Full-color imagery created from black and white prints, a prism, and a little math

Researchers have successfully projected a full color image using a device which contains no colored components(Credit: Hostettler et al. 2015)

An intriguing photo projection system uses only black images and a prism to project full-color imagery. The collaboration between Dartmouth College and Disney Research Zürich could result in future systems that dynamically trade off color fidelity, efficiency, and resolution to create full-color projections.

Those who have studied entry-level physics may have seen the demonstration of splitting white light through a prism into a rainbow. This Dartmouth/Disney concept takes things one step further and develops algorithms for the two masks required to reconstruct an arbitrary full-color image, one on each side of a prism. The whole setup costs less than US$30, presumably not including the laser printer required to print the masks onto transparencies.

The first mask uses slits to create a structured pattern of light which exits as rainbows when passing through the prism. In more familiar parlance, one rainbow corresponds to a single "pixel" or value of color. The second mask reconstitutes the image as it exits the prism, blocking any colors in the rainbow which don't exist in the image.

The team produced three colors with their model, red, green, and blue, so the second mask would block the portion of the spectrum that would display as blue and red to create a green color, or block green to create purple.

By manipulating the mathematical models creating the two images, the researchers could choose to optimize either the saturation of the image or the amount of light returned. Similarly, they could choose to obfuscate the masks so the source images weren't apparent.

Future avenues of exploring this research could use multispectral projections to go beyond the current RGB model. Dynamic projections could be created by using high-resolution greyscale LCDs to create the masks.

Senior author Wojciech Jarosz studies the capture and simulation of complex visual settings, and some of his work was used in the creation of the computer-animated films Tangled and Big Hero 6. He has described this black-and-white projection system as in the vein of recent research which manipulates qualities of light such as shadow, refraction, or attenuation to create surprising or tricky visual effects.

The project was originally presented at the 23rd Pacific Conference on Computer Graphics and Applications earlier this month. The full paper (PDF) is available on Dartmouth's website and its bibliography is a good source for other optical trickery and experiments.

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