Page 266 - The ROV Manual - A User Guide for Remotely Operated Vehicles 2nd edition

10.2 How it works 255
FIGURE 10.6
The Kongsberg OE14-370 Standard Camera System mounted into pressure housing.
(Courtesy Kongsberg Maritime.)
FIGURE 10.7
Lens types by shape.
Lenses are broken into several components including field of view (FOV), focal length, and f-number (also termed “f-stop,” “focal ratio,” or “relative aperture”). As illustrated in Figure 10.8, the FOV metric is expressed in angular degrees in either width-by-height (W3H) or (more typi- cally) corner-to-corner (or “diagonally”).
As illustrated in Figure 10.9, focal length (f) is the measure of the lens’s light-gathering/ magnification ability in that the more acute the angular deflection of the light rays bent in the lens the higher the light magnification (S1 is the distance to subject and S2 is the distance to the light capture mechanism—S2 and f are required to be synched in order for the object to be in focus). The shorter the focal length (f), the higher the concentration of the light upon a discrete point (where the light- gathering mechanism is placed—e.g., CCD or CMOS). Hence, the measure of focal length is the mea- sure of the optical power of the lens. Longer focal lengths are for higher magnification for telephoto applications. The longer focal lengths allow for higher magnification of the object with a correspond- ing loss of angular FOV (i.e., the magnification versus angular FOV are inversely proportional as the object is brought closer to the center of view—Figure 10.8). Also see Figure 10.10.
Biconvex
Plano- convex
Positive meniscus
Negative meniscus
Plano- concave
Biconcave