Patent GB-749447-A (GB)
Title: Improvements in or relating to electronic storage or memory devices
Inventor: DELL HUGH ALEXANDER
IPC: G11C11/23
Filed: 1953-03-23
Abstract: 749,447. Photo-electric memory device. MULLARD RADIO VALVE CO., Ltd. May 21, 1954 [March 23, 1953], No. 7986/53. Class 40 (3). [Also in Groups XIX and XL (c)] A memory or storage device comprises means for exciting in sequence individual areas of a luminescent screen, the brightness of each area representing a particular value of the stored data, means for exploring the areas in the same sequence and obtaining an indication of their individual brightness and means for repeating the excitation of the same or corresponding individual areas in the same sequence. As shown (Fig. 1) information to be stored appears in the form of an intensity modulation of a line trace generated on the screen of a cathode-ray tube 1 by a time base 11. For example, if the information is in binary digit form the black level may indicate zero and peak white unity or vice versa. The image on the face of tube 1 is projected by a lens system 3 on to the photocathode of an image converter 4 provided at its far end with a fluorescent screen 5. The end of this screen is provided with a mask 8 having a central aperture the size of which depends on the resolution of the trace. Behind the aperture is a photo-cell 9. The image converter is provided with focusing means 6 and deflecting means 7. The deflecting means traverse the entire trace along its length across the aperture in mask 8 so that the photo-cell is illuminated by each component part of the trace in turn. However, the deflecting time base of the image converter leads that of the cathode-ray tube, hence during the formation of the first trace the photo-cell receives no signal. During the second scan the photo-cell receives a signal which has decayed to about one-half of its original brightness due to the persistence of the cathode-ray tube and the signal then produced is fed through a delay line 10 the delay of which is equal to the time difference between the deflection of the two bases and brightens the decaying spot once more. This brightened spot is not seen by the photo-cell until the next scan. Thus the signal is retained indefinitely on the screen of the cathode-ray tube. Instead of arranging the deflection of the electron image to take place in advance of the cathode-ray beam the two deflections may be in phase and the mask aperture adjusted to produce the required shift. If much information is to be stored the cathoderay beam may be caused to trace a raster consisting of several lines. In the arrangement of Fig. 2 (not shown), two traces are written alternately on the screen of a cathode-ray tube, a pair of photo-cells and a pair of apertures being provided in the image converter. The arrangement is that the photo-cells are switched in synchronism with the travel of the cathode-ray between the two writing positions, thus each photo-cell receives the decaying trace written on the previous line and is used to regenerate the other trace. An arrangement is mentioned in which mechanically driven optical elements present to the photo-cell a delayed image of the trace on the cathode-ray tube. A mirror drive is suggested as, suitable for this purpose.