JP3066362B2 - Apparatus for measuring the position of a magnetic head with respect to a rotating flat surface - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention relates to U.S. patent application Ser. No. 08/738, filed Sep. 24, 1996.
No. 034 is a continuation-in-part application. The present invention relates to an optical device for measuring a gap between an object, in particular, a magnetic conversion head and a transparent medium when the magnetic conversion head and the transparent medium relatively move. More particularly, the present invention relates to an apparatus for measuring the flying height and direction of a magnetic head with respect to a test disk in a flying height tester.

[0002]

BACKGROUND OF THE INVENTION Most computer systems incorporate a data storage device, which includes a rotating, magnetically coated disk and a converter for reading and writing information on the magnetic material of the disk. And are included. Such computer systems are typically characterized by storage density, speed of access to data locations, and data integrity. One of the main parameters that greatly affects system characteristics is the position of the magnetic transducing head with respect to the rotating disk. The relative airflow between the rotating disk at high speed and the head biased toward the disk causes the head to float on the air cushion created by the airflow. In general, as the distance between the head and the disk becomes smaller, the conversion accuracy of information stored on the disk becomes higher. The gap between the head and the disk is called the "head gap" or "fly height" and is of the order of tens of nanometers in conventional high performance computer systems. The aerodynamics of levitation vary with the rotational speed occurring under the head, disk, different levitation height and head direction. Therefore,
In the design process as well as the manufacturing process, it is important to precisely control the flying height and direction of the head in order to meet a desired performance standard. Currently, several optical techniques are used to measure the gap size in nanometers between a magnetic head and a rotating magnetic disk.

One measurement method uses an optical interferometer. In this method, a mutual interference effect is used, in which the two light beams alternately darken or create different colored lines, bands or fringes. To measure the gap between two objects having substantially parallel opposing surfaces, one of which is transparent, a beam of light is directed through the body of the transparent object into the gap, where the light The axis of the beam should be essentially orthogonal to the opposing surface of each object. The light beams reflected from each surface of the two objects overlap the location of the detection element and the interference fringes are read. It is known optically to be based on the ratio of the path difference between two light beams to the emission wavelength. This relationship is 2
It is used as a calibration table for gap measurements where the path difference between the light beams is twice the gap.

A magnetic head and an optically transparent, flat reference disk made from a material such as glass are disclosed in US Pat. No. 4,813,782. In this U.S. patent, the operating conditions of the hard disk drive are simulated by a reference disk rotating at high speed, and the magnetic head to be tested is biased in the direction of the reference disk, e.g. Levitated. As the reference disk rotates, a light beam is directed through the transparent reference disk from the side opposite the magnetic head. The light beam is reflected from the surface of the reference disk and the surface of the head and interferes with each other to form interference fringes, which are detected.
Analyzed, the gap between the magnetic head and the reference disk is determined using the calibration curve.

A major drawback of the measurement method of US Pat. No. 4,813,782 is that the maximum and minimum point positions of the calibration curve (calibration curve) are such that the measurement accuracy is significantly reduced due to the small signal change due to the gap variation. Inaccuracy in the so-called "flat area" of the curve). This problem is particularly pronounced in systems intended to measure head gaps much smaller than one quarter of an optical wavelength, based on the above principles. Furthermore, commercially available devices cannot simultaneously measure at several point locations on the magnetic head. Therefore, in order to obtain a map of the closeness of the surface, it is necessary to perform a troublesome point-by-point measurement.

[0006] Another optical method used to measure the gap between objects is based on a phenomenon known as "leakage" total internal reflection. Total internal reflection is observed when electromagnetic radiation (eg, a light beam) is incident on the interface between two media at an acute angle of incidence. If the electromagnetic radiation is 2
Propagated from the side of the optically dense one of the two media, for example, the medium with the higher index of refraction, hereinafter referred to as the first medium, and the angle of incidence (measured from the propagation axis). ), Above a certain critical value which depends on the ratio of the refractive indices of these two media, all electromagnetic radiation is reflected back from the first medium and does not penetrate into the other, i.e. the second medium at all, Thus, it is "total" reflected.

However, if the second medium is a thin film, followed by a third medium having a higher refractive index than the first medium, a portion of the emitted electromagnetic radiation will be reflected. To return to the first medium. However, a portion of the electromagnetic radiation still enters the third medium. In other words, the internal reflection in this case is not total reflection. Therefore,
Even if the angle of incidence of the electromagnetic radiation and the respective indices of refraction of the first medium and the second medium seem to be suitable for total internal reflection, the internal reflection in this case will be the leakage total internal reflection and be called. In leaky total internal reflection, the fraction of radiation reflected back into the first medium is the ratio of the thickness of the second medium to the wavelength of the radiation, the composite index of the third medium, and the incident radiation. And the polarization of the light. Such systems are much more sensitive to gap variations in nanometer dimensions, and thus the "fly height" between the magnetic head above the reference disk is measured by a device based on the principle of optical interference. It is suitable for measuring with much more accuracy than that.

[0008] US Patent No. 4,681,451 discloses an apparatus that uses the phenomenon of total internal reflection refraction to determine the distance between a stationary glass surface and another surface. In this device, the glass block is replaced with a conventional magnetic head. The distance between the glass block and the magnetic disk is imaged by a video camera that detects the distribution of light intensity that reflects back into the glass block. The magnetic disk can be rotated to simulate aerodynamic characteristics.

The major disadvantages of this device are the inability to test its dynamic characteristics and the measurement of the actual flying height of the magnetic head, which may be necessary for a magnetic head manufacturer or consumer for quality control purposes. Is that you can't do that. Although some conditions in the disk drive are simulated by the glass head replacement,
The results obtained with this method are inaccurate. Furthermore,
The required dimensions and mass of the optical system are substantial and therefore the device cannot only be used for testing small flying magnetic heads, but also weigh only a few grams, actual spring mounting Nor can we show the dynamics of the performed head. Thus, US Pat.
The 1,451 device cannot be used to test actual head characteristics.

US Pat. No. 5,257,093 shows another device that uses leaky total internal reflection to determine the proximity between a rotating glass surface and another surface. Here, an apparatus for determining a gap between an actual magnetic head and a pair of substitute magnetic disks made of glass lenses is used. One glass lens can be set to a motion state that exhibits aerodynamic characteristics that establishes a distance between the surface of the glass lens and a magnetic head close to the actual device. The other glass lens is stationary, has two prisms, couples light energy into the surface that undergoes leaking total internal reflection and observes the resulting internal reflection for the purpose of determining the distance to the head. And used to measure.

In the device of US Pat. No. 5,257,093, the two glass lenses and the two prisms need to be physically large and heavy. This device requires that the prism be mounted on one surface in a complex alignment. To withstand relative movements at thousands of revolutions per minute, these glass lenses should be made with tight tolerances and housed in a strong housing in case of breaking during rotation. Furthermore, the rotating lens degrades rapidly and therefore must be replaced frequently. The exchange involves a complete and complex alignment procedure. Thus, such systems are costly, complex and have limited application.

The above-mentioned problem has been solved in the device described in co-pending U.S. patent application Ser. No. 08 / 476,626, in which a flat, transparent material such as glass is used. A very simple reference disk is used. Light is incident on a flat surface from one side of the disk at an angle greater than the critical angle for total internal reflection and propagates through the glass. As the magnetic head approaches the flat surface of the disk, leaking total internal reflection occurs. Optically, it is also known that leaky total internal reflection always involves the so-called photon tunneling effect. This effect is based on the fact that light can penetrate from a first medium through a thin second medium to a third medium. The light intensity penetrating the thin second medium, which in the case under consideration is the gap between the magnetic head and the reference disk, reflects back to the reference disk in the case of leaky total internal reflection mentioned above. Complementary to light intensity.

US patent application Ser. No. 08 / 476,626
In the device described in the above item, the distance of the magnetic head to the disk leaves the disk based on the photon tunnel effect,
It is measured as the intensity of light scattered on the surface of the magnetic head. Because the disc is transparent, the scattered light is measured by a detector located on the side of the disc opposite the head. Although this measurement system is very simple and inexpensive, it has the disadvantage that the signals generated are weak and therefore difficult to detect in background noise. Such a system is suitable for testing small batch manufactured magnetic heads. That is, it is suitable for situations where the production of a more sensitive and accurate measuring system is not economically justified.

[0014]

SUMMARY OF THE INVENTION A measurement for measuring the flying height and direction of a magnetic head relative to a reference medium, which overcomes the disadvantages of the device described in the aforementioned U.S. patent application Ser. No. 08 / 476,626. It is an object of the present invention to provide an apparatus for measuring gaps in nanometers with high accuracy based on leaky total internal reflection. It is an object of the present invention to provide a measuring device for simultaneously measuring a gap between a reference disk and a magnetic head at several point positions on the magnetic head. It is an object of the present invention to provide a measuring apparatus which can obtain a map of the proximity of a magnetic head to the surface of a reference disk in a short time.
An object of the present invention is to provide a measuring device suitable for measuring the flying height of an actual magnetic head and testing dynamic behavior. It is an object of the present invention to provide a measuring device that is small and lightweight, does not require complicated alignment procedures, and can be manufactured without tight tolerances. An object of the present invention is to provide a measuring device which is inexpensive to manufacture and has a wide range of practical applications. An object of the present invention is to provide a measuring apparatus suitable for testing a magnetic head which has a high signal-to-noise ratio and is manufactured in large quantities.

[0015]

According to the present invention, there is provided a measuring device for measuring the flying height and direction of a magnetic head with respect to a transparent disk based on leaky total internal reflection. In a preferred embodiment, the measuring device of the present invention comprises a housing fitted with an electric motor that supports the transparent disk described above in rotation. The disc has inclined sides, one of which is fitted with light emitting means, such as a laser, and the disc is provided with light detecting means on the side diametrically opposite the laser. Light from the laser is emitted in a direction perpendicular to the inclined side of the disk. The angle of inclination of the inclined side of the disk is 45 °, so that light is propagated through the body of the disk and the body of the disk with nominal total internal reflection from the two parallel surfaces of the disk. Enter the department. As a result, if there is no magnetic head to test,
The light detecting means indicates a portion where the intensity of the reflected light is uniform. However, if the magnetic head is approached to the disk surface and is supported on a flying height during rotation of the disk, i.e., on an air cushion, the approached magnetic head causes a leak in total internal reflection, and as a result, the detection The intensity of the reflected light detected by the detector decreases. The degree of this reduction can be converted into a value of the flying height via appropriate electronic means and a computer. In another embodiment of the present invention, a measuring device of the type disclosed in U.S. patent application Ser. No. 08 / 476,626 is added, and further a processing network, for example an averaging network, is added. Measuring devices are included. With this dual mode configuration, the fly height measurement for each mode only can be provided separately, or a single composite measurement that can be a weighted or unweighted average as desired. Can be provided. Thus, this dual-mode or two-subsystem type measuring device is similar to the measuring device in the above-described embodiment in the above-mentioned US patent application Ser. No. 08 / 476,763.
626, which has the advantages of the measuring device disclosed in No. 626,
Construct a flying height measurement system. The output signals can be combined and processed for improved fly height measurement.

[0016]

1 to 3 illustrate an apparatus according to one embodiment of the present invention for measuring the flying height and direction of a magnetic head with respect to a transparent reference disk.
The magnetic head has a refractive index IR. FIG. 1 is a schematic side cross-sectional view of the apparatus taken along line II of FIG.
FIG. 2 is a plan view of the apparatus of FIG. 1, and FIG. 3 is a perspective view including respective parts of the apparatus of FIGS. As can be seen from the figures, the device of the invention comprises a housing 10 supporting an electric motor 12 having an output shaft 14 extending vertically upward and having an axis of rotation Z.

A transparent reference disk 20 (hereinafter simply referred to as disk 20) has four pins 19a, 19b, 19 positioned on a rotary drive and support assembly.
It is mounted on the mounting plate 18 by c and 19d. Disk 20 extends into a well-positioned recess in surface 20b. The four pins are equidistant from the rotation axis Z, and a transparent portion for transmitting light is left at the center of the reference disk inside the rotation pins. The four pins 19a, 19b, 19c, 19d extend partially through the disk 20. The disk 20 has a truncated cone shape having two parallel surfaces, a first flat surface 20a and a second flat surface 20b, and an inclined side surface 20c between each of these flat surfaces. In the illustrated embodiment, this inclined side surface 20c, for each flat surface 20a, 20b,
It is converged downward at an angle equal to 45 °. Disk 20
Is polished to an optical grade of 1 nanometer rms or better. Diameter D1 of first flat surface 20a
And the diameter D2 of the second flat surface 20b is equal to an even multiple of the thickness T of the disk, and it is preferable that D1-D2 = 2T. The disk 20 in the preferred embodiment is made of glass and is preferably of the type of glass used as conventional magnetic disk equipment. The refractive index IR1 of the glass disk is about 1.52. in this case,
IR1 is less than IR. The disc 20 has at least its channel portion 49 optically transparent.

The apparatus also includes an illumination assembly 22 secured to the housing 10, for example, by bolts (not shown). The illumination assembly 22 includes a light source such as a laser 24, for example, a semiconductor diode laser (wavelength 670 nm) driven by a power supply 25,
And an associated coupler for coupling inside 0. The coupler includes a collimating lens 26 and a plano-concave lens 2.
8 is included. The laser 24, the collimating lens 26, and the plano-concave lens 28 are arranged in sequence in the emission direction of the light from the laser 24. The plano-concave lens 28 is
Created from the same material as As can be seen from FIG. 2, the plano-concave lens 28 is made of the same material as the disc 20, has the same curvature as the above-mentioned inclined side face 20c, and has a surface 28a on the upper side opposite to the inclined side face of the disc 20. . This surface 28a is spaced from the inclined side surface 20c for a very short distance, such as about 0.1 mm.

A detector assembly 30 (see FIG. 2) is supported in the housing 10 on the side opposite the illumination assembly 22 and adjacent the inclined side surface 20c of the disk 20. The detector assembly 30 includes a plano-concave lens 32, an interference filter 34, a polarizing filter 36, and a detector 38, all of which are arranged in sequence in the direction of propagation of light from the illumination assembly 22. The plano-concave lens 32 is made of the same material as the disk 20, has the same curvature as the inclined side surface 20c, and has a top surface 32a opposite the inclined side surface of the disk 20. The surface 32a is approximately 0.
It is separated from the inclined side surface 20c by a very short distance such as 1 mm. The interference filter 34 allows only light of the operating wavelength to pass, and blocks light of other wavelengths, that is, background noise light.

To increase the signal-to-noise ratio, a polarizing filter 36 is arranged to pass only light linearly polarized along an axis perpendicular to the flat surfaces 20a and 20b to the detector. Detector 38 generates a signal representative of the light coupled from disk 20. The detector 38 may be a rectangular charge-coupled device (hereinafter simply referred to as CCD) camera or a sensitive triplet of photosensitive semiconductor devices. The detector 38 is connected to a data analysis unit, for example a computer 40, which analyzes the output signal from this detector. The computer has a display unit 42 for displaying the analysis result. The results of the analysis are generally
represents the position of the magnetic head with respect to a.

A magnetic head 44 to be tested is mounted on a magnetic head support assembly. A head loader 46 is fixed in a positioner 48 of the magnetic head support assembly. The positioner 48 allows for accurate positioning of the head at any desired point on the flat surface 20a of the disk 20, and allows for changing the head angle with respect to the radius of the magnetic head, the so-called "skew angle". A positioner 48 suitable for this purpose is described in U.S. Pat. No. 5,254,946. Disc 2
Numeral 0 is rotated in a fluid environment A (FIG. 1) such as air or a liquid stored inside the housing 10. It is important that the material of the disc 20 has a refractive index IR1 that is greater than the refractive index IR2 of the surrounding environment. In the case of air,
Refractive index IR2 is equal to about 1.00.

(Explanation of Operation of Apparatus) When the operation of the apparatus is started, first, the light source 24 is turned on. Light from the light source 24 passes through the collimating lens 26 and has a collimated light beam B having a diameter D equal to the lateral length of the inclined side surface 20c of the disk 20 (hereinafter simply referred to as light beam B).
(FIG. 1) is converted into
The collimating light beam B is allowed to pass through the inclined side surface 20c in a parallel state (FIG. 2).

As shown in FIG. 1, the light beam B enters the disk 20 at right angles to the inclined side surface 20c and at an angle of 45 ° which is greater than the critical angle of total internal reflection 41 ° from the glass-air interface. Irradiation is performed on the flat surfaces 20a and 20b. In FIG. 1, the position of such an interface coincides with the flat surfaces 20a and 20b. In other words, as it propagates through the disk 20, the light beam B is totally internally reflected many times from the flat surfaces 20a and 20b, and thus passes through a sawtooth path. The light beam B propagates along the direction of the diameter of the flat surfaces 20a and 20b and in the diametrically overlapping channel portion 49 (FIG. 4).

As mentioned above, the first flat surface 20a
And the diameter D2 of the second flat surface 20b are equal to an even multiple of the thickness T of the disc 20, and light exits the disc 20 at a location on the side of the detector assembly 30, where light The position on the surface where the light exits is the same as the position on the incident surface (FIG. 1). In other words, the point position a ₁ of the start of light at the light source side of the inclined side surface 20c corresponds to a point located a ₂ out of light at the detector side. Furthermore, the projection of the light beam B on the first flat surface 20a (FIG. 2) is symmetric with respect to the center of the disc. As shown in FIG.
1 = 6T, D2 = 4T, and the light beam B is the second
Are reflected three times on the flat surface 20b of the light source. D1 = 4T and D2
= 2T, the light beam B reflects only once at the position of the second flat surface 20b.

The light beam B exiting the disk 20 passes through a plano-concave lens 32 and an interference filter 34 which maintain the light beam B in a parallel state, and then passes through a polarizing filter 36 and enters a detector 38. The detector 38 converts the signal of the optical intensity of the light beam into an electric signal,
Send to Computer 40 analyzes these electrical signals and displays the results on display 42. When the detector 38 is of the CCD sensor array type, the detection result is displayed as a rectangular area 50 corresponding to the shape of the detection area of the CCD sensor array. This is shown in FIG. If the disk 20 is ideal and the light beam is uniform, the brightness of the entire rectangular area 50 will be uniform.

Next, the magnetic head 44 is precisely positioned above the first flat surface 20a at a predetermined position corresponding to the position where the propagating light beam B is projected, using the above-mentioned positioning mechanism 48. Is positioned. Next, the magnetic head is moved toward the first flat surface 20a of the disk 20. The disk 20 is driven at about 4000 rpm by the motor 12.
Rotated about the central axis Z at a speed of m, the resulting relative airflow supports the magnetic head 44 so that it floats above the air cushion, i.e., at a distance G from the disk 20. This distance or gap G is of the order of 20 to 30 nanometers. If the gap is small enough, leaking total internal reflection will occur at the point below the surface of the magnetic head. When leakage internal total reflection occurs, the intensity of light reflected on the first flat surface 20 a in the region where the magnetic head 44 is positioned and returned into the body of the disk 20 decreases. As a result, the portion of the magnetic head 44 approaching the first flat surface 20a becomes dark on the display 42 of the computer, so that the image of the magnetic head 44 is reproduced. This dark portion is shown in FIG. 5 as strips 44a and 44b corresponding to the projection portions 44c and 44d of the magnetic head 44.

As mentioned earlier, brightness has a function that depends on the ratio of the gap to the optical wavelength and others. Therefore, it is possible to convert the output data of the computer into the absolute value of the gap G. As the disk 20 rotates, at a certain time, the light beam B
(FIG. 2). While light beam B encounters pin 19, light source 24 and detector 38 are tuned together so that they are electrically isolated to avoid light scattering and increase the signal to noise ratio. In the case of a CCD sensor array, such an interruption can be implemented by using an electronic shutter which is usually an integral part of a standard CCD camera, and therefore, the description thereof is omitted. In the case of a laser source, the interruption can be achieved in a manner known in the art by the principle of current modulation by the power supply 25.

Other Embodiments of the Invention The device of the present invention may include a detector 38 in the form of a sensitive set of photosensitive semiconductor elements. One of such detectors
An example is schematically illustrated in FIG. 6, in which three high-sensitivity small-area photosensitive semiconductor elements P1, P2 and P3 correspond to predetermined points in the projection range of the magnetic head 44 on the first flat surface 20a. It is positioned at a predetermined point.

The device with the detector of this embodiment operates in the same manner as the device of the first embodiment, but with the first flat surface 2.
The difference is that the intensity of the light beam reflected at Oa is determined at the aforementioned three predetermined point positions. The light beam intensities measured at these predetermined point positions are recalculated using a known relational expression, and are calculated as the value of the gap at those point positions. In other words, measurements at three predetermined point locations provide complete information regarding the relative position and orientation of the surfaces 44c and 44d of the magnetic head with respect to the first flat surface 20a of the disk.

FIG. 7 shows a third embodiment of the present invention.
This embodiment is illustrated as a disk 120 having a reflective coating 121 with its bottom surface 120b on top. The reflective coating 121 is attached to a support disk, such as another glass disk 123, with an adhesive or the like, and the glass disk 123 is eventually mounted on the shaft 160 of the electric motor 132. In this third embodiment, the device is not equipped with pins 19a, 19b, 19c, 19d which block the light beam while the disc is rotating. Therefore, it is not necessary to shut off the detector and the light source in the third embodiment. If not, the system operates in the manner described above.

FIG. 8 shows an alternative embodiment of the system of the present invention. The system is similar to that shown in FIG. 1, but additionally includes a subsystem of the type described in U.S. Ser. No. 08 / 476,626. In FIG. 8, elements corresponding to those in FIG. 1 are denoted by the same reference numerals, but have the same functions as those described above with reference to FIG. The system of FIG. 8 includes a detector 130 and this detector 1.
The third embodiment further includes an assembly for positioning the disk drive 30 toward the lower surface of the disk 20 and toward the magnetic head 44. In the third embodiment, the assembly is positioned to be aligned with the magnetic head 44 in the axial direction. Detector 130 and this assembly functionally correspond to detector 84 and assembly 16 described in U.S. patent application Ser. No. 08 / 476,626.

Thus, the magnetic head 44
As it moves across the upper surface in the figure, the detector moves down in the figure of the disc 20 following this movement. The detector 130 detects light exiting from the inside of the disk 20 across the gap between the upper surface of the disk 20 and the magnetic head. In this case, the light exiting the disk 20 is reflected by the magnetic head 44, returns across the gap, and enters the detector 130 across the disk 20. As in the system described in US patent application Ser. No. 08 / 476,626, detector 130 generates a signal representative of the incident light and sends the generated signal to computer 40.

In one of its operating modes, the computer 40 calculates the gap G from each signal sent by the detector 130 and the detector assembly 30 described with reference to FIG.
Are determined separately. In another mode of operation, the computer 40 combines these determined measurements in a predetermined manner and calculates a single composite measurement of the gap G. For example, the composite measurement may be a simple average or a weighted average of the separately obtained gap G measurements, as desired. In the embodiment shown in FIG. 8, the user can selectively determine the operation mode of the computer 40 in order to optimize the determination of the flying height of the magnetic head 44 above the disk 20.

Thus, the present invention is an apparatus for measuring the flying height and direction of a magnetic head with respect to a transparent medium, wherein the gap size in nanometers is accurately determined based on leaky total internal reflection. It has been shown to provide a device for measuring. According to the apparatus of the present invention, it is possible to simultaneously measure the gap between the magnetic head and the reference disk at several point positions of the magnetic head. According to the present invention, a map of the proximity of the magnetic head to the surface of the reference disk can be obtained within a short time. According to the present invention, the actual dynamic behavior and flying height of a magnetic head can be measured. The device of the present invention is small and lightweight,
It can be manufactured without the need for complex alignment procedures and with tight tolerances, has low manufacturing and operating costs, and has a wide range of practical applications. Finally, the device according to the invention is characterized by a high signal-to-noise ratio and is suitable for testing magnetic heads manufactured in large quantities.

While the present invention has been described with reference to illustrative embodiments, it will be understood that various modifications can be made within the present invention. For example, the light source 24 may be an incandescent light source or a light emitting diode, and may include an optical fiber. It is also possible to coat the inclined side surface of the disk with a total reflection coating material. Although the spatial resolution and the signal-to-noise ratio are low, the lenses 28 and 32, the filter 3
4 and 36 may be omitted. An array of CCD sensors and a set of photosensitive semiconductor elements may be combined as an integrated system using a beam splitter. Further, the first and second flat surfaces of the disk may be reversed with respect to the position of the magnetic head. Also, although the signal-to-noise ratio is reduced, the tilt angle of the disc and the first flat surface 2 of the disc are reduced.
The angle between Oa and the angle between the second flat surface 20b and the light beam B may be an angle other than 45 °.

[0036]

According to the present invention, there is provided a measuring apparatus for measuring the flying height and direction of a magnetic head with respect to a reference medium, wherein the gap in nanometer is measured with high accuracy based on total internal reflection of leakage. A measuring device is provided. A measuring device is provided for simultaneously measuring the gap between a reference disk and a magnetic head at several point locations on a magnetic head. A map of the proximity of the magnetic head to the surface of the reference disk can be obtained in a short time. The above-described measuring apparatus suitable for measuring the flying height of an actual magnetic head and testing dynamic behavior is provided. The measuring device is provided which is small and lightweight, does not require complicated alignment procedures and can be manufactured without tight tolerances. The above-described measuring device is provided which has a low manufacturing cost and a wide range of practical applications. The above-described measuring apparatus is provided, which has a high signal-to-noise ratio and is suitable for testing a magnetic head manufactured in large quantities.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a measuring device for measuring the flying height and direction of a magnetic head with respect to a transparent disk according to one embodiment of the present invention.

FIG. 2 is a schematic plan view of the measuring device of FIG.

FIG. 3 is a perspective view illustrating basic components of the embodiment of the measuring apparatus of FIGS. 1 and 2;

FIG. 4 is a perspective view illustrating a glass disk and a channel portion through which light propagates.

FIG. 5 is an illustration of the detection part of the device in the form of a charge-coupled sensor array.

FIG. 6 is an illustration of the detection part of the device in the form of a highly sensitive photosensitive semiconductor element.

FIG. 7 is a schematic cross-sectional view similar to the embodiment of FIG. 1, with alternative means for mounting the transparent disc to the electric motor.

8 includes a measuring device in the form shown in FIG. 1 and an additional device in the form shown in US Pat. No. 08 / 476,626;
It is a schematic sectional drawing of the measuring device in another aspect which added the network for process processing.

[Explanation of symbols]

 Reference Signs List 14 output shaft 12 electric motor 10 housing 20 reference disk 19a, 19b, 19c, 19d pin 18 mounting plate 20 disk 20a first flat surface 20b second flat surface 20c inclined side surface 49 groove portion 22 irradiation assembly 24 laser 25 power supply 26 Collimating lens 28 plano-concave lens 30, 130 detector assembly 34 interference filter 36 polarizing filter 38 detector 40 computer 42 display unit 44 magnetic head 48 positioner 46 head loader

Claims (5)

(57) [Claims] 1. An apparatus for measuring a position of a magnetic head with respect to a rotating flat surface, the magnetic head including a reference surface having one reference point position, A first circular surface having a diameter D1; a second circular surface having a diameter D2; and a side surface extending between the first and second circular surfaces; A circular frusto-conical disk, each circular surface of which is orthogonal to a common central axis and disposed about the central axis, extending along each diametric direction of said first and second circular surfaces. B. at least one diametrically overlapping channel portion, said channel portion being an optically transparent frusto-conical shaped disc; A magnetic head, the reference surface of the magnetic head being a first
B. a magnetic head support assembly including means for selectively supporting in close proximity to said circular surface; A rotational drive and support assembly for supporting the frusto-conical disk at its second circular surface location and for selectively rotating the frusto-conical disk about the central axis; The magnetic head supported by the magnetic head support assembly is
C. a rotary drive and support assembly spaced apart from the circular surface of the gap G by at least partially the dynamic force of the fluid; A light source and a coupler associated with the light source for partially coupling the light from the light source through the side surface into an angularly frustoconical disk displaced with respect to the central axis; B. a light source and an associated coupler whose total light is totally internally reflected between the first and second circular surfaces; A first photodetector and associated coupler positioned opposite the light source and associated coupler;
The coupler couples light passing through the channel portion and the side surface to the first photodetector, wherein the first photodetector represents light coupled to the first photodetector and A. a first photodetector and an associated coupler, including means for generating a first signal representative of a position of the magnetic head with respect to the one circular surface; A second photodetector disposed opposite the second circular surface of the frustoconical disk and including detection means disposed relative to the magnetic head, wherein the second optical detector includes a reference point on a reference surface of the magnetic head. A second photodetector for detecting the intensity of light propagating from the interior region of the frustoconical disk at a point location relative to the location and generating a second signal indicative of the intensity; G. The truncated conical disk has an index of refraction IR1, the frustoconical disk is positioned in a fluid medium having an index of refraction IR2, and the index of refraction IR1 is IR1.
2 and less than the IR, the first signal and the second signal are sent to a computer, which calculates the gap G from each of the first signal and the second signal.
Apparatus for measuring the position of a magnetic head with respect to a rotating flat surface, wherein the measured values of the magnetic heads are separately determined or the separately determined measured values are combined to calculate a composite measured value of the gap G. . 2. The apparatus of claim 1 including a processing network responsive to the first signal and the second signal to generate a composite fly height measurement signal. 3. The apparatus of claim 1, wherein the processing network establishes a fly height signal that is an average of the first signal and the second signal. 4. The apparatus of claim 3, wherein the average of the first signal and the second signal is a weighted average. 5. The apparatus of claim 3, wherein the average of the first and second signals is a weighted average, and the weight of the first signal is unequal to the weight of the second signal. .