Negative spherical lens can be regarded as the optical basis of glasses.

Concave lens optics. The concave lens diverges the incident light, and the virtual image is vertically reduced through the concave lens, and the object image is on the same side of the lens. Concave lens optics can be regarded as the optical basis of negative lens glasses. The light parallel to the main optical axis of the concave lens will diverge outward after passing through the concave lens, and its reverse extension line will converge on the F point of the concave lens, which is called the virtual focus of the concave lens.