Zoom lens and image-capture device

1. A zoom lens comprising:

a plurality of lens groups having at least first, second, third, fourth, and fifth lens groups arranged in order from an object side, wherein;

the first lens group having a positive refractive power which is firmly secured when the magnification is changed,

the second lens group having a negative refractive power which is shifted to the image side when the magnification is changed from the wide angle end to the telescopic end,

the third lens group having a positive refractive power which is firmly secured when the magnification is changed,

the fourth lens group having a positive refractive power which is shifted to the object side when the magnification is changed from the wide angle end to the telescopic end, and

the fifth lens group having a negative refractive power which is firmly secured when the magnification is changed,

wherein the first lens group is configured by arranging, in order from the object side, a single lens having a negative refractive power, a prism having a reflection surface to create a 90° bend in a light path, and at least one single lens having a positive refractive power, a double convex shape, and a double-aspherical surface,

wherein the prism has a positive refractive power, at least one surface thereof has an aspherical surface, a object side surface thereof has a convex surface directed to the object side, and an image side surface thereof has a convex surface directed to the image side,

wherein the second lens group is configured by arranging in order from the object side, a lens having a negative refractive power, a lens having a negative refractive power, a lens having a positive refractive power, and a lens having a negative refractive power, and

wherein the positive lens, the negative lens and the prism constituting the first lens group satisfy one of the following conditional expressions (1) and (2):

ν1 p−ν 1 n= 33.27  (1), and

ν1 p−ν 1 n= 36.15  (2),

where ν1p is the average value of the Abbe number, at the d line, of the prism in the first lens group and the positive lens arranged on the image side of the prism (the wavelength is equal to 587.6 nm); and ν1n is the Abbe number at the d line of the negative lens arranged at a position most near to the object side in the first lens group.

2. The zoom lens according to claim 1 , wherein;

the third lens group has an aperture, and the position of the aperture is firmly secured during the magnification change.

3. The zoom lens according to claim 1 , wherein;

an image is formed on a solid image-capture element.

4. The zoom lens according to claim 1 , wherein the positive lens, the negative lens and the prism constituting the first lens group satisfies the following conditional expression (2):

ν1p−ν1n=36.15.

5. An image-capture device comprising a zoom lens and a solid image-capture element converting an optical image formed by the zoom lens into electrical signals, wherein;

the zoom lens includes a plurality of lens groups having at least first, second, third, fourth, and fifth lens groups arranged in order from an object side, wherein;

the first lens group has a positive refractive power which is firmly secured when the magnification is changed,

the second lens group has a negative refractive power which is shifted to the image side when the magnification is changed from the wide angle end to the telescopic end,

the third lens group having a positive refractive power which is firmly secured when the magnification is changed,

the fourth lens group having a positive refractive power which is shifted to the object side when the magnification is changed from the wide angle end to the telescopic end, and

the fifth lens group having a negative refractive power which is firmly secured when the magnification is changed,

wherein the first lens group is configured by arranging, in order from the object side, a single lens having a negative refractive power, a prism having a reflection surface to create a 90° bend in a light path, and at least one single lens having a positive refractive power, a double convex shape, and a double-aspherical surface,

wherein the prism has a positive refractive power, at least one surface thereof has an aspherical surface, a object side surface thereof has a convex surface directed to the object side, and an image side surface thereof has a convex surface directed to the image side,

wherein the second lens group is configured by arranging, in order from the object side, a lens having a negative refractive power, a lens having a negative refractive power, a lens having a positive refractive power, and a lens having a negative refractive power, and

wherein the positive lens, the negative lens and the prism constituting the first lens group satisfy one of the following conditional expressions (1) and (2):

ν1 p−ν 1 n= 33.27  (1), and

ν1 p−ν 1 n= 36.15  (2),

where ν1p is the average value of the Abbe number, at the d line, of the prism in the first lens group and the positive lens arranged on the image side of the prism (the wavelength is equal to 587.6 nm); and ν1n is the Abbe number at the d line of the negative lens arranged at a position most near to the object side in the first lens group.

6. The image-capture device according to claim 5 , wherein the third lens group has an aperture, and the position of the aperture is firmly secured during the magnification change.

7. The image-capture device according to claim 5 , wherein an image is formed on a solid image-capture element.

8. A zoom lens comprising:

a plurality of lens groups having at least first, second, third, fourth, and fifth lens groups arranged in order from an object side, wherein;

the first lens group having a positive refractive power which is firmly secured when the magnification is changed;

the second lens group having a negative refractive power which is shifted to the image side when the magnification is changed from the wide angle end to the telescopic end;

the third lens group having a positive refractive power which is firmly secured when the magnification is changed;

the fourth lens group having a positive refractive power which is shifted to the object side when the magnification is changed from the wide angle end to the telescopic end; and

the fifth lens group having a negative refractive power which is firmly secured when the magnification is changed,

wherein the first lens group is configured by arranging, in order from the object side, a single lens having a negative refractive power, a prism having a reflection surface to create a 90° bend in a light path, and at least one single lens having a positive refractive power, a double convex shape, and a double-aspherical surface,

wherein the prism has a positive refractive power, at least one surface thereof has an aspherical surface, a object side surface thereof has a convex surface directed to the object side, and an image side surface thereof has a convex surface directed to the image side,

wherein the second lens group is configured by arranging in order from the object side, a lens having a negative refractive power, a lens having a negative refractive power, a lens having a positive refractive power, and a lens having a negative refractive power, and

wherein the positive lens, the negative lens and the prism constituting the first lens group satisfy the following conditional expression (1):

ν1 p−ν 1 n= 33.27  (1)

where ν1p is the average value of the Abbe number, at the d line, of the prism in the first lens group and the positive lens arranged on the image side of the prism (the wavelength is equal to 587.6 nm); and ν1n is the Abbe number at the d line of the negative lens arranged at a position most near to the object side in the first lens group.