| 摘要 |
A distal end optical unit for an electronic endoscope includes a first supporting tube configured to support an image sensor therein, a second supporting tube, and a third supporting tube configured to support an objective optical system. The first supporting tube includes a first open end, a first sealed end that is hermetically sealed, and a metal-covered inner circumferential surface. The second supporting tube includes a second open end, a second sealed end that is hermetically sealed with a cover lens, and a metal-covered outer circumferential surface. The third supporting tube has an inner circumferential surface with a low reflectivity. The third supporting tube is fitted into the second supporting tube. The second open end of the second supporting tube is fitted into and hermetically joined to the first open end of the first supporting tube.
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