Types of projectors and lasers.
How to choose a projector for a specific type of task

Or logo projectors. These are simple devices designed to project static images on buildings, the pavement, or indoors.

In these projectors, the light from the lamp passes through a special gobo (stencil), or otherwise translucent media with the image, made of glass, metal, or film.

Such projectors are used mainly for advertising. But they can also be used for architectural illumination of buildings, or just to create static and dynamic patterns.

The advantages of such devices:

• ease of fabrication;
• the ability to work both on the street (in hostile conditions) and indoors;
• easy creation of stencils and their quick replacement;
• possibility of automatic slide change
• high brightness of the image;
• possibility of creating large images.

Cons:

• The projector only outputs a pre-prepared image, most often a static image;
• Video and sound cannot be played back;
• Burnout of gobo stencils over time.

In fact, this is the end of gobo projectors capabilities. But it is important to note that they are excellent at attracting people's attention and are well suited for advertising purposes.

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This is a class of devices that are used in ordinary rooms offices, educational classrooms, cafes.

Such projectors are designed to work in rooms that have backlighting, i.e. where there are additional light sources. The purpose of such a projector is to "break" the light and display the required information.

The average brightness or more accurately, the luminous flux of these projectors is 3000 lumens. But this figure is relative because the image brightness depends not only on the projector parameters, but also on the ambient room illumination. It is also possible that the projector has an actual brightness which is different from the claimed brightness. It depends on the quality and honesty of the manufacturer.

Imaging technology

To date, there are two most popular imaging technologies are DLP and LCD.

DLP technology uses special DMD chips to form an image. DMD chip is a device which has on its surface a lot of moving microscopic mirrors with a high reflection ratio. These micro mirrors are capable of directing light from the projector lamp either into the lens or into a special light absorber.

In DLP single matrix projectors between the projection lamp and DMD chip there is a rotating disc with color light filters which give a particular color to the light beam. When light passes through the light wheel, it is colored and hits the chip, the mirrors of which reflect it either to the screen or to the light absorber. The screen creates a picture colored in one of the colors, but because the rotational frequency of the disk is very high, for a person, these colors merge into one multicolor image.

The disadvantages of such projectors are that only one color is projected at a time, and the other colors are discarded, which leads to a loss of brightness and the colors become duller. The efficiency of using the light output is less effective. Also you can see the rainbow effect in dynamic contrast scenes when your look is running across the screen and you can see a color swirl for a split second or color separation effect.

But such problems are solved in 3-chip DLP projectors. In these projectors 3 DMD chips are installed at the same time, each of them works only with its own color, red, blue or green. In these projectors there is no color wheel, and for division of light into colors a special prism is used. Correspondingly the efficiency of light flux utilization in such projectors is better than in single matrix projectors. But these projectors cost much more and this technology is used mostly in large installation projectors or in elite home and cinema projectors.

In LSD projectors the white light from the projection lamp passes through a combination of mirrors which separate it into three basic colors, red, green and blue. These streams of light fall onto three LCD panels made up of multiple pixel crystals. These crystals either allow light to pass through(fully or partially) or not. The colors are then reassembled into a single beam of light using a special dichroic prism, which forms a full color image. The final image is projected on the screen. Thus 3LCD projector, unlike the DLP projector displays all three colors simultaneously, which allows you to create more accurate color reproduction, as well as provide more efficient use of light output. They also have brighter colors in comparison with the single matrix DLP projectors as all colors are projected simultaneously. In addition, this has a positive effect on eye fatigue. Another plus is that there are no rotating parts in the projector, which increases reliability.

3LCD projectors have many advantages, but like any technology, has its disadvantages:

1. The need for quality filtering. The optical components of 3LCD projectors are not sealed, and are very sensitive to dust and cigarette smoke
2. three matrices are more difficult to adjust to a single image, and therefore image distortion can be observed. Also, LCD sensors have a larger inter-pixel space, which can lead to a "grid effect", when the screen appears barely visible grid or lattice.
3. LCD panels burn out over time under the influence of light
4. Large backlighting. In many models, black is obscured by very bright backlighting in other areas.

The general conclusions about projectors can be made as follows. When you use the projector in the office or classroom, if it will display only documents, i.e. mostly black and white, it does not matter which technology you use. Both of these technologies produce about the same brightness in white. Often it is only a question of price. But if you plan to project a bright color image, and it is very critical that the picture looked good (for example, when you use the projector to create a projection design), it is better to use projectors on 3LCD technology, numerous comparisons confirm it.

In practice much depends on projection conditions. If you project in a very bright light then no projector from the office class will create a bright and contrasted image. In addition, no projector is able to interfere with the sunlight, this should be taken into account if one decides to project an image outside in the daytime in the summer.

Recommendations for selecting projectors:

1. If you want the projector to work in 24/7 mode, it is better to take DLP projectors, because 3LCD projectors will eventually burn out the LCD matrix.
2. If you need to link several projectors or work with geometry, you are better to choose DLP technology.

If you need a projector for a standard projector such as a single projector on the wall, then a 3LCD projector is a good choice.

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These projectors work under ideal conditions, i.e. with no external light sources. In this case, the projector does not need high brightness, but accurate color rendering and high contrast are very important.

In addition, these projectors are designed more for video projection, unlike the office projectors which are designed more for text and graphics. This leads to the fact that the projectors for the CD-ROMs use additional technologies to improve the picture. One of the important requirements for such projectors is good color rendering, so such projectors have a lot of color and video control settings.

It is not necessary to have high brightness for such projectors and it is even harmful. The brightness of 2500-3000 lumens in a dark room for such projector is unnecessary. Such luminous flux will strain your eyes.

In most cases, brightness of 1000 lumens will be enough for a DC. If the screen diagonal is 3-4 meters, the brightness can be increased.
Another important parameter for such projector is a low noise level. Though it does not refer to the image parameters, you should take it into account as you can find unpleasant surprise in the form of noisy projector's cooling. Today technologies are improving and projectors are getting quieter, but you should pay attention to the fact that office projectors can't boast of low noise level. Projectors for remote control take this factor into account and the noisiest projector for remote control is quieter than the quietest office projector.

Another important feature of such projectors is that they have a wider range of image control. That means you can get the same size image from a wider range of distances. So the projector will be easier to install in different rooms, especially when we want to install the projector not in a specially prepared room but in a living room or a room. There can be various obstacles like chandeliers for example. In that case the flexible image adjustment can solve the problem of getting the desired image.

Design. As a rule, these projectors make more stylish and pleasant. They are able to blend better into the interior, in contrast to the office projectors, which have a rectangular shape and differ little from each other.

When choosing a projector, you can ignore the technology of the projector. Today both 3LCD and DLP models are able to give a good image, and many of the disadvantages of these technologies were eliminated.

The contrast parameter is important for such projectors to get a clearer and better picture, but often the figures in the specification do not carry any meaning. You do not know how the manufacturer intended this parameter, and often these figures are used as a marketing move. The best way to evaluate the projector is to view it in the seller's showroom or at home, if possible.

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This is a special class of projectors with high brightness, large size and weight.

These projectors are used for projection in large rooms, such as conference halls, concert and assembly halls, as well as for open-air installations to create projections on buildings.

These projectors are much more expensive than their office counterparts, including the fact that they have a lot of additional features.
The brightness of the projectors starts with 5000 lumens and goes up to 40000 thousand (like Barco HDQ-2K40, the brightest projector in the world). Stoimosti approximately $100000)

Office projectors also can have a brightness of 5000-6000 lumens, so let's understand, what is the difference between these projectors from regular office projectors, besides the light output.

1. Case design

Often these projectors are made in a solid protective case, because these projectors are mainly used for installations, exhibitions, shows, and the like. It means that they have to be transported, installed, plugged in and out several times in short time during the whole operation period. Correspondingly the case has to be strong and heavy. Such projectors weigh about 20 kg (you can not go out).

2. Availability of interchangeable lenses

It is not rare that the complete set of projectors includes a set of interchangeable lenses. This allows you to use the projectors for different types of applications (cinema halls, studios, exhibitions, installations, concerts, auditoriums, etc.)

Each lens has its own optical parameters: focal length, aperture ratio, focus range. This allows you to equip the projector with a lens that is suitable for the specific task.

Usually projector manufacturers clearly indicate which lens models are compatible with this or that projector.

In addition, the lenses themselves can have an adjustable or fixed zoom. If you plan to use the projector at different points, choose the adjustable zoom.

Types of lenses:

• Ultra-short-focus lenses. The projection ratio is 0.25-0.5. These are used when you want to place the projector almost close to the screen. For example for rear projection.
• Short-throw: 0.5-1.1. Use for small spaces or when you want to project close to the screen and get a wide image.
• Standard 1.2-2. Suitable for most applications, medium-sized rooms, auditoriums.
• Long-focus and ultra-long-focus 2-4, and over 4. Use when a projector is placed far away from the screen.

3. A motorized lens on a projector

This is a video lens which has an electric motor which allows you to zoom or focus the image. This is done with a remote control. This lens makes the projector more expensive. You should install it if you can't access the projector (e.g. mounted on the ceiling or somewhere else) and you need to focus the image.

If you can access the projector, you can install the standard lens and do it manually.

4. Multiple lamps

Usually installation projectors have several lamps, which gives a high luminous flux, higher reliability. As an advantage it is possible to name a lot of different modes of operation. For example: the lamp can operate in two modes - normal and high brightness. In addition, you can use the remote control to turn on or off one of the lamps, resulting in four modes of operation.

If one lamp fails, you can continue to use the projector without interrupting the show.

Multiple lamps allow you to conserve the life of each lamp by turning them on one at a time. This is important if you run the projector continuously for long periods without interruptions.

In addition to the presence of two lamps, projectors can also use lamp units with up to four lamps.

All this makes for even greater reliability and brightness.

Reliability is especially important for installations where big shows are being held, and every detail counts.

5. Triple matrix DLP technology

Some installation projectors have three DMD chips to handle each color. Using three matrix DLP technology in projectors makes them much more expensive. But it is necessary to note the advantages of this technology in comparison with single matrix DLP projectors. High resolution, excellent color rendering, good performance, absence of flicker.

6. Availability of various connectors

These projectors have a variety of inputs and outputs, for connection of different cables and realization of different tasks. They have HDBaseT technology which allows to transmit both sound and video over long distances (about 100m and more) using twisted pair cable.

This provides high reliability of uncompressed video and audio with high quality and resolution, without time delays. Unlike other cables in which the quality of the signal decreases in proportion to changes in distance, which causes interference in the video and audio, this technology does not suffer from these disadvantages.

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Russian company Outdoor Lasers has developed an acousto-optic laser projector capable of displaying single-color or full-color laser images on different surfaces.

It has a built-in video server. It is able to project a streaming video either from the screen of a built-in Windows-based computer or an external video source via HDMI cable.

Its peculiarity is that the image can be created from a distance of a few centimeters from the projector lens, as well as at a distance of up to 1.5 km to the buildings and other surfaces. The optical system is designed in such a way that when adjusted to infinity, the image remains in focus at all distances.

The projector can create 3d images on buildings, asphalt, mountains, power plants' chimneys, tree tops and any other surface. Image correction is software that allows you to project on uneven surfaces, while creating a distortion-free image.

The projector is made in a protective case and can operate over a wide temperature range, from -35 to +35. It has a built-in thermostat system, external and internal radiators, it is not afraid of moisture and dust.

The outer optical windows are coated with a special hydrophobic coating that allows several cycles of glass cleaning without damaging the antireflective coating.

The amount of light this projector produces cannot be achieved by any other existing projector. For example, in order to cover an area of 300 sq.m. you would need several DLP projectors which have power consumption of about 10 kW. If you have one projector, you can cover the same area and consume 500 W of power. The difference is 20 times. Some models of this type of projectors can cover an area of up to 1000 square meters.

The resolution of this projector is less than the usual DLP or 3LCD, and ranges from 300 to 900 pixels by one coordinate.

In order to create a full color image, the projector has several light channels which are combined into a single image. This convergence occurs in two stages. At first all three channels are combined by means of mechanical optics in approximately the same area, and then the image is combined by means of software pixel to pixel, and colors are mixed directly on the projection surface.

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