Area Scan Cameras for Every Inspection Line

An area scan camera captures a complete two-dimensional image in a single exposure, using a sensor made of a rectangular grid of pixels. It is the most common type of machine vision camera and is used wherever the part, package or scene can be imaged in one shot: inspection, measurement, code reading, robot guidance and presence checks.

An area scan camera captures a full frame at once. A line scan camera has a sensor that is one or a few pixels tall and builds the image one line at a time as the object moves past it, synchronized to an encoder. Area scan suits discrete parts and stationary or indexed objects and is simpler to set up. Line scan suits continuous material such as web, film, paper, steel strip or very long parts, and cylindrical objects that are rotated in front of the camera.

A global shutter exposes every pixel at the same moment, so moving objects are captured without skew. A rolling shutter exposes the sensor row by row, which can bend or skew fast-moving objects unless the light is strobed during a short window. For parts moving on a conveyor, robot picking and most inline inspection, a global shutter is the usual choice. Rolling shutter sensors can be a good value for stationary scenes and microscopy.

Start from the field of view and the smallest feature you must see. Divide the field of view by the smallest feature size, then multiply by the number of pixels you want across that feature: a common starting point is about 2 to 3 pixels for detecting a defect and more for precise measurement. For example, a 100 mm field of view with a 0.2 mm defect at 3 pixels per feature needs about 1,500 pixels across, so a sensor about 2,000 pixels wide gives some margin. Confirm the lens can resolve that detail too.

Choose monochrome unless color itself is what you are inspecting. A monochrome sensor has no color filter over its pixels, so it collects more light and resolves finer detail at the same pixel count. Choose color when the task depends on color: sorting by shade, checking a colored label or cap, verifying wire colors or grading food.

GigE Vision and 10GigE use standard Ethernet cabling, run long distances and need no frame grabber. USB3 Vision is simple and fast over short cables. CoaXPress carries very high data rates and power over coaxial cable into a frame grabber, and suits high-resolution, high-speed cameras. Camera Link is an established frame-grabber interface still found on many existing systems. Choose based on the data rate your resolution and frame rate produce, the cable distance, and the host PC or controller.

GenICam is a generic programming interface standard for machine vision cameras. Cameras that comply with it, together with transport standards such as GigE Vision, USB3 Vision and CoaXPress, describe their features in a standard way, so compliant software and libraries can control cameras from different suppliers without custom drivers. It makes replacing or adding cameras much easier.

Most compact area scan cameras use the C-mount. CS-mount is similar with a shorter flange distance, and a C-mount lens can be used on a CS-mount camera with an adapter ring, but not the other way round. Larger sensors use F-mount or large-format threaded mounts such as M42, and small board-level cameras often use S-mount (M12) lenses. Whatever the mount, the lens must cover the full sensor format.

Keep the distance the part travels during the exposure to a fraction of a pixel. Blur in pixels is roughly the part speed multiplied by the exposure time, divided by the size of one pixel on the object. Shorten the exposure, add brighter or strobed lighting to make up for it, and use a global shutter sensor with a hardware trigger so the image is taken at exactly the same point every time.

Standard silicon sensors respond into the near infrared, and some cameras use sensors tuned for better NIR sensitivity, which helps with see-through inspection of some plastics and with lighting that operators cannot see. Short-wave infrared (SWIR) cameras use a different sensor material and can see moisture, fill levels through some containers, and differences between materials that look identical in visible light.

Lighting often matters more than the camera. Ring lights are a general-purpose start, dome or diffuse lights tame reflections on shiny or curved parts, backlights give crisp silhouettes for edge and dimension checks, low-angle bar lights reveal scratches and embossing, and coaxial lights help on flat reflective surfaces. Strobing the light in sync with the camera trigger gives more light during a short exposure.

Describe what you are inspecting and the smallest feature you need to see, the field of view and working distance, how fast parts move or how many parts per minute, whether you need color, the interface or controller you plan to use, the cable distance, and the environment, such as temperature, washdown or vibration. Quantity and timing help as well.