Patent Application
20050023490
The invention relates to handling media such as data storage media. In particular, the invention relates to sensing the position of an edge of a data storage medium.
Sensing the position of one or more edges of a data storage medium, such as magnetic tape, is useful in many circumstances. For example, the capability to sense an edge position is useful in research and development of the medium itself. Information about edge position may be useful for determining whether the medium is of the proper width, for example.
Information about edge position may also be useful when evaluating performance of a media-handling device, i.e., devices such as drives that move media of a particular kind in a controlled fashion. For example, this information may be valuable when inspecting, troubleshooting or calibrating the media-handling device. Information about edge position may also be used during ordinary operation of the media-handling device. A media-handling device may use such information to control the motion of the medium, for example, or to control a head that reads data from or writes data to the medium.
In general, the invention is directed to devices and methods for sensing one or more edges of a data storage medium. An edge sensor in a media-handling device optically senses the edge of the medium. The edge sensor includes a light emitter that emits a beam of light, a mirror that reflects at least a portion of the emitted beam and a collector that receives at least a portion of the reflected portion of the emitted beam. The edge sensor is deployed so that the medium may block some of the light, preventing the light from being collected by the collector. When the edge of the medium is in one position, the medium blocks more light than when the edge is in another position. Accordingly, the amount of collected light is a function of the position of the edge.
In one embodiment, the invention is directed to an edge sensor that includes the light emitter and collector disposed on one side of the data storage medium, and the mirror disposed on the other side of the medium. In another embodiment, the invention is directed to an edge sensor in which at least a portion of the emitted beam of light is directed obliquely to a plane defined by the data storage medium.
These embodiments are useful in many kinds of media-handling devices, including media-handling devices such as drives that employ automatic loading of the medium. Edge sensors constructed in accordance with the invention do not encroach upon the path of the medium and do not come in contact with the medium during loading. The mirror may be deployed to define a clearance that separates the mirror from contact with the medium. As a result, it is not necessary for the automatic loading apparatus to avoid the edge sensor during load; nor is it necessary to move the edge sensor out of the way during loading.
In these embodiments of the invention, the light emitter may include a light source. A typical light source may comprise a laser or a light emitting diode. Similarly, the collector may include a detector that generates a signal as a function of the quantity of light received by the collector. A typical detector may comprise a single-cell photodiode.
Various embodiments of the invention include optical elements to direct the light. Such optical elements may include a beam-splitter, another mirror, a collimating apparatus, a lens or focusing apparatus, and optical fibers.
In another embodiment of the invention, a light source and a detector may be coupled externally to the media-handling device, supplying light to the emitter by and receiving light from the collector by one or more optical conduits. This embodiment is directed to a device comprising a first optical conduit configured to emit a beam of light when a light source is coupled to the first optical conduit, a mirror to reflect at least a portion of the emitted beam, and a second optical conduit configured to receive at least a portion of the reflected portion of the emitted beam, and configured to be coupled to a detector. This embodiment may be advantageous in applications such as inspection, troubleshooting and calibration of media-handling devices, or in other circumstances in which it may not be practical or economical to install a light source and detector in a media-handling device.
In a further embodiment, the invention is directed to a media-handling device that includes an edge sensor as described herein.
In an additional embodiment, the invention presents a method comprising emitting a beam of light from a first side of a medium, and collecting at least a portion of the emitted beam on the first side of the medium. The collected portion of light includes light reflected in a mirror disposed on a second side of the medium and unblocked by the medium.
The various embodiments may offer one or more advantages, some of which have already been mentioned. The various embodiments of the invention may be incorporated into the design of a media-handling device, or may be added on to a previously existing design. The invention is versatile in application, and although the invention will be described in the context of magnetic tape and a tape-handling device, the invention may be configured to work with a variety of media and media-handling devices.
The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.
The exemplary media-handling device shown in
Although the invention will be described in the context of handling magnetic tape, the invention has applicability to devices that handle other media. The media may be in tape form, such as optical recording tape, or in some other form, such as a disk. Moreover, the invention may be applied to contexts other than writing or reading data from a medium.
In tape-handling device 10, head 12 may include one or more transducers for reading data from the tape or writing data to the tape. When exemplary device 10 is handling the tape, the tape follows a tape path 14. The tape may be stored in a cartridge or on a reel (not shown), and may be drawn across a guide 16. The tape may then be drawn across a bearing element 18, which positions the tape for reading or writing by head 12. After the tape has passed head 12, the tape may be drawn across a second bearing element 20, which may be structurally similar to bearing element 18.
Bearing element 18 includes a bearing surface 22. When tape following tape path 14 is pulled taut, the tape contacts bearing element 18 on bearing surface 22. As shown in
Lateral tape motion may interfere with reading from or writing to a tape. The data stored on the tape may be organized into “data tracks,” and head 12 may write data to or read data from the data tracks, or both. A typical tape includes several data tracks. For proper data storage and recovery, head 12 must locate each track where data are to be written or read, and follow the path of the data track accurately along the media surface. A servo controller (not shown) typically is provided to control the positioning of head 12 relative to the data tracks.
To facilitate reading and writing, pre-recorded servo position information may be included at pre-selected sites on the tape. This servo position information may be used by the servo controller to control the motion of head 12 when seeking between tracks, and to regulate the position of head 12 on a data track during reading and/or writing. The servo information is stored in specialized “servo tracks” on the tape. Under ordinary operating conditions, the servo controller may compensate for lateral tape motion by monitoring the position of the servo tracks.
Exemplary tape-handling device 10 includes an automatic loading apparatus 28. Automatic loading apparatus 28 retrieves an end of the tape and pulls the tape along tape path 14. In
In the example of
Exemplary tape-handling device 10 includes a stand-alone edge sensor 40. Tape-handling device 10 further includes an edge sensor 42 incorporated into bearing element 18.
Stand-alone edge sensor 40 may be coupled to bearing element 18. Stand-alone edge sensor 40 may be deployed at any site along tape path 14. Accordingly, stand-alone edge sensor 40 may be added to a previously established configuration of a tape-handling device. In other words, stand-alone edge sensor 40 may be an “add-on” sensor, and may be anchored to the tape-handling device in any fashion.
Edge sensor 42, by contrast, is built into bearing element 18 of tape-handling device 10. That is, bearing element 18 serves as an anchor for edge sensor 42. The deployment of edge sensor 42 shown in
In
Many embodiments of edge sensors will be described below. Notably, edge sensors 40, 42 do not encroach upon tape path 14. In particular, when automatic loading apparatus 28 loads the tape along tape path 14, the tape will not come in contact with edge sensors 40, 42. Consequently, automatic loading apparatus 28 need not be modified to load the tape around either edge sensor 40, 42. Further, edge sensors 40, 42 need not be retracted or otherwise moved when the tape is loaded along tape path 14.
In the embodiment of edge sensor 50 shown in
The beam portion 60 that passes through beam splitter 56 is directed toward a fully reflective mirror 62. In
Reflected beam 64 strikes beam splitter 56. A known fraction 66 of reflected beam 64 passes through beam splitter 56 and is lost. The remaining portion 68 reflects from beam splitter 56 and is directed to a collector 70, which receives remaining portion 68. Collector 70 may include a detector that responds to the light collected by collector 70. For example, the detector may generate a signal as a function of the quantity of light received by the collector. An exemplary detector is a single-cell photodiode that generates an electrical signal as a function of the intensity of the detected light. The electrical signal may comprise a voltage signal, for example, that varies with the lateral tape motion. An example of a photodiode that may be used as a detector is a reverse biased, high-speed response silicon detector, approximately 15.0 square mm, with a responsivity of 0.55 A/W at a wavelength of 900 nm.
The detector may also include a signal processing module to process the generated signal. The signal processing module may, for example, compute the position of the edge of the tape as a function of the amount of light collected by collector 70. In some embodiments, the computed position of the edge may be used to finely adjust the tracking of head 12 during reading and writing operations. In other embodiments, the computed position of the edge may be used to inspect or troubleshoot the media-handling device.
The invention encompasses other kinds of detectors as well. Furthermore, the invention encompasses embodiments in which the collector need not include a detector. Some embodiments described below, for example, include a collector that is physically separated from a detector.
Beam splitter 56 may be disposed so as to allow different positions of light emitter 52 and collector 70. Use of beam splitter 56 causes some loss of light intensity, however, so edge sensor 50 is ordinarily calibrated to ignore losses of intensity that may be due to beam splitter 56.
The physical components of edge sensor 50, particularly light emitter 52, beam splitter 56, reflective mirror 62 and collector 70, may be coupled to a rigid framework or base (not shown). Coupling the components to a base preserves the alignment of the components with respect to one another, and also keeps the components at known distances from one another.
In a typical operation, not all of the portion 60 of incident light that passes through beam splitter 56 will strike reflective mirror 62. A tape will ordinarily block a fraction of incident light portion 60 from striking reflective mirror 62 and consequently being received by collector 70. As the tape blocks more of incident light portion 60, collector 70 collects less light, and consequently a detector coupled to collector 70 senses less light intensity. Conversely, as the tape blocks less of incident light portion 60, a detector coupled to collector 70 senses more light intensity. The intensity of the light reaching collector 70 is a function of the fraction of light blocked or not blocked by the tape, and the fraction of light blocked or not blocked by the tape is a function of the position of edge of the tape. In this way, the quantity of light received by collector 70 is a function of the position of the edge of the tape.
The tape may bear against a bearing surface 72, shown in dashed lines in
As depicted in
Edge sensor 50 may therefore be deployed as part of a bearing element that includes bearing surface 72. In other words, edge sensor 50 may be deployed in a manner like edge sensor 42 in
In
Tape 80 moves past edge sensor 50 along the tape path direction indicated by reference numeral 84. Reference numeral 86 identifies the direction of “lateral motion,” i.e., a motion that is perpendicular to the direction of motion 84, with the tape bearing against bearing surface 72. In general, edge sensor 50 detects motion of tape 80 in lateral motion direction 86. Lateral motion of tape 80 causes edge 88 of tape 80 to move in lateral motion direction 86, causing tape 80 to block more or less light emitted by light emitter 52. When tape 80 blocks more light, collector 70 receives less light, and when tape 80 blocks less light, collector 70 receives more light.
Beam angle θ is a value between zero and 90 degrees. If beam angle θ were zero degrees, then the rays in the emitted beam would strike tape 80 perpendicularly, rather than obliquely. If beam angle θ were ninety degrees, then the rays in the emitted beam would not strike tape 80 at all, because the rays would be parallel to the plane defined by tape 80. In a typical application, beam angle θ may be approximately 45 degrees, but the invention encompasses embodiments in which other oblique angles are employed.
Tape 80 defines a plane and a perpendicular even if tape 80 is not strictly planar. A tape drawn across bearing surface 22 shown in
Because light emitter 52 emits a beam of light obliquely to the plane of tape 80, mirror 62 may be deployed so as to define a clearance 92 with respect to edge 88 of tape 80. Clearance 92, which separates mirror 62 from contact with tape 80, is useful when tape 80 is loaded by an automatic loading apparatus, such as automatic loading apparatus 28 shown in
In particular, automatic loading of tape 80 will not bring tape 80 in contact with light emitter 52, beam splitter 56 or collector 70, because those components are disposed on the posterior side of bearing surface 72. Furthermore, automatic loading of tape 80 will not bring tape 80 in contact with mirror 62 because of clearance 92. Even though tape 80 may approach bearing surface 72 from the anterior side, and even though mirror 62 is disposed on the anterior side of bearing surface 72, tape 80 does not contact mirror 62 because mirror 62 is deployed to provide clearance 92.
In this way, light emitter 52 emits a beam of light obliquely to the plane of tape 80, resulting in clearance 92, which facilitates automatic loading of tape 80. During loading, edge sensor 50 need not be moved to avoid tape 80 during the loading process. Furthermore, tape 80 need not be moved in any special fashion to avoid edge sensor 50. This is advantageous when edge sensor 50 is added to a previously frozen configuration of a tape-handling device. Edge sensor 50 will not interfere with an automatic loader that is already in use.
The amount of light collected by collector 70 is a function of the motion of tape 80. In particular, the amount of light collected by collector 70 is a function of the position of edge 88. In addition, the amount of light collected by collector 70 is a function of beam angle θ. As tape edge 88 moves in lateral motion direction 86, the amount of light blocked by tape 80 varies according to a trigonometric function of angle θ.
The amount of light blocked by tape 80 is a function of movement in lateral motion direction 86 and also on the amount of “out of plane” movement of tape 80, i.e., the amount of motion of tape 80 away from bearing surface 72. In a typical application, however, tape 80 is taut against bearing surface 72, and the amount of “out of plane” motion is negligible.
Unlike edge sensor 50, however, edge sensor 100 does not include a beam splitter. As a result, none of the beam emitted by light emitter 52 is lost by passing through a beam splitter. Portion 102A of the emitted light strikes tape 80 and is blocked. The remaining portion 102B does not strike tape 80, reaches reflective mirror 62, and is reflected.
Mirror 62 is deployed at an angle φ (not necessarily the same angle φ shown in
Because edge sensor 100 does not include a beam splitter, light intensity is not lost by beam splitting. In some embodiments, the absence of a beam splitter may be advantageous.
Edge sensor 110 does not include a beam splitter, nor does edge sensor 110 include a second mirror like mirror 106 shown in
In the embodiment of
Collimating assembly 122 does not detect any qualities of the collected light, such as the intensity of the collected light. Rather, detector 132 detects the collected light. Detector 132 is optically coupled to collimating assembly 122 by optical conduit 128. Like light source 126, detector 132 may be deployed at any location. As shown in
Optical conduit 128 includes one or more optical fiber. As shown in
The proximal ends of dedicated fiber optic conduits 128A and 128B terminate in sockets 134 and 136, to which light source 126 and detector 132 may be detachably coupled. The advantages associated with having a detachable light source 126 and detector 132 will be discussed below. The invention also includes embodiments in which light source 126 and detector 132 are installed inside media-handling device 130 and are not easily detachable.
In the embodiment depicted in
A light source 126 generates the beam of light that is emitted by collimating assembly 142. Light source 126 is optically coupled to collimating assembly 142 by a dedicated optical conduit 148. Detector 132 is optically coupled to collector 144 by a dedicated optical conduit 150. Detector 132 may be deployed at any location, including exteriorly. Because light source 126 and detector 132 do not share any optical paths, light losses that affect edge sensor 120 need not affect edge sensor 140.
Similar to edge sensor 120 shown in
In embodiments of the invention depicted in
The operator couples a light source or a detector or both to the media-handling device (160), e.g., by coupling the light source and detector to sockets that optically link the light source and detector, respectively, to a light emitter and collector deployed in the interior of the media-handling device. The operator uses the light source and detector to detect the position of the edge of a medium handled by the media-handling device (162).
An exemplary technique for edge detection includes causing the medium to move (164). In the case of tape-handling device 10, for example, the operator may cause tape-handling device 10 to thread a tape along tape path 14 and move the tape past head 12. The operator may also cause tape-handling device 10 to read data from or write data to the tape. While the medium is in motion, the operator may activate the light source, thereby generating light (166) that is transmitted by an optical conduit to the light emitter, where the light is emitted. At least a portion of the emitted light strikes a mirror and is reflected back to a collector, which transmits the reflected light by an optical conduit to the detector for detection (168). The position of the edge of the medium is a function of the quantity of light detected.
The operator may use the detected light for any purpose. In a typical application, the operator assesses the performance of the media-handling device. The operator may further calibrate the device to improve performance (170). When the operator is finished, the operator may disconnect the light source and detector from the media-handling device (172).
The various embodiments of the invention depicted in
Light emitter/collector 182 emits a beam of light that is substantially focused. In particular, light emitter/collector 182 includes a focusing element, such as a lens or a shaped end of an optical conduit, to substantially focus the emitted beam and concentrate the light at a focal spot. The focused rays of light are directed obliquely with respect to the plane of tape 80, but the rays are directed at a variety of different angles due to focusing. Further, light emitter/collector 182 is deployed such that the focal spot that is proximate to edge 88 of tape 80. Mirror 184 is a spherical mirror, with a focus located proximate to the focal spot of light emitter/collector 182. Moreover, light emitter/collector 182 and mirror 184 are deployed such that an incident beam that strikes mirror 184 is reflected substantially back along the incident path of the beam, and is collected by light emitter/collector 182.
As shown in detailed view 188, which is an enlarged view of region 190, focal spot 192 is proximate to edge 88. Focal spot 192 need not be a sharp focal point. In the embodiment shown in
An advantage of edge sensor 180 is sensitivity in some applications. Edge sensor 180 can detect minute lateral motions, such as lateral motion of tape 80 of a few micrometers. The sensitivity afforded by a substantially focused beam of light may be greater than the sensitivity afforded by a collimated beam of light.
In an alternative embodiment, light emitter/collector 182 may be supplanted by a collimating assembly, light source, detector and optical conduit such as are depicted in
Elliptical mirror 202 has two foci. Incident light passing through one focus and striking mirror 202 will be reflected through the complementary focus. As shown in
Similar to edge sensor 180 shown in
The invention may offer one or more advantages, some of which are mentioned above. The various embodiments of the invention may be incorporated into the design of a media-handling device, or may be added on to a previously existing design. The various embodiments are configured to define a clearance, so that the mirror does not encroach upon the path of the medium, and so that an automatic loading apparatus can bring the medium proximate to the edge sensor without having to move the medium around edge sensor or retract or otherwise move the edge sensor.
The invention is versatile in application, and may be configured to work with a variety of media-handling devices. The invention is well suited for monitoring the edge of magnetic of optical tape, but the invention may be applied in other contexts as well. In some applications, the edge sensor may include a light source and detector installed in the media-handling device, and in other applications, the light source and detector may be attachable and detachable.
The invention encompasses a variety of deployments of components. The light emitter and collector, for example, may be deployed in a variety of positions. Beam splitters such as beam splitter 56, and mirrors such as mirror 106 may be deployed to direct incident or reflected light along paths in addition to those shown. One or more mirrors may also direct at least a portion of the emitted beam of light so that the light is directed obliquely with respect to the plane of the medium. Other optical elements, such as lenses and optical conduits, may be employed to direct incident or reflected light. The invention encompasses all of these variations.
Many embodiments of the invention have been described. Various modifications may be made without departing from the scope of the claims. For example, the invention is not limited to the particular kinds of mirrors shown. As described above, the mirror deployed on the anterior side of the medium may be a plane mirror, a spherical mirror or an elliptical mirror. The mirror may include any reflecting element, such as one or more prisms, a phase conjugate mirror, or one or more corner reflectors.
The embodiments of the invention depicted in
Furthermore, the depicted deployments of light emitter and collector are exemplary, and the invention is not limited to the deployments shown. In some deployments, the positions of light emitter and collector may be reversed from the positions shown in the figures, with the medium blocking a portion of the reflected light, rather than a portion of incident light.
Features described in connection with the figures may be combined to create additional variations of the invention. For example, features of
These and other embodiments are within the scope of the following claims.
