An illumination device for illuminating at least one spatial light modulator device. At least one light source device with at least one light source illuminates the at least one spatial light modulator device; a light guiding element through which light emanating from the light source propagates; and at least one light decoupling element arranged on top or inside of the light guiding element. The at least one light decoupling element decouples of a wave field of the light which propagating in the light guiding element into the direction of the spatial light modulator device. The light guiding element has a refractive index which is lower than or at least equal to the refractive index of the at least one light decoupling element. The entrance angle of the wave field entering the light decoupling element is determined by the difference between the refractive indices according to a particular equation.