Institut Jozef Stefan

Matej Bazec

Bojan Marin

Janez Pirs

Silvija Pirs

Andrej Vrecko

Dusan Ponikvar

Bernarda Urankar

A new concept of the LCD light-switching optical filter allowing for very high, electrically controlled, continuously variable light attenuation (up to &#x2267;100,000) optimized/symmetrized for the light incidence along the normal to the LCD plane is proposed. The new LCD light-switching optical filter also exhibits very low light attenuation dependence for the oblique incidence of light within a limited cone of angles off the normal incidence direction in compliance with the international safety and quality regulation EN 379 for personal protection equipment. According to the invention the problem is solved by specific, novel modification of the general principle of highly twisted nematic LCDs, allowing for the adaptation of the light transmission/driving voltage characteristics to specific requirements of the driving electronics as well as 'symmetrizing' the overall optical birefringent properties, which in turn results in a high degree of their angular compensation.

Variable contrast, wide viewing angle LCD light-switching filter

A new concept of the normally open LCD light switching element is proposed, which allows for the superior angular compensation for the light attenuation by using a single simple negative bireffingent c-plate compensation layer. The concept is based on the simultaneous use of highly angularly symmetric STN LC-configuration (preferably 180&#xb0; twist) and maximal use of the single (preferably ordinary ray) light propagation mode. The solution is best suitable for various light switching applications like LCD automatic protective welding light filters, as well as for multi-segment large display panels, where it provides for excellent uniformity of the light-attenuation in the 'dark' state.

High contrast, wide viewing angle LCD light-switching element

Growing community of inventors

Koper, Slovenia

Matej Bazec