A zoom lens includes a first lens group, a second lens group, a third lens group, a fourth lens group and an aperture. The first lens group, the second lens group, the third lens group and the fourth lens group are sequentially arranged in a direction. The aperture is located between the second lens group and the third lens group. When the zoom lens performs a zoom operation, the first lens group and the third lens group are fixed and the second lens group and the fourth lens group are moved, and a moving distance of the fourth lens group on an optical axis of the zoom lens is less than 5 mm.

An interchangeable lens attachable to a camera body, the interchangeable lens including: a focusing optical system configured to vary a focal position of the interchangeable lens; and a transmitter configured to transmit a first value and a second value to the camera body, the first value indicating a relationship between an amount of movement of the focusing optical system and an amount of movement of an image plane at a position to which the focusing optical system has moved, the second value indicating a relationship between an amount of movement of the focusing optical system and an amount of movement of the image plane, the second value being equal to or smaller than the first value.

A zoom lens includes a first lens group and a second lens group. A relative movement between the first lens group and the second lens group is allowed, whereby the zoom lens zooms between a wide-angle end and a telephoto end. While the zoom lens is switched from the wide-angle end toward an intermediate state, the first lens group is moved toward the image side. While the zoom lens is switched from the intermediate state toward the telephoto end, the first lens group is moved toward the object side.

There are provided a variable magnification optical system and a control method thereof which are capable of relatively accurately adjusting a positional relationship between a variable magnification optical device and an imaging surface of an imaging device according to a zoom amount. A zoom lens included in the variable magnification optical device is positioned at a telephoto end and a wide angle end, and shift amounts S1 and S2, tilt angles 1 and 2, rotation angles 1 and 2, and focusing adjustment amounts 1 and 2 of the variable magnification optical device are set by a user and are stored. In a case where a zoom amount of the zoom lens is set to a desired value by the user, a shift amount corresponding to the set zoom amount is calculated by using the stored shift amounts S1 and S2. The positional relationship between the variable magnification optical device and the imaging surface of the imaging device is adjusted so as to have the calculated shift amount.

A lens barrel includes one or more movable lens groups, and a cam barrel associated with the one or more movable lens groups and configured to balance a center of gravity of the one or more movable lens groups.

An image lens assembly includes four lens groups: a first lens group, a second lens group, a third lens group and a fourth lens group along an optical path. The four lens groups include nine lens elements: a first lens element with positive refractive power, a second lens element with negative refractive power, a third lens element, a fourth lens element, a fifth lens element, a sixth lens element, a seventh lens element, an eighth lens element and a ninth lens element along the optical path. At least one lens element of the image lens assembly has at least one inflection point. At least five lens elements of the image lens assembly are made of plastic material. When focusing or zooming, the first lens group and the fourth lens group stay stationary, while the second lens group and the third lens group move along an optical axis.

A zoom/focus apparatus and corresponding zoom lens assembly are provided. The zoom/focus apparatus may include a first focus lens barrel (101), a first zoom lens barrel (102), a first ultrasonic motor and a second ultrasonic motor which are disposed coaxially. The first focus lens barrel and the first zoom lens barrel are radially unmovable. The caliber of the first zoom lens barrel is larger than that of the first focus lens barrel. The two ultrasonic motors are used to drive the two lens barrels to move axially by the rotation of the rotors (103, 104), respectively. Because the zoom lens barrel which needs to be moved is disposed at outside of the focus lens barrel, by driving the lens barrels using the ultrasonic motors, the telescoping of the zoom lens barrel and the adjusting of the zoom position can be achieved simultaneously. Because the zoom lens barrel has larger caliber such that it is suitable for wide-angle lens and the lens assembly becomes gradually larger from inside to outside when the lens group is installed from rear to front, the installing is more convenient and smooth and the miniaturization of the lens assembly is facilitated.

There is provided an optical imaging system including a prism, a first fixed lens group, a first movable lens group, a second movable lens group, and a second fixed lens group. The prism is configured to refract light reflected from an object side toward an imaging plane and a reflecting member. The prism is disposed on the first fixed lens group and the first movable lens group is configured to change a position of the imaging plane so that an overall focal length is changed. The second movable lens group is configured to adjust a position of the imaging plane so that a focal length for an object is adjusted. The imaging plane is disposed on the second fixed lens group.

A zoom lens device includes a focusing lens group arranged on an object side, and a variator lens group next thereto, and a temperature sensor. The focusing lens group includes a focusing lens, and a temperature-based correction lens for correcting changes in focal point caused by temperature changes around the focusing lens group. The temperature-based correction lens is moved by a temperature-based correction lens driving mechanism along an optical axis to a position determined by a temperature detected by the temperature sensor, independently of the positions of the focusing lens or variator lens group. Thereby, the zoom lens device is capable of favorably correcting defocus of the lens group caused by an ambient temperature change with a simple correcting mechanism.

The invention relates to an electronic image pickup system whose depth dimension is extremely reduced, taking advantage of an optical system type that can overcome conditions imposed on the movement of a zooming movable lens group while high specifications and performance are kept. The electronic image pickup system comprises an optical path-bending zoom optical system comprising, in order from its object side, a 1-1st lens group G1-1 comprising a negative lens group and a reflecting optical element P for bending an optical path, a 1-2nd lens group G1-2 comprising one positive lens and a second lens group G2 having positive refracting power. For zooming from the wide-angle end to the telephoto end, the second lens group G2 moves only toward the object side. The electronic image pickup system also comprises an electronic image pickup device I located on the image side of the zoom optical system.