3. LCD와 DLP의 내구성
- DLP(내구성이 우수함)
ONE CHIP의 DLP구조는 단순한 편이다. 그러니 아무래도 색상을 표현하는 부분등에서 문제를 발생한 요인이 적은 편이다
DMD Chip의 수명이 50,000시간 이상이라 정기적인 청소만 해주면 LCD보다 훨씬 오래 사용 가능하다.
- LCD
DLP보다 좀더 복잡한 구조로 되어있다. 아무래도 구조가 복잡하다 보면 문제 발생 요인도 많은 편이다.
두가지의 내부 구조에서 보다시피 빛의 감소 요인이 LCD가 더 많다. 아무리 좋은 거울과 렌즈를 사용한다 하더라도 통과시 마다 빛이 감소되기 때문이다. 그리고 장기간 사용한다고 봤을 때 렌즈나 거울 부분에 먼지가 쌓이게 되면 빛이 현저히 감소하게 된다. 이렇게 해서 밝기나 색상이 제대로 표현되지 못하는 문제점이 발생하게 된다.
4.격자감
약간 생소한 단어일수도 있습니다만 격자감이란 픽셀과 픽셀 사이의 간격을 이야기합니다. LCD 프로젝터와 DLP 프로젝터의
해상도가 동일한 상황일때 LCD프로젝터의 경우 아날로그 방식으로써 픽셀과 픽셀간격이 상대적으로 넓은편입니다.
반면 DLP프로젝터는 DMD 칩으로 투사를 하기때문에 픽셀과 픽셀 사이의 간격이 조금더 세밀하게 되어있습니다.
5. 투사거리
LCD프로젝터는 단초점렌즈가 채택이 된제품이 많이있습니다 때문에 좁은공간에서도 대형화면을 구현할 수 있는 장점이있습
니다. 방안에 설치를 하시거나 협소한공간에서 조금더 유용하게 사용하실수가 있습니다. DLP 프로젝터는 제품구조상 단초점
렌즈채택이 어렵습니다 때문에 상대적으로 투사거리가 어느정도 확보가 되셔야 대형 화면구현이 가능합니다.
6. 기타
LCD프로젝터는 아날로그방식으로써 기본적인 내부구조상 부피가크고 상대적으로 무게가 나가는 제품이 많이있습니다.
또 먼지에 약하기 때문에 지속적인관리(필터청소,정밀 분해소재)를 해주셔야지만 제품을 오랜기간동안 사용할수있는 방법입니다.
Summary
LCD Projectors: 장점
- 충분한 주변광이 있는 방에서 풍부한 색상 표현력을 보여준다.
- 전력 소비가 적다.
- 발열이 적다.
- 컬러필터 휠이 없다. = 레인보우 이펙트가 없다.
- 약간 더 조용하고 선명한 이미지를 보여준다.
DLP Projectors: 장점
- 부드러운 이미지를 표현한다.
- 크기가 작다.
- 픽셀이 덜 눈에 띈다.
- DVD나 HDTV 시청시 더 필름라이크하다.
- 블랙 표현이 좋다.
- 컨트라스트가 높다.
LCD Projectors: 단점
- 픽셀이 더 눈에 띈다.
- 특정 이미지에서 일부 스크린 도어 현상이 있다.
- 부피가 더 크다.
- 컨트라스트가 떨어진다.
- DLP 프로젝터에 비해 블랙이 회색에 가깝게 표현된다.
DLP Projectors: 단점
- 레인보우 이펙트가 일부 발생한다.
- 움직이는 부품이 많다.(컬러 필터 휠)
- 컬러 필터 휠이 가끔 소음을 발생시킨다.
- 빨간색과 노란색의 표현력이 떨어진다.
- 색상 채도가 낮다.
- 주변광이 있을 때, 풍부한 발색을 위해 LCD보다 더 밝아야 한다.(루멘스)
<원문 출처>
http://www.projectorcentral.com/lcd_dlp.htm
The Great Technology War: LCD vs. DLP
Evan Powell, July 7, 2003
ProjectorCentral.com
Introduction
만일 당신이 디지털 프로젝터 세계로 처음 온 것이라면, 어떻게 해서든지 LCD와 DLP라는 두개의 다른 종류의 프로젝터를 발견하기 전에는 멀리 떨어진 시장을 돌아보며 물건을 살 필요는 없다. 어떤 것이 더 좋냐는 명백한 질문을 하기 전에 LCD 와 DLP가 무엇인지도 모를 것이다.
대답은 간단하다. LCD와 DLP는 각자 상대방보다 독보적인 장점들을 가지고 있다. 둘 다 완벽하지는 않다. 그래서 각자가 당신에게 제공하는 것을 이해하는 것이 중요하다. 그러고 나서 당신은 어떤 쪽이 당신에게 더 좋을 것인가에 대해서 좋은 결정을 할 수 있을 것이다.
그런데, LCOS(liquid crystal on silicon)이라고 불리는 제3의 매우 의미심장한 광원 엔진 기술도 있다. 그것은 JVC 와 히타치 같은 몇몇 제작업체에 의해 개발되었다. 몇몇 우수한 홈시어터 프로젝터들이 이 기술로 만들어졌다. 그리고 JVC의 특정 모델이 강추 홈시어터 프로젝터리스트에 올라있다. 하지만 Lcos 기술은 이 게시글의 범위가 아니다.
If you are new to the world of digital projectors, you won't have to shop around the market very long before discovering that "LCD" and "DLP" somehow refers to two different kinds of projectors. You might not even know what LCD and DLP are before asking the obvious question "which one is better?"
The answer is simple. Sort of. LCD and DLP each have unique advantages over the other. Neither one is perfect. So it is important to understand what each one gives you. Then you can make a good decision about which will be better for you.
By the way, there is a third very significant light engine technology called LCOS (liquid crystal on silicon). It is being developed by several vendors, most notably JVC and Hitachi. Several outstanding home theater projectors have been manufactured with this technology, and JVC's LCOS-based DLA-SX21 is currently on our list of Highly Recommended Home Theater Projectors. However the discussion of LCOS technology is beyond the scope of this article. For more on LCOS click here.
The Technical Differences between LCD and DLP
LCD 프로젝터는 보통 프로젝터로 유입되는 화상 신호의 3개의 분리된 LCD 글래스 패널, 각각 빨강, 녹색 그리고 청색의 구성요소를 포함하고 있다. 빛이 그 LCD 패널을 통해 지나갈 때, 각각의 작은 픽셀이 베네치안 블라인드처럼 개별의 픽셀들이 빛이 통과할 수 있도록 개방되거나 빛을 차단하도록 폐쇄될 수 있다. 이 동작이 빛을 조정하고 스크린 상에 투사되는 이미지를 만든다.
DLP 프로젝터는 텍사스 인스트루먼트에 의해 개발된 원천 기술이다. 이것은 LCD와 완전히 다르게 동작한다. 빛이 통과하는 글래스 패널 대신에 DLP 칩은 수천개의 작은 거울로 만들어진 반사 표면이다. 각 거울은 하나의 픽셀을 표현한다.
DLP 프로젝터에서 프로젝터 램프로부터 나오는 빛은 DLP 칩 표면으로 전달된다. 픽셀을 켜기 위해 빛을 렌즈 경로로 보내거나 끄기 위해 경로로부터 분리하면서 거울들이 앞뒤로 흔들린다.
매우 비싼 DLP 프로젝터에는 각각 빨강, 녹색 그리고 청색 채널로 이뤄진 세개의 분리된 DLP칩이 있다. 하지만 2만달러 이하의 DLP 프로젝터에서 단 하나의 칩이 존재한다. 색상을 정의하기 위해서 빨강, 녹색, 청색 그리고 백색의 (클리어)필터가 있다. 이 휠이 램프와 DLP칩 사이에서 회전하고 칩에 충격을 가하면서 빛의 색상을 빨강에서 녹색, 청색으로 바꾼다. 그 거울들이 지정된 시점에 각 픽셀에 대해 요구된 각 색상의 양에 때라 렌즈 경로에서 떨어지거나 보내어지도록 상하로 움직인다.
이 동작은
LCD (liquid crystal display) projectors usually contain three separate LCD glass panels, one each for red, green, and blue components of the image signal being fed into the projector. As light passes through the LCD panels, individual pixels ("picture elements") can be opened to allow light to pass or closed to block the light, as if each little pixel were fitted with a Venetian blind. This activity modulates the light and produces the image that is projected onto the screen.
DLP ("Digital Light Processing") is a proprietary technology developed by Texas Instruments. It works quite differently than LCD. Instead of having glass panels through which light is passed, the DLP chip is a reflective surface made up of thousands of tiny mirrors. Each mirror represents a single pixel.
In a DLP projector, light from the projector's lamp is directed onto the surface of the DLP chip. The mirrors wobble back and forth, directing light either into the lens path to turn the pixel on, or away from the lens path to turn it off.
In very expensive DLP projectors, there are three separate DLP chips, one each for the red, green, and blue channels. However, in DLP projectors under $20,000, there is only one chip. In order to define color, there is a color wheel that consists of red, green, blue, and sometimes white (clear) filters. This wheel spins between the lamp and the DLP chip and alternates the color of the light hitting the chip from red to green to blue. The mirrors tilt away from or into the lens path based upon how much of each color is required for each pixel at any given moment in time. This activity modulates the light and produces the image that is projected onto the screen.
The Advantages of LCD Technology
One benefit of LCD is that it has historically delivered better color saturation than you get from a DLP projector. That's primarily because in most single-chip DLP projectors, a clear (white) panel is included in the color wheel along with red, green, and blue in order to boost brightest, or total lumen output. Though the image is brighter than it would otherwise be, this tends to reduce color saturation, making the DLP picture appear not quite as rich and vibrant. However, some of the DLP-based home theater products now have six-segment color wheels that eliminate the white component. This contributes to a richer display of color. And even some of the newer high contrast DLP units that have a white segment in the wheel are producing better color saturation than they used to. Overall however, the best LCD projectors still have a noteworthy performance advantage in this area.
LCD also delivers a somewhat sharper image than DLP at any given resolution. The difference here is more relevant for detailed financial spreadsheet presentations than it is for video. This is not to say that DLP is fuzzy--it isn't. When you look at a spreadsheet projected by a DLP projector it looks clear enough. It's just that when a DLP unit is placed side-by-side with an LCD of the same resolution, the LCD typically looks sharper in comparison.
A third benefit of LCD is that it is more light-efficient. LCD projectors usually produce significantly higher ANSI lumen outputs than do DLPs with the same wattage lamp. In the past year, DLP machines have gotten brighter and smaller--and there are now DLP projectors rated at 2500 ANSI lumens, which is a comparatively recent development. Still, LCD competes extremely well when high light output is required. All of the portable light cannons under 20 lbs putting out 3500 to 5000 ANSI lumens are LCD projectors.
The Weaknesses of LCD Technology
LCD projectors have historically had two weaknesses, both of which are more relevant to video than they are to data applications. The first is visible pixelation, or what is commonly referred to as the "screendoor effect" because it looks like you are viewing the image through a screendoor. The second weakness is not-so-impressive black levels and contrast, which are vitally important elements in a good video image. LCD technology has traditionally had a hard time being taken seriously among some home theater enthusiasts (understandably) because of these flaws in the image.
However, in many of today's projectors these flaws aren't nearly what they used to be. Three developments have served to reduce the screendoor problem on LCD projectors. First was the step up to higher resolutions, first to XGA resolution (1,024x768), and then to widescreen XGA (WXGA, typically either 1280x720 or 1365x768). This widescreen format is found, for example, on the Sanyo PLV-70 and Epson TW100, (two more products currently on our Highly Recommended list). Standard XGA resolution uses 64% more pixels to paint the image on the screen than does an SVGA (800x600) projector. The inter-pixel gaps are reduced in XGA resolution, so pixels are more dense and less visible. Then with the widescreen 16:9 machines, the pixel count improves by another quantum leap. While an XGA projector uses about 589,000 pixels to create a 16:9 image, a WXGA projector uses over one million. At this pixel density, the screendoor effect is eliminated at normal viewing distances.
Second, the inter-pixel gaps on all LCD machines, no matter what resolution, are reduced compared to what they use to be. So even today's inexpensive SVGA-resolution LCD projectors have less screendoor effect than older models did. And it is virtually invisible on the Panasonic PT-L300U, which is a medium resolution widescreen format of 960x540.
The third development in LCDs was the use of Micro-Lens Array (MLA) to boost the efficiency of light transmission through XGA-resolution LCD panels. Some XGA-class LCD projectors have this feature, but most do not. For those that do, MLA has the happy side effect of reducing pixel visibility a little bit as compared to an XGA LCD projector without MLA. On some projectors with this feature, the pixel grid can also be softened by placing the focus just a slight hair off perfect, a practice recommended for the display of quality video. This makes the pixels slightly indistinct without any noticeable compromise in video image sharpness.
Now when it comes to contrast, LCD still lags behind DLP by a considerable margin. But recent major improvements in LCD's ability to render higher contrast has kept LCD machines in the running among home theater enthusiasts. All of the LCD projectors just mentioned have contrast ratios of at least 800:1. They produce much more snap, better black levels, and better shadow detail than the LCD projectors of years past were able to deliver.
The Advantages of DLP Technology
There are several unique benefits that are derived from DLP technology. One of the most obvious is small package size, a feature most relevant in the mobile presentation market. Since the DLP light engine consists of a single chip rather than three LCD panels, DLP projectors tend to be more compact. All of the current 3-pound miniprojectors on the market are DLPs. Most LCD projectors are five pounds and up.
Another DLP advantage is that it can produce higher contrast video with deeper black levels than you normally get on an LCD projector. DLP has ardent followers in the home theater world primarily due to this key advantage.
While both technologies have seen improvements in contrast in the past two years, DLP projectors still have a commanding lead over LCDs in this regard. Leading-edge LCD projectors like the Sony VPL-VW12HT is rated at 1000:1 contrast, and Sanyo's PLV-70 is rated at 900:1. Meanwhile, the latest DLP products geared toward home theater like NEC's HT1000 are rated as high as 3000:1. Less than two years ago the highest contrast ratings we had from DLP were in the range of 1200:1.
This boost in contrast is derived from Texas Instrument's newer DLP chip designs, which increase the tilt of the mirrors from 10 degrees to 12 degreees, and features a black substrate under the mirrors. These changes produced a significant advance in contrast performance that simply did not exist before.
A third competitive advantage of DLP over LCD is reduced pixelation. These days it is most relevant in the low priced, low resolution SVGA class of products. In SVGA resolution, DLP projectors have a muted pixel structure when viewed from a typical viewing distance. Conversely, most SVGA-resolution LCD projectors tend to have a more visible pixel grid. This is entirely irrelevant if you are using the projector for PowerPoint slide presentations. However, it is more problematic for a smooth video presentation. For this reason, we don't normally recommend SVGA-resolution LCD projectors for home theater. Conversely, the revolutionary InFocus X1 is a DLP-based SVGA resolution projector. It is selling now for under $1,000 and is an incredible deal for the home theater enthusiast on a limited budget.
In XGA and higher resolution, DLP technology pretty much eliminates pixel visibility from a normal viewing distance. However, the latest WXGA resolution LCDs do so as well. So with higher resolutions, differences in pixelation are not the big competitive battleground they used to be. DLP continues to hold a small competitive edge, but the dramatic advantage of DLP over LCD no longer exists. The screendoor effect is receding into history as a problem of days gone by.
A Potential Problem with DLP: The Rainbow Effect
If there is one single issue that people point to as a weakness in DLP, it is that the use of a spinning color wheel to modulate the image has the potential to produce a unique visible artifact on the screen that folks refer to as the "rainbow effect," which is simply colors separating out in distinct red, green, and blue. Basically, at any given instant in time, the image on the screen is either red, or green, or blue, and the technology relies upon your eyes not being able to detect the rapid changes from one to the other. Unfortunately some people can. Not only can some folks see the colors break out, but the rapid sequencing of color is thought to be the culprit in reported cases of eye strain and headaches. Since LCD projectors always deliver a constant red, green, and blue image simultaneously, viewers of LCD projectors do not report these problems.
How big of a deal is this? Well, it is different for different people. For some who can see the rainbow effect, it is so distracting that it renders the picture literally unwatchable. Others report being able to see the rainbow artifacts on occasion, but find that they are not particularly annoying and do not inhibit the enjoyment of the viewing experience. Fortunately, the majority of the population either cannot detect the rainbow artifacts, or if they can they are not overly bothered by them. The fact is if everyone could see rainbows on DLP projectors the technology never would have survived to begin with, much less been embraced by so many as a great technology for home theater video systems. Nevertheless, it can be a serious problem for some viewers.
Texas Instruments and the vendors who build projectors using DLP technology have made strides in addressing this problem. The first generation DLP projectors incorporated a color wheel that rotated sixty times per second, which can be designated as 60Hz, or 3600 RPM. So with one red, green, and blue panel in the wheel, updates on each color happened 60 times per second. This baseline 60Hz rotation speed in the first generation products is also known as a "1x" rotation speed.
Upon release of the first generation machines, it became apparent that quite a few people were seeing rainbow artifacts. So in the second generation DLP products the color wheel rotation speed was doubled to 2x, or 120Hz, or 7200 RPM. The doubling of the refresh rate reduced the margin of error, and so reduced or eliminated the visibility of rainbows for many people.
Today, many DLP projectors being built for the home theater market incorporate a six-segment color wheel which has two sequences of red, green, and blue. This wheel still spins at 120Hz or 7200 RPM, but because the red, green, and blue is refreshed twice in every rotation rather than once, the industry refers to this as a 4x rotation speed. This further doubling of the refresh rate has again reduced the number of people who can detect them. Nevertheless it remains a problem for a number of viewers even today.
How big of a problem is the rainbow issue for you?
If you've seen earlier generation DLP machines and detected no rainbow artifacts, you won't see them on the newer machines either. The majority of people can't see them at all on any of the current machines. However there is no way for you to know if you or another regular viewer in your household are among those that may be bothered either by visibly distracting rainbows, or possibly eyestrain and headaches, without sitting down and viewing a DLP projector for a while.
Therefore, if you think you've identified a DLP projector that is just right for your needs but you are not sure whether this will be a problem, there is an easy solution. Find an alternative product that is either LCD- or LCOS-based that would be your second choice if you find that DLP won't work for you. Then find a customer-service oriented dealer who sells both models, and who will allow you to switch the DLP product for the alternative after testing it out for a few days. There are a number of service-oriented Internet dealers who will be happy to make such arrangements, and there are plenty who will not. But if you choose a dealer who is more interested in your satisfaction than in closing a quick deal (and they are definitely out there), you will end up with a thoroughly satisfying solution in the end.
A Potential Problem with LCD: Long Term Image Degradation
Texas Instruments recently released the results of a lab test conducted last year which highlighted a failure mode in LCD technology that does not exist with DLP. Given enough time, it appears that LCD panels, primarily those in the blue channel, will degrade, causing shifts in color balance and a reduction of overall contrast. The test did not include a large enough array of test units to draw any conclusions about anticipated rates of degradation under normal operating conditions.
However it is possible that those who invest in an LCD projector may find that eventually the LCD panel and polarizer in the blue channel may need replacement. This is not much of a problem if the unit is under warranty. But if it isn't, the replacement of an LCD panel will represent an unpleasant incremental investment in your projector that you were not anticipating. (See more details on TI's test and our thoughts on it.)
The Current State of the Art
The largest developers and manufacturers of LCD technology are Sony and Epson. These companies have no interest in standing by and letting Texas Instrument sweep the digital projector market with its competing DLP technology. So competition has driven both the LCD makers and Texas Instruments to improve their respective products in the ongoing battle for market share.
While LCD technology has made significant improvements in contrast performance over earlier generation machines, DLP maintains its lead in contrast. Meanwhile LCD projector makers have continued to emphasize key advantages in color fidelity, color saturation, and image sharpness for data display.
Both LCD and DLP are evolving rapidly to the benefit of the consumer. The race for miniaturization has produced smaller yet more powerful projectors than we might have even imagined possible just a couple of years ago. Light output per pound has increased dramatically. And video quality on the best LCD and DLP projectors now surpasses that available in a commercial movie theater.
ProjectorCentral continues to recommend both LCD and DLP projectors for a variety of applications. For mobile presentation it is hard to beat the current group of 3-pound DLPs on the market. However LCD products like the Epson 735c at 4.3 lbs make it clear that LCD is still a very strong contender in the mobile presentation market. And for larger conference rooms that require higher light output and greater connectivity, LCD technology holds a commanding lead.
When it comes to home theater, DLP has continued to make competitive advances in color, contrast, and image stability that have served to make it a technology preferred by many for home theater systems. But the fact is that both DLP and LCD continue to improve, and both are capable of delivering much higher quality video for home theater than they ever were before.
Which technology is the best? Well, it depends. Both technologies have advantages, and both have weaknesses. Neither one is perfect for everything. So the technology war continues. The only clear winner in sight is you, the consumer.
