An endoscope includes a single lens that has a square exterior shape in a direction perpendicular to an optical axis, an image sensor that has an square exterior shape which is same as the exterior shape of the single lens, in the direction perpendicular to the optical axis, a sensor cover that has an exterior shape which is same as the exterior shape of the single lens, in the direction perpendicular to the optical axis; and a bonding resin portion that fixes the sensor cover to the single lens, The single lens is a lens which is formed in a prismatic shape. The single lens has first surface on an imaging subject side that has a plane, and has second surface on an imaging side that has a convex surface.
1. An endoscope comprising:
a single lens;
a sensor cover that covers an imaging area of an image sensor and has an exterior shape the same as an exterior shape of the single lens in a plane perpendicular to an optical axis of the single lens; and
a bonding resin portion that fixes the sensor cover to the single lens, the optical axis of the single lens coinciding with a center of the imaging area,
wherein an air layer is disposed between the single lens and the sensor cover glass,
wherein a central portion of the single lens has a convex curved surface which protrudes in a substantially spherical shape configuring a lens surface of the convex surface on an imaging side;
wherein a peripheral edge portion of the single lens has a planar end surface and has a bonding plane with the sensor cover glass over the planar end surface; and
wherein the peripheral edge portion of the single lens has an inclined portion which is tapered so as to be inclined from the planar end surface to the lens surface of the convex surface.
2. The endoscope according to claim 1 , wherein a light-emitting surface of the convex curved surface contacts with the air layer.
3. The endoscope according to claim 1 , wherein the air layer includes dry air.
4. The endoscope according to claim 1 , wherein the air layer includes nitrogen.
5. The endoscope according to claim 1 , wherein the single lens has an square exterior shape in a plane perpendicular to the optical axis.
6. The endoscope according to claim 5 , wherein the image sensor has an exterior shape which is the same as the exterior shape of the single lens, in a plane perpendicular to the optical axis.
7. The endoscope according to claim 1 , wherein the single lens and the sensor cover glass respectively have a thickness with a range of 0.1 to 0.5 mm along the optical axis.
8. The endoscope according to claim 1 , further comprising:
a molded part that covers an exterior peripheral surface of the single lens and the image sensor to fix the single lens and the image sensor,
wherein the molded part forms an exterior shell of a distal portion including the single lens.
9. The endoscope according to claim 8 , further comprising:
a tubular sheath that has an exterior diameter which is the same as an exterior diameter of the distal portion, and is connected to the distal portion by covering at least a portion of the molded part.
10. The endoscope according to claim 1 , wherein the bonding resin has a light-transmitting property.
11. The endoscope according to claim 1 , wherein the inclined portion on opposite sides of the central portion of the single lens define an angle θA therebetween, the angle θA being greater than or equal to 60° and less than or equal to 90°.
12. The endoscope according to claim 1 , wherein the bonding plane has a bonding width Wa which greater than or equal to 50 μm.