Projection lamp

Details Projection lamp Projection lamp

1999-10-27

2002-01-15

Husar, Stephen (Department: 2875)

Illumination

Supported by vehicle structure

Projection-type headlamp

C362S308000, C362S328000

Reexamination Certificate

active

06338568

ABSTRACT:

This invention claims the benefit of Japanese patent Application No. HEI 10-305781, filed on Oct. 27, 1998, which is hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a lamp and, more particularly, to a projection type headlamp for a vehicle in which a projection lens is disposed such that a focus point of the projection lens corresponds to a second focus point f
2
of an elliptic reflection surface. A light distribution pattern of the headlamp is defined by projecting a cross-sectional luminous flux and converging it into the second focus point f
2
.
2. Discussion of the Related art
FIG. 8
illustrates a conventional projection type headlamp in which a light source
92
is located close to a first focus point f
1
of a reflector
91
. The reflector
91
is circular as viewed from the front with an elliptically shaped surface as viewed from the side forming an opening. A projection lens
93
is disposed adjacent the opening in the reflector
91
. The lens
93
has a focus point f
3
located close to a second focus point f
2
of the reflector and into which light emitted from light source
92
converges.
Of the many light rays that converge into the second focus point f
2
, only light rays having an appropriate cross-sectional orientation for forming the specific light distribution pattern for the head lamp
90
can pass through the projection lens
93
. Other light rays are prohibited from passing through the projection lens
93
by a shade
94
.
However, the light from the light source
92
converges into the second focus f
2
and diffuses and radiates through the projection lens
93
toward the direction of irradiation for the headlamp
90
. Accordingly, the light will diffuse in a radiating direction after the light passes through the projection lens
93
.
Therefore, the conventional projection type lamp
90
has a light distribution pattern whose shape is easily determined, but whose luminous intensity distribution can not be freely determined because it is substantially impossible to concentrate or distribute light rays at predetermined positions due to the diffusing characteristic which are maintained even after the light rays pass through the projection lens
93
. Specifically, it is difficult to form a light distribution pattern for high beam mode because it requires a large amount of light directed outwardly from the front of the vehicle to provide long distance visibility in the high beam mode.
The conventional projection type headlamp
90
and the projection lens
93
are formed in a circular shape as seen from the front of a vehicle. This type of circular projection lens
93
is unsuitable for current design trends in automobile body design. To meet current design requirements, it is sometimes preferred to cut of the upper and lower portions of the projection lens
93
. In this case, the amount of light passing through the lens decreases and lowers a driver's ability to see when using the headlamp.
SUMMARY OF THE INVENTION
The invention is directed to a projection type lamp that substantially obviates one or more of the above problems due to the limitations and disadvantages of the conventional projection type lamps.
According to the invention, the above objects are achieved by providing a projection type headlamp including an oval projection lens with a long horizontal diameter, a light source, and a reflector. The oval projection lens can be shaped such that the lens includes two substantially similar to sphericallens portions formed by dividing a substantially hemispherical lens into two parts at its diameter and attaching the similar to sphericallens portions to opposite ends of a semi cylindrical lens portion. The longest width of the oval projection lens is called a horizontal diameter in this specification since the lens is intended to be mounted on a vehicle with the horizontal width substantially parallel to the travel surface for the vehicle. The semi cylindrical lens portion has a focus line extending in the horizontal direction.
The reflector can be elliptically shaped and include a first focus point located close to the light source in a vertical cross-sectional view, and a second focus point located close to the focus line in a horizontal cross-sectional view. In addition, a free curved surface on the reflector can provide a predetermined horizontal irradiation angle to the light emitted from the light source. The width of the free curved surface can be the same as that of the semi cylindrical lens portion in the horizontal direction.


REFERENCES:
patent: SHOU 62-10803 (1987-01-01), None
patent: SHOU 63-111703 (1987-01-01), None
patent: 10-199306 (1998-07-01), None
patent: 10-261302 (1998-09-01), None
patent: SHOU 63-30451 (1998-12-01), None

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