Abstract:
A changeable apparatus for scanning a symbol is disclosed wherein by selectively changing the position of a bending mirror ( 101 ), different scan patterns are produced. In a preferred embodiment, the different positions of the bending mirror ( 101 ) result in a scanning beam ( 107, 108 ) being directed off of different polygon scanning mirrors ( 104, 105 ) to create the different scanning patterns.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    This invention relates to optical scanning, and more particularly, to an improved method and apparatus for permitting raster scanning and linear scanning. 
         [0002]    Laser optical scanning devices are known in the art, and are used to read a variety of one and two dimensional bar code and similar symbols. These devices are typically implemented by having a moving laser beam that repeatedly scans over the areas of black and white, or sometimes color, that are contained within a symbol to be read. 
         [0003]    The required or optimum scanning pattern can be different depending upon the symbol to be read. For example, in cases where a bar code is of poor quality or misaligned, a raster scan pattern may be desirable. Other applications require a single linear scan that simply moves back and forth across a one dimensional bar code. Moreover, a linear scan may be implemented by using a rotating polygon mirror or an oscillating mirror. Often, an enterprise must have plural types of scanners available and deployment ready in order to be capable of reading various types of bar code symbols in an optimal manner. 
         [0004]    To date, there exists no efficient manner of providing different types of scanning without the additional expense and difficulty of maintaining plural scanning devices. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]      FIG. 1  shows a simplified conceptual depiction of a device in accordance with the present invention; 
           [0006]      FIG. 2  shows a side view of a mirror arrangement for use in an exemplary embodiment of the present invention; 
           [0007]      FIG. 3  shows an exemplary motor which can be used to implement the scanning action of the present invention; 
           [0008]      FIG. 4  depicts the motor of  FIG. 3  with the mirror arrangement of  FIG. 2  mounted thereon; 
           [0009]      FIG. 5  depicts a side view of an exemplary embodiment of the present invention in operation; 
           [0010]      FIG. 6  is a two part depiction of a mechanism for selectively positioning the bending mirror of the present invention; and 
           [0011]      FIG. 7  shows an alternative embodiment wherein a selection between a rotating and oscillating mirror is provided. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0012]      FIG. 1  depicts a conceptual diagram of an apparatus in accordance with the present invention. The apparatus of  FIG. 1  includes two polygon scanning mirrors  104  and  105 , which are known in the art for producing a repeated scanning function in laser scanning systems. 
         [0013]    A bending mirror  101  is also shown in both solid and dotted outlines, indicating two different potential positions at which such bending mirror can be placed. Finally, switch  106  is merely shown as an arrow, but may be any system for supporting the mirror and permitting it to selectively be moved into one of two positions for operation. Further details concerning an exemplary such system are shown and described in  FIG. 6 . 
         [0014]    In operation, the bending mirror  101  is set at either one of the two positions shown in  FIG. 1 , depending upon whether it is desired to utilize polygon mirror  104  or  105  for scanning. While  FIG. 1  is a prospective view of the assembled polygon mirrors,  FIG. 2  shows a cross sectional view of the same two polygon mirrors in  FIG. 1 . It can be seen from  FIG. 2  that the top polygon mirror  104  has faces that are disposed at an angle “a” with respect to the axis of rotation of the polygon mirror. As is known in the art, the use of this tilted polygon mirror  104  results in a raster scan pattern which can be utilized to scan poorly printed bar codes or other types of symbols. As shown in  FIG. 2 , the lower polygon scanning mirror  105  has faces that are disposed at zero angle with respect to the axis of rotation, and thus which are parallel with respect to the axis of rotation. 
         [0015]    Returning to  FIG. 1 , in operation, the bending mirror  101  is positioned in its upper dotted position or its lower, depending upon whether a raster scan or a linear scan is desired, respectively. This positioning may be accomplished by mounting the bending mirror on a support (not shown) and providing a means to move the support as described later herein. 
         [0016]    A light source  102  then transmits the laser light through lens  103 . The light is deflected off of the bending mirror  101  and on to the appropriate polygon scanning mirror  104  or  105 . The resulting pattern of emitted light is shown in  FIG. 1  as beams  107  and  108 , but can be seen more clearly in  FIG. 5 , which shows the different potential scanning patterns that emanate from polygon scanning mirror  104  or  105 . 
         [0017]      FIG. 3  is a basic diagram of an exemplary motor for use in accordance with the present invention. In the arrangement in  FIG. 3 , a shaft  302  includes wider portions  303  and  304 , which are rotated under electric power to cause the scanning in accordance with conventional techniques. This is best seen in  FIG. 4 , where mirrors  104  and  105  have been mounted on shaft  302  of motor  301 . 
         [0018]    Ideally, the underside of the two stage polygon mirror  201  of  FIG. 2  has an opening that fits directly over portions  303  and  304 , so that it may compliment the shape thereof. More specifically, the underside of mirror  105  is wide enough to fit over portion  304 , while the underside of mirror  104  fits directly over wider portion  303 . The bore through portion  104  continues, so that the shaft  302  protrudes from the top of polygon scanning mirror  104  as shown in  FIG. 4 . The two stage polygon mirror  201  may then be secured to the shaft  302  by a clip, nut, or any conventional technique for preventing the polygon mirror  201  from slipping off of the shaft  302 . 
         [0019]    In alternative embodiments, the attachment of two stage polygon mirror  201  may be via use of a clip or other attachment means that can be positioned at two different places along the shaft  302 . For example, the bottom of the portion  304  of shaft  302  could include a spring loaded stub that sits in a small opening along shaft  309 , and the openings along shaft  309  could provide for different positions of the rotating polygon mirrors  104  and  105 . Thus, to change positions, the stub  310  is pulled from the opening  311 , the arrangement slid up or down as shown in  FIG. 4  by the arrows, and the spring loaded stub reinserted.  FIG. 5  shows front and side views of the arrangement in operation, wherein both potential paths of the light beam are shown. As can be seen best from the side view shown in  FIG. 5 , a user may implement a raster scan or linear scan by simply switching the bending mirror  101  to one of two different positions. 
         [0020]    In an enhancement, the system may be sold with a plurality of different mirrors that can be mixed and matched to derive any specific combination. More specifically, the distance between scan lines of a raster scan is effected largely by the particular angle as shown in  FIG. 2 . The system can be sold with several different polygon scanning mirrors  104  having different angles a, different dimensions, etc. In an enhanced embodiment, a set can be sold as a configurable optical scanner, where in various different mirrors can be mixed and match to create a custom device. 
         [0021]      FIG. 6  shows one exemplary embodiment for permitting the bending mirror  101  to be moved between the two desired positions. The arrangement includes a switch  601  mounted to a shaft that supports the mirror and which may be slideable upward and downward through a grove  608 . The grove  608  includes two notches  605  and  606  into which the shaft may be slid to support the bending mirror in either of two positions. 
         [0022]    While the arrangement of  FIG. 6  is one exemplary manner in which the bending mirror  101  may be moved, it will be apparent to those of skill of the art that a variety of techniques may be utilized for this function. 
         [0023]    It is also noted that while two polygon scanning mirrors  104  and  105  are shown, more than two scanning mirrors may be used as well. While scanning mirrors  104  and  105  are both polygon scanning mirrors, the bending mirror may be positioned to steer a beam  501  to a different type of scanner other than a polygon mirror. 
         [0024]    For example, the bending mirror  101  could be alternatively positioned to steer the beam  501  to a scanning mirror that simply oscillates, rather than a polygon.  FIG. 7  shows such an arrangement wherein the bending mirror  101  may, be moved to direct the beam at a rotating polygon scanning mirror  702  or a linear oscillating scanning mirror  701 . 
         [0025]    Moreover, a plural function device could incorporate a polygon scanning mirror as well, wherein, in one of several positions, the bending mirror  101  directs the beam  501  to a scanning mirror which further directs it to an omni directional scanner so that the device is selectable between and/or among a variety of different scanning patterns. Omnidirectional scanning mirrors are normally implemented by having a single rotating polygon mirror and several static mirrors. Thus, the bending mirror could be directed at the rotating polygon mirror, which then directs the beam to the static mirrors. 
         [0026]    The bending mirror is also itself optional, as the light source could be directed at the rotating or oscillating mirror, without being bent. In such embodiments, the light source itself could be movable, to serve the selection function otherwise served by the bending mirror. 
         [0027]    The foregoing is intended to be exemplary only, and does not limit the scope of the following claims.