Significance of LCD parameters of projector
Author:Yu Fangmin Time:2021-07-22 12:26 Browse(561)
LCD projector is the product of the combination of LCD display technology and projection technology. It uses the electro-optic effect of liquid crystal to control the transmission and reflectivity of the liquid crystal unit through the circuit, so as to produce beautiful images with different gray levels and up to 16.7 million colors. The main imaging device of LCD projector is LCD board. The size of LCD projector depends on the size of LCD board. The smaller the LCD board is, the smaller the projector is.
LCD projector is the product of the combination of LCD display technology and projection technology. It uses the electro-optic effect of liquid crystal to control the transmittance and reflectivity of the liquid crystal unit through the circuit, The size of the LCD projector depends on the size of the LCD panel.
the smaller the LCD panel, the smaller the size of the projector.
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Significance of LCD parameters of projector

according to the electro-optic effect.
liquid crystal materials can be divided into active liquid crystal and inactive liquid crystal, The active liquid crystal has high light transmittance and controllability.
the active liquid crystal is used in the liquid crystal panel.
people can control the brightness and color of the liquid crystal panel through the relevant control system.
it is the same as the liquid crystal display.
the LCD projector uses twisted nematic liquid crystal.
the light source of the LCD projector is a special high-power bulb.
the luminous energy is much higher than that of the c-lamp using fluorescent light RT projector, so the brightness and color saturation of LCD projector are higher than that of CRT projector.
the pixel of LCD projector is the liquid crystal unit on the liquid crystal panel.
once the liquid crystal panel is selected, the resolution is basically determined, Therefore, the function of adjusting the resolution of LCD projectors is worse than that of CRT projectors.
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according to the number of internal LCD panels, LCD projectors can be divided into single-chip and three chip ones.
most modern LCD projectors use three chip LCD panels.
three chip LCD projectors use red, green and blue LCD panels as red, green and blue LCD panels respectively The white light emitted by the light source passes through the lens group and converges to the color separation mirror group.
the red light is first separated and projected onto the red liquid crystal panel, and the image information "recorded" by the liquid crystal panel is projected to generate the red light information in the image.
the red light information in the image is generatedThe green light is projected onto the green liquid crystal panel.
the green light information in the image is formed, and the blue light information in the image is generated after the blue light passes through the blue liquid crystal panel, The three chip LCD projector has higher image quality and brightness than the single chip LCD projector.
the LCD projector has smaller volume and lighter weight.
the manufacturing process is simple, the brightness and contrast are higher, and the resolution is moderate. Now the market share of LCD projector is about 70% of the total market share, It is the most widely used projector with the highest market share.
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[edit this paragraph] the main technical parameters of LCD.
1 contrast.
the control IC, filter, orientation film and other accessories used in LCD manufacturing.
it is related to the contrast of the panel. For ordinary users, the contrast of 350:1 is enough, However, in the professional field, such a flat contrast can not meet the needs of users.
compared with the CRT display, which can easily reach 500:1 or even higher contrast.
only high-end LCD can achieve such a level.
because the contrast is difficult to be accurately measured by the instrument, So you have to see it yourself.
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tip: contrast is very important.
it can be said that it is a more important indicator of selecting LCD than bright spot. When you know that your customers buy LCD for entertainment, you can emphasize that contrast is more important than no bad spot. When we watch streaming media, generally, the brightness of film source is not big, However, to see the contrast between the light and dark of the character's scene and the texture change from gray to black, it depends on the contrast,Vg910s is 1000:1 contrast, we took this and a Samsung dual head graphics card contrast test, Samsung LCD is obviously better than, you are interested in can try. Test software 256 gray level test in head up when you can see more small gray grid, that is good contrast<
2 brightness.
LCD is a kind of material between solid and liquid.
it can't emit light, so it needs additional light source.
therefore.
the number of lamps is related to the brightness of LCD.
the earliest LCD has only two lamps.
up to now, the lowest popular type is four lamps, The high-end is six lamps.
the design of four lamps can be divided into three types: one is that there is one lamp on each side.
but the disadvantage is that there will be dark shadow in the middle. The solution is to arrange the four lamps horizontally from top to bottom, and the last is the "U" type, In fact, it's two tubes produced by two lamps in disguise.
the design of six tubes actually uses three tubes.
manufacturers bend all three tubes into "U" shape, and then place them in parallel to achieve the effect of six tubes.
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tips: brightness is also an important indicator.
the brighter the liquid crystal is, the better it stands out from a row of liquid crystal walls, The highlight technology that we often see in CRT (youpai is called highlight, Philips is called highlight, Mingji is called ruicai) is to increase the current of the shade tube and bombard the phosphor to produce a brighter effect. Such technology is generally obtained at the expense of the image quality and the life of the display. All products adopting such technology are generally bright by default, and can only be implemented by pressing a button, Click 3x to play the game; Press one more button to turn it into a 5x to light up the video disc. When he looks at it carefully, it becomes pasted,The principle of LCD brightness is different from that of CRT. They rely on the brightness of the backlight lamp behind the panel. Therefore, the lamp needs to be designed more so that the light will be uniform. In the early days, when people sold LCD, they said that the LCD was three, so it was a great thing, In fact, the three tubes were bent into a "U" shape, which became the so-called six tubes; Such a six lamp design, coupled with the lamp light itself is very strong, you can see the panel is very bright, such a representative work in youpai is represented by va712; But all bright panels will have a fatal injury, the screen will leak light, this term is rarely mentioned by ordinary people, the editor thinks it is very important, light leakage means that in the full black screen, the LCD is not black, but white and gray. So a good LCD should not blindly emphasize brightness, but more emphasis on contrast, youpai's VP and VG series is not about brightness, but about contrast products<
3 signal response time.
response time refers to the response speed of LCD to input signal.
that is, the response time of LCD from dark to light or from light to dark, It's usually in milliseconds.
to make this clear, we need to start with the perception of human eyes on dynamic images.
there is a phenomenon of "visual residue" in human eyes.
high speed moving pictures will form a short-term impression in the human brain.
animation Until now, the latest games such as movies have applied the principle of visual residue.
let a series of gradually changing images be displayed in front of people's eyes quickly and continuously to form dynamic images.
generally, people can accept 24 pictures per second.
this is also the origin of the 24 frames per second playing speed of movies,If the display speed is lower than this standard, people will obviously feel the pause and discomfort of the picture.
according to this index, the display time of each picture needs to be less than 40ms.
in this way.
for LCD, the response time of 40ms becomes a barrier, and the display below 40ms will appear obvious flickering phenomenon, It makes people feel dizzy.
if you want to make the image not flicker, you'd better reach the speed of 60 frames per second.
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I use a very simple formula to calculate the number of pictures per second under the corresponding response time as follows:
response time 30ms=1 / 0.030=about 33 pictures per second.
response time 25ms=1 / 0.025=about 40 pictures per second.
response time 25ms=1 / 0.025=about 40 pictures per second Time 16ms=1 / 0.016=about 63 frames per second.
response time 12ms=1 / 0.012=about 83 frames per second.
response time 8ms=1 / 0.008=about 125 frames per second.
response time 4ms=1 / 0.004=about 250 frames per second.
response time 3MS=1 / 0.003=about 333 frames per second.
response time 2ms=1 / 0.002=about 500 frames per second
response time 1ms=1 / 0.001=about 1000 frames per second.
prompt: through the above content, we understand the relationship between response time and the number of frames.
therefore, the shorter the response time, the better.
the response time isAt that time, when the LCD market just started, the lowest acceptance range of response time was 35ms.
it was mainly products represented by Eizo. Later, Mingji's FP series was launched to 25ms, which basically didn't feel from 33frames to 40frames. The real qualitative change was 16ms, which displayed 63 frames per second to meet the requirements of movies and general games. So up to now, 16ms is not out of date, With the improvement of panel technology, Mingji and upai have started a speed battle. Upai has been released from 8ms, 4ms to 1ms, which can be said that 1ms is the end of the LCD speed battle.
for game enthusiasts, fast 1ms means CS will be more accurate in shooting.
at least psychologically, such customers should recommend VX series monitors. But we should pay attention to gray response when selling, Sometimes, the difference between full-color response and gray-scale 8ms and full-color 5ms means the same thing. When we used to sell CRTs, we said dot pitch was. 28, LG had to say it was. 21, while horizontal dot pitch was ignored. In fact, both sides mean the same thing. Now LG has come up with a sharpness of 1600:1, which is also a concept hype. Which screens do you use, How can LG alone achieve 1600:1 while everyone stays at 450:1? As soon as we talk about consumers, we can see clearly the meaning of sharpness and contrast, just like the PR value of AMD, which has no real significance.
4 viewing angle.
the viewing angle of LCD is a headache.
when the backlight passes through the polarizer, liquid crystal and orientation layer, the LCD's viewing angle is a big problem, The output light has directionality.
that is to say, most of the light is emitted vertically from the screen.
therefore, when viewing the LCD from a larger angle,In order to solve this problem,
manufacturers have also started to develop wide-angle technology. So far, there are three popular technologies: TN + film, TN + film, TN + film, TN + film, TN + film, TN + film, TN + film, TN + film, TN + film, TN + film, TN + film, TN + film, TN + film, TN + film, TN + film, TN + film, TN + film, TN + film, TN + film, TN + film, TN + IPS (in-plane-switching) and MVA (multi-domain vertical alignment).
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the technology of TN + film is based on the original.
adding a layer of wide angle compensation film.
this layer of compensation film can increase the viewing angle to about 150 degrees.
it is a simple method, However, this technology can not improve the performance of contrast and response time.
perhaps TN + film is not the best solution for manufacturers, but it is indeed the cheapest solution, so most manufacturers in Taiwan use this method to build 15 inch LCD.
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IPS (in-plane-switching.
on-board switching) technology, It is claimed that it can make the viewing angle of up, down, left and right reach 170 degrees.
although iPS technology increases the viewing angle.
however, using two electrodes to drive liquid crystal molecules requires more power consumption, This will increase the power consumption of liquid crystal display.
in addition, the fatal thing is.
the response time of liquid crystal 32 liquid crystal display driven in this way will be relatively slow.
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the principle of MVA (multi-domain vertical alignment.
multi area vertical alignment) technology is to increase the protrusion to form multiple visible areas.
this paper introduces the principle of MVA (multi-domain vertical alignment.)When the voltage is applied, the liquid crystal molecules are not arranged vertically.
when the voltage is applied, the liquid crystal molecules are arranged horizontally, This technology is developed by Fujitsu Corporation.
at present, Taiwan Qimei (a subsidiary of Qimei in mainland China) and Taiwan Youda are authorized to use this technology.
eupai's vx2025wm is the representative work of this kind of panel.
at the same time, the development level of this technology is very high, The vertical visual angle is 175 degrees, basically no visual dead angle, and promise no bright spot; The viewing angle is divided into parallel and vertical viewing angles. The horizontal angle is centered on the vertical central axis of the liquid crystal, and moves left and right to clearly see the angle range of the image.
the vertical angle is centered on the parallel central axis of the display screen.
move up and down, You can clearly see the angle range of the image.
the visual angle is in degrees.
at present, the most commonly used marking method is to directly mark the total horizontal and vertical range, such as 150 / 120 degrees. At present, the lowest visual angle is 120 / 100 degrees (horizontal / vertical), It's better to be above 150 / 120 degrees.
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there is a strong competition among all kinds of flat panel displays in the domestic computer market.
all businesses want to get the largest share in the cake of flat panel.
when people buy flat panel home just like they did when they moved 15 inch monitors.
we not only need to ask: what's the hot spot of the next generation of displays? LCD has the advantages of clear and accurate image, flat display, thin thickness, light weight, non radiation, low energy consumption and low working voltage
classification of LCD.
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LCD can be divided into passive matrix LCD and active matrix LCD according to different control modes.
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segment code display and dot matrix display.
segment code is the earliest and most common display mode.
for example, calculator and electronic watch.
since we have MP3.
dot matrix display has been developed, such as MP3 and mobile phone screen, Digital photo frames are high-end consumer goods.
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1. Passive matrix LCD is limited in brightness and viewing angle.
the reaction speed is also slow.
due to the problem of picture quality.
this kind of display device is not conducive to the development of desktop display, but due to the low cost, There are still some displays in the market using passive matrix LCD.
passive matrix LCD can be divided into TN-LCD (twisted nematic LCD).
STN-LCD (super TN-LCD) and dstn-lcd (double layer STN-LCD).
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2, Thin film transistor LCD).
TFT LCD is a built-in transistor in each pixel of the picture.
it can make the brightness brighter, the color richer and the visible area wider.
compared with CRT display.
the flat display technology of LCD display embodies less parts, less desktop and less power consumption,But CRT technology is relatively stable and mature.
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[edit this paragraph] the working principle of LCD.
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we have known for a long time that substances have three types: solid state, liquid state and gas state.
although the arrangement of liquid molecular center of mass does not have any regularity.
but if these molecules are long (or flat), the liquid molecular center of mass has no regularity, Their molecular orientation may be regular.
so we can subdivide the liquid into many types.
the liquid with irregular molecular orientation is directly called liquid.
the liquid with directional molecules is called "liquid crystal", also referred to as "liquid crystal" Calculators are all liquid crystal products.
liquid crystal was discovered in 1888 by reinitzer, an Austrian botanist. It is an organic compound with regular molecular arrangement between solid and liquid.
generally, the most commonly used liquid crystal type is nematic liquid crystal.
the molecular shape is slender rod shape, with length and width of about 1nm ~ 10nm. Under the action of different electric current and electric field, the liquid crystal is a kind of liquid crystal, The liquid crystal molecules will rotate 90 degrees regularly, resulting in the difference of light transmittance. In this way, the light and dark will be different when the power supply is on / off. According to this principle, each pixel can be controlled to form the required image.
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1. The working principle of passive matrix LCD.
TN-LCD The display principle between STN-LCD and dstn-lcd is basically the same.
the difference is that there are some differences in the twist angle of liquid crystal molecules.
take a typical TN-LCD as an example.
to introduce its structure and working principle.
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in the TN-LCD panel with thickness less than 1cm.
in the TN-LCD panel with thickness less than 1cmIt is usually made of two large glass substrates with color filters, alignment films, etc? The color filter is composed of red, green and blue colors.
it is regularly made on a large glass substrate.
each pixel is composed of three color units (or sub-pixel).
suppose there is a panel with a resolution of 1280 × 1024.
then it actually has 3840 × There are 1024 transistors and sub-pixels.
the upper left corner (gray rectangle) of each sub-pixel is an opaque thin film transistor.
the color filter can produce RGB primary colors.
each interlayer contains grooves formed on the electrode and alignment film.
the upper and lower interlayer are filled with multilayer liquid crystal elements (the liquid crystal space is less than 5 cm) × On the other hand,
between the different layers, the long axis of the liquid crystal molecules is continuously twisted by 90 degrees along the parallel plane of the polarizing plate.
among them,
the orientation of the long axis of the two layers of liquid crystal molecules adjacent to the polarizing plate, The liquid crystal molecules near the upper interlayer are arranged in the direction of the upper groove.
while the liquid crystal molecules in the lower interlayer are arranged in the direction of the lower groove.
finally, they are packaged into a liquid crystal cell.
the liquid crystal cells are connected with the driving IC, the driving IC, the driving IC, the driving IC, the driving IC, the driving IC, and the driving IC The control IC is connected with the printed circuit board.
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under normal circumstances, when the light irradiates from the top to the bottom.
generally, only one angle of light can pass through, which is led into the groove of the upper interlayer through the upper polarizing plate, and then goes out from the lower polarizing plate through the channel of twisted arrangement of liquid crystal molecules,The arrangement and light transmission angle of the two polarizing plates are the same as the groove arrangement of the upper and lower interlayer.
when a certain voltage is applied to the liquid crystal layer.
due to the influence of external voltage, the liquid crystal will change its initial state and no longer be arranged in the normal way, So the light passing through the liquid crystal will be absorbed by the second layer polarizer, and the whole structure will be opaque.
as a result, black appears on the display screen.
when the liquid crystal layer does not apply any voltage.
the liquid crystal is in its initial state, and the direction of the incident light will be twisted by 90 degrees, so that the incident light of the backlight can pass through the whole structure, Results white color appears on the display screen.
in order to achieve that every independent pixel on the panel can produce the color you want.
multiple cold cathode lamps must be used as the backlight of the display.
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2. Working principle of active matrix LCD.
the structure of TFT-LCD is basically the same as that of TN-LCD.
only the electrodes on the interlayer of TN-LCD are used The working principle of TFT-LCD is different from that of TN-LCD in many ways.
the imaging principle of TFT-LCD is "back transparent" mode.
when the light source irradiates,
the light first penetrates upward through the lower polarizer, Liquid crystal molecules are used to conduct light.
because the electrodes of the upper and lower interlayer are changed into FET electrode and common electrode.
when the FET electrode is turned on, the arrangement of liquid crystal molecules will also change,But the difference is that because of the capacitive effect of the FET, the liquid crystal molecules that previously transmitted light will remain in this state until the next time the FET electrode is electrified to change its arrangement.
difference:
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theoretically speaking.
the biggest advantages of the LCD projector are red, green, light-emitting and light-emitting The blue three primary colors are realized by three separated LCD panels, which can control the brightness and contrast of each color separately, and the three color light can reach the screen almost at the same time, so it can reproduce all kinds of colors.
the color separation of single DLP projector is realized by a color separation wheel.
the three color light uses the same micro mirror to modulate and reflect, so the three color light reaches the screen in time, Due to the limitation of the rotation speed of the color splitter and the deflection speed of the micromirror, the color reproduction is lower than that of the LCD projector.
especially when displaying dynamic video images.
because the image refresh speed is faster, the modulation speed of each color is also higher, LCD technology will have more advantages than DLP technology.
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because most DLP projectors use single-chip structure.
the optical structure is simple, Therefore, it can achieve smaller volume and lighter weight.
due to the reflective principle.
DLP projector can achieve higher black-and-white contrast.
LCD is converged into a pixel by three color light.
single DLP projector is reflected to the same pixel by the same micro mirror, so there is no converging problem, The edge of pixels will not appear some rough edges and shadows in LCD, so DLP projector is clearer than LCD projector when displaying some thin lines and small font size text,Black and white are more pure, and the gray level is more abundant.
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in addition,
because every pixel of LCD projector's LCD panel has a transistor called light switch, the transistor part can't pass through light, and because of the existence of this transistor, There should be a certain gap between the pixels.
and because the control transistor of the DLP projector is on the back of the micro mirror.
it will not form a barrier to light, and the gap between the micro mirrors can also be very small.
therefore.
the gap between the pixels in the image projected by the LCD projector is larger than that of the DLP projector, especially for the low resolution products.
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the gap between the pixels in the image projected by the LCD projector is larger than that of the DLP projector
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