Patent GB-1459678-A (GB)
Title: Image information processing apparatus
IPC: G06V10/20
Filed: 1974-03-27
Abstract: 1459678 Photo-electric image analyzers HITACHI Ltd 27 March 1974 [28 March 1973 30 March 1973] 13664/74 Heading G1A [Also in Division G4] An apparatus for detecting an object in a field of view includes means for scanning the field and means to transform the electrical output image of the scanner to a form which is independent of the brightness of the field, i.e. of the degree of illumination. The transform of the image may be used in a character recognition system (see Division G4) or in a system which determines the orientation of an object or the approximate number of objects, e.g. people, articles or blood corpuscles in the field. The field may be regarded as being divided into an n x m array of cells and the scanner output as being a series of signals each representative of the brightness of one of these cells. The scanner may be a cathode ray tube. Its output passes to an assembly of shift register stores providing an output representing, in one embodiment, the brightness of the cells in a 3 x 3 window that is, in effect, swept over the field so that each cell in turn appears at the centre of the window. For each cell, e.g. f 22 , Fig. 4, the brightness of the cells above it and of the cells below it are summed, as indicated, and the difference of the sums obtained to provide a signal fy representing the change in brightness in the vertical (y) direction. Similarly Fig. 5 (not shown), a signal f x  is calculated for the change in the horizontal direction. Signals f x , fy together define a resultant, here called the brightness vector, which pertains to the cell f 22  being considered. Fractions of signals f x , f y  are passed to comparators to develop a binary signal which approximates to the argument of the vector. The set of such signals resulting from similar operations on each cell of the field is the transform of the image, and is independent of the brightness. To avoid  erroneous signals resulting from noise an argument signal is suppressed if the vector is excessively small, i.e. where there is only a small change in brightness. The transform may be used in a system which controls lifts according to the number of persons on various floors. In such a system the field is regarded as being divided into blocks, each block consisting of 20 x 20 cells for example. The argument signals of each block in turn are examined, and each signal is allotted to one of, for example, 8 sectors Figs. 14a or 14b, (not shown). The numbers of signals in respective sectors are counted to develop a characteristic signal indicative of those sectors containing more than, say, 100 signals or of that sector which contains most signals. The set of characteristic signals pertaining to the whole image is compared with a reference set which represents the background. The background may be patterned. The number of signals in disagreement is counted and the count is indicative of the approximate number of persons in the field. If the scanner views the field slantwise the signals may be weighted according to the distance of the corresponding part of the field from the scanner. The count is applied to threshold units which classify the number into one of, say, 5 degrees of congestion of the field and feed the lift controller. There is a similar arrangement for each floor serviced by the lift. The reference set of characteristic signals (background) may be constant or may be updated periodically. In the latter case, for example, the image characteristic signals may replace the reference set if there is no change in the signals over a pre-set period. In a modification of the apparatus the scanner provides colour and luminance signals. These are used to develop colour difference signals f x , f y . These may be used in a manner generally similar to that described above in order to determine the degree of congestion of the field. In this case the colour difference signals for a cell are independent of those for adjacent cells. They define a vector whose argument, the hue of the cell, is independent of brightness. The orientation of a rectangular object may also be determined. For example, in the case of the body shown in Fig. 39a the argument signals will correspond to vectors oriented at # + n#/2, (n = 0, 1, 2, 3). If the number of vectors is plotted against orientation, Fig. 39b, a peak will appear at each angle # + n#/2. By summing the number of vectors appearing at angles spaced by 90 degrees a single peak at angle # is obtained. In the presence of other non-rectangular objects the peak will be surrounded by smaller peaks which may be ignored as noise Figs. 40a, 40b, (not shown). The orientation of an obliquely viewed three-dimensional object may be obtained in a similar manner.