PATENT DOCUMENT

Publication Number: US-10605774-B2
Application Number: US-201514857534-A
Country: US
Kind Code: B2

Title: Magnetic imaging

Abstract:
A magnetic image system for providing a visible image includes a magnetic substrate having a first and a second opposing surface and formed of material that is magnetized into a pattern of magnetized regions corresponding to the visible image, the magnetized regions forming a magnetic surface having a size and a shape in accordance with the visible image and a magnetic property corresponding to a visible image property, wherein the magnetic surface is rendered visible as the visible image using a magnetic imaging medium that interacts with the magnetic surface in accordance with the magnetic property.

Claims:
What is claimed is: 
     
       1. A method for forming a magnetic image on a magnetic substrate, comprising:
 positioning a magnetic imaging mask between a magnetizer and the magnetic substrate, wherein the magnetic imaging mask includes magnetic shields capable of magnetically shielding masked regions of the magnetic substrate that are overlaid by the magnetic shields from a magnetizing magnetic field, wherein the masked regions are separated by exposed regions of the magnetic substrate; 
 directing, by the magnetizer, the magnetizing magnetic field at the magnetic substrate such as to form a pattern of magnetized regions on the magnetic substrate, wherein the pattern of magnetized regions corresponds to the exposed regions; and 
 forming the magnetic image on the magnetic substrate by using a magnetic imaging medium to magnetically interact with the pattern of magnetizable regions. 
 
     
     
       2. The method as recited in  claim 1 , wherein the magnetic imaging medium magnetically interacts with the pattern of magnetized regions in accordance with a level of magnetization up to and including a saturation level associated with the magnetic substrate. 
     
     
       3. The method as recited in  claim 1 , wherein the magnetic shields include conductive material that causes a formation of eddy currents in response to the magnetizing magnetic field passing through the magnetic imaging mask. 
     
     
       4. The method as recited in  claim 1 , wherein the magnetic imaging medium includes magnetic particles that are capable of interacting with the pattern of magnetized regions. 
     
     
       5. The method as recited in  claim 1 , wherein the magnetic imaging mask includes a printed circuit board having at least one electrical trace corresponding to the magnetic shields. 
     
     
       6. The method as recited in  claim 1 , wherein the magnetic image includes at least one of a bar code, a QR code, an indicium or a magnetic ink identification number. 
     
     
       7. The method as recited in  claim 1 , wherein the magnetic image is rendered visible and characterized as having a gray-scale image. 
     
     
       8. A portable electronic device, comprising:
 a housing including a magnetizable substrate, the magnetizable substrate including a first magnetic region having a first level of magnetization, a second magnetic region having a second level of magnetization, wherein each of the first level of magnetization and second level of magnetization corresponds to a respective magnetically encoded luminance value. 
 
     
     
       9. The portable electronic device as recited in  claim 8 , further comprising an un-magnetized region disposed between the first and second magnetic regions. 
     
     
       10. The portable electronic device as recited in  claim 9 , wherein the un-magnetized region corresponds to a null magnetic pixel having a null luminance value. 
     
     
       11. The portable electronic device as recited in  claim 8 , wherein the first magnetic region corresponds to a first magnetic pixel having a first luminance value and the second magnetic region corresponds to a second magnetic pixel having a second luminance value. 
     
     
       12. The portable electronic device as recited in  claim 8 , wherein each of the magnetically encoded luminance values corresponds to a respective gray-scale luminance value such that the first and second magnetic regions together form a gray-scale visual image. 
     
     
       13. The portable electronic device as recited in  claim 8 , wherein the magnetically encoded luminance information corresponds to a bar code, a QR code, an indicium, or a magnetic ink identification number. 
     
     
       14. A magnetic imaging system for forming a magnetic image on a magnetic substrate, the magnetic imaging system comprising:
 a magnetizer arranged to generate a magnetizing magnetic field at the magnetic substrate such as to form a pattern of magnetized regions on the magnetic substrate; 
 a magnetic imaging mask including magnetic shields that are arranged in a pattern corresponding to the magnetic image; 
 a magnetic fixturing device capable of positioning the magnetic substrate relative to the magnetizer and the magnetic imaging mask such that the magnetic shields are capable of shielding masked regions of the magnetic substrate that are overlaid by the magnetic shields from the magnetizing magnetic field, wherein the masked regions are separated by exposed regions of the magnetic substrate; and 
 a magnetic imaging medium arranged to magnetically interact with the pattern of magnetized regions to form the magnetic image, wherein the pattern of magnetized regions corresponds to the exposed regions. 
 
     
     
       15. The magnetic imaging system as recited in  claim 14 , wherein the magnetic shields comprise a shielding factor corresponding to a magnetic property of the magnetic image. 
     
     
       16. The magnetic imaging system as recited in  claim 15 , wherein the magnetic property comprises a level of magnetization. 
     
     
       17. The magnetic imaging system as recited in  claim 16 , wherein the level of magnetization corresponds to luminance. 
     
     
       18. The magnetic imaging system as recited in  claim 17 , wherein the luminance corresponds to a degree of interaction between the exposed regions and the magnetic imaging medium. 
     
     
       19. The magnetic imaging system as recited in  claim 14 , wherein the magnetic imaging medium includes magnetic particles that are capable of interacting with the pattern of magnetized regions. 
     
     
       20. The magnetic imaging system as recited in  claim 14 , wherein the magnetic shields include conductive material that causes a formation of eddy currents in response to the magnetizing magnetic field passing through the magnetic imaging mask.

Description:
FIELD 
     The described embodiments relate generally to the magnetization of permanent conductive substrates, and more specifically to methods and systems for selectively forming magnetized regions that can be used as a magnetic imaging mask used as part of a magnetic imaging system. 
     BACKGROUND 
     Multi-pole magnetic substrates made from magnetic materials such as rare earth elements have found application in the industrial arts, especially for uses relating to the enclosures and casings for personal computerized products such as laptops, tablets and smart phones. 
     Other uses of multi-pole magnetic substrates are also possible. 
     SUMMARY 
     A method for forming a magnetic image is described. The method is a carried out by using a magnetic imaging mask having a masking element to generate at a magnetic substrate magnetized regions each having a magnetic property and arranged in pattern that corresponds to the magnetic image. A magnetic imaging medium magnetically interacts with the magnetized regions in accordance with the magnetic property. 
     An electronic device includes a housing having a magnetic surface at an exterior surface of the housing, the magnetic surface corresponds to a magnetic image and has a magnetic property corresponding to a visible image property. The electronic device can also have the magnetic surface as a separate piece joined or associated with the housing if the housing is not magnetic. 
     A magnetic image system includes a magnetizer arranged to provide a magnetic field, a magnetic mask having masking elements arranged in a pattern corresponding to a magnetic image, the masking elements are associated with a shielding factor corresponding to an image property. A magnetic substrate is positioned relative to the magnetizer and the magnetic mask such that the magnetic mask shields a corresponding portion of the magnetic substrate from the magnetic field in accordance with the shielding factor resulting in a magnetized region providing a magnetic surface having a magnetic property corresponding to the image property. 
     This Summary is provided merely for purposes of summarizing some example embodiments so as to provide a basic understanding of some aspects of the subject matter described herein. Accordingly, it will be appreciated that the above-described features are merely examples and should not be construed to narrow the scope or spirit of the subject matter described herein in any way. Other features, aspects, and advantages of the subject matter described will become apparent from the following Detailed Description, Figures, and Claims. 
     Other aspects and advantages of the embodiments described herein would become apparent from the following detailed description taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the described embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The described embodiments may be better understood by reference to the following description and the accompanying drawings. Additionally, advantages of the described embodiments may be better understood by reference to the following description and accompanying drawings in which: 
         FIGS. 1A-1C  are perspective, cut-away views of a permanent magnet disposed within the magnetizing zone of a magnetization system, in accordance with one representative embodiment of the present disclosure; 
         FIGS. 2A-2C  shows a representative step wise process for creating a magnetic image; 
         FIGS. 3A-3D  illustrate various exemplary embodiments of magnetic imaging masks; 
         FIG. 4  shows a representative magnetic image in accordance with the described embodiments; 
         FIGS. 5A-5C  shows a representative step wise process for creating a magnetic image based upon printed circuit board (PCB) technology; 
         FIGS. 6A-6C  illustrate the effect of the magnetic properties of the substrate can have on the magnetic image created; 
         FIG. 7  shows an implementation of magnetized magnetic substrate with a magnetic image in accordance with the described embodiments; 
         FIGS. 8A and 8B  illustrate a particularly useful application of magnetic imaging in accordance with the described embodiments; and 
         FIG. 9  shows a flowchart detailing a process in accordance with the described embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     In the following detailed description, references are made to the accompanying drawings, which form a part of the description and in which are shown, by way of illustration, specific embodiments in accordance with the described embodiments. Although these embodiments are described in sufficient detail to enable one skilled in the art to practice the described embodiments, it is understood that these examples are not limiting; such that other embodiments may be used, and changes may be made without departing from the spirit and scope of the described embodiments. 
     The foregoing description, for purposes of explanation, uses specific nomenclature to provide a thorough understanding of the described embodiments. However, it will be apparent to one skilled in the art that the specific details are not required in order to practice the described embodiments. Thus, the foregoing descriptions of specific embodiments are presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the described embodiments to the precise forms disclosed. It will be apparent to one of ordinary skill in the art that many modifications and variations are possible in view of the above teachings. 
     The described embodiments relate to a system and method for forming discrete magnetic regions at a magnetic substrate that can be used to form a magnetic image. The magnetic image in and of itself is not generally visible but can, nonetheless, be rendered visible using a magnetic imaging medium that magnetically interacts with the magnetic regions. An image property, such a luminance, can be related to a nature of the magnetic interaction between the magnetic regions and the magnetic imaging medium and can also be related to a level of magnetization of the magnetic regions. For example, a level of magnetization can range in a stepwise fashion (or in a continuous fashion) between essentially no magnetization to a saturation of the magnetic substrate. In other words, a degree of interaction between the magnetic imaging medium can be related to the level of magnetization that can, in turn, affect aspects of the visible image. 
     More specifically, the described embodiments are related to a capability of creating a magnetic image based upon a two-dimensional array of magnetized regions. In addition to being magnetized simply as North or South, the magnetic regions can be magnetized to include intermediate magnetization levels that can range from essentially no magnetization to a level corresponding to a full magnetic saturation of the magnetic substrate. The magnetic regions can, in turn, magnetically interact with a magnetic imaging medium and be rendered visible as a gray-scale image. As is well known, gray-scale is a range of monochromatic shades from black to white and therefore contains only shades of gray and no color. Each picture element (or pixel) used to form a gray-scale image has a luminance value related to a degree of magnetic interaction between the magnetized regions and the magnetic imaging medium, which can be in accordance with a scale from dark to light. For example, a conventional eight (8) bit digital imaging system can support 2 8 , or 256 levels of luminance per pixel where “0” and “255” represent the range of luminance values available. Therefore, by analogy, a level of magnetization up to and including saturation of the substrate can correspond to a magnetic “luminance” indicating a degree of magnetic interaction with the magnetic imaging medium. In this way, a region (or pixel) having a higher level of magnetization will have a potentially greater magnetic interaction with the magnetic imaging medium. Other optical characteristics besides luminance can be used to render the magnetic image visible. For example, an imaging plate using the Kerr effect (mentioned elsewhere) will have its polarization changed by the magnetic pixels that can result in a color change. 
     For example, if the magnetic region has a low level of magnetization, then the capability of the magnetic region to magnetically interact with the magnetic imaging medium will also likely be low. In this case, visual rendering of the magnetic image will likely result in the magnetic substrate associated with the magnetic region being visible, or at least contributing a substantial proportion of the visible image corresponding to the magnetic region. Accordingly, a degree of magnetic interaction between the magnetized region and the magnetic imaging medium can be correlated to a magnetic luminance value that can be considered a magnetic analog to an optical luminance value. It should be noted that while it is not possible with conventional digital imaging system to extend the luminance range beyond the number of levels associated with the resolution of the system, a magnetically based imaging system, however, can take advantage of the fact that the magnetic regions have two possible polarization states, P 1  or P 2  (or in conventional terms, North or South). Accordingly, an eight bit magnetically based imaging system can support 2×2 8  or 512 levels of luminance per pixel since each pixel can be associated with a luminance level for each polarity. 
     Analogous to conventional photography, a version of the magnetic image can be created by magnetizing a substrate using an external magnetic field attenuated by a magnetic mask having electrically conductive elements patterned in accordance with the magnetic image. It should be noted that a picture element (hereinafter referred to as a magnetic pixel) can be represented as a discrete magnetic region having an associated magnetic imaging property based upon a level of magnetization and polarity. For example, a magnetic region that is not magnetized can be associated with a magnetic pixel having a “luminance” value of “0” indicating zero or no magnetic field and therefore little or no interaction with a magnetic imaging medium. On the other hand, a magnetic pixel having a greater level of magnetization can be associated with a magnetic pixel having a luminance value of “B” where B is the “bit depth” of the system (for example, as above, an 8-bit system will have 255 luminance levels each associated with a different magnetization level for a given magnetic pixel). It should be noted that since any magnetic region can be magnetized to have one of two magnetic polarities, the actual dynamic range of the magnetic imaging system is actually twice as large as a conventional digital optical imaging system. For example, a particular magnetic pixel can have a luminance value based upon a level of magnetization independent of the magnetic polarity. 
     The resolution of the magnetic image can be associated with a number of magnetic regions in a given area and a distance between each. In this regard, controlling a transition zone between each magnetic region is important as the wider the transition zone, the fewer and less dense the magnetic image. In other words, the ultimate resolution of the magnetic image can be bounded by an ability to form distinct magnetic regions with a specified area that can depend upon the ability to create well-defined transition zones between magnetic regions. For example, forming a magnetic region associated with a magnetic pixel can be accomplished using a magnetic masking technique shown an described in co-pending U.S. Patent Application entitled: “Multi-pole Magnetization of a Magnet” by Gery et. al. having patent Ser. No. 14/148,563 filed Jan. 6, 2014 that is incorporated by reference in its entirety for all purposes. 
     In one approach, the conductivity of selected magnetic masking elements can be altered in such a way as to affect the formation of eddy currents in that magnetic masking element that, in turn, affects the ability of a magnetic field to alter the magnetic properties of the underlying magnetic substrate. For example, assuming that a magnetic mask is formed of a conductive material such as copper, by varying the conductivity of the copper (by alloying copper, thinning, etc.) in a range from low conductance to high conductance in discreet steps, a number of discreet magnetic levels can be created in underlying magnetic substrate associated with each step of conductivity in the copper magnetic mask. It should be noted that more or fewer magnetic levels can be produced depending on the size of the magnetic pixels, the grade and thickness of the magnetic substrate, and the magnetic scanning method. It should also be noted that there are two kinds of saturation in hard magnetic materials: 1) saturation of virgin material to assure that all of the magnetic domains have been magnetized. This magnetization is done is two steps with masks that mask opposite regions of the material, and magnetize the substrate in opposite polarities. This is a two-step process, but has the advantage that virgin material requires a lower energy pulse to be fully saturated (since there is not any magnetization that&#39;s already imposed on the material that has to be counteracted). This is actually a big advantage when working with high coercivity grades of rare earth magnets and can enable the use of significantly smaller and cheaper magnetizer circuits; and 2) saturation of domains to align them all in a particular polarization. In the context of this discussion, it is assumed that that any hard magnetic part will have been previously saturated to satisfy in order to satisfy condition (1). 
     It should be further noted that there are many ways to alter the opacity to magnetic flux of a magnetic masking element. For example, the conductivity of the mask material can be altered rendering the mask material more or less able to support eddy currents. Moreover, the thickness of the mask material can be varied, the mask shape can be changed from, for example, a uniform area to a “labyrinth” or “maze” of mask material changing multiple times within the mask, resulting in an average density lower than that of a uniform mask. This approach, in particular, can be especially advantageous if the mask is configured as a multi-layer PCB, in which the conductive traces are the mask material, thus allowing fine control of the mask pattern using printed circuit boards and the manufacturing advantages of this mature technology. Furthermore, the substrate can be magnetized in multiple steps by fixtures having different patterns and opacities, or any combination of the ways listed above. 
     Once a version of the magnetic image has been formed on the magnetic substrate using the magnetic mask, there are multiple ways to scan or view (or “develop) the magnetic image using magnetic imaging medium that can interact with magnetic regions formed in the magnetic substrate. For example, iron filings placed on the magnetic substrate will arrange themselves along magnetic field lines. In another possible implementation, screens that use iron filings encapsulated into plastic laminations are readily available and can be used to view magnetic images. “Magnetic” paper can also be use to view the magnetic image as well as certain materials that react a magnetic field with visible light. 
     A magnetic image can be useful for several purposes: a magnetic film (such as used in recording tape and credit cards) can be applied to the back of an enclosure, a unique and identifying image can be imprinted on the enclosure from the outside. This image will be invisible unless scanned by a suitable method. The image can then be used as a steganographic security feature. By varying the pattern, or applying the pattern in multiple steps with varying imaging fixtures, the pattern can be unique to the particular unit on which it is imprinted. The image can be a novelty decoration that appears only when two parts of a device (one magnetized in a pattern, a second part have a magnetically sensitive area) are brought together. The image can be used to hold coded information meant to be read by another device. In this case it will act like a QR code, bar code, or magnetic ink identification number. However, because it is not limited to a binary pattern (N/S, or black/white) it can hold the information in a denser method (base 4 or 8, for example) and so be much smaller or hold more information in the same space. The enclosure or device can be fabricated from a soft magnetic material that is designed to have a certain amount of coercivity (such as soft, low carbon steel, or 400 series stainless steel). The surface of the device can then itself be magnetically imprinted for the purposes listed above. Note also that while this disclosure emphasizes 2D gray scale patterns, 1D patterns are also possible and may be useful. Moreover, imaging a magnetic pattern on a magnetic substrate such as iron can be used as a magnetic detector by observing a pattern developed in the magnetic substrate caused by the external magnetic field. In this way, a quantitative idea of what iron was subjected to (symmetry, field strength, etc,) be available. 
     It should be noted that unlike other image coding methods, a magnetic image includes both positive and negative values. This can be used to print two different images on the same substrate, one in the positive range and the other in the negative. Then imaging material sensitive to one or the other polarity can be applied to it to produce one or the other image. Moreover, it is also possible to make a substrate having two or more different magnetic materials with different values of coercivity (or alternatively layers of thin substrates). One can then imprint multiple images on the substrate by first applying a field strong enough to magnetize the highest coercivity material; following that, one imprints a second image at a lower field strength that can magnetize a second material with lower coercivity but not the first; and so on until all the various materials are magnetized. 
     Illustrated in  FIGS. 1-9  are several representative embodiments of a system and method for forming a magnetic imaging that can include a magnetic imaging mask that can be used to form the magnetic image. The recited advantages are not meant to be limiting in any way, however, as one skilled in the art will appreciate other advantages may also be realized upon practicing the present disclosure. In addition, it is also to be appreciated that the various aspects, embodiments, implementations or features of the described embodiments can be used separately or in any combination, and that other uses and applications are also possible and may be considered to fall within the scope of the present disclosure. 
     As used herein, the term “permanent magnet” refers to a magnet that is magnetized and maintains its own persistent magnetic field after removal from a magnetizer. The strength and polarity of the magnet&#39;s persistent magnetic field is changeable; however, a change in polarity involves exposure of the magnet to an external magnetic field having sufficient strength to re-align the magnetic domains in the magnetic material. In other words, an amount of energy must be provided by a magnetizing magnetic field to change a magnetic domain from a first polarity to a second polarity (such as N to S or vice versa). 
     Referring now in more detail to the figures, wherein like parts are identified with like reference numerals throughout the several views,  FIG. 1A  is a perspective, cutaway view of a magnetization system  10  for creating a version of a magnetic image in a magnetic substrate using a magnetic imager in the form of a magnetic mask, in accordance with one embodiment of the present disclosure. The magnetization system  10  generally includes a magnetization coil  20  made of windings  24  formed of conductive material. Magnetization coil  20  is depicted as being centered about a central axis  21 . The internal volume defined by the magnetization coil  20  can be considered a magnetization zone  30 . The magnetization coil  20  further includes a power or current source (not shown, but known to one of skill in the art) that is configured to direct an electric current through the windings  24  in the magnetization coil  20  so as to generate a magnetic field  32  within the magnetization zone  30 . As shown in  FIG. 1B , when current is directed through windings  24  of the magnetization coil  20  in a first direction, a polarity of the magnetic field  32  is positive with flux lines  34  directed upwards and substantially parallel to the central axis  21  of the magnetization coil  20 . 
     A magnetic substrate  40  made from a magnetic material, including but not limited to rare earth metal alloys such as Neodymium Iron Boron (NdFeB) or Samarium Cobalt (SmCo), is positioned within the magnetizing zone  30  of the magnetization coil  20 . The magnetic substrate  40  is generally positioned in an orientation that is transverse to the central axis  21  of the magnetization coil  20 , so that the flux lines  34  of the magnetic field  32  are perpendicular (or thereabouts) and extend through the thickness of the magnetic substrate  40 . However, in other aspects the magnetic substrate  40  may be positioned in any orientation relative to the central axis  21  of the magnetization coil  20 . 
     Also shown in  FIG. 1A  is a magnetic mask that includes shield bodies  72  that are patterned that correlates to the magnetic image. The shield bodies  72  can be used to subdivide the magnetic substrate  40  into masked regions  52  and exposed regions  54 , with both sides of the masked regions  52  of the magnetic substrate  40  being covered by shield bodies  72 . The shield bodies  72  are generally formed from a highly-conductive material such as copper or silver, and are provided with a length, width and thickness that allows for the formation of eddy currents  80  within the shield bodies  72  in response to the magnetic field or flux lines  34  ( FIG. 1B ) passing through the shield bodies  72 . In turn, the eddy currents  80  generate a counter magnetic flux  82  ( FIG. 1C ) that opposes the flux lines  34  generated by the magnetization coil  20 , thereby shielding the masked regions  52  of the magnetic substrate  40  from the magnetic field ( FIG. 1A ). As a result, only the magnetic domains located within the exposed regions  54  of the magnetic substrate  40  will be magnetized or re-magnetized with the same polarity as the magnetic field and at a level of magnetization in accordance with coercivity of magnetic substrate  40 . It should be noted, however, that by varying the relevant properties of shield bodies  72 , formation of eddy currents could be enhanced or reduced in accordance with a desired magnetic property of the masked regions  52  that can be used to alter properties of the corresponding magnetized region. 
     When the magnetization coil  20  is activated or energized by directing a current  26  through the windings  24  that form the coil  22 , the shield bodies  72  can function as a stencil that alternately shields the masked regions  52  of the magnetic substrate  40 , while exposing the unprotected regions  54  to the full effects of the flux lines  34  of the magnetic field  32 . As described above, the shielding effects of the shield bodies  72  can be achieved through the induced formation of eddy currents  80  within the shield bodies  72  induced by the applied flux lines  34 . 
     As understood by one of skill in the art, the rare earth magnetic materials that form the magnetic substrate  40  generally have a high coercivity (i.e. resistance to withstand an externally magnetic field) before the magnetic domains in the material changes to a new alignment. In other words, the field strength of the externally magnetic field passing through the magnetic material must exceed an energy threshold before the magnetic domains begin to become aligned with the flux lines  34  of the magnetic field. The counter magnetic flux  82  ( FIG. 1C ) generated by the eddy currents  80  can oppose or deflect the flux lines  34  of the magnetic field to a degree that reduces the magnetic field below the energy threshold in the masked regions  52  of the magnetic substrate  40 . As a result, only the magnetic domains located within the exposed regions  54  will be magnetized or re-magnetized with the same polarity as the magnetic field. In addition, in some aspects the strength of the magnetic field  32  may be controlled over the length of the magnetization cycle to a value that is less than the magnitude needed to saturate the magnetic substrate  40  in the exposed regions  54 . This technique can be used to control the final level of magnetization of the exposed regions  54  that can, in turn, be used to control an amount of interaction between the exposed regions  54  and a magnetic imaging medium. For example, the level of magnetization can be directly related to an ability to magnetically attract, for example, the magnetic imaging medium in the form of iron filings. 
       FIG. 2A  shows magnetic imaging assembly  200  in accordance with the described embodiments. Magnetic imaging assembly  200  can be used with magnetizer system  10  or the like for magnetically imaging a magnetic pattern on a magnetic substrate. Accordingly, magnetic imaging assembly  200  can include magnetic mask system  202  that selectively shields magnetic substrate  204  from magnetic field  32 . Magnetic mask system  202  can include magnetic mask  202 - 1  and magnetic mask  202 - 2  disposed on opposite sides of magnetic substrate  204  and can include masking element  206 . In the described embodiment, masking element  206  can be arranged in a pattern corresponding to a magnetic image (or its inverse). Masking element  206  can be formed of electrically conductive material (such as copper or silver) embedded in a non-electrically conductive bulk portion  208 . Since masking element  206  can attenuate magnetic field  32  in accordance with a corresponding shield factor, a region of magnetic substrate  204  can be associated with a magnetic region having a corresponding level of magnetization depending in part upon an initial magnetic state of substrate  204 . Accordingly the level of magnetization can be related to a magnetic image property. For example, as the level of magnetization varies, so does the ability of the corresponding magnetic region to interact with a magnetic imaging medium. In other words, a higher level of magnetization is generally associated with a correspondingly greater magnetic field strength that, in turn, can result in a higher level of interaction with the magnetic image medium. 
       FIG. 2B  shows a result of a magnetic imaging process whereby magnetic imaging assembly  200  is exposed to magnetic field  32 . Accordingly, magnetic masking element  206  can attenuate to varying degrees (from little or no shielding to substantially completely blocking) magnetic field  32 . In this way, the ability of magnetic field  32  to affect magnetic properties of magnetic substrate  204  can be altered. For example, a high shielding factor can essentially block magnetic field  32  leaving magnetic substrate essentially unchanged. In other cases, magnetic masking element  206  can have little ability to attenuate magnetic field  32  resulting in a potential for a substantial change in magnetic properties of magnetic substrate  204 . Accordingly, regions  212  (that can be referred to as magnetic pixels or as a magnetic stencil depending upon a particular imaging technique used) can be formed in magnetic substrate  204 . In this particular example, regions  212  of substrate  204  shielded by masking element  206  can retain the pre-exposure magnetic properties of magnetic substrate  204  whereas regions not shielded can have their respective magnetic properties altered by the effects of magnetic field  32 . For example, if magnetic substrate  204  has a pre-magnetization polarity of P 1  (opposite to that of magnetic field  32 ), then magnetic field  32  can alter those portions of substrate  204  not shielded by masking elements  206  by either reducing the level of magnetization of the exposed regions, neutralize the magnetic polarity of the exposed regions, or reverse the polarity of the exposed regions, all based upon the magnetic properties of substrate  204  and magnetic field  32 . In this particular example, magnetic regions of substrate  204  exposed to magnetic field  32  can be effectively neutralized thereby rendering those regions essentially magnetically neutral. 
       FIG. 2C  shows magnetic image  220  in accordance with the described embodiments. Magnetic image  220  can be formed by exposing magnetized magnetic substrate  204  having magnetized regions  212  to a magnetic imaging medium. In general, the magnetic imaging medium can be formed of magnetically active material capable of magnetically interacting with magnetized magnetic substrate  204  in many ways. For example, the magnetic imaging medium can take the form of magnetically active particles having a relatively high mobility (such as iron filings). In another example, the magnetic imaging medium can interact with magnetized regions  212  in accordance with a magneto-optical phenomenon such as the Faraday effect in which the magnetic field from magnetized regions  212  magnetically interact with incident light by rotating the plane of polarization of the light. It should be noted that the range of rotation of the plane of polarization is linearly proportional to the component of the magnetic field in the direction of the propagation of the light. Similar to the Faraday effect where the plane of polarization of the transmitted light is rotated, the magneto-optic Kerr effect is a physical phenomenon related to light being reflected from a magnetized material, and as a result of the reflection, incurs a slightly rotated plane of polarization. However, for simplicity and without loss of generality, the magnetic imaging medium in the following examples will be considered to take the form of magnetic particles that in some cases, can be embedded in a substrate in the form of magnetic paper or more simply as mobile magnetic particles such as iron filings and the like. 
     The magnetic imaging medium can magnetically interact with magnetic regions  212  forming visible image  220 . In the example show in  FIG. 2C , an amount of magnetic imaging medium  222  has accumulated at magnetized region  212  having an effect of “developing” magnetic pixel  224  where the amount of magnetic imaging medium  222  associated with magnetic pixel  224  can be considered an image property along the lines a luminance value. For example, if magnetic imaging medium  222  takes the form of iron filings (that are generally dark grey to black in nature), then the greater the amount of iron filings attracted to magnetic region  212  can affect the image properties of magnetic pixel  224 . For example, due to the inherent grey/black color of iron filings, the greater the amount of iron files attracted to magnetic region  212  (due to a higher level of magnetization) will imbue magnetic pixel  224  with a darker appearance. If, on the other hand, adjacent magnetic pixel  226  is associated with a reduced level of magnetization, then less of magnetic imaging medium will accumulate at magnetic pixel  226  giving it a less dark appearance. It is possible, therefore, to vary magnetic properties (such as a level of magnetization) of the various magnetic regions that make up magnetic image  220 . In this way, the range corresponding image properties of visible image  220  can also vary. For example, magnetic pixels  224  and  226  can provide a high contrast ratio due to the disparity in levels of magnetization and corresponding interactions with the magnetic imaging medium. 
     It should be noted that the system and method described herein could be used to magnetize a wide variety of magnetic substrates with different arrangements for creating a variety of magnetic images. For example, shown in  FIG. 3A , magnetic imaging assembly  300  can include substrate  302  positioned between magnetic mask  304  having circular mask elements  306  that are concentrically arranged with respect to each other supported by bulk  308 . In this arrangement, circular mask elements  306  can be formed of electrically conductive material having varying shielding factors. In this way, the resulting magnetic image can have circular concentric regions having different magnetic properties. Moreover, as shown in  FIG. 3B , magnetic imaging assembly  310  can include mask  311  having a variety of shaped magnetized regions  312  within bulk  314  that can be used with substrate  316  that can also have a customized, non-rectilinear shape prior to the magnetization steps that form the magnetic regions. This can result in a curved multi-pole magnet that can be economically produced for inclusion within other curved structures and to perform a variety of applications. In one aspect, the magnet body, the shield bodies of the magnetic imager, and the magnetic field can be optimized to produce magnetized regions or magnetized features in the magnet body having a radius of curvature great than or about 1 millimeter. 
       FIGS. 3C and 3D  shows various rendering of magnetic masks in accordance with other described embodiments. It should be noted that magnetic mask  320 , in general, includes electrically conductive regions suitable for forming eddy currents when exposed to a magnetizing magnetic field. The eddy currents, in turn, generate an opposing magnetic field that acts to attenuate the magnetizing magnetic field. The attenuation (or shield factor) can correspond to a number of properties of the electrically conductive elements, most importantly being those properties the affect the creating of eddy currents and a magnitude of the eddy currents. In addition to the amount of electrically conductive material, a ratio of the amount of electrically conductive material to non-conductive material can also affect the ability to create a magnetic image due. For example,  FIG. 3C  shows serpentine magnetic element  322  formed of conductive material such as copper that winds its way within substrate  324  whereas  FIG. 3D  shows another configuration, where magnetic mask  330  includes conductive material  332  formed into concentric rectangles surrounded by non-magnetic substrate  334 . 
       FIG. 4  shows representative magnetic images on magnetic substrate  400  in accordance with various techniques that can be used in accordance with the described embodiments. It should be noted that in this example, magnetic substrate  400  is considered to have a relatively low level of magnetization (or even null) compared to the levels of magnetization associated with the magnetic regions associated with the images. In this way, magnetic substrate  400  can act as a background that can help bring out the images and make them more clear and obvious. For example, image  402  can be formed of a single magnetic region  404  along the lines of a stencil. In this embodiment, the corresponding magnetic mask would essentially take on the entire shape of image  402  (as noted in the expanded region  406 ). In this case, the magnetic property of magnetic region  404  would exhibit generally constant magnetic properties in order to provide the seamless appearance of image  402 . Image  408 , on the other hand, can be produced using a collection of magnetic image elements (referred to as magnetic pixels) corresponding to individual magnetic regions that taken together can be visualized as image  408 . For example, expanded region  410  highlights individual magnetic image elements  412  corresponding to magnetized regions that have magnetic properties corresponding to a corresponding portion of image  408 . As can be seen, image elements  412  can have a level of magnetization that is substantially less than that of magnetic region  404  (as evidenced by the overall lighter appearance) whereas magnetic substrate  400  as above can have a level of magnetization even further reduced over that of image elements  412  providing good contrast between image  408  and magnetic substrate  400 . Magnetic image  414  highlights a technique whereby both a magnetic stencil and a magnetized region corresponding to a magnetic pixel approach can be used. In particular, magnetic region  416  can have a portion  418  that exhibits substantially different magnetic properties than portion of magnetic region  416  that surrounds magnetic region  418 . In this scenario, and as shown in expanded region  420 , magnetic region  418  can be associated with individual magnetic regions  422  in the form of magnetic pixels whereas magnetic region  416  can be formed using the stencil technique as in image  402 . 
     In another embodiment shown in  FIG. 5A , magnetic imaging assembly  500  can include magnetic mask  502  that can be fabricated using printed circuit board (PCB) technology. For example, mask  502  can include non-magnetic PCB substrate  504  and electrically conductive element  506  that can take the form of electrical traces or patterns formed in PCB substrate  504 . Accordingly, magnetic mask  502  can have electrical traces patterned into PCB substrate  504  using conventional PCB technology. In this way, the electrical traces that can act as magnetic shields arranged in a pattern associated with the magnetic image. For example, as shown in  FIG. 5A , magnetic imaging assembly  500  can include magnetic substrate  508  located between masks  502  where mask elements  506  shield corresponding portions of substrate  508  from magnetic field  32  creating a region corresponding to a magnetic image element. It should be noted that the actual location and properties of the magnetic image element could depend on factors such as the magnetic property of substrate  508 , the shielding factors of the masking element  506 , and relative strength and polarity of the magnetic field  32 . 
     Assuming for the moment that magnetic substrate  508  has an initial polarity P 1  that is opposite to that of magnetic field  32  (i.e., P 2 ). Accordingly, when magnetic imaging assembly  500  is exposed to magnetic field  32 , mask element  506  will attenuate magnetic field  32  in accordance with a corresponding shield factor. As shown in  FIG. 5B , regions  510  in substrate  508  retain the original magnetic property of substrate  508  (i.e., at least polarity P 1 ) whereas regions  512  exposed to magnetic field  32  will be affected by magnetic field  32 . In this case, if the properties of substrate  508  and magnetic field  32  are balanced, then regions  512  can be effectively de-magnetized in that an overall magnetic field can be close to null. In this way, as shown in  FIG. 5C , during a developing process, magnetic imaging medium  514  can magnetically interact with region  510  creating visible magnetic image element  516  separated from each other by region  512  having little or none of magnetic imaging medium  514 . It should be noted that an image resolution could be associated with a distance (also referred to a pitch) between adjacent magnetic image elements. The pitch can therefore be related to a lateral distance “d” between adjacent image elements associated with region  512 . 
       FIGS. 6A-6C  illustrate the effect of the magnetic properties of the substrate can have on the magnetic image created. Accordingly,  FIG. 6A  shows magnetic imaging assembly  600  in accordance with the described embodiment. It should be noted that the only difference between magnetic imaging assembly  600  and magnetic imaging assembly  500  is that substrate  508  is initially un-magnetized. In this situation, masking elements  506  attenuate magnetic field  32  so that regions  512  are magnetized whereas regions  510  remain un-magnetized. In this case, image  604  is a negative version of image  520  and having a pixel pitch of d*. 
     Magnetic imaging as described herein has many uses. For example, since a magnetic image is not visible to the naked eye unless and until a magnetic imaging medium is used to develop or visualize the heretofore not visible magnetic image, information can be encoded into a magnetic substrate that can be kept secure. The secure information can then be unsecured, or viewed, simply by allowing the magnetic imaging medium to interact with the magnetic image. For example,  FIG. 7  shows implementation  800  of magnetized magnetic substrate  508  with regions  510  in accordance with the described embodiments. It should be noted that image  520  could take many forms such as an indicium (such as a logo or trademark), an alphanumeric code indicative of, for example, part identification, and so on. In the embodiment shown, magnetized substrate  508  can be overlaid with non-magnetic substrate  802 . In this way, magnetic field lines  804  emanating from regions  510  can penetrate to exterior surface  806  of non-magnetic substrate  802  forming magnetic surface  808  corresponding to image  520  that can be formed of magnetic pixels  516 . In this way, an interaction between magnetic imaging medium and magnetic surface  808  can visualize image  520 . 
     Accordingly,  FIGS. 8A and 8B  illustrate a particularly useful application of magnetic imaging in accordance with the described embodiments.  FIG. 8A  shows electronic device  900  in accordance with the described embodiments (in this case, electronic device  900  can take the form of a laptop computer). Electronic device  900  can include lid  902  pivotally coupled to base unit  904  which in a closed configuration as shown, has an appearance of a single piece. It should be noted that in this example at least lid  902  can be formed of a non-magnetic material, such as plastic, non-magnetic metal such as aluminum, and so on. Moreover, lid  902  includes magnetic substrate  906  having a magnetic image magnetically encoded therein. It should be noted that the dotted lines indicate that magnetic substrate  906  and the magnetic image are not visible through lid  902 . However, due to the non-magnetic nature of lid  902 , magnetic field lines emanating from magnetic pixels associated with the magnetic image penetrate lid  902  form magnetic surface  908  on exterior surface  910  that is a direct analog of the magnetic image encoded into magnetic substrate  906 . Accordingly, magnetic imaging medium can be used to visualize the magnetic image by allowing the magnetic imaging medium to magnetically interact with magnetic surface  908 . It should also be noted, that due to the non-magnetic nature of lid  902 , magnetic image  908  can be modified by simply applying a magnetizing magnetic field to lid  902  of sufficient strength, duration, and polarity to modify the regions in magnetic substrate  906  corresponding to magnetic pixels. In another embodiment, at least lid  902  (or a portion thereof) can be formed of magnetic material. In this way, a portion of lid  902  can be magnetized to form magnetic surface  908  using magnetic imaging system  10 . 
       FIG. 8B  shows a particular manner in visualizing the magnetic image encoded into magnetic substrate  906  using magnetic imaging medium  912  placed in proximity or in contact with exterior surface  910 . In this case, magnetic imaging medium  912  takes the form of magnetic paper in which magnetic particles are embedded in a sheet formed of non-magnetic material such as plastic. In this case, the magnetic particles will be attracted to the magnetic surface  908  and collectively provide a representation of magnetic image  914  that can now be easily seen due to the collective interaction between magnetic surface  908  and the magnetic particles embedded within magnetic imaging medium  912 . 
       FIG. 9  shows a flowchart detailing process  1000  in accordance with the described embodiments. Process  1000  can be used for rendering magnetic regions on a magnetic substrate visible. In one embodiment, the magnetic regions can collectively form a magnetic image. Accordingly, process  1000  can begin at  1010  by obtaining a magnetic substrate having a pattern of magnetized regions corresponding to a magnetic image. Next at  1020 , a magnetic imaging medium can be caused to interact with the magnetic regions. In one embodiment, the magnetic imaging medium can take the form of mobile magnetic particles along the lines of iron filings or other magnetic particles. The mobile magnetic medium will interact with the magnetic regions in accordance with a magnetic property of the magnetic regions. For example, an amount of the mobile magnetic medium that interacts with the magnetic region can be associated with a magnetic property such as a level of magnetic saturation. Accordingly, a visible variation in the amount or kind of magnetic particles can be perceived as a gradation in “color” (if the mobile particles have an inherent color) or as a grey scale image if the mobile magnetic particles are a mix of mobile magnetic particles (i.e., some particles may be white, some black, some grey each with a different propensity to interact with a magnetic region thereby providing a variation in visible content in the magnetic image). The various aspects, embodiments, implementations or features of the described embodiments can be used separately or in any combination. 
     Various aspects of the described embodiments can be implemented by software, hardware or a combination of hardware and software. The described embodiments can also be embodied as computer readable code on a computer readable medium. The computer readable medium is any data storage device that can store data that can thereafter be read by a computer system. Examples of the computer readable medium include read-only memory, random-access memory, CD-ROMs, DVDs, magnetic tape, hard disk drives, solid state drives, and optical data storage devices. The computer readable medium can also be distributed over network-coupled computer systems so that the computer readable code is stored and executed in a distributed fashion. 
     The foregoing description, for purposes of explanation, uses specific nomenclature to provide a thorough understanding of the described embodiments. However, it will be apparent to one skilled in the art that the specific details are not required in order to practice the described embodiments. Thus, the foregoing descriptions of specific embodiments are presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the described embodiments to the precise forms disclosed. It will be apparent to one of ordinary skill in the art that many modifications and variations are possible in view of the above teachings.

Metadata:
Filing Date: 20150917
Publication Date: 20200331
Grant Date: 20200331
Priority Date: 20150917
Inventors: DIFONZO, JOHN C.
GERY, JEAN-MARC
Assignee: APPLE INC
CPC Classifications: [{"code": "G03G19/00", "inventive": true, "first": true, "tree": "[]"}, {"code": "G01N27/72", "inventive": true, "first": true, "tree": "[]"}, {"code": "G01N27/72", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 58277082