Patent ID: 7593157

Claim:
A zoom microscope comprising a replaceable infinity correction objective lens, an aperture stop, an afocal zoom system, and an imaging optical system which are arranged in this order, seen from a specimen side, wherein said aperture stop is disposed on or near a rear focal plane of said objective lens and at a side closer to said objective lens than all lenses of the afocal zoom system, and wherein the afocal zoom system includes, in order, from the specimen side: a first lens group having a positive refractive power; a second lens group having a negative refractive power; a third lens group having a positive refractive power, and a fourth lens group having a positive refractive power, wherein the afocal zoom system varies by moving the second lens group and the third lens group in an optical axis direction, and wherein a magnification β2L of the second lens group is in a low-power end state, a magnification β3L of the third lens group is in the low-power end state, and a focal length fL of the optical system which is a combination of said afocal zoom system and said imaging optical system in the low-power state, and a maximum image height Y max in the lower-power end state satisfy following conditional expressions: −0.1<β2 L <−0.3 −0.01<1/β3 L <0.04 0.05 <Y max/ fL <0.16.