Process for reducing thermally induced discoloration of melt-processible fluoropolymer resin produced by polymerizing fluoromonomer in an aqueous medium to form aqueous fluoropolymer dispersion and isolating said fluoropolymer from said aqueous medium to obtain said fluoropolymer resin. A first conveying surface transports articles longitudinally from the receiving portion to the discharge portion. A plurality of optical path deflection units deflect the optical paths of the optical beams passed through the first imaging optical system, respectively.