| 摘要 |
PROBLEM TO BE SOLVED: To provide a surface shape measuring method, and a surface shape measuring instrument capable of obtaining a highly accurate measurement result using a simple device constitution. SOLUTION: A surface roughness measuring method measures the surface roughness of a measuring object surface 11 by measuring the reflected light from the measuring object surface 11 by using a focal error detecting method and has a first process BS of branching off the reflected light from the measuring object surface 11 in two directions, a second process S2 (2PD-1, 13) for obtaining detecting light output by extracting a part corresponding to displacement of the measuring object surface from a light-receiving state of the branched-off one reflected light, a third process S3 (2PD-2, 14) of obtaining reference light output by detecting a light-receiving state of other reflected light of the branched-off as it is, and a fourth process S4 (17) of obtaining the difference between the detecting light output and the reference light output.
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