In the past two years, the advancement of projector intelligent technology has begun to really go to the "opposite side" of the TV set. At the same time, the advertising words such as “No Screen TVâ€, “Private Theater†and “Home Theater†gradually entered the public eye. Technically, pico projectors equipped with intelligent systems have become increasingly sophisticated. However, the two are better and worse, and it still needs time to verify. Xiaobian here mainly focuses on the protection of vision.
I believe that anyone who has heard such advice "less watch TV, hurts the eyes", the fact is indeed the case, what is the TV through what hurts our eyes? The same is to look at the eyes, what is the difference between the projector and the TV? How can we avoid this kind of injury and protect our eyes? Let's take a look at Xiaobian!
1. Direct light and reflected light
Most TVs nowadays are "LED backlight LCD TVs", which directly stimulate the human eye with RGB-LED backlight illumination, so we call the TV here direct light; and the pico projector is through RGB-LED The light source illuminates and then projects onto the curtain or the wall is visible to the human eye, so the projection is reflected light. That is to say, we watch TV directly staring at the light source, and looking at the projection is the projection reflection surface. Just like reading a book, it is to reflect the sunlight instead of looking directly at the sun. From this point of view, the TV's damage to the human eye is obviously higher than the projector.
In addition, in order to increase the definition of the liquid crystal display, in addition to the brightness of the light pipe behind the screen, it is also generally used to make the surface of the display surface look like a piece of glass after a special "wiping technology". It also increases the color contrast and saturation of the screen. But it also reflects light like glass. Especially when the light shines on the screen, it will increase the light reflection. Consumers who use this type of display are easily "stabbed" by the light and have symptoms of tired eyes, which can slowly cause health problems such as decreased vision and headache. The wall projected by the projector obviously does not have specular reflection like the display.
2. Blu-ray hazards
When it comes to light, here is the "first killer of the human eye" - Blu-ray, the full name of Blu-ray is called High Energy Visible Lights, we know that light is an electromagnetic radiation, which is enhanced by the increase of energy and frequency. . The blue light is the most energetic light in visible light, which is higher than the UV frequency that we can avoid in our daily life, and the damage is even greater. So it is not horrifying to say that Blu-ray may cause "blindness". This is one of the biggest reasons for the sharp rise in the rate of teenage myopia in the electronic digital age.
Whether it is a projector or a TV, the RGB-LED light source, that is, the red, yellow and blue three-color LED light source, and the three colors of the LED, the "blue LED" is the most important, and the blue light will make the color distortion. The overall picture is reddish yellow. Let's take a look at the spectral composition of the two main LED modules, W-LED (common) and GB-LED. As shown below:
Spectral composition of LED displays
It can be seen that whether it is W-LED or GB-LED, the proportion of short-wave blue component is high, and the long-term use will be more irritating to the human eye. But the same light source, the micro projector that is imaged by reflection is obviously less harmful than the direct TV. Projection has a parameter called brightness. If the brightness is suitable, it will have no effect. If it is too dark and too bright, it will also be bad for vision. The home entertainment suggests that the actual brightness is about 250 ANSI lumens. (A cat has too many virtual marks on a certain treasure, it is recommended to choose a big brand. ).
Three. Screen flicker
In the era when we were still using big-head TV, we could clearly feel the flicker of the screen. This is because the imaging principle of the big-head TV CRT monitor is to use an electron gun to bombard the phosphor on the picture tube to produce an image. The frequency is usually around 20-30 Hz, so we can obviously feel the flicker. The liquid crystal display currently used has a liquid crystal refresh rate, the most common being 60 Hz. But this refresh rate has nothing to do with flickering. No matter how much the LCD refresh rate is, it will not make people feel flicker. The reason that really causes the LCD to flicker is the dimming mode of the LED backlight. The dimming mode of LEDs is a way to adjust the intensity of light emitted by LEDs. It can be roughly divided into PWM dimming and non-PWM dimming.
PWM dimming, which makes the LED tube repeatedly bright and dark in a very short time to adjust the brightness of the screen. This continuous brightening process is actually a visible light flashing impact on the eyes. The higher the PWM frequency. The weaker the human eye perceives the impact; this is why some people feel eye fatigue when using a PWM dimming display, mainly because the frequency of this shock is close to that of the human visual nervous system. The upper frequency limit. Due to individual differences, some people are not aware of this low-frequency flicker, while others are very sensitive. The reason for the widespread adoption of PWM dimming on the market is that this method is easy to implement and can reduce production costs. (See below)
PWM dimming reason
Since the frequency of PWM dimming is higher than the 60HZ of the CRT, it is not easy to be noticed. Due to the working principle of PWM dimming, the degree of flickering of the display at low brightness is more pronounced. All people with sensitive eyes can feel the flicker when they turn down the brightness of the LCD monitor. This is not the case with displays that are not PWM dimmed. However, due to the cost, most manufacturers in the entire TV industry will choose PWM dimming, which is why most of the TV industry does not include the "dimming mode" in the parameter list.
The projector dimming is imaged by the reflection principle, and the projector illuminating elements gather all the beams, and after reaching the mirror for multiple reflections, a uniform and stable rectangular image is formed. The projection picture is stable and does not flicker, which fundamentally eliminates the damage caused by the flashing of the PWM dimming screen. Not only that, the projection diffuse reflection principle imaging can also make the view angle of the picture larger, and there will be no situation where the TV is left or right and the reflection is not clear.
Summary: The results of the comprehensive comparison of the two are high, and the intelligent projection is indeed more eye-protecting than the smart TV. However, in this era of lack of “artisan spiritâ€, not every pico projector is eye-protecting. Not all brands are focusing on products, and there are many speculators who seek benefits through various vicious competitions of “parametersâ€. It is our consumers who are hurt.
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