Conventional colonoscopy is performed with a long, flexible tube called a colonoscope that is equipped with a tiny fiber-optic video camera and light at the end.

VOA: standard.2010.04.07

It is a glass tube. He wants to narrow the light so he puts a couple of slits here.

这是根玻璃管子，他想要减少光的发散,所以在这里开了几个口子。

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