System architecture: Low price and scalability

EasyBlend system architecture is composed of two phases: calibration and display. The primary input to the calibration phase is feedback data from a camera set up to observe the entire image, whether from a single or multiple projectors. Calibration output from this camera is fed to the display phase.

Calibration phase

Measure and compute positional warp:

• Test charts and test projections are used to derive positional mappings between each projector and the screen, and also between the screen and the camera. These mappings pinpoint the exact location on the screen of each pixel from each projector.

Measure and compute intensity and color warp:

• Feedback data from the camera are added to the positional mappings to correct color and intensity across the image.

Display phase

The calibration phase generates a two-dimensional lookup table, used by the image warper to correct projector outputs. The computer applies digital image warping to the image in its frame buffer and outputs appropriately pre-distorted projector input signals. The result is a seamless and geometrically correct image across the entire projector field.

Taking image feedback from the camera, the computer uses digital image processing techniques to compensate for visible imperfections, including:

• Perspective distortions, causing trapezoid-shaped projections
• Pincushion and barrel distortions from the optics, resulting in projection bowing outward and inward
• Alignment distortions between projectors, resulting in misalignment in the overlap regions
• Intensity and color distortions caused by different projectors with varying light sources and optics, plus overlapping regions illuminated by multiple projectors

The 2D lookup table contains parameters to compensate for all of these distortions, remapping the position and intensity of each pixel to display a seamless image. Positional remapping enables the display of straight lines across the projection array, limiting the total displayed image to the largest rectangular region covered by the array of projected images.

Off-the-shelf silicon elements

The  EasyBlend solution capitalizes on the ubiquitous availability of four low-priced, off-the-shelf silicon elements:

1. Microdisplay silicon for projection
2. FPGA/ASIC/GPU silicon for warping
3. CMOS/CCD sensors to provide image feedback
4. Microprocessor for process control

Download the EasyBlend System Architecture brochure