Optical lens and head-mounted display device

A head-mounted display device, comprising:

• an image generator;
• an optical lens, comprising a first lens, a second lens, a third lens, and a fourth lens sequentially arranged from a light exit side to a light incident side, and refractive powers of the first lens, the second lens, the third lens, and the fourth lens being sequentially positive, negative, positive, and positive, wherein the first lens is a biconvex lens, the second lens is a convexo-concave lens and has a convex surface facing the light incident side, the third lens is a biconvex lens, wherein the image generator is set at the light incident side, and the optical lens is configured to receive an image beam provided by the image generator, the image beam forms a stop at the light exit side, and the stop has the minimum cross-sectional area of beam convergence of the image beam;
• a prism, disposed between the optical lens and the image generator, wherein the prism does not have a refractive power and is configured to guide the image beam from the image generator to the fourth lens, and the image beam is directly incident onto the fourth lens after the image beam leaves from the prism, wherein the fourth lens is a concavo-convex lens and has a concave surface facing the light incident side;
• and
• a waveguide element, wherein the stop is formed at a coupling entrance of the waveguide element, the image beam passes through the stop to enter the waveguide element through the coupling entrance, and is transmitted to a coupling exit of the waveguide element for being projected to a target.