Object-Avoiding Lighting Boosts Projection Mapping

Projection mapping has the potential to create shared immersive experiences in exhibitions, commercial facilities, and public spaces. However, the technique is highly sensitive to ambient lighting, meaning that clear projected images are typically only possible when the surrounding environment is darkened.

Now, researchers at The University of Osaka have developed a method that allows projection mapping to remain vivid even in brightly lit indoor environments. Their system uses a compact illumination device based on a digital signage LED display panel combined with a specially arranged lens array.

"Projection mapping has traditionally been difficult to use in bright environments," explains Kotaro Fujimura, lead researcher of the study. "We wanted to overcome that limitation by exploring the idea of illumination that deliberately avoids shining light on the target surface."

Previous approaches have attempted to use projectors themselves as lighting devices that illuminate the surrounding environment while avoiding the projection surface. However, such methods often require multiple projectors, which can lead to large and complex systems that are difficult to deploy in practical environments.

Instead of using projectors for ambient illumination, the researchers repurposed a digital signage LED display as a spatial light source. Each pixel of the LED panel emits light through a lens array that directs the light toward different parts of the room, allowing the surrounding environment to be illuminated.

The researchers also developed an optimization technique that arranges the lenses in a non-repeating pattern, helping distribute unwanted optical interference and preventing visible dark artifacts from appearing when the target-avoiding illumination is used.

To determine which parts of the LED panel should illuminate the environment, the system calculates the region of pixels whose light would reach the projection surface. Those pixels are then selectively turned off so that the target surface remains unlit while the surrounding environment is illuminated naturally.

"To keep the projection surface dark, we simply prevent the pixels that would illuminate that region from emitting light," explains Daisuke Iwai, senior author of the study. "This allows us to maintain high-contrast projected imagery while keeping the surrounding space brightly lit."

The system operates in real time and enables projection mapping that remains clear even in bright indoor environments. This approach could enable new forms of visual experiences in commercial facilities, exhibition spaces, and public environments, where projection mapping can be enjoyed without dimming the room lights.

Fig. 1

Caption: Projection mapping achieved under "target-excluding illumination," which avoids illuminating only the projection target, enabling sharp and high-contrast imagery even in a brightly lit environment (left). (Right: comparison of projection mapping in a dark room and under typical ambient lighting.)

Credit: Daisuke Iwai