LEDs hurt your eyes? Demystifying the evolution of LCD backlighting

  When it comes to LEDs, many people must be very familiar with it. Today’s LEDs can be described as blooming everywhere. They are widely used in LCD monitors, TVs, large screens, projection, and lighting. People seem to be accustomed to LEDs. Up. In the liquid crystal display industry, while LED is gradually replacing the CCFL backlight, it also leaves some internal injuries. This is a "secret" that many consumers don't know much about.

 LEDs hurt your eyes? The evolution of LCD backlights revealed

  Let’s talk about what an “LED display” is. Strictly speaking, there is no such product. However, under the vigorous promotion of various channels, many consumers think that the LED display is the most cutting-edge product at present, and its display effect It is also the best. In fact, this is not the case. LED displays should be called LED-backlit displays, because LEDs themselves are not devices used for imaging (LEDs are not imaging devices in the consumer display industry, but in the field of large screens, the imaging effect is now It has become more and more mature), it only plays a role of light-emitting, and its imaging device is LCD, MVA or IPS panel. For the convenience of this article, the concept of "LED display" can be used temporarily.

  The appearance of the display is changing, and the backlight is constantly upgraded

LED is not used as a display backlight at the beginning, but with the continuous development of LED technology in recent years and the gradual decrease in cost, it has replaced the original CCFL backlight and has become the mainstream backlight choice. Of course, LED is used as a There are also many levels of backlighting. For example, high-end products use RGBLED, while low-end products often use WLED backlight. WLED is the backlight of LED displays that we see daily.

  What is LED?

The full name of LED (English: Light-Emitting Diode, LED for short), although the name of this product has often appeared in front of the public in recent years, it is not a new technology. It was developed as early as 1962. It's just that the early LEDs can only emit monochromatic light, and the brightness is relatively low, so the application market is relatively narrow.

Until recent years, LED began to explode, and the domestic LED industry is also booming. Not only has there been a breakthrough in technology, but due to a large number of enterprises producing, its price has gradually decreased, and finally there has been a wide application market, and now it is everywhere. Visible LED TVs, LED displays, LED projectors, and LED lighting are all variants of LED applications.

Advantages of LED light source

What are the benefits of LED? First of all, it has long life and strong stability. This can be felt from the street LED lights. They are often exposed to the environment of wind and sun, but they can still be used for many years. The second is that they have good energy-saving effects. , Its working current is small, so the power consumption is lower than that of traditional light sources.

From the above understanding, we can find that LED is undoubtedly a very good light source, low cost, good effect, energy saving and durable. This is also the reason why LED backlight is used in the display industry. The use of LED as the backlight source of displays is naturally also Adhering to the characteristics of LEDs, energy-saving and durable, its slim size is also the basis for the existence of ultra-thin displays today.

Shortwave blue light is very harmful to human eyes

Disadvantages of LED backlight

However, the application of LED light source in the display industry also has its own drawbacks, that is, it hurts eyesight, and it is more than the past CCFL backlight, which is the internal injury of the evolution of display backlight.

Why does LED-backlit display hurt eyesight? There are two main reasons. First, the blue light on the spectrum of LED is obvious, and the second is the current PWM brightness adjustment method. First, let us explain the problem of blue spectrum. According to current medical knowledge, blue light of a certain wavelength is the most harmful to human eyes, while the blue light component of LED is very large. Under the same illuminance, it is obviously stronger than CCFL backlight, so The damage to eyesight is even greater.

PWM is a very complicated thing. It means pulse width modulation. Currently, it is widely used in the display industry. Common products use PWM for dimming. It’s not popular science here. Detailed breakdown of PWM can take a lot of space and is very boring. In short, in order to maintain the characteristic brightness of the screen, the pulse current will cause the screen to flicker. This kind of flicker, the brightness is high when the speed is fast, and the brightness is low The time speed is slow, and it has a lot to do with the backlight material. In the past, the CCFL backlight flickered very fast, but the LED backlight flickered much slower than the CCFL. Because the flicker speed is slower, the user is easier to see tired.

Now I have a basic understanding of the whole story of LED backlight display. Many people are familiar with its advantages. It is also the reason why it gradually replaces CCFL backlight. Of course, the performance advantage is only one aspect, and cost control is also very important. Today's LED backlight The industry is very mature, and the price and cost continue to fall, which is also an indispensable factor for its replacement of CCFL.

However, the eye-damaging effect mentioned above is a drawback that many consumers don’t know about. In a society that pays more and more attention to personal health, this drawback is not a small flaw that can be ignored. The harm of blue light and the PWM-driven LED backlight The disadvantages of the LED display still have a lot of room for improvement.

The structure of the LCD screen, the backlight is at the last position

Nowadays, the slogan of eye protection is also put out, but it is only a change in PWM, and it does not really solve the problem of eye injury. Of course, as long as it is a display device, no matter what type of backlight, it will be watched for a long time. It will harm the health of the eyes, so proper rest is very important, but many people are forced to sit in front of the monitor for a long time, so it is very important to minimize the damage to the eyes of the monitor.