Variable focusing lens comprising micromirrors with one degree of freedom rotation

Abstract

A variable focal length lens comprising micromirrors with one degree of freedom rotation is invented. The lens consists of many micromirrors and actuating components. The array of micromirrors with one degree of freedom rotation makes all lights scattered from one point of an object converge at one point of image plane by using rotation of micromirror. The micromirror has the same function as a mirror. Therefore, the reflective surface of the micromirror is made of metal, metal compound, multi-layered dielectric material, or other materials with high reflectivity. The actuating components control the rotational displacements 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 CMOS technologies can remove the loss in effective reflective area due to electrode pads and wires.

Description

BACKGROUND OF THE INVENTION [0001] The present invention relates to a variable focal length lens comprising micromirrors with one degree of freedom (DOF) rotation and operational methods for the lens. [0002] A most widely used conventional variable focal length system is the one using two refractive lenses. It has complex driving mechanisms to control the relative positions of refractive lenses and a slow response time. Alternatively, variable focal length lenses have been made. Variable focal length lenses can be made by changing the shape of the lens, as is found in the human eye; this method has been used in lenses made with isotropic liquids. Other lenses have been made of electrically variable refractive index media to create either a conventional lens or a gradient index lens by means of a voltage gradient. The electrically variable refractive index allows the focal length of the lenses to be voltage controlled. Among them, the most advanced variable focal length lens is a liq...

AI Technical Summary

Benefits of technology

[0006] Conventional micromirror array lens is described in J. Boyd and G. Cho, 2003, “Fast-response Variable Focusing Micromirror Array Lens,” Proceeding of SPIE Vol. 5055: 278-286. The invention works as a variable focal length lens, and consists of many micromirrors to reflect the light and actuating components to control positions of the micromirrors. Each micromirror has the same function as a mirror. By making all lights scattered from one point of an object have the same periodical phase and converge at one point of image plane, the conventional micromirror array works as a reflective focal length lens. In order to do this, the micromirrors were electrostatically controlled to have desired positions by actuating components. A diffraction-limited micromirror array lens is formed by controlling both one degree of freedom (DOF) translation and one degree of freedom (DOF) rotation of each micromirror. The micromirror with both one DOF translation and one DOF rotation has a complex mechanical structure, actuating components and coupled motion. Therefore, fabrication, accurate control, and large motions of the micromirror are difficult. A micromirror array lens with one DOF rotation of micromirrors has a much simple mechanical structure and actuating components. The micromirror array lens formed by the control of one DOF rotation has relatively larger aberration because the same phase condition is not satisfied. Even though the quality of the lens formed by control of one DOF rotation is lower than the lens formed by control of both one DOF rotation and one DOF translation, it can be used as a variable focal length lens such as an imaging lens with low quality or focusing lens because of advantages that its structure and control is much simpler than those of the lens with both one DOF rotation and one DOF translation.

[0007] The micromirror array lens can be formed by a polar array of the micromirrors. For the polar array, each micromirror has a fan shape to increase an effective reflective area, so that the optical efficiency increases. The optical efficiency of the micromirror array lens can be improved by locating a mechanical structure upholding micromirrors and the actuating components under micromirrors to increase an effective reflective area. Electric circuits to operate the micromirrors can be replaced with known semiconductor microelectronics technologies such as MOS and CMOS. Applying the microelectronics circuits under micromirror array, the effective reflective area can be increased by removing necessary area for electrode pads and wires.

[0010] The advantages of the present invention are: (1) the micromirror array lens has a very fast response time because each micromirror has a tiny mass; (2) the lens has a high optical focusing efficiency; (3) the lens can have a large size aperture without losing optical performance. Because the micromirror array lens consists of discrete micromirrors, the increase in the size of the lens does not cause the increase in aberration caused by shape error of a lens; (4) the lens is cost effective because of the advantages of its mass productivity; (6) the lens has simple structure and control.

Problems solved by technology

Therefore, fabrication, accurate control, and large motions of the micromirror are difficult.

The micromirror array lens formed by the control of one DOF rotation has relatively larger aberration because the same phase condition is not satisfied.

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