| 摘要 |
PURPOSE:To execute an exact focusing detection by a simple constitution, by extracting the light of 2 kinds of wavelength areas in an image space side of a photographing optical system, dividing it by a dichroic mirror, and forming an image on a pair of photodetector trains provided on a prescribed position. CONSTITUTION:Light which has passed through a photographic lens 11 passes through a half-mirror 13 in the center part of a quick return mirror 12, and is reflected by a dichroic mirror 14. The dichroic mirror makes a surface being parallel to an optical axis O a border, and one side and the other side reflect red light and blue light, respectively, its luminous flux is made incident to a split prism 15, is divided into refleted red light and transmission blue light by a dichroic mirror 16, and an image is formed on a pair of photodetector trains 17, 18 provided on a coupling surface with a prescribed focal surface. By detecting a shift of the image, a focused position is detected. Since there is no moving part, an exact focusing detection is executed by a simple constitution. |
