the axis of the plate at odd fractions of the primary focus(, , , etc.). Although these contain less energy (counts of the spot) than the principal focus (because it is wider), they have the same maximum intensity . At even fractions of the primary focus (, , , etc.), the intensity on-axis is zero.

Continuous zone plates

If the zone plate is constructed so that the opacity varies in a gradual, sinusoidal manner, the resulting diffraction causes only a single focal point to be formed. This type of zone plate pattern is the equivalent

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