Degree Visual Angle
Degree visual angle is the angle a considered object subtends at the eye, usually stated in degrees of arc. It also is called the object’s angular size. The three lines from object endpoint A guiding toward the eye present the bundle of light rays that pass through the cornea, pupil and lens to form an optical image of degree A on the retina at point a. Degree visual angle is the central line of the bundle constitutes the chief ray For present proposes, point O can represent the eye’s nodal points at about the center of the lens, and also appoint the center of the eye’s entrance pupil that is only a few millimeters in front of the lens. It prevails a series of advanced functions including digital photography, voice memory, high speed USB data assigning and USB charging