If you're designing an optical system - be it a single light-bulb or a petawatt laser - there is a software package that can help. But how do you choose the right one for your needs? Michael Hatcher looks at six of the most popular packages used by the optics industry. vq RW^>~-B kjRL|qx`a; As the processing power of PCs has rocketed over the past decade, so optical design software has evolved. Once a highly specialized tool that had to be operated on mainframes and UNIX workstations, now such software is accessible on the desktop of any average optical engineer.
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fYzZW Whether you are designing cameras or radiotelescopes, a wide choice of packages is available to help you. We have taken a look at six of the most widely-used design programs to help you decide which is the most appropriate for your application.
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SbU / S`d? AV Optical design software falls into two broad categories: "classical" lens-design software, and illumination packages. Lens-design software is used to optimize image-forming optical systems. First, you must provide a starting design that includes data such as the shape, size and position of lenses and other optical elements in the system, the system's aperture and field of view, and the wavelengths being used. The program then traces the paths of light-rays entering the system, optimizing the optics using a mathematical algorithm until your target criteria are met.
.] BJM?9 2^fSC`! Illumination packages are used for more detailed analysis of an optical system - to predict the effect of sunlight on a telescope, for example. Output from lens-design software will often provide the input for an illumination package, enabling you to produce a more detailed analysis of system performance. Illumination packages are also used when designers want to analyse complex light distribution - for instance, that produced by car headlights.
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i5z_tS Three of the major packages are
ZEMAX,
OSLO and CODE V. OSLO and CODE V are older programs, dating back to the 1960s. ZEMAX is a much newer program - the first commercial version appeared in 1990.
!po29w:S )5l9!1j For an independent viewpoint, Opto & Laser Europe contacted Scott Lerner, an optical engineer at the Lawrence Livermore National Laboratory, US. Lerner uses all three lens-design packages to design a wide range of systems.
NplkhgSj S*a_ Broadly speaking, says Lerner, ZEMAX is an entry-level package suited to less experienced designers, whereas CODE V is a high-end solution suited to more demanding tasks. OSLO fills the middle ground.
K2ry@haN pd oCV "Given a specific problem, you could use any of the three codes to generate a solution. But I guess my rule of thumb is that if it's not too complex I'll do it in ZEMAX," Lerner told Opto & Laser Europe. "ZEMAX is accepted to have the lowest learning curve, and it is also the least expensive of the packages. So typically, if you have a relatively simple system to design that doesn't require extensive analysis then ZEMAX is the program of choice - it is cheaper and your customers are more likely to have access to it."
"kkZK=}Nv _.BX#BIF ZEMAX is not best suited to every situation, though. Lerner continued: "However, if you're doing extensive analysis of a system, or if you are developing 10 systems that are fairly similar and analysing all of them, then the macro language used by CODE V becomes extremely valuable. OSLO is kind of the middle ground."
#3((f[ 8\rHS sP Your preferred style of working may come into the equation too. "There's a knack to using each package and in the end, it can simply boil down to personal preference. CODE V tends to be faster, but that's not always what you want," said Lerner.
`YPNVm<3) J@Qw6J Dave Hasenauer is product manager for CODE V at ORA, US. He said: "We are the high-end package and we strive for those applications where the optics are critical to the success of the product."He adds that the applications that best suit CODE V are those that require high-precision optimization and tolerancing. "For example, people use CODE V for microlithography stepper systems and for reconnaissance systems," he said.
'fIirGOl ?iaD;:'qE A crucial point to consider, says Hasenauer, is the level of technical support that you're going to need. How much you get depends largely on the way that the different packages are sold. CODE V, for example, is sold on a leasing basis. This means that the customer pays a monthly fee for a package that includes full technical support.
P*6&0\af| \bumB<w(] On the other hand, ZEMAX customers pay for their package outright. The deal includes one year of technical support, after which there is a smaller fee for subsequent support and upgrades.
j :J{m0 -,} pp TG Mark Nicholson, technical director of ZEMAX vendor Optima Research, UK, says that ZEMAX has the advantage of having been written specifically for a Windows user-interface. "It's a very easy-to-use package, although you still need to be a good designer to use ZEMAX," he said.
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