On-line dirt counter
AssigneePulp and Paper Research Institute of Canada
InventorsByron D. Jordan, Nam G. Nguyen
Life of this patent
Estimating the term…
Abstract
The two-dimensional medium-pass filter principle is used to acquire a sharpened image initially In practice the sharpened image is obtained from the difference of a linear array signal of a partially out-of-focus image from another linear array signal of the same image but in focus. Integrated intensity of dirt specks higher than a user selected threshold are measured and accumulated. Each integrated intensity value is converted into its corresponding speck size with the use of a predefined fined look-up table. The counter generates a dirt speck histogram and statistical data within a preselected time interval or area coverage.
Claims18
An on-line dirt counter for measuring and recording dirt speck sizes and intensities which appear on a first surface of a web of moving paper, comprising:
- a light source spaced from said first surface of said web of moving paper for directing a beam of light at said first surface of said web of moving paper, said beam of light being substantially diffusely reflected from said first surface of said web of moving paper;
- an in-focus sensor means including first focussing means and a first detector placed at an in-focus position to receive a first part of said reflected beam emitted at an angle with respect to said surface, and to provide an in-focus magnitude signal having an in-focus magnitude proportional to the magnitude of the light intensity of said first part;
- an out-of-focus sensor means including second focussing means and a second detector having a same aperture as said first detector placed at an out-of-focus position to receive a second part of said reflected beam emitted substantially at said angle with respect to said surface, and to provide an out-of-focus magnitude signal having an out-of-focus magnitude proportional to the magnitude of the light intensity of said second part;
- means for subtracting said out-of-focus magnitude from said in-focus magnitude to provide a difference magnitude;
- comparator means for comparing said difference magnitude to a threshold magnitude;
- and
- means for storing the occurrences and magnitudes of said difference magnitude on all occasions when said difference magnitude is greater than said threshold magnitude.
A method for measuring and recording dirt speck sizes and intensities which appear on a first surface of a web of moving paper, comprising:
- directing a beam of light from a light source at said first surface of said web of moving paper, said beam of light being reflected substantially diffusely from said first surface of said web of moving paper;
- focusing and receiving a first part of said reflected beam emitted at an angle with respect to said surface in an in-focus sensor means placed at an in-focus position to provide an in-focus magnitude signal having an in-focus magnitude proportional to the magnitude of the light intensity of said first part of said beam;
- focusing and receiving a second part of said reflected beam emitted substantially at said angle with respect to said surface in an out-of-focus sensor means having a same aperture as said in-focus sensor means and being placed at an out-of-focus position to provide an out-of-focus magnitude signal having an out-of-focus magnitude proportional to the magnitude of the light intensity of said second part of said beam;
- subtracting said out-of-focus magnitude from said in-focus magnitude to provide a difference magnitude;
- comparing said difference magnitude to a threshold magnitude;
- and
- storing the occurrences and magnitudes of said difference magnitudes on all occasions when said difference magnitude is greater than said threshold magnitude.
Dependencies are inferred from the claim text.