Machine Vision vs. High Speed Video
When you read that a camera is high speed do you every question why? What qualifies a camera to be high speed? This is a fair question since so many cameras with a vast difference in performance all are described as “high speed”.
High speed use to mean that an industrial camera’s frame rate would determine if the name applied. Standard broadcast cameras operated at 30 frames per second (fps) and were considered a baseline for standard performance. At that time a industrial camera operating at 90 fps or above was considered high speed. In fact, 90 to 180 fps broadcast cameras were known as slowmo cameras used to capture “high speed” images and play these images back in slow motion.
In the late 70’s, a new class of cameras were introduced for industrial use to analyze motion of objects that moved at high speed, too fast for the human eye to observe. The frame rates for these new cameras were 200 fps and then 400 fps. In the 80’s, camera technology advanced where high speed cameras operated at 2000 fps. In the 90s, the high speed bar was moved to 4500 fps. Today, 25000 fps is the norm for traditional high speed video camera.
Another way to define high speed as it relates to cameras is to look at the aggregate bandwidth consisting of resolution x fps = megabytes/second (MPS). Contrasting the camera in the 1980’s that operated 2000 fps @ 240 x 192 pixels = 92 MPS where today, 25000 fps @ 1024 x 1024 x 12 bits = 39 GPS (Gigabytes per second).
Today’s high speed performance of 39 GPS is the top bandwidth possible while most people in the high speed video industry accept greater than 500 fps while others recognize 1000 fps. In the case of 1000 fps, we have 1000 fps @ 1024 x 1024 x 12 bits = 1.57 GPS. As a rule of thumb, high speed could be defined as more than 1000 fps or an aggregate bandwidth greater than 1.57 GPS.
Machine Vision camera manufacturers use a different yardstick for defining what is called high speed. Within the machine vision industry, there are cameras that operate at 120, 180, 240, 340 and above 400 fps. What is very different from the High Speed Video cameras is the camera resolution is significantly higher. There are cameras that some defined as high speed that have 29MP @ 5 fps 12-bits but we define our VA-29MC as a fast camera. Is this really high speed at 5 fps? If we examine the aggregate bandwidth: 29MP @ 5 fps x 12 bits = 217 MPS. As you can see, the aggregate bandwidth does not satisfy the criteria for high speed. Another example, CMOSIS CMOS Image Sensors (CIS) used in our VC-12MX cameras can operate at 12MP @ 180 fps x 10 bits = 2.7 GPS. While 180 fps by High Speed Video standards today is not really considered high speed, the aggregate bandwidth is significant. For machine vision, the aggregate bandwidth test is a reliable metric to determine what is truly deserves the high speed.
As mentione before, some people define 500 fps @ 1024 x 1024 x 8 bits as high speed. If we look at the aggregate bandwidth, we have 524 MPS. Considering this lower aggregate bandwidth as a definition between what is called high speed and what otherwise would be called fast could be used to define the dividing line.
We have looked at two definitions of high speed based on traditional high speed camera industry and that of the machine vision industry. Industrial Cameras that operate above 500 fps or 1000 fps can be considered high speed cameras. Industrial Cameras that have an aggregate bandwidth above 524 MPS can be considered high speed cameras. Industrial Cameras that operate above 120 fps or an aggregate bandwidth below 524 MPS can be considered fast framing industrial cameras.