Patent ID: 7889344

Claim:
A device for measuring intensity of a transmitted light, the device comprising: a first measuring unit that measures a first intensity of a light transmitted through a medium on a conveying path in its thickness direction and outputs a first measured value; a second measuring unit that is arranged adjacent to the first measuring unit, measures a second intensity of the light transmitted through the medium in the thickness direction, and outputs a second measured value; and an operating unit that obtains a true measured value from the first measured value and the second measured value, wherein the first measuring unit includes a first light-emitting unit that is arranged on a first side of the conveying path and emits a first light, and a first light-receiving unit that is arranged on a second side of the conveying path and receives the first light, the second measuring unit includes a second light-emitting unit that is arranged on the second side of the conveying path and emits a second light, and a second light-receiving unit that is arranged on the first side of the conveying path and receives the second light.