Zoom microscope
It is an object to provide a zoom microscope of a simple structure which can expand a variable-power range. In order to achieve the object thereof, the zoom microscope includes a replaceable infinity correction objective lens, an aperture stop, an afocal zoom system, and an imaging optical system which are arranged in this order from a specimen side. Further, the aperture stop is disposed on or near a rear focal plane of the objective lens.
1. 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.
2. The zoom microscope according to claim 1 , further comprising
a holding member that replaces the objective lens with another objective lens while holding a plurality of objective lenses including the objective lens, wherein
said aperture stop is disposed on an image side of said holding member.
3. The zoom microscope according to claim 1 , further comprising
an optical member for phase contrast observation that is removably inserted between said objective lens and said afocal zoom system.
4. The zoom microscope according to claim 3 , further comprising
a fluorescence epi-illuminator provided between said objective lens and said afocal zoom system.
5. The zoom microscope according to claim 3 , wherein:
said objective lens is plural in number and the plural objective lenses are different in magnification from each other; and
distances from abutting joint surfaces of said plural objective lenses to said rear focal plane are substantially same.
6. The zoom microscope according to claim 5 , wherein
said optical member for phase contrast observation is common to said plural objective lenses.
7. The zoom microscope according to claim 3 , wherein
said optical member for phase contrast observation is a birefringence optical member for differential interference contrast observation.
8. The zoom microscope according to claim 1 , wherein:
the afocal zoom system has a variable-power lens group movable in the optical axis direction; and
the aperture stop has a stop diameter that is variable in accordance with movement of the variable-power lens group.
9. The zoom microscope according to claim 8 , further comprising:
a coaxial epi-illuminator provided between the afocal zoom system and the imaging optical system to form an image of a light source on or near the aperture stop.