Mueller calculus is a matrix method for manipulating Stokes vectors, which represent the polarization of incoherent light. It was developed in 1943 by Hans Mueller, then a professor of physics at the Massachusetts Institute of Technology. Light which is unpolarized or partially polarized must be treated using Mueller calculus, while fully polarized light can be treated with either Mueller calculus or the simpler Jones calculus. Coherent light generally must be treated with Jones calculus because the latter works with amplitude rather than intensity of light. The effect of a particular optical element is represented by a Mueller matrix; which is a 4×4 matrix and a generalization of the Jones matrix.
Any fully polarized, partially polarized, or unpolarized state of light can be represented by a Stokes vector (). Any optical element can be represented by a Mueller matrix (M).
If a beam of light is initially in the state and then passes through an optical element M and comes out in a state , then it is written
If a beam of light passes through optical element M1 followed by M2 then M3 it is written
given that matrix multiplication is associative it can be written
Beware, matrix multiplication is not commutative, so in general
Below are listed the Mueller matrices for some ideal common optical elements: