Tag Archives: efficiency

New Pro Polaroid 3D Glasses [Updated]

These are the questions asked, and now answered during an email coorespondance:

Given that darkness is the main issue with 3d and typically glasses contribute to that darkness by some varying degree… How good can polaroid get with circular polarization – We have a transmittance of 42-44% which is as high as one can get without loosing polarizer efficiency. We are looking at AR coating to further improve this value.

What is the light transmission spec for the specs? – 42-44%. More importantly is the transmittance of the polarized light, which in our case can reach as high as 84 to 88%.

What is the polarization efficiency? – It needs to be 99.9% in order to maximise the 3D effect.

Are the lenses matched left and right- tests have shown that this is a common problem with those glasses – From a transmittance point of view, yes.

[It is obvious that there a lot to learn if we’re going to ask the proper questions. Back to the original article.] 

Are the lenses matched left and right – tests have shown that this is a common problem with some glasses.

Is there an AR coating on the inside? Does this reduce transmission more than it helps internal face glare?

Part of the problem that “Pros” face is that they have to look up at 3D screens while they have to look down at computer keys and editing levers and knobs in 2D. They need a dual lens solution, maybe even the ability to have their doctor etch their prescription into the bottom of the lens. Has Polaroid accommodated for this?

Is this line being sold direct through Polaroid?

We wrote an article last year whenn Polaroid announced a line of 3D glasses for consumers. Wonder how that went. RealD and Polaroid — Possible Promise PR.

Here is the new press release:

Polaroid Eyewear Launches Professional Range of 3D Glasses

Zurich, Switzerland, 9 September 2011 – Polaroid Eyewear today announced the launch of the first two styles in its Professional 3D Eyewear Collection.

The Polaroid Professional 3D Collection, which uses passive circular polarization, has been specifically created for 3D professionals and producers of 3D content. These first two styles both have interchangeable lenses, meaning that after work, professionals can simply change the lenses and use them as stylish sunglasses.

The frames are produced using premium quality materials and precision, making them both lightweight and robust. The lenses are produced using ThermofusionTM technology, which is exclusive to Polaroid Eyewear and ensures distortion-free vision.

Polaroid Eyewear already has a wide range of consumer 3D glasses on the market place, which offer high quality and comfortable viewing, and can be used with passive 3D systems, such as RealD and masterImage, as well as a number of passive 3DTVs.

Both the professional and consumer ranges have curved lenses, which wrap around the sides of your face and therefore block out any excess light, providing high contrast vision right across the lens.

“Polaroid Eyewear’s entire range of 3D glasses combines stylish design and expert technology to deliver great quality passive circular-polarized 3D glasses.”, commented Eva Dudek, Marketing Project Manager, Polaroid Eyewear. “With the Professional Range we have taken that one step further to give professionals extra comfort for long viewing periods, as well as a picture-perfect 3D viewing experience.”

The collection is due to be expanded shortly and will offer a choice of exclusive high quality styles.

About Polaroid Eyewear

Polaroid Eyewear is a world leader in optics and lens technology and a global eyewear manufacturer and distributor. Polaroid invented the first man-made polarizer for commercial use in 1929 and has been a pioneer and expert in polarizing lens technology ever since. Polaroid Eyewear remains a market leader in manufacturing high quality polarizing lenses and distributing fashionable polarized sunglasses around the world. Demand for polarizing eyewear is rising steadily as more and more consumers come to realize the benefits of glare-free vision.

Polaroid Eyewear is part of the global StyleMark group and has offices in the UK, Switzerland, the US, Italy, Sweden, Netherlands, China and Russia as well as a comprehensive network of distribution partners around the globe.

Optical Efficiency in Digital Cinema Projectors

What isn’t compared is the energy and materials that go into making a remarkably simple film projector against a remarkably complex digital projector, plus the energy and materials that are needed to create the media server and the local central storage, plus the data farms that create and store the movies in the distribution chain, plus the network operation centers that oversee their constant quality and security. Like projectors, data centers use an astounding amount of energy to keep the air cool and what it takes to constantly keep the disks moving and processors humming.

With just a little thought, one can make a long list of data centers in the digital cinema chain: at the animation studios, at each post-production house, at each specialist render farm, at the sites which create the master Digital Cinema Distribution Master (DCDM), and those facilities that create each separately keyed Digital Cinema Package (DCP).

The efficiency of a digital cinema projector was the topic of a side-discussion at a recent technical meeting, involving a number of engineers who have been intimately involved in the digital cinema evolution. There was only conjectured and estimations based upon hearsay. It was surprising. It came up again on an online chat, where engineers who are not centimeters deep/kilometers wide (as is your author), also didn’t have an answer. It was also part of the discussion in our article:
3Questions – Laser Light Engines

So it is a pleasant and interesting relief to be able to present this document from Barco on the subject. Created by Barco Product Marketing Manager Tom Bert, it lends detail into some of the nuance of optical efficiency inside a digital cinema projector.

Optical efficiency in Digital Cinema projectors

How to get as much light as possible from your lamp onto your screen?

1 Introduction

In this article, we want to discuss everything that has an impact on how much light falls onto the screen… except for the lamp. We will have a close look at all the components that influence parameters such as image quality, total cost of ownership and serviceability.

It is our goal to clarify the impact of product design, craftsmanship and manufacturing on projector performance. We want to provide you an inside view on what’s under the hood of the projector and how it really impacts performance.

We hope that, after reading this article, you better understand how a digital cinema projector works and what contributes to the stunning performance of these state-of-the-art devices.

2. The life of Ray

Digital Cinema projection is all about getting the light from your lamp onto your screen. In this paragraph, we will discuss the different impacting parameters on a ray of light leaving the lamp. We will try to do this in a sequential approach, following the build-up of the light path of your digital cinema projector.

The image below gives an overview of the components involved:

Components of a Digital Cinema Projector2.1 Reflector

The reflector is an elliptical or parabolic structure that is placed around the lamp, in order to capture as much light as possible from the lamp and send it into the optical path of the projector. An important parameter is the surface roughness of the reflector: high end devices use perfectly smooth reflector materials, while others use processing techniques that introduce small imperfections. This can have an impact of as much as 15% on the reflector efficiency.

Important to remember is that a badly designed and manufactured reflector can destroy all of the light concentration that comes from using short arc lamps. A well designed reflector also corresponds with the heat generation and dissipation capacity of the projector.

2.2 Filters

After being captured and sent into the optical path by the reflector, the light is filtered. First it goes through a UV-filter and later on through an IR-filter. These filters get rid of that part of the light that can damage the interior of the projector and have in this way a huge impact on the projector lifetime. Filtering out too much of the spectrum of your light, means you will have to compensate later on, leading to a lower overall optical efficiency. However, it is important to know that these filters work far from the sweet spot of the visible light in the spectrum. This means that their influence on image quality is low. Their impact on lifetime is much more important.

2.3 Optical engine

After being filtered from the dangerous components in the spectrum, the light enters the actual optical engine of the projector. This engine contains passive (light rod, lenses and prism) and active (chip) components. At the interfaces of these components coating materials are applied to improve performance.

2.3.1 Passive optical components

The optical engine contains relay lenses and a light rod to transport and spread out the light. The materials that these components are made off, have an impact on the performance. Badly designed engines use materials that absorb too much of the short wavelength (blue) light. This causes them to turn yellow (cfr. you get a sunburn when you forget to put on your sunblock) or even melt! It is clear that this has a major impact on image quality.

It also defines the energetic capacity of your projector, this is the amount of light you can send through. When not designed to transmit the high load that bright projectors bring, the material can break. The brightest digital cinema projectors, like Barco’s DP2K-32B, were specifically designed to carry the load that comes with projecting more than 32,000 lumens.

2.3.2 Active optical components

In digital cinema, two technologies are used for the active chip: DLP™ (from Texas Instruments, which has ~90% market share) and LCoS (from Sony, which has ~10% market share). A digital cinema projector contains three of these chips, one for each color channel (red, green and blue). This is by far the most important component of your digital cinema projector, also from an optical efficiency viewpoint. Its compact size and accurate angular performance makes it the central component that defines the design of all other optics.

For DLP™ technology, the overall optical efficiency of the chip is defined by a combination of:

  • The chip size: it is easier to “aim” light on a bigger chip than on a smaller chip. This is one of the reasons why projectors using the 1.2” DLP Cinema® chip have a 10% higher efficiency compared to those with the 0.98” DLP Cinema® chip. For that same reason, 4k projectors with a 1.38” DLP cinema® chip will have a higher optical efficiency than those using the 1.2” DLP Cinema® chip.
  • The fill factor: the fraction of the surface that is active and reflects the light.
  • The surface reflectivity: the amount of light that bounces back from each individual mirror. This is defined by the maturity of the manufacturing process and is close to the maximum achievable value for DLP™.
  • Diffraction: when hitting structures with a small features size, such as DLP™-mirrors, a small portion of the light is always diffracted (sent off in non-perpendicular angles). As technology miniaturizes, it will become more important to manage this aspect.

With LCoS projection technology, other parameters come into play, like the inefficiencies related to using polarized light. All this leads to DLP™-based digital cinema projection yielding higher efficiencies than LCoS-based projection.

To maximize the chips’ lifetime and maintain a high image quality over time, it is crucial to keep them away from dust. Sealed engines, as patented by Barco, keep the chip surface clean and help avoid scattered light and spots on the screen.

2.3.3 Coating

Two types of surface coating are typically used on the optical materials:

  • Anti-reflection (AR) coatings: these minimize the light being bounced off the optical materials and maximize the light being injected in and transmitted through the engine. A well designed engine uses these AR-coatings wisely and can achieve a transmittance of more than 99% through the passive optical components. The avoidance of reflection also reduces the amount of the scattered light in the engine, which has a positive impact on contrast ratio.

Be aware: any small dust particles on the interface surfaces undo the benefits of using AR-coatings. They also lead to dark spots or zones on screen. That is one of the reasons why the sealed engine design, as patented by Barco, is so important.

  • Color separation coatings: these are used in the heart of the light engine (the prism) to separate the incoming light into the separate red, green and blue channels that are sent to the 3 different chips. As the name indicates, the coatings have to provide a clear separation between the different parts of the spectrum. Just like you need a sharp knife to have a clean cut, you need a sharp filter to have a good spectral separation. This so-called cut-off of the filter has improved significantly of the last years by improved manufacturing techniques. High-end devices use filters with a sharp cut-off, leading to better color separation. This has impact on optical efficiency and image quality.

2.4 Color calibration

The DCI (Digital Cinema Initiative) standard emphasizes (amongst other things) the white point and color gamut of the image on the screen. These parameters do not 100% match the output of an uncalibrated projector (one where you build in the components, not tune or tweak them and power it up). Achieving the color points set by the DCI specification, means you have to slightly compromise on light output. This has an impact on optical efficiency of 5-10%.

2.5 Projection lens

The final component the light ray goes through before leaving the projector is the projection lens. In order to achieve the high level of focus that we know in digital cinema (and from the distances typical in theatre environments), this has to be a piece of optical top design. While we call it the projection lens, it is actually built up of multiple small lenses, each contributing to the overall performance. Like the other passive optical components described above, lens design also depends largely on choice of materials and careful coating of interfaces. State-of-the-art lenses yield an overall efficiency of about 85%.

2.6 Beyond the projector

Most people neglect the impact of parameters that influence the light after it has left the projector. This can go from dirty porthole windows to dirty screens (with low or high gain). Now that you understand what design and work goes into getting the most out of your projector, you should appreciate what a waste it is to loose your light on dirty material.

3 Putting it into numbers

In order to objectively quantify this, we typically use the unit lumen per watt (lm/W): the light output (in lumens) divided by the electrical power input (in watt). This unit helps taking a holistic approach, making it possible to compare across technologies and across brands.

A typical digital cinema lamp (only the lamp!) achieves 40-50lm/W. A typical digital cinema projector (everything described above + lamp) achieves 4-5 lm/W. This means that all the contributions we discussed before yield on average an optical efficiency of 10%!

4 Conclusion

Many factors influence the optical performance of your projector. Even more, we hope you understand that designing a projector is an art as well as a science. It takes know-how and experience in optics, electronics, mechanics and, cooling techniques to design a top class projector.

When selecting your projector, be sure to inquire on how the supplier took into account these aspects. Choosing a brand that cares for all of them will make your projector a high-quality, high-performance and safe choice for the future!

Dr. Ir. Tom Bert
Product Marketing ManagerBarco logo

Based on the inputs from: Rik Defever, Peter Janssens, Nico Coulier

Barco Digital Cinema

Noordlaan 5
8500 Kortrijk

4K; And Then There Were Two

What does this mean for exhibitors and the audience? More light, and more dark. It seems that each generation of the DLP chip constantly refines the edges of, and space between the mirrors, which refines the amount of “off” – the non-reflecting space – and makes the reflecting segments comparatively more “on”…thus a boost in the dynamic range, or “contrast” spec, which the larger size also adds to. The PR doesn’t list how the 2500:1 contrast ratio is measured, but it is a 25% increase from what Barco prints as their C Series spec of 2000:1, while Christie now specifies >2100:1 full field on/off. Presuming that everyone is using the same measuring technique, with more light, larger screens can be lit. [Side note: Barco’s spec says that it takes 32,000 BTUs per hour to get that kind of light from a 6.5kW zenon bulb, which has an average life of 900 hours. No one is saying that this advance will imply less electricity or longer life for the bulbs.]

4K is a nice number, but no one ever walks out of the theater saying that there were too few pixels. There are those who point out that the constraining factor in quadrupling the pixels from 2K to 4K is actually the lens, which can’t resolve that much resolution anyway. 

Because of the increased area, more light will reflect off the same number of micro-mirrors. Therefore, 3D should get the largest noticeable boost – 5% was the number that one OEM used. In a universe that is starting from 10 candela/meter2, 5% more light would be a greater benefit for a 3D audience than the same higher gain would bring for the 2D audience in a larger auditorium.

So, what does this chip do with a 4K 3D image? It doesn’t. We know that there was surprise when Sony announced that they were creating 3D by breaking up their LCOS imager into two 2K sections, one for each eye’s image. But there doesn’t seem to be any loss for orders after exhibitors saw the results.

TI is also keeping a 3D image at 2K, but they make the point that with this release “we will use the entire imager to display 3D in order to pass the maximum amount of light which is needed for 3D display. In other words the 2K image will be scaled up to 4K. We say, All the Imager, All the Time.”  

It makes sense to go for the increase in light, however small it is. The other part of the equation is the amount of bandwidth that can be pushed into the TI cards, but that is more math than is comfortable in this commentary on a simple press release.


23 degrees…half the light. 3D What?

Laser Light Engines gets IMAX funding– Putting Light on the Subject

Optical Efficiency in Digital Cinema Projectors

3Questions – Laser Light Engines