| 摘要 |
PURPOSE:To perform invariably stable focus detection even by various lighting methods corresponding to objects mainly as to dark visual field lighting for the object by providing an image formation optical system which includes an objective, and a holed reflecting mirror, etc. CONSTITUTION:Coaxial top lighting is performed through the holed reflecting mirror 17a for dark visual field lighting provided between objectives 1a and 1b slantingly to the optical axis of the lenses 1a and 1b. Further, a half-mirror 17b is arranged adjacently to the reflecting mirror 17a and a positive lens 16 is added in a coaxial top lighting optical system to enable the coaxial top lighting of a light visual field while putting the same focus detection in operation. Then luminous flux for focus detection is supplied by reflection at the fixed position of the reflecting mirror 17a, so the accuracy of the focus detection is constant even in the lighting state of the light visual field. Therefore, a focus detecting means is operated with invariably constant accuracy regardless of a lighting method. |
