positionsensitive

Position-sensitive describes the property of a device, sensor, or mechanism that can determine or respond to the precise location of an event within a defined spatial coordinate. In instrumentation, the term commonly refers to position-sensitive detectors (PSDs), devices that output signals proportional to the position of a light spot or particle on a sensing surface. Linear PSDs determine a single coordinate along one axis, while two-dimensional PSDs measure both x and y coordinates. Most PSDs rely on a resistive or segmented sensing layer and use a center-of-gravity or ratio method to compute the incidence position from electrode signals.

Common implementations include lateral-effect photodiodes, which use current division in a resistor network to infer position, and 2D PSDs based on diode arrays. Compared with standard imaging sensors, PSDs can offer high response speed and continuous position readouts without full frame scanning, making them suitable for beam alignment, optical tracking, autofocus, and feedback control in instrumentation.

Position sensitivity is not limited to optics. In other domains, systems may be described as position-sensitive if their outputs vary with the location of a stimulus, such as position-sensitive chemical sensors or tactile arrays that infer contact location. The concept emphasizes spatial resolution and linearity between true position and measured signal, and performance is affected by noise, linearity, and calibration.