Electric heating – Metal heating – By arc
Patent
1997-06-26
1999-03-23
Evans, Geoffrey S.
Electric heating
Metal heating
By arc
21912173, B23K 2606
Patent
active
058863184
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to laser technology, more specifically to processing solid transparent materials such as glass, glass ceramics, transparent ceramics, and diamonds, with laser radiation.
BACKGROUND ART
Known in the prior art is a method for marking glass products by irradiating them with a focused laser beam having an intensity exceeding the glass destruction threshold (cf. RU #1,620,428, IPC C03C 27/12, 1989).
Another method for fancy patterning glass- and crystalware is known, wherein a pattern is made with a laser beam in an air medium at a temperature of from 223.degree. to 253.degree. K, and focusing a laser spot in the bulk of the object under process, spaced apart from the object outer surfaces a distance equal to at least 100 laser spot diameters (cf. RU #1,818,307, IPC C03C 33/00, 1990).
The closest to the proposed method as to its technical essence and attainable results is a method for laser-assisted formation of images in solid media by focusing laser radiation at a preset point of the object and displacing the latter with respect to laser beam in a predetermined manner. The object is irradiated with an energy density exceeding the threshold value of the volumetric disruptive strength of the material, and the objects is displaced in three mutually square directions (cf. RU #2,008,288, IPC C03C 23/00, 1991).
However, images produced by the aforementioned methods are of low contrast. Thus, in order to attain an adequate artistic expressiveness of an image it is necessary to substantially increase the power of laser radiation and the number of radiated pulses required for processing one object. These factors sophisticate much the equipment used for image formation and affects its service life.
DISCLOSURE OF THE INVENTION
It is a primary object of the present invention to provide a higher contrast of the image.
The foregoing object is accomplished due to the fact that prior to image formation a laser beam is established, featuring different angular divergence in two mutually square planes, and an angle between the plane with a maximum laser beam angular divergence and the surface of the image portion being formed is changed to suit the required contrast of said image portion.
It is common knowledge that divergence of laser radiation beam depends on the length of the laser resonator and the size of the aperture of the intraresontaor diaphragm. When a slit diaphragm is located inside the resonator it reduces laser beam divergence in the plane square with the diaphragm slit. Thus, while rotating the slit diaphragm about the resonator axis one can change the direction of the plane of maximum laser beam divergence. By focusing such a beam in the object under process one can obtain the region of maximum focusing (necking) whose transverse dimension `d` can be evaluated from the following formula: or Y (the Z axis being directed along the beam axis, the X axis being parallel to the diaphragm slit).
With the diaphragm fully out, the trace of destruction of the object material has approximately equal transverse dimensions along the X and Y axes, whereas with the diaphragm fully in, said trace features an extended length along the X axis, that is, the contrast of an image element depends on the orientation of the X axis. When forming an image one can orient said axis so as to suit the required image contrast.
The method for laser-assisted image formation in transparent objects disclosed herein is carried into effect as follows.
FIG. 1 represents a block diagram of carrying the method into effect, illustrating the following components:
Given below are some specific examples of carrying the method into effect.
EXAMPLE 1
An object made of grade K-8 glass and shaped as a parallepiped features a destruction threshold about 1010 W/sq.cm for a radiation wavelength of 1.06 micron. A pulsed laser beam is generated by the emitter 1 having the power unit 2, a pulse energy being 0.1 J and pulse duration, 10 ns. A laser radiation pulse having a divergence of 2.10-3 rad is focused in
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Goldfarb Boris Efimovich
Vasiliev Anatoly Valentinovich
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