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la la et which polarized light is backscattered from a diffuse medium. pattern c that was f Asakura. were deve Letter we quite sim on a vec used in th beam is normal. The intensity and polarization of cterized mations y 4 3 4 such a l orders outgoing al angle tion can Muelleron the notion of geometric phase, which was intro-duced by Berry4 in his interpretation of experiments showing optical activity in a helically wound optical fiber.5 Berry’s geometric phase in these references is the phase acquired by light when its direction of propagation is slowly changed on a sphere of di-rections (i.e., in momentum space). This geometric phase is equal to the solid angle on the sphere of wave-vector directions. A different geometric phase, called Pancharatnam’s phase is the phase acquired by paraxial polarized light wave when its polariza-tion undergoes some transformation on the Poincaré sphere. That geometric phase is equal to half the solid angle on the Poincaré sphere.6 So far the ap-plications of geometric phases to polarized light have been limited to situations in which light is traveling in a homogeneous medium. In this Letter we use only matrices. We find that the outgoing intensities in the backscattered direction and between parallel (perpendicular) polarizers are