Patent ID: 7262805
Filing Date: 2007-08-28
Classification: G02B,H04N

Abstract:
1. A focus detecting system for determining the focus state of an imaging lens in an imaging system that includes a location along a first optical axis of the imaging lens where focus state detecting object light is separated from object light that passes through the imaging lens to be incident on a light receiving surface of an image detecting element for image production, the focus detecting system comprising: a relay lens for receiving said focus state detecting object light, wherein the relay lens defines a second optical axis for intersecting the first optical axis; a focus state detection unit that includes two focus state detecting elements, each focus state detecting element including a light receiving surface, and light dividing means for dividing light that passes through said relay lens to direct some of the light toward each of the light receiving surfaces of each of the two focus state detecting elements so that the optical path length along the second optical axis to the light receiving surface of one of the focus state detecting elements is unequal to the optical path length along the second optical axis to the light receiving surface of the other focus state detecting element; means for moving the relay lens relative to the focus state detection unit along the second optical axis while keeping said image detecting element for image production at a fixed position; evaluation means for obtaining an evaluation value indicative of the sharpness of an image at the light receiving surface of a second one of the two focus state detecting elements at a first relative position of the relay lens and the focus state detection unit along the second optical axis while not using the first one of the two focus state detecting elements and for obtaining an evaluation value indicative of the sharpness of an image at the light receiving surface of the first one of the two focus state detecting elements at a second relative position of the relay lens and the focus state detection unit along the second optical axis while not using the second one of the two focus state detecting elements; and comparison means for comparing the evaluation values obtained by the evaluation means at the two relative positions.