| 摘要 |
PROBLEM TO BE SOLVED: To form a compact cap in which a mirror cylinder is made smaller in length. SOLUTION: A tilt part 14c is formed in a through hole 14 of a cap body 12, and low-melting-point glass 18 adhering a spherical lens 16 is made largest in thickness in the vicinity of the projection surface of the inner diameter of a small diameter part 14b or the surface of the spherical lens 16. The breaking strength of the glass 18 is made large enough to withstand a thermal deformation during welding, and a length H and a wall thickness T of a mirror cylinder part 12a are made small, thus making a cap body small for downsizing a package.
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