We offer new equations for phase evaluation in measurements. Several phase-shifting equations with an arbitrary but constant phase shift between captured intensity signs are proposed. We show a mathematical model that seeks new equations by minimizing the uncertainty in measurements. The equations are similarly derived as the so-called Carré equation. The idea is to develop a generalization of the Carré equation that is not restricted to four images. Errors and random noise in the images cannot be eliminated, but the uncertainty due to their effects can be reduced by increasing the number of observations. An experimental analysis of the mistakes of the technique was made, as well as a detailed analysis of mistakes of the measurement. The advantages of the proposed equation are its precision in the measures taken, speed of processing, and the immunity to noise in signs and images.