Led Display mosaic Problem Solved Solution
"Mosaic" has been plagued LED display phenomenon is the manufacturer's problem
. The face of it, LEDdisplay "mosaic" of the phenomenon of performance to show inconsistencies in surface brightness sub-areas, namely, poor uniformity. Full-color LED display brightness uniformity is poor, including poor uniformity and color uniformity of both the poor. Poor uniformity, a "piebald" or "mosaic" has seriously affected the image of the viewing experience. At the same lamp used in a display case of the same wavelength, color uniformity and color uniformity of the performance of the two aspects of fidelity. Color uniformity of each pixel is the same screen, between the module and the module displays the same color of the color; color fidelity refers to the image on the display or source with the source image color reproduction between the scene degree of agreement. LED color related to the causes and measurement, in order to improve color uniformity and color fidelity, the need to reduce chromatic aberration, which has an article related to, but also can choose the appropriate device to correct. However, the brightness of inconsistency is the most common, is purely due to the manufacturing process, are mechanical properties, also contributed to the "mosaic" of the root causes can not be corrected with post-correction equipment, so study this issue is LED display The main task of the manufacturer.
Because the manufacturing process, including manufacturing and screen tube manufacturing process, because according to the present means of electronic technology, and electrical properties as long as the error correction can be improved in the late, late mechanical properties are not improved, only by manufacturing process itself is achieved.
1, Led display "masic" the causes and solutions
As mentioned above, resulting in Led display masic the root causes is the lamp itself, the consistency and the consistency of use caused by a defect.
1.1LED lamp itself causes
The consistency of the lamp itself, including brightness uniformity, color consistency, consistency point of view; Now, after years of development, LED display, the first two people have a deep understanding of a variety of ways have been resolved, which is often been overlooked, and we found in the many years of practice, the angle of the inconsistency is most likely to be overlooked, there are four reasons:
(1) LED lights up and down and inconsistent about the size of the angle,
As we all know, the conventional LED lamp style led display lamp is usually used elliptical tube, the early low efficiency light-emitting LED die, to get a better viewing experience, lamp manufacturers use optical means to observe the habit of using the human eye, by Large left and right angle, narrow angle up and down, effective use of the light volume, a result brought about a large angle, typically 110 , the angle up and down the small, generally only 45 . If the lamp body, then the vertical display screen can be used to angle no greater than 22.5 . For example: display high-8m, from the ground along the high-3m, 50m in the case of viewing distance, will cause loss of 8 angle. We can see the basic point of view changes with the brightness is linear, which corresponds to 50% of the brightness of 22.5 . A variety of tests show that in the case of high brightness, 10% error can be tolerated, in other words, more than 10% can tell; further concluded that the error must be less than 4.2 ; if the tube distortion of the 1 , reflected in the screen is 6 .
(2) LED lamp up and down angle, about the inconsistency of point of view itself;
LED light and the light and down between the point of view, there are also differences between left and right point of view, the author has tested a variety of light-type lamp, the lamp which NICHIA and CREE basic parameters meet the specifications, most point of difference between products exist, such as , with a 110 angle, it may not symmetrical about the angle shown in Figure 5, such as +30 ~ 80 , the same is true up and down, probably at 30 , under 15 , if you choose the correct light such a situation, there will be "dark spots" and "spotted" phenomenon.
(3) LED light angle angle angle and Led display inconsistency;
Usually, people often point the light directly interpreted as Led display point of view, this is some misunderstanding, the first Led display lights are usually relatively speaking, much larger size, and the tube direction and the direction is also inconsistent Led display, light Most of the perspective of the scope tube falls outside the scope of human observation. The principle view from the eyes to see, should be the appropriate observed from 2,000 times the distance between pixels or 5 times the diagonal distance, the larger of the two elections.
(4) the angle of the light color of inconsistency;
Manufacturing process from the LED light to see, red, green, and blue light emitted by the lamp shape is inconsistent. In fact, up until now found only on the light subunit of the compliance curve provided, CREE part of the original product. So, if you use a three-color light-shaped lamp with poor compliance, there will be "dirty spots" and "spotted" phenomenon.
2, LE light the reasons for use
LED light is due to use LED display manufacturers are most concerned about, is the manufacturer of the main tasks, but also reflect the manufacturers technical level and management level, production scale and market the main basis for the composition.
LED in use have to pay attention to select LED uniformity, angle selection, the direction of the calibration lamp, package design, cabinet design, external design.
(1) LED light selection
Try to use the same brand, same model, same grade LED. Consistency the better of the lamp, the price is more expensive, a good consistency to first select the point of the lamp;
(2) LED light angle selection
Try to select the angle, in particular the large upper and lower angle LED light. LED angle usually use on the LED display according to the actual requirements of the selected angle, angle small, relative to high brightness. In the production of display, some of the company to achieve positive brightness requirements, have reduced or so, and even the angle from top to bottom, so to choose according to the actual point of view, such as road traffic screen choose the smaller the angle, or about a small angle angle up and down a large tube. For the square, long-range view of the screen, you can choose or so angle, angle up and down the smaller tube, and if the scene like "across the river" situation, you can choose from top to bottom, left and right are a little smaller more appropriate. For the high altitude, but also from the perspective of recent large perfect circle can choose or select the table attached lamp tube.
(3) LED light correction
Determine the angle of the lamp, the LED lights here that the correction is simply more to ensure that LED lamp with Led display surface or a vertical angle. To this end, the lamp must be in before welding, welding, after welding, to take necessary and effective measures. Tube to be mixed before welding, tube into the cell board, the required fixture card prison, clamp style shown in Figure 6. Welding process must not loose, fall off, remove the light board after soldering action to light, until loaded into the module interior, do not touch the lamp, the lamp should check again before filling plastic tube angle meets the requirements.
(4) Package Design
Led display package is commonly used in various types of modules, including the bottom shell and a mask, on the bottom shell required to have a certain flatness, strength and durability. Cost pressures in the current PC Suite will be mixed with a lot of plastic filler, a certain loss of properties, where the most critical is the flatness requirements of flatness is less than 1:200, the reasons mentioned earlier. Therefore, we must strictly consider the level of PCB's into the bottom shell deviations and fixed to the box on the module, between the bottom shell and the cabinet waterproof pads, tighten the screws can cause the power of the different modules uneven . Otherwise, there will be a modular unit of the "mosaic" phenomenon. For the mask, calls for a tube holes must be in close contact with the lamp, played the role of further fixed; itself must have a certain strength, can protect the lamp against shock; must have a good optical design, the minimum solar reflectance can increase the contrast; hat to guarantee a certain height, can protect the lamp and the prevention of the role of sunlight, but also by the high hat with the site restrictions, such as: screen orientation and latitude in which the principle of not lamp to light the lamp and between, do not affect each other for the purpose; thermal deformation as small as possible, including self-heating and by the impact of sunlight.
"Package design" is the means used by the package must be carefully taken into account the above factors, the block-screen used for lamps and other additional requirements, the market generally, "public version" module, leading to the lamp and module mask a serious mismatch. Public version of the module is suitable for a variety of lamps, must be large enough, once the lamp is easy to use will inevitably lead to "distorted" result. If a coincidence with no problems, and most did not consider the need for integration with the box.
Therefore, once determined to use the display, to be dedicated specially designed modules, success stories such as: Beijing Pangu Building Kang Jiacheng display system, the module is the special project design;
(5) module Glue
Outdoor Led display board installed on lamp module is necessary to add waterproofing sealants, potting materials because usually the black, rubber surface due to the level of the final brightness of the display, if uneven, it will further impact, leading to the "Mosaic" phenomenon Usually, the module is less than the error between the plastic surface of 0.3mm, the level of better than one thousandth.
As shown in Figure 7, the module structure, injecting plastic surface when the plastic surface heights for all metal parts overshadowed tube feet; usually does not exceed a height Glue module mask pillar (hereinafter referred to as cover column) as the base , rubber side down shift, plastic column height to cover the distance is not greater than 0.3mm.
(6) Led display cabinet design and production of related
Led display Cabinet involving flatness and smoothness requirement is to ensure that from beginning to end, and must ensure that Led display Led display box in front of and parallel to the surface a fixed box, requiring Led display box complete flatness of better than five thousandths.
Led display currently used mostly sheet metal cabinet, the use of cold-rolled steel or aluminum, in order to achieve the above technical requirements, must ensure that the cabinet panel and the cabinet is not in the course of deformation. To this end, all the cabinet design must pay attention to back muscle: inter-module must be equipped with ribs, of which the width W must be greater than 15mm, H height with muscle length changes, the data is the result of structural calculations and the actual tested.
Welding each joint must ensure the reliability of solder joints on each side of each corner 3, a total of 36 joints, not allowed to lack. Each bar and panel spacing of welded joints must be at least three joints.
Reinforced by the above method may be to ensure that body surface area in the 300 300mm 100kg load box is not deformed. At present the design of sheet metal box general "tendons without bone", unless required the lifting of the box, do not set the box framework, outside the structure design and installation considerations, without rendering layer laminated box.
(7) Power Supply Design
Led display cabinets for low voltage power supply unit from the electrical characteristics of the design ensures the LED operating current constant. For Full color led display is concerned, the majority of constant current drive chip. Constant current constant current characteristics of the chip is stable and effective control, determines the ability to adapt to load changes. For a constant current of a chip, the different constant current, there will be a constant current into a voltage value, if the control chip output constant current in 20mA, will have to ensure that VDS is greater than 0.5V, 30mA 0.7V or more to ensure that . Changes in load and power supply may cause the chip into the enlarged area, loss of constant current role. For example: full color tubes used in series with two red lights, in the red, green and blue all lit, the wire load current increase, the pressure drop increases, lower voltage power supply board, resulting in constant-current driver chips into the enlarged area , the current decline decrease in brightness, Screen color cast. Some of the actual chips of different specifications may be required to verify the actual use to avoid.
Led display internal wiring for long length of wire, is likely to form excessive pressure drop, in the case of low voltage 5V is not in accordance with the safety of electrical current used to 2.5mm2 wire, for example, resistance per meter 7.44m, The electrical safety current value of about 28A, such as the module with two 10A, consider the situation with only one meter wire, plus or minus a voltage drop of the 0.3V, 4V voltage if the lamp series needs, you must ensure that the cell plate voltage not less than 4.8V, this is very harsh conditions, lead to further extension if the problem is more serious. Led display showed no problems of low brightness, display all white color of some modules when deviations occur, generally two lamps in series with the real point of full color led display, display all white when the red light it up.
(8) Led display module installation
Led display module during the installation process must ensure that: the lamp module from external shocks and the modules must be installed into the box was smooth, so must be dedicated tooling mold to complete the installation process requires the use of fixed screw torque torque wrench to tighten to the same measurement after installation tools needed to measure specific test does not meet the requirements of the standard to be adjusted to the flat.
(9) Led display screen of packing and shipping
Led display production is complete from the manufacturer to the installation site is easily overlooked aspect of many factors mentioned above aim is to ensure the formation of the vertical tube Led display, Led display unit cabinet in the assembly after proper packaging, be sure the box vertically, the box is indeed protective role to avoid the screen surface by a hard object impact deformation.
Led display box in transit for layers, layers must handle the load, must not allow direct compression Led display box, change the box shape. In practice, many times we found a good screen test in the factory after installation through the transfer process is the deterioration of the results, in addition to box their own reasons, transfer of oversight is also important reasons.
(10) designed and installed outside the structure
Led display the last to be installed to steel to form a whole, the outer structure of the design and construction, the same screen installed to keep the plane flat and solid, while installation of structural design to ensure that a single box does not sag, deformation, not pressure, up and down box should be left between the cracks, Led display box directly spread the weight of its own steel bearing.
3, Conclusion
In summary, LED display "masic" phenomenon is a comprehensive system problems in the lights and Led display all aspects of production to ensure smoothness of the lamp is the most fundamental solution, any follow-up of the "brightness, color" correction The premise is to produce a piece of the standard of qualified Led display.
by: hookah
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