Abstract:
A bar code scanner has a housing including a surface having a transparent scanning window. The housing contains optical components including a spinner mounted on a rotating motor; pattern mirrors and a collector for collecting light reflected from a bar code during scanning. Wherein the spinner is an inverted frusto-conical spinner with internal reflecting surfaces, the diameter of the spinner increasing as distance from the motor increases, and wherein the collector is mounted substantially within the body of the spinner.

Description:
The present invention relates generally to bar code scanners and, more specifically, to scanners arranged to scan RSS bar code tags. 
   BACKGROUND OF THE INVENTION 
   Conventional bar codes have varying width bars and spaces suitably printed on a label. The bar code may take any conventional form in one or more dimensions, and includes, for example, the typical one-dimensional UPC form. The UPC symbology is based on a specification enacted by the Uniform Product Code Council, Inc. of Dayton Ohio. The typical UPC bar code includes a series or sequence of alternating dark bars and light spaces of varying widths. The bars and spaces are arranged in groups representing individual characters. The bar code starts with a left margin character and ends with a right margin character, and has a center reference character as well, with the characters provided there between representing any desired data. 
   The minimum width of either a bar or space in the UPC symbology is defined as a single module, which represents a unit width. The width of a single character coded using the UPC symbology is seven (7) modules. A seven module UPC character has two bar and two space elements which have varying widths to differentiate between the respective characters. 
   With the introduction of RSS bar code tags along side UPC tags into the market place, today&#39;s scanners must have higher density scan line patterns to be able to sustain high levels of performance. To consistently read the small RSS tags, the scanner must produce a scan pattern without any holes that would allow the tag to pass through without being read. The NCR 788X series single window bar code scanners have the highest density pattern available for this sized scanner, see  FIG. 1   a . However, its scan pattern is not dense enough for the small RSS tags. 
   Clearly there is a limit to the number and density of scan lines that can be produced by conventional scanners, without increasing the size of the scanner. 
   It is an object of the present invention to produce a bar code scanner, which obviates the problems discussed above. 
   SUMMARY OF THE INVENTION 
   According to a first aspect of the present invention there is provided a bar code scanner having a housing including a surface having a transparent scanning window; and containing optical components including an inverted spinner and pattern mirrors arranged to produce sets of densely packed scan lines 
   According to a second aspect of the present invention there is provided a bar code scanner having a housing including a surface having a transparent scanning window; and containing optical components including a spinner and pattern mirrors, wherein the mirrors are arranged in a partial frusto-conical arrangement around the spinner. 
   According to a third aspect of the present invention there is provided a bar code scanner having a housing including a surface having a transparent scanning window; and containing optical components including, a spinner mounted on a rotating motor, pattern mirrors and a collector for collecting light reflected from a bar code during scanning, wherein the spinner is an inverted frusto-conical spinner with internal reflecting surfaces, the diameter of the spinner increasing as distance from the motor increases, and wherein the collector is mounted substantially within the body of the spinner. 
   An advantage of a bar code scanner in accordance with the present invention is that the scanner is cheaper and less complex to produce than prior art scanners of a comparable size. An additional advantage of the scanner in accordance with the present invention is that the scanner is capable of producing more densely packed scan lines than prior art scanners of a comparable size. 

   
     DESCRIPTION OF THE DRAWINGS 
     The invention, in accordance with preferred and exemplary embodiments, together with further objects and advantages thereof, is more particularly described in the following detailed description taken in conjunction with the accompanying drawings, in which: 
       FIG. 1   a  illustrates a typical scan pattern for a prior art scanner of a comparable size to a scanner in accordance with the present invention; 
       FIG. 1   b  illustrates the scan pattern for a scanner in accordance with the present invention; 
       FIG. 2  is a schematic representation of a the optical arrangement of a prior art scanner; 
       FIG. 3  is a schematic representation of a bar code scanner in accordance with the present invention; and 
       FIGS. 4   a  to  4   d  are schematic representations of the optical arrangement of the scanner of FIG.  3 . 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 2  illustrates the optical arrangement of a prior art bar code scanner  10 . The scanner includes a housing  32  in which its various operating components are suitably mounted. 
   A laser  16 , typically in the form of a laser diode, is mounted in the housing for emitting an outbound laser beam  16   a . A rotary spinner  38  is suitably disposed in the outbound optical beam path with the laser  16  for segmenting the beam in corresponding optical paths in alignment with a plurality of primary pattern mirrors  40  which reflect corresponding scan lines out a transparent window  42  of the scanner  10 . The scan lines may be produced from direct reflection between the spinner and the primary pattern mirrors, or secondary pattern mirrors  44  may be optically aligned with corresponding ones of the primary pattern mirrors to produce the desired scan line pattern emitted through the scanning window  42 . 
   The pattern mirrors may be oriented in the scanner housing  32  in any conventional manner for producing the desired scan line pattern for each revolution of the spinner  38 . In this way, a conventional barcode  12  may be positioned in front of the window  42  for being traversed by any one or more of the scan lines in the pattern for returning reflected light  16   b  therefrom inbound in the opposite direction for collection by the pattern mirrors  40 ,  44  and rotating spinner  38  for decoding. 
   A suitable collection mirror  50  is suitably optically aligned between the laser  16  and the spinner  38 , and may include a center aperture therein, through which the outbound scan beam  16   a  passes without obstruction. Since the reflected light  16   b  is diffuse from being reflected off the barcode  12 , the pattern mirrors, spinner, and collection mirror  50  are suitably sized in area for collecting sufficient reflected light  16   b  for use in decoding the barcode. 
   The reflected or collection light  16   b  is reflected from the collection mirror  50  and focused through a suitable focusing lens  52  onto a conventional photodetector  54 , which produces a corresponding electrical signal which is decoded in the electrical controller of the scanner in a conventional manner. 
   Illustrated schematically in  FIG. 3  is a laser bar code scanner  10  for scanning and decoding a conventional bar code  12  printed on a suitable label  14 . The bar code  12  may take any conventional form in one or more dimensions including the conventional one-dimensional UPC symbology illustrated. The exemplary bar code  12  illustrated in  FIG. 1  includes a plurality of sequential or alternating dark bars  12   a  and white spaces  12   b , which are straight and parallel to each other and have corresponding varying widths W.sub.b and W.sub.s. The bars and spaces are arranged in a plurality of sequential groups defining respective characters of equal width. The minimum width of a bar or a space is defined as the minimum width module, and in the UPC symbology must exceed 9 mils by specification. A single UPC character is defined as having two bars  12   a  and two spaces  12   b  of varying widths. And, the specified widths of a single character coded using the UPC symbology must, by specification, be seven modules. Furthermore, the UPC symbology defines the maximum bar width as being four modules. 
   In the exemplary bar code  12  illustrated in  FIG. 3 , the bar code conventionally starts with a left margin character  12   c , ends with a right margin character  12   d , and has a center reference character  12   d , with the remaining bars and spaces there between defining desired data characters. As indicated above, each of the data characters has a total width of seven modules and includes two bars and two spaces. 
   The exemplary scanner  10  illustrated in  FIG. 3  includes conventional means for optically scanning the bar code  12  sequentially across the bars and spaces  12   a,b  over the total width of the bar code  12  from the left margin character  12   c  to the right margin character  12   d . In the preferred embodiment illustrated, scanning is accomplished by using a conventional laser  16  which emits a suitable laser beam  16   a  which is suitably scanned across the face of the bar code  12  by a conventional sweep generator  18  which may take the form of a rotating multifaceted mirror  38 . The laser beam  16   a  is scanned transversely across the bar code  12  in a scan direction S so that back scattered light  16   b  reflects off the bars and spaces back to the scanner. Since the bars  12   a  are dark, very little light is back scattered therefrom, whereas the spaces  12   b  are substantially white and more effectively backscatter light to the scanner. 
   A conventional photodetector  20  is provided in the scanner  10  and is suitably optically aligned therein for receiving the back scattered light  16   b  and producing an electrical bar code signature  20   s  alternating in intensity between maximum and minimum values corresponding with the back scattered light  16   b  from the spaces  12   b  and bars  12   a , respectively. The time duration of the maximum and minimum intensity portions of the signature  20   s  corresponds with the varying widths of the bars and spaces. Since the scan beam  16   a  is scanned across the bar code  12  at a known and constant rate of speed, the bar code signature  20   s  is representative of the bar code  12  itself and may be decoded in a conventional decoder  22  specifically configured for the corresponding bar code symbology printed on the label  14 . 
   The decoder  22  may take any conventional form and is typically a digitally programmable microprocessor containing suitable software for analyzing the bar code signature  20   s  and decoding the data contained therein. The scanner  10  is electrically joined to a suitable display  24  which may be used for displaying certain information encoded in the bar code  12 , such as the price of a consumer product represented thereby. When the bar code  12  is accurately scanned and decoded, the data may be presented on the display  24 , and a small speaker  26  operatively joined to the scanner  10  may beep to indicate successful decoding of the bar code  12 . 
   The bar code scanner of  FIGS. 4   a-d  is functionally the same as that detailed in  FIG. 3 , although the arrangement of the optical components are very different to those of the prior art arrangement illustrated in  FIG. 2 , as will be described below. 
   The scanner of  FIGS. 4   a  to  4   d  includes an inverted polygon spinner  60  and a collector  62  placed substantially within the body of the spinner for a compact optical design allowing greater volume and optical path length for the generation of scan lines. The spinner is 6 sided and the scanner contains 5 pattern mirrors  64   a  to  64   e  to generate  30  scan lines total. There are 6 horizontal scan lines (from mirror  64   e ), 12 diagonal lines (from mirrors  64   c  &amp;  64   d ) and 12 vertical lines (from mirrors  64   a  &amp;  64   b ). The spinner  60  is mounted substantially vertically with a slight tilt backwards as shown in the aforementioned figures, for compactness and for proper scan line orientation. The inverted spinner has mirrored reflective internal facets, thus allowing the placement of the collector within the spinner, unlike normal spinners in which the outer facets are reflective. 
   As illustrated in  FIG. 4   b , the pattern mirrors  64   a  to  64   e  are laid out such that they form a partial shell or cone around the inverted spinner  60 , starting opposite the spinner facet which reflects the laser out of the spinner, when in use. As the spinner rotates, the laser beam reflects off of each facet, tracing out an arc of light for each spinner facet, see  FIG. 4   d . Each spinner facet is at a unique angle to produce a unique arc of light. The arc of light is then intercepted by the shell of pattern mirrors. The pattern mirrors are angled such that the right and left vertical mirrors will form vertical scan lines, the right and left diagonal mirrors form diagonal scan lines, and the horizontal mirror will form horizontal scan lines. The pattern mirrors are large enough to intercept all the scan lines, with excess room for tolerance buildup, alignment errors, and return light collection. Thus the dense scan pattern illustrated in  FIG. 1   b  is created by the scanner in accordance with the present invention. The passage of light through the scanner is best described with reference to  FIG. 4   a . When in use, light is emitted from the laser  66 , which is reflected, in turn, from the laser mirror  68 , the spinner  60 , the pattern mirrors  64   a  to  64   e  and finally the exit mirror  70 . From the exit mirror the laser light, in the form of scan lines, exits the scanner through the window  72 , whereupon it strikes a bar code to be scanned. Reflected light from the bar code is directed back into the scanner, off of the exit mirror, the pattern mirrors, the spinner and the collector  62  and mirrors  76  and  78  into the detector  22 . 
   The foregoing description of the preferred embodiment of the invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations are possible in light of the above teaching. For example, the configuration of mirrors is not the only configuration, which will produce a useable scan pattern with the inverted spinner. It is intended that the scope of the invention be limited not by this detailed description, but rather by the claims appended hereto.