Abstract: A vari-focal polar alignment scope includes an objective optical system, a relay optical system, and an eyepiece optical system, in that order from the object side. The relay optical system includes an erecting vari-focal viewing optical system, including a positive condenser lens element, and positive second and third relay lens groups which relatively move in the optical axis direction so as to vary the magnification of the polar alignment scope, wherein the following conditions (1), (2) and (3) are satisfied: 6.0<fo/fe<10.0??(1); ?4.0<M2L<?1.0??(2); and 0.2<M3L<0.6??(3); wherein fo designates the focal length of the objective optical system; fe designates the focal length of the eyepiece optical system; M2L designates the lateral magnification of the second lens group of the relay optical system at a low magnification; and M3L designates the lateral magnification of the third lens group of the relay optical system at a low magnification.

Abstract: An image-erecting viewing optical system includes a first prism having an incident surface and at least two reflection surfaces, a front lens group of an objective optical system, a second prism having an incident surface and at least two reflection surfaces, a rear lens group of the objective optical system, a field stop, and an eyepiece optical system, in this order from the object. One reflection surface of the first or second prism includes a roof-mirror surface. The following conditions are satisfied: sin(????)>1/n??(1) 6°<?<16°??(2) wherein ? designates an angle between the incident surface and the first reflection surface of the first prism; ? designates a real field-of-view ? (half amount); ?? designates an angle between a light ray of a real field-of-view ? (half amount) and the optical axis within the first prism; and n designates the refractive index of the first prism.

Abstract: A vari-focal polar alignment scope includes an objective optical system, a relay optical system, and an eyepiece optical system, in that order from the object side.

Abstract: A camera-attachment lens system includes a positive condenser lens system and a positive image-forming lens system, and satisfies the following conditions: 1.5<fa/fco<2.4  (1) 0.08<DO/fa<0.16  (2) 1.65<Nco  (3) wherein fa: the combined focal length of the condenser lens system and the image-forming lens system; fco: the focal length of the condenser lens system; DO: the distance from the image-forming plane of the objective optical system to the most objective-optical-system side surface of the condenser lens system; and Nco: the refractive index of the condenser lens system.

Abstract: An image-erecting viewing optical system includes a first prism having an incident surface and at least two reflection surfaces, a front lens group of an objective optical system, a second prism having an incident surface and at least two reflection surfaces, a-rear lens group of the objective optical system, a field stop, and an eyepiece optical system, in this order from the object. One reflection surface of the first or second prism includes a roof-mirror surface.

Abstract: A camera-attachment lens system includes a positive condenser lens system and a positive image-forming lens system, and satisfies the following conditions:

Abstract: Eyepiece variable focal length optics comprise, in order from the objective optics, a negative lens group, a positive lens group, a positive lens group and a positive lens group; during variable focal length from longest focal length side to shortest focal length side, the first lens group moves monotonically toward the objective optics, the second lens group moves monotonically toward the eye, and the third lens group moves toward the eye in such a way that the distance from the second lens group is first increased and then decreased; the fourth lens group is stationary. The eyepiece variable focal length optics further satisfies the following condition (1): 0.

Abstract: A step zoom lens camera having a zoom lens and a cam ring provided with a cam groove having step portions. The zoom lens camera includes a focusing lens group which serves also as a variable power lens group of the zoom lens; and an adjusting lens group, serving also as another variable power lens group of the zoom lens, which is guided by the cam groove and is moved in the optical axis direction in a non-linear relationship with respect to the rotation angle of the cam ring in each focal length step. The step portions of the cam groove are each provided with a path which enables the adjusting lens group to move so as to provide a linear relationship between the rotation angle of the cam ring and amount of movement of the focal position of an infinite distance object.

Abstract: In a short-focal-length side zooming range, a moveable sub-lens group of a zoom lens system is made stationary at one of the object-side and the image-side end. At the intermediate switching focal length, the moveable sub-lens group is moved to the other of the object-side and the image-side end.

Abstract: An optical system of a composite camera including a first image-forming optical system, a second image-forming optical system, and a condenser lens group, which includes two or more lens elements, or includes a single lens element on which at least one aspherical surface is formed; and at any image height on the equivalent image plane, the following condition is satisfied: &Dgr;&thgr;Pmax−&Dgr;&thgr;Pmin<2° . . .

Abstract: The improved eyepiece variable focal length optics comprises, in order from objective optics with which it is used in combination, a negative first lens group, a positive second lens group and a positive third lens group, the first and second lens groups moving in opposite directions along the optical axis during variable focal length but the third lens group being stationary, and the eyepiece variable focal length optics satisfies the following conditions (1) and (2):

Abstract: The improved eyepiece variable focal length optics comprises, in order from objective optics with which it is used in combination, a negative first lens group, a positive second lens group and a positive third lens group, the first and second lens groups moving in opposite directions along the optical axis during variable focal length but the third lens group being stationary, and the eyepiece variable focal length optics satisfies the following conditions (1) and (2): 2.0<f3/f2<4.0  (1) 7.0<L12/f(h)  (2) where f2 is the focal length of the second lens group, f3 is the focal length of the third lens group, f(h) is the shortest focal length of the overall eyepiece variable focal length optics, and L12 is the axial air gap between the first and second lens groups at the shortest focal length. The eyepiece variable focal length optics achieves a variable power ratio of about three and yet is compact and allows for adequately large apparent visual field and eye relief.

Abstract: A zoom lens system includes a plurality of lens groups being relatively moveable in order to vary the focal length, and at least one lens group is arranged to be a switching lens group which includes two or more sub-lens groups, and in which one sub-lens group is made moveable, along the optical axis, with respect to the other sub-lens group. In the first focal-length range of the zooming range of the zoom lens system, the moveable sub-lens group and the other sub-lens group maintain the first distance; and in the second focal-length range which covers the first focal-length range and a range different therefrom, the moveable sub-lens group and the other sub-lens group maintain the second distance which is different from the first one.

Abstract: A step zoom lens camera having a zoom lens and a cam ring provided with a cam groove having step portions. The zoom lens camera includes a focusing lens group which serves also as a variable power lens group of the zoom lens; and an adjusting lens group, serving also as another variable power lens group of the zoom lens, which is guided by the cam groove and is moved in the optical axis direction in a non-linear relationship with respect to the rotation angle of the cam ring in each focal length step. The step portions of the cam groove are each provided with a path which enables the adjusting lens group to move so as to provide a linear relationship between the rotation angle of the cam ring and amount of movement of the focal position of an infinite distance object.

Abstract: Eyepiece variable focal length optics comprise, in order from the objective optics, a negative lens group, a positive lens group, a positive lens group and a positive lens group; during variable focal length from longest focal length side to shortest focal length side, the first lens group moves monotonically toward the objective optics, the second lens group moves monotonically toward the eye, and the third lens group moves toward the eye in such a way that the distance from the second lens group is first increased and then decreased; the fourth lens group is stationary.

Abstract: In a short-focal-length side zooming range, a moveable sub-lens group of a zoom lens system is made stationary at one of the object-side and the image-side end. At the intermediate switching focal length, the moveable sub-lens group is moved to the other of the object-side and the image-side end.

Abstract: The zoom lens system includes a positive first lens group and a negative second lens group that are arranged from an object side. The lens groups move along an optical axis to change the distance therebetween for zooming. The first lens group includes a negative first lens unit and a positive second lens unit that are arranged from the object side and each of the first and second units of the first lens group includes at least one negative lens. The zoom lens system of the present invention satisfies the following conditions (1), (2), (3) and (4); −3.1<ft/f1a<−2.5  (1) 5.8<ft/f1b<7.0  (2) 1.85<n1an  (3) 1.85<n1bn  (4) where ft is the longest focal length of the entire system, f1a is focal length of the first lens unit; f1b is focal length of the second lens unit; n1an is refractive index of the negative lens in the first lens unit; and n1bn is refractive index of the negative lens in the second lens unit.

Abstract: An anti-vibration lens attachment which is detachably attached to and between a photographing lens and a camera body includes an anti-vibration lens system having at least one correction lens group which is movable in a direction perpendicular to the optical axis, wherein an image formed by the photographing lens system is inverted at least once and is formed again on an image forming surface of the camera body by the anti-vibration lens system. The anti-vibration lens system includes at least six positive lens elements and at least two negative lens elements.

Abstract: A transducer such as used for an electro-dynamic loudspeaker adapted to convert an electric signal into a mechanical motion or, a moving coil type velocity sensor adapted to convert a mechanical motion into an electric signal. The so-called "Bl force factor," representative of the product of the magnetic flux density B and the length l of the main coil, is so controlled as to be made constant, whereby the linearity of the transducer is improved.