What is a frame grabber? What types are there? How do you know when you will need one? These are some of the questions we will answer in this artical. First off what is a frame grabber? A frame grabber is a conduit for video being transferred from a camera to a computer. So look at it this way, if a camera needs one to plug into a computer then it is called a interface camera because it needs the frame grabber to interface with the computer. Chances are if you have one of these cameras it will be using s-video or BNC composite cables . If the camera can plug directly into the computer without needing a interface it is called a direct connect camera. If you are using a camera that plugs into the computer directly chances are it is a USB or Firewire camera. So a frame grabber is essentially a link between cameras and computers. But not all interface cameras need frame grabbers and not all direct connect cameras can be used without them. There are different types of frame grabbers, analog frame grabbers and digital frame grabbers. Analog frame grabbers digitize an analog video signal sent by the camera. They then send the digital data to the host computers memory. Therefore taking a camera that was only built to be plugged in to a monitor or a recording device and making the data digital for real time edit and control from the host computer.
Digital frame grabbers take data that has already been digitized in the camera and manage its transfer rate over the computer bus to the host memory. So all digital frame grabbers do is manages the data as its being transferred to the host computers memory for storage and real time edit and control. Frame grabbers do not just act as an interface between cameras (digital or analog) and computers. Many frame grabbers also have features that will benefit almost any industrial vision system. Trigger inputs and outputs are just one of these beneficial features. An output can be programmed to trigger a light for precisely the right exposure timing and another output can be used to control the cameras shutter timing.
Frame grabbers can also posses processing engines that range from Look-Up tables, Field Programmable Gate Arrays, general purpose processors and Digital Signal Processors.
Frame grabbers also vary in the design in which they plug into the computer or the way their bus architecture is designed. The Peripheral Component Interconnect frame grabbers (PCI) and its newer higher bandwidth PCI-X and PCI Express are the main bus architectures. Frame grabbers are also built in AGP (Accelerated Graphics Processing), ISA, PC104Plus, CompactPCI and VME 9VERSAmodule Eurocard) So, as you can see, there is a multitude of frame grabbers that will use USB and Firewire inputs and some with S-video and BNC inputs. There are basic frame grabbers that serve as interface boards and advanced frame grabbers that trigger certain functions.
They have several types of bus architectures, but that still doesn't answer the question of what system really needs a frame grabber? If you have an interface or analog camera that you want plugged into a computer then you will have to have a frame grabber but if you have a digital camera or direct connect camera you will not have to have one. Many imaging systems still use one because or other features the boards can come with. -BRADLEY FRY