Which microscopy technique uses a pinhole to eliminate out-of-focus light?
Confocal microscopy achieves optical sectioning and improved contrast by rejecting light originating outside the focal plane. A laser scans point-by-point across the specimen, exciting fluorophores only at focus. Emitted light passes through a small adjustable pinhole placed conjugate to the focal plane, so out-of-focus fluorescence and scattered light are physically blocked before reaching photomultiplier detectors. Serial optical sections can be stacked computationally to reconstruct three-dimensional volumes. This principle dramatically enhances lateral and axial resolution, reduces blur in
Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.