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Optics for the material processing with high power C02-lasers are highly stressed during oryation: They are loaded with beam power up to 20 kW and with intensities up to 20 kW/cm . Additionally droplets, dusts and vapor from the workpiece are deposited on the surface during the material processing so that the absorption increases. Semiconductor optics - these are lenses made from Ge, ZnSe or GaAs - will be destroyed in a short time. Transmissive optics have some more disadvantages, which are mainly accepted but have some negative influence on the processing: For the adjustment of the system usually a He-Ne-la-ser is used, emitting in the visible red. This beam is focussed in another way than a CO -laser beam because the wave length is shorter by a factor of sixteen shorter than the CO2-laser radiation. This means, that the position of a He-Ne laser beam only gives appro-ximately a proper adjustment. Furtheron, the small amount of absorbed beam power leads to a heating o the lens and therefor to a variation of focal length depending on the incident power. The same reason leads to deformations of the geometrical form of the two surfaces of the lens in an interesting but hardly predictable way. This leads to lens errors and by this to a deformation of the intensity distribution in the focal spot. Additionally, it is practically impossible to get two lenses with exactly the same focal length, so that after changing the optic the system has to be adjusted in new. Transmissive optics therefore only are a compromise, not always satisfying and should be replaced by mirror optics whenever possible. The state of the art in diamond turning 9f parabolic mirrors allows to manufacture high quality surfaces at a reasonable low price. In this paper a report is given on mirror optics and systems which were developed with the following aims:
- Small losses of laser power in the system with a high efficiency of the laser beam processing system
- Long lifetime of the mirrors under material processing conditions
- High Standard of the optical quality
- Flexibility for different applications. The requested qualities are guaranteed by the whole construction of the optics and the system. The theoretical works, the state of the art of the development and the future aspects of these laser working head systems are reported.
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