Abstract: Wavelength related interference artifacts may appear superimposed on the output data curve of a scanning spectrophotometer utilizing a photodiode array as photometric detector. These may be suppressed by interposing a transparent optical element in the optical beam adjacent to its incidence on the array. Such an element should have no optical power along an axis parallel to the wavelength axis of the array and should provide varying phase displacement of the rays of the beam transverse to the wavelength axis. Several forms such an optical element may take are disclosed.

Abstract: An improvement in the operation of a system where the driving means is a stepper motor comprises provision of a special software routine implemented by a microprocessor controlling the delivery of a counted series of pulses to drive the stepper motor. The improved routine removes excitation from the stepper motor when not receiving a series of stepping pulses thus eliminating the heat dissipation of such a motor when not in motion. Loss of position is avoided by utilizing the inherent detenting action of the stepper motor's permanent magnet field. Provision is also made for proper damping to prevent error due to overshoot. Where several stepper motors are used in a system the reduction of heat dissipation permits a significant simplification of the system cooling requirements. A single power supply may be shared among the motors thus further simplifying the system.