Endoscope optical adapter and endoscope

1. An endoscope optical adapter comprising:

an objective lens for observation;

a lens frame configured to hold the objective lens;

a cover member fixed to an outer circumference of the lens frame and extended to an inner side to surround the objective lens;

an attaching and detaching member provided with a screw mechanism, the attaching and detaching member being coupled to a proximal end side of the lens frame and detachably attachable to a distal end portion of an endoscope; and

a path for discharging a droplet adhering to a distal surface of the objective lens,

wherein the path includes a first groove,

the first groove being configured to allow the droplet adhered to the distal surface of the objective lens to move from a center of the objective lens toward an outer circumference of the objective lens,

an opening of the first groove, in a front view of the distal surface of the objective lens, being formed in an arc shape at least partially along a shape of the outer circumference of the objective lens in a length direction of the first groove,

a bottom of the first groove being formed at a position which is recessed with respect to a distal end face of the cover member and which is recessed with respect to the distal surface of the objective lens, and

the arc-shaped first grove comprises:

an inner surface configured by an outer circumferential surface of the objective lens;

an outer side surface configured by the cover member; and

the bottom configured by the lens frame.

2. The endoscope optical adapter according to claim 1 , wherein the opening of the first groove, in the front view of the distal surface of the objective lens, is provided in a half circumference or more of a peripheral section of the objective lens.

3. The endoscope optical adapter according to claim 1 , further comprising a plurality of second grooves different from the first groove, wherein the plurality of second grooves are formed on one of a distal end face of the lens frame and the cover member,

wherein the plurality of second grooves are configured to allow the droplet temporally accumulated in the first groove to be drawn into the plurality of second grooves.

4. The endoscope optical adapter according to claim 3 , wherein a shape of a cross section of each of the plurality of second grooves is one of a V shape, a rectangular shape, and a semicircular shape, the cross section being orthogonal to an extending direction of each of the plurality of second grooves.

5. The endoscope optical adapter according to claim 3 , wherein the plurality of second grooves have a tapered shape in which a width of each of the plurality of second grooves increases from an inner circumference to an outer circumference of the distal end face of the lens frame or the cover member.

6. The endoscope optical adapter according to claim 3 , wherein the plurality of second grooves are extended in an insertion axis direction to one of a predetermined position of a side surface of the lens frame and a predetermined position of a side surface of the cover member.

7. The endoscope optical adapter according to claim 3 , wherein the plurality of second grooves are extended in an insertion axis direction to one of the proximal end side of the lens frame and a proximal end side of the cover member.

8. The endoscope optical adapter according to claim 3 , wherein the plurality of second grooves are extended in parallel with each other in the front view of the front surface of the objective lens.

9. The endoscope optical adapter according to claim 3 , wherein a depth position of each of the plurality of second grooves is located so as to be recessed with respect to the distal surface of the objective lens.

10. The endoscope optical adapter according to claim 1 , wherein the objective lens includes a plurality of lenses and the lens frame holds the plurality of lenses.

11. The endoscope optical adapter according to claim 10 , wherein the inner side surface of the arc-shaped first groove is configured by an outer circumferential surface of a distal-most lens of the plurality of lenses.