A relay optical system (RL) of this telescope has arranged therein, in the following order from the object side: a first lens group (G1) having positive refractive power; a second lens group (G2) having positive refractive power; a third lens group (G3) having positive refractive power; a fourth lens group (G4) having negative refractive power; and a fifth lens group (G5) having positive refractive power, wherein the magnification of the telescope can be changed by causing an image formed on a first image plane (IM1) to be re-formed on a second image plane (IM2) and further causing the second lens group (G2) and the third lens group (G3) to move along the optical axis, and thereby varying the image-forming magnification of the relay optical system (RL).

A lens barrel including a first main shaft and a first sub-shaft that guide the movement of a third front lens group (G3a), a second main shaft and a second sub-shaft that guide the movement of a fourth lens group (G4), a hall element that is used to detect the position of the third front lens group (G3a), and an MR sensor that is used to detect the position of the fourth lens group (G4) are disposed on a straight line passing through an optical axis in a cross section orthogonal to the optical axis. The first main shaft and the second main shaft overlap each other in a direction of the optical axis. In a drive unit for each lens group, a plurality of drive magnets are arranged symmetrically with respect to the straight line.

A relay optical system (RL) of this telescope has arranged therein, in the following order from the object side: a first lens group (G1) having positive refractive power; a second lens group (G2) having positive refractive power; a third lens group (G3) having positive refractive power; a fourth lens group (G4) having negative refractive power; and a fifth lens group (G5) having positive refractive power, wherein the magnification of the telescope can be changed by causing an image formed on a first image plane (IM1) to be re-formed on a second image plane (IM2) and further causing the second lens group (G2) and the third lens group (G3) to move along the optical axis, and thereby varying the image-forming magnification of the relay optical system (RL).

There is provided a lens barrel that can stably support movable lens groups with compact configuration and accurately detect the positions of the movable lens groups. A first main shaft (48) and a first sub-shaft (50) that guide the movement of a third front lens group (G3a), a second main shaft (58) and a second sub-shaft (60) that guide the movement of a fourth lens group (G4), a hall element (84) that is used to detect the position of the third front lens group (G3a), and an MR sensor (94B) that is used to detect the position of the fourth lens group (G4) are disposed on a straight line passing through an optical axis (Z) in a cross section orthogonal to the optical axis (Z). The first main shaft (48) and the first sub-shaft (50) are disposed on the radially inner side than the second main shaft (58) and the second sub-shaft (60). The first main shaft (48) and the second main shaft (58) are disposed so as to overlap each other in a direction of the optical axis. In a drive unit for each lens group, a plurality of drive magnets are arranged symmetrically with respect to the straight line.

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.

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.

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-banding 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.