Vision Sensors

Vision sensors are video cameras with integrated signal processing and imaging electronics. They are used in industrial inspection, quality control, and design and manufacturing diagnostic applications. They often include interfaces for programming and data output, and a variety of measurement and inspection functions.

When specifying vision sensors, it is important to determine whether a monochrome or color sensor is needed.  Monochrome vision sensors present the image in black and white, or grayscale.  Color sensing vision sensors are able the read the spectrum range using varying combinations of different discrete colors.  One common technique is sensing the red, green, and blue components (RGB) and combining them to create a wide spectrum of colors.  Multiple chip color is available on some vision sensors.   It is a method of capturing color in which multiple chips are each dedicated to capturing part of the color image, such as one color, and the results are combined to generate the full color image.  They typically employ color separation devices such as beamsplitters rather than having integral filters on the sensors.

Important specifications to consider when searching for vision sensors include number of images stored and maximum inspection rate.  The number of images stored represents captured images that can be stored into on-board memory or non-volatile storage.  The maximum inspection rate is the maximum number of parts or process steps that can be inspected or evaluated per unit time.  This is usually given in units of inspections per second.  Other important parameters include horizontal resolution, maximum frame rate, shutter speed, sensitivity, and signal to noise ratio.

Inspection functions include object detection, edge detection, image direction, alignment, object measurement, object position, bar or matrix code, optical character recognition (OCR), and color mark or color recognition.  Imaging technology used in vision sensors includes CCD, CMOS, tube, and film.  Charge Coupled Devices (CCD) use a light-sensitive material on a silicon chip to detect electrons excited by incoming light. They also contain integrated microcircuitry required to transfer the detected signal along a row of discrete picture elements (or pixels) and thereby scan an image very rapidly.  CMOS image sensors operate at lower voltages than CCDs, reducing power consumption for portable applications.  Analog and digital processing functions can be integrated readily onto the CMOS chip, reducing system package size and overall cost.   In a tube camera, the image is formed on a fluorescent screen.  It is then read by an electron beam in a raster scan pattern and converted to a voltage proportional to the image light intensity.  With film technology the image is exposed onto photosensitive film, which is then developed to be played or stored.  The shutter, a manual door that admits light to the film, typically controls exposure.

Other parameters to consider when specifying vision sensors include performance features, physical features, lens mounting, shutter control, sensor specifications, dimensions, and operating environment parameters.

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  Welcome to the "Vision Sensing Overview," a tutorial in which you will learn about using vision sensors in factory automation. Vision sensors are used to automate complex visual inspections....
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