Patent ID: 9030750
Filing Date: 2015-05-12
Classification: G02B

Abstract:
1. An objective lens, consisting of: in order from an object, a first lens group having positive refractive power as a whole, and a second lens group having negative refractive power as a whole, wherein the first lens group including: a positive lens which is disposed closest to the object and of which lens surface closest to the object is a plane or a concave surface; a diffractive optical element in which two diffractive element constituents made from different optical materials are cemented and which has a diffractive optical surface formed with diffraction grating grooves on the cemented surface, the second lens group including a first lens having a concave surface facing an image and a second lens having a concave surface facing the object, the two concave surfaces of the first and second lenses facing with each other, and the second lens group being disposed closest to the image wherein a diameter of a light bundle is the smallest at one of the concave surfaces of the first and the second lenses in the second lens group, the following conditional expression is satisfied: where Φ2-1 denotes a power of the concave surface facing the image, and Φ2-2 denotes a power of the concave surface facing the object in the second lens group.