Illumination – Light modifier – Refractor
Reexamination Certificate
1999-04-16
2001-06-12
Quach, Y. (Department: 2875)
Illumination
Light modifier
Refractor
Reexamination Certificate
active
06244732
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a lamp and, more particularly, to a lamp suitable for use as an illumination lamp for a vehicle such as a head lamp or fog lamp, a signal lamp for a vehicle such as a tail lamp or turn signal lamp, a signal lamp for road traffic, or a signal lamp for railway traffic.
2. Background Art
FIGS. 1
to
3
show conventional lamps of this type. A lamp
90
shown in
FIG. 1
basically includes: a light source
91
; a revolutional paraboloidal reflector
92
having the light source
91
disposed at a focal point thereof; and a lens
93
with a lens cut
93
a
. A light beam from the light source
91
is reflected by the revolutional paraboloidal reflector
92
to form a parallel light beam. The reflected light beam is diffused properly by the lens cut
93
a
of the lens
93
to provide a desired light distribution property.
A lamp
80
shown in
FIG. 2
includes a light source
81
; a reflector composed of a composite reflecting surface
82
; and a lens
83
. The composite reflecting surface
82
has a plurality of cylindrical parabolic reflecting surfaces that are arranged to have a parabolic configuration in a vertical cross section taken when the lamp
80
is in a mounted state and have a linear configuration in a horizontal cross section (the state shown in the drawing). The lens
83
has no lens cut so that it is see-through. In the lamp
80
, the composite reflecting surface
82
provides the light distribution property by itself.
A lamp
70
shown in
FIG. 3
includes: a light source
71
; a reflector composed of an elliptic reflecting surface
72
having the light source
71
disposed at a first focal point thereof; an aspheric lens
73
; and a shade
74
provided if necessary. The elliptic reflecting surface is composed of a spheroid, a composite elliptic surface, or an elliptic free-form surface. In the arrangement, the aspheric lens
73
projects, under magnification, a light source image formed by converging a light beam at a second focal point to provide an irradiating light beam. The lamp
70
of the type using the elliptic reflecting surface
72
is termed a projector type lamp. The light distribution property is obtained by covering an unwanted portion with the shade
74
.
In the lamp
90
shown in
FIG. 1
, however, the lens cut
93
a
should be formed to have high optical intensity, so that a significant variation is produced in the thickness of the lens
93
. This degrades the transparency of the lens and makes it impossible to provide an appearance with enhanced clarity and sense of depth, which is currently preferred on the market.
It is possible to impart an appearance with enhanced clarity to the lamp
80
shown in
FIG. 2
, since the lens
83
without a lens cut is see-through. However, since the composite reflecting surface
82
positioned at a recessed portion forms a light distribution property, the formation of the light distribution property is limited by such a factor as difficulty in determining the light distribution property in the direction of width.
The lamp
70
shown in
FIG. 3
is difficult to mount because of its increased depth dimension. Moreover, the aspheric lens
73
having a small outer diameter leads to a reduced light-emitting area. Therefore, the lamp
70
used as a headlight is inferior in visibility when viewed from an oncoming vehicle.
Each of the conventional lamps
70
,
80
, and
90
with the aforesaid structures is generally in wide use. Hence, it is impossible to distinguish them from other items and achieve novelty in terms of design. Furthermore, since the coefficient of use of a luminous flux from the light source is dependent on the depth dimension, the coefficient of use is lowered if the lamp is reduced in thickness.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a lamp with an unprecedented and novel design including an annular cylindrical lens and a central aspheric lens.
Another object of the present invention is to provide a lamp having a light distribution property free from constraints and exhibiting enhanced flexibility particularly in the horizontal direction.
Still another object of the present invention is to provide a lamp having a given light-emitting area and improved visibility when viewed from an oncoming vehicle.
Yet another object of the present invention is to provide a lamp wherein the coefficient of use of a luminous flux from the light source is unaffected by the depth dimension.
One aspect of the present invention is to provide a lamp comprising: a light source; a tilted ellipsoidal rotation surface reflector formed of an ellipsoidal rotation surface emerging when an ellipsoid, having a first focal point located on a center axis of the light source and adjacent the light source and a second focal point located on an oblique line passing through the first focal point and tilted appropriately from the light-source center axis and assumed on a plane containing the light-source center axis and the oblique line, is rotated around the light-source center axis; and an annular cylindrical lens being obtained by rotating, around the light-source center axis, a cross-sectional configuration of an aspheric lens having a focal point adjacent the second focal point of the ellipsoid and an optical axis nearly parallel to the light-source center axis.
Since the annular cylindrical lens occupying a large area is present at the front face of the lamp, the annular cylindrical lens having a curvature only in the direction of radiation achieves the enlargement of the reflector only in the direction of radiation. This also achieves the effect of providing a lamp with an unprecedented and novel appearance.
In terms of performance, the reflector formed of the tilted ellipsoidal rotation surface reduces the depth dimension, thereby achieving the effects of reducing the thickness of the whole lamp and improving the mountability thereof. Moreover, since light from the single light source forms an image at the annular second focal point, there can be achieved the effects of reducing the temperature of the annular cylindrical lens, allowing the formation of the annular cylindrical lens from a resin, and lowering cost.
At this time, the position of the annular cylindrical lens is preferably determined such that the second focal point of the ellipsoid is within a range extending from the focal point of the aspheric lens to the front end thereof.
Preferably, an aspheric lens having a focal point adjacent the light source is disposed in a hole formed in the center of the annular cylindrical lens. This further increases the coefficient of use of light from the light source.
The lens may have at least a part thereof formed in a Fresnel configuration.
Respective annular shades each for allowing the passage of at least a part of reflected light and direct light may be disposed adjacent the annular second focal point of the tilted ellipsoidal rotation surface reflector and between the aspheric lens and the light source. This enables free control of the light distribution property.
A revolutional paraboloidal reflector having a focal point at the light source may be disposed coaxially with the light-source center axis to correspond to the hole formed in the center of the annular cylindrical lens.
The lamp may have a lens holder portion and the annular shade and the lens holder portion are in a color other than the color of the annular cylindrical lens. This solves the problem of pseudo lighting
There may be further provided: a revolutional paraboloidal reflector having a focal point at the light source and an optical axis identical with the light-source center axis to correspond to a hole formed in the center of the annular cylindrical lens; and a prism lens corresponding to light from the revolutional paraboloidal reflector.
A filter in the form of a cap for diffusing or coloring light from the light source may be disposed between the light source and each of the tilted ellipsoidal rotation surface reflector and th
Futami Takashi
Kawaguchi Yoshifumi
Koike Teruo
Ostrolenk Faber Gerb & Soffen, LLP
Quach Y.
Stanley Electric Co. Ltd.
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