Basic Knowledge of LED Modules (Part 2)
Selection of LEDs in Module Design:
Principles for LED Selection:
- Brightness of the display
- Viewing angle of the display
- Color temperature of the display
- Power consumption of the display
LED Selection Method
Based on the percentage of red, green, and blue contributing to white light.
General Case 1:
- R — 30% W
- G — 60% W
- B — 10% W
Calculate the luminance contribution of each color (R, G, B) per square meter. Divide the luminance by the number of pixels per square meter to determine the luminous intensity per pixel.
Example:
- Screen luminance: 5000 cd/m²
- R: 0.3×5000=1500 cd/m²
- Assuming a pixel pitch of 20 mm, the number of pixels per square meter is: n=1/(0.02×0.02)=2500
- Luminous intensity () of red LED per pixel: 1500/2500=0.6cd (600mcd)
- Similar calculations apply to green and blue LEDs.
Trichromatic Principle and Module White Balance
- Trichromatic Principle: Three primary colors (red, green, blue) are combined in varying proportions to produce different color perceptions.
- Color Matching Equation: C(C)≡R(R)+G(G)+B(B)
(R), (G), (B) represent the units of the three primary colors of red, green and blue that produce mixed colors. R, G, B, C represent the quantity of red, green, blue and the matched color respectively. The quantity has the relationship of C=R+G+B, and the “≡” sign indicates that they are visually equal.
Module White Balance Principle:
Based on the trichromatic principle, the light color is adjusted to meet customer requirements. Basically, the customer’s requirements are macroscopic, that is, the light color is required to be the light color of the display screen. However, the measurement of the module is a small module test. At present, there is no method to measure the light color of the module as the light color of the display screen. Basically, it is still a cycle of first measuring the module, then the screen, and then the module. That is, first measure a value of the module, then install the module on a screen to measure the light color of the screen. If it does not meet the requirements, adjust the light color of the module, and then install the screen to measure the light color of the screen. After cyclic measurement and adjustment, a value can be calibrated as the standard value of the production measurement. Therefore, studying and measuring the relationship between the light color of the module and the light color of the screen is a topic of module white balance design.
