| abstract |
A variable focal-length lens system comprises a first optical unit 1-5 having a switchable focal length and comprising a birefringement lens 3 (with substantially different refraction characteristics depending on the, plane of polarization of an incident light beam) and a device 2 for selectively rotating the plane of polarization of the beam incident on the lens 3; and a second optical unit 6,7 forming a lens with a focal length that is continuously variable over a range equal to or larger than that of the first optical unit. The device 2 is controlled electrically, magnetically or by mechanical stress. The variable lens 6 utilises the Kerr or Pockels effect, or uses a liquid crystal, or is deformable by an actuator. Plural elements 2,3 may be employed and switched under control of a microcomputer. <IMAGE> |