Device for measuring concentration of substance in blood, and method for measuring concentration of substance in blood
The concentration of substance in blood is measured non-invasively, with high accuracy and with simple configuration. Laser light generated by a light source is locally irradiated on the body epithelium of a subject, and the resulting diffused reflected light is detected by a light detector. The laser light has a wavelength of 9.26 μm. The laser light is generated by converting and amplifying pulsed excitation light from an excitation light source to a long wavelength. A plate-shaped window that is transparent to mid-infrared light is brought in close contact with the body epithelium. The glucose concentration in interstitial fluid can be calculated using normalized light intensity calculated from a signal ratio of signals from a monitoring light detector and light detector.
1. A device for measuring a concentration of substance in blood that measures the concentration of the substance that is included in the blood of a body, comprising:
a laser oscillator that oscillates a first laser light having a wavelength that is within the range 2.5 μm to 12 μm, and that is absorbed by the substance;
a light-guiding unit that guides the first laser light to the body, and guides first diffused reflected light that is generated by the first laser light from the body; and
a light-detection unit that detects a light intensity of the first diffused reflected light,
the light-guiding unit comprising: an incident-side optical waveguide that is configured to guide the first laser light to the body; and an exit-side optical waveguide that guides the first diffused reflected light to the light-detection unit,
on a cross section of the light-guiding unit, the incident-side optical waveguide and the exit-side optical waveguide being provided to form a substantially V shape.
2. The device for measuring the concentration of substance in blood according to claim 1 , wherein
the light-guiding unit guides the first laser light to the body at an incident angle of 35° to 85°.
3. The device for measuring the concentration of substance in blood according to claim 1 , wherein
the laser oscillator
is an optical parametric oscillator that uses excitation light having a wavelength that is different than the first laser light and that is emitted from an excitation light source, and that oscillates the first laser light by a first non-linear optical crystal.
4. The device for measuring the concentration of substance in blood according to claim 3 , wherein
the excitation-light source is a passive Q-switched Nd:YAG laser or passive Q-switched Yb:YAG laser.
5. The device for measuring the concentration of substance in blood according to claim 4 , wherein
the excitation-light source oscillates a pulsed excitation light with a repetition frequency of 1 Hz or greater.
6. The device for measuring the concentration of substance in blood according to claim 1 , wherein
the laser oscillator is a carbon dioxide gas laser oscillator.
7. The device for measuring the concentration of substance in blood according to claim 6 , wherein
the laser oscillator oscillates a second laser light having a wavelength within the range 2.5 to 12 μm and that is different than that of the first laser light, and that has a characteristic of being absorbed by the substance less than the first laser light; and
in the light-guiding unit
the incident-side optical waveguide is configured to guide the second laser light to the body, and the exit-side optical waveguide guides second diffused reflected light that is generated by the second laser light to the light-detection unit.
8. The device for measuring the concentration of substance in blood according to claim 7 , wherein
the laser oscillator oscillates the first laser light and the second laser light in a pulsed shape with a repetition frequency of 1 Hz or greater.
9. The device for measuring the concentration of substance in blood according to claim 1 , wherein
the substance is glucose; and
the wavelength of the first laser light is within the range 7.0 μm to 11 μm.
10. A device for measuring a concentration of substance in blood that measures the concentration of the substance that is included in the blood of a body, comprising:
a laser oscillator that oscillates a first laser light having a wavelength that is within the range 2.5 μm to 12 μm, and that is absorbed by the substance;
a light-guiding unit that guides the first laser light to the body, and guides first diffused reflected light that is generated by the first laser light from the body; and
a light-detection unit that detects a light intensity of the first diffused reflected light, wherein
the light-guiding unit comprises:
an incident-side optical waveguide that guides the first laser light to the body; and
an exit-side optical waveguide that guides the first diffused reflected light to the light-detection unit;
the laser oscillator is an optical parametric oscillator that uses excitation light having a wavelength that is different than the first laser light and that is emitted from an excitation light source, and that oscillates the first laser light by a first non-linear optical crystal;
the laser oscillator oscillates a second laser light having a wavelength that is within the range 2.5 to 12 μm and that is different than that of the first laser light, and that has a characteristic of being absorbed by the substance less than the first laser light; and
in the light-guiding unit
the incident-side optical waveguide is configured to guide the second laser light to the body, and the exit-side optical waveguide guides second diffused reflected light that is generated by the second laser light to the light-detection unit.
11. The device for measuring the concentration of substance in blood according to claim 10 , wherein
the optical parametric oscillator comprises a second non-linear optical crystal that generates the second laser light using the excitation light.
12. The device for measuring the concentration of substance in blood according to claim 11 , wherein
in the optical parametric oscillator, the first non-linear optical crystal and the second non-linear optical crystal are arranged in series on an optical path.
13. The device for measuring the concentration of substance in blood according to claim 10 , further comprising
a window that is configured for insertion between the light-guiding unit and the body, and that is made using a material that allows the second laser light to pass through, and has a shape so that when inserted between the light-guiding unit and the body and brought in contact with the body, a space is formed between the window and the body through which the first laser light and the second laser light pass.