1. Field of the Invention
The present invention relates to a headlamp unit for a vehicle and more specifically to a headlamp unit for a vehicle having a structure for maintaining even lighting intensity.
2. Description of the Related Art
As shown in FIGS. 1A and 1B, a conventional headlamp unit for a vehicle is disclosed in Japanese Unexamined Patent Publication No. 2003-229006. The headlamp unit 101 comprises a light-emitting diode (LED) 102, a first reflective member 103, a second reflective member 104, a lens 105, a printed board 106 and a cover 107.
The LED 102 is mounted on the printed board 106. The LED 102 emits light around an optical axis Z forward therefrom.
The first reflective member 103 is disposed so as to surround a front side of the LED 102. The first reflective member 103 has a main body 103a and a reflection coating 103b formed on a rear surface of the main body 103a. The reflection coating 103b is a part of an ellipsoid of revolution formed by rotating an ellipsoid around the optical axis Z, wherein the ellipsoid has a first focus position F1 located near an emitting position of the LED 102 and a second focus position F2 located out of the optical axis Z.
The second reflective member 104 is disposed so as to be opposed to the first reflective member 103. The second reflective member 104 has a main body 104a and a reflection coating 104b formed on a front surface of the main body 104a. The reflection coating 104b is a part of a paraboloid of revolution formed by rotating a parabola around a rotation axis parallel to the optical axis Z, wherein the parabola has a focus position located near the second focus position F2 and the rotation axis passes the focus position.
The lens 105 is annularly disposed to a front side of the second reflective member 104 in order to focus an annularly-shaped beam reflected by the reflection coating 104b and control a distribution of the annularly-shaped beam. The cover 107 is made of a transparent member and mounted to a front side of the lens 105 so as to cover it.
When the LED 102 emits light, the light is reflected by the reflection coating 103b and then focused in the first focus position F1. The light is reflected by the reflection coating 104b and then moves forward as a parallel beam. When the parallel beam enters the lens 105, the parallel beam is focused and distribution-controlled to be emitted in front of the vehicle.
However, the headlamp unit 101 lacks compatibility as a headlamp because it has a non-emission region in a center portion of the cover 107 (see FIG. 1A). The headlamp unit 101 also lacks even lighting intensity because it comprises one LED. These lead to poor visibility.
Further, a lack of lighting intensity causes a plurality of the headlamp assemblies 101 to be installed on the vehicle because the headlamp unit 101 comprises one LED. This leads to a large sized headlamp unit assembly.