Communications: directive radio wave systems and devices (e.g. – With particular circuit – For frequency modulation
Patent
1993-10-04
1995-10-17
Reinhart, Mark J.
Communications: directive radio wave systems and devices (e.g.,
With particular circuit
For frequency modulation
B41J 2435
Patent
active
054595053
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to an internal drum laser image setter, i.e. an apparatus for exposing a film or plate covered with a light-sensitive material, the film or plate being supported to that it constitutes part of a circular cylinder ("drum"), to a laser light beam directed substantially from the center of the cylinder to the film or plate.
Internal drum laser image setters (also called internal laser image drum plotters) are used for high accuracy production of images comprising graphics, maps, and text. Examples of known internal drum laser image setters or plotters are disclosed in U.S. Pat. Nos. 4,853,709, 4,595,957 and 3,958,250, and in EP Patent Application No. 0 127 136. An example of a known, so-called external drum laser image setter is disclosed in U.S. Pat. No. 4,122,496.
An increasingly important use of internal drum laser image setters is for production of films for producing high-quality offset printing masks or plates, or for direct production of offset plates, i.e. so-called "prepress" work.
One type of internal drum laser image setter which has become widely accepted in the graphic industry as an efficient and accurate apparatus comprises a range of laser image setters of the types 5100 and 7100 from the company Purup Electronics A/S, Lystrup, Denmark. In these apparatuses, an assembly, a so-called "spinner assembly" comprising a rotating prismatic, light-reflecting element from which the laser light beam is directed to light-sensitive material arranged in the interior of the drum, is moved along a central axis of the drum of the apparatus. The laser light beam received by the prismatic element is output from a laser arranged at one end of the drum. The rotatable light reflecting element is rotated by means of a motor which constitutes a component of the spinner assembly.
The apparatus of the present invention is based on a construction principle which results in an even higher absolute accuracy than that obtainable in the known apparatuses and which provides a number of important advances and advantages which will be apparent from the following. The increased absolute accuracy is of importance, e.g., in four-colour print work, where four films produced in the apparatus are to be aligned in the preparations for the printing process.
The apparatus of the invention for exposing a film or plate comprising a light-sensitive material to a light beam comprises for supporting the film or plate in such a manner that the supported film or plate constitutes at least a part of a substantially circularly-cylindrical surface defining a central axis, laser light-emitter emitting laser light generated by the laser means, a rotatable optically reflecting element and an element-rotating motor, the laser light-emitter being constituted by the second end of an optical fibre means having a first light-receiving end and a second light-emitting end, the first light-receiving end being arranged in juxtaposition to the laser means for receiving the light beam therefrom, and the second light-emitting end being arranged in and supported by the light-directing assembly housing and being in juxtaposition to the rotatable optically reflecting element at a substantially fixed distance therefrom for emitting the light beam to the rotatable optically reflecting element, the rotatable optically reflecting element being arranged relative to the second light-emitting end of the optical fiber so as to direct the light beam emitted to the optically reflecting element to the light-sensitive film or plate, the element-rotating motor being supported by the light-directing assembly housing and having a rotatable output shaft, the optically reflecting element being connected to the output shaft so as to be rotatably driven thereby, and the light-directing assembly housing being supported by the apparatus housing and being movable relative thereto along the central axis, apparatus housing along the central axis, and laser beam on and off, for controlling the operation of the element-rotating mo
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Journal Of Imaging Technology; vol. 11, No. 6, Dec. 1985, Springfield, Virginia, U.S.; pp. 300-305; G. K. Starkweather: "A High Resolution Laser Printer".
Ballegaard Hans P.
Bering Mikael F.
Hansen Agner
Purup Prepress A/S
Reinhart Mark J.
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