Laser backlight unit based on a leaky optical fiber

Yuuto Okuda; Kousuke Onoda; Ichiro Fujieda

doi:10.1117/1.OE.51.7.074001

5 July 2012 Laser backlight unit based on a leaky optical fiber

Yuuto Okuda, Kousuke Onoda, Ichiro Fujieda

Author Affiliations +

Optical Engineering, Vol. 51, Issue 7, 074001 (July 2012). https://doi.org/10.1117/1.OE.51.7.074001

Abstract

A backlight unit is constructed by laying out an optical fiber on a two-dimensional plane and letting the light leak out in a controlled manner. In experiment, we formed multiple grooves on the surface of a plastic optical fiber by pressing a heated knife edge. The depth of the groove determined the percentage of the optical power leaking out. The optical fiber with multiple grooves was embedded in an acrylic plate with a spiral trench, and a diffuser sheet was placed over it. When we injected laser light into the end of the optical fiber, this configuration successfully worked as an area illuminator. However, the coherent nature of the laser light caused severe speckle noise. We evaluated the speckle contrast under darkness, and it varied from 80% to 23%, depending on the lens aperture used to capture the images of the illuminator. We glued an ultrasound generator to the optical fiber to introduce phase modulation for the light propagating inside the optical fiber. In this way, the speckle contrast was reduced by a factor of seven to four. Under room lighting, the speckle noise was made barely noticeable by turning on the ultrasound generator.

Citation Download Citation

Yuuto Okuda, Kousuke Onoda, and Ichiro Fujieda "Laser backlight unit based on a leaky optical fiber," Optical Engineering 51(7), 074001 (5 July 2012). https://doi.org/10.1117/1.OE.51.7.074001

Published: 5 July 2012

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