Hand held scanner
This application is a continuation of application Ser. No. 07/438,175, filed Nov. 16, 1989, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to optical scanners that convert graphic information and printed text to digital signals. More particularly, the present invention relates to hand-held optical scanners. 
     2. Discussion of Related Art 
     Hand-held scanning wands are well known in the art. These wands are stroked across graphical information such as a strip of bar code or a line of text and, in cooperation with electronic devices located in the wand or communicating with the wand, convert the graphical information into digital signals that can be processed by a computer. 
     For scanning bar code, the wand need only pass from one end of a bar code strip to the other, without regard to the wand&#39;s vertical placement within the strip. However, when other graphical images are scanned, particularly printed text, the position of the wand on the line of text along the axis normal to the wand&#39;s line of travel down the line of text affects the usefulness of the converted information. In particular, where the wand is used in conjunction with optical character recognition (OCR) software to convert printed text to computer-usable text, e.g. ASCII code, entire characters must be scanned in the course of each such stroke of the wand in order to assure that the characters will be accurately reproduced when the line of text is converted to digital data by the OCR software. 
     Thus, it is critically important that the top and bottom edges of the line of text remain within the detection zone of the wand as it is stroked along a line of text. However, the smaller and more convenient a wand is to use, the smaller the detection zone at the tip of the wand will be, and a smaller detection zone makes it more difficult to maintain the necessary alignment between the tip of the wand and the line of text. 
     SUMMARY OF THE INVENTION 
     It is a principal object of the invention to provide improved control of the relationship between a wand and the information it scans as the wand is stroked across an image formed on the object plane. 
     This and other objects of the invention are achieved by a wand that comprises a tip constructed so that the information being scanned on the object plane is substantially or entirely visible through the tip. The tip includes a surface which defines the object plane of the wand. The wand also comprises means for defining a target zone in the wand&#39;s maximum detection zone. The means defining the target zone cooperates with said tip so as to be visible to the operator through the tip of the wand. 
     In a particular embodiment, the wand includes a handle to which the tip is connected, and the longitudinal axis of the handle forms an oblique angle with the object plane. 
     In another embodiment, the wand comprises a sensor having a given maximum detection zone and a light source. The light source is preferably located behind the light sensor, on the opposite side of the light sensor from the light sensor&#39;s object plane, and the light from the light source is provided to the target area on the object plane by a light conduit. The light conduit preferably includes optical fibers that provide light at a plurality of locations for projection onto the target area. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     The features and advantages of the present invention will be better understood when the following detailed description of a preferred embodiment is considered in conjunction with the drawings provided, wherein: 
     FIG. 1 is perspective view of apparatus in accordance with the present invention; 
     FIG. 2 is a top view of the apparatus of FIG. 1; 
     FIG. 3 is a bottom view of the apparatus of FIG. 1 in cross section; 
     FIG. 4 is a partially cut away side view of a first alternative embodiment of the present invention in cross section; 
     FIG. 5 is a front view of the first alternative embodiment; and 
     FIG. 6 is a detail side view of a second alternative embodiment of the present invention in cross section. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference to FIGS. 1 and 2, a scanning wand 10 in accordance with a preferred embodiment of the present invention comprises a slim, rectangular handle 12 and a hollow &#34;bullnose&#34; transparent tip 14 that is approximately 38 mm long. Viewing window openings 15 are provided on either side 16 of the tip 14 and on the upper 17 and lower 18 surfaces of the tip 14 at its distal end. The tip 14 also has a rectangular scanning window opening 19 in the semi-cylindrical curved surface 20 at its distal end. The scanning window opening 19 is continuous with a slot-shaped opening 21 in the curved surface 20 at the end of the tip 14. The slot 21 extends parallel to the axis (A) of the curved surface 20. 
     When the wand 10 is used to provide information input of OCR software, the edges of the scanning window opening 19 that touch the document define target zone within which the entire height of the alphanumeric characters in a given line of text that is being scanned should appear, in order to assure reliable conversion of the characters in the line of text to a computer-usable form. The window opening 19 provides a clear view of the characters being scanned. The slot opening 21 provides a clear view of the areas of the document immediately above and below each character in the line of text, to assist the operator in guiding the target zone tip of the wand 10. In this embodiment the target zone defined on the object plane by the scanning window 19 is also coextensive with the maximum detection zone provided by the wand&#39;s light sensor. Alternatively, a target zone that is somewhat smaller than the maximum detecting zone may be used, thereby providing a safety margin to prevent slight deviations from the correct alignment of the target zone with the line of text from causing errors in the converted text. 
     The handle 12 comprises a straight portion 23 that is approximately 127 mm long and a shorter, curved portion 24. A scanning switch 26 is mounted on the curved portion 24 of the handle 12. This switch 26 enables the wand&#39;s light sensor and increases the brightness of the wand&#39;s light source, to initiate the scanning operation. 
     A programmable function switch 28 is provided behind the scanning switch 26, on the straight portion 23 of the handle 12. This switch may be software programmed to select an alternative scanning mode, a special mode for use with bar code, for example, or to insert an end of line (EOL) code into scanned text, or to provide some other software-defined function. 
     The axis (A) of the semi-cylindrical curved surface 20 and the surface defined by the two edges 29 of the slot 21 that are parallel to the axis (A) of the curved surface 20 form a 49-degree angle α with the longitudinal axis (B) of the handle. Thus the axis (B) of the handle forms an oblique 131-degree angle β to the document being scanned when the two edges 29 of the slot 21 in the tip 14 are stroked across the document, thereby placing the document in the wand&#39;s object plane, as explained in greater detail below. These complementary angles α and β may be varied to accommodate applications where access to the document being scanned is obstructed, as in copier print quality maintenance applications. This particular oblique angle for the handle 12 has been found to be most satisfactory for maximizing target zone visibility and operator comfort. 
     With reference to FIG. 3, it can be seen that the light source 30 of the wand 10 is mounted on a circuit board 32 behind the CCD detector array 34 of the light sensor 36. A bundle of optical fibers 38 directs the light provided by the light source 30 to the scanning end of the handle 12. The fiber bundle 38 is bifurcated so that half of the bundle 38 passes through the circuit board 32, and each half then fans out to form two thin ribbon cables 40 of optical fibers that pass along the length of the handle 23 on either side of the light sensor 36. The ribbon cables 40 terminate at the upper edge of the tip 14 and are glued in place against the inside surface of the tip 14 by adhesive 42. Alternatively, the ribbon cables may be held in place by clips formed on the interior surface of the handle 12. The ends 43 of the ribbon cables 40 are angled inward so as to direct light away from the sides 16 of the tip 14 toward the slot 21, thereby providing illumination of the target zone on the document being scanned. 
     When the two edges 29 of the cylindrical curved surface 20 of the tip 14 on either side of the slot 21 are resting on a document, see FIG. 4, the longitudinal axis (B) of the wand is disposed in a plane perpendicular to the document at a 49-degree angle with the document, and the document is lying in the object plane 44 of the light sensor 36, thereby providing optimum focus for the image of information from the document on the detector array 34. The image on the portion of the wand&#39;s object plane 44 that appears in the window 19 is then inverted and focused on the detector array 34 by a lens 46 having an optical axis (C). The image plane on the detector array 34 is oriented so that lines (D) and (E) normal to the image plane provided by the detector array 34 and normal to the object plane 44 of the light sensor 36, respectively, form angles σ, δ with the optical axis (C) of the lens 46, as is illustrated in FIG. 6. In all embodiments, the image plane of the detector is angled back from the object plane to compensate for the obliqueness of the lens with respect to the object plane. 
     FIGS. 4 and 5 show one alternative embodiment of the present invention. In this embodiment, the hollow transparent tip 50 has a scanning window opening 52 and a slot opening 54 but no viewing window openings. The ribbon cables 40 lie flush against the sides 55 of the curved portion 24 of the handle 12 and ends 43 of the optical fibers in the ribbon cables 40 abut the upper edge 56 of the transparent tip 50 so that the light transmitted by the optical fibers is directed into the solid sides of the hollow tip. 
     The light from the ribbon cables 40 is then conducted by internal reflection within the transparent tip 50 to two planar exit facets 58 that are located along each side of the scanning window 52 parallel to the edges 57 of the slot 54. These planar facets 58 are oriented at a 45-degree angle to the wand&#39;s object plane, so that light exiting through these facets 58 is directed into the scanning window 52 to provide even illumination of the target zone 59 on the object plane. 
     FIG. 6 shows another alternative embodiment of the present invention that is externally similar in appearance to the scanning wand 10 shown in FIG. 1. However, in this scanning wand 60, the light source 62 and a spherical lens 64 for the light sensor (not shown) are oriented so that their respective axes (F) and (C) intersect. The axis (F) of the light source 62 forms a 15-degree angle τ with line (E), and the optical axis (C) of the spherical lens 64 forms a 30-degree angle δ with the line (E) that is normal to the object plane 44, providing optimum illumination for the target area 66 of the light sensor. For applications where access to the document is obstructed, the angle δ may also be varied. The angle δ can even be increased to about 60 degrees by the use of a complex lens. However, the selected offset angles for the handle 12 and δ for the optics 34, 62, 64 provide an optimum combination of scanning accuracy and operator convenience. 
     The present invention has been described with particular reference to presently preferred embodiments thereof. However, variations and modifications thereof will be obvious to one skilled in the art. For example the tip shown in FIG. 1 may be made of stainless steel. The disclosed preferred embodiment is illustrative rather than limitative of the invention. The scope of the invention is defined by the appended claims.