Change of laser light source of the hottest semico

2022-10-18
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This paper introduces the principle and general method of changing the laser source of semiconductor laser Imagesetter from infrared laser source (wavelength 780nm) to red laser source (wavelength 633nm)

"since September, 1998, with the continuous development of China's crackdown on smuggling, the most obvious impact on the printing equipment industry is the rising price of imported Phototypesetting films. The price of imported Phototypesetting films has generally increased by 30% compared with the beginning of 1998. Moreover, the inventory of imported Phototypesetting films on the market shows a downward trend. Insiders estimate that the price of imported Phototypesetting films still has room to continue to rise." (excerpted from "China printing materials business information" 98/10), this has further widened the already large gap between the price of imported Phototypesetting films (yuan/m2) and the price of domestic Phototypesetting films (yuan/m2) (the price of imported Phototypesetting films is about yuan/m2, and the price of domestic Phototypesetting films is about yuan/m2). What makes some Phototypesetting users uneasy is that some imported Phototypesetting films are out of stock nationwide. So why don't these Phototypesetting users use cheap domestic Phototypesetting films instead of expensive imported films with insufficient supply? In addition to the quality and stability, another important reason is the problem of the laser light source used in the laser Imagesetter discussed in this paper

I Laser light source of laser Imagesetter

Table 1 list of light sources used by laser imagesetters at home and abroad

He Ne laser (632.8nm) semiconductor infrared laser (780nm) semiconductor red laser

(nm) semiconductor red laser

(633nm) Agfa selectset series

agfa avantra series

racing angel dolve series

Hangzhou CBTX series from the first time we saw such things when we were young to now series

Changchun jzj series studioset2000

ultre e/p/3000/4000

ecrm VR series

f91 series (some early) Hercules Pro

accuset series

Ultre vision series

pather Pro Series

ECRM is expected to knock out

ECRM vrl/hs series

ECRM drummer

dotmate series

cross field series

F91 series (part) screen ft-r series F91 series (latest)

Table 1 shows the laser light sources used by laser imagesetters at home and abroad. Because the production process and technology of Laser Phototypesetting films become more and more complex with the increase of photosensitive wavelength, and the production of domestic laser phototypesetters began to be put on the market with He Ne laser as the light source (wavelength 632.8nm), the domestic laser Phototypesetting films are dominated by 6328 soft films with shorter wavelength, which have stable quality and large market share. Until recent years, domestic 670 and 780 soft films have been listed, However, there is still a certain gap between its quality and stability and imported film. In order to adapt to this domestic situation, domestic and foreign laser Imagesetter manufacturers have abandoned infrared wavelength laser light sources and used 6328 type He Ne laser light source or semiconductor laser light source (wavelength nm) smeco close to 6328 type. It is worth noting that semiconductor lasers are used by many imagesetter manufacturers because of their simple control and optical system, high light source efficiency and long laser life (about 200000 hours)

II. The photosensitive curve of domestic 6328 type phototypesetting film is shown in Figure 1. From Figure 1, it can be seen that the photosensitive peak of domestic 6328 type phototypesetting film is between nm, and the curve on the left of the peak is flat, and the curve on the right of the peak is steep. Therefore, it is appropriate to use nm laser to expose 6328 type film for semiconductor laser light source, while using nm laser to expose 6328 type film will cause problems such as insufficient blackness and halo

contrary to the influence of laser wavelength control film production process and technology, the shorter the laser wavelength, the more complex the laser production process and technology. Therefore, most imagesetter manufacturers use nm lasers. This is the best compromise scheme when the price difference between imported 670 film and domestic 6328 film is small

now the laser with the wavelength of 633nm has been mature and used in its imagesetter by some foreign companies. Therefore, replacing 780nm infrared laser with 633nm semiconductor red laser can solve the problem of applying domestic 6328 type phototypesetting film to this kind of Phototypesetter on the premise of ensuring the output quality, so as to reduce the production cost

III. semiconductor laser

semiconductor laser is a laser similar to the process structure of crystal diodes and triodes. It can simply adjust different plastic varieties in the range of up to thousands of MHz. As a light source of Imagesetter, its output power can be MW (its maximum exposure is Erge/cm2). The infrared semiconductor laser with a wavelength of 780nm has a common cathode structure, as shown in Figure 2. The semiconductor laser with the wavelength of nm is a common anode structure, as shown in Figure 3

semiconductor lasers are delicate devices, and the following problems should be paid attention to when using: ● prevent static electricity - wear a grounding ring when handling, and cut off the power of the soldering iron when welding, and ensure that the soldering iron head is well grounded; ● prevent overvoltage - its working voltage should be less than 2.5V; ● prevent overcurrent - the working energy of the semiconductor laser is proportional to the current. Adjusting the current can adjust its luminous energy, but the current adjustment should be less than 50mA

IV. semiconductor laser replacement

1 Modification of laser drive circuit: as mentioned above, since 780nm semiconductor laser is a common cathode and 633nm semiconductor laser is a common anode, the relevant circuit of laser drive should be changed to inverse drive

2. Modification of photosensitive amplification circuit: as shown in figures 2 and 3, there are photosensitive detection tubes integrated with light-emitting tubes in both lasers. It is a closed-loop detection and control device, which is to ensure the stable operation of the laser light-emitting tube under a certain energy state when the temperature and other parameters change. The relative sensitivity of the spectral response characteristics of the photosensitive detection tube decreases with the decrease of the light wavelength. After measurement, the photosensitive detection current of 780nm laser is about 8Ma within the normal working energy range, while that of 633nm laser is about 300uA, so the parameters of photosensitive closed-loop detection circuit should be adjusted. Similarly, the parameters of the line start detection circuit should also be adjusted

3. Focusing: 780nm laser is invisible infrared laser, so its focusing can only be adjusted by the instrument at the factory. After replacing 633nm visible red laser, the focusing can be adjusted with the naked eye with the help of optical amplification instrument

v. summary

using this method, we changed the light source of dozens of ultra infrared laser imagesetters, and used Huaguang lp-6328 II and III He Ne imagesetter films after the change, which reached the quality level of imported 780 films

changing the laser light source of the semiconductor laser Imagesetter is a very professional and complex work. Without a careful and thorough analysis of the machine, and without the assistance of professionals, the consequences of blindly moving the machine will be unimaginable

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