source 38 lens 40 serves two functions it collimates the light vertically and together with cylinder lens 42 maps horizontal position in the plane of cell 37 to an output plane 44 containing detector array 45 light undiffracted by cell 37 is blocked by spatial filter 47 other imaging means may be substituted on construction of the wavefront reversing interferometer 30 is pictured in fig3 it is a michelson interferometer with a single mirror 51 in one leg and a roof prism or pair of mirrors 52 in the other light 54 entering the interferometer from object 55 is split by a cube beamsplitter 47 is reflected in both legs and recombines in said beamsplitter before leaving to form object 59 the roof prism 52 serves to reflect the light about the diagonal an image formed through the interferometer results in the superposition of two images one the diagonal reflection of the other it is important to note that this interferometer may be made very small and stable and could in fact be made from a single piece of glass before reaching the output plane 44 fig2 light diffracted by the bragg cell passes through the interferometer 30 thus two contributions are seen at the detector one with horizontal position identifying delay in cell 37 and the other with vertical position doing so the triple product will result from this interference as described below where u03c9 is the.