Old Imaging Technique Gets Quality Boost

Targeting crosstalk problems — visible ghostlike shadows in 3-D images — could significantly increase the quality of a widely used century-old printing technique, new research out of Australia suggests.

Anaglyph printing — a method to transform 2-D images into 3-D using red and blue color channels — came into being when the continuous-tone printed anaglyph was invented by French physicist Louis Ducos du Hauron in 1891.

The stereoscopic 3-D effect is achieved by encoding each eye’s image using filters of red and cyan. With 3-D glasses, the left eye sees only the red channel of the anaglyph image, and the right sees only the blue. If the anaglyph 3-D image is constructed correctly, the viewer can see clean 3-D images on the printed page.

However, printed anaglyph images often suffer from a number of image quality limitations, most notably crosstalk — an undesirable property of some 3-D techniques in which the left eye sees some of the image intended only for the right eye, and vice versa. Crosstalk is visible as ghostlike shadows throughout the image, and when these levels are high, the quality of the 3-D experience is significantly reduced.

An anaglyph 3-D image of a joey used in research experiments at Curtin University enabling improvements in the widely used 2-D-to-3-D printing process. The color bars at the top are used to determine the purity of the color printing process. Courtesy of Andrew Woods.

Now scientists at Curtin University have come up with seven recommendations for overcoming this image disturbance.

“The largest reduction in crosstalk is likely to be achieved by using inks which have a better spectral purity than current process inks used in color printers,” said research engineer Andrew Woods. “We found that an 80 percent reduction in crosstalk was potentially achievable just by changing the cyan ink.”

The anaglyph technique is easy to implement, and the anaglyph 3-D glasses are relatively cheap, so the technique is used very widely, Woods said.

“The printed anaglyph is 121 years old, but this appears to be the first time that a detailed technical simulation of crosstalk in printed anaglyphs has been developed,” he said. “We started by measuring the spectral characteristics of various printing inks, 3-D glasses, light sources and papers. From there we developed a simulation which models the viewing of an anaglyph 3-D image, and subsequently performed an experiment to validate the accuracy of the model. We hope this work will help provide a 21st-century improvement to the 19th-century invention.”

Other recommendations include using high-quality anaglyph glasses, an optimized light source and improved image processing algorithms.

The research, available through SPIE’s Digital Library, was presented at the Stereoscopic Displays and Applications XXIV conference held Feb. 4-6 in Burlingame, Calif.

For more information, visit: www.curtin.edu.au