Basis weight measuring apparatus and method for sheet tobacco, and manufacturing system and method for sheet tobacco

A basis weight measuring apparatus for sheet tobacco, the apparatus comprising:

• a light source disposed on a transport path for the sheet tobacco, and emitting light toward the sheet tobacco passing through a measurement position defined in the transport path, the transport path including an aperture therein and allowing the sheet tobacco passing through the measurement position to be exposed to the light source, the aperture having an axis perpendicular to the transport path;
• and
• a visual sensor including:
• a camera disposed with the transport path put between said visual sensor and said light source, said visual sensor measuring a basis weight of the sheet tobacco based on an image of the sheet tobacco taken by the camera when the sheet tobacco passes through the measurement position;
• a calculation section calculating an average gray level of the image and outputting the average gray level;
• and
• a converter having a conversion map indicating a relationship between the average gray level and an actual measurement value obtained by actually measuring the basis weight of the sheet tobacco, the converter converting the average gray level into the basis weight of the sheet tobacco with reference to the conversion map,
• wherein the camera is disposed on the axis of the aperture while the light source is disposed to deviate from the aperture in a direction along the transport path or a direction across the transport path.