Imaging lens, imaging optical device, digital device, and method of manufacturing imaging lens

A method of manufacturing an imaging lens which comprises, in order from an object, a first lens group having a positive refractive power, a second lens group having a positive refractive power, and a third lens group having a negative refractive power,

• the method comprising arranging the first to third lens groups in a lens barrel such that:
• in focusing from infinity to a close object, the first lens group is fixed in position, the second lens group is moved toward the object, and the third lens group is moved toward an image, whereby the distance between the first lens group and the second lens group is reduced, and the distance between the second lens group and the third lens group is increased,
• the first lens group comprises, in order from the object, a negative lens, a first cemented lens adjacent to the negative lens, and a second cemented lens adjacent to the first cemented lens,
• the second lens group consists of three lenses,
• the third lens group consists of one negative lens, and
• the following conditional expressions (1) and (4) are satisfied:
• 1.0<f1/f<2.5 (1)
• 0.1<|d_2Gr/d_3Gr|<1.5 (4)
• where
• f1:
• is the focal length of the first lens group,
• f:
• the focal length of the entire system when focused on infinity,
• d_2Gr:
• the amoumt of movement of the second lens group during focusing from infinity to an arbitrary object distance, and
• d_3Gr:
• the amount of movement of the third lens group during focusing from infinity to an arbitrary object distance.