Patent ID: 6870669

Claim:
A pair of variable-powered binoculars, comprising: a pair of objective lens systems; a pair of prism systems, each of the prism systems inverting an image that advances through a corresponding objective lens system, from an inverted image to an erecting image; a pair of concave adjusting lenses, each of the concave adjusting lenses placed between a focus formed by the corresponding objective lens system and the corresponding prism system, so that each of the concave adjusting lenses is movable along the optical axis formed by the corresponding objective lens system and the corresponding prism system; and a pair of ocular lens systems, each of the ocular lens systems placed on the optical axis and defining an apparent image forming plane, so that each ocular lens system is movable along the optical axis closer to or away from the corresponding concave adjusting lens, synchronizing with a movement of the corresponding concave adjusting lens, wherein a respective one of the apparent image forming planes is fixed in a stationary state relative to the respective ocular lens system yet movable relative to a respective one of the concave adjusting lenses as each corresponding ocular lens system and each corresponding concave adjusting lens move closer to or away from each other.