| 摘要 |
PURPOSE:To make an optical system for detecting the position of a front focus and an optical system for detecting the position of a rear focus substantially equivalent and to make the processing in focus detection easy by providing an auxiliary lens having the focus coinciding with the exit pupil position of an objective lens between the objective lens and a beam splitter. CONSTITUTION:The luminous flux reflected by a semitransparent mirror 3 passes through an auxiliary lens 5, and is split to roughly equal quantities of light by a beam splitter 6. The transmitted light of the splitter 6 forms the 1st object image 10a, and the reflected light forms the 2nd object image 10b after it is reflected by a mirror 7. A so-called telecentric system is formed of an objective lens 2 and the lens 5 and therefore the object image 11 in the position of the front focus in front of the object image 10 and the object image 12 in the position of the rear focus behind the object image 11 have the same size and have no difference in image-forming magnification so that the image 11 in the position of the front focus is formed on the 1st image sensor 8 and the object image 12 in the position of the rear focus is formed on the 2nd image sensor 9. |
