Patent ID: 7349075

Claim:
A detecting machine for scanning both sides of a sheet-like object fed in a scanning direction and optically detecting compositions of both sides of the object, the detecting machine comprising: a first-side light emitting device and a first-side light detecting device disposed close to each other on a first side of the object, wherein the first-side light emitting device includes a plurality of light emitting elements emitting first light beams in respective different wavelength bands, the first light beams are wider along a direction perpendicular to the scanning direction than along a direction parallel to the scanning direction, and the first-side light detecting device has a light detecting area that is wider along the direction perpendicular to the scanning direction than along the direction parallel to the scanning direction; a second-side light emitting device and a second-side light detecting device disposed close to each other on a second side of the object, wherein the second-side light emitting device includes a plurality of light emitting elements emitting second light beams in respective different wavelength bands, the second light beams are wider along the direction perpendicular to the scanning direction than along the direction parallel to the scanning direction, and the second-side light detecting device has a light detecting area that is wider along the direction perpendicular to the scanning direction than along the direction parallel to the scanning direction; and an emission controller for controlling the first-side light emitting device and the second-side light emitting device so that respective light emitting elements of the first-side light emitting device and respective light emitting elements of the second-side light emitting device emit light at respective different emission times, wherein the first-side light emitting device is disposed at a position opposite the second-side light detecting device, with the object between the first-side light emitting device and the second-side light detecting device, the first-side light detecting device is disposed at a position opposite the second-side light emitting device with the object between the first-side light detecting device and the second-side light emitting device, and in composite detection the first-side light detecting device detects first-side reflected light emitted from the first-side light emitting device and reflected from the first side of the object, and the second-side light detecting device detects transmitted light emitted from the first-side light emitting device and transmitted by the object and second-side reflected light emitted from the second-side light emitting device and reflected from the second side of the object, to detect the compositions of both sides of the object.