| 摘要 |
PURPOSE:To shorten necessary time and to improve focusing accuracy by selectively detecting at least two data from among three luminous fluxes; two luminous fluxes which are in symmetrical areas with the optical axis of the luminous flux of an object as a boundary, and the luminous flux which is in an area where the optical axis is included, and finding a phase difference based on these data. CONSTITUTION:Behind a lens 13 for focusing the image of the object formed on an image plane 12, holes 14a and 14b through which the two luminous fluxes which are symmetrical with the optical axis 0 as the boundary are transmitted and the hole 14c through which the luminous flux in the area where the optical axis 0 is contained is transmitted are provided. And a phase difference arithmetic means 41 arithmetically calculates phase difference data based on the correlation of first, second and third image data which are obtained from photoelectric converting parts 17, 18, and 19. And a reliability judging means 42 compares the first datum or the second datum with the third datum, and judges whether it is suitable to be arithmetically calculated at the means 41 or not. Furthermore, a controlling means 43 makes the means 41 normally work when it is judged that it has high reliability at the means 42, and executes the display of the impossibility of the focusing without making the means 41 work when it is judged that it has low reliability. |
