Super wide angle lens and imaging apparatus using it

摘要

A super wide angle lens substantially consists of a positive first lens group in which a positive first lens, a negative second lens, a negative third lens, a negative fourth lens, a positive fifth lens, a sixth lens unit that is a cemented lens, a seventh lens, an aperture stop, and an eighth lens unit that is a cemented lens are arranged in this order from an object side, a second lens group in which a first lens unit that is a positive single lens or a cemented lens and a second lens unit that is a cemented lens are arranged in this order from the object side, and a third lens group including a positive lens. The super wide angle lens is structured in such a manner to satisfy conditional formula (1): 0.8<(T16+T17)/f<2.5.

主权项

1. A super wide angle lens substantially consisting of three groups of:
a first lens group having positive refractive power; a second lens group having positive refractive power; and a third lens group in this order from an object side, wherein the first lens group consists of: a first-group first lens having a meniscus shape with its convex surface facing the object side and positive refractive power; a first-group second lens having a meniscus shape with its convex surface facing the object side and negative refractive power; a first-group third lens having a meniscus shape with its convex surface facing the object side and negative refractive power; a first-group fourth lens having negative refractive power, and a lens surface of which with a smaller absolute value of a curvature radius faces an image side; a first-group fifth lens having positive refractive power, and a lens surface of which with a smaller absolute value of a curvature radius faces the image side; a first-group sixth lens unit that is a cemented lens composed of a lens having positive refractive power and a lens having negative refractive power cemented together; a first-group seventh lens having a meniscus shape with its concave surface facing the object side; a stop; and a first-group eighth lens unit that is a cemented lens composed of a lens having negative refractive power and a lens having positive refractive power cemented together, in this order from the object side, and wherein the second lens group consists of: a second-group first lens unit that is a single lens having positive refractive power or a cemented lens composed of a lens having positive refractive power and a lens having negative refractive power cemented together; and a second-group second lens unit that is a cemented lens composed of a lens having positive refractive power and a lens having negative refractive power cemented together, in this order from the object side, and wherein the third lens group includes at least one lens having positive refractive power, and wherein the following conditional formula (1) is satisfied:
0.8<(T16+T17)/f<2.5  (1), where T16: a thickness of the first-group sixth lens unit that is a cemented lens, T17: a thickness of the first-group seventh lens, and f: a focal length of an entire lens system when the system is focused on an object point at infinity.