Abstract:
In a preferred embodiment, an optical indicia scanner, including: a housing; a light source disposed in the housing; a photodetector head disposed in the housing; and an optical indicia engaging, clear front plate disposed on the housing through which clear front plate the indicia is scanned when the optical indicia engaging, clear front plate is parallely disposed against the optical indicia.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation-in-part of U.S. patent application Ser. No. 09/563,047, filed May 1, 2000, titled LOW-COST OPTICAL INDICIA SCANNER, now abandoned. Benefit is claimed of the filing date of U.S. Provisional Patent Application No. 60/132,156, filed May 3, 1999, and titled LOW-COST OPTICAL INDICIA SCANNER. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to optical scanners generally and, more particularly, but not by way of limitation, to a novel, hand-held, optical indicia scanner and method of use, which scanner and method are particularly useful in scanning diffraction grating strips and laser-etched bar codes on silicon wafers in the field. 
     2. Background Art 
     Optical indicia scanners are widely used to read a variety of optical indicia and almost everyone is familiar with scanners used to read bar codes on products as they are purchased. Such optical indicia scanners may be fixed and the indicia to be read moved past the scanner or they may be hand-held and directed toward the indicia to be read. 
     A problem exists with hand-held such scanners when they are used to scan diffraction grating strips or bar codes etched on silicon wafers. In these cases, the reading head of the scanner must be held fairly perpendicular to the indicia being scanned and, particularly in the case of diffraction grating strips, it is necessary that the scanner be held fairly parallel to the major axis of the diffraction grating strip. This does not present a problem with fixed installations, since it is relatively easy to make sure that the reading head of the scanner is generally perpendicular to the indicia being scanned and that the path of the reading head is along the major axis of the scanner indicia. However, when it is desired to, for example, authenticate identifying indicia in the field, it is very difficult to properly align the scanner with the indicia being scanned. 
     Also, known hand-held optical indicia scanners generally include relatively complicated and expensive mechanisms and, thus, they are relatively expensive to manufacture. 
     Accordingly, it is a principal object of the present invention to provide an optical indicia scanner that is simple and that can be easily employed to scan diffraction grating strips and laser-etched bar codes on silicon wafers. 
     It is another object of the invention to provide such an optical indicia scanner and method that automatically place the reading head thereof generally perpendicular to the indicia being scanned. 
     It is an additional object of the invention to provide such an optical indicia scanner and method that facilitate the alignment of the scanner with the major axis of the indicia being scanned. 
     It is a further object of the invention to provide such an optical indicia scanner that is economical to manufacture. 
     Other objects of the present invention, as well as particular features, elements, and advantages thereof, will be elucidated in, or be apparent from, the following description and the accompanying drawing figure. 
     SUMMARY OF THE INVENTION 
     The present invention achieves the above objects, among others, by providing, in a preferred embodiment, an optical indicia scanner, comprising: a housing; a light source disposed in said housing; a photodetector head disposed in said housing; and an optical indicia engaging, clear front plate disposed on said housing through which clear front plate said indicia is scanned when said optical indicia engaging, clear front plate is parallely disposed against said optical indicia. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     Understanding of the present invention and the various aspects thereof will be facilitated by reference to the accompanying drawing figures, provided for purposes of illustration only and not intended to define the scope of the invention, on which: 
     FIG. 1 is an isometric view of an optical indicia scanner constructed according to the present invention. 
     FIG. 2 is a bottom plan view of the scanner. 
     FIG. 3 is a top plan view of the scanner. 
     FIG. 4 is a side elevational view of the scanner. 
     FIG. 5 is a cut-away, top plan view of the scanner scanning optical indicia. 
     FIG. 6 is a cut-away, side elevational view of the scanner scanning optical indicia. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Reference should now be made to the drawing figures on which similar or identical elements are given consistent identifying numerals throughout the various figures thereof, and on which parenthetical references to figure numbers, when used, direct the reader to the view(s) on which the element(s) being described is (are) best seen, although the element(s) may be seen on other figures also. 
     The present invention may be employed, for example, with diffraction gratings, holograms (a type of diffraction grating), blaze grating, or pixelgrams, although the operation of the invention is described with reference to diffraction gratings. 
     The drawing figures illustrate an optical scanner, constructed according to the present invention, and generally indicated by the reference numeral  20 . Scanner  20  includes a housing  22  having an integral handle portion  24  (FIG. 4) including a manually depressible activating switch  26  (FIG.  4 ). So arranged, scanner  20  may be manually gripped by handle portion  24  and activating switch  26  manually depressed to activate the scanner, the operation of which is described below. 
     FIG. 1 illustrates scanner  20  as including a power-communication cord  30  attached to housing  22  to furnish electrical power to the internal components of the scanner, although internal batteries (not shown) may be provided to furnish the electrical power and communication to external devices (not shown) or power may be provided by other conventional means (not shown). For this reason, power/communication cord  30  is not shown on the other figures, it being understood that the power/communication cord may or may not be provided as part of the present invention. 
     Referring to FIGS. 1-3, scanner  20  includes a light source/photodetector head  40  disposed in the front of the scanner for transverse movement back and forth in a plane across the front portion of the scanner. A transparent window  42  extends across the face of the front of scanner  20  in a plane parallel to that of the movement of the light source/photodetector head  40  and extends over the top of the space containing the light source photodetector head so as to allow visual sighting through the window by the operator of the scanner. Window  42  includes aligning marks  46  disposed on the front surface thereon, the function of which is described in detail below. 
     FIGS. 5 and 6 illustrate scanner  20  scanning optical indicia  50  disposed or printed on a substrate  52 . Optical indicia  50  may be a strip of diffraction gratings as is described in U.S. Pat. No. 5,627,663, issued May 6, 1997, to James S. Bianco et al., and titled SECURE OPTICAL IDENTIFICATION METHOD AND MEANS, or the optical indicia may be a laser-etched bar code as is described in U.S. Pat. No. 5,175,420, issued Dec. 29, 1992, to James S. Bianco, and titled BAR CODE SCANNER HAVING A LIGHT SOURCE/PHOTODETECTOR MOVABLE IN A RASTER PATTERN. 
     Light source/photodetector  40  includes a light source  80  and four photodetectors  82 . It will be understood that, when indicia  50  comprises a diffraction grating strip (FIG.  5 ), light source/photodetector head  40  will have a least a number of photodetectors equal to the number of different planes in which the diffraction grating strip diffracts light. In the case shown, the number would be four; however, it will be understood that more or fewer than four may be employed depending on the number of different planes. On the other hand, when optical indicia  50  comprises a laser-etched bar code, such as is used on silicon wafers, only one photodetector  82  may be employed in light source/photodetector head  40 . 
     FIGS. 5 and 6 also illustrate the mechanism and method by which light source/photodetector  40  is caused to move transversely back and forth across the front of scanner  20 . As seen on FIG. 5, aligning marks  46  are used to position scanner  20  so that at least the photodetector elements of light source/photodetector head  40  will scan along a line, “A—A” on FIG. 5, coincident with or substantially parallel to the lengthwise axis of optical indicia  50 . This is particularly important when optical indicia  50  comprises a series of diffraction grating elements as described in the above-referenced &#39;663 patent, since misalignment of the photodetector elements of light source/photodetector head  40  with respect to the optical indicia would cause skew which could cause the scanner to misread the optical indicia. As seen on FIG. 5, aligning marks  46  are aligned with an edge of optical indicia  50 , here, a strip of diffraction grating elements. Also, in this case, since the diffraction grating elements diffract light in four different planes, four photodetectors  82  are provided in light source/photodetector head  40 . 
     As seen on FIG. 6, scanner  20  is positioned with window  42  disposed against optical indicia  50  and, most preferably, against, and necessarily parallel to, substrate  52  on which the optical indicia is printed or otherwise formed. In this position, light source  80  of light source/photodetector head  40  is substantially orthogonal to the plane of the optical indicia  50 , thus permitting in the field an accurate scanning of the optical indicia. 
     The greatest accuracy in reading optical indicia  50  occurs when light source  80  (FIG. 6) is perpendicular to the optical indicia and when the light source moves along line “A—A” (FIG.  5 ), that is, when marks  46  are aligned with a path parallel to the line “A—A”. The degrees of perpendicularity and alignment do not have to be precise, although, as noted above, the most accurate reading of optical indicia  50  occurs when the degrees are exact. Whether an accurate reading can be made without such precision depends on a number of factors: the density of lines in optical indicia  50 , the wavelength of light source  80 , how pure the light source is, and the size of photodetectors  82 . 
     Continuing to refer to FIGS. 5 and 6, the mechanism by which light source/photodetector head  40  is moved transversely across the front of scanner  20  includes a reversible electrical motor  60  having a drive pulley  62  attached to the shaft  64  of the motor. A continuous belt  66  to which light source/photodetector head  40  is attached encircles drive pulley  62  and idler pulleys  68  and  70 , all the pulleys being aligned in a common plane. Light source/photodetector head  40  is journaled on a shaft  76  which is fixedly attached to housing  22  and is parallel to a line defined by the apexes of aligned marks  46 . 
     So arranged, selective rotation of motor  60  in one direction and then in the other direction will cause light source/photodetector head  40  to move transversely back and forth in housing  22  on shaft  76  in a plane parallel to the plane of optical indicia  50  so as to scan the optical indicia when the optical indicia are aligned with aligning marks  46 . Operation of the scanning mechanism is activated by the depression of activation switch  26  and conventional internal control circuitry (not shown). Decoding of optical indicia  50  is accomplished by conventional internal or external control circuitry (not shown). 
     Other means of moving light source/photodetector head  40  may be provided as well. 
     Most of the components of scanner  29  can be economically manufactured of thermoplastic materials using conventional techniques know in the art. The moving parts of scanner  20  are simple and the complicated scanning mechanisms of conventional optical indicia scanners are avoided. 
     Scanner  20  can be easily used in the field by employing internal batteries (not shown) or an external battery pack (not shown) to which power/communication cord  30  (FIG. 1) is attached. Whatever, the source of power, the construction of scanner  20  permits the scanner to be used in the field to read otherwise very difficult to read indicia by placing transparent window  42  (FIG. 1) against indicia  50  (FIG. 6) such that the path of light from light source  80  is perpendicular to the indicia and aligning marks  46  (FIG. 5) with a line parallel to the line of reading. 
     In the embodiments of the present invention described above, it will be recognized that individual elements and/or features thereof are not necessarily limited to a particular embodiment but, where applicable, are interchangeable and can be used in any selected embodiment even though such may not be specifically shown. 
     Terms such as “above”, “below”, “upper”, “lower”, “inner”, “outer”, “inwardly”, “outwardly”, “vertical”, “horizontal”, and the like, when used herein, refer to the positions of the respective elements shown on the accompanying drawing figures and the present invention is not necessarily limited to such positions. 
     It will thus be seen that the objects set forth above, among those elucidated in, or made apparent from, the preceding description, are efficiently attained and, since certain changes may be made in the above construction without departing from the scope of the invention, it is intended that all matter contained in the above description or shown on the accompanying drawing figures shall be interpreted as illustrative only and not in a limiting sense. 
     It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.