  Structured illumination enables the tailoring of an imaging device's optical
transfer function to enhance resolution. We propose the incorporation of a
temporal periodic modulation, specifically a rotating mask, to encode multiple
transfer functions in the temporal domain. This approach is demonstrated using
a confocal microscope configuration. At each scanning position, a temporal
periodic signal is recorded. By filtering around each harmonic of the rotation
frequency, multiple images of the same object can be constructed. The image
carried by the $n{\mathrm{th}}$ harmonic is a convolution of the object with a
phase vortex of topological charge $n$, similar to the outcome when using a
vortex phase plate as an illumination. This enables the collection of chosen
high spatial frequencies from the sample, thereby enhancing the spatial
resolution of the confocal microscope.
