The Ronchi test has been consolidated as one of the most successful and powerful techniques applied to determine the quality of optical surfaces.5 In recent years, the development and availability of LCD's (Liquid Crystal Displays) have allowed the incorporation of LCD's instead of the traditional static ruling. The easy change of the characteristics of the fringes in the ruling, such as frequency, position, and geometrical form, transformed this technique into a dynamic test.1, 8 Its physical interpretation fully connected with a lateral sheared interferometer 5, 6 and some concepts and results associated with the interferometric concept of equivalent wavelenght have been applied in this proposal for the evaluation of optical surfaces. The procedure described here to evaluate an optical surface uses the Ronchi test with the equivalent wavelenght.6, 10 This is achieved by registering and computing Ronchigrams obtained by employing, separately, two distinct wavelengths. For a particular mirror, some results are shown in order to demonstrate the enhancement of the test with this proposal.