Framegrabber

The frame grabber or video grabber (in German about frame grabber ) is an electronic circuit that was used for digitizing analog video signals into the original meaning. Meanwhile, since almost all video cameras do the digitization of the signals internally and output only digital video signals lose frame grabber in video technology is becoming increasingly important. Digital frame grabber can be used instead to connect cameras to the different systems when they do not have a common data interface, for example, have as USB.

Function

The task of the frame grabber is always to conform to the data format of the camera and share the picture material in the target format or store. Often, this digital frame grabber already allow intelligent preprocessing of the recorded image sequences, such as brightness and contrast adjustment. In the field of machine vision frame grabbers capture the image data often directly from the solid-state image sensors and perform complex calculations and pre-processing, such as non uniformity correction, binning and scaling by.

Construction of an analog frame grabber

The frame grabber essentially consists of an analog- to-digital converter, to which a sample-and- hold amplifier is connected upstream. The analog-to- digital converter associates a certain voltage level at the signal input for a natural number. Thus, the video signal is converted into a sequence of numbers which are stored in a memory (Random Access Memory). Additional circuitry to determine the timing of the synchronization on the beginning of the image and to the row beginnings and reconstruct the clock signal for digitization. With this information, the number of values ​​of an image array can be arranged, as it can be displayed, for example on a computer screen. A technical realization of the frame grabber can be found eg in the form of PC cards for the ISA or PCI bus and external video digitizer via USB to capture old video films.

Analog frame grabber capture signals of classic analog VGA standard, analog S - Video, SCART analog, analogue RGB CAD (CRT) monitors usually etc.

Building a digital frame grabber

Digital frame grabber capture either a standard image format such as DVI, HDMI or CameraLink or they adapt to a vendor-specific, proprietary format and convert it to a target format. Digital frame grabber exist both as USB and Firewire interfaces, as well as with PCIe and GTP connection that are intended for use in PCs and PC - related applications. Furthermore, encapsulated frame grabbers are like as a module or as a circuit element in existing imaging systems such as lidar systems, radars, X-ray, thermal imaging cameras integrated to convert proprietary formats and to create a connection to the outside world. Often these frame grabber modules have a standardized output, such as Camera Link or Gigabit Ethernet ( GigE or GigE Vision).

Digital frame grabbers are usually equipped with programmable functions whose parameters are influenced by the user. There are also fully programmable systems based on FPGA.

• Video technology
• Image processing