Motor vehicle headlamp

• US 5,897,196 A
• Filed: 03/29/1996
• Issued: 04/27/1999
• Est. Priority Date: 03/29/1996
• Status: Expired due to Term

• Current Assignee: OSRAM Sylvania Inc. (Ams-Osram AG)
• Original Assignee: OSRAM Sylvania Inc. (Ams-Osram AG)
• Inventors: Dorogi, Michael J., Soskind, Yakov G.
• Primary Examiner(s): LEE, Y MY QUACH
• Application Number:
  US08/625,618
• Time in Patent Office: 1,124 Days
• Field of Search: 362/61, 362/80, 362/297, 362/308, 362/311, 362/328, 362/346
• US Class Current: 362/507
• CPC Class Codes: F21S 41/255 Lenses with a front view of circular or truncated circular outline
• CPC Class Codes: F21S 41/275 Lens surfaces, e.g. coatings or surface structures
• CPC Class Codes: F21S 41/28 Cover glass
• CPC Class Codes: F21S 41/334 the reflector consisting of patch like sectors

Abstract

A vehicle headlamp may be formed from a light source; a divergent lens; and a reflector facing in a forward direction to the lens. The reflector has one or more first regions, and one or more second regions. The first region is a section of an ellipsoid of revolution with one focal point coincident with the light source, and one focal point located at the first focal point of the lens. The second regions have a surface with an elliptical vertical cross section having a first focal point coincident with the light source and a second focal point coincident with the first focal point of the lens. The second surface additionally has a horizontal axial cross section having a first focal point coincident with the light source and a second focal point axially offset from the first focal point of the lens. The horizontal axial cross section may be elliptical, parabolic or hyperbolic. Light from the first regions is convenient to form the beam hot spot. Meanwhile, light from the second regions is convenient to form the beam spread. In total the system provides a headlamp with a short axial dimension and a small frontal opening while meeting headlamp beam standards.

Claims

1. A vehicle headlamp comprising:

a light source;

a divergent lens having a first focal point, and a lens axis passing through the light source and the first focal point of the lens; and

a reflector having a reflective surface facing in a forward direction to the light source and the lens to reflect light from the light source towards the lens, the reflective surface having,

at least a first region comprising a portion of a type 1 surface, being an ellipsoid of revolution with a respective first and second focal point, the first reflector region being oriented with the first respective focal point located at the light source, and the second respective focal point located at the first focal point of the lens; and

and at least a second region comprising a portion of a type 2 surface having an elliptical vertical axial cross section with associated first focal point and second focal point; and

having a horizontal axial cross section with associated first focal point and second focal point, the second reflector region being oriented to locate the first focal point of the vertical cross section, and the first focal point of the horizontal cross section at the light source, and the second focal point of the vertical cross section at the first focal point of the lens, and the second focal point of the horizontal cross section axially offset from the first focal point of the lens.

2. The lamp in claim 1, wherein the lens has an active portion having a dimension that is less than a dimension measured across a forward most, active portion of the reflector, with both dimensions being orthogonal through the lens axis, and parallel to each other.

3. The lamp in claim 1, wherein the lens is axially offset from the reflector to be forward of a forwardmost portion of the reflective surface.

4. The headlamp in claim 1, wherein said horizontal cross section of the type 2 surface is elliptical with the second focal point thereof between the light source and the first focal point of the lens.

5. The headlamp in claim 1, wherein said horizontal cross section of the type 2 surface is elliptical with said second focal point thereof between the first focal point of the lens and infinity.

6. The headlamp in claim 1, wherein said horizontal cross section of the type 2 surface is parabolic with said second focal point thereof at infinity.

7. The headlamp in claim 1, wherein said horizontal cross section of the type 2 surface is hyperbolic and the second focal point thereof is an imaginary second focal point behind the reflector.

8. The headlamp in claim 1, wherein said reflective surface having a plurality of regions, each being a portion of the type 1 surface.

9. The headlamp in claim 1, wherein said reflective surface having a plurality of regions, each being a portion of the type 2 surface.

11. The headlamp in claim 1, wherein at least one type 2 surface is defined by the equation:

space="preserve" listing-type="equation">aX.sup.3 +bXY.sup.2 +cXZ.sup.2 +dX.sup.2 +eY.sup.2 +fZ.sup.2 +gX=0

where

X=the lamp axis dimension

Y=the horizontal dimension

Z=the vertical dimension

a=bc=(1+K_z) (1+K_y)

b=(1+K_z)

c=(1+K_y)

d=bf+ce=(-2) (R_y (1+K_z)+R_z (1+K_y))

e=(-2) (R_z)

f=(-2) (R_y)

g=ef=4(R_z) (R_y),

R_y and R_z are positive constants representing radii of curvature at the axial intersection of the surface (vertex) in the horizontal and vertical axial planes respectively, and

K_y and K_z are constants for the horizontal and vertical sectional curves, respectively, with K_z greater than -1.

10. A vehicle lamp providing a hot spot and beam spread portions comprising:

a light source sufficient to meet automotive headlight lumen requirements;

a divergent, concentric Fresnel lens having a first focal point, an axis of rotation passing through the light source and the first focal point of the lens, the lens having a dimension orthogonal and through the lens axis, and

a reflector with a reflective surface, the reflector being axially offset from the lens, and wherein the lens has an active portion having a dimension that is less than a dimension measured across a forward most, active portion of the reflector, with both dimensions being orthogonal through the lens axis, and parallel to each other, the reflective surface further having at least a first region, a second region and a third region each comprising a portion of a type 1 surface, the type 1 surface being an ellipsoid of revolution with a respective first and second focal point, the first region, second region and third region being oriented so that each respective first focal point is located at the light source, and each respective second focal point is located at the first focal point of the lens; and

at least a fourth region and a fifth region each comprising a portion of a type 2 surface, each type 2 surface having an elliptical vertical axial cross section with respectively a first focal point and a second focal point; and

having a horizontal axial cross section with respectively a first focal point and a second focal point, the fourth region and the fifth region being oriented to locate respectively the first focal points of the vertical cross sections, and the first focal points of the horizontal cross sections at the light source, and the second focal points of the vertical cross sections at the first focal point of the lens, and the second focal points of the horizontal cross sections displaced from the first focal point of the lens;

whereby light from the light source reflected from the first region, from the second region and third region enters the lens to be refracted and then exits the lens along substantially axially parallel lines, and whereby light from the light source reflected from the fourth region and the fifth region enters the lens to be refracted and then exits the lens in substantially horizontally parallel planes.