Microscope zoom objective lens

A microscope zoom objective lens system comprising at least three lens groups;

• in order from an object, a first lens group having positive refractive power, a second lens group having negative refractive power and a third lens group having positive refractive power, wherein:
• for zooming from a low magnification side to a high magnification side, said second lens group and said third lens group move along an optical axis of said microscope zoom objective lens system while a separation between said first lens group and said second lens group becomes wide and a separation between said second lens group and said third lens group becomes narrow, and
• said second lens group comprises at least two lens components which face each other at concave surfaces.

A microscope zoom objective lens system comprising at least three lens groups;

• in order from an object, a first lens group having positive refractive power, a second lens group having negative refractive power and a third lens group having positive refractive power, wherein:
• for zooming from a low magnification side to a high magnification side, said second lens group and said third lens group move along an optical axis of said microscope zoom objective lens system while a separation between said first lens group and said second lens group becomes wide and a separation between said second lens group and said third lens group becomes narrow, and
• said third lens group comprises at least two lens components and includes at least one doublet made up of a positive lens and a negative lens.

A microscope zoom objective lens system comprising at least three lens groups;

• in order from an object, a first lens group having positive refractive power, a second lens group having negative refractive power and a third lens group having positive refractive power, wherein:
• for zooming from a low magnification side to a high magnification side, said second lens group and said third lens group move along an optical axis of said microscope zoom objective lens system while a separation between said first lens group and said second lens group becomes wide and a separation between said second lens group and said third lens group becomes narrow, and
• said first lens group comprises lens components wherein a lens component located nearest to an object side of said microscope zoom objective lens system comprises a doublet meniscus lens concave on said object side, said doublet meniscus lens consisting of, in order from said object side, a concave lens and a convex lens.

The microscope zoom objective lens system according to 15, wherein the fourth lens group comprises a doublet meniscus lens component consisting of a positive lens convex on the third lens group side and a negative lens and a lens component concave on the third lens group side and having negative refractive power.

A microscope zoom objective lens system comprising, in order from an object, a first lens group having positive refractive power, a second lens group having negative refractive power and a third lens group having positive refractive power, wherein at least one aspheric surface is used and the following condition (19) is satisfied:

• NA≧0.5 (19)
• where NA is the numerical aperture of the microscope zoom objective lens system on a high magnification side.