A system for reducing speckle artifacts, comprising: a light source (15r, 15g, 15b) configured to emit light that is at least partially coherent; a projection lens (40, 240) configured to output the light as a convergent light beam towards a location on a target surface; and a despeckling device with an optical axis and having an optical plate comprising an inner surface and an outer surface such that light emerging from the projection lens (40, 240) enters the optical plate through the inner surface and exits the optical plate through the outer surface, wherein the despeckling device is positionable between the projection lens (40, 240) and the target surface such that the target surface is displaced from the outer surface by a throw distance D, and wherein said optical plate is rotatable about an axis of rotation equal to the optical axis to temporally and angularly deflect the convergent light beam through a plurality of angular orientations toward the location on the target surface; characterized in that the inner surface and the outer surface of the optical plate are tilted with respect to the optical axis, such that the inner surface has a tilt angle (Φ 1) with respect to a line perpendicular to the optical axis configured to refract the convergent light beam along the optical axis away from the optical axis within the optical plate with a displacement of d at the outer surface and the outer surface has a second angle with respect to the line perpendicular to the optical axis, the second angle being equal to the sum of the tilt angle (Φ 1) and a wedge angle (Φ 2), the wedge angle (Φ 2) being the angular amount that the outer surface is tilted further away from the line perpendicular to the optical axis than the tilt angle (Φ 1), the outer surface being configured to refract the convergent light beam towards the optical axis beyond the optical plate such that the convergent light-beam is re-centred at the throw distance D. a light source (15r, 15g, 15b) configured to emit light that is at least partially coherent; a projection lens (40, 240) configured to output the light as a convergent light beam towards a location on a target surface; and a despeckling device with an optical axis and having an optical plate comprising an inner surface and an outer surface such that light emerging from the projection lens (40, 240) enters the optical plate through the inner surface and exits the optical plate through the outer surface, wherein the despeckling device is positionable between the projection lens (40, 240) and the target surface such that the target surface is displaced from the outer surface by a throw distance D, and wherein said optical plate is rotatable about an axis of rotation equal to the optical axis to temporally and angularly deflect the convergent light beam through a plurality of angular orientations toward the location on the target surface; characterized in that the inner surface and the outer surface of the optical plate are tilted with respect to the optical axis, such that the inner surface has a tilt angle (Φ 1) with respect to a line perpendicular to the optical axis configured to refract the convergent light beam along the optical axis away from the optical axis within the optical plate with a displacement of d at the outer surface and the outer surface has a second angle with respect to the line perpendicular to the optical axis, the second angle being equal to the sum of the tilt angle (Φ 1) and a wedge angle (Φ 2), the wedge angle (Φ 2) being the angular amount that the outer surface is tilted further away from the line perpendicular to the optical axis than the tilt angle (Φ 1), the outer surface being configured to refract the convergent light beam towards the optical axis beyond the optical plate such that the convergent light-beam is re-centred at the throw distance D.