Device for the production and modulation of monochromatic light

In a device for the production and modulation of colored light from light emanating from a suitable source by means of a liquid-crystal electro-optical cell coated with electrodes and combined with a polarizing arrangement and a reflector, the liquid crystal exhibiting a helically twisted structure with a twisting angle of at least approximately 90.degree. along the direction normal to the film-like electrodes, the improvement comprising:

• a linear polarizer positioned between said light source and said liquid-crystal cell and acting as said polarizing arrangement,
• said reflector formed of a substance with a helicoidal structure which reflects colored circularly polarized light of one handedness and transmits colored circularly polarized light of the opposite handedness and a light absorbing material directly adjacent said substance;
• and,
• a circular polarizer formed of a quarter-wave plate positioned between said liquid-crystal cell and said reflector.
• said quarter-wave plate directly adjacent to said liquid-crystal cell on the side facing said reflector and, said substance with a helicoidal structure placed directly adjacent to said quarter-wave plate to minimize undesirable effects due to parallax.