An image generation unit with an illumination unit for generating a plurality of coherent sub-beams and for illuminating an image modulator, including a light source, and a projection lens for superimposing each of the coherent sub-beams onto a projection screen plane. An optical set-up introduces angles between each two of the sub-beams, which are chosen to produce uncorrelated speckle patterns in the projection screen plane, resulting in an interference speckle pattern. A phase modulator including a liquid crystal cell changes its directory profile in a lateral manner, thereby being able to change the phase of light of each sub-beam individually.