Abstract: In a plastic identifying apparatus (1), a reference light (L1) and a detecting light (L2), each having a predetermined wavelength, are irradiated to an object to be identified (4), and the transmitted lights of the reference light (L1) and detecting light (L2) are received. A detecting value expressing the quantity of light received of the detecting light (L2) is divided by a reference value expressing the quantity of light received of the reference light (L1), to obtain a computed value, based on which performed is identification of plastic forming the object to be identified 4. The wavelength of the reference light (L1) is in a wavelength band (hereat, 1550 nm) in which the light absorptances of all the types of plastics are of the lowest level, and the wavelength of the detecting light (L2) is in a wavelength region (hereat, in the range of 1700 to 1760 run) in which the absorption wavelength bands of many plastics except for PET, such as HDPE, are present.

Abstract: A semiconductor light-emitting device which emits first light of a wavelength absorbed by a substance containing an OH group is sent toward a detection object. A semiconductor light-emitting device emits second visible light toward the detection object. A photoreceptor receives light from the detection object and acquires first and second received light-quantities derived from the respective ones of the first and second light. A processing system corrects the first photoreceiving quantity on the basis of the second photoreceiving quantity. The processing system determines the color of the detection object by the second photoreceiving quantity, and corrects the first photoreceiving quantity on the basis of this determination result. Further, it compares the corrected first photoreceiving quantity with a prescribed threshold value, detects whether or not water, which is the subject containing the OH group, is contained in the detection object, and outputs the same as an output signal.

Abstract: A semiconductor light-emitting device which emits first light of a wavelength absorbed by a substance containing an OH group is sent toward a detection object. A semiconductor light-emitting device emits second visible light toward the detection object. A photoreceptor receives light from the detection object and acquires first and second received light-quantities derived from the respective ones of the first and second light. A processing system corrects the first photoreceiving quantity on the basis of the second photoreceiving quantity. The processing system determines the color of the detection object by the second photoreceiving quantity, and corrects the first photoreceiving quantity on the basis of this determination result. Further, it compares the corrected first photoreceiving quantity with a prescribed threshold value, detects whether or not water, which is the subject containing the OH group, is contained in the detection object, and outputs the same as an output signal.