LENS SYSTEM AND OPTICAL DEVICE

PROBLEM TO BE SOLVED: To provide an optical system whose performance is stable even when a varifocal lens having a focal length adjusting means of varying the focal length by using shape variation of fluid is used. SOLUTION: The light from a light source 9 is transmitted through insulating liquid 5 and conductive liquid 4 and photodetected by a photodetecting element 10. When the conductive liquid 4 and insulating liquid 5 vary in refractive index and the shape of their interface varies as their characteristics vary and so on, the light incident on the photodetecting element 10 varies in intensity and distribution and then characteristic variation of a lens system can be known. A controller 11 receives the signal from the photodetecting element 10 and outputs a command to vary a voltage for canceling the characteristic variation of the lens system to a power unit 8. According to the command, the power unit 8 varies the voltage applied between an external electrode 6 and an internal electrode 7. Consequently, the shape of the interface between the conductive liquid 4 and insulating liquid 5 varies to compensate the variation in characteristic of the lens system, so that the optical system has its original characteristics. COPYRIGHT: (C)2007,JPO&INPIT