SPEKTROFLUOROMETER

An energy-compensated spectrofluorometer of the time-shared double beam type employing a rotating chopper mirror disc providing a main measure channel as one of the time-shared outputs of a photomultiplier tube and a compensating reference channel generated by a reference light whose output is conveyed by a light pipe to the cathode of the photomultiplier tube, generating the other time-shared output thereof. The energy correction is derived from a thermal detector cell receiving part of the excitation beam, and the reciprocal of the thermal detector cell signal is subtracted from the dark current-corrected reference channel signal and is employed to adjust the high voltage supplied to the photomultiplier tube, thereby adjusting its gain. The measure channel includes means to compensate the measure signal for non-uniform spectral sensitivity of the photomultiplier tube, as well as for dark current. The reference channel signal is also modified to compensate for wavelength-dependent variations of quantum intensity in the excitation beam.