Abstract: In a telescope, the adjustment order is limited so that dioptric power adjustment is made after adjustment of a distance between a pair of optical systems is completed. A pupil distance and a dioptric power correction amount are stored in a memory for every user. When a user uses the telescope, his or her pupil distance and dioptric power correction amount are read out from the memory to automatically make adjustment.

Abstract: In a telescope according to the present invention, defocus amount of an optical system constituting the telescope is calculated; whether or not the defocus amount is within a predetermined in-focus range obtained from a focal point adjusting ability of human eye is discriminated; and when the defocus amount exceeds the in-focus range as a result of the above discrimination, the optical system is driven. The optical system is driven in a shorter time than a time required for removing a defocus by human eye.

Abstract: A binocular comprising a housing and a pair of first and second optical systems positioned on each side of a central line. Each optical system includes an object lens and ocular lens arranged at a front part and at a rear part of the housing respectively. Further, a light admitting window is placed on the central line between the first and second optical systems for admitting light from an object. A detection module, provided independently of the first and second optical systems is used to output electrical signals which represent the distance to the object. The detection module may include an optical path deflecting means for z-shapely deflecting the light from the light admitting window and for directing the light to a sensor. The binocular is compact and has a hand grip that is designed in order to be holdable and focusable by the use of a single hand.