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Ball point writing quality analysis

  • US 5,467,408 A
  • Filed: 04/22/1994
  • Issued: 11/14/1995
  • Est. Priority Date: 04/22/1994
  • Status: Expired due to Fees
First Claim
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1. A method of measuring ball point pen writing quality including the steps of:

  • preparing ink writing samples from a plurality of ball point pens having acceptable writing quality;

    providing a computer imaging system;

    transforming each ink writing sample and background into a histogram formed of a plurality of pixels by employing the computer imaging system to assign each pixel a gray value from zero which is pure black to 256 which is pure white and to sum the pixels of every gray value to produce a histogram having the values of zero and 256 along the abscissa and the number of pixels of each gray value along the ordinate, each of said histograms comprising a pair of peaks, the ink peak disposed toward the 0 value indicating the maximum pixel value of the ink and the second peak spaced from the ink peak toward the 256 value indicating the maximum pixel value of the background on which the ink sample is formed;

    establishing a plurality of ranges of values derived from the histogram obtained from the acceptable writing sample;

    preparing an ink writing sample from a ball point pen of unknown writing quality;

    employing said computer imaging system to transform said ink writing sample from said ball point pen of unknown writing quality into a histogram formed of a plurality of pixels, each pixel being assigned a gray value from zero which is pure black to 256 which is pure white and to sum the pixels of every gray value to produce a histogram having values of zero and 256 along the abscissa and the number of pixels of each gray value along the ordinate, each of said histograms comprising a pair of peaks, the ink peak disposed toward the 0 value indicating the maximum pixel value of the ink and the second peak spaced from the ink peak toward the 255 value indicating the maximum pixel value of the background on which the ink sample is formed;

    determining the slope of the ink peak toward the zero value side of each histogram by forming a line running from a point about halfway up the ink peak to the point of intersection with the abscissa, and calculating that point along the abscissa where the slope line intersects the abscissa;

    determining the number of pixels from that point to the zero point of each histogram anddividing this number by the total number of pixels in each histogram to determine the fraction of image area covered with blobs of ink material in each histogram; and

    comparing the values derived from the histogram of the ball point pen of unknown writing quality with the range of values established from the acceptable writing samples to determine the acceptability of the ball point pen of unknown writing quality.

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