Christine Connolly, UK Correspondent, firstname.lastname@example.org
Connecting a camera to a computer often involves a tangle of wires. Analog cameras use the television standard interfaces CCIR and RS-170, and the early digital cameras used RS-422 or nonstandardized low-voltage differential signalling, with every camera needing a different connector. In the past decade, the digital interfaces of Camera Link, DCAM and Gigabit Ethernet (GigE) Vision have been adopted by industry, while USB and FireWire have appeared in the consumer market. Out of this muddle, GigE now is emerging as the universal and future-proof industrial standard for machine vision.
Camera Link was the first digital interface to use standard connectors. It is very fast, transmitting up to 680 MB/s, but it has a maximum cable length of 10 m without repeaters. FireWire also is limited to 10 m and is much slower. DCAM is the industrial version of FireWire, with a simpler setup procedure.
Ethernet communications networks have existed for a long time and are familiar to industry, plus the cables and components are standardized and low-cost. Earlier, slower versions necessitated video compression, but GigE allows uncompressed video, and the increasing availability of 10 GigE matches the speed of Camera Link while providing a much longer reach. With standard network cards, the frequent interrupts from the image data reduce PC performance, so GigE Vision improves matters by streaming data directly into memory, but it is specific to the chip set in the card.
The GenICam standard makes interfacing independent of camera brand and physical interface. It incorporates a clever feature called the Factory layer that allows standard GenApi commands to access the real registers of the camera, enabling manufacturers to add whatever controls and features they like to their cameras while users control them all in a high-level language.
Toshiba Teli makes machine vision cameras with FireWire, Camera Link or GigE interfaces. The GiantDragon series of GigE cameras has five monochrome models and four colour, and they are Gen-ICam-compliant. They have a compact and lightweight body measuring 44 × 44 × 29 mm. Spatial resolution ranges from 640 × 480 up to 1360 × 1024 pixels, with 90 and 15 fps, respectively. The cameras have external trigger and progressive-scan, and they take C-mount lenses.
Dr. Julian Parfitt of Framos Electronics Ltd. told EuroPhotonics that he is selling Toshiba Teli cameras for a wide range of applications in Europe, especially those involving high speed and low light. He cited pill counting, mail sorting, printed web inspection, and pharmaceutical label and print verification. Toshiba Teli is relatively unknown in Europe, but robust build quality is giving its cameras a good reception. Toshiba Teli, as a GenICam standards group member, is at the forefront of developments.
Stemmer Imaging is another GenICam member, and its Common Vision Blox version 10 is fully GenICam-compliant and acquires images from any camera with that interface. But Stemmer is taking an extra step by introducing the GigE Vision Server, which makes the computer emulate a GigE Vision camera with freely configurable features. It can add time stamps to images or allow remote computers to control the image-acquisition conditions. It can take images stored on hard disk or acquired by a camera with a different interface and output them to a GigE network. So USB, FireWire and Camera Link cameras acquire long-distance networking capability. Because Vision Server conforms to the GigE Vision and GenICam standards, it is compatible with compliant third-party software.