pointscanning

Pointscanning is a method of acquiring images by interrogating a sample at discrete, focused points rather than across an entire field of view at once. A single optical spot or probing beam is steered to a sequence of locations, and at each point a signal is collected and later assembled into an image or map of the measured quantity.

In practice, point scanning uses a focused beam—often light in optical microscopy or a probe in scanning techniques—coupled with precise scanning hardware such as galvanometric mirrors or acousto-optic deflectors to move the spot. At each coordinate, detectors capture data such as fluorescence intensity, reflected light, or spectral information. The dwell time at each point and the scanning pattern determine image resolution, signal-to-noise, and total acquisition time. Software then reconstructs the two- or three-dimensional representation from the pointwise data.

Common implementations include confocal laser scanning microscopy and two-photon fluorescence microscopy, where point scanning provides optical sectioning and high sensitivity. Point scanning is also used in certain spectroscopic imaging approaches and, in scanning probe contexts, to map local properties by measuring at individual surface points.

Advantages of point scanning include flexible dwell time, high spatial resolution, and compatibility with various detectors and modalities, including nonlinear excitation. Limitations include slower speed for large areas, potential photobleaching at scanned points, and greater sensitivity to sample drift and mechanical complexity compared with wide-field or line-scanning approaches.