Patent GB-778289-A (GB)
Title: Improvements in or relating to apparatus for automatic counting
Inventor: NUTTALL THOMAS CAYTON
IPC: G06M11/04
Filed: 1954-05-28
Abstract: 778,289. Counting objects photo-electrically. CINEMA-TELEVISION, Ltd. May 27, 1955 [May 28, 1954], No. 15849/54. Class 40 (3). In a method of counting objects having re-entrant outlines, the field 4 (Fig. 1) in which the objects are dispersed is scanned downwards in a pattern of closely-spaced lines and the signal derived during the scanning of each line is compared with that derived during the scanning of the preceding line, using a modified form of the apparatus described in Specification 778,288 capable of distinguishing between certain classes of events which arise during the comparison when the objects have re-entrant outlines, so that the number of commencements such as C (or terminations such as D) of the objects as well as the number of convergences such as E (or divergences such as F) of the objects may be counted and the difference between said numbers C and E (or D and F), which gives the number of objects in the field, found. As shown in Fig. 3, signals from a television scanner 11 pass through a masking amplifier 14, controlled by device 15 to give the signal produced when the scanning spot moves outside the boundary of the field 12 a certain value, to an amplitude discriminator 16 giving an output having a first value (hereafter called black) corresponding to those portions of the input signal derived when an object is scanned and a second value (hereafter called white) for all other input signals. The output from 16 is applied to a delay device 17 which stores the signal for a period equal'to the line repetition time of scanner 11 and then reproduces it at a mixer 28 to which the undelayed output from 16 is also applied. The delayed output from 17 is also applied to a pulseformer 18, while the undelayed output from 16 is also fed to a pulse-former 19, each pulse-former being adapted to produce pulses of a duration T 1  and corresponding in time to the scanning of the two edges of each object encountered in a scanning line. The output from 18 is applied to devices 21, 22 of which the former passes only signals corresponding to a transition from black to white whereas the latter only passes signals corresponding to a transition from white to black. The undelayed signal from 19 is also applied to devices 20 and 23 of which the former passes only signals corresponding to a black-towhite transition whereas the latter passes white to black transition signals only. The signals from 20, 21, 22 and 23 are then applied to gate circuits 24, 25, 26 and 27, each of which is connected to a counter 31, 32, 33 and 34. Also applied to each gate circuit is a control signal developed by a bi-stable trigger circuit 30 after a delay T 2  (greater than pulse duration T 1  introduced by device 29, from the delayed and undelayed signals fed to the mixer circuit 28. This circuit 30 provides a control signal to open gates 24 and 25 unless its condition is changed by both signals applied to mixer 28 becoming black in which case gates 24, 25 close and gates 26, 27 open. By this means, device 31 counts the number of commencements of objects in the field, device 32 counts the number of terminations, device 33 counts the number of convergences and device 34 counts the number of divergences. A computer may be used to find the difference in the number of counts recorded by devices 31 and 33 or 32 and 34, the difference in each case being equal to the number of objects in the field.