Abstract:
A bar code scanner for projecting a scanning pattern comprising a plurality of groups of scan lines, where each scan line in a given group is substantially parallel to other scan lines in the same group. The scanning pattern is provided within a relatively narrow, yet diverging, volume, such as a pyramid, cone, etc., as referenced to a projection axis. The scanner includes a housing having a window. Within the housing are a plurality of stationary mirrors, a laser beam generating mechanism, a rotating reflective polygon for sweeping the laser beam across the mirrors and a window, such that the projection axis intersects the window. The scanner also includes a fixed collecting mirror and a concentrating lens to focus light which is reflected off a bar code to a photodector. One mirror extends along an axis substantially parallel to the transverse axis to produce a first group of scan lines. The second and third mirrors are disposed opposite each other laterally of the polygon and extending along respective axes at a first acute angle, illustratively 8 degrees, to the longitudinal axis to produce respective ones of a second and a third group of scan lines. The fourth and the fifth mirrors, respectively, each extend along a respective axis at a second acute angle, illustratively 48 degrees to the longitudinal axis, to produce respective ones of a fourth and a fifth group of scan lines.

Description:
RELATED CASES  
       [0001]    This is a continuation of patent application Ser. No. 09/360,458, filed Jul. 23, 1999, which is a continuation of application Ser. No. 08/943,267, filed Oct. 3, 1997, which is a continuation of application Ser. No. 08/865,257, filed May 29, 1997, which is a continuation of application Ser. No. 08/475,376, filed Jun. 7, 1995, and issued as U.S. Pat. No. 5,637,852, which is a continuation of application Ser. No. 08/365,193, filed Dec. 28, 1994, and issued as U.S. Pat. No. 5,557,093, which is a continuation of application Ser. No. 08/036,314, filed Mar. 24, 1993, now abandoned, which is a continuation of application Ser. No. 07/580,738, filed Sep. 10, 1990 and issued as U.S. Pat. No. 5,216,232.  
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    This invention relates generally to optical scanning devices and, more particularly, to scanners that are adapted to read bar codes within a confined scanning volume.  
           [0004]    2. Background Art  
           [0005]    Various laser-based scanning systems have been disclosed in the patent literature and many are commercially available to read bar codes, e.g., the uniform product code, which is imprinted on packaging for product, or on the product itself, or on some other item.  
           [0006]    One type of scanning system is referred to as a counter or “slot scanner”. Such devices are generally mounted within a housing in a checkout counter of a supermarket or other retail establishment, and include a window at the top thereof through which a scanning pattern is projected. The scanning pattern is created by a laser and associated optical components, e.g., mirrors, etc., which typically produce plural scan lines which are either parallel to one another and/or intersect one another. When an item bearing a bar code is brought into the field of the scan pattern so that the pattern traverses the bar code light is reflected off of the bar code and is received back through the window of the slot scanner, whereupon decoding means converts the received light into an electrical signal indicative of the bar code. These signals can then be utilized to identify the article bearing the code and provide pricing information.  
           [0007]    In order to ensure that a bar code is traversed sufficiently so that it can be read accurately irrespective of its orientation within the scan pattern, prior art counter scanners have utilized various optical configurations including mirrors, prisms, and the like to fold the laser beam and create complex patterns. Examples of such patterns are comb patterns, orthogonal patterns, interlaced patterns, star-like patterns, etc. While such patterns may be suitable for their purposes, the means for creating them has resulted in housings which were quite large in size.  
           [0008]    In my U.S. Pat. No. 4,713,532 there is disclosed a counter or slot scanner producing an aggressive scanning pattern having at three rastered groups of intersecting scan lines to form a large “sweet spot” to enable the bar code to be read omnidirectionally, i.e., irrespective of its orientation with respect to the scanner. That scanner is housed within a very compact, small footprint housing which is arranged to be mounted under a counter or disposed on a counter. Depending upon the orientation of the scanner, its window may be horizontal or at some other orientation, e.g., vertical. Devices embodying the teachings of that patent have been sold by the assignee of that patent (and of this application), Metrologic Instruments, Inc., under the designation MS260.  
           [0009]    Metrologic Instruments, Inc. has also sold other compact counter or slot scanners under the designation MS360. Those scanners also produce a broad, aggressive scan pattern. In that case the pattern is made up of five rastered groups of intersecting scan lines.  
           [0010]    While the aforementioned counter scanners have proved suitable for their intended purposes it has been determined that in certain applications the production of a broad scanning pattern is less than optimum. For example, in some check-out counter applications it is desirable to create a scanning pattern which, although aggressive, is confined within a relatively narrow volume, to prevent unintentional scanning of nearby objects. Hand-held scanners while providing for scanning within a confined volume (to prevent unintentional scanning), nevertheless suffer from various drawbacks, one of which being aggressiveness of the scanning pattern.  
           [0011]    Thus, the need exists for a scanner device which combines the versatility of a hand-held scanner with the aggressiveness of a counter or slot scanner.  
           [0012]    In many mass merchandizing applications it is desirable to have a scanner with the aggressiveness of a counter or slot scanner but which does require that the scanner be mounted or disposed with its window on the counter where it may present a snagging hazard to bar coded items, e.g., garments on hangers or hooks, if they are dragged across the counter for scanning. In other applications, e.g., where bar coded items are packaged in such a way as to require that they not be inverted, it is also desirable to provide an aggressive, fixed mount scanner to project the scanning pattern down toward the counter from above so that items can be scanned right-side-up.  
           [0013]    Thus, the need also exists for a counter mounted scanner which can project an aggressive scanning pattern from the side or above to scan items brought into the pattern, yet which pattern is relatively confined to minimize counter space required to be clear of bar coded items.  
           [0014]    Some commercially available scanners are arranged to be disposed or mounted to project a scanning pattern somewhat laterally to act as a “projection scanner”. Examples of such scanners are the following: the “FREEDOM” scanner sold by Spectra Physics, the “7852” scanner sold by NCR, the “OMISCAN” scanner sold by Microvideo, and the “SLIMSCAN” scanner sold by Fujitsu. While such scanners are generally suitable for their intended purposes they all suffer from one or more drawbacks, such as somewhat large housing and/or “footprint” size, amount of counter space to be kept clear of bar coded items, somewhat restricted working range, inability to scan all types of bar codes omnidirectionally and lack of aggressiveness of such pattern.  
         OBJECTS OF THE INVENTION  
         [0015]    Accordingly, it is a general object of this invention to overcome the disadvantages of the prior art.  
           [0016]    It is a further object of this invention to provide a scanning unit which is arranged to project a rich scanning pattern into a confined volume for scanning a bar coded item brought therein irrespective of the orientation of the bar code.  
           [0017]    It is yet a further object of this invention to provide scanning unit which is arranged to project a rich scanning pattern laterally or downward into a confined volume for scanning a bar coded item brought therein.  
         SUMMARY OF THE INVENTION  
         [0018]    These and other objects of the instant invention are achieved by providing a laser scanning device for projecting a scanning pattern into a volume which may include a code having portions of different reflectivities, e.g., a bar code. The scanning pattern comprises a plurality of groups of scan lines, wherein each scan line in a given group is substantially parallel to other scan lines in the same group. The scanning pattern is provided within a narrow yet diverging volume such as a pyramid, cone, frustrum, and/or column as referenced to a projection axis.  
           [0019]    The device comprises a housing, a laser beam generating mechanism, a light reflecting mechanism, a light collecting mechanism, and a window having a longitudinal axis and a transverse axis. The longitudinal and transverse axes of the window define a plane through which the scanning pattern is projected. The scanning pattern is approximately confined within a relatively narrow, yet diverging, volume, such as a pyramid, cone, frustum, etc., along a projection axis which intersects the plane of the window. For example, the projection axis could be at any angle within the range of from a slight deviation from precise perpendicularity up to approximately thirty (30) degrees therefrom. The light reflecting mechanism comprises plural, e.g., at least three (3), reflecting members, e.g., mirrors. The laser beam sweeping mechanism, e.g., a polygonal member having at least four (4) reflective surfaces arranged to be rotated about a rotation axis, serves to sweep the laser beam across the reflecting members, whereupon each of the reflecting members produces a respective one of the groups of lines of the pattern.  
           [0020]    In one preferred embodiment of the device, five reflecting members are provided. The first reflecting member is disposed on a first axis of the housing opposite the polygonal member, and extends along an axis parallel to the transverse axis. The first reflecting mirror is arranged to reflect the laser beam swept thereacross directly out through the window to produce the first group of scan lines. The second and third reflecting members are disposed on opposite sides of the first axis and closely adjacent laterally of the polygonal member. The first axis is parallel to the longitudinal axis. Each of the second and third members extends along a respective axis at a small acute angle, illustratively 8 degrees, to the first axis, and is arranged to reflect the laser beam swept thereacross out through the window to produce respective ones of the second and third groups of scan lines. The fourth and fifth reflecting members are disposed on opposite sides of the central axis between the second and third reflecting members, respectively, and each extends along a respective axis at a substantial acute angle, illustratively 48 degrees, to the longitudinal axis. Each of the fourth and fifth reflecting members is arranged to reflect the laser beam swept thereacross out through the window to produce respective ones of the fourth and fifth groups of scan lines.  
           [0021]    The light receiving mechanism comprises a light focussing mechanism and a transducer. The transducer is arranged to receive light reflected from the code which enters the window, is reflected by the reflecting members and the beam sweeping mechanism, e.g., the reflecting surfaces of the polygon, and is focussed by the focussing mechanism, to convert it into an electrical signal indicative of the code.  
           [0022]    The light focussing mechanism basically comprises a collecting mirror having a concave reflective surface arranged to receive light from the beam sweeping mechanism, e.g., reflective surfaces of the polygon, and to direct it to a concentrating lens. The lens acts to further focus the light onto the transducer.  
       
    
    
     DESCRIPTION OF THE DRAWING  
       [0023]    [0023]FIG. 1 is a perspective view of one embodiment of a laser scanning device constructed in accordance with the subject invention shown disposed on a conventional check-out counter of a retail establishment;  
         [0024]    [0024]FIG. 2 is an enlarged top plan view, partially in section, of the scanning device shown in FIG. 1;  
         [0025]    [0025]FIG. 3 is a sectional view taken along lines  3 - 3  of FIG. 2;  
         [0026]    [0026]FIG. 4 is a sectional view taken along lines  4 - 4  of FIG. 3;  
         [0027]    [0027]FIG. 5 is a plan view of the scanning pattern produced by the device shown in FIG. 1 at the plane of its window;  
         [0028]    [0028]FIG. 6 is a top plan view, partially in section, similar to that of FIG. 2, but showing an alternative embodiment of the scanning device shown in FIG. 1;  
         [0029]    [0029]FIG. 7 is a sectional view taken along lines  7 - 7  of FIG. 6; and  
         [0030]    [0030]FIG. 8 is a plan view of the scanning pattern produced by the device shown in FIG. 6 at the plane of the scanner&#39;s window.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0031]    Referring now to various figures of the drawing wherein like reference characters refer to like parts there is shown in FIG. 1, one embodiment  20  of a retroreflective, laser bar-code, scanner constructed in accordance with this invention.  
         [0032]    The scanner  20  is mounted on a base  22  disposed on a counter  24 , such as a checkout counter of a store, to project a scanning pattern  26  adjacent the counter. In the embodiment shown in FIGS. 1 and 5 the scanning pattern is projected laterally or downward over the counter. This orientation merely constitutes one of many orientations of the scanning pattern. In any event an article, such as a food container (not shown), having a conventional bar code (not shown), such as the UPC code, printed thereon is brought into the scanning pattern  26  by the checkout clerk, to enable the lines making up the pattern to sweep across the code to illuminate it with laser light, whereupon light reflected off the bar code is received back through the window by the components of the scanner. Such components process the received light into a bar code bearing electrical signal, as is conventional.  
         [0033]    The scanning pattern of the subject invention is confined within a relatively narrow, yet diverging volume centered about a projection axis from the scanner (as will be described later) and includes plural groups of intersecting scan lines to create a “rich” pattern. This “rich” pattern ensures that sufficient lines of the pattern will sweep across the entire bar code to enable the proper reading or decoding thereof by conventional decoding means located within the scanner  20 , irrespective of the orientation of the bar code within the scanning pattern. Moreover, by virtue of the fact that the volume or space in which scanning pattern is projected is somewhat narrow or confined, the amount of counter space which must be kept clear of other bar coded items to enable the proper scanning of the selected bar coded item, can be kept to a minimum. This should be contrasted with the use of conventional “slot-type” scanners, if mounted on a counter to project the scanning pattern thereabove. In such an arrangement the slot scanner produces such a wide or divergent pattern that a large amount of counter space must be reserved for scanning, and thus cannot be used for any other purpose, e.g., cannot be used to display any item bearing a bar code, etc.  
         [0034]    As is conventional the decoder utilized in the scanner  20  is arranged to provide electrical signals indicative of the decoded symbol to peripheral equipment, such as a conventional electronic cash register  27 .  
         [0035]    As will be described hereinafter, the scanner  20  is disposed within a housing  28  which is extremely compact. For example, in one commercial embodiment of the invention, the housing has a height of approximately 6.5 inches (165 mm), a width of approximately 6.5 inches (165 mm), and a thickness of approximately 3 inches (76 mm). The scanner housing  28  includes a window  30  through which the confined scanning pattern  26  is projected.  
         [0036]    As can be seen in FIG. 1 the base  22  on which the scanner is mounted is also extremely compact in size. Moreover, the base  22  is arranged to be adjusted to various orientations to hold the scanner housing with the window  30  in any desired orientation so that the scanning pattern is projected in any desired orientation with respect to the counter, e.g., laterally outward and slightly downward toward the counter as shown in FIGS. 1 and 5, upward with respect to the counter like that of a conventional slot scanner (not shown), or in any other desired orientation (not shown).  
         [0037]    Before describing the details of the construction of the scanner  20 , the scanning pattern produced thereby will be described. That pattern is shown clearly in FIGS. 1 and 5 and is produced within the scanner housing  28  and projected thereout through the window  30 . The window  30  is a generally planar, optically transparent member defined by a longitudinal axis  32  and a normally intersecting transverse axis  34 . The scanning pattern  26  is projected into a confined space or volume  38  (see FIG. 1), which as mentioned earlier is a relatively narrow, yet diverging and is centered about a projection axis  38 . The diverging volume  36  containing the pattern may be of any shape, e.g. pyramidal, conical, irregular, etc., depending upon the length of the various lines of the pattern (i.e., the “envelope” defined by the end points of each line of the pattern) and may be established by the size of the scanner&#39;s mirrors and/or the size and shape of the window. In the interest of drawing simplicity the envelope defining volume  36  is shown as being pyramidal and as such is merely exemplary of the myriad of shapes possible. The projection axis  3 B extends substantially perpendicular to the plane of the window. By “substantially perpendicular” it is meant that the projection axis is not precisely pependicular to the plane of the window, i.e., it deviates from perpendicularity up to a small acute angle, e.g., thirty (30) degrees, to perpendicularity. The reason that the projection axis is not precisely perpendicular to the plane of the window is to preclude overloading of the transducer, e.g. the photodetector (to be described later), in the light receiving means which could occur if the exiting laser beam was reflected back off the window to the transducer.  
         [0038]    It should be pointed out at this juncture that the lines making up the scanning pattern are preestablished in configuration and orientation with respect to one another, but appear differently, depending upon the shape and position of the surface upon which the pattern is projected and depending upon the distance of the surface from the scanner window. In FIG. 1 the scanning pattern  26  shown is merely schematic and indicative of a typical pattern projected on a flat surface within the volume  36 , approximately six inches from the window  30  and generally perpendicular to the projection axis. In FIG. 5 the scanning pattern is shown as it appears within housing at the plane of the window  30 .  
         [0039]    As can be seen the scanning pattern  26  basically consists of five groups  26 A,  26 B,  26 C,  26 D, and  26 E of plural, scan lines  40 . The scan lines in each group are disposed generally parallel to one another and in the embodiment of FIGS.  1 - 4  are preferably substantially equidistantly spaced in a “raster-like” configuration. In the embodiment shown herein there are four scan lines  40  in each group  38 A- 38 E.  
         [0040]    The lines  40  making up group  26 A are disposed generally parallel to the transverse axis  34  of the window. These lines, when projected in volume  36 , are somewhat horizontal and are very powerful in their ability to readily scan “picket fence” oriented bar codes, whether truncated or not. The lines  40  making up group  26 B intersect the lines  40  of group  26 A and extend at a substantial acute angle, e.g., 28°, to longitudinal axis  32  to be oriented generally diagonally when projected into volume  36 . The lines  40  making up group  26 C are mirror images of the lines making up group  26 B and are disposed on the opposite side of the longitudinal axis  32  from the lines making up that group. The two groups  26 B and  26 C serve to readily scan bar codes which are tilted with respect to a “roll” axis (not shown) generally perpendicular to the window. The lines  40  of groups  26 D are each oriented at a small acute angle, e.g., 8°, to the longitudinal axis  32  so as to be oriented generally vertically when projected into the volume  36 . The lines  40  making up group  26 E are mirror images of the lines making up group  26 D and are disposed on the opposite sides of the longitudinal axis from the lines making up that group. The groups  26 D and  26 E serve to readily scan “ladder” oriented bar codes.  
         [0041]    The rastered lines  40  of the groups substantially fill the volume 36 to produce a very rich scanning field having very few gaps. This feature facilitates the assured scanning of a bar code brought into the pattern irrespective of its orientation since the entire bar code will be swept (traversed) by one or more lines. Accordingly, the scanner operator need not precisely place or orient the bar code within the pattern so long as the bar code is within the volume and somewhat directed toward the scanner&#39;s window.  
         [0042]    The means for sweeping the laser beam to create the scan lines  40  making up the groups may consist of any suitable means, e.g., an oscillating mirror, an electro-optic scanner, etc. In the preferred embodiment shown herein the beam sweeping means basically comprises a four sided polygon  42  arranged for rotation about a rotation axis  44 . Each face  46  of the polygon is reflective, e.g., is a mirror (preferably planar), and tilted at a different respective angle with respect to the rotation axis. Thus, as the laser beam  48  is swept by the various faces of the polygon (to be described later) it produces the four generally parallel, generally equidistantly spaced lines  40  of each group. It should be noted that the faces of the polygon need not be oriented so that the line spacing is equadistant, if a different spacing arrangement is desired.  
         [0043]    Referring now to FIGS. 1 and 2- 4  details of the construction of the scanner  20  will now be described. Thus, can be seen the housing  28  basically comprises a front wall  50 , a pair of side walls  52  and  54 , a top wall  56 , a bottom wall  58  (FIGS. 3 and 4) and a rear wall  60  (FIGS. 3 and 4). The housing is preferably formed of two plastic sections  62  and  64  which are each integrally molded and which when joined along their respective periphery edges  66  complete the housing. The two sections  62  and  64  of the housing are arranged to be secured together via conventional threaded fastening means (not shown) extending through respective holes  68  located in the corners of the housing (as shown in FIG. 2).  
         [0044]    As can seen in FIGS. 1 and 3 the front wall  50  of the housing  28  includes an inclined surface portion  50 A at the interface of the front wall  50  and the top wall  56 . It is on the inclined portion that a suitable on/off switch  70  and indicator lights or LED&#39;s  72  are located.  
         [0045]    The window  30  is located within the front wall  50  and, as can be seen in FIG. 1, is of generally rectangular shape.  
         [0046]    The scan pattern  26  is produced by sweeping a sharply defined laser beam  48  across various optical components located within the housing. These components serve to fold the beam into the desired orientations to form the lines  40  making up the pattern. The means for producing the beam, focusing it, sweeping it through the housing, folding it and directing it out of the housing window are all mounted on an optical bench  74  mounted via fasteners  76 , on the inside surface of the rear wall  60  of housing section  64  (see FIG. 3). Those components will be described in detail later. Suffice for now to state that those components basically comprise a visible laser diode  78  (or any other suitable means for generating a laser beam), beam focusing and directing means  80 , a beam sweeping mechanism in the form of the four sided rotating reflective polygon  42  (described heretofore), plural beam-folding reflecting members  82 ,  84 ,  86 ,  88 , and  90 , and a light collecting system  92 .  
         [0047]    The light collecting system  92  basically comprises a collecting mirror  94 , a focusing lens  96 , and a transducer  98 , e.g., photodiode. The light collecting means is arranged to receive the light which is reflected off a bar code held within the scanning pattern to convert the received light into an electrical signal indicative thereof. That signal is provided to signal processing means and associated decoding means all located within the housing  30  on printed circuit boards  100  (to be described later) to effect decoding of the symbol and to provide an electrical signal indicative of the decoded symbol to the cash register  28  or other output device (not shown). The details of the structure and operation of the light collecting system  92  will be described later.  
         [0048]    The optical bench  74 , as clearly seen in FIGS.  2 - 4 , is a generally rectangular, plate-like member which includes a flange  102  extending along its two side edges and along its bottom edge. The laser diode  78  is fixedly mounted on the optical bench adjacent the bottom edge flange and is oriented parallel to the bench so that it projects a laser beam  48  parallel to the optic bench and in a transverse direction, that is parallel to the transverse axis  34  of the window  30 . A beam directing mirror  104  is mounted (e.g., glued) on a bracket  106  disposed opposite the laser diode. The mirror  104  is angled at approximately 45° to the plane of the optic bench to direct the laser beam  48  upward, that is away from the optic bench perpendicularly to the window (see FIG. 3). The lower edge flange of the optic bench includes a bracket  108  on which is mounted another beam directing mirror  110 . The mirror  110  is disposed above the mirror  104  and is oriented at an angle to receive the laser beam  48  from the mirror  104  and to direct it parallel to the longitudinal axis  32  toward the rotational axis  44  of the polygon  42 .  
         [0049]    The polygon is mounted on the rotary output shaft of a motor  112  which is fixedly mounted on the optical bench so that its rotation axis  44  intersects an axis  114 . The axis  114  extends parallel to the longitudinal axis  32  of the window and forms the central longitudinal axis of the optical components making up the scanner.  
         [0050]    As mentioned earlier the polygon  42  basically comprises four reflective, e.g., mirrored, planar surfaces  46 . Each of these surfaces extends at a respective acute angle to the axis of rotation  44  of the polygon. In particular in the preferred embodiment shown herein one face  46  is tilted 2° to the rotation axis, while the other faces are tilted at approximately 4, 6 and 8 degrees, respectively, to the axis of rotation. The polygon is rotated about the rotation axis, via the motor  112 , under power and control of the electronic circuitry mounted on the printed circuit boards  100 .  
         [0051]    The movement of each polygon face about the rotation axis  44  causes the laser beam  48  reflected off of downwardly extending mirror  110  to sweep through an arcuate path in front of and to the sides of the polygon face, to thereby create a scan line which is linear when projected onto a planar surface. The linear scan line produced by each face is folded by the beam folding mirrors  82 - 90  (to be described hereinafter) to form a respective line  40  of each of the respective groups  26 A- 26 E. Inasmuch as the reflective faces  46  of the polygon are each disposed at a slight angle (e.g., 2, 4, 6 and 8 degrees) to the rotational axis  44  each reflective face of the polygon sweeps the laser beam  48  across a different portion of the folding mirrors  82 - 90 , thereby producing the parallel lines  40  (i.e., the “raster”) of the various groups.  
         [0052]    The details of the reflecting means made up of mirrors  82 - 90  will now be described. All of the mirrors are of generally planar and are mounted on the optical bench  74  adjacent the polygon  42  and under the window  30 . In particular the mirrors  82 - 90  are mounted via a spider member  116  having five angled brackets  118 , one for each mirror. The spider  116  secured to the optical bench  74  via the fasteners  76 . Preferably the mirrors  82 - 90  are glued in place on the spider&#39;s brackets  118 .  
         [0053]    As can be seen clearly in FIGS. 2 and 4 the mirror  90  is mounted so that it extends generally transversely, that is perpendicular to the longitudinal central axis  114  of the scanner, while being basically centered with respect thereto. The mirror  82  is tilted upward at an angle of approximately 45° to the plane of the window  30 . The mirror  82  forms the scan lines  40  making up group  26 A.  
         [0054]    The mirrors  84  and  86  are disposed on opposite sides of the central longitudinal axis  114  immediately adjacent the polygon  42 . In fact portions of the mirrors  84  and  86  extend past the forwardly facing face of the polygon. Each of the mirrors  84  and  86  extends at a respective small acute angle, e.g. 8°, to the longitudinal axis  114 , with each of the mirrors being angled upward at approximately 45 degrees to the window  30 . The mirrors  84  and  86  form the scan lines  40  of groups  26 D and  26 E, respectively.  
         [0055]    The mirrors  88  and  90  are disposed on either side of the longitudinal central axis  114 , with mirror  88  being interposed between mirror  82  and mirror  84 , and with mirror  90  being interposed between mirror  82  and mirror  86 . The intermediate mirrors  88  and  90  each extend at a substantial acute angle, e.g., 48°, to the central longitudinal axis  114  of the scanner and each is angled upward at approximately 45 degrees to the window  30 . The mirrors  88  and  90  form the scan lines  40  making up the groups  26 B and  26 C, respectively.  
         [0056]    The formation of one line  40  of each group  26 A- 26 E is accomplished as follows: the rotation of the polygon  42  causes the beam  48  projected onto one face  46  thereof to be swept across the lateral mirror  86 , in the clockwise direction where viewed in FIG. 2 (to form one line of group  26 E) then across mirror  90  (to form one line of group  26 C), then across mirror  82  (to form one line of group  26 A), then across mirror  88  (to form one line of group  26 B), and finally across mirror  84  (to form one line of group  26 D). Inasmuch as each of the mirrors is angled upward with respect to the window the sweep of the beam thereacross causes that mirror to project the laser beam line out of the window, thereby producing a respective line  40  of each of the groups as described above. Moreover, inasmuch as the next successive face  46  of the polygon  42  is at a slight angle (e.g., 2 degrees) with respect to the proceeding face the next scan line  40  swept across the mirror  86 ,  90 ,  82 ,  88 , and  84 , will cross those mirrors at a different location than the beam swept by the previous polygon face. Accordingly, such action produces a second respective scan line  40  of each of the groups  26 A- 26 E.  
         [0057]    The foregoing scanning process is carried out by each successive face of the polygon as it rotates about the rotation axis to produce the rastered lines of the groups. The motor is rotated at a very high rate of speed, e.g., in excess of 5,000 rpm so that the scanner produces in excess of 400 scans per second.  
         [0058]    The details of the light collecting system  92  of the scanner  20  will now be described. As mentioned earlier that system is arranged to receive the light which is reflected off a bar code within the scan pattern volume and which passes back through the window  30  into the interior of the housing  28 . The light coming back through the window is reflected by the mirrors  82 - 90  back to the faces of the rotating polygon, whereupon each of those faces directs the reflected light to the light collecting system, and in particular to heretofore identified collecting mirror  94 .  
         [0059]    As can be seen clearly in FIG. 2 the collecting mirror  94  basically comprises a concave reflecting surface, which in the preferred embodiment is spherical. The mirror is mounted, e.g., glued, onto a bracket  120  projecting upward from the optical bench  74  and is spaced in front of the mirror  110 . In order to enable the laser beam  48  produced by the laser diode  78  from passing from mirror  110  to the rotating polygon  42 , the spherical collecting mirror  94  includes a central opening  122  therein.  
         [0060]    The collecting mirror  94  is oriented slightly downward (see FIG. 3) to be aimed at the polygon. The collecting mirror receives the reflective light from each face  46  of the polygon and concentrates or focuses it and directs it to the focusing lens  96 . The focusing lens  96 , as can be seen in FIGS.  2 - 4  is mounted opposite the collecting mirror along central longitudinal axis  114  and above the polygon  42 . The means for mounting the focusing lens at that position comprises a bracket  124  fixedly secured to the front portion of the optical bench  74 . As can be seen the photodiode  98  is also mounted within the bracket  124 , but behind the lens  96 . The lens is arranged to converge or focus the light reflected by the spherical collecting mirror  94  onto the photodiode  98 .  
         [0061]    The use of the focusing lens  96  in conjunction with the collecting mirror  94  provides the scanner  20  with a greater depth of field for scanning bar codes then would otherwise be possible with a similarly small sized housing. By depth of field it is meant the range of distances measured from the window outward that a bar code can be effectively scanned.  
         [0062]    The use of the focusing lens  96  ensures that the light spot which is projected onto the photodiode is kept sufficiently small for a larger depth of field than would be possible with the use of the spherical collecting mirror alone. Moreover, since the spherical collecting mirror includes the central opening  122 , absent the lens  96  when scanning bar codes disposed close to the window the image projected from the spherical collecting mirror to the photodetector may include an area of no light (e.g., the image of the hole  122 ). Obviously, such action is undesirable. The use of the focussing lens  96  obviates that potential problem.  
         [0063]    It should be pointed out at this juncture that the light collecting system as just described is merely exemplary. Thus, other light collecting systems, e.g., a lens, hologram, etc., may be used in lieu of the collecting mirror  94  and associated focussing lens  96 .  
         [0064]    As mentioned earlier, the electronic and various other electrical components for the scanner  20  are mounted on various printed circuit (PC) boards in the housing. Thus, as can be seen one printed circuit board  100  is mounted, via opposed brackets  126 , so that it is disposed immediately adjacent the bottom wall  58  of the housing  28 , while a pair of printed circuit boards  100  are mounted between opposed brackets  128 , adjacent one side wall  54  of the housing, and another printed circuit board  100  is mounted between opposed brackets  130  adjacent the other side wall  52  of the housing. Another small printed circuit board (not shown) is mounted adjacent the front face of a housing near the inclined portion  50 A.  
         [0065]    As should be appreciated by those skilled in the art, the pattern produced by the scanner  20  is quite effective for scanning various types of bar code labels, be they “picket fence” oriented, or “ladder” oriented. However, if a bar code is a truncated and ladder oriented code and is held a substantial distance from the window, the truncated bar code may be located within a small gap between the lines  40  making up groups  26 D and  26 E, i.e., the portion of the pattern designated by the reference numeral  132  in FIG. 5. Merely broadening the raster, that is the spacing between the various respective lines of the respective groups, will not obviate that problem without generating the attendant problem of creating gaps in the field at other places through which ladder style symbols can slip unread.  
         [0066]    Thus, in order to further augment the coverage of ladder oriented symbols up close to the scanner&#39;s window, the side mirrors  84  and  86  may be modified so that each is split into two parts. This arrangement is shown in the embodiment of the scanner of FIGS. 6 and 7. That scanner produces a scan pattern like that shown in FIG. 8. In such an arrangement the more vertically oriented scan fields  26 D and  26 E can be broadened up close to the window without having an adverse effect at a distance from the window. Thus, one gets the advantage of broadening the field closely adjacent the window of the scanner, but not generating too broad a field at the outer distance limit of the depth of field.  
         [0067]    The embodiment of the scanner  20  shown in FIGS. 6 and 7 is identical in all respects to that shown in FIGS.  1 - 4  except that the two sides mirrors  84  and  86  of the embodiment of FIGS.  1 - 4  are replaced by two pairs of side mirrors  134  and  136  and  138  and  140 , as will be described hereinafter. In the interest of brevity, all of the identical components of the embodiment of FIGS.  1 - 4  are given the same reference numerals in the embodiment of FIGS. 6 and 7, and their structure and function will not be reiterated hereinafter.  
         [0068]    As can be seen in FIGS. 6 and 7, a pair of side mirrors  134  and  136  are mounted on one side of the central longitudinal axis  114 , (and correspond to mirror  84 ) while a similar and mirror image pair of mirrors  138  and  140  are mounted an the opposite side of the central longitudinal axis (and correspond to mirror  86 ). The mirrors  134 - 140  are mounted by respective brackets  118  of the spider and are each oriented so that they extend at the same small acute angle, e.g., 8°, to the longitudinal axis as the mirrors  84  and  86  described heretofore. Moreover, the mirrors  134  and  136  are parallel to each other, and the mirrors  138  and  140  are parallel to each other. The mirrors  134  and  136  jointly establish the lines  40  of the group  26 D, while the mirrors  138  and  140  jointly establish the lines of the group  26 E. The spacing, that is the lateral offset between mirrors  134  and  136 , and between mirrors  138  and  140  produces two sets of lines in groups  26 D and  26 E. As can be seen in FIG. 8, the two sets of lines are spaced slightly from each other so that all of the lines of those groups are not equidistantly spaced, as is the case in the embodiment of scanner  20  shown in FIGS.  1 - 4 . Thus, as shown in FIG. 8, the side groups  26 D and  26 E of the pattern  26  are closer together, thereby eliminating the gap  132  of the pattern of FIG. 5.  
         [0069]    As should be appreciated by those skilled in the art the planes of the pairs of the side mirrors must be parallel. Otherwise, the reflected portion of the beam coming back off the bar code could not be returned through the return focusing system to the photodetector.  
         [0070]    As will be appreciated from the foregoing, the projection scanner  20  as described heretofore, scans omnidirectionally, that is the bar code can be presented in any orientation within the field. Moreover, the scanner provides free-hand scanning productivity as heretofore been provided by conventional counter mounted, slot scanners, plus hand-held scanning flexibility as provided heretofore by hand-held scanners. Furtherstill, being of such a small size, e.g., 6.5 inches long by 6.5 inches wide by 3 inches deep, the scanner is adaptable to fit just about any size, space and mounting requirements, and provides a small, unobtrusive foot print. The highly collimated or focused volume of the scan prevents unintentional scanning of nearby projects.  
         [0071]    Without further elaboration the foregoing will so fully illustrate our invention that others may, by applying current or future knowledge, readily adapt the same for use under various conditions of service.