JP2019174361A - Light measuring device and toothbrush equipped with the same - Google Patents

Abstract

To provide a compact and simply constructed light measuring device with which it is possible to reliably detect a small amount of dental plaque, and which can be easily assembled into a toothbrush.SOLUTION: The light measuring device comprises: a first and a second light source 2, 3 for emitting light of a first wavelength and light of a second wavelength of greater length; a detection unit for detecting first and second fluorescence intensity generated when a sample (tooth) is irradiated with lights of first and second wavelengths; an emission control unit for causing the first and the second light sources 2, 3 to alternately emit light in accordance with a reference signal in a first period and only a third light source to emit light in accordance with the reference signal in a second period, out of the first and second periods that are alternately repeated, each longer than the cycle of a reference signal (timing signal 101); a phase detector 104 for performing phase detection in accordance with the reference signal, and generating a first output signal and a second output signal; and a control circuit 30 for calculating the amount of a fluorescent substance to be measured, by computation using the first and the second output signals.SELECTED DRAWING: Figure 9

Description

  The present invention relates to a light measuring device and a toothbrush provided with the same.

  When brushing teeth, it is possible to remove plaque effectively in a short time by concentrating and polishing the area while monitoring the amount of plaque adhering, so several optical plaque detection methods have been proposed in the past. Has been. A typical example is that bacteria contained in dental plaque or caries portion bacteria produce protoporphyrin IX (hereinafter referred to as PPIX) which is a fluorescent substance in the oral cavity environment. For example, Patent Documents 1 to 5 describe a fluorescence measurement method that quantifies the amount of dental plaque or the degree of caries by irradiating teeth with excitation light of a specific wavelength and detecting the fluorescence emitted by the fluorescent material. ing.

  In Patent Document 6, a liquid sample is introduced into an analytical test strip, a voltage signal is applied between both ends of the test strip, a combined current signal is measured, and in-phase and quadrature signals are continuously generated using the measured combined current signal. And a method for automatically measuring a phase shift corresponding to a liquid sample using a phase shift measurement block based on in-phase and quadrature signals. In the step of generating in-phase and quadrature signals, a combined voltage signal corresponding to the combined current signal is supplied to the phase detector, a first reference signal having a first phase is supplied to the phase detector, A second reference signal having a second phase that is 90 ° different from the first phase is supplied to the phase detector.

Japanese Examined Patent Publication No. 6-73531 Japanese translation of PCT publication No. 2002-515276 JP 2011-131057 A Japanese Patent No. 3737579 International Publication No. 2016/140199 JP 2014-235168 A

  When there is a small amount of plaque adhering to a tooth, among the fluorescence obtained when the adhering site is irradiated with excitation light, the intensity of autofluorescence of the tooth is strong and the fluorescence derived from plaque is weak. Looking at the wavelength band of fluorescence from plaque (630-680 nm), it is a state where weak fluorescence derived from dental plaque is superimposed on strong autofluorescence of teeth, and there is a system that can effectively separate and detect them. Desired. Further, there is a demand for a simple configuration that can easily incorporate the mechanism into a toothbrush.

  In order to remove the influence of indoor lighting or the like and detect fluorescence derived from weak plaque, it is desirable to use a lock-in amplifier for the control unit that calculates the amount of fluorescent substance from the fluorescence intensity. In particular, if a two-phase lock-in amplifier is used, the amount of plaque and the amount of fluorescent substance in the tooth can be obtained simultaneously, and the sensitivity change due to the distance between the tooth and the detection unit can be corrected. However, since the lock-in amplifier is expensive and requires two sets of circuits including an AD conversion circuit, it is an obstacle in terms of cost and size to realize a toothbrush size light measuring device. Therefore, it can be considered that a single-phase lock-in amplifier is equivalently used as a two-phase lock-in amplifier by time-division driving. However, simply by time-division driving, the amount of data in each phase is halved. Furthermore, since it is necessary to make the lighting duty of the light source smaller than 50%, the measurement accuracy is lowered.

  An object of the present invention is to provide a light measuring device having a small and simple configuration that can reliably detect a small amount of plaque and can be easily incorporated into a toothbrush.

  A first light source that emits light of a first wavelength, a second light source that emits light of a second wavelength that is longer than the first wavelength, and a sample that is irradiated with light of the first wavelength And a detection unit that detects the first fluorescence intensity that is generated when the sample is irradiated and the second fluorescence intensity that is generated when the sample is irradiated with light of the second wavelength. Of the longer first and second periods, the first and second light sources alternately emit light according to the reference signal in the first period, and only the second light source emits light according to the reference signal in the second period. Phase detection is performed in accordance with the control unit and the reference signal, and the first output signal corresponding to the first and second fluorescence intensities in the first period and the second output in accordance with the second fluorescence intensity in the second period A phase detector that generates two output signals and a first and second output signal. Optical measurement device is provided, characterized in that a control circuit for calculating a fluorescent substance amount to be measured by.

  In the light measurement device, the light of the first wavelength excites the fluorescent substance contained in the teeth and plaque to generate fluorescence derived from the teeth and plaque, and the light of the second wavelength It is preferable that the excitation efficiency for the fluorescent substance contained in the plaque is lower than that of the first wavelength light.

  In the above optical measurement device, the first wavelength is preferably in the range of 350 nm to 430 nm, and the second wavelength is preferably in the range of 435 nm to 500 nm.

  In the above optical measurement device, it is preferable that the first period is longer than the second period.

  The light measurement device can reliably detect a small amount of plaque and can be easily incorporated into a toothbrush.

It is a graph which shows the spectrum of the light obtained from each tooth | gear when violet light is irradiated to the tooth | gear which the clean tooth | gear and plaque adhered. It is a graph which shows the spectrum of the light obtained from each tooth | gear when blue light is irradiated to the tooth | gear with which the clean tooth | gear and plaque adhered. 1 is a configuration diagram of a fluorescence measuring device 1. FIG. 1 is a configuration diagram of a toothbrush type fluorescence measuring apparatus 400. FIG. 3 is a diagram illustrating a configuration example of a color mixing unit 4. FIG. 2 is a configuration diagram showing the inside of a toothbrush head 41. FIG. It is a block diagram which shows the circuit structure of the control part 310 of a comparative example. 3 is a timing chart showing operation timing of a control unit 310. It is a block diagram which shows the circuit structure of the control part 300 of an Example. 5 is a timing chart showing operation timing of the control unit 300. It is a timing chart which shows the modification of the operation timing of FIG. It is a figure explaining the difference of the output signal by the measurement using the fluorescence measuring devices 1 and 400, and the control parts 300 and 310. FIG.

  Hereinafter, the light measurement device and the light measurement method will be described in detail with reference to the drawings. However, it should be understood that the present invention is not limited to the drawings or the embodiments described below.

  First, the principle of the light measurement method will be described with reference to FIGS. In this light measurement method, excitation light having two different wavelengths is alternately irradiated on the same tooth, and fluorescence generated in the tooth by excitation light of each wavelength is detected in a fluorescence wavelength region derived from plaque. By using the ratio or difference of fluorescence intensity, fluorescence derived from dental plaque, which is a measurement object superimposed on the autofluorescence of teeth, is separated and detected.

  FIG. 1 is a graph showing a spectrum of light obtained from each tooth when violet light having a peak wavelength of 405 nm as a first wavelength is irradiated to a clean tooth and a tooth with plaque attached thereto. The horizontal axis of the graph indicates the wavelength λ (nm), and the vertical axis indicates the fluorescence intensity I that is the first fluorescence intensity. The thin line shows the spectrum S1 obtained from the clean tooth, and the thick line shows the spectrum S1 'obtained from the tooth to which plaque has adhered. A peak E1 in the vicinity of 405 nm is excitation light detected by the reflected or scattered 405 nm purple light on the tooth surface. Broad fluorescence having a peak P0 around 500 nm is tooth autofluorescence. Peaks P1 and P2 near 635 nm and 675 nm are fluorescence spectra obtained from the fluorescent material PPIX contained in plaque.

  In the spectrum S1 obtained from a clean tooth, plaque-derived peaks P1 and P2 are not observed, but in the spectrum S1 'obtained from a tooth to which plaque is adhered, plaque-derived fluorescence peaks P1 and P2 are observed. At the same time, the spectrum S1 'shows a constant attenuation over the entire wavelength range compared to the spectrum S1. This is attenuation caused by absorption of excitation light by the attached plaque, and shows almost constant attenuation regardless of the wavelength, depending on the amount of plaque.

In order to measure the peak P1 of plaque-derived fluorescence with higher accuracy, as shown in the following formula (1), plaque obtained by subtracting the tooth autofluorescence component t1 ′ from the spectral intensity p1 ′ at that wavelength. It is necessary to determine the amount of fluorescent substance Δp derived from it.
Δp = p1′−t1 ′ (1)

  In other words, it is necessary to obtain the auto-fluorescent component t1 'of the tooth in the state where the plaque is adhered and without generating plaque-derived fluorescence. As a result of intensive studies on such conditions, it has been found that it is only necessary to acquire a spectrum when a light source having a first wavelength, here a second wavelength longer than 405 nm, is used.

  FIG. 2 is a graph showing a spectrum of light obtained from each tooth when blue light having a peak wavelength of 465 nm as the second wavelength is irradiated to the tooth having clean teeth and plaque attached thereto. As in FIG. 1, the horizontal axis of the graph indicates the wavelength λ (nm), and the vertical axis indicates the fluorescence intensity I that is the second fluorescence intensity. The thin line shows the spectrum S2 obtained from the clean tooth, and the thick line shows the spectrum S2 'obtained from the tooth to which plaque has adhered.

When blue light with a wavelength of 465 nm is irradiated on clean teeth and teeth with plaque adhered, a broad peak P0 of the tooth autofluorescence is observed in the same manner as when violet light with a wavelength of 405 nm is irradiated. Since the excitation of PPIX becomes weak, the plaque-derived peaks P1 and P2 are not observed. Therefore, the autofluorescence component t2 ′ of the tooth when excited at the second wavelength can be substituted as the autofluorescence component t1 ′ when excited at the first wavelength. The amount Δp can be approximated by the following formula (2).
Δp ≒ p1 '-t2' (2)

In order to establish the approximation, it is necessary to adjust the intensity of the excitation light of the first wavelength and the second wavelength in advance to align the autofluorescence components t1 ′ and t2 ′. On the other hand, the intensity of the excitation light may be adjusted so that the autofluorescence components t1 and t2 measured with a clean tooth coincide with each other by utilizing the fact that the decay of autofluorescence is proportional. Alternatively, if the ratio t1 / t2 of the autofluorescence components t1 and t2 is measured in advance for a clean tooth, it can be corrected as in the following formula (3).
Δp≈p1′−t2 ′ × (t1 / t2) (3)

  According to the principle described above, the excitation light having two different wavelengths is alternately irradiated on the teeth, and the fluorescence generated in the teeth by the excitation light of each wavelength is detected in the fluorescence wavelength region derived from the plaque, and the fluorescence intensities thereof are detected. By using the ratio or difference between the first fluorescence intensity and the second fluorescence intensity, it is possible to separate and detect the fluorescence derived from dental plaque superimposed on the autofluorescence of the tooth.

  Next, a fluorescence measuring apparatus for realizing the above light measuring method will be described. FIG. 3 is a configuration diagram of the fluorescence measuring apparatus 1. The fluorescence measurement device 1 is an example of a light measurement device that uses fluorescence as inspection light. The fluorescence measurement apparatus 1 includes a light source unit 100 for exciting a fluorescent substance contained in dental plaque, a detection unit 200 for detecting the intensity of fluorescence generated on the tooth surface, and plaque from the measured fluorescence intensity. It is comprised from three blocks with the control part 300 which calculates | requires the adhesion amount of and notifies a user.

  The light source unit 100 includes a first light source 2 that emits light at a first wavelength, a second light source 3 that emits light at a second wavelength, a color mixing unit 4, an optical filter 5 for outgoing light, an optical waveguide 6 for outgoing light, and an output light source 6. It has the condensing part 7 for incident light. The color mixing unit 4, the outgoing light optical filter 5, the outgoing light optical waveguide 6, and the outgoing light condensing unit 7 irradiate the measurement target teeth with light from the first light source 2 and the second light source 3. The optical path part of is constructed.

  As the 1st light source 2 and the 2nd light source 3, small and cheap LED (light emitting diode) and a semiconductor laser can be used. The wavelength of the light generated by the first light source 2 or the second light source 3 is selected as follows. The first wavelength includes a wavelength having high excitation efficiency with respect to the fluorescent substance contained in the plaque, and the second wavelength is longer than the first wavelength and the excitation efficiency is lower than the first wavelength. Alternatively, the wavelength is set to almost zero. The first wavelength is preferably a wavelength in the range of 350 nm to 430 nm, and the second wavelength is preferably a wavelength in the range of 435 nm to 500 nm. As a specific example, the first light source 2 may be a violet LED having a peak wavelength of 405 nm, and the second light source 3 may be a blue LED having a peak wavelength of 465 nm.

  The color mixing unit 4 is a light within the light irradiation surface in order to prevent color unevenness when the light generated by the first light source 2 and the second light source 3 is irradiated to the tooth to be measured. It has a function of making the intensity distribution uniform between the light of the first wavelength and the light of the second wavelength. It is important that the light intensity distribution is the same between the first wavelength light and the second wavelength light, and it is permissible to have the light intensity distribution itself. Relatively high.

  The outgoing light optical filter 5 is a filter that allows the light of the first light source 2 and the second light source 3 to pass therethrough and cuts the fluorescence wavelength region derived from dental plaque, and cuts the wavelength of 500 nm or more. When a short pass filter is used for the outgoing light optical filter 5, the cutoff wavelength may be selected to be sufficiently longer than the second wavelength and sufficiently shorter than the fluorescence wavelength of the fluorescent substance contained in the plaque.

  The outgoing light optical waveguide 6 is for carrying the light of the first light source 2 or the second light source 3 without being attenuated to the vicinity of the tooth to be measured, and the material thereof is, for example, plastic or glass. Used. More preferably, the outer periphery of the outgoing light optical waveguide 6 is mirror-coated to prevent light leakage. Further, as the outgoing light optical waveguide 6, a hollow optical waveguide surrounded by a mirror such as a light pipe can be used.

  The outgoing light condensing unit 7 is composed of a lens for condensing and irradiating light propagating through the outgoing light optical waveguide 6 to the size of a tooth. The excitation light from the first light source 2 or the second light source 3 is applied to the teeth 10 as the first irradiation light 8 or the second irradiation light 9 from the output light condensing unit 7.

  The detection unit 200 includes a light receiving condensing unit 21, a light receiving optical waveguide 22, a light receiving optical filter 23, and a photodetector 24.

  The light receiving condensing unit 21 condenses the inspection light 20 including the fluorescence generated by the teeth. The light receiving optical waveguide 22 and the light receiving condensing unit 21 constitute an optical path portion for propagating the condensed light to the photodetector 24. When the fluorescence measuring apparatus 1 is incorporated in the toothbrush, the brush portion of the toothbrush may be used as the light receiving optical waveguide 22 and the tip of the toothbrush may be used as the light receiving condensing unit 21.

  The light receiving optical filter 23 is a filter for cutting wavelength components other than the target fluorescence. The light receiving optical filter 23 is preferably set so as to cut a wavelength region excluding a range of 620 nm to 690 nm which is a fluorescence wavelength region emitted by a fluorescent substance contained in dental plaque. Particularly on the short wavelength side, since the reflected light of the light source directly reflected by the teeth appears strongly, it is preferable that the light receiving optical filter 23 has a sharp attenuation characteristic so that these can be cut off. Since the fluorescence spectrum from dental plaque has two strong peaks at around 630 to 640 nm and around 670 to 680 nm, a band pass filter having transmittance characteristics close to the shape of these fluorescence spectra as the light receiving optical filter 23. Can be used to improve the S / N ratio.

  The control unit 300 includes a control circuit 30 and a notification unit 31.

  The control circuit 30 is constituted by a microcomputer and controls the brightness and lighting time of the first light source 2 and the second light source 3 to alternately irradiate the teeth with light of two wavelengths. In this way, by dividing the lighting time of the first light source 2 and the lighting time of the second light source 3, it is possible to distinguish and receive the fluorescence of the fluorescent material obtained by irradiating each light with the teeth. It becomes. Assuming that the fluorescence intensity obtained by turning on the first light source 2 is P1, and the fluorescence intensity obtained by turning on the second light source 3 is P2, the control circuit 30 can calculate the fluorescence intensity ratio P1 / P2, or By obtaining the difference (P1−P2), as described in the principle section, the amount of fluorescent substance contained in the plaque is obtained.

  The alerting | reporting part 31 alert | reports the calculated | required fluorescent substance amount to the user of a toothbrush. For this notification, a buzzer sound or an electronic sound using a piezoelectric element may be used. In the case of electronic sound, feedback can be provided to the user by changing the pitch and pitch of the sound and the pitch of the intermittent sound according to the amount of fluorescent material. Furthermore, a voice message by voice synthesis, music, or the like may be used. Or the alerting | reporting part 31 may perform alerting | reporting by the vibration alert | report using an eccentric motor, alerting | reporting by LED blinking or the light which changed the color tone, the language, figure, and graph by liquid crystal display. Further, the notification unit 31 may be used in combination with wireless communication, and notification information and information related to measurement may be transmitted to an external device such as a mobile phone or a personal computer to notify the user of the external device.

  The control unit 300 may record the detected fluorescence intensity for each of the two wavelengths of light, and may average them for an arbitrary number of times, thereby reducing noise. In addition, the control unit 300 sets the lighting time of the first light source 2 and the second light source 3 to a time different from the cycle of the commercial power source in order to avoid the influence of room light such as a fluorescent lamp. The influence of illumination light can be reduced.

  Moreover, the control part 300 may irradiate light emission of the 1st light source 2 or the 2nd light source 3 alternately on both sides of light extinction as needed. By subtracting the amount of fluorescent material acquired by turning off the first light source 2 or the second light source 3 from the amount of fluorescent material acquired by turning on the first light source 2 or the second light source 3, it is possible to reduce the influence of ambient light.

  4A and 4B are configuration diagrams of a toothbrush type fluorescence measuring apparatus 400. FIG.

  The toothbrush type fluorescence measurement apparatus 400 is an example of a light measurement apparatus that uses fluorescence as inspection light, and includes a toothbrush head 41, a handle part 42, and a grip part 43. The first light source 2 and the second light source 3 are mounted on a circuit board 44 provided in the grip portion 43 together with the control circuit 30 (see FIG. 3) and the notification portion 31. The light from the first light source 2 and the second light source 3 is emitted from the mixed color portion 4 and the outgoing light optical filter 5 provided in the grip portion 43, and the long tapered light output light provided in the handle portion 42. It is guided to the toothbrush head 41 via the waveguide 6a. The direction of the guided light is changed using means such as a mirror in the toothbrush head 41, and the tooth surface is irradiated as excitation light from the light irradiation unit 50 on the toothbrush head 41. The fluorescence generated in the teeth is guided to the photodetector 24 through a plurality of brushes 40 made of a material that transmits the fluorescence disposed in the light detection unit 51 of the toothbrush head 41.

  In the fluorescence measuring apparatus 400, as shown in FIG. 4B, the light irradiation unit 50 is disposed in the center of the toothbrush head, and the light detection unit 51 is provided adjacent to the light irradiation unit 50. However, the arrangement is not limited to this example. For example, a plurality of light irradiation units 50 and a plurality of light detection units 51 may be provided in the toothbrush head, or they may be alternately arranged in a straight line.

  The fluorescence detected by the photodetector 24 is converted into a photocurrent and transmitted to the circuit board 44 via the wiring 52. The amount of the fluorescent material is obtained from the photocurrent by the control circuit 30 provided in the circuit board 44, and the amount of the fluorescent material is notified to the user by the notification unit 31 with a buzzer or an electronic sound.

  A battery 45 is mounted on the grip 43 as a power source for driving the fluorescence measuring device 400. The grip portion 43 is provided with two switches 46. For example, the fluorescence measurement function can be turned on / off using one switch 46, and the notification sound can be switched or the fluorescence detection sensitivity can be adjusted using the other switch 46.

  FIG. 5A to FIG. 5C are diagrams illustrating a configuration example of the color mixing unit 4. In the toothbrush type fluorescence measuring apparatus 400, it is important that the in-plane intensity distribution of the light irradiated to the teeth from the first light source 2 or the second light source 3 does not change, which is important for determining the detection limit. Index. For this reason, it is necessary that the in-plane intensity distribution of the irradiated light has no wavelength dependence at the stage where the light reaches the outgoing light condensing unit 7 provided in the toothbrush head 41. The color mixing unit 4 has a function of eliminating the wavelength dependency of the in-plane intensity distribution of the irradiation light.

  FIG. 5A is a diagram illustrating a configuration example of a color mixing unit using a tapered light pipe. A long optical path can be obtained by arranging a light pipe as the outgoing light optical waveguide 6a from the handle portion 42 of the toothbrush type fluorescence measuring apparatus 400 to the toothbrush head 41. Since the in-plane distribution of the light from the first light source 2 or the second light source 3 is made uniform by repeating the reflection a plurality of times in the light pipe, the effect of color mixing can be easily enhanced. That is, the outgoing light optical waveguide 6a itself functions as a color mixing portion. The light 62 emitted obliquely from the first light source 2 or the second light source 3 repeats reflection a plurality of times, while the light 61 emitted substantially perpendicular to the end face of the outgoing light optical waveguide 6a has a small number of reflections. However, effective color mixing is possible because of the long optical path.

  By using the tapered light pipe shown in FIG. 5 (A) as the outgoing light optical waveguide 6a, the outgoing light optical waveguide 6a can be provided with the function of the mixed color portion without providing the mixed color portion 4 separately. It is possible to make the in-plane intensity distribution of the irradiation light close to uniform with a simple configuration. Although the light emitted extremely obliquely has a large number of reflections in the light pipe, the reflection loss cannot be ignored. However, by using bullet-type LEDs having a narrow emission angle as the first light source 2 and the second light source 3, It is possible to reduce reflection loss and at the same time increase the optical coupling efficiency.

  The light pipe may be a hollow type using a mirror or made of plastic. In the case of plastic, light leakage can be reduced by coating a metal mirror on the outer periphery. The shape of the light pipe may be a simple linear shape or a tapered shape, but by providing a regular or messy reflective surface inside the pipe, the effect of color mixing can be easily enhanced. The cross-sectional shape of the light pipe may be round, oval, rectangular, polygonal, etc., and among these various shapes, it is easy to properly use a structure suitable for the shape and design of the toothbrush.

  FIG. 5B is an explanatory diagram of a form in which the color mixing portion 4 is added to the outgoing light optical waveguide 6a shown in FIG. In the example shown in FIG. 5B, the color mixing unit 4 in which the microlens array 64 is disposed on the incident end surface is used. Thus, by converting the light from the first light source 2 or the second light source 3 into light 67 and 69 from a plurality of point light sources, the effect of color mixing is further enhanced.

  In the example shown in FIG. 5B, LED chips as the first light source 2 and the second light source 3 are mounted on a mirror-equipped substrate 63 having a 45-degree reflection mirror. With this structure, the light emitted from the first light source 2 and the second light source 3 is guided forward, so that the emission angle is narrowed. Furthermore, since the interval between the light sources can be reduced by using the LED chip, the in-plane intensity distribution of the irradiated light can be made more uniform.

  FIG. 5C is an explanatory diagram of a form in which the color mixing portion 4 having another configuration is added to the outgoing light optical waveguide 6a shown in FIG. In the example shown in FIG. 5C, the color mixing unit 4 includes a scatterer that scatters light emitted from the first light source 2 and the second light source 3. The color mixing portion 4 is a transparent resin including light scattering particles 71 and is formed by sealing the first light source 2 and the second light source 3 mounted on the mirror-equipped substrate 63. By multiplying the light from each light source by multiple light scattering particles 71, the in-plane intensity distribution of the irradiated light can be made close to uniform. Further, a microlens array 64 may be added to the emission end face of the color mixing portion 4, thereby further enhancing the color mixing effect.

  FIG. 6 is a configuration diagram showing the inside of the toothbrush head 41. The light transmitted through the outgoing light optical waveguide 6a is changed in direction by the mirror 6b in the toothbrush head 41 and irradiated as excitation light from the outgoing light condensing unit 7 toward the teeth 10 via the outgoing light optical waveguide 6c. Is done. Plaque adhering to the tooth surface and fluorescence generated from the teeth in the vicinity thereof are detected by the photodetector 24 through the brush 40 and the light receiving optical filter 23. The tip of the brush 40 functions as the light receiving condensing unit 21 by giving a curvature, and the subsequent brush 40 functions as the light receiving optical waveguide 22. Further, a light shielding body 23 a is disposed so as to surround the light receiving optical filter 23, and the light shielding body 23 a prevents ambient light and excitation light from directly entering the light receiving optical filter 23 without passing through the brush 40.

  By adhering the light receiving optical filter 23 and the end surface of the brush 40 with an optical adhesive having a refractive index close to that of the brush 40 and the light receiving optical filter 23, scattering loss can be prevented. Further, the end surface of the brush 40 and the opening 24 a of the photodetector 24 can be bonded using an optical adhesive having the function of the light receiving optical filter 23. Furthermore, a material that functions as an optical filter can be used as the material of the brush 40. In that case, the end surface of the brush 40 is arrange | positioned at the opening part 24a of the photodetector 24, and is adhere | attached with an optical adhesive agent.

  In order to detect plaque using fluorescence, as described above, it is necessary to separately obtain fluorescence from teeth and fluorescence from plaque. For example, when a tooth is excited with violet light having a peak wavelength of 405 nm, both plaque-derived fluorescence and tooth autofluorescence are generated, but when a tooth is excited with blue light having a peak wavelength of 465 nm, only the tooth autofluorescence is generated. Occurs. Therefore, in order to determine the amount of plaque, it is necessary to subtract the fluorescence intensity when the teeth are excited with blue light from the fluorescence intensity when the teeth are excited with purple light. Furthermore, the fluorescence from the plaque is weak, and the peak wavelength 635 nm of the fluorescence derived from the plaque is close to the peak wavelength 620 nm of the fluorescent lamp. Therefore, it is necessary to remove the influence of ambient light such as the fluorescent lamp. Since it is difficult to remove the light from the fluorescent lamp using only the optical filter, the control unit 300 uses a lock-in amplifier that has a high noise removal capability and can measure weak light.

  The control unit 300 drives the one-phase (one set) lock-in amplifier in a time-sharing manner, and equivalently uses it as a two-phase (two sets) lock-in amplifier, thereby measuring the fluorescence intensity of teeth and plaque. . In particular, the control unit 300 improves the measurement accuracy of the fluorescence of the teeth and plaque and the noise removal characteristics of the ambient light by changing the lighting pattern of the light source as compared with the case of simple time division driving. Hereinafter, the circuit configuration and operation of the control unit 300 of the fluorescence measurement devices 1 and 400 (example) will be described in comparison with the control unit 310 (see FIG. 7) of the comparative example that performs simple time-division driving.

  FIG. 7 is a block diagram illustrating a circuit configuration of the control unit 310 of the comparative example. FIG. 8 is a timing chart showing the operation timing of the control unit 310. FIG. 9 is a block diagram illustrating a circuit configuration of the control unit 300 according to the embodiment. FIG. 10 is a timing chart showing the operation timing of the control unit 300.

  9, in addition to the control circuit 30 and the notification unit 31 (see FIG. 3), the control unit 300 includes light source drive circuits 83 and 84, an inverter 85, a current-voltage conversion circuit 86, an oscillation circuit 100A, a thinning-out circuit. A control circuit 102A and a lock-in amplifier 103 are included. These are provided on a circuit board 44 (see FIG. 4) in the grip portion 43. The circuit configuration of the control unit 310 of the comparative example illustrated in FIG. 7 is different from that of the control unit 300 only in that the inverter 85 is replaced with a thinning control circuit 102B. 7 and 9, the first light source 2 and the second light source 3 in the light source unit 100 and the photodetector 24 in the detection unit 200 are also illustrated for convenience.

  The oscillation circuit 100 </ b> A generates a timing signal 101 (an example of a reference signal) that is a rectangular wave with a period T under the control of the control circuit 30.

  The light source driving circuit 83 drives the first light source 2, and the light source driving circuit 84 drives the second light source 3. The light source driving circuits 83 and 84 alternately drive the first light source 2 and the second light source 3 based on the timing signal 101 from the oscillation circuit 100A. In the control unit 300, only the second light source 3 among the first light source 2 and the second light source 3 is connected to the oscillation circuit 100 </ b> A via the inverter 85. And the second light source 3 lights in the opposite phase to the timing signal 101. The first light source 2 emits light in the first half of the timing signal 101 and emits light having the first wavelength (for example, 405 nm purple light). The second light source 3 emits light in the latter half of the timing signal 101 and emits light of the second wavelength (for example, 465 nm blue light).

  The light detector 24 turns on the intensity of fluorescence (first fluorescence intensity) generated from the teeth when the first light source is turned on and light of the first wavelength is irradiated on the teeth, and the second light source 3 is turned on. Then, the intensity of the fluorescence (second fluorescence intensity) generated from the tooth when the second wavelength light is irradiated on the tooth is detected. The current-voltage conversion circuit 86 converts the output signal of the photodetector 24 into a voltage signal, and generates an optical signal PD. In the following, the optical signal PD derived from plaque-derived fluorescence is referred to as “plaque fluorescence amount Pp”, and the optical signal PD derived from tooth autofluorescence is referred to as “dental fluorescence amount Pt”.

  The thinning control circuit 102A sends a signal for prohibiting the light emission of the first light source 2 to the light source driving circuit 83 in the even-numbered time domain among the plurality of time-divided time domains in accordance with the thinning signal 102 from the control circuit 30. In this way, the light emission of the first light source 2 in the time domain is stopped. Hereinafter, among the plurality of time regions, the odd-numbered time region is referred to as “first period T1”, and the even-numbered time region is referred to as “second period T2”. The first and second periods are alternately repeated with a period longer than the period T of the timing signal 101. The thinning-out control circuit 102A may stop the light emission of the first light source 2 not in the second period T2 but in the first period T1, and in either the first period T1 or the second period T2, the light emission stop period Even so, the operation of the controller 300 is essentially the same. In the control unit 300, the oscillation circuit 100A, the thinning-out control circuit 102A, and the inverter 85 function as a light emission control unit.

  The lock-in amplifier 103 includes a phase detector 104 and an A / D converter 106. The phase detector 104 detects the phase of the optical signal PD according to the timing signal 101 and obtains a difference between the optical signals PD, thereby generating an in-phase detection output 105 corresponding to the tooth fluorescence amount Pt and the plaque fluorescence amount Pp. To do. In the control unit 300, the first light source 2 and the second light source 3 are alternately turned on in the first period T1, and only the second light source 3 is turned on in the second period T2. Therefore, the phase detector 104 generates a signal (first output signal) corresponding to the first and second fluorescence intensities in the first period T1 as the in-phase detection output 105, and the second period. At T2, a signal (second output signal) corresponding to the second fluorescence intensity is generated. The A / D converter 106 converts the in-phase detection output 105 into a digital in-phase detection output 107 (IOUT1, IOUT2) and outputs it to the control circuit 30.

  The control circuit 30 controls the operation of the oscillation circuit 100A and the thinning-out control circuit 102A, and from the in-phase detection output 107 in the first and second periods, the tooth fluorescence amount Pt and the plaque, which are the amount of the fluorescent substance to be measured. The amount of fluorescence Pp is calculated.

  In the control unit 310 of the comparative example, as shown in FIG. 7, a thinning control circuit 102A is provided between the oscillation circuit 100A and the light source driving circuit 83, and a thinning control circuit 102B is provided between the oscillation circuit 100A and the light source driving circuit 84. Is provided. The thinning control circuit 102A of the control unit 310 permits light emission of the first light source 2 only in the first period T1 according to the thinning signal 102 from the control circuit 30, and light emission of the first light source 2 in the second period T2. Is output to the light source driving circuit 83. The thinning control circuit 102B permits the light emission of the second light source 3 only in the second period T2 in accordance with the thinning signal 102 and prohibits the light emission of the second light source 3 in the first period T1. Output to. In the control unit 310, both the first light source 2 and the second light source 3 emit light in the first half period of the timing signal 101 in the first period T1 or the second period T2.

  In FIG. 8, the timing signal 101 is represented by TIM, and the lighting timings of the first light source 2 and the second light source 3 are represented by VLED and BLED, respectively. PD is an optical signal output from the current-voltage conversion circuit 86. The same applies to FIGS. 10 and 11 described later. Hereinafter, for simplicity, the first light source 2 that is a purple LED and the second light source 3 that is a blue LED are also referred to as VLED and BLED, respectively.

  In FIG. 8, the thinning signal 102 for controlling the time division driving is represented by DIV. In the time division drive of the comparative example shown in FIG. 8, the period when DIV is “H” is the first half (odd number) time region (first period T1) of the time division, and VLED emits light during this period. . The period in which DIV is “L” is the second half of the time division (even-numbered) time region (second period T2), and the BLED emits light during this period. Ts is a data acquisition interval (sampling time) by the A / D converter 106, and this is the same in FIGS. In the comparative example, as an example, the cycle T of the timing signal 101 is 256 μs (3.91 kHz), and the first period T1, the second period T2, and the data acquisition interval Ts are both 12.5 ms (80 Hz). The period of the time division driving is T1 + T2 = 2Ts = 25 ms (40 Hz).

In the control unit 310 of the comparative example, when the TIM is “H” in the first period T1, the VLED is turned on, and the optical signal PD at this time is the sum of the tooth fluorescence amount Pt and the plaque fluorescence amount Pp. (P1 = Pt + Pp). When the TIM is “H” in the second period T2, the BLED is turned on, and the optical signal PD at this time is the tooth fluorescence amount Pt (P2 = Pt). When TIM is “L”, VLED and BLED are turned off, and the optical signal PD at this time is zero. Therefore, in the case of the comparative example, the in-phase detection output 107 (IOUT1, IOUT2) in the first and second periods is
IOUT1 = (P1-0) / 2 = (Pt + Pp) / 2
IOUT2 = (P2-0) / 2 = Pt / 2
The tooth fluorescence amount Pt and the plaque fluorescence amount Pp calculated by the control circuit 30 are:
Pt = 2 × IOUT2
Pp = 2 × (IOUT1-IOUT2)
It is.

  In this way, a data set of the tooth fluorescence amount Pt and the plaque fluorescence amount Pp is obtained for each time-division driving cycle 2Ts. In the comparative example, the plaque fluorescence amount Pp is obtained by subtracting the output signal IOUT2 in the second period T2 from the output signal IOUT1 in the first period T1. At that time, since the tooth fluorescence amount Pt in the first period T1 is subtracted by substituting the tooth fluorescence amount Pt in the second period T2, the light measurement method of the comparative example uses the first and second periods. When the correlation of noise is small, it is greatly affected by noise.

  In FIG. 10, the thinning signal 102 for controlling the time division driving is represented by VINH. In the time division drive of the embodiment shown in FIG. 10, the period when VINH is “L” is the first half (odd number) time region (first period T1) of the time division, and VLED and BLED are in this period. It emits light alternately. The period during which VINH is “H” is the second half (even number) time region (second period T2) of the time division. During this period, light emission of the VLED is prohibited and only the BLED emits light. In the embodiment, as an example, the cycle T of the timing signal 101 is 256 μs (3.91 kHz), the data acquisition interval Ts is 12.5 ms (80 Hz), the first period T1 is 3Ts / 2 = 18.75 ms, The period T2 is Ts / 2 = 6.25 ms. The period of the time division driving is T1 + T2 = 2Ts = 25 ms (40 Hz).

In the control unit 300 of the embodiment, when the TIM is “H” in the first period T1, the VLED is turned on, and the optical signal PD at this time is the sum of the tooth fluorescence amount Pt and the plaque fluorescence amount Pp. (P1 = Pt + Pp). When the TIM is “L”, the BLED is turned on, and the optical signal PD at this time is the tooth fluorescence amount Pt (P2 = Pt). When the TIM is “H” in the second period T2, the VLED and the BLED are turned off, and the optical signal PD at this time is zero. Therefore, in the case of the embodiment, the in-phase detection output 107 (IOUT1, IOUT2) in the first and second periods is
IOUT1 = (P1-P2) / 2 = {(Pt + Pp) -Pt} / 2 = Pp / 2
IOUT2 = (0−P2) / 2 = −Pt / 2
The tooth fluorescence amount Pt and the plaque fluorescence amount Pp calculated by the control circuit 30 are:
Pt = -2 × IOUT2
Pp = 2 × IOUT1
It is.

  The fluorescence amount Pp of plaque increases as the amount of plaque increases. However, even if the amount of plaque is small, the amount of fluorescence increases as the distance between the measuring device and the tooth to be measured is closer. Therefore, the control unit 300 calculates the tooth fluorescence amount Pt in addition to the plaque fluorescence amount Pp. If the ratio between the two is taken, it is possible to correct the influence of the plaque on the fluorescence amount Pp due to the variation in the measurement distance.

  In the embodiment, since the output signal IOUT1 in the first period T1 is a difference component between the fluorescence amount of the teeth and plaque generated when the VLED is lit and the fluorescence amount of the teeth generated when the BLED is lit, IOUT1 is the fluorescence amount of the plaque. Is required directly. The amount of tooth fluorescence is also directly determined as the output signal IOUT2 in the second period T2. The control unit 300 also takes the difference between the fluorescence amounts P1 and P2 at different times when calculating the plaque fluorescence amount, and the time difference is comparable to the period T of the timing signal 101. This is much smaller than the data acquisition interval Ts, which is the time difference between the fluorescence amounts. For this reason, in the control unit 300, the measurement error caused by the time-division driving is smaller than that in the control unit 310.

  Since plaque fluorescence is weaker than tooth fluorescence, the control unit 300 increases plaque by increasing the proportion of time for detecting plaque, that is, the proportion of the first period T1 in one period of time-division driving. The measurement accuracy of the quantity can be improved. Further, as described above, the tooth fluorescence amount is supplementarily used to correct the influence of the variation in the measurement distance, and therefore the second period T2 during which the tooth fluorescence amount is obtained may be short. . Therefore, in the time division driving of the embodiment, it is preferable that the first period T1 is longer than the second period T2.

  In the embodiment, when T1: T2 = 3: 1, VLED is lit for a period of 3/8 and BLED is lit for a period of 4/8 in one cycle 2Ts. This value is an apparent lighting period, both the VLED and BLED lighting periods in the period T1 during which the plaque amount is measured is 3/8, and the BLED lighting period in the period T2 during which the tooth fluorescence is measured is 1/8. It becomes. This is a substantial lighting period in consideration of measurement accuracy.

When time-division driving is not performed and a VLED and a BLED are driven alternately and with a duty α smaller than 50% using a two-phase lock-in amplifier, α is an apparent lighting time of the VLED and the BLED. Assuming that α = 3/8 in accordance with the time-division driving of the embodiment, the outputs IOUT1 and IOUT2 of the two-phase lock-in amplifier are
IOUT1 = αPp = (3/8) Pp
IOUT2 = (1 / 2−α) (Pp + Pt) = (1/8) (Pp + Pt)
It becomes. The tooth fluorescence amount Pt is obtained from IOUT1 and IOUT2, and the coefficient of each equation is considered to be a substantial LED lighting duty. Considering the detection accuracy, the lighting time when detecting the fluorescence amount of plaque is 3/8 for both VLED and BLED, while the detection accuracy of the tooth fluorescence amount is defined by IOUT2 having a substantially small lighting duty, The substantial lighting time when detecting the fluorescence amount of the teeth is 1 / 2−α = 1/8 from the detection principle.

  Therefore, in the embodiment, although a one-phase lock-in amplifier is used, it is possible to obtain measurement accuracy equivalent to that when a two-phase lock-in amplifier is used. If it is desired to increase the plaque detection sensitivity relative to the teeth, the second period T2 can be shortened and the first period T1 can be lengthened.

  FIG. 11 is a timing chart showing a modification of the operation timing of FIG. FIG. 11 shows the operation timing when the lighting of the BLED instead of the VLED is stopped in the second period T2, and the thinning signal 102 for controlling the time division driving is represented by BINH. In the time division drive of the modification shown in FIG. 11, the period in which BINH is “L” is the first half (odd number) time region (first period T1) of the time division, and VLED and BLED are in this period. It emits light alternately. The period in which BINH is “H” is the second half of the time division (even-numbered) time region (second period T2). During this period, BLED emission is prohibited and only VLED emits light.

In the modification, the in-phase detection output 107 (IOUT1, IOUT2) in the first and second periods is
IOUT1 = (P1-P2) / 2 = {(Pt + Pp) -Pt} / 2 = Pp / 2
IOUT2 = (P1-0) / 2 = (Pt + Pp) / 2
The tooth fluorescence amount Pt and the plaque fluorescence amount Pp calculated by the control circuit 30 are:
Pt = 2 × (IOUT2-IOUT1)
Pp = 2 × IOUT1
It is.

  In the time-division driving of the modified example, it is necessary to take the difference between the output signal IOUT1 in the first period T1 and the output signal IOUT2 in the second period T2 in order to obtain the tooth fluorescence amount Pt. A measurement error equivalent to that in the case of. For this reason, as in the modification, the same lighting pattern as in the case of the example is adopted, and the measurement accuracy is improved even if the lighting time of the VLED in which plaque-derived fluorescence is generated is longer than in the case of the example. Does not contribute. Therefore, it is not necessary to drive two light sources alternately in one period and only one light source in the other period, and only BLED is driven in the other period as in the embodiment. desirable. In the embodiment, by performing time-division driving and driving only the BLED in one period, the amount of fluorescence of teeth and dental plaque is directly obtained as the output signal of each period, and the output signal of two periods is straddled. Since it is not necessary to take the difference, the measurement accuracy is improved as compared with the comparative example and the modified example.

  12A to 12D are diagrams for explaining the difference between the measurement using the fluorescence measuring apparatuses 1 and 400 and the output signals from the control units 300 and 310. FIG. FIG. 12A shows the fluorescence of the teeth and plaque while moving the irradiation spot 12 of the excitation light toward the right in the horizontal direction indicated by the dotted arrow in the figure with respect to the two teeth 10 to which the plaque 11 has adhered. The state of measuring the quantity is shown. Since the plaque adhering to the tooth surface in the vicinity of the interdental is difficult to remove, the situation shown in FIG. 12A is general in measuring the amount of plaque. 12 (B) to 12 (D) show changes in fluorescence intensity of teeth and plaque detected when the dentition is measured along the dotted line shown in FIG. 12 (A). In each figure, the horizontal axis represents time t, and the vertical axis represents fluorescence intensity I.

  FIG. 12B is an ideal case where the data acquisition interval Ts is sufficiently short, and the fluorescence amount when the tooth is excited with 405 nm violet light and the fluorescence amount when the tooth is excited with 465 nm blue light can be measured simultaneously. The fluorescence intensity when using a measuring device is shown. The solid line in the graph is the fluorescence intensity with the excitation light of 405 nm (sum of the plaque fluorescence intensity Ip and the tooth fluorescence intensity It), and the dotted line is the fluorescence intensity with the excitation light of 465 nm (tooth fluorescence intensity It ). The plaque fluorescence intensity Ip and the tooth fluorescence intensity It are substantially the same as the plaque fluorescence intensity Pp and the tooth fluorescence intensity Pt. A vector indicated by an arrow in the drawing, which is the difference between the solid line and the dotted line in the graph, corresponds to the fluorescence intensity Ip of dental plaque. In the fluorescence intensity with 405 nm excitation light, a peak is observed in the portion where plaque near the interdental adheres.

  FIG. 12C shows the fluorescence intensity when measured by time-division driving in the comparative example. In FIG. 12C, the time-divided odd time regions (first period) are represented by T1, T3,..., And the even time regions (second period) are represented by T2, T4,.・ ・P1 is the output signal IOUT1 in the first period T1, and P2 is the output signal IOUT2 in the second period T2. The output signal IOUT1 obtained in the odd-numbered time domain is the sum of the plaque fluorescence intensity Ip ″ and the tooth fluorescence intensity It ″ generated by the excitation light of 405 nm, and the output signal obtained in the even-numbered time domain. IOUT2 is the fluorescence intensity It ″ of the teeth due to the excitation light of 465 nm. These output signals are alternately obtained at every data acquisition interval Ts. Since the plaque fluorescence amount is obtained from the difference between the output signals IOUT1 and IOUT2, the vector indicated by the arrow in the figure corresponds to the plaque fluorescence intensity Ip ''.

  When measuring from the left end of the left tooth 10 in FIG. 12A, the amount of excitation light hitting the tooth 10 increases as the irradiation spot 12 moves, so that the fluorescence intensity also increases. The difference between the fluorescence intensity P1 (= Ip ″ + It ″) in the first period T1 and the fluorescence intensity P2 (= It ″) in the second period T2 is at the left end of the left tooth 10. However, in the comparative example, it is calculated as a large negative value as indicated by the arrow at the left end of FIG. The fluorescence intensity Ip ″ of plaque indicated by an arrow (vector) in FIG. 12C is greatly different from the difference between the solid line and the broken line graph in FIG. It can be seen that a measurement error occurs particularly where the amount of fluorescence changes greatly, such as between the teeth. This measurement error occurs because the amount of plaque is calculated by using fluorescence intensities at different times, that is, at different positions due to the irradiation spot 12 moving with time.

  FIG. 12D shows the fluorescence intensity when measured by time-division driving in the example. In the case of the embodiment, the fluorescence intensity Ip ′ of plaque is obtained by alternately irradiating excitation light of 405 nm and 465 nm in the odd-numbered time region, and in the even-numbered time region, the excitation light of the tooth is obtained by the excitation light of 465 nm. A fluorescence intensity It ′ is obtained. In FIG. 12D, as in FIGS. 12B and 12C, the plaque fluorescence intensity Ip ′ is also indicated by an arrow (vector).

  As can be seen from a comparison between FIG. 12B and FIG. 12D, in the embodiment, a result close to that of an ideal measuring apparatus can be obtained. When time-division driving is performed with an actual measurement apparatus, the data acquisition interval Ts has a finite length and the fluorescence amount at two wavelengths cannot be measured simultaneously. It can be seen that the measurement accuracy is higher than in the example. In the case of the embodiment, since it is not necessary to take the difference between the fluorescence amounts in different time regions divided in time, the error in the fluorescence amount due to the movement of the irradiation spot 12 becomes more problematic as in the comparative example. This is because it must not. In the example, the fluorescence intensity of the teeth and plaque is obtained alternately, and the fluorescence intensity Ip ′ of the plaque and the fluorescence intensity It ′ of the tooth are the fluorescence intensity at different times. Since It ′ can be obtained almost accurately by interpolation, there is no particular problem with the fluorescence amounts obtained at different times.

  As explained above, it is possible to separate and measure plaque-derived fluorescence from autofluorescence by exciting the teeth with two lights of different wavelengths and measuring the fluorescence at one wavelength, with a simple configuration. A fluorescence measuring device that can detect plaque with high accuracy is obtained. Therefore, if it is a toothbrush equipped with this fluorescence measuring device, it can brush a tooth, confirming whether it has brushed properly.

  In particular, in the control unit 300 of the embodiment, the time-division driving shown in FIG. 10 can be used to separate and measure the fluorescence of teeth and dental plaque with one lock-in amplifier, so that the cost reduction effect is great. Further, regarding the fluorescence amount of dental plaque, the measurement error is reduced as compared with the comparative example shown in FIG. 8, and the same accuracy as in the case of using a two-phase lock-in amplifier without performing time-division driving can be obtained. . Regarding the fluorescence amount of the teeth, the accuracy is lower than that in the comparative example, but the same accuracy as in the case of using a two-phase lock-in amplifier is obtained. However, the amount of fluorescence of the teeth is necessary even in the case of the example because it is used as an auxiliary to correct the influence of the distance between the teeth and the measuring device and to determine whether the measurement position is between teeth or the tooth surface. It is possible to ensure high accuracy.

DESCRIPTION OF SYMBOLS 1,400 Fluorescence measuring apparatus 2 1st light source 3 2nd light source 30 Control circuit 100 Light source part 100A Oscillation circuit 102A, 102B Thinning-out control circuit 103 Lock-in amplifier 104 Phase detector 200 Detection part 300 Control part

Claims (5)

A first light source that emits light of a first wavelength;
A second light source that emits light of a second wavelength that is longer than the first wavelength;
A detection unit for detecting a first fluorescence intensity generated when the sample is irradiated with light of the first wavelength, and a second fluorescence intensity generated when the sample is irradiated with light of the second wavelength; ,
Of the first and second periods, which are alternately repeated and each longer than the period of the reference signal, the first and second light sources are caused to emit light alternately according to the reference signal in the first period, and the second A light emission controller that emits only the second light source in accordance with the reference signal during the period of
Phase detection is performed according to the reference signal, and the first output signal according to the first and second fluorescence intensities in the first period and the second fluorescence intensity in the second period A phase detector for generating a second output signal;
A control circuit for calculating the amount of fluorescent substance to be measured by calculation using the first and second output signals;
A light measuring device comprising: The light of the first wavelength excites a fluorescent substance contained in the teeth and plaque to generate fluorescence derived from the teeth and plaque,
The light measurement apparatus according to claim 1, wherein the light of the second wavelength has lower excitation efficiency than the light of the first wavelength with respect to a fluorescent substance contained in plaque. The first wavelength is in the range of 350 nm to 430 nm;
The optical measurement device according to claim 2, wherein the second wavelength is in a range of 435 nm to 500 nm.   The light measurement apparatus according to claim 2, wherein the first period is longer than the second period.   A toothbrush comprising the light measurement device according to any one of claims 1 to 4.

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