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The video tracker operates in two distinct modes, black-on-white or, more usually, white-on-black. It is available either stand-alone or as a card that slots into the dacq system unit, and is compatible with both PAL and NTSC monochrome or colour camera signals. The tracker contains a dedicated image processor which allows parameters such as brightness, contrast, hue, saturation, tracking “window” etc., to be controlled from the PC. Different setups can be stored to and loaded from disk on a trial-by-trial basis, allowing easy reconfiguration for different arrangements of experimental apparatus or lighting.
The tracker computes the centroid of each light/spot to obtain its x-y coordinate, which is uploaded in real time via the dacqUSB system unit (or through a PC plug-in card if the tracker is operating stand-alone). A composite video output signal allows the tracker configuration (window size, brightness, contrast, etc.) to be displayed using marker lines to indicate the position of tracked lights/spots.
In big/small mode the tracker looks for two spots, one large and one small (or one bright light and one dim light, which can be made to appear to a camera as lights of different sizes). This feature allows the tracker to work with monochrome cameras, but still track two reference points, e.g. to monitor instantaneous head direction as well as position information. With an appropriate monochrome camera, this mode also allows the use of infrared LEDs, which may be needed for experiments that must take place in darkness.
There is also a two-camera mode. This allows simultaneous tracking of two cameras and will enable plotting of spatial co-ordinates in three dimesnions. This development was motivated by the development, by our collaborators BioSignalGroup, of a telemetric recording device for the wireless collection of single neuron data. The digital telemeter, in conjunction with two-camera tracking, will enable experiments to be conducted in complex three-dimensional environments. Contact us for more details of the two-camera setup.
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