Abstract:
A system for and a method of optical scanning which provide for converting between a multiple beam and a single beam optical scanner. In a preferred configuration, the scanner can be adapted to operate as either a single beam scanning system or a multiple beam scanning system. Light sources, mirrors, detectors, collection lenses, and other scanner components are added, removed, and/or replaced, thereby allowing the user to avoid having to purchase a new scanner when the user&#39;s performance requirements and/or cost restrictions vary.

Description:
RELATED APPLICATION DATA 
     This application is a continuation-in-part of application Ser. No. 09/360,039 filed Jul. 23, 1999. 
    
    
     BACKGROUND OF THE INVENTION 
     The field of the present invention relates to data reading systems. In particular, an optical scanning system and method for converting between multiple and single beam optical scanners are described herein. 
     U.S. application Ser. No. 09/360,039 to Acosta and Rudeen discloses various multiple beam scanner configurations. In one configuration, multiple laser beams are formed and directed along offset paths onto a scanning mechanism such as a polygon mirror which scans the beams across pattern mirrors to generate simultaneous scan patterns out into a scan volume. Return light from both scan patterns is retrodirectively collected and redirected by a common collection element such as a collection lens. The collection lens focuses return light from the first beam onto a first detector and return light from the second beam onto a second detector. By arranging the outgoing beam paths in an offset condition, the collected light may be focused to different locations. 
     Though the multiple beam system provides a high density and efficient scan pattern generation as well as a versatile scan system, the present inventors have recognized that increasing scan pattern density and scanner versatility can add to the cost of the scanner, thus, it may be advantageous to have a scanner that can be converted from a multiple beam system to a single beam system, or, alternatively, to have a scanner that can be converted from a single beam system to a multiple beam system. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a system for and a method of optical scanning which provide for converting between a multiple beam and a single beam optical scanner. 
     In a preferred configuration, the scanner can be adapted to operate as either a single beam scanning system or a multiple beam scanning system. Light sources, mirrors, detectors, collection lenses, and other scanner components are added, removed, and/or replaced, thereby allowing the user to avoid having to purchase a new scanner when the user&#39;s performance requirements and/or cost restrictions vary. 
     If it is determined that a single beam system would be preferred, second beam optics can be removed from the multiple beam scanning system along with removal or replacement of the corresponding components. For example, when the need for cost savings outweighs the need for enhanced performance, the additional components associated with a multiple beam scanner can be removed from the scanning system so that a single beam system is utilized. 
     Conversely, when it is determined that multiple beam optics are required to meet performance requirements, second beam optics can be added to the single beam scanner along with any corresponding components required to implement the multiple beam system. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a diagrammatic view of a multiple beam scanning system according to a first preferred embodiment. 
     FIG. 2 is a diagrammatic view of a multiple beam scanning system according to a second embodiment. 
     FIG. 3 is a diagrammatic view of a single beam scanning system according to a third embodiment. 
     FIG. 4A is a side plan view of a polygon mirror according to a fourth embodiment. 
     FIG. 4B is a side plan view of the polygon mirror of FIG. 4A separated into sections. 
     FIG. 5A is a perspective view of the polygon mirror of FIG. 4 according to one embodiment. 
     FIG. 5B is a perspective view of the polygon mirror of FIG. 4 according to a different embodiment. 
     FIG. 6 is a diagrammatic view of the scanning system of FIG. 1 utilizing the polygon mirror of FIGS. 4-5. 
     FIG. 7A is a perspective view of a preferred mounting bracket utilized in the scanning systems of FIGS. 1-3. 
     FIG. 7B is a top plan view of the mounting bracket of FIG.  7 A. 
     FIG. 7C is a side plan view of the mounting bracket of FIGS. 7A,  7 B. 
     FIG. 8A is a perspective view of the mounting bracket of FIG. 7 attached to a detector. 
     FIG. 8B is a top plan view of the mounting bracket of FIG.  8 A. 
     FIG. 8C is a side plan view of the mounting bracket of FIGS. 8A,  8 B. 
     FIG. 9 is a top plan view of a preferred scanning system illustrating a scan pattern. 
     FIG. 10 is a schematic diagram of a scan pattern generated by the scanning systems of FIGS. 1-2. 
     FIG. 11 is a schematic diagram of a scan pattern generated by the scanning system of FIG.  3 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Preferred embodiments will now be described with reference to the drawings. To facilitate description, any reference numeral representing an element in one figure will represent the same element in any other figure. 
     FIG. 1 illustrates a first preferred embodiment of a multiple beam optical scanning system  10  inside a housing  50 . In scanning system  10 , a light source  12 , such as a visible laser diode (VLD), produces a laser beam  14  which is split by a beam splitter  16 . The beam splitter  16  divides the beam  14  by reflecting a portion of the beam to generate a first light beam  14   a  and transmitting a second portion of the beam to generate a second light beam  14   b.  The first light beam portion  14   a  reflected by the beam splitter  16  is directed through a channel  17  in lower collection lens  18  and onto a polygon mirror  20 . The second light beam portion  14   b  passing through the beam splitter  16  is reflected by fold mirror  22  and directed through a channel  24  in upper collection lens  26  and onto the polygon mirror  20 . 
     The light beams  14   a,    14   b  are scanned by the polygon mirror  20  across a plurality of pattern mirrors  28 ,  30  which direct the light beams  14   a,    14   b  out through a window  32  and onto a target  34 . Return light from the first light beam  14   a  is retrodirectively collected by the lower collection lens  18 , which focuses the return light onto a first detector  36  bypassing the beam splitter  16 . Return light from the second light beam  14   b  is retrodirectively collected by upper collection lens  26 , which focuses the return light onto a second detector  38  bypassing the fold mirror  22 . The detectors  36 ,  38  detect the return light and generate corresponding electrical signals that are processed by a processing system. 
     FIG. 2 illustrates an alternative embodiment of a multiple beam optical scanning system  10   a  utilizing separate beam sources to generate multiple light beams, such as two laser diodes (VLDs), instead of utilizing a beam splitter. A first light source  12   a  generates a light beam  40   a  which is directed onto fold mirror  19 . Fold mirror  19  reflects light beam  40   a  through a channel  17  in collection lens  18  and onto polygon mirror  20 . A second light source  12   b  generates a light beam  40   b  which is directed onto fold mirror  42 . Fold mirror  42  reflects light beam  40   b  through channel  24  in collection lens  26  and onto polygon mirror  20 . 
     The light beams  40   a,    40   b  are scanned by the polygon mirror  20  across a plurality of pattern mirrors  28 ,  30  which direct the light beams  40   a,    40   b  out through window  32  and onto target  34 . Return light from the first light beam  40   a  is retrodirectively collected by the lower collection lens  18 , which focuses the return light onto first detector  36  bypassing the fold mirror  19 . Return light from the second light beam  40   b  is  120 ; retrodirectively collected by upper collection lens  26 , which focuses the return light onto second detector  38  bypassing the fold mirror  42 . The detectors  36 ,  38  detect the return light and generate corresponding electrical signals that are processed by a processing system. 
     When it is desired to switch the multiple beam scanning system  10  of FIG. 1, or the multiple beam scanning system  10   a  of FIG. 2, to obtain cost savings, the scanners  10 ,  10   a  can be converted into single beam optical scanning systems. 
     FIG. 3 illustrates an embodiment of a single beam scanning system  10   b.  The multiple beam system  10  of FIG. 1 is converted to the single beam system  10   b  of FIG. 3 by removing components associated with the multiple beam system  10  from the scanner housing  50  and adding components suitable for the single beam system  10   b.  A preferred method of converting comprises the steps of: (1) removing the scanning mechanism  20 ; (2) installing a smaller scanning mechanism  44 , such as a polygon mirror with shorter facets; (3) removing the collection lens  26  with the fold mirror  22  attached thereto; (4) removing the beam splitter  16 ; (5) removing the detector  38 ; (6) installing a fold mirror  19  adjacent collection lens  18  (in place of the beam splitter  16 ); (7) adjusting a decoder in the processing system for processing data associated with a single beam system; (8) changing laser power so that it is suitable for the single beam system, either by adjusting laser power in a laser driver or by replacing the light source  12  with a less powerful light source  12   c.  One or several of these steps may be omitted depending on the degree of cost savings that is desired, though eliminating certain steps may impact performance. 
     The multiple beam scanning system  10   a  of FIG. 2 is converted to the single beam scanning system  10   b  of FIG. 3 by removing components associated with the multiple beam system  10   a  from the scanner housing  50  and adding components suitable for the single beam system  10   b.  A preferred method of converting comprises the steps of: (1) removing the scanning mechanism  20 ; (2) installing a smaller scanning mechanism  44 , such as a polygon mirror with shorter facets; (3) removing the collection lens  26  with the fold mirror  42  attached thereto; (4) removing the second light source  12   b;  (5) removing the detector  38 ; (6) adjusting a decoder in the processing system for processing data associated with a single beam system; (7) changing laser power so that it is suitable for the single beam system, either by adjusting laser power in a laser driver or by replacing the light source  12   a  with light source  12   c.  One or several of these steps may be omitted depending on the degree of cost savings that is desired, though eliminating certain steps may impact fit performance. 
     In the single beam scanning system  10   b  of FIG. 3, a light source  12   c,  such as a visible laser diode (VLD), produces a light beam  48  which is directed onto fold mirror  19 . Fold mirror  19  reflects the light beam  48  through a channel  17  in collection lens  18  and onto scanning mechanism  44 , such as a polygon mirror. The scanning mechanism  44  scans the light beam  48  across a plurality of pattern mirrors  28 ,  30  which direct the light beam  48  out through window  32  and onto a target  35 . Return light from light beam  48  is retrodirectively collected by collection lens  18 , which focuses the return light onto detector  36  bypassing the fold mirror  19 . The detector  36  detects the return light and generates a corresponding electrical signal that is processed by a processing system. 
     When it is desired to switch the single beam scanning system  10   b  to a higher density scan pattern for a given application, the scanner  10   b  of FIG. 3 can be converted into a multiple beam optical scanning system. 
     The single beam scanning system  10   b  of FIG. 3 is converted to the multiple beam scanning system  10  of FIG. 1 by removing components associated with the single beam system  10   b  from the scanner housing  50  and adding components suitable for the multiple beam system  10 . A preferred method of converting comprises the steps of: (1) removing the scanning mechanism  44 ; (2) installing a larger scanning mechanism  20 , such as a polygon mirror with larger facets; (3) removing the fold mirror  19 ; (4) installing the beam splitter  16 ; (5) installing the collection lens  26  with fold mirror  22  attached thereto; (6) installing the detector  38 ; (7) adjusting a decoder in the processing system for processing data associated with a multiple beam system; (8) changing laser power so that it is suitable for the multiple beam system, either by adjusting laser power in a laser driver or by replacing light source  12   c  with more powerful light source  12 . Certain of these steps may be omitted depending upon what components are already present in the system, though omission of some steps may impact performance. 
     The single beam scanning system  10   b  of FIG. 3 is converted to the multiple beam scanning system  10   a  of FIG. 2 by removing components associated with the single beam system  10   b  from the scanner housing  50  and adding components suitable for the multiple beam system  10   a.  A preferred method of converting comprises the steps of: (1) removing the scanning mechanism  44 ; (2) installing a larger scanning mechanism  20 , such as a polygon mirror with larger facets; (3) installing the second laser source  12   b;  (4) installing the collection lens  26  with fold mirror  42  attached thereto; (5) installing the detector  38 ; (6) adjusting a decoder in the processing system for processing data associated with a multiple beam system; (7) changing laser power so that it is suitable for the multiple beam system, either by adjusting laser power in a laser driver or by replacing light source  12   c  with light source  12   a.  Certain of these steps may be omitted depending upon what components are already present in the system, though omission of some steps may impact performance. 
     FIGS. 4-6 illustrate an alternative polygon mirror  52  that can be utilized in both the multiple beam scanning systems  10 ,  10   a  of FIGS. 1-2, and in the single beam scanning system  10   b  of FIG.  3 . The polygon mirror  52  is divided into a first section  54  and a second section  56 . The facets of first section  54  may be oriented at the same or at a different angle than the facets of second section  56 . When a multiple beam scanning system is employed, the two sections  54 ,  56  are attached to one another at an attachment section  57  as shown in FIG.  4 A. The attachment section  57  may be threaded so that the sections  54 ,  56  screw together, it may have complementary tabs and slots so that the sections  54 ,  56  engage one another, or the sections  54 ,  56  may be attached to one another by any other suitable means. FIG. 5A illustrates attachment section  57  having threads  58 ,  59  that screw together. FIG. 5B illustrates attachment section  57  having tabs  60  and slots  62  that engage one another. When sections  54 ,  56  are attached to one another, the polygon mirror  52  is suitable for scanning multiple light beams. 
     When a single beam scanning system is employed, section  54  is detached from section  56  at attachment section  57 , as shown in FIG. 4B, and section  54  is removed from the scanning system. Section  56  is suitable for scanning a single light beam. Accordingly, when converting between a multiple beam scanner and a single beam scanner, the convertible polygon mirror  52  can be utilized so that it is not necessary to replace the system scanning mechanism. 
     FIG. 6 illustrates the multiple beam scanning system  10  of FIG. 1 utilizing the polygon mirror  52  of FIGS. 4-5. 
     In a preferred embodiment, the attachments in scanning systems  10 ,  10   a,    10   b  of FIGS. 1-3 can be performed by attaching the desired components to mounting supports, such as plastic brackets, which are fixed to the scanner housing  50 . 
     FIGS. 7-8 illustrate a preferred embodiment of a mounting support  64  that can be utilized in scanning systems  10 ,  10   a,    10   b  of FIGS. 1-3. FIGS. 7A-7C illustrate a plastic bracket  64 , onto which light sources, mirrors, detectors, collection lenses, and other scanner components can be mounted. The mounting support  64  includes a base  66  and a mounting bracket  68 . The base  66  includes apertures  70  adapted to receive screws or any other fasteners suitable for securing the base  66  to a scanner housing. The mounting bracket  68  includes apertures  72  adapted to receive attachment portions of scanner components. In FIG. 7A, the mounting bracket  68  is shown in an “I” shape with four mounting apertures  72 . The size and shape of the mounting bracket  68 , as well as the number of apertures  72 , however, can vary depending on the size, shape, and mounting characteristics of the scanner component being mounted thereon. 
     FIGS. 8A-8C illustrate the mounting support  64  of FIGS. 7A-7C with a detector  36  mounted thereon. The detector  36  includes outwardly extending portions that engage the apertures  72  on the mounting bracket  68 , thereby securing the detector  36  to the mounting bracket  68 . FIGS. 8A-8C illustrate only one possible configuration. The configuration of the mounting support  64  will vary according to the configuration and mounting characteristics of the scanner component being mounted thereon. 
     FIG. 9 is a top plan view of a preferred pattern mirror configuration for the multiple beam scanning system  10  of FIG.  1 . The scanning mechanism, such as polygon mirror  20 , scans light beams across pattern mirrors  28 ,  29 ,  30 ,  31 , which then direct the light beams through a window and onto a target. The beams are then returned from the target and retrodirectively bounced off of pattern mirrors  28 ,  29 ,  30 ,  31  toward collection lens  26 , which focuses the light beam onto detector  38 . The second collection lens  18  is not visible in this view. FIG. 9 also illustrates a scan pattern generated by the multiple beam system  10 . The pattern mirror configuration of FIG. 9 is also applicable to the multi-source multiple beam system  10   a  of FIG.  2  and the single beam system  10   b  of FIG.  3 . 
     FIG. 10 illustrates a scan pattern  100  such as may be produced by the dual beam optical scanning systems  10 ,  10   a  of FIGS. 1-2. 
     FIG. 11 illustrates a scan pattern  110  such as may be produced by the single beam optical scanning system  10   b  of FIG.  3 . 
     The above examples illustrate single beam and dual beam systems. The scanning system may, however, accommodate more than two beams and the corresponding components required for such multiple beam systems. 
     Thus while embodiments and applications of the present invention have been shown and described, it would be apparent to one skilled in the art that other modifications are possible without departing from the inventive concepts herein. The invention, therefore, is not to be restricted except in the spirit of the claims that follow.