Scan pattern generators for bar code symbol readers.

BACKGROUND OF THE INVENTION

1. Field of the Invention

0001This invention generally relates to laser scan­ning systems for reading bar code symbols and, more parti­cularly, to scan pattern generators for generating scan patterns which extend across the symbols to be read.

2. Description of the Related Art

0002Laser scanning systems and components of the type exemplified by U.S. Pat. Nos. 4,251,798; 4,360,798; 4,369,361; 4,387,297; 4,593,186; 4,496,831; 4,409,470; 4,460,120; 4,607,156; 4,673,805; 4,736,095; 4,758,717; 4,760,248; 4,806,742; 4,808,804; 4,825,057; 4,816,661; 4,816,660; 4,845,350; 4,835,374; 4,871,904; as well as U.S. Application Ser. Nos. 519,523; 193,265; 265,143; 265,548; 265,149; 264,693; 367,007; 392,207 and 349,860 --all of said patents and patent applications being owned by the assignee of the instant invention and being incor­porated by reference herein--have generally been designed to read bar code symbols, particularly of the Universal Product Code (UPC) type, at a certain working or reading distance from a hand-held or stationary scanner, and with a reading spot of a certain size, the spot being scanned over each symbol to trace a scan line.

0003It has previously been proposed to generate scan patterns of mutually parallel scan lines extending along one or two directions, as well as omni-directional scan patters of intersecting scan lines, and even curvi­linear scan patterns, for superposition over the symbol to be read to insure that, no matter what the angular orientation of a respective symbol might be within pre­determined limits, at least one of the scan lines or part of the pattern will be scanned over the entire length of the respective symbol. Yet, the known patterns are gen­erated by highly complex and expensive systems.

0004Also, quite apart from the angular orientation of the symbols to be read, one symbol might be located close-in to the scanner, whereas another symbol might be located far-out from the scanner and, in short, successive symbols may be located at different working distances from the scanner. In the case of a scanner which has been designed to read symbols within a certain range of working distances, should it occur that a particular symbol falls outside this range, then the distance between the scanner and the symbol must be adjusted, and usually within a short time interval, for, otherwise, the symbol will not be read. In the case of a hand-held scanner, the scanner is usually manually moved toward or away from the symbol to adjust the distance between the scanner and the symbol. This can be a tiring procedure and require multiple read­ing attempts. It would be desirable, therefore, if the scan pattern generators also incorporated a so-called "zoom" characteristic in which the working distance is automatic­ally changed during scanning.

0005It would further be desirable to change the scan pattern to further insure that at least one of the scan lines, or part of the pattern, will scan the entire length of the symbol to be read. Some symbols may be more rapidly or successfully decoded and read by a particular scan pattern.

0006In the same vein, changing the scan rate from a slow to a faster speed, or vice versa, might spell the dif­ference between a successful and a not-successful decoding and reading of a particular symbol.

0007In order to minimize power consumption, which is of especial concern in a hand-held scanner having an on-board battery, it would be desirable to vary the intensity of the light beam emitted by a light source, typically a laser, mounted within the scanner. For example, the light source, rather than, for instance, being shut down when a symbol is not being read, may be underpowered to generate a low power laser beam which would be useful during aiming. Thereupon, during reading, the laser may be powered up to generate a high power laser beam.

SUMMARY OF THE INVENTION

1. Objects of the Invention

0008It is a general object of this invention to advance the state of the art of laser scanning systems for reading bar code symbols.

0009It is another object of this invention to gener­ate scan patterns of mutually parallel lines or of inter­secting lines over the symbol with a relatively simple pat­tern generator system, with the option of simultaneously changing the working distance of the outgoing laser beam.

0010It is a further object of this invention to gener­ate a bidirectional scan pattern of mutually parallel scan lines, at least one scan line scanning in one direction, and at least another scan line scanning in an opposite direction.

0011It is an additional object of this invention to change the scan pattern generated by the system.

0012Still another object of this invention is to change the intensity of the laser beam generated by the system.

0013Yet another object of this invention is to change the scan rate of the system.

0014Still a further object of this invention is to either automatically or manually change the scan pattern, laser beam intensity, scan rate, or direction of at least one of the scan laser.

2. Features of the Invention

0015In keeping with these objects, and others which will become apparent hereinafter, one feature of this invention resides, briefly stated, in an optical arrangement for use in a laser scanning system for read­ing symbols, particularly bar code symbols having alter­nate bars and spaces arranged in a pattern which, when decoded, identify an object on which the symbol is affixed. The scanning system comprises a housing having an exit port, a laser source, e.g. a gas laser tube or a semi­ conductor laser diode, for generating a laser beam, and scanning means in the housing for scanning the laser beam in scans across successive symbols located exteriorly of the housing. The optical arrangement comprises optical means in the housing for directing the scanning beam along an optical path through the exit port, and for optically forming the scanning beam with a cross-sectional beam spot of a predetermined waist size and at a predeter­mined distance from the exit port of the housing.

0016More particularly, this invention is embodied in pattern means for generating a scan pattern of mutu­ally parallel scan lines extending linearly across each symbol. The scan lines are arranged over the height of the symbol. At least one of the scan lines sweeps across each symbol along one sweep direction, whereas, at least another of the scan lines sweeps across each symbol along an opposite sweep direction countercurrent to said one sweep direction, thereby forming a bidirectional scan in which a respective symbol can be read by the first avail­able scan line no matter what its sweep direction. This improves reading speed.

0017In one advantageous embodiment, the pattern generating means includes a planar rotary mirror consti­tuted of a light-refractive material having an index of refraction and having opposite major mirror surfaces spaced apart by a mirror thickness. The mirror surfaces extend generally parallel to a shaft axis of an output shaft of a scanning drive. One of the mirror surfaces has a light-­reflecting coating thereon. The mirror is impinged at an angle of incidence by the laser beam, and a pair of fold­ing mirrors are arranged for reflecting the light reflec­ted off the mirror through the exit port of the housing. The scan lines are spaced apart from one another in a di­rection parallel to the shaft axis due to the index of refraction, the thickness of the rotary mirror, and the angle of incidence of the impinging laser beam on the rotary mirror.

0018In another embodiment of the pattern generating means, both opposite majcr mirror surfaces of the rotary mirror are provided with light-reflecting coatings. The mirror surfaces extend at an acute angle relative to the shaft axis. During rotation of the output shaft during scanning, the laser beam impinges on both mirror surfaces to generate the scan lines positioned across the height of each symbol.

0019Yet another feature resides in generating an omni-directional scan pattern of intersecting scan lines over each symbol. A rotary mirror is mounted on a shaft for rotation about the shaft axis during scanning. This mirror has a light-reflecting coating on a surface which extends at an angle to the shaft axis. A plurality of folding mirrors are arranged about the rotary mirror to generate the omnidirectional pattern. One of the folding mirrors may be movable so as to change the length of the optical path of the outgoing laser beam. By changing the length of the optical path, the predeter­mined working distance of the beam spot is changed during scanning. This so-called "zoom" feature enables the scan pattern to read close-in and far-out symbols.

0020Still other features are embodied in changing the scan pattern and/or scan direction and/or intensity of the laser beam, and/or scan rate in such systems. Any one or more of these system characteristics can be automatically changed, e.g. by a software program, or can be manually changed, e.g. by an actuator mounted on a hand-held head in such systems. The actuator can advantageously be in­corporated in a manually-operable trigger operative to initiate reading of a symbol by designing the trigger as a multi-position switch. In a first position, for example, the laser can be made to generate a laser beam of low intensity to facilitate aiming the head at a symbol; or, the scan pattern can be a linear scan or beam spot to faci­litate placement on the symbol; or, the scanning can be conducted at a slow or at a zero rate to conserve power. In the second position, for example, the laser beam can be generated at a higher light intensity, or with a dif­ferent scan pattern or scan rate to insure that the de­coding and reading will be successful, even for poorly printed symbols.

0021The novel features which are considered as characteristic of the invention are set forth in particu­lar in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, best will be understood from the following description of specific embodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

0022<ul id="ul0001" list-style="none"><li>FIG. 1 is a diagrammatic view of a scan pat­tern generator for generating multiple scan lines in a laser scanning system in accordance with this invention;</li><li>FIG. 2A is a top plan, diagrammatic view of the scan pattern generator of FIG. 1 during one stage of scanning;</li><li>FIG. 2B is a view analogous to FIG. 2A, but at another stage of scanning;</li><li>FIG. 2C is a view analogous to FIG. 2B, but at still another stage of scanning;</li><li>FIG. 2D is a view analogous to FIG. 2C, but at yet another stage of scanning;</li><li>FIG. 2E is a view analogous to FIG. 2D, but at an additional stage of scanning;</li><li>FIG. 2F is a view analogous to FIG. 2E, but at a further stage of scanning;</li><li>FIG. 3A is a diagrammatic view of another scan pattern generator during one stage of scanning;</li><li>FIG. 3B is a diagrammatic view of the scan pattern generator of FIG. 3A during another stage of scanning;</li><li>FIG. 4 is a perspective view of still another scan pattern generator;</li><li>FIG. 5 is a front view of the scan pattern generator of FIG. 4 during one stage of scanning;</li><li>FIG. 6 is a view analogous to FIG. 5, but during another stage of scanning;</li><li>FIG. 7 is a perspective view of yet another scan pattern generator in accordance with this invention, and diagrammatically illustrating one scan pattern;</li><li>FIG. 7A is a diagrammatic illustration of another scan pattern;</li><li>FIG. 7B is a diagrammatic illustration of yet another scan pattern;</li><li>FIG. 7C is a diagrammatic illustration of still another scan pattern;</li><li>FIG. 7D is a diagrammatic illustration of a further scan pattern;</li><li>FIG. 8 is a perspective view of a further scan pattern generator in accordance with this invention;</li><li>FIG. 9 is a sectional view of the further scan pattern generator of FIG. 8;</li><li>FIG. 10 is a view analogous to FIG. 7, but of yet another scan pattern generator;</li><li>FIG. 11 is a view analogous to FIG. 10, but of an additional scan pattern generator according to this invention; and</li><li>FIG. 12 is a view analogous to FIG. 1 of addi­tional system features.</li></ul>

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

0023Referring now to the drawings, reference numer­al 10 in FIG. 1 generally identifies an arrangement in a laser scanning system of the type generally described in the above-identified patents and patent applications, the entire contents of all of which are hereby incorporated by reference herein, for reading symbols, particularly UPC bar code symbols. As used in this specification and the following claims, the term "symbol" is intended to be broadly construed and to cover not only symbol patterns composed of alternating bars and spaces, but also other patterns, as well as alpha-numeric characters.

0024The arrangement 10 includes a housing 12, shown in dashed lines, and intended to represent either hand-held, desk-top workstation, or stationary scanner, housings having an exit port 14 through which an outgoing laser light beam is directed to impinge on, and to be scanned across, symbols located exteriorly of the housing, each symbol to be scanned and read in its respective turn. A laser source, e.g. a gas laser tube 16 or a semicon­ductor laser diode, is mounted in the housing and, when energized, the source 16 generates a laser beam.

0025A multiple line scan pattern generator 120 is illustrated in FIGs. 1 and 2A-F, and is operative for generating not only multiple scan lines or traces across a symbol to be read, but also for positioning at least some of the scan lines at different working distances from the housing 12 in which the generator 120 is housed. Another feature of generator 120 resides in the bidirec­tional nature of the resulting scan pattern.

0026Laser source 16 directs a laser beam through optical lens 122 for directing the beam onto rotary main mirror 124 which is mounted on a vertical shaft 126 which is rotated by a motor drive 128 about a vertical axis. As shown in enlarged view of FIG. 3B, mirror 124 has op­posite major planar surfaces 130 and 132 which are separ­ated by a mirror thickness dimension T₃. A light-reflect­ing coating 134 is applied over one of the surfaces, e.g. 132.

0027The generator 120 also includes a pair of sta­tionary first surface side mirrors 136, 138 inclined at angles relative to the vertical axis of the shaft 126, and also including an angle with each other. Side mirrors 136, 138 have front surfaces on which light-reflecting coatings 140, 142 are respectively applied. Inclined side mirrors 136, 138 are so positioned relative to main mirror 124 that, during rotation of mirror 124, laser light impinging on mirror 124 will, at certain times, during each revolution of mirror 124, be directed toward one of the side mirrors for reflection therefrom forward­ly to an exterior symbol.

0028The bidirectional multiple scan line pattern 144 depicted in FIG. 1 is generated as follows: Assume that mirror 124 is initially positioned as shown in FIG. 2A with its coated surface 134 directly facing laser source 16. The laser beam emitted by source 16 is re­turned along the same optical path (shown slightly sep­arated for ease of illustration) for impingement on a symbol located at distance Z9. During rotation of mirror 124 about the FIG. 2A position, scan line 150 is generated. Eventually, after movement of mirror 124 in the circum­ferential direction of arrow 146, the mirror 124 will be oriented as shown in FIG. 2B, wherein the mirror 124 di­rects the laser beam incident thereon to side mirror 136 for reflection by coated surface 140 forwardly for impinge­ment on a symbol located at distance Z10. Z10 is shorter than Z9 due to the diversion of the beam to side mirror 136. During rotation of mirror 124 about the FIG. 2B position, scan line 152 is generated. Scan line 152 is swept in the opposite direction to that of scan line 150.

0029Eventually, the mirror 124, during further rotation in direction of arrow 146, is oriented in the FIG. 2C position, wherein the coated surface 134 faces away from the laser source 16 so that the laser beam must initially pass through non-coated surface 130 of mirror 124 prior to reaching the rear coated surface 134. As shown in enlarged view in FIG. 3B, this incident beam impinges at an angle of incidence ϑ, whereupon the beam is refracted at an angle ϑ′ to the extent determined by the index of refraction n′ of mirror 124. The refracted beam reflects off coated surface 134 until it is again refracted at the mirror/air surface 130. A comparison of FIGs. 3A and 3B reveals that the positional shift ΔD between the beam reflected solely off coated surface 134 in the FIG. 2B situation and the beam leaving the mirror 124 after having been refracted therein is:<maths id="math0001"><img file="EP0402952A2_D0001.tif" /></maths>

0030Returning to FIG. 2C, the refracted beam exit­ing mirror 124 is directed to coated surface 142 of the side mirror 138 for reflection forwardly to a symbol lo­cated at working distance Z10. Rotation of mirror 124 about the FIG. 2C position generates scan line 154 which is swept in the same direction as scan line 152.

0031In analogous manner to that described earlier in connection with FIG. 2A, further rotation of the mirror 124 eventually orients the mirror 124 to the FIG. 2D posi­tion, wherein the coated surface 134 converts the mirror 124 into a second surface mirror. In this case, the in­coming beam must pass through the mirror thickness T₃ before being forwardly reflected by coated surface 134 to working distance Z9. Scan line 156 generated by rota­tion of mirror 124 about the FIG. 2D position is swept in the same direction as scan line 150.

0032Scan line 158 is generated by rotation of mirror 124 about the FIG. 2E position in a manner ana­logous to that described earlier in connection with FIG. 2C, except that the beam exiting mirror 124 is directed instead to the other side mirror 136 prior to forward reflection to a symbol located at working distance Z10.

0033Scan line 160 is generated by rotation of mirror 124 about the FIG. 2F position in a manner analo­gous to that described earlier in connection with FIG. 2B, except that the beam leaving mirror 124 is directed to the other side mirror 138 prior to reflection forwardly to a symbol located at working distance Z10. Scan line 160, as well as scan line 158, are swept in the same di­rection as scan line 152.

0034As best shown in FIG. 1, it will be noted that the scan pattern 144 comprises a plurality of scan lines in mutual parallelism, with scan lines 150, 156 swept from left to right, and with the remaining scan lines 152, 154, 158 and 160 swept from right to left. All the scan lines are spread apart over the height of the symbol. This spread can be controlled by, and is a function of, the thickness T3 of mirror 124, the angle ϑ of incidence of the laser beam on mirror 124, and the index of refrac­tion n′ of mirror 124, the latter being preferably con­stituted of glass. Also, as shown in FIGs. 2A through 2F, the beam spot is focused and alternately located at either working distance Z9 or Z10, thereby obtaining a zooming function.

0035Another way of spreading multiple scan lines apart from one another is to replace the vertically ex­tending mirror 124 having a single coated surface with a tilted mirror 162, as shown in FIGs. 4-6, which has two light-reflecting coated surfaces 164, 166 on opposite sides thereof. The tilted mirror 162 is mounted on a shaft 126 of a motor drive 128 at an angle relative to the vertical. When impinged by a light beam emitted by laser source 16, either the coated surface 164 which is oriented at angle ⌀, or the coated surface 166 which is oriented at an angle supplementary to ⌀ will face the source 16. The different angles of inclination of the coated surfaces of mirror 162 results in the desired angu­lar spread between the scan lines.

0036An omni-directional scan line pattern generator 170 is illustrated in FIG. 7, and is operative for gener­ating intersecting line patterns. The generator 170 is simple in construction and comprises a drive motor 172 having a vertical output shaft 174 on which a front sur­face planar mirror 176 is fixedly mounted for rotation in the circumferential direction of arrow 178. A plural­ity of inclined reflecting side mirrors 180, 182, 184 are equiangularly distributed about the vertical shaft 174. The side mirrors are positioned in the light path of a laser beam emitted from source 16 and directed by over­head folding mirror 186 to the center mirror 176.

0037Upon rotation of center mirror 176, the laser beam is successively directed to mirrors 180, 182, 184 each in its turn, for reflection toward a symbol to be read. The resulting multiple line pattern 188 covers the symbol in the FIG. 7 embodiment with three intersecting lines. If four, eight, six, or five mirrors were equi­angularly distributed about vertical shaft 174, then the patterns depicted in FIGs. 7A, 7B, 7C and 7D, respectively, would be generated during each revolution of the center mirror 176.

0038A drive, such as a piston rod 181, reciprocally movable relative to a cylinder 183 along the directions of double-headed arrow 185, is connected to any one of the side mirrors, e.g. 180. As the side mirror 180 is moved radially toward and away from the axis of rotation of the center mirror 176, the focused scan line associated with the side mirror 180 is located at different working distances, thereby achieving a zooming function.

0039Another omni-directional scan line pattern generator 190 is illustrated in FIGs. 8 and 9, and gener­ates not only intersecting scan line patterns, but also individual scan lines which are located at different work­ing distances from the housing, thereby achieving a zoom­ing function. As before, a drive motor 172 rotates a vertically oriented output shaft 174. A plurality of inclined side reflecting mirrors 180, 182, 184 are equi­ angularly arranged about the shaft 174. A housing 12 having exit aperture 14 also supports an overhead folding mirror 186 to which a laser beam from source 16 is di­rected.

0040Rather than rotating a single mirror on shaft 174, as proposed by the previous embodiment, this embodi­ment proposes mounting a mirror assembly on the shaft 174. This mirror assembly includes elongated upper and lower bars 192, 194 whose inner ends are fixed to shaft 174 and rotatable therewith in mutual parallelism. The bars 192, 194 are axially spaced apart by spacer 196. At the outer ends of bars 192, 194 are respectively supported mirrors 198, 200. Mirror 198 is stationarily mounted at the outer end of bar 192. Mirror 200 is mounted for rotation about axis 202 which is parallel to vertical axis 204 of the shaft 174. Mirror 200 is mounted at the outer end of bar 194 on a central shaft of a planetary gear 206 having ex­terior gear teeth which meshingly engage with exterior gear teeth of a stationary sun gear 208. Sun gear 208 coaxially surrounds the shaft 174 and is stationarily mounted on the housing of motor 172. Gears 206, 208 are circular, and sun gear 208 has a much larger diameter than that of planetary gear 206,so that mirror 200 is rotated at a high angular speed about its axis 202.

0041Another mirror 210 is fixedly mounted at the inner end of bar 192, and is located in the optical path of light reflected from overhead mirror 186. The light reflected from mirror 210 is directed to stationary mirror 198, whereupon the reflected light is directed through a hole 212 in bar 192 to the rotary mirror 200 located underneath hole 212.

0042In operation, light from source 16 is directed along an optical path by successive reflections off mir­rors 186, 210, 198 and 200 prior to being directed to side mirrors 180, 182, 184. The relative positions of mirrors 210 and 198 are fixed relative to each other dur­ing rotation of the mirror assembly. At the same time that shaft 174 rotates, the mirror 200 experiences a dual move­ment. First, the mirror 200 rotates about its axis 202 with an angular speed proportional to the ratio of the diameters of gears 206, 208. Second, the mirror 200 is moved along a circular annulus concentric with axis 204. Hence, the light reflected off mirror 200 will, for each revolution of mirror 200 about axis 202, sequentially im­pinge on side mirrors 180, 182, 184 which are inclined to direct successive scan beams out through port 14. Due to the diversion of light and the different optical paths between the rotary mirror 200 and the side mirrors 180, 182, 184 at any one moment, at least some of the scan lines are positioned closer in to the housing 12 than other scan lines, thereby achieving a zooming action. Also, as the mirror 200 is also orbiting about the axis 204, the work­ing distance generated by reflection from any one side mirror is always changing.

0043A three-dimensional coverage of a symbol can thus be achieved with a very sophisticated pattern to­gether with a zooming action. Of course, more than three side mirrors could have been used to obtain even more coverage. The exit port 14 need not be located above the generator 190, as shown in FIGs. 8 and 9 for use in a so-­called "scan-above" system. Alternatively, the port 14 could have been located so as to form a "scan-below" system or even a "scan-out" system.

0044Twc additional omni-directional scan line pat­tern generators are respectively depicted in FIGs. 10 and 11, wherein like parts with the generator shown in FIG. 7 are identified with like reference numerals. FIG. 10 shows an embodiment wherein the inclined side reflecting mirrors are non-equi-angularly arranged about the shaft 174. Specifically, mirror 184′ is located closer to mirror 182 than to mirror 180. This arrangement causes the scan line associated with mirror 184′ to be oriented at a different angle relative to the scan line associated with mirror 182, as compared to the scan line associated with mirror 180.

0045FIG. 11 shows an embodiment wherein the inclined side reflecting mirrors have different lengths. Mirrors 180 and 182 have the same length, but mirror 184˝ is shorter in length. This arrangement causes the scan line associated with mirror 184˝ to be shorter in length than the scan line associated with either mirror 182 or mirror 180.

0046Hence, by changing the angular spacing between the side mirrors (FIG. 10) or by changing the lengths of individual side mirrors (FIG. 11), many different scan line patterns can be generated to suit a particular application.

0047Although the preceding description has been rendered in terms of laser scanning systems and arrange­ments for optically modifying laser beams, it will be ex­pressly understood that this invention is not intended to be so limited and, in fact, is intended to include non-­laser light sources and beams, including non-coherent and coherent light sources such as light-emitting diode sources, incandescent light sources, gas discharge sources, etc.

0048Turning now to FIG. 12, the hand-held scanner 200 has a handle 202, a barrel 204, an exit window 206, and a trigger 208 manually operative among various states by an operator. A light source, e.g.a laser tube 210, a laser diode, a non-laser source, etc., directs a light beam of a certain intensity through an optical component 212 for impingement on a central rotary mirror 214 mounted on a shaft 216 of a drive motor 218 operative for turn­ing the central mirror 214 in a circumferential direction about a drive axis.

0049A plurality of folding mirrors 220, 222 arranged about the drive axis normally intercepts the light beam reflected off the central mirror 214, and direct the light beam outwardly of the window 206 to a symbol. Piezo­electric or bimorph drive elements 224, 226 are respec­tively mounted at the rears of the folding mirrors 220, 222. The drive elements 224, 226 are electrically connected to a mirror control circuit 228 which, in turn, is electric­ally connected to the trigger 208.

0050The drive motor 218 may be electrically connec­ted, in another embodiment, to a motor speed control cir­cuit 230. The lasar tube 210 is electrically connected to a laser power supply 232 which, in turn, is electric­ally connected to the trigger 208.

0051The trigger is normally depressible among an off state, a first state and a second state.

0052In one embodiment, the scan rate at which each scan line of the scan pattern generated by the scanner is varied. For example, in the off state of the trigger, the motor speed control 230 supplies no current to the motor 218 and the central mirror 214 is not turned. In the first state, the motor speed control 230 supplies a low magnitude current to the motor in order to turn the central mirror 214 at a slow rate, e.g. 10 revolu­tions per second, sufficient to read certain symbols. In the second state, the motor speed control 230 sup­plies a high magnitude current to the motor in order to turn the central mirror 214 at a faster rate, e.g. 40 revolutions per second, sufficient to read certain dif­ferent symbols.

0053In another embodiment, the intensity of the light beam is varied. For example, in the off state of the trigger, the power supply 232 supplies no current to the laser 210. In the first state, the power supply 232 supplies a low amplitude current to the laser 210, thereby generating a laser beam of low intensity. In the second state, the power supply 232 supplies a high amplitude current to the laser 210, thereby generating a laser beam of high intensity. Thus, the low intensity beam can be useful for aiming the scanner 200 at a symbol, whereas, the high intensity beam can be used for reading the symbol. In certain applications, both the high and the low intensity beams can be used for reading symbols, the low intensity beam conserving power.

0054Rather than employing a controlled power sup­ply to change the intensity of the laser beam, one of the mirrors, e.g. the central mirror 214, could be pro­vided with different light-absorptive coatings on its front and rear surfaces. Each coating, thus, absorbs more and less light during each revolution of the central mirror.

0055In still another embodiment, the scan direc­tion of at least one of the scan lines is changed by reversing the direction of the motor 218. Thus, in the off state of the trigger, the motor speed control 230 supplies no current to the motor. In the first state of the trigger, the motor speed control 230 supplies a control signal for turning the central mirror 214 in one circumferential direction. In the second state of the trigger, the motor speed control 230 supplies a control signal for turning the central mirror 214 in the oppo­site circumferential direction. The different directions of rotation, in turn, correspond to different scan direc­tions for each scan line.

0056In yet another embodiment, the scan pattern generated by the scanner is changed. For example, in the off state of the trigger, no scan pattern is gener­ated. In the first state, a first scan pattern is gen­ erated. In the second state, a second scan pattern is generated. Each scan pattern overlies the symbol. Each scan pattern can, for example, be one or more beam spots, a single scan line, or a set of mutually parallel scan lines (see FIG. 1), or a set of intersecting scan lines (see FIGs. 7A-7D), or a curvilinear pattern, or an omni-directional pattern, or, in short, just about any pattern at all. Each scan pattern can be useful for reading different types of symbols. Or, one scan pattern can be useful for aiming the scanner at a symbol.

0057In order to generate different scan patterns as a function of actuating the trigger, one or more of the folding mirrors may be moved, or the total number of the folding mirrors may be changed. To that end, move­ment of each folding mirror can be obtained upon ener­gization of the mirror control circuit 228 to actuate the piezoelectric or bimorph drive elements 224, 226. Other types of mirror drives can also be used.

0058Rather than employing a multi-state trigger, a separate manually-operable switch can be mounted on the scanner. Alternatively, a software program can be incorporated into a microprocessor for the scanner. The microprocessor can automatically control the power supply 232, motor speed control 230, or mirror control 228 after each scan, or after a predetermined number of scans, or after a predetermined time has elapsed, or after a symbol has not been successfully decoded within a predetermined time interval, or after a symbol has been successfully decoded and read. Other variations are, of course, possible.

0059It will be understood that each of the ele­ments described above, or two or more together, also may find a useful application in other types of constructions differing from the types described above.

0060While the invention has been illustrated and described as embodied in scan pattern generators for bar code symbol readers, it is not intended to be limited to the details shown, since various modifications and struc­tural changes may be made without departing in any way from the spirit of the present invention.

0061Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific as­pects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

0062What is claimed as new and desired to be pro­tected by Letters Patent is set forth in the appended claims.

0063The invention is summarized as follows: <ul id="ul0002" list-style="none"><li>1. An arrangement in a light scanning system for reading symbols, comprising: <ul id="ul0003" list-style="none"><li>(a) a housing having an exit port;</li><li>(b) light means in the housing for gener­ating a light beam;</li><li>(c) optical means in the housing for direct­ing the light beam along an optical path through the exit port;</li><li>(d) scanning means in the housing for scan­ning the light beam in scans across successive symbols located exteriorly of the housing, said scanning means including a central rotary mirror mounted in the optical path for rotation about an axis, and a plurality of folding mirrors arranged in an annulus about the central mirror, said central mirror directing the light beam to the folding mirrors to generate a scan pattern; and</li><li>(e) means in the housing for changing the scan pattern to a different scan pattern.</li></ul></li><li>2. The arrangement as recited in 1, wherein the changing means changes the scan pattern after each scan.</li><li>3. The arrangement as recited in 1; and further comprising means for automatically deter­mining that a scanned symbol has been read; and wherein the changing means changes the scan pattern after the scanned symbol has been read.</li><li>4. The arrangement as recited in 1; and further comprising means for automatically select­ing the scan pattern to overlie a symbol to be read.</li><li>5. The arrangement as recited in 1; and further comprising means for manually selecting the scan pattern to overlie a symbol to be read.</li><li>6. The arrangement as recited in 5, wherein the selecting means includes an actuator on the housing and manually actuatable between two states, said actuator being operatively connected to the chang­ing means for changing the scan pattern in each state.</li><li>7. The arrangement as recited in 1, wherein each of the central mirror and the folding mir­rors is a generally rectangular, planar mirror, and wherein the folding mirrors are equiangularly arranged about the axis.</li><li>8. The arrangement as recited in 1, wherein the housing has a handle for hand-held use.</li><li>9. The arrangement as recited in 1, wherein the scan pattern is a single linear scan extend­ing longitudinally along the symbol, and wherein the dif­ferent scan pattern is a plurality of linear scans.</li><li>10. The arrangement as recited in 9, wherein the plurality of linear scans is a set of gen­erally parallel scan lines spaced apart transversely of the symbol.</li><li>11. The arrangement as recited in 9, wherein the plurality of linear scans is a set of intersecting scan lines.</li><li>12. The arrangement as recited in 1, wherein the scan pattern is a single linear scan extend­ing longitudinally along the symbol, and wherein the dif­ferent scan pattern is a curvilinear pattern.</li><li>13. An arrangement in a light scanning system for reading symbols, comprising: <ul id="ul0004" list-style="none"><li>(a) a housing having an exit port;</li><li>(b) light means in the housing for generat­ing a light beam;</li><li>(c) optical means in the housing for direct­ing the light beam along an optical path through the exit port;</li><li>(d) scanning means in the housing for scan­ning the light beam in linear scans across successive symbols located exteriorly of the housing, said scan­ing means including a central rotary mirror mounted in the optical path for rotation about an axis, and a plurality of folding mirrors arranged in an annulus about the central mirror, said central mirror directing the light beam to the folding mirrors to generate the linear scans; and</li><li>(e) means in the housing for changing the direction of at least one of the linear scans.</li></ul></li><li>14. The arrangement as recited in 13, wherein the changing means changes the scan direction of each linear scan after each linear scan.</li><li>15. The arrangement as recited in 13; and further comprising means for automatically deter­mining that a symbol has been read; and wherein the changing means changes the scan direction after the symbol has been read.</li><li>16. The arrangement as recited in 13; and further comprising means for automatically select­ing the scan direction to overlie a symbol to be read.</li><li>17. The arrangement as recited in 13; and further comprising means for manually selecting the scan direction to overlie a symbol to be read.</li><li>18. The arrangement as recited in 17, wherein the selecting means includes an actuator on the housing and manually actuatable between two states, said actuator being operatively connected to the changing means for changing the scan direction in each state.</li><li>19. The arrangement as recited in 13, wherin each of the central mirror and the folding mir­rors is a generally rectangular, planar mirror; and wherein the folding mirrors are equiangularly arranged about the axis.</li><li>20. The arrangement as recited in 13, wherein the housing has a handle for hand-held use.</li><li>21. An arrangement in a light scanning system for reading symbols, comprising: <ul id="ul0005" list-style="none"><li>(a) a housing having an exit port;</li><li>(b) light means in the housing for generating a light beam of a given intensity;</li><li>(c) optical means in the housing for directing the light beam along an optical path through the exit port;</li><li>(d) scanning means in the housing for scanning the light beam in scans across successive symbols located exteriorly of the housing, said scanning means including a central rotary mirror in the optical path for rotation about an axis, and a plurality of folding mirrors ar­ranged in an annulus about the central mirror, said central mirror directing the light beam to the folding mirror to generate a scan pattern; and</li><li>(e) means in the housing for changing the intensity of the light beam.</li></ul></li><li>22. The arrangement as recited in 21, wherein the changing means changes the light beam intensity after each scan.</li><li>23. The arrangement as recited in 21; and further comprising means for automatically deter­mining that a symbol has been read; and wherein the changing means changes the light beam intensity after the symbol has been read.</li><li>24. The arrangement as recited in 21; and further comprising means for automatically selecting the light beam intensity to illuminate a symbol to be read.</li><li>25. The arrangement as recited in 21; and further comprising means for manually selecting the light beam intensity to illuminate a symbol to be read.</li><li>26. The arrangement as recited in 25, wherein the selecting means includes an actuator on the housing and manually actuatable between two states, said actuator being operatively connected to the changing means for changing the light beam intensity in each state.</li><li>27. The arrangement as recited in 26, wherein the actuator has a low power state and a high power state, and wherein the changing means changes the light beam intensity to a low power in the low power state, and to a high power in the high power state.</li><li>28. The arrangement as recited in 27, wherein the light means normally generates the light beam with a low power intensity prior to reading a symbol, and wherein the changing means modifies the light beam to have a high power intensity during symbol reading.</li><li>29. The arrangement as recited in 28, wherein the housing is a hand-held aimable at a symbol, and wherein the actuator is a two-position switch on the head and actuatable between the low power state in which the head is aimed at the symbol, and the high power state in which the head scans the symbol.</li><li>30. The arrangement as recited in 21, wherein each of the central mirror and the folding mir­rors is a generally rectangular, planar mirror; and wherein the folding mirrors are equiangularly arranged about the axis.</li><li>31. The arrangement as recited, wherein the light means is a laser.</li><li>32. An arrangement in a light scanning system for reading symbols, comprising: <ul id="ul0006" list-style="none"><li>(a) a housing having an exit port;</li><li>(b) light means in the housing for generating a light beam;</li><li>(c) optical means in the housing for directing the light beam along an optical path through the exit port;</li><li>(d) scanning means in the housing for scanning the light beam in scans at a scan rate across successive symbols located exteriorly of the housing, said scanning means including a central rotary mirror mounted in the optical path for rotation about an axis, and a plurality of folding mirrors arranged in an annulus about the central mirror, said central mirror directing the light beam to the folding mirrors to generate a scan pattern; and</li><li>(e) means for changing the scan rate.</li></ul></li><li>33. The arrangement as recited in 32, wherein the changing means changes the scan rate after each scan.</li><li>34. The arrangement as recited in 32; and further comprising means for automatically determin­ing that a symbol has been read; and wherein the changing means changes the scan rate after the symbol has been read.</li><li>35. The arrangement as recited in 32; and further comprising means for automatically selecting the scan rate.</li><li>36. The arrangement as recited in 32; and further comprising means for manually selecting the scan rate.</li><li>37. The arrangement as recited in 36, wherein the selecting means includes an actuator on the housing and manually actuatable between two states, said actuator being operatively connected to the changing means for changing the scan rate in each state.</li><li>38. The arrangement as recited in 32, wherein each of the central mirror and the folding mir­rors is a generally rectangular, planar mirror; and wherein the folding mirrors are equiangularly arranged about the axis.</li><li>39. The arrangement as recited in 32, wherein the housing has a handle for hand-held use.</li><li>40. The arrangement as recited in 37, wherein the actuator changes the changing means between a slow scan rate and a relatively fast scan rate.</li><li>41. A hand-held bar code reader, comprising: <ul id="ul0007" list-style="none"><li>a) a light source for generating a light beam and directing the light beam along a path toward a bar code symbol to be read;</li><li>b) a hand-held unit for containing said light source, and an exit port in said unit to allow said light beam to be directed to said symbol;</li><li>c) a scan generator included in said path for moving the light beam to create a pattern of multiple scan lines for traversing said symbol to be read, the scan generator including a central mirror rotating about an axis and a plurality of folding mirrors spaced from said central mirror, said path including said central mirror and said folding mirrors, said scan generator altering said path for at least one of said folding mirrors to change at least one of said scan lines.</li></ul></li><li>42. A bar code reader according to 41 wherein said folding mirrors are circumferentially-spaced surrounding said central mirror.</li><li>43. A bar code reader according to 42 wherein the axis of rotation of said central mirror is generally coincident with a central axis of said circumferentially-spaced folding mirrors.</li><li>44. A bar code scanner according to 41 wherein said scan generator alters said path for said at least one of said folding mirrors by changing the radical position of said at least one folding mirror with respect to said central mirror.</li><li>45. A bar code scanner according to 44 wherein said radial position of said at least one folding mirror is changed by an electroresponsive element supporting engaging said at least one folding mirror.</li><li>46. A bar code scanner according to 41 wherein said pattern of multiple scan lines includes scan lines traversing said symbol in opposite directions.</li><li>47. A bar code scanner according to 41 wherein said pattern includes a plurality of parallel scan lines.</li><li>48. A bar code scanner according to 41 wherein said pattern includes a plurality of intersecting scan lines.</li><li>49. A bar code scanner according to claim 41 wherein said pattern includes a plurality of scan lines having different focal lengths.</li><li>50. A bar code scanner according to 41 wherein said light source is dynamically variable to change the intensity of said light beam.</li><li>51. A method of reading bar code symbols, comprising the steps of: <ul id="ul0008" list-style="none"><li>a) generating a light beam in a hand-held unit and directing the light beam in a path through an exit port in the unit toward a bar code symbol to be read;</li><li>b) scanning said light beam in a scan pattern of multiple scan lines extending across a symbol to be read by directing said beam within said unit through a rotating mirror to a plurality of folding mirrors spaced from said rotating mirror;</li><li>c) and altering said scan pattern by changing the path of said light beam through at least one of said folding mirrors.</li></ul></li><li>52. A method according to 51 wherein said rotating mirror is rotated about an axis generally pointing toward said bar code symbol.</li><li>53. A method according to 51 wherein said step of altering said scan pattern includes changing the position of said at least one of the folding mirrors with respect to said rotating mirror.</li><li>54. A method according to 51 wherein said rotating mirror is rotated about a central axis which is generally coincident with a central axis of said plurality of folding mirrors, the folding mirrors being annularly spaced about said rotating mirror.</li><li>55. A method according to 51 wherein said scan pattern includes a plurality of separate scan lines, one scan line generated by each of said folding mirrors, a set of said plurality of scan lines being generated for each rotation of said rotating mirror.</li><li>56. A method according to 51 wherein said step of altering said path for said at least one of said folding mirrors includes changing the radial position of said at least one folding mirror with respect to said rotating mirror.</li><li>57. A method according to 51 wherein said step of altering said path for said at least one of said folding mirrors includes applying signals to an electroresponsive element engaging said at least one folding mirror.</li><li>58. A method according to 51 wherein said pattern of multiple scan lines includes scan lines traversing said symbol in opposite directions.</li><li>59. A method according to 51 wherein said pattern includes a plurality of intersecting scan lines.</li><li>60. A method according to 59 including the step of dynamically altering said pattern of a plurality fo intersecting scan lines to produce a different pattern.</li><li>61. A method according to 51 wherein said pattern includes a plurality of parallel scan lines.</li><li>62. A bar code reader mounted in a hand-held housing, comprising: <ul id="ul0009" list-style="none"><li>a) a light source in said housing generating a light beam for directing through an exit port in said housing toward a bar code symbol to be read;</li><li>b) a scanner in said housing in the path of said light beam for generating a scan pattern which includes a plurality of separate scan lines traversing each said symbol to be read by directing said light beam through a moving mirror to a plurality of folding mirrors spaced about said moving mirror, each folding mirror creating one of said plurality of scan lines, the scanner dynamically altering said scan pattern upon command.</li></ul></li><li>63. A bar code reader according to 62 wherein said folding mirrors are mounted in said housing in an annulus surrounding said moving mirror, and said moving mirror is rotating.</li><li>64. A bar code reader according to 62 including a sensor mounted in said housing receiving light reflected from said bar code symbol and generating electrical signals in response thereto.</li><li>65. A bar code reader according to 62 wherein said moving mirror and said folding mirrors are generally planar.</li><li>66. A bar code reader according to 65 including optical means in said housing in the path of said light beam to shape said light beam.</li><li>67. A bar code reader according to 62 wherein said scanner dynamically alters said scan pattern in response to a manual command by a user holding said reader.</li><li>68. A bar code reader according to 67 wherein said manual command is by a trigger switch.</li><li>69. A bar code reader according to 62 wherein said scanner dynamically alters said scan pattern by changing the configuration of scan lines in said scan pattern.</li><li>70. A bar code reader according to 69 wherein said scan pattern includes a plurality of intersecting scan lines.</li><li>71. A bar code reader according to 69 wherein said scan pattern includes a plurality of parallel scan lines.</li><li>72. In a light scanning system for reading symbols, an arrangement comprising: <ul id="ul0010" list-style="none"><li>(a) a housing having an exit port;</li><li>(b) light means in the housing for generating a light beam;</li><li>(c) optical means in the housing for directing the light beam along an optical path through the exit port;</li><li>(d) scanning means in the housing for scanning the light beam in scans across successive symbols loca­ted exteriorly of the housing, said scanning means in­cluding a drive having an output shaft extending along a shaft axis;</li><li>(e) pattern means for generating an omni-­directional scan pattern of intersecting scan lines ex­tending across each symbol to be read, each scan line being formed by the optical means at a predetermined distance from the exit port of the housing, said pattern means including a planar rotary mirror mounted on the shaft for rotation about the shaft axis by the drive during scanning, said rotary mirror having a light-re­flecting coating on a major mirror surface which extends at an angle to the shaft axis, said pattern means further including a plurality of light-reflecting folding mirrors mounted on the housing and arranged relative to one another about the rotary mirror; and</li><li>(f) means for changing the predetermined dis­tance of at least one of the scan lines during scanning.</li></ul></li><li>73. The arrangement as recited wherein the folding mirrors are equi-angularly arranged relative to one another about the rotary mirror.</li><li>74. The arrangement as recited wherein the folding mirrors are mutually spaced apart at different angles about the rotary mirror.</li><li>75. The arrangement as recited wherein the folding mirrors are planar.</li><li>76. The arrangement as recited wherein the folding mirrors have equal lengths.</li><li>77. The arrangement as recited wherein the folding mirrors have different lengths.</li><li>78. The arrangement as recited wherein the changing means includes means for radially moving at least one of the folding mirrors radially toward and away from the shaft axis.</li><li>79. The arrangement as recited in wherein at least one of the folding mirrors has a light-­reflecting surface; and further comprising means for moving the light-reflecting surface so as to change the length of the optical path along which the light beam travels.</li></ul>