What You Need to Know About Laser Video Projectors

Use lasers to light up your home theater viewing experience

Blue laser light

picturegarden / Getty Images

Video projectors bring the movie-going experience home with the ability to display images that are much larger than what most TVs can deliver. However, in order for a video projector to perform at optimal quality, it has to provide an image that is both bright and displays an broad color range. To accomplish this, a powerful built-in light source is needed.

Over the past several decades, different light source technologies have been employed, with laser being the latest to enter the arena. Let's take a look at the evolution of light source technology used in laser video projectors, and how lasers are changing the game.

The Evolution from CRTs to Lamps

Video Projectors - CRT (top) vs Lamp (bottom)
Video Projectors - CRT (top) vs Lamp (bottom). Sim2 and Benq

In the beginning, video projectors and projection TVs employed CRT technology, which you can think of as very small TV picture tubes. Three tubes (red, green, blue) supplied both the needed light and image detail.

Each tube projected onto a screen independently. In order to display a full range of colors, the tubes had to be converged. This meant that the color mixing actually took place right on the screen and not inside the projector.

The problem with tubes was not only the need for convergence to preserve the integrity of the projected image if one tube fades or fails, but also that all three tubes had to be replaced so that they all projected color at the same intensity. The tubes also ran very hot and needed to be cooled by a special gel or liquid. To top it off, both CRT projectors and projection TVs consumed a lot of power.

Functional CRT-based projectors are now very rare. Tubes have since been replaced with lamps, combined with special mirrors or color wheels that separate the light into red, green, and blue, and a separate "imaging chip" that provides the image detail.

Depending on the type of imaging chip used (LCD, LCOS, or DLP), the light coming from the lamp, mirrors, or color wheel, has to pass through or reflect off of the imaging chip, which produces the picture you see on the screen.

The Problem With Lamps

LCD, LCOS and DLP "lamp-with-chip" projectors are a big leap from their CRT-based predecessors, especially in the amount of light they can emit. However, lamps still waste a lot of energy outputting the entire light spectrum, even though only the primary colors of red, green, and blue are actually needed.

Although not as bad as CRTs, lamps still consume a lot of power and generate heat, necessitating the use of a potentially noisy fan to keep things cool.

Also, from the first time you turn on a video projector, the lamp starts to fade and will eventually burn out or become too dim (usually after 3,000 to 5,000 hours). Even CRT projection tubes, as big and cumbersome as they were, lasted a lot longer. The short lifespan of lamps necessitates periodic replacement at an added cost. Today's demand for eco-friendly products (many projector lamps also contain Mercury), calls for an alternative that can do the job better.

LED to the Rescue?

Video Projector LED Light Source - Generic Example
Video Projector LED Light Source - Generic Example.  NEC

One alternative to lamps is LEDs (Light Emitting Diodes). LEDs are much smaller than a lamp and can be assigned to emit just one color (red, green, or blue).

With their smaller size, projectors can be made much more compact, even inside something as small as a smartphone. LEDs are also more efficient than lamps, but they still have a couple of weaknesses.

  • First, LEDs are generally not as bright as lamps.
  • Second, LEDs do not emit light coherently. What this means is that, as the light beams leave an LED chip-based light source, they have a tendency to slightly scatter. Although they are more precise than a lamp, they are still slightly inefficient.

One example of a video projector that employs LEDs for its light source is the LG PF1500W.

Enter the Laser

Mitsubishi LaserVue DLP Rear-Projection TV
Mitsubishi LaserVue DLP Rear-Projection TV Example.  Mitsubishi 

To solve the problems of lamps or LEDs, a laser light source can be used. Laser stands for Light Amplification by Stimulated Emission of Radiation.

Lasers have been in use since about 1960 as tools in medical surgery (such as LASIK), in education and business in the form of laser pointers and distance surveying, and the military uses lasers in guidance systems, and as possible weapons. Also, Laserdisc, DVD, Blu-ray, Ultra HD Blu-ray, or CD player, use lasers to read pits on a disc that contains music or video content.

The Laser Meets the Video Projector

When used as a video projector light source, lasers provide several advantages over lamps and LEDs.

  • Coherence: Lasers solve the light scattering problem by emitting light coherently. As the light exits the laser as a single, tight beam, the "thickness" is retained over distances unless it is changed by passing through additional lenses.
  • Lower power consumption: Due to the need to provide enough light for the projector to display an image on screen, lamps consume a lot of power. However, since each laser only needs to produce one color (similar to an LED), it is more efficient.
  • Output: Lasers offer increased light output with less heat generation. This is especially important for HDR, which requires high brightness for full effect.
  • Gamut/saturation: Lasers deliver support for wider color gamuts and more precise color saturation.
  • Virtually Instant: The on/off time is more like what you experience when turning a TV on and off.
  • Lifespan: With lasers you can expect 20,000 hours of use or more, eliminating the need for periodic lamp replacement.

Just as with "LED TV," the laser(s) in a projector don't produce the actual detail in the image but provide the light source that enables projectors to display full color-range images on a screen. However, it is easier just to use the term "laser projector" rather than "DLP or LCD video projector with a laser light source."

The Mitsubishi LaserVue

Mitsubishi was the first to use lasers in a consumer video projector-based product. In 2008, they introduced the LaserVue rear-projection TV. The LaserVue used a DLP-based projection system in combination with a laser light source. Unfortunately, Mitsubishi discontinued all of their rear-projection TVs (including the LaserVue) in 2012.

The LaserVue TV employed three lasers, one each for red, green, and blue. The three colored light beams were then reflected off of a DLP DMD chip, which contained the image detail. The resulting images were then displayed on screen.

LaserVue TVs provided excellent light output capability, color accuracy, and contrast. However, they were very expensive (a 65-inch set was priced at $7,000) and although slimmer than most rear-projection TVs, they were still bulkier than Plasma and LCD TVs available at the time.

Video Projector Laser Light Source Configuration Examples

DLP Laser Video Projector Light Engines - RGB (left), Laser/Phosphor (right) - Generic Examples
DLP Laser Video Projector Light Engines - RGB (left), Laser/Phosphor (right) - Generic Examples.  NEC

The above images and the following descriptions are generic; there may be slight variations depending on manufacturer or application.

Although LaserVue TVs are no longer available, Lasers have been adapted for use as a light source for traditional video projectors in several configurations.

RGB Laser (DLP)

This configuration is similar to that used in the Mitsubishi LaserVue TV. There are 3 lasers, one that emits red light, one green, and one blue. The red, green, and blue light travel through a de-speckler, a narrow "light pipe" and lens/prism/DMD Chip assembly, and out of the projector onto a screen.

RGB Laser (LCD/LCOS)

Just as with DLP, there are 3 lasers, except that instead reflecting off DMD chips, the three RGB light beams are either passed through three LCD Chips or reflected off 3 LCOS chips (RGB) to produce the image. Although the 3 laser system is currently used in some commercial cinema projectors, it is not currently used in consumer-based DLP or LCD/LCOS projectors due to cost. There is another, lower-cost alternative that is popular for use in projectors: the Laser/Phosphor system.

Laser/Phosphor (DLP)

This system is a little more complicated in terms of the required number of lenses and mirrors needed to project a completed image, but by reducing the number of lasers from 3 to 1, cost of implementation is greatly reduced. In this system, a single laser emits blue light. The blue light is then split in two. One beam continues through the rest of the DLP light engine, while the other strikes a rotating wheel that contains green and yellow phosphors, which, in turn, create two green and yellow light beams.

These added beams join the untouched blue light beam, and all three pass through the main DLP color wheel, a lens/prism assembly, and reflect off the DMD chip, which adds the image information to the color mix. The completed color image is sent from the projector to a screen. One DLP projector that employs the Laser/Phosphor option is the Viewsonic LS820.

Laser/Phosphor (LCD/LCOS)

For LCD/LCOS projectors, incorporating a Laser/Phosphor light system is similar to that of DLP projectors, except that instead of using a DLP DMD chip/Color Wheel assembly, the light is either passed through 3 LCD chips or reflected off of 3 LCOS chips. However, Epson employs a variation that employs 2 lasers, both of which emit blue light.

As the blue light from one laser passes through the rest of the light engine, the blue light from the other laser strikes a yellow phosphor wheel, which, in turn, splits the blue light beam into red and green light beams. The newly created red and green light beams then join up with the still intact blue beam and pass through the rest of the light engine. One Epson LCD projector that uses a dual laser in combination with a phosphor is the LS10500.

Laser/LED Hybrid (DLP)

Another variation used primarily by Casio in some DLP projectors is the Laser/LED hybrid light engine. In this configuration, an LED produces the needed red light, while a laser is used to produce blue light. A portion of the blue light beam is then split off into a green beam after striking a phosphor color wheel.

The red, green, and blue light beams then pass through a condenser lens and reflect off of a DLP DMD chip, completing the image, which is then projected onto a screen. One Casio projector with a Laser/LED Hybrid Light Engine is the XJ-F210WN.

The Bottom Line

BenQ Blue Core LU9715 Laser Video Projector
BenQ Blue Core LU9715 Laser Video Projector. BenQ

Laser projectors provide the best combination of needed light, color preciseness, and energy efficiency for both cinema and home theater use.

Lamp-based projectors still dominate, but the use of LED, LED/laser, or laser light sources is growing. Lasers are currently used in a limited number of video projectors, so they will be the most expensive. Prices range from $1,500 to well over $3,000, but you also have to consider the cost of a screen, and in some cases, lenses.

As availability increases and people buy more units, production costs will come down, resulting in lower-priced laser projectors. Also take into consideration the cost of replacing lamps vs. not having to replace lasers.

When choosing a video projector—no matter what type of light source it uses—make sure it fits your viewing environment, budget, and personal taste.