In certain applications, there is a desire to display two (or more) images onto a single display plane of a display system. For example, in the projection of three dimensional (3-D) images using stereoscopy, two component images of a single three dimension image are displayed on the single display plane using polarized light with orthogonal polarizations. Audiences using special optical devices, such as 3-D glasses, can cancel out one of the two images per eye can then see a single 3-D image on the display plane. Additionally, it is possible to reduce color flicker and color banding on a display system if two (or more) images, each being displayed with a different colored light, were displayed simultaneously on a single display plane. Each of the images contains color image data from a single image being displayed by the display system. For example, at a given time, a first image may contain green color image data and a second image may contain blue color image data, whereas at some other time the images displayed may contain blue and red color image data or red and green color image data. In a three-color display system, it may be possible to display image data for all three colors.
With reference now to FIG. 1, there is shown a diagram illustrating a display system 100, wherein the display system can display two images simultaneously on a single display plane 105. In order to display two images onto the single display plane 105, the display system 100 can make use of two arrays of light modulators, with spatial light modulators (SLM) being used as light modulators. The diagram shown in FIG. 1 illustrates the display system 100 making use of a particular implementation of the array of light modulators referred to as a digital micromirror device (DMD). A DMD is an array of positional micromirrors that can reflect light from a light source onto the display plane 105 with the position (state) of the individual micromirrors being dependent upon the value of the image data being displayed. For example, if the image data being represented by a positional micromirror indicates that light should be placed onto the display plane 105, then the positional micromirror will be moved into a position so that light from a light source will reflect off the positional micromirror onto the display plane 105.
The diagram shown in FIG. 1 illustrates two DMDs, a first DMD 110 and a second DMD 111 in the display system 100. A light source 115 and a light source 116 can be used to provide the light needed to project the image data onto the display plane 105. A color filter 120, used in conjunction with the light source 115, and a color filter 121, used in conjunction with the light source 116, can be used to filter light provided by the light source 115 and light source 116 to provide necessary colors, such as red, blue, and green in a three-color display system. Although shown in FIG. 1 as being two distinct light sources, similar lighting performance can be achieved by using a single light source and a light splitter (not shown) that can split the light from the single light source into two light beams. The display system 100 shown in FIG. 1 displays significant components used in the display system 100, but for simplicity purposes, may leave out components that are required for proper operation, such as integrating rods, relay optics, beam shapers, and so forth.
If the display system 100 is to be used to project 3-D images using stereoscopy, the light source 115 and the light source 116 can be configured to produce light with orthogonal polarizations with respect to one another. If the display system 100 is to be used to project images with reduced color flicker and banding, then the light source 115 and the light source 116 can be configured to produce different colored lights.
The display system 100 can be formed from two separate projector systems, with the DMD 110 and the light source 115 forming one projector system and the DMD 111 and the light source 116 forming another projector system. Alternatively, both the DMD 110 and DMD 111 and the light source 115 and the light source 116 can be contained within a single projector system. Although shown as a display system comprised of two separate projector systems or a single projector system with two DMDs, it is possible to make use of more than two separate projector systems or DMDs. For example, in a display system that makes use of three component colors, such as red, green, and blue, it is possible to create three separate projector systems with one separate projector for each of the three component colors. This can be extended to an even larger number of projectors, such as in a display system that makes use of more than three component colors.
One disadvantage of the prior art is that with more than one separate projector or DMD, maintaining good alignment of the individual pixels can be very difficult. A small bump to the display system can result in misalignment of the images produced by the display system. Therefore, expensive optical components and regular calibration must be done regularly to ensure that the images remain aligned. Furthermore, since separate projectors or DMDs are used, differences in thermal expansion may result in a misalignment of the images that occurs only after the display system has been powered for a period of time.
Another disadvantage of the prior art is that the optics required to combine the images from the separate projectors or DMDs can be prohibitively expensive. Therefore the display systems that make use of separate projectors or DMDs are typically too expensive for all but high-end and commercial installations.