Preliminary Laboratory Test for the Fred Young Sub-mm Telescope Holography

A novel high-frequency holography system is developed for measuring the surface shapes of the two mirrors of the Fred Young Sub-mm Telescope (FYST). It operates at 295.74GHz (wavelength of $1.0137$mm) and measures the complex (amplitude and phase) beam maps in near field. The system is designed to achieve a measurement accuracy of $<3\mu$m and 100mm spatial resolution for mirror error maps. A new inference approach is studied to resolve the surface error maps of the two mirrors from 4 or more measured beams. We employ the new system to a 1/15th-scale FYST telescope constructed in our laboratory and test the system feasibility. The spatial resolution of the lab system is changed to 10mm. A conventional one-beam holography is firstly carried out. Measured data is analyzed by the well-known Fourier Optics technique and our new inference approach. The artificial errors on the mirrors are measured with a statistic error of $<1\mu$m. The results also prove that the new inference approach is generally applicable for conventional one-beam holography analysis.