Human nature is designed in such a way that we constantly strive for perfection. In their childhood, our grandparents were in seventh heaven when their parents turned on a slide projector and arranged to watch filmstrip fairy tales, hanging white material on a free wall. A little later, many accessible cinemas were built throughout the country, and television receivers firmly settled in our apartments. And now our parents took seats in front of the screen – at home or in the cinema, and with bated breath followed the development of the plot of their favorite film.
Today, we can say that among all kinds of video information display devices, the “popular” popularity of multimedia projectors is growing exponentially. Their functionality boggles our imagination. The screen size can reach tens of meters. Smart projectors support 4K or even 8K resolution. The strength of the luminous flux allows you to comfortably use the equipment in bright sunlight.
In this article, we will cover the main imaging technologies used in modern projectors .
Problem with projectors
I must say that projection equipment, which has the best characteristics in comparison with TVs and has functions that are not available to them, has been produced for more than a dozen years. But when we think about “whether to change the old TV for a projector”, “negative, not in defense of the projector” arguments begin to appear in our heads:
- grabber manufacturers unreasonably inflate selling prices for projectors, their real price should be at least an order of magnitude lower,
- how and where to install the projector? and the screen on the opposite wall, like a white thorn, not that the TV is the perfect complement to the home interior,
- whether the projector will cope with the solar lighting of the apartment – “nothing is visible”, even if the image on the TV screen fades on a sunny day.
And the truth lies in the fact that projectors and everything connected with them seem to us to be devices of high technical complexity. And to achieve acceptable image quality from them is possible only for very big money, after having previously studied the technical documentation in terms of volume comparable to the novel “War and Peace”.
In this relatively short text, we will show that the projection technique is a technique for you and me, ordinary people, and in order to master it, you do not need to graduate from special technical “universities”.
Film projectors
And modern projection technology began with film projectors. Simply put, a powerful light lamp and a system of focusing lenses were installed in the body of the device. A film was placed on the path, using a special tape drive mechanism for this, focusing the lenses to achieve a clear image on the screen. All! This is how our parents watched movies and programs – today it is called the buzzword “video content”.
This technique is a thing of the past, it can only be found in museums.
The modern electronics industry offers us various models of multimedia projectors. We will consider them in more detail.
1LCD projectors
The first type of vice-rectors built on a modern element base were the so-called LCD projectors . Their design is very similar to the device of a film projector. The main difference is that instead of a film reel and a tape drive mechanism, they began to use a color liquid crystal matrix. By the way, it is practically no different from those installed in modern LCD-screens of monitors, tablets and laptops.
I must say that 1LCD projectors are not the best representatives of projection technology. They have a number of significant disadvantages:
- Each light point on the screen (pixel) is formed due to the passage of the light flux through 3 RGB subpixels located on the LCD matrix in close proximity to each other. As a result, on a screen located at a sufficient distance from the projector, we observe the color structure of the pixel, which is clearly seen in the figures presented.
- Secondly, the screen brightness is increased by increasing the power of the light sources, and this in turn causes the LCD matrix to overheat.
3LCD projectors
1LCD projectors have such significant drawbacks that already in 1989, projection equipment manufacturers replaced one color matrix with three monochrome ones. It is logical that projectors using the new technology began to be called 3LCD. From the point of view of technological excellence, these are much more complex devices, in contrast to those previously considered.
Consider the block diagram of a 3LCD projector and the main paths of light fluxes.
Through a complex optical system consisting of a number of dichroic mirrors and light filters, the beam from the light source breaks up into three color components: R ed – red, Green – green, Blue – blue. Further, each of these components falls on its own (one of three) monochrome matrix. The main purpose of this element is to regulate the passing light flux under the influence of a control electrical signal. The final formation of an integral color beam occurs in a special prism, where the color components ( R ed, Green , Blue ) fall after the LCD matrices.
The idea to control not the light beam, but its color components turned out to be very successful, which ensured the commercial success of 3LCD projectors.
Their most significant benefits:
- high brightness and saturation of the image,
- versatility of installation schemes,
- moderate power consumption and heat generation,
- lack of the “rainbow” effect inherent in 1LCD projectors.
After listing the advantages, it is appropriate to acquaint the reader with the list of disadvantages of 3LCD devices:
- the complexity of the design caused an increase in the price of projection equipment,
- projectors are characterized by increased weight and increased dimensions,
- heat generation requires forced heat removal circuits, which are noisy in operation,
- optical systems require careful alignment,
- the main technological disadvantage is low contrast and the inability to form deep blacks.
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LCoS projectors
The invention of LCoS technology is the result of developers working to improve LCD projectors. The basic principles of the new projectors remain the same. The main changes affected LCD-matrices. If translucent matrices were previously used, then matrix elements using a reflective layer began to be used in LCoS projectors . This characteristic determined the name of the LCoS technology or Liquid Crystal on Silicon, which means “liquid crystals on silicon”.
Leading manufacturers of projection equipment register their own abbreviations, which indicate the use of LCoS technologies in their devices. For example:
- JVC – D-ILA (Direct Drive Image Light Amplifier),
- Sony – SXRD (Silicon X-tal Reflective Display).
findings
You learned the basics of existing imaging technologies used in today’s multimedia projectors. It is clear that the small volume of the article does not allow us to give a detailed description of them, to talk about all the advantages and disadvantages of both technologies and projectors that use them.
But, in our opinion, the knowledge gained will help determine the area of a wide range of projection devices, where you will select a specific model, in accordance with your desires.
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