| 摘要 |
<p>The invention relates to a measuring method, cell and assembly for determining the optical birefringence of the liquid crystals, depending on the temperature. The method consists in the fact that there are processed some images of the light transmitted as interference rings, by a sample of directed liquid crystal, situated in a thermally stable measuring cell, with relatively high precision, between a plane-convex lens and a parallel-plane surface, by using a measuring system which includes elements of sample uniform lighting and a camera, for obtaining the values of the parameters needed for determining, by calculation, the birefringence. According to the invention, the cell wherein the method is applied, consists of a plane-convex lens (1) and a plane-parallel plate (2), removably fixed, some supports (3 and 4), the distance between the lens (1) and the plane-parallel plate (2), as well as the centering of the interference figure being provided by means of three screws (5), placed at an angle of 120 degrees therebetween, assisted by some elastic elements (6) and a system (b) of three guiding holes, whose axes are shifted therebetween by an angle of 120 degrees. According to the invention, the assembly for applying the method within the cell, consists of a source (7) of monochromatic light, a light diffuser (8) for rendering the lighting uniform, an auxiliary polarizer (9) for the final control of the lighting level, a main polarizer (10), the cell (A) for measuring being placed inside a thermostatable enclosure (B), on a rotating little table (C), an analyzer (11) directed, in a crossed way, in relation to the main polarizer (10), a camera (D) focused on the interest area of the cell (A), a main computer (E), which takes over the image from a camera (D) and processes it by means of an adequate program, a temperature controller (F) connected to the thermostatable enclosure (B) and to the computer (E) whereto it communicates the temperature value.</p> |
