Optical system for microscope, and microscope in which same is used

An optical system for a microscope used in a microscope that captures an image of a specimen to be observed by a camera function provided in a portable information terminal, and displays the captured image on a display of the portable information terminal, comprising:

• a lighting optical system for applying light from a light source to the specimen;
• and an objective optical system for forming the light that has passed through the specimen into an image,
• wherein the objective optical system has an objective lens group disposed inside the microscope, a first image forming lens group disposed inside the microscope, and a second image forming lens group disposed inside the portable information terminal, which are arranged in this order from an object side,
• the objective lens group forms an image of the specimen on a first image plane positioned between the objective lens group and the first image forming lens group,
• the first image forming lens group and the second image forming lens group re-forms the image formed on the first image plane on a second image plane that coincides with an imaging surface of an image pickup element for constituting a camera function of the portable information terminal,
• focusing is performed by moving a part or all of the second image forming lens group along an optical axis,
• the specimen is disposed in contact with or adjacent to a surface of the objective lens group, the surface being closest to an object, and
• conditional expressions (1), (2-1), (4-2) and (5-1) given below are satisfied:
• NAL×2≤NAO≤NAL×15 (1)
• 0.07≤NAL0.09 (2-1)
• 4.8 mm≤Ed≤5.2 mm (4-2)
• 28 mm≤D≤35 mm (5-1)
• where NAL denotes a numerical aperture of the lighting optical system, NAO denotes a numerical aperture of the objective lens group, Ed denotes an effective diameter of the lighting optical system, and D denotes a distance from the specimen-side end surface of the lighting optical system to the specimen.