Vehicle headlamp

Details Vehicle headlamp Vehicle headlamp

2001-12-11

2003-09-16

O'Shea, Sandra (Department: 2875)

Illumination

Supported by vehicle structure

Projection-type headlamp

C362S538000, C362S509000, C362S503000, C362S305000, C362S494000

Reexamination Certificate

active

06619827

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a novel vehicle headlamp and, more particularly, to the art of canceling an extreme light-and-shade difference in a light-and-shade boundary portion produced by a headlamp.
There is a prior-art vehicle headlamp or projector type headlamp, comprising a reflector having a substantially spheroidal reflective surface, a light source disposed at the first focal position of the reflector, a projection lens disposed in front of the light source and used for projecting forward the light of the light source reflected from the reflector, and a cutline-forming shade whose upper edge is substantially disposed in the focal position of the projection lens.
With respect to the reflector having the spheroidal reflective surface, reflected light having a considerably large angle with the optical axis is emitted from the reflector—when the surface perpendicular to the optical axis including the second focal point, that is, the surface extending up to the vicinity of the focal surface, is used as the reflective surface. As the light directed upward is shaded by the cutline-forming shade, no problem arises. However, the light emitted downward subsequently is reflected upward by a member, such as a bumper, positioned close to the headlamp. Such light then is either subjected—by dust in the air—to irregular reflection, or reflected from drops of rain, which produces an optical film phenomenon developing a problem of glare that results in a driving impediment.
Therefore, an attempt has been made to provide a dimming shade for the purpose of cutting the downwardly emitted light (from the reflector) that is subject to upward reflection by the bumper, and this has contributed to obviating the glare phenomenon in its own way.
However, the conventional vehicle headlamp is arranged so that the downwardly emitted light from the reflector is cut in the vicinity of the second focal point by disposing the front is end portion of the dimming shade in the vicinity of the second focal point of the reflector. Therefore, the cutline sharply emerges and the problem is that an extreme light-and-shade difference arises in the light distribution.
With respect to the upper edge of a low-beam light distribution, the cutline must sharply emerge for the purpose of preventing the driver of any oncoming car from receiving dazzling light. However, occurrence of such an extreme light-and-shade difference on the lower edge of the light distribution tends to lower the visibility of the driver because of the time lag associated with the change of pupil size when the eye is turned to the dim portion from the bright portion
SUMMARY OF THE INVENTION
An object of the present invention is to slow light-and-shade changes in a light-and-shade boundary portion on the lower edge of the light distribution.
In order to accomplish the above and other objects, a dimmer shade, whose front end portion is positioned closer to a reflective surface of the reflector than it is to the converging point of the reflector, is disposed above the optical axis of the reflector.
Therefore, in the vehicle headlamp according to the invention, emitted light (from the reflector), for forming a light-and-shade boundary portion at the lower end of a light distribution, is cut while the luminous flux density is relatively low. Therefore, variation of irradiation light with respect to variation in the size and shape of the dimmer shade is small, so that delicate adjustment of the irradiation light is easy. As a result, there is reduced risk of lowering a driver's visibility when the driver's eyes are moved between the light and shade portions.


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