Laser safety clearly, or why you should not look into the laser beam

Today's article will be somewhat boring, because it raises issues that usually no one likes to discuss. And it will focus on the main, most important issues related to TB for working with lasers. I will try to talk about this unpleasant, but very important topic with a minimum of tedious letters and numbers that are so fond of giving in various "reference books on safe operation rules", having analyzed the main issues with the help of illustrative and accessible examples in the spirit of "what will happen if". What danger does the laser have in it? Are all lasers equally dangerous? We'll figure out.
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 3r33380. ATTENTION: This article may contain errors and inaccuracies, since I am not an expert in medical matters.
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 3r33380. for my 5w laser, , power density in the beam is 16 mWmm2. If we assume that such a beam is accidentally hit in the eye, then the damage will be comparable to that of a completely ordinary laser pointer at 100 mW, provided that the pupil diameter at this point is about 3 mm. But these are just my assumptions, I do not advise anyone to check in practice. Eye protection when working with such a laser is absolutely necessary.
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 3r33380. If we again refer to the damage dependence of the wavelength table shown at the beginning of the article, one might get the impression that lasers with radiation outside the visible and near-IR ranges do not need protection because the radiation will not reach the retina, because the ocular media are opaque at lengths waves shorter than 400 nm and longer than 3 microns. This is partly correct. Indeed, the retina will not suffer, since radiation with a wavelength of more than 3 μm is absorbed by the tear film, and with low power it is not dangerous. That is why low-power laser sources like laser range finders just translate into a wavelength of about 3 microns (erbium lasers). On the other hand, there is a serious risk of burning the cornea if the power is sufficient. When exposed to high-power UV radiation, damage occurs mainly through the photochemical mechanism, and in the case of far-infrared, through thermal damage. But power is needed more, by orders of magnitude greater than for lasers of the visible range. Figuratively speaking, lasers can be compared with different kinds of snakes, among which are poisonous, killing with one short bite, and boas, killing with the help of large and brute force for a long time and tediously until the victim suffocates. Lasers from the invisible UV and far IR ranges can be compared precisely with boas, since their power is the very “brute force”, especially for CO2 lasers emitting hundreds and thousands of watts at a wavelength of 10.6 microns. Here is an example of corneal burns from a CO2 laser.
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 3r33380. Laser safety clearly, or why you should not look into the laser beam
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 3r33380. With the question of "who is to blame," figured out, now turn to the question of "what to do." Or, what protection measures should be chosen when working with laser radiation. The main measure of protection from laser radiation is primarily the fencing of the path of movement of the beam, limiting its spread by scavengers at the end of the optical path. If the fence can not be organized - then eye goggles are necessary. Better when both protection measures complement each other. However, universal safety glasses do not exist, except, perhaps, such. Therefore, before choosing glasses you need to know exactly which lasers to deal with.
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 3r33380. All goggles are designed to protect against specific wavelengths emitted by lasers, and for good glasses the optical density is always normalized at each wavelength. Optical density is the coefficient of attenuation of points; in English-language standards, it is called OD-X, where X is a number indicating the number of orders of attenuation. Thus, for example, OD-6 means that glasses weaken radiation by 6 orders of magnitude, i.e. at ?00?000 times at a given wavelength. The attenuation of 1000 times will be referred to as OD-3 and so on. Good glasses always have instructions to them, in which it is written from which wavelengths of radiation they protect, and which ODs are for each wavelength. Also, good glasses always have a closed structure and fit snugly to the face, so that glare from radiation cannot pass under the glasses, bypassing the filters. Here are examples of really GOOD points. For example, the Soviet ZND-4-72 — SZS22 — OS23–? which I use. This is an example of an attempt to make more or less universal glasses, designed to work with common types of lasers. To do this, they have two types of filters. Glasses are made of soft rubber, well-fitting to the face, and have instructions.
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 3r33380. Blue light filters are designed to protect against lasers operating at a wavelength of ??? microns and ??? microns (ruby and neodymium lasers). An OD-6 density is guaranteed at these wavelengths. The same filters provide protection from radiation in the 630-680 nm wavelength range (helium-neon, krypton lasers) and in the 1.2-1.4 μm range, and OD-3 is stated for them. Orange filters provide protection against wavelengths in the range from 400 to 530 nm (blue and green lasers) with OD-6 and also in the range 1.2-1.4 microns with OD-3. Orange filters by themselves cannot provide any protection against the radiation of red lasers — they require blue filters. For convenience, the blue filters are made reclining.
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 3r33380. I always use these glasses when working with all of my powerful lasers, and they can guarantee protection, subject to the instructions. Unfortunately, they have a gap for yellow lasers, i.e. They do not provide guaranteed protection instructions and, therefore, do not possess complete universality. These glasses have a modern analogue for sale, but it is less versatile, since it does not have orange filters.
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 3r33380. Here is another example of GOOD foreign-made glasses. They have a solid rectangular glass that does not obstruct the review, and the text with the wavelength and OD parameters is cast directly on the glasses body.
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 3r33380. Now let's look at no examples of bad points, which I categorically do not recommend. This is all that plastic Chinese slag sold on aliexpress for 1-2-10 dollars. These glasses have neither full adherence to the face, nor instructions with the declared optical density at different wavelengths, nor certificates, nothing. And they are made of a rather delicate plastic. Are you ready to entrust the safety of your eyes to some nameless Chinese working for a bowl of rice? I am not ready. Do not buy Chinese slag, shown below.
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 3r33380. The only exception is CO2 lasers. Their radiation, generally speaking, "thermal" - the wavelength is too large, and does not even pass through a simple transparent glass and through a simple transparent plastic. Those. The GOOD glasses shown above are also suitable for protection against CO2 lasers. The BAD glasses shown here will also provide sufficient protection against the scattered CO2 laser radiation, but no more. I would still recommend glass, since the direct beam of such a laser will simply burn plastic.
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 3r33380. Separately, I would like to dwell on the security measures to which manufacturers of laser technological installations resort. In principle, if there is a CO2 laser on our laser machine, the protection that completely covers the processing field is not necessary at small power levels, such as up to 50 W. And so enough fencing of ordinary glass or plastic. In principle, even on laser machines with a CO2 laser with a power of many kilowatts, it is not always possible to encounter a fence against scattered radiation, since it does not pose a great danger, since this radiation is thermal and is perceived simply as heat flow when you look at Infrared heater. You feel discomfort - you can and go away. The lack of protection on machines with CO2 lasers is quite acceptable. But it is strictly forbidden on installations with receiving wide distribution of fiber lasers! The fiber laser operates at a wavelength of about 1 μm, which, as mentioned above, easily reaches the retina, at power levels already in units of watts, the scattered radiation is very dangerous for the eyes, and for such laser installations, the protection of the working field with blocking is MANDATORY Here is an example where this is done correctly. The entire working area of ​​these cutting machines is covered with glass that does not transmit diffuse radiation.
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 3r33380. Laser markers, engravers must also necessarily have a closed field, since this is also either fiber lasers or neodymium lasers operating in the Q-switching mode, very dangerous for the eyes. An example of how this should be correct.
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 3r33380. And now, a graphic picture of how the Chinese relate to our health. For such a performance of a laser engraver, you need to hit the head with a stick, write out a multi-million fine and deny the right to produce these machines. After all, the buyer, having seen such a machine without protection of the working field, decides that it is not needed, since the manufacturer has not installed it. When working, all the scattered and reflected radiation, especially during engraving on metal, will fly straight into his eyes. Unless of course he wore glasses. And I'm not sure that he will wear them. And if, when working with such a machine, he receives damage to the retina, he will have the full right to file a lawsuit against the manufacturer and easily win it by slup a large amount of money.
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 3r33380. So, do not buy Chinese slag, use the correct means of protection and do not look into the beam with the remaining eye!
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 3r33380. When writing the article, materials from the following sources were used, in addition to the bottomless depths of the Internet:
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 3r33380. 1. Grankin V.Ya. Laser radiation, 1977 3r33370.  3r33380. 2. www.repairfaq.org/sam/laserfaq.htm
 3r33380. 3. www.laserkids.sourceforge.net 3r33381. 3r33380. 3r33380. 3r33380.
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