Two sets of experiments are described which indicate that Wood’s diffraction-grating anomalies are a local phenomenon, associated with the action of a single grating line and its interaction with nearest neighbors. The first set shows that the character of an anomaly, irrespective of its appearance, remains virtually unaffected by very drastic phase and amplitude distortions of the incident wavefronts, suggesting that anomalous behavior may be observable with only a few lines. The second set of experiments confirms this hypothesis, and shows that gratings with only two or three lines exhibit almost the same anomalous behavior as a many-line grating of the same profile.
C. HARVEY PALMER and FREDERICK W. PHELPS,JR., "Grating Anomalies as a Local Phenomenon," J. Opt. Soc. Am. 58, 1184-1188 (1968)