Lang Evaluates Laser/Phosphor and Laser Projectors
By Matt Brennesholtz
At ISE 2014 in Amsterdam, Lang AG (Lindlar, Germany) had both a booth and a private viewing room. The viewing room focused on laser/phosphor and pure laser projectors and I got a tour of it hosted by Markus Ries, director of Lang Academy, and Peter Mathia, product manager for projectors.
Lang AG is a sales and rental company for professional AV equipment. According to Ries, the company is not a rental and staging company that serves end users directly. Lang acts as a “dry-hire” cross-rental company, serving the market with large quantities of projection, display, LED and image processing equipment. Its customers are not end users, but the rental and staging companies.
Lang Academy is the branch of Lang that does training for ProAV people. This training is more than simple hands-on training for Pro AV installers and operators. For example, last fall it hosted the 4K Forum and in May it’s hosting a free all-day seminar, “Women @ Interactive – Seminar For Women In Media Technology.”
As part of his duties as product manager of Lang AG, Peter Mathia evaluates projectors that Lang is considering purchasing to add to its rental inventory. As part of this projector evaluation program, there were three demos of laser/phosphor and laser projectors in the Lang viewing room at ISE. Mathia also provides feedback, based on measurements he makes, to the projector manufacturers on the suitability of projector prototypes to the Pro AV industry and suggests modifications to designs that would simplify their use in the field. It is then up to the projector makers to decide if these suggestions can be implemented and then do the necessary design work.
The first projector I saw was the NEC pure laser projector. The projector is a 4K, three-panel DLP projector and the lasers are external and connected to the projector by fiber optic cables. Each external laser module provides enough light to produce 5,000 lumens at the screen and the projector I saw was using two modules for 10K lumens. Each laser source was connected to the projector via two fiber optic cables, as can be seen in the photo. The image produced on the screen was excellent, with good colors. Slight speckle was visible in the image when viewed close up, but at normal viewing distances this speckle was invisible.
Left is the NEC laser projector, with the four fiber optic connections visible. Right is the image produced.
There has been debate about whether laser projectors should have the lasers embedded in the projector itself or if they should be external, perhaps in a central laser room, and connected to the projector via optical fiber. Mathia pointed out to me that these fibers capable of carrying high-powered laser beams cost about $1,000/meter ($305/foot) and this could impose an impossible cost burden on lasers any significant distance from the projector, especially if four fibers were needed to connect the lasers to the projector.
The second demonstration was a side-by-side comparison of the DPI HIGHlite 12K laser projector and a lamp-based projector from Panasonic, using dual 355W UHM lamps. The two projectors had WUXGA (1920×1200) resolution, although the DPI projector used 0.67” DLP imagers and the Panasonic used 0.9” imagers. The two projectors were set up for the same luminance at the screen.
Mathia said he did this side-by-side comparison to show laser/phosphor projector colorimetry now equaled the colorimetry of lamp-based projectors, with both projectors matching Rec. 709 very closely.
While this photograph shows the two projected images as virtually identical, with different content the images often looked different from each other. In general, when the images looked different, the DPI projector produced the subjectively better image. Mathia pointed out that while the Panasonic projector used larger DLP imagers than the DPI projector, it was actually smaller, quieter, lighter and lower power than the DPI unit. He had measured the power for each projector and they were 960W and 1300W for the Panasonic and DPI projectors respectively. These values are significantly different than the specified values in the company literature.
The third demo was a side-by-side comparison of two Panasonic projectors that were virtually identical except one had dual mercury lamps and the other had laser/phosphor illumination. For these two projectors, the colorimetry did not match, with the lamp based unit a close match for Rec. 709 and the laser/phosphor having the “wrong” colors. Subjectively, however, the larger color gamut of the laser/phosphor projector produced a more pleasing image for the video content shown than the lamp projector with Rec. 709 colorimetry.
The important take-away from the Lang viewing room was that while laser/phosphor projectors can equal (or exceed) the performance of lamp-based projectors, there are associated issues yet to be solved by the projector manufacturers. These can include size, weight, cost, noise, etc. On the other hand, mercury lamps are a well developed, mature technology while high-output laser and laser/phosphor projectors are just entering the market and presumably will improve significantly as they mature.