In order to quickly determine the quality of LED display screens, the following 9 important items of LED display screens are integrated from various viewpoints. The first eight projects are for general LED displays and the ninth project is for small-pitch LED displays.
First, the maximum brightness
Refers to the brightness of the LED display screen in the highest gray level, the highest brightness, under certain ambient illumination. In short, the software uses the software to set the brightness measured in the normal direction using the light gun when the display is white at 255 levels. For the outdoor LED display, according to the environment used, there will be different requirements for the maximum brightness, because in the case of relatively strong ambient light, the brightness of the LED display is required to be higher, so that the masses can clearly see the content displayed on the screen. Under normal circumstances, the display sat south to the north with a minimum requirement for maximum brightness, as long as 4000CD/m2 can meet the requirements, while the north-south display requires the entire screen brightness can reach 7000CD/m2, facing east and west with The requirements for facing south are the same, because there will be a part of the time when the sun will shine directly on the LED display. It is sufficient that the brightness requirement is greater than 5500 CD square meters in theory.
Second, the color temperature
When we see in the display screen the image color is inconsistent or different from the material, our screen is seriously distorted. This is related to the color temperature of the white balance of the LED display. If the human eye directly watches the display, its white balance The color temperature value between 6500 and 8000K is more appropriate, and if it is the display screen used by the television station, the actual color temperature of the screen needs to be adjusted to about 5500K, so that the screen on the screen is real after being recorded and relayed by the camera. .
Third, the refresh rate
The refresh rate refers to the number of times the LED display is displayed in full every second. If the refresh frequency is too low, the human eye will see jitter in the LED display. Normally, we will see the scanning line appear when shooting with the camera. Normally, the human eye requires a refresh frequency of 300 Hz or more. That is, as long as the refresh rate exceeds 300 Hz, the LED display will not feel jittery when viewed with the naked eye. However, if the camera is used to shoot, the minimum requirements are generally based on different settings of different cameras. Above 600Hz can not capture the scan line. A high refresh can improve the brightness and vividness of the display. It can be detected with a digital camera. If it is a high refresh, the picture taken by the camera is very clear, there is no snow point and scan lines. This indicator is particularly important at rental screens and television broadcasts.
Fourth, wavelength
The wavelength determines whether the color is pure and the color is the same. The resolution is very simple; if there is no professional equipment, how to use the eye to distinguish? First: The whole screen is shot white, the screen should be pure white, without any other noise. If you think that there is a little reddish or bluish, it will prove that there are problems with display materials and process quality control. If you use it for a long time, it will become more and more serious. Second: The colors of red, green, and blue are single-colored. The color of the center wavelength is what we usually call positive, blue, positive, and green. If the color is darker or lighter, it is proved to be a partial wavelength. If a certain color is inconsistent, it is proved that the wave difference is too large, the quality display screen is within the range of the center wavelength, the blue-green wave difference is controlled at 3 nm, and the red wave difference is less than 5 nm.
Five, luminous tube perspective
The luminous viewing angle of the luminous tube refers to the included angle between the two observation directions of the same plane and the normal direction when the brightness of the observation direction drops to half of the brightness of the direction of the normal direction of the LED display screen. Divided into horizontal and vertical perspectives. For outdoor LED advertising displays generally use elliptical light emitting tube or patch LED, elliptical light emitting tube has a small angle, high brightness characteristics, and the vertical angle of view of the LED light emitting tube is much larger than the elliptical tube, but its brightness is smaller than the elliptical light tube From the user's point of view, the LEDs of different viewing angles should be selected according to the audience surface of the LED display and the surrounding light environment. For indoor LED display due to its low brightness requirements, the audience is generally broader, so SMD LED is the best choice. It should be noted that some manufacturers of light emitting diodes currently on the market have to reduce costs, confuse users, and make the luminance of light emitting diodes relatively high. The angle of view is smaller than that of conventional light emitting diodes. This leads to LED display screens. The brightness at the front is very high, but the viewing of the image from the side with a large angle does not allow a clear view of the image. Small-size LED chips usually use a small-angle package to increase brightness. Large size does not require a small angle package because it does not require such high brightness. Therefore, high angle (110) high brightness and low current is the best.
Sixth, circuit design part
The circuit board design and the use of materials have a crucial role in the stability and display of LED displays. There are mainly the following requirements: 1. Material requirements: PCB thickness, generally 1.6mm thickness; Material: FR-4 glass fiber board, some manufacturers may use FR-2 paper substrate in order to reduce costs Copper foil thickness: The thickness of the copper foil has a non-negligible effect on the heat dissipation of the PCB board and the stability of the circuit. The normal copper foil thickness is 35um (1Oz), and some manufacturers will use 18um (0.5Oz) copper foil thickness. To shoddy; then as a consumer how to identify it? You can use an empty PCB to distinguish by weight, under normal circumstances, the heavier the better. 2, the design of several key points: connectors, connectors refers to the connector between the module and the module, and now there are more on the market there are two main, one is a horn, one is row needle. The advantage of ox horn is that it can block the cable through two card slots, and it is not prone to malfunctions caused by the connector problems. For the selection of electrolytic capacitors and tantalum capacitors, tantalum capacitors are undoubtedly the first choice for applications requiring long life. Where low prices are required, electrolytic capacitors are preferred.
Seven, automated production equipment LED
Most of the screens are electronic components, and the static electricity is very harmful to the electronic components. Sometimes static electricity directly breaks down the components to make them damaged. Sometimes it does not directly breakdown, but the hidden troubles are the side effects. The components are damaged after a period of use. In the electronics manufacturing industry, people think of a lot of methods for the treatment of artificial static electricity, including wearing static electricity rings, wearing static clothing, and using dust-free workshops. In fact, the most effective method is to avoid human contact with electronic components as much as possible, and the use of automation equipment achieves this goal.
Eight, the average power consumption
The square power consumption refers to the power consumption of a square meter of LED display. The unit of power that we usually say is watts/hour. For example, the power consumption of a square meter LED display is 300 watts, and this display consumes 300 watts/hour per hour per square meter, which is what we often call 0.3 kWh. The power consumption of LED display generally has two indicators, one is the maximum power consumption, and the other is the power consumption. The maximum power consumption refers to the power consumption of the maximum brightness of the LED display. How to use the eye to distinguish the maximum power consumption? The method is very simple: to see the amount of power behind the cabinet, multiplied by the maximum power of each power supply, according to the size of the box can be calculated the maximum power consumption of square meters, the general use of power in two, 200W and 300W power supply.
Nine, indoor small pitch: low light high gray
Low-light and high-gray, specifically explained as follows: When the brightness of a small-pitch LED display is in the range of 100cd/O-300cd/O, the gray level of the display screen is not lost, or the degree of gray-level loss is within the range that is hardly noticeable to the human eye. . Low-light and high-gray will be one of the key factors in distinguishing the quality of small-pitch LED display products. For small-pitch products, the LED display will no longer be a comparison of high brightness, but rather low brightness. It is better than the display of one's home that can reduce the brightness without losing the grey scale and picture quality. In other words, only the low-gray and high-gray small-pitch LED display is a good product that meets user requirements and has competitive strength. The human eye is under the indoor dark environment, and looks closely at the high-pitch, small-pitch LED display for a long period of time. The unique high luminance of the LED often causes people to feel dazzling, and even causes eye pain, tears, and reduced vision. Therefore, LED display brightness is too high, will give the user of indoor applications visual fatigue, and even serious may cause irreparable damage to the human eye! It can be said that the brightness of a small-pitch LED display is definitely not as high as possible, and its brightness must be reduced. A large number of tests show that the LED display's brightness range is controlled at a brightness range of 100cd/O-300cd/O, and the human eye feels comfortable. But this problem can be solved by not directly adjusting the brightness of the display. Because, the conventional LED display has the characteristics of low-light and low-gray, that is to say, the brightness of the display screen decreases while the loss of gray scale of the screen is accompanied.
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