Digital Signal Processing Reference
In-Depth Information
must be fused, overlaid, and further processed for local display
and/or for transmission.
Figure 8.5
shows a high-level block diagram of a typical signal
chain implemented in an electro-optical infrared (EOIR) system.
As shown, the processed image is compressed many times
(usually using lossless techniques) before being transmitted over
a communications link.
The first group of algorithms shown is responsible for the
configuration and operation of the image sensor (also called focal
plane array (FPA)). These algorithms include the generation of
video timing and control signals for exposure control, readout
logic, and synchronization.
Once this is completed, the pixel streams are processed by
a second group of algorithms that addresses the imperfections of
the focal plane. Functions such as non-uniformity correction,
defective pixel replacement, noise filtering, and pixel binning
may also be used to improve image quality. For a color-capable
focal plane, demosaicing may be performed. The corrected video
stream is then processed to implement functions such as auto-
matic gain and exposure control, wide dynamic range (WDR)
processing, white balancing and gamma correction.
In addition, FPGA-based camera cores are able to implement
video processing algorithms that further enhance the output
video. These processing stages may include functions such
as image scaling (digital zoom), (de)warping, windowing,
electronic image stabilization, super-resolution, external video
overlay, image fusion, and on-screen display. In some cases, the
captured and processed video streammay need to be compressed
before it is transmitted to a control station.
The EOIR system implements high-quality sensor control and
image processing within a tightly constrained power budget, yet
Figure 8.5. Typical top level
structure of an EOIR system.
