Microscope adapter unit

1. A microscope adapter unit disposed on an optical path of illumination light leading from a light source unit including a light source to a sample surface via a microscope main body, the microscope adapter unit comprising:

a first lens group including at least one lens; and

a second lens group including at least one lens;

wherein:

the first lens group converts the illumination light into roughly parallel luminous fluxes, and makes the illumination light enter the second lens group;

the light source unit includes an optical system that converges or makes parallel the illumination light from the light source, and is used together with fibers disposed between the light source unit and the microscope main body;

the microscope adapter unit is disposed between the fibers and the light source unit; and

the microscope adapter unit comprises, in order starting from a side of the light source unit: (i) a lens that is included in the first lens group and that has a positive power, (ii) a lens that is included in the first lens group and that has a negative power, (iii) a lens that is included in the second lens group and that has a negative power, and (iv) a lens that is included in the second lens group and that has a positive power.

2. The microscope adapter unit according to claim 1 , wherein an optical device or an optical unit including the optical device is detachably disposed between the first lens group and the second lens group in the microscope adapter unit.

3. The microscope adapter unit according to claim 1 , wherein a distance between the first lens group and the second lens group is variable.

4. The microscope adapter unit according to claim 3 , further comprising:

a first adapter including the first lens group; and

a second adapter including the second lens group;

wherein the microscope adapter unit is separated into the first adapter and the second adapter by a space between the first lens group and the second lens group.