Selecting the right type of Frame Grabber

I need a frame grabber to acquire images from my camera.
How do I select the right type?

Firstly you have to consider the camera output. Is it analogue or digital?

If its analogue it will most like be either CCIR.PAL or Y/C. Most analogue
frame grabbers will accept all these types of inputs at full resolution and at
full frame rate. The required bandwidth is not high and well with the specification
of most boards and PCs.

If its digital you will need to consider the exact type of digital signal as
different types of boards are needed for RS422, RS644 and Camera Link. 

Secondly you will need to consider what you want to do with the
images once you have them in the PC.

If you just want to save images to hard disk you will need to consider how
you want to do this. The simplest scenario would be to grab images into
computer memory review them one by one and just save the ones you want
to keep.

More complex if you want to save a sequence of images. You have to decide
how many you want to save in a sequence, the time interval between frames
and the how fast (or slow) you want this to be. Always remember images are
large files and fill up hard disks very quickly if too many long sequences are
captured.

We need the answers to these questions before we can advise on the correct
software control package for your application. 

Thirdly you need to think about what you want to with the images
once you have them in the PC.

Do you want to just save them to disk or do you wish to do image processing
on the fly as the images are captured or are you going to post process the
images after they have been captured. 

Fourthly are you synchronising the image capture with some external
device (e.g.: triggering of a laser, a conveyor belt or moving web). If so the
frame grabber will need to support these functions. 

Are there compatibility issues between cameras and frame grabbers? 

This was always a problem particularly with digital cameras. You will find that
not all cameras most of these problems have been eliminated since the move
to the “Camera Link” standard as most revolved around cabling issues and
with “Camera Link” interfacing you have one standard cable for nearly all
camera types so the problem is very much reduced. The other issue relates
to camera configuration files. These are the software interface files that talk
to the cameras through the frame grabbers. These files are normally supplied
by the frame grabber manufacturer so it is important to check that the grabber
software libraries support the camera you are using. 

How is the frame grabber powered? 

All grabbers are fully PCI compatible and powered via the PC bus 

Can I power my camera from the frame grabber? 

Maybe. Some grabbers allow you to drive analogue cameras, some don’t.
In which case you will have to use a separate power supply for your camera.
In general all digital RS644 or CameraLink cameras will require a separate
power supply. 

With the advent of USB, IEEE-1394 and Gig Ethernet Interfacing will there be any advantages in using frame grabber technology?

Frame grabbers will be around for a long time to support the existing range of cameras in the market place. The new camera technologies of IEEE-1394, USB2.0 and Gig E interfacing will have a huge impact on frame grabber usage as more of these cameras become available.

Cameras with high end specifications will most likely move to Gig –E interfacing.

Over the coming years new design of products will start to use non frame grabber technology unless the frame grabber offers on board processing that is not possible or as quick to do on the host computer. For most applications the plug and play attraction of the new interfacing technologies will mean that if a frame grabber is not required for a specific reason ( ext triggering, strobing, on board Trimedia/DSP, real time compression etc) then they will offer no advantage to the newer technologies.

Can one frame grabber support a number of different camera types? 

In most cases a frame grabber will either support digital cameras or analogue
cameras and not both. In the analogue world most grabbers can support a
wide range of camera outputs, (eg: PAL, CCIR, Y/C etc).

In the digital case normally the deciding factor is the type of interface.
(eg RS422, RS644 or CameraLink) you cannot transfer interfacing technology
on one board although many cameras of the same interfacing technology
will run off the same board. However the exact cameras supported will
depend on how the board is structured. For example RS644 interfacing
on cameras can be single, dual or sometimes even quad output so the
board must be capable of supporting the formats of the cameras you are
using.   

Can  I buy a frame grabber for use in my PCI EXPRESS based computer system.

Yes. Infact because PCI EXPRESS (PCIe) is backward compatible to PCI, any PCI based frame grabber could be compatible. However, if you wish to make the most of the PCIe technology you need to use a PCI EXPRESS board. These boards are now available and will grow in numbers as time goes on. PCI EXPRESS frame grabbers are detailed separately on our web site.

If you would like further information on how to select the right frame
grabber for an application please talk to our sales staff on 01635 30345

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Further information available from Geoff Smith.

Alrad Imaging, a trading division of Alrad Instruments Ltd.
Alder House, Turnpike Road Industrial Estate Newbury, Berkshire RG14 2NS

Telephone: +44(0) 1635 30345   Fax No. +44(0) 1635 32630
Email: sales@alrad.co.uk