Ensure safety and enjoyment in laser light shows with our comprehensive guide on audience scanning safety, including irradiance measurement, pulse width calculation, and peak power management for secure and dazzling performances.
Ensuring Safe and Enjoyable Audience Scanning Laser Shows
(This article is based on an earlier version first published in the Fall 1997 edition of The Laserist magazine.)
Introduction
Successfully determining the safety level of an audience scanning show requires not only the proper tools but also an understanding of the theory behind safety exposure limits and the ability to correctly interpret measurement data. This blog aims to explain the fundamental concepts of audience scanning evaluation and provide a practical "hands-on" approach to assessing audience scanning effects in laser shows.
The Importance of Evaluating Show Safety
If an unsafe laser show causes vision damage to a viewer, the venue owner and show producer might face legal action, especially in litigation-prone regions like the USA. Ensuring a show operates at safe levels can prevent such damage and reduce the likelihood of successful legal claims, even if frivolous.
Achieving Safety is Feasible
Understanding laser safety may initially seem daunting due to the numerous variables and calculations involved. However, with proper guidance and tools, ensuring the safety of audience scanning can be straightforward. This blog will define key terms and demonstrate how to evaluate the safety of audience scanning performances.
Key Terminology
Irradiance
Irradiance is a fundamental concept in laser safety, representing the concentration of laser power per unit area. For example, if a 1-watt laser beam covers an area of 1 cm², its irradiance is 1 watt/cm². If the beam diverges to cover 2 cm², its irradiance decreases to 0.25 watts/cm², even though the total power remains 1 watt. For safety assessments, the eye's pupil is assumed to have a diameter of 7 mm, so any beam smaller than this delivers its full power into the eye.
Average Power vs. Peak Power
When projecting a circle onto a screen using either a diffraction grating or a fast-scanning system, the perceived brightness might be similar, but the risks differ. The scanning system’s peak power at any given point can be the full laser power, which poses a significant risk if the beam enters the eye. For instance, a 1-watt laser with an average power of 1 mW can deliver a peak power of 1 watt to the eye, a crucial consideration in safety evaluations.
Practical Application in Laser Shows
To ensure the safety of your laser light shows, it’s essential to use reliable laser projectors and to understand how to measure and manage irradiance and peak power. By following safety guidelines and properly assessing your laser effects, you can create visually stunning and safe audience scanning performances.
Whether you are using a mini laser projector for a small venue or a high-power laser light projector for a large event, prioritizing safety will enhance the overall experience for your audience. Remember, safe laser stage lighting not only protects your viewers but also elevates the professionalism of your show.
For those interested in implementing safe and engaging laser light effects, consider investing in high-quality DJ laser lights or party laser lights. Products like the Luminesse Laser or the LaserCube offer innovative options for dynamic and secure laser projection.
By understanding and applying these key principles, you can ensure that your laser light shows are both spectacular and safe, providing an unforgettable experience without compromising on safety.
Pulses and Multiple Pulses
As a laser beam scans across the pupil, it creates pulses of light. The pulse width depends on the beam diameter and scan rate, typically ranging from 20 to 500 microseconds in audience scanning shows. Effects like tunnels or sheets of light create multiple pulses, and safety standards dictate the maximum permissible exposure for single and multiple pulses in a laser light show.
Evaluating Audience Scanning Shows
Required Tools for Manual Calculations
1.Calibrated Laser Power Meter: Designed for measuring static (non-moving and non-modulated) beams with a silicon detector of a 1 cm² effective area.
2.Fast Silicon Photodiode with Amplifier: Available from suppliers like Hamamatsu, Centronic, and UDT, these are used with an oscilloscope to measure pulse width and repetition rate.
3.Oscilloscope: A 50 MHz or higher bandwidth analog oscilloscope, or a digitizing oscilloscope, for detailed measurements.
4.Scientific Calculator: Capable of performing exponential and power of ten calculations, such as the one included with Microsoft Windows in scientific mode.
Technical Skills Required
Conducting a manual audience scanning safety assessment can be tedious and prone to errors. Using the mentioned tools requires knowledge and experience and should only be performed by technically skilled personnel.
Evaluating the Show
Once the equipment is ready, run the entire show multiple times to identify and list particularly bright and dangerous effects. Once these effects are identified, evaluate them by performing the following steps:
Step 1: Measure Beam Irradiance
Measure the irradiance of the laser beam closest to audience entry points. Project a non-moving beam into the venue, ideally in a studio with prior knowledge of the show site. The beam must match the color and power level of the effect being evaluated. Carefully place the detector head into the closest beam to the audience, ensuring the beam overflows (or at least fills) a one-centimeter detector area. Record the meter reading as “watts per square centimeter” (W/cm²).
Step 2: Measure Pulse Width
Measure the pulse width when the effect passes through the eyes. Project the effect into the venue and place a fast photodiode at the brightest part of the effect. Use an oscilloscope to measure and record the pulse width, adjusting the horizontal time base as necessary.
Step 3: Measure Pulse Repetition Rate
Increase the horizontal scan time until you see two or more consecutive pulses. Measure the time between pulses, and calculate the repetition rate using a scientific calculator.
Step 4: Calculate Single Pulse Maximum Permissible Exposure (MPE)
Calculate the MPE, which is the maximum irradiance considered safe for a given pulse width. Use the formula: Pulse Width (in seconds) raised to the 3/4 power, multiplied by 0.0018, then divided by the pulse width.
Step 5: Calculate Multi-Pulse MPE
Calculate the multi-pulse MPE based on the number of pulses the audience will be exposed to. Multiply the exposure time by the pulse repetition rate and raise the number to the -1/4 power. Multiply this factor by the single pulse MPE to get the multi-pulse MPE.
Step 6: Calculate Average Power
Multiply the irradiance measured in step 1 by the pulse width and pulse repetition rate to calculate the average power. Compare this with the average MPE for the exposure time.
Simplifying the Process
To simplify the safety evaluation of audience scanning shows:
Ensure actual scanning and beam modulation occur quickly enough to keep the pulse width experienced by the eyes around 1 millisecond or faster.
Measure the maximum irradiance of the beam at the closest audience entry point and ensure it falls between 5mW/cm² and 10mW/cm².
If these conditions are met, use a simplified method for assessing audience scanning safety by measuring the irradiance of a non-moving, non-modulated beam at the closest audience entry point.
Ensuring Show Safety
Passing all evaluations doesn’t guarantee ongoing safety. Be mindful of potential failures such as sudden beam power increases or projection system malfunctions. Consider reasonable failure modes and provide control measures like scan fail-safes to limit consequences. For instance, Pangolin's PASS system monitors projected beam power and other related systems to ensure they operate within safe levels.
Ensuring Safe and Enjoyable Laser Shows: Understanding MPE Measurements
As a laser artist, ensuring the safety and enjoyment of your audience is paramount. A crucial aspect of this is understanding the concept of Maximum Permissible Exposure (MPE). Research has shown that effects exceeding the MPE can often lead to afterimages, while those staying within MPE limits do not. By learning from MPE measurements, you can create laser shows that are both safe and captivating for everyone.
What is MPE?
MPE, or Maximum Permissible Exposure, is a crucial guideline in laser safety, defining the level of laser radiation to which a person can be exposed without harmful effects. These values are derived from extensive research and are outlined in various safety standards, including ANSI Z136.1 for the Safe Use of Lasers.
The Importance of Staying Within MPE Limits
Exceeding the MPE can result in temporary visual disturbances such as afterimages. This occurs because the intensity of the laser beam light exceeds the safe threshold, affecting the retina. On the other hand, effects within the MPE limits are safe and do not cause such issues, ensuring that your audience can enjoy the laser show without any discomfort or risk.
Learning from MPE Measurements
By understanding and utilizing MPE measurements, you can design laser effects that are both visually stunning and safe. Here are some key points to consider:
Tailoring Effects to MPE Guidelines
Different laser effects have varying exposure times and intensities. For example, moving effects like fan and tunnel effects quickly sweep across the eyes, resulting in very short exposure times—often just one scan. In contrast, stationary effects may repeatedly sweep across the eyes, leading to longer exposure times. When in doubt, using a quarter-second (0.25 seconds) as a benchmark is recommended, as this accounts for the natural aversion response (such as blinking or turning the head).
Regional Safety Standards
It's important to note that MPE values referenced here are based on the ANSI Z136.1 standard. While technically different from other international safety standards, the primary distinction lies in the units of measurement. For instance, ANSI uses watts per square centimeter, whereas some other standards use watts per square meter. Despite these differences, the actual "exposure limit" tends to be surprisingly consistent across standards. Always refer to your country's specific laser safety standards and seek regulatory guidance. In some regions, such as Sweden, scanning audiences with laser beams is illegal.
Understanding and adhering to MPE measurements is essential for creating safe laser shows. By doing so, you can ensure that your audience enjoys the mesmerizing effects of laser lights without any risk to their eyesight. As an artist, this knowledge empowers you to craft shows that are both safe and spectacular, solidifying your reputation as a responsible and creative professional in the laser entertainment industry.
Key Points to Consider
Points to Consider
Remote Control: Utilizing remote control technology for your laser projectors can enhance safety by allowing you to make real-time adjustments to ensure all effects stay within MPE limits.
Laser Lights: Selecting the appropriate laser lights for your show, including mini laser projectors and rgb lasers, ensures that you have full control over the intensity and exposure times.
Laser Projection: Employing advanced laser projection techniques can help in designing effects that are visually appealing and within safety standards.
Laser Light Projector: Investing in high-quality laser light projectors, such as those used in rave lasers and dj laser light setups, can provide better control over laser beam light exposure.
Laser Mapping: Implementing laser mapping technology can create stunning visual effects while maintaining safe exposure levels.
Party Lights and Disco Lights: Combining traditional party lights and disco lights with laser effects can enhance the overall experience without compromising safety.
Laser Zone: Designating a specific laser zone for laser shows can help in controlling the audience's exposure to laser beams.
Christmas Laser Lights: When using laser lights for seasonal displays, such as christmas laser lights, ensure they comply with safety standards to avoid any harm to spectators.
Luminesse Laser: Utilizing advanced luminesse laser technology can help in achieving bright, vibrant effects that are safe for the audience.
By incorporating these considerations into your laser show planning, you can create a memorable experience that is both safe and enjoyable for your audience. This approach not only enhances the artistic quality of your shows but also demonstrates your commitment to safety and professionalism in the laser entertainment industry.