TFCalc 3.3 Changes

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Major New Features

These features and many others are described in more detail below. There are a number of very minor changes that are not described here.


  • Simultaneous analysis at wavelengths and angles. This feature enables the designer to easily analyze the performance of a coating for ranges of wavelengths and angles. An example of this capability is displayed in the Fabry-Perot movie, which displays a movie of how the performance of this narrow-band filter changes as the incident angle varies from 0 to 60 degrees.

    This new feature works with almost all aspects of the TFCalc software. In the Plot, Color Chart, and Table windows, use the left and right arrow keys to advance to the next angle (or wavelength). In the Plot window, if you hold down the shift key while the window is being drawn, then curves at all angles (or wavelengths) will be drawn. This is illustrated in the Immersed Wide-Angle Polarizer design.

    The various commands (print, copy to clipboard, save to file, and compute statistics) on the Options menu work with this feature also. Sensitivity analysis works with this feature also. Each of the random trial designs is evaluated at all wavelengths and angles specified by the user. Up to 32000 wavelength/angle combinations can be analyzed at one time.

  • Coatings may contain active materials. TFCalc can now design "active" coatings; that is, coatings in which the refractive index of one or more layers changes due to some outside influence. Examples of such influences are temperature, light intensity, electric current, magnetic fields, and moisture. Birefringent layers, for which the refractive index depends on the polarization and incident angle, may be modeled also. Another application is the design of coatings whose performance is less sensitive to index variation at time of manufacture.

    An active coating is composed of one or more layers of active materials. Up to three of these materials may be entered in the Environments window.

  • More layers. A design may now contain up to 5000 layers.

  • Stack formulas may be more complex. TFCalc's stack formula capabilities have been expanded. The formula can be up to 32000 characters long and can contain up to 26 symbols. Also, the thickness associated with each symbol can be given in either nanometers or QWOTs.


  • Faster optimization. The speed of the variable metric optimization method -- also known as quasi-Newton -- has been increased by up to 100%. That is, it can perform up to twice as many iterations as the previous version of this method. This improved method also may converge in fewer iterations.

  • Group factors can be constrained. Now the user may constrain the group factors when groups of layers are optimized.

  • Use constraints in the Simplex optimization method. Previously, the Simplex method ignored any thickness constraints.

  • Improved the global search method. When the user selects random search, then stratified sampling is now used to find designs which are (in some sense) more uniformly distributed. This technique increases the probability that the global minimum will be located.

  • Delayed quit in optimization. Sometimes, when using needle optimization, the user may want to quit optimizing after the next local optimization is complete. This is accomplished by pressing the control key while clicking on the Quit button. The Quit button's title changes to "Quit*".

  • More variable materials. The maximum number of variable materials has been increased to 150. Be aware that using a large number of variable materials during optimization can require a large amount of memory.

  • Targets displayed in color. If the user chooses to display the optimization targets in the Plot window, each polarization (P, S, and average) is displayed in a different color. The target deviations in the optimization dialog are also displayed in colors are each polarization.

Sensitivity Analysis

  • Worst-possible sensitivity analysis. On occasion, the designer may want to know what the worst possible performance is for a given manufacturing error. In the "Set Sensitivity Parameters" dialog, there is a new analysis type: Worst-possible. When this option is selected, then subsequent use of the Run menu's "Compute Sensitivity" command will compute the upper and lower bounds of the design's performance. Unlike the other two analysis types, which use random numbers to simulate manufacturing errors, the "worst-possible" calculation is deterministic; at each wavelength, optimization is employed to find the two designs (with thicknesses within the manufacturing tolerance) having the highest and lowest performance.

  • Sensitivity analysis: vary QWOT. The designer may choose to vary the quarter-wave optical thickness of layers. This type of analysis, which can be used only on dielectric (k < 0.01) layers, is important for studying the effects of thickness errors when coatings are optically monitored during their production.

  • Index variation in sensitivity analysis. In the past, sensitivity analysis varied only the physical thickness of the layers. Now the refractive index can also be varied. When index is varied, the layers' optical thickness remains unchanged. It is possible to vary thickness and index simultaneously.

  • Increased the number of trials allowed in the sensitivity computation. The maximum number of trials was 32,767. It has been increased to 2,147,483,647.

Refractive Index

  • Determining the substrate index. TFCalc can now be used to determine the index of a substrate from reflectance and transmittance measurements. The thickness of the substrate must be known. Previously, TFCalc could determine the index of a thin film layer on a known substrate.

  • Fixed constraints in index fitting. Parameters in dispersion formulas were constrained only if the user pressed the "Set Constraints" button. Now those parameters are always constrained.

  • Allow the user to save data files as text files. The Option menus for the Material, Substrate, Illuminant, and Detector data windows have a new command for writing the data to a tab-delimited text file. This command may be useful if the user wants to transfer data to another program.


  • Different monitor ratio for each material. There is a new capability of using a different monitor ratio for each coating material. The dialog shows the new "Set Monitor Ratios" button. When pressed, this button leads to a new dialog that lists each coating material and its ratio. Also, the "Set Monitor Chart Parameters" dialog has new options for displaying the material name and monitor ratio of each layer.

  • Zooming Plot, Color Chart, and Monitor Charts. While viewing one of these windows, the user may zoom an area by holding down and mouse button, dragging the cursor over the area, and holding down the control key when releasing the mouse button. This procedure may be used repeatedly to zoom into small areas of the window. To return to the unzoomed window, press the control key and click the cursor in the plot area.

  • New option for layer windows: Substitute. This new option enables the user to change many data items quickly. Here are some examples: (1) change all TIO2 layers to TA2O5, (2) change all thin layers, say < 10 nm, to 10 nm and set constraints for those layers. The dialog works as follows: it finds all layers that match all the conditions in the first column, then it changes the fields of those layers to the values given in the second column. If the first column is all blank, then it matches all layers. In the first column, the QWOT and Thickness items can be inequalities, such as < 10.

  • File menu change: Close and Save. A common error is to accidentally choose the Save command instead of the Close command -- causing unwanted changes to be saved. To make it more difficult for this error to occur, a divider has been placed between the two commands.

  • Thinnest layer. The "Show Thickness Totals" dialog -- an option on the Layers windows -- now displays the thinnest layer also.

  • Equivalent index calculation improved. The "Compute Equivalent Index" command, which computes the equivalent index of a symmetric series of layers, does not require the layers to be exactly symmetric.

  • Greater range in the EFI plot. The range in the EFI plot has been increased to 10000.

Windows-Only Changes

  • Better help in Windows. If the user presses the F1 function key in any window or dialog, then help for that window or dialog is displayed.

  • Year-2000 compliant dates on printouts. In TFCalc, dates are used only on printouts. The Macintosh version of TFCalc has long had the capability of printing 4-digit years. Now the Windows version also has this capability. In both Windows and Macintosh, the printing of 4-digit years is controlled by a control panel in the operating system.

  • Function key F7 for showing color chart. In Windows, pressing the F7 function displays the color chart.

  • Comment character lost. In Windows, the last character in the Comments window was not saved.

  • Shortcuts for New, Open, Save, and Print. In Windows, The control-N, control-O, control-S, and control-P keys can be used to run the New, Open, Save, and Print commands on the File menu.

  • Coating name shown in menu and taskbar. In Windows, the name of the coating design file is displayed in the main menu and also in the task bar. Thus, if the user is running multiple copies of TFCalc, it is easy to identify the coating file being worked on.

Macintosh-Only Changes

  • PowerMac: faster math library. A faster math library has been linked into TFCalc. This library will increase the speed of most calculations by at least 10%.

  • File reading improved. Corrupt files and files created in Windows are now handled better.
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