Classifications

• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
  • G11B5/62—Record carriers characterised by the selection of the material
  • G11B5/64—Record carriers characterised by the selection of the material comprising only the magnetic material without bonding agent
  • G11B5/66—Record carriers characterised by the selection of the material comprising only the magnetic material without bonding agent the record carriers consisting of several layers
• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
  • G11B5/02—Recording, reproducing, or erasing methods; Read, write or erase circuits therefor
  • G11B5/027—Analogue recording
  • G11B5/03—Biasing
• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
  • G11B5/02—Recording, reproducing, or erasing methods; Read, write or erase circuits therefor
• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
  • G11B5/02—Recording, reproducing, or erasing methods; Read, write or erase circuits therefor
  • G11B5/09—Digital recording
• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
  • G11B5/74—Record carriers characterised by the form, e.g. sheet shaped to wrap around a drum

Definitions

• This invention is in the field of magnetic signal processing involving signal storage and transfers relative to a magnetic storage medium. More particularly, it concerns a magnetic storage medium having, in addition to a high coercivity magnetic storage layer, a magnetically permeable layer in which adjacent regions of different permeabilities are selectably established that permits improved magnetic signal processing .
• magnetic flux to be transferred to or from a magnetic storage medium permeates a magnetic core of a magnetic transducer (head).
• this flux produces an induced output voltage in an associated coil winding which, after suitable amplification, is a reproduced representation of the magnetic flux that permeates the core suitable for use by a utilization device.
• the permeating flux results from current applied to the coil winding, and fringes from a physical gap provided in the core for recording a representative signal in the magnetic storage medium.
• Various losses typically occur during such transfers that affect the resulting signal quality adversely.
• spacing loss One of the more significant losses is called “spacing loss” and results from the physical spacing between the magnetic storage medium and the transducer.
• the spacing loss is particularly deleterious to reproduction operations, where the effects of such loss are more significant.
• Prior efforts to reduce spacing loss primarily involved reducing the physical spacing by placing the transducer as close to the magnetic storage medium surface as operating conditions permitted, This, however, is accompanied by increases in the likelihood of damaging collisions between the transducer and medium in devices in which the transducer is supported above the medium surface out of contact therewith, i.e., in which the transducer "flies" relative to the medium, or excessive medium and/or transducer wear in devices in which the transducer is in contact with the medium during signal transfer operations.
• Reproduce gap loss is an example of one of the sources of poor efficiency. This is caused by the finite length of the physical gap within the transducer that is responsible for effecting signal transfers between the transducer and medium, and is manifested by a loss of output signal at shorter wavelengths. Reproduce gap loss is considered to be an inherent result of transducer geometry.
• the present invention provides for the reduction in spacing loss without need, of moving the transducer physically closer to the medium. The quality of signals transferred relative to the magnetic storage medium can thus be improved without increasing the likelihood of damage or wear to the transducer and/or medium.
• the method and apparatus of the present invention permits improvement in the efficiency of signal transfers, such as by reduction of reproduce gap loss that enables transducers to achieve improved signal reproduction at short wavelengths.
• the cross-referenced, commonly owned patent applications referred to above concern arrangements of magnetic transducers and associated bodies of magnetic material that cooperate to form a transducing zone free of a physical gap for effecting signal transfers relative to a magnetic storage medium. More specifically, in the embodiments illustrated in the figures and described in these applications, the associated body of magnetic material is located to be magnetically proximate the magnetic storage medium and the transducer, with the transducing zone located for the coupling of flux between the body, transducer and the magnetic storage medium.
• magnetically proximate means that the body of magnetic material is positioned relative to the proximate object or field so that flux coupling between the two occurs, assuming that saturation or some similar magnetic affect does not prevent coupling.
• the preferred material of the associated body has a high absolute permeability and, as compared to magnetic storage media, low coercivity and low magnetic saturation density. Such a material is commonly designated a soft magnetic material and is to be contrasted with "hard” magnetic materials, i.e., materials having a high coercivity and magnetic saturation density, such as those that magnetically store information.
• Keepers are bodies of magnetic material having such characteristics. Keepers are commonly placed over the ends of permanent magnets to capture and provide paths for flux between the magnetic poles of the magnets to protect them against being demagnetized.
• the magnetic material typically used to make cores of magnetic transducers has characteristics similar to those of a keeper.
• the transducing zone is formed in the associated body or keeper by creating in the same one or more significant magnetic discontinuities, i.e., areas of substantially different magnetic permeability, such as typically are provided in magnetic transducers by the inclusion of a physical transducing gap.
• a permeability gradient provides such discontinuity, and in the embodiments of the cross referenced applications, it is preferred a steep permeability gradient be established between adjacent magnetically saturated and magnetically unsaturated regions that define the transducing zone.
• a steep permeability gradient also is desired in the preferred embodiments of the present invention. The nature of such gradient and a preferred manner of achieving the same will be described in more detail hereinafter. In the apparatus of the present invention, such discontinuity is most simply provided in the region defining the transducing zone by having adjacent magnetically saturated and unsaturated regions.
• a transducing zone can be easily generated and defined in the region through the cooperation of a physical gap in a conventional magnetic transducer and a source of magnetic bias flux. While in the embodiments of the cross referenced applications, this source of bias flux can be associated solely with the transducer or solely associated with the keeper body and, in some instances, associated with both of the same, in accordance with the present invention, the bias flux source is associated with the transducer. Moreover, during record operations, the source of bias flux simply can be provided by record signal flux passing through the region defining the transducing zone. As described in the cross referenced applications, the thickness of the keeper is important in determining the performance of the keeper. The selection of the thickness of the keeper depends on its purpose and its location.
• a well defined transducing zone is preferred, and for short wavelength signals, one having a short length. Relatively thin keepers are best for such operations. In applications where head and medium wear avoidance is important, such as In contact record and/or reproduce devices, a thicker keeper is preferred.
• the transduce-keeper-magnetic storage medium arrangement also can influence the keeper thickness. In any case, the thickness of the keeper is selected relative to potential flux therein to create the transducing zone at the location desired.
• the keeper engages the face of a magnetic core defining a physical gap so aa to physically bridge such gap and a predominant amount of the bias flux flows in the head as well as in the keeper
• the keeper is selected to be thin with respect to the core adjacent the gap, and the keeper-core cross-sectional area perpendicular to the bias flux path adjacent the gap is selected to be large, so the portion of the keeper which bridges the physical gap will have a high flux density, preferably one which saturates the region having the same.
• the permeability of the saturated regions is low, i.e., similar to nonmagnetic materials, while the permeability of the surrounding regions remains high. These regions cooperate to define a transducing zone within the body.
• a transducer having a keeper in close proximity of the transducer core and bridging the physical gap of the transducer is described in which the core is mechanically movable and the keeper is stationary. Means are associated with the transducer core and are coupled to provide a flux directed by the physical gap in the core to saturate the keeper in an area which bridges the physical gap. This saturated area represents a magnetically formed transducing gap.
• the keeper is interposed the transducer core and medium.
• the keeper eliminates wear of the physical transducer gap and, if the medium is in contact with the keeper during signal transfers, reduces spacing losses as well.
• the keeper and transducer core are in direct contact and stationary with respect to each other. This arrangement, too, eliminates direct physical contact between the physical gap in the transducer core and the medium, and in arrangements where the keeper is also in direct contact with the magnetic storage medium, reduces spacing losses.
• a magnetic recording medium that has, in addition to a high coercivity magnetic layer for storing magnetic signals, a magnetically permeable layer in which adjacent regions of different permeabilities are selectably established.
• the differentially permeable layer and high coercivity magnetic storage layer are separate discrete contiguous layers supported upon a substrate.
• a source of magnetic flux is arranged to direet a bias flux to the differentially permeable layer and locally establish therein adjacent regions of different permeabilities in a zone opposite to and bridging the physical gap of a magnetic transducer to form a virtual gap in the zone that functions as a gap-less transducing zone.
• the bias flux Upon application of the bias flux, the resulting establishment of adjacent regions of different permeabilities enables signal flux transfers between the magnetic transducer and the magnetic storage layer through the highly permeable areas adjacent the zone.
• the formation of the transducing zone in the differentially permeable layer contiguous with the magnetic storage layer functionally eliminates the physical spacing between the magnetic transducer and magnetic storage layer, and allows magnetic coupling between the magnetic core of the transducer and storage layer for the transfer of signals. It has also been unexpectedly found that signal transfers are improved at shorter wavelengths through use of the media of the present invention.
• Empirical plots (signal strength vs wavelength) for playback signal transfers of data indicate the presence of the differentially permeable layer in the media of the present invention causes a favorable shift towards shorter wavelength at which the first order, wavelength dependent null in response occurs (commonly referred to as "gap null").
• the differentially permeable layer in which the gap-less transducing zone is formed is a continuous, magnetically saturable layer of high permeability, low coercivity magnetic material that is an integral part of a laminated composite magnetic recording medium.
• the adjacent regions of different permeabilities are conveniently provided in preferred embodiments of the present invention by establishing adjacent magnetically saturated and unsaturated regions.
• the layer also advantageously serves to retain flux from signals recorded in the magnetic storage medium in absence of a bias flux that magnetically effects the formation of the transducing zone in the saturable layer.
• High permeability, nonsaturable underlayers have been used previously in perpendicular magnetic storage media to direct record flux along a well defined path and to provide a flux path for reproduction.
• the underlayera in these prior media are designed to be unsaturable by making them thick relative to the expected flux density during record signal transfers to the media.
• These underlayers do not function as the differentially permeable or saturable layer in the medium of the present invention, do not form a defined transducing zone for effecting signal transfers between transducers and media, and have no effect on spacing and reproduce gap losses, nor wear of magnetic transducers and storage media.
• a magnetic signal processing apparatus uses such magnetic storage medium.
• This apparatus includes magnetic flux generating moans, such as a permanent magnet associated with the transducer, an external bias coil in proximity to the transducer, or a source of auxiliary current coupled to the signal winding associated with the magnetic core of the transducer, for generating the bias field that forms the zone of adjacent regions of different permeabilities in the differentially permeable layer proximate the physical gap of the transducer.
• Existing magnetic record and/or reproduce devices may be readily modified to include such means. There is thus no need to radically redesign conventional transducers or record and/or reproduce circuitry in order to implement the advantages of the method and apparatus of the present invention in existing magnetic record and/or reproduce devices.
• the transducer and magnetic record medium surface may be spaced to lessen the likelihood of transducer and/or medium damage or wear, as there is no need to space them as close as possible to lessen spacing loss.
• Figure 1A is a schematic partial view of a conventional (prior art) magnetic medium and transducer in a reproduce operation mode
• Figure 1B is a schematic partial view of one embodiment of the magnetic record medium of the present invention in operative association with a magnetic transducer under a non-biased reproduce operation condition;
• Figure 1C is a view of the same arrangement as shown in Figure 1B under a biased reproduce operation condition
• Figure 2 is a schematic, partial view of a second embodiment of the magnetic record medium of the present invention in operative association with a magnetic transducer under a biased reproduce operation condition;
• Figure 3 is a schematic, partial view of a third embodiment of the magnetic record medium of the present invention in operative association with a magnetic transducer under a biased reproduce operation condition;
• Figure 4 is an example of a flux density versus permeability characteristic of a well known magnetic material
• Figure 5 shows flux density versus permeability characteristic across the length of a transducing zone established in the differentially permeable layer of an embodiment of the magnetic record medium of the present invention.
• Figure 6 is a block diagram of a system for recording and reproducing signals in relation to a magnetic record medium in accordance with the present invention.
• Magnetic record media embodiments in accordance with the present invention will be described now which are laminated composite structures having a high coercivity (hard) magnetic layer for receiving and storing magnetic signals, and a saturable, high magnetic permeability, low coercivity (soft) layer that effects the transfer of magnetic signal flux between a magnetic transducer and the high coercivity magnetic layer.
• a high coercivity (hard) magnetic layer for receiving and storing magnetic signals
• a saturable, high magnetic permeability, low coercivity (soft) layer that effects the transfer of magnetic signal flux between a magnetic transducer and the high coercivity magnetic layer.
• a magnetic record medium II comprising a substrate layer 12 made of a nonmagnetic material, such as aluminum or plastic, a hard magnetic layer 13 made of a high coercivity magnetic material, and an overlying magnetically saturable layer 14 made of a high magnetic permeability, low coercivity material, such as a Ni-Fe alloy (e.g., permalloy) or an Fe-A1 alloy (e.g., Alfesil).
• the high coercivity magnetic layer 13 may be in the form of magnetic particles dispersed in a binder or a continuous film of high coercivity magnetic metal or metal alloy.
• a magnetic transducer 15 In opposed spaced relationship to the medium 11, is a magnetic transducer 15 having a magnetic core 16 with confronting poles 17, 18 defining a physical gap 19 therebetween.
• the core 16 is fabricated from a magnetic material suitable for conventional magnetic transducers, such as ferrite, and preferably, a nonmagnetic material, for example glass or silicon dioxide, is provided between the poles 17, 18 of the core to obtain a well defined physical transducing gap 19.
• the magnetic core 16 defines a magnetic flux path for transferring information signals between the magnetic storage medium 13 and a means, such as a coil winding 20 disposed about the core.
• transducer core 16, poles 17, 18, transducing gap 19 and coil winding 20 may be made in a known manner and a detailed description thereof, is therefore, not provided.
• the magnetic record medium 11 may be made using fabrication techniques that are well known in the magnetic record media art, and a detailed description thereof is therefore not provided.
• the layer in media in which the hard magnetic layer 13 is made of a dispersion of magnetic particles in a binder, the layer may be deposited on a suitable substrate 12 using casting procedures commonly used to make conventional magnetic tape.
• the layer may be deposited by plating (electro or electroless) or sputtering.
• the magnetically saturable layer 14 may also be deposited by plating or sputtering.
• other layers, such as durable overcoats, or conducting coats may be included in the laminated composite.
• a conventional magnetic recording medium 11' comprising only a substrate layer 12 and a hard magnetic layer 13 is shown in Figure 1A.
• Digital or analog signals may be recorded on magnetic medium 11 in a conventional manner as is known in the art.
• Figures 1A-C illustrate the recording of digital signals in the magnetic storage layer 13 in longitudinal fashion.
• the recorded magnetic layer 13 is depicted as having a multiplicity of individual regions 21 in which the magnetic signals or bits (depicted by solid arrows) are stored.
• the axes of magnetization of the regions 21 are oriented horizontally relative to the plane of the magnetic layer 13.
• the bias flux emanating from the physical gap 19 of the transducer 11 permeates the high permeability, saturable layer 14 and creates a zone of saturation 23 in that layer proximate of the physical gap. Such saturation lowers the permeability in the zone 23, The zone thus defines an magnetically formed virtual gap in the layer. Because the zone 23 is saturated by the bias flux, the signal flux from magnetic storage layer 13 is not shunted through the zone. Instead, the signal flux from the storage layer 13 is directed to the magnetic core 16 of the transducer 11 through unsaturated regions of the saturable layer 13 adjacent the zone 23.
• the portion of the layer 13 located opposite the physical gap 19 of the transducer 11 functions to couple the signal between the transducer 11 and magnetic storage layer 13, and thereby functionally eliminating the physical spacing between the transducer and storage layer that contributes to spacing loss.
• the magnitude of the bias flux required to saturate zone 23 will depend upon the particular magnetic characteristics of the material forming the saturable layer 14 and the cross-sectional area of that layer in a direction perpendicular to the surface of the magnetic record medium 11 , hence the layer ' s thickness .
• the material characteristics and area of saturable layer 13 are selected relative to the magnetic characteristics and thickness of the high coercivity magnetic layer 14 such that the bias flux required to saturate the layer 13 and form zone 23 is less than the flux required to erase or otherwise undesirably alter or affect aignala recorded in the high coercivity magnetic layer 13. Further, the saturation value (flux density at saturation) of the saturable layer 14 should be. such that this layer is not saturated by the signal flux alone emanating from the magnetic record medium 11. The saturation value of the layer 14 is also a function of the magnetic characteristics of the material from which it is made and its thickness.
• the saturable layer have a sharp saturation transition in the B-H (flux density vs field strength) profile at the boundaries between the saturated zone 23 and adjacent unsaturated regions to enhance efficiency (reduce or minimize the portion of the signal flux that bridges the saturation zone 23 and thus does not contribute to signal transfers between the transducer 15 and magnetic storage layer 13).
• B-H flux density vs field strength
• the saturable layer 14 can be formed of materials, such as permalloy or Alfesil, commonly used to fabricate keepers for permanent magnets.
• the keeper layer is fabricated to provide a reluctance to flux along a path within the keeper relative to the reluctance along a path that extends through the magnetic core 16 of the transducer 15 (see 24 in Figure 1C) to assure that the desired transmission of information signals occur between the magnetic storage layer 13 and the magnetic core 16 of the transducer.
• the relative reluctances are achieved through the selection of appropriate combinations of various characteristics, such as materials, thickness of materials, size of area of transducer polea that face the magnetic record medium 11, size of area of saturated zone 23 of the keeper 14 in a plane perpendicular to the surface of the medium 11, thickness of the keeper layer 14, distance (if any) separating the transducer 15 and the keeper 14, and the length, width and depth, of physical gap 19.
• the keeper 14 has a very small thickness t in the direction of the depth of the physical gap 19 so as to have a small cross-sectional area at such gap for saturation by bias flux as will be described.
• Figure 4 shows a permeability ra versus flux density B characteristic of a suitable magnetic material for fabrication of the keeper layer 14, As seen from that characteristic, the material has a large difference in permeability over a narrow range of flux densities.
• Figure 5 illustrates the effect of saturating the keeper layer 14 at the localized zone 23. From Figures 4 and 5, it is seen that it is desirable that the overall permeability versus flux density gradient be as sharp as possible in order to obtain well defined boundaries between the saturated zone 23 and the adjacent unsaturated regions through which signal flux is coupled between the transducer 15 and magnetic storage layer 13.
• keeper layers 14 of permalloy having a thickness in the range of about 300 to 1000 Angstroms were deposited on a cobalt-phosphorus electroless plated magnetic storage layers 13 having a thickness in the range of about 700 to 1500 Angstroms.
• the thualy deposited keeper layer 14 had a magnetic coercivity of less than one, whereas the magnetic storage layer 13 had a coercivity of about 1000.
• the magnetic permeability of the keeper layers were in the range of 1000 to 2000 in the unsaturated regions. In the saturated region of the transducing zone 23, the permeability was in the range from that approaching 1 to about 100.
• the permeability difference between the adjacent saturated and unsaturated regions of the transducing zone 23 should be as large as practicable. However, a 10:1 ratio of unsaturated-to-saturated permeability will enable transfers of signal information between the transducer 15 and magnetic storage layer 13.
• the thickness of the keeper 14 influences the length of the transducing zone 23, i.e., the dimensions in the direction of separation of the poles 17 and 18 of the transducer 15. Moreover, keepers of greater thickness require more bias flux to establish the desired transducing zone.
• a well defined transducing zone of small length dimension is not as critical as for playback operations, because recording in the magnetic storage medium is primarily determined by the magnetic state occurrences at the trailing edge of the transducing zone 23, i.e., the edge of the transducing zone 23 last able to influence the recording on the medium 11 during relative motion between the transducer 15 and the medium 11.
• a well defined transducing zone 23 with a small length dimension is preferred.
• the thickness of the keeper layer 14 and the strength of the magnetic field bias for establishing the transducing zone 23 should be selected so that the length dimension of the transducing zone is not so large as to permit objectionable fringing flux wavelength dependent coupling from the physical gap 19 of the transducer 11 to the magnetic storage layer 13. Such objectionable coupling will occur at least when the length dimension of the transducing zone 23 becomes so large that It appears to the transducer 11 and magnetic storage layer 13 equivalent to an air space that exists in arrangements without a keeper layer 14, such as depicted by Figure 1A.
• the thickness and bias flux needed to achieve the desired reduction in playback loss can be determined empirically.
• FIG 2 shows a second embodiment of a magnetic record medium 11 of the present invention.
• the keeper layer 14 underlies (relative to the transducer 15) the hard magnetic layer 13.
• FIG IB when no bias flux is applied, flux from recorded signals in the hard magnetic storage layer 13 is captured by the underlying keeper layer 14 and shunted therethrough rather than being linked to the magnetic core 16 of the transducer 15.
• bias flux when bias flux is applied, however, the flux produces a magnetically formed high reluctance saturation zone 23 in the underlying keeper layer.
• signal flux transferred with respect to the magnetic storage layer 13 is directed along the path represented by dotted lines 24 between layer 13 and the high permeability magnetic core 16, rather than being shunted through the keeper layer 14 to adjacent magnetic transitions.
• Figure 3 shows another embodiment of the magnetic record medium 11 of the present invention that is similar to the embodiment of Figures 1B and 1C, except that the signals are recorded on the magnetic storage layer 13 in vertical (perpendicular) fashion.
• the axes of magnetization of regions 21 are substantially perpendicular relative to the plane of the hard magnetic storage layer 13.
• the signal flux recorded in the hard magnetic storage layer 13 is attracted by unsaturated regions of the overlying keeper layer 14 adjacent a magnetically formed high reluctance saturation zone 23, which is established by a bias flux from the transducer 15.
• the attracted signal flux is prevented from being shunted through the high reluctance saturation zone 23, it flows between the magnetic core 16 of the transducer 15 and the magnetic storage layer 13 along a path depicted by dotted line 24.
• Figure 6 shows a block diagram of a signal processing system 28 that uses a magnetic recording medium 11 corresponding to that described with reference to Figures 1B, 1C, 2 and 3.
• the medium 11 is shown in the form of a rigid disc. It will be appreciated that the method and apparatus of the present invention may be adapted to other forme of magnetic recording media, such as tape and flexible discs.
• Disc 11 is mounted on a motor spindle 32 for rotation beneath a magnetic transducer 15 that has a winding 20 for carrying current during record and playback operations.
• the single winding 20 is employed to carry the input signal and bias currents during record operation modes, and the bias and reproduce signal currents during playback operation modes. As described hereinbefore, if record current of sufficient strength is provided during record operation modes, a separate bias current need not be provided.
• a switch 36 In a record operation mode, a switch 36 is open and a switch 37 is in its first position (indicated by solid lines). Signal current from a source 38 is amplified by a record amplifier 39, and transmitted through switch 37 and line 40 to winding 20. This signal current generatea a signal flux in transducer 15 that leaves the physical gap of the transducer 15, permeates disc 11, and is recorded in the hard magnetic layer of the disc. The magnitude of the signal current is adjusted so that the flux that leaves the physical gap is sufficient to form the zone of saturation in the keeper that effects the desired signal transfer from before with reference to Figures 1-3.
• switch 36 In a reproduce operation mode, switch 36 is closed and switch 37 is in its second position.
• the closing of switch 36 couples an adjustable D.C. current source 48 to line 40.
• Source 48 provides the bias current, I b ias' that is transmitted through line 40 to winding 20.
• the bias current generates a bias flux that leaves the physical gap of the transducer to permeate the keeper layer of disc 11, thus creating the zone of saturation in the keeper that effects the coupling of recorded flux from the disc 11 to the magnetic core of the transducer 15.
• the reproduce signal flux intercepts the winding 20 and generates an induced voltage signal therein. This signal is transmitted by line 42 and switch 37 to a reproduce amplifier 43.
• the amplified playback signal is transmitted from the amplifier 43 to the utilization device 45.
• a capacitor 44 is connected in line 43 to block any DC component of the reproduce signal that may have been generated by the bias. If a bias source is needed for record operation modes, a similar capacitor is provided between the record amplifier 39 and switch 37 for the same purpose. While the embodiment of Figure 6 utilizes a D.C. bias to establish the saturated zone in the keeper layer of the disc record medium 11, the bias can be established various ways. For example, a permanent magnet in proximity to the keeper layer of the magnetic record medium can be employed to interact with the magnetic core of the transducer 15 and effect the localized saturation of the keeper layer needed to form a transducing zone. An A.C. current source may be employed as well. When using an A.C. bian it is preferred an A.C.
• current source be used providing transitions between bias signal states that are very fast relative to those of the information signals to be transferred relative to the magnetic record medium. If AC bias is used, it may be necessary to replace capacitor 44 with an AC filter to prevent unwanted bias-generated signals from being coupled into the reproduce circuitry.
• Synchronization of the motor 46 that drives the motor spindle 32 on which the disc is mounted is accomplished by a servo 47 that uses a tachometer signal provided by a tachometer mechanism operatively linked to the spindle 32, or a signal recorded on the disc record medium 11 along a dedicated servo track.
• servo 47 receives the tachometer, servo or equivalent signal and compares it with a system reference signal, and adjusts the motor drive, if necessary, to synchronize the rotation of the disc 11 to the system reference signal.

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• Magnetic Record Carriers (AREA)
• Recording Or Reproducing By Magnetic Means (AREA)
• Manufacturing Of Magnetic Record Carriers (AREA)
• Magnetic Heads (AREA)

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• 1986
  • 1986-12-15 JP JP62500601A patent/JP2704957B2/ja not_active Expired - Fee Related
  • 1986-12-15 WO PCT/US1986/002732 patent/WO1987003728A1/en not_active Application Discontinuation
  • 1986-12-15 EP EP19870900560 patent/EP0250560A4/en not_active Withdrawn
  • 1986-12-15 AU AU68474/87A patent/AU594998B2/en not_active Expired
  • 1986-12-15 KR KR1019870700719A patent/KR950000948B1/ko not_active IP Right Cessation

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