| 摘要 |
PROBLEM TO BE SOLVED: To provide a light source unit realizing a long service life by simply and surely preventing a reflector or a light-transmitting plate from cracking. SOLUTION: In this light source unit U1, an opening in a reflector R is covered with a light-transmitting plate 20 by fixing the light-transmissive plate 20 to an opening peripheral part A of the reflector R, and thus a structure suitable for explosionproof is obtained. During light emission, not only the reflector R but the light-transmissive plate 20 is exposed to a high temperature, and air inside the reflector R maintains at an extremely high temperature. Then, the reflector R and the light-transmitting plate 20 are thermally expanded by the high temperature, and they sometimes crack due to the difference in their coefficients of thermal expansion. To avoid such a situation, a part is cut out of the opening peripheral part A of the reflector R so that a light- transmissive plate housing part 21 is not formed over the entire circumference of the opening peripheral part A of the reflector R. By forming such a cutout in the opening peripheral part A, an escape for stresses due to thermal expansion can be creased, thus surely achieving the crack prevention of the reflector R and of the light-transmissive plate 20. |
