Although it is now generally accepted that all surfaces may be to some extent less than perfect, there is still little objective information available on the relation between the severity of a particular imperfection and its impact on the quality of the system in which it occurs. It is to be hoped, now that objective methods of measuring imperfections have been developed, that the necessary research will take place to determine imperfection tolerances appropriate to particular applications. Meanwhile, the data given below provide some insight into the current practice of component design. This chapter is concerned with the quality control of optical components.
A survey of 30 organizations across the world, almost equally divided between manufacturers of optical systems and research-and-development groups, was undertaken in 1993 in an attempt to determine the mean levels of imperfection and roughness tolerances in use at that time. A measure of the importance attached to this subject can be judged from the fact that 88% of those responding indicated they would be in favor of seeing the data published. A few organizations (12%) expressed concern that, due to the complexity of the subject and its contentious history, some readers might mistakenly regard the table containing the data as a standard rather than simply a guideline to quality. Readers were invited to report to the author the results of studies to update the values quoted, but apart from one observation that there could be no equivalence between different approaches, additional data has not so far been forthcoming.
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