Printing – Multicolor
Reexamination Certificate
2000-01-10
2003-04-08
Hirshfeld, Andrew H. (Department: 2854)
Printing
Multicolor
C400S076000, C400S070000, C400S061000
Reexamination Certificate
active
06543349
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image recording method and apparatus using a multi-beam, in which an image is recorded by moving a plurality of light beams relatively to a sub-scan direction of a photosensitive material and simultaneously carrying out main scan of a plurality of light beams, namely, an image recording method and apparatus in which an image is recorded on a photosensitive material by carrying out main scan of a plurality of light beams while the photosensitive material is being moved in a sub-scan direction.
2. Description of the Related Art
There has conventionally been known, as a method of recording an image on a photosensitive planographic printing plate such as a PS plate, a method in which a photographic film for plate-making (process film) on which the image is recorded is superposed on the photosensitive planographic printing plate.
The photographic film for plate-making on which the image is recorded is generated by image recording processing of an image recording apparatus referred to as a film setter, and development processing of a developing apparatus.
A magazine in which an elongated photographic film for plate-making wound in a layered form is accommodated is set in the film setter.
An exposure drum is rotated at a predetermined speed so as to move the photographic film for plate-making in a sub-scan direction. An image recording apparatus is disposed in a radial direction of the peripheral surface of the exposure drum on which the photographic film for plate-making is closely held.
The image recording apparatus distributes (swings) a plurality of light beams emitted from a laser in an axial direction of the exposure drum by a plurality of optical systems (main scan by a multi-beam system). As a result, main scan is carried out with the plurality of light beams while the photographic film for plate-making is being subjected to sub-scan, and the main scan is carried out repeatedly. The light beams are subjected to on-off control (or duty control) based on image information, and therefore, a predetermined image is recorded on the photographic film for plate-making.
The photographic film for plate-making on which an image is recorded is guided to an ordinary conveying path and discharged from the film setter, and further conveyed to a developing apparatus in a subsequent process.
When a print obtained from a photosensitive planographic printing plate is a color image, it is necessary that photosensitive planographic printing plates be provided respectively for four color components of cyan (C), magenta (M), yellow (Y), and black (K), that is, four sheets of photosensitive planographic printing plate, be prepared for each image.
Respective relative positions of images recorded on four photosensitive planographic printing plates are provided to coincide with one another, and a print of a full-color image can be obtained with four images overlapping with one another.
During recording of images, sub-scan movement of the photographic film for plate-making constantly continues, and therefore, recording of an image is started from a starting position of image recording (an initial position in a region to which light beam is applied in main scan), which comes first after a leading end of the photographic film for plate-making, that is, a position of a line at which main scan can be started, has been detected by the image recording apparatus. At this time, there is no correlation between the sub-scan movement of the photographic film for plate-making and the main scan of light beam.
Accordingly, respective images of the component colors are recorded in a state of being displaced from one another by an amount of about one sub-scan at the maximum. The amount of one sub-scan becomes larger in the widthwise dimension as a beam number of a multi-beam (the number of light beams) increases. For example, when exposure is carried out for 96 lines/mm using 6 light beams, a beam pitch is about 10 &mgr;m, and therefore, the maximum amount of displacement becomes 60 &mgr;m. An allowable amount of displacement in a print is limited to 100 &mgr;m at its maximum, and if an amount of displacement at a starting position of writing amounts to 60% or more of the allowable amount of displacement, the displacement caused by other factors such as a conveying system, a positioning punch hole, and the like is hardly allowed. As a result, color displacement occurs to thereby deteriorate image quality.
SUMMARY OF THE INVENTION
In view of the above-described circumstances, an object of the present invention is to provide an image recording method and apparatus in which an amount of displacement of relative positions of images on a plurality of photosensitive materials can be limited to a pitch of one line irrespective of the beam number of a multi-beam and deterioration of image quality caused by color displacement or the like can be prevented.
A first aspect of the present invention is an image recording method, comprising the steps of: (a) providing at least two sets of image data separated by color, for an image; (b) recording a separated image corresponding to each set of image data on a section of photosensitive material moving in a sub-scan direction while the photosensitive material is being subjected to main scanning by a plurality of light beams; and (c) providing for relative positions of separated images on the section of photosensitive materials to substantially coincide with each other by setting a blank raster line in a first main scan for each section of the photosensitive material.
A second aspect of the present invention is an image recording method according to the first aspect, wherein in the step of providing for relative positions of the images, the number of blank raster lines in the first main scan is set for each section of the photosensitive material, based on a distance between a predetermined reference position on each section of the photosensitive material and a position at which the first main scan is started on that section.
A third aspect of the present invention is an image recording method according to the second aspect, wherein as the distance between the predetermined reference position and the position at which the first main scan is started becomes smaller, the number of blank raster lines is set larger.
A fourth aspect of the present invention is an image recording method according to the second aspect, wherein the upper limit of the number of blank raster lines is equal to the number of light beams in the plurality of light beams, minus one light beam.
A fifth aspect of the present invention is an image recording method according to the first aspect, wherein the blank raster lines are set in order from a leading end of the sheet of photosensitive material, the blank lines being substantially transverse to a direction in which the sheet of photosensitive material is conveyed.
A sixth aspect of the present invention is an image recording apparatus for recording an image on photosensitive material, wherein the image is represented by at least two sets of image data separated by color, the apparatus comprising:(a) image recording means for recording a separated image corresponding to each set of image data on a section of photosensitive material, by carrying out main scans of the photosensitive material with a plurality of light beams; (b) photosensitive material detecting means for detecting that a section of photosensitive material has been conveyed to a position at which an image can be recorded thereon; (c) state detecting means for detecting a state in which a main scan by the plurality of light beams can be started; (d) controlling means for controlling starting a main scan by the plurality of light beams, when the controlling means being in communication with the state detecting means receiving a signal therefrom that a main scan can be started and the photosensitive material detecting means has detected that a section of photosensitive material has been conveyed to a position at which
Fuji Photo Film Co. , Ltd.
Hirshfeld Andrew H.
Nolan, Jr. Charles H.
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