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Marginal changes in geometrical dimensions due to temperature changes affect the performance of optical instruments. Highly dimensionally stable materials can minimize these effects since they offer low coefficients of thermal expansion (CTE). Our dilatometer, based on heterodyne interferometry, is able to determine the CTE in 1 0 − 8 K − 1 range. Here, we present the improved interferometer performance using angular measurements via differential wavefront sensing to correct for tilt-to-length coupling. The setup was tested by measuring the CTE of a single-crystal silicon at 285 K. Results are in good agreement with the reported values and show a bias of less than 1%. [ABSTRACT FROM AUTHOR]

In this article, we present the current status of our high-sensitivity compact heterodyne interferometer and highlight its application in high-accuracy dilatometry and industrial surface metrology. The linear coefficient of thermal expansion (CTE) of dimensionally highly stable carbon-fiber reinforced plastic (CFRP) was measured with 10-7 K-1 accuracy. A very compact and quasi-monolithic interferometer setup is currently developed utilizing ultra-low expansion glass material. We present first investigations on the corresponding integration technologies, hydroxide-catalysis bonding and adhesive bonding. For high resolution 3-D profilometry and surface property measurements, a low-noise actuator will be implemented in the interferometer, which enables a scan of the measurement beam over the surface under investigation. [ABSTRACT FROM AUTHOR]