Patent GB-1316528-A (GB)
Title: Data sensing system
IPC: F21K2/00
Filed: 1971-09-16
Abstract: 1316528 Data sensing NATIONAL CASH REGISTER CO 16 Sept 1971 [29 Sept 1970] 43181/71 Headings G4H and G4M [Also in Divisions C4 and G1] A data sensing system for sensing, e.g. prices on articles at a supermarket checkout comprises carrier members each bearing data consisting of symbols in denominational orders the data being represented by a plurality of areas respectively corresponding to the denominational orders, each area being provided with selected ones of a first plurality of photoluminescent substances which when subjected to energizing radiant energy, e.g. U.V. each emit radiation in one or more narrow wavebands characteristic of the substance, which selected substances define the relevant denominational order, and selected ones of a second plurality of photoluminescent substances of similar properties which determine the relevant symbol, all the said substances having different luminescence characteristics. Data bearing articles 22, 24 are moved by a conveyer 28 singly past a rotating disc 34 having 4 peripheral holes 38 to allow light from the coded labels derived from a U.V. source 66 to impinge on to an array 50 of photocells 48, each photocell being associated with a filter 52 allowing only a single narrow frequency band to pass to an associated photocell 54, thus in any one scanning operation, certain photocells indicative of the substances present will provide an output to a reader circuit shown in Fig. 4. A further photocell 54a responsive only to visible light from a source 68 is employed to detect the presence of an object and this source is extinguished in favour of the U.V. source when an object is sensed in the scanning zone. Outputs from the photocells 54, Fig. 4, are then amplified at 84, passed through threshold detectors 86 to eliminate noise and through gates 90 controlled by a controller 93 which also controls the energy sources, which are opened only whilst the U.V. source 66 is on. The outputs together with their inverses are taken to a decoding matrix, not shown, to derive a signal on one of 16 leads (Y 1 )-(Y 16 ), Fig. 5 (not shown) indicative of a symbol and on one of 8 leads (X 1 )-(X 8 ) indicative of the denomination which leads serve as inputs to a 16 Î 8 storing matrix (104). Each cell of the matrix contains an AND gate having an output connected to a respective capacitor each corresponding to a symbol in one of the denominational orders. At each scan, an incremental charge is placed on the appropriate capacitors, this process continuing during an interval governed by a pulse width generator 100. Each capacitor is connected to the first input of a respective comparator, and the capacitors in each column, corresponding to a particular order, are connected to an input of a negative gain amplifier caused to provide an output of approx. ¥ of the highest voltage appearing across any one capacitor, this output being connected to the other input of each comparator. Each comparator is associated with a bi-stable circuit, and when a signal K is produced derived from cell 54a, to indicate the object has passed, the comparators are caused to trigger and only the bi-stable of any one column associated with the capacitor of greatest charge is caused to change state. If an article is detected and its passage past is also detected without any coding therebetween, an alarm 78 is given.