Coherent light generators – Particular resonant cavity – Specified output coupling device
Utility Patent
1999-04-19
2001-01-02
Healy, Brian (Department: 2874)
Coherent light generators
Particular resonant cavity
Specified output coupling device
C372S020000, C372S038060, C372S029011, C372S109000, C372S010000, C372S058000, C219S121600, C219S121610, C219S121620
Utility Patent
active
06169758
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a laser output detector of dry type which is capable of continuously determining a laser output through computation even during a laser beam machining process.
2. Description of the Prior Art
Various laser output measuring apparatuses have been hitherto known, one example of which is a water-cooled laser output measuring device which includes a sensor disk disposed in the center of the water-cooled vessel and adapted to absorb an incident laser beam as much as possible and detect the energy amount of the laser beam . The laser output measuring device is placed under a laser beam projector for measurement of the laser output. The laser beam projected from the laser beam projector is received by the sensor disk, which absorbs the laser beam as much as possible and converts the laser beam into an electrical signal for determination of the energy amount of the laser beam.
The laser output measuring device of this type has the following drawbacks:
(1) While the measurement accuracy is high because the projected laser beam is virtually entirely absorbed by the sensor disk, it is necessary to locate the measuring device at a work piece machining position so that the work piece machining should be stopped when the measurement is to be performed.
(2) Since the measuring device is of a water-cooled type, a cooler is required for keeping the temperature of the cooling water constant. Therefore, the device has a large and complicated construction and requires higher costs, whereby the number of laser output measuring devices relative to the number of the laser machining apparatuses is inevitably limited.
It is a first object of the present invention to provide a laser output detector which is capable of directly detecting a laser beam projected from a laser beam projector for continuous measurement of a laser output even during a laser machining process. In other words, such a laser output detector is capable of constantly performing the measurement of the laser output, while ensuring continuous laser machining.
It is a second object of the present invention to provide a laser output detector of a simplified construction which can be fabricated at lower costs and employed as an essential component for a laser machining apparatus.
SUMMARY OF THE INVENTION
In accordance with the present invention, there is provided a laser output detector adapted to directly sample laser energy from a laser beam projected from a laser beam projector for measurement of a laser output, the laser output detector comprising: a convertor unit having a light sampling port to be located adjacent a projecting portion of the laser beam projector for sampling a fraction of a convergent portion of the projected laser beam or a fraction of a non-convergent portion of the laser beam outside the convergent portion of the laser beam, and adapted to convert the sampled laser beam fraction into an electrical signal; and a detection circuit for computing the energy amount of the projected laser beam on the basis of the electrical signal outputted from the convertor unit.
The laser beam is focused on a surface of a work piece by means of an optical system of the laser beam projector for welding, cutting or engraving the work surface.
Even if the fractional laser beam is sampled from the convergent portion of the laser beam to be used for the laser machining, the energy amount of the fractional laser beam accounts for a very small proportion of the total amount of the laser energy, so that the sampling does not profoundly affect the machining performance. The amount of the sampled energy is linearly proportional to the energy amount of the projected laser beam (which is, in practice, represented by a value obtained through the conversion to an electrical signal and the computation on the basis of the electrical signal), and equals to 1
of the energy amount of the projected laser beam.
In other words, the energy amount of the projected laser beam can be estimated by multiplying the energy amount of the sampled laser beam fraction by n.
As shown in
FIG. 2
, the energy level of the laser beam progressively decreases as a distance from the center axis of the convergent portion of the laser beam increases toward the periphery thereof. The laser beam may be sampled at any position between the center axis and the periphery of the laser beam for the detection of the energy. However, sampling from the central portion of the laser beam is not preferred in terms of the machining efficiency, because an energy intensity at the central portion is excessively high thereby resulting in a great energy loss.
Since the central portion of the convergent portion of the laser beam is mainly used for the laser machining, the peripheral portion thereof makes little contribution to the machining. Therefore, sampling from the peripheral portion of the laser beam for the measurement exerts no adverse influence on the machining.
Thus, the energy amount of the convergent portion of the laser beam projected from the laser beam projector to be used for the machining can be determined for every laser shot on a real time basis by converting the sampled laser beam fraction into an electrical signal, computing the energy amount of the laser beam fraction on the basis of the electrical signal and multiplying the energy amount of the laser beam fraction by a predetermined multiplication factor. Then, the energy amount thus determined is displayed on a display unit. The displaying method will be described later in detail.
REFERENCES:
patent: 5050174 (1991-09-01), Wani et al.
patent: 5132528 (1992-07-01), Barton et al.
patent: 5339324 (1994-08-01), Eguchi et al.
patent: 5636232 (1997-06-01), Goto
patent: 6002706 (1999-12-01), Staver et al.
Healy Brian
O.M.C. Co., Ltd.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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