A rear attachment lens according to the aspect of the embodiments is configured to vary a focal length of a system by being attached to an image side of a master lens. The rear attachment lens includes a positive lens arranged closest to the image side in which a lens surface on the image side of the positive lens has a shape convex toward the image side. A focal length of the rear attachment lens, a magnification of the rear attachment lens when attached to the master lens, and a distance from the lens surface on the image side of the positive lens to a rear principal point position of the rear attachment lens when attached to the master lens are appropriately set.

A rear attachment lens according to the aspect of the embodiments is configured to vary a focal length of a system by being attached to an image side of a master lens. The rear attachment lens includes a positive lens arranged closest to the image side in which a lens surface on the image side of the positive lens has a shape convex toward the image side. A focal length of the rear attachment lens, a magnification of the rear attachment lens when attached to the master lens, and a distance from the lens surface on the image side of the positive lens to a rear principal point position of the rear attachment lens when attached to the master lens are appropriately set.

A lens structure formed by materials in different refractive indexes includes a sphere which is a round ball formed by a first portion and a second portion, a first lens which is formed on the first portion, a separation layer which is disposed between the sphere and the first lens, a second lens which is formed on the second portion, and a third lens which is formed on the second lens and opposite to the sphere. The first lens, the second lens and the third lens are formed respectively by a material in different refractive index and are provided respectively with a light absorption curve in different curvature, so that a light beam can pass through these light absorption curves to form plural times of light condensing effect.

A lens structure formed by materials in different refractive indexes includes a sphere which is a round ball formed by a first portion and a second portion, a first lens which is formed on the first portion, a separation layer which is disposed between the sphere and the first lens, a second lens which is formed on the second portion, and a third lens which is formed on the second lens and opposite to the sphere. The first lens, the second lens and the third lens are formed respectively by a material in different refractive index and are provided respectively with a light absorption curve in different curvature, so that a light beam can pass through these light absorption curves to form plural times of light condensing effect.

A lens structure formed by materials in different refractive indexes includes a transparent sphere in a first refractive index as well as a transparent second lens in a second refractive index. The first refractive index is different from the second refractive index, and the sphere is a round ball formed by a first portion and a second portion which are equipped with a first light condensing effect. The first lens is formed on the first portion of the sphere, the second portion of the sphere is exposed out of the first lens, and the first lens is provided with a first light absorption curve opposite to the first portion of the sphere, so that a light beam can pass through the second portion of the sphere to form the first light condensing effect, and then pass through the first light absorption curve to form a second light condensing effect.

A lens structure formed by materials in different refractive indexes includes a transparent sphere in a first refractive index as well as a transparent second lens in a second refractive index. The first refractive index is different from the second refractive index, and the sphere is a round ball formed by a first portion and a second portion which are equipped with a first light condensing effect. The first lens is formed on the first portion of the sphere, the second portion of the sphere is exposed out of the first lens, and the first lens is provided with a first light absorption curve opposite to the first portion of the sphere, so that a light beam can pass through the second portion of the sphere to form the first light condensing effect, and then pass through the first light absorption curve to form a second light condensing effect.

A lens structure formed by materials in different refractive indexes includes a sphere, a first lens and a separation layer which is disposed between the sphere and the first lens. The sphere and the first lens have a different refractive index and the sphere is a round ball. The first lens is formed on the sphere that part of the sphere is exposed out of the first lens, and the first lens includes a first light absorption curve. The separation layer includes a transparent section opposite to the first light absorption curve. When a light beam passes through the second portion of the sphere to form a first light condensing effect and enter the sphere, the light beam will then pass through the transparent section to enter the first lens, forming a second light condensing effect after passing through the first light absorption curve.

A lens structure formed by materials in different refractive indexes includes a sphere, a first lens and a separation layer which is disposed between the sphere and the first lens. The sphere and the first lens have a different refractive index and the sphere is a round ball. The first lens is formed on the sphere that part of the sphere is exposed out of the first lens, and the first lens includes a first light absorption curve. The separation layer includes a transparent section opposite to the first light absorption curve. When a light beam passes through the second portion of the sphere to form a first light condensing effect and enter the sphere, the light beam will then pass through the transparent section to enter the first lens, forming a second light condensing effect after passing through the first light absorption curve.

An image pickup apparatus includes an image forming optical system which includes an aperture stop that determines an axial light beam, and one cemented lens, and an image pickup section which is disposed on an image side of the image forming optical system, and which has a surface which is not flat and is curved to be concave toward the image forming optical system, wherein the cemented lens includes in order from an object side, a first lens having a negative refractive power, a second lens, and a third lens having a positive refractive power.

An image pickup apparatus includes an image forming optical system which includes an aperture stop that determines an axial light beam, and one cemented lens, and an image pickup section which is disposed on an image side of the image forming optical system, and which has a surface which is not flat and is curved to be concave toward the image forming optical system, wherein the cemented lens includes in order from an object side, a first lens having a negative refractive power, a second lens, and a third lens having a positive refractive power.