If asked which company has done the most work to bring high brightness to cinemas, some might point to the projector manufacturers, pointing to the several public demonstrations this year of laser light illuminators. Those who better understand the drivers behind laser light illuminators might point to Laser Light Engines, a company that has done a tremendous job of researching and developing laser technology specifically for the cinema. Some might say Kodak or IMAX. But those who pay less attention to high technology and more attention to what they can buy will say that RealD has done the most work towards higher brightness for 3-D. With that in mind, we’ll recap a recent presentation by RealD to the American Society of Cinematographers (ASC) on laser illuminators.
In terms of high brightness for 3-D, RealD offers the XL light doubler, which captures light reflected by the polarizer at the projector and retransmits it to the screen. As RealD’s technology is polarization based, it requires use of a silver screen. RealD has invested in new silver screen technology, which this author has yet to see, but which is receiving a lot of praise from those who have. These technologies could be looked at as competitors to laser light illumination, which would cause RealD to be overly critical. However, one of life’s dirty little secrets about Christie Digital’s 72,000 lumen laser light illuminated demonstration in Beijing this month is that it used a silver screen to achieve 14 ft-L brightness on a 20 meter screen. No one is without their bias, but RealD has more to lose by promising things it can’t control. The reason for this short sidetrack is that RealD didn’t paint the most promising future for laser illumination in cinema.
The two big concerns for laser illuminators, often pointed to by this publication, is return-on-investment and color uniformity across a large population of viewers. RealD pointed to both. Unlike the projector manufacturers that avoid any discussion of critical problems, RealD dived in and shared its research to validate these issues.
Earlier this year, this publication estimated that the payback period for laser illuminators is approximately 8 years, based on figures shared by Laser Light Engines. RealD estimates that the life cycle of laser illuminators is 7-10 years, which doesn’t give exhibitors much room, and perhaps negative room, to enjoy an ROI on their investment.
Bringing down the cost of laser illuminators is challenging. There are various ways to establish the correct primary colors for the “DCI” color space. (The color space of digital cinema projectors is often called the “DCI” color space, but in fact, DCI doesn’t specify the color space of the projector.) The methods used in demonstration systems today often use frequency division of an infrared laser, infrared lasers being relatively plentiful in supply. But this leads to a less efficient product. A more efficient product would employ laser diodes whose frequency of light emission lines up with the “DCI” color primaries. While some laser diode products qualify for certain primaries, the green primary in particular is not supported in this way. Green laser diodes exist, but they are designed for pico projectors, and manufacturers are unlikely to build a specialized product for the relatively small digital cinema market.
A competing 3-D technology to that of RealD’s is spectral division for left and right eye viewing. Dolby 3-D is based on spectral division, and so was Panavision’s 3-D scheme. One of the promises of laser illumination is that the color wheels used by Dolby 3D could be eliminated if the different primaries needed for left and right eyes were generated by laser. RealD pointed to the expense of 6 color laser systems, which in their view would make such schemes impractical.
Refreshingly, RealD was the first company to go public in discussing the effect of metamerism caused by laser illuminators. Metamerism is the name for the effect that occurs for the different interpretation of tristimulus colorimetry when narrow tristimulus primaries are used. In other words, you’ll see slightly different colors than me when we look at laser illuminated projected images. Matt Cowan, Chief Scientific Officer for RealD, researched the subject, and found no formally published papers on it, pointing to the need for formal studies. But he did find an unpublished paper where the researcher demonstrated that the effect was real and manifests over the entire color spectrum.
The earlier topic of a 6 color laser spectrum is also a possible technique to offset the effect of metamerism. The added expense to do this was noted.
Unlike the usual projector company presentation that ends with “lasers will be ready within 2 years,” (if not 1 year), RealD predicted 5 years. And it wasn’t a promise.