Method for producing molding die for synthetic resin lens barrel having a helicoid and for producing the lens barrel

摘要

An inner barrel includes a male helicoid, and an outer barrel includes a female helicoid which can engage with the male helicoid of the inner barrel. The included angle of trapezoidal threads of the male helicoid are identical to an included angle of trapezoidal grooves of the female helicoid in a section perpendicular to a direction of an extension of the threads.