Optical scanning apparatus and method.

0001The present invention relates to an optical scanning apparatus and method.

0002In the present-day merchandising point-of-sale checkout systems, data pertaining to the purchase of a merchandise item is obtained by reading data encoded indicia such as a bar code label printed on or attached to the purchased merchandise item. Reading systems which have been constructed to read this type of bar code include stationary optical scanning systems normally located within the cabinet structure of a checkout counter or hand-held bar code scanners which emit a single or multiple line scan pattern which are manually moved pass the bar code label that is to read. Where a hand-held bar code scanner is utilized in scanning a bar code label, it has been found that the distance between the laser scanner and the bar code label is critical in locating the scan pattern on the label. As the distance between the scanner and the label increases, the scan pattern becomes larger but the intensity of the scan pattern is reduced which presents problems in targeting a scan pattern on the bar code label. Known scanners exhibit such problems.

0003It is an object of the present invention to provide an optical scanning apparatus and method that does not exhibit the above-mentioned disadvantages.

0004According to one aspect of the present invention there is provided optical scanner apparatus comprising means for transmitting a light beam along a first light path, rotatably mounted deflection means having a first deflecting surface for rotation in said first light path and arranged to deflect said light beam from said first light path along a second light path towards a plurality of reflecting elements located around said deflection means to reflect said light beam along a third light path, characterized in that said deflection means has a second deflection surface for rotation in said third path for deflecting said light beams in the same direction as said first light path for forming a scan pattern having a plurality of intersecting scan lines.

0005According to another aspect of the present invention there is provided a method of forming an optical scan pattern comprising transmitting a light beam along a first light path and rotating deflection means having a first deflection surface about a spin axis parallel to said first light path to deflect said light beam along a second light path, characterized by reflecting said light beam travelling along said second light path along a third light path towards a second surface of said deflection means to deflect said light beam along a forth light path in the same direction of said first light path so form a scan pattern.

0006Advantageously, the invention provides an optical scanning device which generates a scan pattern whose center does not change as the distance between the scanner and the bar code label is varied. Also, the invention provides a compact optical scanning device which generates a scan pattern which has a definite center, and provides a central spot to direct an operator to the center of the scan pattern.

0007Further, an optical scanning device is provided which advantageously forms a series of scan lines with appropriate angular spacing to achieve an omnidirectional scan pattern for use in scanning high aspect ratio bar code labels and which is simple in construction and low in cost.

0008The invention is described further hereinafter, by way of example only, with reference to the accompanying drawings in which:- <ul id="ul0001" list-style="none"><li>Fig. 1 is a partial side view of a hand-held bar code scanner embodying present invention;</li><li>Fig. 2 is a sectional side view of the scanning unit shown in Fig. 1;</li><li>Fig. 3 is an exploded view of the scanning unit used in the present invention showing the elements which generate a scanning pattern including the cylindrical shaped array of pattern forming mirrors and the collector elements which collect the reflected light beams from the scanned bar code label;</li><li>Fig. 4 is a diagram showing the size of the scan pattern generated by the present invention as the scanner is moved away from the bar code label; and</li><li>Fig. 5 illustrates the size and the configuration of the scan pattern of present day scanners showing the distortion of the scan pattern as the bar code scanner is moved away from the bar code label.</li></ul>

0009As described in further detail below, the invention provides for an optical scanning device which may be mounted in a portable hand-held scanner or other types of optical scanners. The scanning unit includes a housing member within which is mounted a motor for rotating a hollow drive shaft through 360° of rotation. Mounted adjacent to one end of the shaft is a laser member which projects a laser light beam through the shaft. Mounted on the other end of the shaft is a deflector member which includes two deflecting mirror surfaces, one of which deflects the light beam outwardly to a cylindrical shaped array of pattern forming mirrors. The cylindrical array of mirrors remains stationary. The scanning beams are reflected back by the pattern forming mirrors and towards the second deflecting mirror surface on the deflecting member secured to the rotating shaft. The second deflecting mirror surface comprises a pattern forming mirror which rotates about the spin axis of the drive shaft and moves with the first deflecting mirror surface. The pattern mirror surface deflects the scanning beam in the direction of the spin axis. As the second deflecting mirror surface rotates about the spin axis, a plurality of intersecting scan lines 106 (Fig. 4) are generated, each having the same center 108, and spreading out in the same direction as the distance between the scanner and the bar code increases (Fig. 4). The scan lines are all angularly separated to give an omnidirectional effect. The common axis provides an aiming line at a central reference point for targeting the scan pattern on the bar code label. Collection means are mounted in the front portion of the scanning unit for collecting and generating electrical signals in accordance with the collected light beams reflected from the scanned bar code label collected by the collecting means.

0010Referring now to Fig. 1, there is shown a partial side view of a hand-held bar code scanner which includes a scanning unit incorporating the present invention. While the present invention is shown mounted in a hand-held optical scanner, it is obvious that the present invention may be employed with any type of optical scanning system which utilizes pattern forming mirrors for generating a scan pattern. As shown, the hand-held bar code scanner generally indicated by the numeral 20 comprises a handle portion 22 and a main body portion 24. A scanning unit 26 is mounted within the main body portion 24 by means of a support ring 28 which, in addition to supporting the scanning unit 26, also supports a cover member 30 having an opening 32 in which is positioned the face portion 34 of the scanning unit 26. The cover member 30 may be constructed of a transparent material such as acrylic and is shock mounted with respect to the face portion 34 by means of a ring of elastic foam material 36. Slidably mounted on a rear extension portion 38 of the scanning unit 26 (Fig. 3) is a bracket member 40 supporting a printed circuit board 42 which contains the video circuits associated with the operation of the scanning unit. The bracket member 40 may be constructed of a hard plastic material such as polycarbonate.

0011Positioned on the extension portion 38 (Fig. 1) is a printed circuit board 44 containing the laser drive circuit for a laser diode 45 (Fig. 2). The board 44 is secured to the extension portion 38 of the frame support member 48 of the scanning unit 26 (Figs. 2 and 3). Mounted along the lower edge of the main body portion 24 is a printed circuit board 50 which contains the digital interface logic circuits for controlling the processing of digital signals generated as a result of the operation of the scanning unit 26.

0012Secured to the printed circuit board 50 is a light emitting diode 52 for use in indicating the occurrence of a good read operation by the scanning unit in a manner that is well known in the art. The diode 52 can be viewed through a transparent member 54 mounted in the rear surface of the main body portion 24. Also secured to the printed circuit board 50 is a circuit board 56 which is located in the handle portion 22 of the scanner and which controls the power supply to the scanning unit 26. A button mechanism 58 located along the forward edge of the handle portion 22 is connected to the printed circuit board 56 to provide an on/off operation of the scanning unit. Located in the lower edge of the handle portion 22 is a recessed plug portion 60 for receiving a cable (not shown) which supplies power to the scanner and also transmits electrical signals outputted by a microprocessor (not shown) located on the printed circuit board 50 representing the data signals generated as a result of scanning the bar code label.

0013Referring to the drawings, Fig. 2 is a cross-sectional view of the assembled scanning unit 26 while Fig. 3 is an exploded perspective view of the scanning unit. As shown in those figures, the frame support member 48, which may be molded of any type of a shock resistant plastic materials such as polycarbonate, includes a plurality of latching portions 62. Mounted within the support member 48 is a motor 64. Journaled within the motor by bearings 66 (Fig. 2) is a hollow drive shaft 68 extending through the motor 64. Mounted within the rear extension portion 38 of the frame support member 48 is a brass laser diode support member 46 which supports the laser diode 45 and a collimating and focusing lens member 70, both of which are in alignment with the spin axis 72 of the drive shaft 68. The diode 45 outputs a diverging light beam which is collimated and focused on a reference plane (not shown) in front of the scanning unit by the lens member 70. A circular aperture stop 74 positioned adjacent the lens member 70 has a cross-section which is smaller than the lens member 70 for controlling the size of the laser light beam projected at the reference plane in a manner that is well known in the art.

0014Slidably mounted within the frame support member 48 is a molded mirror support member 76 constructed of any type of polycarbonate plastic which rigidly supports a cylindrical shaped array of pattern forming mirrors 78. The cylindrical mirror array 78 typically has an odd number of mirrors, in the order of seven or nine, to handle large aspect ratio tags having an aspect ratio on the order of 6. The support member 76 includes a rearwardly extending key rib portion 80 which is positioned within a key slot 82 located in the frame support member 48 for snap fitting the support member 76 within the support member 48. Secured to the front end of the drive shaft 68 is a wide deflecting member 84 of substantially triangular cross-section (Figs. 2 &amp; 3) which includes a rearwardly facing deflecting mirror surface 86 and a forward deflecting pattern forming mirror surface 88. The surfaces 86 and 88 form an angle of ninety degrees (Fig. 2). The mirror surface 88 utilizes the total width of the deflecting member 84 while the mirror surface 86 utilizes a small portion of the width of the deflecting member 84.

0015Mounted within a ring portion 90 of the frame support member 48 is a glass face member 34 (Figs. 2 and 3). Also mounted within the ring portion 90 of the support member 48 are a pair of light collecting elements generally indicated by the numeral 92 which includes a light collection facet 94 and a photodetector 96 for converting the light collected by the collection facet 94 into electrical signals in a manner that is well known in the art.

0016The operation of the laser diode 45 will output a narrow laser light beam along the spin axis 72 of the scanning unit 26. The laser light beam will be projected through the bore 98 located in the drive shaft 68 where it impacts on the rotating deflecting mirror surface 86. The light beam designated as 100 will be deflected radially outwardly by the mirror surface 86 to impact on the cylindrical array of mirrors 78 which in turn deflect the light beam in a generally downward direction towards the deflecting mirror surface 88 of the deflecting member 84. The light beams impacting on the deflecting surface 88 will be deflected in a generally horizontal forward direction through the acrylic face member 34 forming a multi-line scanning pattern 106 (Fig. 4) for scanning a coded bar code label (not shown) positioned adjacent the front portion of the bar code scanner 20. The scattered light beams reflected from the scanned bar code label are detected by the collection lens member 94 and transmitted to the detector member 96 which converts the received light beams into electrical signals in a manner that is well known in the art.

0017Referring now to Fig. 5, there are shown examples of how a scan pattern generated by the prior art expands as the distance between the bar code scanner and the bar code label increases. As shown, the center portion 102 of the scan pattern 104 will contract as the distance increases and then expand to provide a wide center area which is hard to locate on a bar code label when moving the bar code towards or away from the scanner during a reading operation. As shown in Fig. 4, the scan pattern 106 produced by the present invention has a concentric center portion 108 which remains constant as the scan pattern expands when the distance between the bar code label and the bar code scanner increases. It will thus be seen that the concentric center portion 108 will always be at the same point location and it will be easily visible to locate the scan pattern on the bar code label.