Volumetric Display Based on Vibrating Mylar Beam Splitter and LED Backlit LCD
West Building, Ballroom B
This new volumetric display produces full-color, high-spatial-resolution aerial images out in front of the apparatus. It is based on a new optical element: the large, tunable-resonance, edge-driven, varifocal beam splitter.
Previous varifocal systems stretch an opaque Mylar mirror over the aperture of a loudspeaker. The speaker vibrates the mirror. making it alternately concave and convex. A synchronized, high-speed (oscillograph) image is viewed in the mirror and swept in depth. This type of display was commercialized as Spacegraph 3D in the late 1970s, but a number of problems limited its acceptance. The loudspeaker was noisy. The image was virtual (behind the mirror), since the mirror curvature is insufficient to create real images. The systems had small viewing apertures, since the display blocked the user's mirror view. Non-standard (now obsolete) oscillograph displays were used, and the systems were bulky, since it was difficult to fold their optical paths.
This new display uses a circular Mylar beam splitter and adds a tension-adjusting metal hoop pressed against its surface. The beam splitter is adjusted, with high Q, to a specific resonance frequency. Three rim-mounted impulse drivers apply low-amplitude sinusoldal drive. Due to the high Q, the diaphram's sympathetic vibration is large. The beam splitter folds the optical path, and the system includes a fixed-curvature concave mirror to create real images that appear out in front of the apparatus. It produces high-quality 3D images that occupy a one-third-meter cube 1/3 meter out in front of the apparatus. The image is viewable over a 30 degree viewing angle.