An objective optical system for endoscope consists of a front group having a negative refractive power, an aperture stop, and a rear group having a positive refractive power. The front group consists of a first lens having a negative refractive power and a second lens having a positive refractive power. The rear group consists of a third lens having a positive refractive power, a cemented lens of a fourth lens having a positive refractive power and a fifth lens having a negative refractive power, and a sixth lens having a positive refractive power. A shape of the second lens is a meniscus shape having a convex surface directed toward an image side. The sixth lens is cemented to a plane parallel plate, and the following conditional expressions (1) and (2) are satisfied:
1.0<f3/d6<2.8  (1)
1.7<|f1/f1<10  (2).

An objective optical system for endoscope consists of a front group having a negative refractive power, an aperture stop, and a rear group having a positive refractive power. The front group consists of a first lens having a negative refractive power and a second lens having a positive refractive power. The rear group consists of a third lens having a positive refractive power, a cemented lens of a fourth lens having a positive refractive power and a fifth lens having a negative refractive power, and a sixth lens having a positive refractive power. A shape of the second lens is a meniscus shape having a convex surface directed toward an image side. The sixth lens is cemented to a plane parallel plate, and the following conditional expressions (1) and (2) are satisfied:
1.0<f3/d6<2.8  (1)
1.7<|f1/f1<10  (2).

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.

An imaging lens includes first, second, third, fourth, fifth and six lens elements arranged in order from an object side to an image side along an optical axis. Each of the lens element has a thickness along the optical axis. Two of thicknesses of the first to the fourth lens elements along the optical axis are the thickest and the second thickest among the abovementioned six lens elements, respectively.

An imaging lens and an imaging apparatus capable of acquiring a long-distance object image at high resolution and capable of acquiring a short-distance object image in a wide range while, as a whole, being configured small. In order to achieve the object, an imaging lens according to the present invention is an imaging lens consisting of n (n is a natural number equal to or larger than six) lenses including a first lens having negative refractive power and a second lens having positive refractive power in order from an object side and including an n-th lens having negative refractive power and an n−1-th lens having positive refractive power in order from an image side, the imaging lens satisfying a predetermined conditional expression.

An optical image capturing system includes, along the optical axis in order from an object side to an image side, a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, and a seventh lens. At least one lens among the first to the sixth lenses has positive refractive force. The seventh lens can have negative refractive force. The lenses in the optical image capturing system which have refractive power include the first to the seventh lenses. The optical image capturing system can increase aperture value and improve the imaging quality for use in compact cameras.

An optical image capturing system comprising, in order from an object side to an image side, a first lens element, a second lens element, a third lens element, a fourth lens element, a fifth lens element, a sixth lens element and a seventh lens element. The first lens element with negative refractive power has a concave image-side surface. The second lens element, the third lens element and the fourth lens element have refractive power. The fifth lens element has refractive power. The sixth lens element with refractive power has an image-side surface being concave in a paraxial region and includes at least one convex shape in an off-axial region, wherein the surfaces thereof are aspheric. The seventh lens element refractive power has an image-side surface being concave in a paraxial region and includes at least one convex shape in an off-axial region, wherein the surfaces thereof are aspheric.

An optical image capturing system comprising, in order from an object side to an image side, a first lens element, a second lens element, a third lens element, a fourth lens element, a fifth lens element, a sixth lens element and a seventh lens element. The first lens element with negative refractive power has a concave image-side surface. The second lens element, the third lens element and the fourth lens element have refractive power. The fifth lens element has refractive power. The sixth lens element with refractive power has an image-side surface being concave in a paraxial region and includes at least one convex shape in an off-axial region, wherein the surfaces thereof are aspheric. The seventh lens element refractive power has an image-side surface being concave in a paraxial region and includes at least one convex shape in an off-axial region, wherein the surfaces thereof are aspheric.

This invention provides an optical lens assembly comprising, in order from an object side to an image side: a first lens element with negative refractive power having an image-side surface being concave in a paraxial region thereof; a second lens element having positive refractive power; a third lens element having an object-side surface being concave in a paraxial region thereof; and a fourth lens element having an object-side surface being convex in a paraxial region thereof and an image-side surface being concave in a paraxial region thereof, the image-side surface thereof having at least one convex shape in an off-axis region thereof; wherein the optical lens assembly has a total of four lens elements. With such configuration, the optical lens assembly of the present disclosure is characterized by a reduced size and a wide field of view.

This invention provides an optical lens assembly comprising, in order from an object side to an image side: a first lens element with negative refractive power having an image-side surface being concave in a paraxial region thereof; a second lens element having positive refractive power; a third lens element having an object-side surface being concave in a paraxial region thereof; and a fourth lens element having an object-side surface being convex in a paraxial region thereof and an image-side surface being concave in a paraxial region thereof, the image-side surface thereof having at least one convex shape in an off-axis region thereof; wherein the optical lens assembly has a total of four lens elements. With such configuration, the optical lens assembly of the present disclosure is characterized by a reduced size and a wide field of view.