Box 2 Explanation

2. 4.

Box 2 represents what the detector "sees"as a function of time as X-ray photons from the off-axis point source indicated in Box 1 pass through the grids. The bottom grid is directly above the detector so that the two rotate together. The detector "sees" the bottom grid as a stationary object with bars. Because the top grid is rotated closer to the point source, the slats of the front grid seem to overlap the slats of the bottom grid leaving an ever narrowing slit of photons. Then the top grid seems to slide back revealing matched open slits. This variation in apparant slit width modulates the photon flux hitting the detector. That intensity variation as a function of time is represented in Box 4.

Return to HESSI Imaging Technique Box 2.