FEATURE
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Show stopper

Greg Blackman looks at the laser technology wowing audiences at shows from the likes of Coldplay, as well as seeing how new laser pistols used in modern pentathlon performed at this summer`s London Olympics

As far as spectacles go, you can’t get much better than the London Olympic opening and closing ceremonies. Danny Boyle supposedly held back the start of his ‘Isles of Wonder’ opening ceremony until dusk to get the full effect of the light show, which included 70,500 LED ‘pixels’ in the stands that transformed the audience into a giant LED screen. Laser light shows are now part of most large arena music concerts; they illuminate buildings and are even now a tool for marketing, tracing out company logos and slogans. Walt Disney World in Florida holds a firework and laser light show every evening.

Of all the effects that can be created with a laser, audience scanning, where the beams are scanned into the crowd, is one of the most popular. Justin Perry, chief operating officer at Pangolin Laser Systems, which provides laser control software and hardware to production companies engineering laser light shows, comments: ‘This [audience scanning] is the most beautiful effect in a laser light show, because it brings the audience into the show. Laser is the only medium that can do this. No other light source allows people in the audience to interact with it the way a laser does and audience scanning is the epitome of that.’

Perry goes on to add the caveat that, as with all laser light shows, audience scanning has to be safe and in most countries there are strict laws concerning laser safety for shows and audience scanning. Pangolin produces its PASS (Professional Audience Safety System) device, a circuit board based on analogue components designed as a safety controller for laser projectors. Embedding PASS in the projector ensures laser shows comply with regulations.

The device continually monitors the laser power, the scanner signal and other projector-related parameters. ‘If there’s a problem during the show, such as the beam is travelling too slowly or scanning an area that is too small or if a beam becomes static, which is a really dangerous situation, PASS will momentarily interrupt the light from the projector by manipulating the colour and blanking signals,’ explains Perry. ‘It ensures that no level of laser light harmful to the human eye will pass through a specified projection zone and if something fails inside the projector, i.e. if the scanners break or if there’s a power surge, PASS will shut the laser down.’

Pangolin also provides a SafetyScan lens, which causes the beam to diverge slightly as it is scanned into the audience, but does not affect the laser beam as it is scanned over peoples’ heads. This makes the beam shining into an audience much safer because its divergence is increased slightly, but it retains its coherence when scanning above the audience. ‘When you experience the show you can’t perceive the small increase in the beam size and people in the audience report a much more enjoyable show experience,’ states Perry.

Pangolin’s software also incorporates a beam attenuation map, with which clients can use to set parameters to modulate the laser power when projecting into or onto certain areas, so a lower power when scanning into the audience.

Pangolin’s systems have been used as part of Coldplay’s Mylo Xyloto world tour, the 2012 NBA All Star Game, and the 2012 Grammy Awards. In addition, the company has products being used in prominent outdoor installations, such as those on the seafront in Weymouth, Dorset, in the UK and a new installation on the MGM Grand Hotel in Connecticut which celebrates the building’s 20th anniversary. The Weymouth installation uses seven laser systems, each with a Coherent OPSL 8W green laser, designed by Arctos Laser Systems in Germany, to shine out over the sea.

Green has always been the most common colour for laser light shows, as the wavelength is a natural laser transition – a frequency-doubled Nd:YAG laser produces light at 532nm. Laser company Coherent produces its optically-pumped semiconductor laser (OPSL) technology, which is not dependant on natural laser transitions. ‘The beauty with the OPSL is that the wavelength can be tailored for a specific application,’ explains Andreas Zuck, market development manager for instrumentation at Coherent.

OPSL technology is based on an epitaxy grown semiconductor laser material, which is optically pumped using common 810nm pump light. Depending on the composition of the chip material, the lasing wavelength can be shifted and locked. The lasers can also scale in power, with more pump light equating to higher power, in general. Coherent’s Taipan product family offers 10 different visible wavelengths, from dark blue to red, and very high wall plug efficiency compared to diode-pumped solid state or gas laser technologies.

During the recent Berlin Festival of Lights, a laser projector with five Coherent Taipan lasers designed by LaserAnimation Sollinger was used to illuminate the 200m high Berlin radio tower. The laser created animated plants which grew up the tower.

These sorts of outdoor projections and shows like the Olympics opening and closing ceremonies are all benefitting from, initially higher power lasers from companies like Coherent that cover the entire visible spectrum, and also from advances in laser scanning technologies. In addition, advances in software are making it easier to engineer laser shows. Pangolin’s Beyond software, which is based on the company’s Lasershow Designer 2000 (LD2000) platform, aims to simplify the process of creating laser light shows. ‘With LD2000 there was a lot of editing and pre-programming needed to generate the content, but with Beyond we’ve really simplified the process,’ says Perry. ‘In addition, we have incorporated advanced tools for live shows, which sometimes can’t really be pre-programmed in the sense that DJs or performers might be switching tracks on set to match the artist’s style. Beyond has great live controls to create the light show as the concert is happening.’

Sharp shooting

Returning to the Olympics, athletes competing at the London 2012 Games in modern pentathlon fired laser pistols for the shooting portion of the sport, as opposed to the standard pellet guns.

Modern pentathlon, a contest where athletes battle it out over five events comprised of fencing, swimming, horse riding, shooting, and running, has been in the Olympic programme since 1912. The rationale behind introducing the laser pistol by the sport’s governing body, the UIPM, in 2010 was largely to make modern pentathlon more accessible to younger, budding pentathletes who would otherwise have to contend with restrictions on firing pellet guns.

The new kit has come under some criticism though since its introduction and there have been problems, both to do with the gun itself and the target – the guns were trialled during competitions run throughout 2011, including the World Cup and World Championships. Steve Candy is the combined event manager for LOCOG, the London 2012 organising committee: ‘There were some issues around the new technology and for the London Olympics we wanted to eliminate as many as possible. With any changes in a sport it takes a little while to settle down, but it was the Olympics and we didn’t want any issues so we spent a lot of time deciding how to resolve them.’

One of the improvements Candy wanted to see was surrounding the testing of the laser pistol and ensuring each pulse of light met set criteria. Candy notes that up until the Olympics there hadn’t been much testing and the laser shooting was open to both abuse and safety concerns. ‘I wanted to make sure the athletes had a level playing field and that nobody had tweaked the lasers to make them more powerful or fire a longer shot,’ he says. Candy invested in a hand-held laser power meter from British company Lasermet to test the pistols. The meter, the ADM1000, has a response time of 700ns and a sampling rate of 1MHz enabling the user to view the power output of pulsed waveforms up to 400kHz in oscilloscope mode.

The laser pistol is designed to simulate firing a pellet. Effects like the time taken for the pellet to travel down the barrel of the gun, which is in the order of milliseconds, are recreated in the laser version, as it’s that time delay that can magnify any slight shift in aim from the pressure of pulling the trigger and cause an athlete to shoot wide. In addition, each laser pistol has to have a similar pulse width; a continuous beam would mean the athlete would simply have to wave the gun across the target and at some point it would register a hit.

‘What I particularly wanted to test was the length of the shot and the power,’ states Candy. ‘There were other aspects I would have liked to test like the trigger delay mechanism and the waveform of the beam, but these were less critical. I wanted to make sure the athletes had a level playing field.’

In the sport’s current form, the running and shooting are combined in a final event that sees the athletes go through three bouts of shooting each followed by a 1km run. The points from the three previous disciplines are added up and the difference between them equates to a time handicap for the final run/shoot. This makes it a straight race in the final combined event, with whoever crosses the line first taking Gold. ‘In the shooting, the lead can change several times depending on how accurate or inaccurate the athletes are with their shots,’ states Candy.

Lasermet’s power meter was used at the equipment control testing that took place the day before the competition, but also, according to Candy, actually during the event. Under the rules of the sport, Candy would be allowed to move an athlete to another firing bay if there was a technical malfunction with the target, but not if there’s a problem with the pistol, which is deemed ‘kit’ and is the responsibility of the athlete. Each competitor will have a reserve pistol, but it’s part of the sport in that if the pistol fails – just as if the épée fails in fencing or the fact that the athletes select a horse at random they’ve never ridden before – then that’s unlucky and the athletes might lose points because of it. Candy has to make snap decisions on the day, which is where the power meter was invaluable. ‘Athletes won’t say they missed; laser manufacturers won’t say there’s anything wrong with the laser and the target manufacturer will deny any fault as well. I have to make decisions very quickly,’ states Candy.

Candy relates that there was a pistol failure during the warm up before the woman’s final at the London Games: ‘At this point, the coaches get agitated and everybody’s blaming everyone else. We quickly got the meter out; we did a test on the pistol and found that the power was way down and that the rechargeable battery was almost flat. We were able to prove this straight away.’ The athlete used the spare pistol and the situation was dealt with. ‘It meant we weren’t trying to guess,’ he continues. ‘Before purchasing the meters to test the laser pistols, we would literally hold our hand out in front of the pistol and see if a red dot appeared. Now we had a bit of technology with which we could prove the performance of the pistol.’

Speaking to Electro Optics, Sam Weale, who competed in the London Games for Team GB, finishing 13th overall, gives his opinion that, ‘due to the format of the running/shooting event if something does go wrong there isn’t much you can do about it’. He says that, on the plus side, the laser pistol removes any issues with loading pellets and they are also safer than the pellet version. However, the guns are more expensive, he says, since the laser portion is an adaption to the existing gun. He quotes around €500 for the laser barrel on top of €1,000 for the original pistol. He also draws attention to the different feeling when firing the gun, stating there’s a ‘lack of feel on shot release’. He does say that there were fewer problems during the 2012 season due to a more efficient targeting system, which, he says, is where most of the problems occurred rather than with the laser pistol per se.

The testing equipment used during the London Olympics is a step up from previous modern pentathlon competitions in that it can pinpoint whether the laser pistol is at fault or whether by deduction it’s more likely to be the target. Candy states that one progression for the future for laser pistol testing would be to include laser safety criteria in the test.