Patent ID: 7277225

Claim:
Binoculars which include a pair of observation optical systems each having an objective optical system, an erecting optical system and an eyepiece optical system, the binoculars comprising: a focusing mechanism that is used to move a part of the observation optical system for focusing; and a convergence value compensating mechanism that compensates for a convergence value by displacing displaceable optical elements which are at least parts of the objective optical systems, respectively, in association with actuation of the focusing mechanism, wherein a distance between optical axes of the eyepiece optical systems is adjustable in line with a width between eyes of a user, wherein a maximum value of a distance between optical axes of the displaceable optical elements is smaller than a minimum value of the distance between the optical axes of the eyepiece optical systems; wherein the convergence value compensating mechanism compensates for the convergence value by varying the distance between the optical axes of the displaceable optical elements; wherein the displaceable optical elements are installed rotatably around straight lines parallel to the optical axes thereof, and the distance between the optical axes of the displaceable optical elements varies in accordance with rotating motion of the displaceable optical elements; and wherein, when viewed along an optical axis direction of the objective optical systems, centers of the displaceable optical elements are respectively located on outer sides of lines respectively passing turning centers of the displaceable optical elements and parallel to a vertical direction of the binoculars in a state where an observation object at infinity is focused, wherein, when viewed along the optical axis direction of the objective optical systems, the centers of the displaceable optical elements are respectively located on inner sides of the lines respectively passing the turning centers of the displaceable optical elements and parallel to the vertical direction of the binoculars in a state where an observation object at a closest focusable distance is focused, and wherein if each of inclination angles of line segments connecting the centers of the displaceable optical elements with the turning centers thereof, respectively, with respect to the vertical direction of the binoculars in a focused state corresponding to the observation object at infinity is represented by α, the inclination angle “α” is maintained to be constant until a focusing distance becomes a predetermined value when gradually carrying out the focusing from the focused state corresponding to the observation object at infinity to a shortest distance side.