Abstract: A zoom lens includes a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a fourth lens group having a positive refractive power or a negative refractive power. The lens groups are arranged in order from the object side toward the image side. The focal lengths of the system at a wide angle end and a telephoto end, the focal lengths of the first and second lens groups, the distance between the position of the first lens group, the position being closest to the object side upon zooming, and the position of the first lens group at the wide angle end, and the difference between the largest distance between the first and second lens groups upon zooming and the distance between the first and second lens groups at the wide angle end are determined.

Abstract: A zoom lens includes, in order from an object side to an image side, a first lens unit having a positive refractive power configured not to move for zooming, a second lens unit having a negative refractive power configured to move during zooming, a third lens unit having a positive refractive power configured to move during zooming, and a fourth lens unit having a positive refractive power configured not to move for zooming. The third lens unit includes a positive lens, a negative lens, and a diffractive optical element. A focal length of the third lens unit (fc), a focal length of the diffractive optical element (fdoe), a focal length at a wide angle end of the zoom lens (fW), and a focal length at a telephoto end of the zoom lens (fT) satisfy the following conditions: 0.35<fc/?{square root over ((fW·fT))}<0.81, and 45<fdoe/fc<300.

Abstract: A zoom lens includes, in order from an object side to an image side, a first lens unit having a positive refractive power configured not to move for zooming, a second lens unit having a negative refractive power configured to move during zooming, a third lens unit having a positive refractive power configured to move during zooming, and a fourth lens unit having a positive refractive power configured not to move for zooming. The third lens unit includes a positive lens, a negative lens, and a diffractive optical element. A focal length of the third lens unit (fc), a focal length of the diffractive optical element (fdoe), a focal length at a wide angle end of the zoom lens (fW), and a focal length at a telephoto end of the zoom lens (fT) satisfy the following conditions: 0.35<fc/?{square root over ((fW·fT))}<0.81, and 45<fdoe/fc<300.

Abstract: A drive controller of a lens apparatus including a first lens unit moving for performing manual focus and a second lens unit moving for performing auto-focus has a control device switchable between a first mode for performing an auto-focus control of the second lens unit and a second mode for making the second lens unit unmovable at a predetermined position. The control device has a third mode for controlling drive of the second lens unit, upon receiving a command for switching from the first mode to the second mode, so as to maintain a focus state of the lens apparatus, on the basis of positional information of the first lens unit. The controller moves to the second mode upon detecting that the second lens unit has reached the predetermined position in the third mode.

Abstract: A drive controller of a lens apparatus including a first lens unit moving for performing manual focus and a second lens unit moving for performing auto-focus has a control device switchable between a first mode for performing an auto-focus control of the second lens unit and a second mode for making the second lens unit unmovable at a predetermined position. The control device has a third mode for controlling drive of the second lens unit, upon receiving a command for switching from the first mode to the second mode, so as to maintain a focus state of the lens apparatus, on the basis of positional information of the first lens unit. The controller moves to the second mode upon detecting that the second lens unit has reached the predetermined position in the third mode.

Abstract: An automatic focusing apparatus repetitively detects a defocus amount of a photographing lens, discriminates whether or not an object is moving, and calculates a pursuit correction amount for a moving object on the basis of present and previous defocus amounts. When a non-moving object is discriminated, a drive amount of the lens is calculated on the basis of the present defocus amount, and when a moving object is discriminated the drive amount is calculated on the basis of a pursuit drive amount as a sum of the present defocus amount and the pursuit correction amount. A pursuit enable/disable determining device determines whether the drive amount is calculated on the basis of the discrimination result or on the basis of the present defocus amount.