Sony has adopted the IEEE 1394 serial bus for several of its industrial cameras, including the DFW family shown above: from left, the DFW VL500, the DFW V500, and the DFW V300.

Its official name is IEEE 1394. It is also called FireWire^® by Apple and i.LINK^® by Sony, which has licensed this name to several other companies. It was created in the late 1980s as a digital technology designed to satisfy the ever-increasing demand for communications bandwidth for video. It was also designed to simplify and reduce the number of cables and connectors between devices. Simple one-cable connectivity has become a necessity brought about by miniaturization and increasing device functionality as ports have been reduced in size and number.

The IEEE 1394 high-performance serial bus has already found its way into consumer products and one day probably will link every digital appliance in the house: TV, DVR, camcorder, high-fidelity stereo, computers, and peripherals. Now it is poised to make the same impact on the industrial/scientific imaging world.

Guaranteed Bandwidth, Guaranteed Delivery

IEEE 1394 offers high-speed, bidirectional transfer of high-volume digital data. It moves up to 400 Megabits/second of data, for applications requiring guaranteed bandwidth (isochronous mode), such as the delivery of video streaming images in real time, or guaranteed delivery (asynchronous mode) for the transfer of content-critical commands and file transfers that are not time-sensitive. Data transfer speeds are expected to double this year, with a top rate of up to 800 Megabits/second. Rates of up to 1200 Megabits/second are anticipated for next year.

IEEE 1394 is flexible and can be used with "tree" or "star" network topologies, connecting multiple devices together in a dynamic unsupervised network. Devices can be linked by low-cost serial cable with inexpensive four- or six-pin connectors. IEEE 1394 allows for cable lengths up to 14.8 feet and up to 236.1 feet between devices. Up to 16 hops are allowed between any two devices, and up to 63 devices can share the same bus. A single network can accommodate up to 1024 buses and 64,512 devices.

IEEE 1394 enables dynamic unsupervised bus management by facilitating automatic nonmanual bus configuration and reconfiguration. This includes automatic address selection and hot connect/disconnect of devices without loss of data. If a device is added or removed from the network, there is no need for the system to reboot, and there is no need for ID switches. Communications within the network are peer to peer; there is no need for a computer, just a bus manager on the network. The network can handle multiple CPUs and such devices as cameras, printers, CD-ROM drives, hard drives, and other storage devices, greatly enhancing flexibility and ease of maintenance.

Speed plus Bandwidth

IEEE 1394 supports bidirectional data transmission at speeds of 100, 200, or 400 Mb/s (megabits/second), or approximately 10, 20, and 40 MB/s (Megabytes/second). Future planned transmission rates are 800 Mb/s (80 MB/sec) and 1.6 Gb/s (160 MB/s). By contrast, the common USB (universal serial bus) 1.0 interface only supports about 1.2 Mb/s. The SCSI (small computer system instruction) interface supports a small number of devices on the network while providing data transfer at 5 to 30 MB/s with large, expensive cables and connectors. Traditional video interfaces such as SDTI and RS-422 support rates of approximately 25 MB/s and 1 to 16 MB/s respectively. SDTI and RS-422 also have the disadvantage of utilizing large, expensive connectors, and have limited networking capability. On the horizon are interfaces such as USB 2.x and Channel Link^TM. USB 2.x has limited networking capability and is computer-concentric, supporting speeds of approximately 30 MB/s. Channel Link, the fastest of these interfaces, supports 100 MB/s, but has no networking capability -- it is strictly a point-to-point connection -- and it requires four or five pairs of cables and connectors to link devices. Channel Link is a very specialized connection, one usually used in video applications.

The bottom line is that the IEEE 1394 interface supports more bandwidth, flexibility, reduced cabling, and lower costs than anything on the market today.

In 1995, 1394 was officially adopted by the Institute of Electrical and Electronics Engineers (IEEE) as a high-speed digital interface among audio/video products, personal computers, and peripheral devices. It has also been adopted as a standard by the Digital Audio Video Council (DAVIC) for home networks. The Digital Video Broadcasters (DVB) and the Electronics Industry Association (EIA) have also adopted 1394 for digital broadcast receivers. In addition, IEEE 1394 is gaining rapid acceptance in the industrial and scientific arenas.

Sony and IEEE 1394

Because Sony saw IEEE 1394's potential immediately, the company joined the IEEE 1394 Trade Association in 1994. There are many working groups within the trade association that are developing standards for digital cameras for industrial markets. For example, DCAM^® Version 1.2 defines specifications on how 1394 cameras should work. It has evolved to support new triggering, partial scan interfaces, a wider range of operating systems, and connectors.

IEEE 1394 is graduating from theory into practice in the world of imaging. IEEE 1394 cameras are now used in videoconferencing, photo kiosks, multimedia, and ID badging and machine vision/scientific applications such as laboratory analysis and inspection systems. Among consumer products, it is nearly a standard for most digital camcorders and personal computers. IEEE 1394 has spawned the consumer acceptance of PC-based DV home editing.

This year Sony introduced two digital eight-bit monochrome 256-gray-scale cameras specifically designed for high-resolution machine vision and scientific applications. The Sony XCD-SX900 camera delivers uncompressed video image output of 1.45 million pixels (1280 x 960) at 7.5 frames per second, for use with microscopes in applications such as semiconductor inspection. The XCD-X700 delivers 0.8 million pixels (1024 x 768) at 15 frames per second and is suitable for digital inspection of high-end machine vision applications such as the manufacture of auto parts.

Both cameras employ half-inch progressive scan CCD sensors with square pixels. These cameras also have a partial-scan function that allows output selection of a smaller rectangular portion of the full image to increase the frame rate or reduce processing time. This is particularly valuable in scientific applications, where only part of the image needs to be captured before moving to the next image.

The "one cable" 1394 connection links the camera to a computer for all image transfer, camera control and status, and power. In fact, multiple cameras and compatible devices can all be connected via the IEEE 1394 bus to further extend the camera's suitability for machine vision and other industrial applications.

Into the Future

IEEE 1394 technology has brought digital bandwidth, capability, and cabling/cost savings to the high-resolution imaging market. Like Sony, other companies have brought increasingly powerful, feature-rich cameras to the technology. Now very high-resolution IEEE 1394 cameras, such as the new Sony XCD series, have the capacity to capture an entire detailed image (or a reduced field image) and send it to any other device on the network -- PC, printer, storage device -- in one pass, thereby eliminating the need for framegrabbers, add-in boards, or multiple passes to assemble a complete image from several smaller fields. These cameras can be externally controlled and linked to other devices or to each other.

The "glue" that brings PCs and 1394 digital cameras together is software. Matrox and National Instruments are two pioneers of application-oriented software designed to enable users to take advantage of the remote control capabilities needed to set up machine vision or laboratory analysis systems. Windows^® 2000 software is designed to offer complete 1394 support (Windows 98 software offers partial support, primarily for videoconferencing functions). Other vendors are sure to follow Microsoft's, Matrox's, and National Instruments' lead. As 1394 gains wider acceptance in nonconsumer applications, more off-the-shelf application-oriented software is expected.

As of this writing, IEEE application-specific software development has not yet caught up to high-end industrial/scientific hardware, such as the Sony 1394 cameras. The user will need to work with available off-the-shelf software solutions, or seek out a consultant or fellow early adopter to create an application-specific high-resolution digital imaging solution.

Because 1394 is so new to the high-end imaging marketplace, these consultants are still relatively few in number. With the introduction of Windows 2000 and more application-specific 1394 software, this situation should reverse itself.

Like many new technologies, IEEE 1394 imaging technology in the machine vision/scientific arenas may at present be the province of users who demand a digital solution, who need digital imaging for specific applications, or who may want to try it just to "get their feet wet" with a prototype while waiting for the next generation of improved devices and shrinking costs.

That next generation is not far off. As was said above, Windows 2000 software offers full IEEE 1394 support, and other software vendors are following suit. In all likelihood, 1394 adoption will mirror the development of the Internet: as a technology comes of age and the marketplace gains critical mass, hardware and software manufacturers will rush to support it.

The benefits of IEEE 1394 are clear. In the high-resolution industrial imaging world, they translate into improved image capture and data transmission capabilities, both in sensitive real-time applications, such as video streaming or high-end machine vision inspection, and delivery-sensitive applications, such as microscopic and scientific inspection.

Clearly the world is going digital, and the machine vision/scientific imaging world will follow. How long before this happens? It is hard to say. But one thing emerges clearly: in the industrial and scientific arenas, the IEEE 1394 serial bus is the bandwidth of the future.

This article is based on a white paper delivered by Jerry Fife, product manager, Visual Imaging Products, Broadcast and Professional Company, Sony Electronics Inc., at SPIE's Photonics West 2000 conference. For further information on Sony imaging products, contact Sony Electronics, 1 Sony Drive, Park Ridge, NJ 07656; phone 1-800-686-SONY.