Glossary 105
• Double buffering
Alternating the destination of an operation between two buffers. Double buffering
allows you to, for example, process one buffer while grabbing into the other buffer.
• Dynamic range
The range of values present in a buffer. An unsigned 8-bit buffer, for example, has
an allowable range of 0 to 255; its dynamic range can be any range within these
values.
• Exposure signal
The signal generated by one of the programmable timers of the frame grabber
module. The exposure signal can be used to control external hardware. For
example, it can be fed to the video source to control its exposure time or used to
fire a strobe light.
• Exposure time
Refers to the period during which the image sensor of a video source is exposed
to light. As the length of this period increases, so does the image brightness.
• Field
One of the two halves that together make up the image grabbed from an interlaced
video source. One half consists of the image’s odd lines (known as the odd field);
the other half consists of the image’s even lines (known as the even field).
• FPGA
Field-programmable gate array. An array of digital electronic components that can
be programmed to perform a specific function. An FPGA can contain logic gates,
lookup tables, flip-flops and programmable interconnect wiring. This
combination of customizability and functionality allows for the same FPGA
design to be used in a variety of projects.
• Frame
A single image grabbed from a video source.
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