Optical measuring device and toothbrush provided with same

1. An optical measuring device detecting fluorescence of a substance to be measured, the substance adhering to a sample emitting intrinsic fluorescence, the optical measuring device comprising:

first and second light sources that respectively emit first light and second light exciting the sample, the second light having a longer wavelength and lower excitation efficiency for the substance than the first light;

an optical filter on which the fluorescence is incident, the optical filter substantially transmitting only light in a wavelength region including a peak wavelength of the fluorescence of the substance, wherein the light in the wavelength region is such that first intensity of fluorescence generated by the first light is different from second intensity generated by the second light,

a detection unit that detects light transmitted through the optical filter,

a control unit that calculates a ratio or difference between the first intensity of fluorescence detected when the sample is irradiated with the first light and second intensity of fluorescence detected when the sample is irradiated with the second light,

thereby obtaining an intensity of fluorescence without the intrinsic fluorescence, to calculate the amount of fluorescence of the substance.

2. The optical measuring device according to claim 1 , wherein the sample is irradiated alternately with the first light and the second light.

3. The optical measuring device according to claim 1 , wherein the first light has a wavelength in a range from 350 nm to 430 nm, and the second light has a wavelength in a range from 435 nm to 500 nm.

4. The optical measuring device according to claim 1 , wherein the first light and the second light have wavelengths in a range from 350 nm to 430 nm, and

a difference between the wavelengths is 5 nm or more.

5. The optical measuring device according to claim 1 , further comprising a color mixture unit that makes intensity distributions uniform in a surface irradiated with the light emitted from the first light source and the second light source.

6. The optical measuring device according to claim 1 , further comprising a second optical filter on which the first light and the second light are incident, wherein the second optical filter transmits only light in a wavelength region of the first light source and the second light source.

7. The optical measuring device according to claim 1 , wherein

the first and second light sources comprise an optical waveguide for emitting light, through which the first light and the second light are guided,

the detection unit comprises an optical waveguide for receiving light, through which the fluorescence emitted by the substance is guided, and

the optical waveguide for emitting light and the optical waveguide for receiving light are formed by a same optical waveguide.

8. The optical measuring device according to claim 1 , wherein the sample is a tooth, and the substance is protoporphyrin IX included in dental plaque.

9. The optical measuring device according to claim 8 , wherein the first intensity and the second intensity are intensities of fluorescence at a wavelength corresponding to a peak at around 635 nm in a spectrum of fluorescence of the dental plaque.

10. The optical measuring device according to claim 1 , wherein

turning on the first light source, turning on the second light source, and turning off both the first light source and the second light source are repeated,

the detection unit further detects an intensity of environmental light when both the first light source and the second light source are turned off, and

the control unit calculates the amount of the fluorescent substance, based on a difference between the first intensity and the intensity of environmental light, and a difference between the second intensity and the intensity of environmental light.

11. The optical measuring device according to claim 1 , wherein

the first light source is turned on in phase with a timing signal,

the second light source is turned on in a phase opposite to the timing signal, and

the control unit includes

a phase detector that performs phase detection using the timing signal and thereby outputs a difference between the first intensity and the second intensity, and

a control circuit that calculates the amount of fluorescence of the substance from the difference.

12. The optical measuring device according to claim 1 , wherein

the first light source is turned on in phase with a timing signal,

the second light source is turned on with delay of a predetermined phase with respect to timing of turning on the first light source, and

the control unit includes

a first phase detector that performs phase detection using the timing signal and thereby generates a first output signal according to the first intensity and the second intensity,

a second phase detector that performs phase detection using a signal obtained by delaying the timing signal and thereby generates a second output signal according to the first intensity and the second intensity, and

a control circuit that calculates the amount of the fluorescent substance to be measured and an amount of a fluorescent substance of the sample, from the first output signal and the second output signal.

13. The optical measuring device according to claim 12 , wherein

the first light source and the second light source are light-emitting diodes, and are alternately turned on in accordance with a second timing signal having a frequency twice as large as the timing signal, and

currents for driving the light-emitting diodes are decreased by a factor of a predetermined constant in intervals where the timing signal is low, as compared to the currents in intervals where the timing signal is high.

14. A toothbrush comprising the optical measuring device according to claim 1 .