Nonmechanical bifocal zoom telescope

We report on a novel zoom lens with no moving parts in the form of a switchable Galilean telescope. This zoom telescope consists of two flat liquid-crystal diffractive lenses with apertures of 10 mm that can each take on the focal lengths of -50 and +100 cm, with a spacing of 50 cm and, hence, a zoom ratio of 4x. The lenses are driven using a low-voltage ac source with 1.6 V and exhibit millisecond switching times. The spectral characteristic of this diffractive zoom system is evaluated for light sources of various bandwidths. Potential applications for this technology include a zoom lens with no moving parts for camera phones and medical imaging devices.