WO1995002889A1 - Dispositif de lecture a main, a elements optiques replies et a glissiere de guidage - Google Patents

Dispositif de lecture a main, a elements optiques replies et a glissiere de guidage Download PDF

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Publication number
WO1995002889A1
WO1995002889A1 PCT/US1994/007967 US9407967W WO9502889A1 WO 1995002889 A1 WO1995002889 A1 WO 1995002889A1 US 9407967 W US9407967 W US 9407967W WO 9502889 A1 WO9502889 A1 WO 9502889A1
Authority
WO
WIPO (PCT)
Prior art keywords
scanner
document
casing
palm
guide rail
Prior art date
Application number
PCT/US1994/007967
Other languages
English (en)
Inventor
Weng-Lyang Wang
Robin S. Lo
Original Assignee
Fullon Image, Inc.
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Fullon Image, Inc. filed Critical Fullon Image, Inc.
Priority to AU73352/94A priority Critical patent/AU7335294A/en
Publication of WO1995002889A1 publication Critical patent/WO1995002889A1/fr

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
    • H04N1/04—Scanning arrangements, i.e. arrangements for the displacement of active reading or reproducing elements relative to the original or reproducing medium, or vice versa
    • H04N1/10—Scanning arrangements, i.e. arrangements for the displacement of active reading or reproducing elements relative to the original or reproducing medium, or vice versa using flat picture-bearing surfaces
    • H04N1/107—Scanning arrangements, i.e. arrangements for the displacement of active reading or reproducing elements relative to the original or reproducing medium, or vice versa using flat picture-bearing surfaces with manual scanning
    • H04N1/1071—Scanning arrangements, i.e. arrangements for the displacement of active reading or reproducing elements relative to the original or reproducing medium, or vice versa using flat picture-bearing surfaces with manual scanning using a folded light path
    • 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
    • G06K7/14—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation using light without selection of wavelength, e.g. sensing reflected white light
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
    • H04N1/04—Scanning arrangements, i.e. arrangements for the displacement of active reading or reproducing elements relative to the original or reproducing medium, or vice versa
    • H04N1/047—Detection, control or error compensation of scanning velocity or position
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
    • H04N1/04—Scanning arrangements, i.e. arrangements for the displacement of active reading or reproducing elements relative to the original or reproducing medium, or vice versa
    • H04N1/10—Scanning arrangements, i.e. arrangements for the displacement of active reading or reproducing elements relative to the original or reproducing medium, or vice versa using flat picture-bearing surfaces
    • H04N1/107—Scanning arrangements, i.e. arrangements for the displacement of active reading or reproducing elements relative to the original or reproducing medium, or vice versa using flat picture-bearing surfaces with manual scanning
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
    • H04N1/04—Scanning arrangements, i.e. arrangements for the displacement of active reading or reproducing elements relative to the original or reproducing medium, or vice versa
    • H04N1/10—Scanning arrangements, i.e. arrangements for the displacement of active reading or reproducing elements relative to the original or reproducing medium, or vice versa using flat picture-bearing surfaces
    • H04N1/107—Scanning arrangements, i.e. arrangements for the displacement of active reading or reproducing elements relative to the original or reproducing medium, or vice versa using flat picture-bearing surfaces with manual scanning
    • H04N1/1072—Means for guiding the scanning, e.g. rules
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
    • H04N1/04—Scanning arrangements, i.e. arrangements for the displacement of active reading or reproducing elements relative to the original or reproducing medium, or vice versa
    • H04N1/10—Scanning arrangements, i.e. arrangements for the displacement of active reading or reproducing elements relative to the original or reproducing medium, or vice versa using flat picture-bearing surfaces
    • H04N1/107—Scanning arrangements, i.e. arrangements for the displacement of active reading or reproducing elements relative to the original or reproducing medium, or vice versa using flat picture-bearing surfaces with manual scanning
    • H04N1/1077—Arrangements for facilitating movement over the scanned medium, e.g. disposition of rollers
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N2201/00—Indexing scheme relating to scanning, transmission or reproduction of documents or the like, and to details thereof
    • H04N2201/024—Indexing scheme relating to scanning, transmission or reproduction of documents or the like, and to details thereof deleted
    • H04N2201/02406—Arrangements for positioning elements within a head
    • H04N2201/02439—Positioning method
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N2201/00—Indexing scheme relating to scanning, transmission or reproduction of documents or the like, and to details thereof
    • H04N2201/04—Scanning arrangements
    • H04N2201/047—Detection, control or error compensation of scanning velocity or position
    • H04N2201/04701—Detection of scanning velocity or position
    • H04N2201/0471—Detection of scanning velocity or position using dedicated detectors
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N2201/00—Indexing scheme relating to scanning, transmission or reproduction of documents or the like, and to details thereof
    • H04N2201/04—Scanning arrangements
    • H04N2201/047—Detection, control or error compensation of scanning velocity or position
    • H04N2201/04701—Detection of scanning velocity or position
    • H04N2201/04715—Detection of scanning velocity or position by detecting marks or the like, e.g. slits
    • H04N2201/04724—Detection of scanning velocity or position by detecting marks or the like, e.g. slits on a separate encoder wheel
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N2201/00—Indexing scheme relating to scanning, transmission or reproduction of documents or the like, and to details thereof
    • H04N2201/04—Scanning arrangements
    • H04N2201/047—Detection, control or error compensation of scanning velocity or position
    • H04N2201/04701—Detection of scanning velocity or position
    • H04N2201/04734—Detecting at frequent intervals, e.g. once per line for sub-scan control
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N2201/00—Indexing scheme relating to scanning, transmission or reproduction of documents or the like, and to details thereof
    • H04N2201/04—Scanning arrangements
    • H04N2201/047—Detection, control or error compensation of scanning velocity or position
    • H04N2201/04753—Control or error compensation of scanning position or velocity
    • H04N2201/04758—Control or error compensation of scanning position or velocity by controlling the position of the scanned image area
    • H04N2201/04767—Control or error compensation of scanning position or velocity by controlling the position of the scanned image area by controlling the timing of the signals, e.g. by controlling the frequency o phase of the pixel clock
    • H04N2201/04781—Controlling the phase of the signals
    • H04N2201/04786—Controlling a start time, e.g. for output of a line of data
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N2201/00—Indexing scheme relating to scanning, transmission or reproduction of documents or the like, and to details thereof
    • H04N2201/04—Scanning arrangements
    • H04N2201/047—Detection, control or error compensation of scanning velocity or position
    • H04N2201/04753—Control or error compensation of scanning position or velocity
    • H04N2201/04794—Varying the control or compensation during the scan, e.g. using continuous feedback or from line to line

Definitions

  • the present invention relates to an image scanner, and more particularly to a hand-held or "palm" scanner having thin, vertical profile.
  • Image scanners convert optical images into digital electronic signals. Most typically, the optical images are derived from documents containing graphical information (e.g. , pictures) or character information (e.g. , text) .
  • graphical information e.g. , pictures
  • character information e.g. , text
  • conventional image scanners employ three primary elements: (1) a light source to illuminate the document to be scanned; (2) an image sensor to convert an optical image of the document to an electronic signal; and (3) an optical system to focus the imag of the document on the image sensor.
  • the electronic signals output by the image sensor (usually a charge coupled device or "CCD") are transmitted to a computer through an interface such as an interface card in the computer.
  • the image data is stored or used in software (e.g. by data processing or imag processing software) .
  • OCR optical character recognition
  • image editing software can convert graphical images to pictorial or graphic files for desktop publishing applications.
  • Many scanners employ a stepper motor or other drive mechanism to automatically move the scanner with respect to th document. Two types of such scanner are widely used: (1) the "flatbed” scanner, and (2) the "sheet-feed” scanner.
  • Flatbed scanners contain a bed to hold the document during scanning an one or two metal bars at the edge(s) of the scanner bed guide scanner body over the document.
  • flatbed scanners generally produce reliable images, their applicability is limited to scanning documents that can lie flat on the scanner bed.
  • books and magazines, for example are not easily scanned without first making a photocopy of the pages or images to be scanned.
  • flatbed scanners must be large enough to hold the largest document that might be scanned.
  • sheet-feed scanners the document to be scanned is fed through rollers in front of an imaging region of a fixed scanner body.
  • the scanner reads the first line of a document, then moves the document through the rollers to the second line, reads the second line, moves the document to the next line, and so on. Because no bed is required, sheet-feed scanners are smaller than flatbed scanners.
  • application of sheet- feed scanners is still limited to thin, flexible documents, typically sheets of paper.
  • sheet-feed scanners sometimes skew or chew the document between the feed rollers.
  • a completely different type of scanner overcomes many of the problems associated with flatbe and sheet-feed scanners.
  • Hand-held scanners are moved over a document manually, and therefore contain no stepper motors or other document handling mechanisms. Thus, they can, in some cases, scan various types of documentation, including books an magazines as well as sheets of paper. The user simply grasps the scanner body and rolls it across the contours of the document to be scanned.
  • Some hand-held scanners have thin, vertical profiles (see, for example, U.S. Patents Nos. 4,899,228 and 4,887,165). Although they overcome some disadvantages of the flat body scanners, these devices still have drawbacks. For example, i can be difficult to align the scanner at the proper starting position on the document. Further, it can be difficult to mo hand-held scanners across the scanning region in a straight 5 line, especially when the document is a book or magazine.
  • hand-held scanners have various advantages such as flexibility and low price, they are not without certa drawbacks. Thus, there exists a need for improved hand-held scanners. 5
  • the present invention provides a hand-held "palm" scanner including a scanner body and a separate guide rail.
  • the guide rail is a long thin strip of material having a rail 0 protruding along its length.
  • the guide rail When the guide rail is placed o a document, it defines a straight path over which the scanner body is directed during the scanning operation.
  • the guide rail includes a stop against which the scanner body rests before beginning a scan.
  • the preferred guide rail will
  • the scanner body 25 also include a mark defining the beginning of the scan region so that a scanner body - positioned against the stop - begins scanning at the top of the scanning region.
  • the scanner body includes a rigid outer casing having a bottom side with one o more rollers and one or more recesses or notches complementar
  • the scanner body interior houses optical elements for image conversion including a light source, a len an image sensor, and preferably one or more mirrors.
  • the scanner body also houses a photocoupler and optical chopper o other mechanism for detecting how far the scanner has moved
  • the operator first places the guide rail on the document such that it is located adjacent to all some fraction of the length of the area to be scanned.
  • the operator places the scanner body on the document to be scanned such that one of the notches on bottom side of the scanner body engages the guide rail.
  • Light is then directed from the scanner body light source onto the document to be scanned, and scanning is performed by.manually moving the scanner body along the path of the guide rail and over the region to be scanned.
  • the scanner body has a vertical profile that is ea for the operator to handle during scanning. Inside the scan body, an interior casing holds in place the various optical elements such as two or more mirrors. The use of two mirror allows the light path to double back on itself, thus substantially reducing the height of the scanner body. With mirrors, the scanner body height would be approximately equa to the optical path length between the document and the imag sensor.
  • the mirrors each have a surface definin an angle of between about 10 and 80 degrees - and more preferably between about 20 and 45 degrees - with the surfac of the document.
  • the guide rail is pliabl so that when it is placed on a document, it assumes the contours of that document.
  • the guide rail will lie flus with the page of the book to be imaged. In this way, the scanner body can be moved in a straight line by the operator even when the document has a non-flat surface.
  • the guide rail is transparent or near transparent so that the operator can see the edge of the reg being scanned.
  • FIG. 1 shows a perspective view of a scanner body associated guiding rail according to the present invention
  • Fig. 2 shows a cross-sectional front view of the p scanner riding on a guide rail
  • Fig. 3a-c show a perspective view and two side views of a guide rail according to the present invention
  • Fig. 4 shows a cross-sectional side view of the palm scanner body including an outer casing and an inner casing wit associated optical elements;
  • Fig. 5 depicts a preferred optical system of the pal scanner body
  • Fig. 6 depicts a preferred inner housing for the pal scanner body
  • Fig. 7 shows a CCD assembly ⁇ including a ceramic fram and CCD sensor chip according to the present invention
  • Fig. 8 shows the details of a preferred photocoupler assembly according to the present invention
  • Fig. 9 shows a block diagram of the signal processin electronics residing in the scanner body.
  • Fig. 10 shows a block diagram of the signal processing electronics residing in the interface card for the palm scanner.
  • a palm scanner of this inventio including a scanner body 1 and a guide rail 2 is shown.
  • the scanner body 1 includes a top side on which switch 8 is mounte and a front surface on which ruled markings 9 defining the document width are provided.
  • the scanner body also includes a bottom side having recesses or notches 3 which span the width of the scanner body from front to back and are located near th left and right sides of scanner body. The notches engage the guide rail during operation.
  • the scanner body also includes a cable or connector 12 which connects the image sensor with a computer.
  • the cable carries only fi lines, as opposed to the eight lines carried in many conventional hand-held scanners.
  • t cable is thin and flexible. Thus, it becomes easier to manipulate the scanner body during alignment on the document be scanned and during actual scanning.
  • the following five lines are employed: Vdd:12 Volt power from the computer interface card GND:Signal ground
  • the scanner body length (distance from left to right sides) is preferably long enough that a standard page of information can be input in a maximum of two scans.
  • the length of the scanner body is about 136 mm, while the width (distance between the front and back surfaces) is about 32 mm, and the height (distance between the top and bottom surfaces) is about 55 mm.
  • scanner bodies of varying dimensions may be employed as necessary for particular applications.
  • the scanner body should have a vertical profile as opposed to the flat profile of many prior hand-held scanners.
  • the width (the dimension parallel to the direction in which the scanner body moves) should be fairly small so that the scanner body can easily ride over the contours of a book or magazine page.
  • the width of the scanner body will be between about 30 and 50 mm.
  • the height of the scanner body is preferably short enough that the device does not become unwieldy to handle. In preferred embodiments, the height is between about 55 and 65 mm. As explained below, the arrangement of optical elements in the present invention allows for the reduced height.
  • the scanner length is preferably between about 125 and 145 mm.
  • the guide rail 2 defxnes a path along which the scanner body 1 moves during a scanning operation.
  • Notches 3 on the left and right sides of the bottom of the scanner body are shaped to compliment the guide rail such that when the rail is under a notch, lateral motion of the scanner is restricted.
  • Notches 3 are sufficiently deep that the entire length of the scanner body will sit flat on the document being scanned.
  • the scanner body is provided with notches 3 on both the left and right sides so that the user may scan on either the right or left side of guide rail 2.
  • guide rail 2 is placed on the document along the edge of a desired scanning region.
  • Reference marks on the guide rail 2 define the region to be scanned.
  • the scanner body 1 is then placed on 5 the document such that notch 3 engages guide rail 2 and reference mark 7 on the edge of the scanner body is aligned with a selected reference mark 6 on the guide rail.
  • Referenc mark 7 on the scanner body defines the reading position of th scanner. 0
  • the operator actuates switch 8 whi lights up LED 11 indicating that the scanner is ready for operation.
  • switch 8 is the only control on the scanner body. This allows for easy assembly a manufacturing while improving reliability.
  • Most conventional 5 hand-held scanners have switches or controls for resolution, brightness, contrast, etc. All these functions are preferabl controlled by software for the palm scanner of this invention
  • Fig. 2 provides an enlarged cross-section of scann body l as it rides on guide rail 2. Notch 3 of the scanner body contacts guide rail 2 such that lateral movement is 35 prevented during scanning. Thus, a stable reliable image is produced.
  • the scanner body rolls across the document 5 on a roller 1 .
  • the depth of notch 3 and the height of rail 2 ar selected so that the bottom 16 of scanner body l is substantially parallel with document 5 and the entire length o roller 14 contacts the document surface.
  • the roller extends slightly below the lower surface 16 of the scanner body.
  • roller 14 is isolated by the lower surface 16 to minimize the amount of dust finding its way into the scanner body interior.
  • the guide rail should be sufficiently long to accommodate the area of most documents to be scanned. It has been found that a length of between about 10 and 12 inches is suitable.
  • the guide rail preferably is made of a transparent material so that the operator can see the underlying document.
  • the guide rail is preferably made from a soft material to allow an operator to bend it over non-flat documents. Suitable materials for the guide rail include flexible plastics and rubbers, and, in some cases, more rigid materials such as aluminum.
  • the guide rail is preferably provided with two separate rails - on on top 17 and one on the bottom 18.
  • each rail ha a stop which prevents the scanner body from moving beyond reference mark 6.
  • the guide rail can be turned over to presen either rail 17 or 18 depending upon whether the scanner is moved by the left or right hand of the user.
  • Fig. 4 is a cross-sectional view through slice B-B' of Fig. l.
  • the palm scanner contains outer housing 19 and inner housing 20.
  • the outer housing provides the user accessible features of the palm scanner and defines the surfaces which can be gripped by the user during scanning.
  • Th inner housing 20 defines the optical path of the light containing the document image and also defines the positions o the various optical elements and image sensor.
  • the outer housing is made from a rigid material that resists flexure during the scanning process.
  • the outer housing will be made from steel or aluminum, but a variety of other suitable metals may be used.
  • a rigid plastic material such as polyvinyl chloride may be employed.
  • the outer housing 19 includes an upper casing 27 and a lower casing 28.
  • the upper casing defines the top of the scanner body and accommodates a switch 33.
  • the lower casing defines the bottom of the scanner body and includes a window 22 through which light from light source 21 is shown on document 5.
  • the window 22 is curved avoid scratches and other damage caused by contact with the document.
  • a curved window may also serve to focus light from light source 21 onto the document.
  • the lower casing 28 also has openings through which rollers 32 protrude.
  • two rollers are provided - one near the front and the other near the back of the scanner body - to ensure that the bottom of the scanner body remains substantially parallel to the document.
  • An optical chopper 30 and photocoupler 29 are attached to the upper casing 27.
  • The"chopper is rotatably coupled to the roller 32 through wheels 31 and 38.
  • the chopper turns by an amount proportional to the distance traversed by the roller 32.
  • the palm scanner keeps track of the distance travelled-on the document and thereby ascertains the "height" of the optical data detected the image sensor.
  • the chopper and wheel 31 are show to have axes parallel to that of roller 32, this is by no mea necessary.
  • inner housing 20 includes mounting region for light source 21, first mirror 23, second mirror 24, lens 25, and image sensor 26.
  • the inner housing is oriented withi the outer housing 19 so that light from the light source 21 i directed through the window 22 at a selected angle to illuminate document 5.
  • light source 21 will be a array of light emitting diodes (LEDs) , ' but may also be a lamp(s) or other conventional source. As shown by light path
  • first and second mirrors 23 and 24 are parallel, so that the light path from the second mirror to the image detector is parallel to the light path fro the document 5 to the first mirror.
  • first and second mirrors are parallel and oriente at angles of between about 10 and 80 degrees from the plane of the document. Most preferably, the first and second mirrors are oriented at between about 20 and 45 degrees from the plane of the document.
  • the optical path length necessary to reduce the document image to a size suitable for the image sensor can be quite large.
  • CCD image sensors are typically about one inch long.
  • a standard 8.5 inch page requires a light path length of about 10 to 30 centimeters between the image sensor and the document.
  • the mirrors employed in this invention must be precisely and accurately aligned wit the other optical elements to ensure that the optical image is correctly focused on the image sensor.
  • the palm scanner of this invention employ inner casing 20 to provide stable and consistent mounting regions for the optical elements.
  • FIG. 5 A perspective view of a preferred palm scanner optic system is provided in Fig. 5.
  • An LED array 35 including LEDs 36 and resistors 37 directs light onto document 5.
  • the LEDs illuminate the document at an angle such that the image width is decreased over the light path, as it approaches lens 33.
  • the LEDs illuminate the document at about 45 degrees.
  • the reflected light passes unhindered to first mirro 39 and then onto second mirror 40. From there, the light passes through lens 33 (which has a focal point 42) which produces an image of the document on image sensor 41.
  • the image sensor 41 is preferably a CCD assembly including a CCD image sensor and peripheral circuitry (passive or active components, not shown) .
  • the lens 33 is mounted in the lens housing 34.
  • magnification of lens 33 should be chosen so th the image of each "pixel" on the document occupies one detect on the CCD array. Because the area of each photodetector in typical CCD assembly is about 14 microns by 14 microns, and t pixel size is 63.5 microns by 63.5 microns for 400 dot per in (dpi) resolution, the magnification of the lens is preferably provided as follows:
  • Fig. 6 shows a partial cutaway view of the inner housing 43 of the palm scanner.
  • the inner housing defines the light path of the optical image.
  • the inner housing is preferably colored black.
  • the inner housing provides prec mounting regions for the various optical elements. This all the palm scanners to be produced in volume without requiring individual alignment of the optical elements in each unit.
  • the scanners of this invention can employ relatively tortuous light paths and consequently have relatively short heights.
  • the housings are made of molded plasti but other materials and fabrication techniques may be employ
  • inner housing 43 includes a total of six openings for six optical components.
  • first opening 44 is used to attach a light source 35.
  • a sec opening 46 holds the window 47.
  • a third opening 48 is used attach the first mirror 39.
  • a fourth opening 50 is used to attach the second mirror 40.
  • a fifth opening 52 is used to insert and adjust the optical lens 33.
  • a sixth opening 54 is used to attach the CCD assembly 41.
  • the inner housing includes a total of six layers (i.e. relatively flat portions of the molded housing body) which define the optical path. These layers include 56, 57, 58, 59, 60,. and 61.
  • the layers 56 and 57 are generally parallel to the path of the reflected light from the document to the first mirror 39.
  • the light path from the first mirror to the second mirror 40 is generally parallel to the layers 58 and 59, and the light path from the second mirror through optical lens 33 to the CCD assembly 41 is generally parallel to the layers 60 and 61. Because the optical path is well defined by the housing, the optical elements can be mounted in the openings and require few if any adjustments.
  • a preferred ceramic substrate CCD assembly is shown in Fig. 7.
  • preferred palm scanners of this invention include a CCD assembly on a ceramic substrate 69.
  • the rigidity of the ceramic substrate ensures that the assembly is easily mounted in the inner housing in the appropriate alignment.
  • the CCD assembly includes various capacitors 72, transistors 70, and resistors 71 in addition to the CCD 73. Each of these elements is mounted to the ceramic substrate 69.
  • the CCD chip 73 is die attached to the ceramic substrate. After a wire bond from the CCD chip 73 to the ceramic substrate 69, a ceramic frame 74 is attached to the substrate 69. A glass window 75 is then attached to the ceramic frame 74 using either epoxy or preform. Because the CCD chip 73 is directly attached to the ceramic substrate 69, the photodetector plane will be parallel to the ceramic substrate 69.
  • Fig. 8 shows a photocoupler mechanism for detecting the moving distance of the palm scanner body l.
  • the components of the photocoupler arrangement are mounted on a wall between outer casing lower surface 78 and outer casing upper surface 92.
  • the operation of photocoupler arrangement may generally described as follows.
  • a roller 77 which moves across the surface of the document being imaged is coupled via shaft 81 wheel 82 such that wheel 82 rotates at the same rate as rolle 77.
  • the rotation of wheel 82 is translated through a series wheels 83, 84, 85, and 86 to optical chopper 87.
  • optic chopper 87 rotates at a rate proportional to the roller rate.
  • the chopper includes angularly displaced notches 88 which pas through a photocoupler 76 as the palm scanner moves across th document.
  • angularly displaced notches 88 which pas through a photocoupler 76 as the palm scanner moves across th document.
  • other combinations of wheels could be employed.
  • the number, sizes, and arrangement of wheels is chosen to ensure that the chopper moves by one scale (notch) each time the roller moves by a defined amount (e.g. one pixe length) .
  • optical chopper 87 is preferably moved by one scale when the roller 7 is moved by 63.5. microns.
  • the photocoupler 76 may be any of various widely- available devices. Typical photocouplers include a light source (e.g. a LED) which shines on a photodetector when a chopper notch 88 passes between the light source and the photodetector. By alternately blocking and transmitting ligh from the light source, the chopper induces electric pulses fr the photocoupler. The pulse counts correspond to the distanc traveled by the palm scanner over the document being spanned. This allows the processing electronic circuitry of the palm scanner to identify each new line of the image signal.
  • a light source e.g. a LED
  • the distance travelle by the scanner body is monitored by reference to the guide rail.
  • the markings on the guide rail are noted by the scanner and converted to distance information used by the processing circuitry.
  • the light beam from the light source can be split so that some light detects markings or the guide rail and the remaining light is used to carry the optical image of the document.
  • Fig. 9 depicts the signal processing electronics residing in the scanner body, signals from the photocoupler 76, the toggle switch 8, and clock 104 are fed to an ASIC chip 101 which controls the CCD image sensor 105.
  • the lines connecting the scanner engine to the interface card include a ground line (GND) , clock pulse lines associated with the image pixel (WG) and the image line (ST) , a power line (VDD) , and an analog video signal line 108.
  • the image pixel clock pulse (WG provides the information for converting a line of analog image data from the CCD into discrete pixels.
  • the image line clock pulse (ST) provides information to the interface card to indicate when a complete line of data is received.
  • the photocoupler module provides some indication of when a line of image data has been taken.
  • the analog video signal from CCD 105 is amplified by preamp 106 and passed through a sample and hold module 107 which samples a new line of data from the CCD and holds that data until a complete line has been received. Then the complete line of image data is released to the interface card.
  • the image data volume provided from the image sensor can be quite large.
  • the total character data for an A4 size document having 400 dpi and 256 grade is about 16 Mbytes. If the operator moves the scanner body rapidly, the data transfer rate can overwhelm some interfaces.
  • the present invention employs advanced analog/digital circuitry to increas the PC bus throughput. This coupled with a 2.5 MHz CCD allows scanning speeds of as much as 2.5 inches/second.
  • the video signal is transmitted by the palm scanner as an analog rather than digital signal. This is beneficial when grey scale or color data is being transmitted because only a single is required. To transmit grey scale or color data in digital form requires multiplexing of multiple lines.
  • Compression logic may be employed in the palm scanne interface card to compress the image data from the scanner before sending it through a PC bus.
  • the data will be compressed by a ratio of about two to four times its original size.
  • the compressed data is later decompressed by the host computer software.
  • the compression logic should be able to complete processing the data for each image pixel within one microsecond.
  • One way to realize such processing speed is through an algorithm that employs the "difference" of each pixel in two successive line
  • Fig. 10 depicts the signal processing electronics i a preferred interface card of the palm scanner of this invention.
  • the analog video signal first passes through a lo pass filter 111 to remove noise from the signal line. .
  • the video signal passes through a multiple digital-to-analog converter (MDAC) 112 which provides uniformity correction.
  • MDAC digital-to-analog converter
  • T features of the scanner optical signal generally require correction to provide a more uniform signal from pixel to pixel.
  • the LED source is typically provided as an linear array of discrete sources.
  • the illumination intensity oscillates across the width of the scanning region the document. Those regions of the document that are closer an LED source receive stronger illumination, while those regions of the document that are further from an LED source receive weaker illumination.
  • the optical signal reaching the CCD is most intense from pixels near the center the line being scanned. This is because the document is clo to the lens and CCD at the center of the document.
  • the opti path length between the document and the CCD is greater at t edges of a line than at the center of that line.
  • the MDAC multiplies the signal from each pixel. y a uniformity correction value that accounts for both of the above factors.
  • the MDAC obtains the proper correction value for each pixel from SRAM which has stored data from a previous calibration the scanner. Uniformity correction is conventionally done b software after the image data is transmitted to the host; th is an inherently slow process.
  • the present invention employ MDAC 112 to do the uniformity correction in hardware and thereby streamline the scanning process.
  • the corrected analog video signal from MDAC 112 is passed to analog-to-digital converter 113.
  • Two digital-to- analog converters 114 and 115 control the upper and lower threshold of the A/D converter 113 and thereby set the brightness and contrast of the signal. This allows software control of these parameters; as opposed to the controls on the scanner body employed in conventional designs. As explained above, the scanner body of this invention has only one control switch, greatly simplifying manufacture.
  • the digitized video signal is compressed by an algorithm provided by compression ASIC 116 and compression RAM 117. Various compression algorithms can be used, but a preferred "difference" algorithm is described below.
  • An SRAM "first in first out” buffer (FIFO) 118 is employed to buffer the image data from the interface board through the PC bus.
  • a 36Kx8 SRAM FIFO - preferably used with this invention - normally has the capacity to buffer 20 to 40 lines of uncompressed data and 60 to 120 lines of compressed data.
  • a control ASIC 119 is used to control the D/A converters 114 and 115 and the FIFO SRAM 118, and also communicate with compression ASIC 116.
  • a preferred compression method of this invention employs the following steps.
  • First image data from analog-to- digital converter 113 is converted to a "difference code" whic is the difference between the signals of pixels on two successive lines of image data. Because most grey scale or color images have few abrupt changes in the image signal, the signal difference between successive lines reduces the image data value (the number of bits required) without losing significant information.
  • the method of generating a differenc code depends on which of the two image datum pixels comprising a difference datum is greater. If the n'th pixel in the m'th line is greater than the n'th pixel in the (m+1) 'th line, the .
  • difference code is the absolute magnitude of the difference between the two pixels incremented by'3 and followed by changing the last three bits of value to zeros. If, on the other hand, the pixel on the (m+1) 'th line is greater, then th difference code is the absolute value of the difference betwee the two pixels with bits 0-2 being "100". In this way, bit 2 is used as a direction bit to indicate if the difference value is positive or negative.
  • the compression method uses three escape codes to implement further compression of the image data.
  • the three escape codes are OxBB, OxCC, and OxDD.
  • the data stream after OxBB is treated as source data which has not had been convert to difference code or otherwise compressed.
  • Oxcc treated as difference code and data after OxDD is treated as compressed and repackaged (described below) difference code.
  • Two adjacent pixels having a difference code of les than 0x40 may combined as follows. Their difference codes ar first right shifted by two bits into a 4-bit value. These tw 4-bit values are then combined into one byte to achieve a 2-t 1 compression ratio. To prevent confusion with the OxCC esca code while in OxDD mode, the value OxCC is converted to OxCE when in OxDD mode. For example, the following difference cod can be combined into a compressed output stream as follows:
  • the difference code can be further compressed by packing multiple contiguous difference code having a value of zero.
  • a value of 0x05 within a OxDD sequence indicates an array of five contiguous difference code values being zero, while OxOF indicates an array of fifteen contiguous differenc code values being zero.

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Abstract

Dispositif de lecture comprenant un corps (1) et une glissière de guidage (2) séparée. La glissière de guidage permet de définir une trajectoire rectiligne sur laquelle le corps du dispositif est déplacé au cours de l'opération de lecture. Le corps du dispositif présente un boîtier externe (19) comprenant une base munie d'un ou plusieurs rouleaux (14, 32) et d'un ou plusieurs évidements (3) complémentaires à la glissière. Dans le corps du dispositif sont logés des éléments optiques destinés à la conversion d'images, et comprenant une source de lumière (21), une lentille (25), un ou plusieurs miroirs (23, 24), ainsi qu'un capteur (26) d'images. Dans le corps du dispositif sont logés également un photocoupleur (28) et un découpeur optique (30) permettant de détecter jusqu'où le dispositif s'est déplacé sur le document lu par balayage.
PCT/US1994/007967 1993-07-16 1994-07-15 Dispositif de lecture a main, a elements optiques replies et a glissiere de guidage WO1995002889A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU73352/94A AU7335294A (en) 1993-07-16 1994-07-15 Palm scanner having folded optics and a guide rail

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US9297293A 1993-07-16 1993-07-16
US08/092,972 1993-07-16

Publications (1)

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WO1995002889A1 true WO1995002889A1 (fr) 1995-01-26

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0998116A2 (fr) * 1998-10-28 2000-05-03 Fujitsu Limited Dispositif de lecture

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4814877A (en) * 1983-02-21 1989-03-21 Canon Kabushiki Kaisha Image reading apparatus provided with correction for shadings in image data
US4899228A (en) * 1986-06-12 1990-02-06 Casio Computer Co., Ltd. Manually sweeping apparatus with image sensor
US5058188A (en) * 1989-11-10 1991-10-15 Kabushiki Kaisha Manual scan type image reader for correcting read image data to faithfully reproduce read image
US5200597A (en) * 1991-02-07 1993-04-06 Psc, Inc. Digitally controlled system for scanning and reading bar codes

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4814877A (en) * 1983-02-21 1989-03-21 Canon Kabushiki Kaisha Image reading apparatus provided with correction for shadings in image data
US4899228A (en) * 1986-06-12 1990-02-06 Casio Computer Co., Ltd. Manually sweeping apparatus with image sensor
US5058188A (en) * 1989-11-10 1991-10-15 Kabushiki Kaisha Manual scan type image reader for correcting read image data to faithfully reproduce read image
US5200597A (en) * 1991-02-07 1993-04-06 Psc, Inc. Digitally controlled system for scanning and reading bar codes

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0998116A2 (fr) * 1998-10-28 2000-05-03 Fujitsu Limited Dispositif de lecture
EP0998116A3 (fr) * 1998-10-28 2003-09-24 Fujitsu Limited Dispositif de lecture
US6744537B1 (en) 1998-10-28 2004-06-01 Fujitsu Limited Image reader
US7292378B2 (en) 1998-10-28 2007-11-06 Fujitsu Limited Image reader

Also Published As

Publication number Publication date
AU7335294A (en) 1995-02-13

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