Patent Description:
This invention furthermore relates to a tooth brush incorporating such a plaque detecting device.

Plaque detecting devices of this sort known in the prior art include, for example, devices which compare the intensity of fluorescent light coming from a tooth surface substantially without deposits (plaque, bacteria, tartar, calculus, etc.) to the intensity of fluorescent light from the tested tooth surface to determine the presence or absence of biological deposits on the tested tooth surface, as disclosed in patent document <NUM> (Published Japanese Translation of a <CIT>).

As a further example, Patent Document <NUM> discloses a toothbrush capable of detecting a plaque status of an investigated tooth in three different ways. For instance, a plaque status of the investigated tooth can be determined based on a ratio between a spectra measured with a long distance light receiving element and a spectra measured with a short distance light receiving element. In this case, presence of plaque can be determined by comparing an actual value of said ratio to a value of a ratio associated with a clean tooth. Alternatively, a plaque status of the investigated tooth can be determined by fitting measured spectra to a scattering model suitable for making distinction between scattering effects and absorption effects. As a further alternative, a plaque status of the investigated tooth can be determined by evaluating scattering at two different wavelengths, and calculating a predefined ratio, the result of which can be used as a plaque differentiator.

When using the device described in aforementioned patent document <NUM>, the user needs to find a "tooth surface without biological deposits" to serve as a basis for comparison, and save the intensity of fluorescent light from that tooth surface as a reference. However, this involves the problem that it is difficult for a regular user to find a "tooth surface without biological deposits" (usually, the user cannot be sure), and a calibration-like operation of saving the reference becomes necessary, which takes time and is troublesome.

The problem to be solved by this invention therefore consists in providing a plaque detecting device allowing a user to determine the presence or absence of plaque through a simple operation.

The problem to be solved by this invention further consists in providing a tooth brush incorporating such a plaque detecting device.

To solve the aforementioned problem, there is the plaque detecting device as defined in the claims.

As is known, in the light radiated from a tooth surface, "fluorescent light specific to plaque" has a peak wavelength of approximately <NUM>, and the spectral component of this peak is distributed over a range of approximately ±<NUM> relative to the peak wavelength. Furthermore, "fluorescent light specific to enamel" has a peak wavelength of approximately <NUM>. The spectral component to the longer wavelength side of this peak is broadly distributed to about <NUM> from the peak wavelength.

The upper limit wavelength of the first wavelength region may be left undetermined or may be determined to be, for example, <NUM> or lower. The upper limit wavelength of the second wavelength region may be left undetermined or may be determined to be, for example, <NUM> or lower.

The "intensity" of the spectral components of the first wavelength region and second wavelength region corresponds to the magnitude obtained by integrating (or summing) the spectral component of the extracted wavelength region over that wavelength region.

For the "ratio" between the first output value and the second output value, either the first output value or the second output value may be used as the numerator (or denominator). Similarly, for the "difference" between the first output value and the second output value, either one may be used as the minuend (or subtrahend).

In the plaque detecting device of this invention, the light emitting unit irradiates ultraviolet or blue excitation light toward the tooth surface. The first light receiving unit and second light receiving unit each receive the radiated light from the tooth surface induced by the excitation light. The first light receiving unit extracts, from the radiated light, a spectral component of a first wavelength region having a predetermined lower limit wavelength and including the wavelength range of fluorescent light specific to plaque, and obtains a first output value corresponding to the intensity of the spectral component of this first wavelength region. Furthermore, the second light receiving unit extracts, from the radiated light, a spectral component of a second wavelength region having a predetermined lower limit wavelength lower than the lower limit wavelength of the first wavelength region and including the wavelength range of fluorescent light specific to enamel, and obtains a second output value corresponding to the intensity of the spectral component of this second wavelength region. The first determination unit performs determination of the relative magnitude of the ratio between the first output value and the second output value as compared to a predetermined first threshold value. According to the determination results from this first determination unit, substances which may be present on the tooth surface (namely, enamel, resin, metal teeth, artificial teeth (ceramic or plastic), tartar and plaque) can be identified as belonging either to the group consisting of enamel, resin and artificial teeth (ceramic or plastic), or the group consisting of metal teeth, tartar and plaque (the basis for such identification will be described later). The second determination unit performs determination of the relative magnitude of the difference between the first output value and the second output value as compared to a predetermined second threshold value. According to the determination results from this second determination unit, the substances which may be present on a tooth surface can be identified as belonging either to the group consisting of enamel, resin, metal teeth and artificial teeth (ceramic or plastic), or the group consisting of tartar and plaque. Furthermore, the group consisting of metal teeth can be identified in distinction to the group consisting of enamel, resin, artificial teeth (ceramic or plastic), tartar and plaque (the basis for such identification will be described later). Therefore, based on a combination of the determination results from the first determination unit and the determination results from the second determination unit, it can be identified if the substance present on a tooth surface is plaque (or tartar) or not.

For instance, if the substance present on a tooth surface is plaque (or tartar), for example, first, based on the determination of the first determination unit, the substance present on the tooth surface will be identified as being a substance belonging to the group consisting of metal teeth, tartar and plaque. Next, based on the determination of the second determination unit, the substance will be identified as being not metal teeth but rather plaque (or tartar).

In this way, with this plaque detecting device, the substance present on a tooth surface can be identified as being or not being plaque (or tartar) based on a combination of the determination results from the first determination unit and the determination results from the second determination unit.

Here, with this plaque detecting device, unlike the device described in patent document <NUM>, the user does not need to find a "tooth surface without biological deposits" to serve as a basis for comparison, nor is there a need for the calibration-type operation of saving a reference. Therefore, the user is able to obtain determination results concerning the presence or absence of plaque (or tartar) through a simple operation, for example, by simply arranging the light emitting unit and light receiving unit so as to face a tooth surface, and instructing the start of operation (switching on) of the plaque detecting device. Since tartar is plaque which has gradually changed and become deposited on a tooth surface, it is difficult to completely distinguish the two in terms of substance.

In one embodiment, the plaque detecting device is characterized in that it comprises a first zero point adjustment unit which performs adjustment by subtracting the component due to ambient light around said tooth surface from said first and second output values,
wherein said first and second determination units use said first and second output values, which have been adjusted by said first zero point adjustment unit, for said determination.

In the plaque detecting device of this embodiment, the first zero point adjustment unit performs adjustment by subtracting the component due to ambient light around the tooth surface from the first and second output values. The first and second determination units use the first and second output values which have been adjusted by the first zero point adjustment unit for determination. Therefore, the accuracy of determination can be increased.

In one embodiment, the plaque detecting device is characterized in that said first zero point adjustment unit, upon start of operation or during operation, obtains said first and second output values when said light emitting unit is turned off, and respectively subtracts said first and second output values when said light emitting unit is turned off, as said component due to ambient light, from said first and second output values when said light emitting unit is turned on.

With the plaque detecting device of this embodiment, the component due to ambient light can be suitably eliminated, making it possible to increase the accuracy of determination.

It should be noted that when this plaque detecting device is incorporated into a tooth brush, "upon start of operation or during operation" corresponds to upon start of tooth brushing or during tooth brushing.

In one embodiment, the plaque detecting device is characterized in that it comprises a signal processing unit which, in order to make said difference between said first output value and said second output value different for predetermined different types of substances which may be present on said tooth surface, computes said difference after multiplying said first output value and said second output value respectively by a first coefficient and second coefficient, which differ from each other.

In the present specification, "substances which may be present on a tooth surface" are envisioned as being enamel, resin, metal teeth, artificial teeth (ceramic or plastic), tartar and plaque. As regards "predetermined different types of substances," for example, tartar and plaque can be said to be a different type of substances in contrast to metal teeth and artificial teeth.

In the plaque detecting device of this embodiment, in order to make the difference between the first output value and the second output value different for predetermined different types of substances which may be present on the tooth surface, the signal processing unit computes said difference after multiplying the first output value and the second output value respectively by a first coefficient and second coefficient, which differ from each other. As a result, the difference between the first output value and the second output value come to differ between predetermined different types of substances which may be presented on the tooth surface. Therefore, with this plaque detecting device, it can be easily identified if a substance present on a tooth surface is plaque (or tartar) or not, based on a combination of the determination results of the first determination unit and the determination results of the second determination unit.

In one embodiment, the plaque detecting device is characterized in that said signal processing unit multiplies said first output value and said second output value respectively by said first coefficient and said second coefficient by means of amplifying said first output value and said second output value respectively by a first amplification factor and a second amplification factor, which differ from each other.

In the plaque detecting device of this embodiment, the processing of the signal processing unit is simplified.

In one embodiment, the plaque detecting device is characterized in that, in order to make said difference between said first output value and said second output value different for predetermined different types of substances which may be present on said tooth surface, the light receiving surface area of said first light receiving unit and the light receiving surface area of said second light receiving unit are set to be different from each other.

In the plaque detecting device of this embodiment, in order to make the difference between the first output value and the second output value different for predetermined different types of substances which may be present on the tooth surface, the light receiving surface area of the first light receiving unit and the light receiving surface area of the second light receiving unit are set to be different from each other. As a result, the processing of multiplying the first output value and the second output value respectively by a first coefficient and second coefficient, which differ from each other, can be omitted, and it suffices to simply take the difference between the first output value and the second output value. Therefore, the processing of the signal processing unit is simplified. As a result, the difference between the first output value and the second output value comes to be different for different types of substances which may be present on the tooth surface.

In one embodiment, the plaque detecting device is characterized in that it comprises an annunciation unit which annunciates the determination results concerning the presence or absence of plaque on said tooth surface.

Here, "annunciation" by the annunciation unit broadly includes the sounding of a buzzer, the illumination or flashing of a lamp, display by means of a display screen, etc..

In the plaque detecting device of this embodiment, an annunciation unit annunciates the determination results concerning the presence or absence of plaque on the tooth surface. Therefore, the user can easily learn if plaque is present or absent on the tooth surface.

In a different aspect, the tooth brush of this invention is characterized in that it comprises a main body including a head section having a bristled surface on which bristles are provided, a grip section intended to be gripped by a hand, and a neck section which joins said head section to said grip section,
wherein a plaque detecting device as described above is incorporated into said main body.

In the tooth brush of this invention, a plaque detecting device as described above is incorporated into the main body. Therefore, the user can learn the determination results concerning the presence or absence of plaque (or tartar) while brushing teeth. As a result, it is possible to do without an optical fiber, wire, etc. extending from the tooth brush to the outside. In such a case, when a user performs tooth brushing using this tooth brush, there are no obstacles and tooth brushing can be easily carried out.

In one embodiment, the tooth brush is characterized in that said light emitting unit and said first and second light receiving units are arranged in an internal portion of said head section corresponding to a specified region of said bristled surface;.

In the tooth brush of this embodiment, the first light receiving unit and second light receiving unit can both be made with a simple configuration. Therefore, this tooth brush can be manufactured compactly and at low cost.

It will be noted that in the "specified region" of the bristled surface, it is preferable for bristles to be omitted.

In one embodiment, the tooth brush is characterized in that it comprises a second zero point adjustment unit which performs adjustment by subtracting the component due to internally reflected light in said head section from said first and second output values,
wherein said first and second determination units use said first and second output values, which have been adjusted by said second zero point adjustment unit, for said determination.

In the present specification, "internally reflected light" in the head section refers to the portion of excitation light from the light emitting unit which is reflected by the constituent elements of the head section and inputted into the first and second light receiving units without reaching the tooth surface. Specifically, internally reflected light includes light reflected by the boundary surface of the specified region in the bristled surface, light reflected by the wall surfaces inside the head section (which contain the light emitting unit and the first and second light receiving units), light which has exited through the boundary surface of the specified region of the head section but was reflected by the bristles and returned, and the like. Furthermore, internally reflected light may include light which enters the fist and second optical filter members directly from the light emitting unit and is then inputted into the first and second light receiving units.

With the tooth brush of this embodiment, the second zero point adjustment unit performs adjustment by subtracting the component due to internally reflected light in the head section from the first and second output values. The first and second determination units use the first and second output values, which have been adjusted by the second zero point adjustment unit, for determination. Therefore, the accuracy of determination can be increased.

In one embodiment, the tooth brush is characterized in that it comprises a light shielding member which covers said head section along with said bristles and blocks ambient light around said head section,
wherein said second zero point adjustment unit, in the light shielded state in which said ambient light has been blocked by said light shielding member, with a timing inputted as an instruction through a manipulation unit or preset by means of a timer, obtains said first and second output values after turning on said light emitting unit, and also obtains said first and second output values after turning off said light emitting unit, and subsequently subtracts said first and second output values when said light emitting unit is turned off respectively from said first and second output values when said light emitting unit is turned on, to obtain the component due to said internally reflected light.

In the tooth brush of this embodiment, in the light shielded state in which the ambient light has been blocked by the light shielding member, with a timing inputted as an instruction through a manipulation unit or preset by means of a timer, the second zero point adjustment unit obtains the first and second output values after turning on the light emitting unit, and also obtains the first and second output values after turning off the light emitting unit. Subsequently, the second zero point adjustment unit subtracts the first and second output values when the light emitting unit is turned off respectively from the first and second output values when the light emitting unit is turned on, to obtain the component due to internally reflected light. Therefore, the component due to said internally reflected light can be suitably obtained in a state in which the ambient light around said head section is approximately zero.

In one embodiment, the tooth brush is characterized in that it comprises an illuminance measurement unit which measures illuminance due to ambient light around said main body,
wherein said second zero point adjustment unit, using the fact that said illuminance has dropped below a predetermined illuminance threshold value as a starting condition, obtains said first and second output values after turning on said light emitting unit, and also obtains said first and second output values after turning off said light emitting unit, and subsequently subtracts said first and second output values when said light emitting unit is turned off respectively from said first and second output values when said light emitting unit is turned on, to obtain the component due to said internally reflected light.

In the tooth brush of this embodiment, the second zero point adjustment unit, using the fact that the illuminance has dropped below a predetermined illuminance threshold value as a starting condition, obtains the first and second output values after turning on the light emitting unit, and also obtains the first and second output values after turning off the light emitting unit. Subsequently, the second zero point adjustment unit subtracts the first and second output values when the light emitting unit is turned off respectively from the first and second output values when the light emitting unit is turned on, to obtain the component due to internally reflected light. Therefore, the component due to internally reflected light can be suitably obtained in a state where there is little ambient light around the head section. Furthermore, the need to install the aforementioned light shielding member on the head section does not arise. As a result, the need for the user to perform operations for acquiring calibration data can be eliminated.

In one embodiment, the tooth brush is characterized in that said illuminance measurement unit consists of one or both of said first and second light receiving units.

With the tooth brush of this embodiment, the illuminance measurement unit consists of one or both of the first and second light receiving units. Therefore, illuminance due to ambient light can be measured without increasing the number of component parts of the tooth brush.

In one embodiment, the tooth brush is characterized in that said second zero point adjustment unit, at a timing corresponding to nighttime, set in advance by means of a timer, obtains said first and second output values after turning on said light emitting unit, and also obtains said first and second output values after turning off said light emitting unit, and subsequently subtracts said first and second output values when said light emitting unit is turned off respectively from said first and second output values when said light emitting unit is turned on, to obtain the component due to said internally reflected light.

In the tooth brush of this embodiment, at a timing corresponding to nighttime, set in advance by means of a timer, the second zero point adjustment unit obtains the first and second output values after turning on the light emitting unit, and also obtains the first and second output values after turning off the light emitting unit. Subsequently, the second zero point adjustment unit subtracts the first and second output values when the light emitting unit is turned off respectively from the first and second output values when the light emitting unit is turned on, to obtain the component due to the internally reflected light. Therefore, the component due to internally reflected light can be suitably obtained in a state where there is little ambient light around the head section. As a result, the need for the user to perform operations for acquiring calibration data can be eliminated.

As is clear from the foregoing, with the plaque detecting device of this invention, a user is able to determine the presence or absence of plaque by means of a simple operation.

Furthermore, with the tooth brush of this invention, the user can learn the determination results concerning the presence or absence of plaque while brushing teeth.

Modes of embodiments will be described in detail below with reference to the drawings.

<FIG> schematically illustrates the simplified configuration of a plaque detecting device (represented as a whole by reference symbol <NUM>) of one embodiment of this invention. Furthermore, <FIG> illustrates the block configuration of the control system of plaque detecting device <NUM>.

As shown in <FIG>, this plaque detecting device <NUM> comprises a stabilized power supply <NUM>, an LED (light emitting diode) <NUM> as the light emitting unit, a forward waveguide <NUM>, a tooth brush <NUM>, a return waveguide <NUM>, a spectrometer <NUM> and a data analysis computer <NUM>.

The stabilized power supply <NUM>, in order to cause the LED <NUM> to emit light, supplies direct current to LED <NUM> through wire <NUM>, in this example, with a voltage of <NUM> V to <NUM> V, at about <NUM> mA to <NUM> mA.

The LED <NUM> receives the supply of direct current from the stabilized power supply <NUM> and emits light having a peak wavelength corresponding to ultraviolet or blue (which becomes the excitation light L shown in <FIG>). In this example, the LED <NUM> is a DIP type ultraviolet LED (model number UV3TZ-<NUM>-<NUM>) made by Bivar, Inc. , and emits light L having a peak wavelength of <NUM>.

Forward waveguide <NUM> comprises a fiber cable 461A, plastic optical fiber 461C, and a feed-through connector 461B which optically links the fiber cable 461A and the plastic optical fiber 461C. The entry side end 461e of the fiber cable 461A is arranged facing the light radiating surface of the LED <NUM>. Light taken in through the end 461e of the fiber cable 461A passes through the fiber cable 461A, feed-through connector 461B and plastic optical fiber 461C, and reaches the exit side end 461f of the plastic optical fiber 461C. The end 461f of plastic optical fiber 461C penetrates through the head section <NUM> of the tooth brush <NUM> and is arranged so as to face the surface 99a of the subject's teeth <NUM>. Therefore, light emitted by the LED <NUM> is irradiated as excitation light onto the tooth surface 99a, as shown in <FIG>.

The return waveguide <NUM> shown in <FIG> comprises a fiber cable 462A, plastic optical fiber 462C, and a feed-through connector 462B which optically links the fiber cable 462A and plastic optical fiber 462C. The entry side end 462e of plastic optical fiber 462C penetrates through the head section <NUM> of the tooth brush <NUM> alongside the end 461f of plastic optical fiber 461C and is arranged opposite the surface of the teeth <NUM>. Light taken in through the end 462e of the plastic optical fiber 462C (radiated light L' generated by the tooth surface 99a due to excitation light L shown in <FIG>) passes through plastic optical fiber 462C, feed-through connector 462B and fiber cable 462A, reaches the exit side end 462f of fiber cable 462A, and is inputted into spectrometer <NUM>.

In this example, a fiber patch cable made by Thorlabs Japan, Inc. (step index multimode, core diameter <NUM>,<NUM>, numerical aperture NA <NUM>, connector SMA-SMA, length <NUM>) was used for the fiber cables 461A, 462A. Furthermore, plastic optical fiber cable <NUM>,<NUM> (outside diameter <NUM>) made by Edmund Optics Japan, Ltd. was used for the plastic optical fiber 461C, 462C. By using relatively light weight plastic optical fiber 461C, 462C for the tooth brush <NUM> side portion of the forward waveguide <NUM> and return waveguide <NUM>, it is possible to avoid the tooth brush <NUM> being felt to be heavy.

The spectrometer <NUM> in this example consists of the SEC <NUM> Spectrometer made by ALS Co. , and outputs a signal representing the intensity per wavelength of inputted light (radiated light L'). The resolution in the vicinity of wavelength <NUM> to <NUM> is approximately <NUM>.

The data analysis computer <NUM>, as shown in <FIG>, comprises a control unit <NUM>, storage unit <NUM>, data input unit <NUM>, manipulation unit <NUM>, display unit <NUM> and power supply unit <NUM>.

The control unit <NUM> includes a CPU (central processing unit) operated by software, and executes the various types of processing described below.

The data input unit <NUM> comprises a known input interface, inputs the output of spectrometer <NUM>, that is, a signals representing the intensity for each wavelength of light (radiated light L') inputted into the spectrometer <NUM>, and passes them to the control unit <NUM>.

The manipulation unit <NUM> includes a known keyboard and mouse and works for inputting commands and various information from the user. Commands include a command instructing the start of processing, a command instructing the recording of computation results, etc. Inputted information includes information (identification number) for identifying the subject, and the like.

The storage unit <NUM> includes a hard disk drive or EEPROM (electrically rewritable non-volatile memory) capable of non-temporary storage of data. The storage unit <NUM> stores a control program for controlling the control unit <NUM>. Furthermore, the storage unit <NUM> stores signals representing the intensity of each wavelength of radiated light L' inputted from the spectrometer <NUM> via the data input unit <NUM>.

The display unit <NUM>, in this example, comprises an LCD (liquid crystal display element), and displays various types of information, such as computation results produced by the control unit <NUM>.

The power supply unit <NUM> supplies power to the various units in the computer <NUM>.

This plaque detecting device <NUM> operates according to the processing flow shown as a whole in <FIG>, based on manipulations by the user (referring to the person manipulating the device <NUM>). It will be noted that the user may be either the same person as the subject or a different person.

This radiated light L' has a wavelength spectrum corresponding to the substance irradiated by the excitation light L. Generally speaking, tooth enamel, resin, metal teeth, artificial teeth (ceramic or plastic), tartar and plaque may be present on the tooth surface. If the substance irradiated by excitation light L is, for example, tartar, as shown in <FIG>, the radiated light L', in addition to the peak PO generated due to scattering of excitation light L, contains the peak wavelength P1 (≈<NUM>, red) of fluorescent light specific to tartar. Similarly, if the substance irradiated by excitation light L is, for example, plaque, as shown in <FIG>, the radiated light L' contains, in addition to the peak PO generated due to scattering of excitation light L, the peak wavelength P2 (≈<NUM>, red) of fluorescent light specific to plaque. The spectral component of these peaks is distributed over a range of approximately ±<NUM> from the peak wavelength. It will be noted that tartar is plaque which has gradually changed and become deposited on the tooth surface, and thus it is difficult to complete distinguish the two substances. The designation "tartar (and plaque)" is used in <FIG> for this reason (the same applies to <FIG>, described below).

If the substance irradiated by excitation light L is tooth enamel, as shown in <FIG>, the radiated light L', in addition to the peak PO generated due to scattering of excitation light L, contains the spectral component P3 (green) of fluorescent light specific to enamel. More specifically, in <FIG>, the peak wavelength of fluorescent light specific to enamel is approximately <NUM>, although it is hidden by the peak PO generated due to scattering of excitation light L. The spectral component to the longer wavelength side of that peak is distributed broadly from the peak wavelength to about <NUM>.

Furthermore, if the substance irradiated with excitation light L is resin and artificial teeth (ceramic), as shown in <FIG>, the radiated light L', in addition to the peak PO generated due to scattering of excitation light L, contains the spectral components P4, P6 of the respective specific fluorescent light. On the other hand, if the substance irradiated with excitation light L is metal teeth, the radiated light L' contains only the peak PO generated due to reflection or scattering of excitation light L and its tail P5.

The spectrometer <NUM> in <FIG> outputs a signal representing the intensity of each wavelength of radiated light L'. This signal is inputted into control unit <NUM> via data input unit <NUM>. In this example, the control unit <NUM>, acting along with the spectrometer <NUM> as the first light receiving unit, as shown in step S2 in <FIG>, extracts the spectral component of a predetermined first wavelength region from the radiated light L', and acquires a first output value OUT1 corresponding to the intensity of the spectral component of this first wavelength region. Furthermore, the control unit <NUM>, acting along with the spectrometer <NUM> as the second light receiving unit, as shown in step S3, extracts the spectral component of a predetermined second wavelength region from the radiated light L', and acquires a second output value OUT2 corresponding to the intensity of the spectral component of this second wavelength region. It will be noted that the first output value OUT1 and second output value OUT2 correspond to a magnitude obtained by integrating (or summing) the spectral component of the respective wavelength region over that wavelength region (the same applies to the first output value OUT1b and second output value OUT2b, described later).

Here, the first wavelength region, in this example, is defined as the wavelength region from a lower limit wavelength of <NUM> to an upper limited wavelength of <NUM>. As can be seen from <FIG>, the lower limit wavelength <NUM> of the first wavelength region is defined as a wavelength just below the peak wavelength of approximately <NUM> specific to plaque (and tartar). The upper limit wavelength <NUM> of the first wavelength region is defined as the wavelength at which the tail on the longer wavelength side of the peak specific to plaque (and tartar) goes substantially to zero. As a result, the first wavelength region includes substantially the entire region of the wavelength range of fluorescent light specific to plaque.

Furthermore, the second wavelength region, in this example, is defined as the wavelength region from a lower limit wavelength of <NUM> to an upper limit wavelength of <NUM>. As can be seen from <FIG>, the lower limit wavelength <NUM> of the second wavelength region is defined as a wavelength which exceeds the peak wavelength of approximately <NUM> of fluorescent light specific to enamel and is below the lower limit wavelength <NUM> of the first wavelength region. The upper limit wavelength <NUM> of the second wavelength region, in this example, is defined so that the second wavelength region does not overlap the first wavelength region. As a result, the second wavelength region does not include the wavelength range of fluorescent light specific to plaque (and tartar), and includes the wavelength range of fluorescent light specific to enamel (a portion to the longer wavelength side from the peak wavelength). Moreover, as can be seen from <FIG>, this second wavelength region also includes the wavelength range of fluorescent light specific to resin and artificial teeth (ceramic) (a portion to the longer wavelength side from the peak wavelength) and the tail of scattered light from metal teeth.

(<NUM>) Next, the user causes the control unit <NUM> to perform the first zero point adjustment processing SP1 shown in <FIG>.

Here, the first zero point adjustment processing SP1 has been introduced by the inventors in consideration of the fact that, for example, with a plaque substitute sample (porphyrin solution), when one compares the spectrometer output when the light emitting unit (LED <NUM>) is turned on under indoor lighting (the spectral component shown in <FIG>) to spectrometer output when the light emitting unit (LED <NUM>) is turned on in a dark room (the spectral component shown in <FIG>), under indoor lighting (<FIG>), components B1 through B4, which are due to ambient light Lb around the tooth surface 99a, are present as external interference. Namely, with the aforementioned plaque substitute sample (porphyrin solution), under the same indoor lighting, the components due to ambient light Lb around the tooth surface 99a can be eliminated, as shown in <FIG>, by subtracting the spectrometer output when the light emitting unit (LED <NUM>) is turned off (the spectral component shown in <FIG>) for each wavelength from the spectrometer output when the light emitting unit (LED <NUM>) is turned on (the spectral component shown in <FIG>).

Specifically, the user, as shown in step S4 of <FIG>, stops direct current from the stabilized power supply <NUM> to turn off the LED <NUM> as the light emitting unit. Thereupon, only the ambient light Lb around the tooth surface 99a shown in <FIG> is inputted into the spectrometer <NUM>.

Here, the spectrometer <NUM> in <FIG> outputs a signal representing the intensity for each wavelength of ambient light Lb. This signal is inputted via the data input unit <NUM> into the control unit <NUM>. In this example, the control unit <NUM>, acting together with the spectrometer <NUM> as the first light receiving unit, as shown in step S5 of <FIG>, extracts the spectral component of the first wavelength region of the ambient light Lb, and acquires a first output value OUT1b corresponding to the intensity of the spectral component of this first wavelength region. Furthermore, the control unit <NUM>, acting together with the spectrometer <NUM> as the second light receiving unit, as shown in step S6 of <FIG>, extracts the spectral component of the second wavelength region of the ambient light Lb, and acquires a second output value OUT2b corresponding to the intensity of the spectral component of this second wavelength region. It will be noted that the acquisition of the component due to ambient light Lb (that is, the first output value OUT1b and second output value OUT2b) may be carried out either at start of operation or during operation.

Next, the control unit <NUM>, acting as the first zero point adjustment unit, as shown in step S7 of <FIG>, performs adjustment by subtracting the component due to ambient light Lb around the tooth surface 99a (i.e. OUT1b, OUT2b) from the aforementioned first output value OUT1 and second output value OUT2.

Specifically, the differences <MAT> <MAT> are computed as the adjusted first output value ΔOUT1 and second output value ΔOUT2. It will be noted that the processing of steps S4 through S7 in <FIG> is referred to together as the first zero point adjustment processing SP1. Performing this first zero point adjustment processing SP1 makes it possible to suitably eliminate the effect of the component due to ambient light Lb and increase the accuracy of determination of the presence or absence of plaque, as described below.

(<NUM>) Next, the control unit <NUM>, as shown in step S8 of <FIG>, computes the ratio A between the above-described adjusted first output value ΔOUT1 and second output value ΔOUT2. Specifically, in this example, <MAT> is computed. Moreover, the control unit <NUM>, acting as the first determination unit, as shown in step S9 of <FIG>, performs determination of the relative magnitude of this ratio A as compared to a predetermined first threshold value α. According to the results of this determination, the substance which may be present on the tooth surface (namely, enamel, resin, metal teeth, artificial teeth (ceramic or plastic), tartar and plaque) can be identified as belonging either to the group consisting of enamel, resin and artificial teeth (ceramic or plastic), or the group consisting of metal teeth, tartar and plaque. As stated already, it is difficult to completely distinguish tartar and plaque as substances, so when simply "tartar" is mentioned, strictly speaking, "tartar (and plaque)" is indicated.

More specifically, the ratio A between the first output value ΔOUT1 and the second output value ΔOUT2 for enamel, resin, metal teeth, artificial teeth (ceramic or plastic), tartar and plaque is as indicated by the bar graph shown in <FIG>. In <FIG>, the horizontally arrayed bars correspond to samples of enamel, resin, metal teeth, artificial teeth (ceramic or plastic), tartar and plaque. In this example, the total number of samples was <NUM>. The vertical axis of <FIG> represents ratio A as a dimensionless quantity. As can be seen from <FIG>, for the group consisting of enamel, resin and artificial teeth (ceramic or plastic), the ratio A is generally smaller than <NUM>. On the other hand, for the group consisting of metal teeth, tartar and plaque, the ratio A is generally greater than <NUM>. Therefore, defining a first threshold value α = <NUM> in advance makes it possible to distinguish the group consisting of enamel, resin and artificial teeth (ceramic or plastic) from the group consisting of metal teeth, tartar and plaque.

(<NUM>) Furthermore, the control unit <NUM>, as shown step S10 of <FIG>, computes the difference B between the above-described amended first output value ΔOUT1 and second output value ΔOUT2. Specifically, in this example, <MAT> is computed. Moreover, the control unit <NUM>, acting as the second determination unit, as shown in step S11 of <FIG>, performs determination of the relative magnitude of this difference B as compared to a predetermined second threshold value β. According to the results of this determination, the substance which may be present on the tooth surface (namely, enamel, resin, metal teeth, artificial teeth (ceramic or plastic), tartar and plaque) can be identified as belonging either to the group consisting of enamel, resin, metal teeth and artificial teeth (ceramic or plastic) or the group consisting of tartar and plaque.

More specifically, the difference B between the first output value ΔOUT1 and the second output value ΔOUT2 for enamel, resin, metal teeth, artificial teeth (ceramic or plastic), tartar and plaque is as indicated by the bar graph shown in <FIG>. In <FIG>, the horizontally arrayed bars correspond to samples of enamel, resin, metal teeth, artificial teeth (ceramic or plastic), tartar and plaque. The vertical axis of <FIG> represents difference B in arbitrary units (a. As can be seen from <FIG>, for the group consisting of enamel, resin and metal teeth and artificial teeth (ceramic or plastic), the difference B is generally smaller than <NUM>,<NUM> (a. On the other hand, for the group consisting of tartar and plaque, the difference B is generally greater than <NUM>,<NUM> (a. Therefore, defining a second threshold value β = <NUM>,<NUM> (a. ) in advance makes it possible to distinguish the group consisting of enamel, resin, metal teeth and artificial teeth (ceramic or plastic) from the group consisting of tartar and plaque.

It will be noted that the determination of the relative magnitude of the ratio A as compared to the first threshold value α under (<NUM>) above and the determination of the relative magnitude of the difference B as compared to the second threshold value β under (<NUM>) above can be carried out either one after the other or in parallel.

(<NUM>) Next, the control unit <NUM>, as shown in step S12 of <FIG>, based on a combination of the determination results of the relative magnitude of the ratio A as compared to the first threshold value α under (<NUM>) above and the determination results of the relative magnitude of the difference B as compared to the second threshold value β under (<NUM>) above, determines if the substance present on the tooth surface 99a is plaque (or tartar) or not.

Specifically, in the case where the substance present of the tooth surface 99a is plaque (or tartar), for example, first, through the determination according to (<NUM>) above, as shown in <FIG>, the substance present on the tooth surface 99a is identified as being a substance belonging to the group consisting of metal teeth, tartar and plaque. Next, through the determination according to (<NUM>) above, as shown in <FIG>, that substance is identified as being not metal teeth but rather plaque (or tartar). In this example, the plaque-tartar determination rate (the proportion of samples correctly determined to be plaque or tartar from among <NUM> samples of plaque or tartar) was<MAT>.

Furthermore, the false determination rate (the proportion of samples incorrectly determined to be plaque or tartar out of <NUM> samples of enamel, resin, metal teeth and artificial teeth (ceramic or plastic)) was <MAT>.

In this way, determination was successfully performed with good accuracy.

Conversely, in the case where the substance present on the tooth surface 99a is plaque (or tartar), if the determination according to (<NUM>) above is to be performed before the determination according to (<NUM>) above, first, through the determination according to (<NUM>) above, the substance present on the tooth surface is immediately identified as being a substance belonging to the group consisting of tartar and plaque rather than the group consisting of enamel, resin, metal teeth and artificial teeth (ceramic or plastic). In this case, the determination according to (<NUM>) above becomes unnecessary.

Here, with this plaque detecting device <NUM>, unlike the device described in patent document <NUM>, the user does not need to find a "tooth surface without biological deposits" to serve as a basis for comparison, and there is also no need for the calibration-type operation of saving a reference. Therefore, the user can obtain determination results concerning the presence or absence of plaque (or tartar) through a simple operation, for example, by simply arranging the light emitting unit and light receiving unit (including the forward waveguide <NUM> and return waveguide <NUM>) opposite the tooth surface 99a and instructing (switching on) the start of operation of the plaque detecting device <NUM>.

(<NUM>) Subsequently, the control unit <NUM>, acting as an annunciation unit, in this example, displays the determination results concerning the presence or absence of plaque (or tartar) on the display screen of display unit <NUM>, which comprises an LCD. Therefore, the user is able to easily find out if plaque (or tartar) is present on the tooth surface.

It will be noted that, instead of display using a display screen, or in addition thereto, the presence or absence of plaque (or tartar) may also be annunciated by sounding a buzzer or by turning on or flashing a lamp.

In the above example, the first wavelength region, from a lower limit wavelength of <NUM> to an upper limit wavelength of <NUM>, and the second wavelength region, from a lower limit wavelength of <NUM> to an upper limit wavelength of <NUM>, were both defined to be of the bandpass type, but the invention is not limited thereto. It is also possible to define only the lower limit wavelength for the first wavelength region and second wavelength region while leaving the upper limit wavelength undefined (no upper limit), in other words, to define regions of the high-pass type.

<FIG> illustrates, in correspondence with <FIG>, the ratio A' between the first output value ΔOUT1 and second output value ΔOUT2 obtained in step S8 of <FIG> in the case where the first wavelength region and second wavelength region were defined as having lower limit wavelengths of <NUM> and <NUM> respectively, with an undefined upper limit wavelength (no upper limit).

It will be noted that in this example, the ratio A' is defined as <MAT> similarly to the preceding example. As can be seen from <FIG>, for the group consisting of enamel, resin and artificial teeth (ceramic or plastic), the ratio A' is generally less than <NUM>. On the other hand, for the group consisting of metal teeth, tartar and plaque, the ratio A' is generally greater than <NUM>. Therefore, setting the first threshold value α' = <NUM> in advance makes it possible to distinguish the group consisting of enamel, resin and artificial teeth (ceramic or plastic) from the group consisting of metal teeth, tartar and plaque.

Similarly, <FIG> illustrates, in correspondence with <FIG>, the difference B' between the first output value ΔOUT1 and second output value ΔOUT2 obtained in step S10 of <FIG> in the case where a lower limit wavelength of <NUM> and <NUM> has been defined for the first wavelength region and second wavelength region respectively, with the upper limit wavelength being undefined (no upper limit). It will be noted that in this example, for the difference B', the minuend and subtrahend have been reversed relative to the previous example, as follows: <MAT>.

As can bee seen from <FIG>, for the group consisting of metal teeth, the difference B' is generally less than <NUM>,<NUM> (a. On the other hand, for the group consisting of enamel, resin, artificial teeth (ceramic or plastic), tartar and plaque, the difference B' is generally greater than <NUM>,<NUM> (a. Therefore, defining a second threshold value β' = <NUM>,<NUM> (a. ) in advance makes it possible to distinguish the group consisting of metal teeth from the group consisting of enamel, resin, artificial teeth (ceramic or plastic), tartar and plaque.

Therefore, in step S12 of <FIG>, based on a combination of the determination results of the relative magnitude of the ratio A' as compared to the first threshold value α' in <FIG> and the determination results of the relative magnitude of the difference B' as compared to the second threshold value β' in <FIG>, it can be determined if the substance present on the tooth surface 99a is plaque (or tartar) or not.

Specifically, in the case where the substance present of the tooth surface 99a is plaque (or tartar), for example, first, through the determination according to <FIG>, as shown in <FIG>, the substance present on the tooth surface 99a is identified as being a substance belonging to the group consisting of metal teeth, tartar and plaque. Next, through the determination according to <FIG>, as shown in <FIG>, that substance is identified as being not metal teeth but rather plaque (or tartar). In this example, the plaque-tartar determination rate (the proportion of samples correctly determined to be plaque or tartar from among <NUM> samples of plaque or tartar) was<MAT>.

Furthermore, the false determination rate (the proportion of samples incorrectly determined to be plaque or tartar out of <NUM> samples of enamel, resin, metal teeth or artificial teeth (ceramic or plastic)) was<MAT>.

In this way, determination was successfully performed with good accuracy also when the first wavelength region and second wavelength region were of the high-pass type, just as in the case of bandpass type.

<FIG> illustrate the external appearance of an electric tooth brush (the entirety is denoted by symbol <NUM>) of one embodiment incorporating the plaque detecting device of this invention, viewed in each case in perspective from opposite sides. This electric tooth brush <NUM> comprises a head section <NUM> with bristles <NUM> provided thereon, a grip section <NUM> intended to be gripped by hand, and a neck section <NUM> which links the head section <NUM> and grip section <NUM>. The head section <NUM> and neck section <NUM> are integrally configured as a brush member <NUM> removable with respect to the grip section <NUM>. The head section <NUM>, neck section <NUM> and grip section <NUM> are referred to together as main body <NUM>. For convenience of tooth brushing, the main body <NUM> has a slender shape in one direction. It will be noted that a charger <NUM> is illustrated in <FIG>.

<FIG> illustrates the longitudinal cross-section of electric tooth brush <NUM> cut in the lengthwise direction. The grip section <NUM> has a stem <NUM> provided so as to protrude to the neck section <NUM> side from the outer housing of the grip section <NUM>. The stem <NUM> has a tubular shape with a closed tip end. In this example, the neck section <NUM> of the brush member <NUM> is installed by fitting so as to cover this stem <NUM>. The brush member <NUM> is a consumable part, and thus is configured to be removable with respect to the grip section <NUM> so as to allow replacement with a new part. On the surface (bristled surface) 4a on one side of the head section <NUM> of the brush member <NUM>, bristles (brush) <NUM> are provided so as to protrude about <NUM> to <NUM> from the bristled surface 4a, in this example, by flocking. It will be noted that the bristles <NUM> may also be fused or adhered instead of flocking.

A slide switch SW1 for turning the power supply on/off, a push switch SW2 for performing calibration data acquisition, described below, and LED lamps 140A, 140B are provided on the outer surface of the grip section <NUM> of the main body <NUM>. Furthermore, a driving source in the form of motor <NUM> and driving circuit <NUM>, and a power supply section including a rechargeable battery <NUM> and charging coil <NUM>, etc., are provided inside the grip section <NUM>. When charging the rechargeable battery <NUM>, charging can be carried out in noncontact fashion through electromagnetic induction simply by placing the main body <NUM> on the charger <NUM> shown in <FIG>.

As shown in <FIG>, a bearing <NUM> is provided inside the stem <NUM>. The tip end of eccentric shaft <NUM> coupled to rotary shaft <NUM> of motor <NUM> is inserted into the bearing <NUM>. The eccentric shaft <NUM> has a weight <NUM> in the vicinity of the bearing <NUM>, and the center of gravity of the eccentric shaft <NUM> is offset from its center of rotation. When the driving circuit <NUM> supplies a drive signal (for example, a pulse width modulation signal), corresponding to the operating mode, to the motor <NUM>, causing the rotary shaft <NUM> of the motor <NUM> to rotate, the eccentric shaft <NUM> also rotates along with the rotation of rotary shaft <NUM>. Since its center of gravity is offset from its center of rotation, the eccentric shaft <NUM> performs slewing motion about the center of rotation. Thus, the tip end of the eccentric shaft <NUM> repeatedly collides with the inner wall of the bearing <NUM>, causing the bristles <NUM> to vibrate (move) at high speed.

In a specified region 4c substantially in the center of the bristled surface 4a of the head section <NUM>, bristles are omitted. In the inner part of the head section <NUM> corresponding to the specified area 4c, a light emitting unit <NUM>, first light receiving unit <NUM> and second light receiving unit <NUM> are arranged side by side. A portion (outer housing) of the bristled surface 4a of the head section <NUM> including at least the specified region 4c is formed from a transparent resin material (for example, acrylic resin) about <NUM> to <NUM> thick.

As shown in <FIG>, the light emitting unit <NUM> comprises a light emitting diode which irradiates excitation light L having a peak wavelength corresponding to ultraviolet or blue toward the tooth surface 99a through the specified region 4c. This light emitting diode, in this example, is an LED (model number SM0603UV-<NUM>) made by Bivar, Inc. , and emits light L having a peak wavelength of <NUM>.

The first light receiving unit <NUM> comprises a first optical filter member 51F which receives radiated light L' from the tooth surface 99a through the specified region 4c and transmits only the spectral component of a first wavelength region of the radiated light L'; and a first photodiode 51D which receives only the spectral component of said first wavelength region which has been transmitted through the first optical filter member 51F. The first optical filter member 51F, in this example, is a long-pass filter (model number LV0610) made by Asahi Spectra Co. , which allows light with a wavelength of <NUM> or greater to pass through as said first wavelength region, while blocking light with a wavelength under <NUM> (high-pass type). The first photodiode 51D, in this example, consists of a PD (photo diode) (model number NJL6401R-<NUM>) made by New Japan Radio Co. It will be noted that the first optical filter member 51F may also be customized so as to pass through light of wavelengths of <NUM> or greater as the first wavelength region and to block light of wavelength below <NUM>. In the following description, it will be assumed that a filter suitably customized in this manner is used as the first optical filter member 51F.

The second light receiving unit <NUM> comprises a second optical filter member 52F which receives radiated light L' from the tooth surface 99a through the specified region 4c and transmits only the spectral component of a second wavelength region of the radiated light L'; and a second photodiode 52D which receives only the spectral component of said second wavelength region which has been transmitted through the second optical filter member 52F. The second optical filter member 52F, in this example, is a long-pass filter (model number LV0550) made by Asahi Spectra Co. , which allows light with a wavelength of <NUM> or greater to pass through as said second wavelength region, while blocking light with a wavelength under <NUM> (high-pass type). The second photodiode 52D, in this example, just as the first photodiode 51D, consists of a PD (photo diode) (model number NJL6401R-<NUM>) made by New Japan Radio Co.

It will be noted that the light emitting unit <NUM>, first light receiving unit <NUM> and second light receiving unit <NUM> are each electrically connected to driving circuit <NUM> via lead wire <NUM>, contact terminal <NUM> and spring terminal <NUM>, as shown in <FIG>.

The first light receiving unit <NUM> and second light receiving unit <NUM> may also each consist of a phototransistor instead of a photodiode.

Furthermore, on the outer surface of the specified region 4c of the head section <NUM>, along the bristles <NUM> in each of the areas corresponding to the light emitting unit <NUM> and first and second light receiving units <NUM>, <NUM>, plastic optical fibers (POFs) may be vertically arranged for guiding light. In such a case, the tips of the POFs are preferably retracted, for example by about <NUM> from the tips of the bristles <NUM> so that they do not cause interference during tooth brushing.

<FIG> illustrates the block configuration of the control system of the electric tooth brush <NUM>. This electric tooth brush <NUM>, inside the grip section <NUM>, comprises a control unit <NUM> which constitutes the above-described driving circuit <NUM>, a storage unit <NUM>, manipulation unit <NUM>, annunciation unit <NUM> and power supply unit <NUM>. It should be noted that the drive unit <NUM> represents the already described motor <NUM>, rotary shaft <NUM>, eccentric shaft <NUM>, bearing <NUM> and weight <NUM>.

The control unit <NUM> comprises a CPU (central processing unit) which operates based on software, and in addition to driving the motor <NUM>, performs processing for determining the presence or absence of plaque (or tartar) on the tooth surface 99a, and various other processing.

The manipulation unit <NUM> includes the previously described switches SW1, SW2, and functions to allow the user to turn the power supply of the electric tooth brush <NUM> on and off.

The storage unit <NUM>, in this example, comprises an EEPROM (electrically rewritable nonvolatile memory) capable of non-temporary storage of data. The storage unit <NUM> stores a control program for controlling the control unit <NUM>.

The annunciation unit <NUM>, in this example, comprises a buzzer, and annunciates the presence or absence of plaque (or tartar) by sounding the buzzer. It will be noted that, instead of a buzzer, or in addition thereto, the presence or absence of plaque (or tartar) may also be annunciated by turning on or flashing the LED lamps 140A, 140B.

The power supply unit <NUM> includes the previously described rechargeable battery <NUM>, and supplies power (in this example, DC <NUM> V) to the various units inside the electric tooth brush <NUM>.

In <FIG>, the spectral sensitivity of the first light receiving unit <NUM> (first wavelength region is <NUM> or greater) in the head section <NUM> of this electric tooth brush <NUM> is shown as a dashed line, and the spectral sensitivity of the second light receiving unit <NUM> (second wavelength region is <NUM> or greater) is shown as a solid line. In <FIG>, the horizontal axis represents wavelength (units: nm), and the vertical axis represents the relative optical sensitivity (units: %) when the maximum sensitivity is taken as <NUM>%. These spectral sensitivities, unlike the case of the spectrometer <NUM> in the first embodiment, are cut off on the low wavelength side by the first optical filter member 51F and second optical filter member 52F, while on the high wavelength side, the sensitivity is gradually reduced due to the characteristics of the first photodiode 51D and second photodiode 52D. As a result, the first light receiving unit <NUM> and second light receiving unit <NUM> both exhibit maximum sensitivity in the vicinity of the wavelength of <NUM>.

Furthermore, <FIG> show the spectral output of the first light receiving unit <NUM> (first wavelength region is <NUM> or greater) when the substance present on the tooth surface 99a is tartar (and plaque), plaque, enamel, resin, metal teeth and artificial teeth (ceramic), respectively. Similarly, <FIG> show the spectral output of the second light receiving unit <NUM> (second wavelength region is <NUM> or greater) when the substance present on the tooth surface 99a is tartar (and plaque), plaque, enamel, resin, metal teeth and artificial teeth (ceramic), respectively. In <FIG>, the horizontal axis represents wavelength (units: nm), and the vertical axis represents the output intensity in arbitrary units (a. The presence or absence of plaque on the tooth surface 99a is determined, in this electric tooth brush <NUM>, based on such output.

The present inventors evaluated the output level of the first light receiving unit <NUM> and second light receiving unit <NUM> in the above-described electric tooth brush <NUM> using the experimental system shown in <FIG>.

The experimental system shown in <FIG> comprises a light emitting diode <NUM>, plaque substitute sample (porphyrin solution) <NUM>, optical filter member <NUM> and photodiode <NUM>.

Here, the light emitting diode <NUM> consists of an LED (SM0603UV-<NUM>, made by Bivar, Inc. The light emitting diode <NUM> irradiates excitation light L toward the plaque substitute sample <NUM>.

The concentration of the plaque substitute sample (porphyrin solution) <NUM> was variably set between <NUM> and <NUM> (mg/L). This concentration range, from the standpoint of fluorescent light emission, covers a concentration range of <NUM> to <NUM> (mg/L), corresponding to plaque (or tartar) on the tooth surface 99a.

As the optical filter member <NUM>, the same long-pass filter LV0610 and long-pass filter LV0550 that formed part of the first light receiving unit <NUM> and second light receiving unit <NUM> were used in alternation.

The photodiode <NUM> consisted of a PD (mode number NJL6401R-<NUM>) made by New Japan Radio Co. The photodiode <NUM> receives radiated light L" (including fluorescent light) from the plaque substitute sample <NUM> through the optical filter member <NUM>.

Furthermore, in the experimental system shown in <FIG>, the distance between the light emitting diode <NUM> and plaque substitute sample <NUM> was set at <NUM>. The plaque substitute sample <NUM> and optical filter member <NUM> are arranged in contact with each other. The distance between the optical filter member <NUM> and photodiode <NUM> is set at <NUM>. These distance settings correspond to the configuration of the head section <NUM> shown in <FIG> (a configuration in which bristles <NUM> protrude about <NUM> to <NUM> from the bristled surface 4a, and the thickness of the outer housing in the specified region 4c is about <NUM> to <NUM>).

In the experimental system shown in <FIG>, when an energizing current of <NUM> mA was supplied to the light emitting diode <NUM>, an output of photodiode <NUM> was obtained as shown in <FIG>. In <FIG>, the horizontal axis represents the concentration of the plaque substitute sample (porphyrin solution) <NUM>, and the vertical axis represents the output of the photodiode <NUM>. Furthermore, the symbol □ represents data when the optical filter member <NUM> consists of a long-pass filter LV0610 and the first wavelength region is <NUM> or greater. The symbol ◇ represents data when the optical filter member <NUM> consists of long-pass filter LV0550 and the second wavelength region is <NUM> or greater. Furthermore, C1 and C2 represent straight lines fitted to the data of symbol □ and data of symbol ◇ respectively. From this <FIG>, it can be seen that in the concentration range of <NUM> to <NUM> (mg/L) corresponding to plaque (or tartar), photodiode output of approximately <NUM>µA to <NUM>µA is obtained. If this photodiode output is passed, for example, through a resistor of <NUM> kΩ, a voltage drop of <NUM> mV to <NUM> mV is obtained. This is a voltage level that can be evaluated with a common CPU.

The present inventors, based on the output of the first light receiving unit <NUM> (first wavelength region is <NUM> or greater) and second light receiving unit <NUM> (second wavelength region is <NUM> or greater) in the above-described electric tooth brush <NUM>, determined the ratio A' = ΔOUT1/ΔOUT2 using previously described (Formula <NUM>) and determined the difference B' = ΔOUT2 - ΔOUT1 using (Formula <NUM>). The results obtained were as shown in <FIG>. In <FIG>, the bars arrayed horizontally correspond to samples of enamel, metal teeth, artificial teeth (ceramic), tartar (and plaque), and plaque. The vertical axis in <FIG> represents ratio A' as a dimensionless quantity, and the vertical axis in <FIG> represents difference B' in µA units (the same applies to <FIG>, described later). As can be seen from <FIG>, in this example, for all the samples, the ratio A' was close to <NUM>. Namely, the output ΔOUT1 of the first light receiving unit <NUM> and the output ΔOUT2 of the second light receiving unit <NUM> were nearly identical. Furthermore, as can be seen from <FIG>, the difference B' was distributed with nearly the same overlap among the groups consisting respectively of metal teeth, artificial teeth (ceramic), tartar (and plaque), and plaque. With such results, it would be difficult to distinguish and identify substances present on the tooth surface 99a.

The reason for such results may have been the presence of internally reflected light in the head section <NUM>. "Internally reflected light" in the head section <NUM>, as shown in <FIG>, refers to excitation light L from the light emitting unit <NUM> which is reflected by constituent elements of the head section <NUM> and is inputted into the first light receiving unit <NUM> and second light receiving unit <NUM> without reaching the tooth surface. Specifically, the internally reflected light includes light Li2 which is reflected by the boundary surface of the specified region 4c in the bristled surface 4a, light Li3 which is reflected by the wall surfaces inside the head section <NUM> (which holds the light emitting unit <NUM>, first light receiving unit <NUM> and second light receiving unit <NUM>), light Li4 which exits outside through the boundary surface of the specified region 4c of the head section <NUM> but is reflected by the bristles <NUM> and returns, and the like. Moreover, internally reflected light may include light Li1 which enters directly from the light emitting unit <NUM> into first optical filter member 51F and second optical filter member 52F and is inputted into the first light receiving unit <NUM> and second light receiving unit <NUM>. These lights will be hereinafter referred to collectively as internally reflected light Li.

Thus, the present inventors conceived of performing the adjustment of subtracting the components due to internally reflected light Li (which shall be represented by the symbols ΔOUT1z and ΔOUT2z) from the first output value OUT1 and second output value OUT2 in order to increase the accuracy of determination.

Specifically, for example as shown in <FIG>, a light shielding member <NUM> is provided for blocking ambient light Lb around the head section <NUM>. In this example, the light shielding member <NUM> is configured as an openable and closeable box-shaped head cover consisting of a black plastic material. More specifically, the light shielding member <NUM> is made by integrally molding a half-box part <NUM> on the left side in the drawing and a half-box part <NUM> on the right side across one edge <NUM>. The left side half-box part <NUM> comprises a main wall 81b, and an annular circumferential wall <NUM> which extends perpendicularly from the edge of the main wall 81b. Similarly, the right side half-box part <NUM> comprises a main wall 82b and an annular circumferential wall <NUM> which extends perpendicularly from the edge of the main wall 82b. The left side half-box part <NUM> and right side half-box part <NUM> rotate relative to each other about one edge <NUM>, thereby making the light shielding member <NUM> openable and closeable. Furthermore, as shown in <FIG>, the corresponding parts of the circumferential walls <NUM>, <NUM> of the light shielding member <NUM> (in this example, the centers of the bottom part) are provided with semicircular cutouts 81c, 82c for just allowing the neck section <NUM> of the electric tooth brush <NUM> to pass through when the light shielding member <NUM> is closed. Therefore, as shown in <FIG>, when the light shielding member <NUM> is closed so as to cover the head section <NUM> along with the bristles <NUM>, a light shielded state is achieved in which ambient light Lb around the head section <NUM> is substantially blocked.

In the light shielded state in which ambient light Lb has been blocked by the light shielding member <NUM> in this manner, the first output value and second output value (which shall be represented respectively by the symbols OUT1x and OUT2x) are obtained after turning on the light emitting unit <NUM>, and the first output value and second output value (which shall be represented respectively by the symbols OUT1y, OUT2y) are also obtained after turning off the light emitting unit <NUM>. Subsequently, the first output value OUT1y and second output value OUT2y when the light emitting unit <NUM> is turned off are subtracted respectively from the first output value OUT1x and second output value OUT2x when the light emitting unit <NUM> is turned on, to find the components ΔOUT1z, ΔOUT2z due to internally reflected light Li.

More specifically, as shown in Table <NUM> below, in the "light shielded, light emitting unit off" state A1, the first output value OUT1y and second output value OUT2y contain only the noise light component due to light (represented by symbol Lb0) consisting of ambient light Lb which has leaked past the light shielding member <NUM> and reached the head section <NUM>, without any signal light component. In the "light shielded state, light emitting unit on" state A2, the first output value OUT1x and second output value OUT2x contain light Lb0 consisting of ambient light Lb which has leaked past the light shielding member <NUM> and reached the head section <NUM>, without any signal light component, and internally reflected light Li, as noise light components. Therefore, the components ΔOUT1z, ΔOUT2z due to internally reflected light Li can be found based on <MAT> <MAT>.

Here, the amount of light Lb0 resulting from ambient light Lb which has leaked past the light shielding member <NUM> and reached the head section <NUM> is much lower than the amount of ambient light Lb in a state without light shielding, for example, the "during tooth brushing, light emitting unit off" state A3 or the "during tooth brushing, light emitting unit on" state A4, being nearly zero. Therefore, the components ΔOUT1z and ΔOUT2z due to internally reflected light Li can be suitably obtained. As a result, the accuracy of determination can be increased by performing adjustment whereby components ΔOUT1z and ΔOUT2z due to internally reflected light Li in the head section <NUM> are subtracted respectively from the first output value OUT1 and second output value OUT2, as in the operation flow described later.

It will be noted that the light shielding member <NUM> may either be provided as a separate member, separated from the main body <NUM> and charger <NUM>, or may be linked to the charger <NUM>, for example by means of a string (not illustrated), for loss prevention purposes. Furthermore, the light shielding member <NUM> may also be configured so as to cover not only the head section <NUM> of the electric tooth brush <NUM> but also so as to cover, for example, the entirety of the main body <NUM>, or the entirety of the main body <NUM> and charger <NUM>.

The present inventors, after subtracting the components ΔOUT1z and ΔOUT2z due to internally reflected light Li respectively from the first output value OUT1 and second output value OUT2, determined the ratio A' = ΔOUT1 / ΔOUT2 based on previously described (Formula <NUM>) and the difference B' = ΔOUT2 - ΔOUT1 based on (Formula <NUM>). The results shown in <FIG> were thereby obtained. As can be seen from <FIG>, in this example, the ratio A' for groups consisting of enamel was between <NUM> and <NUM>, while the ratio A' for groups consisting of metal teeth, artificial teeth (ceramic), tartar (and plaque), and plaque was generally greater than <NUM>. Therefore, the group consisting of enamel can be identified in distinction to the group consisting of metal teeth, artificial teeth (ceramic), tartar (and plaque), and plaque. Furthermore, as can be seen from <FIG>, the differences B' are distributed with nearly the same overlap among the groups consisting respectively of metal teeth, artificial teeth (ceramic), tartar (and plaque), and plaque. With such results, it would be difficult to distinguish and identify substances present on the tooth surface 99a.

The reason for such results may have been that when computing the difference B' = ΔOUT2 - ΔOUT1 based on (Formula <NUM>), the coefficient of ΔOUT1 and the coefficient of ΔOUT2 were the same. In actuality, in the above example, the amplification factor using by the control unit <NUM> on the first output value ΔOUT1 and second output value ΔOUT2 was in each case <NUM>-fold. The control unit <NUM> was determining the difference between the first output value ΔOUT1 which had been multiplied <NUM>-fold and the second output value ΔOUT2 which had been multiplied <NUM>-fold.

Here, it is preferable, for example, to compute the aforementioned difference B' between the first output value ΔOUT1 and the second output value ΔOUT2 after multiplying the first output value ΔOUT1 and second output value ΔOUT2 respectively by a first coefficient and second coefficient, which differ from each other, so that said difference B' will be different for substances of predetermined different types which may be present on the tooth surface 99a. Specifically, in the example of <FIG>, it is preferable to be able to identify the group consisting of metal teeth and artificial teeth in distinction to the group consisting of tartar (and plaque) and plaque.

Thus, the control unit <NUM>, acting as the signal processing unit, for the processing of multiplying the first output value ΔOUT1 and second output value ΔOUT2 respectively by a first coefficient and second coefficient, which differ from each other, is made to amplify the first output value ΔOUT1 and second output value ΔOUT2 respectively by a first amplification factor and second amplification factor. As a result, the signal processing of multiplying by different coefficients is simplified. In this example, the first amplification factor for the first output value ΔOUT1 is made <NUM>-fold, and the second amplification factor for the second output value ΔOUT2 is made <NUM>-fold. As a result, instead of the ratio A' based on previously described (Formula <NUM>) and difference B' based on (Formula <NUM>), a ratio A" based on the following (Formula <NUM>) and difference B" based on (Formula <NUM>) are computed. <MAT> <MAT>.

<FIG> illustrate the ratio A" obtained based on (Formula <NUM>) and the difference B" obtained based on (Formula <NUM>) for the same samples as in <FIG>. The vertical axis in <FIG> represents ratio A" as a dimensionless quantity, and the vertical axis in <FIG> represents the difference B" in µA units (the same applies for <FIG>, <FIG>, described later). As can be seen from <FIG>, the ratio A" for groups consisting of enamel was <NUM> to <NUM>, while the ratio A" for groups consisting of metal teeth, artificial teeth (ceramic), tartar (and plaque), and plaque was generally greater than <NUM>. Therefore, for example, as shown in <FIG>, by defining a first threshold value α" = <NUM> in advance, it is possible to identify the group consisting of enamel in distinction to the group consisting of metal teeth, artificial teeth (ceramic), tartar (and plaque) and plaque. Furthermore, as can be seen from <FIG>, while the difference B" for groups consisting of enamel, metal teeth and artificial teeth (ceramic) was greater than -<NUM> (µA), the difference B" for groups consisting of tartar (and plaque) and tartar was generally less than -<NUM> (µA). Therefore, for example, as shown in <FIG>, by defining a second threshold value β" = -<NUM> (µA) in advance, it is possible to identify the group consisting of enamel, metal teeth and artificial teeth (ceramic) in distinction to the group consisting of tartar (and plaque) and plaque.

Here, <FIG> shows the first output value ΔOUT1 × <NUM> and second output value ΔOUT2 × <NUM> in µA units for the case where the concentration of the porphyrin solution is varied within the concentration range of <NUM> to <NUM> (mg/L) when the amplification factors used by the control unit <NUM> for the first output value ΔOUT1 and second output value ΔOUT2 were both <NUM>-fold. In this <FIG>, the first output value ΔOUT1 × <NUM> is represented by the symbol □ and the second output value ΔOUT2 × <NUM> is represented by the symbol ◇. Furthermore, C3 and C4 represent straight lines fitted to the data of symbol □ and the data of symbol ◇, respectively. The slope of straight line C3 was <NUM>µA/dec, while the slope of straight line C4 was <NUM>µA/dec (where dec indicates a <NUM>-fold difference in concentration). Furthermore, <FIG> shows the first output value ΔOUT1 × <NUM> and second output value ΔOUT2 × <NUM> in µA units for the case where the concentration of the porphyrin solution was varied within the concentration range of <NUM> to <NUM> (mg/L) when the amplification factors used by the control unit <NUM> for the first output value ΔOUT1 and second output value ΔOUT2 were respectively <NUM>-fold and <NUM>-fold. In this <FIG>, the first output value ΔOUT1 × <NUM> is represented by the symbol □ and the second output value ΔOUT2 × <NUM> is represented by the symbol ◇. Furthermore, C5 and C6 represent straight lines fitted to the data of symbol □ and the data of symbol ◇, respectively. The slope of straight line C5 was <NUM>µA/dec, while the slope of straight line C6 was <NUM>µA/dec. As can be seen from <FIG> here, the effect of having different amplification factors of <NUM>-fold and <NUM>-fold was maintained for up to a <NUM>-fold change in concentration of the porphyrin solution.

This electric tooth brush <NUM> operates as a whole according to the processing flow shown in <FIG>, in response to manipulations by the user.

Specifically, first, the control unit <NUM> turns on the light emitting unit <NUM> (step S53 of <FIG>) and obtains the first output value OUT1x and second output value OUT2x from the first light receiving unit <NUM> and second light receiving unit <NUM> (steps S54 and S55 of <FIG>). Next, the control unit <NUM> turns off the light emitting unit <NUM> (step S56 of <FIG>), and obtains the first output value OUT1y and second output value OUT2y from the first light receiving unit <NUM> and second light receiving unit <NUM> (steps S57 and S58 of <FIG>). Then, as indicated in previously described (Formula <NUM>), the first output value OUT1y and second output value OUT2y when the light emitting unit <NUM> is turned off are subtracted respectively from the first output value OUT1x and second output value OUT2x when the light emitting unit <NUM> is turned on to find the components ΔOUT1z and ΔOUT2z due to internally reflected light Li (step S59 of <FIG>). Namely, <MAT> <MAT> are found. It is thereby possible to suitably obtain the components ΔOUT1z, ΔOUT2z due to internally reflected light Li in the state where ambient light Lb around the head section <NUM> is nearly zero. The control unit <NUM> stores the found components ΔOUT1z, ΔOUT2z due to internally reflected light Li in storage unit <NUM>. It will be noted that steps S51 through S59 of <FIG> as a whole represent the calibration data acquisition processing SP2 for finding the components ΔOUT1z, ΔOUT2z due to internally reflected light Li.

The control unit <NUM> then stands by (step S60 of <FIG>) and waits for the user to turn on the operation start switch SW1.

(<NUM>) Here, as shown in <FIG>, when the user places the bristles <NUM> of the head section <NUM> of the electric tooth brush <NUM> against the tooth surface 99a and turns the operation start switch SW1 on (step S61 of <FIG>), the control unit <NUM> causes the motor <NUM> to rotate, causing the bristles <NUM> to vibrate (move) at high speed (tooth brushing start). Furthermore, the control unit <NUM>, as discussed below, executes processing for determining the presence or absence of plaque (or tartar) on the tooth surface 99a.

(<NUM>) Specifically, the control unit <NUM> turns on the light emitting unit <NUM> (step <NUM> of <FIG>) and causes excitation light L to be irradiated from the light emitting unit <NUM> through the specified region 4c toward the tooth surface 99a, as shown in <FIG>. In response, radiated light L' is radiated from the tooth surface 99a. This radiated light L' passes through the specified region 4c and is received by the first light receiving unit <NUM> and second light receiving unit <NUM>. As a result, the control unit <NUM> acquires the first output value OUT1 and second output value OUT2 from the first light receiving unit <NUM> and second light receiving unit <NUM> respectively, as shown in steps S102 and S103 of <FIG>. The first output value OUT1 and second output value OUT2 contain a component due to ambient light Lb and a component due to internally reflected light Li as noise light components, in addition to the signal light component due to radiated light L', as indicated for state A4 "during tooth brushing, light emitting unit on" in Table <NUM>, discussed previously.

(<NUM>) Subsequently, the control unit <NUM> turns off the light emitting unit <NUM> (step S104 of <FIG>). Thereupon, only the ambient light Lb around the tooth surface 99a (or head section <NUM>) is received by the first light receiving unit <NUM> and second light receiving unit <NUM>, as indicated for state A3 "during tooth brushing, light emitting unit off" in Table <NUM>. As a result, the control unit <NUM> acquires the first output value OUT1b and second output value OUT2b representing components due to ambient light Lb from the first light receiving unit <NUM> and second light receiving unit <NUM>, as shown in steps S105 and S106 of <FIG>. It will be noted that this acquisition of components due to ambient light Lb may be carried out either at start of tooth brushing or during tooth brushing.

(<NUM>) Next, the control unit <NUM>, acting as the first and second zero point adjustment units, as shown in step S107 of <FIG>, performs adjustment by subtracting components due to ambient light Lb around the tooth surface 99a (namely, OUT1b and OUT2b) and components due to internally reflected light Li (namely, ΔOUT1z and ΔOUT2z) from the first output value OUT1 and second output value OUT2. Specifically, the differences <MAT> <MAT> are computed respectively as the adjusted first output value ΔOUT1 and second output value ΔOUT2. It will be noted that the processing from step S104 to S107 in <FIG> is referred to collectively as zero point adjustment processing SP3. Performing this zero point adjustment processing SP3 makes it possible to suitably eliminate the effect of the component due to ambient light Lb and the component due to internally reflected light Li and increase the accuracy of determination of the presence or absence of plaque, described below.

(<NUM>) Next, the control unit <NUM>, as shown in step S108 of <FIG>, multiplies the aforementioned adjusted first output value ΔOUT1 and second output value ΔOUT2 respectively by a first coefficient and second coefficient which differ from each other (namely, in this example, the first output value ΔOUT1 and second output value ΔOUT2 are amplified by a first amplification factor (<NUM>-fold) and second amplification factor (<NUM>-fold which differ from each other), and then computes the ratio A" between them. Specifically, the ratio A" is computed according to previously described (Formula <NUM>) as follows.

Furthermore, the control unit <NUM>, acting as the first determination unit, as shown in step S109 of <FIG>, performs determination of the relative magnitude of this ratio A" as compared to a predetermined first threshold value α".

More specifically, in this example, it will be assumed that the ratio A" between the first output value ΔOUT1 and the second output value ΔOUT2 is as shown by the bar graph in <FIG>. As discussed previously, in the example of <FIG>, the ratio A" for the groups consisting of enamel is between <NUM> and <NUM>, while the ratio A" for groups consisting of metal teeth, artificial teeth (ceramic), tartar (and plaque), and plaque is generally greater than <NUM>. Therefore, setting a first threshold value α" = <NUM> in advance makes it possible to identify the group consisting of enamel in distinction to the group consisting of metal teeth, artificial teeth (ceramic), tartar (and plaque), and plaque.

(<NUM>) Next, the control unit <NUM>, as shown in step S110 of <FIG>, multiplies the aforesaid adjusted first output value ΔOUT1 and second output value ΔOUT2 by coefficients that differ from each other (namely, in this example, the first output value ΔOUT1 and second output value ΔOUT2 are amplified respectively by a first amplification factor (<NUM>-fold) and second amplification factor (<NUM>-fold) which differ from each other), after which the difference B" between them is computed. Specifically, the difference B" is computed according to above-described (Formula <NUM>) as follows.

Furthermore, the control unit <NUM>, acting as the second determination unit, as shown in FIG. S111 of <FIG>, performs determination of the relative magnitude of this difference B" as compared to a predetermined threshold value β".

More specifically, in this example, it will be assumed that the difference B" between the first output value ΔOUT1 and the second output value ΔOUT2 is as shown by the bar graph in <FIG>. As discussed previously, in the example of <FIG>, the difference B" for the groups consisting of enamel metal, teeth and artificial teeth (ceramic) is greater than -<NUM> (µA), while the difference B" for the groups consisting of tartar (and plaque) and plaque is generally less than -<NUM> (µA). Therefore, setting a second threshold value β" = -<NUM> (µA) in advance makes it possible to identify the group consisting of enamel, metal teeth and artificial teeth (ceramic) in distinction to the group consisting of tartar (and plaque) and plaque.

It will be noted that the determination of relative magnitude between the ratio A" and first threshold value α" under (<NUM>) above and the determination of relative magnitude between the difference B" and second threshold value β" under (<NUM>) above may be carried out one after the other or in parallel.

(<NUM>) Next, the control unit <NUM>, acting as a combined determination unit, as shown in step S112 of <FIG>, based on a combination of the determination results of the relative magnitude of ratio A" as compared to the first threshold value α" under (<NUM>) above and the determination results of the relative magnitude of the difference B" as compared to the second threshold value β" under (<NUM>) above, determines if the substance present on the tooth surface 99a is plaque (or tartar) or not.

Specifically, in the case where the substance present on the tooth surface 99a is plaque (or tartar), for example, first, based on the determination according to (<NUM>) above, as shown in <FIG>, the substance present on the tooth surface 99a is identified as being a substance belonging to the group consisting of metal teeth, artificial teeth (ceramic), tartar (and plaque), and plaque. Next, based on the determination according (<NUM>) above, as shown in <FIG>, that substance is identified as being not metal teeth or artificial teeth (ceramic), but rather tartar (and plaque) or plaque. In this example, the plaque-tartar determination rate (the proportion of samples correctly determined to be plaque or tartar from among <NUM> samples of plaque or tartar) was<MAT>.

Furthermore, the false determination rate (the proportion of samples incorrectly determined to be plaque or tartar out of <NUM> samples of enamel, metal teeth or artificial teeth (ceramic)) was <MAT>.

In this way, by performing the zero point adjustment processing SP3 of <FIG> (steps S104 through S107), the effect of the component due to ambient light Lb and the component due to internally reflected light Li can be suitably eliminated and the accuracy of determination of the presence or absence of plaque can be increased.

(<NUM>) Subsequently, as shown in step S113 of <FIG>, the control unit <NUM> annunciates the presence or absence of plaque (or tartar), in this example, by sounding a buzzer using the annunciation unit <NUM>. It will be noted that, instead of sounding a buzzer, or in addition thereto, the presence or absence of plaque (or tartar) may also be annunciated by turning on or flashing the LED lamps 140A, 140B.

Therefore, the user is able to find out the determination results concerning the presence or absence of plaque (or tartar) while brushing teeth. This makes it possible to omit optical fiber, wires or the like extending to the outside from the electric tooth brush <NUM>. Doing so allows the user to easily perform tooth brushing without obstacles when tooth brushing is performed using this electric tooth brush <NUM>.

Furthermore, in this electric tooth brush <NUM>, the first light receiving unit <NUM> and second light receiving unit <NUM> can be configured more simply, without using a spectrometer or the like. Therefore, this electric tooth brush <NUM> can be manufactured compactly and at low cost.

In the above example, for the processing of multiplying the first output value ΔOUT1 and second output value ΔOUT2 respectively by a first coefficient and second coefficient which differ from each other in (Formula <NUM>) and (Formula <NUM>), the control unit <NUM> is made to amplify the first output value ΔOUT1 and second output value ΔOUT2 respectively by a first amplification factor and second amplification factor which differ from each other. However, the invention is not limited thereto. It is also possible to make the light receiving surface area of the first light receiving unit <NUM> and the light receiving surface area of the second light receiving unit <NUM> different from each other such that the difference B" between the first output value ΔOUT1 and the second output value ΔOUT2 will differ for predetermined different types of substances which may be present on the tooth surface 99a. It would thereby be sufficient for the control unit <NUM> to simply find ratio A' of (Formula <NUM>) and difference B' of (Formula <NUM>), instead of ratio A" of (Formula <NUM>) and difference B" of (Formula <NUM>), allowing the signal processing to be simplified. As a result, just as in the example described above, the difference B" between the first output value ΔOUT1 and the second output value ΔOUT2 will differ for predetermined different types of substances which may be present on the tooth surface 99a.

<FIG> shows the external appearance of an electric tooth brush 90A, which is a modification of the electric tooth brush <NUM> described above. Furthermore, <FIG> shows the block configuration of the control system of this electric tooth brush 90A.

This electric tooth brush 90A, as shown in <FIG>, comprises a clock display unit (in this example, consisting of an LCD) for displaying the current time on the surface of the grip section <NUM> (also shown in <FIG>). As shown in <FIG>, the control unit <NUM> comprises a clock <NUM> which counts the current time. The clock display unit <NUM> is made to display the current time counted by the clock <NUM>. In this electric tooth brush 90A, the timing (time) t at which calibration data acquisition processing is to be performed is made settable the user by means of a timer through the manipulation unit <NUM>.

In this electric tooth brush 90A, calibration data acquisition processing (represented by reference symbol SP2') is carried out according to the processing flow shown in <FIG>. It will be noted that, in <FIG>, steps which are the same as steps in <FIG> are assigned the same step numbers.

More specifically, first, as shown in step S51 of <FIG>, the user installs the light shielding member <NUM> on the head section <NUM> of the electric tooth brush 90A as shown in <FIG> to place it into a light shielded state. Next, the user sets the timing (time) t at which calibration data acquisition is to be performed (step S52A of <FIG>). Subsequently, the control unit <NUM> waits until the current time reaches time t based on the output of the clock <NUM> (step S52B of <FIG>).

Once the current time reaches time t (YES in step S52B of <FIG>), the control unit <NUM>, acting as the second zero point adjustment unit, performs the processing of steps S53 through S59 of <FIG> to acquire the components ΔOUT1z and ΔOUT2z due to internally reflected light Li contained in the first output value OUT1 and second output value OUT2. Namely, <MAT> <MAT> are found. It is thereby possible to suitably obtain the components ΔOUT1z, ΔOUT2z due to internally reflected light Li in the state where ambient light Lb around the head section <NUM> is nearly zero. The control unit <NUM> stores the found components ΔOUT1z, ΔOUT2z due to internally reflected light Li in storage unit <NUM>.

Further, as shown in <FIG>, when the user places the bristles <NUM> of the head section <NUM> of the electric tooth brush 90A against the tooth surface 99a and turns the operation start switch SW1 on (step S61 of <FIG>), the control unit <NUM> performs the processing of steps S101 through S112 of <FIG> to determine the presence or absence of plaque (or tartar) on the tooth surface 99a. Then, as shown in step S113 of <FIG>, the control unit <NUM> annunciates the presence or absence of plaque (or tartar), in this example, by sounding a buzzer using the annunciation unit <NUM>.

In this electric tooth brush 90A, just as in electric tooth brush <NUM> described previously, performing the zero point adjustment processing SP3 (steps S104 through S107) of <FIG> makes it possible to suitably eliminate the effect of the component due to ambient light Lb and the component due to internally reflected light Li and increase the accuracy of determination of the presence or absence of plaque.

It will be noted that if the time t set by means of a timer for performing calibration data acquisition processing is at night (for example, <NUM> am), it can be expected that the room in which the electric tooth brush 90A and charger <NUM> are installed will be dark and that there will be little ambient light Lb. In this case, the user can omit the process of installing the light shielding member <NUM> around the head section <NUM> to place it into a light shielded state (step S51 of <FIG>).

Furthermore, the time at which calibration data acquisition processing is to be performed may be set in advance to nighttime (for example, <NUM> am) by default, rather than being set by the user by means of a timer. The need for the user to perform an operation for calibration data acquisition can thereby be eliminated.

Furthermore, the time display unit <NUM> does not need to be provided on the surface of the grip section <NUM>. For example, a time display unit <NUM>' may be provided on the surface of the charger <NUM>, as in electric tooth brush 90A' shown in <FIG>.

<FIG> shows the external appearance of an electric tooth brush 90B, which is a modification of the above-described electric tooth brush <NUM>. Furthermore, <FIG> shows the block configuration of the control system of this electric tooth brush 90B.

This electric tooth brush 90B comprises an illuminance measurement unit <NUM> (in this example, consisting of a photodiode) on the surface of the grip section <NUM>, as shown in <FIG> (also shown in <FIG>). The illuminance measurement unit <NUM> measures and outputs the illuminance due to ambient light Lb around the main body <NUM> (the output representing this illuminance will be represented by the symbol OUTO). The control unit <NUM> is configured to determine whether or not the output OUT0 of illuminance measurement unit <NUM> is below a predetermined illuminance threshold value Lα. In this example, the illuminance threshold value Lα will be assumed to have been set to a level where the electric tooth brush 90B and charger <NUM> have been placed in a room which is dark and where there is little ambient light Lb (for example, Lα = <NUM> lux).

In this electric tooth brush 90B, calibration data acquisition processing (represented by symbol SP2") is performed according to the processing flow shown in <FIG>, under the starting condition that illuminance due to ambient light Lb around the main body <NUM> has fallen below a predetermined illuminance threshold value Lα. It will be noted that in <FIG>, steps which are the same as steps in <FIG> are assigned the same step numbers.

More specifically, first, as shown in step S51' of <FIG>, the control unit <NUM> acquires the output OUT0 of the illuminance measurement unit <NUM>. Next, the control unit <NUM> determines if the output OUT0 of the illuminance measurement unit <NUM> has fallen below the predetermined illuminance threshold value Lα (step S52" of <FIG>). Here, if the output OUT0 which represents illuminance is at or above the illuminance threshold Lα (NO in step S52" of <FIG>), the control unit <NUM> waits until the output OUT0 drops below the illuminance threshold value Lα.

When the output OUT0 of the illuminance measurement unit <NUM> drops below the illuminance threshold value α (YES in step S52" of <FIG>), the control unit <NUM>, acting as the second zero point adjustment unit, performs the processing of steps S53 through S59 of <FIG> and acquires the components ΔOUT1z and ΔOUT2z due to internally reflected light Li contained in the first output value OUT1 and second output value OUT2. Namely, <MAT> <MAT> are found. It is thereby possible to suitably obtain the components ΔOUT1z, ΔOUT2z due to internally reflected light Li in the state where ambient light Lb around the head section <NUM> is low. The control unit <NUM> stores the found components ΔOUT1z, ΔOUT2z due to internally reflected light Li in storage unit <NUM>.

Then, as shown in <FIG>, when the user places the bristles <NUM> of the head section <NUM> of the electric tooth brush 90B against the tooth surface 99a and turns the operation start switch SW1 on (step S61 of <FIG>), the control unit <NUM> performs the processing of steps S101 through S112 of <FIG> to determine the presence or absence of plaque (or tartar) on the tooth surface 99a. Subsequently, as shown in step S113 of <FIG>, the control unit <NUM> annunciates the presence or absence of plaque (or tartar) by sounding a buzzer using the annunciation unit <NUM>.

In this electric tooth brush 90B, just as in electric tooth brush <NUM> described previously, performing the zero point adjustment processing SP3 (steps S104 through S107) in <FIG> makes it possible to suitably eliminate the effect of the component due to ambient light Lb and the component due to internally reflected light Li and increase the accuracy of determination of the presence or absence of plaque. Moreover, unlike in the electric tooth brush 90A described previously, the need to install a light shielding member <NUM> on the head section <NUM> can be eliminated.

It should be noted that the illuminance measurement unit <NUM> does not need to be provided on the surface of the grip section <NUM>. For example, an illuminance measurement unit <NUM>' may be provided on the surface of the charger <NUM>, as in electric tooth brush 90B' shown in <FIG>.

Furthermore, the illuminance measurement unit <NUM> does not need to be provided separately from the first light receiving unit <NUM> and second light receiving unit <NUM>, and may consist of either the first light receiving unit <NUM> or second light receiving unit <NUM> or both. In such a case, illuminance due to ambient light Lb can be measured without increasing the number of constituent parts of the electric tooth brush.

<FIG> shows the external appearance of an electric tooth brush 90C, which is a modification of the above-described electric tooth brush <NUM>. Furthermore, <FIG> shows the block configuration of the control system of this electric tooth brush 90C.

This electric tooth brush 90C comprises the time display unit <NUM> illustrated in <FIG> and the illuminance measurement unit <NUM> shown in <FIG> on the surface of the grip section <NUM>, as shown in <FIG> (also shown in <FIG>). Furthermore, as shown in <FIG>, the control unit <NUM> includes the clock <NUM> shown in <FIG>.

In this electric tooth brush 90C, the control unit <NUM> determines if the current time has reached time t at which calibration data acquisition processing is to be performed based on the output of the clock <NUM>. The control unit <NUM> also determines if the output OUT0 of the illuminance measurement unit <NUM> has dropped below a predetermined illuminance threshold value Lα. The control unit <NUM> then performs calibration data acquisition processing under the starting condition that the current time has reached time t and that illuminance due to ambient light Lb around the main body <NUM> has dropped below a predetermined illuminance threshold value Lα. Namely, it acquires the components ΔOUT1z, ΔOUT2z due to internally reflected light Li in the head section <NUM>.

It is thereby possible to suitably obtain the components AOUT1z, ΔOUT2z due to internally reflected light Li in a state where ambient light Lb around the head section <NUM> is reliably low.

In this electric tooth brush 90C, just as in electric tooth brush <NUM> described previously, performing the zero point adjustment processing SP3 (steps S104 through S107) of <FIG> makes it possible to suitably eliminate the effect of the component due to ambient light Lb and the component due to internally reflected light Li and increase the accuracy of determination of the presence or absence of plaque. Moreover, just as in the previously described electric tooth brush 90B, the need to install a light shielding member <NUM> on the head section <NUM> can be eliminated. This makes it possible to eliminate the need for the user to perform operations for calibration data acquisition.

It should be noted that the time display unit <NUM> and illuminance measurement unit <NUM> do not need to be provided on the surface of the grip section <NUM>. For example, a time display unit <NUM>' and illuminance measurement unit <NUM>' may be provided on the surface of the charger <NUM>, as in electric tooth brush 90C' shown in <FIG>.

In the electric tooth brushes described above, the detection results concerning the presence or absence of plaque were annunciated to the user by means of an annunciation unit <NUM> provided on the main body <NUM>, but the invention is not limited to this. For example, a communication unit capable of wireless or wired communication may be provided in the main body <NUM>, and data representing the detection results concerning the presence or absence of plaque may be outputted via this communication unit to an external smartphone or other device which is essentially a computer device. In this case, detection results concerning the presence or absence of plaque can be displayed on the display screen of that computer device.

Furthermore, in the above embodiments, an electric tooth brush was discussed, but the invention is not limited to this. The plaque detecting device of this invention can also be incorporated into a manual tooth brush.

Claim 1:
A plaque detecting device (<NUM>) which determines the presence or absence of plaque on a tooth surface (99a), comprising:
a light emitting unit (<NUM>) which irradiates ultraviolet or blue excitation light (L) toward said tooth surface (99a), and
a first and second light receiving units (<NUM>, <NUM>) which receive radiated light (L') from said tooth surface (99a) induced by said excitation light (L),
characterized in that
said first light receiving unit (<NUM>) extracts, from said radiated light (L'), a spectral component of a first wavelength region having a predetermined lower limit wavelength and including the wavelength range of fluorescent light specific to plaque, and obtains a first output value (OUT1) corresponding to the intensity of the spectral component of this first wavelength region, and
said second light receiving unit (<NUM>) extracts, from said radiated light (L'), a spectral component of a second wavelength region having a predetermined lower limit wavelength lower than the lower limit wavelength of said first wavelength region and including the wavelength range of fluorescent light specific to enamel, and obtains a second output value (OUT2) corresponding to the intensity of the spectral component of this second wavelength region,
the plaque detecting device (<NUM>) further comprises a control unit (<NUM>) configured to act as:
- a first determination unit (<NUM>) which performs determination of a relative magnitude of a ratio (A) between said first output value (OUT1) and said second output value (OUT2) as compared to a predetermined first threshold value (a), and
- a second determination unit (<NUM>) which performs determination of a relative magnitude of a difference (B) between said first output value (OUT1) and said second output value (OUT2) as compared to a predetermined second threshold value (β), wherein a substance present on a tooth surface (99a) is identified as being or not being plaque based on a combination of the determination results from the first determination unit (<NUM>) and the determination results from the second determination unit (<NUM>).