US 6,192,261 B1 · Photosensor with multiple light sources

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.

Claims19

Dependent claims

The method of determining parameters of a highly scattering medium, which comprises:

passing at least two groups of modulated beams of light, each group being of a single wavelength, through differing distances of said medium, said beams of light being modulated at a first frequency, each group of light beams comprising light of a wavelength which is different from the wavelength of the other group;
detecting said beams of light which transverse said medium using at least one light sensor, modulated at a second frequency that is different from said first frequency but phase-coherent with said modulated light;
deriving at a third frequency resultant signals from said light beams detected at said second frequency, said third frequency being the difference between said first frequency and said second frequency;
determining data comprising at least two of phase shift, DC and AC components of said light;
an determining a parameter of said medium from said data, said method being free of a step of comparing said beams of light which traverse said medium with beams of said light as emitted prior to transverse said medium.

2 more elements

The method of sample analysis which comprises:

sequentially illuminating and shutting off a plurality of light sources which are spaced at different distances from at least one light sensor while modulating the intensity of light from said light sources at a first frequency, while also passing said modulated light through a highly scattering sample for testing and then to said at least one sensor;
providing a signal coherent with said modulated light at a second frequency to said at least one light sensor;
modulating the gain of, or multiplying the output of, said at least one light sensor by said coherent signal, said second frequency being different from said first frequency;
and
driving resultant signals from the at least one sensor while sequentially receiving said modulated light from said plurality of light sources, said resultant signals being at a frequency of the difference between the first and second frequencies;
and determining at least two of phase shift, DC and AC components of said modulated light as sensed by the at least one sensor, compared with the modulated light as originally emitted by the light sources, said method being free of a step of directly comparing beams of light which transverse said highly scattering sample with beams of light as emitted prior to traversing said highly scattering sample.

3 more elements

Dependencies are inferred from the claim text.

Photosensor with multiple light sources

Life of this patent

Photosensor with multiple light sources

Life of this patent

Abstract

Claims19