Vol.11 no.3 2019

Research paper : Development and commercialization of laser inspection system to detect surface aws of machined holes (S. OKADA et al.)−135−Synthesiology - English edition Vol.11 No.3 (2018) the phototransmitter system of laser beams. As shown in Fig. 6, the multi-segmentation planar photodetector is made by bundling about 3,000 optical bers of a diameter of 0.5 mm in a semicircular form, and these are divided into four in a radial direction, and into 12 in a circumferential direction. Then light intensity entering a total of 48 blocks is photoelectrically converted using photodiodes. This detector has rougher resolution compared to camera images but is adequate in grasping the characteristics of the reected light patterns, and also has the advantage that the measurement time per point is high speed at 1 msec or less, and the data volume can be reduced to 1/500 or less.Of the types of defects produced in steel sheet manufacturing shown in Table 1, the most frequently found scratches and abrasions are shown as examples in Fig. 7 that shows light intensity distribution by LED that was measured by a multi-segmentation planar photodetector and camera images of their reflected scattered light. It was demonstrated that the types of defects could be identied by the multi-segmentation planar photodetector. Here, linear light in the vertical direction is the diffracted light produced by roll marks, and this is detected on the entire surface of rolled steel sheets. However, since the roll direction is only in one direction in the steel sheet rolling process, the diffracted light of roll marks is produced only in a vertical direction, and this is discriminated from defects by removing the diffraction light that occurs in this direction from the inspection. Table 1. Type of awsMoving tableJackStepping motorSampleParabolic cylindrical mirrorOptical berMulti-segmentation planar photodetectorLaser beam sourceParabolic cylindrical mirrorVibrating mirrorCCD cameraPlanar mirrorPlanar mirrorPhotoreception systemPhototransmission systemRust, contamination, abrasionDistributed defectScab, sliver, scratchLinear defectRoll markPointlike defectName of awForm of awFig. 5 Laser defect inspection system for at sheetsFig. 6 Multi-segmentation planar photodetectorPSDPSDPSDPSDPSDPSDXZr1r2dPosition of PSDMeasurement principleFig. 4 Measurement system for curved mirror objects

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