Practice question

Confocal optical sectioning eliminates physical slicing by utilizing combined laser scanning and spatial filtering. A focused laser raster-scans specimen, exciting fluorophores point-by-point at defined focal depth. Fluorescence returning through objective is focused onto a pinhole aperture conjugate to focal plane, which blocks rays from above and below focus. Only in-focus photons reach detector forming one thin optical slice. Moving focus through depth collects serial sections for three-dimensional reconstruction. This approach surpasses electron-based sectioning and does not rely on oil immersion or passive filters alone for contrast.