Illumination – Light modifier – Refractor
Reexamination Certificate
2000-06-24
2001-09-18
Tso, Laura K. (Department: 2875)
Illumination
Light modifier
Refractor
C362S331000
Reexamination Certificate
active
06290374
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a refractive lens system, and more particularly to a refractive lens system illuminated by light emitting diodes for traffic signal lamps.
BACKGROUND OF THE INVENTION
A traffic signal lamp is used to control vehicles and passengers so that traffic can flow smoothly and both drivers and passengers are safe. Brightness and viewing angle are two important requirements that have to be considered in manufacturing a traffic signal lamp. Most countries require very high brightness and limited viewing angle for traffic signal lamps. In general, there should be no brightness above the horizontal line of a traffic signal lamp. The primary light source of a conventional traffic signal lamp has been an incandescent lamp.
In recent years, light emitting diodes are gradually used to replace the incandescent lamp. However, it has been difficult to design traffic signal lamps illuminated by light emitting diodes to satisfy the brightness and viewing angle requirements. One conventional approach to manufacturing a traffic signal lamp illuminated by light emitting diodes is to use a large number of diodes without adding any lens. Because light is emitted towards all directions from the diodes, the illumination above the horizontal viewing angle is completely wasted. In order to satisfy the brightness, many light emitting diodes are required in this approach.
To reduce the number of light emitting diodes required and limit the viewing angle, some manufacturers have tried to add lenses in front of the light emitting diodes. Nevertheless, it is difficult to design high efficiency lens that can greatly increase the brightness of a traffic signal lamp. Most of the design still requires a fairly large number of light emitting diodes. With some complex lens design, it may require a less number of light emitting diodes. However, complex lens design makes the manufacturing difficult and the cost of a lamp too high.
As described above, the conventional approaches to manufacturing traffic signal lamps can not meet the objectives of saving energy and reducing cost. There is a strong need in designing traffic signal lamps illuminated by light emitting diodes that meet the requirements of high brightness, desired viewing angle, and low power consumption.
SUMMARY OF THE INVENTION
The present invention is designed to overcome the above-mentioned drawbacks in manufacturing the conventional traffic signal lamps. A primary object of the present invention is to provide a high brightness but limited viewing angle traffic signal lamp illuminated by light emitting diodes. Accordingly, the traffic signal lamp of this invention comprises two lens sets. A first lens set collimates light emitted from light emitting diodes in a horizontal direction and limits light in a viewing angle in a vertical direction. A second lens set redistributes the light within a viewing angle in the horizontal direction.
It is also an object of the invention to provide the design of a lens set that can collimate light in a horizontal direction and limit light angle in a vertical direction. The first lens set of the traffic signal lamp has an entrance surface comprising a plurality of convex cylindrical surfaces in the vertical direction and an exit surface comprising a plurality of slanted planar or cylindrical surface segments in the horizontal direction. The convex cylindrical surfaces collimate light into parallel light in the first lens set in the horizontal direction. The slanted surface segments limit light in a viewing angle in the vertical direction.
It is yet another object of the invention to provide the design of a lens set that can redistribute and limit light in a viewing angle in the horizontal direction. The second lens set of the traffic signal lamp has an entrance surface comprising a plurality of elongated concave cylindrical surfaces in the vertical direction and a convex exit surface with a small curvature. Light passing through the first lens set is redistributed and limited by the second lens set in a viewing angle in the horizontal direction uniformly.
Another object of the invention is to provide lens sets that are low cost and easy to manufacture. According to the invention, the first and second lens sets have simple cylindrical or planar surfaces that can be manufactured without difficulty. At least one of the convex cylindrical surfaces of the first lens set can be a recessed cylindrical surface to reduce the thickness as well as the cost of the first lens set. The light transmission through the first lens set is also increased.
Other features and advantages of the invention will become better understood from the following description of the invention which refers to the accompanying drawings.
REFERENCES:
patent: 4120018 (1978-10-01), Nagel
patent: 4158222 (1979-06-01), Cook
patent: 5055976 (1991-10-01), Aria
patent: 5584570 (1996-12-01), Binder et al.
Chang Chong-Min
Chen Chung-jung
Chuang Keng-Han
Shieh Han-Ping
You Ju-Yuan
Opto Tech Corp.
Tso Laura K.
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