We built and characterized an optical system that emulates the optical characteristics of an 8m-class telescope like the Very Large Telescope .
The system contains rotating glass phase-screens to generate realistic atmosphere-like optical turbulence , as needed for testing multi-conjugate adaptive optics systems .
In this paper we present an investigation of the statistical properties of two phase-screens etched on glass-plate surfaces , obtained from Silios Technologies .
Those etched screens are highly transmissive ( above 85 % ) from 0.45 to 2.5 \mu m. From direct imaging , their Fried parameter r _ { 0 } values ( 0.43 \pm 0.04 mm and 0.81 \pm 0.03 mm , respectively , at 0.633 \mu m ) agree with the expectation to within 10 % .
This is also confirmed by a comparison of measured and expected Zernike coefficient variances .
Overall , we find that those screens are quite reproducible , allowing sub-millimetre r _ { 0 } values , which were difficult to achieve in the past .
We conclude that the telescope emulator and phase-screens form a powerful atmospheric turbulence generator allowing systematic testing of different kinds of AO instrumentation .