Patent Application
20080174703
Tiled projection digital display systems use multiple projectors to produce a large, high resolution image. In many known systems, multiple screens are placed next to each other to form a large image display. A problem with many of the multi-projector display systems is that the multiple images often do not appear as one single continuous image on the display screen. When multiple images are projected on a single screen, typically the composite image includes alignment errors and optical distortions. In the composite image, often there are seams or bright lines between the multiple images. Consequently, a need exists for an improved method for aligning multi-projector display systems.
As shown in the drawings for purposes of illustration, a sensing modulator and a method of use thereof is disclosed. In an embodiment, the sensing modulator includes a light modulator array and a plurality of photosensors wherein each of the plurality of photosensors are adjacent to the light modulator array. Accordingly, the modulator provides for the registration of multiple projection images to within 1 pixel as well as brightness and color calibration between the images. From the end user perspective, no hardware is needed other than the individual projectors and the only setup procedure required is to guarantee that the multiple projected images overlap.
A CMOS-based image sensor is a chip that records the intensities of light as variable charges similar to a charge-couple device (CCD) chip. Although initially used in less expensive digital cameras, the quality of CMOS sensors has improved steadily. Additionally, CMOS sensors have advantages over CCDs. They can be made like other CMOS chips on standard CMOS fabrication lines. As a result, no additional masking steps or process changes would be necessary which makes development less costly, and auxiliary circuitry, such as analog-to-digital conversion, can be combined on the same chip.
As previously articulated, varying embodiments of this concept include a method for displaying at least two projected overlapping images. By ascertaining the relative positions of the two projected images, the overlapping pixels can be removed or merged together programmatically.
In order to accomplish the above-delineated method, the above described sensing modulator is employed in conjunction with an image projection device. Accordingly,
The image projecting mechanism 308 is employed to re-image the sensing modulator onto a projection surface.
In accordance with an embodiment, the image projection device 300 can be implemented with another image projection device to create a multi projector display system whereby overlapping images can be displayed.
In the system 500, the method for displaying at least two projected overlapping images is accomplished by re-imaging a projected image from adjacent projector 520 onto the photosensors of the sensing modulator of the leftmost projector 510. This involves projecting a scanned calibration pattern from the second projector 520 over the photesensor position of the leftmost projector 510. By projecting a scanned calibration pattern from the second projector 520 onto the display screen 501, and re-imaging the scanned calibration pattern over the photesensor position of the leftmost projector 510, the relative position of the overlapping projected images can be determined to within one pixel.
Furthermore, in order to increase the Signal to Noise ratio, reduce noise and reject ambient illumination, an alternate embodiment includes measuring the photosensor signal differentially whereby two photosensors are used and only the differential signal is measured. In this instance, the sensor spacing and calibration image are chosen so that one of the two photosensors detects the signal from the calibration image while the other sensor detects only the screen ambient.
In addition to calibrating for adjacent image position, the photosensors may be employed to calibrate the image brightness, color balance and the relative projector focus. For color calibration, the scanned calibration image projected from one projector could include sequential imaging of each primary color (red, blue and green) whereby the results are stored. Alternatively, two different primary colors could be scanned simultaneously at the differential photosensor spacing thereby generating a differential color signal directly.
Furthermore, in order to detect the calibration images at a sufficient signal to noise ratio, the illumination to the sensing modulator could be cut off during calibration. For Light Emitting Diode (LED) or laser illumination this would not be problematic, but for Ultra High Pressure Mercury lamp illumination, a shutter would probably need to be installed in the illumination path.
Finally, although the above-described embodiment is disclosed in the context of being implemented with a computer 530, it should be understood that the inventive concept is not limited to this particular embodiment. For example, two projectors could be implemented whereby the calibration of the two overlapping images is performed with one or both of the respective image processing mechanisms.
A sensing modulator and a method of use thereof is disclosed. In an embodiment, the sensing modulator includes a light modulator array and a plurality of photosensors wherein each of the plurality of photosensors are adjacent to the light modulator array. Accordingly, the modulator provides for the registration of multiple projection images to within 1 pixel as well as brightness and color calibration between the images. From the end user perspective, no hardware is needed other than the individual projectors and the only setup procedure required is to guarantee that the multiple projected images overlap.
Without further analysis, the foregoing so fully reveals the gist of the present inventive concepts that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention. Therefore, such applications should and are intended to be comprehended within the meaning and range of equivalents of the following claims. Although this invention has been described in terms of certain embodiments, other embodiments that are apparent to those of ordinary skill in the art are also within the scope of this invention, as defined in the claims that follow.
