GB1150080A - Apparatus for measuring a dimension of a body - Google Patents

Abstract

1,150,080. Photo-electric dimension measurement. EMHART ZURICH S.A. Aug.1, 1966 [July 30, 1965], No. 34495/66. Heading G1A. [Also in Division G4] The dimension of an object is measured by directing two parallel beams of radiation one to either end of the dimension and simultaneously photo-electrically scanning the parts of the beams not cut-off by the object to determine their width: both beams being scanned in the same direction, namely from the cut-off region to the uncutoff region or vice versa, which compensates for movement of the object in the direction of the dimension i.e. perpendicular to the beams. In one arrangement shown in Fig. 1 optical fibre light guides 18a, 18b present the uncut-off part 15a, 15b of two light beams 14a, 14b to the respective one of two photo-cells 32 positioned diametrically beneath an interposed rotating disc 22 having diametrically arranged pairs of slits Fig.2 (not shown). Simultaneous passage of a slit over each photo-cell generates a pulse from each photo-cell whose time width is indicative of the width of the uncut-off regions 15a, 15b, from which the diameter of the object 10, which may be a moving cable, can be evaluated and displayed at 38 or passed to a reject evaluation circuit 40. Any divergence of the beams is compensated by projecting them in opposing directions. Instead of a rotating disc a pair of slits may move rectilinearly, or be stationary and a moving image of beams 15a, 15b projected on to them. Mirrors or prisms may replace the optical fibres and electromagnetic radiation other than light and particle radiation may be used; the use of a laser is mentioned. By chopping the beams, intensity modulating the radiation source or introducing a grid the photocells generate a series of pulses instead of one of variable width for each passage of the slit: the number of such pulses per slit passage indicates the width of the uncut-off region 15a, 15b.