22-01-2013, 09:45 AM
Smart Cameras
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OVERVIEW:
A "smart camera" is basically a video camera coupled to a computer vision system
in a tiny package. This communication begins stating the main differences between smart cam-
eras and standard smart vision systems. A smart camera architecture is described whereby a
combination of an on-board microprocessor and PLD’s allow for the embedding of image
processing algorithms in the camera. A static thresholding algorithm is presented which demonstrates
the ability to track non-uniformity in the inspection target. A multi camera inspection
system application is presented where a maximum of twenty smart cameras may be networked
together to a single host computer. Finally, a prediction is made of technological and application future
evolution on smart cameras.
The smart camera – a whole vision system contained in one neat housing – can be used
anywhere, in any industry where image processing can be applied. Companies no longer
need a cabinet in which to keep all their computing equipment: the computer is housed
within the smart camera. In the pharmaceutical industry and in clean rooms – when not
even dust is allowed – this can be a big advantage. A single square meter of space can be
comparatively very expensive – if there is no need for a component rack or cabinet, simply
a smart camera, then this could save a lot of money. In particular, there would not be the
usual cabling involved for other vision systems, and set-up is simple [1]. Later in this
communication are stated some advantages of using smart cameras or PC-based systems in
vision applications.
Smart Cameras vs. Standard Smart Vision Systems
The question often comes up as to what is the most appropriate approach to take in implementing
a vision system - using a smart camera or using some sort of PC-based approach.
There is no question that as the microprocessors, DSPs and FPGAs are getting faster and,
therefore, more capable, smart cameras are getting smarter. Therefore, they are a challenge
to more ''traditional'' approaches to vision systems. Significantly, however, ''traditional''
approaches are also taking advantage of the advances and so, too, are faster and smarter.
Traditional approaches usually mean a PC-based implementation. This could be either
using a camera with the capability to interface directly to the PC (IEEE 1394/Firewire,
CameraLink, LVDS, USB, etc.), or a system based on a frame grabber or other intelligent
image processing board or vision engine that plugs into the PC. In this latter case, more
conventional analog cameras are used as the input device.
A smart camera, on the other hand, is a self-contained unit. It includes the imager as well
as the ''intelligence'' and related I/O capabilities. Because this format resembles the format
of many intelligent sensors, these products are often referred to as ''vision sensors.''
However, a vision sensor often has a limited and fixed performance envelope, while a
smart camera has more flexibility or tools, inherently capable of being programmed to
handle many imaging algorithms and application functions. A PC-based vision system is
generallyrecognised as having the greatest flexibility and, therefore, capable of handling a
wider range of applications.
ADVANTAGES:
Flexibility: The PC offers greater flexibility in the number of options that can be se-
lected. For example one can use a line scan versus an area scan camera with
the PC. Onecan use third party software packages with the PC approach
(smart cameras tend to be sin-glee source software).
Power : PC's tend to offer greater power and speed due in large part to the speed of the
Intel processors used internally. This power in turn means that PC's are used to
handlethe''tougher'' applications in vision systems.
Cost : Smart cameras are generally less expensive to purchase and set up than the PC-
based solution, since they include the camera, lenses, lighting (sometimes), cabling
andprocessing
Smart Camera Architecture
The smart camera presented in this communication reduces the amount of data generated
to the ‘data of interest’ by making use of embedded image processing algorithms. The data
of interest might be, for example, defective areas of the product being inspected. Multiple
cameras can route their data to a single frame grabber and computer due to the reduction of
data stream, thus dramatically reducing system cost and increasing inspection bandwidth
capability. This smart camera also makes use of an on-board microprocessor for communi-
cation with the inspection systems’ host computer and for internal control functions [6].
Image Sensor Basics
In this smart camera, a CCD (Charge Coupled Device) image sensor converts photons
(light) into electrons (charge). When photons hit an image sensor, the sensor accumulates
electrons. This is called charge integration. The brighter your light source, the more pho-
tons available for the sensor to integrate, and the smaller the amount of time required to
collect a given amount of light energy.
Finally, the sensor transfers its aggregate charge to readout registers, which feed each
pixel’s charge from the image sensor into an output node that converts the charges into
voltages. After this transfer and conversion, the voltages are amplified to become the cam-
era’s analog output [6].
Analog to Digital Conversion Electronics
The analog output of the CCD is converted to a digital output for further processing. The
camera presented here sub-divides the CCD analog output into eight channels of 256 pixel
elements each. Analog to digital conversion is performed at a 20 MHz data rate for each
channel thus yielding an effective camera data rate of 160 MHz. The digital data is then
passed along to the image processing electronics for processing and analysis [6].
CONCLUSION:
Looking into the future, we can foresee an infinite number of applications for the smart
camera; in fact, as many as there are potential image processing uses
Asmart camera has more flexibility or tools, inherently capable of being programmed to
handle many imaging algorithms and application functions
The 21st century smart-camera systems will perform real-time, pixel-data ex-
traction and processing operations within the camera at extremely high speeds and at a
cost, which is considerably less than required today for comparable capabilities