WO1998043407A1 - Procede de balayage optoelectronique - Google Patents

Procede de balayage optoelectronique Download PDF

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Publication number
WO1998043407A1
WO1998043407A1 PCT/DE1998/000445 DE9800445W WO9843407A1 WO 1998043407 A1 WO1998043407 A1 WO 1998043407A1 DE 9800445 W DE9800445 W DE 9800445W WO 9843407 A1 WO9843407 A1 WO 9843407A1
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WO
WIPO (PCT)
Prior art keywords
scanning
line
voltage values
charge
pixels
Prior art date
Application number
PCT/DE1998/000445
Other languages
German (de)
English (en)
Inventor
Jens Flick
Uwe Rudi Albrecht
Original Assignee
Heidelberger Druckmaschinen Ag
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 Heidelberger Druckmaschinen Ag filed Critical Heidelberger Druckmaschinen Ag
Publication of WO1998043407A1 publication Critical patent/WO1998043407A1/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
    • H04N1/40—Picture signal circuits
    • 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
    • H04N1/40068—Modification of image resolution, i.e. determining the values of picture elements at new relative positions

Definitions

  • the invention relates to the field of electronic reproduction technology and relates to a method for pixel-by-line and line-by-line optoelectronic scanning of image originals.
  • image values are obtained and further processed in scanning devices, also called scanners, by pixel-by-line optoelectronic scanning of image templates to be reproduced.
  • the image original to be scanned is arranged on a flat original carrier which moves perpendicular to the direction of the scanning lines relative to a scanning element.
  • the scanning element essentially has a light source for line-by-line illumination of the original image, a photo diode line (CCD line) as an optoelectronic converter and a scanning lens for imaging the scanning lines on the photo diode line.
  • CCD line photo diode line
  • a photodiode line essentially consists of a number of light-sensitive sensor elements arranged in the direction of the scanning lines, a transfer gate and an analog shift register with a number of memory cells corresponding to the number of sensor elements.
  • the scanning light modulated with the image content of the individual pixels of a scanning line is stored in the light-sensitive sensor elements of the photodiode line as charge packets.
  • the charge packets of the current scan lines are transferred from the sensor elements via the transfer gate to the memory cells of the analog shift register.
  • the charge packets are then read out serially from the shift register and converted into an analog voltage, the image signal, in a charge / voltage converter.
  • the image signal is converted into digital image values in a downstream A / D converter, which are then temporarily stored and further processed in a signal processing stage.
  • the scanning speed with which a scanning line is scanned essentially depends on the specific conversion speed per voltage value of the A / D converter used. An increase in the scanning speed There is a limit to the fact that fast A / D converters with correspondingly high operating frequencies are not available or are very expensive.
  • the scanning fineness (pixels / cm) in the direction of the scanning lines depends on the number of light-sensitive sensor elements of the photodiode line and on the width of the image to be scanned.
  • the scanning fineness perpendicular to the direction of the scanning lines is determined by the relative speed between the original image and the scanning element.
  • the scanning fineness can be varied by the imaging scale, in which the scanning objective maps the respective original width onto the photodiode line.
  • Another possibility for changing the scanning fineness is to interpolate between stored image values in order to achieve a greater scanning fineness or to combine stored image values in order to achieve a coarser scanning fineness.
  • 1 is a basic block diagram of a scanner for optoelectronic scanning of image templates
  • FIG. 3 timing diagrams for explaining the invention 1 shows a basic block diagram of a compartment bed scanner for point-by-line and line-by-line optoelectronic scanning of black and white images.
  • a light source (1) for see-through scanning or a light source (2) for top-up scanning illuminates line by line an image template (3) arranged on a template carrier (not shown).
  • the illuminated scanning lines (4) are successively imaged on the light-sensitive surface of an optoelectronic converter in the form of a photodiode line (6) (CCD line) by means of a scanning lens (5), the image template (3) being perpendicular to the direction of the scanning lines (4) directed relative movement to the light sources (1; 2) and to the photodiode array (6).
  • the photodiode line (6) essentially consists of a row of sensor elements (7) aligned in the direction of the scan lines (4) with a number of light-sensitive sensor elements (8) arranged next to one another, a transfer gate (9) and an analog shift register (10) with a number of memory cells (11) corresponding to the number of sensor elements (8).
  • the number of sensor elements (8) determines the number of pixels that can be scanned in a scanning line (4), with each pixel of a scanning line (4) a sensor element (8) of the sensor element series (7) and a corresponding memory cell (11 ) of the shift register (10) is assigned.
  • the photodiode array is, for example, of the KLI 8013 type from Kodak.
  • the photodiode array (6) may have, for example, 8000 light-sensitive sensor elements (8) and memory cells (11). In this case 8000 pixels per scan line (4) can be scanned.
  • the imaging scale with which a scanning line (4) is imaged by the scanning objective (5) onto the sensor element row (7) determines the scanning fineness (pixels / cm) in the line direction, while the scanning fineness perpendicular to the line direction is determined by the relative speed between the image template (3) and the photodiode array (6) is determined.
  • the scanning light modulated with the image information of the individual pixels of a currently scanned scanning line (4) is stored as charge packets Q in each case within an integration time in the light-sensitive sensor elements (8) of the sensor element row (7).
  • the stored charge packets Q of the individual pixels of the current scanning line are removed from the sensor elements (8) via the Transfer the transfer gate (9) into the assigned memory cells (11) of the shift register (10).
  • the charge packets Q are then read out serially from the shift register (10) and fed to a charge / voltage converter (12) of the photodiode line (6).
  • the transfer gate (9) is enabled by a transfer clock of a transfer clock sequence TT on a line (13).
  • the charge packets Q are read out from the shift register (10) by means of a shift clock sequence T s on a line (14).
  • the charge / voltage converter (12) converts the charge packets Q of the individual pixels into voltage values U which are proportional to the charge packets Q. After converting the charge packet Q of a pixel into the voltage value U, the analog charge / voltage converter (12) is reset by a reset clock of a reset clock sequence TR on a line (15) and thus prepared for the conversion of the charge packet Q of the next pixel.
  • the voltage values U generated in the charge / voltage converter (12) are converted into digital image values in an A / D converter (17) clocked by a digitizing clock sequence T D on a line (16), which are then converted into a digital image / D converter (17) downstream signal processing stage (18) are temporarily stored and processed.
  • Transfer clock sequence T ⁇ , shift clock sequence T s , reset clock sequence T R and digitizing clock sequence T D for controlling the scanner are generated in a clock generator circuit (19).
  • Fig. 2 shows timing diagrams for explaining the control of the scanner according to the prior art.
  • the timing diagram (2A) shows the shift clock sequence Ts, which is fed to the shift register (10).
  • the timing diagram (2B) shows the reset clock sequence T R , which resets the analog charge / voltage converter (12).
  • the timing diagram (FIG. 2C) shows the voltage values U which are generated in the analog charge / voltage converter (12) by converting the charge packets Q of the individual pixels according to the prior art.
  • the clock period of the shift clock sequence Ts is equal to the clock period of the reset clock sequence TR and corresponds to the conversion time tw per voltage value of the A / D converter (17) used.
  • the charge packet Q of a pixel is read out of a memory cell (10) of the shift register (10) and processed further.
  • the analog charge / voltage converter (12) is reset by a reset clock of the reset clock sequence TR and is thus prepared for converting the charge packet Q of the subsequent pixel, with the output of the analog charge / voltage converter ( 12) first at the respective black reference level U ref . lies.
  • the voltage values U of the pixels scanned in the image template (3) which represent the scanned image information, appear at the output of the charge / voltage converter (12). These are, for example, the voltage value Ui for the first pixel, the voltage value U 2 for the second pixel and the voltage value U n for the nth pixel.
  • the scanning time is advantageously shortened in the case of a coarser scanning fineness in the line direction in that the number of voltage values U of the pixels of each scanning line to be converted analog / digital is reduced as a function of the desired coarser scanning fineness by At least two adjacent pixels of a scan line are combined and the charge packets Q of the combined pixels are read out in the charge / voltage converter (12) after being read out from the shift register (10), a voltage value U 'representing the image information of the respectively combined pixels.
  • a reduction factor is first determined as the quotient from the number of maximum possible voltage values U per scanning line, which corresponds to the number of sensor elements of the photodiode line, and from the number of voltage values U 'per scanning line resulting from the desired coarser scanning fineness.
  • the reduction factor determines the number of neighboring pixels to be combined and thus the number of charge packets Q to be added in each case.
  • the reciprocal reduction factor is a measure of the shortening of the sampling time according to the method according to the invention compared to the sampling time which results from the prior art.
  • the method according to the invention advantageously ensures that no image information is lost during the scanning of the original and that scanning light sources with a lower light intensity can be used.
  • the method according to the invention can be implemented in a simple manner by a modified control when reading the charge packets Q from the shift register (10) and when converting the read charge packets Q into voltage values U 'in the analog charge / voltage converter (12).
  • the cycle period of the modified shift cycle sequence T's is shortened compared to the shift cycle sequence Ts by the reduction factor or the frequency is increased by the reciprocal reduction factor. The same applies to the transfer clock sequence T' ⁇ .
  • the clock period of the reset clock sequence T'R remains unchanged compared to the reset clock sequence TR according to the prior art and in turn corresponds to the conversion time tw per voltage value of the A / D converter (17) used.
  • the integration time of the photodiode line (6) ie the duration of exposure of the scanning light on the sensor elements (8) of the photodiode array (6), reduced in accordance with the reciprocal reduction factor. Due to the shortened readout time due to the shortened residence time of the charges Q in the sensor element row (7) and in the shift register (10) and due to the shortened integration time, the noise of the photodiode array (6) is advantageously reduced.
  • Fig. 3 shows timing diagrams for explaining the control of the scanner according to the invention for a reduction factor "2".
  • the modified shift clock sequence T's which is fed to the shift register (10), is shown in the time diagram (FIG. 3A).
  • the unchanged reset clock sequence T'R which is fed to the analog charge / voltage converter (12), is shown in a time diagram (3).
  • the timing diagram (2C) shows the voltage values U 'which are generated in the analog charge / voltage converter (12) by converting the added charge packets Q of the combined pixels according to the invention.
  • the clock period of the modified shift clock sequence T's is halved compared to the clock period of the shift clock sequence Ts according to the prior art (FIG. 2; time diagram 2A).
  • the clock period of the reset clock sequence T'R is unchanged from the clock period of the reset clock sequence TR according to the prior art (FIG. 2; time diagram B) and in turn corresponds to the conversion time tw per voltage value of the A / D converter (17) used.
  • a corresponding reduction in the scanning time for a coarser scanning fineness perpendicular to the line direction is achieved in a simple manner by changing the relative speed between the image template (3) and the photodiode line (6).
  • the corresponding charge packets can also be suppressed in the analog charge / voltage converter (12) by a modified residual clock sequence TR, which leads to a shortening of the sampling time, but disadvantageously to loss of Image information would result.
  • the scanner described is used to scan black and white originals.
  • the scanning method according to the invention can of course also be used in color scanners for scanning color originals.
  • the white light coming from the light source is broken down into red, green and blue scanning light by means of a rotating color filter wheel, and the color template is sequentially illuminated with the colored light. tet.
  • the scanning light is then converted in a monochrome photodiode line into the image signals for "red”, "green” and "blue".
  • the color template is illuminated with white light and the scanning light coming from the color template is divided into three color components by color division using dichroic color filters and three monochrome photo diode lines for conversion into the image signals for "red”, “green” and “Blue” fed.
  • the color template is also illuminated with white light and the colored scanning light coming from the color template is converted into the image signals for "red”, “green” and “blue” in a color-selective photodiode array.
  • Corresponding shift registers and A / D converters are then assigned to the individual color channels during color scanning.
  • the invention is also not limited to the field of electronic reproduction technology, but can be used wherever optoelectronic scanning and analog / digital conversion are coupled to one another.

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  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Facsimile Heads (AREA)
  • Facsimile Scanning Arrangements (AREA)
  • Transforming Light Signals Into Electric Signals (AREA)

Abstract

L'invention concerne un procédé pour effectuer un balayage optoélectronique, pixel par pixel et ligne par ligne, de modèles (3) au moyen d'une rangée de photodiodes (6). Cette rangée de photodiodes (6) présente un convertisseur de charge/tension (12) pour convertir les paquets de charge obtenus par conversion de l'information d'image des pixels, en valeurs de tension qui sont converties en valeurs d'image numériques dans un convertisseur A/N (17) monté en aval. Afin de réduire le temps de balayage dans le cas d'un balayage plus grossier, le nombre de valeurs de tension destinées à la conversion analogique/numérique, par ligne de balayage, est réduit par regroupement d'un nombre de pixels adjacents correspondant à un facteur de réduction. Les paquets de charge des pixels regroupés respectifs sont additionnés dans le convertisseur de charge/tension (12) et les paquets de charge additionnés sont convertis en valeurs de tension (U1+U2) des pixels regroupés respectifs. Le facteur de réduction est égal au quotient du nombre des éléments détecteurs (8) de la rangée de photodiodes (6) et du nombre plus faible des valeurs de tension, nécessaire en raison au balayage plus grossier.
PCT/DE1998/000445 1997-03-25 1998-02-16 Procede de balayage optoelectronique WO1998043407A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE19712459.3 1997-03-25
DE1997112459 DE19712459A1 (de) 1997-03-25 1997-03-25 Verfahren zur optoelektronischen Abtastung

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Publication Number Publication Date
WO1998043407A1 true WO1998043407A1 (fr) 1998-10-01

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WO (1) WO1998043407A1 (fr)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2002044421A (ja) * 2000-07-28 2002-02-08 Ricoh Co Ltd 画像読取装置および画像読取装置の制御方法および画像処理装置
DE10146583A1 (de) * 2001-09-21 2003-04-17 Siemens Ag Vorrichtung und Verfahren zum optischen Abtasten einer Substratscheibe

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3867569A (en) * 1974-02-25 1975-02-18 Bell Telephone Labor Inc Compact flatbed page scanner
EP0185487A2 (fr) * 1984-12-14 1986-06-25 Polaroid Corporation Balayeur d'image électronique avec réhaussement des images au niveau du réseau matriciel des couleurs
US5461491A (en) * 1993-12-29 1995-10-24 Hewlett-Packard Company Procedure for reducing processing time for image elements by combining charge of adjacent pixels into a new composite pixel
US5585620A (en) * 1993-12-06 1996-12-17 Nikon Corporation Image signal resolution changing system

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3220667A1 (de) * 1982-06-02 1983-12-08 Canon K.K., Tokyo Festkoerper-bildaufnahmeelement
JPH05122503A (ja) * 1991-10-29 1993-05-18 Ricoh Co Ltd 画像読取装置

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3867569A (en) * 1974-02-25 1975-02-18 Bell Telephone Labor Inc Compact flatbed page scanner
EP0185487A2 (fr) * 1984-12-14 1986-06-25 Polaroid Corporation Balayeur d'image électronique avec réhaussement des images au niveau du réseau matriciel des couleurs
US5585620A (en) * 1993-12-06 1996-12-17 Nikon Corporation Image signal resolution changing system
US5461491A (en) * 1993-12-29 1995-10-24 Hewlett-Packard Company Procedure for reducing processing time for image elements by combining charge of adjacent pixels into a new composite pixel

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