Abstract: An optical system including a transparent fluid and a container filled with the fluid as well as at least one optical element having an index of refraction which approximately matches that of the fluid. The fluid is chosen to have a viscosity no greater than 40 centistokes. As a result, the low viscosity of this optical fluid reduces thermal irregularities. Also, improved transmission, particularly in the blue spectrum is achieved as compared to conventional optical fluids.

Abstract: A birefringent element is patterned such that for light of a first polarisation the element acts as a first refractive optical element and for light of a second polarisation the optical response of the element changes. The element can be used in conjunction with a polarisation selecting means, such as a liquid crystal device, to provide an electrically controllable optical element that can be used in light beam manipulation applications.

Abstract: An ophthalmologic alignment device for aligning a measuring system at a predetermined position for an eye to be examined. The user moves the measuring system with a joystick for aligning purposes while observing a frontal eye image with an observation unit. A second moving unit further moves the measuring system moved by the user. An index projection/detection system projects an index onto the eye and detects the reflected index. The controller causes drivers to drive the second moving unit on the basis of the result of the detection of the index projection/detection system. A mode switch switches the movement of the measuring system from a mode in which the observation unit is moved by the first moving unit to a mode in which the observation unit is moved by the second moving unit, whereby the alignment of the eye and the measuring system is achieved easily and with high accuracy, irrespective of the degree of the user's skillfulness in handling the alignment device.