Fluid-actuated variable focal length polymer microlens system

Abstract

A polymer-based dynamic microlens system that can provide variable focal length and field-of-view (FOV) is fabricated and tested for its optical imaging characteristics. A flexible polydimethylsiloxane (PDMS) polymer membrane is used to form the lens surface. Two such membranes are combined with a spacer in between to form the fluidic lens chamber. The entire assembly is actuated by fluidic pressure using an external syringe pump to form either a double convex (DCX) or double concave (DCV) lens. The relationship between the focal length (f) and FOV of this dynamic lens as a function of the volume of the fluid pumped into or out of the lens chamber is investigated. The focal length of the single dynamic lens system can be tuned over the range of 75.9 to 3.1 mm and -75.9 to -3.3 mm, respectively, for the DCX and DCV lens configurations. The FOV that could be achieved using this dynamic lens system as DCX and DCV lenses is in the range of 0.12 to 61 degrees and 7 to 69 degrees, respectively. The smallest f-number (f/#) of 0.61, which corresponds to a numerical aperture of 0.64, could be achieved for a single dynamic lens system. An integrated two or three variable focal length DCV microlens system to provide wide FOV has also been fabricated and tested. The effective focal length of the integrated dynamic microlens system with two and three DCV lenses can be tuned in the range of -37.9 to -2.1 mm and -25.3 to -1.8 mm, respectively. The FOV achieved using the integrated two and three variable focal length DCV microlens systems were in the range of 8 to 76.7 degrees and 11.5 to 90.4 degrees, respectively.