Patent Publication Number: US-6219332-B1

Title: Slider for optical disc data storage system

Description:
This is a Divisional patent application of U.S. Ser. No. 08/920,243, filed Aug. 28, 1997 now U.S. Pat. No. 5,870,362, which is based on Provisional application No. 60/050,409, filed on Jun. 20, 1997. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates generally to optical disc data storage systems. More specifically, the present invention relates to a slider for use in an optical head gimbal assembly of an optical disc data storage system. 
     Optical data storage disc systems are a promising technology for storing large quantities of data. The data is accessed by focusing a laser beam onto a data surface of the disc and detecting light reflected from or transmitted through the data surface. 
     In general, in optical storage systems, data is in the form of physical or magnetic marks carried on the surface of the disc which are detected using the reflected laser light. There are a number of different optical disc technologies which are known in the industry. For example, compact discs are currently used to store digital data such as computer programs or digitized music. Typically, compact discs are permanently recorded during manufacture. Another type of optical system is write-once read-many (WORM) systems in which a user may permanently write information onto a blank disc. It is also desirable to provide a system which is erasable, such as phase change and magneto-optic (M-O) systems. Phase change systems detect data by sensing a change in reflectivity. M-O systems read data by measuring the rotation of the incident light polarization due to the storage medium. 
     High density optical recording, particularly for near-field recording (i.e., M-O or phase change systems) typically requires an optical head gimbal assembly (OHGA) for carrying the transducing device over the data surface of the optical media. The OHGA includes a slider which “flies” proximate the data surface of the optical disc as the disc rotates at a high speed. An actuator is used to radially position the slider over the disc surface. U.S. Pat. No. 5,497,359 shows an example of a slider for use with an optical disc data storage system. 
     Optical disc data storage systems which use the “near field” (or evanescent field) include a Solid Immersion Lens (SIL). Such near field technology is shown in U.S. Pat. No. 5,125,750 to Corle et al. which issued Jun. 30, 1992 entitled “OPTICAL RECORDING SYSTEM EMPLOYING A SOLID IMMERSION LENS” and in U.S. Pat. No. 5,497,359 to Mamin et al. entitled “OPTICAL DISC DATA STORAGE SYSTEM WITH RADIATION-TRANSPARENT AIR-BEARING SLIDER” which issued Mar. 5, 1996. Typical SIL structures include a hemispherical lens cap positioned on a top side of the slider and an optical mesa structure positioned on the air bearing side of the slider. The optical mesa must be positioned very close to the data surface of the optical disc in order for their to be near field optical coupling. Typically this is on the order of less than a few wavelengths. 
     SUMMARY OF THE INVENTION 
     The present invention provides a slider having a mesa which is protected from contact with the optical disc data storage system. In an optical disc data storage system, an optical disc includes a data surface. An actuator arm having a distal end is selectively radially positioned adjacent the data surface. A transducing element including an optical source is provided for transducing information. A controller coupled to the actuator arm and the transducing element positions the actuator arm and transduces information on the data surface through the transducing element. A slider coupled to the distal end of the actuator arm carries the transducing element. The slider includes a top surface, and an air bearing surface adapted to move adjacent the data surface as the disc rotates. A mesa is carried on the air bearing surface. In one aspect of the present invention, the air bearing surface includes a protrusion. The optical mesa is spaced apart from the protrusion in a direction away from the data surface whereby the protrusion prevents contact between the data surface and the optical mesa. Another aspect of the invention includes pitching the slider whereby the mesa does not contact the data surface. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a simplified diagram showing an optical storage system in accordance with the present invention. 
     FIG. 2 is a side plan view of the slider of FIG. 1 in accordance with one embodiment of the present invention. 
     FIG. 3A is a bottom plan view and FIG. 3B is a side plan view of a slider in accordance with another embodiment. 
     FIG. 4 is a bottom plan view of a slider having protrusions in accordance with another embodiment. 
     FIG. 5 is a side plan view of a slider having a protrusion between a rail of the slider and a mesa in accordance with another embodiment. 
     FIG. 6A is a side plan view and FIG. 6B is a bottom plan view of a slider in accordance with another embodiment in which the pitch of the slider is used to space the mesa apart from a data surface of an optical disc. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention relates to optical data storage systems. In particular, the present invention relates to sliders for use with optical data storage systems which employ near-field (or evanescent field) optical recording techniques having a slider for carrying a transducing head to optically couple to a data surface to read and/or write information thereon. Such optical data storage systems use a slider to carry the optical transducing elements adjacent the data surface of an optical storage medium such as an optical disc. U.S. Pat. No. 5,497,359 issued Mar. 5, 1996 entitled “OPTICAL DISC DATA STORAGE SYSTEM WITH RADIATION-TRANSPARENT AIR-BEARING SLIDER” illustrates one slider designed for optical recording. 
     When optically recording information using the near field (or evanescent field) the optical transducing element includes, for example, a Solid Immersion Lens (or SIL) carried on the slider which flies over the magnetic disc. Such a Solid Immersion Lens is shown in U.S. Pat. No. 5,125,750, entitled “OPTICAL RECORDING SYSTEM EMPLOYING A SOLID IMMERSION LENS.” To write a bit of data on the disc, a laser heats up a small spot on the disc through the Solid Immersion Lens to a temperature above the Curie temperature of the medium. A magnetic coil carried on the air bearing surface of the slider is energized and the laser is turned off. As the magnetic medium cools below the Curie point, the heated spot is left with the desired magnetic orientation. 
     Solid Immersion Lenses include a hemispherical pattern or lens cap positioned on a top surface of the slider and an opposed optical mesa located on the air bearing surface of the slider. One aspect of the present invention is the recognition that the optical mesa is a key element in optical recording and even minor degradation in its optical characteristics can significantly affect system performance. In typical prior art sliders, no effort was made to protect the mesa from undesirable contact with the data surface. Further, in typical prior art systems it was possible for particulate build up to occur on or in the vicinity of the mesa. These conditions can change the optical properties of the mesa. The present invention further includes recession of the mesa relative to a protrusion which extends from the air bearing surface. The protrusion thereby ensures that the mesa is always spaced apart from the data surface during operation of the optical disc storage system. 
     FIG. 1 is a simplified illustration of an optical recording system  10  employing a slider  20  in accordance with the present invention. System  10  includes optical disc  12  having a data surface which carries optically encoded information. Disc  12  rotates about spindle  14  and is driven by a spindle motor  16  mounted on base  18 . The slider  20  is positioned proximate disc  12  and is coupled to an actuator  22  which includes armature  24  and actuator motor  26  which couples to base  18 . Slider  20  includes an optical transducer  30 . An optical transducing element includes optical source/sensor apparatus  32 . A controller  34  couples to apparatus  32 , actuator  26  and data bus  36  and is used for controlling operation of system  10 . 
     During operation, disc  12  rotates and slider  20  is positioned radially along the data surface of disc  12  using actuator  22 . Controller  34  controls the position of slider  20 , whereby information may be read from the data surface of disc  12  using optical source/sensor apparatus  32  and received or transmitted over data bus  36 . 
     FIG. 2 is a simplified side view of slider  20  in accordance with the invention and shows transducer element  30 . Slider  20  is shown proximate data surface  48  of optical disc  12  which is illustrated as a series of asperities. Transducer element  30 , in the embodiment shown, includes a SIL-type (Solid Immersion Lens) lens (which is formed by lens cap  50  and of the body of slider  20 ) and electrical conductors  52  formed in a coil shape. Conductors  52  are coiled about optical mesa  54  in accordance with the present invention. Slider  20  includes an air bearing surface  56  and a top surface (or opposing surface)  58 . Mesa  54  is carried on air bearing surface  56 . Disc  12  rotates in the direction indicated by arrow  60  whereby slider  20  has a leading edge  62  and a trailing edge  64 . 
     In accordance with the present invention, slider  20  shown in FIG. 2 includes a protrusion  70  on air bearing surface  56  which extends in a direction toward data surface  48 . Protrusion  70  acts as an air bearing contact region and extends a distance d below the distal edge of mesa  54 . Also shown in the embodiment of slider  20  is an air bearing rail  72 . Protrusion  70  provides a contacting island region wherein the mesa is recessed from the distal edge of the protrusion  70  in a direction away from the data surface. This configuration prevents damage to the mesa, wear to the mesa, or debris build up on the sensitive optical surface. 
     The embodiments set forth herein can be fabricated using known techniques such as ion beam etching, machining, lapping, chemical etching, or deposition processes. Preferably, the slider air bearing surface  56  is adapted for interaction with the data surface  48  based upon characteristics of the medium. In general, the recession of the mesa structure with respect to the distal surface may be achieved through any appropriate technique including the physical recession as set forth in FIG. 2 or other techniques such as using the pitch of the air bearing to locate the mesa “upwardly” from the air bearing surface to thereby avoid damage and debris accumulation. 
     FIG. 3A is a bottom plan view and FIG. 3B is a side plan view of a slider  100  in accordance with another embodiment. In FIGS. 3A and 3B, sacrificial wear pads  102  on the air bearing surface  56  of slider  100  are provided. For simplicity, similar elements have retained their numbering from FIG.  1 . This design is particularly well suited for a very low contact force design in which continuous contact between data surface  48  and sacrificial wear pads  102  occurs. Preferably, the total wear on the sacrificial wear pads  102  is less than the distance d by which the mesa is recessed from the wear pads. This design is particularly well suited for many portable applications. The sacrificial pads  102  provide protrusions in accordance with the present invention. 
     FIG. 4 is a bottom plan view of a slider  120  in accordance with another embodiment. In the embodiment of FIG. 4, wear pads (or protrusions)  112  are positioned closer to the leading edge  62  of air bearing surface  56 . The pads form a tripod configuration for stability. However, other configurations are considered to be within the scope of the invention. 
     FIG. 5 is a side plan view of a slider  130  in accordance with another embodiment. In the embodiment of FIG. 5, slider  130  includes wear pad or protrusion  132  positioned between mesa  54  and rail  72  to provide the desired recess d. The embodiment of FIG. 5 provides a hybrid design in which the air bearing characteristics of rail  72  provide the desired stiffness for operation and reduced sensitivity to mechanical vibration of slider  130  while any contact occurs on sacrificial wear pad  132 . 
     FIGS. 6A and 6B are side plan views and bottom plan views, respectively, of a slider  140  in accordance with another embodiment of the present invention. In the embodiment of slider  140 , the pitch of the slider is used to achieve the spacing d between the mesa  54  and data surface  48 . In this design, the mesa  54  is located adjacent rails  72 . A trailing pad  142  provides a minimum spacing s at the trailing edge  64  of slider  140  between the air bearing surface  56  and the data surface  48 . In this embodiment, the rails  72  and/or trailing pad  142  provide a protrusion in accordance with the present invention. The sliders set forth herein may be fabricated in accordance with any appropriate technique for processing of optical sliders. Furthermore, although the present invention has been illustrated with a Solid Immersion Lens optical element, any appropriate optical element may be used which has a mesa or other protruding optical element for coupling to the data surface through the near field. 
     Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention. The invention may be used with any type of slider design. Further, the protrusion can be positioned to deflect particulate contamination from impacting or building up proximate the mesa.