A high directional LED system to form holographic light patterns
Holograms are recordings of light formed by the interference fringe between object and reference light beams. They enable the display of fully 3D images, and have applications in 3D displays, computer memory, and microscopes. As part of our recent research into holographic head mounted 3D display and quantitative phase microscopy,1 3 we have produced a high directional LED lighting device known as HOLOLIGHT.4, 5 Currently, highdirectional lighting is achieved chiefly using laser technology. However, our approach offers a safer method of achieving highvisibility displays. Our device emits a high visibility light that appears parallel. We achieve this through the use of a combined high brightness LED and a lens, which are both enclosed in the same packaging. Light emitted by the LED is expanded and imaged by an optical system such that the expanded light behaves like parallel light (see Figure 1) It is therefore possible to achieve the light intensity distribution of rectangular pseudo parallel light. Our LED system manipulates the expanded image with optics to enable the formation of light patterns as squares, circles, lines, and arches (see Figure 2) These patterns, whose shape is determined by the shape of the LED emitter, can be used in inspection, on stage, and in architecture, road safety, art, and entertainment. HOLOLIGHT gives out light with high directivity, and enables the formation of arbitrary light patterns at a distance, in a way analogous to pixel art. The size of the image is proportional to the distance of the lens from the projection plane, and the divergence angle during imaging is narrow 1) Using such a system, it is possible to produce an image of 20cm2 at a distance of 10m from the projector. We call the resultant image a 'multipoint' light pattern. We demonstrated a multipoint lighting event with 300 devices at Mount Ookusa at Hamamatsu Kanzanji in 2009. On that occasion, the irradiation distance was 500m (see Figure 3) Figure 1. The image expanding optical system used in HOLOLIGHT enables high directional lighting for holographic display.