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Internal diameter measuring method for transparent tube

  • US 10,060,727 B2
  • Filed: 11/30/2016
  • Issued: 08/28/2018
  • Est. Priority Date: 12/15/2015
  • Status: Active Grant
First Claim
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1. An internal diameter measurement method for an internal diameter of a transparent tube using a parallel laser light beam, the method comprising:

  • emitting, using a light projector, a first laser light beam and a second laser light beam, the first laser light beam being parallel to the second laser light beam;

    receiving, using a photoreceiver, the first laser light beam and the second laser light beam, the first laser light beam and the second laser beam passing through the transparent tube interposed between the light projector and the photoreceiver;

    obtaining, from the photoreceiver, a first detection signal indicating an amount of received light corresponding to a width direction position of the first laser light beam;

    obtaining, from the photoreceiver, a second detection signal indicating an amount of received light corresponding to a width direction position of the second laser light beam;

    detecting a first peak point in the first detection signal formed by the first laser light beam reflected by an inner circumferential surface of the transparent tube and incident to the photoreceiver, the first peak point having a slope on each side of the first peak point;

    detecting a second peak point in the second detection signal formed by the second laser light beam reflected by the inner circumferential surface of the transparent tube and incident to the photoreceiver, the second peak point having a slope on each side of the second peak point;

    detecting a first set of width direction positions of two intersections where the slopes of first peak point cross a predetermined threshold value;

    detecting a second set of width direction positions of two intersections where the slopes of second peak point cross the predetermined threshold value;

    averaging values of the two intersections for the first peak point for calculating an averaged first peak point;

    averaging values of the two intersections for the second peak point for calculating an averaged second peak point;

    calculating, from a distance between the averaged first peak point and the averaged second peak point, a third set of width direction positions of the first laser light beam and the second laser light beam; and

    performing a geometric calculation from the third set of width direction positions of the first laser light beam and the second laser light beam for measuring the internal diameter of the transparent tube.

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