Thermal imagers using liquid crystal sensing elements

摘要

It is known to use liquid crystal cells for thermal imaging. However, the sensitivity of the liquid crystal cell is reduced due to the walls of the cell absorbing some of the incident radiation and locally heating the crystal thereby producing localized changes in phase. Liquid crystal materials which have sufficient surface tension to form a film without forming a part of a cell are disclosed where the pitch of the helix of the film exhibits a strong temperature dependence. In one embodiment the liquid crystal film is mounted wtihin a Fabry-Perot resonant cavity so that detection of the change in the crystal due to a change in temperature is enhanced.