GB1070945A - Improvements in or relating to devices for measurement of filament thickness - Google Patents

Abstract

1,070,945. Photo-electric measuring apparatus. ROLLS ROYCE Ltd. June 30, 1964, No. 27011/64. Heading G1A. Apparatus for measuring the size of a filament, thread or rope comprises a support for the test object, means for illuminating it, a rotating reflector and photo-electric detector scanning the shadow pattern caused by the object and timing means determining the time between a point on the first dark-going slope of the cell output and a point on a subsequent light-going slope. The arrangement shown comprises a support 2 between the ends of which is mounted a drawn fused silica filament 1. The filament holder may be raised or lowered by means of knob 8 to investigate different parts of its length. It is also possible to move the filament holder and its guide and support means by rotation of handwheels 18 and 19 to position the portion of the filament under test at the focus of the inspection system. A light projection arrangement comprising a source 10 and optical system 11 illuminates the filament and light not obstructed or otherwise directed out of the system by the test object passes through projection lens 12 to mirror 15 mounted for rotation on a heavy flywheel 16 and driven by synchronous motor 17. The single mirror 15 may be replaced by a multi-faced reflector assembly to increase the scan frequency. The scanned shadow of the filament is focused on a narrow slit 13 in front of photo-electric detector 14 which may be a photo-multiplier. The timing circuit Fig. 3 (not shown) includes a manual switch settable to choose a point on the next light-going slope of the cell output after the commencement of timing to terminate timing if the test object is opaque and to select a point on the second following light-going slope if the test object is transparent. Timing may be effected by using a cathode-ray tube display incorporating timing markers or by counting clock pulses and displaying the count made in the preceding scanning cycle. The apparatus may be modified to view a continuously travelling test object.