Design of the HAM mask for the Keck OSIRIS Imager. Subapertures that are combined in one or more interferograms have the same color. Top: subaperture combinations and baselines of the HAM mask. Bottom: monochromatic simulation of the HAM PSF with indications of the location of the resulting interferogram(s). The HAM mask incorporates a SAM mask design as the central component (leftmost panels) and adds a holographic component with off-axis interferograms (other panels). The baselines of the central component have been omitted for clarity.