Nouvelle Méthode de Mesure de la Visibilité de la Modulation Spectrale pour de Grandes Différences de Marche

A novel method for determining the visibility of the spectral modulation in a white light interference experiment is described. Essentially, one measures the ratio of the total intensity to the sum of the intensities of the individual beams at the exit of a system composed of two interferometers in series. Contrary to the usual method, the novel one is applicable to any path difference. In practice, the method has been tried for a path difference up to 23 cm. This limit has been imposed by the maximum displacement of the movable mirror of the interferometer. The experiment shows that the visibility of the spectral modulation of a white light source is still very high for a path difference as large as 23 cm.