Protective Safety Goggles is a filter that changes the intensity and spectrum of transmitted light. The most effective and common way to avoid radiation damage to the eyes is to wear protective glasses. These glasses can absorb certain wavelengths of light, and let other wavelengths of light through, so they show a certain color, the color presented for the color of transmitted light. One for the absorption type, one for the reflection type, the former is used most. Goggles are used to change the intensity and spectrum of transmitted light, you can avoid radiation light on the eyes caused by a kind of glasses. These glasses are divided into two categories, one is the absorption type, one is the reflection type, the former is used most.
These glasses can absorb certain wavelengths of light, and let other wavelengths of light through, so they show a certain color, the color presented for the transmitted light color.
Manufacturing materials
This lens in the manufacture of the general optical glass formula and then add a part of the metal oxides, such as iron, drill, chromium, strontium, nickel, manganese and some rare earth metal oxides such as and neodymium. These metal oxides can make the glass selective absorption of electromagnetic waves in certain wavelengths of light, such as cerium and iron oxides can absorb a large number of ultraviolet light. The use of such glass lenses can reduce the amount of certain wavelengths through the lens to reduce or prevent damage to the eye. Different colors of protective lenses can absorb different colors of predominantly light. These glasses are divided into two categories, one for absorbing and one for reflecting, the former being the most used.
The lenses are generally round, and the specifications are expressed by their diameters in mm, such as φ48, φ50, φ52, φ56, φ60, φ65 and φ70. The most commonly used are φ56, φ60 and φ65. Due to the popularity of large frames, the use of large size lenses such as φ70 has increased.
Lens size
The size and shape of the eyeglass lenses that conform to the shape of the frame after processing of the rough lenses naturally depend on the curve of the inner edge of the frame. The lenses should indicate the horizontal direction and the nose side, otherwise the non-symmetrical shape of the lenses will become a completely different shape after turning. The size of the lens is indicated by the length of the baseline and the height of the baseline (baseline method), i.e. AA'×B'B, in mm (e.g. 46×40); or by the horizontal and vertical dimensions of the outer cut rectangle (box method).
The shape of the lens is expressed by the shape difference. The so-called shape difference is the difference between the length of the baseline and the height of the baseline (baseline method), or the difference between the horizontal and vertical dimensions of the outer cut rectangle (box method). Not specified for the baseline method. For example, for a 46 x 40 size lens, the shape difference is 6 (i.e. 46-40). Some lens families have different piece shapes that are indicated by the difference in shape. A shape difference of 3 or 4 is a high shape; a shape difference of 10 is a short shape. Earlier lenses were symmetrical - round or oval. Round lenses have a shape difference of 0, short oval 4, long oval 9. The semicircle is connected to the semi-ellipse as "Pantoscopic Round Oval" (PRO), and there are various shape differences, the larger one is called "wide field" shape. There are also "contour shapes". There are also "contour", "square", "infinity" and "sports" shapes. The changes in the shape of lenses are mainly due to the constant renovation of modern eyeglass frames. Frames with different baseline lengths (e.g. 40, 42, 44, 46) can have the same shape difference4 (e.g. 40×36, 42×38, 44×40, 46×42), but they are not proportional to each other, so the shape varies.
Mirror cut
In the box method, it is the difference from the horizontal dimension of the outer cut rectangle. Therefore, LSWF should indicate whether the box method. the LSWF is determined by finding the geometric center of the frame or the cut lens that conforms to the shape of that frame, which is the M point in the baseline method; measuring the maximum distance from the center of the collection to the edge of the frame or lens; twice that distance is the diameter of the smallest uncut lens; in measuring the baseline length of the scene or lens; finding the difference between the diameter of the smallest uncut lens and the length of the baseline, which is the LSWF. The maximum distance from the geometric center of the lens (M) to the edge of the lens is 29 mm, so 58 mm is the minimum diameter of the required lens. If the baseline length (AA') is 48mm, the LSWF is 10mm. The LSWF, which can be cut by selecting the appropriate size of hair piece, is especially important when the lens needs to be center-shifted. If the manufacturer can indicate on each pair of frames the LSWF of the frame, it will be easy to determine the minimum size of the required hair piece before cutting the lens to be centered. The thickness of the lens can be measured with a lens thickness caliper (thicknesscaliper). Placing the lens between the jaws J, the pointer P will move a certain distance d on the circular surface, which indicates the thickness of the measured lens, with a scale accurate to 0.1 mm, which can be obtained by the principle of similar triangles: moving distance d = thickness of the lens × CP/CJ Usually the long and short arms of the caliper are designed in a 4:1 ratio, i.e. CP/CJ is 4, then the thickness of the lens is d/4 mm, and the circular scale can be determined from this.
Diopter
Lens diopter meter (spherical meter).
The meter measures the dip s between K of L. Where the distance from K to L is 2y, the middle movable stylus is connected to the surface pointer by a gear, and the surface scale is the diopter.
Goggle
According to the approximate vertical formula in Chapter 6, the resulting diopter is: F = s × 2000 (n-1) / y2 formula in 2000 (n-1) / y2 for the table is a constant. If the table between the two fixed stylus distance of 20mm, the measured lens emissivity set at 1.523, then the constant is: 2000 (n-1)/y2 = 2000 × 0.523/102 = 10.46
Then the formula (16-1) is: F=10.46×s If the middle active stylus is 1mm below the fixed stylus line, the reading of the lens meter will be F=10.46×1=+10.46D; if s is 0.5mm higher, the scale reading will be +5.23D. If the middle active stylus is longer than the two fixed stylus lines, the pointer will turn in the opposite direction and the reading will be negative. Some lens meters can measure in the ±20.00D range. Although the approximate dip formula has been able to explain the principle of the lens meter, in practice, the scale of the lens meter is still corrected for the exact dip formula. When the middle active stylus is compressed by 1mm, the corrected scale is actually +10.37D instead of +10.46D. When measuring the spherical lens reading, the stylus is placed vertically on the concave surface of the lens being measured, and when all three styli are in contact with the mirror surface, the reading indicated by the surface pointer is read, and then the convex surface is measured to obtain another reading, and the algebraic sum of the two numbers is added, that is, the reading of the lens, and the absolute value of the larger reading is in the - or + mark that the lens is a negative lens or positive lens.
Measure the column mirror, the lens clockwise rotation, one side (generally in the convex side) the pointer indicates a change in the reading, the side that is the astigmatism. The difference between the largest and smallest scale on the surface for the astigmatism reading, the smallest scale of the meridian direction for the column mirror axial. The error measured with the meter, 6.00D below the lens in 0.1D or less, 6.00D or more in 0.25D or less. However, when the stylus is worn or the stylus is not perpendicular to the mirror surface, there can be a larger error. Attention should be paid to the correct measurement and regular correction of the zero position with the standard plane.
Classification
Absorptive
Absorption filters are lenses that absorb certain wavelengths of light in order to reduce the intensity of light entering the eye.
Sun shading glasses
Also known as sunglasses, the transmission rate of visible light is about 20%, and the absorption of ultraviolet and infrared light is better. There are light green, light gray, light tea and other colors, used to create sun shading and snow work protective glasses. Among them, light gray lenses have the least effect on color recognition; light tea glasses make the blue sky look darker and make green light transmittance reduced; light green lenses make red light transmittance reduced.
Gas welding goggles
The coloring agent used in this lens is mainly iron oxide, cobalt oxide, etc., yellow-green, can absorb all the light waves below 500urn wavelength, the transmission rate of visible light is below 1%, only a small amount of infrared light can pass. These glasses are designed for gas welding operation welding.
Eye protection glasses for welding
The ultraviolet light produced by welding can cause damage to the cornea and conjunctival tissue (28nm light is the most serious) when irradiated to the eye for a short time. The intense infrared light produced can easily cause clouding of the eye lens. Goggles for welding are good at blocking the above infrared and ultraviolet rays. These lenses are based on optical glass and use coloring agents such as iron oxide, cobalt oxide and chromium oxide, in addition to adding a certain amount of cerium oxide to increase the absorption of ultraviolet light. The appearance is green or yellow-green. Can block all ultraviolet light, infrared transmission rate is less than 5%, visible light transmission rate is about 0.1%.
Blue eye protection glasses
There are two kinds of these glasses, one for iron oxide and cobalt oxide coloring, with it to see the filament for purple, the other is to copper oxide, manganese oxide coloring, with it to see the filament for white. They can all absorb 500-600nm (visible light sensitive area of the human eye) band of dazzling glare, light transmission rate at 400nm at 12% or less, also has a certain absorption effect on ultraviolet light, suitable for a variety of industrial high-temperature furnace furnace operators to wear.
5, crimson glass glasses This kind of glasses lens is a cadmium sulfide, cadmium sulfide selenide coloring of crimson glass, it can absorb all the light in the wavelength band below 600nm. Can be used as medical or industrial personnel operating X-ray fluoroscopic equipment goggles.
Laser protective glasses
These glasses have two forms, namely reflective and absorptive, the former surface using vacuum coating method coated with a metal film, the wavelength of 532nm, 694nm and 1060nm and other laser wavelengths reflectivity of more than 99.5%; the latter lens to 1060nm laser wavelengths can be absorbed. The lenses must be equipped with a closed or semi-closed frame to prevent the laser from bypassing the lens and entering the eye. They can be used as protective eyewear for laser operators.
Microwave Protective Eyewear
Microwave is a wavelength of about 1nm-lM electromagnetic wave, it can also cause harm to people, especially the eyes. If under the effect of strong microwave, it can cause eye fatigue, dry eyes and dizziness, and can even lead to crystal clouding, cataract and retinal damage. It is protected by using a lens surface sprayed with tin tetrachloride and metal compounds that can increase the conductivity, forming a multi-layer conductive film on the surface of the lens, which acts as a shield against microwaves. Because microwaves can bypass the lens and enter the eye, the frame should also be shielded to prevent microwave damage to the eye.
Reflection type
Absorption filters, because the lens absorbs some light, into heat release, especially infrared and some other waves of longer light, due to the accumulation of heat generated, so that the eyes feel very uncomfortable. If the use of reflective filters can be a good solution to this problem. As introduced in the previous coated glasses, if the surface of the lens is coated with a layer of refractive index higher than the refractive index of the lens itself, it will increase the reflection of light and reduce the transmission of light intensity, so that the eyes can be protected from bright light and harmful rays. In actual working life, many cases of absorption and reflection are used in combination, that is, the tinted lens and then coated with a highly reflective film, so that the filtering effect is stronger, such as welding, chlorine arc welding, plasma cutting and other operators wear glasses, can be solved by this one method. Glass factory production of optical glass blanks, by a series of optical factory grinding, polishing and other processes, made with a certain diopter and shape of the glass sheet, known as the lens (gross, uncut lens). To make eyeglasses is to select the appropriate lenses for cutting, grinding and other processes to make them conform to the shape of the frame, and then put on the frame. Although the lenses are inspected and marked at the factory, the dispenser should also measure, mark and inspect the lenses to ensure that each pair of eyeglasses meets the prescription requirements accurately, and ultimately achieves correction, comfort and cosmetic purposes.
Viewing the Solar Eclipse
The most common goggles are the welding goggles with a shade number of 14, which can be bought in the welding equipment market. a common color goggles price is generally about 5 yuan. The German Bard film silver lens goggles 10 yuan, black lens of 15 yuan. Most of these store owners selling goggles are "halfway", taking advantage of the sky to earn a fortune.
According to experts, with astronomical telescopes or naked eye observation of the sun, must be added beforehand Bard film or other light filtering devices, otherwise it will burn the fundus and instruments. Among them, Bard film is not only stronger contrast, and can make the sun show the true color. The reporter searched Taobao and found that in most of the online stores selling paper eclipse observation mirrors, they are under the banner of "Bard film", but most of them do not indicate whether they have been tested by professional departments. In this regard, experts reminded that, according to international standards, the use of density value 5.0 Bard film observation mirror can be used for the observation of the total solar eclipse, and such a reasonable price of solar eclipse observation mirror in about 5 yuan. Qualified protective mirror surface to look at the sun, the sun will appear gray-white, see the ground for black, basically can not see other things.
