| 摘要 |
Low-power objective lenses for a microscope are disclosed. The objective lenses exhibit apochromatic optical performance at a numerical aperture of at least 0.1 and have a magnification of about 2x or less. Each such objective lens comprises, in order from the object side, a first lens group having positive refractive power; a second lens group having negative refractive power and comprising a negative meniscus lens with a concave surface oriented toward the image side; a third lens group having negative refractive power and having at least one cemented surface; and a fourth lens group having positive refractive power and comprising a positive meniscus lens element with a convex surface oriented toward the image side, and a positive cemented lens including a negative lens element cemented to a positive lens element. The objective lenses satisfy the condition: 1.2<f1/D1 <2.3 and other conditions, wherein fl is focal length of the first lens group and D1 is the axial distance from a lens surface in the first lens group closest to the image side to a lens surface in the second lens group closest to the object side.
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