Illumination – Light source and modifier – Including reflector
Reexamination Certificate
1999-08-06
2001-03-13
O'Shea, Sandra (Department: 2875)
Illumination
Light source and modifier
Including reflector
C362S348000, C362S517000, C362S518000, C362S346000, C362S305000, C362S499000
Reexamination Certificate
active
06200006
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a vehicle lamp, more particularly, to the construction of the reflective surface of its reflect component.
A typical modern type of vehicle lamps is shown in
FIG. 7
; the reflective surface
114
a
of the reflector
114
is composed of a plurality of diffusing reflector elements
114
s
and used in combination with a glass
116
having little or no refractive power to provide the light with a feeling of transparency or greater depth.
As is clear from
FIG. 7
, the plurality of diffusing reflector elements
114
s
are formed with reference to a single paraboloid of revolution P′, so the increase in the diameter of the opening of the reflector
114
results in a corresponding increase in its depth dimension. If the vehicular structure and other design considerations limit the space for installing the identification lamp, the diameter of the opening of the reflector
114
has to be reduced but then the light emitting surface is reduced accordingly to make the lighting device look less attractive.
An improvement over this light is shown in
FIG. 8
; a reflective surface
214
is composed of a plurality of diffusing reflector elements
214
s
formed on a free curved surface Cf′. This increases the degree of freedom in the shape of the reflector
214
and even if only a limited space is available for installing the identification lamp, the reflective surface of the reflector
214
can be composed while ensuring a sufficient diameter for its opening.
However, the mere formation of diffusing reflector elements
214
s
on the free curved surface Cf to compose the reflective surface
214
a
causes the following problems. To assure the intended luminous intensity distribution from a vehicle lamp, diffusing light must be created in all directions from the optical axis Ax′ of the reflector
214
. If a plurality of diffusing reflector elements
214
s
are simply formed on the free curved surface Cf′, the direction of the diffusing reflected light from each element varies randomly with the shape of the free curved surface Cf′; as a result, the directivity of the illuminating light from various parts of the reflective surface
214
a
cannot be sufficiently controlled to ensure the intended luminous intensity distribution for the lighting device. Further, depending on the position of individual diffusing reflector elements
214
s
on the free curved surface Cf′, there will be no reflected light that travels from certain elements toward the optical axis Ax′ and those elements are invisible if they are viewed right from the front of the lighting device being lit up. This makes the lighting device look less attractive.
SUMMARY OF THE INVENTION
The present invention has been accomplished under these circumstances and has as an object providing a vehicle lamp which has its reflector component composed of a plurality of diffusing reflector elements formed on a free curved surface and which is characterized by ease in assuring the intended luminous intensity distribution and by the ability to prevent the light from looking less attractive when it is lit up.
This object of the invention can be attained by setting a plurality of sector segments about the optical axis of a reflector for assignment of diffusing reflector elements, setting specified paraboloids of revolution in accordance with the positions of the respective sector segments, and setting the surface geometries of the individual diffusing reflector elements with reference to the respective paraboloids of revolution.
The present invention provides a vehicle lamp comprising a light source and a reflector that allows the light from the light source to be reflected in a forward direction and the reflective surface of which is composed of a plurality of diffusing reflector elements formed on a free curved surface, characterized in that the individual diffusing reflector elements are respectively assigned to a plurality of sector segments centering on the optical axis of said reflector and that the surface geometry of each of said diffusing reflector elements is set on a specified curved surface that is referenced to a paraboloid of revolution which, among a plurality of paraboloids of revolution having different focal lengths that center on said optical axis with a common focus lying at a single point on said optical axis, passes a specified point of a sector segment to which said diffusing reflector element is to be assigned on said free curved surface.
The term “free curved surface” as used hereinabove means any curved surface other than a quadratic curved surface.
The “sector segments” may be set on equal pitches in both a radial and a circumferential direction as long as they center on the optical axis of the reflector; alternatively, they may be set on varying pitches in either a radial or a circumferential direction or in both directions.
The “specified point” may be the center or an end point of each sector segment or it may be any other point of the sector segment.
The “specified curved surface” is not limited to any particular curved surface as long as it is formed as a curved surface (which may be a plane) referenced to a paraboloid of revolution and if it has diffusing and reflecting capabilities.
In this invention, the reflective surface of the reflector in the vehicle lamp of the invention is composed of a plurality of diffusing reflector elements formed on a free curved surface. This increases the degree of freedom of the reflector's shape and even if only a limited space is available for installing the identification lamp, the reflective surface of the reflector can be composed while ensuring a sufficient diameter for its opening.
Given this basic design, the individual diffusing reflector elements are respectively assigned to a plurality of sector segments centering on the optical axis of the reflector and the surface geometry of each of the respective diffusing reflector elements is set on a specified curved surface that is referenced to a paraboloid of revolution which, among a plurality of paraboloids of revolution having different focal lengths that center on said optical axis with a common focus lying at a single point on said optical axis, passes a specified point of a sector segment to which said diffusing reflector element is to be assigned on said free curved surface. As a result, the diffusing reflected light from each diffusing reflector element can be controlled in diffusion with reference to the axial direction of the reflector and the directivity of the diffusing illumination from the reflective surface taken as a whole can be easily controlled. In addition, when the lighting device is lit up and viewed right from the front, the entire part of its reflective surface is visible and can be seen bright although in a discrete manner.
Thus, according to the present invention, there is provided a vehicle lamp in which the reflective surface of the reflector is composed of a plurality of diffusing reflector elements formed on a free curved surface and which is characterized by ease in assuring the intended luminous intensity distribution for the lighting device while preventing it from looking less attractive when it is lit up.
The invention is also characterized in that the individual diffusing reflector elements are respectively assigned to the plurality of sector segments centering on the optical axis of the reflector and this offers the following advantage in the way the lighting device looks externally when it is lit up.
If the construction of the present invention is adopted, a plurality of diffusing reflector elements are formed stepwise on a free curved surface and a difference in level occurs between adjacent diffusing reflector elements. Depending on the orientation of such level differences, shades will be cast on the reflective surface against the light from the light source in the lighting device being lit up. If such shades are shaped randomly, the lighting device being lit up and viewed externally will look
Kubota Mitsuru
Natsume Kazunori
Alavi Ali
Koito Manufacturing Co. Ltd.
O'Shea Sandra
Sughrue Mion Zinn Macpeak & Seas, PLLC
LandOfFree
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