Weak current College】 【display luminance calculation method.

<br> To full color screen, for example, usually red, green, blue and white balance ratio is 3: 4: 1 <br> <br> To P16 (2R1GB) 5000CD/square as an example: <br> Red LED .lamp brightness: brightness 5000 (CD) / M2 & # 247; point/M2 & # 215; 0.3 (white balance proportion accounted for 30 per cent) & # 247; 2 & # 247; 0.8 (System loss) .= 240CD <br> Green LED lamp brightness: brightness 5000 (CD) / M2 & # 247; point/M2 & # 215; 0.6 (white balanced ratio of 60 per cent) & # 247; 0.8 = 960 <br .> Blue led brightness: brightness 5000 (CD) / M2 & # 247; point/M2 & # 215; 0.1 (white balance proportion accounted for 10 per cent) & # 247; 0.8 = 160 <br> <br> .(240 & # 215; 2 + 960 + 160) & # 215; 0.8 & # 3906/215; = 5000CD/square meters points <br> <br> (1) known exactly rejecting and brightness for single-tube .brightness. <br> For example: 2500 point density per square meter, 2R1G1B requests per m² brightness for 5000cd/m2, then: <br> Red LED lamp brightness: 5000 & # 247; & # 215 2500; 0.3 & .# 247; 2 = 0.3cd = 300mcd <br> Green LED lamp brightness: 5000 & # 247; & # 215 2500; 0.6 = 1.2cd = 1200mcd <br> Blue led brightness: 5000 & # 247; & .# 215 2500; 0.1 = 0.2cd = 200mcd <br> The brightness of each pixel is: 0.3 & # 215; 2 + 1.2 + 0.2 = 2.0cd = 2000mcd <br> <br> (2) a known single tube brightness .for full screen brightness. <br> For example: P31.25, Nichia tube, for example. <br> The main aspects of a specification HSM display the red and green <br> HSM-PH-A + (Nichia) 180 - .440mcd1020-2400mcd <br> Because white balance with luminance ratio of red green blue = 3: 1; 6: white balance in proportion to the Green tube brightness to match other tubes. So are as follows: <br> Red: Green = 3 .: 6, green tube brightness is 2 x red tube, ie Red tube brightness: 2400 (blue) & # 247; 2 = 1200mcd again because the red, green, blue, four tube, red tube 2, therefore, a single red .tube brightness: 1200 & # 247; 2 = 600mcd. <br> Green: Blue = 6: 1, brightness of the Green tube is the blue tube of 6 times, that is, the blue tube brightness: 2400 (blue) & .; # 247; 6 = 400mcd <br> Because, 1 light pixels = 2 red tube + 1 green tube + 1 blue tube; <br> That is one pixel brightness = 600 (red) & # 215; 2 + 2400 ( .green) + 4 (blue) = 3400mcd = 3.4cd <br> Per m2 brightness = 1 glow brightness of pixels; & # 215 per square meter of the pixel density (number) = 3.4cd & # 215; 1024 (pixel .count) = 3482cd. To calculate the optical loss of 20 percent, the actual brightness should be: 2785.28cd. <br> Additional knowledge: <br> Control LED brightness: <br> There are two ways to control the LED brightness. One .is to change the current flows through the LED, LED tube allows continuous operating current in 20 MA or so, in addition to the Red LED a saturation, other flows through the LED brightness is basically the current proportion; another option is to use the Visual .of the human eye with inert, pulse-width modulation method to implement gamma control, which is a cyclical change optical pulse width (the duty), as long as the repeating cycle of lightened short enough (that is, the refresh rate is high enough .), the human eye is not luminescent pixel in dithering. Since the pulse width modulation is more suitable for digital control, so in general using computer to provide LED display content today, almost all of the LED screen are using pulse width modulation to control the .levels of gray. <br> LED control system is scanning bed centralized control of all pixel point grayscale, scan panels from the control box of the pixel brightness value decomposition (ie pulse width modulation), and then to the row the opening signal LED to .pulse form (lit 1, off to 0) the row for serial transmission to the appropriate control of the LED, lit. This method uses the device less, but the serial transmission data volume is large, because a duplicate lit cycle, each pixel in .16-level gray require 16 pulse, 256-level gradation of need 256 pulses, because devices operating frequency limit, usually only LED screen do 16-level gray scale. <br> Another way is to scan the contents of the plate serial transmission not .every LED switch signal is an 8-bit binary value of brightness. Each LED has an own pulse width modulator to a control point on time. Thus, in a repeat lit cycle, each pixel in 16-level gray only need four pulse, 256 .-level grayscale with just eight pulse, greatly reduce the serial transmission frequency. This decentralized control LED grayscale method can easily achieve 256-level gradation control. Often the master box, scan panels and display and control unit consists of three parts. Master box from .the computer's display card gets one screen pixel color brightness data, and then reassign the number block scanning panels, each scan Board is responsible for controlling the LED screen on the number of rows (columns), and each row (column) on led display and .control signals are transmitted using serial manner.BR> <br> <br>.