Patent GB-1388107-A (GB)
Title: Method of and apparatus for examination of objects
IPC: G01N15/14
Filed: 1970-11-28
Abstract: 1388107 Photo-electric measuring G K SKINNER 28 Feb 1972 [28 Nov 1970] 56633/70 Heading G1A Optical information in respect of an object being investigated is determined by an arrangement in which E.M. radiation e.g. light transmitted by, or reflected from at least three spots on the object is directed on to respective photo-cells and the spots are moved simultaneously across the surface of the object to scan adjacent parallel tracks, signals derived from areas having different optical characteristics being analyzed to determine the dimensions of said areas longitudinally of the tracks and to determine whether the areas extend into adjacent ones of said tracks. The invention may be used in the investigation of for example diseased cells in a cervicle smear, the outputs of the photo-cells being modulated for example by the different optical property of the nuclei against the cytoplasm to provide data whereby longitudinal and lateral dimensions and area of the nuclei may be determined. The image of an area 16, Fig. 2, of a smear on a slide 13 in a microscope 10 is repeatedly scanned across the ends of a line of light-guides F1-16 by a rotating multi-facetted mirror 11 and the slide is traversed on its table relative to the optical axis of the microscope to provide contiguous or overlapping scans. The arrangement includes an automatic focusing arrangement in which two auxiliary beams are focused in front of, and behind, two further respective photo-cells the illumination conditions of which are balanced when the image is focused; alternatively the focus control beams may be differentially polarized by a birefringent body. The output from at least three scanning photo-cells is applied after amplitude discrimination against a pulsed reference to a corresponding number of similar circuits in which pulses resulting from the discrimination are counted in a counter (63) Fig. 7 (not shown) correlated with data from adjacent channels, bistable (64) providing the indication that an area extends into an adjacent track and fed to counters to determine the sought after parameters. The largest count is selected to indicate maximum dimension, and the number of successive cells producing outputs is determined by addition to indicate width. The acquired information is passed successively through the logic circuits associated with the respective photo-cells but may be rejected by pulses resulting from unsuccessful auxiliary tests. The radiation may be light or infra-red, and scanning speeds are exemplified. The photo-cell assembly may include an additional cell or cells for establishing a reference signal based on the average intensity of illumination of the frame area. The auxiliary reject tests may determine whether the contents of counters in adjacent channels differ by more than a predetermined amount, whether the length is within a given range, or whether there are excessive peripheral indentations. The investigated spot areas could be spaced on the object, the spots could be aligned obliquely to the direction of scanning or could be staggered on either side of a reference line. Alternatively the focusing arrangement could have respective concave and convex lenses directing a beam portion on to photo-cells.