| 摘要 |
PROBLEM TO BE SOLVED: To obtain an objective lens which eliminates the need of focusing at the time of performing photographing by switching the objective lens by setting so as to include the perfocal position of the objective lens attached at the microscope and having a different magnification within the physical depth of focus regulated by the NA of an extremely low magnification objective lens. SOLUTION: This device has an optical system set so as to include the parfocal position of the objective lens attached at the microscope and having a larger magnification than an extremely low magnification microscope objective lens within the physical depth of field regulated by the NA of the extremely low magnification objective lens. Then, in the case of an infinity system, since a parallel luminous flux is made between the objective lenses 10 and 11 and an image formation lens 17, an image- formation position is decided only by the adjustment error of the image-formation lens 17. A parfocal error is suppressed to be equal to or below a specified value with respect to the parfocal distance of the objective lens 10 of 10×magnification case of the objective lens 11 of 1×magnification, so that focusing is made only by switching the objective lens when the objective lens 10 of 10×magnification is used and the focusing is made and focused photographing is performed.
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