The Research On System Of The Quality Examination And Control Of The Printing Plate Stipple

The modern printing technique is a kind of process to make information transfer and duplicate among different bodys, and the printing plate stipple is the least and most basic printing unit, the microcosmic variety changes the variety that the rank of picture adjusts layer and color on the macro view.Regardless is the tone replication of the whole toneses or a half, the technical keys all rest with the controlling of the degree of the printing plate stipple quality. Although the Computer to Plate(CTP) has already resolved this problem in a large degree, but this problem will be still very outstanding in the most situations of the industrial application at least in the coming several years. The Desk-Top Publishing (DTP), CTF and the color printing technique all have get greater advancement, at the same time the control of the printing plate stipple quality has become the main bottleneck to limit the final product quality int the processing of block insolation, any loss of degree and transforming and extending of the printing plate stipple will result in the serious deviation on the color to print an article.The printing plate stipple optical density not only is the most important foundation physics quantity int the estimating the print quality and control of the print process, but also is the main parameter to evaluate the film produce quality and control print picture effects.And the small variety time of exposure in the process block creation, will result in the obvious variety in the printing plate stipple develops size, that is to say the printing plate stipple optical density will be variety.Meanwhile development of chip stimulated the appearance of the high performance, low cost MCU. Hereafter, design for the small-sized, standardized, intellectualized, high accuracy, high stability of the instrument for measuring the printing plate stipple optical density becomes the very realistic demand."The System of the Quality Examination and Control of the Printing Plate Stipple" design in this article measures and analyzes the printing plate stipple optical density, the printing plate stipple percentage and prints contrast, and can achieve overall accurate enactment in the time of exposure.So it relate to more extensively basic knowledge about the principle of the colorimetry and the density and the halftone color copy.The optical densityand the printing plate stipple percentage calculate expressions have the Moil-Davis' expressions and the Yore-Nielsen expressions etc.. What we use is the Moil-Davis' expressions.The system includes two parts:The first part is an optics system,The optics system includes the optical source, color filter, sample set, and photoelectric detector etc..The light emitting diode, modify light filter, collimation focused lens, color filter group etc. constitute optical system. The light from light source which constituted by light emitting diode and modify light filter through collimation focused lens change into parallelism light, as if demand through color filter, by modulate the color filter can produce red, green and blue ray and carry on an examination to the black and white or the colorful transparent manuscript (Yin slice or sun slice).The second part is an electric circuit system.The electric circuit system is to enlarge signal and make use of SCM to carry on a data calculation, handle, show, control to expose and communicate with computers. For removing zero drift and improve accuracy, we adopted the cut wave amplifier TC7650 and use the double automatically chooses circuit that constituted by the OP07, this road automatically chooses circuit to amplify the weak signal from the silicon battery, the signal after amplify through the voltage-frequency transformation machine VFC320 becomes frequency signal (namely TTL pulse) to send into MCS-51 SCM.The VFC320 which produced by the BB company is a high performance high accuracy V/F conversion machine, its conversion dynamic scope is great, transformation precision is high, the temperature drift is small, linearity degree is nice.Passing by saving and calculation, the SCM send the calculate result into LED to display, and the display part is composed by MAX7219.This instrument used the 232 interface chip MAX232 to transform, and make sure the MCS-51 single chip machine data traffic with the computer and carry on the test data to the computer, and the test data would be carried on a further processing by the computer.After system design complete, I trial-manufactured one experiment sample machine which based on the design project. For the sake of testing the accuracy of the sample machine, I tested the standard density slice, and get the printing plate stipple optical density, the printing plate stipple percentage etc..The testing numerical data manifested:First, the machine is satisfactory to the design request schedule on the accuracy,we can use it to get a valid examination to various physical quantity which include the printing plate stipple optical density, the printing plate stipple percentage, the prints contrast etc. from monochrome and colorful transparent manuscript(Yin slice or sun slice) and so on.Secondly, the machine is intelligentize and miniaturization. The design adopted the automatic control technology by the MCS-51 SCM, we can use it to examine sample on-line, and all measure processes include obtaining the signal, signal amplification, analogy to numeral conversion, data processing, data displaying, controlling exposing expose can automatically achieved.And the stability, precision of the system work attains the design request.However, this is the sample machine for test only, and it is still not perfect somewhere, so produced the certain error.The reason is various: Power supplies inaccurately, unsteadily, which leads to poor quality of the light source; Incomplete machine structure affects the test result by miscellaneous light outside; Certain linearity the silicon battery exists and two amplifier way of the electric voltage in the circuit make measurement not accurate enough. If we take into the improvement from this several aspects, the instrument can completely attain the function practicably.