Zoom lens, imaging device and method for manufacturing the zoom lens

A method for manufacturing a zoom lens comprising, in order from an object, a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, and a fourth lens group having positive refractive power, the method comprising:

• performing zooming by changing an air gap between the lens groups,
• the fourth lens group including, in order from the object, a first positive lens component, a second positive lens component having a convex surface facing the object, and a negative lens component, the first positive lens component, the second positive lens component and the negative lens component being at least partially spaced from each other by air gaps, and
• the method further comprising:
• assembling each lens in a lens barrel so that the following conditional expression is satisfied:
• 0.00<(Rb2−Rb1)/(Rb2+Rb1)<1.00
• where Rb2 denotes a radius of curvature of an image side surface of the second positive lens component which constitutes the fourth lens group and has the convex surface facing the object, and Rb1 denotes a radius of curvature of an object side surface of the second positive lens component which constitutes the fourth lens group and has the convex surface facing the object, so that
• the following conditional expression is satisfied:
• 0.50<(−F2)/Fw<2.00
• where F2 denotes a focal length of the second lens group and Fw denotes a focal length of the zoom lens upon focusing on infinity in the wide-angle end state, and so that
• the following conditional expression is satisfied:
• 0.45<(−Fc)/F4<3.00
• where Fc denotes a focal length of the negative lens component constituting the fourth lens group, and F4 denotes a focal length of the fourth lens group.

A zoom lens comprising, in order from an object:

• a first lens group having positive refractive power;
• a second lens group having negative refractive power;
• a third lens group having positive refractive power;
• and
• a fourth lens group having positive refractive power,
• performing zooming by changing an air gap between the lens groups,
• the fourth lens group including, in order from the object, a first positive lens component, a second positive lens component having a convex surface facing the object, and a negative lens component,
• the following conditional expression being satisfied:
• 0.00<(Rb2−Rb1)/(Rb2+Rb1)<1.00
• where Rb2 denotes a radius of curvature of an image side surface of the second positive lens component which constitutes the fourth lens group and has the convex surface facing the object, and Rb1 denotes a radius of curvature of an object side surface of the second positive lens component which constitutes the fourth lens group and has the convex surface facing the object, and
• the following conditional expression being satisfied:
• 1.031≦(−Fc)/F4<3.00
• where Fc denotes a focal length of the negative lens component constituting the fourth lens group, and F4 denotes a focal length of the fourth lens group.

A zoom lens comprising, in order from an object:

• a first lens group having positive refractive power;
• a second lens group having negative refractive power;
• a third lens group having positive refractive power;
• and
• a fourth lens group having positive refractive power,
• performing zooming by changing an air gap between the lens groups,
• the fourth lens group including, in order from the object, a first positive lens component, a second positive lens component having a convex surface facing the object, and a negative lens component, the first positive lens component, the second positive lens component and the negative lens component being at least partially spaced from each other by air gaps, the second positive lens component being the only lens component between the first positive lens component and the negative lens component, and
• the following conditional expression being satisfied:
• 0.00<(Rb2−Rb1)/(Rb2+Rb1)<1.00
• where Rb2 denotes a radius of curvature of an image side surface of the second positive lens component which constitutes the fourth lens group and has the convex surface facing the object, and Rb1 denotes a radius of curvature of an object side surface of the second positive lens component which constitutes the fourth lens group and has the convex surface facing the object, and
• the following conditional expression being satisfied:
• 0.538≦Fab/F4<2.00
• where Fab denotes a combined focal length of the first positive lens component and the second positive lens component having the convex surface facing the object, which constitute the fourth lens group, and F4 denotes a focal length of the fourth lens group.

A zoom lens consisting of, in order from an object:

• a first lens group having positive refractive power;
• a second lens group having negative refractive power;
• a third lens group having positive refractive power;
• and
• a fourth lens group having positive refractive power,
• performing zooming by changing an air gap between the lens groups,
• the fourth lens group consisting of, in order from the object, a first positive lens component, a second positive lens component having a convex surface facing the object, and a negative lens component, the first positive lens component, the second positive lens component and the negative lens component being at least partially spaced from each other by air gaps, and
• the following conditional expression being satisfied:
• 0.00<(Rb2−Rb1)/(Rb2+Rb1)<1.00
• where Rb2 denotes a radius of curvature of an image side surface of the second positive lens component which constitutes the fourth lens group and has the convex surface facing the object, and Rb1 denotes a radius of curvature of an object side surface of the second positive lens component which constitutes the fourth lens group and has the convex surface facing the object.

A method for manufacturing a zoom lens comprising, in order from an object, a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, and a fourth lens group having positive refractive power, the method comprising:

• performing zooming by changing an air gap between the lens groups,
• the fourth lens group including, in order from the object, a first positive lens component, a second positive lens component having a convex surface facing the object, and a negative lens component, and
• the method further comprising:
• assembling each lens in a lens barrel so that the following conditional expression is satisfied:
• 0.00<(Rb2−Rb1)/(Rb2+Rb1)<1.00
• where Rb2 denotes a radius of curvature of an image side surface of the second positive lens component which constitutes the fourth lens group and has the convex surface facing the object, and Rb1 denotes a radius of curvature of an object side surface of the second positive lens component which constitutes the fourth lens group and has the convex surface facing the object, and so that
• the following conditional expression is satisfied:
• 1.031≦<(−Fc)/F4<3.00
• where Fc denotes a focal length of the negative lens component constituting the fourth lens group, and F4 denotes a focal length of the fourth lens group.

A method for manufacturing a zoom lens comprising, in order from an object, a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, and a fourth lens group having positive refractive power, the method comprising:

• performing zooming by changing an air gap between the lens groups,
• the fourth lens group including, in order from the object, a first positive lens component, a second positive lens component having a convex surface facing the object, and a negative lens component, the first positive lens component, the second positive lens component and the negative lens component being at least partially spaced from each other by air gaps, the second positive lens component being the only lens component between the first positive lens component and the negative lens component, and
• the method further comprising:
• assembling each lens in a lens barrel so that the following conditional expression is satisfied:
• 0.00<(Rb2−Rb1)/(Rb2+Rb1)<1.00
• where Rb2 denotes a radius of curvature of an image side surface of the second positive lens component which constitutes the fourth lens group and has the convex surface facing the object, and Rb1 denotes a radius of curvature of an object side surface of the second positive lens component which constitutes the fourth lens group and has the convex surface facing the object, and so that
• the following conditional expression is satisfied:
• 0.538≦Fab/F4<2.00
• where Fab denotes a combined focal length of the first positive lens component and the second positive lens component having the convex surface facing the object, which constitute the fourth lens group, and F4 denotes a focal length of the fourth lens group.

A method for manufacturing a zoom lens consisting of, in order from an object, a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, and a fourth lens group having positive refractive power, the method comprising:

• performing zooming by changing an air gap between the lens groups,
• the fourth lens group consisting of, in order from the object, a first positive lens component, a second positive lens component having a convex surface facing the object, and a negative lens component, the first positive lens component, the second positive lens component and the negative lens component being at least partially spaced from each other by air gaps, and
• the method further comprising:
• assembling each lens in a lens barrel so that the following conditional expression is satisfied:
• 0.00<(Rb2−Rb1)/(Rb2+Rb1)<1.00
• where Rb2 denotes a radius of curvature of an image side surface of the second positive lens component which constitutes the fourth lens group and has the convex surface facing the object, and Rb1 denotes a radius of curvature of an object side surface of the second positive lens component which constitutes the fourth lens group and has the convex surface facing the object.