© 2008 Lumenera Corporation. All rights reserved.
Sitemap | Legal | Privacy | Quality | RMA | Warranty
May 2005
Test & Measurement World
Presentations at the Vision Show West (May 17-19, 2005, San Jose, CA, Automated Imaging Association, www.machinevisiononline.org) covered a plethora of machine-vision topics. Among the highlights, speakers representing JAI PULNiX, Basler, Lumenera, and StockerYale described Camera Link, color-line-scan, high-resolution area-scan, and LED illumination innovations.
Steve Kinney, a product manager at JAI PULNiX and chair of the Camera Link committee of the Automated Imaging Association, provided an overview of Camera Link and described ongoing initiatives. Those include the adoption of a specification of a miniature Camera Link connector and a smaller, more flexible (although probably more expensive) cable. Acceptance of both could occur within 90 days, he said. Also on the agenda is the adoption of a cable that carries camera power as well as data. Discussion of that feature, he said, will likely occur at the September meeting of the Camera Link committee.
Camera Link itself is a trademark of the AIA, and vendors displaying the Camera Link logo must certify that their products meet the Camera Link spec. In a nutshell, Camera Link defines an interface between a compliant camera and frame grabber. Based on the National Semiconductor Channel Link chip set, a Camera Link interface carries up to 4.7 Gbps of image data as well as camera timing and control signals using a 66-MHz version of the National chips. Data rates extend to 6 Gbps using 85-MHz versions. For more information click on the "Camera Link" tab at the AIA's home page, www.machinevisiononline.org.
Color line-scan applications
Arndt Bake of Basler described the increasing importance of color in line-scan-camera applications. He said that Basler, as a seller of both area-scan and line-scan cameras, has noted that about one-third of area-scan applications employ color cameras, while the figure is only 10% for line-scan cameras, with customers reporting that color line-scan technology is awkward and expensive to deploy.
That's changing, though, he said, as the Camera Link standard and better frame grabbers are making it easy to get color data out of line-scan cameras, even as line widths extend from 1k or 2k pixels to 8k pixels or more. He cited many applications that can benefit from color line-scan cameras such as his firm's L304kc trilinear model: separating red from green peppers, for example, or--more germane to Test & Measurement World, differentiating copper PCB traces from green PCB material.
High-resolution area-scan cameras
While Bake promoted color line-scan cameras, Drew Buttress, director of business development at Lumenera, touted high-resolution area-scan cameras such as his firm's new LW620, a 6.6-megapixel (3000 x 2200 pixels) product available in color and B&W versions and which sports a USB2 interface for connection to host computers and which comes in board-level and enclosed configurations.
High-resolution cameras, he said, provide more pixels for better analysis, making it easier to provide the minimum of two or three pixels per defect necessary to reliably detect defects. A single high-resolution camera, he said, can replace multiple analog cameras and can make it easy to digitally zoom in on regions of interest. He provided several application hints to employing high-resolution cameras: for example, use sufficiently large-diameter lenses to avoid keyhole effects on the cameras' image sensors.
LEDs for line-scan applications
Simon Stanley of StockerYale described the application of LED illumination to line-scan applications, which often, he said, involve line speeds of 5 meters per second, 100 micron-per-pixel resolution, and 50-kHz rates, which combine to place significant demands on illumination schemes. Typically, he said, such applications have been served by fluorescent lighting or by halogen or metal-halide sources and fiber-optic light guides. Those approaches, he said, suffer from frequent burnout as well as unstable power outputs and color temperatures, and they are difficult to control.
As an alternative, he said, StockerYale developed its Cobra line-scan illuminator, which employs a patented chip-on-board technology to pack LEDs much closer together than is possible with discrete, packaged LED devices. (Cobra stands for Chip On Board Reflective Array.) The result, he said, is an LED line-scan illuminator that achieves an illumination level of 220,000 lux, vs. 195,000 lux for a typical halogen line-scan illuminator.
Advantages of Cobra, he said, include low thermal resistance from LED to heat sink; there's no need for heat transfer across the relatively high thermal resistance of the leads of packaged devices. To assure stability, he added, Cobra sources employ an internal power supply that regulates current through the LEDs. Other features, he said, include remote intensity control and a TTL on/off input, with a computer-controlled version in the works.
