Noise reduction in speckle pattern interferometer

In speckle pattern interferometry the starting phase is distributed randomly. Furthermore the background intensity and the modulation also are structured stochastically. This leads to a significant amount of noise in the interferogram analysis. Low modulated speckles are more difficult to evaluate than high modulated ones. We report on a method to reduce this problem. The principle is to use more than one wavelength at the same time and to separate the different wavelengths in the recording plane. With this method the precision can be improved by factor up to 2.3. Our first experiments show the high potential of this method.