Patent ID: 8360967

Claim:
A distal end optical unit for an electronic endo scope, comprising: 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, wherein the first supporting tube includes: a first open end provided at a distal end thereof; a first sealed end provided at a proximal end thereof that is hermetically sealed; and a metal-covered inner circumferential surface, wherein the second supporting tube includes: a second open end provided at a proximal end thereof; a second sealed end provided at a distal end thereof that is hermetically sealed with a cover lens; and a metal-covered outer circumferential surface, wherein the image sensor is entirely housed inside the first supporting tube in an axial direction of the first supporting tube, wherein the third supporting tube has an inner circumferential surface with a low reflectivity, the third supporting tube being fitted into the second supporting tube, wherein the second open end provided at the proximal end of the second supporting tube is fitted into and hermetically joined to the first open end provided at the distal end of the first supporting tube, wherein the second supporting tube is fitted into the first supporting tube and fitted around the third supporting tube such that the third supporting tube is entirely housed inside the second supporting tube in an axial direction of the second supporting tube, and wherein the second supporting tube includes a first portion at a side of the second open end, in which the third supporting tube is not fitted, and a second portion in which the third supporting tube is fitted, the first portion having an inner diameter larger than that of the second portion.