Abstract: A probe for a spectrometer has a slot for receiving a sample, an illuminating fiber optic bundle directing light to the sample in the slot, and first and second collecting fiber optic bundles transmitting light from the sample to the spectrometer, wherein the first collection fiber optic bundle is positioned to optimize the collection of transmitted light without scattering through the sample, and the second collection fiber optic bundle is positioned to optimize the collection of light diffusely reflected from the sample. In one embodiment, the first collection bundle is arranged in an annulus around the illuminating bundle, and the second collection bundle is arranged in an annulus around the first collection bundle. In a second embodiment, the second collection bundle is arranged in an annulus around the illuminating bundle, and the first collection bundle terminates in an interface with the sample located across the slot from the illuminating bundle and the second collection bundle.

Abstract: In a spectrophotometer, a light source is provided in the form of a multiplicity of light emitting diodes which transmit light through an entrance slit to irradiate an oscillating grating. The light is dispersed by the grating toward an exit slit which transmits a narrow bandwidth of light to irradiate a sample. As the grating oscillates, the wavelength transmitted through the exit slit is scanned through a selected spectrum. The diodes in the array each emit light in a different wavelength band so that the diodes as a group emit light throughout the selected spectrum. As the grating oscillates, the diodes are energized and extinguished in sequence so that no more than two diodes will be energized at any given instant of time and the energized diode will be emitting light at the wavelength dispersed by the grating to the exit slit.

Abstract: In a fiber optic probe for an infrared analysis instrument, a window block made of sapphire is provided having an inner face in the shape of a truncated cone. A fiber optic cable has its distal end adjacent to the inner face of the window block and the optic fibers in the distal end are segregated into transmitting fibers adjacent to said conical section of the inner face of the window block and receiving fibers abutting the central circular portion formed by the truncated cone shape of the inner face. A cylindrical separator separates the receiving and transmitting fibers at the distal end of the fiber optic cable.

Abstract: In a system for measuring moisture content of powder, such as powdered milk while the powder is being dried, the powder is contained in a fluidized bed and a fiber optic probe is inserted through the wall of the container of said bed to be immersed in the fluidized bed. The fluidized bed continuously scrubs the outer surface of the probe window and prevents it from being coated with the powder. Near infrared light is transmitted through a cable optic fiber and said probe to irradiate the powder in said fluidized bed and is reflected back from the powder into said probe and transmitted by said fiber optic cable to a spectroscopic analyzing instrument. The fiber optic probe includes a sapphire rod having a back surface abutting the end of the fiber optic cable and an angled front surface. The front of the probe is closed by a quartz window spaced from the angled front surface of the sapphire rod and held in position by an inwardly directed flange on the outer tubular casing of the fiber optic probe.

Abstract: In a system for measuring moisture content of powder, such as powdered milk while the powder is being dried, the powder is contained in a fluidized bed and a fiber optic probe is inserted through the wall of the container of said bed to be immersed in the fluidized bed. The fluidized bed continuously scrubs the outer surface of the probe window and prevents it from being coated with the powder. Near infrared light is transmitted through a cable optic fiber and said probe to irradiate the powder in said fluidized bed and is reflected back from the powder into said probe and transmitted by said fiber optic cable to a spectroscopic analyzing instrument. The fiber optic probe includes a sapphire rod having a back surface abutting the end of the fiber optic cable and an angled front surface. The front of the probe is closed by a quartz window spaced from the angled front surface of the sapphire rod and held in position by an inwardly directed flange on the outer tubular casing of the fiber optic probe.

Abstract: In a spectrophotometer having an oscillating grating, an automatic calibration system is provided to ensure that the instrument constants are recomputed before each measurement of an unknown sample. In the system, whenever a reference scan is carried out, a second scan through an absorbance standard is carried out automatically and the data obtained is used to correct the instrument coefficients relating the angular position of the grating to the wavelength. The corrected coefficients are then stored to be used in the measurement of the unknown sample immediately thereafter. For near infrared spectrum measurements, the absorbance standard is a polystyrene plate. For visual measurements, the absorbance standard is a didymium plate. The didymium plate is mounted on the polystyrene plates eclipse a portion of the polystyrene plate.

Abstract: In a method for measuring protein content of whole grain kernels with a near infrared spectrophotometer, reflectance measurements are made at wavelengths shorter than 1600 nanometers. The wavelengths are selected to correspond with absorbance bands of the constituents of the sample. The measurements are encoded into absorbance data and are normalized by subtracting the absorbance value at a first wavelength and then dividing the resulting data by the value at a second wavelength. In accordance with one embodiment, the normalized data is substituted in a formula having coefficients determined by regression from samples having known percentages of protein in the sample to yield the percentage of protein in the unknown sample. In accordance with a second embodiment, the second differential of the absorbance data is determined and the resulting differential values are inserted in the formula having coefficients obtained from the known samples to yield the percentage or protein in the unknown sample.

Abstract: In a spectrophotometer having an oscillating grating, an entrance slit and an exit slit and a light source to irradiate said grating through said entrance slit, the grating and the light source are mounted on a heat sink plate and a fan is provided to blow air over both sides of said heat sink plate. A temperature sensing transducer is mounted in the heat sink plate to sense the temperature of the heat sink plate and the output of the temperature sensor is amplified by an amplifier to energize the electric motor of the fan to control the speed of the fan in accordance with the temperature sensed by the temperature sensor to thereby maintain the temperature of the heat sink plate at a constant value upon the system reaching equilibrium. In this manner, the wavelength drift of the system is reduced to a very low value.

Abstract: An improved near infrared spectrophotometer is disclosed which reduces wave shift errors arising from hot spots in a light source. A ground quartz plate uniformly diffuses radiation from the light source to evenly illuminate the entrance slit for a diffraction grating. Radiation emerges from the entrance slit with a uniform angular intensity distribution and is dispersed into a spectrum by a reflecting diffraction grating towards an exit slit. A narrow wavelength band of radiation passes through the exit slit to illuminate a sample. Because the entrance slit is uniformly illuminated, without regard to variations in radiation intensity due to hot spots in the source, wave shift errors in the reflectivity measurements for the sample are reduced.

Abstract: In a spectrophotometric instrument, a system is provided to correct for distortion caused by rapid scanning of the spectrum. In the instrument, photodetectors detect light energy which is scanned through a spectrum at a rapid rate. An amplifier amplifies the output signal generated by the photodetectors. The output signal of the amplifier is sampled at increments and the samples are converted to digital values. A first derivative is determined from the digital values by subtracting from each value the value from the preceding increment. The first derivative values are multiplied times a constant selected to correct for the distortion and the resulting product values are added to the amplitude digital values to provide a set of corrected values representing the intensity detected by the photodetectors.

Abstract: An optical grating is oscillated at a high rate to scan a narrow wavelength band of light through the spectrum dispersed by the grating. The grating is connected integrally with the rotor of a motor, which is energized to oscillate its rotor between selected limits. The direction of rotation of the motor is controlled by an H drive circuit connected to a coil of the motor. The speed of the motor is controlled by a pulse train applied to the motor coil through the H drive. The pulse train has a duty cycle varying inversely with the motor speed. The duty cycle of the pulse train is controlled by a counter which is connected to count high frequency pulses and which is reset each time the grating rotates through an angular increment. The limits of the oscillation of the grating and the rate of rotation of the grating between the limits are selectively variable.