Manufacturing method of front-end component of endoscope

1. A method of manufacturing a front-end optical component in which a lens is mounted on the front end of a metallic lens-barrel provided on the front end of the inserting portion of an endoscope, comprising the steps of:

placing a lens raw material on the front-end side in the lens-barrel,

press-forming the lens raw material in a heat-softened state with a pair of upper and lower shaping dies,

tightly joining the outer edge of the pressed lens raw material to the inner peripheral surface of the lens-barrel; and

wherein the front end of the lens-barrel is placed so as to straddle an outer periphery of a transfer surface shaped on a top surface of the lower die of said pair of upper and lower shaping dies, a guide die is provided so as to enclose the periphery of the lens-barrel, the upper die has a transfer surface shaped on a bottom surface thereof and is provided in the lens-barrel so as to able to be inserted in and withdrawn from it, a portion of the lens raw material press-formed by the upper and lower dies is formed projecting toward the front-end side of the lens-barrel from its inside, and the projection-shaped portion is polished and finished.

2. The method of manufacturing a front-end optical component of an endoscope according to claim 1 , wherein a coefficient of linear thermal expansion of a metallic material configuring said lens-barrel is selected to be equal to or more than the coefficient of linear thermal expansion of the lens raw material such that the lens-barrel can fasten the lens raw material in a cooling process after heat pressurizing.

3. The method of manufacturing a front-end optical component of an endoscope according to claim 1 , wherein the coefficient of linear thermal expansion of a metallic material configuring the lens-barrel is 100 to 170, and the coefficient of linear thermal expansion of the lens raw material is 70 to 160.

4. The method of manufacturing a front-end optical component of an endoscope according to claim 3 wherein a difference between the coefficients of linear thermal expansion of the lens-barrel and the lens raw material is not more than 100 at most.

5. The method of manufacturing a front-end optical component of an endoscope according to claim 2 , wherein the coefficient of linear thermal expansion of a metallic material configuring the lens-barrel is 100 to 170, and the coefficient of linear thermal expansion of the lens raw material is 70 to 160.

6. The method of manufacturing a front-end optical component of an endoscope according to claim 5 wherein a difference between the coefficients of linear thermal expansion of the lens-barrel and the lens raw material is not more than 100 at most.

7. A method of manufacturing a front-end optical component in which a lens is mounted on the front end of a metallic lens-barrel provided on the front end of the inserting portion of an endoscope, comprising the steps of:

placing a lens raw material on a front-end side in a lens-barrel,

press-forming lens raw material in a heat-softened state with a pair of upper and lower shaping dies, and

tightly joining the outer edge of the pressed lens raw material to an inner peripheral surface of the lens-barrel; and

wherein a guide die is mounted on the lower die having a transfer surface shaped on a top surface thereof, a step portion is shaped on an inner peripheral surface of the guide die, a flange portion shaped on an outer peripheral surface of the lens-barrel is engaged with the step such that the lens-barrel may be supported by the guide die, thereby shaping space between the front end of the lens-barrel and the lower die, the lens raw material is placed on the transfer surface of the lower die, the upper die having a transfer surface shaped on the bottom surface thereof is inserted into the lens-barrel to press-form the lens raw material, a portion of the press-formed lens raw material is formed projecting toward the front-end side of the lens barrel from its inside so as to cover the front end of the lens-barrel, and the projection-shaped portion is polished and finished except for the covered front end portion of the lens-barrel.

8. The method of manufacturing a front-end optical component of an endo scope according to claim 7 , wherein a coefficient of linear thermal expansion of a metallic material configuring said lens-barrel is selected to be equal to or more than a coefficient of linear thermal expansion of the lens raw material such that the lens-barrel can fasten the lens raw material in a cooling process after heat pressurizing.

9. The method of manufacturing a front-end optical component of an endoscope according to claim 7 wherein a coefficient of linear thermal expansion of a metallic material configuring the lens-barrel is 100 to 170, and a coefficient of linear thermal expansion of the lens raw material is 70 to 160.

10. The method of manufacturing a front-end optical component of an endoscope according to claim 9 , wherein a difference between the coefficients of linear thermal expansion of the lens-barrel and the lens raw material is not more than 100 at most.

11. The method of manufacturing a front-end optical component of an endoscope according to claim 8 wherein the coefficient of linear thermal expansion of a metallic material configuring the lens-barrel is 100 to 170, and the coefficient of linear thermal expansion of the lens raw material is 70 to 160.

12. The method of manufacturing a front-end optical component of an endoscope according to claim 11 wherein a difference between the coefficients of linear thermal expansion of the lens-barrel and the lens raw material is not more than 100 at most.