BEAM SCANNING APPARATUS

Abstract: In beam scanning apparatus for scanning bar coded indicia light from a laser source (22) is directed towards a rotating polygonal mirror (20), the reflected beam being focused by a plurality of lenses (30) successively onto a corresponding plurality of mirrors (32) which reflect the beam back through the corresponding lens (30) onto the polygonal mirror. As the polygonal mirror (20) rotates there are generated successively a plurality of parallel light beams (36) which are directed by further mirrors (38) onto a further rotating polygonal mirror (42) to produce corresponding beam scans directed by a mirror system (46) to form the desired scan pattern at a location through which a bar coded label passes.

Description: BEAM SCANNING APPARATUS Technical Field This invention relates to beam scanning apparatus of the kind including light beam generating means adapted to provide a generated light beam, dis¬ placed beam generating means adapted to generate a plurality of displaced light beams from said generated light beam, and scanning means adapted to generate a scan pattern from said displaced light beams. The in- vention has a particular application to the scanning of bar codes such as the Universal Product Code (UPC) . Background Art Beam scanning apparatus of the kind specified is known from U.S. Patent Specification No. 4,057,784. In such known apparatus a light beam provided by a laser source is directed onto a dichroic beam splitter to cause some of the light to be deflected at right angles to form a first beam, and pass the remainder of the light so that it strikes a mirror angled at 45° to pro- vide a second beam parallel to the first beam. The first and second beams are then directed to respective oppo¬ sitely rotating polygonal mirrors, the output beams from which impinge in an alternating manner on a vibrating mirror assembly, and thence are reflected via further mirrors to cause the production of a desired scan pat¬ tern. The known system has the disadvantage of requir¬ ing the utilization of specialized beam splitting coat¬ ings and the further disadvantage that the capability of such beam splitting coatings to produce a plurality of displaced, equal-power light beams is restricted. Disclosure of the Invention It is an object of the present invention to provide beam scanning apparatus capable of providing a plurality of displaced light beams of substantially equal power without the use of specialized beam-splitting coatings. According to the present invention, there is provided beam splitting apparatus of the kind specified, characterized in that said displaced light beam gener¬ ating means includes a rotatable member having a first reflective surface located in the path of said gener¬ ated light beam and adapted to reflect the generated light beam to provide a reflected light beam, a plural¬ ity of lens members arranged to successively receive the reflected light beam as said rotatable member rotates- and to focus the reflected light beam successively onto a plurality of second reflective surfaces which are adapted to reflect the focused beam back through the respective lens members onto said first reflective sur¬ face, thereby providing said plurality of displaced light beams. It will be appreciated that beam scanning apparatus according to the invention has the capability of producing multiple spatially displaced beams of equal power for use in scanning a coded member. Furthermore the apparatus according to the invention has the capa¬ bility of readily providing a desired number, in a pre¬ ferred embodiment four, such scanning beams of equal power. Beam scanning apparatus according to the inven¬ tion has the advantage of providing a simple, low-cost construction for generating a complex scan pattern at a high, uniform power suitable for scanning bar codes. Brief Description of the Drawings One embodiment of the present invention will now be described with reference to the accompanying drawings, in which: Fig. 1 is a schematic representation of a first part of beam scanning apparatus for producing a plurality of displaced beams; Fig. 2 is a schematic representation of a second part of said beam scanning apparatus for pro¬ ducing a scan pattern from the displaced beams; and Fig. 3 is a schematic diagram useful for under¬ standing the operational principle of the beam scanning apparatus. Best Mode for Carrying Out the Invention Referring now to Figs. 1-3 inclusive, there is shown schematic representations of one embodiment of the beam scanning apparatus of the present invention. Inclu- ded in the scanning apparatus is a multifaceted polygonal mirror 20 rotating in a counterclockwise direction as indicated by the arrow shown in the drawing. Associated with the mirror 20 is a source of laser beams such as a helium-neon laser 22 which outputs a high spectral radiance light beam 24. It is to be understood that the aforementioned laser 22 is cited as one example of a laser that may be employed in the utilization of the present invention and that any other type of laser generating the required light beam may be used. The light beam 24 is directed so as to impinge on one of the facets 26 of the rotating mirror 20 which reflects a light beam 28 in a direction which is offset to the original direction of propagation of the light beam 24 due to the rotational displacement of the facet 26. The reflected light beam 28 is directed at one of a plurality of focusing lenses 30 which focuses the light beam on one of a plurality of stationary mirrors 32 orientated so as to reflect a light beam 34 back through the lens 30 which focuses the light beam at the surface of the facet 26 of the mirror 20. The focusing of the light beam on the mirror 20 by the lens 30 results in the angular change produced by the rotation of the facet 26 of the mirror being subtracted from the net angle of orientation of an output light beam 36. The use of the stationary mirror 32 adds to the orientation of the light beam 36 in angular displacement due to the orientation of the mirror 32. The resulting light beam 36 reflected from the facet 26 is then used in scanning a coded label in a manner to be described hereinafter. As the mirror 20 rotates in the counterclockwise direction, a plurality of serially-produced light beams 36 will be generated • as the reflected beam 28 passes over the mirrors 32 successively. The beams 36 are of equal power and par- allel to and displaced from the incident beam 24 by amounts dependent on the orientation of the mirrors 32. As shown in Fig. 2, the output light beams 36 are directed at a plurality of second stationary mirrors 38 which are orientated to direct the reflected light beams 36 at a spot on one of the facets 40 of a second rotating polygonal mirror 42 which is rotating at the same speed as the mirror 20 in the counterclockwise direction as indicated by the arrow in Fig. 2. The light beams 44 reflected from the facets 40 are directed at a mirror system 46 which directs the light beams 44 into a scan pattern for scanning a bar coded label 48. The mirror system 46 is an arrangement of mirrors which results in directing a single light beam along a pre- determined path. Since each of the light beams 44 will be along a different path coming from a facet 40, the mirror system 46 will provide a multi-line scan pattern for scanning the bar code. Light beams reflected from the label 48 are directed by the mirror system 46 at one of the facets 40 of the mirror 42 which reflects the light beams towards a focusing lens 50. The focusing lens 50 directs the light beams at a detector member 52 which converts the light beams into electrical signals in a manner that is well-known in the art. In order to explain the control of the direc¬ tion of the light beams 36, there is shown in Fig. 3 an arrangement in which the facet 26 of the mirror 20 (Fig. 1) is orientated at an angle ec with the plane in which the laser beam 24 impinges on the facet 26 directing the reflected light beams 28 towards the focusing lens 30 which has focal lengths f. and f_ and which focuses the light beams 28 at the surface of the stationary mirror 32. The mirror 32 reflects the light beams 34 towards the lens 30, which directs the light beams 34 at the facet 26. Due to the orientation of the mirror facet 26, such facet will direct the parallel light beams 36 in a direction parallel to the laser beams 24 but dis¬ placed from the position of such beams 24.

Claims: CLAIMS : 1. Beam scanning apparatus including light beam generating means (22) adapted to provide a gener¬ ated light beam (24), displaced beam generating means (20, 26, 30, 32) adapted to generate a plurality of dis- placed light beams (36) from said generated light beam (24), and scanning means (38, 40, 42, 46) adapted to generate a scan pattern from said displaced light beams (36), characterized in that said displaced light beam generating.means includes a rotatable member (20) having a first reflective surface (26) located in the path of said generated light beam (24) and adapted to reflect the generated light beam (24) to provide a reflected light beam (28), a plurality of lens members (30) ar¬ ranged to successively receive the reflected light beam (28) as said rotatable member (20) rotates and to focus the reflected light beam (28) successively onto a plu¬ rality of second reflective surfaces (32) which are adapted to reflect the focused beam back through the respective lens members (30) onto said first reflective surface (26), thereby providing said plurality of dis¬ placed light beams (36) . 2. Beam scanning apparatus according to claim 1, characterized in that said displaced light beams (36) are parallel to said generated light beam (24). 3. Beam scanning apparatus according to claim 1, characterized in that said rotatable member (20) in¬ cludes a plurality of first reflective surfaces (26) located around a periphery thereof. 4. Beam scanning apparatus according to claim 1, characterized in that said light beam gener¬ ating means is a laser device (22). 5. Beam scanning apparatus according to claim 1, characterized in that said scanning means in¬ cludes a further rotatable member (42) having a plurality of third reflective surfaces (40) adapted to receive said displaced light beams (36) thereby providing a plurality of beam scan paths. 6. Beam scanning apparatus according to claim 5, characterized in that said beam scan paths are directed by a mirror system (46) to form said scan pat¬ tern. 7. Beam scanning apparatus according to claim 5, characterized in that a plurality of fourth reflective surfaces (38) are located in the paths of said displaced light beams (36) to direct the displaced light beams (36) onto a spot through which said third reflective surfaces (40) successively pass. 8. Beam scanning apparatus according to claim 5, characterized in that light reflected from a record medium scanned by said scan pattern is directed by one of said third reflective surfaces (40) towards detecting means (50, 52).

Inventors: HARDY JAMES ALAN, HARDY, JAMES, ALAN
Applicants: NCR CO, NCR CORPORATION
Application year: 1983
Main classification: G06K7
IPC codes: G06K7