In the present time is the quality of optical components in lithography systems not on-line tested. The common indicator used for replacement of optics is the laser counter. With the present invention the life-time of these expensive parts can be monitored and analyzed the induced fluorescence in these components during laser operation and the parts will only be exchanged when necessary. All of the following references, as well as the Background, Title and Summary of the Invention, are hereby incorporated by reference into the detailed description of the preferred embodiments as disclosing alternative features and elements not particularly set forth in the detailed description:    1. M. Mizuguuchi et al.: Time-resolved photo luminescence for diagnosis of resistance to ArF excimer laser damage to CaF2 single crystals, J. Opt. Soc. Am. B 16, 1153-1159,1999    2. L. L. Clarke, M. S. Mendicino: Investigating Excimer Laser Induced Fluorescence in CaF2, 1999    3. Triebel, W. et. al.: Fused Silica Evaluated for Excimer Laser Applications, Euro Photonics, Dec./Jan. 30-31, 2001    4. U.S. Pat. No. 5,894,352    5. U.S. patent application Ser. No. 09/726,871, which is assigned to the same assignee as the present application.