Patent ID: 8687291
Filing Date: 2014-04-01
Classification: G02B

Abstract:
1. An optical system comprising: in order from an object side to an image side, a first lens unit configured to be fixed during a focusing operation, the first lens unit having a positive refractive power as a whole; a second lens unit configured to move in an optical axis direction during the focusing operation, the second lens unit having a negative refractive power as a whole; and a third lens unit positioned at the image side relative to the second lens unit, the third lens unit having a positive or negative refractive power as a whole, wherein the first lens unit is, in order from the object side to the image side, configured by a first partial lens unit, a second partial lens unit, and a third partial lens unit, wherein the first partial lens unit is configured by two positive lens components, wherein the second partial lens unit is configured by one cemented lens having a negative combined refractive power configured by cementing at least one positive lens and one negative lens, or configured by one positive lens and one negative lens having a negative combined refractive power, wherein the third partial lens unit is positioned between the second partial lens unit and the second lens unit, the third partial lens unit having a positive refractive power as a whole, and wherein following conditional expressions are met: where f is a focal length of a total system during focusing on infinity, f