| 摘要 |
PURPOSE:To make highly accurate focus detection possible by measuring characteristic of a focus detecting system beforehand without measuring distortional aberration caused mainly by a field lens by an optical means, and correcting by arithmetic means based on the result. CONSTITUTION:A field lens 3 is provided to make areas 7-1, 7-2 of an exit pupil and entrance pupils 6-1, 6-2 conjugative relation, it is desirable to use a plano-convex or similar-shaped lens. However, the plano-convex shape produces large positive distortional aberration at the time of secondary image forming and an image having distribution of quantity of light more elongated in peripheral part is formed on sensor strings 5-1, 5-2. Influences of distortional aberration at this time is measured without using an optical means, but measuring characteristic of the focus detecting system beforehand and corrected by arithmetic means based on the result to improve accuracy of focus detection. That is, it is intended to eliminate or lower influences of distortional aberration using a relational expression including influences of the distortional aberration when calculating the quantity of defocus. |
