抄録
In double-beam spectrometer observation using optical null method, it is necessary to move the optical wedge in one direction or in the other to balance the intensities of the sample and reference beams. To facilitate this operation, a tuning fork with a small mirror is used as a chopper, and the output power of the tuning fork oscillator is used as one of the two inputs of the servomotor which drives the optical wedge. The other input of the servomotor is supplied by the amplified power of the detector, whose phase is adjusted to be either 90° ahead or behind of that of the first input depending upon which of the two beams is stronger. Using this system with a PbS photoconductive cell, near-infrared absorption spectrum of liquid chloroform is recorded.
