JPH079738B2 - Magnetic recording / reproducing device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a magnetic recording / reproducing device such as a hard magnetic disk device, a flexible magnetic disk device, a magneto-optical disk device, etc., and particularly, the magnetic recording / reproducing device is made highly reliable. Also, the present invention relates to an improvement in a configuration for avoiding the influence of defects, protrusions, foreign matters, etc. on the recording medium, which has been an obstacle to higher density.

[Technical background of the invention and its problems] Conventionally, in a rigid or flexible magnetic disk device, in order to avoid a medium crash or a head crash caused by a collision between a recording medium and a magnetic head, (1) the surface roughness of the recording medium is made small. The chances of mutual contact are reduced as much as possible. (2) The recording medium and the magnetic head peripheral part have a semi-enclosed structure to prevent dust and foreign matter from admixing and adhering. (3) With respect to protrusions generated during recording medium manufacture. Had to take measures such as removing the protrusions with a vanish head after its manufacture.

However, in the above measure (1), it is difficult from the viewpoint of coating technology to set the maximum height of the surface roughness to 0.15 μm or less particularly in the case of a flexible medium.

Further, according to the above countermeasure (2), although it is a semi-enclosed structure,
Mixing of dust and foreign matter is unavoidable and causes a medium crash or a head crash.

Regarding Countermeasure (3), for example, Kogure et al., “Mechanical characteristics of floating heads and media for 3,2 gigabyte aggregate magnetic disk devices”, Research Report of Telecommunications Research Institute, Vol. 31, No. 1 , pp291-303 (1982), an AE (Acoustic Emission) sensor is used to remove the protrusion while monitoring the collision phenomenon between the protrusion on the recording medium surface and the burnish slider (head). Is being done.

However, the height of the protrusion that can be removed in this way is 0.15 μm as shown in the above-mentioned reference example.
As described above, therefore, the above measure (3) cannot be immediately applied to a high-density and highly reliable magnetic disk system.

Further, for example, even if the protrusions and the magnetic head do not come into contact with each other immediately after the burnishing, in the case of a thin film type disk, due to the flow of the lubricant formed on the surface of the magnetic layer during the operation of the device,
Further, in the case of a coated disk, the unevenness is formed on the surface of the magnetic layer due to plastic flow or the like, so that in any case, the recording medium and the magnetic head eventually collide and crash.

Therefore, even if the conventional measures (1) to (3) are taken, there is a problem that the relationship between the highly reliable magnetic head and the recording medium interface is not completely guaranteed.

For this reason, in the past, the magnetic head has been designed with a sufficient margin in advance so as to have a large floating clearance as compared with the height of the protrusion burnt by the burnish head in advance.

However, in this case, it is attempted to realize high density recording by realizing a low floating gap, but the recording wavelength λ and the floating clearance d
There is a problem in that the spacing loss increases due to the known relational expression of spacing loss = 54.5d / λ (dB) between and, and as a result, high density recording cannot be achieved.

That is, in the conventional magnetic recording / reproducing apparatus, there is a problem that highly reliable and high density magnetic recording / reproducing cannot be achieved due to defects, protrusions, foreign matters, etc. on the surface of the recording medium.

[Object of the Invention] The present invention has been made in view of the above problems, and an object of the present invention is to provide a magnetic recording / reproducing apparatus capable of performing magnetic recording / reproducing with high reliability and high density.

[Summary of the Invention] In order to achieve the above object, a magnetic recording / reproducing apparatus of the present invention records information with a recording medium formed of a magnetic thin layer formed on a rigid body or a flexible substrate via a magnetic head. In the magnetic recording / reproducing apparatus for reproducing, an optical head including an optical lens and an actuator to which the optical lens is attached is provided so as to coincide with the moving direction of the recording medium and precedes the magnetic head.
Means for detecting defects, protrusions, foreign matters, etc. on the surface of the magnetic thin layer in response to focus control of the optical head, the actuator and the magnetic head being coupled via a gimbal; Etc. are detected, it is determined whether or not the height and / or size of the defect or the like is a certain value or more in response to the focus control of the optical head, and more than a certain value. In this case, means for avoiding the recording or reproducing operation of information by the magnetic head is included.

Embodiments of the Invention Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a configuration explanatory view showing an outline of a main part and a recording medium of a magnetic recording / reproducing apparatus to which the present invention is applied.

In the magnetic recording / reproducing apparatus of this embodiment, the magnetic head 2,
Basically, an optical head 1 is provided so as to match the moving direction of the recording medium 16 and precedes the magnetic head 2, and a gimbal 12 that connects the optical head 1 and the magnetic head 2 together. There is.

The optical head 1 reflects the light beam 4 of the light source 3 by the mirror 5, irradiates the recording medium 16 with the optical lens 6, and receives the irradiation reflected light by a light receiver (not shown). Then, the actuator 7 also serving as a protection means for the optical lens 6
And 8 are attached to the support 10 by the support 9.

The magnetic head 2 following the optical head 1 is provided with a coil 11 at its tip and is connected to the actuators 7 and 8 of the optical head 1 by a gimbal 12.

The recording medium 16 includes a magnetic information carrier 13 and a track guide means 14.
And are provided on the substrate 15.

In each of these sections, the actuators 7 and 8 of the optical head 1 include means for feeding back focus servo and tracking servo information, which will be described later, to correct the optical lens 6. Here, the correction operation means is
The magnetic circuit may include a coil, or may be a means such as an electrostrictive element. Further, illustrations of optical lenses, mirrors, detectors, coils, etc. necessary for focus servo and racking servo are omitted.

Similarly, the light source 3 of the optical head 1 may be a focused beam such as an electron beam even if it is a laser. For example, in the case of an electron beam, the optical lens 6 may be replaced with a magnetic field lens. Further, the light source may be integrated with the optical lens or may be a so-called light source / optical lens separated type structure.

The magnetic head 2 may be a contact type or a levitating type,
A so-called floating head in which the head and the recording medium are stably held at submicron or less is preferable from the viewpoint of improving the high-density recording property and the reliability described above.

The structure of the magnetic head 2 may be either a bulk type or a thin film type, and the floating mechanism may be any of a positive pressure type, a negative pressure type, and a positive / negative dual type. Further, it may be a so-called single pole type for perpendicular recording, an auxiliary magnetic pole excitation type, a ring type, or a magnetoresistive head. Further, it may be a head of a system in which light is guided to the tip of the magnetic head to perform magneto-optical reproduction. It should be noted that a recording current generation circuit for flowing to the magnetic head,
Not shown are a reproduction circuit, detection means and circuits for focusing, tracking, etc., a servo circuit, an actuator control circuit for the optical head, and the like.

The magnetic information carrier 13 of the recording medium 16 may be a so-called thin film or a coating film containing a magnetic material. The remanent magnetization state of the magnetic information carrier 13 may be horizontal to the substrate 15, vertical, or in the middle thereof.

Similarly, the track guide means 14 of the recording medium 7 may be a groove used in an optical disk or the like, or may have different light reflectance and refractive index between a recorded area and a so-called unrecorded area, or other means. It may be. Although the track guide means 14 is attached to the substrate 15 in FIG. 1, the track position is changed by a predetermined amount corresponding to the rotation angle of the magnetic pole of the so-called stepping motor, thereby positioning the track. It may be a means for performing.

Substrate 15, the material may be either inorganic or organic,
The rigid body 2 may be any flexible body, and may be transparent or opaque to light.

Reference numeral 17 is an arrow indicating the moving direction of the recording medium 7.

Next, in this embodiment, a structure for performing the focus servo and the trunking servo while irradiating the track guide means 14 of the recording medium 16 with the light beam 4 will be described.

As the technique for performing the focus servo and the tracking servo, a known technique used for, for example, an optical disc may be used, and as an example thereof, FIG. 2 shows a circuit for obtaining a defocus signal from a detector.

In the figure, 20 is a four-division photodetector, 21 is a preamplifier, 22 is a differential amplifier, and 23 is a defocus signal output terminal. In this figure, if a normal focus servo is performed, a circular beam such as b shown in the four-division photodetector 20, a beam that is too close, and a beam that is too far c
The optical system is configured to obtain a beam such as. Since the optical structure is known, it is not shown.

As a result, the relationship between the defocus signal (detector output voltage) and the defocus amount becomes the relationship shown in FIG. Here, in order to make the defocus signal have a linear relationship with the defocus amount, a compensating circuit is provided as necessary. However, in (3-1) to (3-2) shown in the schematic diagram, The range becomes a focus controllable dynamic range, and its value is about I200 to I300 μm as the range of the defocus amount ΔZ, although it varies depending on the characteristic control method of the optical head.

Next, an operation of detecting a medium defect or a protrusion when there is a medium defect or a protrusion in the detection area of the focus control circuit having these control loops and an operation of avoiding the magnetic head will be described.

FIG. 6 shows the time variation of the defocus signal output voltage (defined as function x) and the operation of each circuit generated from it. (A) is the analog waveform of x, (b) is the pulsed circuit output value when pulsed at a point exceeding the slice level (voltage) S ₁ , and (c) is the slice level S
₂ shows the pulsed circuit output value corresponding to ₂ (> S ₁ ). Further, (d) is the differential waveform (x) of (a), the voltage at the differential circuit output point, and (e) is the pulsed circuit output signal obtained by pulsing the differential waveform at a value exceeding the slice level S ₁ ′. is there.

Considering the case where a protrusion or a foreign substance adheres to the surface of the recording medium, the defocus signal shown in FIG. 6 (a) generates a signal that exceeds the slice level S ₁ at point (6-1) and then exceeds the slice level S _2. To do. At this time, the height and size of the protrusion or the foreign substance can be determined by the presence or absence of the signal pulse shown in (b) and (c) and the duration. For example, if a pulse occurs at the slice level S _{1 and} at the same time as the slice level S ₂ , it is a protrusion or a foreign object having a high height, and if the duration of the pulse is long, it has a size corresponding to the length. You can tell if you are.

When an optical beam is used for this defocus signal, the intensity distribution thereof is usually a Gaussian distribution, so that the volume of the protrusion or defect must be a certain value or more, (6) in FIG.
The defocus signal as shown after the point -1) is not obtained.

For example, suppose you have a projection with a small projected area but a high height. In this case, by using the time differential waveform information x shown in FIG. 6 (d) together, it is possible to detect a protrusion or a foreign substance having a certain height or more. In Figure 6 of (a) (6-2) with respect to is a sudden small change that does not reach the slice level S ₁ shown in point, the (d) of FIG on indicated as slice level S ₁ 'or more A circuit for generating a pulse is provided. Note that if the level of S ₁ ′ is too low, so-called noise and disturbance will affect the entire control system. Since these values depend on the performance of the beam intensity, the characteristics of the distribution detector, etc., it may be determined in consideration of the detection capability of the protrusion or the foreign matter depending on the case.

In FIG. 6, the values of S ₁ , S ₂ , and S ₁ ′ are taken as their respective voltage levels for the sake of simplicity, but the number (the number of levels) and the level values are not necessarily limited.

In the above description, the light beam has a Gaussian distribution, but the present invention is not limited to this example. For example, when the light beam is applied to a magnetic disk device, the beam may be expanded in any direction in the track width direction. Alternatively, the entire track width may be covered. The embodiment in this case will be described below in some detail.

First, the physical size of defects, protrusions, foreign matters, etc. to be detected will be described. There are two types of defects, concave defects and convex defects. Most of the concave defects are pinholes, which are formed during the formation of alumite by forming an intermetallic compound in the substrate due to the impurity elements such as Fe, Si, and Mn mixed in the aluminum substrate material. Therefore, the substrate base material is highly purified and the alumite conditions and alumite polishing conditions are optimized, but defects of 10 μm or more per disk surface
There are about 50 defects, and those having a size that affects the signal quality have defects of 3 μmφ or more at most.
For example, Hattori, 3 "Renzoku Thin Film Media for 3,2 Gigabyte Aggregate Magnetic Disk Drives", Research Report on Practical Use of Telecommunications, Vol. 31, No. 1, pp277-289 (1982), and Nakanishi, 3
"Electromagnetic conversion characteristics of a gigabyte magnetic disk unit"
Reference pp259-276 (1982).

Next, in the case of a convex defect, the minimum value that can be taken by the varnish is about 0.15 μm, and the length on the disk substrate surface is generally about 100 times the above height, that is, several tens of μm. That is clear from the difference in the dimensions of height and length when these surface roughness profiles are taken.
In other words, even for convex defects, the projected area on the substrate surface
It is understood that the target size is 100 μm ² or more, and at most 10 μmφ.

In order to detect these defects, a method of uniformly irradiating a light beam in the track width direction and an embodiment of the structure of the optical head will be described below. That is, (i) The light beam is changed from a circular shape to an elliptical beam using an elliptical lens.

(Ii) Further split the beam to cover a wider track width.

(Iii) There is a method of covering an area equivalent to the track width by using a circular beam.

First, regarding (i), if the laser diode is used to focus on the surface of the recording medium, the major / minor axes of the ellipse are 10
It is easy to set the size to about μm × 1 μm. in this case,
If the track width is 10 μm or more, the beam is further divided into a plurality of portions (method (ii)) to cover the entire track width. Here, in the recent so-called Winchester type magnetic disk device, the track width is about 20 μm
Since it is equivalent to about 50 μm and 1 to 400 Tpi, it is considered that the beam splitting is at most about 5 beams. In consideration of the fact that the present invention does not require recording unlike an optical disk, it is a sufficiently practical range from the viewpoint of laser power. Is.

Now, consider a convex defect (projection) head structure as shown in FIG. That is, the projected area of the convex defect 42 on the substrate is 10
μmφ, track width 20μm, light beam from optical head
It is assumed that 41 has an elliptical shape of 20 μm × 1 μm. In this case, assuming that the reflectance changes most simply due to the presence of the convex defect, the convex defect has a reflectance change ΔR / R = 50%.
(R: reflectance when there is no defect), which is sufficient for detection.

Next, there is a method of modulating the circular light beam in the track width direction. FIG. 5 shows an example of the system configuration of the optical modulator. 31
Is an acousto-optic light modulator, 32 is a condenser lens, 33 is the 0th-order light (non-diffracted light; this is not used), 34 is the 1st-order diffracted light, which is normal optics used in optical disks, etc. Guided to system 35. The optical system 35 focuses the recording medium up to about 1 μm.
36 is a carrier wave transmitter (c), 37 is a modulated signal (m), 38
The modulator 39 is an amplifier. θ is an incident angle to the optical modulator 31, 2θ is a diffraction angle, and is represented by a relationship of 2θ = · λ / ν. (: Frequency, λ: wavelength, ν: sound velocity transmitted in TeO ₂ ) The optical modulator may be an ultrasonic modulator used in laser printers and laser facsimiles, and the principle of optical modulation is known. As an example, an optical modulation element using tellurium dioxide single crystal (TeO ₂ ) (for example, NEC OD
-8823 type; carrier beam frequency 80MHz) incident beam system 100μm
, The modulation bandwidth (△ i) is △ i ～ 0.54
ν / d to 22.7 (MHz) However, the velocity of sound transmitted in the ν: TeO ₂ medium (= 4.2 × 10 ³ m / s). At this time, the change Δ (2θ) of the first-order diffraction angle with respect to the modulated frequency width 2Δi is Δ (2θ) = 2Δi · λ / ν (0.633 nm when λ: He-Ne laser light source wavelength) Δ (2θ ) = 6.84 × 10 ^-3 (rad). If the distance from the light modulation element 31 to the recording medium (not shown) through the engineering system 35 is 50 mm, the deflection Δ2x (μm) of the first-order diffracted beam on the recording medium is Δ (2x) = Δ (2θ) · 50 × 10 ³ = 342 (μm), which is on the order of sufficiently covering the track width of the magnetic head.

As described above, (a) a single beam is used to form an elliptical beam using a cylindrical lens to irradiate the recording medium, and (b) a multi-beam is used to cover the track width in the same manner as in (a). It is possible to irradiate the light beam at least over the entire track width by the method, (c) the method of modulating the circular beam with the light modulator, or the like. With these methods, it becomes possible to detect defects on the recording medium.

At this time, since the convex defect causes a crash of both the magnetic head and the recording medium when the magnetic head contacts, it is particularly important to detect and avoid the defect as described later. On the other hand, in the case of a concave defect, particularly the defect (pinhole) of about 3 μmφ described above, if the signal quality is significantly deteriorated, error skipping, selection of an alternate track, etc. may be performed as described later.

The preferred detection range of the present invention will be described. As is already clear, when the beam scanning is performed by modulating a spot of about 0.8 μmφ, it is possible to instantaneously detect a change in reflectance of about 50% up to a half of the area, that is, a region of about 0.63 μmφ. However, it becomes difficult to detect a defect having a size of 0.5 .mu.m.phi. Having a projected area on the surface of the substrate having a reflectance change of about 30% or less. In this case, the height of the defect of the usual type is 10
Since 0 is 0.005 μm, there is no risk of a crash, but if a foreign substance on the ball comes in, it will cause a crash. Including such an extremely rare case, the preferred detection range of the present invention minimizes spherical defects having a diameter of about 0.5 μm.

Next, a method for avoiding this after detecting the protrusion or the foreign matter on the recording medium as described above will be described with reference to FIG.

FIG. 7 (a) shows the signal at the output end of the pulse conversion circuit shown in FIG. 6 (b). When such a signal is received, the sixth
As shown in FIG. 7B, the focus servo is turned off after a time of τ ₀ , and at the time when a time of τ ₁ (≧ τ ₀ ) is passed, a current is applied to the coil of the actuator shown in FIGS. The optical head is activated (Fig. (C)), and the optical head is forcibly lifted off. At this time, the current passed through the coil is judged whether or not a pulse is detected at the slice levels S ₁ , S ₂ , S ₁ ′ shown in FIG. 6, and the height of the medium defect is recognized, and according to the value. And decide. Next, looking at the pulse trailing edge in (a), the coil conduction is cut off after time τ _{1 and the} delay time τ ₂ (τ ₂ ≧ τ ₁ + τ ₀ ) the focus servo is turned on (c). As a result, the magnetic head 2 shown in FIG. 1 can effectively avoid protrusions or foreign matter on the recording medium 16. It should be noted that τ ₀ is a delay time determined by the distance from the center of the optical head 1 to the magnetic head 2 in FIG. 1 and the relative speed between the magnetic head 2 and the recording medium 16. The difference between τ ₁ and τ ₀ and the difference between τ ₂ and τ ₁ are not essential in principle, and it is only necessary to obtain an operation margin that can realize the operation of this method.

In FIG. 7, the case where a current is passed through the coil to activate the actuator having the optical head has been described. For example, when the actuator of the electrostrictive element is used, the voltage applied to the electrostrictive element is In other words, any means can be used as long as it is a means for controlling the optical head coupled with the magnetic head. Further, any method may be used as long as the operation of this method can be obtained even if the waveform of the current passed through the coil is not a pulse. For example, a bang-bang control waveform 7 indicated by a broken line
It may be -1. Further, in FIG. 7, FIG. 6 (b)
Although the operation has been described by taking the waveform of FIG. 2 as an example, the present invention is not limited to this, and in short, the signal of the final stage of the protrusion or the foreign substance detection circuit (not shown) may be targeted.

In FIGS. 6 and 7, the case where the protrusion or the foreign substance, that is, the protrusion from the surface of the recording medium is described, but in the case of a concave defect such as a pinhole, the defocus signal appears on the negative side. . In this case as well, a negative slice level may be provided in the same manner, and the subsequent signal processing is also the same as the method described above. However, in this case, since the magnetic head and the concave defect portion do not come into direct contact with each other, the avoiding means does not necessarily have to be executed, and the defect skip, that is, the recording or reproducing is not performed on the portion determined to be the defect. May be taken. In this case, a memory for storing the track number and sector number of the defective portion may be provided.

Further, in the present embodiment, the method applying the focus servo technique (four-division detector) using the laser light source is described, but the present method is not limited to this, and defects on the recording medium,
Anything can be used as long as it can detect protrusions, foreign matters, and the like.

For example, it is possible to apply a Michelson interferometer. In this case, change "R _O , R _S " on page 22, line 20 of the specification. When and are wave vector of incident light and scattered / reflected light, k is wave number and n is refractive index, the focal plane is The optical path point Δl when moving only It is represented by. Now, when it is considered that the head recording medium relative speed is small, , N = 1, Δl becomes approximately Δ1 to 2Δγ, which causes the movement of interference fringes of one wavelength with respect to the projection of half a wavelength. This movement amount / direction may be detected to determine / avoid by the above method.

Lastly, it will be described that when the medium defect detecting and avoiding means according to the present invention is incorporated into an actual apparatus and used, the reliability is further enhanced. As can be understood from what has been described above, first, if there are many defects (protrusions) on the recording medium during recording, it is expected that skip (avoidance) operations will occur frequently and the processing capability will decrease. However, this suggests that the recording capacity of the medium has deteriorated and is considered to be a sign of medium deterioration. Therefore, processing such as recording on the replacement track and exchanging the recording medium itself is executed. In this case, the error detection means also functions as the recording medium deterioration prevention means.

Next, suppose that a defect (protrusion) is detected during repeated reproduction although the recording was normal. In this case, it suffices to be able to relieve within the range of the error correction function that is usually provided, but if it gets worse, the same check function as described above will be activated. Further, when the reproduction is absolutely necessary, it is possible to perform a contact reducing operation such as reducing the degree of the defect jump.

The improvement in reliability by these systematic means is due to the fact that it has a means for detecting defects (protrusions), and it has been possible to improve both the reliability of data and the reliability of heads and recording medium parts in the past. It is clear that it has no advantages.

EFFECTS OF THE INVENTION As described above, according to the present invention, the following magnetic head collides with a defect or the like by detecting the defect or the like with the preceding optical head that coincides with the recording medium moving direction. Since it is configured to avoid the above, it is possible to prevent a decisive crash factor of the magnetic head. Further, according to the present invention, since the focused beam is used as a means for detecting a defect or the like, it is possible to detect a defect or the like with a high accuracy of 1 μm or less, and the height, size, etc. of the defect or the like can be obtained using a simple circuit. The magnetic head does not come into contact with the above-mentioned defects, protrusions, foreign matter, etc. on the medium, and the magnetic support is used by using the systematic support together. There is an advantage that the head, the recording medium, and the recorded information can be highly reliable.

Further, the magnetic head has the advantage that the floating gap with the recording medium can be reduced to the marginal limit because of the above advantage, and thus high density recording can be performed. Further, since the components of the present invention can be used as general-purpose components and can be constructed within the range of existing assembly technology, there is an advantage that they are small in size, inexpensive, and excellent in productivity.

[Brief description of drawings]

FIG. 1 is a structural explanatory view showing an outline of a main part of a magnetic recording / reproducing apparatus and a recording medium to which the present invention is applied, FIGS. 2 and 3 are explanatory views of a focus servo detecting structure, FIG. 4 and FIG. FIG. 6 is an explanatory view of a tracking servo configuration, FIG. 6 is a time chart explaining an operation of detecting / determining a defect of a recording medium,
FIG. 7 is a time chart for explaining the operation of avoiding the magnetic head. 1 ... Optical head, 2 ... Magnetic head 3 ... Light source, 6 ... Optical lens 7,8 ... Actuator 12 ... Gimbal, 16 ... Recording medium

Claims (1)

[Claims] 1. A magnetic recording / reproducing apparatus for recording / reproducing information via a magnetic head 2 between a recording medium 16 composed of a magnetic thin layer formed on a rigid body or a flexible substrate, and an optical lens 6 The optical head 1 including the actuators 7 and 8 to which the optical lens 6 is attached is provided so as to match the moving direction of the recording medium 16 and precedes the magnetic head 2, and the actuators 7 and 8 are provided.
8 is connected to the magnetic head 2 via a gimbal 12, and means for detecting defects, protrusions, foreign matters, etc. on the surface of the magnetic thin layer in response to focus control of the optical head 1. , When the defect or the like is detected, in response to focus control of the optical head, it is determined whether or not the height and / or size of the defect or the like is a certain value or more, and A magnetic recording / reproducing apparatus comprising means for avoiding an operation of recording or reproducing information by the magnetic head 2 if the value is a certain value or more.