Patent ID: 7848630
Filing Date: 2010-12-07
Classification: G02B,H04N

Abstract:
1. An autofocus adapter being placed detachably between an imaging lens and a camera main body and detecting a focus state of the imaging lens and performing autofocus control of the imaging lens, the autofocus adapter comprising: a first optical system placed on a first optical axis of the imaging lens; a second optical system placed on a second optical axis different from the first optical axis; and an imaging device receiving first subject light for detecting the focus state of the imaging lens, through the second optical system, wherein the first optical system comprising: a first light split unit being placed on the first optical axis and splitting subject light, which is passed through the imaging lens, into the first subject light and second subject light for image formation; a first lens group having a negative power and placed on an object side with respect to the first light split unit; and a second lens group having a positive power and placed on an image side with respect to the first light split unit, wherein the first lens group comprises a first cemented lens comprising a negative lens and a positive lens, and the second lens group comprises a positive lens and a second cemented lens, the second cemented lens comprising a positive lens and a negative lens, wherein the first optical system satisfies Conditional Expression: wherein d is a thickness of the first light split unit along the first optical axis, and h is a maximum height from the first optical axis of a light flux passing through the first light split unit.