Position detecting method and position detecting device

A position detecting device for detecting a winding position of a reinforced fiber impregnated with resin when a plurality of hoop layers is formed in a cylindrical portion of a liner by winding the reinforced fiber around the cylindrical portion in hoop winding with the winding position of the reinforced fiber reciprocating in an axial direction of the liner, the position detecting device comprising:

• a lighting assembly configured to illuminate a hoop layer with oblique light from a direction inclined from a central axis of the liner;
• an imaging portion configured to take a captured image of the reinforced fiber just after the reinforced fiber is wound around the hoop layer illuminated with oblique light by the lighting assembly, the imaging portion having an optical axis set at the same angle as an optical axis of the lighting assembly around the central axis of the liner;
• and
• a detecting portion configured to binarize the captured image taken by the imaging portion into high intensity pixels and low intensity pixels and to detect the winding position of the reinforced fiber based on the number of high intensity pixels or the number of low intensity pixels in each pixel column arranged in the axial direction of the liner in the binarized captured image.