Projector Light Sources

Trying to determine what type of projector to use? The first thing you need to look at is the projector's Lumens. Lumens is an industry standard term that basically describes how much light a projector can put on screen and in turn, how bright the images appear on the screen. So how do you tell how bright a projector is? That can be a little complicated.

There is a standard for determining a projector's brightness called ANSI Lumens. An ANSI Lumen rating uses an average of several brightness measurements taken across the face of the light source. The problem is there is no requirement for any manufacturer to use this specification.

So how many Lumens are right for your application? A good rule of thumb is if it's too bright you can turn it down, but you can't turn it up if it's not bright enough, at least not without sacrificing image size. So, the simple answer is, that depends. But to start with getting the brightest projector, for the budget, is a good place to start. Obviously, there will be other considerations like screen size, black levels, shadow detail, and color accuracy to name a few. All of this is determined by the intended use of the projector.

Today's projectors produce light in three different ways – lamps, lasers, and LED. In this article, we're going to take you through the advantages and disadvantages of each technology as well as help you understand which light source could better complement the environment that the projector is going to be installed.

Lamp Based Light Sources

The oldest projector light source still in use today, is the lamp. Metal halide and UHP (Ultra High Performance) are the two types of lamps most commonly used. Metal halide lamps use a combination of rare earth metal salts and mercury vapor to deliver light. Mercury lamps produced a really bright light but have a significant downside. Because of the mercury, there is a high cost of operation and there can be disposal issues.

The UHP lamp, created by Philips, was designed to be a more efficient alternative to metal halide lamps. They provide similar brightness with lower energy consumption and the UHP lamps produce a lot of light and are more affordable. The downside is their effective brightness degrades from day one, which means a UHP projector will never be as bright as the first time you turn it on.

Also, lamps generate a lot of heat and thus require cooling, which requires more space, increasing the projector's size, number of cooling fans, and the amount of noise. Lamps have the shortest life span of all the lighting solutions available today and the simple act of turning the projector on and off diminishes the lamp's operating life.

So why would you recommend a lamp as a light source projector? It comes down to cost and light quality. As we mentioned, lamp-based systems are less expensive but have the shortest life. Lamps could be the choice if the projector is not being heavily used. For example, where the projector is only being used for an hour or two each day, the lamp's reduced initial hardware costs can make it a better value.

While lamps are less expensive than LED or laser light sources, they are still an excellent light source. This is why they are still utilized in many higher-end home theater projectors from companies like JVC and Sony. Producing the same quality light as a bulb requires high-power RGB LED or multi-channel laser light source, which still commands a premium.

As the price of better LED and laser light sources comes down, lamps will eventually be phased out. It's likely just a matter of time.

Laser Based Light Sources

There are several benefits shared by all projectors that use lasers as a light source. First, laser-based light engines turn on within seconds of pressing the power button. There is no time wasted waiting for a lamp to warm up or cool down. Old mercury lamps can be damaged if unplugged before the cooling-down period ends.

Laser-based light engines are incredibly reliable, lasting anywhere from 20k to 30k hours, and are mostly maintenance-free. Chances are, you would need to replace the entire projector long before the laser light engine fails.

Laser light engines are incredibly bright compared to lamps and most LED-based light systems, so they would typically be the best option for projecting on large surfaces. There are typically three types of laser-light engine designs used by today's projector manufacturers.

Laser Phosphor

Most laser projectors utilize the least expensive solution, which is a single blue laser diode array that provides the blue light and excites a yellow phosphor color wheel. Filters are then used to break up the yellow into red and green elements.

For higher brightness, some projectors use a dual blue laser light engine. One blue laser ultimately hits phosphor wheels to generate red and yellow beams, while the other blue laser handles the solely the blue component.

Hybrid Laser Light Engine

For improved color reproduction, another laser light configuration combines a red LED and a blue laser that uses a phosphor chip or a color wheel to generate green light. These hybrid laser projectors out-perform lamp-based projectors in brightness while delivering superior color and long life.

Discrete RGB Laser

The best solution is to utilize multiple RGB lasers instead of a phosphor wheel and filters to create clean primary colors. Multi-channel laser light engines tend to produce a wider color gamut, making them a perfect choice for installations that require color accuracy in their displayed content.

In addition to much more accurate colors, because red, green, and blue light is produced by different lasers, a wider color gamut is also possible. Since the RGB laser wavelengths are specifically chosen to optimize the primary colors of red, green, and blue, a RGB laser projector has the ability to reproduce DCI-P3 or even the Rec. 2020 color gamut without the need for a color filter.

Discrete RGB laser light engines are considered to be the best projector light source available, but this performance comes at a price. Laser projectors tend to be physically larger than other types of projectors and are also very expensive. These systems offer the best brightness, so for installations requiring a huge projection screen, this would be the best solution.

LED Light Engine

LED light engines use inorganic LED light-sources in place of a consumable lamp. Like laser light sources, LED light engines are also highly reliable and can offer up to 20,000 hours of use with no maintenance needed resulting in lower-cost operations. LED light sources are mercury-free and can power off and on quickly, even compared to laser light engines.

Using LED as a light source has been growing in popularity, mainly due to their small size, low heat, and affordability. Traditionally LED light engines are found in smaller, more portable projectors like a PICO projector. What PICO projectors lack in Lumens output is more than made up for in their size, power consumption, and portability. In some cases, PICO projectors can fit in a briefcase, purse, or even a pocket.

Although historically LED's light output was far less than lamp and laser-based projectors, things are changing. Developers of high-output LED lights, like OSRAM, Samsung, and others, have made remarkable strides in increasing the Lumens of the LED light engines. These next generation LED lights can generate up to 3500 lumens of light output.

Summary

Wanting to utilize laser, hybrid, and LED as light sources make sense, especially since they're often rated for 20,000 hours and higher. These projectors also require virtually no maintenance. However, the total cost over the lifetime of a UHP lamp projector can't be beaten. Having to spend a little extra (likely less than $200) every few years might be worth it, depending on the application.