Are lasers the future for home theatre projectors?
Once the stuff of the future, these days laser projectors are becoming more and more commonplace in the world of home theatre. Sure, they are still quite a bit more expensive than traditional light bulb projectors. But a lot is moving when it comes to projectors. Terms such as “laser”, “LED” or “hybrid” are used commonly. But what is what? What is worth your penny at this stage? And what does the future hold?
Time to shed some light in the lay of the land in light-generation for projectors.
A time flashback
Unlike Televisions, where light is “shot” at your eyes, and current light sources are arrays of LEDs or OLEDs, projectors are still based on the original principle of the brothers Lumiere: shoot moving images at a white (or grey, or other) surface and use the reflection of that projection to hit our retina.
For the last 122 years since that first movie projector, the light source in projectors changed from the original incandescent lights (and even lime lights! Hah, nostalgia…), to carbon arc lamps (that were used from the early 1900s until the late 1960s). In the 1950’s the Xenon arc lamp was introduced and ever since, nothing much has changed.
Until a few years ago, when the first laser projectors saw the light (pun intended). When Epson introduced the LS10000, laser projectors became closer within reach of affordability, but the sweet spot of $4,000-$6,000 of home theatre projectors has not yet been reached.
Light Generation Technology
At the very heart of a projector there is the light source. This is the bright concentrated light that gets shone to the micro display (either Liquid crystal or DLP, which we have covered in an earlier blog here).
There have only been minor tweaks to projector light source technology in the past few years. But the introduction of laser has shown the future for projectors. They are more efficient, environmentally-friendly and long lasting.
At the very beginning of a projector’s mechanism to produce the end picture is the light source. The 3 light sources that are used are projector lamp (incandescent light), LED (Light Emitting Diode), and Laser. All light sources must start with “white light” in order to illuminate micro displays.
Projector Lamp
The very first and most common in current projector’s light source is the lamp. Almost all business and home theater projectors rely on lamps that use mercury. We’ll call them UHP lamps which stands for Ultra-High-Pressure lamps, but they are also known as HID or High Intensity Discharge Lamp and half a dozen plus other acronyms like UHM, NSH, UHE, etc. Bottom-line is that they are all pretty much the same thing: they are mercury vapor lamps. Basically they are a cousin of the mercury vapor lamps used in street lights.
The UHP lamp was developed by Philips in 1995. The main advantages of UHP lamps are that they can get very bright, and they are relatively inexpensive to replace.
The downsides to UHP is their inability to produce fully saturated reds and their colour consistency will change over time. A projector using UHP starts loosing light almost immediately and most have lost 50% brightness by 2500 – 5000 hours. As you probably know, Projector Lamp lifetime is rated by what is known as ‘Half-Life’, which is the life time of the projector lamp till the lamp brightness becomes half as bright as it was when it was new.
Since these lamps are very bright they produce a lot of heat and require noisy fans for cooling.
An important factor to UHP lamps is that they cannot be instantly turned off, they require a period of warming up and cooling down for optimal performance. Turning them off without cooling will damage them.
Most of the popular home theatre projectors in the affordable range including the Sony VPL-HW45ES, EPSON EH-TW6600W, EPSON EH-TW9300, BenQ W1110 and JVC DLA-X5000 all fall into this category.
This will also be the case for the newly announced Sony VPL-VW675ES.
The alternative to UHP is Xenon lamps. These are most often used in professional projectors. The biggest advantage is that the white light produced by Xenon bulbs are better saturated in the three primary colours, which gives a more consistent performance. They produce less heat than UHP bulbs, so they require less cooling from fans. The major downside of Xenon lamps is that they have a lower optimal lifespan which is only around 1,000 to 2,000 hours. Due to their shorter lifespan and expense Xenon lamps are rarely found in domestic projectors.
The scientific and technical difference between lamps and the rest (LED, laser and hybrid) is that lamps create illumination through a hot filament, while LED, laser and hybrids work by corralling and manipulating electrons below the surface and forcing them to emit light at certain frequencies. These newer types of light sources are called ‘solid state’, with no moving parts resulting in much longer lifespans.
LED
This kind of light source technology is found in low end small and portable projectors. The light source consists of red, green and blue LEDs that results in a more accurate and consistent colour performance and their lifespan is much longer than UHP’s at about 10,000 hours. They do not dim like a regular lamp will, which means consistency will tend to last for its active lifespan. LEDs can be instantly turned off, with no warming or cooling down period.
The biggest downside to LEDs is that they are limited in brightness. You rarely see LED light source projectors in the high end home cinema models (although there are some like the Optoma HD90). In general, the cheaper models simply cannot perform at large sizes and distances away from the screen. Right or wrong, for most home cinema fundamentalists LED projectors are a no go.
Laser
Laser is the short form of “Light Amplification by Stimulated Emission of Radiation”. To explain in layman’s terms; a laser is a device that amplifies light and focuses it into a narrow beam of parallel rays of light. The light in lasers are of the same wave length or same color, and do not interfere with each other which makes the parallel beam of a laser able to travel very far without losing its strength.
In the projector industry, there are two main ways lasers are used as light sources. One is called the ‘laser phosphor projector’, the other one is a ‘true laser projector’ or ‘RGB (red-green-blue) laser’.
To increase output, most domestic laser home theatre projectors use two lasers; one for red and green and one for blue. Why not a laser for each primary color? It comes down to economics. Both diodes are blue; one excites a phosphor that creates yellow light (for the red and green primaries) and the other remains blue by using a neutral phosphor.
Examples of projectors that use laser-phosphor as their light source are the Panasonic PT-RZ570B and PT-RZ575E, the extremely high-end Sony VPL-VW5000ES, the newly announced JVC DLA-RS4500, the Epson LS10000 and its announced successor the LS10500.
Pure laser projectors use a separate laser diode for each of the red, green and blue source and go beyond the 12k-lumen limit of the laser-phosphor to a whopping 60k-lumens and over.
As we just mentioned earlier, projectors use red, green and blue light to create every color you see on the screen.
A normal projector lamp creates white light. This may seem like a good thing, but the fact is, projectors have to ‘throw away’ (absorb or otherwise block) most of this light, leaving only the red, green, and blue parts. It then projects those on the screen so you can see — wait for it — white light. Mildly inefficient, that.
True lasers only create the exact colors needed, which uses less power. And turns out that efficiency does mean laser projection systems can get brighter. Much brighter. Perhaps most interesting, lasers can be built to create whatever wavelength of light you want (within reason, of course). So wider color gamuts are possible without brightness issues. That translates to deeper, richer colors that come closer than ever to the vast range of colors our eyes can appreciate.
Of course, there is a considerable financial trade-off for the ultimate performance and pure laser projectors are mainly found in commercial cinema’s rather than the domestic environment.
In the past there have been concerns in the area of projector cooling in pure lasers linked to fire hazards. These concerns are starting to ease and regulatory bodies are relaxing as the new technology matures.
Faster on and off-times, and far greater lifespan and consistency in brightness and colour during its lifespan make laser projectors superior to incandescent light sources. They produce less heat, meaning less fan noise and you avoid the cost and burden of replacing lamps and getting your projector recalibrated every 500 hours or so.
Hybrid (LED-Laser)
Hybrid technology capitalises on laser and LED technologies. There are a few methods in which hybrid models use to create the white light. One way is through combining red and blue LEDs with a blue laser emitting through phosphor to create the green.
Hybrids produce images just as bright as lamps, but are longer lasting and far less power consuming. They outshine LED-only processors with 2,000 to 3,000 lumen capabilities. Hybrid mean fewer lasers and lower prices.
Panasonic offers several home theatre projectors in this category, like the Panasonic PT-RZ470EAK and the PanasonicPT-RZ370EA.
The Future of Projectors
So, what does the future hold? At this stage, the majority of projectors still use UHP bulbs, but until laser becomes cheaper and easier to implement, this is unlikely to change.
LED offer some of the widest colour gamuts, just behind lasers. LED would be suited for applications where colour accuracy is desired. Their lumen outputs are generally low, so they should be kept in controlled, low light conditions. If that is the case in your home theatre, they are a good option to consider.
Full laser projectors are generally limited to cinemas and commercial applications. This is because laser sources are still very expensive, and are used to power high lumen applications.
Laser phosphor projectors were developed for the mainstream market, and are coming down in price. They will generally be for home theatre customers who are in the market for a near cinema experience. Compared to true laser projectors, they still lack in the true colour department as the red and green light is generated from the phosphor wheel and are considered not as “pure” as a laser source. Just being pedantic here. If your budget allows, they are the bees knees.
Hybrid projectors may be a good compromise option, as they are lower in price than laser projects, are brighter than LED projectors and don’t have the fading brightness and fan noise that is typical to the lamp projectors.
Bottom-line: At this stage, lamp-based projectors are by no means obsolete, they are still the most affordable option. As things stand today, to restore the bulb back to its original brightness doesn’t offset the extra cost of a laser-phosphor projector. Especially for applications that don’t have heavy usage the cost of ownership would be lower than LED and Laser.
But with superior and more consistent picture quality, lasers do last longer than traditional projector lamps, they aren’t as fragile, and offer nearly instant on/off. Given a future price drop, lasers will be the future of front projection, we predict.
Sources: Projector Reviews, AV interactive, Cnet, Home Theater Hifi