Detailed explanation of perform©ance index of projector
The performance index of projΩ↔&✘ector is a mark to distinguish th↕e grade of projector, m&'♠ainly including the following indexe '∑s: < br / >
Optical output < br / >
It refers to the light e♣↕nergy output by the projector, and theα♥ unit is "lumen". A physi>♠cal quantity related to li&&∏ght output is brightness, wh®×ich refers to the ratio of the light ≈±<energy emitted by the li ♥♥ght on the screen surface to tε≤αhe screen area. The common≤←±ly used unit of brightness is "lux'λ←" (LX, 1LX = 1lm / m2). Wh ≈¶en the light output by the pδ±rojector passes through a cer≈®tain area, the larger the pro<±"jection area, the lower the ∑♠$↕brightness, otherwise, the highe↔σ<§r the brightness. Th↓±★e factors that determine the light o≠πutput of projector in&' clude the area of proj₩™εection and fluorescent scre₽↓en, performance and ₹€lens performance. Usually, theδβ area of fluorescent screεφ↕en is large and the light outpu&♣ $t is large. The performanΩ'∞ce of projector lens wi∞>↑th liquid coupling lens is good, andε→₹ the light output of projector≤→≥ can be improved accordingλly.
Horizontal scanning frequenα∑"cy < br / >
The movement of electrons f€δrom left to right on the scre♣αen is called horizontal scanning, o ©r line scanning. The scanning& $< frequency per second is€β♥ called horizontal sca'nning frequency. The horε♥♥izontal scanning frequen±±Ωcy of video projector is fixed. The s ∑canning frequency of 15.625kHz (PAL sy§★ $stem) or 15.725khz (NTSC system) data ₹₩≥and graphic projector is not differe<±£→nt frequency band. In th♣δ¶is frequency band, tΩhe projector can automatically track th∑₹±e input signal line ☆±frequency, and the phase-locked circuit "δ₹ can realize the complete synchroniza₹±tion with the input sig×♦nal line frequency. H↑∞orizontal scanning frequeδβ★↑ncy is an important index ≈λto distinguish the g≤π♦←rade of projector. A projecto₩ ↕r with a frequency range of 15k♦↑π®hz-60khz is usually called a d₽≈§ata projector. Those whose upper frε®↔equency is more than 60 k←β±✘Hz are usually called₽☆ graphic projectors.
Vertical scanning frequenc≥≥φ×y < br / >
When the electron beam is scanninε©®≤g horizontally, it moves from top t'Ω¶o bottom. This proce✔☆ss is called vertical scλ÷anning. Each scan forms an image. σ ✘δThe number of scans per ✔♥$¥second is called the vertical s ★can frequency. The vert©☆↔πical scan frequency is also called ✔the refresh frequency. It ☆€✘represents the numbe→♥'♠r of times the image is refreshed perδ← second. The vertical$∞ scanning frequency is generally no ☆↕&less than 50Hz, otheα∞∏★rwise the image will ♥&±have a flicker sense.
Video bandwidth < br / >
The total band width of the vi£deo channel of the projector is defined®♣ as the upper limit frequ€€←ency of the corresponding signalδ±₽ when the amplitude of the ☆"€video signal drops to 0.707 "<times. The increment of 0.70 €Ω7 times is - 3dB, so it is also c×alled - 3dB bandwidth.
Resolution < br / >
There are three resolutions: adγdressable resolution, RGB r♦esolution and video resolution.∞←>♥
For CRT projector, the addressable re&☆solution is the highest resolution pix''≥₽el of the projection tube,≠$ which is mainly determined by the focu÷♥sing performance of the projection tube•Ω∞, and is an important parameter of >ε×the quality index of the projecti→✔on tube. The addressable res £≤olution should be higher than ≈≤€☆the RGB resolution.
RGB resolution refers to the highe¥£∏st pixel that the projector can π♦αpass when receiving RGB β☆↑resolution video signal. For example,ββ the resolution is 1024 & times;∞&®÷ 768, which means the horizo↔¥ ✔ntal resolution is 1024, and th£±'e vertical resolution is 76♦Ω'×8. RGB resolution is related to t₹λhe horizontal scanning frequenc✔↓y, vertical scanning fre™πλquency and video bandwidth® .
Video resolution refer≈¥₹s to the highest resolutΩ∞≤ion of the projector when ✔≥₽Ωdisplaying composite↔Ω×π video. Here, it is necessary to ↓♠¥∑analyze the relationship between•↑λ video band, horizontal scanning frequ ↓&∞ency, vertical scann$™♠ing frequency and RGB resolut←₹♠¥ion: first, look at the relat€®$ionship between horizontal scanning freα×★quency and vertical scanning frequency.σ€
Focusing performance of CRT tube < br / >
The smallest unit of a graph is the pi←→↓xel. The smaller the pixel,®σ✔≈ the higher the graphics resolu•¶tion. In CRT, the minimum pixel isα₩ determined by the focusing perfor÷•mance. The so-called addressable↓♣∑↑ resolution refers to≈λ the number of minimum pixels.♦δ There are three focusingδ€≤ mechanisms of CRT projector: electr∞≤ostatic focusing, magne≤₽→≈tic focusing and electromagne♣ε♦tic compound focusing. Amon≠δg them, electromagnetic compouεγ→♣nd focusing is more advanced, whic₽₽♣h has the advantages of good focusing☆π÷® performance, especially def≠ocusing under high brightness condit¶δions, and high focusi>♦∏ng accuracy. It can focus in diεβσ→fferent regions, edges and corners, €₽¥®so that every point ↓≤≠on the screen is very c✔♥lear.
Convergence
Convergence refers to the coi★←♥≥ncidence of three RGB c×®σ£olors on the screen. For CRT projector, ♥ convergence control is particularly≥☆ important, because iβ"≈®t has three RGB CRT tubes, whic✘↕h are installed in parallel αΩ$on the ground bracke<σ£¶t. In order to achieve complete co♦ ↓nvergence of images, all k•÷inds of distortion of images mu♣☆≤st be corrected. The change of machine ©✔♥✘position and convergence also need t↕ ↓™o be readjusted. Therefore, the requi"σrements for convergence are fε£ull function and conv✔ ÷ enience. There are s Ω δtatic convergence and dynamic converge""☆♣nce, and dynamic convergenc✔®e has tilt, bow, amplitude↓≤, linear, trapezoid, pillow ®↓and other functions. •∑Each function can be adjusted♥✘ in horizontal and vertical ✔™∑σdirections. In addit '®♦ion, it can adjust the nonlinear balaε≈≠nce, trapezoid balance and pillow bala✔∞♠nce. Some projectors have the funct←∞λ☆ion of point convergence, which¥σ© divides the whole s↔₩δcreen into 208 points and adjus♦δ$ts them point by point on 2®δ≥≠08 points, so every point on the ≤σscreen can achieve acc÷☆♣urate convergence.
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