D*: (pronounced “Dee-star”), a metric used to allow comparison of some different kinds of detectors. A larger value of D* is considered better.
Delta-T: The difference between the temperatures of the target and the background.
Detection Range: The maximum range at which a target can be detected, though not recognized or identified. For military/security applications, the target is often specified as either an upright, 6’ man, or a vehicle such as a pickup truck, though simple detection cannot make distinction between any of these targets. See Probability of Detection/Recognition/Identification.
Depth of Field: The Depth of Field (DOF) is the range of distances from the lens, for a given focus setting, at which objects in the field of view are in sharp focus. DOF is smallest for objects close to the lens, but increases as range increases. DOF also increases as F# increases.
Dewar: Typically, a storage device for a cryogenic liquid, such as liquid nitrogen.
Diffuse Surface: A surface that emits or reflects evenly in all directions, regardless of the direction of the incoming light (in the case of reflection).
Digital Signal: A discretely varying signal, as opposed to a continuously varying (analog) signal.
Digitization: The process of breaking up an analog signal into a discrete, or ‘digital’ signal.
Discrimination Range (also, Resolution Range): The maximum range at which a specified target can be identified by target type. See “Detection Range”.
Dynamic Range: The maximum temperature range that can be observed by the imaging system without saturation of the image.
