Principle:
Laser light drawing machine uses laser scanning film to generate graphics, and its principle is the same as that of the fluorescent substance on the screen scanned by the electron gun in the TV picture tube. Firstly, the printed circuit board is mapped into a large storage array, and then the laser beam is turned on or off (modulated) according to the values of the corresponding cells in the storage array, so as to obtain the required process film. Laser light drawing machine takes laser as light source, which has the advantages of easy focusing and concentrated energy, which is very beneficial to the instantaneous rapid exposure of negative film. The drawn negative has neat edges, high contrast and no false light. The exposure is scanning, no matter how dense it is, it can be completed in the shortest time, and it only takes a few minutes to draw a negative. So it has become the mainstream of today's light painting industry.
Gas lasers, such as argon, helium, neon, etc. , mainly used as the light source of laser plotter. Gas laser has a strong light source, but its service life is limited, about 6000 ~ 10000 h, and it needs to be replaced after more than one year of use. Some light drawing machine manufacturers use semiconductor lasers as light sources, but the production of high-power semiconductor lasers is not very mature.
Classification:
The negative film, represented by the crescent series laser light drawing machine developed by Gerber Company, USA, is adsorbed on a barrel-shaped inner wall by vacuum. The blue laser emitted by the argon-hydrogen laser passes through the electronic shutter and the spot selection port of the beam intensifier, and then passes through two 45. The mirror is reflected on an inclined mirror rotating at a high speed (200 revolutions per second) and then on the substrate. Due to the high-speed rotation of the oblique mirror, the reflected light spots on the negative form a continuous line. When rotating at high speed, the mirror moves laterally along its bottom "rotating mirror" at a speed of 300px/mln. Therefore, the distance between each ray is only 10btm, forming strips of scanning exposure. At the same time, under the control of the electronic shutter of 200 million times per second, the laser can be turned on and off to complete the exposure of positive and negative images.
The negative drawn by the inner cylinder laser light drawing machine can reach a very high resolution (1/4-mil), and it only takes 5 minutes to draw a 2 zlin×30in negative. However, due to the extremely high rotating speed of the self-rotating lens (12000r/rain), the inner cylinder laser light drawing machine adopts air bearings, which is expensive and difficult to maintain, and it is difficult to popularize.
2) external drum laser light drawing machine
Represented by I. P5008 series laser light drawing machine produced by Israel Aobao Technology Company.
This kind of laser light drawing machine uses a powerful vacuum pump to suck the negative film outside a circular drum, which rotates rapidly at a speed of 500 rpm. In order to make the film firmly adsorbed on the drum, the drum speed of 1500r/min cannot be increased, otherwise the film will be thrown out at high speed. Therefore, the rotational speed of the external drum laser plotter is quite different from that of the internal drum laser plotter 12000r/mln, and the scanning exposure speed will be reduced accordingly. In order to solve this problem, Aobao developed its own patented technology, which decomposed the laser beam into 32 beams and exposed 32 pixels at a time on the negative, which is equivalent to increasing the scanning speed by 32 times.
The laser beam emitted by the laser is reflected by the reflection ballast to the light source seat, which is divided into 32 light elements, and the optical drawing data is also sent to the light source seat through the cable; 32 laser beams are controlled, and 32 pixels are simultaneously exposed in one line on the negative. When the roller rotates, the light source base moves horizontally and left and right to complete scanning exposure.