An imaging optical system comprising, in order from the object side, a first
positive
meniscus lens having a convex surface on the object side, an aperture stop, a second
negative meniscus lens having a convex surface on the image side, and a third positive
lens having an object side aspherical surface which has curvature lowered toward
a marginal portion of the aspherical surface and an image side surface which has
curvature enhanced toward the marginal portion of the aspherical surface. This
imaging optical system allows its performance to be degraded due to manufacturing
errors and exhibits high performance even when the optical system is configured compact.
