Facsimile and static presentation processing – Facsimile – Recording apparatus
Patent
1997-03-06
1998-05-05
Wong, Peter S.
Facsimile and static presentation processing
Facsimile
Recording apparatus
355 77, 428212, 358461, G03B 2732, B32B 702
Patent
active
057483310
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention is in the field of electronic reproduction technology and is directed to a process control strip for visual monitoring and calibration of an exposure process for a recording material, particularly for a printing plate, and is also directed to a method for recording the process control strip.
The point-by-point and line-by-line, rastered exposure of a recording material, for example a film, usually occurs with an electronic recording device, also called an exposer or recorder. For that purpose, image signal values that represent the tonal values to be recorded are supplied to a raster generator in which the image signal values are converted according to a raster function into control signal values for an exposure beam generated in an exposure unit of the exposer. The pixel-by-pixel and line-by-line exposure of the film occurs during a relative motion between the exposure beam and the film to be exposed in that the control signal values turn the exposure beam on and off and thus determine which pixels are exposed as parts of the raster points on the film or are not exposed. The raster function thereby determines the size of the raster points dependent on the tonal values to be recorded.
In the exposure of the film, the real tonal values or, raster point sizes deviate from the desired, nominal tonal values since every pixel and, thus, every raster point is recorded more or less enlarged due to blooming. The deviations between the tonal values that are really generated and the nominal tonal values are referred to as point growths that lead to disturbing changes in tonal value in the reproduction.
The point growths are thereby compensated in the exposer during the film exposure in that the image signal values that represent the nominal tonal values are corrected by what is referred to as a film linearization according to a correction curve determined before the film exposure such that the tonal values really recorded on the film correspond to the nominal tonal values.
After the film exposure, the film exposed in the exposer is developed in a developing station and is used for manufacturing a printing form.
The traditional manufacture of printing plates occurs in two sub-processes. In a first sub-process, a film is exposed with an exposer and the exposed film is developed in a developing station. In a second sub-process, the exposed and developed film, as a master, is copied onto a light-sensitive printing plate in a copier device, whereby slight positive or negative point growths and, thus, falsifications of tonal value can likewise occur. After the copying process, the exposed printing plate is then likewise developed in a developing station.
Calibrations, i.e. settings and checks of the optimum process parameters, corresponding to two sub-processes must thus be undertaken in the traditional manufacture of a printing plate.
The traditional calibration of the first sub-process, namely the point-by-point and line-by-line film exposure in an exposure and the film developing in a developing station, occurs, for example, with the assistance of graduated standardized step wedges that are exposed on the film and co-developed, and via the measurement of the full-tine densities. A constant monitoring of the stability of exposure and development is also involved in practice with the known means. For this reason, adhering to a stable work process has previously occured indirectly by monitoring and by controlling or, setting suitable process parameters such as the intensity of the exposure beam and/or the correction curve in the exposer as well as the development temperature and/or the regeneration rates in the developing station.
The traditional calibration of the second sub-process, namely the image-wise exposure of the printing plate in a copier device and the development of the exposed printing plate in a developing station, often occurs according to the micro-line method with the assistance of precision measuring strips, for example with the FOGRA precision measuring strip P
REFERENCES:
patent: 4004923 (1977-01-01), Hensel
patent: 4183990 (1980-01-01), Uchida
patent: 4504141 (1985-03-01), Yamakoshi
patent: 4588298 (1986-05-01), Nakamura
Patent Abstract of Japan--vol. 8, No. 51 P-259, 1488, Mar. 8, 1984.
Linotype-Hell AG
Toatley , Jr. Gregory J.
Wong Peter S.
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