PHILIPS UHP LAMPS OVERVIEW

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In the next lines we will try to explain how work a modern PHILIPS UHP Lamp
 

LIGHT SOURCE

The light system in a projector may seem trivial; shine a light on or through an imaging device, and look at the results on a screen. What's the big deal?

The big deal is that photons (light particles) are notoriously difficult to control. Trying to get them to go where you want is a lot like trying to herd cats. You also have to cope with lamp life, and uniformity issues. As a result, projector engineers spend a lot of time struggling with light source problems.

Consider the size of the light source itself. You may know the special property of an ellipse; if you put a radiating source at one focus of an ellipse, the radiating beams that hit the ellipse are reflected so that they come together at the other focus of the ellipse (see diagram below). This effect is used to concentrate the light from a lamp onto a lens or other optical device, so that as much light as possible is delivered to the imaging engine, and from there to the screen. If your source is bigger than a single point, however, not all the beams originate precisely at the focus, and they are likely to end up missing the other focus point. Also, the wider the ellipse--meaning a greater distance between the two focal points, then the larger the beam spot will be at the second focus.

Note the focused area in the left image is closer to the reflector, and much smaller as well. (From "Fundamentals of Projection Displays" by Terry Schmidt, Christie Digital Systems--a course presented at SID conference, June 3, 2001)

Stray light can cause a number of problems at this stage, as well as in other parts of the projector along the light path. First, light that is not funneled through the optics ends up striking other surfaces inside the projector. This can result in reduced brightness at the screen, and increased heat in the projector. Some light may even escape through openings in the case, creating annoying and distracting light leaks.

The other problem is that the stray light may well find its way back into the optics, and end up striking the screen in places where it should not. This can reduce the overall contrast of the image, because instead of showing solid black when needed, the stray light will turn the black to gray.

One key element of controlling the light beam is to reduce the size of the light source. The ideal source would be infinitely small without any loss of brightness, or luminance (the amount of light produced). Unfortunately, practice can't measure up to theory.

Until recently, most projectors relied on metal halide lamps that use a spark across a gas-filled gap to create the light. The gaps are typically 2 mm or larger. These can have color and luminance stability problems. They also tend to deposit materials such as tungsten on the walls of the lamp during operation, resulting in reduced brightness starting early in the useful life.

Now, most projectors use Ultra High Pressure (UHP) lamps invented by Philips. These use an arc in a pure mercury vapor under high pressure. The arc gap can be 1.3 to 1.0 mm across, creating a much smaller light source. This results in much greater lighting efficiency; a 100 watt UHP lamp in a projector can deliver more light to the screen than a 250 watt metal halide lamp. This advantage increases as the imaging panels get smaller.

Exceeding the brightness of the sun, the UHP lamp is the ideal light source for demanding optical applications.
 

UHP lamps range from 100 to 200 watts, with useful lifespan ranging from 3,000 to 10,000 hours. To prevent reduced light output, small amounts of oxygen and halogen are mixed with the mercury vapor, and these help remove tungsten deposits from the lamp's walls, and redeposit them back on the electrodes. The result is a lamp that regenerate itself and maintains almost all of its initial brightness up until the day it fails.

The pattern of the light output can vary as the shape of the arc electrodes change over time. The glowing plasma between the electrodes can also change rapidly. As a result, you can get areas on the screen that are brighter or dimmer than the rest. Some of these problems can be addressed by optics. Philips has also developed a way to modulate the power pulses that are applied to the arc that results in a more stable light output and extended lifespan. 

UNDER PRESSURE

UHP lamps operate at pressures above 200 atmospheres. The scuba divers reading this know well that an atmosphere, corresponding to standard atmospheric pressure at sea level, is about 14.7 pounds per square inch. 200 atmospheres is then about 3,000 pounds per square inch.

The extremely high lamp pressure is important to achieve the desired light output, because not only is more red light emitted at the higher pressure level (above 200 atmospheres, about 20 percent more red light is emitted than at 160 atmospheres), but also at such high pressures the nature of the emission spectrum is more continuous and less a combination of a few atomic spectral lines.

While the operating voltage requirement for a small-arc UHP lamp is low, a much higher striking voltage must be used to shock the mercury atoms into the luminescent plasma state when the lamp is first ignited.

To generate the very high luminance in the small beam of light required by a liquid crystal microdisplay, the lamp's arc must be quite short. Current UHP lamps have arc lengths of about one millimeter.

To give an idea of the parameters for a UHP projector lamp, we will look at an example of a UHP 100W 120W Philips lamp for LCD projection:
 

Manufacturer: Philips Lighting
Max Lamp Power: 120 Watts
Max Lamp Current: 2.0 Amps
Max Lamp Operating Voltage: 65 Volts

Ignition Voltage: 5 KV
Bulb Finish: Hard Dichroic Cold Mirror
Bulb Type: PAR-22 Borosilicate with front glass

Reflector Size: Parabolic 65x70mm
Arc Gap: 1.0 mm
Electrodes: Solid tungsten
Atmosphere: Argon + bromine
Luminous Flux: 6000 lm at 100W

                       7000 lm at 120W
Luminous Efficacy: 58 lm/W
Colour Temperature & CRI: CCT : 7600K CRI : Ra 57
Chromaticity Co-ordinates: CCx : 0.298 CCy : 0.311
Rated Life: 8000 hours at 100 W

                 6000 hours at 120 W
Factory: Turnhout, Belgium

DIFFERENCES: Metal Halide and UHP Mercury Lamps

Some metal halide lamps have short arc construction. These include most metal halide lamps under 100 watts. However, the arc is larger in a metal halide lamp since the metal vapors in the arc easily glow at lower temperatures than mercury vapor do. For this reason, the arc is less intense than the UHP mercury arc. When maximum light concentration is required, "true" UHP arc lamps based on mercury are used.
 

As for why specialty Projector Lamps cost so much?

LCD projector lamps (also called LCD projector bulbs, LCD projector modules, data projector bulbs, data projector modules, or video projector bulbs) are highly specialized lamps with a high cost of production and development.

Many things contribute to the high cost of projector lamps, in this particular case, Philips invested hundreds of millions in the development of the UHP lamp and, of course, they want a return.

UHP Projector lamps are made of borosilicate glass and fused quartz. Quartz is hard as a rock at the melting point of iron (1535 degrees C). Steel tools melt before quartz gets workable. And you need torches using oxygen to get hot enough - a regular Bunsen burner or even a "MAPP" gas blowtorch from a hardware store is not hot enough.

And if you have the heat and the tools, there is still another problem - quartz has a narrow plastic range of temperature. The temperature needed to get quartz barely as soft as taffy or frozen chewing gum is only a few dozen degrees short of making quartz liquid enough to pour. Quartz is trickier to work than glass and glassblowers that can work quartz will not be working for minimum wage!

Although we are in a world of mass-production, many steps of the UHP Lamp manufacturing process still are hand-made by a skilled craftsmen and will cost many times the cost of a mass-produced lamp.

Production machinery that can mass-produce quartz lamps is so expensive that only lamps that will sell in huge quantities (hundreds of thousands) can be made economically by such machinery. Otherwise it would cost even more to get the machines made and set up than it would be to hire those highly skilled glassblowers.

If you have a specialty ARC lamp design that would use the same bulb and the same leads as a lamp that is in mass-production, then maybe you could make a deal with an existing lamp manufacturer. (Expect a minimum production run of thousands - perhaps many thousands - of lamps at a price at least a few times that of a mass-production lamp in order to make it worthwhile to the manufacturer.)
 

HAZARDS OF AND SAFETY PRECAUTIONS FOR UHP LAMPS

Projector lamps have numerous hazards. They do not make good toys.

The arc light is about as intense as a welding arc or a carbon arc. One should not look directly at the arc. If your eyes are already adapted to bright light, you may get away with looking at the arc for up to a few seconds with no permanent eye damage - but doing this is NOT a good idea. You won't hurt your eyes looking at the arc through #12 welding glass - but there are other hazards. All projectors have a series of filters installed between the light patch to ensure an efficient block of UV radiation. Filters made for looking directly at the sun will also make the arc safe to look at directly. Most other dark transparent materials will not protect your eyes since they let through enough infrared to risk cooking spots on your retina - an eye damage phenomenon notoriously lacking warning signs.

The arc emits almost every kind of ultraviolet in the book, including large amounts of UV-A, UV-B, and some UV-C. These different ultraviolet bands are bad for different parts of your eyes. Number 12 welding glass and sun-viewing filters will protect your eyes. However, the UVC, UVB, and the shortest UVA wavelengths can sunburn your skin. Serious sunburn and increased risk of skin cancer may result from significant exposure to this radiation. These wavelengths are blocked by ordinary glass, but for other reasons below it is HIGHLY RECOMMENDED to only operate UHP lamps in fixtures designed and made for them by qualified personnel - typically engineers and technicians who work for the fixture manufacturers.

The shortest ultraviolet wavelengths emitted by UHP lamps can generate ozone. Operate the lamps in an adequately ventilated area. If you can smell the ozone, it can noticeably irritate your lungs within hours.

UHP Projector Lamps operate at red-hot temperatures of up to 900, sometimes even 1050 degrees C (approx. 1650-1900 degrees F) and contain very high pressure usually in excess of 160 atmospheres and often near or over 200 atmospheres, and in a few cases 300-plus atmospheres. They can explode. Rarely, but who knows how rarely, they explode when nothing can be detected as wrong. If operated in any way other than as specified or past their intended life expectancy, the risk of explosion increases. Explosions can be dangerous since they can result in red-hot (or hotter) pieces of glasslike quartz being shot out in all directions, possibly with considerable force. These lamps should only be operated in fixtures made for these lamps and designed to contain a lamp explosion. These lamps contain mercury, so you might not want one to explode in your home even if there was no risk of fire or red-hot glass shrapnel.

UHP Projector lamps require forced air cooling. This is another reason to operate them only in fixtures designed for the particular lamp being operated.

UHP lamps have pressure well above 30-50 atmospheres even when they are cold. You don't want to drop one and have it break......... think of a hand-grenade!

UHP Projector lamps have quartz bulbs operated under stress at high temperature. The usual halogen lamp rules for bulb cleanliness apply. Carbon and oil deposits can absorb light and make hot spots. Traces of any sort of ash, salts, metal oxides, or alkalis can leach into hot quartz and cause strains which can weaken the quartz.

You should not touch the bulb. If you touch the bulb, you can clean it with alcohol so that no skin oil traces are left on the bulb. It may also be a good idea to rinse the bulb with distilled water.

Do not operate a UHP lamp that has been scratched or chipped.

UHP Projector lamps should be operated only at the wattage they were designed for and with the type of current they were designed for. Overpowering them is obviously bad. Underpowering an UHP lamp can also be bad, since a slightly-too-cool electrode does not emit electrons easily, and the voltage drop in the cathode region of the arc increases and causes positive ions to hit the cathode harder, which "sputters" off cathode material. This will discolor the bulb and may cause the bulb to overheat or have an abnormal temperature gradient somewhere and could make the bulb explode. Discolored bulbs as well as abused electrodes can really overheat if operated at full power.
UHP Projector lamps are designed for AC, and typically have two identical main electrodes. Operating an AC lamp on DC will overheat and/or excessively age at least one electrode. Aging electrodes have limits in the peak rate at which they can emit electrons without overheating or sputtering, and peak current has to be minimized. Excessive peak current may accelerate aging of electrodes that are in good shape.

UHP Projector lamps may have to be operated in a specific position so that convection currents - internal and external - don't cause vulnerable parts of the lamp to overheat. This is another reason to use them only as directed in proper fixtures designed specifically for the lamp being used. Follow all directions that come with the lamp and all directions that come with the fixture.

With all this trouble and the high cost of UHP Projector lamps, it is no wonder why they are only used where there is no substitute for a small, very intense light. UHP lamps are not good toys for casual experimenters.
 

OPERATING INSTRUCTIONS:

   Manufacturer guidelines

• Do not touch or handle this lamp without wearing glove.

• If this lamp touched by bare hands, the lamp must be cleaned with towel and alcohol solution.

• Do not touch a lightened lamp or a lamp immediately after off-operation; High heat may cause sever damage.

• The lamp generates UV radiation, do not look directly into the light; Avoid directly exposing skin to the light.

• The lamp may only operates properly in an approved and appropriately operated projector.

• Fast on-off switching may cause short lamp life.

• For lamp replacement, the power must be switched off when operating in equipment.

• Safety protection is needed for the lamp area because of high ignition pulses.

• Surrounding temperature should be less than 55 C

• Operating voltage : The average operating voltage should deviate from the rayed voltage indicated on the type plate by no more than 3%
  Sudden voltage deviations of more than +/- 10% may cause the lamp to go out.
  Permanent operation at a voltage above or below the rated supply voltage may lead to changes in the light color and a reduction in the life of the lamp.

• The lamp take about 2-5minutes after being switched on to reach its full luminous flux.

• Color variations : As with all metal halide lamps, there may be difference in color from lamp to lamp. This may be due to external factors such as mains voltage, control gear and luminaries design.
   

When a lamp comes to the end of its life it must be replaced as soon as possible to prevent damage to the control gear and radio interference.

These lamps can be considered to have come to the end of their service life if:

• the light color of the lamp changes dramatically or-

• there is an appreciable loss of brightness or

• the lamp periodically goes out and restarts or

• the lamp no longer ignites

Sometimes a UHP lamp end it's life with a explosion or a big pop.

Also in general:

The high pressure lamps require an incrementally higher start voltage at each start. At the end of life the lamp might still be capable of firing, but requires more voltage than the ballast can provide. It explains the cases when a set would not start for several days, then it starts the first time but maybe not again until the lamp is replaced.

UHP LAMPS FAQ

What is "Lumen"?

A unit of measure for the amount of light emitted by a source.? 0.98 Ft-c (foot-candles) of light covering a surface of 1 square foot.
The international unit of luminous flux or quantity of light. If a uniform point source of one candela is at the center of a sphere of one foot radius, having an opening in the surface of one square foot area, the quantity of light that passes through is called a lumen. The sphere has a total surface area of 12.57 square feet. Since, by definition, a lumen flows to each square foot of surface area, a uniform point of one candela produced 12.57 lumens.

What is "ANSI Lumens?

A standard for measuring light output, used for comparing projectors. Unfortunately, there are enough variables, that the eye will often disagree radically with the ANSI rating. At best, ANSI lumens do fairly well comparing "apples" to "apples". If however one projector uses Halogen lamps and another metal-halide, the halogen projector will seem noticeably dimmer even if the two units rate the same. Other variables, including type of LCD technology (active matrix TFT, Poly-Si, passive), type of overall technology (LCD vs. DLP vs. CRT), contrast ratios, etc. all effect the end result. Example, We often find that a projector with a power rating of only 400 lumens appear to the eye more powerful than a another Projector of 2000 lumens

What is "Lux"?

SI (international system) unit of illumination. One lumen uniformly distributed over an area of one square meter.

What is "Lumens per Watt"?

A ratio expressing the luminous efficacy of a light source; light output divided by power watt.
Examples: Edison's first lamp 1.4 L/W
Fluorescent lamps 35-100 L/W
Infrared lamps 6-9 L/W
Incandescent lamps 10-40 L/W
Mercury lamps 50-60 L/W
Metal Halide lamps 80-125 L/W
High Pressure Sodium lamps 100-140 L/W
Theoretical max for white light 225t L/W

What is "Color Temperature"?
Apparent color temperature (or correlated color temperature) of a light source-indicating its degree of warmth or coolness, with the higher number being "cool".
 

Please check the Philips research website to know the status of new developments about UHP lamps, It is a rich website, you can watch videos of the new lamps and information.

http://www.research.philips.com/profile/people/researchers/uhp.html

Return to PHILIPS PROJECTOR LAMPS

NOTE: Some PHILIPS lamps are not longer available, hard to get or extremely expensive but we have a source of Philips bulbs (without case) with a price range between $250 to $390

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