A projector is a device that connects to a video camera, laptop, PC, or tablet in order to display an image on a large screen. The remote control is used to control the operating device. The device of a video projector is quite complex, and may differ depending on the technology used to compose the image. How the projector will work depends on the technology used. Today on the market you can find LCD, DLP, LCoS models. Let’s take a closer look at these and other less popular technologies.
Today, LCD models are the most common due to their affordable cost. However, besides the low price, they can hardly stand out with other advantages. Of course, you can watch video at home on such projectors, but you need to do this from afar. Nearby, only multi-colored dots will be visible. In addition, the contrast also leaves much to be desired. Do not forget that these models are initially positioned as budget, so the lamp in the projector is installed the cheapest, and the resolution of the matrix does not reach HD. You can enjoy viewing on this projector only in completely darkened rooms. However, even in such conditions, due to the poor quality of the transmitted image, some particularly small details will simply not be visible.
Projectors with three LCD panels have higher image quality, which does not degrade even when viewed closely. The use of advanced image transmission technology transmits much more color tones. In 3LCD video projectors, image enhancement is achieved through the use of special technologies. Each color has its own monochrome matrix. First, each light flux passes through its own matrix, and then, using a prism, they are combined into one bright and multi-color image.
Although 3LCD projectors have much better brightness and color reproduction than their budget counterparts, they also have their drawbacks. Compared to DLP projectors contrast is not too high. This is due to the peculiarities of the LSD matrix. None of them, even the most expensive, is capable of providing complete non-transmission of color; as a result, it will not be possible to achieve deep blacks.
In addition, all liquid crystal matrices need regular cold air blowing. This procedure is mandatory in order to reduce the negative impact of high temperatures on them. However, constant blowing causes the formation of a layer of dust on the matrixwhich cannot be avoided even by installing filters and cleaning them regularly.
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The work of DLP projectors is based on the action special DMD chip, which houses a lot of small swivel mirrors. They are responsible for the formation of the matrix.
High-resolution DMD chips contain a huge number of microscopic mirrors. The principle of operation is that through a disk with multi-colored sectors that rotates, light passes from the lamp and enters the matrix. As a result, when the projector is turned on, the picture appears as the light beam passes through the corresponding colored sectors of the disk.
Controls in DMD chips are located differently than in LSD models. They are behind mirrors, so there is almost no distance between pixels in DLP projectors.
The technology used in these models allows you to get an image with high contrast. This can be achieved due to the fact that the mirrors that are responsible for the black pixels are located in a certain position. Because of this, it is possible to achieve appearance of true black.
Although DMD chips are much less affected by high temperatures, there is a heat sink on the back side. At the same time, there is no need to worry about dusting — the projector optics are located in a hermetically sealed case.
At present, the most widespread LED-DLP projectors. They do not use the passage of light through a moving wheel. Instead, there are colored LEDs that turn on in turn. Their brightness is too weak. However, unlike gas-charging lamps, LED lamps are small in size and weight, and also last much longer.
The main disadvantage of DLR projectors is the appearance of a rainbow effect, which is especially noticeable during dynamic scenes. This is due to the fact that the color components are projected alternately and can be mixed with frequent frame changes. In addition, gray color is very difficult to reproduce on DLP projectors. The mirror must be rotated as precisely as possible so that the eye catches the sequence of changing pixels of different colors into a gray tint.
See also: which projector to choose for home theater.
LCoS (SXRD, R3LCD, D-ILA)
The developers of this technology managed to eliminate all the shortcomings of previous models of video projectors. At the same time, all their most positive qualities were preserved and improved.
Here, the image is formed, as in 3LCD projectors, by passing rays through the matrices. However, they do not pass through the light, but are reflected from a layer of mirrors, as in DLP models. The pixel controls are on this specular layer behind the pixels that are next to each other. This allows get rid of the rainbow effect and improve image quality.
Of course, this technology has disadvantages. Chief among them — high price. LCoS projectors are significantly more expensive than similar DLP and 3LCD models, which have the same and sometimes even higher specifications. Therefore, these projectors are currently used only by professionals to create high-quality presentations and installations.
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This technology can be considered the oldest, since it is based on cathode-ray tube (CRT). Although CRT technology has been used for several decades, nevertheless, it is still relevant and in terms of image quality (clarity, resolution, color reproduction) is not inferior to modern and more expensive methods of image formation. Another plus of CRT is the greater reliability of electrical circuits and the duration of continuous operation of the tube, exceeding the limit of 10,000 hours.
Also, this technology has a wide dynamic brightness range and black depth, which cannot be provided by any other.
Despite the undoubted advantages, CRT-devices are still inferior in some respects to modern devices.
- Units have a large mass (several tens of kilograms). If the manufacturer made them a little lighter, it would be possible to more conveniently transport and install this equipment.
- Brightness level is in the range from 100 to 300 ANSI-lm, while in modern devices the level can reach 10,000 ANSI-lm or more. For this reason, video viewing is only possible in a well-darkened room.
- To achieve good image quality, you need to make a lot of settings, and it is sometimes difficult to do without the involvement of a specialist.
It is worth noting that today it is almost impossible to meet a projector of this type in retail. It has been superseded by the more modern technologies described above.
Inside the CRT video projector are 3 CRTs with screens ranging from 7 to 9 inches. Each CRT is designed to output one color (green, red, blue) of the RGB color model.
The principle of operation of the projector can be described as follows: the input signal is divided into components by color, which are involved in the control of the modulators. In this case, the intensity of the beam begins to change. At this moment, the beam, passing through the magnetic field and the deflecting system, exposes the surface of the screen with the applied phosphor coated scanning from the inside. After that, a single-color image is created on the screen. Further, it is projected through the lens onto an external screen.
As a result, 3 images are simultaneously projected on the external screen, when mixed, a full-color picture is obtained.
See also: what are the types of projectors.
The most advanced and most expensive technology for the formation of the highest quality image is laser. ViewSonic LS830 can be called a representative of a new type of projection equipment.
The principle of operation of the unit is the same as in the models discussed above: with the help of a laser, 3 color components are formed, which, ultimately, are mixed. Further, through a complex system, including focusing and sweeping, an image is created using a system of mirrors. It becomes possible to form an image on almost any surface, including uneven.
The total cost of ownership is greatly reduced by the use of laser technology, as the laser can be considered conditionally eternal. The estimated period of its operation is 20,000 hours that do not require special maintenance. In this case, the device will produce excellent brightness that does not decrease over time. Throughout the years of operation of the equipment, the quality of the picture will remain at a high level. The brightness level of the Viewsonic is quite high at 4,500 lumens, which is suitable for watching videos in a well-lit room.
Almost all modern laser projectors have ultra-short throw lenses (0.23). This allows the projector to be positioned at a distance of 21 cm from the screen, making it almost invisible.
In the figure below, the projectors are placed 17 cm from the wall.
Laser technology is capable of producing colors with great depth and saturation, high brightness and detail, and a wide color gamut. Due to the high contrast ratio (100,000:1), the picture is characterized by perfect sharpness and smooth transitions of halftones.
Also, the use of laser technology makes it possible to project a color image. Full 1080p HD resolution practically no deformation.
One of the most important advantages of laser video projectors is the ability to project an image onto huge screens.
Thus, there are a considerable number of models on the video projector market, both expensive and budget. They differ mainly in the technologies that are used to form the image, and, accordingly, in price. The more advanced the technology, the higher the price of the device.
See also: which is better to choose, a projector or a TV.