Projector-type head lamp for motor vehicles

Abstract

In a projector-type head lamp, a reflector having a concave inner reflecting surface, a light source, a shade with a cut-off edge and a projection lens are arranged in order. The inner reflecting surface of the reflector has at least 2 foci and is so designed as to reflect the rays of light emitted from the light source in a direction crossing the optical axis. The light source is disposed near one of the foci of the reflector while the cut-off edge of the shade is arranged in the vicinity of the other focus. The projection lens has an optical axis nearly coincident with that of the reflector and is so formed that the power of refraction thereof becomes progressively greater from the optical axis toward the outer circumference, namely, its peripheral lens area has a focus located in the vicinity of the cut-off edge while its central lens area has a focus located between the cut-off edge and the light source. The colored rays having passed through the peripheral lens area near the outer circumference of the projection lens form a sharp image of the cut-off edge of the shade on a screen, while the white rays having passed through the central lens area in which the optical axis lies form a blurry image of the cut-off edge on the screen. In an illumination pattern defined on the screen, the color fringes formed in the vicinity of the cut-off line are covered by the blurry image defined by the white rays having passed through the central lens area, thereby making the color fringes sufficiently unnoticeable.