MAY 10--Until now, video enhancement has typically been performed as part of post incident investigations by trained specialists using high-performance workstations and sophisticated software packages. The IPM-1000 from Enpiction (North Kingstown, RI; www.Enpiction.com) performs adaptive contrast enhancement to improve performance of video cameras under difficult lighting conditions. The module accepts NTSC video signals and works as a front end to network video servers and wireless video transmitters.
Nonideal lighting interference limits visibility in video surveillance. The IPM-1000 is designed to improve visibility under low light, backlighting, nonuniform lighting, extreme dynamic range, haze or fog and other low -contrast situations. Backlighting causes silhouetting that may impede recognition. Features and details may be obscured by compressed contrast for scenes with extreme dynamic range that is when both very bright and very dark areas occur in the same image. Automatic exposure controls used in video cameras compress contrast in scenes with extreme lighting.
Alternate approaches to address video performance limitations such as relocating the camera may be unsuitable. Supplemental lighting is impractical for outdoor daylight scenes or adjacent to windows. Upgrading the camera may reduce contrast issues, but even the best available cameras are unable to adequately render scenes that combine bright light and deep shadows, and benefit from contrast enhancement. Contrast enhancement may increase visibility of graininess, the random salt and pepper effect that results from amplification of subtle pixel to pixel variations.
All video images contain a degree of noise as a result of random signals generated by detectors, amplifiers, transmission, recording, and display electronics. Imaging systems are usually configured to minimize visibility of noise. This approach improves image aesthetics, but frequently results in a loss of visual data. Increased graininess visible in images processed with the IPM-1000 results from amplification of subtle differences between adjacent pixels, which often contain visual information that may not be evident without enhancement.
