Source: http://www.google.com/patents/US6454167?dq=6,826,762
Timestamp: 2016-08-27 06:59:57
Document Index: 193374639

Matched Legal Cases: ['art. 2', 'art.\n13', 'art.\n14', 'art. 28', 'art 202', 'art 204', 'art 202', 'art 204', 'art 204', 'art 202', 'art 262', 'arts 264', 'art 262', 'art 276', 'art 276', 'arts 290', 'art 306', 'art 352', 'art 358', 'art 374', 'art 382', 'art 382']

Patent US6454167 - Laser focusing aperture and method - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inPatentsLight is focused in a system for electro-optically scanning and reading bar code symbols by an aperture stop having a first optical portion for optically modifying a first part of a light beam to have a beam cross-section of a known size within a depth of field in which a symbol to be read is scanned...http://www.google.com/patents/US6454167?utm_source=gb-gplus-sharePatent US6454167 - Laser focusing aperture and methodAdvanced Patent SearchPublication numberUS6454167 B1Publication typeGrantApplication numberUS 09/373,279Publication dateSep 24, 2002Filing dateAug 12, 1999Priority dateFeb 28, 1985Fee statusLapsedAlso published asEP1119791A1, EP1119791A4, WO2001013158A1Publication number09373279, 373279, US 6454167 B1, US 6454167B1, US-B1-6454167, US6454167 B1, US6454167B1InventorsEdward Barkan, Chinh Tan, Vikram Bhargava, Miklos SternOriginal AssigneeSymbol Technologies, Inc.Export CitationBiBTeX, EndNote, RefManPatent Citations (5), Referenced by (15), Classifications (15), Legal Events (4) External Links: USPTO, USPTO Assignment, EspacenetLaser focusing aperture and method
US 6454167 B1Abstract
Light is focused in a system for electro-optically scanning and reading bar code symbols by an aperture stop having a first optical portion for optically modifying a first part of a light beam to have a beam cross-section of a known size within a depth of field in which a symbol to be read is scanned by the first beam part, and a second light-transmissive, optical portion bounding the first portion and operative for optically modifying and directing a second part of the light beam away from the first part.
We claim: 1. A light focusing arrangement in a system for electro-optically scanning and reading indicia, comprising:
a) a light emitter for emitting a light beam; and b) an optical component impinged by the light beam and having a first optical portion for optically modifying a first part of the light beam to have a beam cross-section of a known size within a depth of field in which an indicium to be read is scanned by the first beam part, and a second light-transmissive, optical portion adjacent the first optical portion and operative for optically modifying and directing a second part of the light beam away from the first beam part. 2. The arrangement of claim 1, wherein the emitter includes a laser source for emitting the light beam as a laser beam.
3. The arrangement of claim 2, wherein the emitter includes a focusing lens for focusing the laser beam.
4. The arrangement of claim 1, wherein the light beam is visible, and wherein the second beam part is a visible aiming beam for illuminating an aiming region on the indicium.
5. The arrangement of claim 1, wherein the second optical portion bounds the first optical portion.
6. The arrangement of claim 1, wherein the first optical portion is a reflector for reflecting the first beam part to the indicium, and wherein the second optical portion is a light-transmissive substrate on which the reflector is mounted, the second beam part passing through and past the substrate.
7. The arrangement of claim 6, wherein the substrate is constituted of glass, and wherein the reflector is a coating deposited on an area of the glass.
8. The arrangement of claim 1, wherein the first optical portion is a light-transmissive element having a generally planar exit surface, the first beam part passing through and past the exit surface along a first direction; and wherein the second optical portion has generally planar reflecting surfaces that are inclined relative to the exit surface and are operative for reflecting the second beam part along a second direction.
9. The arrangement of claim 8, wherein the first and second directions are mutually orthogonal.
10. The arrangement of claim 1, wherein the optical component is constituted of transparent, synthetic plastic material.
11. The arrangement of claim 1, wherein the first optical portion is a focusing element having a curved exit surface, the first beam part passing through and past the exit surface along a first direction; and wherein the second optical portion has generally planar reflecting surfaces that are inclined relative to the first direction and are operative for reflecting the second beam part along a second direction different from the first direction.
12. The arrangement of claim 1, wherein the first optical portion includes a first focusing element having a first curved exit surface to focus a portion of the first beam part within a near depth of field, and a second focusing element having a second curved exit surface to focus another portion of the first beam part within a far depth of field which is farther away from the emitter than the near depth of field; and wherein the second optical portion has generally planar reflecting surfaces for reflecting the second beam part.
13. The arrangement of claim 1, wherein the first optical portion is an aperture, and wherein the second optical portion is a light-transmissive aperturing element for directing the second beam part away from the first beam part.
14. The arrangement of claim 13, wherein the emitter includes a focusing lens mounted within the aperture.
15. The arrangement of claim 13, wherein the aperturing element is an optical grating.
16. The arrangement of claim 13, wherein the aperturing element is a digital optical element.
17. The arrangement of claim 13, wherein the aperturing element is a hologram.
18. The arrangement of claim 13, wherein the aperturing element includes a plurality of light-transmissive segments objective for illuminating a plurality of aiming regions on the indicium.
19. An optical aperture, comprising: an optical component incident to light, the component having a first optical portion for directing a first part of the incident light along a first optical path, and a second light-transmissive optical portion bounding the first optical portion and operative for separating and directing a second part of the incident light along a second optical path different from the first optical path.
20. The optical aperture of claim 19, wherein at least one of the optical portions is a reflecting element.
21. The optical aperture of claim 19, wherein at least one of the optical portions is a transparent element.
22. The optical aperture of claim 19, wherein at least one of the optical portions is a focusing element.
23. An optical aperture of claim 19, wherein at least one of the optical portions is an aperture.
24. An arrangement in a system for electro-optically reading indicia, comprising:
a) a light emitter for emitting a light beam; b) an optical component impinged by the light beam and having a first optical portion for optically modifying a first part of the light beam to have a beam cross-section of a known size within a depth of field, and for directing the first beam part to an indicium within the depth of field, the optical component having a second light-transmissive, optical portion for optically modifying and directing a second part of the light beam to the indicium to illuminate an aiming region on the indicium; c) a detector having a field of view for detecting light from the first beam part that is reflected off the indicium; and d) a scanner for scanning at least one of the first beam part and the field of view. 25. The arrangement of claim 24, wherein the first optical portion has a first focusing element to focus a portion of the first beam part at close-in distances relative to the emitter, and a second focusing element to focus another portion of the first beam part at far-out distances relative to the emitter.
26. The arrangement of claim 24, wherein the second optical portion has a plurality of light-transmissive segments for illuminating a plurality of aiming regions on the indicium.
27. A light focusing method during electro-optical scanning and reading of indicia, comprising the steps of:
a) separating a light beam into first and second parts; b) optically modifying the first part of the light beam to have a beam cross-section of a known size within a depth of field in which an indicium to be read is scanned by the first beam part; and c) optically modifying and directing the second part of the light beam away from the first beam part. 28. The method of claim 27, wherein step (c) is performed by directing the second beam part to the indicium for illuminating an aiming region on the indicium.
29. The method of claim 27, wherein the separating step is performed by an optical component having a first optical portion for performing step (b) and a second optical portion for performing step (c); and wherein the second optical portion is transmissive to the light beam.
30. The method of claim 27; and further comprising the step of detecting light from the first beam part that is reflected off the indicium over a field of view; and the step of scanning at least one of the first beam part and the field of view.
This application is a continuation-in-part of pending application Ser. No. 08/353,682, filed Dec. 9, 1994 now U.S. Pat. No. 6,308,892, which was a division of application Ser. No. 6,08/074,641, filed Jun. 11, 1993, now U.S. Pat. No. 5,468,949, which was a continuation of application Ser. No. 07/931,728, filed Aug. 18, 1992, now U.S. Pat. No. 5,250,792, which was a division of application Ser. No. 07/690,702, filed Apr. 24, 1991, now U.S. Pat. No. 5,149,950, which was a division of application Ser. No. 07/454,144, filed Dec. 12, 1989, now U.S. Pat. No. 5,021,641, which was a division of application Ser. No. 07/295,151, filed Jan. 9, 1989, now U.S. Pat. No. 4,897,532, issued Jan. 30, 1990, which was a continuation of application Ser. No. 07/148,669, filed Jan. 26, 1988, now U.S. Pat. No. 4,825,057, issued Apr. 25, 1989, which was a division of application Ser. No. 06/706,502, filed Feb. 28, 1985, now abandoned. The following continuing applications were also based upon said application Ser. No. 06/706,502: application Ser. No. 07/196,021, filed May 19, 1988, now U.S. Pat. No. 4,816,660, issued Mar. 28, 1989; application Ser. No. 07/148,438, filed Jan. 26, 1988, now U.S. Pat. No. 4,806,742, issued Feb. 21, 1989; application Ser. No. 07/113,898, filed Oct. 29, 1987, now U.S. Pat. No. 4,760,248, issued Jul. 26, 1988; application Ser. No. 07/230,746, filed Aug. 9, 1988, now U.S. Pat. No. 4,835,374, issued May 30, 1989.
The present invention generally relates to laser scanning systems for reading symbols such as bar code symbols and, more particularly, to a lightweight, multi-component, portable laser diode scanning head supportable by a user and aimable at each symbol to be read. Still more particularly, this invention relates to a light focusing arrangement and method in which a light beam is separated into a first part useful for scanning a symbol to be read, and a second part useful for illuminating an aiming region on the symbol.
However, in the event that the laser light beam was generated by a semiconductor laser diode, as by way of example, see U.S. Pat. Nos. 4,397,297; 4,409,480 and 4,460,120, then the aiming of the head relative to the symbol was rendered more difficult when the laser diode emitted laser light which was not readily visible to the user. For some laser diodes, the laser light was emitted at a wavelength of about 7800 Angstrom units, which was very close to infrared light and was on the borderline of being visible. This laser diode light was visible to the user in a darkened room, but not in a lit environment where ambient light tended to mask out the laser diode light. Furthermore, if the laser diode light was moving, for example, by being swept across the symbol, and especially if the laser diode light was being swept at fast rates of speed on the order of a plurality of times per second, for example, at a rate of 40 scans per second, then the laser diode light was not visible to the user, even in a darkened room. Hence, due to one or more of such factors as the wavelength of the laser light, the intensity of the laser light, the intensity of the ambient light in the environment in which the laser light was operating, the scanning rate, as well as other factors, the laser diode light was rendered, in effect, “invisible”, or, as alternately defined herein and in the claims, as being “non-readily visible”.
However, despite the above advantages, certain optical properties of the laser diode beam itself, aside from its invisibility, did not readily enable the laser diode beam to be focused to a desired spot size (e.g. a 6 to 12 mils circular spot) at a given reference plane exteriorly of the head, and to maintain said spot size within specified tolerances at either side of the reference plane within a predetermined depth of focus or field, i.e. the working distance in which a symbol located anywhere within the field can be successfully decoded and read. For example, the longer wavelength of the laser diode beam, as compared to that of the helium-neon gas laser dictated a shorter working distance for the same spot size. The laser diode beam was also highly divergent, diverged differently in different planes, and was non-radially symmetrical. Thus, whereas the gas laser beam had the same small divergence angle of about one milliradian in all planes perpendicular to the longitudinal direction of beam propagation, the laser diode beam had a large divergence angle of about 200 milliradians in the plane parallel to the p-n junction plane of the diode, and a different larger divergence angle of about 600 milliradians in the plane perpendicular to the p-n junction. In the single transverse mode (TEM00), the gas laser beam had a radially symmetrical, generally circular cross-section, whereas the laser diode beam had a non-radially-symmetrical, generally oval cross-section.
By way of example, in a so-called geometrical approach to solve the aforementioned focusing problem, and ignoring the non-radially symmetrical nature of the laser diode beam, optical magnification factors in excess of 80 were obtained if one wished to focus the beam spot to have about a 9.5 mil spot diameter at a reference plane located about 3�″ from the head. However, such high magnification factors dictated that, if one optical focusing element were employed (e.g. see U.S. Pat. No. 4,409,470), it would have to be critically manufactured, positioned and adjusted. If one employed several optical focusing elements in a lens system designed with a large numerical aperture, i.e. on the order of 0.25, as suggested by U.S. Pat. No. 4,387,297 to accept a large divergent laser diode beam and to distribute the magnification among the elements, then the mechanical tolerances for each element would be looser, and the positioning and adjustment procedures would be easier. However, a multiple, as opposed to a single, optical element design occupied more space within, and increased the weight and expense, of the head.
Also, although an oval laser diode beam spot was, in certain cases, desirable in ignoring voids in, and dust on, the symbol, as well as in rendering the light-dark transitions more abrupt, as compared to a circular gas laser beam spot during a scan across a symbol, these advantageous features occurred when the longer dimension of the oval spot was aligned along the height of the symbol. Thus, to obtain such desirable features, the laser diode beam had to be correctly aligned in a certain orientation relative to the symbol. In a situation where the symbols were oriented in a random manner relative to the laser diode beam, the head had to be frequently manipulated to correctly orient the laser diode beam on the symbol, and this further aggravated the already less-than-efficient and time-consuming procedure for reading symbols, particularly on a mass basis, with laser diode light. Although it was possible to circularize the oval laser diode beam spot using an anamorphic collimator, this further increased the number of optical elements, the space, the weight and the expense.
Another object of the invention is to use one part of the laser beam for scanning, and another part of the laser beam for aiming.
In keeping with these objects and others which will become apparent hereinafter, one feature of the invention resides, briefly stated, in an aiming light arrangement for use in aiming a hand-held laser scanning head in a laser scanning system for reading symbols at which the head is aimed. Several components are conventionally mounted in the head. For example, means, e.g. a semiconductor laser diode or possibly a gas laser, are provided within the head for generating an incident laser beam. Optic means, e.g. a positive lens, a negative lens, reflecting mirrors, or other optical elements, are also provided within the head for optically modifying, i.e. forming, and directing the incident laser beam along a first optical path toward a reference plane located exteriorly of the head and lying in a plane generally perpendicular to the direction of propagation of the incident laser beam, and to a symbol located in a working distance range in the vicinity of the reference plane. For convenience, a symbol that is located between the reference plane and the head is defined hereinafter as a “close-in” symbol, whereas a symbol that is located on the other side of the reference plane away from the head is defined as a “far-out” symbol.
Sometimes, but not always, decode/control electronic circuitry is provided locally in, or remotely from, the head. The decode/control electronic circuitry is operative for decoding the digitized signal to the aforementioned data, for determining a successful decoding of the symbol, and for terminating the reading of the symbol upon the determination of the successful decoding thereof. The reading is initiated by actuation of a manually-actuatable trigger means provided on the head, and operatively connected to, and operative for actuating, the laser beam generating means, scanning means, sensor means, signal processing means, and decode/control means. The trigger means is actuated once for each symbol, each symbol in its respective turn. In a preferred embodiment, the actuation of the trigger causes the actuation of the decode/control means which, in turn, causes the actuation of the laser beam generating means, scanning means, sensor means and signal processing means.
As noted above, a problem arises when the incident laser beam or the reflected laser light are not readily visible, which can occur due to one or more of such factors as the wavelength of the laser light, the laser light intensity, the ambient light intensity, the scanning rate, as well as other factors. Due to such “invisibility”, the user cannot see the laser beam and does not know readily when the invisible laser beam is positioned on the symbol, or whether the scanning laser beam is scanning over the entire length of the symbol.
Hence, in accordance with this invention, the aiming light arrangement assists the user visually to locate, and aim the head at, each symbol when such non-readily-visible laser light is employed. The aiming light arrangement includes means including an actuatable aiming. light source, e.g. a visible light emitting diode, mounted in the head, and operatively connected to the trigger means, and operative, when actuated by the trigger means, for generating an aiming light beam whose light is readily visible to the user; and aiming means, also mounted in the head, for directing the aiming light beam along an aiming light path from the aiming light source toward the reference plane and to each symbol in turn, visibly illuminating at least a part of the respective symbol and thereby locating the latter for the user. The aiming light path lies within, and preferably extends parallel to, either the first optical path or the second optical path, or both, in the portion of such paths which lie exteriorly of the head. Thus, the user is assisted in correctly aiming the head at the respective symbol to be read.
In one advantageous embodiment, the aiming light arrangement directs a single aiming light beam to each symbol to illuminate thereon a generally circular spot-region within the field of view, and preferably near the center of the symbol. It is further advantageous if this single spot region remains stationary or static during the scanning of the symbol so that both close-in and far-out symbols can be seen and located by the user, both prior to and during the scan. However, one drawback associated with such static single beam aiming is that the user cannot track the linear scan of the scanning beam across the symbol during the scan. In other words, the user does not know where the ends of the laser scans are and, hence, does not know whether the linear scan is extending across the entire length of the symbol, or is tilted relative thereto.
In another advantageous -embodiment, the aiming light arrangement directs a pair of aiming light beams to each symbol to illuminate thereon a pair of generally circular spot regions that are within, and spaced apart of each other along, the field of view. Preferably, the two spot regions are located at, or near, the ends of the linear scan, as well as remaining stationary or static during the scanning of the symbol so that both close-in and far-out symbols not only can be seen and located by the user both prior to and during the scan, but also can be tracked during the scan. However, one drawback associated with such static twin beam aiming is that two aiming light sources and associated optics are required, and this represents increased system complexity, weight, size and expense.
In still another advantageous embodiment, the aiming light arrangement directs a single aiming light beam to a reciprocally oscillating focusing mirror operative to sweep the aiming light across each symbol to illuminate thereon a line region extending along the field of view. Such dynamic single beam aiming is advantageous because close-in symbols can be more readily seen, located and tracked, as compared to static aiming. However, one drawback associated with such dynamic aiming is that far-out symbols cannot readily be seen, located or tracked, particularly when the focusing mirror is being swept at high scan rates on the order of 40 scans per second due to the inherently reduced intensity of the light collected by the human eye.
In addition, it is well known that for a given beam cross-section, i.e. spot size, of the incident laser beam, the depth of focus in an optical system having an aperture stop will be less than that for an optical system which does not have an aperture stop. Since, as a general rule, a laser scanning system designer wants as large a depth of focus as possible so that the working distance is correspondingly as large as possible the use of an aperture stop is something to be avoided.
Rather than using an aperture stop in which the walls bounding a central aperture are opaque and block a portion of the incident laser diode beam, still another aspect of this invention resides in making the walls bounding the aperture light-transmissive. The portion of the incident beam that is transmitted through the aperture can be directed to the symbol to illuminate an aiming region thereon, or can be directed to a black body for absorption, or can simply not be used whatsoever. In any event, rather than blocking and not using the heretofore blocked portion of the incident beam, this invention proposes the use of a novel laser focusing aperture in which non-opaque walls bound the aperture and enable the portion of the beam that passes through the non-opaque walls to be used affirmatively and effectively, for example, for aiming purposes.
A particularly compact optical folded path assembly is achieved when an optical element such as a so-called “cold mirror” is utilized to reflect the visible aiming light beam to a collecting mirror of the sensor means, but to transmit therethrough the reflected laser diode light reflected by the symbol and collected by the collecting mirror. Still another efficient aspect of the overall optical assembly is to integrate the collecting mirror for the reflected laser light, together with the aforementioned scanning mirror for the incident laser diode beam, as well as with the aforementioned focusing mirror for the aiming light beam into a multi-purpose mirror of one-piece construction.
FIG. 2 is an enlarged cross-sectional view taken on line 2—2 of FIG. 1;
FIG. 3 is a section view taken on line 3—3 of FIG. 2;
FIG. 4 is an enlarged sectional view taken on line 4—4 of FIG. 2;
FIG. 8 is an enlarged sectional view of a one-piece scanning/collecting/focusing mirror component as taken along line 8—8 of FIG. 1;
FIG. 13 is an enlarged view of a symbol and the parts thereof which are illuminated by a dynamic single beam aiming;
FIG. 14 is a view analogous to FIG. 2, but of a currently preferred commercial embodiment of the head in accordance with this invention;
FIG. 15 is a schematic view of one embodiment of a focusing aperture in accordance with this invention;
FIG. 16 is a schematic view of another embodiment of a focusing aperture in accordance with this invention;
FIG. 17 is a schematic view of still another embodiment of a focusing aperture in accordance with this invention;
FIG. 18 is a schematic view of yet another embodiment of a focusing aperture in accordance with this invention;
FIG. 19 is a schematic view of a further embodiment of a focusing aperture in accordance with this invention; and
FIG. 20 is an end view of an additional embodiment of a focusing aperture in accordance with this invention.
Referring now to FIGS. 1-8 of the drawings, reference numeral 10 generally identifies a lightweight (less than one pound) narrow-bodied, streamlined, narrow-snouted, hand-held, fully portable, easy-to-manipulate, non-arm-and-wrist fatiguing laser scanning head supportable entirely by a user for use in a laser scanning system operative for reading, scanning and/or analyzing symbols, and aimable both prior to, and during, the reading thereof, by the user at the symbols, each symbol in its turn. The term “symbol”, as used herein, is intended to cover indicia composed of different portions having different light-reflective properties at the wavelength of the light source, e.g. a laser, being utilized. The indicia may be the aforementioned black and white industrial symbols, e.g. Code 39, Codabar, Interleaved 2 of 5, etc., and also the omnipresent UPC bar code symbol. The indicia may also be any alphabetic and/or numeric characters. The term “symbol” is also intended to cover indicia located in a background field, wherein the indicia, or at least a portion thereof, have a different light-reflective property than that for the background field. In this latter definition, the “reading” of the symbol is of particular benefit in the fields of robotics and object recognition.
Turning now to FIGS. 1-3, the head 10 includes a generally gun-shaped housing having a handle portion 12 of generally rectangular cross-section and generally vertically elongated along a handle axis, and a generally horizontally elongated, narrow-bodied barrel or body portion 14. The cross-sectional dimension and overall size of the handle portion 12 is such that the head 10 conveniently can fit and be held in a user's hand.
The body and handle portions are constituted of a lightweight, resilient, shock-resistant, self-supporting material, such as a synthetic plastic material. The plastic housing preferably is injection-molded, but can be vacuum-formed or blow-molded to form a thin, hollow shell which bounds an interior space whose volume measures less than a value on the order of 50 cubic inches and, in some applications, the volume is on the order of 25 cubic inches or less. Such specific values are not intended to be self-limiting, but to provide a general approximation of the overall maximum size and volume of the head 10.
A manually-actuatable, and preferably depressible, trigger 32 is mounted for pivoting movement about a pivot axis 34 on the head in a forwardly-facing region where the handle and body portions meet and where the user's forefinger normally lies when the user grips the handle portion in the intended position of use. The bottom wall 26 has a tubular neck portion 36 which extends downwardly along the handle axis, and terminates in a radially-inwardly extending collar portion 38 of generally rectangular cross-section. The neck and collar portions have a forwardly facing slot through which the trigger projects and is moved.
The handle portion 12 has a radially-outwardly extending upper flange portion 40 of generally rectangular cross-section which also has a forwardly-facing slot through which the trigger 32 projects and is moved. The upper flange portion 40 is resilient and deflectable in a radially-inward direction. When the upper flange portion 40 is inserted into the neck portion 36, the upper flange portion 40 bears against the collar portion 38 and is radially-inwardly deflected until the flange portion 40 clears the collar portion 38, at which time, the upper flange portion 40, due to its inherent resilience, snaps back to its initial undeflected position and engages behind the collar portion with a snap-type locking action. To disengage the handle portion from the body portion, the upper part of the handle portion is sufficiently deflected until the upper flange portion 40 again clears the collar portion, and thereupon the handle portion can be withdrawn from the neck portion 36. In this manner, handle portion 12 can be detachably snap-mounted and demounted from the body portion 14 and, as explained below, another handle portion from a set of interchangeable handle portions, each containing different components of the laser scanning system, may be mounted to the body portion to adapt the head 10 to different user requirements.
A plurality of components are mounted in the head and, as explained below, at least some of them are actuated by the trigger 32, either directly or indirectly, by means of a control microprocessor. One of the head components is an actuatable laser light source (see FIG. 4) , e.g. a semiconductor laser diode 42, operative, when actuated by the trigger 32, for propagating and generating an incident laser beam whose light, as explained above, is “invisible” or non-readily visible to the user, is highly divergent, is non-radially symmetrical, is generally oval in cross-section, and has a wavelength above 7000, e.g., about 7800, Angstrom units. Advantageously, the diode 42 is commercially available from many sources, e.g. from the Sharp Corporation as its Model No. LTO2OMC. The diode may be of the continuous wave or pulse type. The diode 42 requires a low voltage (e.g. 12v DC or less) supplied by a battery (DC) source which may be provided within the head, or by a rechargeable battery pack accessory 44 (see FIG. 7) detachably mounted on the head, or by a power conductor in a cable 46 (see FIG. 2) connected to the head from an external power supply (e.g. DC source).
As best shown in FIG. 4, the laser diode 42 is mounted on a printed circuitboard 48. An optical assembly is mounted in the head and adjustably positioned relative to the diode 42 for optically modifying and directing the incident laser beam along a first optical path toward a reference plane which is located exteriorly of the head, forwardly of the nose portion 20 and which lies generally perpendicular to the longitudinal direction along which the incident laser beam propagates. A symbol to be read is located in the vicinity of the reference plane, either at, or at one side, or at an opposite side, of the reference plane, that is, anywhere within the depth of focus or field of the optically modified incident laser beam, said depth of focus or field also being known as the working distance in which the symbol can be read. The incident laser beam reflects off the symbol in many directions, and that portion of the reflected laser light which travels along a second optical path away from the symbol back toward the head is known herein as the returning portion which, of course, also is non-readily visible to the user.
The portion of the incident laser beam that passed through the aperture stop 56 is directed rearwardly by the optical assembly along an optical axis 102 within the head to a generally planar scanning mirror 66 for reflection therefrom. The scanning mirror 66 forwardly reflects the laser beam impinging thereon along another optical axis 104 through a forwardly-facing, laser-light-transmissive window 68 mounted on the upper front wall 68, and to the symbol. As best shown in FIG. 9, a representative symbol 100 in the vicinity of the reference plane is shown and, in the case of a bar code symbol, is comprised of a series of vertical bars spaced apart of one another along a longitudinal direction. The reference numeral 106 denotes the generally circular, invisible, laser spot subtended by the symbol. The laser spot 106 in FIG. 9 is shown in an instantaneous position, since the scanning mirror 66, when actuated by the trigger 32, is, as explained below, reciprocally and repetitively oscillated transversely to sweep the incident laser beam lengthwise across all the bars of the symbol in a linear scan. The laser spots 106 a and 106 b in FIG. 9 denote the instantaneous end positions of the linear scan. The linear scan can be located anywhere along the height of the bars provided that all the bars are swept. The length of the linear scan is longer than the length of the longest symbol expected to be read and, in a preferred case, the linear scan is on the order of 5 inches at the reference plane.
Referring again to FIG. 2, the returning portion of the reflected laser light has a variable light intensity, due to the different light-reflective properties of the various parts that comprise the symbol 100, over the symbol during the scan. The returning portion of the reflected laser light is collected by a generally concave, spherical collecting mirror 76, and is a broad conical stream of light in a conical collecting volume bounded, as shown in FIG. 2, by upper and lower boundary lines 108, 110, and, as shown in FIG. 3, by opposed side boundary lines 112, 114. The collecting mirror 76 reflects the collected conical light into the head along an optical axis 116 (see FIG. 3) along the second optical path through a laser light-transmissive element 78 to a sensor means, e.g. a photosensor 80. The collected conical laser light directed to the photosensor 80 is bounded by upper and lower boundary lines 118, 120 (see FIG. 2) and by opposed side boundary lines 122, 124 (see FIG. 3). The photosensor 80, preferably a photodiode, detects the variable intensity of the collected laser light over a field of view which extends along, and preferably beyond, the linear scan, and generates an electrical analog signal indicative of the detected variable light intensity.
Referring again to FIG. 9, the reference numeral 126 denotes an instantaneous collection zone subtended by the symbol 100 and from which the instantaneous laser spot 106 reflects. Put another way, the photosensor 80 “sees” the collection zone 126 when the laser spot 106 impinges the symbol. The collecting mirror 76 is mounted on the support bracket 74 and, when the scanner motor 70 is actuated by the trigger 32, the collecting mirror 76 is reciprocally and repetitively oscillated transversely, sweeping the field of view of the photodiode lengthwise across the symbol in a linear scan. The collection zones 126 a, 126 b denote the instantaneous end positions of the linear scan of the field of view.
The scanning mirror 66 and the collecting mirror 76 are, in a preferred embodiment, of one-piece construction and, as shown in FIG. 8, are light-reflecting layers or coatings applied to a plano-convex lens 82 constituted of a light-transmissive material, preferably glass. The lens 82 has a first outer substantially planar surface on a portion of which a first light-reflecting layer is coated to constitute the planar scanning mirror 66, and a second outer generally spherical surface on which a second light-reflecting layer is coated to constitute the concave collecting mirror 76 as a so-called “second surface spherical mirror”.
The digitized video signal is conducted to an electrical interlock composed of a socket 88 provided on the body portion 14, and a mating plug 90 provided on the handle portion12. The plug 90 automatically electromechanically mates with the socket 88 when the handle portion is mounted to the body portion. Also mounted within the handle portion are a pair of circuitboards 92, 94 (see FIG. 1) on which various components are mounted. For example, a decode/control means comprised of components 95, 97 and others are operative for decoding the digitized video signal to a digitized decoded signal-from which the desired data descriptive of the symbol is obtained, in accordance with an algorithm contained in a software control program. The decode/control means includes a PROM for holding the control program, a RAM for temporary data storage, and a control microprocessor for controlling the PROM and RAM. The decode/control means determines when a successful decoding of the symbol has been obtained, and also terminates the reading of the symbol upon the determination of the successful decoding thereof. The initiation of the reading is caused by depression of the trigger 32. The decode/control means also includes control circuitry for controlling the actuation of the actuatable components in the head, as initiated by the trigger, as well as for communicating with the user that the reading has been automatically terminated as, for example, by sending a control signal to an indicator lamp 96 to illuminate the same.
In another embodiment, a local data storage means, e.g. component 95, is mounted in the handle portion, and stores multiple decoded signals which have been read. The stored decoded signals thereupon can be unloaded to a remote host computer. By providing the local data storage means, the use of the cable 46 during the reading of the symbols can be eliminated—a feature which is very desirable in making the head as freely manipulatable as possible.
In further accordance with this invention, an aiming light arrangement is mounted within the head for assisting the user in visually locating, and in aiming the head at, each symbol to be read in its turn, particularly in the situation described above wherein the laser beam incident on, and reflected from, the symbol is not readily visible to the user. The aiming light arrangement comprises means including an actuatable aiming light source 130, e.g. a visible light emitting diode (LED), an incandescent white light source, a xenon flash tube, etc., mounted in the head and operatively connected to the trigger 32. When actuated either directly by the trigger 32 or indirectly by the decode/control means, the aiming light 130 propagates and generates a divergent aiming light beam whose light is readily visible to the user, and whose wavelength is about 6600 Angstrom units, so that the aiming light beam generally is red in color and thus contrasts with the ambient white light of the environment in which the symbol is located.
Aiming means also are mounted in the head for directing the aiming light beam along an aiming light path from the aiming light source toward the reference plane and to each symbol, visibly illuminating at least a part of the respective symbol. More specifically, as best shown in FIGS. 2 and 3, the aiming light 130 is mounted on an inclined support 132 for directing the generally conical aiming light beam at the optical element 78. The conical aiming light beam is bounded by upper and lower boundary lines 134, 136 (see FIG. 2) and by opposed side boundary lines 138, 140 (see FIG. 3) en route to the optical element 78. As previously noted, the optical element 78 permits the collected laser light to pass therethrough to the photosensor 80, and filters out ambient light noise from the environment from reaching the photosensor. The optical element 78 also reflects the aiming light beam impinging thereon. The optical element is, in effect, a so-called “cold” mirror which reflects light in wavelengths in the range of the aiming light beam, but transmits light in wavelengths in the range of the laser light. The aiming light beam is reflected from the cold mirror 78 along an optical axis which is substantially colinear with the optical axis 116 of the collected laser light between the collecting mirror 76 and the photosensor 80, and impinges on the concave mirror 76 which serves to focus and forwardly reflect the aiming light beam along an optical axis which is substantially colinear with the same optical axis of the collected laser light between the concave mirror 76 and the symbol 100. The concave mirror 76 which serves as a focusing mirror for the aiming light beam focuses the same to about a one-half inch circular spot size at a distance about 8 inches to about 10 inches from the nose 20 of the head. It will be noted that the portion of the aiming light path which lies exteriorly of the head coincides with the portion of the collected laser light path which lies exteriorly of the head so that the photosensor 20, in effect, “sees” the non-readily-visible laser light reflected from that part of the symbol that has been illuminated, or rendered visible, by the aiming light beam. In another variant, the aiming light beam could have been directed to the symbol so as to be coincident with the outgoing incident laser beam by placing a cold mirror in the first optical path and directing the aiming light beam at the cold mirror so that the optical axis of the aiming light beam is coincident with that of the outgoing incident laser beam.
Turning next to a second static twin beam aiming embodiment, as shown in FIG. 12, a pair of aiming LEDs 130 a, 130 b, identical to aiming LED 130, are angularly positioned relative to the stationary focusing lens 142 which, in turn, is operative to direct the aiming light beams of both LEDs 130 a, 130 b to the same respective symbol, visibly illuminating thereon a pair of spot regions 152, 154 that are within, and spaced linearly apart of each other along the field of view. The spot regions 152, 154 preferably are circular, near the ends of the scan, and are illuminated both prior to and during the scan to locate and track the respective symbol both before and during the reading thereof. Both close-in and far-out symbols can be located and seen by the static twin beam aiming embodiment of FIG. 12, the far-out symbols, due to their greater distance from the head, being illuminated to a lesser intensity, but visible, nevertheless, by the user. As explained previously, the pair of fixed spots 152, 154 provide valuable assistance in terms of tracking the scan across the symbol.
It should be noted that the laser scanning head of this invention can read high-, medium- and low-density bar code symbols within approximate working distance ranges of 1″ to 6″, 1″ to 12″, and 1″ to 20″, respectively. As defined herein, the high- medium- and low-density bar code symbols have bars and/or spaces whose smallest width is on the order of 7.5 mils, 15-20 mils and 30-40 mils, respectively. In the preferred embodiment, the position of the reference plane for a symbol of a known density is optimized for the maximum working distance for that symbol.
As for the differences between the FIG. 2 and FIG. 14 embodiments, one important distinction shown for the head 10′ in FIG. 14 is that the body portion 14′ is composed of two housing portions, namely, upper housing 180 and lower housing 182, which are assembled together, preferably by a snap-fit engagement. The lower housing 182 is constituted of a light-blocking opaque material such as colored synthetic plastic material, but the upper housing 180 is constituted of a light-transmissive transparent synthetic plastic material. Since both the outgoing light and the incoming light can pass through the transparent upper housing 180, a cover 184 of light-blocking material covers the entire exterior surface of the transparent upper housing 180, except for a window region 186 and an indicator region 188. The cover 184 is constituted of an injection-molded thermoset rubber-like material whose interior surface closely matches and conforms to the outer surface of the upper housing 180 so as to be in intimate contact with the entire exterior surface thereof and to be frictionally held thereon. The snugly fitting cover, in effect, masks all the portions of the transparent upper housing 180, other than the window region 186 and the indicator region 188, and prevents any outgoing light or incoming light from passing therethrough.
In addition, the indicator region 188 is not covered by the cover 184, so that light from the indicator lamp 96′ can shine therethrough. Again, the prior art necessity to mount a separate window at the region of the indicator lamp 96′ has been eliminated, thereby further contributing to the very effective sealing of the interior of the head.
Still another difference between the FIG. 2 and FIG. 14 embodiments is the provision of a sealing diaphragm 190 in the region of the trigger 32′. The sealing diaphragm 190 has a central actuator 192, one surface of which engages button 164′ of switch 160′. The opposite surface of the actuator 192 engages a ramp portion 194 of the trigger 32′. In operation, whenever the trigger is manually depressed, the ramp portion 194 urges the actuator 192 into engagement with the button 164′ to actuate the switch 160�′. During this operation, the diaphragm 190 isolates the interior of the head from the exterior thereof in the region of the trigger, thereby closing off another avenue through which dust, contaminants, moisture, etc. could otherwise freely enter as in the prior art.
Still another distinction between the FIG. 2 and FIG. 14 embodiments is that the laser diode, the optical assembly, the aiming light and the motor portion of the scanner motor are all mounted within and on a common support also known as an optical cradle 200. The cradle 200 has an upper part 202 and a lower part 204 which are assembled together as follows. At the front end of the cradle, a projection 206 on the upper part 202 is passed through and snappingly engages behind a recess 208 formed in a channel provided on the lower part 204. At the rear of the cradle, a threaded fastener 210 passes through a clearance hole in lower part 204 and threadedly engages a threaded hole formed in the upper part 202. The front shock isolator 172′ is located between the front of the housing and the front of the cradle 200, and the rear shock isolator 174′ is located between the rear of the cradle and inwardly-extending partitions 175, 177 provided at the rear of the head.
Still another difference lies in mounting the printed circuitboard 86′ not above the printed circuitboard 84′, but, instead, in a rearwardly-extending compartment 212 formed between the aforementioned partitions 175, 177 and the rear wall of the body portion 14′.
Another difference lies in the provision of an 0-ring seal 214 mounted in an annular groove formed at the inner end region of the handle insert 128′.
Turning now to FIGS. 15-20, rather than employing an aperture stop comprising a central aperture 56 bounded by opaque walls 58 which prevent the remaining portion of the laser beam from reaching the symbol, another feature of this invention resides in a laser focusing system and method in which the heretofore blocked portion of the laser beam may be affirmatively used, for example, for aiming purposes.
An optical component 250 is depicted in FIG. 15 in the path of the laser beam 260 emitted by the laser diode 42 and focused by the focusing lens 62. The component 250 includes a reflector 252, especially a metallic coating, deposited on a transparent substrate 254 such as glass. The area of the reflector 252 has the same shape and size (in projection at 45�) as the aforementioned aperture 56. A scan part 262 of the laser beam 260 that reflects off the reflector 252 will be focused just as if it had passed through the aperture 56 bounded by opaque walls 58.The non-scan parts 264 of the laser beam 260 that pass around the reflector can be directed in a harmless direction, absorbed by a black surface, or directed out the front of the scanner as an aiming spot to facilitate aiming the scanner in brightly illuminated environments. Thus, the component 250 separates the light beam 260 into a first part 262 (shown in stippling) for scanning the symbol and a second part (also shown in stippling) for illuminating an aiming region on the symbol. The region 266 not shown in stippling in FIG. 15 represents a shadow area since the laser beam cannot pass through the reflector 252.
FIG. 16 depicts another optical component 270 operative for separating the incident laser beam 260 into two parts, and preferably is molded of a one-piece, transparent synthetic plastic material having no opaque or partially opaque surfaces. The component 270 has a central portion having a generally planar exit surface 274 through which a scan part 276 of the beam 260 passes toward a symbol located somewhere within the depth of field between the imaginary lines 278, 280. The beam part 276 scans the symbol to read the same. The size of the central portion is chosen to be the same as the aperture would be.
The component 270 has outer portions 282, 284 bounding the central portion and having inclined, generally planar, exit surfaces 286, 288 diverging apart as considered along the downstream direction of the beam 260. The parts 290, 292 of the beam 260 that impinge on the inclined exit surfaces 286, 288 are reflected therefrom by total internal reflection and pass outwardly as exit beams 294, 296. These exit beams 294, 296 shown in stippling can be directed to a harmless location, or absorbed, or directed out the front of the scanner to illuminate a pair of aiming regions on the symbol.
FIG. 17 depicts a focusing aperture analogous to that shown in FIG. 16, except that the focusing lens 62 and the optical component 270 have been incorporated into a combined optical component 300 having a central portion 302 whose exit surface 304 is convexly curved to focus a part 306 of a laser beam 308 to a beam spot of a known size within the depth of field in which a symbol to be read is located. The component 300 has outer, light-transmissive portions 310, 312 bounding the central potion 302 and having inclined, generally planar, exit surfaces 314, 316 for reflecting by total internal reflection a pair of exit beams 318, 320 that are separated from the beam 308. As before, the exit beams 318, 320 can be used for aiming or for other purposes, or can not be used, depending upon the application.
FIG. 18 depicts another focusing aperture analogous to that shown in FIG. 17, except that the central part of the optical component 330 is not constituted of a single focusing lens, but instead, is constituted of a plurality of lenses of different focal lengths, for example, an inner lens 332 surrounded by an outer lens 334. The transition from the inner lens to the outer lens acts as the aperture for the inner lens. The optical element 330 has outer portions 336, 338 bounding the outer lens 334 and having inclined, generally planar, exit surfaces 340, 342. The transition from the outer lens to the exit surfaces acts as the aperture for the outer lens.
A main beam 350 emitted by the laser diode 42 impinges on the component 330. A first scan part 352 is focused by the inner lens 332 as a first scan beam 354 having a beam waist located at a focal distance 356 spaced at a near distance from the diode 42. A second scan part 358 is focused by the outer lens 334 as a second scan beam 360 having a beam waist located at a focal distance 362 spaced at a far distance from the diode 42. The two coaxial scan beams 354, 360 enable an extended depth of field in which the symbol to be read may be successfully read.
As before, the exit surfaces 340, 342 reflect by total internal reflection a pair of exit beams 364, 366 which are separated from the main beam 350. These exit beams are useful for aiming and other purposes, as previously discussed.
Thus, the FIG. 18 embodiment discloses the use of multiple scanning beams and multiple aiming beams and, as with the other embodiments, no opaque walls bounding an aperture are present to block portions of the main incident beam. Instead, the walls bounding the aperture are light-transmissive and perform the separation of the main beam into constituent parts by reflection, diffraction, or refraction.
FIG. 19 depicts an optical aperturing component 370 which is shown in front elevational view in FIG. 20. A central opening 372 constitutes the aperture through which a part 374 of the main beam 380 passes to constitute a scanning beam. The opening 372 is bounded by light-transmissive outer portions 376, 378 operative for directing another part 382 of the main beam 380 outward away from the main beam. The opening 372 is shown as being rectangular in shape, but can have any shape, especially circular. The outer portions 376, 378 have a grating, a hologram, or a digital optical element 390 on an exit surface of the component 370 to cause the beam part 382 to diverge, as shown, as exit beams. The element 390 could also be deposited on an incident surface of the component 370.
In other variant constructions, the focusing lens 62 in FIG. 19 can be mounted or incorporated, in the opening 372. Also, a grating, a hologram, or a digital optical element that works as a focusing lens can replace the clear opening 372. Alternately, the grating, hologram or digital optical element can be deposited on an outer surface of the conventional focusing lens 62, thereby replacing the component 370.
The element 390 in FIG. 20 has four segments that frame the opening 372. Hence, there are four exit beams 382 that, when used for aiming purposes, can advantageously be used to mark four corners of a scanning field, especially a bidirectional or omnidirectional field, at which a symbol to be read is located. The symbol is effectively targeted between these four marked corners.
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