Authored By: Mark Nicholson

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Introduction
Zemax Development Corporation thanks Opsira GmbH for providing the source data used in this article. This article is also available in Japanese.

The most accurate way to model sources in Zemax is to use measured sources, like Radiant Imaging's Radiant Sources, and Opsira's Luca'Raymaker. Our article on how to model LEDs describes the use of Radiant Sources in detail. This article describes how to enter Opsira source data.

Luca'Raymaker can export its data in binary and ASCII formats. The binary format is recommended, as the read time of a binary file is about 20x faster, and the file size about 70% smaller, than the same data in ASCII format. Note that if an ASCII file contains more than one million rays, Zemax will offer to convert it to binary format for you. The data is read into Zemax using the Source File object, which can read in a maximum of 4 billion (4*10⁹) rays.

Generating Source Files
After installation, an Opsira model folder contains three files:

The .orf file is the ray database file, the .igs is a CAD model that represents the physical structure of the lamp, and the .pdf is a manufacturer's datasheet. The main luca'Raymaker program is:



The 'origin file' refers to the *.ort file, and the total number of rays included in the measurement is displayed. Any number of rays up to this limit can be generated. The generated ray set is placed in the {Zemaxroot}/objects folder, and must have the extension .DAT

Loading into Zemax
The lamp datasheet states a total output power of 5800 lumens for this lamp. No specific wavelength data is given, so we will assume that a wavelength of .555 microns (the peak of the photopic response) is used.

A new Zemax file is opened. The wavelength is entered via the wavelength dialog box:

and the source units set to kiloLumens:

Importing the supplied CAD object is optional. The ray generation does not require the CAD model, but it can be useful. For example, if light is re-imaged on the source it is good to be able to specify reflectivity, scattering functions etc. Also, sometimes it is useful to trace rays back to the source object. This is particularly true in identifying troublesome rays. In automotive headlamp applications, rays which glare into oncoming drivers eyes can be traced back to the source to help identify improved baffling.

In this case, we import both the CAD object and the source ray set. A Source File object is used to import the rays:

with the result:

Other Opsira sample files.
There are two other sample files supplied with the Luca'raymaker evaluation version. Here is the Philips 1242N compact halogen lamp placed at the focus of a parabolic reflector:

and here is a detailed view of the CAD file that defines the lamp:

Here is the Luxeon LXHL_PW09 LED source:

Note that the data is not complete in the demonstration version, which is why half of the irradiance pattern is missing. This limitation is in the demonstration version dataset, and is not a fault.