Lens unit

Abstract

A lens unit is provided capable of reducing the shift of the focal position when the temperature rises. The lens unit includes a plurality of lenses and a cylindrical holder configured to internally hold the plurality of lenses. The holder has a smaller coefficient of thermal expansion, compared to single lenses (i.e., the second lens and the third lens) that are meniscus-shaped plastic lenses. The side surfaces of the second lens and the third lens are press-fitted such that the concave side portions corresponding to the positions of the concave lens surfaces abut the inner surface of the holder, the second lens and the third lens including the concave lens surfaces and the convex lens surfaces. Therefore, when the ambient temperature rises, the refractive index of the plastic lens decreases but the convex lens surface deforms such that the curvature radius becomes smaller.

Dependencies are inferred from the claim text.