20 February 2014 Manufacturing process to improve roughness on aspheric surfaces
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Abstract
For many applications, such as spectrometers and high power lasers, roughness is an important parameter that has been discussed again and again. Especially for high power systems, the surface quality is crucial for determining the damage threshold and therefore the field of application. Every application has different needs with respect to roughness, while most of them have additional needs as regards surface defects and waviness as well. For high power lasers, it is important to reduce absorption and scatter light, as absorption increases the temperature of the elements, which results in movement of the optical focus (thermal lensing) or, even worse, damage to the lens. This paper will focus on roughness, especially because the specific roughness for aspherical elements is very different compared with spherical/plano surfaces. Furthermore, it has often been difficult to compare roughness measurements because of different measurement methods and the usage of filters and surface fits. Measurement results differ significantly depending on filters and, in particular, on the size of the measured surface. Insights will be given as to how values behave depending on the quality of the surface and the size of the measured area. Most of these applications also require low roughness on aspheric surfaces. Because of small tool sizes in aspherics, it has not yet been possible to achieve the same low level as for spheres and plano optics. In addition, the results of a new manufacturing process will also be shown, allowing low roughness on aspherics, even with a remarkable departure from the best-fit sphere.
© (2014) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
S. Kionkte, "Manufacturing process to improve roughness on aspheric surfaces", Proc. SPIE 8963, High-Power Laser Materials Processing: Lasers, Beam Delivery, Diagnostics, and Applications III, 89630F (20 February 2014); doi: 10.1117/12.2039655; https://doi.org/10.1117/12.2039655
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