EP0553286A1 - Numeriseur pour grandes surfaces - Google Patents

Numeriseur pour grandes surfaces

Info

Publication number
EP0553286A1
EP0553286A1 EP91920622A EP91920622A EP0553286A1 EP 0553286 A1 EP0553286 A1 EP 0553286A1 EP 91920622 A EP91920622 A EP 91920622A EP 91920622 A EP91920622 A EP 91920622A EP 0553286 A1 EP0553286 A1 EP 0553286A1
Authority
EP
European Patent Office
Prior art keywords
signals
camera
signal
magnitude
elements
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.)
Withdrawn
Application number
EP91920622A
Other languages
German (de)
English (en)
Other versions
EP0553286A4 (en
Inventor
Raymond J. Phillips
Mark Ryvkin
John Owen Gerety
Ronald J. Straayer
Thomas John Bergel
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Gerber Systems Corp
Original Assignee
Gerber Systems Corp
Gerber Scientific Instrument Co
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 Gerber Systems Corp, Gerber Scientific Instrument Co filed Critical Gerber Systems Corp
Publication of EP0553286A1 publication Critical patent/EP0553286A1/fr
Publication of EP0553286A4 publication Critical patent/EP0553286A4/en
Withdrawn legal-status Critical Current

Links

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
    • H04N1/1013—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 sub-scanning by translatory movement of at least a part of the main-scanning components
    • H04N1/1039—Movement of the main scanning components
    • H04N1/1043—Movement of the main scanning components of a sensor array
    • 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
    • H04N1/1013—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 sub-scanning by translatory movement of at least a part of the main-scanning components
    • H04N1/1017—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 sub-scanning by translatory movement of at least a part of the main-scanning components the main-scanning components remaining positionally invariant with respect to one another in the sub-scanning direction
    • 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
    • H04N1/19—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 multi-element arrays
    • H04N1/191—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 multi-element arrays the array comprising a one-dimensional array, or a combination of one-dimensional arrays, or a substantially one-dimensional array, e.g. an array of staggered elements
    • H04N1/1911—Simultaneously or substantially simultaneously scanning picture elements on more than one main scanning line, e.g. scanning in swaths
    • 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
    • H04N1/40—Picture signal circuits
    • H04N1/40056—Circuits for driving or energising particular reading heads or original illumination means
    • 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
    • H04N1/40—Picture signal circuits
    • H04N1/401—Compensating positionally unequal response of the pick-up or reproducing head
    • 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
    • H04N2201/0402—Arrangements not specific to a particular one of the scanning methods covered by groups H04N1/04 - H04N1/207
    • H04N2201/0436—Scanning a picture-bearing surface lying face up on a support
    • 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
    • H04N2201/0402—Arrangements not specific to a particular one of the scanning methods covered by groups H04N1/04 - H04N1/207
    • H04N2201/0438—Scanning displays; Scanning large surfaces, e.g. projection screens, writing boards
    • 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
    • H04N2201/04727—Detection of scanning velocity or position by detecting marks or the like, e.g. slits on a linear encoder
    • 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
    • H04N2201/04731—Detection of scanning velocity or position in the sub-scan direction
    • 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

Definitions

  • the present invention relates to optical scanning systems and more particularly to optical scanning systems adapted to scan large surface areas.
  • optical scanning systems have become generally known in the art. These systems are used to digitize either text or two dimensional images. The digitized signals are then stored in a computer memory for later access. Scanning systems typically are one of two types. Flatbed or sheet fed scanners are adapted for use with computer peripheral equipment and scan with a camera in a raster fashion relative to a flat image to generate corresponding digital signals. Smaller, hand held scanners are manually moved relative to an image and generate digital signals in much the same manner.
  • An object of the present invention is to provide a system capable of digitally scanning a very large document.
  • Another object of the present invention is to provide a highly accurate large area scanning system capable of interfacing with a larger assembly of digital equipment.
  • Another object of the present invention is to provide a digital scanning system characterized by high optical resolution.
  • Still another object of the present invention is to provide a digital scanning system of the foregoing type that is characterized by software selectable optical resolution.
  • Another object of the present invention is to provide a digital scanning system of the foregoing type that is characterized by great depth of field.
  • a system for use in scanning large areas includes, a table having an upper surface with a length and a width, a scanning mechanism affixed to the surface for moving thereabout in response to control signals, and a camera attached to the scanning mechanism that includes an array of photoelectric elements each receiving an optical image from the surface and each generating signals indicative thereof.
  • An illumination mechanism is configured with the camera for illuminating the surface optical images.
  • a controller receives signals from the camera and includes a mechanism for generating scan signals for the scanning mechanism to move the camera across the table surface width in a sequence of scan strips each having an approximate extent equal to that of the photoelectric element array.
  • the present system also includes a mechanism for configuring the sampled scan signal arrays in a sequence of scan lines extending across the table surface width and a mechanism for compressing the signals in the scan lines into a data format of reduced size.
  • a controller for use in controlling illumination in a scanning system having a scanning mechanism configured with a camera and a mechanism for controllably illuminating a surface, the controller controls the surface illumination in accordance with a method including the steps of providing drive signals to a lamp to increase optical intensity therefrom; measuring signals from an optical feedback device indicative of optical input to the camera; measuring camera output signals and determining the camera mechanism optical saturation.
  • the method also has the steps of computing signals corresponding to a selected magnitude of the lamp drive signals at camera optical saturation; providing signals to the lamp to generate a known percentage of camera saturation; comparing the required lamp setting with signals from the optical feedback device and adjusting the lamp drive signals should the illumination not equal the set magnitude.
  • a controller for use in compensating for variations in the signal gain and surface light in accordance with a method including the steps of providing the camera elements with light having a minimum intensity; generating camera output signals indicative of the minimum light intensity, with each of the elements providing a respective minimum light intensity signal? providing the minimum light intensity signals to a signal subtracter fi w — » _- V _. _ _ _• ⁇ ⁇ -» "i _"* « ⁇ . -_ 1 .
  • the method further includes the steps of generating camera output signals indicative of the maximum light intensity, which allows the camera to operate at a fixed percentage below camera saturation with each of the elements providing a respective maximum light intensity signal; subtracting, for each of the elements, the camera minimum light intensity signal from the corresponding maximum light intensity signal and generating a difference signal therefrom computing, for each of the elements, a gain adjustment factor whose magnitude is dependent on the respective element difference signal magnitude and a desired maximum signal magnitude and multiplying, for each of the elements, the selected light intensity signals by the gain adjustment factor to generate a corrected maximum signal whose magnitude corresponds to the desired maximum signal magnitude.
  • a controller for use with a scanning system having a camera receiving light from a surface and generating therefrom camera output signals having a plurality of pixels includes a video processor receiving the camera signals and generating digital video signals of more than two bits per pixel; a mechanism for displaying to an operator for the purpose of optimum threshold selection a visual image on a display corresponding to the digital video signal and a mechanism for interactively changing the threshold bifurcation of the video signal while viewing the results.
  • the desired threshold is achieved it is sent to the video processor to perform (during normal scanning) threshold bifurcation of the digital video signal into a bit corresponding to minimum and maximum levels of optical intensity.
  • a controller for use in controlling illumination in a scanning system having a scanner configured with a camera and a surface illumination apparatus controls illumination of the surface in accordance with a method that includes the steps of providing drive signals to a lamp to increase optical intensity therefrom to a maximum value, measuring camera output signals corresponding to a saturation thereof and providing signals to the lamp corresponding to a selected reduced magnitude of the lamp drive signals at camera saturation.
  • the method also includes the steps of measuring the camera signals at the reduced magnitude lamp drive signals and adjusting the lamp drive signals should the camera signals not be reduced in magnitude by a selected amount from the saturation magnitude.
  • Fig. 1 is a simplified schematic illustration of a large area scanning system provided according to the present invention.
  • Fig. 2 is a simplified schematic illustration of a portion of the system of Fig. 1 used for illumination.
  • Fig. 3 is a diagrammatic illustration of an algorithm executed by the controller of Fig. 1 in maintaining optimum illumination.
  • Fig. 4 is a simplified illustration showing a portion of the controller of Fig. 1 used to provide black signal compensation.
  • Fig. 5 is a simplified illustration showing a portion of the controller of Fig. 1 used to provide white signal compensation.
  • Fig. 6 diagrammatically shows the uncompensated and compensated dynamic range of the camera of Fig. 1.
  • Fig. 7 is a simplified illustration of a portion of the controller of Fig. 1 used in video signal processing.
  • Fig. 8 is a top view of the scanning system of Fig. 1 showing the relative movement of a camera across a table surface in the system of Fig. 1.
  • Fig. 9 is a schematic illustration showing the operation of a threshold selection mechanism in the system of Fig. 1.
  • Fig. 10 is a simplified diagrammatic illustration of a video processor associated with the controller provided according to the present invention.
  • Fig. 11 is a simplified top plan view of the table surface of Fig. 8 showing the location of several documents scanned by the system of Fig. 1.
  • DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to Fig. 1 there is shown in simplified form a large area scanning system 10 provided according to the present invention.
  • the system includes a scanning table 12 having an active scanning surface of approximately 48" x 148".
  • a scanner head 14 which includes a camera and illumination optics is configured with a scanning mechanism 16 which is preferably of a gantry type.
  • the preferred scanning system includes elements from the Gerber Model 278 Scanner.
  • the scanning mechanism comprises a device, including motors, gears and the like for moving the scanning mechanism along the length of the table and a similar device for moving the scanning head across the table width, both in response to control signals.
  • Both the scanning mechanism and the scanner head receive signals from controller 18, as detailed hereinafter.
  • the controller provides signals to control the operation of the camera and illumination mechanism 23 in the scanner head.
  • the controller generates control signals for the motors associated with the scanner mechanism for moving the scanner head relative to the table surface 20.
  • the controller receives signals from the scanner head indicative of the image as well as signals from a photoelectric feed back sensor used in controlling the illumination of the surface. As detailed hereinafter, the controller processes the received signals and stores them in either memory 22 associated with the controller and displays a digitized image of the scanned document on work station display 24. Further, the controller provides signals to a local area network or equivalent as indicated schematically at line 26 for use by other computer equipment.
  • the system 10 also includes a linear encoder 28 positioned on the scanning mechanism extending along a scan axis 30.
  • _oni- tables such as the Model 278 table sold by the assignee of the present invention typically provide a rotary linear encoder and determine the actual position of the scanner head along the scan access by mechanism of software algorithms.
  • a linear encoder such as encoder 32, is used to directly measure the scanner head position along the scan axis.
  • the present scanner head a portion of which is shown in Fig. 2 contains an illumination mechanism preferably comprised of a plurality of optical fiber elements extending out of the Figure.
  • the fiber optic elements are arranged in two arrays 34 and 36 juxtaposed about a CCD camera 38, preferably a Fairchild CCD 143 linear array having 2048 13 x 13 micron elements on 13 micron centers with an approximate overall length of 1 inch.
  • An optical source (not shown) is remotely located from the camera to provide illumination at an intensity in accordance with received control signals.
  • the optical source for the fiber-optic illumination mechanism of the preferred embodiment is a Tungsten halogen lamp which can be color filtered in order to improve the contrast on difficult to read documents.
  • the lamp is driven by a DC power supply which is modulated from the controller to select a desired image intensity.
  • the scanner mechanism also contains the requisite drive electronics to locally control the operation of the illumination mechanism components.
  • the image on a document 40 is transmitted from the table through a linear graded index lens 42 such as a SELFOC lens sold by the Nippon Sheet Glass Company.
  • a linear graded index lens 42 such as a SELFOC lens sold by the Nippon Sheet Glass Company.
  • the preferred lens is telecentric which kes it highly iiu ⁇ tu ⁇ e Lo the accuracy problems caused by variations in table flatness.
  • the lens is characterized by its ability to provide to the camera only light reflected off that portion of the image which lies in registration with the camera.
  • the lens 42 has good depth of field to ensure image fidelity throughout the scan.
  • the preferred lens also possesses high contrast and is extremely compact.
  • a photoelectric device such as diode 44 is also included to generate a feed back signal to amplifiers 46 and 48.
  • the illumination intensity is selected to be approximately 90% of the CCD's element's saturation level in accordance with an algorithm 50 outlined in Fig. 3.
  • the controller When the system is initially energized and the scanner head positioned over a white surface (blocks 52,54), the controller will present signals to the illumination mechanism to raise the lamp intensity to its maximum (block 56). The controller measures the output of the camera elements or a subset thereof at block 58. Next, the lamp power is lowered incrementally and the camera element signal values are monitored (blocks 60,62). In the preferred embodiment, the center 2000 camera elements are monitored for an element signal decrease of at least 5 counts from the levels initially measured.
  • the 5 count decrease corresponds to CCD element output signal levels have fallen below saturation (blocks 63, 64). Thereafter, the light intensity is measured by the photodiode (block 65) the output signal from the photodiode is used to maintain the optical output of the lamp at the computed level (block 66) by adjusting lamp drive power when necessary (block 67). This optical output level is thereafter defined to constitute "full" illumination. Although the 90% value is preferred, another value may be chosen depending on the application and on the target document.
  • the present system has a calibration process which is characterized by the above referenced saturation detection scheme and black and white signal level compensation detailed hereinbelow.
  • Figs. 4 - 6 there is schematically shown portions 68, 70 of the controller of Fig. 1 respectively used for black and white signal level compensation.
  • the present invention provides for signal compensation to ensure that signals which fall within the dynamic range of the CCD array contain information, and likewise eliminate any situation where information could lie on or beyond the dynamic range limits.
  • Fig. 4 there is shown the portion 68 of the controller of Fig. 1 which generates compensation for dark or "black" signal levels.
  • the output of each element should be uniform for the darkest portion of the document to be scanned without illumination, that is the document portion which corresponds to a black or dark image. This is graphically represented in Fig. 6 as curve 72.
  • the initial signal level comparison between the different CCD elements more closely approximates curve 74 in Fig. 6.
  • video signals taken from the darkest portion of the surface to be scanned are initially received. These signals are provided both to random access memory (RAM) 78 and simultaneously to subtracter 80.
  • RAM random access memory
  • the output signals therefrom corresponds to a true "0" signal level as indicated by curve 72 in Fig. 6.
  • Gain compensation by the present invention is demcnstr ed by reference to Fig. 5.
  • video signals from the whitest or brightest portion of the document image with full illumination are received at block 82.
  • These signals are provided to subtracter 84 which also receives signals from RAM 78.
  • signals correspond to the video signals for the respective CCD elements from the darkest portion of the surface without illumination.
  • the output signals from subtracter 84 correspond to the difference signal magnitudes of each of the respective elements between that element's maximum white and minimum black signals.
  • the controller computes a gain factor at block 86 for each element to adjust the gain of the element such that the maximum light intensity at some level below CCD staturation will yield a preselected maximum output signal.
  • the algorithm executed by the controller ensures that the maximum signal output by the CCD element for the whitest portion of the surface at full illumination corresponds to the maximum gain available. In the preferred embodiment the algorithm computation is as follows:
  • the present controller also provides for a signal threshold selection.
  • a signal threshold selection As is known, scanning using a full 8 bit grayscale generates a substantial volume of data; a problem that is magnified by the very large documents which are to be scanned by the present scanner.
  • the present controller includes a computation assembly 92 having a workstation 122 and a grayscale processor card or equivalent 94 for processing full 8 bit grayscale information from video signals 96 presented via buffer 98.
  • a threshold selection mode the controller requires the operator to select defined areas of approximately one inch square to be scanned and shown on display 24 in full grayscale.
  • the controller includes a separate hardware path, 8 bits per pixel, as detailed hereinafter.
  • the operator manually selects a threshold which is used by the workstation to bifurcate the 8 bit grayscale information for each pixel.
  • This bifurcation is performed by the workstation such that, an 8 bit video pixel acts as an index into a table.
  • the table locations are filled with values such to produce either a black or white level pixel.
  • the operation changes the threshold by moving the bifurcation point in the look up table.
  • the workstation will directly recompute the full 8 bit grayscale information to a binary representation as detailed above. This will be displayed directly to the operator for approval or further selection. Once the operator is satisfied with the threshold selection it is down loaded to the video processor board and used for normal scanning to produce bilevel images. This provides substantial savings r in the data storage and manipulation capacity which would otherwise be needed, and improves the response speed of the present system.
  • the preferred camera 38 comprises a linear array 102 of photoelectric elements 104, such as a CCD array, extending over a length of approximately one inch.
  • the output signals from the array then are equivalent to a one inch by 13 micron section of the scan surface.
  • the length of the array is oriented to the table length, with the controller programmed to move the array across the table width at a selected rate hile sa ⁇ i.pliuy the cam ra elements acco dingly.
  • Each scan l ⁇ contains image data over approximately one inch of the table length.
  • the surface is preferably scanned in only one direction.
  • the controller includes an algorithm for "stitching" the signals from adjacent scans to ensure the pixels are in registration and that no image gap or overlap occur.
  • Mini-raster format is the term used to describe the present data format of the sampled camera signals.
  • the video signals comprise image information for a particular strip of the surface parallel to the table edge.
  • the signals provided to the controller therefore, have local coordinate information pertaining to that strip in that scan.
  • a scan comprises a sequence of strips extending the table width. This data format is different as compared to a raster format wherein each point on the table surface has a unique pair of coordinates and the camera signals are received in scan lines.
  • the present system is characterized by a software selectable resolution.
  • the highest possible accuracy is delivered with the preferred system having resolution capabilities of between 200 and 1200 DPI (dots per inch).
  • DPI dots per inch
  • changes are accomplished as follows.
  • the CCD array is advanced from right to left in Fig. 8 and from a lower to an upper portion sequentially. It is preferred that a single pass scanning technique be used. Signals from the CCD array are then provided to the controller which generates therefrom pixel data in mini raster format comprising a X and Y position vector and a value for intensity for that pixel at that scan position. Note that an effective pixel is formed by integrating the signals from a select number fractions of adjacent CCD elements in the array as determined by the selected resolution.
  • a 200 dots per inch resolution will have 6 times the number of CCD clement signals integrated n will a resolution of 1200 DPI.
  • Resolution is varied in the scan direction by varying the speed of the advance of the camera with a constant sample rate. Therefore, the camera will be advanced across the surface 6 times more quickly for a resolution of 200 DPI then for 1200 DPI.
  • the present controller allows for conversion to an English spatial frequency by a correction in the integration computation rather than require the hardware to conform.
  • the camera requires a transfer clock and pixel clock signal provided by clock 108.
  • the transfer clock signal controls the integration time of the sensor and the pixel clock signal controls the read out rate of the video data from the sensor.
  • the sensor provides odd pixel information on Channel A and even pixel information on Channel B (lines 110 and 112).
  • the pixel signal information is provided to the video signal buffer which amplifies and removes any DC offset from the signals provided on the CCD video channels.
  • the two channels are also summed and digitized.
  • the 8 bit signals are then sent to the video processor.
  • the video processor comprises a single VME6U board which conforms to the known VME bus specifications.
  • the video processor performs the following functions; pixel compensation, digital resampling and integration for various resolutions, and generation of bilevel video signals after the threshold selection process.
  • a direct memory access (DMA) controller path is provided to supply grayscale data through the CPU directly to the work station 122 only during the thr_shol _ __ 1ec-tion. process.
  • Fig. 9 is a simplified schematic illustration of a portion 124 of the controller used during the threshold selection process.
  • the full grayscale data from the user defined areas reside in a controller memory portion 126 associated with the workstation.
  • the full 8 bit wide data then has 255 states, indicated at 128.
  • Each pixel has a signal value associated therewith, such as values 130, 132.
  • a look up table 134 with pointer 136 is also provided. Prior to entry into the threshold selection mode, the data is provided to the look up table also in full grayscale. However, once the threshold selection mode is selected, the look up table is programmed to have all signals below the selected threshold to be output to the display as "black” and those above to be output as "white”.
  • the pointer i.e.
  • threshold setting is set at level 140, with "black” and “white” being indicated by “00" and “ff”, respectively.
  • the video pixels act as indexes into this table.
  • a histogram of grayscale magnitudes and their occurrence frequency in the defined area are shown to the operator.
  • Selection of an 8 bit threshold level shows the operator in real time the effect on the grayscale information stored in the work station and indicates the information content of the data of the subsequent scan.
  • the 8 bit video data signals are, as shown in Fig. 10, compared in a digital comparator 138 with the threshold level indicated at 140. Again, all those pixel signals having a value below the selected value will be processed as a "black” pixel, while all those signals whose value exceeds the threshold will be processed as "white”.
  • a data formatter 114 is provided and is preferably comprised of a single VME6U board which conforms to the VME bus speci ication.
  • the data formatter provides motion control and pixel re£urmatting.
  • a clock signal is presented on line 116 for the two axis motors in the scanner mechanism to position the scanner head.
  • Position counters which are read by the controller indicate the actual position of the scanner head. All X axis (table length) and Y axis (table width) moves of the scanner head other than the actual scanning of the camera are performed elsewhere in the controller.
  • the data formatter also reformats the video signals (now bilevel) to convert the CCD array scan signals into actual raster data in scan line format.
  • a signal compressor 118 is provided and is comprised of a single VME6U board that conforms to VME bus specifications.
  • This portion of the controller receives the raster data signals from the data formatter and performs a run length encoding data compression process (RLS) thereon before passing these compressed signals onto a central processing unit (CPU) 120.
  • the RLS format is an efficient data compression code which minimizes the document transmission time and file size.
  • the central processing unit comprises a Motorola Model 147 processor on a single VME6U board. This CPU is a double high VME module with a 68030 CPU.
  • This CPU provides a small computer system interface (SCSI) bus controller with direct memory access (DMA), floating point processor, tick timer, watch dog timer, and time of day clock calender with a battery backup.
  • SCSI small computer system interface
  • DMA direct memory access
  • the CPU perl ⁇ rius scanner calibration overall scanner control and supplies the pixel data to the controller work station such as personal VAX (P- VAX) marketed by the Digital Equipment Corporation.
  • P- VAX personal VAX
  • the reformatted data is compressed into a run length encoded short (RLS) code, blocked and transmitted to a remote computer by mechanism of a small computer system interface (SCSI) bus.
  • RLS data file can be reprocessed to alternative formats such as the CCITT Group 4 data format.
  • the work station 122 includes a model 9700S work station with video monitor having the following functions; 1) selectable scan resolution (scanning speed is implied); 2) file naming capability; 3) CCITT format (Group 4) optional format; 4) interactive threshold setting from scanner display; and 5) storage on magnetic tape. Access to video signals for real time processing (composite video 75 ohm impedance) is provided at the scanner head.
  • the present system includes the capability of scanning several smaller documents in sequence as shown in Fig. 11.
  • Documents 142 - 146 are located on the table surface.
  • the controller determines the coordinates of the extent thereof and advances from one to the next at the completion of each scan.
  • the present invention includes the capability of software selectable zoom for display.
  • the controller can display very large areas by the simple selection for display of selected scan lines (i.e., every third line). Zoom is accomplished by adding to the display the deleted information or a portion thereof.
  • the present invention encompasses scanning systems wherein the scan strips are lengthwise and those scanning systems wherein the scanner head is configured to sample the document in a bidirectional manner.

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  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Facsimile Scanning Arrangements (AREA)
  • Image Input (AREA)

Abstract

Système de numérisation pour grandes surfaces (10) s'utilisant pour la lecture de documents à grande dimension et comprenant une table (12) ainsi qu'un mécanisme de lecture (16) sur lequel se trouve une tête de lecture (14). La tête de lecture comprend un mécanisme d'éclairage et une caméra servant à recevoir la lumière réfléchie par un document placé sur la table. Le système de numérisation (10) est caractérisé par un contrôleur (18) qui effectue la lecture initiale du document en une série de bandes (106) et génère, de ce fait, des données recomposées sous forme d'une séquence de lignes de lecture. Afin d'augmenter la vitesse de fonctionnement, le contrôleur (18) permet la compression des données avec des données à deux niveaux.
EP19910920622 1990-10-15 1991-10-11 A large area digital scanner Withdrawn EP0553286A4 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US59772790A 1990-10-15 1990-10-15
US597727 1990-10-15

Publications (2)

Publication Number Publication Date
EP0553286A1 true EP0553286A1 (fr) 1993-08-04
EP0553286A4 EP0553286A4 (en) 1993-11-03

Family

ID=24392691

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19910920622 Withdrawn EP0553286A4 (en) 1990-10-15 1991-10-11 A large area digital scanner

Country Status (3)

Country Link
EP (1) EP0553286A4 (fr)
JP (1) JPH06501364A (fr)
WO (1) WO1992007441A1 (fr)

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US9013761B2 (en) 2013-04-16 2015-04-21 Hewlett-Packard Development Company, L.P. Scanner with a scan sensor having a width smaller than the platen

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Also Published As

Publication number Publication date
JPH06501364A (ja) 1994-02-10
WO1992007441A1 (fr) 1992-04-30
EP0553286A4 (en) 1993-11-03

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