1. Field of the Invention
The present invention relates to a plasma lamp system, and more particularly, to a plasma lamp system and a bulb therefor capable of maximizing lighting efficiency by improving a point source of light characteristic and a spectrum characteristic.
2. Description of the Background Art
In general, a plasma lamp system is a lighting system which emits visible rays and ultraviolet rays when a filling material within a bulb is excited by microwave energy or electric discharge, has a long life span compared to an incandescent lamp or a fluorescent lamp, and has excellent efficiency in lighting.
A bulb of a plasma lamp system is filled with high-pressure mercury or metal halide as a primary light-emitting material leading light-emitting when excited by microwave energy or electric discharge, together with inert gas for forming a plasma at an initial stage of lighting-emitting, additives which make lighting easy and the like.
Such a conventional plasma lamp system shows different characteristics according to types of the primary light-emitting materials within the bulb.
In a UHP (ultra high performance) lamp system having a bulb filled with high-pressure mercury, mercury of about 200 atm or more emits light in operation and shows a spectrum characteristic as shown in FIG. 1. That is, in the UHP lamp system, intensity of light is high in a blue color region where a wavelength of light is about 400˜500 nanometers and in a green color region where a wavelength of light is about 500˜600 nanometers. But, intensity of light is low in a red color region where a wavelength of light is about 600˜700 nanometers. Accordingly, the UHP lamp system cannot obtain high reddish color purity, thereby having limitations on improving display performance.
In an MH (metal halide) lamp system having a bulb filled with metal halide, since intensity of light shows an independent peak in each of red, green and blue color regions, it is easy to make a proper optical spectrum. But, optimum pressure of the metal halide is relatively low because of a characteristic of metal halide, and thus the light is emitted not in parallel but radially, whereby it is not easy to apply the MH lamp system to an optical system that requires a point source of light. Therefore, in case of applying the MH lamp system to an optical system which requires a point source of light, such as a projector or a projection display, as shown in FIG. 2, the center of an arc 40 of a bulb 10 should be positioned at a focal point of a reflector 20 for reflecting light in order to obtain parallel light 30, thereby causing intricacy in manufacturing and degrading productivity.