Colour fringing in lamps suppression method - uses mask between light source and projector lens to define cutoff in projected beam

摘要

Lamp has an optical system comprising a light source, a projection lens, a mask disposed between the light source and the projection lens to define a cut-off in the projected beam and an optical element forming an image of the light source at or near the mask. The mask comprises a mask element which is further from the projection lens. The optical element forms a light source image between the mask elements. The projection lens has first and second parts which correspond with the masked and unmasked areas of the light source image. The nearer mask element is between the projection lens and the focus of the first part, whereby the first part produces a virtual erect mask image and the focus of the second part is between the projection lens and the further mask element, whereby the second part produces a real inverted mask image.