GB1328124A - Counting apparatus - Google Patents

Abstract

1328124 Counting apparatus BAUSCH & LOMB Inc 23 June 1970 [23 June 1969] 13329/73 Divided out of 1328121 Heading G4D The subject matter of this Specification is identical to that of the main Specification but the claims relate to the particle counting arrangements. A counter is incremented once for each particle at the last intercept of the scanning beam with that particle. The binary signal derived by the threshold circuit 53 from the output of the television camera as described in Specification 1,328,123 is applied to a processor 5801 which effectively diminishes the width of each image to avoid counting errors which would otherwise occur when particles were close together. The altered signal is then fed through a circuit 5804 which ensures that only particles within a frame 5845, 5846, 5847, 5849 and those intersecting two of its boundaries 5847, 5849 are counted; by superimposing a frame 5842 particles 5843 intersecting the other boundaries are all counted as one and this one count is erozed since it occurs during the frame sync. period. The modified binary signal is then applied to the counting circuit 5808-5816. A latching circuit comprising gates 5806, 5807 is set by the leading edge of the first intercept pulse corresponding to each particle and reset by its trailing edge so that a pulse exactly corresponding to the intercept pulse is passed by the latching circuit to a delay line 5811 of approximately one line scan period. In subsequent scans the latching circuit is only reset at the end of an intercept pulse if the pulse from the delay line 5811 has also ended. This ensures that holes or indentations in the particle are "filled in" and the limbs of the particle are not separately counted (Fig. 23). In the scan line following the last intercept with the particle the latching circuit will not be set so that the pulse emerging from the delay line 5811 passing through a delay 5813 will be allowed through a gate 5815, opened by the output of the latching circuit, to set a monostable 5816 whose output pulses are counted to indicate the total number of particles. The output of the monostable is also fed back to the monitor to insert a marker 5854 on the display against each counted particle. A further circuit permits the counting of only particles greater than a preset size (Fig. 26, not shown). The binary signal from 53 is fed to an adjustable timer (6703) which produces an output only when an intercept greater than its set period appeats. This output is fed via gate 5803 into the counting circuit to start a count operation. A gate 5802 is normally closed when a connection 5820 is made, thus blocking the output of processor 5801. Once a counting operation is commenced the delay line 5811 issues pulses to open the gate 5802 allowing the binary signal through for counting as above. Since delay 5811 is slightly less than a line period gate 5802 will be opened slightly earlier on each succeeding line until the whole of the intercept pulses are allowed through. This ensures that any particles having a narrow waist portion are counted once only. The result of the count is displayed on the monitor screen as described in the main Specification.