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The clinical feasibility of photorefractive keratectomy depends on the surface structure of the ablated cornea. Two factors that influence the remodeled surface are the homogeneity of the energy distribution and the properties of the laser source (energy and wavelength). Currently, the homogeneity of the beam is difficult to control. The second factor, laser source properties, was the focus of this study. We investigated the effect of laser wavelength and energy by analyzing the reaction products of photoablation. We monitored the fragments produced by UV-laser ablation of human corneas using mass spectroscopy in the range of 0 to 100 atomic mass units. At 248 nm (KrF), average photon energy was 5 mJ/cm2, increased to 90 mJ/cm2 by intervals of 5 mJ/cm2. At 193 nm (ArF), photon energy was increased by the same interval from 5 mJ/cm2 to 80 mJ/cm2. Our experiments showed that there was a fluence threshold of approximately 40 mJ/cm2 at 193 nm (ArF) and 50 mJ/cm2 at 248 nm (KrF). Exceeding this threshold led to sudden increases in the number and relative intensity of fragment peaks in mass spectroscopy. This indicates the onset of multiple-photon processes and effective photochemical breakdown. There was a significant difference between both wavelengths in the distribution of mass peaks, indicating higher ionization power at 193 nm.

One of the major developments in optics industry recently is the commercial manufacturing of freeform surfaces for optical mid-and high performance systems. The loss of limitation on rotational symmetry enables completely new optical design solutionsbut causes completely new challenges for the manufacturer too. Adapting the serial production from radialsymmetric to freeform optics cannot be done just by the extension of machine capabilities and software for every process step. New solutions for conventional optics productions or completely new process chains are necessary.

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Surface plate inspectors can appro~imate a number of functional gages using standard fixtures. This approach fits nicely into situations where a lot (batch) of similar parts do not all require variables inspection data.. These go or not-go surface plate gages will be as accurate as the care and,planning taken by the inspector in their setup.