ABSTRACT Wavelength measurement is a Critical topic in many applications. Stationary mterferometers, such as Fizeau and Murty,can be successfully used, considering the proportionality between the wavelength and the fringe spacing in the interferencepattern In this work we present a onedimensional algorithm for the calculation of the fringe spacing and error sources. Thefinal accuracy that can be achieved is also assessed. The experimental data are taken from fringe patterns recorded with aMwty interferometer.Keywords: Murty interferometer, fringe pattern, wavelength measurements, least squares methods 1. iNTRODUCTION One technique of measuring the wavelength consists in the comparison of the fringe spacings of two intensity recordings, of which one is obtained usinga reference wavelength (from a Stabilized He-Ne laser for instance) and the otherwith the unknown light.Such a technique uses the Murty mterferometer1' (figure 1), which has the advantages of extreme simplicity, mechanicaland thermal stability. it consists in a simple planeraI1e1 glass plate. When illuminated with a Spherical wave under anarbitrary angle, two sheared waves are reflected and a xittem of approximately straight ecpiispced parallel fringes appears.Transmission fringes are visible too, but with much less contrasi as while the amplitudes of the first two interfering wavesare nearly equal in reflection they have very different magnitodes in transmission. if quartz is used instead of glass, thewavelength precision is increased by a better thermal stability.