Abstract:
A mirrored spinner with paired offset facets for scattering a laser beam. The mirrored spinner includes a first number of mirrored facets, including a second number of pairs of offset mirrored facets.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to optical scanners and more specifically to a mirrored spinner with paired offset facets. 
     Typical bar code scanners use mirrored spinners to scan an incident laser beam into a series of ray fans. These fans, when projected onto a plane, produce a series of approximately straight curves (scan lines). Typically, the several facets of a mirrored spinner are inclined at different angles, so as to produce a set of spaced apart parallel lines. The length of these lines is proportional to the tangent of the facet scan angle and the distance between the spinner and the projection plane. Conventional spinners are regular polygons and produce sets of equal length scan lines. 
     In scanners incorporating conventional spinners for producing parallel horizontal scan lines for scanning vertically oriented bars and spaces and parallel vertical scan lines for scanning horizontally oriented bars and spaces, some of the vertical scan lines are redundant and wasted. The vertical lines fill the scan volume by their length, and do not require as much repetition. 
     Therefore, it would be desirable to provide a mirrored spinner with paired offset facets. 
     SUMMARY OF THE INVENTION 
     A mirrored spinner with paired offset facets is provided. 
     A mirrored spinner with paired offset facets for scattering a laser beam. The mirrored spinner includes a first number of mirrored facets, including a second number of pairs of offset mirrored facets. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram of an example optical scanner; 
         FIG. 2  is a schematic of an example mirrored spinner with paired offset facets; 
         FIG. 3  illustrates the difference between conventional scan lines and example scan lines produced using the example mirrored spinner; and 
         FIG. 4  illustrates an example scan pattern produced using the example mirrored spinner. 
     
    
    
     DETAILED DESCRIPTION 
     With reference to  FIG. 1 , an example bar code scanner  10  includes laser  12 , mirrored spinner  16 , pattern mirrors  18 , collector  20 , detector  22 , and control circuitry  24 . Laser  12  produces a laser beam. 
     Mirrored spinner  16  directs the laser beam to pattern mirrors  18 . Mirrored spinner  16  further directs light reflected from item  30  to collector  20 . Motor  28  rotates mirrored spinner  16 . 
     Pattern mirrors  18  produce scanning light beams for scanning bar code  32  on item  30 . Pattern mirrors  18  further collect light reflected from item  30  and direct the reflected light to mirrored spinner  16 . 
     Collector  20  collects the reflected light from mirrored spinner  16 . 
     Detector  22  converts the reflected light into electrical signals based upon the intensity of the reflected light. 
     Control circuitry  24  controls operation of laser  12  and motor  28  and decodes bar code information contained within the electrical signals received from detector  22 . Control circuitry  24  sends decoded bar code information to a computer  26 , such as a retail terminal. 
     Referring to  FIG. 2 , an example mirrored spinner  16  is illustrated in detail. Example mirrored spinner  16  includes six mirrored facets  40 - 50 . Four or more mirrored facets are envisioned. 
     Example mirrored spinner  16  includes two pairs of offset mirrored facets,  40 ,  42  and  44 ,  46 . The offset nature of the facets in this example is defined relative to a polygon spinner with six equal sides. Facets  40  and  44  are oriented at a vertex angle θ 1  from a line  64  through vertex  60  and normal to centerline  62 . Facets  42  and  46  are oriented at vertex angle θ 2  from a line  68  through vertex  66  and normal to centerline  62 . 
     Any method of determining offset that produces different vertex angles θ 1  and θ 2  is envisioned. One example way of determining offset is to define an offset angle Δ, and substract it from one pair of facet angles and add it to another pair of facet angles. 
     For example, in a polygon spinner with six equal sides, all six sides have the same vertex angle of 30°. Vertex angle θ 1  equals 30°−Δ, and vertex angle θ 2  equals 30°+Δ. In the illustrated example, offset angle Δ is about 15°. Therefore, vertex angle θ 1  is about 15°, and vertex angle θ 2  is about 45°. 
     Facets  48  and  50  link the pairs of offset facets together. Facet  48  link facet  40  to facet  46 . Facet  50  links facet  44  to facet  42 . 
     With reference to  FIG. 3 , offset mirrored facets  40 ,  42  and  44 ,  46  produce a set of scanning beams  70 . Relative to scanning beams produced by a conventional mirrored spinner with substantially equal facet angles, whose scanning beams extend from reference line  72  to reference line  74 , mirrored spinner  16  produces scanning beams  70  that are each shortened on one end and extended on an opposite end. 
     Mirrored facets  40 ,  46 , and  50  contribute to production of scanning beams  78 . Mirrored facets  42 ,  44 , and  48  contribute to production of scanning beams  76 . Scanning beams  76  and  78  may be interlaced or not. 
     Mirrored spinner directs scanning beams  70  towards pattern mirrors  18 , which use portions of scanning beams  70  to produce scan lines  80 . In this example, the portions are defined by reference lines  72 ,  73 ,  74 , and  75 . 
     With reference to  FIG. 4 , an example scan pattern  80  is illustrated that is based upon use of mirrored spinner  16 . Using an arbitrary arrangement of pattern mirrors  18 , scan pattern  80  includes six horizontal scan lines  82  from the portion of scanning beams  70  between reference lines  72  and  74 . Mirrored facets  40 - 50  all contribute to production of horizontal scan lines  82 . 
     Scan pattern  80  further includes three left vertical scan lines  84  and three right vertical scan lines  86 . Left vertical scan lines  84  use the portion of scanning beams  70  left of reference line  73 . Mirrored facets  42 ,  44 , and  48  contribute to production of left vertical scan lines  84 . 
     Right vertical scan lines  86  use the portion of scanning beams  70  right of reference line  75 . Mirrored facets  40 ,  46 , and  50  contribute to production of right vertical scan lines  86 . 
     Use of spinner  16  reduces the number of vertical scan lines on each side from six, as with a conventional spinner, to three. However, spinner  16  makes left and right vertical scan lines  84  and  86  longer than the vertical scan lines produced by a conventional spinner. Therefore, fewer vertical scan lines are required. 
     Advantageously, use of spinner  16  provides flexibility in pattern design. For many barcode scanner applications, generating fewer but longer vertical scan lines and generating additional scan lines in the center of the scan pattern results in a far superior scan pattern. To this end, additional pattern mirrors  18  may be added in order to devote laser power that would otherwise be used by a conventional spinner to generate six left and six right vertical scan lines to generate additional scan lines in the center of scan pattern  80 . 
     Example scan pattern  80  further includes three left and three right diagonal scan lines  88  and  90 . Use of spinner  16  makes left and right diagonal scan lines  88  and  90  longer than the diagonal scan lines produced by a conventional spinner. 
     Left diagonal scan lines  80  use the portion of scanning beams  70  between reference lines  72  and  73 . Mirrored facets  42 ,  44 , and  48  contribute to production of left diagonal scan lines  88 . 
     Right diagonal scan lines  80  use the portion of scanning beams  70  between reference lines  74  and  75 . Mirrored facets  40 ,  46 , and  50  contribute to production of right diagonal scan lines  90 . 
     Although particular reference has been made to certain embodiments, variations and modifications are also envisioned within the spirit and scope of the following claims.