Just how strong is class IV laser actually is?

Not that i doubt how strong they are... but let say comparing to these stuffs, how many times over is the strength of direct beam , diffused reflection beam?

1. Looking directly at the sun at 12 pm for a few second
2. Looking directly at electrical weld

Class 4 lasers start at 500mw.
Without defining beam parameters, viewing distance, power output your question is a bit to broad to answer. So let's say the brightness of class 4 lasers can exceed by many orders of magnitude any source of light you will likely see during your life.

Class 4 is the highest and most dangerous class of laser, including all lasers that exceed the Class 3B AEL. By definition, a class 4 laser can burn the skin, or cause devastating and permanent eye damage as a result of direct, diffuse or indirect beam viewing. These lasers may ignite combustible materials, and thus may represent a fire risk. These hazards may also apply to indirect or non-specular reflections of the beam, even from apparently matte surfaces—meaning that great care must be taken to control the beam path. In most states it is illegal to sell preassembled class 4 lasers, however a citizen can construct a class 4 laser for personal use. Class 4 lasers must be equipped with a key switch and a safety interlock. Most industrial, scientific, military, and medical lasers are in this category.

Strong 1W+ lasers can have over 10.000 times the brightnes of the sun.. You just don't want that in you're eyes

You can find more info here:

Laser safety - Wikipedia, the free encyclopedia

Looking at the sun in broad daylight is close to looking at about a 10mW laser, ENOUGH TO BLIND YOU. Now, say you're using a 1W laser, that's 1000mW, 100 times what looking at the sun is, ENOUGH TO BLIND YOU INSTANTLY.

I lit paper on fire within 3 seconds with ~700mW's, focused of course. Your eyes focus the light into a small spot on your retina, what will it do to your eye's sensitive tissue?

Considering that Class IV covers the widest range of power levels of any class that question is hard to answer. Every laser from 500mW to the biggest in the world (many kW) is class IV, and so their effects will vary greatly, from a tiny burn over a couple seconds to instantaneous explosive destruction of material.

Lets just say it's bad....mkay? Really really bayad

I didn't apply my previous answer to eye damage, so I should add that in terms of danger to eyes, Class IV lasers generally cause instant burn damage to soft tissue when focused, and that includes being focused on a retina by the lens of an eye. In some cases, when the wavelength is such that it won't pass through the eye lens, it will instead heat the lens itself, also resulting in burn damage that can obscure vision. No matter what, any laser at or above 500mW poses a serious hazard if the beam enters the eye directly.

Typically, blindness does not occur except in cases of extremely high power or if the lens or other tissue (besides the retina) of the eye is severely damaged by either longwave IR or shortwave UV burns. Visible light and near IR/UV pass through the lens without heating (much) and are focused on the retina, increasing the already high intensity of the beam by compressing all the power into a smaller area, guaranteeing burn damage. Since the burned area will be small when the burn is created in the short time it takes for your blink reflex to kick in, the result is usually a dead area in the field of vision, not blindness. This dead area is very often not easy to notice afterwards since your brain "makes up" for the missing data. If you suspect you've taken a direct hit from a class IV laser you should go to an eye doctor ASAP.

I have a couple of 455 (1.5 - 2W) which are indeed class IV. However even before hitting those numbers, how about we consider something at the lower end of the classification ... around 500mw....

Im just fascinated by and scared of my collections. Some of the brightest things that i usually encounter are the sun and the flashes of cameras. And so, I cant help but wonder just how bright those 445 actually are hehe. Regardless of my fascination, i am still not mad enough to look at the direct dot. Sadly documentations use scales such as mW, W, as the representation of their power. Those scales are very hard to relate to in the real world. Replies such as 100 or 10000 times brighter than the sun are however, very easy to relate to, and im thankful for them ...even though 100-10000 is rather a large range lol....

I am rather a skeptic that i always dissemble my laser after use and wont even assemble them without goggles on. I dont want the risk of having them accidentally switched on.

thx heheh

Just keep the bullet-I mean battery- out of the barrel of your gun-I mean laser....

Dang, lots of slips there....wonder why..... :thinking:

How do Class 4 lasers compare to other forms of light-based devices? They're all dangerous and you should show caution. Concentrated sunlight is an environment hazard, can cause cancer, skin-burns, blind you, etc. It's like a Class 4 laser, but it's not a laser. Likewise a high powered flashlight can do the same, but again, not a laser.

What makes the laser different? Well, there are properties of lasers that make them more dangerous than other forms of light (coherency, etc.). What is important is that for lasers, the power-rating/wavelength/spot-size is known and therefore we can make good judgements on it might interact with the environment. If such a class system were made for flashlights, or sunlight, it would be the same thing, only those light sources usually aren't such a problem in their normal use. Lasers are a relatively exotic light source, so their properties are more precisely categorized for their purposes.

The major distinction between a Class 3b and Class 4 laser is that the Class 4 laser is an environment hazard, not just a eye hazard. You should treat anything Class 3b or above as permanent-damage dangerous to your eyes, but afford Class 4 lasers the additional precaution that they can be hazardous by just being in their vicinity during operation.

Eye damage due to reflections off non-specular sufaces, fires, skin damage due to indirect irradiation, etc. all constitute effects a Class 4 laser can produce. All this depends on wavelength, power density, etc. so what might be a Class 3b dangerous power level at one wavelength may be a Class 4 for another.

The "500mW" rating for Class 4 is just a catch-all power level so users don't need to work through calculations to determine what the "threshold" level is for a laser at a particular wavelength, spot size, etc. Note that laser Classes also depend on the environment they're in. A Class 3 or 4 laser can be treated as a Class 2 or Class 1 laser if it is properly sealed away so it is not a hazard. For example, you don't see laser projectors--with their 24x 1.5W 445nm lasers--rated as Class 4 laser devices. Rather they're only Class 4 when you put the laser diode in a device that can interact with other things in an unsafe manner.

So overall: with a Class 3b laser or above, you need eye protection. With Class 4 lasers, make sure your environment is made safe before using it, like make sure the beam doesn't hit something that'll burn or reflect and hurt your eyes that way. I've accidentally had a computer power cord in the beam of a 445nm laser and it started melting. That was stupid of me, but it was hard to see where the laser beam was going with goggles on. Make sure everything is secure before you run your lasers, so your laser doesn't accidentally roll off and hit you in the eye like it did with Xoul.

Comparing laser strength to sun strength is like comparing being hit by a bullet and beachball

ones energy is concentrated into a very small area, whilst the other isn't

from past reading, I believe <10mW is the strength of directly looking at the sun

wannaburnstuff said:

Just keep the bullet-I mean battery- out of the barrel of your gun-I mean laser....

Dang, lots of slips there....wonder why..... :thinking:

Click to expand...

While I definitely get your point and I agree that there is danger, I've never liked the laser = firearm analogy. There is danger, but being hit nearly anywhere on your body by hot lead is much more dangerous than almost any hit you could take from 99.9% of all lasers, and you're NOT going to die from being hit by any non-military hobbyist/show class laser, so the fatality potential with guns is WAY higher.

The reason I think that making this distinction is important is due to legislation. The last thing laser enthusiasts need is for legislators to begin comparing lasers to firearms. That outcome is probably far-fetched, as there isn't any real-world evidence to back the idea that lasers and firearms are equally dangerous, but who knows.. lawmakers are an odd bunch.

Shining a class 4 laser into your eyes will blind you - no need to discuss that much further.

However, the question of looking at the dot compared to a surface illuminated by maximum sunlight is interesting. Considering the light is reflected of some diffuse surface, is 1 cm2 in area, and the laser is powered at 1 watt:

Maximum sunlight rains down about 1300 watts of light per square meter. Conventient as the metric system is, that equates to 0.13 watts per cm2. Your laser will put a full watt on that same surface area, making that dot 7000 times brighter compared to the sunlight.

This may seem like a staggering figure, but the good thing about is that this laser dot will be point source that reflects in roughly 180 degrees in evenly. Looking at this dot from a meter away will -not- pose any permanent eye danger given the previous provisions, though it will be -very- uncomfortable in a dim environment.

Sorry to bump an older post, but I'm having trouble following this math.

I will take for granted 1300 watts of sunlight per m² and 1 watt of laser light per m². And a square meter contains 10,000 square centimeters by definition (100cm x 100cm). That gives us 0.13 watts of sunlight per cm² (1300W / 10000cm²).

The problem I have is with the 7000x figure. Because 1W / 0.13W = 7.69, so the laser is only about 7 times brighter than the sunlight.

I read this post earlier today, and I was just now thinking about it and it seems like you mixed up the units and converted the laser to mW before you made the calculation: 1000mW / 0.13W = 7692

But, no doubt the dot from a 1W laser is extremely bright and looking directly at it is dangerous.

Benm said:

However, the question of looking at the dot compared to a surface illuminated by maximum sunlight is interesting. Considering the light is reflected of some diffuse surface, is 1 cm2 in area, and the laser is powered at 1 watt:

Maximum sunlight rains down about 1300 watts of light per square meter. Conventient as the metric system is, that equates to 0.13 watts per cm2. Your laser will put a full watt on that same surface area, making that dot 7000 times brighter compared to the sunlight.

This may seem like a staggering figure, but the good thing about is that this laser dot will be point source that reflects in roughly 180 degrees in evenly. Looking at this dot from a meter away will -not- pose any permanent eye danger given the previous provisions, though it will be -very- uncomfortable in a dim environment.

Click to expand...

Only problem with that is that our eyes don't perceive brightness on a linear scale, it's more of a power squared curve. (Such as, 4W is about twice as bright as 1W)

bungy said:

Sorry to bump an older post, but I'm having trouble following this math.

I will take for granted 1300 watts of sunlight per m² and 1 watt of laser light per m². And a square meter contains 10,000 square centimeters by definition (100cm x 100cm). That gives us 0.13 watts of sunlight per cm² (1300W / 10000cm²).

The problem I have is with the 7000x figure. Because 1W / 0.13W = 7.69, so the laser is only about 7 times brighter than the sunlight.

I read this post earlier today, and I was just now thinking about it and it seems like you mixed up the units and converted the laser to mW before you made the calculation: 1000mW / 0.13W = 7692

But, no doubt the dot from a 1W laser is extremely bright and looking directly at it is dangerous.

Click to expand...

Your numbers are WAY off, mostly because a few faulty assumptions were made.

First, the human eye has an opening of about 8mm in the dark, 4mm in a lit room, and 2-3mm in broad daylight.

So, if you looked at the sun with fully dark adjusted eyes, you'd receive about a 65mW dose. If your eyes were bright adjusted, that drops to around 4-9mW.

Moreover, and this is the most important bit, THE SUN IS NOT A POINT SOURCE. It occupies a space of about 0.5 degrees in your field of view. So, when the image of the sun is projected on the retina, that 65mW is divided over a small area of the retina.

A laser, on the other hand, will be focused to what amounts to a POINT on the retina. This means that the power density of a 65mW laser shone into the eye would reach well over 100 times the power density on the retina.

This is why a 65mW laser will cause a retinal burn upon accidental exposure, but the sun will not (again, upon an accidental, brief exposure). A 1W laser is nearly twenty times that power. It will cause instant, irreparable damage. Class IV lasers have also been known to sever the optical nerve.

The power density of lasers on the retina ranges from hundreds to thousands of times higher than the sun.

So no, a 1W laser isn't 7 times worse in any way, shape, or form.

It concerns me that people newer to lasers are used to a 1W+ laser being "normal" and "boring." They do a few math problems, figure all the old-timers are overly concerned idiots, and then proceed to put themselves and others at risk (including those who land on this forum through Google searches). Safety glasses, people.

Wear your damn safety glasses.

Trevor