| 摘要 |
Inspecting paired sheets of transparent material for determining their fit or conformity to one another. A highly collimated light beam, such as a laser beam, is directed through a pair of transparent sheets supported in closely spaced or nested relationship. The major surfaces of each sheet are known to be substantially parallel. As the primary beam passes through the sheets, beams are reflected from each of the four surfaces. The reflected beams are re-reflected from the next surface encountered to pass beyond the pair of sheets. Beams reflected from the parallel front and rear surfaces of each sheet exit the sheets parallel to and closely spaced from the primary transmitted beam. If the adjacent interior or second and third surfaces of the pair of sheets are not parallel at the point of inspection, as where the two sheets do not properly nest or conform, the beam reflected from the third surface and re-reflected from the second surface is deflected relative to the primary beam. The beams are intercepted upon emerging from the sheets. The displacement of the reflected beam from the transmitted beam indicates the angular relationship between the sheets at the point of inspection.
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