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Electronic Imaging & Signal Processing

PATENTS: Movies raise the curtain on digital cinema projectors

This patent review from Nerac explores some new developments in digital cinema that may speed its widespread adoption.
30 January 2008, SPIE Newsroom. DOI: 10.1117/2.2200801.0001

   

Theatrical motion picture projection has been among the last digital dinosaurs in the media industry, but in the past year, NEC, Sony, Technicolor Digital Cinema, and others have started unveiling digital cinema projectors that will change the way the industry operates. Even today, most movies arrive at theaters on several reels of large, heavy film, which have to be shipped in advance to get there in time for the first showing. These reels have to be queued up on multiple projectors, each requiring separate focusing and control. The reels are transitioned by a symbol that appears visibly on the upper left corner of each reel to signal the next reel. Like all film, a faulty projector can damage or burn the film, leading to poor image quality. Then there's all the dust and debris that collects on film that detracts from the image.

Texas Instruments began developing Digital Light Processing (DLP) in the late 1990s, and the company now has DLP projectors based on micro-mirror technology installed in about 15 percent of theaters worldwide. However, the battle to establish dominance is far from over, as the movie industry and theater owners have been slow to accept digital cinema.

The main inhibitors are the familiar ones of resolution and picture quality, common standards for the industry, and investment in capital equipment. In addition, digital cinema increases the problems of copyright security and could potentially make film piracy easier. The new formats that Sony, NEC, and others are installing offer better resolution suitable for even larger screens, higher lamp power for better picture quality and contrast, and algorithms that improve the efficiency of image display and transition.

Digital projection solves a host of problems, as it allows the entire film to be stored and transported digitally. Rather than waiting for a shipment, theaters will be able to download films over the Internet and run them in their entirety from a single projector. This will allow for easier incorporation of digital sound, which will always track exactly with the image. Picture quality will be limited only by the projector's resolution.

These new digital cinema projectors have been adapted to provide outstanding resolution even on large, movie theater screens. NEC, in partnership with Technicolor Digital Cinema, is installing three such projectors in Hollywood at the Mann Village Theatre, considered by many as the birthplace of modern movies. These particular projectors deliver 2K resolution and contrast ratios of 2000:1 and can easily project onto screens 49 feet wide or larger without pixelation. Sony's projector offers 18,000 lumen projection and can display at 4K resolution on screens 55 feet or larger.

Within a few years, we can expect all theaters to become digital, providing superior image and sound quality for us all. Below are a few of the recent patents in this field.

06805445 - Projection display using a wire grid polarization beamsplitter with compensator

PDF of full patent

This is one of a series of patents by Eastman Kodak Company. The main inventors are Barry Silverstein, Andrew Kurtz, and Xiang Dong Mi. This particular patent relates to a digital projection device that employs a liquid crystal display (LCD) to achieve high levels of contrast using a wire grid polarization beam splitter. The light source is polarized and then reflects off a second polarizer that selectively modulates the polarized beam of light. The modulated beam reflects back onto the wire grid polarization beam splitter, which conditions oblique and skew rays, thus improving the contrast.

05461423 - Apparatus for generating a motion vector with half-pixel precision for use in compressing a digital motion picture signal

PDF of full patent

Sony Corporation's apparatus compresses a digital motion picture signal to reduce the quantity of data transmitted. Generally, movies have high correlation of picture signal from frame to frame unless the scene changes. Thus, a motion picture signal can be compressed or "blocked" by determining the differences in the pixel data between consecutive frames, assuming there is not a large amount of motion in the picture signal. This patent discloses a means of using parallel pixel data and an expanded search area to identify matching picture blocks even when there is a large amount of motion or action in the picture signal.

2007030610/WO-A1 Motion picture projector with electrodeless light source

PDF of full patent

The projector described in this patent capitalizes on the fact that digital cinema projectors no longer need a shutter to chop the film into discrete images to simulate motion for the human eye. Digital cinema is unshuttered as it is already a series of continuously updating discrete images. The advantage of an electrode-less lamp is that it can be made as an array of varying colors and used reflected off digital micro-mirrors rapidly and with high intensity but at a much cooler operating temperature.

Nerac Analyst Deborah Schenberger, Ph.D., analyzes mechanical devices and machines for novelty by working across industries to find other applications that may help provide design solutions. Before joining Nerac, Dr. Schenberger was a research scientist and teaching professor at University of the Pacific. She spent several years designing mechanical systems with controls for NASA, and later for an entertainment robotics application. She is well-versed in patents and intellectual property, bioinstrumentation, MEMS, biomedical sensors, and nanotechnology. Dr. Schenberger is section chair for the American Society of Mechanical Engineers (ASME), and a member of the American Society of Biological and Agricultural Engineers (ASABE), the Biomedical Engineering Society (BMES), and the Institute of Biological Engineering (IBE). She has presented at such forums as the Institute of Biological Engineering Annual Meeting, the 24th Aerospace Mechanisms Symposium at NASA, John F. Kennedy Space Center, and Society of Women Engineers International Conference.

Nerac analysts deliver custom assessments in the following areas:

  • Product and technology development opportunities
  • Competitive intelligence
  • Intellectual property strategies
  • Compliance requirements
  • Scientific review and problem-solving.