| 摘要 |
The athermal lens device includes lenses, a lens holding frame, a coil spring for pressing the lens holding frame toward an imaging surface direction, a ring formed by looping a round bar, and a lens barrel for containing them. The lens holding frame includes a pressing surface intersecting with an optical axis at the imaging surface side. The lens barrel has a sliding contact surface formed with a conical shape at an end of the imaging surface side of the lens container. The ring is made of an invar material whose thermal expansion coefficient is very small, and disposed between the sliding contact surface and the pressing surface formed with a plain shape. The ring is constantly pressed to the sliding contact surface by bias of the coil spring via the pressing surface. Position of the lens holding frame changes according to environmental temperature to correct focus point.
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