Dioptic GmbH has introduced the LRT (large radius test) system for interferometric characterization of spheric and toric mirror surfaces with radii of curvature up to several meters. Tuning of the spherical test wave generated by the system is accomplished by combining a diffractive Fizeau null lens and an achromat. The range of radii that can be tested is between 1 m and ∞, convex or concave. Travel distance of the achromat is 600 mm, and maximum test mirror diameter is 60 mm. A GUI drives the stepping motor moving the achromat, computes the radius of the mirror from the adjusted Z-position and stores relevant measurement parameters to disk.