Optical zoom lens for webcam

The line connecting the centers of curvature on both sides is called the principal axis, and the central point O is called the optical center. Light passing through the optical center does not refract no matter where it comes from. The beam parallel to the main axis refracts on the concave lens and diverges to the four directions. The extension line against its divergence direction will all be at a point F on the same side as the light source, and its refracted light will just be emitted from point F, which is called the virtual focus. One on each side of the lens. Biconcave lens is also called divergent lens. The focal length of a concave lens refers to the distance from the focal point to the center of the lens. The larger the radius of the lens, the longer the focal length. If it is a thin lens, the focal lengths on both sides are equal.