This paper reviews the development of low temperature poly Si TFT, scattering light valves addressed by TFTs and a brighter video projection system using them, with the attensin of their optical aspects. The first includes main feature which are laser induced crystallization of PECVD a-Si in almost entirely solid phase by high speed scanning CW Ar laser beam. The second includes photo-polymerization induced phase separation method for the preparation of liquid crystal polymer composite (LCPC) material and scattering light valve with low driving voltage of 6 Vrms. The last gives a brighter video screen image with high contrast ratio and includes higher light efficiency through LCPC light valves and projection lens unit by about four times than that of conventional LC light valves with polarizers.

A yellow light emitting display using neon-hydrogen-argon mixture as filling gas is presented. Strong "monochromatisation" of the emitted light is reported for the first time on the wavelength λ585.3 nm. Experimental results on the dependence of the "monochromatisation effect" is given for various pressure values and filling gas composition. It is underlined the existence of a process of selective population of the upper level 3p[1/2]0 of the transition corressponding to the wavelength 585.3 nm. The obtained results are discussed in relation with the reported results on yellow light laser in which a discharge in neon-hydrogen mixture is used for laser radiation generation at λ585.3 nm. The proposed explanation of different authors on the upper level population through radiative or dissociative recombination of neon ions is discussed and a new hypothesis is advanced for the strong monochromatisation observed in neon-hydrogen or neon-hydrogen-argon filled displays. According to this hypothesis, in the feeding process of the upper level 3p[1/2]0 are taking part the neon metastable states too. If such an assumption will come true, cyclic processes in yellow light generation might appear.