English: An incoming light beam is split into its spectrum by an optical separator (4) and passes through an optical mask. The light is either absorbed, let through, or reflected at a 90 degree angle. This is based on the elements of a corresponding weighing matrix, corresponding to the values 0, 1, and -1 respectively. The light then hits one of two intensity sensors (1,2). The difference between the first and second sensor produces a measurement, with 7 measurements in total. Using the weighing matrix and the least-squares method, a more accurate estimate for the spectrum of light can be produced than measuring each band directly.