NachhaltigAngewandte Naturwissenschaften und WirtschaftsingenieurwesenIPH Teisnach
R. Schachtschneider, I. Fortmeier, M. Stavridis, J. Asfour, G. Berger, R. Bergmann, A. Beutler, T. Blümel, H. Klawitter, K. Kubo, Johannes Liebl, F. Löffler, R. Meeß, C. Pruss, D. Ramm, M. Sandner, G. Schneider, M. Wendel, I. Widdershoven, M. Schulz, C. Elster
Interlaboratory comparison measurements of aspheres
Measurement Science and Technology, vol. 29, no. 5
The need for high-quality aspheres is rapidly growing, necessitating increased accuracy in their measurement. A reliable uncertainty assessment of asphere form measurement techniques is difficult due to their complexity. In order to explore the accuracy of current asphere form measurement techniques, an interlaboratory comparison was carried out in which four aspheres were measured by eight laboratories using tactile measurements, optical point measurements, and optical areal measurements. Altogether, 12 different devices were employed. The measurement results were analysed after subtracting the design topography and subsequently a best-fit sphere from the measurements. The surface reduced in this way was compared to a reference topography that was obtained by taking the pointwise median across the ensemble of reduced topographies on a $1000 \times 1000$ Cartesian grid. The deviations of the reduced topographies from the reference topography were analysed in terms of several characteristics including peak-to-valley and root-mean-square deviations. Root-mean-square deviations of the reduced topographies from the reference topographies were found to be on the order of some tens of nanometres up to 89 nm, with most of the deviations being smaller than 20 nm. Our results give an indication of the accuracy that can currently be expected in form measurements of aspheres.
Beitrag (Sammelband oder Tagungsband)
K. Berger, Y. Koudota, Marcus Barkowsky, P. Le Callet
Subjective Quality Assessment Comparing UHD and HD Resolution in HEVC Transmission Chain
2015 Seventh International Workshop on Quality of Multimedia Experience (QoMEX)
Ultra High Definition Television (UHDTV) is an emerging broadcasting system, aiming to replace the current High Definition Television (HDTV) in the near future. One aspect of UHDTV is to allow for higher resolutions, notably UHD1, which requires a four times increased datarate for uncompressed transmission compared to Full-HD resolution. As bandwidth for transmission channels in television broadcast is often a fixed value, this study provides information about the perceived quality for transmitting UHD1 content compared to Full-HD content at the same bitrate encoded with HEVC. Content influence is tested with 15 video contents and 4 bitrates are individually chosen per content to span the range of the perceptual scale. The methodology of Absolute Category Rating with Hidden Reference (ACR-HR) is used to collect votes from 24 viewers. The statistical analysis of the collected data shows that, in most cases, there is no significant quality difference between videos transmitted in Full-HD and UHD1 resolution but that the results strongly depend on the content type and on the capture quality. It is also shown that the required bitrate for achieving a chosen broadcast quality level varies with content by a factor of about 14 in HEVC coding.