Laser has the characteristics of high brightness, good monochromaticity, good coherence and strong directivity. It is a scientific research equipment often used by researchers, and it also plays an important role in our life, such as the laser pen in Figure 1. However, improper use will cause serious damage to human eyes and skin, and may lead to explosion, fire and other serious accidents. How to use laser correctly is an important matter related to personal safety. < / P > < p > in the process of using laser, the most easily injured organs are the eyes, including cornea, retina and lens. The damage of laser to human eyes mainly comes from the absorption of light. In the visible and near-infrared regions, due to the high transmittance of the refractive medium to the excitation light in this band, the refractive medium will focus the laser on the retina, and the external light will pass through the pupil The diameter of the pupil is 2.5-4 mm when there is light, while the diameter of the image point focused on the retina is about 10-20 μ M. therefore, the luminous flux density of external light entering the retina will be increased by more than 100000 times, In the dark environment, the pupil diameter is about 7-8 mm, which leads to higher luminous flux and greater damage to the retina. The laser with the wavelength range of 315 nm-400 nm is mainly absorbed by the lens. The damage caused includes photochemical damage and photothermal damage, and the consequences include cataract. Laser with wavelength range of 100 nm-315 nm and laser wavelength of 1.4 μ M-100 μ m mainly cause corneal damage. When the intensity of the light is high enough and the irradiation time is long enough, the laser will cause thermal damage to the cornea, and the ultraviolet part will lead to keratitis. < / P > < p > in addition to the eyes, laser can also easily cause skin damage during the use of laser. First of all, the exposure of laser to the skin will cause skin burning. The main reason is that the skin tissue has poor heat conduction capacity, and the heat can not be rapidly diffused, resulting in high local temperature, which leads to tissue protein modification. The degree of skin injury is related to the wavelength of laser, irradiation time and laser intensity. Ultraviolet light may cause skin cancer. < / P > < p > in our daily life, the common lasers are class I laser and class II laser. For class I laser, its power is in the order of micro Watt, which will not damage human skin or eyes without dismantling its internal devices, as shown in the laser printer), CD player, etc. The second type of laser is more common in our life, such as laser pen as shown in Figure 2), aiming device, distance measuring equipment, etc. For this kind of laser, we should avoid looking at the laser source for a long time, and do not aim the laser at other people’s eyes. In addition, the power of the laser pen sold on the Internet is a little too high. We should pay special attention to the laser equipment with power greater than 5 MW. In addition, try not to buy toys with lasers for children. If you have to buy them, you should try to ensure that the power is below 0.4 MV. Once the parents find the laser eye injury, they should go to the hospital in time. < / P > < p > Fig. 2 laser printer, laser pen, semiconductor laser, laser cutting machine. < / P > < p > in the laboratory, we are most exposed to three types of lasers. Improper operation of these lasers can easily hurt our eyes. In the laboratory with three types of lasers, we should pay attention to the following points: < / P > < p > 5. The height of the optical path should be designed to avoid being consistent with the height of the human eye when standing or sitting. The laser should be fixed firmly, and all optical elements in the optical path should also be fixed firmly to ensure that the laser only propagates along the predetermined path. Do not wear metal jewelry, such as watches, earrings, bracelets, etc. in the process of adjusting the light path, the reflection of these substances will make the laser randomly reflect the light path, and hurt the eyes of yourself or other people in the laboratory. When using infrared or ultraviolet laser or high-power pulse laser in optical laboratory, you should wear goggles, as shown in Figure 3. When selecting goggles, you should pay attention to the working wavelength range and other necessary parameters. < / P > < p > for class IV laser, in addition to the requirements of class III laser, due to its high power, the radiation of laser beam is enough to cause serious skin or fire threat, and protective measures must be taken on the surface of laser beam, people and inflammables. With the development of society, laser plays an increasingly important role in our life, from laser pen and printer in life to laser drilling in medical treatment and laser processing in industry. Therefore, we should know more about lasers and avoid the possible harm of lasers to us. Waistcoat line type abdominal abuse posture, shaping the perfect abdominal curve!