elevated operational temperatures above ambient room temperatures. The second section is thermally insulated from the first section and contains a plurality of disk drive test units. One test unit is coupled to each Winchester disk drive being tested, and the test units have the ability to apply digital signals to the drive for writing and reading signals onto tracks of the drives, determining malfunctions, and imperfections in the disk media of the hard disk drive systems.

Abstract: An apparatus and method for testing a variety of hard disk drives is disclosed. The apparatus includes a computer connected to a control board and an interface board. The interface board is connected to a testing board. The hard disk drive is connected to the control board and testing board. The hard disk is tested by first erasing a track of data bits at full write current in one direction or polarity and second erasing the track at minimal write current in the opposite direction. The track is read and compared to a predetermined threshold and any level exceeding the threshold is considered defective.

Abstract: Primary and secondary coils are wound on a differential type magnetic head, and a low frequency signal is applied on the primary coil. Based on the difference between the output voltages from the head when an object of detection is placed near the magnetic head on the detection side and the output voltage therefrom when an object is not placed near the magnetic head, the magnetization characteristic curve of the magnetic flux and the magnetic field is calculated. Since the magnetization characteristic detection is determined by dividing a magnetic flux by the measured area cross section, once the magnetic flux is determined, a general B-H curve can be simply calculated. The magnetization characteristic measurement device includes a differential type magnetic head portion having plural differential type magnetic heads in linear arrangement which is positioned on or near the magnetic thin film of a detection object.

Abstract: A method and apparatus for increasing the throughput of memory disk drive quality control testing. The apparatus consists of a delay line for delaying the input signal from the read circuitry by one period of said input signal. A difference amplifier subtracts the delayed input signal from the undelayed input signal and couples the difference to one input of a comparator. The comparator compares the difference signal to a threshold used to indicate the presence of an "additional pulse". This test is performed simultaneously with a "missing pulse" test. The method involves delaying the input signal by one period and subtracting the delayed signal from the undelayed signal. A comparison of the difference to a predetermined threshold is then performed and where the threshold is exceeded, the corresponding location on the track under test is recorded as a probable defect. This method is performed simultaneously with a conventional method of performing a "missing pulse" test.

Abstract: A magneto-optic Kerr effect hysteresis loop measuring apparatus is provided which employs a pair of pole-pieces of the same magnetic polarity providing a high and uniform magnetic field strength in the gap between the oppositely disposed faces of the pole-pieces. The spot on the product which is to be nondestructively tested is placed in the gap between the pole-pieces in a region of uniform saturating magnetic field. A laser beam having a high polarization ratio is directed along an incident path with a spot on the surface of the product to be nondestructively tested, and a reflected beam is processed in a Kerr effect detector to provide hysteresis loop data. This data is capable of providing information sufficient to determine the squareness of the hysteresis loop and the coercivity of high coercivity material being nondestructively tested.

Abstract: Method and apparatus for determining the alignment of a data track on a magnetic disc, for example a floppy disc and for determining the alignment of a read/write head in disc drive writing apparatus. In the method the radius of the circumferential center line of the track is determined by determining the radius of the peak value of the transverse envelope of the signal on the data track. The peak value is determined by computing the track average amplitude at a number of incremental positions transversely across the data track. The peak value and its radial position is then computed using a parabolic curve fitting technique.

Abstract: A magnetic head and disc tester imitates motions of the head on a hard disc drive and comprises a stationary base (22), a slide mechanism (24) which can be installed in any required position on the base (22) with respect to a center of rotation of a magnetic disc (D). The disc (D) is rotatingly supported by a spindle unit (42) fixed to the stationary base (22). A magnetic head (52) to be tested is attached to the end of an arm (16) which is pivotally supported on a slide (36) of the slide mechanism. The angular position of the longitudinal axis of the magnetic disc with respect to a tangent to a given track of magnetic disc (52) , i.e., a skew angle, can be adjusted and the head can be fixed in the adjusted position. For measuring the parameters of the head or the disc, the slide (36) is moved linearly and carries the magnetic head over the disc in a linear direction, the head being installed at a required skew angle by means of the above-mentioned angular adjustment.

Abstract: A method of determining the angular and radial location of defects causing dropouts on a magnetic disc, and using this information to position individual dropouts in the field of view of a microscope.

Abstract: The present invention relates to a tape winding method comprising the steps of inspecting an elongated tape for one or a plurality of positions for defects contained in the tape in a state where the tape is wound onto a tape supply reel prior to being wound into a cartridge; and winding the inspected tape into a cartridge wherein when a part of the tape corresponding to the next reel has any defect, its part is cut out and removed or discarded, and on the other hand when a part of the tape corresponding to the next reel does not have any defect its part is wound into the cartridge, all of such processing being performed by means of a machine or apparatus of the present invention.

Abstract: Because of increase in data recording density on a magnetic disk in recent years, a minute defect which posed no problem in the past exerts adverse influence upon the recording and reproducing characteristics. An object of the present invention is to provide a method and an apparatus for detecting minute defects on a magnetic disk. In order to achieve this object, the present invention was made on the basis of the recognition that a large defect on the magnetic disk largely decreases the amplitude of the reproduced signal and shifts its phase, whereas a small defect does not decrease the amplitude of the reproduced signal so largely but causes a phase shift. Therefore, defects on the magnetic disk are detected by monitoring the amplitude decrease and phase shift of the reproduced signal.

Abstract: Apparatus and method are disclosed for handling a flexible disk for testing. The apparatus includes guide rails for initially positioning a disk for test. The apparatus also includes a variable speed motor for rotating the disk at a preselected rotation speed. The disk is rotated by clamping the disk betwen a motor driven rotating spindle and a retractable collet. The collet passes through an aperture in the disk to center and position the disk. Testing is accomplished by a test head assembly which is moved by a voice coil actuator. Positioning of the test head assembly is controlled by a light detector and ground glass scale coupled to the actuator and to the test head assembly.

Abstract: When recording information, a write switching current of a write signal is directed through a coil of a magnetic head, whereby the information corresponding to the write signal is to be recorded on a magnetic recording medium. Hence, a back electromotive voltage is inevitably produced at the coil of the magnetic head. Based on the level of this back electromotive voltage, the quality of the magnetic head can be detected. In this case, by use of a synchronizing circuit, the detected timing of the back electromotive voltage is synchronized with a switching timing of the write switching current. Due to this synchronizing circuit, the back electromotive voltage is detected only at the switching timing of the write switching current, whereby it becomes possible to detect the back electromotive voltage, regardless of noise. Thus, it is possible to detect the quality of the magnetic head with accuracy.

Abstract: This invention relates to an instrument or device capable of performing a non-destructive evaluation of the major magnetic properties of a recording disc member that determines the basic digital recording performance of said member. These measurements include the non-destructive evaluation of parameters including coercive force and remanence-thickness product of the recording member as a function of the circumference and/or the radius of the recording member. These parameters determine the signal amplitude as well as the frequency response of the disc member.

Abstract: The manufacture of digital magnetic recording discs for computer disc drives requires the monitoring and control of the M-H hysteresis loop properties of the magnetic film deposited on the disc substrate. Several methods exist for measuring this M-H hysteresis loop, but they all have serious disadvantages. One method consists of cutting samples and measuring them with a vibrating sample magnetometer. This is a destructive test and requires a lot of time per sample. Another method uses the Kerr-rotation of polarized light. However, it samples only the mangetization of the surface and cannot determine the magnetic thickness of the film. A third method magnetizes the entire disc and samples a large region along a diameter. This method cannot distinguish between the top and bottom films of the disc, and cannot resolve circumferential variations of th M-H loop properties.

Abstract: An automatic disk testing apparatus and method for testing flexible disks is disclosed. The apparatus includes a gravity feed disk hopper and vacuum disk plate which sequentially present a series of disks for test. Each disk drops by gravity from the vacuum disk plate to a test position including a drive mechanism. The drive mechanism rotates the disk, in its disk jacket, at a predetermined rotational speed for testing. Each disk is tested and the test results are stored in memory. After testing, the disk is automatically sorted and moved to an output location based on the test results. The sorting is accomplished by dropping the tested disk into a motor driven shuttle which conveys the disk to the proper output location and drops the disk at that location.

Abstract: A method of inspecting surface defects in a magnetic disk. First, a predetermined inspection signal is recorded on a randomly selected track of the magnetic disk during a first rotation of the disk. Second, during a second rotation of the disk, the inspection signal is read and a read signal is produced. Then, during a third rotation of the disk, the value of the read signal is compared with a reference value to determine whether any surface defect exists, and a seek operation is performed to move to the next track of the magnetic disk which is inspected. During one of the second and third rotations of the disk, the read signal is used to set a new reference value to be used in a surface defect inspection of a new track to be inspected.

Abstract: An automatic disk positioning apparatus and method for its use in handling of flexible disks in an automatic testing apparatus is disclosed. The apparatus includes a gravity feed disk hopper and vacuum disk plate which sequentially present a series of disks for test. Each disk drops by gravity from the vacuum disk plate to a test position including a drive mechanism. The drive mechanism rotates the disk, in its disk jacket, at a predetermined rotational speed for testing. Each disk is tested and the test results are stored in memory. After testing the disk is automatically sorted and stored in an output container based on the test results. The sorting is accomplished by dropping the tested disk into a motor driven shuttle which conveys the disk to the proper output container and drops the disk into that container.

Abstract: A magneto-optic Kerr effect hysteresis loop measuring apparatus is provided which employs a small relatively low weight ring magnet having a small gap and a high magnetic field strength in the deep gap and in the adjacent external gap. The spot on the product which is to be non-destructively tested is placed in the external gap field next to the small gap in a region of saturating magentic field. A laser beam having a high polarization ratio is directed along an incident path to the spot on the surface of the product to be non-destructively tested and the reflected beam is processed in a Kerr effect detector to provide hysteresis loop data which is capable of providing information sufficient to determine the squareness of the hysteresis loop and the coercivity of the material being non-destructively tested.

Abstract: An apparatus and method for locating dropouts. Information as to dropouts in a length of tape is stored in memory and then used to compute data as to location of the dropouts. The data is used to position a tape-inspecting instrument such as a microscope over successive dropouts.