Lasers are not only used in an industrial factory but also at a wide variety of daily life situation such as medical or cosmetic fields.
Although lasers are now common place, some lasers can be dangerous and even cause bodily harm. Therefore, workers and managers who handle lasers need to know their characteristics and protect themselves from the dangers of laser light.
What makes lasers dangerous?
Lasers are a special type of artificial light that does not exist in nature world. Its properties are completely different from natural light, general light sources such as light bulbs, and welding light.
Characteristic 1: Directivity
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Typical light source
Typical light scatters in all directions. Therefore, the absolute amount that enters the eye is small.
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Laser light
Laser light shines far and regularly toward a single point, known as "directivity". Even if the laser power is low, the energy applied is high.
Characteristic 2: Monochromatism
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Typical light source
A polychromatic light source that mixes multiple lights (wavelengths). Even if the light enters the eye, the crystalline lens's refraction index for each wavelength differs, spreading the light so it does not focus on one location.
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Laser light
Monochromatic light source. High energy density due to single wavelength. When laser light enters the eye, it condenses at the crystalline lens and the powerful light concentrates on one spot in the retina, which is extremely dangerous.
Wavelengths' effect on the eye
As for types of lasers, there are visible lasers which the eye can detect and invisible lasers which the eye cannot detect.
The part of the eye which can be harmed and the extent of the harm differs by the laser's wavelength, time, and strength. Even low-output lasers can greatly affect the eye, causing more damage to the retina than expected, which can result in vision loss, or in worst case scenario, permanent vision damage like blindness.
Lasers can harm not only the eyes but also cause injury to the skin. Care is also required in using lasers as respiratory disorders from workers breathing in the fine particulate matter created through use of laser equipment, electrocution, and gas poisoning can occur.
Basic approach to laser safety measures
The most important issue with laser safety is devising a method of use which will not expose the eyes or skin to a laser.
First (Step 1), set up the work environment and safety measures so as not to expose the laser to the outside.
Next (Step 2), devise a way in which workers will not have to look directly at laser light by removing any direct exposure to it. Considering whether a substitute for visual confirmation, such as use of a laser window or remote operation of a camera, etc., is possible.
Finally (Step 3), be sure to wear protective equipment suited to the situation should direct confirmation of the machining state or finished product be necessary while working and in an environment using laser light.
Safety measures for protection from laser light
Laser safety equipment must be suited to the laser device's wavelengths, output, and oscillation method. Using a safety filter (eyewear, window, curtain, etc.) attenuates the laser light entering the eye to a safe level.
• What is optical density (OD)?
Optical density (OD) is the density required for harmful light not to pass through and harm the eyes even if laser irradiation is experienced. An OD value indicates the numerical value and makes it easy to understand the absorption and dampening abilities as laser light passes through a protective filter. The higher the OD value, the better the filter blocks laser light and offers more protection.
| Optical density (OD) | Permeation rate | Dampening rate |
|---|---|---|
| 0 | 100% | 0 |
| 1 | 10% | 1/10 |
| 2 | 1% | 1/100 |
| 3 | 0.1% | 1/1000 |
| 4 | 0.01% | 1/10000 |
| ↓ | ↓ | ↓ |
| 10 | 0.00000001% | 1/10000000000 |
• What is maximum permissible exposure (MPE)?
Maximum permissible exposure (MPE) is the amount of light which will be least dangerous should you be exposed to a laser. The MPE is determined as 1/10th of 50% incidence of harm due to irradiation to the body (eyes or skin).
