# How to Buy Laser Goggles?

When you want to buy laser goggles, open the browser and you will see a wide range of laser goggles.

Click in and you will see lenses of various colors and various parameters.

At this time, how do you choose the laser goggles you need?

First of all, we need to understand what the various parameters of laser goggles mean.

For laser protective products, especially laser protective glasses and protective windows / glasses, the three most important parameters are protective wavelength, OD value and VLT.

The protection wavelength means that the product is effectively protected against a certain wave band.

If you fill in 190-540nm OD4 +, it means that the average minimum protection from 190nm near UV laser to 540nm green laser is OD4, and the protection of some wavelengths will be OD5, OD6 or even close to OD7. Each product will be very different in this part.

When you have a 532nm laser, you should first see whether the protection band of the protection product includes 532nm.

Sometimes the product will indicate that it is a dual band protection product.

The protection wavelength is 190-400nm / 800-1100nm, which means that the wavelengths of 190-400nm and 800-1100nm are protected at the same time.

If you want to operate 532nm and 1064nm laser equipment, this dual band protection product is the most applicable.

However, if you only operate 355nm and will not touch devices with wavelengths above 800nm, you can choose 190-540nm or 190-400nm products that are not dual band protection, covering the wavelengths you want to protect, because generally speaking, the price of dual band protection products will be higher.

OD value, which is fully called optical density in English, is translated as optical density value. Optically, it is the logarithm of the ratio of incident light power (EI) / energy (HI) to transmitted light energy (EL) 10.

The calculation formula is: D = LG (EI / EL) or D = LG (HI / EL).

Simply put, if the OD value is n, the intensity of light will be attenuated by 10N times.

For example, if OD = 1, the intensity of light will be attenuated by 10 times; OD = 2, the intensity of light will be attenuated by 100 times.

Then someone will ask, my laser is 100W, and the attenuation is 100 times, that is 100W / 100 = 1W.

If you wear OD2 glasses, 1W will enter your eyes. Usually 1W laser seems to be no danger.

Is OD2 enough?

Firstly, EI / hi takes laser irradiance / irradiation amount, which is related to many coefficients, such as output power, pulse energy, distance between human eye and beam, incident angle, light reflectivity of surrounding environment, etc.

It is not a simple output power.

To put it simply – in fact, workers who know about laser know this better.

For the same output energy, the peak power of picosecond laser and femtosecond laser must be different, and the corresponding protection coefficient (OD value) must be different;

Secondly, the human eye has a protection threshold for lasers of different wavelengths, that is, at a certain value, the human eye can absorb the laser of a specific wavelength and will not be damaged, but this threshold changes with the wavelength and pulse width.

For example, 532nm is usually referred to as blinding light, that is, because the human eye is more vulnerable to 532nm damage, that is, the threshold is low, and the human eye has a relatively high tolerance for CO2 laser.

Therefore, the calculation of OD value needs professional calculation.

After selecting the protection band, it is recommended that you show the detailed parameters of the laser equipment to the salesperson, who will give you professional OD value suggestions.

Then there is VLT, the full English name is visible light transmission, and the Chinese name is visible light transmittance, which is simply how much visible light can be transmitted by the lens.

What is visible light?

Encyclopedia’s explanation is: visible light is the part of the electromagnetic spectrum that the human eye can perceive, and the visible spectrum has no precise range;

The frequency of electromagnetic wave that can be perceived by ordinary people’s eyes is 380 ~ 750thz, and the wavelength is between 780 ~ 400nm, that is, people can see color light in daily life, such as 450nm (blue light), 532nm (green light), 600nm (red light) and so on.

However, many fiber lasers are invisible light, such as 1064nm, because the wavelength of most light lasers is greater than 800nm.

Back to VLT, if the product is marked with 70% VLT, it means that 70% of visible light can pass through.

This concept is a little abstract if you don’t pay much attention to it at ordinary times, but it affects the detailed operation of some work, such as laser correction, equipment inspection, troubleshooting, and laser surgery of medical laser.

This is why medical laser goggles generally have higher VLT.

The following is a general visual experience of different VLTs, which can be used as a reference:

In addition, the color of the lens itself will also affect the visual appearance.

The following is the visual effect comparison diagram and corresponding parameters:

Through the upper and lower comparison diagram from left to right, we can feel that the VLT of SD-4 is lower than that of SD-1, which shows that the overall visual brightness is darker.

When the sunlight is stronger, the contrast will be more obvious – the light seen by SD-1 will be much weaker with SD-4;

The medical version of SD-3 has higher definition and brighter field of vision than SQ-1 used for IPL photon beauty;

However, in the third group of pictures, we can see that sd-12 has the same VLT value (≥ 40%) as sdua due to its heavy lens color.

At the same time, if we compare SD-1 (VLT ≥ 70%) and SD-3 medical Version (VLT ≥ 60%), we can also see that although the VLT of SD-3 medical version is lower, because the absorbed wavelengths are different and the lens is light green, the human eye is more adaptable, resulting in better visual feeling.

When the protection band, OD value and VLT have been determined, you can choose your favorite style.

The styles vary according to different needs:

If you wear it for a long time, it is recommended to choose a small and lightweight one, which will not bring great pressure to the bridge of the nose and ears;

If you pursue the sense of fashion and texture, you can choose the frame and one-piece lens with silicone gel, which are very similar to some sunglasses in fashion blockbusters, and the silicone is matte to highlight the texture;

If you pay attention to the safety of protection (applicable to ultra-high-power equipment), you can choose glasses similar to ski goggles.

There are various styles of glasses, and you can choose according to your preferences, but there are three principles when choosing styles.

1. Try not to choose the type of glasses clip.

According to the requirements of GIB1762 for laser protective glasses, article 4.7 clearly requires that protective glasses should have the ability to prevent lateral laser eye damage, and the glasses clip obviously does not meet this requirement;

2. Don’t blindly pursue beauty and choose glasses with metal parts, and don’t wear metal jewelry next to laser equipment exposed to the laser, which should prevent mirror reflection from causing damage to others;

3. If you need to wear glasses at work, you must choose the style that can be worn with glasses at the same time.

Here, you should pay attention to it, because large frame glasses are popular now, so when selecting and wearing glasses, you should focus on the height in the frame of protective glasses. Sometimes, it is not applicable to large frame glasses.

Finally, the after-sales service also needs our attention, because although the protection of laser glasses on the market can cover the protection requirements of almost all types of laser wavelengths, there will always be differences between different laser equipment due to different manufacturers.

It is inevitable to encounter individual situations in the production process, which makes the purchased protective glasses unusable: for example, the collimation spot of some 266nm UV marking machines is purple.

However, generally, the protection wavelength of UV marking machine is 190-540nm, which absorbs all purple light, and the collimating spot is invisible.

At this time, although the protection requirements are met, the workers cannot operate;

It also helps cosmetologists buy IPL goggles, but the operation spot cannot be seen because the VLT is too low.

Therefore, the manufacturer can be consulted in advance before purchase.

In case of similar situation, the manufacturer should recall the impractical products and recommend them again.

The capable manufacturer will also customize a product more in line with the actual scene according to the actual situation.

The above is the professional advice on choosing laser protection products. I hope everyone can find their own laser protection glasses!