Incremental printing of symbolic information – Light or beam marking apparatus or processes – Scan of light
Reexamination Certificate
1999-07-28
2001-06-19
Yockey, David F. (Department: 2861)
Incremental printing of symbolic information
Light or beam marking apparatus or processes
Scan of light
C347S234000, C358S001800
Reexamination Certificate
active
06249306
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to methods and apparatus for drawing with multi-beam, and more specifically to a method and apparatus for drawing on a sensitive material or printing plate having a cylindrical shape and rotated about its center axis by applying thereto multi-beam emitted from a light-emitting device line which is composed of a plurality of light-emitting devices arranged along a sub-scanning direction parallel to the center axis and is moved along the sub-scanning direction.
2. Related Art Statement
To make a printing plate (a cylindrical printing plate with many cells engraved according to an image) for use in a rotary press, an original (original film) is conventionally made in advance and then exposed on the printing plate. In this case, drum-type scanners for scanning a film being fixed to a drum for rotation with multi-beam are generally used as image recording devices for making an original.
FIG. 14
is a diagram showing the structure of main parts of a conventional multi-beam (drum-type) scanner.
In
FIG. 14
, the conventional multi-beam scanner includes a drum
141
placed so that its center axis
141
a
is parallel to a sub-scanning direction indicated by an arrow X, and a multi-channel optical head
142
.
The drum
141
is fixedly provided with a photosensitive material (film)
143
along its side surface. The multi-channel optical head
142
includes a plurality of light-emitting devices (LDs)
142
a
arranged along the sub-scanning direction X and a lens
142
b
for forming an image
144
out of beams emitted from the plurality of LDs
142
a
on a drum surface.
The drum
141
is driven by a motor not shown to rotate in reverse to a main-scanning direction indicated by an arrow Y, while the multi-channel optical head
142
is driven by another motor not shown to move along the sub-scanning direction X. At this time, the multi-channel optical head
142
moves a distance equal to the length of the image
144
while the drum
141
rotates once.
With the above described manner, a two-dimensional image is drawn in a spiral fashion onto the photosensitive material
143
(this drawing method is hereinafter referred to as spiral drawing).
In this way, the scanner of
FIG. 14
scans the photosensitive material
143
with the multi-channel optical head
142
including the plurality of LDs
142
a
, thereby allowing high-speed drawing according to the number of LDs
142
a.
In recent years, a Computer to Plate (CTP) system for drawing an image by directly applying laser beams to a printing plate has been widely employed for plate making instead of exposing the original onto a printing plate as described above. This CTP direct plate making eliminates processes of making and exposing an original, thereby allowing great reduction in time required for plate making.
In the CTP system, as the image recording device for drawing an image onto a printing plate, the scanner of
FIG. 14
is used, for example, with a printing plate instead of the drum
141
and the plurality of high-power LDs
142
a
so as to engrave pits on the printing plate.
As a result of using the plurality of high-power LDs, however, the conventional multi-beam CTP scanner is prone to be out of order due to damage to part of the LDs, and therefore plate making operation cannot be performed until the damaged LD is repaired or exchanged. If drawing processing is performed with the damaged LD line (in which one or more LDs out of the plurality of LDs are damaged), an image obtained thereby is of poor quality, lacking a lot of lines.
Note that the above mentioned problem exists in other multi-beam scanners not for CTP, with varying frequencies of occurrence of LD damage.
Therefore, a drawing method or apparatus capable of drawing an image using multi-beam even with partially damaged LDs has been highly expected.
SUMMARY OF THE INVENTION
Therefore, an object of the present invention is to provide a multi-beam drawing method and apparatus capable of drawing with partially damaged LDs.
The present invention has the following features to attain the object above.
A first aspect of the present invention is directed to a multi-beam drawing method for drawing on a sensitive material or printing plate having a cylindrical shape and rotated about a center axis thereof by applying thereto multi-beam emitted from a light-emitting device line which is composed of a plurality of light-emitting devices arranged along a sub-scanning direction parallel to the center axis and is moved along the sub-scanning direction, the method comprising the steps of:
detecting damage to any of the light-emitting devices;
selecting one of a plurality of partial light-emitting device lines obtained by partitioning the light-emitting device line at a damaged light-emitting device as an effective light-emitting device line; and
applying the multi-beam emitted from the partial light-emitting device line selected as the effective light-emitting device line to the photosensitive material or printing plate for drawing.
According to the first aspect, drawing can be made with partially damaged LDs. As a result, inconvenience that drawing cannot be made until exchange or repair of the damaged LD
12
a
is completed can be eliminated, allowing direct drawing onto the printing plate using vulnerable, high-power LDs.
According to a second aspect, in the first aspect, in the selecting step, a partial light-emitting device line including the largest number of light-emitting devices is selected from among the plurality of partial light-emitting device lines.
According to the second aspect, drawing can be made at high speed.
According to a third aspect, in the first aspect, in the multi-beam applying step, a moving speed of the light-emitting device line is changed according to the number of light-emitting devices included in the partial light-emitting device line.
According to a fourth aspect, in the third aspect, the moving speed of the light-emitting device line is changed so that the light-emitting device line is moved a distance equal to a length of an image to be formed on the photosensitive material or printing plate out of the multi-beam emitted from the partial light-emitting device line selected as the effective light-emitting device line while the photosensitive plate or printing plate rotates once.
A fifth aspect of the present invention is directed to a multi-beam drawing apparatus for drawing on a sensitive material or printing plate having a cylindrical shape and rotated about a center axis thereof by applying thereto multi-beam emitted from a light-emitting device line which is composed of a plurality of light-emitting devices arranged along a sub-scanning direction parallel to the center axis and is moved along the sub-scanning direction, the device comprising:
detecting means for detecting damage to any of the light-emitting devices;
selecting means for selecting one of a plurality of partial light-emitting device lines obtained by partitioning the light-emitting device line at a damaged light-emitting device as an effective light-emitting line; and
means for applying the multi-beam emitted from the partial light-emitting device line selected as the effective light-emitting device to the photosensitive material or printing plate for drawing.
According to the fifth aspect, drawing can be made with partially damaged LDs. As a result, inconvenience that drawing cannot be made until exchange or repair of the damaged LD
12
a
is completed can be eliminated, allowing direct drawing onto the printing plate using vulnerable, high-power LDs.
A sixth aspect of the present invention is directed to A recording medium recording a program to be executed in a multi-beam drawing apparatus for drawing on a sensitive material or printing plate having a cylindrical shape and rotated about a center axis thereof by applying thereto multi-beam emitted from a light-emitting device line which is composed of a plurality of light-emitting devices arranged along a sub-scanning direction parallel to the center
Isono Koichi
Matsuo Takahiro
Dainippon Screen Mfg. Co,. Ltd.
Ostrolenk Faber Gerb & Soffen, LLP
Yockey David F.
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