CA2062819A1 - Oscillatable holographic optical element for bar code scanning - Google Patents
Oscillatable holographic optical element for bar code scanningInfo
- Publication number
- CA2062819A1 CA2062819A1 CA 2062819 CA2062819A CA2062819A1 CA 2062819 A1 CA2062819 A1 CA 2062819A1 CA 2062819 CA2062819 CA 2062819 CA 2062819 A CA2062819 A CA 2062819A CA 2062819 A1 CA2062819 A1 CA 2062819A1
- Authority
- CA
- Canada
- Prior art keywords
- optical element
- integral optical
- holographic
- bar code
- code symbol
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
- G06K7/00—Methods or arrangements for sensing record carriers, e.g. for reading patterns
- G06K7/10—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation
- G06K7/10544—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation by scanning of the records by radiation in the optical part of the electromagnetic spectrum
- G06K7/10821—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation by scanning of the records by radiation in the optical part of the electromagnetic spectrum further details of bar or optical code scanning devices
- G06K7/10861—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation by scanning of the records by radiation in the optical part of the electromagnetic spectrum further details of bar or optical code scanning devices sensing of data fields affixed to objects or articles, e.g. coded labels
- G06K7/10871—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation by scanning of the records by radiation in the optical part of the electromagnetic spectrum further details of bar or optical code scanning devices sensing of data fields affixed to objects or articles, e.g. coded labels randomly oriented data-fields, code-marks therefore, e.g. concentric circles-code
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
- G06K7/00—Methods or arrangements for sensing record carriers, e.g. for reading patterns
- G06K7/10—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation
- G06K7/10544—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation by scanning of the records by radiation in the optical part of the electromagnetic spectrum
- G06K7/10821—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation by scanning of the records by radiation in the optical part of the electromagnetic spectrum further details of bar or optical code scanning devices
- G06K7/10881—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation by scanning of the records by radiation in the optical part of the electromagnetic spectrum further details of bar or optical code scanning devices constructional details of hand-held scanners
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- Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- Engineering & Computer Science (AREA)
- Health & Medical Sciences (AREA)
- General Health & Medical Sciences (AREA)
- Toxicology (AREA)
- Artificial Intelligence (AREA)
- Computer Vision & Pattern Recognition (AREA)
- General Physics & Mathematics (AREA)
- Theoretical Computer Science (AREA)
- Mechanical Optical Scanning Systems (AREA)
- Diffracting Gratings Or Hologram Optical Elements (AREA)
Abstract
An oscillating holographic optical element for scanning a light beam across a bar code symbol. The holographic element (36) is mounted on a holding frame which is connected to a stepper motor (38) that is excited by electrical signals to cause the holographic element to oscillate. The holographic element can either transmit light outwardly toward the bar code symbol, or collect light scattered from the bar code symbol, or both. The holographic element can consist of a single hologram, two separate holograms, or two holograms superimposed over one another. The holographic element can also serve to filter received light.
Description
20~2819 Wo 9l/17516 Pcr/USs1/030s~
l:)esc~iption OSCILL~TABLE HOLOGRAPHIC OP IIC~L ELE~T FOR B~R CODE
SCANN~G
s Technic~l F;eld This ~nvention relates to a holographic optic~l element and, more p~rtic~ rly, to a holographic optical element thnt can be osci~lated ~r use witb3 bar code scann~ng re~der.
Baclcground Art A bar code reader typically uses a beam of Iight to scan across a bar code, which consists of alternating strips ("bars`') of diffenng reflectivities.
Thc sc~nner then receives and interprets the fluctuations in the returning Ligbt15 that are caused by the bar code~ It is known in the prior art to read bar codes by means of a hand^held wand which malces contact with the surface on which the bar code is printed. However, the need to make contact with thc surface is frequently inconvenient and gives unintespre~ble readings because the wand is not moved ~cross thc bar code with a sufficiently uniform velocity.
An alternative to a hand-held wand is a scanning re~der which does not require physic~l contact with the bar code which is to be read. A
sc3nning reader typic~lly produces a beam of light which is repetitively scannedacross an are~ If the be ~n of light is incident upon a bar code (or some other symbology), the modulated light which is scattered by the bar code is returned to ~5 sensing circuitry in the sc~nning reader for interpretation. The widths of the altern2ting are~s of different reflectivity are measured on the basis of the relative times required for the be~n of light to sc n them. This allows the reader to be used with bar codes which have a wide variety of sizes as long as the rehtive widths of the eiements of the bar codes are preserved. Accordingly, it is 30 preferable, although not necessary, that the light beam be sc~ned across the bar code at a substantially uniform rate in order to e~se the task of interpreting the bar code.
Tn order to insure that the light beam is sc~ned at a subsuIltially uniform rate, it is typic311y re~ected from a mirror within the srlnner that moves 35 repetitively at a uniform rate. The mirror is generally driven by a small 2 0~2~ l6 Pcr/US91/03055 electric~l motor under the control of electronic control circuitry. The mirror is typically either rotating at a cons~nt speed or oscillating on the end of a sh~ft attached to a motor which c~n step between two extreme angular positions.
Examples of rot~ting optic~l elements are shown i~ U.S. Patent Nos. 4,0~5,761, 5 4,097,7'~9, 4,~5Q350, 4,575,6'~5, and 4,69 603. E~nples of oscill~ting ~s~irror optic31 elements are shown in U.S. Patent Nos. 4,5g3,186, 4,736,095, and 4,50~,804. In handheld applications, an oscillating mirror is generally preferable, since it c~n be made both lighter ~nd more compactly than a rotaùng opùc~l element. Conta~ned with the mirror ;s typically a collecting rnirror which 10 receives and focuses the li~ht scatter from the bar code s~mbol which is sc~nned.
In order to reduce power consurnption, it is import~nt top keep the oscillating mirror as light as possible.
pisclosure of the Invention It is an object of the present invention to provide a holographic optical element for scanning an oscillating li~ht beam onto a bar code symbol.
It is another object of the present invention to provide an integral optical element including a holographic optical element which transrnits an oscillating light beam osto an bar code symbol and focuses the lig`ht received 20 from the bar code symbol onto a fixed point with respect to the integral optical element.
It is a ~rther object of the present invention to provide a ligh~
weight optic~l elemest for scanning a beam of light onto a bar code symbol.
It is still another object of the present invention to provide a light weight opticnl element which requires reduced power to scan a beam of light onto a bar code symbol.
These and other objects can be provided by an integral optic~l 30 element for tr~smitting light in an oscillating manner across a bar code svmbol and for focusing light sc2ttered from the bar code symboL the integral optic~l element comprising a holographic element.
Is addition, these and other objects can be provided by an 35 oscillatory scanner for reading a bar code symbol and for focusing light received 20~2819 W O 91/17516 PC~r/US91/03055 from the bar code symbol. The sc~nner comprises means for producing a coherent be~n of light, means for direc~ing the beam of light onto the bar code symbol, a holographic element for focusing the received light~ and me ns for moving the holographic element in an oscillatory manner so that the holographic 5 element is directed to receive the light scattered by the bar code symbol.
Further, these and other objects ~n be provided by a sc nner for re~ding bar code symbols h3ving dist- ct areas of contrasting re~lectivi~y~ The sc ner compnses means for producing a coherent be~n of light, means for lO directin3 the beam of light onto the bar code symbol, a holographic element for focusing the received light, me ns for moving the holographic element in an oscillatory manner so that the holographic element is directed to receive the light scattered by the bar code symbol, and transducer means located at the substantially fixed point for converting the received light into an electrical signal 15 representative of the distinct areas of contrasting reflectivity.
Brief Description of the Drawings Figure 1 is a perspective diagram of a scanning laser bar code reader.
Figure 2 is an end-on view of the top end of the scanning laser bar code reader shown in Figure 1.
Figure 3 is an exploded perspective view of the optics portion of the scanning laser bar code reader shown in Figure 1.
Figure 4 is a top view of the opùcs portion of the scann~ng laser ~5 bar code reader shown in Figure 1.
Figure S is a schemaùc diagram of the circuiuy of the motor drive electronics of the sc~nning laser bar code reader shown in F;gure 1.
Figure 6A is a top view of a oscillatable holographic optic~l element for use in the scanning laser bar code reader shown in Figure 1.
Figure 6B is a front elevation view of the oscillatable holographic optical element shown in Figure 6A~
Figure 6C is a side elevation view of the oscillatable holographic opùcal element shown in Figure 6A~
wo gl/17516 Pcr/ussl/030ss 2`~28~9 Best Modes fnr CarT~ing QsLIb~
One embodiment of a l~ser sc~nner of the type with which the inventive holographic optic31 element is intended to operate is shown in Figures1 ~nd 2. While Figures 1 a~d 2 show a handheld integral laser sc3nner, the 5 inventive hologr~phic optical element can also be used with other optical sc3nn~ng systems, including in-the-counter and desl~top scanners~ Further, such opticDI scann~ng systems are not necessarily limited to bar code sc~nning. Figure 1 is ~ perspective diagr~n of the laser sc~nner. Figure 2 is an end-on view of the top end of the laser sc~nner shown in Figure 1. The laser sc~nner 10 cl)ntains 10 electronic circuitry and optical components contained within a case 12. It includes a keyboard 14 and liquid crystal display (LCD) 1~ for the display of bar codes which have been read by the laser sc nner 10 as well as for programming a microprocessor (not shown) contained within the laser scanner 10~
Upon actuating a pair of opposed triggers 18 (one shown in Figure lS 1), the laser scanner 10 is activated, as will be described subsequently, to produce a sc~nning beam 22 of laser light. The scanning beam 22 passes through the window 20 placed in the top cnd of the laser scanner lQ as shown in Figure 2. The scGng occurs in the plane 24 (shown in Figure 2). The light from the scanning beam 22 is projected forwardly of the laser scanner 10. If it reaches a20 surface, some of the impinging energy is scattered and returns to the window 20.
If the scattering surface happens to contain bar code svmbology which the scanning laser beam impinges upon, the remrning light will be modulated by the pattern of reflectivities which the bar code symbology contains. The light received by the laser scanner 10, if it is scattered from a bar code symbology, c~n be amplified and processed by circuitry in accordance with techniques which are conventional to those sldlled in the art of bar code reader design.
Figure 3 ;s an exploded perspective view of the optics portion of the laser sc~nner 10, shown in Figure 1. Figure 4 is a top view of the optics 30 portion of the sc~nning laser bar code reader shown in Figure 1. The laser sc~nner 10 shown in Figures 3 and 4 uses a visible beam to sc~n the bar code symbology.
The optics portion of the internal components of the laser scanner 10 is preferably included on a two-piece support frame 30. Support frarne 30 3~ include parts 30a and 30b which snap together to form a unitary support for the wo gl/17516 Pcrtus91/0305~
2~ .2~`~.9 optic~l and assoàated components. The components in the support fr~ne 30 c~n be sep rated into two c~tegories. One c~tegory includes the components which deal with generating and transmitting the scanning be~m Z. The other category includes the components which deal with receiving any light which m~y S be retur~ing as a result of transmitting the sc~n~ing be3m ?7, Those components in the first category include a l&ser diode 32, a turning ~irror 34, a holographic element 36, and a motor 38~ The laser diode 3~
is supplied with eleccric31 power through electrical leads 40 by electTonic circuitry contained elsewhere in the 13ser sc~nner 10. Associ3ted with the laser10 diode 32 is a holder 42 which contains and holds, as a fixed assembly, lenses and other optic~l elements which are required to ~orm the scann~ng be~n ~ ~ into thedesired formL For example, the sc nning beam 22 may be generated from the be~m of laser light produced by the laser diode 32 by passing the beam from the laser diode 32 through one or more lenses to aid in focussing the scanning beam 15 22 at a particular plane exterior to the laser scanner 10 and/or through an aperture stop to reshape the beam to have a desired cross-sectiorL
After the scarming light beam 22 passes through the optical elements held by the holder 42, it passes through a hole 44 in the turning mirror 34 to the holographic element 36. The holographic element 36 is attached to the ~0 motor 38 by the shaft 46, which causes the holographic element 36 to oscillate with the motor 38 about the axis aligned with the shaft 46. Plane 24 (see Figure2) is perpendicular to the axis aligned with the shaft 46. The scanning beam Z is diffracted from the holographic element 36 and is direaed through the window 20 within the plane 24 in accordance with the position of the holographic ~5 element 36.
Any light that is received due to scattering from an object, such as a bar code, which is exterior to the laser scanner 10 is transmitted through thewindow ~Q The window ~0 protects the interior of the laser scanner 10 from contaminants outside the laser sc~nner 10. The returning light is diffracted by 30 the holographic element 36 onto the turning mirror 34, which directs the light to the photodiode 60 after the light passes through a filter 62. The holographic element 36 is at least as large as the window 20, so that essentially all of thereceived light energy is directed to photodiode 60. This maximizes the strength WO 91/17516 Pcr/ussl/o3o~
2 0 ~ g of the signS~I produced by the photodiode 60, thereby improving the performance of the electronic circuitry which processes the sign~ls produced by the photodiode 60.
Figure S is a schematic diagr~n of the circuùtry of the motor drive electronics of the sc~nning lascr bar code reader shown in Figure 1. The motor 38 is a stepper motor having, for ex~nple, the c~pability of producing steps which ~re eighteen degrees wide. The motor 38 includes two wmdings 80A and 80B. Each of the wind~ngs 80A and 80B is center-tapped, dividing the winding 10 into two legs. The center of each of the windings is held at a substantially fixed first voltage, such as the supply voltage for the electrorlic circuit of the laser sc3nner lQ Typicq11y, the supply voltage is five volts~ Each of the legs of the two windings 80A and 80B c~n be excited separately. To accomplish this, the end of each of the legs is capable of being grounded (or held at some other voltage, if15 appropriate) respectively through a circuit induding one of the transistors 82~
, 8:t4. For example, if an appropriate signal is applied at point A, the gate of the tran~stôr 821 will cause current to pass through the upper leg of the winding 80A. This will cause the motor 38 to rotate slightly. If signals are applied to points A, Abar, B, and Bbar in the correct order, the motor 38, and ~0 conseqùently, the oscillating holographic element 36, can be caused to oscillate~
This, in turn, will cause the light beam æ tO be scanned through the window ~0 It will also cause the light received from the direction in which the light be~m 7~
is being transmitted to be focused on the photodiode 60~ If the signals are applied properly to the points A, Abar~ B, and Bbar, the light beam æ can be 25 caused to move in successive passes within an angular range having two angular extremes. If desired, the motion of the light beam ~ between extremes can be msde to have a substantially constant angular velocity~
The signals applied to the points A, Abar, B, and Bbar c n be generated by an electronic log~c device 84~ Device 84 also receives a pulse tr in, 30 or other appropriate signal, from an oscillator 86, as well as a motor motio~ detect signal on line 88.
Logic device 84 may be produced as a gate array. In response to a signal generated when the user simultaneously aclivates both of the triggers 18,the logic device 84 generates a number of signals~ Among the siznals it 35 generates are the signals reqnired to drive the motor 38 at points A, Abar, B, wo 9l/17516 Pcr/ussl/o3os5 20~2819 and Bbar, a "St~rt of Sc~n" signaL and a "Motion OK" signal. lhe "Start of Sc n"signal is directed to other electronic circuitry in the laser scanner 10 to initiali7e signal processing which reads the bar code symbology (if any) as represented by the signal produced by the photodiode 60~ If the "Motion O}r signal indicates thnt the motor 38 is not worlcing, other circuitry connected to logic device 84 within the laser sc~nner 10 can c~use the laser diode 32 to be deactivated.
Figures 6A, 6B, and 6C are respectively top, front elevation, and side elevation views of the holographic opùcal clement 36~ The holographic 10 opùcnl element 36 can be oscillated for use in the sc~ning laser bar code render shown in Figure 1. The oscillation can be accomplished by me~Lns of the shaft 46which is attached to the holographic optical element 36 through a holding means (not shown). The holding means can be a fixture for holding the holographic optical element 36 (which can be substantially flat) in a fixed position with 15 respect to the shaft 46. The holographic optical element 36 can be glued, or othe~wise semipe~nanently fLsed, to the shaft 46. Accordingly, the holographic opticDl element 36 oscillatcs when the shaft oscillates with the motor 38 (see Figure 3). The oscillation can occur about a fixed a~s relative to the integral optical element 36 If desired, the holographic optical element 36 can be made on a light-weight plastic substrate by conventional processes well l;~own to those sldlled in the art~ In one embodiment, the surface 120 of the holographic optical element 36 can be segmented into two separate optical elements, elements lZ
and 124~ Optical element 122 is shown surrounding optical element 124 in 25 Figure 6, although this configuration is not necessary to the invenùon. At least one of the optical elements 122 and 124 should be a hologTaphic optical element. Both can be holographic if desired. If one of the opùcal elements, say element 124, is not holographic, it can be a mirror~ Such a mirror c2n be usefulfor transmitting the light beam 2'' onto the bar code symbol~ In this 30 configuration, the other opùcal element (say, element 122), which is holographic, can be used to collect light reflected from the bar code symbol and focused to asubstantially fL~ced point with respect to the holographic opùcal element 36~ The opùcal element 122 can be made to focus by proper development in accordance with well-known holographic principles~
WO 91/1~516 PCltUS91/03055 ~`0`~2.``~
If it is desired that both optical elements 1~ and 12~ be holographic optic~l elements, the optical element which transmits the light ontothe bar code symbol c n also be made holographically to perforrn as a mirror.
In another embodiment, the two optical elements 1'~ ' and 124 c~n S effectively be m~de with the holograms superimposed over one another. This can be accomplished by successively exposing the medium from which the holographic optical element 36 is made to two separate sets of light be~ms. One set of light beams forms the out~oing holographic optical element and the other set of light beams forms the receiving holographic opùc~l element. One set of 10 light beams will match the entry and exit be lms that forrn the scanning beam~
The other set of light beams will match the enuy and exit beams that are for nedby the collecting mirror~ In both cases, the holographic opùc~l element is defined by the interference pattern produced by each set of beams.
The holographic optical element 36 can exhibit further 15 advantageous features over the osciUating mirror assembb now known in the ar~Since the optical efflcien~y is wavelength selective, the holographic optical element 36 can also senrc as a filter, capable of filtering out all light except that hanng the wavelength of the laser light with which the scanner is to be used.
This may eliminate the need for use of a separate filter 62 (see Figure 3).
~0 While the detaiied description above has been expressed in terms of a specific example, those skiUed in the art wiU appreciate that many other circuits could be used to accomplish the purpose of the disclosed inventive apparatus. Accordingly, it can be appreciated that various modifications of the 2S above-described embodiments may be made without departing from the spirit and the scope of the invenùon. Therefore, the spirit and the scope of the present invention are to be limited only by the foUowing claims.
l:)esc~iption OSCILL~TABLE HOLOGRAPHIC OP IIC~L ELE~T FOR B~R CODE
SCANN~G
s Technic~l F;eld This ~nvention relates to a holographic optic~l element and, more p~rtic~ rly, to a holographic optical element thnt can be osci~lated ~r use witb3 bar code scann~ng re~der.
Baclcground Art A bar code reader typically uses a beam of Iight to scan across a bar code, which consists of alternating strips ("bars`') of diffenng reflectivities.
Thc sc~nner then receives and interprets the fluctuations in the returning Ligbt15 that are caused by the bar code~ It is known in the prior art to read bar codes by means of a hand^held wand which malces contact with the surface on which the bar code is printed. However, the need to make contact with thc surface is frequently inconvenient and gives unintespre~ble readings because the wand is not moved ~cross thc bar code with a sufficiently uniform velocity.
An alternative to a hand-held wand is a scanning re~der which does not require physic~l contact with the bar code which is to be read. A
sc3nning reader typic~lly produces a beam of light which is repetitively scannedacross an are~ If the be ~n of light is incident upon a bar code (or some other symbology), the modulated light which is scattered by the bar code is returned to ~5 sensing circuitry in the sc~nning reader for interpretation. The widths of the altern2ting are~s of different reflectivity are measured on the basis of the relative times required for the be~n of light to sc n them. This allows the reader to be used with bar codes which have a wide variety of sizes as long as the rehtive widths of the eiements of the bar codes are preserved. Accordingly, it is 30 preferable, although not necessary, that the light beam be sc~ned across the bar code at a substantially uniform rate in order to e~se the task of interpreting the bar code.
Tn order to insure that the light beam is sc~ned at a subsuIltially uniform rate, it is typic311y re~ected from a mirror within the srlnner that moves 35 repetitively at a uniform rate. The mirror is generally driven by a small 2 0~2~ l6 Pcr/US91/03055 electric~l motor under the control of electronic control circuitry. The mirror is typically either rotating at a cons~nt speed or oscillating on the end of a sh~ft attached to a motor which c~n step between two extreme angular positions.
Examples of rot~ting optic~l elements are shown i~ U.S. Patent Nos. 4,0~5,761, 5 4,097,7'~9, 4,~5Q350, 4,575,6'~5, and 4,69 603. E~nples of oscill~ting ~s~irror optic31 elements are shown in U.S. Patent Nos. 4,5g3,186, 4,736,095, and 4,50~,804. In handheld applications, an oscillating mirror is generally preferable, since it c~n be made both lighter ~nd more compactly than a rotaùng opùc~l element. Conta~ned with the mirror ;s typically a collecting rnirror which 10 receives and focuses the li~ht scatter from the bar code s~mbol which is sc~nned.
In order to reduce power consurnption, it is import~nt top keep the oscillating mirror as light as possible.
pisclosure of the Invention It is an object of the present invention to provide a holographic optical element for scanning an oscillating li~ht beam onto a bar code symbol.
It is another object of the present invention to provide an integral optical element including a holographic optical element which transrnits an oscillating light beam osto an bar code symbol and focuses the lig`ht received 20 from the bar code symbol onto a fixed point with respect to the integral optical element.
It is a ~rther object of the present invention to provide a ligh~
weight optic~l elemest for scanning a beam of light onto a bar code symbol.
It is still another object of the present invention to provide a light weight opticnl element which requires reduced power to scan a beam of light onto a bar code symbol.
These and other objects can be provided by an integral optic~l 30 element for tr~smitting light in an oscillating manner across a bar code svmbol and for focusing light sc2ttered from the bar code symboL the integral optic~l element comprising a holographic element.
Is addition, these and other objects can be provided by an 35 oscillatory scanner for reading a bar code symbol and for focusing light received 20~2819 W O 91/17516 PC~r/US91/03055 from the bar code symbol. The sc~nner comprises means for producing a coherent be~n of light, means for direc~ing the beam of light onto the bar code symbol, a holographic element for focusing the received light~ and me ns for moving the holographic element in an oscillatory manner so that the holographic 5 element is directed to receive the light scattered by the bar code symbol.
Further, these and other objects ~n be provided by a sc nner for re~ding bar code symbols h3ving dist- ct areas of contrasting re~lectivi~y~ The sc ner compnses means for producing a coherent be~n of light, means for lO directin3 the beam of light onto the bar code symbol, a holographic element for focusing the received light, me ns for moving the holographic element in an oscillatory manner so that the holographic element is directed to receive the light scattered by the bar code symbol, and transducer means located at the substantially fixed point for converting the received light into an electrical signal 15 representative of the distinct areas of contrasting reflectivity.
Brief Description of the Drawings Figure 1 is a perspective diagram of a scanning laser bar code reader.
Figure 2 is an end-on view of the top end of the scanning laser bar code reader shown in Figure 1.
Figure 3 is an exploded perspective view of the optics portion of the scanning laser bar code reader shown in Figure 1.
Figure 4 is a top view of the opùcs portion of the scann~ng laser ~5 bar code reader shown in Figure 1.
Figure S is a schemaùc diagram of the circuiuy of the motor drive electronics of the sc~nning laser bar code reader shown in F;gure 1.
Figure 6A is a top view of a oscillatable holographic optic~l element for use in the scanning laser bar code reader shown in Figure 1.
Figure 6B is a front elevation view of the oscillatable holographic optical element shown in Figure 6A~
Figure 6C is a side elevation view of the oscillatable holographic opùcal element shown in Figure 6A~
wo gl/17516 Pcr/ussl/030ss 2`~28~9 Best Modes fnr CarT~ing QsLIb~
One embodiment of a l~ser sc~nner of the type with which the inventive holographic optic31 element is intended to operate is shown in Figures1 ~nd 2. While Figures 1 a~d 2 show a handheld integral laser sc3nner, the 5 inventive hologr~phic optical element can also be used with other optical sc3nn~ng systems, including in-the-counter and desl~top scanners~ Further, such opticDI scann~ng systems are not necessarily limited to bar code sc~nning. Figure 1 is ~ perspective diagr~n of the laser sc~nner. Figure 2 is an end-on view of the top end of the laser sc~nner shown in Figure 1. The laser sc~nner 10 cl)ntains 10 electronic circuitry and optical components contained within a case 12. It includes a keyboard 14 and liquid crystal display (LCD) 1~ for the display of bar codes which have been read by the laser sc nner 10 as well as for programming a microprocessor (not shown) contained within the laser scanner 10~
Upon actuating a pair of opposed triggers 18 (one shown in Figure lS 1), the laser scanner 10 is activated, as will be described subsequently, to produce a sc~nning beam 22 of laser light. The scanning beam 22 passes through the window 20 placed in the top cnd of the laser scanner lQ as shown in Figure 2. The scGng occurs in the plane 24 (shown in Figure 2). The light from the scanning beam 22 is projected forwardly of the laser scanner 10. If it reaches a20 surface, some of the impinging energy is scattered and returns to the window 20.
If the scattering surface happens to contain bar code svmbology which the scanning laser beam impinges upon, the remrning light will be modulated by the pattern of reflectivities which the bar code symbology contains. The light received by the laser scanner 10, if it is scattered from a bar code symbology, c~n be amplified and processed by circuitry in accordance with techniques which are conventional to those sldlled in the art of bar code reader design.
Figure 3 ;s an exploded perspective view of the optics portion of the laser sc~nner 10, shown in Figure 1. Figure 4 is a top view of the optics 30 portion of the sc~nning laser bar code reader shown in Figure 1. The laser sc~nner 10 shown in Figures 3 and 4 uses a visible beam to sc~n the bar code symbology.
The optics portion of the internal components of the laser scanner 10 is preferably included on a two-piece support frame 30. Support frarne 30 3~ include parts 30a and 30b which snap together to form a unitary support for the wo gl/17516 Pcrtus91/0305~
2~ .2~`~.9 optic~l and assoàated components. The components in the support fr~ne 30 c~n be sep rated into two c~tegories. One c~tegory includes the components which deal with generating and transmitting the scanning be~m Z. The other category includes the components which deal with receiving any light which m~y S be retur~ing as a result of transmitting the sc~n~ing be3m ?7, Those components in the first category include a l&ser diode 32, a turning ~irror 34, a holographic element 36, and a motor 38~ The laser diode 3~
is supplied with eleccric31 power through electrical leads 40 by electTonic circuitry contained elsewhere in the 13ser sc~nner 10. Associ3ted with the laser10 diode 32 is a holder 42 which contains and holds, as a fixed assembly, lenses and other optic~l elements which are required to ~orm the scann~ng be~n ~ ~ into thedesired formL For example, the sc nning beam 22 may be generated from the be~m of laser light produced by the laser diode 32 by passing the beam from the laser diode 32 through one or more lenses to aid in focussing the scanning beam 15 22 at a particular plane exterior to the laser scanner 10 and/or through an aperture stop to reshape the beam to have a desired cross-sectiorL
After the scarming light beam 22 passes through the optical elements held by the holder 42, it passes through a hole 44 in the turning mirror 34 to the holographic element 36. The holographic element 36 is attached to the ~0 motor 38 by the shaft 46, which causes the holographic element 36 to oscillate with the motor 38 about the axis aligned with the shaft 46. Plane 24 (see Figure2) is perpendicular to the axis aligned with the shaft 46. The scanning beam Z is diffracted from the holographic element 36 and is direaed through the window 20 within the plane 24 in accordance with the position of the holographic ~5 element 36.
Any light that is received due to scattering from an object, such as a bar code, which is exterior to the laser scanner 10 is transmitted through thewindow ~Q The window ~0 protects the interior of the laser scanner 10 from contaminants outside the laser sc~nner 10. The returning light is diffracted by 30 the holographic element 36 onto the turning mirror 34, which directs the light to the photodiode 60 after the light passes through a filter 62. The holographic element 36 is at least as large as the window 20, so that essentially all of thereceived light energy is directed to photodiode 60. This maximizes the strength WO 91/17516 Pcr/ussl/o3o~
2 0 ~ g of the signS~I produced by the photodiode 60, thereby improving the performance of the electronic circuitry which processes the sign~ls produced by the photodiode 60.
Figure S is a schematic diagr~n of the circuùtry of the motor drive electronics of the sc~nning lascr bar code reader shown in Figure 1. The motor 38 is a stepper motor having, for ex~nple, the c~pability of producing steps which ~re eighteen degrees wide. The motor 38 includes two wmdings 80A and 80B. Each of the wind~ngs 80A and 80B is center-tapped, dividing the winding 10 into two legs. The center of each of the windings is held at a substantially fixed first voltage, such as the supply voltage for the electrorlic circuit of the laser sc3nner lQ Typicq11y, the supply voltage is five volts~ Each of the legs of the two windings 80A and 80B c~n be excited separately. To accomplish this, the end of each of the legs is capable of being grounded (or held at some other voltage, if15 appropriate) respectively through a circuit induding one of the transistors 82~
, 8:t4. For example, if an appropriate signal is applied at point A, the gate of the tran~stôr 821 will cause current to pass through the upper leg of the winding 80A. This will cause the motor 38 to rotate slightly. If signals are applied to points A, Abar, B, and Bbar in the correct order, the motor 38, and ~0 conseqùently, the oscillating holographic element 36, can be caused to oscillate~
This, in turn, will cause the light beam æ tO be scanned through the window ~0 It will also cause the light received from the direction in which the light be~m 7~
is being transmitted to be focused on the photodiode 60~ If the signals are applied properly to the points A, Abar~ B, and Bbar, the light beam æ can be 25 caused to move in successive passes within an angular range having two angular extremes. If desired, the motion of the light beam ~ between extremes can be msde to have a substantially constant angular velocity~
The signals applied to the points A, Abar, B, and Bbar c n be generated by an electronic log~c device 84~ Device 84 also receives a pulse tr in, 30 or other appropriate signal, from an oscillator 86, as well as a motor motio~ detect signal on line 88.
Logic device 84 may be produced as a gate array. In response to a signal generated when the user simultaneously aclivates both of the triggers 18,the logic device 84 generates a number of signals~ Among the siznals it 35 generates are the signals reqnired to drive the motor 38 at points A, Abar, B, wo 9l/17516 Pcr/ussl/o3os5 20~2819 and Bbar, a "St~rt of Sc~n" signaL and a "Motion OK" signal. lhe "Start of Sc n"signal is directed to other electronic circuitry in the laser scanner 10 to initiali7e signal processing which reads the bar code symbology (if any) as represented by the signal produced by the photodiode 60~ If the "Motion O}r signal indicates thnt the motor 38 is not worlcing, other circuitry connected to logic device 84 within the laser sc~nner 10 can c~use the laser diode 32 to be deactivated.
Figures 6A, 6B, and 6C are respectively top, front elevation, and side elevation views of the holographic opùcal clement 36~ The holographic 10 opùcnl element 36 can be oscillated for use in the sc~ning laser bar code render shown in Figure 1. The oscillation can be accomplished by me~Lns of the shaft 46which is attached to the holographic optical element 36 through a holding means (not shown). The holding means can be a fixture for holding the holographic optical element 36 (which can be substantially flat) in a fixed position with 15 respect to the shaft 46. The holographic optical element 36 can be glued, or othe~wise semipe~nanently fLsed, to the shaft 46. Accordingly, the holographic opticDl element 36 oscillatcs when the shaft oscillates with the motor 38 (see Figure 3). The oscillation can occur about a fixed a~s relative to the integral optical element 36 If desired, the holographic optical element 36 can be made on a light-weight plastic substrate by conventional processes well l;~own to those sldlled in the art~ In one embodiment, the surface 120 of the holographic optical element 36 can be segmented into two separate optical elements, elements lZ
and 124~ Optical element 122 is shown surrounding optical element 124 in 25 Figure 6, although this configuration is not necessary to the invenùon. At least one of the optical elements 122 and 124 should be a hologTaphic optical element. Both can be holographic if desired. If one of the opùcal elements, say element 124, is not holographic, it can be a mirror~ Such a mirror c2n be usefulfor transmitting the light beam 2'' onto the bar code symbol~ In this 30 configuration, the other opùcal element (say, element 122), which is holographic, can be used to collect light reflected from the bar code symbol and focused to asubstantially fL~ced point with respect to the holographic opùcal element 36~ The opùcal element 122 can be made to focus by proper development in accordance with well-known holographic principles~
WO 91/1~516 PCltUS91/03055 ~`0`~2.``~
If it is desired that both optical elements 1~ and 12~ be holographic optic~l elements, the optical element which transmits the light ontothe bar code symbol c n also be made holographically to perforrn as a mirror.
In another embodiment, the two optical elements 1'~ ' and 124 c~n S effectively be m~de with the holograms superimposed over one another. This can be accomplished by successively exposing the medium from which the holographic optical element 36 is made to two separate sets of light be~ms. One set of light beams forms the out~oing holographic optical element and the other set of light beams forms the receiving holographic opùc~l element. One set of 10 light beams will match the entry and exit be lms that forrn the scanning beam~
The other set of light beams will match the enuy and exit beams that are for nedby the collecting mirror~ In both cases, the holographic opùc~l element is defined by the interference pattern produced by each set of beams.
The holographic optical element 36 can exhibit further 15 advantageous features over the osciUating mirror assembb now known in the ar~Since the optical efflcien~y is wavelength selective, the holographic optical element 36 can also senrc as a filter, capable of filtering out all light except that hanng the wavelength of the laser light with which the scanner is to be used.
This may eliminate the need for use of a separate filter 62 (see Figure 3).
~0 While the detaiied description above has been expressed in terms of a specific example, those skiUed in the art wiU appreciate that many other circuits could be used to accomplish the purpose of the disclosed inventive apparatus. Accordingly, it can be appreciated that various modifications of the 2S above-described embodiments may be made without departing from the spirit and the scope of the invenùon. Therefore, the spirit and the scope of the present invention are to be limited only by the foUowing claims.
Claims (34)
1. An integral optical element for transmitting light in an oscillating manner across a bar code symbol and for focusing light reflected from the bar code symbol, comprising a holographic element.
2. The integral optical element of claim 1, further comprising a holder means attached to the holographic element.
3. The internal optical element of claim, further comprising means for moving the holder means in an oscillatory manner so that the light reflected by the optical element scans across an area.
4. The integral optical element of claim 1 wherein the holographic element focuses light reflected from the bar code symbol.
5. The integral optical element of claim 4 wherein the holographic means focuses the received light onto a substantially fixed point relative to the integral optical element.
6. The integral optical element of claim 4, further comprising a holder means attached to the holographic element.
7. The integral optical element of claim 6, further comprising means for moving the holder means in an oscillatory manner so that the light reflected by the optical element scans across an area.
8. The integral optical element of claim 4, further comprising a mirror for directing light onto the bar code symbol.
9. The integral optical element of claim 8, further comprising a holder means attached to the holographic element.
10. The integral optical element of claim 9, further comprising means for moving the holder means in an oscillatory manner so that the light reflected by the mirror means scans across an area.
11. The integral optical element of claim 10 wherein the holographic element focuses the received light onto a substantially fixed point relative to the integral optical element.
12. The integral optical element of claim 11 wherein the movement of the holder means occurs about a fixed axis relative to the integral optical element.
13. The integral optical element of claim 4, further comprising a holographic optical element for directing light onto the bar code symbol.
14. The integral optical element of claim 13, further comprising a holder means attached to the holographic element.
15. The integral optical element of claim 14, further comprising means for moving the holder means in an oscillatory manner so that the light reflected by the mirror means scans across an area.
16. The integral optical element of claim 15 wherein the holographic element focuses the received light onto a substantially fixed point relative to the integral optical element
17. The integral optical element of claim 16 wherein the movement of the holder means occurs about a fixed axis relative to the integral optical element.
18. The integral optical element of claim 4, further comprising means for filtering the wavelength of the light reflected from the bar code symbol.
19. The integral optical element of claim 1 wherein the holographic means focuses the received light onto a point.
20. The integral optical element of claim 1 wherein the holographic element directs light onto the bar code symbol.
21. The integral optical element of claim 20, further comprising a holder means attached to the holographic element.
22. The integral optical element of claim 21, further comprising means for moving the holder means in an oscillatory manner so that the light reflected by the optical element scans across an area.
23. The integral optical element of claim a wherein the holographic element focuses the received light onto a substantially fixed point relative to the integral optical element.
24. The integral optical element of claim 23 wherein the movement of the holder means occurs about a fixed axis relative to the integral optical element.
25. An oscillatory scanner for reading a bar code symbol and for focusing light received from the bar code symbol, comprising:
means for producing a coherent beam of light;
means for directing the beam of light onto the bar code symbol;
a holographic element for focusing the received light; and means for moving the holographic element in an oscillatory manner so that the holographic element is directed to receive the light reflected by the bar code symbol
means for producing a coherent beam of light;
means for directing the beam of light onto the bar code symbol;
a holographic element for focusing the received light; and means for moving the holographic element in an oscillatory manner so that the holographic element is directed to receive the light reflected by the bar code symbol
26. The integral optical element of claim 25 wherein the holographic means focuses the received light onto a substantially fixed point relative to the integral optical element
27. The integral optical element of claim 25 wherein the means for moving the holographic element comprises a holder means attached to the holographic element.
28. The integral optical element of claim 27 wherein the holographic element focuses the received light onto a substantially fixed point relative to the integral optical element.
29. The integral optical element of claim 27 wherein the movement of the holder means occurs about a fixed axis relative to the integral optical element.
30. A scanner for reading a bar code symbol having distinct areas of contrasting reflectivity, comprising:
means for producing a coherent beam of light;
means for directing the beam of light onto the bar code symbol;
a holographic element for focusing the received light;
means for moving the holographic element in an oscillatory manner so that the holographic element is directed to receive the light reflected by the bar code symbol; and transducer means located at the substantially fixed point for converting the received light into an electrical signal representative of the distinct areas of contrasting reflectivity.
means for producing a coherent beam of light;
means for directing the beam of light onto the bar code symbol;
a holographic element for focusing the received light;
means for moving the holographic element in an oscillatory manner so that the holographic element is directed to receive the light reflected by the bar code symbol; and transducer means located at the substantially fixed point for converting the received light into an electrical signal representative of the distinct areas of contrasting reflectivity.
31. The integral optical element of claim 30 wherein the holographic means focuses the received light onto a substantially fixed point relative to the integral optical element.
32. The integral optical element of claim 30 wherein the means for moving the holographic element comprises a holder means attached to the holographic element.
33. The integral optical element of claim 32 wherein the holographic element focuses the received light onto a substantially fixed point relative to the integral optical element.
34. The integral optical element of claim 32 wherein the movement of the holder means occurs about a fixed axis relative to the integral optical element.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US51853790A | 1990-05-02 | 1990-05-02 | |
| US518,537 | 1990-05-02 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2062819A1 true CA2062819A1 (en) | 1991-11-03 |
Family
ID=24064364
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2062819 Abandoned CA2062819A1 (en) | 1990-05-02 | 1991-04-30 | Oscillatable holographic optical element for bar code scanning |
Country Status (4)
| Country | Link |
|---|---|
| EP (1) | EP0481055A4 (en) |
| JP (1) | JPH04506880A (en) |
| CA (1) | CA2062819A1 (en) |
| WO (1) | WO1991017516A1 (en) |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3919527A (en) * | 1973-07-26 | 1975-11-11 | Ibm | Omnidirectional optical scanner |
| US4266846A (en) * | 1976-12-28 | 1981-05-12 | University Of Delaware | Two-dimensional scanners |
| US4687282A (en) * | 1985-04-25 | 1987-08-18 | Ncr Corporation | Method and apparatus for making and utilizing a holographic bifocal lens element |
| US4794237A (en) * | 1986-11-10 | 1988-12-27 | Ncr Corporation | Multidirectional holographic scanner |
| US4800256A (en) * | 1986-12-08 | 1989-01-24 | International Business Machines Corporation | Halographic scanner having adjustable sampling rate |
-
1991
- 1991-04-30 CA CA 2062819 patent/CA2062819A1/en not_active Abandoned
- 1991-04-30 EP EP19910909133 patent/EP0481055A4/en not_active Withdrawn
- 1991-04-30 JP JP50891391A patent/JPH04506880A/en active Pending
- 1991-04-30 WO PCT/US1991/003055 patent/WO1991017516A1/en not_active Application Discontinuation
Also Published As
| Publication number | Publication date |
|---|---|
| EP0481055A4 (en) | 1992-07-08 |
| WO1991017516A1 (en) | 1991-11-14 |
| EP0481055A1 (en) | 1992-04-22 |
| JPH04506880A (en) | 1992-11-26 |
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