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Point Grey Research Insights Newsletter
  January 2008 

SPEEDING UP THE BUS:
PCI EXPRESS INTERFACE TRANSFERS IMAGE DATA

Article reprinted, with permission, from the January 2008 issue of
Vision Systems Design

PCI Express-based cameras

PCI Express-based cameras have been demonstrated by Point Grey Research. The first, (on the left), a 5-Mpixel CCD camera, uses the PCI Express interface to transfer 1920 × 1080-pixel images at speeds of up to 22 frames/s to a host PC. The second (on the right), a novel lightfield design, uses a 5 × 5 array of cameras, each with different lenses to capture multiple views also uses a PCI Express interface. Image-reconstruction software can then perform synthetic refocusing of the scene.

More than three years ago, Vision Systems Design predicted that because of the flexibility offered by the scalable serial point-to-point architecture of the PCI Express (PCIe) interface, it might be adopted by camera vendors as the next high-speed digital interface. However, up until VISION 2007 in Stuttgart, Germany, held in November, no camera vendors had adopted the standard. But at the show, Point Grey Research exhibited two technology demonstrations of prototype cameras that used the PCI Express 1.1 standard to interface two very different cameras to a PCIe digital interface housed in a PC.

In the design of its first camera, Point Grey engineers chose to build on their existing Grasshopper camera platform. The Grasshopper couples the new ICX625 5-Mpixel Super HAD CCD from Sony with a dual-channel, 14-bit, 65-MHz analog front end (AFE) from Analog Devices, used for sensor timing and control.

PCI Express Grasshopper

A new physical layer and FPGA, however, were required for the PCIe interface to work. "The Virtex-5 LX FPGA from Xilinx implements the logical and transport layers of the PCI Express 1.1 interface," says Vladimir Tucakov, director at Point Grey Research, "while the x1 physical interface is performed by an XIO1100 dedicated PHY from Texas Instruments (TI). "Although a Virtex-5 LXT or SXT Series FPGA could have been used to implement transaction layer, data link layer, and physical layer functions," says Tucakov, "this solution would have been more expensive. The camera was intended solely as a technology demonstration, so we chose to minimize extra costs by using the Virtex-5 LX."

To interface the PCI Express camera to the host PC’s PCI Express bus, an EEX1 PCIe host adapter card from Magma was used. Using a 3m PCI Express-approved cable from Molex, the camera was demonstrated streaming 1920 × 1080-pixel 24-bit RGB images at 22 frames/s from the dual-tap CCD imager to the host PC, for a total data rate of 136 Mbytes/s. Under the PCI Express 1.1 specification, cable lengths up to 7 m are allowed.

ProFUSION 25 image

Equally if not more impressive was a demonstration of a lightfield camera with PCI Express interface, the ProFUSION 25, which was developed by Point Grey’s Japanese distributor, ViewPLUS. "With lightfield cameras, several images of a scene are taken from physically offset viewpoints," says Tucakov. "This gives us directional information about the light hitting the camera in a plane—the "light field"—rather than just a single point, such as a traditional lens. The applications of light fields are still emerging. However, examples are the ability to select the depth-of-field of a photograph after it is taken, or the ability to render novel 3-D views of the scene without explicitly reconstructing a 3-D model of the image.

The image above shows how the ProFUSION 25 can be used for digital refocusing using a "synthetic aperature". Contact us for more sample images, or download a movie presentation (~77MB).

These types of cameras can be designed in different ways, namely with a very large imager using multiple lens systems such as those recently developed by Adobe Systems or by using multiple cameras, each with different lens elements. While the recently announced lightfield camera from Adobe uses a 16-Mpixel CCD imager and a hexagonal array of lenses (see "New Light Field Camera Designs," Todor G. Georgiev: www.tgeorgiev.net/LightFieldCamera.pdf), the ProFUSION 25 uses 25 VGA sensors, each with separate micro lenses in a 5 x 5 grid (see figure).

"By using low-cost MT9V022 wide-VGA CMOS sensors from Micron Technology, we have reduced the cost of such camera systems," says Tucakov. "At the same time, the use of the PCI Express 1.1 interface allows the camera to transfer 640 × 480 images from all 25 imagers directly to the host computer’s main memory at rates as fast as 25 frames/s, for a total data rate of more than 192 Mbytes/s."

Article reprinted, with permission, from the January 2008 issue of

VSD logo

NOTE: The PCI Express Grasshopper featured in this article was a technology demonstration only, and is not available for purchase.

More Information

Vision Systems Design website
Point Grey Research Evaluation Program
Request Grasshopper pricing
Request ProFUSION sample images


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