The present application describes a system and method for determining characteristics (e.g., exact band location, orientation and height and the spot shape and size of a single wavelength and the like) of an optical signal projected on a spatial light modulator. In an embodiment, images with sharper edges (i.e. clear boundary between ‘on’ pixels and ‘off’ pixels) on the spatial light modulator are used to obtain spectral information from a referenced broadband source. The spectral information can be used to determine the desired characteristics of optical signals projected on the spatial light modulator.