US 5,398,681 AGranted

Pocket-type instrument for non-invasive measurement of blood glucose concentration

AssigneeSunshine Medical Instruments, Inc.

InventorVladimir Kupershmidt

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Abstract

A pocket-type apparatus for non-invasive measurement of blood glucose concentration based on producing a polarized-modulated laser beam via an optical phase shifter (32), measuring a phase difference introduced, e.g., by a finger (F) or a ear lobule (E) of a subject, measuring phase difference between a reference signal (SR) and a measurement signal (SM), and processing the obtained data which are then presented as blood glucose concentration. The optical phase shifter (32) comprises a pair of fiber-optic arms (40 and 42). The laser beam is fed to one of the fiber-optic arms (4), then both arms are guided through an input optical coupler (44) which splits the laser beam into a first component, which further propagates through the first optic-fiber arm (40), and a second component, which propagates through second optic-fiber arm (42). An optical phase shifter (48) which is attached to the first fiber-optic arm (40) modulates the first component of the laser beam. Both arms are then guided through an output optical coupler (46) which coherently mixes the light-propagating modes of the fiber-optic arms so that the output of each arm has a complementary coherent mixture of the beam first and second components with an orthogonal direction of polarization. An output of one of the fiber-optic arms is used as a reference optical signal and an output of the other fiber-optic arm is used as a measuring optical signal.

A method for determining non-invasively the concentration of glucose in a blood-carrying body part of a patient comprising the steps of:

(a) splitting a laser beam into two polarized components and phase modulating one of the components with a modulation frequency above a range of mechanical vibrations and a phase, thereby providing a modulated component and an unmodulated component;
(b) combining the modulated and unmodulated components and forming therefrom a reference optical beam and a measurement optical beam, each of which is a polarized-modulated laser beam;
(c) passing the reference optical beam through a polarizer, sensing the polarized reference optical beam with a photodetector, and producing an electrical reference signal corresponding to the phase of the polarized-modulated optical beam;
(d) passing the measurement optical beam through a blood carrying body part having glucose to be measured and a thickness to provide a passed measurement optical beam having a phase and
(i) splitting the passed measurement optical beam into a polarized component and a depolarized component;
(ii) converting the depolarized component into a depolarized component electric signal;
(iii) converting the polarized component into a polarized component electric signal;
(iv) subtracting the depolarized component electric signal from the polarized component electric signal to provide a first subtracted signal;
(v) low-pass filtering the depolarized component electric signal to provide a low-pass filtered signal;
and
(vi) dividing the first subtracted signal by the lowpass filtered signal, thereby providing an electrical measurement signal corresponding to the phase of the passed measurement optical beam;
(e) determining a phase difference between the electrical reference and measurement signals;
and
(f) determining the concentration of the glucose in the blood carrying body part illuminated by the measurement optical beam based on the determined phase difference.

11 more elements

Facts

Application

08/007,568Filed 22 Jan 1993 · continuation in part

Priority

10 Dec 1992

Granted

21 Mar 1995

Term ends

Not estimatedThe source records don’t support an estimate.

Classification4 codes

A61B 5/14558
Using optical sensors, e.g. spectral photometrical oximeters: by polarisation
G01N 21/21
Systems in which incident light is modified in accordance with the properties of the material investigated: polarisation-affecting properties
A61B
Medical diagnosis and surgery
G01N
Investigating or analysing materials by determining their chemical or physical properties

Abstract

Claims27