| 摘要 |
PROBLEM TO BE SOLVED: To increase beams of light through an increase in the area over which a phosphor is applied by providing inside a discharge bulb either a built-in bulb with the phosphor applied thereto or a fin-shaped or columnar projection. SOLUTION: This electrodeless lamp emits light by converting power taken in from a base 6 into high-frequency power by means of a lighting circuit 4, and generating a plasma through the generation of a high-frequency electromagnetic field inside a discharge lamp 1 by means of an excitation coil. A spherical built-in bulb 9 to which a phosphor 10 is applied is installed inside the discharge bulb, and when a beam of light from a phosphor 8 applied to a dent 2 is (a), a beam of light from the phosphor on the inside of the built-in bulb 9 is (b), a beam of light from the phosphor on the outside of the built-in bulb 9 is (c), a beam of light from a phosphor 7 on the inside of the discharge bulb 1 is (d), the total transmittance of the built-in bulb 9 and the phosphor applied thereto is×1, and the total transmittance of the discharge bulb 1 and the phosphor applied thereto is×2, then the beams of light from the whole electrodeless lamp are (a+b)×1×2+c×2+(d), i.e., increase by (a+b)×1×2+(c-a)×2.
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