Abstract:
A spectrophotometer of the two-beam type employing two adjustable monochromators and employing a rotating chopper disc to provide time-sharing operation, such as split-beam operation, dual wavelength operation, or other desired modes of operation. The chopper disc motor is stabilized by a fiber optic feedback system and cooperating electronic system utilizing light beams reflected by the underside of the chopper disc and photo diodes responding to these reflections. The main optical system includes an adjustable lens element coupled to one of the monochromators to compensate for variations in refractive index of the lens element with wavelength. The electronic readout system is gated by the chopper disc stabilizing system to maintain synchronism of the readout signals with the two monochromatic excitation beams.