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Line Scan Versus Area Scan Technology

There are two types of methods to acquire an image of an object: area scan and line scan. One key difference between area scan and line scan cameras is how the image is captured.

Cognex In-Sight 9902L embedded industrial line scanner processes images directly on the camera.

In area scan cameras, a rectangular-shaped sensor captures an image in a single frame with the resulting image having a width and height that corresponds to the number of pixels on the sensor. Because of this, area-scan cameras are ideal for machine vision tasks, where the objects are small and have almost the same size in both dimensions.

Unlike area-scan cameras that capture the entire object in one frame, line scan cameras contain a single row of pixels, building the final 2D image pixel line by pixel line as the object moves past the camera. Production and distribution lines in manufacturing and logistics rely on this special technology to acquire high resolution images quickly for detailed part inspections.

In certain applications, line scan systems have specific advantages over area scan systems. For instance, in challenging machine vision tasks, where the object has increased beyond the size, speed, accuracy, and resolution capabilities of area-scan cameras, line-scan cameras are the preferred solution.

Line Scan Cameras Better-Suited For Advanced Applications

With today’s line scan imagers available from 500 to 8000 pixels per line, and some even able to match high speed line acquisition rates of 67,000 lines per second, the latest generation of line scan cameras generate all the power necessary for applications that formerly required a cluster of high-resolution vision imagers. These attributes make line scan cameras an ideal choice for capturing target objects in continuous or discrete ‘web’ surface inspections, such as for plastic, textiles, metal, or paper.

Line scan cameras can also ‘unwrap’ cylindrical objects to capture their entire surface area. Large objects that require high-resolution imaging for precise measurement and defect detection, such as flat panel displays, solar cells, and automotive parts, are also well-suited to this technology. And because line scan systems only need to view a small portion of the target object for each line acquisition, they did not require a large, unobstructed view of the target object. For this reason, they work well in installations with restricted fields of view or mounting space.

As with most machine vision systems, line scan systems can be configured with a camera and PC or vision controller running machine vision software, or as an embedded system with the camera and software contained in one package. So line scan camera technology can help manufacturers acquire high-resolution images for fast-moving, large, and cylindrical objects that challenge area scan cameras.

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