Method of and apparatus for inspecting honeycomb-shaped object having plural through holes
First Claim
1. A method of inspecting a honeycomb-shaped object having a plurality of through holes defined therein by partitions, comprising the steps of:
- introducing a parallel light beam into the through holes at an angle with respect to an axis of the through holes;
generating at least one Fourier-transform image from the honeycomb-shaped object by passing light through the honeycomb-shaped object; and
determining whether there are interstices in the partitions based on the at least one Fourier-transform image, by observing whether said at least one Fourier-transform image includes a Fourier-transform image of interstices in the partitions, which includes a pattern of periodic images, said periodic images including equidistantly spaced parallel stripes.
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Abstract
A parallel light beam is introduced from a collimator lens into through holes defined in a honeycomb-shaped object, and any light emitted from the honeycomb-shaped object is read by a CCD camera through a Fourier-transform lens to produce a Fourier-transform image of the honeycomb-shaped object. The honeycomb-shaped object is tilted such that the axis of the through holes is inclined at a certain angle to the optical axis of the parallel laser beam. If the partitions contain interstices spaced at intervals and light introduced into the through holes passes through such interstices, the Fourier-transform image includes a stripe pattern induced by diffracted light from the interstices. Since the stripe pattern can easily be distinguished from a dot-matrix pattern representing light emitted from the through holes, the interstices contained in the partitions can reliably be detected.
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Citations
13 Claims
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1. A method of inspecting a honeycomb-shaped object having a plurality of through holes defined therein by partitions, comprising the steps of:
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introducing a parallel light beam into the through holes at an angle with respect to an axis of the through holes; generating at least one Fourier-transform image from the honeycomb-shaped object by passing light through the honeycomb-shaped object; and determining whether there are interstices in the partitions based on the at least one Fourier-transform image, by observing whether said at least one Fourier-transform image includes a Fourier-transform image of interstices in the partitions, which includes a pattern of periodic images, said periodic images including equidistantly spaced parallel stripes. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. An apparatus for inspecting a honeycomb-shaped object having a plurality of through holes defined therein by partitions, comprising:
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first means for introducing a parallel light beam into the through holes at an angle with respect to an axis of the through holes; second means for generating at least one Fourier-transform image from the honeycomb-shaped object based on light which has passed through the honeycomb-shaped object; and third means for determining whether there are interstices in the partitions based on the at least one Fourier-transform image, by observing whether said at least one Fourier-transform image includes a Fourier-transform image of interstices in the partitions, which includes a pattern of periodic images, said periodic images including equidistantly spaced parallel stripes. - View Dependent Claims (9, 10, 11, 12, 13)
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Specification