Patent Number: 042648246
Section: description

DESCRIPTION Collimator 10 has spaced, radiation absorbing sheets 12, and may be of the same general construction described in said patent and application. However, sheets 12, rather than being parallel, lie along planes 14 the continuations of which intersect in a common focal axis 16. In a typical preferred embodiment the collimator would have 100 sheets 12, equally angularly spaced to give a total field of view of 10.degree. about axis 16. Sheets 12 extend along axis 16 sufficiently to give about the same 10.degree. field of view about axis 18 perpendicular to axis 16. A separate detector strip 20, parallel to axis 16, is mounted between the converging ends of each pair of sheets 12. The detectors are of the sort described in said patent. The collimator and detectors are mounted (using appropriate and conventional hardware, not shown) for oscillation through 180.degree. about an axis 22 perpendicular to axes 16 and 18, under the control of drive unit 24. Conventional signal processing circuitry 26 is connected to detectors 20 to initially process the information sensed during operation of the device. Computer 28 is provided for data reduction. Stepping motor drive unit 24 provides clock inputs to the computer. The extent of sheets 12 along planes 14 is such that each central viewing plane 30, bisecting a collimator slit 31, is parallel to the "boundary" viewing plane 32 (which runs between the forward edge 34 of one sheet 12 and the rear edge 36 of the other sheet defining the slit) of an adajacent slit 31. OPERATION The instrument is set up by pointing axis 22 at the estimated position of the radiation source to be imaged, e.g., a cellestial body, to bring the source into the overall field of view of the collimator. Drive 24 is turned on and collimator 10 is rotated, in steps, 180.degree. about axis 22. After each step detectors 20 are turned on and readings are taken. For a given angular position of the collimator about axis 22, radiation from a given source within the field of view will be received primarily through one slit (by its associated detector 20), though there will be some reception through neighboring slits. In other words, the effect of making sheets 12 non-parallel is that, for a given angular position of the collimator, the slits have different transmissivities of radiation from a given source. Rotation of the collimator serves to vary those transmissivities with time. In general, circuitry 26 will note the response of each detector 20 for each angular position of the collimator about axis 22. Data defining these responses, and the angular positions about axis 22 at which they occur, is fed to computer 28. Using a data reduction procedure substantially identical to that described in said patent, angular coordinates (rather than Cartesian coordinates as in the near field case) of each radiation source within the field of view are computed. Embodiments of the invention using diverging sheets are also useful in near field imaging. Other embodiments are within the following claims. For example, instead of stepping the collimator, it might be rotated continuously, with the time of arrival of each photon, and the slit through which it arrived, being recorded. Further, the slit-to-slit difference in transmissivity might be achieved other than by angling the sheets, and the variation of transmissivity with time other than by rotating the collimator.