Product Focus: Using Ophir’S BC20 to Evaluate Scanned Effects in Light Show Applications

September 19, 2017

OphirBlog

Music concerts, along with other entertainment venues such as nightclubs and theme parks, use laser sources to create colorful and vivid lighting effects.

Even with advances in non-coherent lighting, technology has not been able to replicate the unique appearance of laser lighting effects.

The types of lasers used for light show applications typically emit radiant powers in excess of 20W over a range of common wavelengths based on the technology employed in the projection device. Devices emitting such powers place them firmly into Class 4 laser product territory. How do laser officers deal with the challenge and what does Ophir have to offer? Coming up…

Laser hazards

Laser beams that are categorized as Class 4 laser product territory can be hazardous, particularly for the eye (and sometimes also for the skin), mostly because they can have high optical intensities even after propagation over relatively long distances. Even when the intensity at the entrance of the eye is moderate, laser radiation can be focused by the eye’s lens to a small spot on the retina, where it can cause serious permanent damage within fractions of a second – even when the power level is only of the order of a few milliwatts.

Damage can result from both thermal and photochemical effects. Laser damage of the eye is not always immediately noticed: it is possible e.g. to burn peripheral regions of the retina, causing blind spots which may be noticed only years later.

Laser show safety in practice

Every Laser Safety Officer has the same goal – to keep the workplace safe from hazards associated with lasers. The laser show provider assigns a Laser Safety Officer to establish a laser safety program designed to address all the possible risks of using lasers in open beam path settings; procedural control measures, including use of the laser system’s lowest power setting possible for alignment and zoning, must also be set.

Engineering controls are always the preferred method of risk mitigation. Projectors are required to have emission indicators that light up when a laser is active and interlock switches to prevent lasers from firing if the projector housing is opened. Each projector must have proper labeling, such as a warning label at aperture to warn against looking into the aperture. Once laser systems are mounted properly, the beams must be tuned to where they will be propagated during the show, avoiding areas that could directly hit audience members.

Where personnel or members of the public are directly irradiated with laser radiation, (a practice more commonly referred to as audience scanning), a combination of separation distances, limiting exposure time, and attenuating the beam at source are necessary to ensure that exposure levels are not exceeded.

Ophir BC20 Detector

The Ophir BC20 detector provides a peak-hold detector/amplifier in its connector. This makes it capable of accurately registering short exposure emissions and reporting the peak value to the user via any of Ophir’s standard meter displays, such as the Nova II and Vega.

The BC20 is able to overcome the deficiencies in using a standard power meter detector. The peak hold detector of the BC20 is able to register pulses as short as 10us, thus making the device suitable for directly measuring the peak power present in the majority of scanned laser show emissions.

Once the peak power present in the emission at the point of accessible contact has been determined, and following a straightforward power-to-irradiance conversion, the assessor is able to evaluate the exposure against the applicable irradiance based exposure limit. With only a single pulse needed to register a reading, the BC20 can be used to immediately determine the peak power present in an operational laser effect. This is something that has been impossible to achieve using a standard power meter.

The combination of the BC20 and PD300-CDRH with an Ophir meter provides instrumentation that, with a little care, is straightforward to use and allows for a better assessment of a range of difficult exposure conditions commonly experienced in entertainment applications.