Photon counting for enhanced resolution spatial frequency modulation imaging.

Spatial frequency modulation imaging (SPIFI) has previously been demonstrated in multiphoton modalities with resolution enhancement. When signal light levels are low enough, signals consist of discrete pulses: this is a photon-counting regime. By binning photon counts into discrete time bins, SPIFI signals can be built up by incrementing the photon counts over many modulation periods. The result is an increase in the signal-to-noise ratio (SNR) over analog SPIFI acquisition, enabling higher fidelity in the greater orders of resolution enhancement that SPIFI can produce.