Magnification assembly for digitizer cursor
This is a continuation-in-part of the commonly-assigned U.S. patent application Ser. No. 199,674 filed May 27, 1988, now U.S. Pat. No. 5,014,044.. This invention relates to an assembly utilizable with a digitizer cursor for increasing the accuracy of position determinations. 
    
    
     BACKGROUND OF THE INVENTION 
     Digitizers generally include a manually movable cursor and a digitizing surface or tablet. A sheet of paper or other surface bearing a two-dimensional graphic illustration or design to be converted into digital coordinates for use by a computer is laid on the digitizing surface. The cursor is then placed on the sheet of paper and manually moved from position to position to trace the illustration or design. At each desired position of the cursor, the operator customarily actuates a switch on the cursor to cause the coordinates of the position to be stored in a computer memory operatively connected to the cursor. To facilitate the alignment of the cursor with a feature of the illustration or design, the cursor is provided with cross-hairs which the operator aligns with the desired feature. 
     The position coordinates of a point on the digitizing surface are sensed through inductive or capacitive elements in the digitizing tablet and the cursor. Since the introduction of digitizers almost two decades ago, gradual improvements have increased the accuracy of the position sensing to a point now where accuracy limitations arise more from human error than from the crudeness of the digitizer design. 
     OBJECTS OF THE INVENTION 
     An object of the present invention is to provide an assembly for use with a digitizer cursor for increasing the accuracy of position determinations. 
     Another object of the present invention is to provide such an assembly which is easily mounted to a digitizer cursor and can be used on existing cursors. 
     Another, more particular, object of the present invention is to provide such an assembly which is easily moved to facilitate making coarse position determinations. 
     A further particular object of the present invention is to provide such an assembly which includes a magnification lens. 
     Yet another particular object of the present invention is to provide such an assembly with a magnification lens which is replaceable by lenses of different powers of magnification. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a digitizer cursor and an assembly utilizable with a digitizer cursor for increasing the accuracy of position determinations made on a surface, the cursor having a viewsight including cross-hairs for facilitating the positioning of the cursor at a desired point on the surface. The cross-hairs extend parallel to the surface. The viewsight limits the visibility of the area on the surface that is under the cursor. 
     An assembly in accordance with the present invention comprises in combination an optical element and a connector adapted to be attached to the cursor for mounting the optical element to the cursor so that the optical element can be swung into a position above the cross-hairs of the cursor. The connector includes a first member being attached to a surface of the housing of the cursor and the second member attached to the optical element. 
     In a particular embodiment, the connector includes a first member adapted to be affixed to the cursor and a second member attached to the lens, the first member and the second member being releasably connectable to one another. Preferably the first member takes the form of a retainer attachable to a surface of the housing of the cursor; and the other connector member includes a pivot adapted to be held by the retainer so that the lens may be swung down to a position over the cross-hairs. 
     In a particular embodiment of the present invention, the retainer is a capturing hinge and the pivot is provided by bosses. Preferably the bosses are held between two hooks. 
     In another particular embodiment of the present invention, the retainer is a clip. 
     Preferably the second member includes a camming surface. In a preferred embodiment the camming surface also has a stop at each end. 
     A magnifying assembly in accordance with the present invention is easily mounted to a digitizer cursor and can be used on existing cursors. In addition, the magnifying lens component of the assembly is easily neutralized, i.e., easily swung completely out of the viewing path to facilitate the making of coarse position determinations. The lens is retained in each of its two operative positions for operator convenience. The magnification lens of an assembly in accordance with the present invention is also easily interchangeable with lenses of different powers of magnification, should the circumstances of use warrant a different magnification power. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 is a partially schematic perspective view of a magnifying assembly in accordance with the present invention for increasing the accuracy of position determinations by digitizers, showing in exploded view a magnifying lens insertable into a cradle. 
     FIG. 2 is a top view of a cursor with the magnifying assembly of FIG. 1 mounted thereto in an operative configuration. 
     FIG. 3 is a side elevational view of the cursor and magnifying assembly of FIG. 2. 
     FIG. 4 is a perspective view, taken from the rear, of the magnifying assembly of FIGS. 2 and 3. 
     FIG. 5 is a side elevational view, on an enlarged scale, of the magnifying lens component illustrated in FIG. 1. 
     FIG. 6 is a bottom view, on an enlarged scale of the magnifying lens of FIGS. 1 and 5. 
     FIG. 7 is a partial bottom view, on a still larger scale, of a portion of the magnifying lens shown in FIG. 6. 
     FIG. 8 is a top view of the cradle component of FIG. 1. 
     FIG. 9 is a cross-sectional view, taken along line IX--IX in FIG. 8. 
     FIG. 10 is an elevational view of the cradle of FIGS. 1, 8 and 9, taken from the right-hand side in FIGS. 8 and 9. 
     FIG. 11 is a side elevational view, on an enlarged scale, of another magnifying lens component in accordance with the present invention. 
     FIG. 12 is a partial bottom view, on an enlarged scale, of the magnifying lens shown in FIG. 12. 
     FIG. 13, is a perspective view of the magnifying lens of FIG. 12 in exploded relation to a corresponding cradle component. 
     FIG. 14 is an exploded persppective view of another embodiment of the magnifying assembly in accordance with the present invention in an operative configuration. 
     FIGS. 15a and 15b are two side views of the assembly shown in FIG. 14. 
     FIG. 16 is a variant of the assembly shown in FIG. 14. 
    
    
     DETAILED DESCRIPTION 
     As illustrated in FIG. 1, an assembly 20 utilizable with a digitizer cursor 22 (FIGS. 2 and 3) for increasing the accuracy of position determinations comprises a magnifying lens 24 and a receptacle 26 for the lens 24. Integral with the magnifying lens 24 is a mounting pivot arm 28 which is insertable into a receiving recess 30 provided in receptacle 26. 
     As depicted in FIGS. 2 and 3, the receptacle 26 is a cradle that is attachable, e.g., via an adhesive, to a forward-facing surface 32 of cursor 22. The illustrated cursor 22 is part of a capacitive-type digitizer and is provided with a conductive ring 33 embedded in a plastic paddle 34 that is affixed to the underside of the housing 35 on the body of the cursor 22, and extends forward therefrom with respect to the forward-facing surface 32 of the cursor. The paddle 34 has a shielding layer 36 on its upper surface, at the exposed end thereof. In an operative orientation of magnifying lens 24, shown in solid lines in FIG. 2, the lens is disposed in vertical alignment with crosshairs 38 which may be molded or otherwise formed on the paddle centrally of the conductive ring. The magnifying lens enables an operator to position the cross-hairs in registration with a desired feature or position on a digitizing surface with an accuracy which is greater than possible with the unaided eye. As shown in broken lines in FIG. 2, magnifying lens 24 may be temporarily swung to a neutral or storage position to enable viewing of cross-hairs 38 with the unaided eye for the purpose of making coarse adjustments in the position of cursor 22. 
     Cursor 22 may be of a type utilizable with a capacitive digitizing tablet of the kind disclosed in U.S. Pat. No. 4,705,919 to Dhawan. It is of course apparent that the cursor may alternatively be of a type adapted for use with other types of digitizing tablets. As shown in FIGS. 1, 2 and 3, the housing 35 on the cursor 22 is provided on an upper surface 40 with a plurality of pushbuttons 42 whose functions are determined by programming and accordingly may be changed in accordance the particular application and in conformity with the desires of the operator. 
     FIG. 5 shows magnifying lens 24 and mounting arm 28 as a unitary or integral molded component. Magnifying lens 24 takes the form of a solid bubble section or swelling 44 protruding from an upper side of a circular body portion 46. As illustrated in FIGS. 5 and 6, body portion 46 is provided with an extension 48 located in the plane of body portion 46. Mounting arm 28 takes the form of a cylindrical projection extending perpendicularly with respect to the plane of body portion 46 and connected to extension 48 on a lower side thereof, i.e., on a side of body portion 46 opposite lens bubble section 44. At a free end, mounting arm 28 is provided with a beveled surface 50 for facilitating the insertion of the magnifying lens into recess 30 in cradle 26. 
     As shown in FIGS. 5, 6 and 7, mounting arm 28 is provided with three circumferentially spaced longitudinally extending ribs 52 each having a cylindrical outer surface 54. Ribs 52 are shorter than mounting arm 28 and are connected at an upper end to extension 48. A fourth rib 56 integral with mounting arm 28 has the same length as ribs 52 but a greater radial dimension or width. 
     FIGS. 8-10 illustrate cradle 26 in detail. Recess 30 includes a cylindrical lower or inner portion 58 and a cylindrical upper or outer portion 60. Outer recess portion 60 has a greater diameter than inner recess portion 58, thereby defining a shoulder 62. Ribs 52 and 56 engage shoulder 62 in an assembled configuration of the magnifying assembly 20, shown in FIGS. 2 and 3. 
     Outer portion 60 of cradle recess 30 is provided with a notch 64 in which is seated the longitudinally extending free side of rib 56 in the operative configuration of the magnifying assembly, shown in solid lines in FIGS. 2. Rib 56 accordingly acts as a detent to lock magnifying lens 24 in position over cross-hairs 38. Magnifying lens 24 may be rotated by exerting sufficient torque on the lens component to snap rib 56 out of notch 64. The lens component is then swung to the storage position shown in broken lines in FIG. 2. During the rotation of magnifying lens 24, cylindrical outer surfaces 54 of ribs 52 slide along the cylindrical surface of outer recess portion 60. To facilitate the sliding of ribs 52 against the recess wall and to ensure a medium friction fit of the mounting arm to the cradle, particularly in neutral positions of the lens component, the radius of curvature of outer rib surfaces 54 is essentially equal to the radius of curvature of the cylindrical wall of outer recess portion 60. 
     As shown in FIGS. 1 and 8, cradle 26 has a rearwardly facing planar surface 66 to which adhesive is applied for attaching the cradle to forward facing surface 32 of cursor 22. As depicted in FIGS. 9 and 10, planar surface 66 may be provided with a multiplicity of triangular and rhomboid recesses 68 and 70 for maintaining a rearwardly disposed wall of cradle 26 at a substantially uniform thickness and to thereby relieve undesired stresses which may arise during fabrication of the cradle. 
     Both cradle 26 and magnifying lens 24 are manufactured by injection molding. Typically the lens has a magnification power of three. However, in accordance with the present invention, one lens component 24 may be replaced by another component having a greater magnification power, if warranted by the circumstances. 
     As shown in FIG. 11, a magnifying lens component 72 in accordance with another embodiment of the present invention includes a lens portion 74 integral with a disk-shaped body portion 76 in turn integral with an extension 77. Lens portion 72 is disposed on a side of body portion 74 opposite a cylindrical mounting arm 78 attached to extension 77 and projecting perpendicularly to the plane of body portion 74. A longitudinally oriented locating rib 80 is formed along mounting arm 78 and extends approximately halfway along the length thereof. The free end of mounting arm 78 is provided with an annular beveled surface 82. 
     Mounting arm 78 is received in a cylindrical recess 84 in a cradle or receptacle 86 attachable by adhesive along a planar face 88 to a cursor in a region about the cross-hairs of the cursor. Locating rib 80 acts as a detent seatable in groove or notch 90 about recess 84. The magnifying lens of the embodiment of FIGS. 11-13 thus has four orthogonally disposed rest positions in which the lens component is locked to the cradle. 
     As shown in FIGS. 14 and 15, a plastic lens 90 is mounted for rotation in a vertical plane on a pivot bar 92. The pivot bar 92 is snap fit into a clip 94 that is solvent bonded or ultrasonically welded to the upper surface 40 of the housing 35. The lens 90 is molded as a unit with the pivot bar 92 and connected to it by two mounting arms 96. The arms 96 include an upper per stop 98a and a lower stop 98b, and a camming surface 100 between them. The camming surface 100 presses lightly against the upper surface 40 as the pivot bar 92 rotates, to resist movement of the lens 90 between the positions shown in FIGS. 15a and 15b, respectively, so that the lens is stable in either position and does not fall back into the operator&#39;s way while the operator is moving the cursor 22. This provides an unobstructed view of the viewsight 33 and the surface visible through the paddle 34 so that the cursor can be quickly repositioned over the digitizing surface. 
     Finally, the embodiment shown in FIG. 16 shows another lens 110 held in a split-ring rim 112. The mounting arms 114 have upper and lower stops 116a and b, respectively, and a camming surface 118, as discussed above. However, the arms 114 pivot on two bosses 120 that are adapted to be captured between two hooks 122, 124. The hooks 122, 124 are formed on a mounting plate 126 that is bonded to the upper surface 40 of the housing 35. 
     Although the invention has been described with reference to particular embodiments and applications, one of ordinary skill in the art, in light of this teaching, can generate variations and modifications thereof within the spirit and scope of the claimed invention. For example, other optical enhancements, such as using high speed optics that maximize the operator&#39;s field of view while magnifying the area near the cross-hairs are clearly conceivable by one skilled in the art. Accordingly, it is to be understood that the drawings and descriptions herein are proferred by way of example to facilitate comprehension of the invention and should not be construed to limit the scope thereof.