GB1375036A - - Google Patents

Abstract

1375036 Measuring dimensions photoelectrically VICKERS Ltd 13 Nov 1972 [11 Aug1971] 37811/71 Heading G1A The size of an object is determined by viewing it with a TV camera and monitor system arranged to display two laterally spaced images of the object, the distance between which can be adjusted. In a first embodiment, Fig.1, a microscope 3 with its eye-piece replaced by a TV camera 4 is focused on the object 1, and the resulting video signal Fig.1a is applied directly to one input of a summing amplifier 7 and also via a calibrated variable delay circuit 8 to the other input of the amplifier 7. The resulting signal Fig.1b is displayed on an oscilloscope or TV monitor 10 in the form of two superimposed images the displacement between which is proportional to the delay. This enables the size of the object to be determined e.g. by adjusting the delay until the images just touch one another, the width of the object then being proportional to the delay time. In modifications, a variable gain control (20) is inserted between the summing amplifier and the display unit to provide contrast adjustment Fig.3 (not shown), a colour display unit is used the delayed image being red and the undelayed image being blue, Fig.4 (not shown), and the delayed channel may comprise two parallel variable delay circuits the outputs of which are gated alternately at line frequency so that on the display the image appears to vibrate, Fig.5 (not shown). In a second embodiment, Fig.2 (not shown), the TV camera (4) produces a composite video signal from which the sync pulses are separated and applied to line and frame time base generators (12, 13). The frame scan is applied directly to the display unit 10 and is also squared (17) and triggers a bi-stable divider (18) which produces an output of earth and a positive potential on alternate frames. A proportion of this output is tapped off by a calibrated potentiometer (19) and is added to the line scan signal to provide a lateral shift between alternate frames. This results in the display of two laterally spaced images, the position of one of which can be varied by the potentiometer. In a modification the system utilizes an interlaced scan and the circuit is arranged so that alternate pairs of fields (i.e. alternate frames) are laterally separated by the shift circuit.