NAB 2014 Panel Looks at Laser Projectors
April 5, 2014, NAB, Las Vegas—Bill Beck from BTM Consulting moderated a panel on laser illuminated projectors. Panelists were Pete Ludé from Mission Rock Digital, Goran Stojmenovik from Barco, Richard McPherson from NEC Display, and Don Shaw from Christie.
Ludé stated that the laser illumination projector association is working on educational, regulatory, and quality issues for the industry. There is little difference between laser and xenon projectors. Other than the light source, the optics and micro-displays are the same. The xenon bulb uses about the same amount of electricity as the laser, while the laser has a much longer projected lifetime. The xenon bulb produces a near-white light. Lasers are in one of two variants, a single color exciting phosphors to get full color, or a trio of lasers to be diffused and mixed for a white light.
One issue facing the industry is that the existing regulations from the FDA (food and drug administration) are not harmonized with international standards. The output levels of the projector lasers are treated as industrial laser emissions, even though the light and power levels are similar to those of a xenon bulb. Current regulations consider the laser light to be at level 3 or 4, the sane as an outdoor laser show.
Even the international standards from the IEC are incomplete. Most of the regulations affecting projectors are regulated at the illumination source level and only address the lamps, and not lasers. The various regulations need more work.
Another issue is laser speckle, which is supposed to be less than 5 percent. One problem with the specs is that the measurement techniques are not well defined. The LIPA is working on a metrology group and defining methodologies for speckle measurements. The group is defining the reference laser, and the camera, which can influence the measurement due to pixel size. In addition, they are working on image processing, sources, and moiré geometry.
Stojmenovik talked about the emerging RGB laser projectors. The latest products are now moving to the theaters. The underlying technologies are phosphors that are excited by a laser source and are capable of emitting up to 6,000 lumens, and RBG sets of lasers that reach up to 60,000 lumens. Both technologies promise increased brightness, especially for 3-D, and have constant brightness over their lifetimes with no lamp flicker.
The challenges for the laser projectors are speckle and relatively high costs in an industry that just got through an equipment upgrade cycle. Overall, however, the lasers offer a better user experience than xenon bulbs and have lower lifetime operating costs. Some products offer a 30,000 hour operating life before degrading to 80 percent of original brightness.
A new variant in the business is a projector with 6 primary colors for stereo. The two sets of RGB are tuned from each other so the viewers need special glasses to separate the light spectra from each set for stereo. Hi anaglyph.
McPherson espoused a blue pumped yellow phosphor that emits red and green light. This illuminator is a part of an integrated system including the media server with 2TB of storage. the laser is composed of over 100 redundant solid-state laser diodes. The system includes an automatic compensation system for diode loss and color compensation and provides a flat white across the screen.
Shaw also touted a 6 primary color laser projector for premium, large theaters showing 3-D films. The new projector is positioned to address the existing problems of physical side effects and low brightness. The stereopsis from the alternating left and right eye images causes crosstalk and the glasses further dim the image. The overall system light efficiency can drop to less than 10 percent of the total illumination output. This low intensity requires a silver screen that further detracts with its hot spots and speckle.
The premium 3-D theaters need better contrast, more brightness, and would like to have a white screen for projection. A projector that provides simultaneous left and right eye images in a 4k, high frame rate format is the desired solution. The 3 primary laser projectors can emit up to 72,000 lumens from a single head with water cooling. This setup provides more colors and higher contrast.
A 6-primary color projector uses two different sets of RGB lasers to provide slightly different color spectra to the left and right eyes. The color differences are separated by specially tuned glasses. A 6-primary projector can achieve 42-45 percent efficiency with built-in 3-D color separation. The stereo contrast can be as high as 1000:1 which stops ghosts and crosstalk.
This system is a dual-head full-time laser that is fiber coupled to the projector. It is modular and upgradeable. The fiber coupling allows the lasers to be located remotely from the projector, allowing for easier cooling design for the theater.
