Abstract: A system and method is provided for improved fluorescence decay time measurement. A digital heterodyning technique is disclosed in which a photon detector is sampled at a rate slightly faster than a digitally pulsed excitation signal. A resulting cross correlation frequency is low enough to be read by inexpensive electronics such as by a field programmable gate array. Phase information in the signal provides correlation with corresponding photon detections.

Abstract: A system and method is provided for improved fluorescence decay time measurement. A digital heterodyning technique is disclosed in which a photon detector is sampled at a rate slightly faster than a digitally pulsed excitation signal. A resulting cross correlation frequency is low enough to be read by inexpensive electronics such as by a field programmable gate array. Phase information in the signal provides correlation with corresponding photon detections.

Abstract: A fluorescence spectrometer comprises a laser and at least one beam splitter positioned to receive a light beam from the laser and to divide it into several first light beam portions. Dichroic mirrors are positioned to separately receive the first light beam portions and to reflect the beam portions at an angle to the first light beam portions. Transparent chambers are provided for holding the samples. Objective lens systems are respectively positioned in the path of the reflected beam portions to respectively focus each reflected beam portion to a point within one of the separate transparent chambers. Lenses are positioned to receive fluorescence from a sample for testing within the transparent chambers and to respectively focus the fluorescence at pin holes in opaque partitions. The lenses are positioned to receive the fluorescence, which passes back through the objective lens system and the dichroic mirror.

Abstract: A fluorescence spectrometer comprises a laser and at least one beam splitter positioned to receive a light beam from the laser and to divide it into several first light beam portions. Dichroic mirrors are positioned to separately receive the first light beam portions and to reflect the beam portions at an angle to the first light beam portions. Transparent chambers are provided for holding the samples. Objective lens systems are respectively positioned in the path of the reflected beam portions to respectively focus each reflected beam portion to a point within one of the separate transparent chambers. Lenses are positioned to receive fluorescence from a sample for testing within the transparent chambers and to respectively focus the fluorescence at pin holes in opaque partitions. The lenses are positioned to receive the fluorescence, which passes back through the objective lens system and the dichroic mirror.

Abstract: The quantitative determination of various materials in highly scattering media such as living tissue may be determined in an external, photometric manner by the use of a plurality of light sources positioned at differing distances from a sensor. The light from said sources is amplitude modulated, and, in accordance with conventional frequency domain fluorometry or phosphorimetry techniques, the gain of the sensor is modulated at a frequency different from the frequency of the light modulation. Data may be acquired from each of the light sources at differing distances at a frequency which is the difference between the two frequencies described above. From these sets of data from each individual light source, curves may be constructed, and the slopes used to quantitatively determine the amount of certain materials present, for example glucose, oxyhemoglobin and deoxyhemoglobin in living tissue.

Abstract: A method and apparatus for determining parameters of a medium, preferably a highly scattering medium such as living tissue. At least two spaced light sources provide light through the tissue or other medium to at least two spaced detectors, with the spacing between the light sources and the detectors being constrained to certain dimensions. The combined data received by such detectors can provide data that is substantially independent of the intensity of the light sources, the sensitivity of the detectors, the coupling efficiency of light from the light sources into the medium, and the coupling efficiency of light from the medium to the detectors. The light from the two sources is of substantially identical wavelength.

Abstract: The quantitative determination of various materials in highly scattering media such as living tissue may be determined in an external, photometric manner by the use of a plurality of light sources positioned at differing distances from a sensor. The light from said sources is amplitude modulated, and, in accordance with conventional frequency domain fluorometry or phosphorimetry techniques, the gain of the sensor is modulated at a frequency different from the frequency of the light modulation. Data may be acquired from each of the light sources at differing distances at a frequency which is the difference between the two frequencies described above. From these sets of data from each individual light source, curves may be constructed, and the slopes used to quantitatively determine the amount of certain materials present, for example glucose, oxyhemoglobin and deoxyhemoglobin in living tissue.

Abstract: The quantitative determination of various materials in highly scattering media such as living tissue may be determined in an external, photometric manner by the use of a plurality of light sources positioned at differing distances from a sensor. The light from said sources is amplitude modulated, and, in accordance with conventional frequency domain fluorometry or phosphorimetry techniques, the gain of the sensor is modulated at a frequency different from the frequency of the light modulation. Data may be acquired from each of the light sources at differing distances at a frequency which is the difference between the two frequencies described above. From these sets of data from each individual light source, curves may be constructed, and the slopes used to quantitatively determine the amount of certain materials present, for example oxyhemoglobin and deoxyhemoglobin in living tissue.

Abstract: An apparatus for cross-correlation frequency domain fluorometry-phosphorimetry comprises a source of electromatic radiation and means for amplitude modulating the radiation at the first frequency. The amplitude modulated radiation is directed at a sample, while an optical array detector measures the resulting luminescence of the sample. A signal is provided coherent with the amplitude modulated electromagnetic radiation signals, at a second frequency which is different from the first frequency. The apparatus has the capability for shutting off and turning on the coherent signal at the second frequency in a cycle which is at a third frequency that is different from the difference between the first and second frequencies. This produces a resultant signal at a frequency derived from the difference and the third frequency. The resultant signal, when turned on, modulates the gain of the detecting means or multiplies its output, depending upon the nature of the detecting means.