Color adaptation in a projection system
Publication Date: 2004-Feb-26
The IP.com Prior Art Database
Color adaptation in a projection system.
The invention relates to a projection system for displaying image information The projection system comprises an illumination system for generating red, green and blue light beams, a modulation system for modulating the generated light beams, a recombination system for combining the modulated light beams in a single modulated light beam and a projection lens for projecting the modulated light beam on a screen. The modulation system comprises a transmissive or reflective liquid crystal display panel for modulating the light beams. According to the invention the modulation system further comprises electrochromic devices and a controller for generating control signal for adapting the transmission of the electrochromic devices in order to obtain predetermined color points and a predetermined white point. The electrochromic device can be positioned in the light paths of the colored light beams. For example, near the liquid crystal display panels.
Fig.1 shows an example of an electrochromic device 1 that can be used in the projection system. The electrochromic device 1 comprises of two glass substrates 2, 3 between which the following layers are present: a transparent ITO layer 4, an ion- storage layer 5, an ion conducting electrolyte layer 6, an electrochromic electrode layer 7 and a transparent ITO layer 8. In operation, a voltage difference 9 is supplied to the transparent ITO layers 4,8, so that an electric field is present between these ITO layers. Due to the electric field ions move from the electrolyte layer 6 into or out of the electrochromic layer 7 in dependence of the direction of the electric field. The optical properties i.e. transmission, reflection and absorption of the electrochomic electrolyte layer 7 varies in dependence of the electron density in the electrochromic material. In this particular case the electrochromic electrode layer comprises a electrochromophore i.e. a dye that changes its color in dependence of either addition or removal of electrons.
Fig.2 shows a projection system 20 comprising a light source 21, a reflector 22, an integrator system 22,23, a polarization conversion system 24, a set of dichroic mirrors 25,27 a set of plane mirrors 26,28,29, liquid crystal...