| 摘要 |
PURPOSE:To economize storage capacity without damaging accuracy by calculating the reference moving amount of a focusing lens from an object distance, calculating a conversion coefficient from a focal length and defining the product of the reference moving amount and the conversion coefficient as the moving amount of the focusing lens. CONSTITUTION:A distance measuring means 3 measures the object distance by using infrared rays, far example, and sends the value of the inverse to an arithmetic means 5. A focal length detecting means 4 detects the position of a magnification lens 1 by using an encoder the like and sends the detected value of the focal length corresponding to this position to the arithmetic means 5. The arithmetic means 5 calculates the reference moving amount of a focusing lens 2 by using a secondary expression concerning the inverse value of the object distance and calculates the conversion coefficient by using a third-order expression concerning the detected value of the focal length. Further, the arithmetic means 5 defines the product of the reference moving amount and the conversion coefficient as the moving amount of the focusing lens and sends this moving amount to a focusing lens group driving means 7. |
