| 摘要 |
PURPOSE:To prevent a mirror surface from the generation of distortion even if expansion or contraction is generated due to the change of environment by arranging the surface of a thin film material in the same direction over the whole surface of a coat base material. CONSTITUTION:If a light source is arranged on a focus 5 when the surface of a parabolic reflector is linearly symmetrical about a mirror axis, light beams are reflected by the mirror surface formed on the surface of the coat base material 2 to obtain parallel light beams orientated in a constant direction. Since the surface of the thin film material is cut off and laminated so that the face direction coincides with the direction of parallel beams, the direction of the thin film material is uniformized also on dividing lines 4 to be border lines of respective divisions in case of dividing the core 1. Therefore the reflector is contracted as shown by double dotted chain also at the time of drop of atmospheric temperature. Namely the thin film material of the core 1 is always contracted in the same direction as the parallel beams and an FRD plate 2 is not partially deformed at the dividing parts 4 of the core 1, so that the peripheral part of the reflector surface is not deformed upward and infrared rays or light beams are reflected in a prescribed direction.
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