Figure 5 Figure 6 Figure 7 Garden Hand Tools,Hoe Garden Tool,Gardening Hoe,Hand Shovel Ningbo Smile tools Co.,ltd , https://www.nbsmiletools.com
The contact screen is affixed with the photosensitive film and placed on the photosensitive film holder in the camera dark box (the “contact†of the contact screen results from this), and when the light is exposed, the light passes through the light hole on the screen. Exposure imaging on the photosensitive sheet. Because the edge of the screen surf hole is smudged, the exposure amount in the middle of the exposure point is large, the exposure amount to the surrounding is gradually reduced, and the sensitization characteristics of the photographic film are combined, thereby forming a network with different sizes and equal intervals, as shown in FIG. 5 shows. 
3, electronic laser screening:
As shown in Fig. 6, whether it is a glass screen screen screen or a contact screen screen screen screen, it is done by hand; and the screen angle of each color screen is different, and the workload is large; the type of screen screen is limited, and the special network points are applied. restricted.
With the development of the electronic color separation machine, the appearance of the dot network computer enables the electronic color separation machine to transmit the obtained digital signal to the outlet computer of the electrical extension image output recording system according to the strength of the scan input light, and through the comparison circuit. Calculate the size of the outlets by the outlet computer, control the control signals of the laser recording system together with the addresses of outlets, such as the shape of the outlets, the angle of the outlets, and the number of screens, etc., and add the control signals to the optical modulator to control the input of the optical modulators. In the working state, the optical signal controlled by the modulator is finally scanned on the photosensitive film of the output roller of the electronic color separation machine to meet the requirements of the original document and the design requirements (Figure 7).
Electronic laser screening advantages:
(1) The network is real, with high density, good precision, and clear edges.
(2) Each mesh network point consists of many tiny ideas. The number of these dots can be determined by the resolution of an output system such as a laser photosetter. Therefore, it is possible to satisfy the reproduction of fine-graded images with high definition, rich gradation, and good reproducibility. Figure 8 shows a 50% halftone screen with 40 sub-network dots. The output of the laser imagesetter is 1270 dots per inch.
(3) Dots of different shapes can be generated at different tones, and it is easy to control the dot expansion. In different color versions, it is possible to obtain dots with different screen angles and different screens, which makes it easy to control the printing quality.
Figure 8
The formation and production mechanism of dots in printing manuscripts
2. Contact screen screening: