Patent GB-1358315-A (GB)
Title: Visual display device
IPC: G06T13/00
Filed: 1971-06-11
Abstract: 1358315 Cathode-ray tube displays O L E NILSSON 11 June 1971 [15 June 1970] 27560/71 Heading H4T The Specification describes apparatus for controlling the production on a display device of sequences of graphic images, in which successive images exhibit successive changes so as to create the impression of "moving pictures. As shown, input data are supplied, e.g. from a computer via AND gate 2 (conditioned by a pulse from a reset monostable 1) to a distributer 3 which delivers the data to memories 4, 5, 6, 7, memory 4 storing data specifying the number of pictures in a sequence, memory 5 storing data specifying the number of picture elements to be changed in position between successive pictures, memory 6 storing the position co-ordinates of the picture elements in the first picture and memory 7 storing the desired changes in the position co-ordinates. At the commencement of each sequence of pictures all devices are reset by monostable 1, the data indicated above is stored in the memories 4 . . . 7 and the numbers in memories 4 and 5 are transferred to counter units 11 and 10 respectively which include comparators for comparing the setting of the counter unit with the numbers derived from memories 6 and 7, counter unit 11 inhibiting the transfer of data out of memory 7 when its own number setting is zero. Otherwise, the changes in the position co-ordinates values from memory 7 are added to the actual co-ordinate positions stored in memory 6 in an adder 8 and the corresponding sums stored in memory 6. As each addition is effected adder 8 conditions gate 9 which then feeds the co-ordinate values in memory 6 to the output of the apparatus and also signals counter 10 to prevent transmission of data from memory 6 whenever the count therein is zero or not less than the value stored in memory 5. In operation, assuming that the picture sequence comprises three pictures and that the number of picture elements whose positions are to be changed is two, the value "3" is stored in memory 4, the value "2" is stored in memory 5, memory 6 stores the X and Y co-ordinates of the two elements for the first picture and memory 7 stores the increments of the co-ordinates between successive pictures. Since the count in counter unit 11 is zero at the commencement of a sequence the transfer of data from memory 7 to adder 8 is inhibited and adder 8 receives only the co-ordinate data related to the first of the elements to be changed and supplies this data unchanged to the output of the apparatus via gate 9 and additionally, supplies it to memory 6 where it replaces prior co-ordinate values. Also, gate 9 signals the counter unit 10 to count up one step and the latter then signals memories 6 and 7 to supply new data to adder 8. Since memory 7 is still inhibited by the zero count in counter unit 11 no summation occurs in adder 8 which functions to open gate 9 for the direct supply of the co-ordinate data related to the second of the elements to be changed to the output of the apparatus. This causes counter unit 10 to count-up one step so that its count now is "2" which corresponds to the value stored in memory 5 and counter unit 10 now resets to zero and signals counter unit 11 to count-up one step and therefore causes the data in memory 7 to be transferred to adder 8. This data, the position change data, is then summed with the data from memory 6 related to the first element and supplied to memory 6 to replace the prior co-ordinate data and additionally memory 8 opens gate 9 to supply the co-ordinates related to the first element of the second picture to the output. The operation continues in this manner until the number in counter unit 11 becomes equal to that in memory 4 when counter unit 11 signals the input data source (e.g. the computer) which causes all units except the memories to be reset and supplies new input data relating to the next following picture sequence on receipt of which the prior data is automatically erased except data which do not change between subsequent picture sequences. To facilitate a change in the direction of the displacement of an element an additional memory 12 stores data related to the element and numerical information specifying between which pictures within a sequence the change is to occur and an additional comparator unit 13 compares the numerical information with the numbers in the counter units 10 and 11. When correspondence is detected counter unit 13 signals the data input source which then supplies new displacement (change) data for the particular element considered. Memory 12 and counter unit 13 may alternatively be employed to cause a change of a parameter other than position.