| 摘要 |
PURPOSE:To preclude deterioration and clouding even when germ reduction using high-temperature and high-pressure steam by covering the external end surface of at least either of an observation and a lighting optical system with cover glass which uses borosilicate glass. CONSTITUTION:An objective window in front of an objective 11 forming the observation optical system of an endoscope 1 is covered with the objective cover glass 14 and an ocular window behind an ocular 13 is covered with ocular cover glass 15. Those objective cover glass 14 and ocular cover glass 15 are both made of borosilicate glass, which consists principally of 80% SiO2, 2% Al2O3, 13% B2O3, and <=5% Na2O. Then, this material has water resistance and excellent heat resistance, and the resistance is maintained even in high- temperature and high-pressure steam. Consequently, even when the germ reduction is performed by using the steam, the cover glass surfaces never deteriorate to become clouded.
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