| 摘要 |
A method and apparatus for compensating for temporally varying effects, such as temperature, in a liquid-crystal cell, particularly a wedge-shaped liquid-crystal cell (10). The temperature of the liquid crystal (10) is measured, either directly with a thermocouple or the like, or by optical means (82, 86) which depend upon the temperature of the liquid crystal. For example, an intensity detector (86) monitors the polarization rotation of a probe beam (84) of light having a substantially different wavelength than that of the beam (28) modulated by the liquid crystal, and a feedback circuit (90) keeps the intensity at a predetermined value corresponding to the optimum path length in the liquid crystal of the modulated beam (28). The feedback signal from the temperature measurement is used to effectively change the gap filled with liquid crystal. For a wedge-shaped cell, the gap size is changed by moving the cell in the wedge direction. Other cell structures are available in which the gap size is physically changed by mechanical movement of the cell walls.
|
