A beam focusing and scanning system using a micromirror array lens (optical system) includes a light source configured to emit light and a micromirror array lens, including at least one micromirror, optically coupled to the light source, configured to reflect the light onto a projection medium (projection plane). The optical system also includes at least one actuating component coupled to the at least one micromirror, configured to move the at least one micromirror to enable the at least one micromirror to focus the light on the projection medium. The advantages of the present invention include high speed variable focusing and scanning, large focal length variation, phase compensation, high reliability and optical efficiency, low power consumption and low cost.