Method of and apparatus for measuring concentration

• US 20040036854A1
• Filed: 05/30/2003
• Published: 02/26/2004
• Est. Priority Date: 06/17/2002
• Status: Active Grant

• Current Assignee: Citizen Watch Co Limited (Citizen Electronics Company Limited)
• Original Assignee: Citizen Watch Co Limited (Citizen Electronics Company Limited)
• Inventors: Matsumoto, Kenji, Yano, Takakazu, Fukuda, Tadahiro
• Granted Patent: US 7,248,905 B2
• Time in Patent Office: Days
• US Class Current: 356/39
• CPC Class Codes: A61B 5/14558 by polarisation
• CPC Class Codes: A61B 5/6826 Finger
• CPC Class Codes: A61B 5/6838 Clamps or clips
• CPC Class Codes: G01N 21/21 Polarisation-affecting properties G01N21/19 takes precedence

Abstract

An optical rotation angle of linearly polarized light is modulated to obtain modulated light. The modulated light is passed through an inspection object containing an optically active substance. The optically active substance rotates an optical rotation angle of the modulated light. An intensity of light coming out of the inspection object is measured. Variation in the optical rotation angle of the modulated light is calculated based on the measured intensity and the angle to which the linearly polarized light is modulated. A concentration of the optically active substance in the pulsing component of the inspection object is calculated based on the variation in the optical rotation angle. Thus, concentration of glucose in the blood can be calculated without harming the patient.

Claims

1. A concentration measuring apparatus comprising:

a linearly polarized light supplier that supplies linearly polarized light;

an optical rotation angle modulator that modulates an optical rotation angle of the linearly polarized light to obtain modulated light;

a light intensity detector that detects an intensity of light coming out of an inspection object when the modulated light is passed through the inspection object, wherein an optically active substance in the inspection object optically rotates the modulated light when the modulated light passes through the inspection object;

a variation calculator that calculates a variation in the optical rotation angle of the light coming out of the inspection object based on an angle to which the optical rotation angle modulator has modulated the linearly polarized light and the intensity of the light detected by the light intensity detector, wherein the optical rotation angle of the light coming out of the inspection object varies in response to a pulsation of a pulsing component of the inspection object; and

a concentration calculator that calculates a concentration of the optically active substance based on the variation in the optical rotation angle.

2. The concentration measuring apparatus according to claim 1, wherein the concentration calculator calculates the concentration of the optically active substance based on a preset optical rotation coefficient of the optically active substance.

3. The concentration measuring apparatus according to claim 1, wherein the variation calculator comprises:

a sampler that samples a first optical rotation angle and a second optical rotation angle from among plural optical rotation angles modulated by the optical rotation angle modulator, wherein the first optical rotation angle corresponding to an intensity detected by the light intensity detector at which an amplitude of the pulsing component is maximum, and the second optical rotation angle corresponding to an intensity detected by the light intensity detector at which an amplitude of the pulsing component is minimum; and

a difference calculator that calculates a difference between the first optical rotation angle and the second optical rotation angle as the variation in the optical rotation angle.

4. The concentration measuring apparatus according to claim 1, wherein the variation calculator comprises:

a sampler that samples a first optical rotation angle and a second optical rotation angle from among a plurality of optical rotation angles modulated by the optical rotation angle modulator within a pulsing period for the pulsing component to pulse, wherein the first optical rotation angle corresponding to an intensity detected by the light intensity detector at which an amplitude of the pulsing component is maximum, and the second optical rotation angle corresponding to an intensity detected by the light intensity detector at which an amplitude of the pulsing component is minimum; and

a difference calculator that calculates a difference between the first optical rotation angle and the second optical rotation angle as the variation in the optical rotation angle.

5. The concentration measuring apparatus according to claim 1, wherein the optical rotation angle modulator is a liquid crystal cell.

6. The concentration measuring apparatus according to claim 1, wherein the optical rotation angle modulator is a Faraday cell.

7. The concentration measuring apparatus according to claim 1, wherein the optical rotation angle modulator is a Pockels cell.

8. The concentration measuring apparatus according to claim 1, wherein the optical rotation angle modulator comprises a combination of a homogeneous liquid crystal cell and a λ

/4 wavelength polarizer.

9. The concentration measuring apparatus according to claim 1, wherein

the optical rotation angle modulator comprises a combination of a homogeneous liquid crystal cell and a first λ

/4 wavelength polarizer, and a second λ

/4 wavelength polarizer,

the combination is configured to modulate the linearly polarized light and emit the optical rotation angle modulated linearly polarized light to the inspection object, and

the second λ

/4 wavelength polarizer has an optical axis perpendicular to an optical axis of the first λ

/4 wavelength polarizer.

10. The concentration measuring apparatus according to claim 1, wherein the linearly polarized light supplier comprises:

a light source that projects light;

a light polarizer that polarizes the light to obtain linearly polarized light; and

a beam diameter adjusting lens disposed between the light source and the light polarizer, and configured to adjust a beam diameter of the light to a predetermined beam diameter.

11. The concentration measuring apparatus according to claim 1, further comprising a collecting lens that collects the light coming out of the inspection object on the light intensity detector.

12. The concentration measuring apparatus according to claim 1, wherein the optically active substance is glucose in the blood.

13. The concentration measuring apparatus according to claim 1, wherein the optically active substance is plasma protein in the blood.

14. The concentration measuring apparatus according to claim 1, wherein the optically active substance is cholesterol in the blood.

15. A concentration measuring method comprising:

supplying linearly polarized light;

modulating an optical rotation angle of the linearly polarized light to obtain modulated light;

passing the modulated light through an inspection object containing an optically active substance;

detecting an intensity of light coming out of an inspection object, wherein the optically active substance in the inspection object optically rotates the modulated light when the modulated light passes through the inspection object;

calculating a variation in the optical rotation angle of the light coming out of the inspection object based on the optical rotation angle to which the linearly polarized light was modulated and the intensity of the light detected, wherein the optical rotation angle of the light coming out of the inspection object varies in response to a pulsation of a pulsing component of the inspection object; and

calculating a concentration of the optically active substance based on the variation in the optical rotation angle.

16. The concentration measuring method according to claim 15, wherein the concentration of the optically active substance based on a preset optical rotation coefficient of the optically active substance.

17. The concentration measuring method according to claim 15, wherein the calculating a variation comprises:

sampling a first optical rotation angle and a second optical rotation angle among a plurality of optical rotation angles modulated by the optical rotation angle modulator, wherein the first optical rotation angle corresponding to an intensity detected at the detecting an intensity at which an amplitude of the pulsing component is maximum, and the second optical rotation angle corresponding to an intensity detected at the detecting an intensity at which an amplitude of the pulsing component is minimum; and

calculating a difference between the first optical rotation angle and the second optical rotation angle as the variation in the optical rotation angle.

18. The concentration measuring apparatus according to claim 15, wherein the calculating a variation comprises:

sampling a first optical rotation angle and a second optical rotation angle among a plurality of optical rotation angles modulated by the optical rotation angle modulator within a pulsing period for the pulsing component to pulse, wherein the first optical rotation angle corresponding to an intensity detected at the detecting an intensity at which an amplitude of the pulsing component is maximum, and the second optical rotation angle corresponding to an intensity detected at the detecting an intensity at which an amplitude of the pulsing component is minimum; and

calculating a difference between the first optical rotation angle and the second optical rotation angle as the variation in the optical rotation angle.