The FilmStar Workbook is a spreadsheet module built into DESIGN and
MEASURE. Utilizing familiar spreadsheet syntax, it provides a powerful
programmable interface for analyzing and optimizing spectral response.

Click for full size image
FilmStar Workbook for
Average/Maximum %T & %R

Click for full size image
On-line Function Reference

Introducing the Workbook

Once a spectrum is calculated or scanned a single click or keyboard shortcut pops-up the workbook and transfers the new spectrum. Multiple spectra can be inserted into adjacent columns. Formulas are virtually identical to those in Microsoft Excel.

Since the workbook includes macro capabilities, it can serve as an alternative FilmStar front end with the spreadsheet paradigm replacing the normal spectral plot. This is useful for evaluating and optimizing coatings when integrated performance is defined without reference to a particular spectral shape.

Optimization using  Generalized
Merit Function and Constraints
(4 layer AR with unusual
thickness constraints)

Optimization in DESIGN

Supplementing DESIGN's traditional optimization target list, FilmStar supports generalized merit functions and constraints for meeting system performance requirements. Constraints such as total layer thickness or stress can be included. These capabilities are not available in other optical thin film software.

Essentially, a spreadsheet cell is treated as a merit function and a group of cells defines constraints. Since these cells can be general functions of multiple spectra and/or layer thickness there are many options. Most importantly for active devices such as solar cells, integrated absorption in specified layers can be optimized.

Click for full size image
5% Coating Errors
(but what's the % yield?)

Tolerancing in DESIGN

Tolerancing uses Monte Carlo techniques to estimate coating yields. Graphically, errors affects coating performance as shown here.

But we don't know the yield from looking at the graph. Workbook tolerancing provides a way to estimate yields. The workbook is set up so that named cell
Passed ($E$9) has value TRUE or FALSE depending on whether the coating passes or fails the specification. Assuming that the average cannot exceed 0.5% over the range 450-750 nm and the maximum cannot exceed 1%, the following formulas are all that is required:

$E$9 =AND($E$5<0.5,$E$6<1)
$E$5 =100*AVERAGE($B$5:$B$35)
$E$6 =100*MAX($B$5:$B$35)

Here's the results (100 iterations at each error level):

2% -> 100% yield
4% -> 73%
6% -> 51%

Tolerancing can also be performed under FilmStar BASIC control. This might be appropriate when independent layer errors are insufficient to describe the situation or when pass/fail criteria are exceedingly complex.

Click for full size image

Quality Control Calculation

Quality Control in MEASURE

The MEASURE workbook is virtually identical to the one in DESIGN and shares the same source code. The model shown here is used in the example in the Report Generator page.

Essentially, the same workbook model used for design tolerancing is used for quality control. The only difference is that a pass/fail label like MEETS specifications is generated instead of percent yield.

Copyright 2018 FTG Software Associates
Last updated on January 01, 2018