Is there harm to eyes and computer by sticking screen saver on notebook LED LCD screen
Author:Li Zhixin Time:2021-10-09 11:22 Browse(413)
First of all, I'll help you to find out. It seems that you don't understand LCD and led. Computers are usually LCD displays with LED backlight and non LED displays. The price is different. LED screens are more than several times more expensive.
First of all, I'll help you to find out. It seems that you don't understand LCD and led. The backlight of computer is usually LCD screen, and the backlight is led. The price of LED screen is different, but the price of LED screen is more than several times higher.

Is there harm to eyes and computer by sticking screen saver on notebook LED LCD screen


next, I'll tell you.
pasting screen is only used to protect the screen surface, prevent scratches, gray points and other protective functions, What's the harm to the eyes.
besides, if you are afraid of eye damage, you have to install a oscillograph screen.
to prevent secondary radiation is helpful to the eyes.
LED overview

LED (light emitting diode).
light emitting diode is a solid-state semiconductor device, which can directly convert electricity into light.
the heart of LED is a semiconductor chip.
one end of the chip is attached to a bracket, One end is the negative electrode, and the other end is connected to the positive electrode of the power supply, so that the whole wafer is encapsulated by epoxy resin.
the semiconductor wafer is composed of two parts.
one part is p-type semiconductor, in which the holes are dominant, and the other end is n-type semiconductor, There are mainly electrons here.
but when the two semiconductors are connected, a "p-n junction" is formed between them.
when the current acts on the chip through the wire.
electrons will be pushed to the p region, where electrons and holes compound and then emit energy in the form of photons, This is the principle of LED light emission.
and the wavelength of light is also the color of light.
is determined by the material forming the p-n junction.


LED history
50 years ago, people already knew the basic knowledge that semiconductor materials can produce light.
the first commercial diode was produced in 1960.
the first commercial diode was produced in 1960LED is the abbreviation of light emitting diode (LED).
its basic structure is a piece of electroluminescent semiconductor material, which is placed on a shelf with leads, and then sealed with epoxy resin around, that is, solid packaging, so it can protect the internal core wire, Therefore, LED has good seismic performance.


the core part of LED is a wafer composed of p-type semiconductor and n-type semiconductor.
there is a transition layer between p-type semiconductor and n-type semiconductor, which is called p-n junction.
in some semiconductor materials, when the injected few carriers combine with the majority carriers, the excess energy will be released in the form of light, When the reverse voltage is applied to the PN junction,
minority carriers are difficult to inject, so they do not emit light.
this kind of diode made by injection electroluminescence principle is called light-emitting diode.
it is generally called led.
when it is in the forward working state (that is, when the forward voltage is applied at both ends).
when the current flows from the anode to the cathode of the LED, Semiconductor crystals emit different colors of light from ultraviolet to infrared, and the intensity of light is related to the current.


at first, led was used as the indicator light source of instruments and meters.
later, LED of various colors was widely used in traffic lights and large area displays, It has produced very good economic and social benefits.
take the 12 inch red traffic light as an example.
in the United States, a long-life, low light efficiency 140 watt incandescent lamp was originally used as the light source, which produced 2000 lumens of white light.
after passing through the red filter.
the light loss was 90%, leaving only 200 lumens of red light.
in the new design of the lamp.
in the new design of the lampLumileds uses 18 red LED light sources, including circuit loss, which consumes 14 watts of power, In 1998, white LED was successfully developed.
this kind of LED was made by packaging Gan chip and YAG together.
Gan chip emits blue light( λ The blue LED substrate is installed in a bowl shaped reflecting cavity.
it is covered with a thin layer of resin mixed with YAG, about 200-500nm.
part of the blue light emitted by the LED substrate is absorbed by the phosphor.
another part of the blue light is mixed with the yellow light emitted by the phosphor, White light can be obtained.
now.
for InGaN / YAG white LED, by changing the chemical composition of YAG phosphor and adjusting the thickness of phosphor layer, white light with color temperature of 3500-10000k can be obtained.
this method of obtaining white light through blue LED has the advantages of simple structure, low cost and high technology maturity, Therefore, it is most widely used.


in the 1960s.
scientific and technological workers developed LED based on the principle of semiconductor pn junction light emitting.
the LED developed at that time was made of GaAsP, and its luminous color was red.
after nearly 30 years of development.
now in the familiar led,It can emit red, orange, yellow, green, blue and other kinds of color light.
however, white light LED for lighting is only developed in recent years.
here we introduce the white light LED for lighting.


1. The relationship between visible light spectrum and LED white light.
it is well known that the wavelength range of visible light spectrum is 380nm ~ 760nm, which is the seven color light that can be felt by human eyes Yellow, green, cyan, blue and purple, but each of these seven colors is monochromatic light.
for example, the peak wavelength of red light emitted by LED is 565nm.
in the visible light spectrum, there is no white light.
because white light is not monochromatic light, but a composite light composed of multiple monochromatic lights, just as sunlight is white light composed of seven monochromatic lights, The white light in color TV is also composed of three primary colors of red, green and blue.
it can be seen that to make LED emit white light, its spectral characteristics should include the whole visible spectral range.
however, it is impossible to produce LED with this performance under the current process conditions.
according to the research on visible light.
the white light visible to human eyes, At least two kinds of light are needed, i.e. two wavelength light (blue light + yellow light) or three wavelength light (blue light + green light + red light), That is, the "blue light technology" pursued by the major LED manufacturing companies.
at present, there are only a few manufacturers mastering the "blue light technology" in the world.
for example, Japan's Nichia chemical, Japan's Toyota synthetic, America's Cree, Germany's OSRAM and so on, so the promotion and application of white LED,In particular, the promotion of high brightness white LED in China has a process.


2. The process structure and white light source of white LED.
for general lighting.
in terms of process structure, white LED is usually formed by two methods.
the first method is to use "blue light technology" and phosphor to form white light; The second is a variety of monochromatic light mixing methods.
these two methods have been successfully used to generate white light devices.
the system of the first method to generate white light is shown in Figure 1.
the ledgam chip in the figure emits blue light( λ When the phosphor is excited by blue light, it emits yellow light. As a result, the blue light and yellow light are mixed to form white light (the structure of LED is shown in Figure 2).
in the second method, chips with different colors are packaged together.
white light is generated by mixing different colors.


3 In order to illustrate the characteristics of white LED, we first look at the status of the light sources currently used.
incandescent lamps and tungsten halogen lamps.
their luminous efficiency is 12-24 lumens / watt; The luminous efficiency of fluorescent lamp and hid lamp is 50-120 lumen / W.
for white LED: in 1998, the luminous efficiency of white LED is only 5 lumen / W, and it has reached 15 lumen / W in 1999, which is similar to that of ordinary household incandescent lamp. In 2000, the luminous efficiency of white LED has reached 25 lumen / W, which is similar to that of tungsten halogen lamp.
some companies predict that the luminous efficiency of LED will reach 50 lumen / W by 2005, By 2015, the light efficiency of LED is expected to reach 150-200 lumen / W.
the results show that the light efficiency of LED can reach 150-200 lumen / WAt that time, the working current of white LED could reach ampere level.
it can be seen that the development of white LED lighting source will be possible.


although the incandescent lamp and halogen tungsten lamp for general lighting are cheap.
but the light efficiency is low (the thermal effect of the lamp is white power consumption), the service life is short, and the maintenance workload is heavy, At present, Hella company of Germany has developed the aircraft reading lamp with white LED; A street in Canberra, the capital of Australia, has been illuminated with white LEDs; China's urban traffic management lights are also using white led to replace the early traffic order indicator lights.
it can be predicted that in the near future.
White LED will enter the home to replace the existing lights.


LED light source has the advantages of low-voltage power supply, low energy consumption, strong applicability, high stability, short response time, no pollution to the environment, low energy consumption, low energy consumption and so on Although it is more expensive than the existing lighting equipment, it is still considered that it will inevitably replace the existing lighting devices.


LCD is the full name of LCD: it includes TFT.
OLED, ufb, TFD, STN and other types of LCD, Its advantage is low power consumption and power saving is its biggest advantage. Its working principle is to add a color filter on the monochromatic STN liquid crystal display, and divide each pixel in the monochromatic display matrix into three sub pixels to display red through the color filter,Green, blue three primary colors, you can display the color picture, the general maximum display 65536 colors. The disadvantage is that the color is not real, almost invisible in the sun due to its high power consumption and high cost,
this undoubtedly increases the usability and mobile phone cost, so TFD technology is developed by Seiko Epson, a mobile phone screen giant, and is specially used on mobile phone screens.
it is a compromise between TFT and STN.
it has better brightness and color saturation than STN, However, it is more power-saving than TFT.
the characteristics of TFD are "high image quality, ultra-low power consumption, miniaturization, dynamic image display ability and fast response time."
the display principle of TFD is that it is equipped with a separate diode as the control source for each pixel on LCD.
due to such a separate control design, each pixel will not affect each other, As a result, the dynamic picture without residual shadow and bright colors can be displayed on the picture of the TFD.
like the TFT, the TFD is also an active matrix driver.

The first developed TFD can only display 4096 colors.
but if image processing technology is used, it can display images equivalent to 260000 colors.
however, compared with TFT, ufb is still inferior in color display.
ufb is a display developed by Samsung itself.
it combines the advantages of TFT and STN, that is, high brightness and bottom power consumption, because it adopts a special grating design, It can reduce the moment between pixels to get better image quality. It can display 65536 colors, which is comparable to the brightness of TFT, and the power consumption is much smaller than that of TFT! The price is similar to STN, it can be said that it is a kind of cheap and beautiful display screen
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