Table 1. Main variables and operators defined in Section 2 .

Notations	Explanations
	Measured intensities
	Elemental thickness maps of the sample
	Spectrum dictionary
	Sample spectral contrast maps
	Probe
	Binary matrix to take image patches
	Forward operator for ptychography
	Poisson likelihood estimation
	Real part of spectrum dictionary
	Non-negative thickness constraint
	Normalized constraint of the probe
TV	Total variation regularization