Tunable lens

The shape of a tunable lens by Optotune AG, and in particular its focal length, can be electrically controlled. The animation on the left side of the figure is recorded by a color video camera at 60 fps. Camera provides an image through the lens, but not the lens topography. A constant and precise control of the lens shape is nevertheless important to ensure high quality and aberration free performances. DHM enables to measure it with an interferometric resolution.

One interest among others is the dynamical analysis of the shape of the lens when applying a square input voltage. After each voltage change, a ringing effect appears before the lens shape stabilization. The highspeed DHM has been used to characterize efficiently this behavior, affecting both the optical properties of the lens and its operating frequency specification range. The animation shows a comparison of the time sequence 3D topography recorded at 60 fps with normal camera and at 12’800 fps with the highspeed DHM when driving the lens with a square signal at a frequency of 30Hz.