Imaging device for endoscope, and method of manufacturing imaging device for endoscope
An imaging device includes: an optical element including a metal layer adapted to be brazed and arranged on an outer peripheral surface of the optical element; a first frame body including a metal part adapted to be brazed and arranged at least on an inner peripheral surface and an outer peripheral surface of the first frame body, the inner peripheral surface being brazed onto the outer peripheral surface of the optical element; and a second frame body including a metal part adapted to be brazed and arranged at least on an inner peripheral surface of the second frame body, the inner peripheral surface being brazed onto the outer peripheral surface of the first frame body. A coefficient of thermal expansion of the first frame body is closer to a coefficient of thermal expansion of the optical element than a coefficient of thermal expansion of the second frame body.
1. An imaging device for an endoscope, the imaging device comprising:
an optical element including a metal layer adapted to be brazed and arranged on an outer peripheral surface of the optical element;
a first frame body including a metal part adapted to be brazed and arranged at least on an inner peripheral surface and an outer peripheral surface of the first frame body, the inner peripheral surface being brazed onto the outer peripheral surface of the optical element; and
a second frame body including a metal part adapted to be brazed and arranged at least on an inner peripheral surface of the second frame body, the inner peripheral surface being brazed onto the outer peripheral surface of the first frame body, wherein
a coefficient of thermal expansion of the first frame body is closer to a coefficient of thermal expansion of the optical element than a coefficient of thermal expansion of the second frame body.
2. The imaging device according to claim 1 , wherein
the first frame body comprises:
a holding frame to which the outer peripheral surface of the optical element is brazed; and
a distortion absorbing part that is positioned between the holding frame and the second frame body and absorbs distortion of the second frame body.
3. The imaging device according to claim 2 , wherein
the holding frame and the distortion absorbing part are arranged in parallel along a center axis of the first frame body, and
a thickness dimension in a radial direction of the distortion absorbing part is smaller than a thickness dimension in a radial direction of the holding frame.
4. The imaging device according to claim 1 , wherein the coefficient of thermal expansion of the first frame body is a value between the coefficient of thermal expansion of the optical element and the coefficient of thermal expansion of the second frame body.
5. The imaging device according to claim 1 , wherein the optical element is sapphire glass.
6. A method of manufacturing an imaging device for an endoscope, the imaging device including an optical element including a metal layer adapted to be brazed and arranged on an outer peripheral surface of the metal layer, a first frame body including a metal part adapted to be brazed and arranged at least on an inner peripheral surface and an outer peripheral surface of the first frame body, and a second frame body including a metal part adapted to be brazed and arranged at least on an inner peripheral surface of the second frame body, the method comprising:
brazing the outer peripheral surface of the optical element and the inner peripheral surface of the first frame body; and
brazing the outer peripheral surface of the first frame body and the inner peripheral surface of the second frame body, wherein
a coefficient of thermal expansion of the first frame body is closer to a coefficient of thermal expansion of the optical element than a coefficient of thermal expansion of the second frame body.