A micromirror array lens consists of many micromirrors with two degrees of freedom rotation and actuating components. As a reflective variable focal length lens, the array of micromirrors makes all lights scattered from one point of an object converge at one point of image plane. As operational methods for the lens, the actuating components control the positions of micromirrors electrostatically and/or electromagnetically. The optical efficiency of the micromirror array lens is increased by locating a mechanical structure upholding micromirrors and the actuating components under micromirrors. The known semiconductor microelectronics technologies can remove the loss in effective reflective area due to electrode pads and wires. Independent control of each micromirror is possible by known semiconductor microelectronics technologies. The micromirror array can form a lens with arbitrary shape and/or size, as desired.