Endoscope

1 . An endoscope comprising:

a distal end optical system that is movable forward and backward in an optical axis direction;

a shaft that has a shaft axis, is configured to rotate in a rotation direction about the shaft axis, and moves the distal end optical system in the optical axis direction in a case in which the shaft rotates in the rotation direction;

a knob;

a slider that moves forward and backward in a direction of the shaft axis according to a rotating operation of the knob; and

a power conversion transmission mechanism that rotates the shaft by the forward and backward movement of the slider, wherein

the power conversion transmission mechanism includes

an engagement member comprising a nut or a cam pin provided on the slider, and

a shaft member that is linked with the shaft and is formed with a spiral engaged part, on an outer peripheral surface, with which the engagement member is engaged, and

the shaft member rotates the shaft by linear movement of the engagement member accompanied by the forward and backward movement of the slider.

2 . The endoscope according to claim 1 ,

wherein the knob is a rotational operation member configured to be rotationally operated, and

the endoscope further comprises:

a swing member that swings in a case in which the rotational operation member is rotationally operated; and

a link member that links the swing member with the slider and moves the slider forward and backward in the direction of the shaft axis in a case in which the swing member swings.

3 . The endoscope according to claim 1 ,

wherein the engagement member is a nut including a female screw, and

the shaft member is a screw shaft including a male screw which is the engaged part.

4 . The endoscope according to claim 1 ,

wherein the engagement member is a cam pin, and

the shaft member is a cam shaft including a cam groove which is the engaged part.

5 . The endoscope according to claim 1 , further comprising:

a rotary encoder that detects a rotation angle of the shaft.

6 . The endoscope according to claim 1 , further comprising:

an insertion part; and

a hand operating part that is connected to a base end side of the insertion part,

wherein the knob, the slider, and the power conversion transmission mechanism are provided on the hand operating part,

the shaft is provided from the hand operating part to the insertion part, and

the distal end optical system is provided on a distal end side of the insertion part.

7 . The endoscope according to claim 6 ,

wherein the knob is a rotational operation member configured to be rotationally operated,

a bending operation knob that performs a bending operation of the insertion part is provided to be rotationally operated, on the hand operating part, and

a rotation axis of the rotational operation member is disposed coaxially with a rotation axis of the bending operation knob.