Measurement device and measurement method for measuring a physical quantity of a sheet

A measurement device to measure a physical quantity of a measurement target with a sheet-like shape, the measurement device comprising:

• a first integrating sphere which is separated by a gap from a first surface of the measurement target, has a first opening facing the first surface, and is not provided with a light detector to detect an intensity of light;
• a second integrating sphere which is separated by a gap from a second surface of the measurement target, where the second surface is positioned opposite to the first surface, and has a second opening facing the first opening with the measurement target sandwiched therebetween;
• a light source unit to emit light into the first integrating sphere;
• a light detecting unit to detect an intensity of light inside the second integrating sphere;
• and
• a calculating unit to calculate the physical quantity of the measurement target based on the intensity of light detected by the light detecting unit, wherein
• the first integrating sphere includes a first shielding plate adapted to shield a part of the light emitted by the light source unit,
• the second integrating sphere includes a second shielding plate adapted to reflect at least a part of the light inside the second integrating sphere to transfer the at least part of the light into the second integrating sphere, and
• a length of the second shielding plate is identical to or smaller than a length of the first shielding plate in a longitudinal direction and a width direction of the measurement target.