Guide de démarrage (anglais)
Obtaining and installing OpenFilters
You can download the latest version of OpenFilters on the download page. You may download a Windows installer (32 or 64 bits), a Mac OS X installer, or the source code.
On Windows, it is very easy to install OpenFilters: download the installer and run it.
On Mac OS X, download the disk image (.dmg file), mount it, and install OpenFilters by draging it onto the application folder.
There is no official compiled version of OpenFilters available for other operating systems (such as Linux). In that case you need install Python and wxPython on your system, download the source code, and run the file Filters.py using Python. We have tested OpenFilters with success on Ubuntu, OpenSUSE, and FreeBSD. We believe it should work on any system where Python and wxPython are installed.
The first time you run OpenFilters
The first time you run OpenFilters, you will be requested to choose a directory for the user materials. User materials are materials created by the user, in addition to those provided by default with OpenFilters. Any advanced use of OpenFilters will require the use of user defined material, so you should not skip this step. Obviously, you should choose a directory where you have write access, or otherwise you will not be able to create new materials.
Designing an AR coating
To demonstrate some of the basic features of OpenFilters as well as a typical workflow, we will design an antireflective (AR) coating for a fused silica lense in the visible spectrum. We will demonstrate the use of refinement.
The first step in using OpenFilters is creating a project (menu item File|New Project). A project is meant to group many filters designed to respect a set of targets.
Once you have created a new project, you can add filters to it (menu item Project|Add Filter). When you add a filter to a project, you are presented a dialog to set some of its basic properties (Fig. 1). You should first set the substrate and medium. For this example, let the substrate be fused silica and the medium be vacuum (void).
Then, you should set the wavelength range and resolutions. This determines the spectrum where the filter properties will be calculated. Since we want to design a AR coating for the visible, let's set the wavelength range from 380 nm to 780 nm, with an increment of 1 nm. The reference wavelength is the wavelength at which the index profile is shown, and it is used to calculate the optical thickness of the layers. Let us set it to the middle of the visible, 580 nm.
Finally, the lens will need an AR coating on both its front and back sides. However, it is simplier to design them one at a time. Therefore, we will only consider the front surface by unchecking the Consider backside checkbox in the Analysis box at the bottom left.
Other properties apply to graded-index filters, color calculation, and monitoring. They will not be used in this example.
Click OK. You can modify the properties of a filter at a later moment by using the menu item Filter|Properties.
We are now ready to begin adding layers to the filter. A well know way to design a broadband AR coating is to use a quarter wave of a medium index material, followed by a half wave of the hign index material and, finally, a quarter wave of low index material. To add a layer, select the menu item Filter|Add layer and a dialog box shown in Fig. 2 will be shown. Put SiN in the material box and 71.5 in the thickness box. Repeat the operation to add a 120 nm thick layer of TiO2 and a 80 nm thick layer of SiO2.
Now that you have defined a filter, you can calculate its optical properties. In the present case, we are mainly interested by the reflection, which can be calculated by selecting the menu item Analyse|Calculate Reflection. After you have calculated the reflection, the main window of OpenFilters should look like that shown in Fig. 3.
The top part of the main window has tabs to show the filters and the targets included in a project. This is also a tab to put a text comment. If you double-click on a filter, you can see the layers of that filter (see Fig. 4). To go back to the list of filters, click the button Back to filter list.
We are interested in optimizing a filter that minimizes the reflection in the visible. For that, we can add a continuous target by selecting the menu item Project|Add Target|Add Reflection Spectrum Target. Select a range of wavelength and an increment (from 380 nm to 780 nm by 5 nm) and indicate that you want 2 definition points. Enter 2 points at the two extremes of the visible range with a reflection of 0 (as in Fig. 5}); the reflection for wavelengths in between those 2 points will be interpolated.
Then you can optimize the filter by selecting the menu item Design/Optimize|Refine. You will be presented with the dialog shown in Fig. 6}. Click Go to optimize the filter and Ok when you are done. You can finally calculate the reflection of the optimized filter as you did before and the main window should look like that presented in Fig. 7}. By comparing Figs. 4 and 7, you can see that the reflection is now smaller over most of the visible spectrum.