Laser engraving machine

 

(57) Abstract:

Usage: in the technique of optical recording graphic information, as well as in printing, phototelegraphy, office equipment, computing devices, automatic design. The essence of the invention: laser engraving machine is entered, the system automatically maintain the optimal position of the focusing spot of the laser radiation on the surface of a processed form, operating on the principle of feedback sensor which is a two-band photodetector, and the output drive of the carriage with the focusing lens. 3 Il.

The invention relates to the field of optical recording graphic information and can be used in the printing industry, in particular for the manufacture of film, offset printing and flexo printing forms, as well as raster shafts, phototelegraphy, office equipment, computing devices, automatic design, in particular, for the manufacture of photomasks.

Known laser engraving machine for manufacturing cliche [1] using continuous wave laser, containing the laser, the plate drum driven rotation system flat turning mirrors and turbana and serving for the longitudinal displacement of the spot of laser radiation, focused on the surface of the plate drum.

The disadvantage of this setup is the lack of ability to adjust the position of the focusing lens relative to the surface of the plate drum to maintain the optimal position of the focusing spot of the laser radiation on the surface of the plate drum when changing the plate material on the drum.

The prototype is laser engraving machine [2] contains a laser radiation source, a plate, a cylindrical drum, a guide parallel to the axis of rotation of the drum, mounted on a guide carriage for longitudinal movement of the spot of laser radiation focused by the lens on the surface of the plate drum, mounted on a carriage for longitudinal movement in an extra carriage that moves perpendicular to the axis of rotation of the plate drum and containing a focusing lens, a microscope and a manual drive of the focusing lens. Microscope and manual drive used for adjusting the focusing of the focusing lens each time before starting work.

The disadvantage of this system is the inconvenience associated with the need for subjective contralto affects the reproducibility and quality of laser writing on the form and also reduces the performance of the recording process.

The purpose of the invention improve the reproducibility of the recording process, improving the quality of your pictures and print forms in the manufacture of laser engraving machine and increase productivity.

This goal is achieved by the fact that laser engraving machine, containing a laser light source, the plate drum driven rotation, the guide parallel to the axis of rotation of the drum, mounted on a carriage for longitudinal movement of the spot of laser radiation focused on the surface of the plate drum by using a lens system to maintain the optimal position of the focusing spot of the laser radiation on the surface of the plate drum, a system for maintaining optimal position of the focusing spot of the laser radiation on the surface of the plate drum is made in the form of automated device and contains an optical part including a point light source, dual-zone sensor light and optical system for forming images of the light source to the photodetector, which consists of the first focusing lens installed between the light source and the surface of the plate drum is Kai part and a lens for forming a laser spot is rigidly mounted on a single supplemental carriage, connected to the actuator to move perpendicularly to the axis of rotation of the plate drum. Sensor feedback system is a two-band photodetector that generates an electrical signal proportional to the difference between the illumination of its light-sensitive zones, and the output drive additional carriage. The magnitude of the stroke additional carriage is determined by the ratio of 3h(L-f')cos i/f,, where h is the side area of the surface of the photodetector, L is the distance between the image of the light source on the surface of the plate drum and the second focusing lens, f' is the focal length of the second focusing lens, the first angle of incidence of the radiation after the first focusing lens.

In Fig. 1 shows a diagram of a laser engraving machine; Fig. 2 scheme of the optical part of the system maintain the optimal position of the focusing spot of the laser radiation; Fig. 3 diagram dual-zone sensor with symmetric and asymmetric illumination spot focused on its sensory surfaces.

The device operates as follows. Laser radiation from the source 1 passes through the lens 5 and the objective lens 7 focuses the necessary spot size on the surface of the rotating plate of the drum 2. The computers what about the laser spot along the generatrix of the cylinder of the plate drum. On the carriage for longitudinal movement placed an additional carriage 6 is rigidly mounted on it a focusing lens 7 and the optical part of the system to maintain optimum focus 8. Additional carriage 6 has the ability to move relative to the carriage 4 in the direction perpendicular to the axis of rotation of the plate drum 2, with the actuator 9 is mounted on the carriage 4. In the case of optimal focusing of a laser beam on the surface of the outer drum optical part of the system to maintain optimum focus provides balanced coverage areas a and b of the photodetector 13. In the care of the focused laser spot from the position 14 of the optimal focus position of the planes 15 or 16 spot on the two-band photodetector 13 is shifted to the right in the zone b in position 15 or to the left in the area and when leaving the focusing plane in position 16. In both cases light zones a and b are different, which changes the values of the corresponding photocurrent. The output of the photodetector is a device that generates an electrical signal proportional to the difference of illumination zones a and B. At the output of the differentiating device signal is positive or EDI, which is the output of the feedback circuit. Moving additional carriage 6 causes the spot of laser radiation in position 14 optimal focus. A differential electrical signal becomes zero. The feedback system is standard [3]

System for maintaining the position of optimum focus is characterized by the value of the permissible stroke additional carriage 6, within which is the purpose of the invention. For the optical part of the system for maintaining the position of optimal focus based on the analysis of Fig. 2 and 3 found the following relationship between the parameters of elements of the optical part:

3h (L-f')cos i/f', where h is the side area of the surface of the photodetector;

L is the distance between the image of the light source on the surface of the plate drum 2 and the second focusing lens 12;

f' is the focal length of the second focusing lens 12;

i the angle of incidence of the radiation of a point source 10 light after the first focusing lens 11.

When the output of the additional carriage outside, determined by the value of the goal is not achieved.

The invention improves the performance and quality screened printing forms received on izlucheniya, plate drum driven rotation, the guide parallel to the axis of rotation of the drum, mounted on a carriage for longitudinal movement of the spot of laser radiation focused on the surface of the plate drum by using a lens system to maintain the optimal position of the focusing spot of the laser radiation on the surface of the plate drum, characterized in that the system maintain the optimal position of the focusing spot of the laser radiation contains an optical part including a point light source, dual-zone sensor light and optical system for forming images of the light source to the photodetector, which consists of the first focusing lens installed between the light source and the surface of the plate drum, and the second focusing lens installed between the surface of the plate drum and a photodetector, while the optical part and the lens for shaping the laser spot is rigidly mounted on a single supplemental carriage, which is connected with a drive of its movement perpendicular to the axis of rotation of the plate drum, and a feedback system, a sensor which is a two-band photodetector that generates an electrical signal, preparedi, moreover, the magnitude of the stroke additional carriage is determined by the ratio

D 3h(L-f)cos i/f,

where h is the side area of the surface of the photodetector;

L is the distance between the image of the light source on the surface of the plate drum and the second focusing lens;

f focal length of the second focusing lens;

i the angle of incidence of the radiation after the first focusing lens.

 

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