Tunable Birefringent Filters Using Liquid Crystal Elements

液晶技术的最新进展使得构建可调谐的双折射滤光片成为可能，其工作范围为3500-20,000埃，通带窄至100埃。滤光片的中心波长可以电子方式选择，只需几毫秒，没有移动部件。这些过滤器的生产成本应该相对较低(2-3000美元)。当液晶元件与由双折射石英或方解石制成的固定延迟器串联放置时，人们可以构造通带更窄的滤光片，范围从30埃到0.25埃不等。当液晶执行调谐动作时，固定延迟器提供高分辨率。产生的过滤器是高度选择性的，而且灵活。这些仪器的光学质量是由固定的延迟器决定的，对液晶元件只有轻微的限制。在第一阶段中，测量了单个液晶元件的性能。根据这项第二阶段合同，将建造两种类型的完整过滤器，并在正在进行的太阳能和夜间项目中进行测试。

Recent advances in liquid crystal technology make it possible to construct tunable birefringent filters operating over the range 3500-20,000 Angstroms, with passbands as narrow as 100 Angstroms. The center wavelength of the filter can be selected electronically, in a few milliseconds, with no moving parts. These filters should be relatively inexpensive to produce ($2-3K). When liquid crystal elements are placed in series with fixed retarders made of birefringent quartz or calcite, one can construct filters with narrower passbands, ranging from 30 Angstroms to as narrow as 0.25 Angstroms. The fixed retarder provides the high resolution while the liquid crystal performs the tuning action. The filter that results is highly selective, and agile. Optical quality in these instruments is determined by the fixed retarders, and only mild restrictions are placed on the liquid crystal elements. In Phase I the performance of individual liquid crystal elements was measured. Under this Phase II award, complete filters of two types will be constructed and tested in ongoing solar and night- time programs.