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  • Laser Diodes Headlining in Hollywood

Photonics Spectra
Jun 2002
Brent D. Johnson

Many studios producing this summer's blockbuster films will be using the digital intermediate process, wherein the camera negative is scanned and all postproduction operations -- from editing to special effects and color timing -- are performed in the digital realm. To do this, it is necessary to digitize the analog film. After postproduction is completed, technicians restore the digital copy to a Super 35-mm negative for release as a print for distribution.

More and more films are incorporating digital effects requiring film recorders to convert the analog original to a digital version for postproduction, and then converting it back to an analog print. Semiconductor laser technology has helped reduce the recording process by a factor of six. Courtesy of Pierre Vinet/PRNewsFoto.

This process can take weeks to months. Hence, in the world of filmmaking, streamlining the steps between analog and digital operations is a much-desired goal.

The process of transferring the digital version to a 90-minute analog film is prolonged by traditional recorders based on cathode-ray tubes, which suffer from low light output, restricted contrast range and problems relating to grain structure, blooming and insufficient color fidelity. An alternative is gas laser systems, but they also have problems caused by mode shifts, energy output instability, heat production and a tremendous power draw.

Arnold & Richter Cinetechnik GmbH sought a faster and better technique that would also have better saturation without degradation. It produced the Arrilaser, a film recorder that reduces exposure times and improves resolution with the help of semiconductor lasers. More recently, the company incorporated Coherent Inc.'s Sapphire 460-nm, 10-mW semiconductor laser, which consumes 98 percent less power than air-cooled argon sources, and a Compass 532-nm diode-pumped solid-state laser, which has an intracavity frequency-doubling crystal to convert IR emissions to green wavelengths.

A graduated neutral-density filter attenuates -- and equalizes -- the configuration's red, green and blue output. Three acousto-optic modulators encode the information on the beams to transfer it to film.

A single penta prism rotating at 60,000 rpm combines and scans the three laser beams. Each rotation of the prism scans one line onto the xfilm, converting the 3000 lines in a 4096 x 3112-pixel frame in approximately three seconds.

This configuration has helped reduce conventional recording times from six weeks to one. It also earned the Arrilaser a Scientific and Engineering Award from the Academy of Motion Picture Arts and Sciences.

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