Illumination design program delivers enhanced optimisation

Paul Boughton

Version 6.3 of the LightTools illumination design, analysis, and optimisation software package includes many new features and enhancements. Among these are enhancements to an already robust illumination optimisation algorithm to improve convergence for some systems and features to ease the process of creating an accurate light source model, such as a light-emitting diode (LED).

LightTools 6.3 introduces a second optimisation algorithm to complement its current optimisation capabilities. Automatic optimisation algorithms have been used in the optical design process for decades.

Until recently, illumination designers could not leverage the power of optimisation, because the algorithms were not compatible with Monte Carlo simulations. However, in recent years, algorithms have advanced to the point that they work well in these statistically noisy situations. The original LightTools algorithm has been shown to have robust convergence for a wide variety of illumination systems; this new algorithm was added to provide better convergence for scenarios in which the original algorithm converges slowly. The new algorithm, dubbed the 'alternate engine', converges well when the merit function is relatively flat and has many local minima. The Alternate engine also works well in situations in which there are more optimisation variables than merit function metrics.

Source modelling capabilities

Perhaps the most critical component of an illumination design is the light source; consequently, the fidelity of the light source model is paramount for an accurate simulation of any illumination system. In the past, a good LED source model has been difficult to quantify. In the past year, however, LED manufacturers have begun to publish models of their sources. LightTools 6.3 ships with a library of more than 400 LED models, some of which were provided by the manufacturers.

Additionally, LightTools ray data files now support spectral information. Ray data files are one of several methods of representing a source. In this case, the distribution of light from the source is modeled directly as a series of rays. The location, direction, power, and now the wavelength of the rays are all contained within the file. This enhancement is especially important for modeling white LEDs, which can either be the combination of several discrete spectra or the combination of a narrow blue spectrum and a yellow phosphor.

Two new utilities are introduced in LightTools 6.3. The Thin Film Utility allows a user to place a thin film coating on any surface. The performance of the coating is calculated for each wavelength and angle of incidence during the ray trace based upon the coating's stack and material definitions, ensuring accuracy throughout the simulation. The IES Import Utility creates an apodised source from an industry-standard far-field intensity distribution file. This utility provides an easy mechanism for creating a source model in LightTools from a data file that many luminaire companies provide for their lamps.

LightTools continually strives to provide industry-leading design and analysis tools for illumination design. Version 6.3 continues in this tradition through accurate modeling of LED systems and robust optimization of all illumination systems.

Enter XX at www.engineerlive.com/eee

Michael Zollers is Senior Optical Engineer, Marketing, Optical Research Associates, Pasadena, California, USA. www.opticalres.com

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