The present invention generally relates to projection cockpit displays, and even more particularly relates to such displays having multiple tiled display surfaces.
In the past, designers of avionics displays have endeavored to provide projection displays with ever-increasing image quality, reliability, and economic efficiency. Projection displays based on liquid crystal display (LCD) technology generally use a single, linear polarization state for light incident upon the display element. Typically, this is accomplished by the use of a linearly polarizing filter, prism, or reflector disposed in front of the LCD device. Linearly polarizing filters, prisms, and reflectors are all well known in the art. These polarizing devices typically transmit one linear polarization state, while a second orthogonal polarization state is either reflected into a different path, or absorbed within the polarizing element. In either case, the state which is not transmitted becomes unusable by the display. This results in a significant (typically greater than 50 percent) attenuation of the light flux which is usable by the display.
In the past, display designers have proposed methods and devices to capture and reuse the otherwise discarded orthogonally polarized light and direct it into the display device, along with the polarized light originally produced from the incident light. These devices have been called xe2x80x9cpolarization recovery devicesxe2x80x9d, which are typically an array of prisms and half-wave retarders which divide the light into two polarization states, rotate one polarization state by 90 degrees, then recombine the now parallel polarization states. These xe2x80x9cpolarization recovery devicesxe2x80x9d have found limited acceptance in the LCD projector industry because they are quite expensive to fabricate, and they can also result in significant other performance deficiencies.
Consequently, there exists a need for improvement in illumination of tiled projection displays.
It is an object of the present invention to provide tiled projection displays having a superior image luminance characteristic.
It is a feature of the present invention to utilize multiple tiled viewing surfaces which receive illumination through the same front-end polarizer.
It is another feature of the present invention to utilize a polarizing prism or reflector as the front-end polarizer.
It is an advantage of the present invention to optically divide light from a single light source and use the divided light through multiple LCDs.
It is another feature of the present invention to include a half wave retarder to rotate the polarization state of light directed to an adjacent LCD.
It is another advantage of the present invention to increase commonality of component parts by having the same polarization state for all light incident on the LCDs in both optical channels in pairs of tiled projection displays.
The present invention is an apparatus and method for illuminating tiled projection displays designed to satisfy the aforementioned needs, provide the previously stated objects, include the above-listed features, and achieve the already articulated advantages. The present invention is carried out in an efficient manner that wastes less light flux than is typically done when an absorbing polarization filter is used to provide linearly polarized light.
Accordingly, the present invention is a tiled projection display system which utilizes a tiled multi-viewing surface display where multiple viewing segments are illuminated by light, which has been conditioned by the same polarizing device prior to its passing through separate liquid crystal display (LCD) devices.