Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Patent
1987-07-13
1996-05-07
Allen, Stephone
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
25055924, 2502061, 2191216, 356123, G01J 104, G01N 2100, B23K 2600
Patent
active
055148670
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The invention relates to an apparatus for determining the radial intensity distribution of laser radiation, accompanied by the selective blocking out of a partial beam from the total beam.
When machining workpieces by means of a laser beam, the result is inter alia significantly determined by the radial intensity distribution of the laser radiation. The knowledge of this intensity distribution is consequently important. However, the investigation of the beam quality of the unfocussed laser beam is not sufficient for evaluating the machining result. In fact, for the machining process, significance is attached to the beam distribution and beam cross-section in the focus, as well as the focus position, relative to the workpiece surface.
PRIOR ART
It is known to allow a wire to rotate through the beam cross-section and on whose highly reflecting surface is expanded the laser radiation and deflected onto a detector positioned at an appropriate point with respect to the beam axis (Optics and Laser Technology 6, pp 149-153, 1982). However, with such an arrangement it is not possible to adequately determine the beam distribution in the focus and in the area in front of and behind the focus of a laser beam located between the focussing lens and a double focal length, due to the distortion errors which then occur. Moreover, several detectors are required for determining the complete two-dimensional intensity profile, it being necessary to align the arrangement with the beam centre, because otherwise a false picture would be obtained, which would lead to an incorrect valuation of the beam characteristics.
DESCRIPTION OF THE INVENTION
The problem of the present invention is to provide an apparatus making it possible to determine the intensity distribution both in an unfocussed and in a focussed laser bear using a minimum number of detectors, the arrangement being alignment-insensitive and also usable in the case of laser power levels exceeding 10 kW.
This problem is solved by an apparatus with the characterising features of claim 1.
On revolving the support in the case of the apparatus according to the invention, a section is taken through the laser beam. For detecting the complete profile, with the aid of a plurality of sections through the laser beam taken at different points, according to another development of the invention the support pivot pin can undergo parallel displacement by means of a stepping motor.
The particular advantages of the invention are that with the inventive apparatus the intensity distribution and beam cross-section can be determined both in an unfocussed laser beam and in the focussed, as well in the region located between the focussing lens and its double focussing length in front of and behind the focus of a focussed laser beam; only one detector is required, there is no need to centre to the beam centre, but deviations of the beam position can be determined and it is also possible to investigate high intensity laser beams.
BRIEF DESCRIPTION OF THE DRAWINGS
Embodiments of the invention are described hereinafter relative to the drawings, wherein show:
FIG. 1, a longitudinal section through an apparatus according to the invention.
FIG. 2, a larger scale detail of FIG. 1.
FIG. 3, a support with a straight tube closed at the ends by in each case one plug serving as the waveguide.
FIG. 4, a support with a light guide bent over at both ends as the waveguide.
FIG. 5, a support with a straight light guide, whose ends are partly ground at an angle of 45.degree..
FIG. 6, a support with a straight light guide with protective caps, whose bottoms are chamfered by 45.degree. on the inside.
FIG. 7, a support with several waveguides in side view.
FIG. 8, a support formed from two disks in longitudinal section.
FIG. 9, the same in side view.
FIGS. 10 and 11 show a further embodiment of the invention.
WAYS OF PERFORMING THE INVENTION
In FIG. 1, 1 is a support mounted in rotary manner, whose pivot pin or axis 2 is oriented parallel to the axis of laser beam 3. A hollow waveguide i
REFERENCES:
patent: 3617755 (1971-11-01), Arnaud
patent: 4009392 (1977-02-01), Hanley
patent: 4035088 (1977-07-01), Jenkins et al.
Beyer Eckhard
Kramer Reinhard
Loosen Peter
Allen Stephone
Siegemund Ralf H.
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