| 摘要 |
PURPOSE:To decide a focusing and a defocusing state by detecting a deviation in focus from the signal of a linear photoelectric element. CONSTITUTION:A focus detector is constituted including an objective 1, an image pickup surface 4, a split prism for projection which is placed at a position conjugate to the image pickup surface 4, the linear photoelectric element 13 which is placed at a position conjugate to the image pickup surface 4, a light source 12 which projects a pattern on the slit prism for projection, a lens 11 for projection, half-mirrors 2 and 3, and an arithmetic part 20 which detects the deviation in focus from the electric signal from the linear photoelectric element 13. Then the linear photoelectric element 13 is arranged at an angle to the split line of the split prism 10 while the center of a rotary figure on the split prism is set at a position conjugate to the image pickup surface and the length to which the image signal of the linear photoelectric element and a projection image counted by a pulse counter cross the line photoelectric element 13 is found to find the length at the time of focusing. Consequently, a front focus, an in-focus, and a rear focus state are decided. |
