RGB digitizers target medical, military applications

With the image-processing and machine-vision market becoming increasingly fragmented, many OEM frame-grabber vendors are turning their attention to other markets.

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With the image-processing and machine-vision market becoming increasingly fragmented, many OEM frame-grabber vendors are turning their attention to other markets. Most notably, these include the medical and military industries, where displayed images need to be digitized exactly as they appear on the display monitor.

In the medical industry, image-processing boards are used to digitize high-resolution ultrasound or x-ray images for further data transmission or printing across digital networks. In the military, these boards are useful in the development of ship's data recorders, performing similar functions as flight-data recorders do for the aircraft industry (see Vision Systems Design, July 2000, p. 39).

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To digitize these images at screen rates, RGB frame-grabber boards use high-speed A/D converters to grab images for loop-through display and/or transfer over the PCI or VME bus for hard disk storage. Of the number of high-speed RGB frame grabbers currently available that are targeting these applications, the UFG-01 from Unigraph (Espoo, Finland) is the only one without video loop-through capability. Acting as a bus master, however, the board is capable of transferring captured data across the bus in bursts of up to 100 Mbytes/s.

"Of course," says Tony Molinari, vice president of marketing at Foresight Imaging (Chelmsford, MA), "at rates as high as these, some form of image decimation is required for images to be transferred at captured rates over the PCI bus. And to view these images as they are captured, some form of pass-through mode is required." Foresight's latest board, the I-RGB 200, is the fastest RGB converter currently targeting these applications. At data rates of 200 MHz per RGB channel, the board captures images at a data rate of 600 Mbytes/s.

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Foresight Imaging's I-RGB 200 board acquires analog RGB signals, locks automatically to the input signal of up to 1600 x 1200 x 75 Hz, provides real-time video loop-through, and saves the images as video streams or single frames.
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To display these images in real time, the board features a display pass-through mode. "To capture images to the PC and reduce bandwidth, the board can perform direct memory access to every Nth image or deliver parts of the image to system memory at a sustained 120-Mbyte/s data rate to support video streaming applications," he adds.

The Perusa board from Barco (Kortrijk, Belgium) also features a pass-though mode that allows captured images to be displayed as they are acquired. And, for long-term acquisition, the board also features an optional CODEC add-in board for JPEG compression.

For their products, RGB frame grabber vendors are also providing application software and a variety of operating system support. The Sentinel VME board from Primagraphics (Royston, Herts, England), for example, is supplied with an optional GUI-based PC application for control of the capture unit. Unigraph's board features on-screen panels for adjustment of input and output, software support for Windows NT/2000 and Linux, and support for up to four frame grabbers in one system. Foresight Imaging's I-RGB 200 board ships with its Auto-SYNC software for analyzing RGB or monochrome video signal up to 200 MHz and automatically creating a configuration file for image capture. Also, it provides a VESA mode video detection application for instantly locking up to a VESA type RGB signal, a full programmer's toolkit, a Video for Windows driver, and extensive example programs.

While the limitations of input resolution are now being overcome in many of these RGB frame-grabber designs, bus interface speeds still limit data transfer to the host. "To speed the data transfer between board and PC, we are developing a 64-bit, 66-MHz bus-based version of the board for introduction in the second half of this year," says Foresight's Molinari.

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