EP0854034A1 - Verfahren und Vorrichtung zur Belichtung von blattförmigem Material - Google Patents

Verfahren und Vorrichtung zur Belichtung von blattförmigem Material Download PDF

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Publication number
EP0854034A1
EP0854034A1 EP98200125A EP98200125A EP0854034A1 EP 0854034 A1 EP0854034 A1 EP 0854034A1 EP 98200125 A EP98200125 A EP 98200125A EP 98200125 A EP98200125 A EP 98200125A EP 0854034 A1 EP0854034 A1 EP 0854034A1
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EP
European Patent Office
Prior art keywords
irradiating
central axis
sheet
angle
irradiating means
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Withdrawn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
EP98200125A
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English (en)
French (fr)
Inventor
Peter Videcrantz
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.)
Scanview AS
Original Assignee
Scanview AS
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Filing date
Publication date
Application filed by Scanview AS filed Critical Scanview AS
Publication of EP0854034A1 publication Critical patent/EP0854034A1/de
Withdrawn legal-status Critical Current

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41B—MACHINES OR ACCESSORIES FOR MAKING, SETTING, OR DISTRIBUTING TYPE; TYPE; PHOTOGRAPHIC OR PHOTOELECTRIC COMPOSING DEVICES
    • B41B19/00—Photoelectronic composing machines
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41B—MACHINES OR ACCESSORIES FOR MAKING, SETTING, OR DISTRIBUTING TYPE; TYPE; PHOTOGRAPHIC OR PHOTOELECTRIC COMPOSING DEVICES
    • B41B21/00—Common details of photographic composing machines of the kinds covered in groups B41B17/00 and B41B19/00
    • B41B21/16—Optical systems

Definitions

  • the present invention relates to an apparatus for and a method of irradiating a sheet-like material, in particular irradiation of a sheet-like material in an internal drum image setter.
  • This problem may be caused by temperature differences in the image setter or ageing, deformation or offsetting of the drum or the guides guiding the spinner assembly therein.
  • Image setters may nowadays be manufactured and temperature controlled in a manner so that the error relating to deformation of the drum is quite small. For this reason, these image setters are rendered very expensive due to the thermostating and the rugged and heavy design of e.g. the drum in order to prevent thermal deformation thereof.
  • the typical acceptable error of the relevant parts of an internal drum image setter is ⁇ 10 ⁇ m.
  • JP 6198956 A a method of compensating for the tilting of a drum is disclosed.
  • the distance between the rotating drum and a LED print head is kept constant by driving piezoelectric elements upon which the LED is mounted.
  • a correction which may take into account misalignment of e.g. the guides or the spinner assembly in relation to the drum is provided by e.g. controlling the movement of at least part of the spinner assembly in the internal drum at an angle to the axis of the internal drum.
  • the would-be optical axis of the spinner assembly as defined by the guides guiding the spinner assembly i.e. the optical axis of a standard spinner assembly guided by the guides
  • the deviation may be compensated for by this movement of the at least part of the spinner assembly in order to, in fact, e.g. have the optical axis of the spinner assembly coincide with (or at least be brought closer to) the axis of the internal drum.
  • the present invention relates to an apparatus for irradiating a sheet-like material, the apparatus comprising:
  • a typical deviation in e.g. internal drum image setters is the problem that the guides guiding the irradiating means do not guide the irradiating means correctly either due to offsets in the positioning of the guides or due to irregularities of the guides themselves.
  • deformations or deviations on the order of ⁇ 0-50 ⁇ m may be compensated for.
  • larger deformations such as ⁇ 0-1000 ⁇ m, ⁇ 0-500 ⁇ m, ⁇ 0-200 ⁇ m, or ⁇ 0-100 ⁇ m may be compensated for - depending solely on the moving means selected.
  • a "substantially circularly cylindrical surface” may and, in fact, will typically be slightly deformed from the perfect circularly cylindrical shape. This deformation may be counter-acted by the movement according to the invention.
  • the term "substantially along the first central axis" will cover the typical situation where path of the irradiating means actually deviates from this axis. This deviation is that compensated for or at least reduced by the present invention.
  • the movement of the irradiating means may be both a simple translation thereof or e.g. different movements of different parts thereof in order to obtain a rotation thereof.
  • the direction of the movement of the irradiating means is a direction substantially perpendicular to the first central axis.
  • the preferred moving means are adapted to move the irradiating means in two different directions both being at an angle to the first central axis.
  • providing means for moving the irradiating means i.e. typically at least the part of the spinner assembly holding the optical elements thereof, will enable the apparatus to compensate for alignment errors caused by thermal changes in the apparatus or wear/ageing causing the drum to e.g. not being perfectly circular or causing the guides to e.g. not guide the irradiating means along the correct path.
  • Typical alignment errors of the guides may be those of the guides not being perfectly plane, the guides being bent due to contraction or prolongation of the frame or other parts of the image setter - due to temperature changes or the like.
  • the present irradiating means may be a standard spinner assembly or only the part thereof holding the optical elements thereof.
  • the spinner assembly that define the optical axis, that is, at least the light directing element, typically being the rotating mirror, and a light emitting means, typically being a laser, a modulator or a lens, launching the radiation towards the light directing element, movable by the moving means.
  • the apparatus comprises an elongated means having a second central axis extending at least substantially along the first central axis inside the holding means, and usually the irradiating means are adapted to be translated along the elongated means.
  • the elongated means may be the guides along which the spinner assembly is translated.
  • One of several possibilities of moving the irradiating means in relation to the axis of the holding means is to have the moving means be adapted to move the elongated means in the direction at an angle to the first central axis.
  • a standard spinner assembly or the like may be used, whereby the irradiating means may be substantially immovable in relation to the second central axis in a direction at an angle to the second central axis.
  • standard spinner assemblies are not able to move in directions at an angle to that defined by the guides.
  • the moving means be adapted to move the irradiating means in a direction at an angle to the second central axis of the elongated means.
  • the elongated means may be standard guides in internal drum image setters, where only e.g. the spinner assembly need be replaced in order to obtain the advantages of the present invention.
  • the second central axis of the elongated means is substantially immovable in relation to the first central axis in a direction at an angle to the first central axis.
  • the holding means may, for a number of reasons, become deformed.
  • the most suitable axis of the holding means for the irradiating means to follow will be an axis following the centre of the holding means.
  • the centre of a deformed drum may not be straight throughout the drum.
  • a deformity of the holding means may mean that the axis defined thereby is not straight or that it does not coincide with that defined by the optical elements of the irradiating means when guided by the guides.
  • the optimal axis to follow will depend on the deformity - and, in fact, the size of the sheet of material to be irradiated.
  • the irradiating means should follow the axis of the holding means.
  • the moving means are adapted to move the irradiating means in a manner so that an optical axis of the irradiating means is translated substantially along the first central axis and in a predetermined relationship thereto.
  • This predetermined relationship may be a constant distance therefrom in a given direction or any other reproducible relationship.
  • controlling means for controlling the moving means may comprise storing means for holding information for use in the controlling means when controlling the moving means.
  • Such information may be information depending on a position of the irradiating means along the first central axis. In this manner, the information may be read from the storing means and used in the movement of the irradiating means.
  • One manner of holding the data and using it is having the data relate to a number of positions along the first central axis.
  • This data may be stored consecutively in the order in which the irradiation means travels along the axis of the holding means in the storing means. From the storing means, the data may be read consecutively or it may all be read at the same time.
  • Another manner of holding the data may be in the form of equations or parameters for use in equations, such as parameters for polynomials.
  • the data relating to a given position along the first central axis may then be calculated when required.
  • a suitable moving means is one comprising a first and a second element flexibly interconnected and a first force exerting means engaging the first element and exerting a force on the second element in a first direction.
  • the first element at least partly encloses the second element in a given plane, and wherein at least part of the second element is displaceable in the given plane in relation to the first element, and the first force exerting means is fastened to the first element and acts on the second element in the first direction being at least partly in the given plane.
  • two such elements may be assembled, or a signal moving means may be adapted to movement in two directions.
  • Such a moving means may further comprise a third element flexibly interconnected to the first element, and a second force exerting means engaging the first element and exerting a force on the third element in a second direction being different from the first direction.
  • the first and second force exerting means comprise piezo-electric means.
  • the second element at least partly encloses the third element in the given plane, the second and third elements being flexibly interconnected, and the third element being displaceable in relation to the second element in the given plane, the second piezoelectric means is fastened to the first or second element and acts on the third element in the second direction being at least partly in the given plane, and the first and the third elements comprise means for engaging with or for fastening to the frame and the irradiating means, respectively.
  • a central part thereof (the third part) may be moved in two dimensions in the given plane, which normally does not comprise the first or the second axes.
  • This element has the advantage that it may be quite stiff in the direction perpendicular to the plane in which the central part may be moved.
  • elements providing three dimensional translation may be used so as to e.g. also provide translation of the irradiating means in the direction of the first axis.
  • the present invention relates to a method of irradiating a sheet-like material, the method comprising:
  • the irradiating means may be moved so as to correct any misalignments or the like in the apparatus.
  • the irradiating means are translated along an elongated means defining a second, central axis substantially along the first central axis.
  • the movement of the irradiating means is in a direction toward the first central axis, so as to have an optical axis of the irradiating means follow the path intended - or at least be brought closer thereto.
  • the first of the many methods of providing the movement of the irradiating means is that wherein the elongated means are moved in the direction at an angle to the first central axis.
  • the irradiating means need not be moved to any substantial degree in the direction at an angle to the first central axis in relation to the elongated means, as the movement may be obtained by the movement of the elongated means.
  • the elongated means may be substantially stationary in relation to the first central axis.
  • the irradiating means may be moved in the direction at an angle to the first central axis in relation to the elongated means in order to provide the movement desired
  • movement of the irradiating means is effected by moving means controlled by controlling means on the basis of data stored in a storing means.
  • moving means controlled by controlling means on the basis of data stored in a storing means.
  • the invention relates to a method of calibrating an apparatus for irradiating a sheet-like material, the apparatus comprising:
  • the reference image comprises alignment marks
  • the test image comprises corresponding alignment marks
  • the relative positioning therebetween is used in the comparison step.
  • the reference image may be a virtual reference image, such as an image stored digitally in a memory and relating to a pre-defined reference image, a picture of which has been obtained by eg a digital camera.
  • a relatively simple pattern of marks may be used for determining the position and angle of the irradiating means in relation to the actual center of the holding means at the longitudinal position of the irradiating means thereof.
  • the means for determining the offsets comprise an image generating device, such as a digital camera or a scanner obtaining images of the vicinities of the alignment marks of the reference image and means for, on the basis of the images acquired, determining the offsets.
  • the comparison of the two images may be on a point-to-point basis, where the relation between a point in the irradiated test image and the corresponding point in the reference image. In this situation, only the areas of the two images close to the points need be evaluated and eg obtained using a digital camera.
  • the full images may be eg scanned in order to generate two images to be compared (of which the reference image may be an image stored and used for each calibration).
  • a high-resolution image of the test image may be obtained using eg a flat-bed scanner.
  • a calculating means may be comprised in the system in order to receive the image or offset data and for determining the data for use in the irradiating apparatus and method for compensating the alignment errors in subsequent irradiations.
  • irradiating apparatuses of the present type automatically position the sheet-like material in the drum, irradiate, and some even and develop, the sheet-like material afterwards.
  • the present method may electronically correct the apparatus or, if the misalignments etc. are too large, print out a set of instructions to eg an operator in order to have this person perform a first coarse re-alignment of the instrument. Subsequently, a new test image is produced, and the method may decide to perform the remaining correction electronically.
  • the electronic calibration may be a dynamic correction which requires data to be read in each subsequent calibration.
  • the method preferably comprises the step of storing the data for use in subsequent irradiations.
  • the present invention relates to a calibrating means for providing calibration data for use in calibration of the above-mentioned irradiating apparatus, the calibrating means comprising:
  • the information relating to the reference image may be the image itself (any physical representation thereof) or data relating to the image having been generated by eg a digital camera, a scanner or the like.
  • the calibrating means may comprise means for transferring the data derived to the irradiating apparatus for future correction during irradiations.
  • the deriving means also derive data relating to the direction of the irradiating means, typically of the optical axis thereof, in relation to a given direction, such as the actual direction of the first central axis on the actual position along this in the holding means.
  • the means for determining the relative positioning of one or more of the alignment marks preferably comprise a digital camera for generating image data relating to the one or more alignment marks, the image data relating to an alignment mark comprising image data relating to both the actual alignment mark of the reference image and to the corresponding alignment mark of the test image.
  • the preferred spinner assembly 10 is guided by linear guides 12 inside a drum (not illustrated).
  • the optical axis of the spinner assembly 10 is believed or hoped to be identical to the axis of the drum (not illustrated).
  • Both the present spinner assembly 10 and in standard spinner assemblies typically comprises a laser/modulator 2 and a spinner 3 comprising a spinner motor and a rotating mirror.
  • the spinner assemblies 10 are usually translated along the axis of the drum by a lead screw 6 driven by a motor 5.
  • the spinner assembly 10 has been divided into two parts 10' and 10'' where the part 10' is in direct engagement with the guides 12, but where the part 10'' is not. This is the major difference between the present spinner assembly 10 and those of standard internal drum laser image setters.
  • the parts 10' and 10'' are interconnected by moving means 7 and 8, as described below, in order to allow the part 10'' to move in relation to the part 10' and the guides 12, which may define a path where the optical axis of the optical elements on the part 10'' if not movable in relation thereto, does not coincide with the axis of the drum.
  • Fig. 2 illustrates the preferred moving means 20 having two piezo-electric elements 24 and 26 anchored in the parts 28 and 30 of the means 20 and acting, when prolonged or shortened, on the parts 32 and 34 of the means 20.
  • a hole 40 is provided, through which the optical axis of a standard spinner assembly is to pass.
  • the broken lines indicate holes in which the piezo-electric elements 24 and 26 are positioned and fastened (at the ends thereof remote from the hole 40).
  • Providing a means 20 at each end of the part 10'' for interengagement with the part 10' will enable the system to translate or rotate the optical axis of the assembly in relation to the path defined by the guides 12 of the system.
  • the spinner assembly part 10'' is fastened to the means 20 adjacent to the hole 40.
  • the element 24 when being prolonged, will push that part of the means 20 which is encircled by the cut-away part 36 and, thus, the hole 40 (and therefore the actual end of the part 10'' of the spinner assembly 10), away from the anchoring part 28.
  • the element 26 when being prolonged, will push that part of the means 20 which is encircled by the cut-away part 38 and, thus, the hole 40 (and therefore the actual end of the part 10'' of the spinner assembly 10), away from the anchoring part 30.
  • the means 20 are furthermore, at the side 42, in engagement with the part 10' and therethrough with the guides 12 of the image setter.
  • the spinner assembly part 10'' of the present system may be translated or rotated in relation to the path defined by the guides 12 by supplying a voltage to the elements 24 and 26 and thereby prolonging/shortening these.
  • the piezo-electric elements 24 and 26 preferably bias (i.e. continuously exert a force on) the respective elements. Translating the hole 40 towards a piezo-electric element 24 or 26 is then performed by shortening the element 24 or 26.
  • the interconnection between the elements may be a resilient interconnection, or resilient means may be inserted to provide this counteracting.
  • the means 20 should be manufactured from a suitable material. Providing a moving means 20 from e.g. 25 mm steel will provide a means 20 suitably stiff in order to not vibrate during translation of the spinner assembly 10 during operation.
  • the force to be exerted by the elements 24 and 26 will be substantial - such as in the area of up to 100 N.
  • a maximum prolongation of the elements 24 and 26 of 100 ⁇ m is desired.
  • a prolongation of this size will require the exertion of on the order of 70 N by the elements 24 and 26.
  • This, however, is not a problem using standard piezo-electric elements, such as P-245.30 or P-244.30 from Physik Instrumente GmbH & Co.
  • One of the advantages of using piezo-electrical elements is that they are able to perform small translations with a high precision and while exerting a large force and in a well-controlled manner. This provides a precise control of the movement of the irradiating means.
  • the presently preferred piezoelectric elements are able to exert a force in the vicinity of 600N.
  • the voltages fed to the elements 24 and 26 of the moving means 7 and 8 are constantly updated in order to maintain the optical axis defined by the optical elements 2 and 3 of the part 10'' as close as possible to the axis of the drum as defined at the actual position of the assembly 10 in the drum.
  • Data relating to the voltages required at a given position in the drum may be derived from a storage means of the system. These data may be stored in any suitable manner, such as in digital form for use in a computer means controlling the voltages fed to the elements 24 and 26.
  • This data may, as described above, e.g. be read consecutively as a function of the position of the assembly 10 in the drum.
  • the preferred method of providing data relating to the desired movement of the spinner assembly 10 is: providing an irradiated test image of a standard pattern comprising a number of marks - typically crosses, and comparing the resulting image to a similar calibration image.
  • the difference in locations of the resulting marks in the image and the reference image will provide information relating to the desired translation of the part 10'' of the spinner assembly 10 in relation to the axis of the drum.
  • a cross section of a drum 1 is illustrated wherein a sheet 50 of photo-sensitive material is positioned during irradiation. Also illustrated is the optical axis of the spinner assembly part 10'' - the z-axis -, and x- y-axes have been defined perpendicular to the z-axis.
  • the irradiation is performed while providing a constant voltage to the elements 24 and 26, the voltage being one providing a prolongation half the maximum prolongation of the elements 24 and 26.
  • Fig. 3 the final, resulting image is illustrated comprising a number of irradiated crosses 52 having been irradiated directly in the y- and the x-direction from the optical axis (the z-axis) of the spinner assembly part 10'' towards the drum 1.
  • the desired translation and/or rotation of the spinner assembly part 10'' in the x- and y- direction may be determined for each position along the first central axis in which crosses are generated and therefrom, such as by interpolation, as a function of the position along the z-direction of the spinner assembly 10 in the drum 1.
  • Fig. 4 is illustrated one method of obtaining the images from which the determination of the offsets may be performed.
  • a digital camera 100 is moved in the illustrated x- and y-directions and obtains pictures each illustrating one cross 52 from the test image and a circle 54 from the reference image. From this image, the offset of the centers of the two figures may easily be determined. Alternatively, the camera 100 may obtain a picture having all the crosses and circles at the same time. This, however, requires a higher resolution.
  • the offsets may be put into a calculation routine in order to provide information of the required prolongation/shortening of the elements 24 and 26 - or the voltage required in order for it to have the correct length - at each of the positions of the spinner assembly part 10'' along the z-axis.
  • the required voltages of the two elements 24 and 26 may be fitted by a curve or intermediate values may be determined in order to, in fact, correct the position and/or angle of the irradiating means at more positions than there are cross-positions in the reference image. This also provides a better accuracy of the irradiation between the positions along the z-axis used for the calibration.
  • the moving means 7 and 8 may be positioned at the ends of the guides 12 instead of the spinner assembly 10. In this manner, a standard assembly 10 may be used.
  • the correction may also be performed by not displacing the spinner assembly or the guides but the drum itself.
  • the drum is typically desired positionally stable in order to have its position known in relation to eg the feeding mechanisms, but a correction thereof is quite possible.
EP98200125A 1997-01-20 1998-01-19 Verfahren und Vorrichtung zur Belichtung von blattförmigem Material Withdrawn EP0854034A1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DK7097 1997-01-20
DK7097 1997-01-20

Publications (1)

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EP0854034A1 true EP0854034A1 (de) 1998-07-22

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0217136A2 (de) * 1985-09-03 1987-04-08 Scangraphic Dr. Böger GmbH Photosetzgerät
JPH0286263A (ja) * 1988-09-21 1990-03-27 Fuji Photo Film Co Ltd 画像情報読取方法および装置
GB2264793A (en) * 1992-02-19 1993-09-08 Gerber Systems Corp Error compensating optical scanner
JPH0792414A (ja) * 1993-09-22 1995-04-07 Dainippon Screen Mfg Co Ltd 円筒内面走査装置

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0217136A2 (de) * 1985-09-03 1987-04-08 Scangraphic Dr. Böger GmbH Photosetzgerät
JPH0286263A (ja) * 1988-09-21 1990-03-27 Fuji Photo Film Co Ltd 画像情報読取方法および装置
GB2264793A (en) * 1992-02-19 1993-09-08 Gerber Systems Corp Error compensating optical scanner
JPH0792414A (ja) * 1993-09-22 1995-04-07 Dainippon Screen Mfg Co Ltd 円筒内面走査装置

Non-Patent Citations (3)

* Cited by examiner, † Cited by third party
Title
G.K. STARKWEATHER: "A High Resolution Laser Printer", JOURNAL OF IMAGING TECHNOLOGY, vol. 11, no. 6, December 1985 (1985-12-01), SPINGFIELD,VIRGINIA,USA, pages 300 - 305, XP002035425 *
PATENT ABSTRACTS OF JAPAN vol. 014, no. 273 (E - 0940) 13 June 1990 (1990-06-13) *
PATENT ABSTRACTS OF JAPAN vol. 095, no. 007 31 August 1995 (1995-08-31) *

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