Abstract:
A bar code scanner and method of operation thereof is disclosed. The bar code scanner comprises a housing including a surface having a transparent scanning window; and optical components including a spinner located within the housing. The optical components are arranged to produce both a first set of scan lines focused outside of the housing and remote from the scanning window; and a second set of scan lines focused outside of the housing and adjacent the scanning window. The method includes the steps of placing a bar code to be read in either a first position where said first set of scan lines are focused or in a second position wherein said second set of scan lines are focused.

Description:
The present invention relates generally to bar code scanners and, more specifically, to scanning both small and large bar codes with the same scanner. 
     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. 
     There are many types of bar code symbologies (encoding schemes). For example, there are a number of different one-dimensional bar code symbologies. These symbologies include UPCIEAN, Code 39, Code 128, Codabar and Interleaved 2 of 5. There are also 2 dimensional bar code symbologies. 
     Bar code scanners utilize a laser beam in order to illuminate a bar code, during the scanning process. The light reflected from the pattern of bars and spaces is analyzed in order to read the bar code. For the bar code to be read clearly the laser beam must be focused at or adjacent the bar code. Laser beams used to illuminate bar codes have a limited depth of field over which they are focused. Typically, the beam will focus several inches beyond the scanner window in order to maximize the portion of its usable range that is in the scan zone. 
     However, this results in the laser spot at the scan window being large and unfocused. When the operator encounters a small (demagnified) bar code he or she typically places the bar code on the window, where unfortunately it is even less likely to be read by 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 optical components including a spinner located within the housing and arranged to produce both a first set of scan lines focused outside of the housing and remote from the scanning window; and a second set of scan lines focused outside of the housing and adjacent the scanning window. 
     According to a second aspect of the present invention there is provided a method of scanning a bar code, utilizing a bar code scanner having a housing including a surface having a transparent scanning window; and optical components including a spinner located within the housing and arranged to produce both a first set of scan lines focused outside of the housing and remote from the scanning window; and a second set of scan lines focused outside of the housing and adjacent the scanning window, including the steps of placing a bar code to be read in either a first position where said first set of scan lines are focused or in a second position wherein said second set of scan lines are focused. 
    
    
     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 is a schematic representation of a bar code scanner in accordance with the present invention; and 
     FIG. 2, is a schematic representation of the optical arrangement of the scanner of FIG.  1 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Illustrated schematically in FIG. 1 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. 1, 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. 1 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 . 
     FIG. 2 illustrates a barcode scanner  10 , which may be configured for presentation or pass-by operation as desired. 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 typically includes 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  46 , 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. 
     The scanner  10  further comprises a beam splitter  56  and an additional mirror  58 . The beam splitter  56  creates a secondary laser beam  16   c , which is directed through the scanning window  42  via the additional mirror  58 . In this way the secondary laser beam  16   c  travels a greater optical path than the primary laser beam, prior to leaving the housing  32 . Consequently, the secondary laser beam will be focused closer to the scanning window  42  than the primary laser beam. If the optical path lengths are adjusted accurately the secondary laser beam can be focussed adjacent the scanning window  42 . 
     In another embodiment, not shown, the additional mirror  58  can be replaced by a slab of material with a high refractive index, which is placed in the path of the secondary laser beam, thus increasing its optical path length prior to reaching the scanning window  42 . If the slab is wedge shaped the specific increase in optical path length can be adjusted by varying the width of the material in the optical path of the secondary laser beam. Thus the point of focus of the secondary laser beam, i.e. its distance from the scanning window, can be adjusted. 
     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. It is intended that the scope of the invention be limited not by this detailed description, but rather by the claims appended hereto.