Abstract: An infrared spectrometer includes an infrared source system that is stabilized to provide a substantially constant output light intensity. The infrared source system includes a source element adapted to receive electrical power and to emit light at an intensity related to the electrical power received by the source element. A light detector is mounted in position to receive light emitted from the source element and to provide an output signal related to the intensity of the light received by the detector. A feedback control loop receives the signal from the detector and provides electrical power to the source element to maintain the intensity of the light output from the source element at a selected level as detected by the detector.

Abstract: A mirror alignment and damping device (10) maintains orthogonality between the fixed mirror and the moving mirror in an interferometric spectrometer. The device (10) includes electromagnetic motion imparting units (32, 34, 36, and 38) which have electromagnetic coils (40) and threadedly adjustable pole pieces (44). The electromagnetic motion imparting units (32, 24, 26, and 38) are preferably arranged along perpendicular axes along a base (12) in order to enable independent orthogonal tilting of the mirror (26). Each voice coil consists of a wound wire coil (40) immersed in an annular magnetic field created by permanent magnets (42) which are mounted on a mirror support (44).

Abstract: The velocity of a moving mirror in a Fourier-transform infrared spectrometer is controlled by a circuit which utilizes a preset counter to generate pulses with a preset duration which are initiated at the zero-crossings of the signal from a detector of a laser light beam passed through the interferometer. This pulse signal is averaged and summed with a bias voltage and integrated and amplified to produce a drive current which is supplied to a drive coil which drives the moving mirror. When the mirror is moving too slowly, such that the preset duration pulses become a smaller fraction of the total time between zero crossings, the integrator provides an increased driving current and hence an increase in the speed of the mirror. If the mirror is moving too rapdily, the preset duration of the counter pulses will become a larger fraction of the time between zero crossings with a resultant reduction in the driving current and hence the velocity of the moving mirror.

Abstract: The position of the moving mirror (20) in a Fourier-transform infrared spectrometer is monitored with a circuit which has an incremental counter formed of a plurality of cascaded up/down counters (82, 84, and 86) that count the pulses received by a laser detector (42) to yield a relative position count. A microprocessor (100) maintains an absolute position count by reading the counters (82, 84, and 86) and updating its absolute position count at regular intervals. A portion of the circuit is dedicated to discriminating the direction of the moving mirror (20) by gating circuitry connected to the digitized output of the laser detectors (42, 44).