This book describes the theoretical design of a three camera Michelson interferometer set-up for quantitative refractive index measuerments. Although a two camera system is easier to align and less expensive, a three camera interferometer is preferred because the expected measuring accuracy is much better. Here analytical expressions are found for the calculation of the required alignment accuracy of the interferometer's components: three CCD-cameras (six degrees of freedom each), a quarter wave plate (one degree of freedom) and a polariser (one degree of freedom). Also the required accuracy in the normalization of the intensity levels on the CCD-cameras is calculated.