Testing of a convergent optics system off-axis using a Ronchi rule on a nodal bench

In this paper, we propose to use a Ronchi rule on a Nodal Bench to test convergent optics system. The Ronchi rule is of frequency medium, between 200 and 500 lines/inches. Besides, this test takes advantage to measure nodal plane and focal distance on-axis and off-axis of some system optics with Nodal Bench. The optics system under test is illuminated with a plane wavefront and it is focused to focal distance of the optics system under test. Ronchi rule is placed in exit pupil of optics system, it generate interferograms with the aberrations of optics system. In this interferograms we observe fines fringes of interference which are generated by the rule frequency like the rule works as a reflections multiples interferometer. The interferograms are displayed on a computer by a CCD, it is placed on the focal point of the system under test. We show some preliminary results of this test.