An imaging optical system includes, sequentially from an object side toward an image side, a first lens group; an aperture stop; and a second lens group. The first lens group includes a negative lens; and a positive lens formed of a plastic lens. The second lens group includes a plastic lens and satisfies Conditional Expressions (1) and (2) as follows:

c31a>c32a, and (1)

c31b<c32b, (2)

where c31a is an on-axis curvature of an object-side surface of the plastic lens of the second lens group, c32a is an on-axis curvature of an image-side surface of the plastic lens of the second lens group, c31b is an off-axis curvature of the object-side surface of the plastic lens of the second lens group, and c32b is an off-axis curvature of the image-side surface of the plastic lens of the second lens group.

An imaging optical system includes, sequentially from an object side toward an image side, a first lens group; an aperture stop; and a second lens group. The first lens group includes a negative lens; and a positive lens formed of a plastic lens. The second lens group includes a plastic lens and satisfies Conditional Expressions (1) and (2) as follows:

c31a>c32a, and (1)

c31b<c32b, (2)

where c31a is an on-axis curvature of an object-side surface of the plastic lens of the second lens group, c32a is an on-axis curvature of an image-side surface of the plastic lens of the second lens group, c31b is an off-axis curvature of the object-side surface of the plastic lens of the second lens group, and c32b is an off-axis curvature of the image-side surface of the plastic lens of the second lens group.

An optical system comprises, in order from an object side, a front group GF having positive refractive power, an aperture stop S and a rear group GR. The front group

FR comprises a front focusing group GFF having positive refractive power, and the rear group GR comprises a rear focusing group GRF having positive refractive power, upon focusing the front focusing group GFF and the rear focusing group GRF being moved toward the object side, and a predetermined condition being satisfied. Thus, an optical system having a superb optical performance, an optical equipment equipped therewith and a manufacturing method for the optical system are provided.

An optical system comprises, in order from an object side, a front group GF having positive refractive power, an aperture stop S and a rear group GR. The front group

FR comprises a front focusing group GFF having positive refractive power, and the rear group GR comprises a rear focusing group GRF having positive refractive power, upon focusing the front focusing group GFF and the rear focusing group GRF being moved toward the object side, and a predetermined condition being satisfied. Thus, an optical system having a superb optical performance, an optical equipment equipped therewith and a manufacturing method for the optical system are provided.

An imaging lens includes: an aperture stop; a biconvex first lens directing convex surfaces toward an object and an image; a second lens directing a convex surface toward the object near the optical axis and having negative refractive power; a biconvex third lens directing convex surfaces toward the object and the image near the optical axis; a fourth lens directing a concave surface toward the object near the optical axis and having positive refractive power; and a fifth lens directing a convex surface toward the object near the optical axis and having negative refractive power. The aperture stop and the first to fifth lenses are arranged in this order from the object side, and a conditional expression 1 being 0.50<f1/f<0.76 is satisfied, where f1 represents the focal length of the first lens and f represents the focal length of the entire imaging lens.

An imaging lens includes: an aperture stop; a biconvex first lens directing convex surfaces toward an object and an image; a second lens directing a convex surface toward the object near the optical axis and having negative refractive power; a biconvex third lens directing convex surfaces toward the object and the image near the optical axis; a fourth lens directing a concave surface toward the object near the optical axis and having positive refractive power; and a fifth lens directing a convex surface toward the object near the optical axis and having negative refractive power. The aperture stop and the first to fifth lenses are arranged in this order from the object side, and a conditional expression 1 being 0.50<f1/f<0.76 is satisfied, where f1 represents the focal length of the first lens and f represents the focal length of the entire imaging lens.

A wide-angle lens includes a front group, an aperture, a rear group, and an infrared cut filter. The front group includes a first lens and a second lens arranged in order from a side closest to an object to an image side. In the wide-angle lens, an anti-reflection layer having a reflectance of 1.5% or less in a wavelength range from nm to 850 nm is provided on a lens surface of the first lens on the image side to suppress an occurrence of a ghost caused by light passing through a peripheral portion of the lens surface. Therefore, even if a film forming the anti-reflection layer is thinner than an appropriate value at the peripheral portion of the lens surface, the anti-reflection layer appropriately prevents reflection of light in a long wavelength range.

A light blocking sheet having a central axis includes a central hole and a plurality of inner extended portions. The central axis passes through the central hole, which is enclosed by a hole inner surface. The hole inner surface has a first corresponding circle and a second corresponding circle, wherein a diameter of the first corresponding circle is greater than a diameter of the second corresponding circle. The inner extended portions are adjacent to and surround the central hole, wherein each of the inner extended portions is extended and tapered from the first corresponding circle towards the second corresponding circle and includes an inner surface, and the inner surface includes a line pair. The line pair includes two line sections, wherein one end of one line section thereof and one end of the other line section thereof are towards the second corresponding circle and approach to each other.

A light blocking sheet having a central axis includes a central hole and a plurality of inner extended portions. The central axis passes through the central hole, which is enclosed by a hole inner surface. The hole inner surface has a first corresponding circle and a second corresponding circle, wherein a diameter of the first corresponding circle is greater than a diameter of the second corresponding circle. The inner extended portions are adjacent to and surround the central hole, wherein each of the inner extended portions is extended and tapered from the first corresponding circle towards the second corresponding circle and includes an inner surface, and the inner surface includes a line pair. The line pair includes two line sections, wherein one end of one line section thereof and one end of the other line section thereof are towards the second corresponding circle and approach to each other.

The present invention relates to projection and schlieren optical measurement technology, and more particularly to an integrated projection-schlieren optical system. The system includes a parallel light source system, a first positive lens, a diaphragm, a second positive lens, an image sensor, a negative lens, a knife edge device and a sample stage. In the system, a projection telescopic optical system and a schlieren camera optical system are respectively formed through the combination of optical characteristics of two movable lenses, enabling the integration functions of the projection optical system and the schlieren optical system.