1. A method of viewing an image, the method comprising transmitting an image into an eye of an observer by means of a dynamic optical device, the dynamic optical device being operative to create a modulation in respect of at least one of phase and amplitude in light transmitted or reflected thereby, said modulation being variable from one point or spatial region in the optical device to another, and wherein the modulation at any point or spatial region can be varied by the application of a stimulus, and altering the characterstics of the dynamic optical device so that the dynamic optical device acts sequentially to direct light of different colours to the observer's eye.