High precision differential Astrometry is the branch of astronomy that evaluates the relative position, distance and motion of celestial objects with respect to the stars present in the field of view. A mission called Theia has been submitted in 2022 for ESA's M7 call for missions, using a diffraction-limited telescope about 1m in diameter and with a field of view of 0.5 degrees, capable of achieving sub-microsecond angular accuracy. Such precision makes it possible to study the nature of dark matter in our galaxy and to reveal the architecture of exoplanetary systems close to the Sun, down to the mass of the Earth. But for the moment the technology readiness levels (TRL) of the detector plane and the telescope stability are too low. The aim of the experimental tests presented in this poster is to improve the TRL of 2 specific aspects: the calibration of new detectors with very large number of pixels and the calibration of the field distortion thanks to the stars in the field of view. First, a key element of such a space telescope is the focal plane, which must be calibrated spatially with an extreme precision down to the 1e-5 pixel level. Previous work has shown that this is possible with small detector matrices (Crouzier et al. 2016, A&A 595, A108). The goal is now to check the performances and validate this method with the new very large detectors. Pyxalis, a company based near Grenoble, is developing very large detectors that have a low noise level and high sensitivity. The aim is to use this type of detectors for a laboratory demonstration, to ensure that the performance achieved meets the required specifications. In addition, recent work on telescope stability (Malbet et al. 2022, SPIE 12180, 1F) has shown that the reference stars in the field of the telescope can be used as actual metrology sources in order to compute the distortion function of the field. The second goal of these test bed is to experimentally show the performances of this new field calibration method. This poster will present the latest developments of these laboratory experiments.