Electric heating – Metal heating – By arc
Reexamination Certificate
2003-05-16
2004-11-23
Heinrich, Samuel M. (Department: 1725)
Electric heating
Metal heating
By arc
C219S121680
Reexamination Certificate
active
06822186
ABSTRACT:
The invention relates to a laser processing apparatus in particular a medical laser processing apparatus, for plasma-induced ablation, which comprises a laser light source for generating a processing laser beam, a focussing means for focussing the processing laser beam and an optical detection device for detecting the plasma radiation generated during an ablation.
Such laser processing apparatuses are used in different areas and for different purposes in diverse forms. They are used in particular in the medical field, primarily in dentistry, where they are used instead of a mechanical drill for the ablation or removal of tooth material, in particular carious tooth material.
In contrast to mechanical drill devices, in which a contact between the processing device and the region to be worked is always prescribed for removal purposes, in the case of the laser processing apparatuses which enable contactless processing and removal, the correct positioning or the correct processing distance with respect to the material to be processed is of major importance.
Therefore, it has been proposed in the prior art to equip such laser processing apparatuses, in particular handpieces for such laser processing apparatuses, with a device for distance measurement.
The German patent application (official file reference 100 42 220.9) describes a handpiece for a laser processing apparatus which is provided with a distance measuring device which monitors the distance between a handpiece and the material to be processed. The distance measuring device proposed is a proximity sensor, for example an ultrasonic sensor, for contactlessly measuring the required distance or a mechanical distance pin which is fitted to the handpiece in the vicinity of the region to be processed and to the handpiece preferably in the direction of the emerging laser light.
However, such distance measuring devices are in part complex and costly and in some instances susceptible to faults and make the laser processing apparatus more expensive.
Therefore, it is an object of the present invention to provide a laser processing apparatus which enables a cost-effective and largely fault-unsusceptible ablation of a material and, in particular, satisfies very stringent safety requirements during the operation of the apparatus and precludes endangerment of the patient and/or also of the user or the operator of such a laser processing apparatus or, if appropriate, also of third parties.
This object is achieved by means of a laser processing apparatus according to claim
1
; claims
2
to
13
relate to particularly advantageous embodiments of the laser processing apparatus according to the invention.
According to the invention, the laser processing apparatus comprises a laser light source for generating a processing laser beam, a focussing means for focussing the processing laser beam and an optical detection device for detecting the plasma radiation generated during the ablation of the material, the laser processing apparatus furthermore comprising an evaluation and/or a control unit, which are designed in such a way that it automatically switches the laser processing apparatus from a processing mode into a quiescent mode of the laser processing apparatus or of the laser light source and/or vice versa in a manner dependent on the values for the intensity of the plasma radiation which are determined by the detection device.
The invention has the advantage that it is not necessary for the distance to be measured by means of an additional distance measuring device; by contrast, it is possible to ensure that the correct distance or the desired distance range is complied with merely by monitoring the plasma radiation which arises during the ablation or the removal of the material to be processed. By way of example, if the laser processing apparatus is not operated correctly by the operator, e.g. by virtue of a dental handpiece of such a laser processing apparatus being held in such a way that the distance between the handpiece and the material to be processed becomes too large or too small, the excessively low power density or the excessively low fluence at the material to be processed means that no plasma-induced ablation and therefore no plasma radiation arises or the intensity of the plasma decreases at least to a very great extent, so that, from monitoring the plasma radiation alone, it is possible to draw the desired conclusions with regard to the correct distance from the material to be processed.
In the case, moreover, where an operator holds the laser processing apparatus or a corresponding handpiece in such a way that an emitted laser processing beam does not impinge on the material to be processed, which can lead to endangerment of the patient, no plasma radiation is detected and the laser processing apparatus is automatically put into a quiescent mode, thus enabling a secure and hazard-free treatment.
It shall be pointed out at this juncture that the intensity of the plasma can be measured essentially independently of wavelength, in particular can be measured over the entire wavelength range. However, it is also possible for the intensity to be measured only in a specific selected wavelength range or in a plurality of wavelength ranges, which can preferably be chosen depending on the area of application, or else only at one or a plurality of specific wavelengths.
The values determined by the optical detection device are preferably forwarded to the evaluation and/or control unit in the form of a signal, the evaluation unit regarding a sharp drop in the intensity of the plasma radiation, if appropriate a drop down to 0, as an indicator of the fact that the material to be processed is no longer situated in the region of the focus or of a predetermined depth of field range and the desired distances between, for example, a handpiece and the area to be processed or the material to be processed are therefore not being complied with, so that effective or secure processing is longer ensured.
In this case, according to the invention, the evaluation and/or control unit are designed in such a way that they automatically switch the laser processing apparatus or the laser light source back and forth between a processing mode and a quiescent mode in a manner dependent on the values determined by the optical detection device and the corresponding signal generated by the detection device. It can thus be ensured that the laser processing apparatus is switched into a quiescent mode in the event of a processing or treatment in which the required distances are not complied with, which leads to a change in the intensity of the plasma radiation or a complete extinction of the plasma.
The laser processing apparatus according to the invention thus ensures, in a simple and cost-effective manner, that the laser processing apparatus is in a processing mode and a laser processing beam can be emitted only when the correct and desired distances for processing or for treatment are complied with, and an effective and secure processing or treatment is therefore ensured. Therefore, in the case of a laser processing apparatus according to the invention, it is possible to dispense with a distance monitoring device, it being ensured at the same time, however, that the laser processing apparatus or the laser light source does not emit a processing laser beam unless a plasma-induced ablation is also brought about by the latter.
Emission of a processing laser beam without a plasma-induced ablation must be avoided in particular because the energy radiated in by the laser, if it does not lead to the desired ablation, may lead in particular to heating of the material being irradiated, which can lead to undesired damaged to the material or to injuries. The laser processing apparatus according to the invention therefore ensures, in a simple and cost-effective and also a reliable manner, that a laser power is output only when it also actually leads, as desired, to the plasma-induced ablation.
The optical detection device may be a photodetector or else a spectrometer, but it i
Kassenbacher Anton
Schörghofer Harald
Strassl Martin
Frommer & Lawrence & Haug LLP
Heinrich Samuel M.
Santisi Leonard J.
W&H Dentalwerk Bürmoos GmbH
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