KEYWORDS: Metrology, Temperature sensors, Data modeling, Temperature metrology, Model based design, Thermal modeling, Error analysis, Systems modeling, Sustainability
Variations in environmental temperature conditions during the mask writing process are recognized for their potential to adversely impact the achievable placement precision. A laser writer sequentially exposes the mask area along a stripe-by-stripe writing trajectory. Any time-dependent position drift between the mask coordinate system and the write field centre is recorded along this trajectory. Depending on the inherent time scale of the drift process, the effect on the mask can manifest as a deformation of the stripe itself, a stripe displacement, or a global grid error. In this study, we present a model-based compensation method that predicts thermal position drifts based on temperature sensor readings. The approach has been implemented in a proof-of-concept study on an ULTRA mask writer system, leveraging two essential hardware features. Firstly, the common capability of laser mask writers to function as a placement metrology tool through the same lens as in exposure mode. Secondly, the standard system has been equipped with additional, suitably positioned precision temperature sensors. By combining these features, we create a time series database of synchronous placement error and temperature readings that allows us to train a predictive drift model. Once the model is trained, it can be operated in real-time compensation mode during placement metrology or exposure to counteract thermal drifts.
We describe the optical design of a calibration unit for the off-axis laser guide stars at the Large Binocular Telescope's ARGOS facility. Artificial stars with the desired wavefront are created using a computer generated hologram.
Effective calibration procedures play an important role for the efficiency and performance of astronomical
instrumentation. We report on the calibration scheme for ARGOS, the Laser Guide Star (LGS) facility at the LBT. An
artificial light source is used to feign the real laser beacons and perform extensive testing of the system, independent of
the time of day and weather conditions, thereby greatly enhancing the time available for engineering. Fibre optics and
computer generated holograms (CGHs) are used to generate the necessary wavefront. We present the optomechanical
design, and discuss the expected accuracy, as well as tolerances in assembly and alignment.
When hemoglobin concentration in a beating heart muscle was determined before and after hemodilution by remission spectrometry and calculated on the basis of classical integration of the area between the hemoglobin spectrum and the dark current no meaningful changes in Hb concentration could be found. In a study performed in suspensions of scattering particles a first attempt was made to find a rational explanation for these observations.
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