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Safe Design and Usage of a Laser Instrument

By Dr. Scott Feister

January 16, 2020

Lasers, while wonderful in many respects, pose a serious and permanent accidental damage risk to eyes. In this guide, I will walk you through several safety considerations for constructing laser-based instruments in the middle school environment. These safety considerations do not apply to instruments that use LEDs instead of lasers. (LEDs pose none of the safety risks of lasers, but also have different qualities.) The target audience for this guide is: first the teacher, and then middle school students. Please read this guide in its entirety before deciding whether to incorporate lasers into your instrument.

Additional Resources on Laser Safety

In addition to reading this guide, I highly encourage all teachers to explore the OSHA Laser Hazards Website prior to deciding whether to incorporate lasers into your classrooms. OSHA is a reputable governmental institution concerned with workplace safety.

What follows is complementary to the OSHA website, and is tailored specifically to building a laser instrument.

Adult Supervision Required for All Laser Usage

Uncontrolled laser pointers pose a serious and permanent accidental damage risk to eyes. If students are using lasers in their instrument, it is essential that knowledgeable adults individually supervise the installation of the lasers (from start to finish).

NEVER, EVER LOOK INTO A LASER BEAM, even for a moment.

Depending on the power of the laser pointer, having it even just sweep across your open eye for 1/100th of a second may cause damage.

Lasers may become even more dangerous after striking items like reflective surfaces (e.g. a glossy whiteboard) and lenses (e.g. eyeglasses).

An adult knowledgeable in laser pointer safety should be at the table and individually supervising each team of middle schoolers:

  1. Whenever lasers are first powered on

  2. During laser mounting and alignment (NEVER stoop down to eye level with the beam, despite the temptation -- even from the opposite side of the beam, because it could reflect off of something!)

  3. Until both lasers and their 'light catchers' are firmly glued into place, such that no laser light escapes the instrument

The following precautions should be taken during laser mounting and alignment:

  • Set up the table so you point your beams at the wall, not towards the classroom

  • Nobody should be standing anywhere in front of the laser (the whole team and all other students should stand behind the laser)

  • Do not point the beam towards anything reflective, such as a glossy table or a glossy whiteboard

  • Angle your instrument slightly down, so that any reflections will be likely to bounce into the ground

Prior to leaving the table, the supervising adult should perform a careful check of the following:
  • Check for stray light using a white paper or tissue. (See example image of stray light.)
  • Check for firmness of the glued lasers & catchers

Laser Safety Considerations for Final Product

Consider where your beams will point during usage

Laser beams should always point down into the floor; they should not be aimed to be above horizontal with the floor. So, for example, if you are making a laser harp, you will want your lasers to point down towards the ground, not up towards the sky. If you are designing a laser guitar, you will want your lasers to point from the fretboard down towards the floor, not up towards the guitarist's eyes. Even though you will add other physical safeguards to prevent laser light from leaving the instrument at all under normal circumstances, considering beam direction will increase the safety of your final laser instrument.

Design to prevent users from casually looking into the beams

You need to physically block all possible ways for users to look into the lasers. Even adult users may be curious and may attempt look into the beams. So be creative, and test the safeguards thoroughly. For example, if you are designing a laser harp, you may wish to design the openly-accessible 'strumming' area to be too narrow for anyone to fit their head. Your goal is to make it physically impossible to stare into the lasers.

These physical protections are in addition to the verbal protections that you will give your users, telling them "Do not try to look into the lasers, as this can cause permanent eye damage." Also, these are in addition to your constant supervision during usage (you will warn them once, and then shut off the instrument if they are attempting to look into the lasers.)

Build physical protections to prevent your lasers and light catchers from being knocked loose

You should build into your design physical protections for your laser mounts and light catchers, to prevent them from being accidentally being knocked loose by rough usage. The reason for this is: if lasers or their catchers get knocked loose, lasers can point anywhere, and your safe instrument will instantly become a serious safety hazard. To mitigate this risk, for example, you may put a an additional enclosure over both your lasers and laser catchers. That way, if someone bumps into the instrument, neither the lasers nor the laser catchers will come loose.

These physical protections are in addition to your constant supervision during usage (you will intervene and shut off the instrument if anything becomes loose).

Consider your target audience:

If you are designing something that small children may use, you may decide that you are better off using something less dangerous than a laser pointer in your instrument. LEDs can be focused as well!

A laser instrument is never suitable for unsupervised usage by young children. This is because young children may find a way to break the lasers free from their mounts, cram their head in just the right way to stare at the lasers, etc.

Constant Supervision is Required for Laser Instruments

The target audience for this section is, especially, the middle schoolers:

Even with physical safeguards in place, an adult or a safety-trained middle-schooler will need to supervise the usage of your laser instrument every time it is powered on.

There are safety requirements that you should communicate before you let someone touch your instrument, and that everyone must follow:

  • "Don't attempt to look into the source of the laser beams, as even momentarily looking into the beam can cause permanent and serious eye damage."

  • "Be gentle with the instrument, and do not attempt to pull anything off the instrument as doing so could make it unsafe."

Even after verbally giving your instructions, it is your responsibility to stay present with the instrument and intervene if anyone break any rules. This will ensure their safety, your safety, and the safety of all people nearby. Here are some actions you should be prepared to take during the course of your supervision:

  • If someone is using your instrument too roughly, verbally instruct them to stop. If they persist after your warning, take back your instrument immediately.
  • If anything on your instrument becomes loose, especially if any physical safeguards become loose, take back your instrument immediately and shut it off.
  • If you (or anyone else) notices any funny smells or see any smoke, take back the instrument immediately and shut it off.

People using your laser instrument may not fully appreciate the dangers of your instrument, but you do. So, remember, you are the authority and it is your responsibility to intervene!

What's Next?

Now that you have set up your Raspberry Pi and its software, and become informed on unique safety considerations for a laser instrument, you are ready to begin physical construction and implementation of circuits. You can learn how to do this in the next section of this documentation: Building the Instrument Hardware.