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How Microroughness Impacts Optical Performance from Optical Surfaces Ltd.

September 26, 2019

Optical Surfaces Ltd. has undertaken a study to determine how microroughness impacts the performance of Aspheric lenses and mirrors.

Microroughness is a quantity which considers features which are even smaller than slope errors and is often expressed in RMS terms after integrating over spatial periods that are usually less than 0.25mm.

Such features, when pronounced, tend to cause effects that may be compared to mild scattering. For many applications such effects may not be so critical. However, for high power laser applications using mirrors or lenses as key focusing elements these effects can play an important role and therefore microroughness needs to be well controlled.

Although it is not fully understood, Optical Surfaces Ltd. has found that microroughness can be controlled during manufacturing using a pitch-polishing technique which regularly produces very good results that consistently do not exceed 1 nm RMS.

Data is presented on a selection of microroughness measurements performed on over 25 high precision aspheric optics manufactured by Optical Surfaces in recent years. Some evidence is shown that the more challenging optics, that manifest higher asphericity, are the ones that exhibit microroughness closest to 1 nm RMS.

For a copy of the new microroughness study please visit www.optisurf.com/index.php/news/technical-tips/ or contact Optical Surfaces Ltd. on +44-208-668-6126 / sales@optisurf.com.

Optical Surfaces Ltd has been producing optical components and systems for more than 50 years and is now accepted as one of the world’s leading manufacturers of high-precision optics for aerospace and space research. The company’s ISO 9001-2015 approved manufacturing workshops and test facilities are deep underground in a series of tunnels excavated in solid chalk where temperature remains constant and vibration is practically non-existent. With such stable conditions testing, particularly with long path lengths, becomes quantifiable and reliable. Working with these natural advantages is a highly skilled team of craftsmen with a commitment to excellence in both product quality and customer service.