| 摘要 |
PURPOSE:To ensure an assured detection of focus, by providing a field lens having different degrees of power according to the position of the radiation iris of a photographing lens at an area near the focal surface of the photographing lens. CONSTITUTION:A radiation iris 1 of a photographing lens having a long focal distance is sent along with a radiation iris 2 of a photographing lens having a short focal distance. The effective luminous fluxes which are made incident to image reforming lenses 6 and 7 after passing through two points on a focal surface 3 overlap to each other at the position of the iris 2. Then a field lens 4 is provided with a curvature by which the luminous flux is not impaired by the iris 2, and image position detecting arrays 8 and 9 are provided on or near the focal surfaces of the lenses 6 and 7. At the same time, a field lens 5 having such curvature as to make the effective luminous fluxes overlap to each other at the position of the iris 1 is provided. Thus the power of a field lens is varied in accordance with the positions of the irises 1 and 2 to make even the size of each luminous flux. As a result, an assured detection is possible for the focus. |
