Sigurthr
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- Dec 11, 2011
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I was recently contacted about writing "instructions" on how to properly operate a >5mW laser pointer for people new to lasers. Here is the result:
It is either goggles or a cane and a seeing eye dog.:
Once you recognise the need for goggles, it is important to know how they work, and how you work with them. Goggles (good ones) reduce the target wavelength's light going through them by a factor so high that if a direct hit should happen, you would not be injured at all. Normally a direct hit would cause permanent damage, if not total blindness. The fraction of the laser's light that reflects off the air or particles in the air that allows you to view the beam is often very very small compared to the total power of the laser. So when you see the beam only a very very small amount of the laser's light is actually reaching your eyes. The goggles block so much of a direct hit that they totally block any light from the beam itself. You cannot see a beam through proper goggles, no matter how strong your laser is. If you can see the beam through the goggles, the goggles are not strong enough. This does not apply when you add fog to the air though, the fog increases how much light the beam reflects, which is why it makes the beam visible. You can see a strong laser's beam through proper goggles when you use a fog machine.
Knowing where you're pointing the laser at:
How dangerous the laser actually is to use in practice depends on the surroundings and the potential targets the laser's spot can hit. Reflective objects such as mirrors, metal surfaces, glassware, polished surfaces, or objects the same color as the laser pose the greatest hazard. Even if these objects scatter the light in all directions they only absorb a tiny fraction of the light, so the reflected light retains it's total power even if spread over a large area. Even when scattered over a wide angle, each miniscule point in the swath of area irradiated contains enough power density to be dangerous to eyes. Whatever the laser points to should be dark enough that the spot appears to be MUCH dimmer. For example; a blue laser can shine on a matte unpolished dark red plastic box. The distance of the target from the laser is also a factor. You should have goggles on if the target is close unless it is very very nonreflective or shielded. A shielded beamstop allows for closer targets because it blocks the light that is reflected. A simple shielded beamstop is a capped off PVC tube that is painted matte black inside. None of the direct reflected light will make it back out of the tube to your eyes.
Setting yourself up for safety:
If you set up your laser on a stable flat surface and secure it so that it can not move/roll/fall/turn etc, and aim the laser at a black nonreflective surface that is also fixed so it cannot move, then danger is greatly reduced. If you do this so that the height of the surface is far from eye level and you (or anyone else with eyes) cannot enter in the path of the beam; you do not need to wear goggles. This is a lab style set up. I do this with my ~25mW 473nm laser. It has more than enough power to cause eye damage, but since it is fixed in a safe designated location and nothing can enter the beam, it is safe to use without protection. I often just admire the beam with fog in the air while doing other things in the room.
For portable lasers you need to be hyper-aware of your surroundings, and it is wisest to have your goggles on from before you turn your laser on until the point in time you are absolutely certain about where it is shining is safe or until you turn it off. One of the greatest dangers in portable lasers is scanning (shining while moving) the laser past an object that is reflective. In doing so there is a high chance the beam will quickly reflect towards the user, often right across their face, faster than they can react to it. Shine your portable laser first at the ground at distance between you and your intended target object while wearing goggles, then move it slowly to the target taking care to pay attention to what it is shining over. Once you have it where you want it; (pointed at a nonreflective object at a safe distance) you can use your other hand to flip up your goggles to admire the beam/spot.
The distance at which it is safe to look at the spot is determined by how nonreflective the target is and how much power the laser puts out. At 1.3W I find anything closer than 50ft is too close, even if it is dark wood. At 100mW I'm comfortable with a 15ft distance. If you have to squint to look at the spot, it is too close, far too close.
Burning without burning up your retinas:
If you plan on burning anything you need to have your goggles on 100% of the time. The reflectivity of an object changes as it's state changes. This is especially true for plastic or rubber based objects. As the spot under the laser's dot melts it becomes reflective, once it is liquid it often becomes as reflective as a mirror. At such a close distance
reflection from 100mW can blind. Never burn very close to the laser's aperture as this often causes a build up of particles on the lens which will destroy it over time. 6" is a good distance between laser and target when burning, and keep your face back about 1ft at minimum.
I don't enjoy burning, but I do enjoy engraving and cutting with lasers. I do a lot of DIY electronics and those cheap black plastic enclosures are a bitch to cut in to without a ton of tools. They are too thick for a nibbler and too hard to use most hand tools on. Dremels and the such work well but leave nasty edges and a ton of dust. A 1W 450nm laser will cut through thick black thermoplastic very nicely leaving a rounded edge and no dust. 200mW of 650nm is enough to engrave most plastics with initials or labels, you just can't work on red, white, or bright orange plastic.
Looking out for others:
Most people are not trained/informed on laser safety and have no clue what you are doing could be dangerous. Unless you make it known to them specifically they will often put themselves, and you, into dangerous circumstances without thinking twice about it. Know where others are, restrict access to your lasers and the beam paths. If someone enters the area where you are lasing in, cease what you are doing and don't continue until they put on proper goggles or leave. YOU are responsible for others' eye safety when you are using your lasers. If you wish to show off your laser to someone and don't have goggles for them, set things up in the lab style or properly aim your portable as explained above without them there. Bring them in and instruct them to not look at the spot, keep an eye on them and turn the laser off if they are about to do anything stupid.
In Closing:
By participating in this hobby you are vowing to be responsible in your actions and activities. Do not put others in danger because of your own stupidity/ignorance/laziness. Be ever-vigilant and hyper-aware. Be careful. Enjoy the coherent photons we all love safely, and you can continue to enjoy them for the rest of your life.
Happy Lasing!
-Sig
It is either goggles or a cane and a seeing eye dog.:
Once you recognise the need for goggles, it is important to know how they work, and how you work with them. Goggles (good ones) reduce the target wavelength's light going through them by a factor so high that if a direct hit should happen, you would not be injured at all. Normally a direct hit would cause permanent damage, if not total blindness. The fraction of the laser's light that reflects off the air or particles in the air that allows you to view the beam is often very very small compared to the total power of the laser. So when you see the beam only a very very small amount of the laser's light is actually reaching your eyes. The goggles block so much of a direct hit that they totally block any light from the beam itself. You cannot see a beam through proper goggles, no matter how strong your laser is. If you can see the beam through the goggles, the goggles are not strong enough. This does not apply when you add fog to the air though, the fog increases how much light the beam reflects, which is why it makes the beam visible. You can see a strong laser's beam through proper goggles when you use a fog machine.
Knowing where you're pointing the laser at:
How dangerous the laser actually is to use in practice depends on the surroundings and the potential targets the laser's spot can hit. Reflective objects such as mirrors, metal surfaces, glassware, polished surfaces, or objects the same color as the laser pose the greatest hazard. Even if these objects scatter the light in all directions they only absorb a tiny fraction of the light, so the reflected light retains it's total power even if spread over a large area. Even when scattered over a wide angle, each miniscule point in the swath of area irradiated contains enough power density to be dangerous to eyes. Whatever the laser points to should be dark enough that the spot appears to be MUCH dimmer. For example; a blue laser can shine on a matte unpolished dark red plastic box. The distance of the target from the laser is also a factor. You should have goggles on if the target is close unless it is very very nonreflective or shielded. A shielded beamstop allows for closer targets because it blocks the light that is reflected. A simple shielded beamstop is a capped off PVC tube that is painted matte black inside. None of the direct reflected light will make it back out of the tube to your eyes.
Setting yourself up for safety:
If you set up your laser on a stable flat surface and secure it so that it can not move/roll/fall/turn etc, and aim the laser at a black nonreflective surface that is also fixed so it cannot move, then danger is greatly reduced. If you do this so that the height of the surface is far from eye level and you (or anyone else with eyes) cannot enter in the path of the beam; you do not need to wear goggles. This is a lab style set up. I do this with my ~25mW 473nm laser. It has more than enough power to cause eye damage, but since it is fixed in a safe designated location and nothing can enter the beam, it is safe to use without protection. I often just admire the beam with fog in the air while doing other things in the room.
For portable lasers you need to be hyper-aware of your surroundings, and it is wisest to have your goggles on from before you turn your laser on until the point in time you are absolutely certain about where it is shining is safe or until you turn it off. One of the greatest dangers in portable lasers is scanning (shining while moving) the laser past an object that is reflective. In doing so there is a high chance the beam will quickly reflect towards the user, often right across their face, faster than they can react to it. Shine your portable laser first at the ground at distance between you and your intended target object while wearing goggles, then move it slowly to the target taking care to pay attention to what it is shining over. Once you have it where you want it; (pointed at a nonreflective object at a safe distance) you can use your other hand to flip up your goggles to admire the beam/spot.
The distance at which it is safe to look at the spot is determined by how nonreflective the target is and how much power the laser puts out. At 1.3W I find anything closer than 50ft is too close, even if it is dark wood. At 100mW I'm comfortable with a 15ft distance. If you have to squint to look at the spot, it is too close, far too close.
Burning without burning up your retinas:
If you plan on burning anything you need to have your goggles on 100% of the time. The reflectivity of an object changes as it's state changes. This is especially true for plastic or rubber based objects. As the spot under the laser's dot melts it becomes reflective, once it is liquid it often becomes as reflective as a mirror. At such a close distance
reflection from 100mW can blind. Never burn very close to the laser's aperture as this often causes a build up of particles on the lens which will destroy it over time. 6" is a good distance between laser and target when burning, and keep your face back about 1ft at minimum.
I don't enjoy burning, but I do enjoy engraving and cutting with lasers. I do a lot of DIY electronics and those cheap black plastic enclosures are a bitch to cut in to without a ton of tools. They are too thick for a nibbler and too hard to use most hand tools on. Dremels and the such work well but leave nasty edges and a ton of dust. A 1W 450nm laser will cut through thick black thermoplastic very nicely leaving a rounded edge and no dust. 200mW of 650nm is enough to engrave most plastics with initials or labels, you just can't work on red, white, or bright orange plastic.
Looking out for others:
Most people are not trained/informed on laser safety and have no clue what you are doing could be dangerous. Unless you make it known to them specifically they will often put themselves, and you, into dangerous circumstances without thinking twice about it. Know where others are, restrict access to your lasers and the beam paths. If someone enters the area where you are lasing in, cease what you are doing and don't continue until they put on proper goggles or leave. YOU are responsible for others' eye safety when you are using your lasers. If you wish to show off your laser to someone and don't have goggles for them, set things up in the lab style or properly aim your portable as explained above without them there. Bring them in and instruct them to not look at the spot, keep an eye on them and turn the laser off if they are about to do anything stupid.
In Closing:
By participating in this hobby you are vowing to be responsible in your actions and activities. Do not put others in danger because of your own stupidity/ignorance/laziness. Be ever-vigilant and hyper-aware. Be careful. Enjoy the coherent photons we all love safely, and you can continue to enjoy them for the rest of your life.
Happy Lasing!
-Sig
