Abstract: A Hadamard domain encoder wherein adding and subtracting operations on digitized intensities of 2 .times. 2 picture points yield secondary results. Likewise processing of groups of 2 .times. 2 secondary results yields further intermediate and/or final results. The complement of unprocessed secondary and final results fully characterizes the original picture but is better suited for data storage and/or transfer because the energy content of the picture is substantially restricted to a limited region. Redundancy in the stored/transmitted data is thus reduced.

Abstract: The invention relates to an X-ray installation which comprises a television display device and an automatic exposure device and in which dominant selection is no longer required. The television image produced during fluoroscopy is sub-divided into a large number of sub-fields, a storage position being assigned to each sub-field. In each storage position the part of the video signal is stored which corresponds to the assigned sub-field. The sub-fields are then determined which contain the regions of the maximum and the minimum brightness. An effective, organ-programmed intermediate value is derived therefrom. Moreover, the mean value of the video signal is obtained in the part of the television image assigned to the sole central measuring field of the automatic exposure device. The mean value is compared with the intermediate value, and the switch-off dose or switch-off voltage is corrected in dependence of the difference thus found.

Abstract: The invention relates to an automatic X-ray exposure device having a measuring member, for example, an ionization chamber comprising a large number of measuring fields, for example, 5 .times. 5. Each measuring field is associated with a capacitor which, during television fluoroscopy, receives the part of the video signal which is derived from the part of the television image in which the dose or the dose power is to be measured in the associated measuring field. Therefore, the capacitors having the highest and the lowest voltage, respectively, have associated therewith the measuring fields having the largest and the smallest, respectively, dose or dose power. Subsequently, the measuring fields whose dose or dose power is situated in a given organ-dependent range between a maximum and a minimum value are determined and actuated for the automatic exposure in a subsequent exposure.