Self referencing photosensor
First Claim
1. The method of determining parameters of a medium which comprises the steps of:
- passing a first portion of light from a first light source through said medium to a first detector, and passing a second portion of light from said first light source through said medium to a second detector;
passing a third portion of light from a second light source through said medium to the second detector, the distance between said first light source and said first detector and the second light source and said second detector being substantially equal, and passing a fourth portion of light from said second light source through said medium to said first detector, the distance between said first light source and the second detector and the second light source and said first detector being substantially equal; and
combining data received by said detectors in a manner that is substantially independent of;
intensity of the light sources, sensitivity of the detectors, coupling efficiency of light from the light sources into said medium, and coupling efficiency of light from said medium to said detectors; and
determining a parameter of said medium from said data, said light portions being of substantially identical wavelength.
1 Assignment
0 Petitions
Accused Products
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.
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Citations
22 Claims
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1. The method of determining parameters of a medium which comprises the steps of:
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passing a first portion of light from a first light source through said medium to a first detector, and passing a second portion of light from said first light source through said medium to a second detector; passing a third portion of light from a second light source through said medium to the second detector, the distance between said first light source and said first detector and the second light source and said second detector being substantially equal, and passing a fourth portion of light from said second light source through said medium to said first detector, the distance between said first light source and the second detector and the second light source and said first detector being substantially equal; and combining data received by said detectors in a manner that is substantially independent of;
intensity of the light sources, sensitivity of the detectors, coupling efficiency of light from the light sources into said medium, and coupling efficiency of light from said medium to said detectors; and
determining a parameter of said medium from said data, said light portions being of substantially identical wavelength. - View Dependent Claims (2, 3, 4, 5, 6)
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7. The method of determining parameters of a highly scattering medium, which comprises the steps of sequentially:
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passing a first modulated portion of light from a first light source through said highly scattering medium to a first detector, and passing a second modulated portion of light from said first light source through said highly scattering medium to a second detector; passing a third modulated portion of light from a second light source through said highly scattering medium to said second detector, the distance between said first light source and said first detector and the second light source and said second detector being substantially equal, and passing a fourth modulated portion of light from said second light source through said highly scattering medium to said first detector, the distance between said first light source and the second detector and the second light source and said first detector being substantially equal; said modulated portions of light being of substantially the same wavelength and each being modulated at the same frequency, said first and second light detectors being modulated at a second frequency that is different from said first frequency; and determining data points comprising a combination of data from said first and second detectors and determining a parameter of said medium from said data points. - View Dependent Claims (8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
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19. A self-referencing photosensor which comprises a probe having a face for contact with a medium for testing with a photosensing technique;
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a controller electrically connected to said probe for receiving signals from said probe; and a computer for receiving and processing signals from said controller responsive to the signals from said probe, and for converting said signals into data; said probe having spaced first and second light sources positioned to emit light of substantially identical wavelength through apertures of said face, said probe also having spaced first and second detectors positioned to receive light from said medium passing through other apertures of said face; said first light source having a spacing from said first detector which is equal to the spacing between said second light source and said second detector, said first light source having a spacing from said second detector which is equal to the spacing between said second light source and said first detector. - View Dependent Claims (20, 21, 22)
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Specification