Variable-focus liquid-filled optical lens.

A variable-focus liquid-filled optical lens consists of a solid plate, a ring spacer, and an elastic film; a liquid fills this lens-shaped container. One varies the focus by changing the liquid volume in the lens. The lens shape calculated theoretically is a paraboloid. However, it is approximately a sphere near the central area. The deformation of the lens shape by gravity was also calculated with a simplified structure in which the lens was held vertically and found to be independent of the elastic properties of the film. The effect of gravity was found to be negligible when the pressure at the liquid pump was more than 30 times that induced in the liquid at the bottom of the lens by the gravity. The aberrations of the lens were calculated and observed to be negligibly small compared with the normal convex spherical single-glass lens. A liquid-filled lens was fabricated and experimentally evaluated.