Showing posts with label Polyvision. Show all posts
Showing posts with label Polyvision. Show all posts

Tuesday, February 27, 2018

What Makes a Projector? -DLP

Projectors have come a long way over the years.  At first they used film to feed through a mechanical shutter with the 2 large reels holding the film. Now they have become stand alone display devices.  More similar to a TV screen than a slide projector.

What makes them what they are today? There are essentially two answers to that question.  One is LCD technology and the other is DLP technology.  They both use replaceable lamps, but how they use those lamps to create the image is what sets them apart.

This begins a short series on Projector display technology.  This post we will cover DLP Projectors.

DLP is an acronym for Digital Light Processing. Invented in 1987 by Larry Hornbeck of Texas Instruments the digital mirrored device chip(DMD).

The first video projector to use this technology was built by Digital Projection in 1997.  Both Digital Projection and Texas Instruments won an Emmy Award for the use of DLP technology.

A DMD chip(pictured above) is made up of microscopic mirrors arranged in an array on the chip surface.  The mirrors are controlled via small electrostatic pulses to adjust their angle.  The angle causes them to either reflect the light out the lens onto the screen or away from the lens to create black or lack of light.  Each mirror is made up a microscopic yoke, torsion spring, and the electrostatic pads that affect the memory cells that set the position.

The diagram to the right shows the construction of each pixel.  Depending on the resolutions the amount of pixels changes. For instance an 800 x 600 DMD has (800*600 pixels= 480,000) pixels or mirrors that are controlled.  However some chips use a method of oscillating the mirrors to have them act double duty, halving the amount of mirror elements needed in a DMD chip.  

DLP Chips are monochrome or single colored. They can only turn light on and off and adjust its brightness. It cannot color the light.  This is where the next most important device of a DLP projector comes into play.

The Color wheel is a glass wheel made up of multiple segments all with a different color glass light filter.  On average they use 4 segments: red, blue, green and clear. Some models have multiples of the same color.  Others use 6 segments colors red, purple, blue, light blue, green and yellow.  The projector syncs the rotation of the color wheel and the color needs of the DMD while the image is being projected. DLP uses optical persistence to "fool" our eyes into seeing a mix of colors when in reality the projector is only projecting one color at a time for a fraction of a second.  If you blink your eyes quickly while looking at the DLP projected image, you can see the colors by themselves.

These 2 devices more than any other set the DLP projector apart from LCD.  Other differences are in the electronics.  There are a whole set of electronics that only are there to support and control the DMD chip.  These electronics are not as physically obvious but are no less important. These chips are for driving the electrostatic control signals to the DMD, as well as the video processing chips that prepare the signal to the DMD controller.  There is a motor control chip that keeps the color wheel in sync so that why the DMD is projecting the red portion of the image, the red color wheel segment is in position.  These all work together to ensure a pleasant and vibrant image.  

The main benefit of DLP over LCD(at the time) was the contrast ratio. Contrast ratio is the difference between a full white and full black image. When using a lamp to create an image there is almost no chance of having true black as black is the absence of light.  Turning off the lamp for the black portions of the picture is not practical.  Rather the pixels that require black merely point their light away from the main lens creating black on the screen.  Since the mirrors are only pointing away, there is some minor light leakage so the "blacks" are not as black as they could be.  The higher the ratio, the darker the blacks and brighter the white bits of the image will be. This was more of an issue with DLP first came to market as LCD had abysmal contrast.  These days they are pretty much the same contrast ratio-wise.

The last and most obvious difference is the lamp used in DLP.  Both DLP and LCD use Short ARC Mercury vapor lamps but only DLP uses this particular arrangement.

DLP Lamps commonly use a non-optical lens. Meaning there is no focusing or change in direction of the light beam.  Rather they have lenses inside the optics that do any light adjustment needed.  The lamps do have a special coating on the lens(ND filter lens). That coating prevents UV(ultraviolet) and IR(infrared) light from being injected into the light path.

DLP Lamp with UV/IR coating

LCD LampThese can harm your eyes and the optics due to heat and radiation.  This coating is a big reason why we do not recommend replacing only the bare bulb. If that coating fails or fails just a little it can cause your color wheel problems and possibly even melt some of the lenses.

Here is a picture of the internals from a Polyvision PJ905 that uses a 2002031-00 Lamp that has the proper coating.

PJ905 Internal diagram of DLP projector.

This about sums up the DLP video projector.  They are a reliable and well proven piece of technology.  Pureland Supply takes a lot of pride in our lamps and we make sure every lamp that is used in a DLP projector(as well as LCD) is configured correctly to perform as well as possible for you.  Check our selection of lamps here. 

Stay tuned for next week when we discuss LCD projectors. If you have any questions please do not hesitate to contact us at 1-800-664-6671 or

Friday, January 5, 2018

6 Steps to Change Your Projector Lamp

Here are 6 Basic Steps for Lamp Replacement. 

You should always refer to the owners manual for the proper specific steps but if you have a pretty basic Projector or Rear Projection TV, these steps should get you back up and running.

    1. Preparing the Projector to Be Opened
Before attempting to open the projector, users should turn off and unplug the device. They should also allow the device to cool down. It could take anywhere from 30 to 45 minutes for the projector to cool down completely. Then remove any dust on the outside casing with a soft, dry, and clean cloth. This will ensure that dust does not enter into the machine and get onto the vulnerable interior parts.

2. Remove Lamp Access Door
Some projectors may have covers that come off completely while other models just have a smaller compartment door that gives users access to the lamp housing unit. Projector owners can determine what kind of opening they have by looking at the projector and consulting the manual. 
No matter what the cover or the compartment door must be opened.  You will most likely need a screwdriver to remove the screws that keep the cover or door closed. Once the screws have been removed, you can carefully remove the panel or door. You should also take the time to unscrew any screws that may be keeping the housing unit of the lamp in place before attempting to remove it.

3. Taking Out the Old Projector Lamp 
This is a step that users must take care to complete properly. Doing otherwise may cause the old projector lamp to burst, which is dangerous for both the projector and the user. Because projector Bulbs inside the lamps are very fragile.  They can burst after starting because they have come into contact with the natural oils that are present on fingers.  this causes the glass of the bulb to expand at different rates when it heats.  For this reason you should always use the handle on the lamp to pull it out.  As an example the Christie 003-120507-01 
lamp has two points on the bottom to grab the lamp for removal.

4. Putting In the New Lamp
Once the old lamp is removed, the user can then place the new lamp housing unit inside of the Projector/TV. Users should make sure to slide the housing unit fully into the projector, with the new lamp in the same position that the old one was in. Certain projectors may require that power cables be reconnected to the new lamp. If this is the case, users should follow the manuals for specific instructions on how to do this.

5. Getting the Projector Ready to Run Again
   When the switch has been made, you can screw the new lamp housing unit into place and then re-attach the lamp access panel. Be sure to not over-tighten the screws.  At this point, the users can reconnect the projector to the electrical outlet and turn on the project to see if the new lamp works. If the projector still does not work after the lamp replacement has been made, there may be a larger issue that is causing the problem. In this case, users should seek the help of professionals specializing in projector repair in order to determine the right course of action.

6. Resetting the Lamp timer
If the projector is working properly, then the user will need to reset the lamp counter so that it can begin tracking time for the new lamp that has just been installed. Some projectors might reset lamp counters automatically, but for those that do not, users may need to do this manually through the projector menu. After completing all of these steps, the projector should be ready to provide hours and hours of entertainment once again.

If at any point you are uncomfortable or unable to perform these steps, please do not hesitate to contact our world class customer service department for assistance.  We have one of if not the best trained representatives to help you with your problems.

We can be reaching by calling our office at 1-800-664-6671. You can also email us at 

Thursday, December 14, 2017

4 Common Mistakes that Projector Owners Must Avoid

Your projector might be a small unassuming device you throw in your laptop bag between presentations. It might also be a venerated piece of gear carefully installed into your Home Theater.  Maybe you are tasked with handling a school districts worth of SmartBoards...

In any of these situations there are 4 common mistakes people make when they own a projector. These mistakes are not only annoying but can also be costly to rectify.

1. Ordering a Cheaper lamp that "looks" OK.  

Sure, that lamp might be under $50 and says it will run in your projector but as I mentioned in an earlier blog, your cost of ownership can be over 4X what it should be if you had purchased an Original Inside lamp.  Check with the company and see what brand bulb is inside.  Your old lamp will have markings on that bulb. Make 100% sure your new lamp is the same as the old one.  The adage of "if it looks too good to be true, it probably is" holds very true here.

2. Replacing the bulb portion only. 

Always buy a full lamp if its available.  This is/has been advertised by many companies over the years. They offer an explanation that you can get away with only replacing the bulb since the bulb is the only part of your lamp that goes bad right?  In most cases this is not true. While the plastic and metal structure of the lamp will handle tens of thousands of hours of heat, the other parts, such as the lamp's lens and wires will not.  On a lamp for a DLP projector, there is a special coating that is applied to the lens. That coating blocks harmful ultraviolet and Infrared light from entering the optic path of your projector. Since that coating has degraded over the years, your 2500 hours lamp housing now is only blocking a percentage of that UV/IR light.  That now un-blocked light is attacking your optics.  It will cause the lenses inside to heat-up and eventually start melting. The more concerning problem is that you are exposing you, your family or coworkers to dangerous invisible UV/IR light over a few dollars.   I will say, there are a handful of projectors who use a built in IR/UV filter that is made to handle repeated bulb replacement. These are few and far between. For a few dollars more you will have the peace of mind knowing you are protecting your investment as well as the safety of yourself and those around you.  This BenQ 5J.05Q01.001 is a good example. The lens on the front shows the coating. This is also a problem for cheap lamps. They use an inexpensive coating that will not work as well. The glass has a 'green' shine to it. If you see that send the lamp back.

3. Resetting the Lamp timer without replacing the lamp.  

This is a bad idea. While you are probably thinking you are putting one over on the manufacturer, you are only putting your projector at risk.  The time limit on your projector lamp is determined by the manufacturer of your projector. They determine this by seeing how long the lamp can run before the light output drops past a certain threshold (varies per model) and/or when the lamp may be getting deformed from heating cycles(on and off).  Once a lamp begins to deform, it has an increased chance of rupturing.  If you lamp ruptures while running, the chances of damaging the projector also increase dramatically. That "replace lamp" warning is the best time to buy a new lamp.  If your old lamp still works, then put it away as a backup. Your new lamp will be much brighter and will ensure longer functional life of your projector.

4. Not cleaning your projector often enough.  

This is by far the most common mistake I see with projectors. A dirty projector is a projector that is unable to cool properly.  That will lead to shortening the life of the lamp and the projector itself.  No matter how clean your house is, there is dust in the air.  That dust is pulled into the projector via the cooling fans. Electricity generates a static charge which causes the dust to stick to components inside. Over time that dust will cover the heatsinks that cool electronics like the DLP chip. That dust will build up on the leading edge of the Lamp cooling fan blades. Once enough blades are coated the fan will no longer push enough air through the lamp.  When your lamp is running at 500F and that air stops flowing, you can expect 700F+ at the lamp. That corresponds to increased heat throughout the projector. The lamp will finally reach the temperature for the Quartz to become soft. Once that happens it’s only a moment before the arc tube in the center of the lamp ruptures. I recommend having your projector opened and cleaned at least once a year.  At the least, take a vacuum cleaner and some canned air (air duster, not Perri-Air) and blow out and dust through the intake/exhaust vents on the side.   In the future I will address cleaning to a more direct degree.

There are other mistakes and suggestions, but these are the top 4 that I see. A few weeks ago, I had the pleasure of cleaning some NEC V260X projectors that had never been cleaned in 7 years.  They had enough dust that I could weigh it.  They also had bad color wheels because of the heat and would sometimes get as much as 200 hours before a new lamp would fail. After cleaning them and replacing the color wheel, the NP18LP lamp I installed will run for its entire expected life.

Monday, December 4, 2017

How Close Can I Get? Short Throw Projectors

What is a Short Throw projector? I promise it's not what you do when your lamp dies early..

Buying a new projector can be daunting. There are so many to pick from. Especially if you need a specific type like a Short throw.  What is a short throw projector you ask and why might you need one?

Sometimes your space doesn't allow for a standard distance from the screen.  Many basements and home theaters allow the projector to be installed 10-20 foot back from the screen.  Occasionally you need to mount the projector very close (less than 1-5foot back).  The problem then becomes the image cannot be made large enough with the standard lens. This is where the short throw projector comes into play.

A short throw lens uses a special optical design that makes it easy to position the projector close to the screen without sacrificing image size.  You will see this very often in schools.

When the schools use a Smartboard system, it relies entirely on short throw projectors such as the Smartboard UF55 which uses a 20-01032-20.  This lamp with housing uses an original 215W Osram lamp, projecting 2000 lumens via the projectors short throw lens.
These models use the short throw lens design to allow a 100" image from only 2 feet away. This allows the mounts to be very close to the screen. They both utilize a standard projector lamp, part # but allow a full sized image without sacrificing space.

This can be useful at home. You can use a smaller room and still enjoy movie theater-like image sizes.  The Steelcase Polyvision PJ905 with a 2002031-20 lamp is a short throw projector that supports up to a 1080p input.  There are other models that use short throw lenses as well. Picking the right projector will be a series in this blog by itself so I wont go into it here.
Steelcase Polyvision PJ905 Projector 2002031-001 lamp

Using a short-throw projector at home can save you a lot of setup and configuration hassle. It opens up a lot of spaces that used to not be convenient for a projector. Even if you live in a narrow apartment, a short throw projector can work in as little as 10" from the screen. Many projectors have a short throw lens as an option.  That would manufacturer dependent.  Buying a lens already installed is also an option.

Stay tuned for our upcoming series on choosing a projector. In the meantime feel free to contact us with any  questions you might have at or