To provide an optical surface defect detection method and an optical surface defect detector for reliably detecting even minute defects with high S/N ratio.
The method and apparatus for detecting surface have a process for setting a strip of inspection region on the surface of a magnetic tape 12, irradiating an irradiation region including the strip of inspection region with beams of light La, Lb from an inspection light irradiator, forming strip of long light source image regions 18A, 18B in the direction of the width of a tape adjacent to both the outside of the strip of inspection region, further inclining the light axis of a camera 22 of a CCD line camera with an inclination angle of β (0<β≤10°) for setting to a first virtual plane 16 including a center line in the width direction of the light source image region while orthogonally crossing the surface of the magnetic tape, allowing the irradiation light axis of the beams of light La, Lb to pass the mirror image position of the CCD line camera, setting an inclination angle α between a set straight line passing the center in the width direction of the strip of inspection region from a light projection opening and a camera symmetrical light axis 23 of a camera light axis to 0<α<25°, and outputting a defect detection signal in a judging apparatus 24 when a reception signal by the CCD line camera becomes at least a constant level.
Satoshi Takaya
Tsuyoshi Makino
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