Objective lens and microscope

An objective lens comprising, in order from an object, a first lens group having positive refractive power and a second lens group having negative refractive power,

• the first lens group including, in order from the object, a positive meniscus lens having a concave surface facing the object, a positive lens disposed adjacent to an image side of the positive meniscus lens, and a diffractive optical element which has a diffractive optical surface,
• the second lens group being composed of at least one cemented lens configured with a positive lens and a negative lens cemented to each other,
• the following conditional expression being satisfied:
• 0.11≦d00/TL0≦0.19
• where d00 denotes a distance on the optical axis from the object to a surface facing the object of the positive meniscus lens, and
• TL0 denotes a distance on the optical axis from the object to a rear end lens surface of the whole objective lens, and
• wherein the second lens group can move relative to the first lens group in an optical axis direction depending on thickness of a light-transmitting member disposed between the object and the first lens group so that aberration can be corrected.

An objective lens comprising, in order from an object, a first lens group having positive refractive power and a second lens group having negative refractive power,

• the first lens group including, in order from the object, a positive meniscus lens having a concave surface facing the object, a positive lens disposed adjacent to an image side of the positive meniscus lens, and a diffractive optical element which has a diffractive optical surface,
• the second lens group being composed of at least one cemented lens configured with a positive lens and a negative lens cemented to each other,
• the following conditional expression being satisfied:
• 0.11≦d00/TL0≦0.19
• where d00 denotes a distance on the optical axis from the object to a surface facing the object of the positive meniscus lens, and
• TL0 denotes a distance on the optical axis from the object to a rear end lens surface of the whole objective lens, and
• wherein the second lens group is composed of, in order from the object, a first cemented lens which is configured with a positive lens and a negative lens cemented to each other, a second cemented lens which is configured with a positive lens having a convex surface facing the object and a negative lens having a concave surface facing an image, a third cemented lens which is configured with a negative lens having a concave surface facing the object side and a positive lens having a convex surface facing the image.