How Digital light processing projectors work?
Just as you have heard, Digital light processing is the latest technology when it comes to image display and projection. DR. Larry Hornbeck was the brainchild behind the DLP projector. He was working for the Texas instruments. In a our previous article on how modern LCD projectors work , we discussed how projectors work i general. Well, let us take a look at how digital light processing projectors work.
Digital light processing (DLP) is based on a digital micromirrors device. It is an optical semiconductor device. Just like many mirrors you may have used for reflection, aluminium is used to reflect light so that an image can be well displayed on the screen. For your information, digital micromirrors are also referred to as a DLP chip. Like many other chips you may have come across, these DLP chips can be held by the palm of your hand; Yet, a single chip contains more than 2 million mirrors.
Each mirror is as small as a fifth width of your hair and each mirror represents a single pixel. The micromirrors are arranged in a matrix manner; they can be compared to a photo mosaic. If you closely look at the DMD you can see tiny mirrors inside. Today, the highest resolution achievable by this technology is the 1080p or the 1920 x 1080P where there are more than 2 million micromirrors or pixels. The high number of pixels is meant to reduce the screen door effect on the projected images.
HISTORY OF DIGITAL LIGHT PROCESSING
The Work of Dr. Larry Hornbeck began in 1977. It is only in the year 1987 when the prototype of the optical semiconductor device was created, the first digital micromirror device. This device is capable of steering light particles with an incredible level of accuracy. In the year 1992, the project team explored the market viability of the project for the device. After two years, in 1992, the first DLP projector prototype was created.
In the year 1997, the Motion Picture Academy of Arts used the new technology to project the Oscars. The year that followed, the technology was awarded an Emmy Award for exceptional achievement in engineering development.
Now you are wondering when was the first home theatre projector developed, it was in the year 2001; it was a 16:9 projector. In the year that followed, the year 2002, Samsung, HP, Dell, and NEC produced DLP projectors. Lastly, by the year 2004, InFocus announced they had shipped 1 million DLP projectors.
We cannot do justice to this topic on how digital light processing projectors work without discussing the DLP.
DLP technology works by manipulating light so that film-like and digital images. Digital light processing (DLP) projectors are also called the digital cinema package (DCP).
Two things are required for the processing to take place, a projection lamp and an electronic signal from sources such as a computer or a VCR. The two are processed and an all-digital picture is produced. The whole process is hinged on the Digital micro-mirror device that has more than two million mirrors. Each microscopic mirror is hinged on a structure that makes tilting it back and forth an easy process at an individual level.
Football field scenario
For you to understand this, think of a football field where light is projected towards a given section of the fans. When cued, the fans tilt their seat cushions towards a surface say a blimp. And what do tilt cushions stand for? You guessed it right, they act as pixels of light towards that surface. The result is that there is a pattern that appears on the blimp or the surface where the cushions were tilted towards or away from. It could be a name, a number, a symbol, or anything. Any of your friends who is some distance from the blimp or the surface sees the image on the blimp or surface.
Now digital light processing projector works similarly but it works in the light that is focused on the DMD. The micro-mirrors are electronically tilted at 1kHz (or 1000 times per second). The DMD projects the image onto a screen through a projection lens. There is a different system that contains a color wheel to add color to the projected image.
The color wheel contains the primary colors ( red, blue, green) and it is placed on the optical path. The color wheel and the micro-mirrors are simultaneously controlled such that the tilting is done at the same time as the color wheel spinning.
Digital light processing projector structure
The components of DLP are projection optics, DMD, color filter, illumination, and cooling system. There is a memory chip included along-side signal processing so that it can be described as a digital system. Digital micromirror device (DMD) commonly known as the chip is the heart of this latest technology in the display. DMD is a semiconductor light switch. When an electrical signal is received, the chip tilts the mirror accordingly.
The DLP projectors can receive both digital and analog signals but the latter has to be converted into the former.
DLP chip is not restricted to any one source of light for the lamp. This is why DLP has used the following sources of light; LED-based lamps, Xenon arc lamps, and laser-based lamps.
The use of LASER as a source of light eliminated the need to use a color wheel. The first DLP projector was made commercially available in the year 2008 by Mitsubishi– L65-A95 LaserVue.
Xenon arc lamp
The lamp requires voltages as high as 20kV so that an arc between the electrodes can be generated. A constant current supply is needed for this type of light source. A lot of heat is generated which causes the electrodes to wear out. The amount of visible light decreases. However, you do have to worry, the lamps are replaceable. In case you are wondering how do you know it is time to replace the lamp, there is an on-screen warning message saying a new lamp is needed.
Prolonged use of the lamp past its life expectancy does not only increases the inefficiencies but also causes enough that melts the power wires.
Furthermore, the start-up voltage also rises so high that sparks no longer occurs. It is important to not overly stress quartz tube is likely to crack.
I know you wish to know how modern LED projector work. To begin with, LED projectors got their name from the light source, LED lamps. There three LED lamps, one red, one green, and the other one blue. The three beams are directed towards the DMD. this is how modern LED projectors work.
The rainbow effect problem is associated with the mechanically spun wheel that contains the colors. The rainbow effects are perceived briefly as red, blue, and green shadows in the areas where the high contrast parts of an image are featured. An example is where a white object is moving on a black background. Additionally, as a viewer, you can note this effect when you move your eyes speedily across the image being projected. However, while some people may be quick to note them, some never notice them at all; you could be in any of those categories.
DLP and 3D printing
PROS AND CONS OF THE DLP
Rainbow effect: There is a problem associated with the DLP that is known as the rainbow effect. This problem is quite well defined in the older projectors. It can perceptively keep you very uncomfortable.