Abstract: An illumination unit is suggested in which at least one light selecting element (20) is disposed between and assigned to a primary illumination light providing portion (10) and a secondary illumination light providing portion (30). Said light selecting element (20) is simultaneously adapted to select one or a plurality of predefined spectral components (B) or of one and/or a plurality of predefined polarization components from incident primary illumination light (L1) and to thereby generate secondary illumination light (L2) to be irradiated.

Abstract: An optical device (20) is provided using at least one film (23) of cholesteric liquid crystal to reflect at least one predetermined wavelength band from an incident light. This device is characterized in that a non zero birefringence gradient is present in a portion or the entire thickness of said film. The gradient may be obtained in particular by superposing layers (24a-24j) having increasing or decreasing respective birefringence coefficients. The birefringence gradient has the effect of removing the lateral bands of the reflection spectrum, hence making the color of the reflected light more brilliant and more saturated. The effect is particularly advantageous in the case of the color red, for which the lateral band located on the yellow side is perceived strongly by the human eye.