Protect your cameras
Jon Titus, Contributing Technical Editor -- Test & Measurement World, 10/1/2006 2:00:00 AM
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Camera demonstrations usually take place in clean or benign environments that come close to ideal. But cameras on production lines often must operate in toxic or dirty environments and must withstand shock and thermal stress. Cameras chosen for industrial use, therefore, require special protection—an aspect of system design engineers might forget.
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The protective enclosure that holds this camera gives technicians access to components and controls through hatches. Technicians can remove a front shroud and easily adjust a lens or filter. Note the use of chains and captive screws to keep parts nearby. Gaskets create a tight seal between the body and hatch lids. Courtesy of Tectivity. |
Several years ago, in response to an auto manufacturer's requirement to protect cameras, Tectivity, a distributor of imaging components, developed a protective housing that accepts a variety of commercial cameras. “Our VideoModule protects a camera, as well as an optional LED light source, from heat, dirt, oil, physical damage, and tampering,” said Jon Heywood, president of Tectivity. “A sealed hatch lets technicians quickly adjust lens settings without removing the camera and without disturbing the camera’s calibration.”
Generally, it costs less than $500 to protect a camera, but costs increase when customers choose options such as internal light sources or special connectors. Most options and add-ons reside within a VideoModule enclosure. If a camera will point upward, at the bottom of a product, Tectivity can equip a VideoModule with an air blow-off and a mechanical eyelid that opens, lets a camera take a picture, and then closes to protect the camera.
Cohu Electronics offers cameras in sealed containers filled with dry nitrogen at a positive pressure of 5 psi. “You can hose down the enclosures without affecting the camera,” explained Tim Jones, Cohu’s OEM products manager. “We use a metal MIL-Spec connector on our enclosures, and we 'pot’ the cable with a two-part epoxy to prevent the condensation of moisture, which could short-circuit signal pins.” Cohu also offers a wash-wipe unit that can pump washer fluid to the camera and wipe grime off a transparent face plate.
In addition to being protected by special enclosures, cameras themselves must be able to withstand extreme temperatures. “Often, cameras must work at high temperatures and undergo many temperature changes, both of which can damage sensitive components,” said Scott Massey, program manager at Dalsa. “We qualify our cameras to ensure they function properly across the 0°–50°C temperature span for their specified life.”
To support operation in these extreme environments Dalsa offers cooling options, such as heat sinks or a capability to attach a solid-metal plate to a camera to dissipate heat. Cameras that operate under extreme conditions may require a special enclosure that should provide a way to cool a camera directly, noted Massey. Or, enclosures should include the means to attach passive or active cooling equipment.
Dalsa also tests cameras to ensure they stand up to jarring and rapid motion. “We test to guarantee the durability of the camera’s electronics and to make certain the image sensor’s alignment remains true,” said Massey. “When a camera undergoes stress, its sensor must stay aligned.”
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