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60 m Fibre Bundle Enables Laser Projection in the Louvre Museum

For laser projection of videos in Louvre Museum, a 60-meter bundle of 169 optical fibres was needed. AMS Technologies prepared the specification, supplied the fibre bundle and successfully oversaw the delicate installation from floor level to a height of 10 m.

When visitors to the Louvre Museum queue up for admission, videos with information about the museum and its exhibits are supposed to pass the time. These videos are projected from a great height onto the floor of the huge entrance hall beneath the famous glass pyramid – in these conditions, creating a bright and attractive high-resolution video image even in bright sunlight is not an easy task. The optical impression with conventional projection technology based on xenon discharge lamps is not really convincing here, but laser projection with six primary colours (6P) can help: A number of individual laser sources emitting the primary colours are combined to form a bright light beam.

Fig 1: A high-resolution 6P laser source "CineCloud Lux" containing 169 lasers in two racks supplies the light for video projection in the foyer of the Louvre Museum (Photo: Cinemeccanica)

The renowned Italian company Cinemeccanica is a market leader in laser projection. Part of Cinemeccanica's broad product portfolio is "CineCloud Lux", a 6P laser light source for DLP projectors consisting of one or two compact racks, which contain a variable number of RGB laser modules mounted in slide-in units, and offering light outputs of up to 60,000 lumens. Each of the RGB modules is coupled to a bundle of optical fibres, which establishes the connection from the light source to the projection head.

Projection at Great Height

When Cinemeccanica received a request from the Louvre Museum in Paris to realize a laser projection in the entrance hall of the renowned museum, the responsible technicians quickly realized the challenge of this special application: while the two "CineCloud Lux" laser source racks are operated in a technology room at floor level, a more than 60 meter long bundle of 169 individual special optical fibres must establish the connection to the projection head, mounted at a height of 10 meter under the ceiling of the entrance hall (below the striking glass pyramid).

Fig 2: From the projection head under the ceiling of the spacious Louvre foyer, the laser light is directed to the floor 10 m below - videos on the history of the Louvre, the exhibition contents or other activities of the museum are projected

Because each of the fibres transports optical power in the range of a few watts, not a single fibre must be damaged during the production or installation of this fibre bundle in narrow cable ducts with many directional changes, neither due to a too small bending radius nor due to mechanical effects. Laser light of this power, scattered or emitted at a damaged point in the fibre, would immediately set the coating of the fibre on fire and thus also affect the surrounding fibres – resulting in an avalanche reaction until the system fails completely. In common applications of “CineCloud Lux” projection technology, for example in the projection room of a cinema, this danger is virtually non-existent as the fibre bundle is considerably shorter and usually very easy to route from laser source to the projector.

First Attempt had to be Successful

From intensive cooperation on previous projects, Cinemeccanica had already got to know AMS Technologies as a competent supplier of fibre bundles with great expertise and therefore turned to AMS for this sensitive project. It was also particularly tricky that there was only "one shot" for this project: Not only did the specifications have to be worked out very precisely and reliably – it was not economically feasible to produce a prototype or a reserve copy of this very high-priced fibre bundle due to its complexity. So, the first attempt had to be a success under all circumstances.

Fig 3: Rolled up and ready for installation: Each of the 169 optical fibres in a 60 m long bundle can conduct laser light with a power of several Watts from the source at floor level to the projection head at a height of 10 m

In intensive discussions with the Cinemeccanica technicians, the AMS specialists worked out a detailed specification for a fibre bundle with a robust outer sheath that meets the mechanical requirements. When implementing the fibre bundle, the engineers of the fibre bundle manufacturer achieved very low overall optical losses by optimizing the fibres as well as the optical interfaces to the laser unit and to the projection head. This enabled Cinemeccanica to reduce the number of laser units required, thus lowering the overall cost of the projection system.

Complex Bundle, Tricky Installation

After production and delivery of the fibre bundle, representatives of AMS Technologies and the fibre bundle manufacturer supervised installation and assembly and instructed the fitters. During the subsequent optical test, an AMS Technologies employee checked the optical loss of each individual fibre on a lifting platform 10 m above the floor of the Louvre Museum using a laser power meter. The result: Not one of the fibres was damaged during installation, and the measured values corresponded exactly to the measurements taken by the fibre bundle manufacturer before delivery.

Fig 4: A technician installs the stainless-steel-covered fibre bundle in the installation shafts and conduits that lead through the "catacombs" of the Louvre museum - too small bending radii are to be avoided at all costs - a defect in a single fibre would lead to a total failure of the entire bundle

"Our confidence in the know-how of AMS Technologies was fully justified," says Lorenzo Branca, Technical Director at Cinemeccanica, "the complex fibre bundle supplied by AMS not only meets all our requirements, the specialists from AMS also ensured that the bundle survived the delicate installation in the Louvre Museum completely unscathed".

The laser projection system has been in operation at the Louvre Museum since July 2017. Since then the museum has been showing visitors art content, animations and various presentations relating to the activities of the "Museum Le Louvre" on an area of about 10 m x 10 m during opening hours – without the fibre bundle in the projection system showing a single problem or defect.

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