| 摘要 |
A capsule type endoscope includes an illumination device, an imaging device, and a transparent cover covering the illumination device and the imaging device. The imaging device has an objective optical system and an image sensor. When the objective optical system satisfies Condition (1) described below and a white cylinder with a reflectance of 90%, satisfying Condition (3) described below, is observed, illuminance of the imaging surface of the image sensor satisfies Condition (2) described below, in a state where a longitudinal center axis of a capsule coincides with the center axis of the white cylinder with a reflectance of 90%. <?in-line-formulae description="In-line Formulae" end="lead"?>omega>=50° (1)<?in-line-formulae description="In-line Formulae" end="tail"?> <?in-line-formulae description="In-line Formulae" end="lead"?>T<SUB>1</SUB>x0.5<=T<SUB>2</SUB> (2)<?in-line-formulae description="In-line Formulae" end="tail"?> <?in-line-formulae description="In-line Formulae" end="lead"?>D=1.2xPhi (3)<?in-line-formulae description="In-line Formulae" end="tail"?> where omega is a half of a field angle of the objective optical system, T<SUB>1 </SUB>is the maximum illuminance in an area on the imaging surface of the image sensor corresponding to a field region of the objective optical system, T<SUB>2 </SUB>is illuminance at a position on the imaging surface of the image sensor corresponding to a half of the maximum image height of the objective optical system, D is the inside diameter of the white cylinder, and Phi is the outside diameter of the capsule type endoscope.
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