Abstract:
A retractable camera apparatus is disclosed. Through the use of the apparatus, a video teleconference environment can communicate, in real time, such personal features as gesture, expression and body language. The apparatus includes a housing portion, at least one arm portion coupled to the housing portion wherein the at least one arm portion is capable of being moved between a retracted position and a deployed position and a plurality of cameras coupled to the at least one arm portion.

Description:
FIELD OF THE INVENTION 
     This invention relates generally to digitizer input devices, and in particular to the use of soft-reference magnetic random access memory (commonly referred to as “MRAM”) as a digitizing array. 
     BACKGROUND OF THE INVENTION 
     Providing an alternative means of user input, digitizer systems are commonly found in an ever increasing variety of computer applications. Typically, a sensing array is responsive to a stylus used by a user to enter data directly upon the array. The placement and/or movement of the stylus in pointing, writing and or sketching upon the array is used to control various computer functions. 
     In some embodiments the digitizer is provided directly over the visual display monitor (a touch screen), whereas in other embodiments the digitizer is provided as a separate and apart from the display (a touch pad). Use and application of either may be employed in various types of computer systems including laptops, home systems, kiosk, or other system displays. 
     Several types of stylus input digitizing devices are known in the prior art. One type involves direct contact of a stylus tip against a capacitive-resistive array. When the tip of the stylus is placed proximate to an area of the digitizing surface, a capacitive-resistive circuit within the pad detects the placement of the stylus and computes its location according to well-known mathematical formulas associated with grid-based arrays. 
     Other types of prior art system use an RF transmitter to send signals from the digitizer to the stylus or vis-a-versa, or may use a light source (visible or infrared) within the tip of the stylus which is directed by the user upon desired portions of the digitizer pad. In such cases the location of the stylus is determined by a processor decoding information from RF or light receivers. Yet another type of prior art system uses a surface-acoustic wave (SAW) device. With SAW, two transmitters set up a surface acoustic wave on the surface of the digitizer. The position of a person&#39;s finger or other stylus is detected by the finger or stylus reflecting/disturbing the acoustic wave. 
     Another type of prior art system uses an electromagnetic digitizer. The input of data by the user is realized as the result of a magnetic field emanating from the user&#39;s stylus interacting with the magnetic field or fields of the digitizer. Typically a grid of intersecting lines produces a field that can be either actively or passively modified by the field emanating from the stylus. 
     Each of these systems has had some success, yet each also has limitations that make them difficult if not undesirable for use. For example, direct contact technologies are subject to scratches and wear during normal operation. Wire-grid electromagnetic technology is quite expensive to implement and often requires additional heavy magnetic shielding behind the wire array to shield the system from undesirable magnetic influence. Light and RF systems require sophisticated electronics both for the source and for the receiver. Additionally, each and every one of these systems requires continuous power be supplied to the digitizer array in order to maintain the affect of stylus interaction. 
     In an effort to overcome one or more of these disadvantages applicants have recently proposed the use of an array of magnetic memory cells (each cell having a sense layer, intermediate layer and pinned reference layer) to provide an improved digitizer. While indeed an improvement in some ways, use of pinned reference magnetic memory cells presents certain disadvantages. 
     Generally, the principle underlying the storage of data in a magnetic media is the ability to change, and/or reverse, the relative orientation of the magnetization of a storage data bit (i.e. the logic state of a “0” or a “1”). The coercivity of a material is the level of demagnetizing force that must be applied to a magnetic particle to reduce and/or reverse the magnetization of the particle. Generally speaking, the smaller the magnetic particle the higher it&#39;s coercivity. 
     A prior art magnetic memory cell may be a tunneling magneto-resistance memory cell (TMR), a giant magneto-resistance memory cell (GMR), or a colossal magneto-resistance memory cell (CMR). These types of magnetic memory are commonly referred to as magnetic tunnel junction memory (MTJ). A magnetic tunnel junction memory generally includes a sense layer (also called a storage layer, data layer or bit layer), a reference layer, and an intermediate layer between the sense layer and the reference layer. The sense layer, the reference layer, and the intermediate layer can be made from one or more layers of material. 
     The sense layer is usually a layer of magnetic material that stores a bit of data as an orientation of magnetization M 2  that may be altered in response to the application of an external magnetic field or fields. More specifically, the orientation of magnetization M 2  of the sense layer representing the logic state can be rotated (switched) from a first orientation representing a logic state of “0” to a second orientation, representing a logic state of “1”, and/or vice versa. 
     The reference layer is a layer of magnetic material in which an orientation of magnetization M 1  is “pinned”, as in fixed, in a predetermined direction. Often several layers of magnetic material are required and function as one to effectuate a stable pinned reference layer. The direction is predetermined and established by microelectronic processing steps employed in the fabrication of the magnetic memory cell. 
     Typically, the logic state (a “0” or a “1”) of a magnetic memory cell depends on the relative orientations of magnetization in the sense layer and the reference layer. For example, when an electrical potential bias is applied across the sense layer and the reference layer in a MTJ, electrons migrate between the sense layer and the reference layer through the intermediate layer. The intermediate layer is typically a thin dielectric layer commonly referred to as a tunnel barrier layer. The phenomena that cause the migration of electrons through the barrier layer may be referred to as quantum mechanical tunneling or spin tunneling. 
     The logic state may be determined by measuring the resistance of the memory cell. For example, if the overall orientation of the magnetization in the sense layer is parallel to the pinned orientation of magnetization in the reference layer the magnetic memory cell will be in a state of low resistance. If the overall orientation of the magnetization in the sense layer is anti-parallel (opposite) to the pinned orientation of magnetization in the reference layer the magnetic memory cell will be in a state of high resistance. 
     In an ideal setting the orientation of the alterable magnetic field in the sense layer would be either parallel or anti-parallel with respect to the field of the reference layer. As the sense layer and the reference layer are generally both made from ferromagnetic materials and are positioned in close permanent proximity to each other, the generally stronger reference layer may affect the orientation of the sense layer. More specifically, the magnetization of the reference layer may generate a demagnetization field that extends from the reference layer into the sense layer. 
     The result of this demagnetization field from the reference layer is an offset in the coercive switching field. This offset can result in asymmetry in the switching characteristics of the bit: the amount of switching field needed to switch the bit from parallel to anti-parallel state is different from the switching field needed to switch the bit from anti-parallel state to parallel state. To have reliable switching characteristics and to simplify the read/write circuitry, it is desirable to have this offset reduced to as near zero as possible. 
     The magneto-resistance ΔR/R may be described as akin to a signal-to-noise ratio S/N. A higher S/N results in a stronger signal that can be sensed to determine the state of the bit in the sense layer. Thus, at least one disadvantage of a tunnel junction memory cell having a pinned reference layer in close and fixed proximity to the sense layer is a potential reduction in the magneto-resistance ΔR/R resulting from the angular displacement. 
     To pin the reference layer during manufacturing, the reference layer must be heated to an elevated temperature in an annealing step. The annealing step typically takes time, perhaps an hour or more. As the reference layer is but one part of the memory being produced, the entire memory must be subject to temperatures ranging from about 100 to 300 degrees centigrade while under the influence of a constant and focused magnetic field. Such manufacturing stresses may permit the reference layer to become un-pinned and lose it&#39;s set orientation if the memory is later subjected to high temperatures. In addition, the characteristics of the sense layer may be unknowingly affected by heat during some manufacturing processes. 
     To facilitate establishing a pinned reference layer it is not uncommon for the reference layer to include multiple layers of material. While utilizing multiple layers may help ensure that the reference layer remains pinned, it also raises the complexity of manufacturing each and every memory cell present in the magnetic memory. 
     When employed in a digitizer array, the magnetic memory cells are initialized such that each sense layer is oriented in a predetermined direction. As the users moves the stylus across the array, the magnetic field emanating from the stylus re-orients the sense layers most proximate to the stylus. The user directed re-orientation is registered by the system when the digitizer array is scanned. To register the user&#39;s next movement of the stylus, the digitizer array is re-initialized. As the scanning and re-initializing are performed every few microseconds the movements of the stylus by the user are recognized to the system. 
     Because of the ever present magnetic field of the pinned reference layer, the coercivity of the sense layer must at a minimum be greater than the offset in the coercive switching field described above. More specifically, the minimum coercivity of the sense layer is dictated at least in part by the offset force created by the pinned reference layer. In addition, as the magnetic field of the reference layer is constant, the coercivity of the sense layer must be great enough that the sense layer will maintain orientation at least until the system cycles through a read scan operation. Such longevity of orientation and heightened level of coercivity directly require higher levels of current to pass through the digitizer array. As such the size of the power supply and current conductors must be larger than might otherwise be desired as an issue of space and manufacturing cost. 
     As noted above, digitizers may exist as touch pads connected to a removed display or as touch screens that immediately display information beneath the stylus. The disadvantages noted above are present as well in such touch screen displays. Additionally, as a touch screen application requires both the elements of the display and the elements of the digitizer to be proximately located, the issues of size and space between components are even greater. 
     Hence, there is a need for an improved digitizing magnetic memory cell array that overcomes one or more of the drawbacks identified above. The present invention satisfies one or more of these needs. 
     SUMMARY 
     This invention provides soft-reference magnetic memory digitizing device for use in a touchpad/touch-screen device. 
     In particular, and by way of example only, according to an embodiment of the present invention, this invention provides a soft-reference magnetic memory digitizing device including: an array of soft-reference magnetic memory cells, each characterized by an alterable orientation of magnetization, the orientation changing upon the substantially proximate application of at least one externally-applied magnetic field as applied by a magnetically tipped stylus. 
     Moreover, according to an embodiment thereof, the invention may provide a method of using a soft-reference magnetic memory digitizing device having an array of magnetic memory cells, each memory cell characterized by at least one ferromagnetic sense layer characterized by an alterable orientation of magnetization, the orientation changing upon the substantially proximate application of at least one externally-applied magnetic field; and at least one ferromagnetic soft-reference layer having a non-pinned orientation of magnetization; wherein the alterable orientation of the sense layer is not substantially affected by the soft-reference layer, the method including: applying an external magnetic field to at least a portion of the array to change the magnetic orientation of at least one sense layer; reading the array by applying a sense current to the magnetic memory cells and reading the resistance of each cell, the sense current also sufficient to establish a magnetic field to orient the soft-reference layer during the read operation; and refreshing the array by applying a refresh current sufficient to align substantially all the sense layers to a predetermined orientation. 
     These and other objects, features and advantages of the preferred method and apparatus will become apparent from the following detailed description, taken in conjunction with the accompanying drawings which illustrate, by way of example the principles of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of a soft-reference magnetic memory digitizing device according to the present invention; 
         FIG. 2A  is a plain cross sectional view of a portion of soft-reference magnetic memory digitizing device shown in  FIG. 1 ; 
         FIG. 2B  is a perspective view of a portion of soft-reference magnetic memory digitizing device shown in  FIG. 1 ; 
         FIG. 3  is a plain cross sectional view of a portion of the soft-reference magnetic memory digitizing device of  FIG. 1  further including an integrated display; 
         FIG. 4  is a schematic diagram of a soft-reference magnetic memory cell shown in  FIG. 3  controlling a display pixel; 
         FIG. 5  is a flow diagram of the operation of the soft-reference magnetic memory digitizing device shown in the above figures; 
         FIG. 6  is a perspective view of a portion of the soft-reference magnetic memory digitizing device shown in  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION 
     Before proceeding with the detailed description, it is to be appreciated that the present invention is not limited to use or application with a specific type of magnetic memory. Thus, although the present invention is, for the convenience of explanation, depicted and described with respect to typical exemplary embodiments, it will be appreciated that this invention may be applied with other types of magnetic memory. 
     Referring now to the drawings, and more particularly to  FIG. 1 , there is conceptually shown a portion of a soft-reference magnetic memory digitizing device  100  comprising an array  102  of soft-reference magnetic tunnel junction memory cells  104  (MTJ), functioning as a stylus-based input device. Operating as a touch-pad, the digitizer may be coupled to a processor which receives information from the digitizer  100  and directs appropriate output upon a display  106 . Operating as a touch-screen, the digitizer is coupled directly to the display such that the state of the memory cells  104  directly drives the display  106  without need of an intervening processor. The digitizer  100  further includes control logic  108  that is used to control the digitizer  100  during operations such as read array and initialize array, which are well known to those skilled in the art and further discussed below. 
     The MTJ cells  104  are capable of storing at least two magnetic state possibilities. When initialized, for the sake of this discussion, the initial state of magnetic orientation stored within each MTJ cell  104  is oriented to the right. A stylus  110  with a magnetic tip providing a magnetic field external to the MTJ cells  104  is also shown. As the stylus  110  is moved across the surface of the digitizer  100  (shown as trace line  112 ), the magnetic field emanating from the tip of the stylus  110  is sufficient to reorient the field of the MTJ cells  114  which are substantially proximate to the tip of the stylus  110 . 
     In at least one embodiment the tip of stylus  110  is characterized by a permanent magnet that provides a known field. In an alternative embodiment the tip of stylus  110  is characterized by a current carrying coil. It is further understood that the size of the MTJ cells  104  relative to the size of the tip of the stylus  110  may be such that placement and movement of the stylus  110  invariably affects more than one MTJ cell  104  at a time. In at least one embodiment the multiplicity of MTJ cells  104  proximate to the tip of the stylus  110  provides enhanced granularity in determining the position and movement of the stylus  110 . The granularity or ratio of MTJ cells  104  to the stylus may be adjusted in accordance with the specific application desired for the digitizer  100 . 
     The ability of a given MTJ cell  104  to respond to the substantially proximate application of the magnetic stylus  110  may be more fully appreciated with respect to  FIGS. 2A and 2B , illustrating a cross sectional side view portion of digitizer  100  ( FIG. 2A ) and a prospective view of a portion of the digitizer  100  ( FIG. 2B ). As the interaction between the stylus  110  and the MTJ cells  104  is due to magnetic fields, physical contact is not required. Accordingly the array  102  of MTJ cells  104  may be protectively located below the outer surface  200  of the digitizer  100 . Moreover, in touch-screen applications, the digitizer  100  may be located behind the display (such as for example a liquid crystal display). 
     As shown, MTJ cell  104  has at least one ferromagnetic sense layer  202 , an intermediate layer  204 , and at least one soft-reference layer  206 . The ferromagnetic sense layer  202  is characterized by an alterable orientation of magnetization M 2 . As stated above, in the initial state M 2  is oriented to the right, as is the condition of MTJ cells  104 ′ and  104 ″. The orientation of magnetization M 2  is changed upon the substantially proximate application of at least one externally-applied magnetic field  212 . More specifically, as shown the stylus  110  provides a magnetic field  212  that for the portion imposed upon MTJ cell  104  is oriented to the left. As implied by  FIGS. 2A and 2B  showing first the proximate application of magnetic field  212  to MTJ cell  104  to chanae M 2  to left orientation ( FIG. 2A ), and the subsequent removal of magnetic field  212  from MTJ cell  104  which remains with M 2  having a left orientation, it is understood and appreciated that the magnetic field  212  provided by stylus  110  is sufficient to overcome the coercivity of sense layer  202 , and thus change the orientation of M 2  from right to left. More simply stated, the sense layer “senses” the presence of an external magnetic field  212  and can reorient itself accordingly. The intermediate layer  204  has opposing sides such that the sense layer  202  in contact with one side is in vertical alignment with, and substantially uniformly spaced from, the soft-reference layer, in contact with the second side of the intermediate layer  204 . 
     The soft-reference layer  206  is so named because the direction of orientation of magnetization M 1  can be dynamically set to a known direction. Unlike a tynical reference layer which are hard-pinned in a selected orientation, the soft-reference layer  206  is unpinned. In the presence of magnetic fields the soft-reference layer  206  will achieve an orientation, however such orientation is dynamic. Magnetic field  212  may cause a temporary alignment of soft-reference layer  206  as the magnetic field  212  orients M 1  of the sense layer, however the temporary orientation of M 1  is of substantially no consequence as the orientation of M 1  is not permanent. The orientation of the soft-reference layer  206 , i.e., M 1 , is truly only at issue when it is dynamically set during a read operation, further discussed below. Such dynamic setting during a read operation may be achieved by magnetic fields provided by an externally supplied current flowing through the row  208  and column  210  intersecting at MTJ cell  104 . More specifically, the current flowing through row  208  produces a first magnetic field, and the current flowing through column  210  produces a second magnetic field. The two fields are orthogonal and substantially combine at their cross point intersection and are sufficient to orient the soft-reference layer  206 . 
     As the MTJ cells  104  are located at cross point intersections such a system permits the individual selection of a given MTJ cell  104 . In this case, the current magnitude applied to the row  208  and the column  210  to set the magnetization M 1  of the soft reference layer  206  to a known direction is relatively small. This current will not alter the magnetization state M 2  of the sense layer  202  or other unselected memory cells, which at most are subjected to half the combined field. In the absence of this current applied to the row  208  and column  210  the orientation of M 1  is affectively released. As the current flowing through row  208  and column  210  in a read cycle provided combining fields sufficient to align M 1  (the soft-reference layer  206 ) without altering M 2  (the sense layer  202 ), they are understood and appreciated to be low read fields. 
     Generally, aligning the soft-reference layer  206  is an event that occurs during a read cycle when the magnetization M 1  of the soft-reference layer  206  is set to a known direction and then compared with the direction of M 2  of the sense layer  202  to determine the “0” or “1” state of the memory bit cell. It is termed “soft” because it generally comprises materials that are magnetically soft and are not of the usual hard-pinned materials used for more traditional pinned reference layers. When utilizing a soft reference layer, a convention is generally adopted as to which way M 1  will be oriented. 
     The comparison of M 1  and M 2  is achieved by measuring resistance in the MTJ cell  104 . As current is flowing through row  208  and column  210  to dynamically align soft-reference layer  206 , current is also being provided to flow through MTJ cell  104 . If the orientation of M 2  of the sense layer  202  is parallel to the dynamic orientation of M 1  of the soft-reference layer  206  the MTJ cell  104  will be in a state of low resistance. If the orientation of M 2  of the sense layer  202  is anti-parallel to the dynamic orientation of M 1  of the soft-reference layer  206  the MTJ cell  104  will be in a state of high resistance. A convention is generally adopted to indicate that high resistance is a logical “1” and low resistance is a logical “0”, or vis-a-versa. The phenomenon that causes the resistance in the MTJ cell  104  is well understood in the magnetic memory art and is well understood for TMR memory cells. GMR and CMR memory cells have similar magnetic behavior but their magneto-resistance arises from different physical effects as the electrical conduction mechanisms are different. For instance, in a TMR-based memory cell, the phenomenon is referred to as quantum-mechanical tunneling or spin-dependent tunneling. In a TMR memory cell, the intermediate layer  204  is a thin barrier of dielectric material through which electrons quantum mechanically tunnel between the sense layer  202  and the soft-reference layer  206 . 
     In a GMR memory cell, the intermediate layer  204  is a thin spacer layer of non-magnetic but conducting material. Here the conduction is a spin-dependent scattering of electrons passing between the sense layer  202  and the soft-reference layer  206  though the intermediate layer  204 . In either case, the resistance between the sense layer  202  and the soft-reference layer  206  will increase or decrease depending on the relative orientations of the magnetic fields M 1  and M 2 . It is that difference in resistance that is sensed to determine if the sense layer  202  is storing a logic state of “0” or a logic state of “1”. 
     In at least one embodiment, the ferromagnetic sense layer  202  has a coercitivity higher than the soft-reference layer  206 , and may be made from a material that includes, but it not limited to: Nickel Iron (NiFe), Nickel Iron Cobalt (NiFeCo), Cobalt Iron (CoFe), and alloys of such metals. In addition, both the soft-reference layer  206  and the sense layer  202  may be formed from multiple layers of materials. However, for conceptual simplicity and ease of discussion, each layer component is herein discussed as a single layer. 
     In at least one embodiment, the intermediate layer  204  is a tunnel layer made from an electrically insulating material (a dielectric) that separates and electrically isolates the sense layer  202  from the soft-reference layer  206 . Suitable dielectric materials for the dielectric intermediate layer  204  may include, but are not limited to: Silicon Oxide (SiO 2 ), Magnesium Oxide (MgO), Silicon Nitride (SiN x ), Aluminum Oxide (Al 2 O 3 ), Aluminum Nitride (AlN x ), and Tantalum Oxide (TaO x ). 
     In at least one other embodiment, the intermediate layer  204  is a tunnel layer made from a non-magnetic material such as a 3d, a 4d, or a 5d transition metal listed in the periodic table of the elements. Suitable non-magnetic materials for a non-magnetic intermediate layer  204  may include, but are not limited to: Copper (Cu), Gold (Au) and Silver (Ag). While the actual thickness of the intermediate layer  204  is dependent upon the materials selected to create the intermediate layer  204  and the type of tunnel memory cell desired, in general, the intermediate layer  204  may have a thickness of about 0.5 nm to about 5.0 nm. 
     The use of a soft reference layer has several advantageous benefits in the MTJ cell  104 . As a soft-reference layer is not substantially fixed in orientation, it may not be necessary to subject the MTJ cell  104  to high temperatures during manufacturing as is often required to establish a fixed reference layer. Further, achieving a pinned reference layer often entails complex fabrication procedures involving multiple layers of specialized materials. In addition, the lack of a substantial and constant magnetic field in the soft-reference layer  206  reduces the likelihood of a demagnetization field from the soft-reference layer  206  acting upon the sense layer  202 , thus reducing if not eliminating the offset in the coercive switching field. 
     The substantial elimination of the offset field is quite advantageous. As a direct result, when selecting the coercivity for the sense layer  202 , the issue of the offset field need not be considered. Further, so long as the coercivity of the sense layer  202  is greater than the coercivity of the soft-reference layer  206 , and understanding that the soft-reference layer  206  need only have purposeful orientation during a read operation, the presence of a magnetic field within the soft-reference layer  206  itself may be largely discounted when selecting the desired coercivity of the sense layer  202 . 
     In other words, the coercivity of sense layers  202  may be significantly lower than the coercivity in sense layers of prior art digitizing devices. Reducing the coercivity in the sense layer  202  advantageously reduces the current need required for initializing the MTJ cell  104  and might therefore permit a smaller power source, and/or transistor to be used. In addition, as the sense layer  202  coercitivity decreases, the intensity of the magnetic field  212  emanating from the stylus  110  may also be decreased. Reducing the required magnetic field  212  of the stylus  110  advantageously reduces magnetic shielding that may be required where the digitizer is proximate to other sensitive electronics. 
     It shall be recognized that the MTJ cells  104  comprising the array  102  may operate independently of one another and the stylus. As such more than one stylus  110  may be utilized, each of which operates independently of the other, such as, for example in the case of a multi-fingered stylus glove. 
     As stated above, control logic  108  within the display directs operations such as read array (a reading state) and initialize array (a refreshing state). These tasks are performed with supporting drive electronics within the digitizer that are well known to those skilled in the art. Movement of the stylus  110  proximate to a MTJ cell  104  causes the sense layer  202  to switch orientation from it&#39;s initialized position, i.e., from M 2  oriented to the right to M 2  oriented to the left as described above. To register this switch, in at least one embodiment the control logic  108  operates in cycles. In a first cycle, a low read current is systematically directed to each MTJ cell  104  in the array  102  by systematic row  208  and column  210  selection, and the detected resistance noted. In a second cycle, a higher initialize current is directed to each cell by rows  208  and columns  210 , thus providing higher fields which when combined are sufficient to overcome the coercivity of each sense layer  202  so as to re-set the orientation M 2  of any and all sense layers  202  that may have been reoriented. As the reading state involves low read currents providing low read fields, the orientation of each sense layer  202  is unaffected during the reading cycle or state. As the initialize operation is applied to all MTJ cells  104  in the array  102 , it may be applied substantially simultaneously to all MTJ cells  104  without specific row  208  and column  210  addressing. As described above, the orientation of each soft-reference layer  206  is dynamic. The temporary alignment of M 1  that may occur during the refreshing of the sense layers  202  is of no more conseguence then the temporary alignment of M 1  that may occur in the presence of the magnetic field provided by the external stylus. Again, the orientation of each soft-reference layer  206  is dynamically set during each read cycle by providing low read fields as described above. To insure a high probability of detecting the presence and position of the stylus, the cycle time is about 0.1 to 5 milliseconds. Moreover, the cycle time is set to be faster than a user is likely to move the stylus  110 . 
     In at least one embodiment the read cycle may be an active condition. Specifically the digitizer  100  cycles between the read state and the initialize state such that at substantially all times a current is flowing through the array  102  of MTJ cells  104 . In an alternative embodiment, the read cycle may be passive. Specifically the digitizer  100  cycles through an “off” state as well, i.e. read, refresh, off, and then read, refresh again. The inclusion of a rest state may be desired for the conservation of power. 
     As the condition of the sense layer  202  need only be maintained through a read cycle, in at least one embodiment the coercivity of the sense layer  202  may be so low that unlike a traditional prior art MTJ cell  104  the sense layer  202  does not hold it&#39;s condition substantially indefinitely. In light of the reduced manufacturing costs and complexities, significant reduction in power requirements (physical size and current strength), reduced stylus  110  and initialization magnetic fields, and intention to re-initialize the MTJ cells  104  at regular intervals, the traditional longevity is in many applications an un-necessary and superfluous condition. 
     As shown in  FIG. 3 , in at least one embodiment, a display  300  is at least partly integrated with the array  102  of MTJ cells  104 . The display  300  is characterized by an array of pixels  302 . In such a setting, each MTJ cell  202  is further coupled to at least one pixel  302 , such that the MTJ cells  104  of the digitizer  100  actively controls the pixels  302  of the display  300 , thus providing a touch-screen.  FIG. 6  provides a partial perspective view of magnetic memory digitizing device  100  incorporating a display  300  above the array  102  of MTJ cells  104 . Display  300  includes an array of pixels  600 , of which pixel  302 ,  302 ′,  302 ″ . . .  302 ″ are exemplary. As shown, both the display  300  and the array  102  of MTJ cells  104  are below the encasing outer surface  200 . In at least one embodiment the encasing outer surface of the display may be encasing outer surface  200 . It is understood and appreciated that display panels such as display  300  provide visual information in the form of text, shapes, images or the like. Fundamentally, such information is composed of pixels, the smallest complete component of the image. As one or more MTJ cells  104  of the array  102  activate their associated pixels  302 , visual information is created and perceived by the user. As pixel  302  is above MTJ cell  104 , when activated by the sense layer of MTJ cell  104  being reoriented, the illumination of pixel  302 , and thus it&#39;s component of visual information, is displayed upon the display  300  proximate to the sense layer  202  of MTJ cell  104 . Display panels used in such touch screen applications typically employs transistors in an active matrix, and are well known to those skilled in the art. Here, the MTJ cells  104  of the array  102  are mated to the array of transistors in at least a one-to-one relationship as is further shown in  FIG. 4 . The condition of the sense layer  201  in each MTJ cell  202  is thereby used to control the pixels  302  of the display  300 . 
       FIG. 4  illustrates a schematic diagram of a portion of an array of pixels as controlled by a MTJ cell  104  as integrated in a single touch-screen display system. Shown are a pixel  400  (represented as the contents within the dotted line), a pixel enable line  402 , a row voltage line  404  and a column voltage line  406 . A MTJ cell  104  is fixed between the row  404  and column  406  voltage lines. Voltage line  406  is then further coupled to a field effect transistor  408 , or other appropriate switching device. The power source for the transistor  408  is coupled to the pixel enable line  402 . Transistor  408  thereby controls pixel diode  410  in accordance with the state of the MTJ cell  104 . Each pixel diode  410  is coupled to a capacitor  412  to provide a constant source of power to the pixel diode  410  when it is active. 
     The single schematic shown may be reproduced for red, green and blue pixels thereby permitting the display to provide color as a RGB matrix. Further, it shall be noted that to balance color intensity more pixels of one color may be provided over another color. Alternatively, the color intensity may be controlled by another memory cell. 
     Having described the physical structure of the soft-reference magnetic digitizer  100 , a method of operating same is now described with reference to the flow diagram provided in  FIG. 5 . It will be appreciated that the described method need not be performed in the order in which it is herein described, but that this description is merely exemplary of one method of using a soft-reference magnetic digitizer  100 . 
     Initially, as shown in block  500 , a soft-reference magnetic digitizer  100  as described above is formed and provided to the user. Depending on how the digitizer is provided, it may be appropriate to initialize the sense layer  202  of each MTJ cell  104  in the array  102  to align substantially all the sense layers to a predetermined orientation, as shown in block  502 . 
     The user applies an external magnetic field  212  via the use of a stylus as indicated in block  504 , and as represented in the trace line  112  of  FIG. 1 . The sense layers  202  of MTJ cells  104  proximate to the magnetic field  212  of the stylus  110  will re-orient themselves in accordance with the affect of the stylus  110  magnetic field  212 . 
     At cyclical intervals the control logic  108  of the digitizer  100  will systematically apply a sense current to the MTJ cells  104  of the array  102 , as shown in block  506 . The sense current is sufficient to align the soft-reference layer  206  in a predetermined orientation. The resistance of the MTJ cell is then measured and evaluated to determine if the sense layer  202  has been changed from it&#39;s original predetermined orientation. 
     As shown in decision block  508 , if the evaluation of the resistance indicates no change, the control logic  108  will continue on through the remaining MTJ cells  104  of the array  102 . If the evaluation of the resistance indicates that the sense layer  202  has indeed changed, the control logic will direct the performance of some event as indicated in block  510 . In at least one embodiment this event will be the display of an image upon a display that corresponds to the trace of the magnetic stylus  110  upon the digitizer  100 . Additional and alternative events may also be performed such as a signal from the digitizer to a computer system to perform a desired event such as the launch of an application. 
     In certain instances the digitizer may be provided as a touch-screen device. In accordance with the above description of pixel control being tied to the state of the MTJ cells  104 , the pixels  400  of the display will provide a visual image corresponding to the location proximate to where the user has applied the magnetic field  212 . 
     Following the commencement of the event in block  510  the control logic  108  will continue on through the remaining MTJ cells  104  of the array  102 . Following the read scan of the array  102 , the control logic  108  will refresh the array  102  as shown in block  512  by applying a refresh current sufficient to align substantially all the sense layers within the array  102  to a predetermined orientation. In at least one embodiment the refresh array operation is performed in a systematic process of accessing one MTJ cell  104  at a time. In an alternative embodiment the refresh array operation is performed by accessing a plurality of MTJ cells  104  substantially simultaneously. 
     As shown in decision block  514 , if it is desired to continue operation of the soft-reference magnetic digitizer  100 , the method returns to block  504  where the user again provides an external magnetic field  212  with the stylus  110 . 
     It is further understood and appreciated that the control logic  108  may be enhanced to recognize a user&#39;s desire to invoke an event, such as by prolonged stationary placement of the stylus  110 . In an alternative embodiment, such as where the stylus  110  utilizes a field coil to provide the magnetic field  212 , a depressing of the stylus  110  against the surface  200  of the digitizer  100  may briefly intensify the magnetic field  212 , and thus affect a greater radius of MTJ cells  104 . 
     As noted above, the digitizer  100  may accommodate more than a single stylus  110 . In such situations the control logic can and will properly associate the MTJ cells  104  affected by the multiple stylus  110 . 
     While the invention has been described with reference to the preferred embodiment, it will be understood by those skilled in the art that various alterations, changes and improvements may be made and equivalents may be substituted for the elements thereof and steps thereof without departing from the scope of the present invention. In addition, many modifications may be made to adapt to a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Such alterations, changes, modifications, and improvements, though not expressly described above, are nevertheless intended and implied to be within the scope and spirit of the invention. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.