Abstract:
A bar code scanner with laser beam oscillator which rasters a laser beam to produce more scan line coverage. The bar code scanner includes a laser for producing a laser beam, a mirrored spinner, and a laser beam oscillator optically located between the laser and the mirrored spinner for continuously deflecting the laser beam about an undeflected path of the laser beam.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates to bar code readers and more specifically to a bar code scanner with laser beam oscillator.  
         [0002]     Bar code readers are well known for their usefulness in retail checkout and inventory control. They are typically connected to a point-of-sale (POS) terminal, along with other peripherals.  
         [0003]     Typical bar code scanners generally have very good throughput on easy to read bar code labels. What separates the exceptional scanners is the ability to read difficult bar code labels such as small, poorly printed, low contrast, wrinkled, Reduced Space Symbology (RSS), and two-dimensional (2D) bar code labels. Because most scanners have a distinct, stationary scan pattern with a finite number of scan lines, the probability of the lines locating and reading these difficult bar code labels may be quite low. Furthermore, a raster scan pattern is required to be able to read the new 2D bar code labels.  
         [0004]     Therefore, it would be desirable to provide a bar code scanner that is capable of reading a wide variety of bar code labels.  
       SUMMARY OF THE INVENTION  
       [0005]     In accordance with the teachings of the present invention, a bar code scanner with laser beam oscillator is provided.  
         [0006]     The bar code scanner includes a laser for producing a laser beam, a mirrored spinner, and a laser beam oscillator optically located between the laser and the mirrored spinner for continuously deflecting the laser beam about an undeflected path of the laser beam.  
         [0007]     It is accordingly an object of the present invention to provide a bar code scanner with laser beam oscillator.  
         [0008]     It is another object of the present invention to provide a bar code scanner capable of reading a wide variety of bar code labels, including small, poorly printed, low contrast, wrinkled, Reduced Space Symbology (RSS), and two-dimensional (2D) barcode bar code labels. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]     Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which this invention relates from the subsequent description of the preferred embodiments and the appended claims, taken in conjunction with the accompanying drawings, in which:  
         [0010]      FIG. 1  is a block diagram of a bar code scanner;  
         [0011]      FIG. 2  is a block diagram of a laser beam oscillator;  
         [0012]      FIG. 3  is a diagrammatic view of the bar code scanner illustrating operation of the laser beam oscillator;  
         [0013]      FIG. 4  is a diagrammatic view of an alternative oscillator for the laser beam oscillator;  
         [0014]      FIGS. 5A-5D  are diagrammatic views illustrating operation of various types of laser beam oscillating elements; and  
         [0015]      FIGS. 6A and 6B  illustrate the difference between a stationary scan pattern and a scan pattern having a laser beam oscillator.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0016]     Referring now to  FIG. 1 , bar code reader  10  includes laser  12 , laser beam oscillator  14 , spinner  16 , pattern mirrors  18 , collector  20 , and detector  22 .  
         [0017]     Laser  12  produces a laser beam. Laser  12  preferably includes a laser diode, and may additionally include a focusing lens or lenses, and a collimating aperture for directing the laser beam along a path from laser  12 .  
         [0018]     Laser beam oscillator  14  deflects the laser beam from its undeflected path. Laser beam oscillator  14  continuously varies the angle of the laser beam to generate groups of raster scan patterns containing an infinite number of scan lines about original stationary scan lines. This raster effect causes the scan lines to fill much more of the exit window, making detection and reading of bar code labels easier. This raster effect also allows scanner  10  to read two-dimensional bar code labels. The substantial increase in pattern density allows scanner  10  to read truncated bar code labels and Reduced Space Symbology (RSS) bar code labels.  
         [0019]     Advantageously, deflection of the laser beam prior to spinner  16 , as opposed to after spinner  16 , requires much less power, space, and cost, and is more reliable.  
         [0020]     Spinner  16  directs the oscillating laser beam to pattern mirrors  18 . Spinner  16  preferably includes planoreflective mirrored surfaces oriented at different angles to produce a plurality of different oscillating scanning beams from the oscillating laser beam. Spinner  16  additionally directs light reflected from item  30  to collector  20 . Spinner  16  is rotated by motor  34 .  
         [0021]     Pattern mirrors  18  direct oscillating scanning beams from spinner  16  to create oscillating scan lines for scanning item  30 . Pattern mirrors  18  also direct the light reflected from item  30  to spinner  16 .  
         [0022]     Pattern mirrors  18  preferably include a plurality of flat mirrors arranged in different positions and different orientations so as to create a plurality of different oscillating scan lines that scan item  30  from a plurality of different directions.  
         [0023]     Collector  20  collects the light reflected from item  30  and directs it to detector  22 . Collector  20  may include a focusing mirror or lens.  
         [0024]     Detector  22  converts the light reflected from item  30  into electrical signals.  
         [0025]     Processing and decoding circuitry  24  processes the electrical signals, converts the electrical signals to digital signals, and decodes the digital signals to produce bar code information associated with bar code  32 .  
         [0026]     Turning now to  FIG. 2 , laser beam oscillator  14  includes oscillating element  36 .  
         [0027]     Oscillating element  36  rotates, translates, tilts, or otherwise deflects laser beam  60  from laser  12  about an undeflected path  66  to produce a variable scan pattern. Oscillating element  36  may include a window flat, wedge, prism, mirror, piezoelectric device, acousto-optical beam deflector, diffractive beam deflector, or any other optical element that would produce a rotation or linear translation of laser beam  60  about its undeflected path  66 .  
         [0028]     Oscillator  38  causes oscillating element  36  to rotate, translate, or tilt. Oscillator  38  may include a motor or propeller driven by windage from spinner  16 . Oscillator  38  may also include a piezoelectric device, a galvanometer, an acousto-optical device, or a voice coil.  
         [0029]     With reference to  FIG. 3 , an example embodiment of bar code reader  10  is illustrated in more detail.  
         [0030]     Oscillating element  36  includes a flat mirror and oscillator  38  includes a motor.  
         [0031]     Oscillating element  36  oscillates and reflects laser beam  60  towards spinner  16 . Oscillating element  36  is mounted within aperture  52  of collector  20 .  
         [0032]     Pattern mirrors  44  and  48  direct oscillating laser beam  62  along a ray path from spinner  16  through window  50 .  
         [0033]     With reference to  FIG. 4 , oscillator  38  may include a propeller to eliminate the cost, power consumption, and reliability issues of a second motor. The propeller is driven by windage  74  from spinner  16 . Wall  72  creates a channel which directs windage  74  to airflow tube  70 . Airflow tube  70  directs windage  74  to the propeller. Oscillating element  36  is mounted to the hub of the propeller.  
         [0034]     Turning now to  FIGS. 5A-5D , operations of various optical elements used as oscillating element  36  are illustrated.  
         [0035]      FIG. 5A  illustrates a flat refractive window element. This type of optical element produces translation of laser beam  60  through tilting of the refractive window element, and rotation of laser beam  60  through tilting and rotation of the refractive window element.  
         [0036]      FIG. 5B  illustrates a refractive wedge window element. This type of optical element produces a tilt and rotation of laser beam  60  about the unoscillated beam path  66  through rotation of the refractive wedge window element.  
         [0037]      FIG. 5C  illustrates a prism element. This type of optical element produces a rotation of laser beam  60  about the unoscillated beam path  66  through rotation of the prism element.  
         [0038]      FIG. 5D  illustrates a flat mirror element. This type of optical element reflects laser beam  60  to produce a tilt and rotation of laser beam  60  about the unoscillated beam path  66  through rotation of the mirror element.  
         [0039]     Turning now to  FIGS. 6A and 6B , the difference in area coverage of exit window  50  is illustrated. Area coverage is related to pattern density and ease of detecting and decoding bar code label  32 .  
         [0040]     With reference to  FIG. 6A , five groups of scan lines  82 - 88  in an example scan pattern each contain four scan lines. The four scan lines are produced by a mirrored spinner  16  having four planoreflective surfaces oriented at different angles.  
         [0041]     With reference to  FIG. 6B , the scan lines in the same five groups of scan lines  82 - 88  are made to oscillate by laser beam oscillator  14 . Oscillation provides greater scan line coverage. A large enough amplitude can cause oscillating scan lines to overlap, resulting in a dramatic increase in scan line coverage of window  50 . In more complex scan patterns containing many more groups of scan lines, a higher percentage of window  50  may be covered.  
         [0042]     Although the invention has been described with particular reference to certain preferred embodiments thereof, variations and modifications of the present invention can be effected within the spirit and scope of the following claims.