optical software
that location. The software must determine
which surfaces the light hits first, examine to
what extent the light reflects or refracts, and
then finds the next surface to analyse. This
involves many thousands of calculations
that also include the effects of materials
and surface qualities. Beyond ray tracing,
LightTools includes an optimisation module
that helps zoom in on the best possibilities.
You select the light source, some reflector or
lens optics and note the headlamp’s output
requirements. The software then makes
thousands of modifications to the reflector
and optics and eventually converges on a
design or points out where major problems
are.
To illustrate the power of such software,
Zollers recalls a recent design for a projector-
type headlamp and recounts that he was in a
a simple road schematic is overlaid on the output of lighttools analysis of a headlamp; it
sense replicating work he did five years ago
shows the driver’s lane (right-hand traffic), the oncoming traffic lane and the horizon. in
when still active in the automobile industry. addition to the absolute magnitude of the light being >3x more in the optimised system,
In a projector headlamp, a filament is located
there is more foreground light just in front of the car, and the brightest portion of the
at one focus of a reflector that is parabolic in
beam has been shifted into the driver’s lane of traffic.
one axis and elliptical in the other; the light
passes through a condenser lens. A shade the windshield can be particularly annoying On top of the CATIA materials library,
that creates a very sharp low-beam cut-off and can also affect instrument readability by Optis adds information related to surfaces
is located at the lens’ focal point. Not only causing glare on the glass of an instrument and each material’s optical properties. Users
must the design optimise the shape of the face. simply add information regarding the type of
reflector and the lens, a curved shield can Simulations are also useful because sources – whether LEDs, displays or ambient
compensate for field curvatures (a flat cut-off aircraft manufacturers typically subcontract light. The software works with ray tracing
shield produces a ‘smiling’ cut-off pattern). various elements including instrument for photometric analysis as well as visual
Zollers explains that, when interacting with panels and windshields, so nobody has an ergonomics to integrate the overall scene
the software for only a few hours and letting overall view of the design until it all comes and get the pilot’s point of view. It not only
it run for roughly a day, he arrived at a very together. Final testing is done with test does physics-based rendering, it performs
satisfactory solution. At his previous job, pilots flying real aircraft, and if contrast is quantitative and spectral analysis as well
in contrast, he spent weeks working full- lost or there are bothersome reflections, it as examines chromaticity and luminance
time with earlier optics software to achieve can be extremely expensive to rectify such levels – all of which are tightly regulated
similar results. situations. Not only might it entail moving by aerospace authorities, so it is important
instruments around and rewiring them, it to know in advance if a flight deck will be
when regulations rule could also mean that hydraulics, ventilation approved.
In applications such as automobiles, proper or electrical systems must be repositioned. Designers at Bombardier in Montreal,
illumination is a factor that can lead to a Because mechanical elements and systems Canada, choose SPEOS CAAV5 Based
product’s consumer acceptance and thus are often designed and evaluated with MCAD software because it shows the crew interface
market success, but in other areas regulations software such as CATIA, one optical package as it will be seen in its final context. It
in this regard can be quite strict. One example that has become popular is SPEOS CAAV5 simulates visual perception based on a
concerns the flight decks of commercial Based from Optis, a company that believes physiological human vision model and
airliners, where aircraft manufacturers it was the first to integrate the simulation of predicts visual obstructions, glare and
prefer to perform simulations in software light, based 100 per cent on a physical model, reflection; it improves perceived quality by
and thereby reduce the number of physical within CAD software. This proves especially optimising colour, contrast, harmony, light
mockups, even though simulation does not useful, for example, if it is determined that uniformity and intensity as well as cabin
replace the requirement for mockups in the the shield on top of an instrument panel is lighting; it takes into account ambient
certification process. This is to ensure that not large enough or has the wrong shape to conditions for sun, clouds, day and night
the pilot can see instruments clearly at all block sunlight. In CATIA, designers can vision; and it checks that the design complies
times under extreme conditions: bright direct make the necessary geometry changes in with aerospace standards. Richard Heppell,
sunlight must not wash out an instrument’s minutes and relaunch the simulation process manager of core systems engineering at
display, and at night reflections and glare on without the need to import any new data. Bombardier Aerospace, says that it took his
www.scientific-computing.com scieNtific coMpUtiNG worlD february/march 2009
21
SCWfeb09 pp20-24 Optical.indd 21 4/2/09 10:47:26
Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44