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Technical requirements for anti-laser goggles

by:LASERRPAIR     2020-06-03
Laser light can damage the retina and even cause loss of visual function. ?????????? ????????People's instinctive defense response to strong light is: blink reflex is about 150 ~ 250ms, and pupil reduction reaction is about 0.25s. However, the time limit of pulsed laser is 10-3s, 10-9s, 10-12s. Therefore, it is not possible to rely on instinctive blink reflection to protect against the hazards of laser protection, and must wear laser protection goggles or goggles. ????????1. Performance ???????Anti-laser goggles should have the following characteristics: ???????1. Good attenuation to laser; ???????2. Strong visibility; ???????3. Maintain the transmittance of visible light. ???????Second, anti-laser goggles products ???????1. Reflective anti-laser glasses ???????Structure: On the surface of the general lens, on the side receiving light radiation, the optical thickness of the dielectric film with high refractive index and low refractive index is alternately sprayed by spraying method, which is 1/4 of the wavelength of the laser to be protected. ???????(1) Protection principle: When the laser passes through this multilayer dielectric film, due to the reflection and interference of the film to the laser, the transmitted laser is attenuated. As the number of layers increases, the attenuation index can be very high. ???????(2) Materials: There are many types of materials with high and low refractive index. Such as high refractive index material ZnS (zinc sulfide), low refractive index material MgF2 (magnesium fluoride). Reflective protective goggles with alternately sprayed multi-layer dielectric film (for any reflection of 1/4 of the fixed laser wavelength is the thickness of each film), 13 layers of sprayed laser can reduce the transmittance of the laser to be prevented by 99.6% : If ZrO2 is used as the dielectric film, it needs to be plated with 25 layers to reach 99. 6% attenuation rate. ???????(3) Matters needing attention: ???????a. Reflective protective glasses can attenuate the reflection of the laser beam incident on the protective glasses by 99.6%, and the intensity of the reflected back is still very high, causing damage to the reflected laser light to other people present on the scene, so no protection is worn Personnel with mirrors are not allowed to enter the laser working place; ???????a. Secondly, after the dielectric film is sprayed, there is a possibility of looseness and falling off; ???????a. It can only adapt to the irradiation of the specified laser wavelength without harming the eyes; different wavelength lasers should use different designated reflection-proof laser glasses; ???????a. When the second harmonic (that is, frequency-doubled light) occurs, the reflective goggles do not work. ???????Reflective anti-laser glasses are suitable for medical laser diagnosis and treatment. In use, in addition to doctors, nurses, and operators, patients should also wear. ???????2. Absorptive anti-laser glasses ???????These are goggles made of materials that absorb laser light. The thickness of the lens is proportional to the laser attenuation index. However, the thickness of the lens increases and the visibility decreases. With this absorption-type anti-laser glasses, it is necessary to have a certain degree of protection efficiency and a certain degree of visibility. ???????At present, there are no absorption type anti-laser glasses products on the market. Abroad reports that the absorption coefficient of green cellophane to neon laser is 98. Colored glass also has a certain protective effect against ultraviolet lasers. ???????3. Absorption reflection type anti-laser glasses ???????(1) Structure: ???????A glass with a thickness of 3 mm that can absorb ultraviolet light is used as a front lens, and a glass with a thickness of 3 mm that absorbs infrared light is used as a rear lens. ???????(2) Dielectric film material: ???????High refractive index zinc sulfide (ZnS), low refractive index magnesium fluoride (MgF2) and sodium fluoroaluminate are used interchangeably, and the coating thickness is 1/4 of the specified laser-resistant wavelength. ???????(3) Protection principle: ???????When the laser is incident on the lens, the laser in the ultraviolet band absorbs part of the glass that can absorb ultraviolet, and the other part is transmitted and reflected by the multilayer dielectric film out of the glass. The laser light that cannot be reflected by the multi-layer film belongs to the infrared band and is absorbed after entering the lens. This is a combined defense and absorption method to attenuate the incident laser light to a minimum. ???????Absorption-reflective anti-laser glasses have the highest attenuation rate at laser wavelength 900nm; followed by 300nm and 1000-1100nm; followed by 700-800nm ??and the worst effect at 400-600nm. ???????4. Explosion-proof laser glasses ???????(1) Structure: ???????Apply a layer of transparent special chemical film on the flat lens (the side that contacts the incident light). In this kind of glasses, the objects can be seen clearly. ???????The special chemical film is a polyvinyl alcohol lead azide film containing 1% carbon black, with a thickness of 10 (m. ???????(2) Protection principle: ???????Carbon black can absorb electromagnetic radiation in a wide range from the ultraviolet band to the far infrared band. When the laser incident exceeds the amount of injury, it will cause the film chemical to explode and blacken, making the lens completely opaque, thus protecting the eyes from laser damage . There is no selectivity for the wavelength of incident laser light. ???????(3) Matters needing attention: ???????a Applicable to the protection of laser and long pulse laser emitted by continuous laser; ???????b Because the reaction explosion time is 20 (s, it is not suitable for the protection of the Q-switch pulse laser; c c After the film detonates and turns black, the lens needs to be replaced, that is, it can only be used once. ???????5. Photochemical reaction type anti-laser glasses ???????(1) Structure: ???????Between the two lenses, a solution is injected, which produces a deep color after being irradiated by the laser to prevent the laser from damaging the eyes. ???????Solution: According to information reported in the United States, the solution uses a mixture of triphenylmethane dye and papain. ???????(2) Matters needing attention: ???????a. Lasers of different wavelengths only react to the color change of different specific chemical solutions; ???????a. The photochemical reaction time is 1 (s, only applicable to the protection of continuous wavelength and long pulse laser; ???????a. When the laser of another wavelength needs to be protected, the corresponding solution should be replaced. ???????6. Photoelectric type anti-laser glasses ???????(1) Structure: ???????The lens is composed of two pieces of polarized light glass. When assembling, the polarization direction of the light is vertical, and a ceramic piece containing Lan, lead, zirconium or lead titanium elements is sandwiched inside. A photodiode is also installed between the lenses, which can convert the incident laser light into a voltage. When the voltage applied to the electrodes on both ends of the ceramic sheet is different, the optical rotation performance is also different. ???????(2) Protection principle: ???????Since the lens is assembled in such a way that the polarization direction of the light is perpendicular, when the optical rotation performance of the ceramic sheet is 'zero', the glasses are opaque. The stronger the optical rotation performance of the ceramic sheet, the smaller the angle between the polarization directions, and the stronger the transparency of the glasses. By adjusting the voltage on the ceramic sheet, the optical rotation of the ceramic sheet can be adjusted. When the photodiode is irradiated with laser light, it generates a voltage that reduces the optical rotation performance of the ceramic sheet to zero, and the glasses are opaque, thereby protecting the eyes from laser damage. After that, the light transmittance of the glasses can be restored to the original state. ???????(3) Matters needing attention: ???????The photoelectric conversion time is 10ms, the scope of application is limited, the structure is complex, the mirror weighs 280g, and it is currently difficult to reach the practical stage. ???????7. Color-changing liquid crystal glass type anti-laser glasses ???????It is an absorption type protective glasses. It is made of silicon glass or special plastic containing halide crystal core. When the lens is not irradiated with laser light, it is transparent, and when it is irradiated with laser light, it changes color. Absorb the laser. After that, the lens returned to a transparent state. These materials have a broad absorption spectrum after changing color, and can absorb from near ultraviolet to visible and near infrared.
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