Split means in order to split into the block which the parallel slit detection device, the photoreceptor drum survey instrument which uses that and the liquid crystal panel survey instrument which uses that, parallel slit method of detection and

摘要

PROBLEM TO BE SOLVED: To provide a stripe detector which can compute the characteristic quantity of fringe including a direction of fringe. SOLUTION: This fringe detector is provided with a square block dividing part 21 to dividing an optical fringe picture of a photographed object to be tested into blocks comprising a plurality of assembled picture elements, a DCT processing part 22 to convert through discrete cosine an information within the blocks divided by the square block dividing part 21, a fringe candidate block extraction part 24 to extract a fringe candidate block every conversion coefficient on the basis of the processing result by the DCT processing part 22, and a directional filter processing part 25 to apply a filter for processing in consideration of directionally to the fringe candidate block extracted every conversion coefficient by the fringe candidate block extraction part 24.