Changes In The Projector Light Source Technology

Last Updated January 16,2019

Nowadays, the majority of homes, offices, workplaces, and commercial establishments are fitted with projectors. These devices have become an integral part of professional and personal lives. There are different types of projectors being sold today. One of the primary differences between various projector models is the light source technology they employ.

All projectors make use of one or multiple light sources for projecting an image. The type of light source used in a projector impacts the brightness, quality, and clarity of the imagery projected by the projector. While earlier projectors primarily used halogen or metal halide lamps, modern projector models also employ Light Emitting Diodes, lasers and even a combination of these light source technologies.

There are primarily following types of light source technologies used in projectors:

• Traditional Lamps
• LEDs
• Laser
• Hybrid Light Sources


Traditional Lamps

In the early days of projector technology, projectors made use of lamps as a light source. Even today, most projectors employed in home theatres and offices feature lamps. Lamps have been used in projectors since the introduction of over head projectors (OHPs).  

Incandescent lamps were the first type of lamps to be employed in projectors. These lamps had a wire filament that was heated by passing electricity through it causing it to glow and produce light. They were inefficient and converted most of the electricity into heat.

Incandescent lamps were phased out from projectors with the introduction of halogen lamps. They had a tungsten filament surrounded by a mixture of halogen and an inert gas. Halogen lamps were brighter, had higher efficiency and lasted longer than incandescent lamps, but they also ran hotter.

The introduction of metal halide lamps in the 1960s revolutionized the projector landscape. Metal halide lamps produce light by breaking down a gas which results in plasma generation. They are exceptionally bright as compared to other lamps that were used in projectors before them and project imagery with more accurate colors. Metal halide lamps are more efficient than incandescent and halogen lamps. However, they require warmup before they can reach their full efficiency and must be cooled down after use.

Ultra High Performance (UHP) lamps is another popular modern projector lamp category. These lamps were introduced in 1995 by Philips and were developed primarily for projectors. Unlike metal halide lamps that have metal halides and mercury, UHP lamps only use mercury. They are the most efficient out of all types of projector lamps and have a decent lifespan though less than that of LEDs and lasers.

Epson has recently introduced its Twin Optimized Reflection lamp or E-TORL for short. It is an improvement of UHP lamp that enhances the optical quality of light. Its reflector has an elliptical shape while the UHP lamp has a parabolic reflector. The E-TORL lamp also has a separate sub-reflector to improve its light quality further. E-TORL lamps direct light efficiently to improve the brightness of onscreen imagery.

Most modern projectors make use of metal halide and UHP lamps while E-TORL is a relatively new light source technology. There are a few disadvantages of using lamps in projectors as compared to LEDs and Lasers:

-- Short Life Span: Lamps have a short life span generally varying from 3,000 to 6,000 hours. They have to be replaced often and are quite expensive which can increase the maintenance cost of projectors.

-- Immense Heat Generation: Lamps produce extensive amounts of heat when the projector is in operation. They require powerful fans to keep them cool which also leads to noise.

-- Loss Of Performance: As lamps age, their efficiency gradually reduces which lowers the brightness of the imagery with time.

Light Emitting Diodes

The second major type of light source technology used in projectors is LED or Light Emitting Diode. LEDs are based on the principle of electroluminescence wherein passing current through a diode releases photon resulting in light. While lamps are only able to produce white light, LEDs exist in multiple colors. Some LED projectors use separate red, green and blue LEDs leading to exceptional color quality in the projected imagery.


JMGO N7L LED projector

LEDs overcome some of the disadvantages of lamps. They are more efficient, can last from anywhere between 10,000 to 30,000 hours and generate less heat while in operation than lamp projectors. The less heat means low noise as the fan used to keep them cool can operate at lower speeds. LED projectors are more economical to maintain and don’t require warmup or cooldown period. As LEDs are small in size, they also allow the creation of portable projectors. 

The only disadvantage of using LEDs in projectors is that their brightness is lower than the brightness of lamps. They are therefore not recommended for environments that have high amounts of ambient light.

Laser  

Lasers are the latest addition to the list of light source technologies used in projectors. Sony was the first company to announce the use of lasers as a light source in projectors. Many other companies followed in the footsteps of Sony and introduced laser projectors. A laser is characterized by its coherent emission of light. As the light travels in a straight beam with minimum divergence, the impact of the environment is minimal.

 
JMGO SA Laser projector

Lasers are more efficient than LEDs and last as long if not more. Projectors can use multiple lasers just like LEDs, each producing light of a different wavelength (red, green and blue). A laser projector projects brighter imagery with accurate colors as compared to LED projectors. They are slowly becoming popular among residential, business and professional users.

The primary disadvantage of using lasers in projectors is their high cost. Laser projectors are very expensive as compared to LED projectors which deters buyers. However, the improvements in laser technology may result in lower prices which can improve the rate of adoption of laser projectors.

Hybrid Light Source Technologies 

While laser technology is the best for projectors in terms of picture quality, its high cost is a big drawback. Some projector manufacturers employ more than one type of light source for improving the quality of projected imagery while keeping the price within check.


Casio hybrid projector

Typically, the projector uses a combination of LED and laser technologies. Most projectors have a red LED and a blue laser as primary light sources. The blue light from the laser is split into blue and green using monochromatic filters. It results in better image quality than an LED projector at a much cheaper cost than a laser projector. Using hybrid light sources helps to lower the cost of the projector and makes it more affordable for the masses. It also improves the brightness and quality of the imagery projected.

Despite the advantage of LEDs and lasers, lamp projectors still hold the major share in the market owing to their low cost. Buyers who are going to use projectors for extensive durations regularly will benefit from LED projectors. While laser projectors are expensive, future advancements may reduce their cost, allowing more people to buy them. 

 


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