Page 263 - The ROV Manual - A User Guide for Remotely Operated Vehicles 2nd edition

252 CHAPTER 10 Video
White card
5
Black “5”
Minimum beam intensity (black)
Maximum beam intensity (white)
Start of beam
Light striking card
Maximum beam intensity (white)
5
Camera side
Display side
·
·
Minimum beam intensity (black)
5
Retrace (blanked)
Final retrace (blanked)
FIGURE 10.1
Beam sweep pattern
Camera captures image and transmits it to display.
analog devices converting light signals one pixel at a time; circuits then convert the voltage to digi- tal information (Figures 10.3 and 10.4).
The smallest element of the light sensor is the pixel. In the low-light subsea environment, there may not be sufficient light energy (“illuminance” or total luminance flux per unit area with the SI unit of “Lux” as the metric) falling upon the individual pixels to produce sufficient voltage under normal conditions; therefore, some type of light/video multiplier is needed in order to produce a useful image in low lighting conditions. This is the realm of the “high-sensitivity camera” (HSC).
HSCs enhance the light-gathering capabilities of the sensor elements and are generally grouped into charge integration and electron multiplication types:
Charge integration—essentially, this type of camera enhances sensitivity by extending the exposure time (charge integration time), allowing for signal strength gathering/boosting of the available light energy. An example of this type of camera is a so-called cooled CCD.