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First, the material type of LED lens:
1. Silicone lens; a. Because silicone is high temperature resistant (can also be reflow soldered), it is usually packaged directly on the LED chip; b. The general silicone lens is small in volume, diameter 3-10mm;
2, PMMA lens a. Optical grade PMMA (polymethyl methacrylate, commonly known as: acrylic) b. Plastic materials, advantages: high production efficiency (can be completed by injection molding); high transmittance (3mm thickness penetration) 93% or so); Disadvantages: 70% temperature resistance (heat distortion temperature of 90 degrees, in order to match the temperature range that PMMA can withstand, when using PMMA lampshade, it is often necessary to consider increasing the distance between the light source and the lampshade or reducing the output power of the light source);
3. PC lens a. Optical grade nylon material Polycarbonate (referred to as PC) polycarbonate b. Plastic materials, advantages: high production efficiency (can be completed by injection molding); high temperature resistance (130 degrees or more); disadvantages: light transmittance is slightly lower (87%); 4. Glass lens optical glass material, with high light transmittance (97%) high temperature resistance, shortcomings: fragile, aspherical accuracy is not easy to achieve, low production efficiency, high cost.
Second, the application classification of LED lenses
1. Primary lens a. The primary lens is directly encapsulated (or bonded) on the LED chip holder and integrated with the LED; b. The LED chip is 360 degrees theoretically, but the chip is actually placed on the LED holder. It can be fixed and packaged, so the maximum illumination angle of the chip is 180 degrees. In addition, the chip will have some stray light, so that all the light of the chip can be effectively collected by a single lens and can be obtained, for example, 160 degrees, 140 degrees, 120 degrees, 90 degrees. The angle of light of even 60 degrees (different needs); c. The primary lens uses PMMA or silica gel material.
2. Secondary lens a secondary lens and LED are two independent objects, but they are inseparable when applied; b secondary lens function is to condense the large angle light of LED (usually 90-120 degrees) into 5 degrees to 80 degrees of any desired angle; c secondary lens material mostly uses PMMA or glass.
Third, LED lens specification classification
1. Transmissive (convex lens, the radius of curvature of the convex surface of a single convex lens is calculated by the following formula: 1/r1-1/r2=1/f(n1-1) where f-lens focal length, r1, r2- are the two surfaces of the lens respectively Radius of curvature. nl - the refractive index of the lens material. When a surface is a plane, the radius of curvature is infinite.) a. When the LED light passes through a curved surface of the lens (double convex has a curved surface), the light will be refracted and concentrated. And when the distance between the lens and the LED is adjusted, the angle will also change (in inverse proportion). The surface spot designed by aspherical technology will be very uniform, but due to the limitation of the lens diameter, the light on the side of the lens cannot be utilized. (light leakage); b. Generally used in large angle (40-80 degrees) concentrating, such as table lamps, street lamps, indoor lamps, etc.;
2. Fully reflective (cone or cup) a, the lens is designed to be concentrating in front of the concentrating, while the tapered surface can collect and reflect all the sidelights (reflective material), and the two rays The overlap (the same angle) can get the most perfect light utilization and beautiful spot effect; b. It is also possible to make some changes on the surface of the tapered lens, which can be designed as a mirror surface, a frosted surface, a bead surface, a striped surface, a thread surface, a convex surface or a concave surface to obtain different spot effects.
3, LED lens module a. is to complete a single multi-head lens by injection molding a plurality of single lenses, according to different needs can be designed into 3, 1, 5 or even dozens of lens modules; b. This design effectively saves production costs, achieves consistent product quality, saves space in the luminaire, and is easier to achieve "high power".
Fourth, light loss discretion
1. The luminous flux of a luminaire with a bulb or a lens actually meets the light distribution required by the standard, and factors such as the transmittance of the outer casing, the lens, and the loss of light are also considered. The high power of the lamp or the general illumination requires the lens to diffuse the parallel beam to meet the standard requirements. In order to make the optical effect more reasonable, the lamp cover should be divided into rectangular small units in the design. The purpose of this is to break the wave surface of the light wave, so that the product has a uniform appearance. In each small unit, an ellipsoid is used because the surface has curvatures in both the horizontal and vertical directions, so that different diffusion radii can be achieved with different radii of curvature in both directions. Its fundamental purpose is to overcome the deficiencies of traditional technologies and make rational use of luminous flux to achieve uniform and efficient light distribution.
In fact, the outer shell of the bulb is PC material (injection finished), and the spherical, pear-shaped and cylindrical bulbs are non-small units and non-planar whole shells, and the light loss is large and the light angle is small.
2. Since one surface of the lens is a curved surface having a radius of curvature in both the horizontal and vertical directions, incident light can be diffused both in the horizontal direction and in the vertical direction. Since the radii of curvature in the two directions are independent of each other, the two curvatures can be separately adjusted as required, so that the light output is diffused to different extents in both directions. Therefore, using a lens composed of a bidirectional curvature surface, the light output can be more freely distributed according to design requirements, and the luminous flux can be utilized more efficiently, thereby reducing unnecessary waste and glare. Furthermore, since a smooth transition surface is used, the lamp has a uniform transition light distribution and a good appearance. A completely transparent PMMA lighting or lampshade can cause dazzling or glaring chords in the center of the light source, but the brightness is rapidly reduced at the periphery of the light source. Many social occasions and work environment lighting must eliminate this unpleasant atmosphere or minimize the source of eye discomfort.
3. The projection of each lens unit on the body is rectangular, so that the units can be arranged closely and neatly. The parallel incident beam passes through the refraction of the lens unit to form a uniform diffusion in the horizontal direction and a uniform diffusion in the vertical direction. By adjusting the size of each unit in a group of lenses and the radius of curvature of the two directions, the distribution of the emitted light flux in different solid angle ranges is adjusted to achieve the light distribution required by the design.
Since the effect of the incident curved surface is to deflect the light to form a diffusion, the number of cells, the size of the unit, and the radius of curvature of each lens in the product design can be changed according to the actual situation. The actual situation is that the internal grain on the lens of the high-power lens (for dividing the small unit) is made by the manufacturer, and only the lens height, angle, and material are considered when selecting.
4. We choose to place the light source on the inner side of the lens focus. The farther the light source is from the lens, the less the light flux of the light source collected by the lens, and the lower the efficiency of the lens system. According to the calculation formula of single convex lens: r=(nL-1)f. Where r? convex surface curvature radius, nL? lens material refractive index, f? lens focal length in the case of selected lens material, the larger the focal length, the larger the radius of curvature. Under the same lens aperture, the larger the radius of curvature, the thinner the lens. The thicker the lens, the more obvious the aberration will be, which will affect the effect. Therefore, choose a lens with a larger focal length as much as possible. At the same time, the focal length increases and the size of the optical system increases. Therefore, the focal length of the lens cannot be pursued to the maximum. Since the lens thickness is not very large, the Fresnel lens is not used, and the cumbersomeness and cost of processing are avoided. 