| 摘要 |
PURPOSE:To obtain an inexpensive focal length variable lens, by impressing an electric field upon a lens group containing an electrooptic crystal by a parallel plate electrode, and changing the focal length of the lens action by changing the impressed voltage. CONSTITUTION:KH2PO4 crystals 11 and 12 having the primary electrooptic effect (Pockels effect), a transparent electrode plate 13, a deflected light source 14, a polarizing plate 15, and a variable power source 16 are provided to this device. The KH2PO4 crystals 11 and 12 have a four rotational inversion axis at its Z-axis and two two-rotational axes of symmetry at its X- and Y-axes, and the Z-axis coincides with the optical axis. When an external electric field is impressed in the direction of the Z-axis, the index ellipsoid of the crystal changes as well known. A light proceeding in the direction of Z-axis in the crystal, upon which the electric field is impressed in the direction of Z-axis, is permitted to proceed in the direction of the polarizing direction of X'- and Y'-axes. Thus the crystals 11 and 12 have a converging lens action and the focal length can be changed continuously by controlling a voltage V from the variable power source 16. |
