A popular mode of optical microscopy in which a focused laser beam is scanned
laterally along the x and y axes of a specimen in a raster pattern. The emitted fluorescence (reflected light signal) is sensed by a photomultiplier tube and displayed in pixels on a computer monitor. The pixel display dimensions are determined by the sampling rate of the electronics and the dimensions of the raster. Signal photons that are emitted away from the focal plane are blocked by a pinhole aperture located in a plane confocal with the specimen. This technique enables the specimen to be optically sectioned along the z axis.