DLP Technology

With all the talk of Plasma technology and the great quality of television it produces, it seems that other competing technologies are getting left by the wayside. But one of these, DLP technology, is gaining huge ground not only based on its picture quality, but also on its cost-effectiveness.

DLP images are basically created by a set of over one million microscopic mirrors that each represent one pixel, and by flicking ‘on’ or ‘off’ thousands of times per second, with coloured light shone upon them, can create millions of colours. The result is a very crisp, clean, and clear image.

HOW IT WORKS
THE BASICS

DLP stands for Digital Light Processing, and is a technology that was first envisioned in the mid-eighties. It is basically a projection system that is based on an optical semiconductor known as the Digital Micromirror Device, or DMD chip, which was first invented by a scientist at Texas Instruments in 1987.

The DLP board contains three components: on-board memory, the DMD chip, and a processor to run everything. The DMD chip is quite complex in design, yet is fairly easy to understand in terms of operation. In simplest terms, it is a sophisticated ‘light switch’: it contains a rectangular array of approximately 1.3 million microscopic mirrors, attached with hinges to the chip itself. Each of these micromirrors correspond to one pixel of a projected image, and measures less than one-fifth the width of a human hair, which means the picture that is produced is amazingly detailed. Light is projected onto the chip, and the hinges on the mirrors enable them to be tilted in any direction to an angle of about 12º, but more importantly, either towards the light or away from the light. This allows the mirrors to move to an ‘off’ position, where no light is being reflected, or to an ‘on’ position, where all the light is being reflected, creating a black pixel or a white pixel on the projection surface, depending on the signal that the DMD receives for each mirror. Each micromirror can switch on or off several thousand times per second, and it is the amount of time that the mirror stays on or off that dictates the shade of grey it will produce: on more than off reflects a light grey pixel, and off more than on reflects a dark grey pixel. So it is not difficult to see that hundreds of shades of grey can be created. In fact the DLP projection system can create up to 1,024 shades of grey when converting video or graphic signals through the DMD chip, for which your dog will be eternally grateful. This becomes even more useful when we add colour to the equation.

BOLD COLOUR

In order to produce a colour picture, and not just a detailed black and white display, the white light generated from the lamp in a DLP system passes through a constantly spinning colour wheel before it reaches the surface of the micromirrors on the DMD chip. The colour wheel simply filters the light into three additive primary colours – red, green, and blue – and the DMD chip is then able to create, based on the times per second that a micromirror turns on and off, at least 16.7 million colours in home-theatre applications. In cinema applications – such as movie theatres, which use an extended set-up – there are no fewer than 35 trillion colours created.

This is accomplished by the fact that the on and off positions of each mirror are co-ordinated with the spinning of the colour wheel allowing the DMD chip to create any colour imaginable. If green light, for instance, is coming through the colour wheel, then only those mirrors that are supposed to be reflecting green for the current picture – or reflecting a colour that includes green in its makeup – will be turned to the on position. For example, if a mirror is needed to project a purple pixel, it will only reflect red and blue light towards the projection surface, and these alternating flashes of red and blue are blended by our eyes to produce the intended tint or hue of colour within the image.

PROJECTION SYSTEMS

There are two different projection configurations involving DLP technology: the 1-chip configuration, and the 3-chip configuration. Televisions, home theatre systems, and business projectors use a single DMD chip configuration – like the one described above – to operate. The basic components are a lamp, a colour wheel, a DMD chip, and a projection lens. White light is sent thorough a condensing lens before passing through the colour wheel. This coloured light is then taken through a shaping lens onto the DMD chip and co-ordinated with the on/off switching of each mirror. The light is subsequently reflected through a projection lens onto the surface of a screen.

In a 3-chip configuration – such as in movie theatres and very large displays – the white light is divided into red, green, and blue light by a prism and sent to one of the three DMD chips, and each of the three chips is dedicated exclusively to one of these colours. This vastly increases the quality of the picture which decreases the degradation of each image on very large screens. After being reflected off the DMD chips, all three light streams are then recombined and sent through the projection lens onto a screen.

Currently, there are movies running in theatres using DLP technology, including T3:Rise of the Machines, Pirates of the Caribbean, and Spy Kids: 3D.

So all this techno-babble is great and all, but how exactly does this translate into better picture quality for you, the viewer?

IMAGE

For the most part, the improvements for home theatre applications involving DLP technology are that televisions based on this platform provide highly detailed, crisp, and clear pictures – so much so that they rival plasma.

The images created by DLP technology appear very clear because they are so closely reproduced to that of the exact mirror image of the source material. This happens because the thousands of mirrors on each DMD chip are spaced less than one micron apart, resulting in a very high “fill factor.” Minimizing the gaps between pixels in a projected image creates a seamless digital picture that’s sharp at any size – without any pixilation or ‘screen door’ effect.

Because DLP systems are mirror based, the use of light is more effective, and so more light is brought from the lamp to the screen, creating a visually stunning effect.

This however has also been a drawback for DLP applications: some televisions using DLP technology are too bright. Some users have commented that certain scenes cannot be viewed in absolute darkness because of the extreme glare, and that some sort of ambient light is required. The biggest drawback has always been its inability to create deep blacks, in part because so much light bounces around inside the engine. Some of that light eventually reaches the screen, which is why early DLP displays produced a grey, washed-out image that lacked depth and contrast. However, newer generations of chips – the HD2 for instance – have eliminated this problem, and pictures with black areas now appear as they should. And in fact, these new technologies produce deep, vibrant colours, with rich blacks and darker shades than is possible with most other technologies. And the thousand-times-per-second on/off capability of each mirror on the DND chip enables the creation of millions of colours, permitting colours that truly mimic real life. DESIGN Because the DLP system can modulate light faster than most other systems, only one chip is needed, which helps to reduce bulky television sets and projectors. Because less space is then needed within the unit itself, the result is lighter, slimmer and more elegant products. Also, not only is the DLP system not susceptible to heat, humidity, or environmental-vibration factors that can degrade the picture quality over time, there is also no risk of burn-in on the screen from gaming-consoles or internet-TV, unlike certain other technologies. (A burn-in can occur when there is a static, e.g. non-animated, picture on the screen for an extended period of time, and when taken off, or when the power is switched off, a ‘burned-in’ after-image remains.) FURTHER APPLICATIONS The bulk of the DLP technology is currently being used in televisions and projectors, however other applications do exist. Optical signal processing (data transfer), index printing for photography, commercial and industrial printers, digital image rendering, holographic storage, and true 3D monitors are all in the process of being improved and brought to market based on the DLP technology. FINALLY… Whether or not a DLP television is right for you is based on the same criteria for all other televisions: is the size and picture quality worth the price that you can afford? And in this respect, DLP shines: the price of DLP televisions is quite below the same quality in other technologies and in some cases is more than half the cost. The best way to really understand the DLP experience is to go and see for yourself, and compare with other technologies. There are several companies that are currently producing DLP televisions, including Hitachi, Samsung, Panasonic, Mitsubishi, and LG, all with their own configurations and features. And as far as picture-quality-per-dollar, there is no one that can yet beat DLP, as plasma TVs are about double the price, and conventional projection TVs just don’t compare. So in the end, this new technology is quite impressive indeed: better picture quality, sharpness, and clarity, along with a price tag that makes DLP quite an intriguing affair.

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