A single lens is an optical element that focuses or disperses light. It is usually made of a transparent material, such as glass or plastic, and has a radius of curvature to control the focusing or dispersion of light. Single lenses can be widely used in various optical systems, such as glasses, cameras, telescopes, etc.

The advantage of a single lens lies in its simplicity and flexibility. Since it is composed of only one optical element, its design and manufacturing are relatively simple and can be used in various optical systems. In addition, a single lens can control the focusing or dispersion of light by changing the curvature radius, thus adapting to different optical application requirements.