1. Field of the Invention
The present invention relates to an endoscope apparatus having a hood member provided at an end portion of an inserted portion of an endoscope.
2. Description of the Related Art
A conventional example of an endoscope apparatus for use in an operation is formed by disposing an objective lens, a light guide, an air and water supply port, and a suction port in an end portion of an inserted portion of an endoscope. Such an endoscope apparatus irradiates a subject such as living tissue with light from the light guide and allows the lighted subject to be viewed via the objective lens so as to suck, through the suction port, air, water, or other substances fed through the air and water supply port.
In this regard, when an attempt is made to insert the endoscope into, for example, the stomach, the mucous membrane of the stomach often contacts with and covers the objective lens provided in the end portion of the inserted portion of the endoscope. Thus, more inner areas of the stomach can no longer be viewed.
Correspondingly, Jpn. Pat. Appln. KOKAI Publication No. 11-206702 discloses an end structure of an endoscope in which the end portion of the inserted portion of the endoscope is provided with a guide portion to prevent the mucous membrane from covering the objective lens and blocking the view. The guide portion of the end structure of the endoscope is a hood-like member having an inner peripheral surface gradually widened so as to draw a curve starting from an end surface of its end portion.
Jpn. Pat. Appln. KOKAI Publication No. 11-313795 discloses an endoscope in which a hood member is formed to have a thickness or projecting height varying depending on a view angle. Such an endoscope has a smaller thickness or projecting height in a direction in which the view angle is larger or at a position close to an observing optical system.