When you want to buy laser glasses, open the browser and you will see a wide variety of laser glasses.
Click and you will see lenses of various colors and various parameters.
At this time, how do you choose the laser glasses you need?
This article is designed to answer that question for you.
First of all, we need to understand what the various parameters of laser glasses 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 shielding wavelength means that the product is effectively shielded against a certain wavelength range.
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, first check whether the protection range of the protection product includes 532nm.
Sometimes the product will indicate that it is a dual-band protection product.
The shielding wavelength is 190-400nm/800-1100nm, which means the wavelengths of 190-400nm and 800-1100nm are shielded 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 do 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.
The OD value, which is fully called optical density in English, is translated as optical density value. Optically, it is the logarithm of the ratio between incident light power (EI)/energy (HI) and 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 light intensity will be attenuated by 10N times.
For example, if OD = 1, the light intensity will be attenuated 10 times; OD = 2, the light intensity 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. Normally the 1W laser seems to pose no danger.
Is OD2 enough?
The answer is no.
Firstly, EI/hi considers the amount of laser irradiance/irradiance, which is related to many coefficients such as output power, pulse energy, distance between the human eye and the beam, angle of incidence, reflectivity of laser light. surrounding environment, etc.
It is not a simple power output.
Simply put – in fact, laser-savvy workers know this best.
For the same output power, the peak power of the picosecond laser and the femtosecond laser must be different, and the corresponding protection coefficient (OD value) must be different;
Secondly, the human eye has a protective 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, 532 nm is generally referred to as dazzling light, that is, because the human eye is more vulnerable to damage than 532 nm, that is, the threshold is low and the human eye has a relatively high tolerance to CO 2 laser.
Therefore, the calculation of OD value requires 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 transmittance, and the Chinese name is visible light transmittance, which is simply the amount of visible light that can be transmitted by the lens.
What is visible light?
The 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 the 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 colored 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 1064 nm, because the wavelength of most light lasers is greater than 800 nm.
Going back to VLT, if the product is marked 70% VLT, it means that 70% of visible light can pass through.
This concept is a bit abstract if you don't pay much attention to it in normal times, but it affects the detailed operation of some jobs such as laser correction, equipment inspection, troubleshooting and medical laser surgery.
This is why medical laser glasses generally have higher VLT.
The following is a general visual experience of different VLTs, which can be used as a reference:
| VLT% | Lens perception | Application |
| 80-100 | No or very slight lens background | For beauty, fashion or visual comfort purposes, can be used at night |
| 43-80 | Some lens background colors can be seen | I can faintly feel the sunlight |
| 18-43 | Medium Tone | Relatively low brightness sunlight |
| 8-18 | Heavy tone | Suitable for strong light |
| Below 8 | Very deep lens tone | For extremely bright light, but not for night driving |
Additionally, the color of the lens itself will also affect the visual appearance.
The following is the comparison diagram of visual effects and corresponding parameters:
From the top and bottom 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 sunlight is stronger, the contrast will be more obvious – the light seen by the SD-1 will be much weaker with the SD-4;
The medical version of the SD-3 has higher definition and brighter field of view than the SQ-1 used for IPL photon beauty;
However, in the third group of photos, we can see that the sd-12 has the same VLT value (≥ 40%) as the sdua due to the intense color of the lens.
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 the SD-3 medical version is smaller, because the absorbed lengths of wave are different and the lens is light green, the human eye is more adaptable, resulting in a better visual sensation.
Once the guard band, OD value, and VLT are determined, you can choose your favorite style.
Styles vary according to different needs:
If you use it for a long time, it is recommended to choose a small and light one, which does 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 one-piece silicone gel frame and lens, which are very similar to some fashion blockbuster sunglasses, and the silicone is frosted to enhance the texture;
If you pay attention to the safety of protection (applicable to ultra-high-power equipment), you can choose glasses similar to ski glasses.
There are several styles of glasses, and you can choose according to your preferences, but there are three principles when choosing styles.
Please remember:
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 have the ability to prevent laser side eye damage, and the glasses clip obviously does not meet this requirement;
2. Do not blindly pursue beauty and choose glasses with metal parts, and do not wear metal jewelry near laser equipment exposed to laser, which should prevent mirror reflection from causing harm to others;
3. If you need to wear glasses at work, you should choose the style that can be worn with glasses at the same time.
Here, you should pay attention to this, because large-frame glasses are popular now, so when selecting and wearing glasses, you should focus on the frame height of the goggles. Sometimes it is not applicable to large frame glasses.
Finally, 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 make purchased protective glasses unusable: for example, the collimation point of some 266nm UV marking machines is purple.
However, generally, the protection wavelength of the UV marking machine is 190-540nm, which absorbs all the purple light, and the collimation point is invisible.
At this time, although protection requirements are met, workers cannot operate;
It also helps cosmetologists to buy IPL glasses, but the operation site cannot be seen because the VLT is too low.
Therefore, the manufacturer can be consulted in advance before purchasing.
In case of a similar situation, the manufacturer will have to recall the impractical products and recommend them again.
The competent manufacturer will also customize a product more in line with the actual scene according to the actual situation.
The above is professional advice on choosing laser protection products. I hope everyone can find their own laser protective glasses!
