Glass inspection method and apparatus

Claim 1

Apparatus for detecting a flaw in a glass bottle, comprising: means for directing a light beam at a region of said bottle; means for rotating said bottle with respect to said beam to cause said beam to scan said region of said bottle; at least two spaced apart sensors disposed to sequentially detect a fluctuation in said light beam as the light beam emerges from said region of said bottle; a difference amplifier connected to said sensors for generating a difference signal based on the sequential detection of said fluctuation in intensity of said light beam; means for inverting said difference signal; means for rectifying said difference signal and the inverted difference signal; means for combining the rectified signals; and a comparator for detecting whether the combined signal exceeds a predetermined threshold value; whereby the passage of a flaw through said beam within a predetermined time interval causes the combining means to generate a combined signal which exceeds said predetermined threshold value, said predetermined time interval being substantially equal to the time taken for the leading edge of a shadow cast by said flaw as said flaw passes through said beam to intercept one of said sensors after having intercepted the other of said sensors.

Claim 5

A method of detecting a flaw in a glass bottle, comprising: directing a light beam at said bottle; rotating said bottle with respect to said beam to cause said beam to scan a region of said bottle; sequentially detecting a fluctuation in the intensity of said light beam caused by said flaw at first and second locations as said bottle is rotating, said first and second locations being spaced apart from each other and from said bottle; generating a difference signal based on the sequential detection of said fluctuation in intensity of said light beam; inverting said difference signal; rectifying said difference signal and the inverted difference signal; combining the rectified signals and comparing the combined signal to a predetermined threshold value; generating a reject signal when the combined signal exceeds said predetermined threshold value within a predetermined interval of time substantially equal to the time required to detect said fluctuation at said second location after detecting said fluctuation at said first location.

Claim 6

A method of detecting a flaw in a glass bottle, comprising: directing a light beam at said bottle; rotating said bottle with respect to said beam to cause said beam to scan a region of said bottle; sequentially detecting a fluctuation in the intensity of said light beam caused by said flaw at first and second locations as said bottle is rotating, said first and second locations being spaced apart from each other and from said bottle; generating a difference signal based on the sequential detection of said fluctuation in intensity of said light beam; inverting said difference signal; rectifying said difference signal and the inverted difference signal; combining the rectified signals and comparing the combined signal to a predetermined threshold value; generating a reject signal when the combined signal exceeds said predetermined threshold value within a predetermined interval of time substantially equal to the time required to detect said fluctuation at said second location after detecting said fluctuation at said first location.