A display apparatus of the type which forms a color image by modulating a plurality of lights different from each other in color by one or more display elements, includes a device for changing the color purity of at least one light by inserting or extracting a wavelength selection element into or out of the optical path of at least one of the plurality of lights, or changing the attitude of the wavelength selection element, and a device for supplying information as to whether the wavelength selection element is in the optical path of the at least one color light or information on the attitude of the wavelength selection element in the optical path of the at least one color light.
A projector includes a light source, a color separating optical system, liquid crystal panels, a cross dichroic prism, and a projection lens, in which an optical filter is disposed to reflect a predetermined spectral component in the light flux between a dichroic mirror and a dichroic mirror where an angle by which the light flux expands falls within 20.degree. with respect to an illumination optical axis L of the light flux on an optical path from the light source device to a light flux-emitting surface of the projecting lens. Thus, carrying out spectrum correction can reduce or prevent the contrast degradation of the projected image. Furthermore, it allows the difference of an incident angle to the light flux-incident surface of the light flux to be smaller, thereby reducing color unevenness.
The application of microstructures which improve the quality of light available to the viewer of an optical display system, or any display which works on the concept of moving one surface into direct contact or close proximity of a light guide to extract light through frustrated total internal reflection. Optical microstructures are introduced on one or both of the surfaces of the active layer to enhance its performance. Since the active layer has both an input and an output function, means for enhancing both are presented. The input function to the active layer occurs on the internal surface, so this is where the present invention adds a collector-coupler, a means for facilitating the migration of light from the waveguide into the active layer. The output function occurs on the external surface, where the present invention adds a collimator, a means for both increasing the probability that a light wave will be released from the active layer, and improving the apparent intensity by redirecting light waves so that more of them reach the viewer. Compound microlenses on the internal surface of the active layer can serve as both collector-couplers and collimators, substantially improving light extraction from the light guide and light distribution to the viewer. Depositing a reflective or colored material in the interstitial spaces between these compound microlenses improves the contrast ratio and mitigate pixel cross-talk. The opaque material can be conductive for use in actuating the display.
