Tuesday, 24 December 2013

The Working Of An RGB Laser

By Cornelia White


A laser that emits three primary colors, red, green and blue is an RGB laser, the name coming from the three primary colors. These can be emitted in a single beam for all the three colors or a separate beam for each of the color. Through additive mixing which involves combination of the three basic colors at different frequencies, a number of several other colors can be obtained.

RGB lasers are being exploited as an alternative to arc lamps sources (beamers). Although arc lamps have been used for a long period as a source of beams particularly because they are much cheaper, they suffer from setbacks such as limited lifetime, high wall-plug efficiency is impossible, poor image quality as a result of poor spatial coherence and the fact that available color space is not wide enough. For this reasons, the former is becoming more popular RGB sources are much more popular.

These types of lasers achieve coherence of wavelengths, a reason why they outperform many other sources of beams. The coherence is on both time and space allowing for inferences. The consistency in the change of phase properties over a long distance results into high quality images that make them preferred for entertainment and other professional applications.

These lasers are known to produce beams of the three primary colors with very narrow optical bandwidth making them close to the monochromatic light beams. They are thus capable of producing very clear images on mixing, the reason why they are getting more application like in cathode tube displays, color printers and lamp-based beamers.

RGB sources however suffer from a major setback given that the power level that is emitted is usually of low level. Most cinema projectors for instance require up to 10 W per color or even more. This level of power sufficiency, maturity or even cost effectiveness is still beyond the existing RGB scanners. When it comes to beam quality, these machines have to operate with high quality beams for them to perform effectively.

External optical modulators are normally used in these types of beamers although RGB sources are fitted with power-modulators for better signals in situations where the optical modulator use is made impossible as a result of low power miniature devices. Laser diodes for instance are used to achieve modulation bandwidth between 10 to 100 megahertz or even much higher resolutions.

There are many methods of constructing RGB lasers. Three lasers with each emitting a particular light of a wanted color is for instance an approach that has been used for long. These visible light beams are however limited in performance as compared to those that are infrared based.

The use of infrared solid-state lasers involves application of a single laser that emits a beam of near infrared (invisible) nature. Such a beam then undergoes through several stages of nonlinear frequency conversion the end of which a three colored beam is produced. The other methods that have also been used to obtain these colors are the combination of parametric oscillators, the use of frequency doublers and the use of frequency mixers.

With the technological advancement, better performing RGB laser machines are being produced. With the current attempt to introduce the fourth color in this type of laser, something that will even improve their performers for the better. The expert prediction is that these forms of lasers will be replacing the other forms of beamers.




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