| 摘要 |
A method for optically measuring an elongate timber cant, regardless of whether in upright of inverted orientation, said cant having top and bottom substantially flat, mutually parallel surfaces separated by longitudinal wanes and having a generally trapezoidal cross section, and thereby locating the narrowest flat surface of the cant and the longitudinal boundaries thereof. The method is accomplished by effecting relative transverse movement between the cant and a crossed light pattern such that the longitudinal boundaries of the flat surfaces momentarily interrupt and restore a plurality of light beams forming the crossed light pattern, detecting four beam interruption and restoration events, and recording the amount of relative transverse movement between each of the four detected events. The resultant measurement data on the cant is used to space and orient a pair of edge trimming saws and to orient the cant in preparation for its advancement to the saws. Broken beam scanning is combined with intensity variation of the plurality of light beams at a frequency higher than any fluctuations occuring in the ambient light surrounding the measurement site, thereby providing cant measurement data which is substantially independent of ambient light fluctuations.
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