David G. Pelka

Uniformly illuminating dual-lens system for LED collimation

We present an efficient and effective collimating lens system for LEDs. It consists of two lenses: an immersive ball lens within which an LED die is optically bonded, and an adjacent collimating lens that produces uniform illumination at its output plane. The three surfaces of the system are numerically tailored in accordance with the angular distribution of light emitted by the die. When the immersion lens is surface-tailored, the resultant shapes are sufficiently close to a spherical surface that the manufacturing convenience and low cost of an exact sphere make it the preferred shape. The immersion ball-lens reduces the angular spread of the LEDs light from +/- 90 degrees to +/- 60 degrees in air. The bottom surface of the collimating lens redirects each light ray to its proper place (axial radius) in the output beam, at which point the top surface redirects the ray to become parallel to the optical axis. Uniformity of output illuminance occurs when a rays proper place is determined by its place in the cumulative angular distribution near the immersed source. Three surfaces suffice to give highly efficient collimation as well as spatial uniformity of the output beam.

Size- and structure-dependent efficiency enhancement for luminescent solar concentrators

Size- and structure-dependent efficiency enhancement methods are studied for luminescent solar concentrators (LSCs) fabricated by casting organic laser dyes into PMMA matrixes. The enhancement are achieved mainly by attaching a white diffuser with an airgap at the bottom of the LSC and adding refractive index matched optical gel between the LSCs edges and the attached photovoltaic cells. The size-dependent efficiency enhancement is studied for a single layer by changing the size up to 120 cm. The results show that the enhancement from the white diffuser drops and then tends to plateau at a certain size of LSC. This also applies to multilayer LSCs. Together with optical gel, the efficiency enhancement is higher for multilayer structures than that for single layers. We also demonstrate the optimal length for the design of LSCs due to reabsorption of dyes. These results could be applied to optimize the design of other LSCs.

Publisher's Note: Journal of Photonics for Energy, Volume 1

This PDF file contains the errata for “JPE Vol. 1 Issue 1 Paper 3567199” for JPE Vol. 1 Issue 1

Black hole: cuspated waveguide injectors and illuminators for LEDs

Powerful new LEDs provide enough luminosity for a single one to illuminate a transparent EXIT sign, but efficient injection means are required, with luminance-uniformity a prime goal. We present a totally-internally-reflecting `Black Hole indentation on the waveguide surface. This cuspated configuration deflects the light from an immersed LED, aimed perpendicular to the plane of the waveguide, into guided light trapped within the slab, to be extracted by the signs alphabetic features. In spherical coordinates, a +/- 60 degree(s) output cone (for example) is deflected into the 360 degree(s)-azimuth guided range of +/- 47 degree(s). That is, this reflector transforms a polar cone into an equatorial swath, a symmetry that is useful whenever the total horizon must be dealt with, just as a lighthouse, or better yet a marker buoy, must send warning light to all the quarters of the compass. In its circularly symmetric configurations, this device offers a removable disc, optically bonded to the LED source, that completely hides the source from view above the indentation. Non-waveguide, stand-alone illumination applications include aircraft-warning beacons, alarm flashers, and near-field illuminators.