Application of flash lamp in digital monitoring system of high-speed printing machine (II)
2 flash lamp realizes the function of electronic shutter "Although this is only a high-speed printer in the load experiment, when the working speed is more than 3 M/s, considering that the print image captured by this system is not deformed and the detection accuracy of this monitoring system, the maximum distance of the print movement during the exposure period cannot exceed 0.1 mm, it can be concluded that the maximum exposure time of the image sensor is
, that is, the minimum required shutter speed is 1/30 ms, about 33% 8. It is realized by mechanical structure or electronic shutter At present, the design of such shutter speed is more complex, but the light and off of the flash can achieve such a fast shutter speed. Cover the lens with an opaque shell, and use the flash as the light source. When the flash does not flash, because the shell is opaque, the light entering from the outside can be ignored, and the image sensor is in a dark environment, which is equivalent to the state before the shutter is not opened; When the flash lamp flashes, the image sensor is exposed instantly, which is equivalent to the shutter opening; After the flash, the image sensor is in a dark environment, which meets the experiment of large samples and full-size samples when the shutter is closed. In this way, the light of the flash plays the role of the shutter, and the shell reduces the external light entering the image sensor as much as possible, so as not to affect the image quality.
of the above two flash trigger circuits, the first is the simplest trigger method, The realization is also the simplest. In the digital monitoring system of high-speed printing machine, the aperture, zoom and focusing electric three variable lenses are used, so the first kind of flash trigger circuit that is easy to realize can be used. As shown in Figure L, resistance ruler The ruler limits the current action when charging capacitors C and C, and the size of and C determines the length of time from charging to flash preparation of J trigger circuit on flash J. according to the law of capacitor charging, Assuming that C. and the time of full charge are T1 and T2 respectively:
3 application in the digital monitoring system of high-speed printing press
the digital monitoring system of high-speed printing press is a system for digital real-time monitoring of the print quality of high-speed printing press. When this system monitors the print quality, once the flash trigger circuit receives the synchronous trigger pulse signal sent by the image sensor or the main control system, When the working speed of the printing machine reaches 200 m/min or above, when the incandescent lamp or natural light is used as the light source, the print image captured by the digital monitoring system of the high-speed printing machine is deformed, even blurred, and cannot truly reflect the quality of the print. When the flash is used under the same other conditions, Figure 3 and 4 show the images of the high-speed moving fan (greater than 200 m/min) taken by the system when using different light sources.
this paper introduces the application of flash lamp in the digital monitoring system of high-speed printing machine. The effect of successful application in industrial field shows that, The flash lamp can provide a stable light source with sufficient brightness, and the most important thing is that its continuous time of illumination can be used as the shutter opening time of CMOS image sensor and easy to control the display in the data center. It can enable the high-speed printer monitoring system based on CMOS image sensor to clearly touch the digital photos of high-speed moving prints, and can make this system meet the requirements of high-speed printers for print quality monitoring. Therefore, CMOS light lamps can be used in the industrial full digital screw monitoring system based on CMOS sensors.
Wang Dawei, Xu Yaoliang, Li yuzeng, sun Xusheng
(1. School of mechanical and electrical engineering and automation of Shanghai University; 2. Department of information control of Shanghai Electric Power University)
Journal of Shanghai University: Natural Science Edition
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