PERFORMANCE CALCULATIONS
The Essential Macleod provides a comprehensive set of performance calculations. In
addition to the usual Reflectance and Transmittance calculations, the package also
includes Density, Absorptance, Ellipsometric parameters, Ultrafast parameters
(Group Delay, Group Delay Dispersion, Third Order Dispersion) and Chromatic Dispersion.
Color calculations are also available. Tolerancing calculations are provided to enable you
to judge the sensitivity of a design to minor thickness changes.
ADAPTIVE PLOTTING
The Essential Macleod features adaptive plotting for performance calculations. This
automatically adjusts the plotting interval so that fringes are faithfully followed. The
magnitude of the fringes would be lost without the adaptive plotting process.
REVERSE ENGINEERING
The Essential Macleod provides support for the identification of errors committed during
the manufacturing process. This support is provided by enhancements to the Simplex
refinement method.
Simplex provides both index and thickness refinement. It may be readily constrained in
different ways so that specific features of manufacturing inaccuracies and other problems
may be matched. These constraints may be altered and gradually relaxed until a solution is
found, pointing to the nature and magnitude of the possible errors.
Variations in index are reported in terms of changes in packing density. If desired a
new material can be created from an existing material modified by the packing
density
ANALYSIS TOOLS
Additional analysis tools include Admittance diagrams, Circle (reflection coefficient)
diagrams and Electric Field plots.
The electric field plot calculates absolute electric field amplitude. This provides you
with the information to compare either energy absorption of several coatings, so that
relative damage likelihoods may be estimated, or energy absorption at different
wavelengths for the same coatings. Such calculations are inappropriate with relative field
calculations.
Admittance and Circle diagrams help you to understand how a design works. They can be
looked on as a complete visual record of the way in which the various layers build the
performance of a coating by transforming the admittance, or the complex amplitude
coefficient, from the rear through to the front of the system.
DESIGN TOOLS
The Essential Macleod provides a variety of tools to support the design process. Editing
tools make manipulations of designs easy. These tools include: reversing the layers in a
design, changing all materials in a design, design by formula, scaling thicknesses, match
angle calculations, and cutting, copying and pasting of non-contiguous layers. Similar
powerful tools edit requirement specifications, materials data, tables and plots.
Tools are also provided for designing Induced Transmission Filters, Non-polarising Edge
Filters, and the calculation of equivalent (Herpin) layer parameters. The Induced
Transmission Filter tool calculates potential transmittance for a specified metal layer
and calculates dielectric layer thickness required for matching the filter with
quarter-wave dielectric layers. It can also be used simply to determine the maximum
possible transmittance from a defined thickness of a particular absorbing material. The
Non-polarising Edge Filter tool creates an initial symmetrical periodic design based on a
five layer two material symmetrical structure. The outermost layers can be subsequently
refined to match the filter design to the substrate and incident medium.
N & K DERIVATION
Although the Essential Macleod is supplied with a comprehensive materials database, a
particular coating plant will, in general, not produce films with the same optical
constants as stored in the database. The n & k derivation tool provides the facilities
to determine n & k from spectrophotometer measurements of the reflectance and
transmittance of a test film.
The method used in the package is based on the envelope technique and is extremely
stable. It works with transmittance-only data, reflectance-only data or transmittance and
reflectance data. Depending on the data, the tool can detect either inhomogeneity,
absorption or both.
ENHANCEMENTS
Enhancements for performing additional user-defined calculations, planning coating
production, and communicating with deposition controllers are available. The following
enhancements are currently available:
|
USER DEFINED UNITS
Units can often be a problem for users, but not in the Essential Macleod where
virtually any consistent set of units for the independent variables may be used.
Electron-volts or Gigahertz or wavenumbers for frequency and Angstroms or nanometres or
microns or even micro-inches for wavelength are possible. Changing from one unit system to
another is simple.
REFINEMENT
Optimac, Nonlinear Simplex, and Simulated Annealing refinement methods are
supplied. Optimac is a powerful technique which we recommend for normal use. Simplex is
fast and stable. Simulated Annealing is a statistical technique that can be effective in
resistant cases, but is time-consuming. Layers may be locked during a refinement
process so that their thicknesses are not changed during refinement. Linking causes
thickness changes to occur in step.
Refinement targets may be defined in terms of any of the calculated performance
parameters including color, wavelength (or frequency), incident angle, weight and
tolerance. Target linking allows more complex merit functions. A target generator tool
helps with the creation of multiple targets at different wavel engths and incident angles.
SYNTHESIS
The Optimac technique may also be operated in a synthesis mode where it will add and
remove layers in a design in order to meet the required specification.
Synthesis may be used to improve an existing design or to generate a design from just a
materials list and a specification. The figure shows the progress of an antireflection
coating design started in this way.
Optimac is archival. It maintains the complete history of the optimised designs
allowing trade-offs of performance against complexity.
COLOR CALCULATIONS
Color calculations are provided for the most popular color spaces:
- Tristimulus
- Chromaticity
- CIE L*a*b*
- CIE L*u*v*
- Hunter Lab
A selection of sources are pre-defined, and you may define others as necessary. The CIE
1931 and 1964 color matching functions are included. Again you may define any other you
may require. As well as calculations of the transmitted and reflected color, color may
also be specified as a target for refinement and synthesis.
OPTICAL ASSEMBLIES
Most coated components have at least two surfaces. A cemented filter assembly or coated
compound lens can have many more. The substrates for the coatings may absorb light to a
varying degree as a function of wavelength. The Essential Macleod includes a tool for the
calculation of the performance of many coatings and substrates in series. An effective
editor assembles parts into a stack, which can have a virtually limitless number of
components even including uncoated absorption filters. Surfaces may be parallel or wedged
simplifying estimates of glare or stray light.
MATERIALS MANAGEMENT
Real materials exhibit dispersion of their optical constants, that is the optical
constants vary with wavelength. Realistic calculations of properties must include such
variations. Each material is stored as a table of refractive index and extinction
coefficient values as a function of wavelength. This permits any dispersion to be modeled.
Powerful editing tools including spline interpolation are provided together with
import/export facilities that are easy to use.
Material behavior is not always ideal and optical constants often depend on the
particular coating machine and on the deposition parameters. Operating conditions also
affect material properties. For example, the operating performance of a cooled infra-red
filter may be substantially different from its performance at room temperature. Multiple
materials databases are therefore provided. Designs may easily be moved from one materials
database to another facilitating the investigation of temperature and coating plant
effects. Multiple materials databases have other advantages. For example, they permit
materials data belonging to a client to be completely isolated and protected.
TOLERANCING
The Essential Macleod's tolerancing capability allows you to investigate the sensitivity
of a design to manufacturing errors. Alternative designs may be compared and the best
design selected. Although designs may be similar, their sensitivity to errors may not and
this will be shown up by the tolerancing feature.
SUPPORT SERVICE
The support offered by Thin Film Center is quite simply the best in the business. Members
of the Update Service always have the latest version of the software, and technical
support without further charge backed by over 35+ years' of experience.
They also receive a quarterly newsletter with news, tutorials, tips and puzzles. The
service is free for the first year after purchase and a modest annual fee is
charged thereafter.
Thin Film Center also provides regular courses both on general design and manufacture
of thin film coatings as well as making the most of the Essential Macleod and its optional
enhancements.
|
