A novel optical instrument is proposed and studied to measure the deformation of each connection point for a mirror, which includes 24 multi-matrix base units and can be used in millimeter-scale signal reflection systems. Experimental investigations reveal that the error of measurement is σ=8.7×10-3 mm at a distance of 5 500 mm, which allows to measure the linear deformation of a radiotelescope with the mirror diameter of 70 m.