| 摘要 |
For determining the absorption distribution in a plane of a body by means of a fan of radiation beams from an approximately point-shaped radiation source and in different positions of the body with respect to the radiation source, a detector element comprising only one amplifier is used for a number of adjacent radiation beams or all radiation beams. For determining the intensity profile in each measuring position, the radiation beams are modulated by time functions which form a complete, linearly independent function system (Walsh functions). Modulation is realized by means of an aperture which is constructed as a rotating disc which comprises transmissive and non-transmissive sectors. At each change of a function value, a discrete signal value is derived from the detector signals, so that the total number of signal values equals the number of functions of the function system. The signal values are multiplied by a back transformation matrix and therefrom the intensity profile is recovered. This profile is processed in known manner in order to obtain an absorption image. This principles is also suitable for a two-dimensional fan of radiation beams for the simultaneous determination of the absorption distribution in a plurality of planes.
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