DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0046] A preferred embodiment of the present invention is now described with reference to the figures where like reference numbers indicate identical or fictionally similar elements. Also in the figures, the left most digit(s) of each reference number correspond(s) to the figure in which the reference number is first used.

[0047] FIG. 2 is an illustration of an apparatus for measuring properties of the thin film according to the preferred embodiment of the present invention. The apparatus uses a focused laser light signal whose angle of propagation can be between zero degrees from normal and ninety degrees from normal.

[0048] One embodiment of the apparatus 200 includes a conventional laser diode 202 , e.g., SLD 104AU available from Sony, Tokyo, Japan, which has been collimated by Hoetron Corp., Sunnyvale, Calif., e.g., a conventional linear polarizer 204 , e.g., made of Polarcor that is commercially available from Newport Corp., Irvine, Calif., a conventional liquid crystal variable retarder 206 that is commercially available from Meadowlark, Longmont, Colo., a conventional non-polarizing beam splitter 208 that is commercially available from Newport Corp., Irvine, Calif., a conventional diffuser 210 that is commercially available from Spindler Hoyer, Germany, a conventional feedback photodiode 212 that is commercially available from Hamamatsu Corp., Hamamatsu City, Japan, a feedback amplifier and receiver preamplifier 214 that is commercially available from Analog Design, San Francisco, Calif., a conventional focusing lens 216 that is commercially available from Newport Corporation, Irvine, Calif., a custom integrating sphere 218 that is commercially available from Labsphere, North Sutton, N.H., made from an approximately 0.62 inch cube aluminum block, which has a 0.54 inch diameter spherical section removed from its center, a 4 mm diameter hole at the bottom for the scattered light to enter the sphere, another 4 mm diameter hole at the top for the light to reach a photodetector, two holes at opposite sides for the specular light to enter and exit the sphere, the internal surfaces are coated with a reflective surface that scatter light, e.g. Spectralflect, available from Labsphere, North Sutton, N.H. The integrating sphere 218 has an input hole that is designed to be slightly larger than the laser beam diameter so as not to occlude the beam, the output hole diameter is chosen to be large enough to allow the beam to exit the sphere and small enough to allow for the detection of the minimum spatial frequency according to equation (3), the diameter of the holes and the diameter of the sphere are chosen so that the total surface area of the holes is preferably less than five percent of the total surface area of the sphere, although the use of a larger percentage is possible. The integrating sphere 218 preferably has a baffle extending through its center in the same plane as the incidence light, the baffle has a circular region at its center which is the same diameter as the hole provided for the scattered photodetector. The baffle prevents any first reflection from the disk from reaching the photodetector without first striking the surface of the integrating sphere. The integrating sphere 218 is preferably miniaturized to keep the entire optical device small.

[0049] One embodiment of the apparatus 200 also includes a conventional collimating lens 220 that is commercially available from Newport Corporation, Irvine, Calif., a conventional diffuser 222 , that is commercially available from Spindler Hoyer, Germany, a conventional specular photodetector 224 A and scattered photodetector 224 B that is commercially available from Hamamatsu Corp., Hamamatsu City, Japan, a custom baffle 226 that is commercially available from Labsphere, North Sutton, N.H., a liquid crystal variable retarder (LCVR) driver 228 , and a conventional computer 240 , for example a microcontroller or an IBM personal computer, commercially available from IBM Corporation, Armonk, N.Y. having a conventional input/output device 242 , a conventional memory module 244 having unconventional applications stored therein, e.g., the analysis unit 248 , and a conventional processor 246 , e.g., a Pentium Pro Processor that is commercially available from Intel Corporation, Santa Clara, Calif. It will be apparent to persons skilled in the art that the apparatus 200 is the preferred embodiment of the present invention and that alternate designs can be used without departing from the present invention. The operation of the apparatus 200 is now described in greater detail.

[0050] A laser diode 202 emits an electromagnetic signal toward the thin film disk. In the preferred embodiment the electromagnetic signal is a light signal having a wavelength of 780 nanometers (nm) although a wide variety of wavelengths can be used. The angle of propagation of the light signal can be any angle between zero and ninety degrees. However, in the preferred embodiment the angle need not be substantially Brewster's angle for the carbon in the thin film. That is, the angle of propagation differs from the Brewster's angle of the carbon by a minimum of two to five degrees, for example, at which angle the change in the reflectivity of the thin film based upon the carbon changes significantly when compared to the reflectivity at Brewster's angle. The emitted light passes through the linear polarizer 204 . The linear polarizer 204 improves the linear polarization of the laser light signal. The polarized light signal passes through a liquid crystal variable retarder (LCVR) 206 . The LCVR 206 switches the polarization of the light between P and S linear polarizations in response to an instruction received from the LCVR driver 228 . The LCVR driver 228 can be located external to or integral with the computer 240 . As described below, P and S linear polarizations enable the apparatus 200 to measure a variety of properties of the thin film 100 . A description of one example of the LCVR driver is now described with reference to FIG. 3 .

[0051] FIG. 3 is a more detailed illustration of the LCVR driver 228 according to the preferred embodiment of the present invention. The LCVR driver 228 includes an amplitude control module 302 , a gaussian noise module 304 , a crystal oscillator 306 , and a low pass filter 308 . In the preferred embodiment the crystal oscillator is a 2 kHz square wave oscillator whose fundamental frequency is modulated by five percent in a random manner by Gaussian noise generated by the gaussian noise module 304 . The 2 kHz square wave amplitude is controlled in two states by the amplitude control module 302 that receives signals from the computer 240 so that the P and the S polarizations are achievable. The output of the oscillator is low pass filtered by the low pass filter 308 having a cutoff at approximately 15 kHz before being directed to the liquid crystal. The random modulation of the square wave helps prevent crosstalk in the apparatus 200 from being synchronous with the data sampling.

[0052] The linear polarized signal is received by the non-polarizing beam splitter 208 that splits the linear polarized signal. A portion of the linear polarized signal is split and is directed toward a diffuser 210 and to a feedback photodetector 212 . The output of the feedback photodetector 212 is received by a feedback amplifier in the feedback amplifier and receiver preamplifier 214 . FIG. 4 is an illustration of the feedback amplification system of the preferred embodiment of the present invention. The feedback amplification system of the preferred embodiment includes a negative feedback amplifier 402 that receives the output of the feedback photodetector 212 . The negative feedback amplifier 402 outputs a signal to the laser diode that precisely controls the intensity of the laser diode 202 . In one embodiment of the present invention the bandwidth of the feedback loop is limited to 15 Hz. This allows stablilization of the laser power between DC and 15 Hz. The bandwidth of the feedback loop is sharply cut off above 15 Hz to prevent power frequencies (60 Hz and its harmonics) from modulating the laser power. An advantage of the external beam splitter 208 together with the reference photodiode 212 is improved temperature stability. The improved temperature stability is achieved since the reference photodiode 212 is identical to the specular 224 A and the scattered 224 B photodetectors. Any temperature changes in the optical sensitivity of the reference photodiode 212 are substantially compensated by similar changes in the specular 224 A and scattered 224 B photodetectors.

[0053] Laser diodes are well known to have an internal photodiode to monitor the laser output power. Another embodiment of a feedback control circuit to control the optical intensity is to use such a photodiode, which is internal to the laser diode. This laser diode feeds back a control signal to the circuitry described in FIG. 4 and by doing so keeps the intensity of the laser at a constant value.

[0054] Conventional systems, for example those described in Meeks, et al., Optical Surface Analysis of the Head - Disk - Interface of Thin Film Disks , ASME Transactions on Tribology, Vol. 117, pp. 112-118, (January 1995)) describe the use of narrow band pass filters (NBPF) on the photodetectors in order to minimize interference from external light sources. The NBPF allows only the specified wavelength to reach the detector. One drawback of this method is that it requires the laser to be stable at the specified wavelength. This is difficult as the laser wavelength is affected by temperature change, thus the system has to be thermally stabilized.

[0055] To eliminate the effect of external light on the instrument, the entire device 200 is enclosed in a light tight container which eliminates the possibility of external light from reaching the detectors. As a result the NBPF can be eliminated from the design. Removing the NBPF greatly reduces the effect of temperature changes on the signal amplitude. This improves the thermal stability of the system.

[0056] Another means to improve the stability of the system is to remove electronic zero drift by use of a black standard. A black standard is a device that absorbs any light coming toward it. One version of a black standard is a cylindrical cavity with a pointed cone inside the cylinder, with all the internal surfaces coated with a black, light absorbing material. This is type of black standard is commercially available from Labsphere, North Sutton, N.H. The electronics typically drift over time due to thermal changes, component age, and other factors. The black standard provides a stable zero level reference to measure and cancel the drift. Prior to each scan the laser beam is directed into the black standard, the electronics signals are then measured and the zero level is defined. This results in improved stability in the long-term drift of the zero levels of the system.

[0057] The linearly polarized signal that passes through the non-polarizing beam splitter 208 is directed toward a focusing lens 216 that focuses the light signal onto an area of the thin film 100 that is located beneath the integrating sphere 218 (a cross-sectional view of the integrating sphere is illustrated in FIG. 2 ). A first portion of the focused light signal reflects off the thin film 100 toward a collimating lens 220 and a second portion scatters within the integrating sphere 218 . A more detailed discussion of the reflecting and scattering of the focused light signal is now set forth.

[0058] FIGS. 5 ( a )-( c ) are illustrations of the reflective and scattering properties of P and S polarized radiation according to the preferred embodiment of the present invention. The view of FIGS. 5 ( a )-( c ) are from a reverse-angle view in comparison to the view of FIG. 2 . FIG. 5 ( a ) illustrates the reflection of the focused light signal (P polarized light) off the thin film 100 . As described above, the focused P polarized light signal is directed toward the thin film 100 at an angle, e.g., an angle that is not substantially Brewster's angle. Some of the focused P polarized light signal reflects off the lubricant layer 102 . Some of the focused P polarized light signal reflects off the carbon layer 104 while some of the focused P polarized light is absorbed by the carbon layer, and some of the P polarized light reflects off the magnetic layer 106 . FIG. 5 ( b ) illustrates the reflection of the focused light signal (S polarized light) off the thin film 100 . As described above, the focused S polarized light signal is also directed toward the thin film 100 at an angle that is not substantially Brewster's angle. The reflection of the S polarized light is similar to the reflection of the P polarized light described above. Specifically, some of the focused S polarized light signal reflects off the lubricant layer 102 . Some of the focused S polarized light signals reflect off the carbon layer 104 while some of the focused S polarized light is absorbed by the carbon layer, and some of the S polarized light reflects off the magnetic layer 106 .

[0059] The reflected (specular) light signals I _sp pass through an opening in the integrating sphere 218 toward an optional collimating lens 220 . The collimating lens collimates the reflected light signals which enables the diffuser 222 and specular photodetector 224 A to be positioned at a further distance from the reflection area on the thin film disk 100 than would otherwise be possible. The diffuser spreads the beam in a manner such that the position sensitivity of the specular photodetector is reduced. This reduces the sensitivity of the photodetector to motion of the optical beam induced by wobble of the disk. The diffuser 222 and the specular photodetector 224 A are positioned at an angle that is slightly off the normal (e.g., five degrees) of the reflected light path. This geometry reduces the amount of light signals that are reflected off of the diffuser 222 and/or the specular photodetector 224 A and propagate back into the integrating sphere which can possibly affect the detection of scattered light, as described below. That is, the addition of the collimating lens 220 which collimates the light allows the path length to be increased so that the amount of tilt of the specular photodetector 224 A and the diffuser 222 is minimized. When the amount of tilt of the specular photodetector 224 A and diffuser 222 is reduced, the specular photodetector will receive a greater portion of the reflected signal since the amount of the specular signal lost due to a reflection off the diffuser 222 or the specular photodetector 224 A is minimal. In the preferred embodiment, the collimating lens 220 is used for a high resolution (short focal length) design. A lower resolution system (longer focal length lens) generally allows sufficient length between the specular photodiode and the integrating sphere to require only a small tilt of the specular photodiode. The specular signal must not be allowed to return to the integrating sphere since this corrupts the scattered signal and causes a crosstalk between the scattered and specular signals. The diameter of the light port in the optic main body is kept to a minimum to block most of the light that is reflected by any surface in the specular detector area toward the integrating sphere. The port diameters are made just slightly larger than the beam diameter itself. They can be stepped (not continuously tapered) to make it easier to fabricate. The specular photodetector 224 A outputs a signal representing the amount of light received to the receiver preamplifiers in the feedback amplifier and receiver preamplifiers board 214 . The received light is interpreted using the computer 240 in the manner described below. The operation of the specular photodetector 224 A is described in greater detail below.

[0060] FIG. 5 ( c ) illustrates the scattering effect of the S or P polarized light signals. When the focused light signal strikes the lubricant layer 102 , the carbon layer 104 , and/or the magnetic layer 106 , a portion of the light will scatter at angles that are not equal to the angle of incidence. For simplicity, FIG. 5 ( c ) only illustrates reflection off the lubricant layer 102 . The scattered component of the light is measured by the scattered photodetector 224 B attached to the integrating sphere 218 . Internal to the integrating sphere 218 is a baffle 226 which does not permit any first reflection scattered light to reach the scattered photodetector 224 B. This baffle 218 reduces the measurement of hot spots caused by a direct reflection from the disk into the scattered photodetector 224 B. The baffle 218 prevents this by forcing any reflections from the thin film disk 100 to take two or more reflections before reaching the scattered photodetector 224 B.

[0061] As described above, the LCVR 206 allows the polarization to be switched between P and S linear polarizations. The P specular light signal primarily gives information regarding changes in the thickness, or the absolute thickness of the carbon layer on the thin film disk. The S specular light signal primarily gives information regarding changes in the lubricant thickness which has been applied to the carbon surface. The scattered light, together with the specular light gives a measurement of the roughness of the thin film disk surface. The method for using the specular and scattered components of the P and S polarized light to measure thin film 100 characteristics is described below.

[0062] FIG. 6 is a more detailed illustration of a photodetector 224 according to the preferred embodiment of the present invention. The photodetector can be the specular photodetector 224 A or the scattered photodetector 224 B. The photodetector 224 of the preferred embodiment includes a biased photodiode 602 , a transconductance preamplifier 604 , a buffer amplifier 606 , signal conditioning circuitry 607 (available from Analog Design, Inc. in Topanga, Calif.) and a GAGE Applied Sciences, Inc. analog to digital board 608 , e.g., model number CS1012/PCI that is commercially available from GAGE Applied Science, Inc., Montreal, Canada. The biased photoconductor 602 receives a light signal and generates a signal reflecting the intensity of the received light. The biased photodiode signal is amplified by the transconductance preamplifier 604 which is transmitted to the buffer amplifier 606 . Before being digitized by the analog to digital board the signal passes through signal conditioning electronics 607 . The signal conditioning electronics 607 subtracts the DC offset of the signal, passes the signal through a variable anti-aliasing filter and provides up to 64 times multiplication of the encoder signal from the spindle which rotates the thin film disk 100 , in the preferred embodiment. The multiplied encoder signal and the index from the spindle are used as the clock and trigger, respectively for the analog to digital board. After the specular and scattered signals have been conditioned they are passed to the analog to digital board 608 where they are digitized. The digitized signal is transmitted to the computer 240 for analysis. The method for analyzing the received signals to determine properties of the thin film disk 100 is set forth below.

[0063] The properties of the entire thin film disk 100 can be measured by focusing the light signal on all areas of the thin film disk 100 . This can be accomplished by precisely moving the thin film disk 100 or by moving the apparatus 200 . In the preferred embodiment the apparatus 200 is attached to a very accurate stepper motor (not shown) and the apparatus 200 is stepped over the surface of the thin film disk 100 . One example of such a stepper motor is Newport's Mikroprecision stage that is commercially available from Newport, Irvine, Calif.

[0064] FIG. 7 is a flow chart illustrating a method for measuring thin film properties according to the preferred embodiment of the present invention. In the preferred embodiment a differential technique is used such that reference images of the thin film disk are made at the beginning of the experiment and the reference images are subtracted from each of the subsequent images. The resulting differential images show only what has changed as a result of interacting with the disk during the period of time between the reference and subsequent images. The reference images are not a requirement to analyze the data but it makes any changes in the disk surface easier to identify and increases the sensitivity to changes. However, in alternate embodiments only a single set (Ssp, Ssc, Psp, and Psc) of images is measured (at a angle that is not substantially Brewster's angle for the carbon layer 104 , for example) and lubricant thickness and degradation, carbon wear and surface roughness is determined.

[0065] The apparatus 200 measures 702 reference values of the thin film disk at an angle that is not substantially Brewster's angle (as described above). These reference values include the specular and scattered components of the P and S polarized signals received by the specular photodetector 224 A and the scattered photodetector 224 B, respectively. The measurements can be taken in situ or ex situ, as described below. The user then performs 704 an action on the thin film disk 100 . For example, the thin film disk 100 is subjected to repeated start-stop actions such that a ceramic slider of the read/write head repeatedly contacts the thin film disk 100 . This simulates repeated power on/off cycles of a hard disk drive, for example. This contact can cause lubricant depletion, lubricant degradation, and carbon layer wear. After the first iteration of action is performed on the thin film disk 100 , e.g. a thousand start/stop simulations, the apparatus measures 706 new values of the thin film disk 100 . These new values include the specular and scattered components of the P and S polarized signals received by the specular photodetector 224 A and the scattered photodetector 224 B, respectively. The signals representing these values are stored in the computer memory module 244 and an analysis unit 248 in the memory module analyzes the values in conjunction with the processor 246 . The functions performed by the analysis unit 248 are described below.

[0066] The analysis unit 248 determines 708 differential values by determining the difference in values between each reference value and the corresponding value in the subsequent measurement of the thin film disk 100 . The differential values include the difference (delta) in the specular component of the S polarized light (ΔS _SP ), i.e., the reflectance received by the specular photodetector 224 A when S polarized light is transmitted toward the thin film disk, the delta in the specular component of the P polarized light (ΔP _SP ), the delta in the scattered component of the S polarized light (ΔS _SC ), and the delta in the scattered component of the P polarized light (ΔP _SC ). These differential values are used to identify thin film properties as described below. One technique for measuring the reflectance of a laser signal striking the thin film disk 100 at Brewster's angle of the carbon layer 104 is described in the S. Meeks et. al., Optical Surface Analysis of the Head - Disk - Interface of Thin Film Disks , ASME Transactions on Tribology, Vol. 117, pp. 112-118, (January 1995), that was incorporated by reference above.

[0067] The subtraction of the reference and subsequent images is degraded by the presence of thermal drift during the time between the gathering of the reference and subsequent images. This thermal drift is caused by the thermal expansion of the disk and other components with variations in environmental temperature. The thermal drift can be corrected by shifting each image with respect to the other in the radial direction of the thin film disk. The shifted images are shifted and the cross correlation between the two images is computed. The amount of shift is increased and the cross correlation is repeated until a maximum is reached. The shift at which the maximum in the cross correlation occurs is the optimal shift, i.e., the one which corrects for the thermal drift of the components. An alternative to using the cross correlation is to subtract the images and compute the variance or standard deviation between the two images. The shift is then increased and the variance or standard deviation is again computed. The amount of shift which minimizes the standard deviation or variance is the optimal shift which will correct for the thermal drift.

[0068] In order to better understand the method for analyzing the differential values, a description of the effect of the thickness of the lubricant layer and the thickness of the carbon layer 104 on the amount of light received by the specular photodetector 224 A and the scattered photodetector 224 B is now set forth.

[0069] FIG. 8 is a graph illustrating the reflectance of P and S polarized radiation off a thin film having no lubricant layer 102 and having a lubricant layer 102 whose depth is ten nanometers according to the preferred embodiment of the present invention. FIG. 8 shows the simulated specular reflectivity of the S and P polarized light versus the angle of incidence of the light signal on the thin film disk. In this example the light signal has a wavelength of 650 nm. Two curves are shown, one with no lubricant applied (black) to the carbon surface and the other with ten nm of lubricant (white) applied. An unrealistically thick layer of lubricant has been shown in this figure to illustrate the differences between the curves. The difference between the two curves represents the P and S polarized specular light sensitivity to lubricant. At angles between zero degrees and approximately 53 degrees the reflectivity of the disk decreases when lubricant is added to the disk for both the P and S polarized light signals. At angles above approximately 53 degrees the reflectivity of the disk decreases for S polarized light and increases for P polarized light, when lubricant is added to the carbon surface. At approximately 53 degrees, the P polarized light is insensitive to lubricant on the surface, because this is the Brewster's angle of the lubricant. At angles near 80 degrees the P polarized light reaches a maximum in its sensitivity to lubricant—approximately 2 or 3 times the sensitivity of the S polarized light. The angle of 53 degrees is a specific example of the Brewster's angle of the lubricant which is defined as the Arc Tan of [index of refraction of lubricant/ index of refraction of air].

[0070] The ratio between the P sensitivity to lubricant and the S sensitivity changes as a function of the angle as can be seen in FIG. 8 . At a fixed angle of incidence this ratio is related to the index of refraction of the lubricant. Therefore, if the lubricant degrades, the index of refraction also changes and the ratio of the change in the specular component of the S polarized light (ΔS _SP ) to the change in the specular component of the P polarized light (ΔP _SP ) will change. This is one technique for measuring the degradation of the lubricant on a thin film disk 100 . The angle of 53 degrees is particularly good for this since even a very small change in the lubricant index will generate a large change in the ratio of delta S (ΔS _SP ) to delta P (ΔP _SP ).

[0071] FIG. 9 is a graph illustrating the reflectance of P and S polarized radiation off a thin film having a carbon layer 104 of twenty nanometers and having a carbon layer of fifteen nanometers according to the preferred embodiment of the present invention. The black curve shows the S and P reflectivity versus angle of incidence with 20 nm of carbon present. The white curve shows the same curves when 5 nm of carbon has been removed. Both the S and P polarization's can be used to measure carbon wear, but in general P is more sensitive and more linear in its response to wear of the carbon. The S reflectivity increases when carbon is removed at all angles of incidence. The P polarized light increases for carbon removal for angles less than approximately 71 degrees, is zero at approximately 71 degrees and decreases when the angle is greater than 71 degrees. The maximum sensitivity to carbon thickness or carbon wear occurs near zero degrees. The angle of 71 degrees is a specific example of the “P polarization crosspoint angle” which is defined as the angle at which the P polarized beam reflection coefficient is insensitive to the carbon thickness change.

[0072] In the preferred embodiment the angle of incidence is 58 degrees to measure all lubricant features, carbon thickness and wear and surface roughness. However, as described above, many angles can be used. Operation at 58 degrees allows the user to easily separate lubricant thickness increase (P reflectivity increase, S decrease, see FIG. 8 ) from carbon wear (S and P reflectivity increase). This technique for measuring carbon wear is not limited to carbon overcoats. The wear of any absorbing layer can be measured by the embodiments discussed here. In particular, overcoats such as Zirconium Oxide, Silicon Dioxide, organic materials and plastics, for example, can be used. If these alternative overcoats have lubricant on them, then the lubricant thickness, depletion and degradation may be measured as well.

[0073] One technique for identifying the lubricant thickness change from carbon wear based upon ΔS _SP and ΔP _SP is to use a two-dimensional concentration histogram. A technique for generating and using a two-dimensional concentration histogram is described by S. Meeks et. al., Optical Surface Analysis of the Head - Disk - Interface of Thin Film Disks , ASME Transactions on Tribology, Vol. 117, pp. 112-118, (January 1995), that was incorporated by reference above. To construct a two dimensional histogram small regions (known as buckets) are defined in the P, S plane (the space of the histogram) which have a certain ΔP by ΔS dimension. Each coordinate pair (x,y) in the real space image is selected and its corresponding bucket into which its P, S coordinate falls is identified. After going through the entire image the total number of points in each bucket is identified and a color, for example, is assigned based upon the number of points in the bucket. The completed two dimensional image is known as a two-dimensional concentration histogram. The two-dimensional concentration histogram separates the regions of lubricant pooling, depletion, carbon wear and debris into separate regions. Debris are products generated as a result of the wear process on the disk. In addition, the slope of the histogram is related to the index of refraction of the layer being altered. As described below, the slope of the histogram can be used to differentiate between lubricant depletion and carbon depletion. Some examples of histograms which each corresponds to a different embodiment of the present invention are set forth in FIGS. 10 - 13 .

[0074] FIG. 10 is a histogram illustrating the relationship between changes in S polarized radiation (ΔS _SP ) and P polarized radiation (ΔP _SP ) with respect to thin film measurements when an angle of incidence of the radiation source is between approximately 53 degrees and approximately 71 degrees according to the preferred embodiment of the present invention. The angle of 53 degrees is a specific example of the Brewster's angle of the lubricant which is defined as the Arc Tan of (index of refraction of lubricant/index of refraction of air). The angle of 71 degrees is a specific example of the “P polarization crosspoint angle” which is defined as the angle at which the P polarized beam reflection coefficient is insensitive to the carbon thickness change.

[0075] In the preferred embodiment, the analysis unit 248 identifies 710 lubricant pooling or depletion or identifies 712 carbon wear using the differential specular values (ΔS _SP , ΔP _SP ) in the following manner. When the angle of incidence that the focused light signal strikes the thin film is between approximately 53 degrees and 71 degrees, if the value of ΔS _SP is positive and the value of ΔP _SP is negative then the analysis unit 248 determines that thin film disk 100 has experienced lubricant depletion. Using the histogram illustrated in FIG. 10 this is determined by locating the quadrant in which the ΔS _SP , ΔP _SP data is located, in this example, the data is located in quadrant II which is identified as lubricant depletion. The analysis unit 248 determines the amount of lubricant depletion or pooling based upon the value of ΔS _SP and a calibration of the amount of ΔS _SP change per angstrom of lubricant change.

[0076] This range of angle of incidence allows easy distinction in the measurements of lubricant pooling/depletion, carbon wear, and debris. The lubricant pooling, depletion, carbon wear, and debris will be in different quadrants of the two dimensional histogram, making it easier to separate the data. This data from each of the four quadrants can be traced back to the original images (P and S images in real space) indicating the locations on the disk of lubricant pooling, depletion, carbon wear, and debris.

[0077] If both ΔS _SP and ΔP _SP are positive then the analysis unit 248 determines that the thin film disk 100 experienced carbon wear. The analysis unit can determine the amount of carbon wear using a variety of techniques. Some of these techniques are described below. If ΔS _SP is negative and ΔP _SP is positive then the analysis unit 248 determines that the thin film disk 100 experienced lubricant pooling. As described above, the ratio of ΔS _SP /ΔP _SP correlates to the index of refraction of the lubricant. The expected value of this ratio is known and is stored in the computer memory module 244 . If the analysis unit 248 determines that the ratio of ΔS _SP /ΔP _SP does not correspond to the expected value of this ratio, the analysis unit determines 714 that lubricant of the lubricant layer degraded.

[0078] FIG. 11 is a histogram illustrating the relationship between changes in S polarized radiation (ΔS _SP ) and P polarized radiation (ΔP _SP ) with respect to thin film measurements when an angle of incidence of the radiation source is approximately 53 degrees (in general, Brewster's angle of the lubricant) according to one embodiment of the present invention. This angle of incidence enhances sensitivity to changes in the lubricant index of refraction. This is an embodiment which is optimized for measuring lubricant degradation. A change in the lubricant index of refraction is related to the degradation of the lubricant.

[0079] FIG. 12 is a histogram illustrating the relationship between changes in S polarized radiation (ΔS _SP ) and P polarized radiation (ΔP _SP ) with respect to thin film measurements when an angle of incidence of the radiation source is less than 53 degrees according to one embodiment of the present invention. This range of angle of incidence enhances sensitivity to lubricant, carbon thickness change and absolute carbon thickness. This embodiment is optimized for measuring lubricant pooling/depletion, carbon wear and carbon thickness.

[0080] FIG. 13 is a histogram illustrating the relationship between changes in S polarized radiation (ΔS _SP ) and P polarized radiation (ΔP _SP ) with respect to thin film measurements when an angle of incidence of the radiation source is between 71 degrees and 90 degrees according to the preferred embodiment of the present invention. This range of angle of incidence has the highest sensitivity to lubricant thickness change, specifically the P-polarized light. This embodiment is optimized for measuring lubricant pooling/depletion. When in this range of angles, the spatial frequency of the measured surface roughness is nearly twice as large as when measured at near normal incidence. This allows the measurement of high spatial frequency roughness (microroughness).

[0081] The technique used for analyzing these histograms is similar to the description set forth above. With respect to FIG. 12 , since the values of ΔS _SP and ΔP _SP are both positive for lubricant depletion and carbon wear, one technique for identifying which occurs is to determine the point at which the slope of the histogram changes, as illustrated in FIG. 12 . The ΔP _SP , ΔS _SP histograms are constructed by subtracting the reference images (taken before any testing has begun) from data gathered during the testing procedure (start/stops, thin film head flying or dragging). The differential images are constructed as described earlier and the analysis described above is applied to the histograms. A time sequence of histograms can be constructed by subtracting images at various time points from the reference images. In this manner the evolution of the histograms and hence the disk surface can be followed and analyzed.

[0082] The analysis unit 248 identifies 716 the surface roughness of the thin film disk 100 . The roughness is measured simultaneously with the measurement of the specular light and the scattered light. The analysis unit 248 uses the equation (1) to determine the RMS (root means square) roughness of the thin film disk 100 . 1 $\begin{array}{cc}\mathrm{RMS}\mathrm{roughness}=R_Q=\frac{\left[{\left(\mathrm{TIS}\right)}^{1/2}*\lambda \right]}{4*\pi *\cos \left(\varphi \right)}& \left(1\right)\end{array}$

[0083] Where λ is the wavelength of the light signal, φ is the angle of incidence of the light signal, and TIS is the total integrated scattered portion of the light signal and is defined by equation (2). 2 $\begin{array}{cc}\mathrm{TIS}=\frac{\mathrm{SC}}{\mathrm{SP}+\mathrm{SC}}& \left(2\right)\end{array}$

[0084] Where SC is the total scattered light and SP is the total specular light. As indicated above, the wavelength in the above equation is the wavelength of the incident light. In the preferred embodiment the wavelength is either 7 80 nm or 650 nm, but in alternate embodiments the wavelength can be any visible or invisible light wavelength. The maximum spatial frequency over which the roughness is measured is determined by the wavelength of light and the angle of incidence according to equation (3), for example.

f _g =(sin((φ ₁ )−sin((φ ₁ ))/λ (3)

[0085] Where f _g is the maximum spatial frequency, φ ₁ is the maximum scattering angle and φ _i is the angle of incidence. The minimum spatial frequency is determined by the spot size or the exiting hole of the sphere, whichever yields a higher number.

[0086] The measurement of the scattered light is used to measure the amount of carbon wear and the carbon thickness. The incident intensity is given in equation (4). Equation (4) is simply a statement of the conservation of energy.

I _i =I _A +( I _SP +I _SC ) (4)

[0087] Where I _i is the incident intensity and I _A is the absorbed intensity, which is related to the wear of the carbon film and the thickness of the carbon, I _sp is the specularly reflected intensity and I _SC is the scattered intensity. The incident intensity is kept fixed and in order to measure the absorbed intensity and hence the carbon wear or carbon thickness it is necessary to measure both the specular and scattered light at the given angle of incidence. The algorithm for measuring carbon wear can be separated into two cases. The first case is known as an in situ wear measurement described above. FIG. 18 shows the flow chart for determining carbon wear for the in situ case. The process includes placing a disk within a test stand and taking 1802 reference images at the very beginning of the experiment. The reference images are the S _SP , S _SC and P _SP , and P _SC images before anything has been done to the surface of the disk. The disk is then subjected 1804 to start/stop actions of a thin film magnetic head or any other process which might cause wear of the carbon protective overcoat. Intermediate to the start/stops, the disk is scanned 1806 numerous times to follow the wear process. At the completion of the experiment the differential images are constructed 1808 by subtracting the reference images from the images taken before the start/stop actions upon the disk. The two dimensional concentration histograms are constructed by summing ΔP _SP and ΔP _SC (the difference images formed by subtracting the reference image from the intermediate image) and making the two-dimensional concentration histogram with the corresponding ΔS _SP summed with ΔS _SC . The images can be low pass filtered 1810 and high pass filtered 1811 , if necessary and the two dimensional histograms are constructed 1812 . The histograms may appear as shown in FIG. 10 and if so the region, which lies in the first quadrant, corresponds to carbon wear.

[0088] The carbon wear can be calibrated 1814 by a curve of P specular light versus carbon wear such as that shown in FIG. 14 . FIG. 14 is a theoretical graph illustrating the change in P reflectivity and the absolute P reflectivity verses the thickness of a carbon layer in nm. The theoretical curve shown in FIG. 14 has been computed from knowledge of the complex indices of refraction of the layers of the thin film disk shown in FIG. 1 using a thin film analysis program called “Film Star” that is commercially available from FTG Software Associates, Princeton, N.J. Alternate ways to compute the curves of FIG. 14 are discussed by Born and Wolf in “Principles of Optics” 6 ^th Edition Cambridge University Press, 1997 beginning at page 51, and by Azzam and Bashara in “Ellipsometry and Polarized Light” North-Holland, 1987 pgs. 270-315, for example. The equations relating reflectivity of a thin film to the absorbing layer thickness can be found in “Ellipsometry and Polarized Light” referenced above on pages 283 through 288, for example. These equations or similar ones referenced in Born and Wolf may be incorporated into the computer software to automatically predict the film thickness from the reflectivity of the disk. In order to predict the film thickness it is first necessary to know the complex indices of refraction of the carbon 104 and magnetic layers 106 . The change in reflectivity of the points in the first quadrant of the histogram can be related to the wear of the carbon through the theoretical change in reflectivity scale (on the right side of FIG. 14 ) such as the curve illustrated in FIG. 14 . The absolute reflectivity scale on the left of FIG. 14 can be used to compute the absolute thickness of the carbon. The computation of the absolute thickness of the carbon requires knowledge of the complex indices of refraction of the carbon and magnetic layers. A similar curve can be computed with the S polarized reflectance from the thin film disk.

[0089] The reflectance on the left and right scales of FIG. 14 are those measured experimentally by the sum of P _sp and P _sc . A system which uses only the specular component of light will ignore the light which has been scattered and will give a measurement of carbon thickness or wear which is incorrect. An additional advantage of using the sum of the specular and scattered components is that the signal from the carbon wear is essential doubled. This is because as the carbon wears the P specular component increases as well as the P scattered component. The P scattered component increases since most of the P light penetrates the absorbing film and scatters off the magnetic layer 106 . As the carbon is thinned the amount of scattered light from the magnetic layer 106 will increase, since there is less carbon to absorb the scattered light from the magnetic layer.

[0090] An alternative method for identifying the amount of carbon wear is to measure the k (complex part of the index of refraction) of the carbon and use the percentage reflectivity change per angstrom of carbon wear. FIG. 15 is a graph illustrating the sensitivity of P polarized light reflectivity to carbon wear verses the k of carbon for a light signal having a wavelength of 650 nm and having an angle of incidence of 58 degrees. FIG. 15 illustrates the relationship between the sensitivity of P polarized light to carbon wear versus the imaginary portion of the index of refraction (k) of the carbon. The initial slope (at 200-Angstrom thickness) of the curve in FIG. 14 is similar to the ordinate illustrated in FIG. 15 where the changes in the ordinate are due to the changes in the k of the carbon. The abscissa is the k of the carbon and the ordinate is the sensitivity of the P specular light to changes in carbon thickness, expressed in the percentage of P polarized light reflectivity change per Angstrom of carbon wear. Typical carbons have k values near 0.4, making the sensitivity about 0.07 percent per Angstrom of carbon wear. This technique allows the detection of 0.01 percent change in the reflectivity and, therefore changes in carbon wear of less than one Angstrom. The graph of FIG. 15 can be used to determine an approximate measure of the carbon wear. The initial slope of the curve in FIG. 14 is given as the k=0.4 value illustrated in FIG. 15 . The first technique, using FIG. 14 , has the advantage of accounting for the nonlinearity of the reflectivity change vs. wear. The second technique, using FIG. 15 , has the advantage of simplicity. The analysis of the carbon wear is aided by the use of a one-dimensional wear histogram. The pixels in the image corresponding to carbon wear (the first quadrant if the angle of incidence is 58 degrees) are plotted in a histogram. This one-dimensional histogram has as the ordinate the number of pixels and the abscissa is the amount of carbon wear as calibrated above. The histogram allows the user to display the amount of the surface which is worn (the number of pixels) versus the amount of wear. In this manner the user can select the amount of wear (a point on the abscissa) and determine the percentage of the surface area, which is worn above or below this amount of wear. This aids the comparison of different carbon surfaces in their response to wear induced by the thin film head.

[0091] The analysis of the data is accomplished by analyzing the images of the thin film disk as a function of time. The disk is subject to some action such as start/stops of the thin film head, which may alter the disk surface as described above. Images of the disk are repeated at certain time intervals and these images are analyzed in steps 702 - 716 via the two dimensional histograms. An example of carbon wear analysis using an in situ procedure is shown in FIG. 18 . The steps of collecting images and analyzing them 702 - 716 are repeated until the experiment comes to a conclusion. The images are constructed by moving the apparatus 200 across a radius of the thin film disk with a very accurate stepper motor while rotating the disk at a high rate of speed (1000 to 20000 rpm).

[0092] The spindle which rotates the disk at a high rate of speed contains an encoder which produces 1024 pulses as it rotates through 360 degrees, for example. This encoder is used to determine the circumferential positions around the disk. The present invention preferably utilizes a very high-resolution determination of the position around the circumference of the disk. This is accomplished by using a phase locked loop to multiply the encoder signal by a selectable factor of up to 64 times. The phase locked loop, which multiplies the 1024 encoder pulses, has the ability to track any velocity jitter in the encoder. This feature allows averaging of repeated revolutions to be done with no loss of lateral resolution. That is, subsequent revolutions lie in phase with one another and when averaged, the resulting image is not smeared by any jitter effect. Averaging is done to improve signal-to-noise ratio.

[0093] The spectrum of spindle jitter is assumed to be related to the frequency of spindle rotation, and limited to some multiple of it. Jitter can be due, for example, to the variations in torque from the motor poles. Regardless of spindle-frequency jitter, the encoder output nonetheless exactly tracks data on the disk. It would be ideal therefore to synchronize the data-acquisition clock to the encoder. In practice, there are limitations on the frequency at which the clock can be made to track the encoder. In the phase-locked loop (which generates the clock for the Analog to digital converter from the encoder) the encoder is compared to the internal clock reference, generating phase-error pulses. The duty cycle of these pulses constitutes an error signal indicating whether the internal reference matches the encoder frequency or should be adjusted to maintain tracking. To convert these pulses to an average voltage useful as an error signal requires a low-pass filter, which limits the tracking bandwidth. A conflicting parameter is the error-signal ripple, which diminishes as the low-pass filter cutoff frequency is lowered. Ripple on the error signal leads to small variations in the frequency of the multiplied clock. This rise and fall of the clock frequency during each encoder period, while consistent from scan to scan, and therefore not a threat to averaging could, if large in magnitude, distort the appearance of data features. The repeatable part of the spindle jitter is not a threat to averaging (although it may distort the image). The non-repeatable part of the jitter will smear out the averaged image and this circuit will remove this smearing resulting in high resolution, high signal to noise images.

[0094] Since the encoder frequency is 1024 times the spindle frequency, compromise can be struck, placing the cutoff frequency of the low-pass filter at about 50-100 times higher than the spindle frequency, and about 10-20 times lower than the encoder frequency. In this way, spindle jitter up to >50 times the spindle frequency is tracked, while the clock frequency remains stable to within±a few percent. Since the encoder frequency varies widely, the cutoff frequency of the low-pass filter should be adjusted to maintain the ratios set forth above. The 68:1 encoder-frequency range of one embodiment of the present invention is divided into seven 2:1 ranges, each of which uses a different, fixed filter configuration set by switching the appropriate capacitor through an analog multiplexer.

[0095] As described above, in the preferred embodiment, the measurement of the thin film disk properties is accomplished in situ. In an alternate embodiment, the measurement of the thin film properties is accomplished ex situ. FIG. 19 is a flow chart illustrating the method for measuring carbon wear using an ex situ procedure according to the present invention. One technique for measuring the thin film disk properties ex situ is to test the thin film magnetic disk on a separate test stand. This means that no reference image needs to be taken. The user places the disk on the spindle and the apparatus illustrated in FIG. 2 scans the disk for carbon wear. This scan provides a measure of the carbon wear, lubricant depletion, lubricant pooling, and surface roughness changes at the completion of the experiment. The user measures 1902 P _sp , P _sc , S _sp , and S _sc . The images are high pass filtered 1904 to remove any background variations and the DC value of the reflectivity is removed 1906 by setting the average value of the image to zero. The summed images P _sp +P _sc and S _sp +S _sc are then computed 1908 and low pass filtered 1910 to remove noise, if necessary. The two dimensional histogram is then computed 1912 and the points corresponding to carbon wear are identified. The intensities of these points are related 1914 to the carbon wear in angstroms via such curves as FIG. 14 and FIG. 15 .

[0096] The absolute thickness of the carbon may be computed by relating the sum of P _sp and P _sc or the sum of S _sp and S _sc via a theoretical model such as shown FIG. 14 to the carbon thickness. This method is not limited to measuring carbon thickness but can be applied to any reflective substrate which is coated with an absorbing coating.

[0097] Manufacturers make thin film disks with a known carbon overcoat thickness. The control of the carbon thickness is on the order of +/−10%. The knowledge of absolute thickness and the complex indices of refraction of the carbon allow one to construct calibration curves such as FIGS. 14 and 15 and as a result one can determine the amount of carbon wear. The change in the thickness of the lubricant can be determined from the second or fourth quadrants of the two dimensional histogram. The calibration factors for the lubricant are taken from a curve, as described above. The calibration factor will depend at what angle the particular embodiment is operating. If the embodiment is operating at an angle between 53 and 71 degrees then the data falling in the fourth quadrant corresponds to lubricant pooling and in the second quadrant to lubricant depletion. The absolute thickness of the lubricant can be determined by removing a section of the lubricant on the disk 100 with a suitable solvent. The reflectivity corresponding to the step may be measured in P or S specular reflectivity. This reflectivity change may be related to the thickness of the lubricant via curves such as FIG. 8 . Curves such as FIG. 8 may be computed with software such as “Film Star” that is commercially available from FTG Software Associates, in Princeton, N.J. Either S or P reflectivity may be used but S reflectivity is preferred since the sensitivity to lubricant in S reflectivity is nearly independent of the k of the carbon when k is less than 1.

[0098] When the embodiment is operating at an angle between 53 and 71 degrees the measurement of a step in the lubricant can be enhanced by performing the ratio of the S image to the P image or vice versa. This gives an enhanced contrast to lubricant for two reasons: 1) the ratio of P to S or S to P removes most reflectivity variations on the disk and shows only the step in the lubricant. 2) The response of S light to the lubricant step is opposite to that for P light and as a result the ratio image increases the signal from the lubricant step. The sensitivity of the ratio of the S to P image (or P to S) to lubricant may be calibrated in a manner similar to the S or P specular images are calibrated for lubricant thickness.

[0099] Tribologists need to measure how lubricants move on the surface of thin film disks 100 since the motion of the lubricant is very important in determining the durability of the carbon protective layer. The ratio may also be used to observe the motion (mobility) of the lubricant. The ratio gives enhanced contrast and removes reflectivity variations unrelated to the lubricant step, as discussed above. The ratio also allows the user to remove the disk with a lubricant step and place them under some environmental stress (such as humidity or temperature) and then replace the disk and measure how far the lubricant step has moved. This would not be possible without using the ratio, as the absolute images do not have sufficient contrast to pick out the lubricant step.

[0100] The ratio of the P to the S images can also be used to identify deep or unusual texture lines on the disk surface. This is possible since the ratio of these images is related to the index of refraction of the area being sampled by the optical beam. Unusual or deep texture lines have less carbon on them or contaminates within them. As a result the ratio image gives a strong contrast to deep or unusual texture lines since the lack of carbon or contaminates changes the index of refraction and as a result the ratio of P to S or S to P. The ratio of the P to the S images can also be used to identify contamination on the disk since contamination on the disk will cause the optical properties to change. In particular, the complex index of refraction will be changed by a contaminate beneath or upon the film and the ratio of P to S will show this as a contrast between various areas of the disk. The individual images will also show contaminates as changes in reflectivity, however the ratio of P to S or S to P will show the changes more clearly since the ratio is constant except for areas where contamination is present.

[0101] In addition to measuring the lubricant properties and carbon wear, the present invention can simultaneously measure the surface roughness of the thin film disk 100 using the technique described above. The image of the roughness of the thin film magnetic disk gives the variation of the roughness of the disk with position. The roughness or polish of the disk is typically due to a mechanical polish, which produces polish marks, which are roughly circumferential in nature. By making the Fast Fourier Transform (FFT) of the roughness image (obtained from equation 1) or one of the specular images one can display the spatial frequencies of the roughly circumferential polish in the spatial frequency domain. The FFT can be used to measure the angular distribution of the polish lines, which is a parameter of interest in the manufacture of thin film disks. The FFT of the roughness image gives the angular distribution of the roughness of the texture lines and the roughness power density of the texture lines running along a particular direction. FIG. 16 is an illustration of a FFT of a disk texture taken from the roughness image or one of the specular images as utilized by the preferred embodiment of the present invention. A cut through this FFT provides the roughness power density of the texture lines verses the angle and the angular width of the texture line roughness distribution. FIG. 17 is an illustration of a cut through the fast Fourier transform showing the texture angles, width and texture power density distribution of a disk texture line pattern.

[0102] Another feature of the present invention is a method of automatically focusing the apparatus 200 shown in FIG. 2 . Automatic focusing can be accomplished by placing a laser zone textured disk on the spinstand, which accompanies the instrument. A laser zone textured disk is a magnetic thin film disk which has a series of laser melted protuberances placed in a spiral pattern near the inner diameter of the disk. The laser-melted protuberances prevent the thin film head from sticking to the disk when the disk is stopped. A spin stand is a test stand upon which the disk is placed which rotates the disk and simulates the action of a disk drive. The apparatus 200 shown in FIG. 2 is placed over the laser textured zone of the thin film magnetic disk and the specular and scattered output is observed on an oscilloscope while the focus is adjusted. When the instrument comes to a focus the specular and scattered signals from the laser bumps will reach a maximum value.

[0103] The properties of lubricants are sensitive to humidity, therefore it is important to measure lubricant property as the humidity changes. Often the instrument 200 will operate in a high humidity environment. Heated optics allows operation of this embodiment of the present invention in high humidity environment. The optics of the instrument are heated to slightly above the environment temperature so that when used in a humid environment water will not condense upon the optics. One technique for heating the optics is to use the heat generated by the electronics within the optical enclosure. An alternative technique is to place a small heater in or near the optical assembly 200 .

[0104] In an alternate embodiment of the present invention the above optical surface analysis apparatus and method are used for rapid measurement of RMS roughness of laser bumps on thin film disk magnetic media which can be correlated to laser bump heights. This is useful as a process control feedback in the manufacture of laser-bumps on thin film disks. The preferred embodiment of the present invention includes a small spot size scatterometer (3-micron resolution) which allows one to resolve the scattered light from individual laser texture bumps. The RMS roughness of the individual laser bumps can be determined from the ratio of the scattered to the specularly reflected light as computed from equation (1). The RMS roughness of individually resolved laser bumps is a function of the height of the laser bumps. Therefore the measurement of the RMS roughness of laser texture bumps can be used to monitor the height and the height distribution of laser texture bumps. This technique has the distinct advantage of being extremely fast (10 MHz data rate)—orders of magnitude faster than conventional optical or mechanical techniques for determining laser bump height.

[0105] In an alternate embodiment of the present invention the above optical surface analysis apparatus and method are used to help identify the effects of burnish or glide head on the lubricant layer 102 and/or the carbon layer 104 . A burnish head is a low flying ceramic slider that flies near the surface of the disk. In doing so it removes asperites from the surface of the disk. A glide head is a low flying ceramic slider that is equipped with a piezoelectric sensor, in the preferred embodiment. The glide head is flown over the surface of the disk and when it encounters an asperity it sends a signal that indicates a defect is present on the disk.

[0106] It is typically difficult to observe the effects of a burnish or glide head on the lubricant layer 102 or the carbon layer 104 since there is no conventional system or method for observing these effects in situ, i.e., while in the process of burnishing or gliding the disk. One embodiment of the invention combines the system and method described above for measuring thin film disk properties with magnetics, friction, stiction, burnish heads and acoustic emission for glide in the manner described below. The combination permits inspection of the effects of burnish and glide on the carbon layer 104 , e.g., changes in roughness, texture, and/or carbon layer thickness.

[0107] During track following, which is when the thin film slider stays at one particular radius of the thin film disk for a prolonged period of time, or during accessing on a thin film disk it is possible for the slider to deplete, pool, or degrade the lubricant layer 102 . This embodiment of the present invention measures and analyzes these effects while they occur. For example, a layer of degraded lubricant can form on the disk as a result of prolonged track following. This embodiment measures the lubricant layer 102 properties by measuring the effect the changes in the lubricant has on the magnetic signals. The result of changes in carbon thickness are measured by changes in the amplitude of the magnetic signal. In addition, all of the measurements can be made in situ, i.e., without removing the disk from the spindle.

[0108] This embodiment of the present invention is a tool for characterizing surface properties such as roughness, lubricant depletion/pooling, lubricant degradation, surface debris, and carbon wear. It measures and images the disk surface. There are tools with a spindle and a rotary actuator that can simulate the action of a disk drive, they are commonly known as “spinstands”. It also simulates the wear and tear done by the magnetic head as it contacts the disk surface during starting and stopping of the spindle. In addition, the spinstand can include tools that measure other properties of the disk. For example, head to disk stiction/friction, magnetic signal amplitude of the disk, acoustic emission from contacts between the head and the disk, and sensors that detect and map surface features that protrude above the mean fly-height of the head.

[0109] In one embodiment the above described capabilities are combined, which enables the data from each tool to be correlated to the measurements of the other tools. This allows the user to correlate the data because the various measurements can be done simultaneously or sequentially and in-situ. This significantly enhances the usefulness of the tool. For example, the mechanism behind the failure of a thin film disk during spindle start/stop can be better understood. In addition, the evolution of lubricant degradation/depletion, carbon wear, and surface roughness changes can be followed as a function of the number of spindle start/stops.

[0110] In combining this embodiment of the present invention with the spinstand, the optical component of the invention 200 and the spinstand rotary actuator and magnetic head are in very close vicinity. The optical components 200 optimally should not take up more than one half of the disk area, otherwise it could collide with the spinstand rotary actuator. The invention 200 has a miniaturized form; in particular the integrating sphere is miniaturized because it is the closest to the rotary actuator, which holds the magnetic head.

[0111] Another embodiment of the present invention combines the apparatus and method for measuring thin film properties, described above, with high resolution optical or mechanical tools such as an atomic force microscope (AFM) to quickly and easily identify damaged areas on a thin film disk. A conventional atomic force microscope, for example model DI-5000 from Digital Instruments, Santa Barbara, Calif., is capable of providing a very high resolution image of a surface but has a very small detection range (viewing diameter), e.g., approximately 100 micrometers. Accordingly, it is extremely difficult to find areas on a thin film disk that are damaged using conventional AFMs. However, the apparatus 200 and method described above easily and quickly locates damaged areas on a thin film disk 100 . As described above, one embodiment of the present invention identifies thin film disk damage in the form of carbon wear, surface roughness, lubricant depletion, lubricant pooling, and lubricant degradation, for example. This embodiment of the present invention uses the optical analyzer apparatus 200 to quickly and inexpensively locate damaged portions of a thin film disk 100 . The apparatus 200 precisely identifies the damaged locations. The AFM is directed to examine the precisely identified damaged locations. This embodiment enables the AFM to locate and perform a very detailed analysis of the damaged portion of the disk. Accordingly, this embodiment of the present invention enables a user to quickly and inexpensively locate one or more damaged portions on a thin film disk 100 and enables the user to direct an AFM directly onto the damaged portions much more quickly than is possible using conventional systems and methods.

[0112] A specific example is the study of carbon wear on laser bumps, it is desirable to be able to find specific laser bumps (from hundreds of thousands of laser bumps) which have carbon wear. It is preferable to locate these worn bumps quickly and to study these laser bumps under a high power and high resolution measurement or imaging tool. The present invention is able to locate the laser bumps quickly but it does not have the resolution for studying the laser bumps in extreme detail. Conversely, high resolution tools, such as an Atomic Force Microscope (AFM) are too slow to analyze large number of bumps. A combination of the two types of tools provides the advantages of both tools. Laser bumps of interest (with carbon wear) can be found quickly using the present invention, the position encoder of the spindle holding the disk can track their locations. The same spindle can also calibrate the relative location of the optical beam position to the location of the AFM. These laser bumps can then be placed under the high-resolution tool (e.g. AFM) for further study.

[0113] Another embodiment of the present invention is a system and method for performing high temperature film measurement. FIG. 20 is an illustration of a high temperature thin film measurement system 2000 according to one embodiment of the present invention. The high temperature system 2000 is a reverse angle illust