Audience Scanning Laser Safety: MPE, Irradiance Testing & Setup

If you’ve ever run a laser show projector in a club, concert, or festival, you’ve heard some version of: “Can we scan the crowd a bit more? Make it feel bigger.” That’s where audience scanning laser work stops being “just programming” and becomes laser safety engineering.

Here’s the most important mindset shift:

This guide is a practical, field-friendly explanation of how to do laser beam measurement, how laser MPE limits are used in real shows, and how to build a process that’s consistent enough to repeat (and explain to a venue, inspector, or client if you ever have to). I’ll lightly reference Starshine as a brand example because many teams ask us how to set up a repeatable measurement workflow, but the safety principles apply to any laser show system.

Some regions don’t enforce laser rules aggressively. Some venues don’t know what to check. Some shows “get away with it” for years.

None of that proves the crowd wasn’t exposed above MPE.

If you want to run audience scanning like a pro, you need two things:

• Measured exposure at the closest plausible audience distance
• A show design + safety system that prevents exposure spikes (scan failure, hotspots)

A common question is: “Is 5W safe? Is 10W safe?” On its own, that question doesn’t have a meaningful answer.

A 1W beam can be dangerous if it’s tight, static, and aimed at eye level.
A higher-power projector can be safer if the beam is widened, scanned properly, and heavily attenuated in audience zones.

What actually matters is:

Irradiance = power per unit area (what lands on a 1 cm² sensor). That’s why many safety workflows talk in mW/cm², not watts.

Two key real-world notes:

• Closer looks brighter. A lower-power beam near the audience can look as bright as a higher-power beam above them.
• Beam size and dwell time are everything. A tight beam or a “stuck point” (hotspot) can spike exposure fast.

MPE means Maximum Permissible Exposure—a published limit intended to reduce the risk of eye injury under defined assumptions.

MPE values are discussed in standards like ANSI and IEC documents, and they form the backbone of many national laser safety regulations. In practice, show operators use MPE as a reference point when deciding whether a certain crowd scanning laser approach is defensible.

Two important ideas can be true at the same time:

1. MPE is a serious, widely accepted baseline for safety.
2. Real shows add non-lab factors (movement, brief exposures, audience behavior, scanning characteristics), which is why the industry has debated different scanning approaches for decades.

No matter what “mode” someone uses (strict MPE or higher scanning levels under special conditions), the foundational requirement is the same:

Instead of trying to measure every frame of the show at every seat, many experienced operators use a simpler workflow:

1. Measure one static beam at the closest exposure point
2. Decide your show mode (static elements? continuous scanning? special scanning policy?)
3. Set the projector output and zone attenuation so your measured value supports that mode

This doesn’t remove responsibility—what it does is give you a repeatable baseline that can be checked and documented.

You cannot judge safety by eye. Your eyes are not a calibrated instrument, and perceived brightness does not track exposure reliably.

To measure irradiance, you need:

• A power meter/radiometer with a suitable detector head
• A known sensor area (ideally 1 cm²)

• Silicon detectors: Very sensitive, but response varies by wavelength. For RGB, you typically need wavelength compensation/flattening to avoid under- or over-reading certain colors.
• Thermal detectors: Often less sensitive at very low mW levels, but usually less biased across visible wavelengths.

If your detector area isn’t 1 cm², convert the reading by area ratio so your final result is expressed in mW/cm².

This is the part most people think they do correctly… until you watch their setup.

A) Same distance as the closest possible exposure
Measure at the closest point where an audience member or performer could realistically be exposed. If you measure farther away “because it’s easier,” you can dramatically understate risk.

B) All colors ON at maximum show output
If you run RGB during the show, measure with R+G+B enabled at the max output your cues will reach.

C) Ensure the software outputs a true full-power static dot
Some laser show software may add blanking points or “safety dots” automatically. Confirm your test pattern is truly steady ON, not pulsed or blanked.

If you’re using common tools in the industry—like Pangolin BEYOND, Pangolin QuickShow, or other ILDA laser software—make sure you understand what your test frame is actually outputting.

D) Beam must be static
You want a single point, not scanning, not a shape, not a “fast circle.” Static. One dot.

1. Place the detector at the closest exposure distance
2. Turn on your full-power static dot (all colors used in show)
3. Find the peak reading position (center of beam)
4. Record the power on the detector
5. Convert to mW/cm² if needed (based on detector area)

This result is your static beam baseline.

Different operators and jurisdictions choose different policies. What follows is a practical summary of commonly discussed levels in show-world language. Always follow your venue/jurisdiction requirements.

If your show includes static beams, “laser sculpture,” held points, or anything that can behave like a hotspot, the safer approach is to treat it under a static-style limit.

When the beam is truly scanning continuously, each pass across an eye is like a pulse. Under conservative assumptions, operators often use a lower scanned-beam limit.

This is only meaningful if you’re sure the show contains no hotspots.

ILDA has discussed conditions where higher scanning levels may be considered acceptable under strict constraints. In practical terms, this approach is sometimes summarized in conversation as “10× MPE scanning.”

Three clear warnings:

1. It may not be legal where you operate.
2. Some venues/clients will not accept it.
3. It requires extremely disciplined engineering, monitoring, and documentation.

Scanning reduces risk only when two conditions are true.

A scan-fail detection system should detect scanner/control failures or dangerous output conditions and shut off the beam fast.

If you’re building a professional laser show system, this is not optional.

Hotspots are where “it’s scanning” becomes “it’s dangerous.”

Common hotspot creators:

• two-point “jumping” beams where each point lingers too long
• slow corners or sharp corners at high power
• “scan-looking” effects that actually dwell at endpoints
• low-speed beam chases across faces
• mis-tuned scanners that slow down unpredictably

Even worse: a good scan-fail system may correctly detect hotspots and kill your output—so hotspots aren’t just risky, they’re show-breaking.

If your static measurement is above your chosen limit, you have two main tools:

Wider beams reduce irradiance by spreading power over more area. A concave lens or beam expander can help.

Yes, beams get softer. But a slightly softer beam that’s legally and ethically defensible is better than a razor beam that puts you at risk.

This is how many great shows keep strong beams overhead while staying safer in the crowd.

Two ways:

• Physical attenuation for lower zones (must be rigidly mounted—movement changes everything)
• Software attenuation (often called an attenuation map / beam attenuation map)

With attenuation mapping, the lower (closer) zones are darker on the map and receive more power reduction. The overhead zone remains bright and crisp.

Use this as a “muscle memory” routine before every show—especially if you’re doing audience scanning laser effects.

• [ ] Confirm show policy: static / scanned / special scanning level
• [ ] Identify closest exposure point and measure at that distance
• [ ] Verify all colors used in show at max output during measurement
• [ ] Confirm test frame is true static dot (no hidden blanking)
• [ ] Confirm scan-fail protection is enabled and tested
• [ ] Confirm emergency stop works and is reachable
• [ ] Scan cues for hotspots (corners, endpoints, point-jumps)
• [ ] Confirm audience zone attenuation mapping is correct
• [ ] Post laser warning signage; audio warning if required
• [ ] Assign a trained operator to monitor continuously

If you only do one thing: measure + confirm scan-fail + remove hotspots.

These are the traps I see most often:

1. “It doesn’t look bright, so it must be safe.”
2. Measuring farther away than the closest audience distance
3. Measuring only one color (then running full RGB in the show)
4. Assuming “fast scanning” means safe while using slow corners/pauses
5. No real scan-fail protection (or it’s disabled because it “interrupts the show”)
6. Point-to-point beam jumps mistaken for “scanning”
7. No documentation—which becomes a problem the moment anyone asks questions

If you do audience scanning, documentation is part of professionalism.

Event:
Venue / City:
Date & Time:
Operator:
Laser Safety Officer (if applicable):

Projector / Laser show projector model:
Control method: (e.g., ILDA interface, network, internal SD)
Software: (e.g., laser show software, Pangolin BEYOND, etc.)
Scan-fail protection: enabled / tested / time of test

Closest exposure distance:
Measurement device & sensor area:
All colors enabled at max show power: yes / no
Static dot test confirmed true ON (no blanking): yes / no

Static beam reading: ____ mW on sensor
Converted irradiance: ____ mW/cm²

Chosen limit policy: (2.5 / 10 / 100 mW/cm² or local rule)
Audience zone attenuation: yes / no (notes)
Hotspot review completed: yes / no (notes)

Warnings posted / announcements: yes / no
Operator monitoring plan:

Signature: ___________________

This report alone won’t make an unsafe show safe—but it proves you ran a responsible process.

These are written in a practical, decision-helping style because many readers land here while comparing gear.

A show that looks incredible is not automatically a show that’s safe. If you want to run audience scanning laser effects responsibly, aim for a workflow that’s:

• measurable (irradiance in mW/cm²)
• repeatable (same steps every time)
• defensible (scan-fail + hotspot control + documentation)

That’s the difference between “we ran lasers” and “we ran a professional laser show.”