Design of a Micro-Integrated Optical MEMS for Camera Applications

摘要

The micro-integrated optical device presented in this paper addresses two challenges encountered in digital camera design. Today's digital cameras can produce high resolution images but at a high cost of manufacturing because their autofocus and zoom mechanisms require assembling of many small plastic components. Furthermore, there are limits to the miniaturization of the zoom mechanism. Cell phone cameras today allow the use of lower quality fixed lens systems. Beyond 3 MPixel imaging chip resolution, variable focus lens systems are necessary to provide for the required depth of field. Since cell phone cameras will see a move towards these higher resolution imaging chips in the coming years, additional pressure is mounted on the camera manufacturers to find solutions for miniature zoom and autofocus mechanisms. The integrated Silicon micromachined device presented here couples a deformable polydimethylsiloxane (PDMS) lens to a radial microlens actuator, thereby mimicking the focus mechanism used in the human eye. Via radial deformation, a single plano-convex lens can take the shape of a biconvex and concave lens and the focal plane is changed as a result. The in-plane motion allows the actuation mechanism, the microautofocus and aperture, to be created at the wafer-level and directly attached to a CMOS imaging chip. Each of these components is integrated at the die level with a digital imaging sensor to produce a microcamera of dimensions 1.8mmx2.0mmx2.0mm. The current design is capable of varying the focal length between 5 to 50mm with a stop range of f/2.8 to f/5.6. The design can also be adapted to provide a variable pinhole aperture.