Spurred by the efforts of Sony Electronics (Park Ridge, NJ; bssc.sel.sony.com/professional) to promote and support the transfer of imaging data over the FireWire (IEEE 1394) camera interface, the digital-camera specification supports different camera resolutions, pixel depths, triggering modes, and partial scan interfaces. Despite this progress, the standard is still somewhat limited in terms of both resolution and frame rates, especially when high-resolution/low-frame-rate or low-resolution/high-frame-rate devices need to be interfaced over FireWire.
Accordingly, several manufacturers including Vitana Corp. (Ottawa, Ont., Canada; www.pixelink.com) and Hamamatsu Corp. (Bridgewater, NJ; usa.hamamatsu.com) have developed software so that specialized FireWire cameras can be more easily interfaced to host computers. While other companies have successfully developed similar software packages, their algorithms have seldom fully served the full 400-Mbit/s bandwidth of FireWire. Instead, these companies use the interface to transfer single images to the host computer.
While this software is useful in low-frame-rate image capture, such as for microscopy and other scientific-based image-processing applications, it often does not take full advantage of the camera's frame rates. To overcome this limitation, NorPix (Montreal, QC, Canada; www.norpix.com) has developed StreamPix digital video recording software that supports a number of available FireWire cameras (see table). Announced recently at Photonics Boston, this software allows systems integrators to acquire frame-rate data from these cameras up to the maximum 400-Mbit/s limitation of the FireWire specification (see figure on p. 8). At the show, the company demonstrated the QICAM camera from QImaging (Burnaby, BC, Canada; www.qimaging.com) interfaced over FireWire to a dual AMD-based processor motherboard from Asus Computer International (Newark, CA; www.asus.com).
During operation, the complete system transferred 1400 × 1200 × 10- or 12-bit images from the cameras at frame rates of between 10 and 15 frames/s directly to the disk drive of the host PC while performing a Bayer color conversion and image display. According to Luc Nocente, NorPix president, the frame-transfer rate of the system is limited only by the throughput of the FireWire bus. Moreover, the length of the sequence of images is limited only by the size of the system's disk drive.
After images are captured, the StreamPix video recording software can be used in video-cassette-recorder mode to replay image sequences, rewind, fast forward, resequence, or play at faster or slower rates, and the images can be exported as BMP, TIFF, JPEG, or AVI files. "Because the system is based around the FireWire interface standard," says Philippe Candelier, director of research and development at NorPix, "up to four cameras can be networked together." At present, the company has demonstrated support of up to two networked FireWire cameras. "But to maximize throughput to the host PC," says Candelier, "two host FireWire inputs would be required."
According to Nocente, future support will add analog and digital I/O capability to FireWire systems so that developers can simultaneously capture analog data from sensors, such as thermocouples and temperature sensors, to correlate with image information.