corresponding to the two wavelengths a third light measuring member measures the intensity of the light radiated by the target with respect to those two wavelengths to produce third signals an emissivity is assumed for the target based on the predetermined wavelengths and a temperature is calculated on the basis of the minimum value of the difference between the assumed radiation intensity calculated according to the assumed emissivity of the target and the measured radiation intensity in accordance with the third signals application_number US 78275091 A description one embodiment of the present invention will now be described in conjunction with the drawings fig1 is a construction diagram of a pyrometer of one embodiment of the present invention in the present embodiment light having three different wavelengths u03bb 1 u03bb 2 u03bb 3 will be measured an intermittent light emitting part 101 constituting a body 100 of the pyrometer comprises a light source which produces reference light including light having three different wavelengths u03bb 1 u03bb 2 u03bb 3 and a mechanism which intermits the reference light from the light source and emits intermittent light to an optical fiber 150 the intermittent reference light is directed to a measuring head part 200 through the optical fiber 150 and reflected by mirrors m 1 m 2 the reflected light is focused through the central portion of a lens le and projected toward a target tg the measuring head part 200 receives light radiated by the target tg itself and the reference light reflected by the target tg simultaneously through an identical angle of view and transmits.