Pointers are used for teaching, industry and entertainment. Pointers can be battery cells and devices with solid-state lasers inside. The cost and power of laser pointers differ depending on the color.

Red light pointer

Red laser pointers are the cheapest in production, as the color spectrum does not require energy consumption and has the following characteristics:

• battery - ordinary batteries;
• the power of such a beam ranges from 1 to 100 mW;
• the service life of such products does not exceed 1-2 years.

Over time, the wavelength of the red laser decreases, the rays lose power due to a decrease in the safety factor of battery cells or due to burnout of diodes.

Red lasers

Green laser pointers

Devices equipped with a green color are more perceived by the human eye than all others, however, this rule is applicable only during daylight hours, at night the green color is perceived worse.

The green beam laser has the following features:

• basis for use - solid-state lasers equipped with diodes;
• efficiency factor - 20% of the rated power;
• power supply - button battery;
• the beginning of production - 2006 along with other color elements;
• the wavelength of the green laser is 532 nm.

Blue laser pointer

Blue laser pointers have a control and operation principle similar to green ones. Such pointers have the following characteristics:

• beam length - varies depending on the shade and is 445 nm for bright blue, 473 nm for dull (turquoise), and 490 nm for blue;
• probable harm to human health - the largest among all colors used in pointers;
• efficiency factor - 3%, which is one of the smallest indicators;
• the main element is solid state diodes.

Lu yellow

Yellow pointers are less common among others and have the following characteristics:

• beam length - 594 nm (one of the largest indicators);
• efficiency - less than 1% - the lowest in the class;
• service life - 2-4 years;
• working principle - solid state diodes;
• development - 2008.

Lu purple

A special type of light pointer associated with the emergence of a new technology for digitizing Blu-ray media. Such pointers have the following functions:

• light beam length - 405 nm;
• commissioning date - 2008;
• service life - 3-5 years;
• principle of operation - high power solid-state diodes.

Using laser pointers

The use of laser pointers has a wide range and extends to many areas of life. Most often they are used:

• for highlighting targets in collimator sights of firearms (pistols, rifles, machine guns), as well as target designators for artillery or aviation at short distances;
• in scientific activity, such pointers are used to detect gas in liquids when it is impossible to recognize it with an ordinary human eye;
• the Chinese green laser is used in astronomical research. Such pointers are used to study the boundaries visible to the eye and designate space objects, fix them. At night, scientists use pointers of various spectra to determine the direction of the stars, fixing it with a directed beam of light;
• in educational activities, such pointers are used to demonstrate presentations, lectures and scientific seminars that require demonstration using a color pointer;
• in political and social activities, pointers are used for presentations, to explain the schemes of social processes and to concentrate the attention of the hall, public, meeting.

Laser safety

The safety of using lasers, an integral part of their daily operation, such devices are not harmless and may pose a certain danger, depending on how the laser pointer is designed. The green ray has the highest danger.

The negative consequences when using the most powerful laser pointer without observing safety precautions can be as follows:

• if it gets into the eyes, even for a short time, the laser light can burn the retina of the eye, which will lead to visual impairment or partial loss of it. Such a hit can lead to fatal consequences if such a beam is used for pilots or car drivers (in 2013, blinding of civil aviation pilots on approaching cities became massive cases in Russia, which could lead to plane crashes);
• damage to the skin - when using powerful lasers with a strong light beam for several minutes, a 2-3 degree burn may remain on an open skin area.

These consequences have led to the legal prohibition of the possession of laser pointers in the territory of some countries, and from them follow the precautions when using such means:

• do not shine in the eyes- when using a pointer, it is forbidden to direct the light beam into the eyes of a person even for a short period of time in order to avoid burns to the retina;
• do not aim at open areas of the body- when using powerful lasers, it can also cause burns to the surface of the body;
• do not irradiate vehicle drivers - this can lead to transport accidents and property damage, up to and including death.

Photo of a laser pointer

What is the most powerful laser pointer

The market of laser pointers is saturated with new models every year, the trend of which is to increase the power due to the use of modern LEDs.

It is no secret that each of us in childhood wanted to have a device such as a laser machine that could cut metal seals and burn walls. In the modern world, this dream can easily come true, since now it is possible to build a laser with the ability to cut various materials.

Of course, at home it is impossible to make such a powerful laser installation that will cut through iron or wood. But with a homemade device, you can cut paper, plastic seals, or thin plastic.

The laser device can burn various patterns on plywood sheets or wood. It can be used to illuminate objects located in remote areas. Its area of ​​application can be both entertaining and useful in construction and installation work, not to mention the realization of creative potential in the field of engraving on wood or plexiglass.

Cutting laser

Tools and accessories that will be required in order to make a laser with your own hands:

Figure 1. Diagram of a laser LED.

• faulty DVD-RW drive with a working laser diode;
• laser pointer or portable collimator;
• soldering iron and small wires;
• 1 ohm resistor (2 pcs.);
• capacitors 0.1 uF and 100 uF;
• AAA batteries (3 pcs.);
• small tools such as a screwdriver, knife and file.

These materials will be quite enough for the upcoming work.

So, for a laser device, first of all, you need to choose a DVD-RW drive with a mechanical breakdown, since the optical diodes must be in good working order. If you don't have a worn drive, you will have to purchase it from the people who sell it for parts.

When buying, it should be borne in mind that most drives from the manufacturer Samsung are not suitable for making a cutting laser. The fact is that this company produces DVD drives with diodes that are not protected from external influences. The lack of a dedicated housing means the laser diode is susceptible to thermal stress and contamination. It can be damaged by light hand touch.

Figure 2. Laser from DVD-RW drive.

The best option for a laser would be a drive from LG. Each model is equipped with a crystal with different power levels. This metric is based on the writing speed of dual layer DVDs. It is extremely important that the drive is a writing drive, since it contains an infrared emitter, which is needed to make a laser. The usual one will not work, since it is intended only for reading information.

DVD-RW with 16X recording speed is equipped with a 180-200 mW red crystal. The 20X drive contains a 250-270 mW diode. The 22X high speed recorders are equipped with laser optics with a power of up to 300 mW.

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Dismantling a DVD-RW drive

This process must be done with great care, as internal parts are fragile and easily damaged. Having dismantled the case, you will immediately notice the necessary part, it looks like a small piece of glass located inside the movable carriage. Its base and needs to be removed, it is shown in Fig. 1. This element contains an optical lens and two diodes.

At this stage, you should immediately warn that the laser beam is extremely dangerous for human eyes.

If it hits the lens directly, it damages the nerve endings and a person can remain blind.

The laser beam is blinding even at a distance of 100 m, so it is important to be aware of where you point it. Remember that you are responsible for the health of those around you while such a device is in your hands!

Figure 3. Microcircuit LM-317.

Before starting work, you need to know that the laser diode can be damaged not only by careless handling, but also by voltage drops. This can happen in a matter of seconds, which is why diodes operate on a constant source of electricity. When the voltage rises, the LED in the device exceeds its brightness norm, as a result of which the resonator is destroyed. Thus, the diode loses its ability to heat, it becomes an ordinary flashlight.

The crystal is also affected by the temperature around it; when it falls, the laser performance increases at a constant voltage. If it exceeds the standard rate, the resonator collapses according to a similar principle. Less often, the diode is damaged by sudden changes, which are caused by frequent switching on and off of the device for a short period.

After removing the crystal, it is necessary to immediately tie up its ends with bare wires. This is to create a connection between its voltage outputs. A small capacitor of 0.1 μF with negative polarity and 100 μF with positive polarity must be soldered to these outputs. After this procedure, you can remove the wound wires. This will help protect the laser diode from transients and static electricity.

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Nutrition

Before creating a battery for a diode, it is necessary to take into account that it must be powered from 3V and consumes up to 200-400 mA, depending on the speed of the recording device. Avoid connecting the crystal directly to batteries as this is not a simple lamp. It can deteriorate even with normal batteries. A laser diode is a self-contained element that is supplied with electricity through a regulating resistor.

The power supply system can be adjusted in three ways with varying degrees of complexity. Each of them assumes feeding from a constant voltage source (batteries).

The first method involves regulation of electricity using a resistor. The internal resistance of the device is measured by detecting the voltage as it passes through the diode. For drives with a 16X write speed, 200 mA is sufficient. With an increase in this indicator, there is a possibility of damage to the crystal, so it is worth sticking to the maximum value of 300 mA. It is recommended to use a telephone battery or AAA finger batteries as a power source.

The advantages of this power scheme are simplicity and reliability. Among the disadvantages are the discomfort with regular recharging of the battery from the phone and the difficulty of placing the batteries in the device. In addition, it is difficult to determine the right time to recharge the power source.

Figure 4. Microcircuit LM-2621.

If you are using three AA batteries, this circuit can be easily fitted into a Chinese-made laser pointer. The finished design is shown in Figure 2, with two 1 ohm resistors in sequence and two capacitors.

For the second method, the LM-317 microcircuit is used. This method of arranging the power system is much more complicated than the previous one; it is more suitable for stationary type of laser systems. The circuit is based on the manufacture of a special driver, which is a small board. It is designed to limit the electric current and create the required power.

The connection circuit of the LM-317 microcircuit is shown in Fig. 3. It will require elements such as a 100 ohm variable resistor, 2 10 ohm resistors, a 1H4001 series diode and a 100 μF capacitor.

A driver based on this circuit maintains electrical power (7V) regardless of power supply and ambient temperature. Despite the complexity of the device, this circuit is considered the easiest to assemble at home.

The third method is the most portable, making it the most preferred of all. It is powered by two AAA batteries, maintaining a constant voltage level to the laser diode. The system retains power even when the battery level is low.

When the battery is completely discharged, the circuit will stop functioning, and a small voltage will pass through the diode, which will be characterized by a weak glow of the laser beam. This type of power supply is the most economical, with an efficiency of 90%.

To implement such a power system, you will need an LM-2621 microcircuit, which is located in a 3 × 3 mm case. Therefore, you may encounter certain difficulties during the period of soldering parts. The final size of the board depends on your skills and dexterity, since the parts can even be placed on a 2 × 2 cm board. The finished board is shown in Fig. 4.

The choke can be taken from a regular power supply for a stationary computer. A wire with a cross section of 0.5 mm is wound on it with a number of turns up to 15 turns, as shown in the figure. The throttle diameter from the inside will be 2.5 mm.

Any Schottky diode with a 3A value is suitable for the board. For example, 1N5821, SB360, SR360 and MBRS340T3. The power going to the diode is adjusted by a resistor. It is recommended to connect it with a 100 ohm variable resistor during the setup process. It is best to use a worn out or unnecessary laser diode when performing a functional test. The current power indicator remains the same as in the previous diagram.

Once you find the method that works best for you, you can upgrade it if you have the skills to do it. The laser diode must be placed on a miniature heat sink so that it does not overheat when the voltage rises. After completing the assembly of the power system, you need to take care of installing the optical glass.

Laser pointer- portable quantum-optical generator of coherent and monochromatic electromagnetic waves of the visible range in the form of a narrow beam. In most cases, it is made on the basis of a red laser diode, which emits in the range of 635-670 nm, and a collimator - a biconvex lens for organizing a narrowly directed beam. A similar device has rarer blue and purple pointers and so far (2016) even rarer green ones. Until the early to mid-2010s, green laser pointers had a complex structure and consisted of a solid-state laser pumped with an infrared laser diode and a subsequent nonlinear frequency doubling element.

The most common red laser pointers are up to 1-20 mW; pointers up to 100-200 mW are somewhat less common. The most powerful mass-produced pointers: green up to 1W and blue up to 5W, green up to 2W.

• Laser pointer

First, a neodymium-doped yttrium orthovanadate crystal (Nd: YVO 4) is pumped with a powerful (usually 200-1000 mW) infrared laser diode with λ = 808 nm, where the radiation is converted to 1064 nm. Then, passing through a crystal of potassium titanyl phosphate (KTiOPO 4, abbreviated as KTP), the radiation frequency is doubled (1064 nm → 532 nm) and visible green light is obtained. Generation and output of green radiation is provided by mirrors, one of which fully reflects radiation with a wavelength of 1064 and 532 nm and completely transmits pumping radiation of 808 nm, and the other fully reflects radiation of 1064 nm, but completely transmits 532 nm. The pump radiation is also partially reflected.

In most modern green laser pointers, yttrium vanadate and KTP crystals, together with resonator mirrors, are combined into a so-called "microchip" - a gluing of two crystals with mirrors deposited on the edge. To generate laser radiation, it is sufficient to focus the radiation of a pump laser diode inside the Nd: YVO 4 crystal.

The efficiency of the circuit strongly depends on the pump power and can reach no more than 20%. In addition to green light, such a laser emits significant power in IR at wavelengths of 808 and 1064 nm, so an infrared filter (IR filter) must be installed in such pointers in order to remove the remnants of IR radiation and avoid damage to eyes. In inexpensive versions of green pointers, such a filter may not be installed, in which case even a pointer with a power of 1-5 mW poses a serious danger to eyesight, since the power of infrared radiation can reach tens of milliwatts. The 1064 nm radiation is focused almost as well as the green one and poses a hazard when it hits the eye even at a great distance, while the 808 nm pump radiation is highly defocused and not concentrated along the beam, posing a hazard at a distance of up to several meters.

It is worth noting the high power consumption of green lasers - the consumed current reaches hundreds of milliamperes. Since the efficiency of generation and doubling rapidly increases with increasing pump power, an increase in the output power from 5 to 100 mW requires an increase in the consumed current only approximately twofold.

The small size of the green laser pointer does not allow installing a temperature stabilization system for the laser diode and active media in them. Temperature has a particularly strong effect on the wavelength emitted by the laser diode, which leads to its departure from the maximum of the neodymium absorption line and a drop in the output power. This leads to the fact that such pointers are unstable when the temperature changes. This disadvantage is partially eliminated by stabilizing the radiation power at the laser output. For this, a beam splitter is installed at the output (the role of which is played by an IR filter, from which part of the radiation is reflected) and a photodiode, and negative feedback is introduced. The disadvantage of this solution is the possibility of failure of the laser diode with a significant temperature deviation, at which the stabilization system, compensating for the drop in output power, is forced to significantly increase the current through it.

Blue laser pointers (473 nm)

These laser pointers appeared in 2006 and have a principle of operation similar to green laser pointers. 473 nm light is usually produced by doubling the frequency of 946 nm laser light. To obtain 946 nm, a crystal of yttrium aluminum garnet with additions of neodymium (Nd: YAG) is used.

Blue laser pointers (445 nm)

In these laser pointers, light is emitted by a powerful 1-5W blue laser diode. Most of these pointers belong to the 4th class of laser hazard and pose a very serious hazard to the eyes and skin, both directly and in the form of radiation scattered by the surface.

Blue pointers are widely used in connection with the serial production of high-power laser diodes, mainly for compact LED-projectors, for example, Casio Slim.

Violet laser pointers (405nm)

The light in the violet pointers is generated by a laser diode that emits a 405 nm beam. These lasers are used in Blu-ray Disc players. The 405 nm wavelength is at the edge of the human vision range and therefore the laser radiation from these pointers appears dim. However, the light from the pointer causes some objects it is directed at to fluoresce, which is brighter to the eye than the laser itself. Even the smallest of them are extremely harmful to the skin and eyes.

Purple laser pointers have been around since the advent of Blu-ray drives, with the introduction of the mass production of 405 nm laser diodes.

Using laser pointers

• Laser pointers are commonly used in educational settings and in business presentations instead of conventional pointers. They are built into projector remote controls or computer remote controls for presentations. Red laser pointers can be used indoors and outdoors in the evening. Green laser pointers can be used in the same conditions, but, unlike red ones, they are clearly visible on the street during the day and at long distances. The only drawback of laser pointers when pointing to a target is point jerking, since the human hand cannot remain stationary for a long time due to tremors.
• The spot of light produced by the laser pointer attracts cats, dogs and other pets, causing a strong urge to catch it, which is often used by people when playing with these pets. However, green laser pointers, due to the significantly higher beam brightness, can scare the animal. It should also be borne in mind that a laser pointer beam directed into the eyes of a person or animal can damage the retina.
• Green laser pointers can be used for amateur astronomy. On a moonless night, a green laser pointer can be used to point to the stars and constellations. Also, the laser pointer can be used to align telescopes and to study the shape of the surfaces of telescope mirrors (both by the shadow method and interferometrically).
• Precisely positioned laser pointer can be used as a laser designator to aim firearms or airguns.
• Laser pointers are used in their designs by radio amateurs, as a communication element within sight.
• The red pointer with the collimator removed is used in amateur holography. This is one of the few applications of a laser in everyday life, where the most valuable property of a laser is used, which fundamentally distinguishes it from an LED - the coherence of radiation. Not all laser pointers have sufficient coherence, so it may be necessary to select a suitable specimen and select a laser diode current. Coherence can be assessed at home, for example, by observing the interference with a 1 to 2 cm thick plane-parallel glass plate.
• In laboratory practice, a laser pointer (especially a green one) is a very useful tool that has many applications - in particular, it can be used to detect in a liquid, gas or any transparent substance (for example, optical glass) a small amount of mechanical impurities or suspensions, invisible to the unarmed the eye. Green, and in particular blue or violet pointers, in combination with a suitable filter that does not transmit its radiation, allow visual detection of weak fluorescence, for example, associated with surface contamination by organic substances.
• A laser pointer, as a source of narrowly directed coherent light, can be used in school physics lessons to demonstrate visual experiments in optics: reflection and refraction of light, diffraction and interference, fluorescence (with a green or blue pointer), light guides, and the like.

Safety

Laser radiation is hazardous in contact with eyes.

Conventional laser pointers have a power of 1-5 mW and are classified in hazard class 2-3A and can be dangerous if the beam is directed into the human eye for a long enough time or through optical devices. Laser pointers with a power of 50-300 mW belong to class 3B and are capable of causing severe damage to the retina of the eye even with short-term exposure to a direct laser beam, as well as specularly or diffusely reflected. Even low-power green DPSS pointers use much more powerful IR lasers internally and often do not provide sufficient IR filtering. Such radiation is invisible and because of this it is more dangerous for the eyes of humans and animals.

At best, laser pointers are only annoying. But the consequences will be dangerous if the beam hits someone's eye or is directed at the driver or pilot and can distract them or even blind them. In some countries, this can lead to criminal liability. For example, in 2015, a US resident was sentenced to 21 months in prison for briefly blinding a police helicopter pilot with a laser pointer. In 2017, in Germany, a 22-year-old resident of Germany was sentenced to a year and a half in prison for similar actions.

More and more "laser incidents" in Russia, Canada, the United States and the UK are demanding to restrict or ban laser pointers. Already in New South Wales, a fine is provided for possession of a laser pointer, and for "laser attack" - a term of imprisonment of up to 14 years.

The use of laser pointers is prohibited by FIFA football stadium safety regulations. One example of the application of this ban was a fine of 50,000

Laser pointers were originally marketed to replace conventional wooden pointers. Their main purpose continues to remain the same - indication on wall boards, maps, posters, paintings. However, most of the pointers sold on the wide sale are used with might and main not for their intended purpose. They are bought as toys, which is actively used by marketers and manufacturers. They offer hundreds of different models, with hundreds of times the power required to write on a board.

The device and principle of operation of laser pointers

All modern laser pointers from the lowest to the highest are semiconductor lasers. Gas lasers are not used. Semiconductor lasers have a simple design, they do not require complex power supplies, but it is theoretically impossible to build them at high power. It is limited to a few watts. This is more than enough for household pointers. A one watt laser beam with good converging optics will be confidently visible at a distance of up to 10 km.

Semiconductor lasers are very similar to LEDs. Light is generated in resonant structures. To understand the process, they can be represented in the form of antennas that are assembled into an array of many identical elements. This principle is used in television antennas (many of the same elements are installed one after another on the traverse) and in radars. In lasers, the role of "antennas" is played by the crystal structures of semiconductors. When a current is applied, electrons are converted into photons and the process of monochrome optical radiation begins.

The wavelength of laser light is very small - from 0.2 to one micrometer, so the emitting cells in the semiconductor crystal are nanoscopic in size. The crystal provides exactly the same lattice formation with a large number of cells. That is why the laser wavelength is strictly defined and cannot be changed after its production.

Power, drivers, batteries and accumulators

The laser diode can only be powered directly from the battery at very low power. For diodes from 50 milliwatts, a dedicated power supply is required. Its main function is voltage stabilization. Even a 0.1 volt change can drastically shorten the life of a laser diode.

The type of power supply determines the power of the laser pointer. It is always done with a power reserve. By the way, the power supply is one of the simplest and cheapest parts of the pointer. A typical option is a simple power driver on a circular board across the case. In the same way, power supplies for LED flashlights are made or, conversely, step-up converters, for example, for compact fluorescent lamps. Of the rechargeable batteries, 18650, 16340, 32650 are used. Batteries are ordinary AA, AAA, C and D. Watch batteries are often found in keychain pointers.

Typical models, form factors and power

The lower power limit for laser pointers is 1-5 milliwatts. The most powerful laser pointer is 10-20 watts. There are only three colors available for laser pointers: red, blue and green. Sometimes there are yellow models, but they are very expensive, these are exotic products. There are also greenish-blue lasers as a middle option. It is best to use green lasers - green laser. Their wavelength is as close as possible to the peak of the sensitivity of the human retina.

Based on green laser, there is a popular laser pointer for presentations in the form of a pen. There are models that are built into a regular handle. Large power from such products is not required, on the contrary, it will interfere and harm vision, making the light spot too bright.

Choosing laser pointers: what to look for

• Power is key. It is indicated in milliwatts and directly affects the price. The higher the power, the higher the price and the overall complexity of the product. More powerful laser diodes have a shorter lifespan. They heat up intensively during operation, and their luminous efficiency drops faster;
• Nutrition. Replaceable batteries are the best option. Laser pointers powered by watch batteries are completely unsuitable for continuous use. Another good option is the unified AA and AAA batteries. They are suitable for infrequent use. If the laser is taken as a rarely used toy, then AA batteries are the best option. Batteries are only justified with frequent use, or if you have another device that runs on the same batteries. Then they can be quickly rearranged;
• Case and heat sink. Die-cast aluminum body is the best heat dissipation. The tin and plastic case is only applicable for low-power models.

If a laser pointer is purchased not for presentations, but as an interesting souvenir or toy, then more power will be useful. The more power, the more interesting the laser pointer becomes. Its pointer will be visible from a greater distance.

The regulated power mode is very important. This will allow the laser diode to operate more sparingly and will last longer. Also, adjustable power adds new functions, for example, for a cat you need to set the lowest power mode. Cats respond well to red and green lasers. The precautions here are the same as with people. The feline eye is just as unprotected from lasers as the human eye.

What opportunities does a powerful laser open up?

• Long distance alarm. A powerful laser can replace pyrotechnic signaling devices. It is especially effective in mountainous areas with good visibility from settlements;
• Long distance measurements. For example, a 10 W green laser pointer can measure the curvature of the earth's surface;
• Using a high-power laser as a light source for strobe lights and other entertainment devices. Optical attachments for dividing the beam, highlighting various shapes and inscriptions come in countless varieties. You can always find the most unexpected options in them;
• Laser shooting range with laser burning of balls. The device works only at a short distance;
• Long distance laser fence. Photo relays, homemade lidars, optical communication stations and other devices.

Clouds can be illuminated with a powerful laser, which is an effective means of signaling. With a good set of circumstances, such a signal is even more noticeable than a flare. In the devices, powerful lasers operate in a pulsed mode.

A separate direction is associated with the use of powerful laser pointers for engraving. Only the most powerful models over 10W are suitable for this. Engraving is possible on soft materials such as wood.

Laser Pointer Precautions

Any, even the most low-power laser is extremely dangerous for eyesight, therefore the first and main safety rule when handling a laser pointer is not to direct it into the eyes. Green laser is the most dangerous for eyesight.

It is forbidden to use pointers at airports and on highways. There, a bright light spot (even if it does not blind anyone) can still create an emergency. The driver or pilot can be blinded by the laser pointer from a long distance. For high-power lasers, this distance exceeds one kilometer. This must be considered for safe handling. Safety glasses are included with the powerful laser pointers. They must be worn according to the instructions.

Advanced development of laser pointers

Semiconductor lasers already have very high efficiency. Nevertheless, the main direction of further developments is to increase the efficiency by selecting the composition and production technology. A powerful laser heats up quite intensely, which means that its efficiency is far from ideal. The efficiency of lasers grows in about the same way as LEDs. There is a similar production technology. Both are semiconductor light sources.

Other developments are underway in obtaining new colors for laser pointers. Oddly enough, this technical problem has not been solved either. Green laser and red have already become too familiar. Other colors of laser pointers would be very interesting, but semiconductors for producing yellow and orange lasers are still very expensive. Development is underway to make them cheaper.

I came across such statements on the net:
You can move the laser from the balcony and burn someone's retina. To you, parents, your children. Do you understand, huh? It is freely available on sale, without restrictions.
The burnt-out retina is not restored. Idiots who sell such things to the same idiots should be punished. If I see an idiot on the street with such a toy, I will take it away from the youngster and give it a couple of slaps in the face. For those who are older, I will punish them much more seriously, up to stab-cut and gunshot ones. Bought - burn the retina yourself. You expose others to danger - get it.

We will not discuss the question of the mental state of the author of such statements here, but we can talk about the safety of laser pointers.

To begin with, it is worth noting that a laser is, of course, a device that poses a threat to vision, and sometimes to life. In general, it should not be directed to where a person's face might be. And you can play with cats only using the least powerful models. For lasers more powerful than 5 mW, it is very desirable to have protective goggles, and if the power is measured in hundreds of milliwatts, it is not only dangerous, but also simply unpleasant to work without them.

BUT, the danger of modern pointers in the mass consciousness is greatly exaggerated. I have already touched on this topic in this article. Here I will cite separately the question of the danger of pointers, compressed from the point of view of artistry and expanded from the point of view of information.

Firstly, it is worth noticing right away that "bam - and you are blind" laser pointer cannot provide. Even if you deliberately direct the most powerful model directly into your eye. As a rule, this leads to the fact that another blind spot appears on the retina (in addition to what everyone already has from birth). Within a few months after the injury, the brain updates the "dead pixel map" and the stain ceases to cause discomfort. But the image of objects falling into the spot area, of course, is not perceived by the eye. Usually you need to make a special effort to notice this (search the Internet for "blind spot detection"). An acquaintance of mine, who was engaged in laser alignment, has several such spots, but in life they do not interfere with him in any way. Of course, this is not a reason to "get on the wrong side", especially since in some cases a much more serious loss of vision is possible. But this is a reason to stop being afraid that at any second someone can deprive you of your sight, shining a pointer from the balcony.

Secondly, it would be a serious mistake to assume that the light from the laser propagates strictly parallel. It has a certain divergence. For most pointers, it is within 1-2 mrad, and for the worst - 5 mrad and even more. Dangerous for vision is only the light that has entered the pupil of the eye, whose area does not exceed 50 mm 2 even on a dark night. The farther the eye is from the pointer, the smaller the fraction of its power can get into the eye. One well-known manufacturer of heavy-duty pointers lists in their characteristics, among other things, the range to which they pose a danger. For a 1000 mW (exactly a thousand) pointer with a divergence of 1.5 mrad, this is 150 m. Further, it does not pose a serious threat. But most of the pointers of such enormous power sold now have at least twice the divergence, which proportionally reduces the dangerous distance. So a ray that has "arrived" hundreds of meters away can no longer injure anyone. The same applies to the accidental hit of the reflected beam in the eye: in most cases, only specular reflection from a flat or slightly concave surface is dangerous. Reflections from a convex or matte surface can damage vision only with prolonged observation. only a small part of the radiated power enters the eye.

Finally, the power records have nothing to do with the power of those pointers that are sold in underground passages. Most likely, you will not find even 500 mW models there. On the strength of 200-300 mW. But even these numbers are greatly overestimated. Experience has shown that Chinese green pointers usually have a power that is 1.5-3.0 times less than the declared one. Sometimes they cheat even 10 times ... Although high-quality powerful pointers are getting cheaper, they are not at all as fast as they scare us. If five years ago a high-quality 300 MW model cost $ 1000, now the price has dropped to $ 300. Even if after another 5 years the price drops to $ 100, this is still clearly not the price at which schoolchildren will buy it en masse.