JPWO2018155289A1 - Dryness sensor - Google Patents

Abstract

The dryness sensor (1) extracts a first bandpass filter (32) that extracts light in a first wavelength band that is highly absorbed by water, and light in a second wavelength band that is less absorbed by water than the first wavelength band. A second band pass filter (42) to be extracted and a first light receiving unit that converts light in the first wavelength band reflected by the object (2) and transmitted through the first band pass filter (32) into a first electric signal. (33), a second light receiving unit (43) that converts light of the second wavelength band reflected by the object (2) and transmitted through the second bandpass filter (42) into a second electrical signal, An arithmetic processing unit (56) for detecting the dryness of the object (2) based on the electrical signal and the second electrical signal. The center wavelength of the first wavelength band and the center wavelength of the second wavelength band are combinations selected from 1400 nm to 1600 nm, and each of the plurality of material candidates constituting the object (2) changes in signal ratio. Is a combination that can be obtained.

Description

  The present invention relates to a dryness sensor.

  Conventionally, for example, an infrared moisture meter that measures the amount of moisture contained in an object using absorption of infrared rays by moisture is known (see, for example, Patent Document 1). If the amount of water contained in the object can be measured, the dryness of the object can also be detected.

Japanese Patent Laid-Open No. 5-118984

  By the way, since the infrared absorption characteristic varies depending on the material of the object, the actual condition is that the detection result of the dryness sensor varies depending on the material. If variations occur in the detection results of the dryness sensor, the dryness detection also lacks accuracy.

  Accordingly, an object of the present invention is to improve the accuracy of dryness detection by suppressing variations in the results of moisture content detection due to differences in materials of objects.

  In order to achieve the above object, a dryness sensor according to one embodiment of the present invention is a dryness sensor that emits light to an object and detects the dryness of the object based on reflected light from the object. A light emitting unit that emits detection light including a first wavelength band in which absorption by water is greater than a predetermined value and reference light including a second wavelength band in which absorption by water is equal to or less than the predetermined value toward an object. A first bandpass filter that extracts light in the first wavelength band, a second bandpass filter that extracts light in the second wavelength band, and detection light reflected by the object and transmitted through the first bandpass filter A first light receiving unit that receives the reference light reflected by the object and transmitted through the second bandpass filter, and a second light receiving unit that converts the light into a second electric signal; Calculate the signal ratio of the first and second electrical signals And a processing unit that detects the dryness of the object based on the change in the signal ratio, and the center wavelength defined by the center value of the wavelength that is half the maximum transmittance of the optical bandpass filter The center wavelength of the first wavelength band and the center wavelength of the second wavelength band are combinations selected from 1400 nm to 1600 nm, and the signal ratio changes in each of a plurality of material candidates constituting the object. Is a combination that can be obtained.

  The dryness sensor according to the present invention can improve the accuracy of dryness detection by suppressing variations in the results of moisture content detection due to differences in the materials of the object.

Drawing 1 is a mimetic diagram showing composition and a subject of a dryness sensor concerning an embodiment. FIG. 2 is a block diagram illustrating a control configuration of the dryness sensor according to the embodiment. FIG. 3 is a diagram showing absorption spectra of moisture and water vapor. FIG. 4 is a diagram showing an absorption spectrum of a plurality of material candidates constituting the object according to the embodiment. FIG. 5 is a graph showing the relationship between the change rate of the normalized signal ratio and the dryness.

  Below, the dryness sensor which concerns on embodiment of this invention is demonstrated in detail using drawing. Note that each of the embodiments described below shows a preferred specific example of the present invention. Therefore, the numerical values, shapes, materials, components, component arrangements, connection forms, and the like shown in the following embodiments are merely examples, and are not intended to limit the present invention. Therefore, among the constituent elements in the following embodiments, constituent elements that are not described in the independent claims showing the highest concept of the present invention are described as optional constituent elements.

  Each figure is a mimetic diagram and is not necessarily illustrated strictly. Therefore, for example, the scales and the like do not necessarily match in each drawing. Moreover, in each figure, the same code | symbol is attached | subjected about the substantially same structure, The overlapping description is abbreviate | omitted or simplified.

(Embodiment)
[Overview]
First, an outline of the dryness sensor according to the embodiment will be described.

  FIG. 1 is a schematic diagram illustrating a configuration of a dryness sensor 1 and an object 2 according to an embodiment. FIG. 2 is a block diagram showing a control configuration of the dryness sensor 1 according to the embodiment.

  The dryness sensor 1 is a dryness sensor that emits light to the object 2 and detects the dryness of the object 2 based on the reflected light from the object 2.

  In the present embodiment, as shown in FIGS. 1 and 2, the dryness sensor 1 detects moisture contained in the object 2 located at a position separated from the space 3.

  The object 2 is, for example, clothing or the like when not particularly limited. Examples of the object 2 other than clothing include bedding such as sheets and pillow covers. For example, by attaching the dryness sensor 1 to a clothes drying device or the like, it is possible to check the drying condition of the clothes. Thereby, generation | occurrence | production of the pain of the clothing by drying too much can be suppressed.

  The space 3 is a space (free space) between the dryness sensor 1 and the object 2. The space 3 is an external space of the casing 10 of the dryness sensor 1.

  As shown in FIGS. 1 and 2, the dryness sensor 1 includes a housing 10, a light emitting unit 20, a first light receiving module 30, a second light receiving module 40, and a signal processing circuit 50.

  Below, each component of the dryness sensor 1 is demonstrated in detail.

[Case]
The housing 10 is a housing that houses the light emitting unit 20, the first light receiving module 30, the second light receiving module 40, and the signal processing circuit 50. The housing 10 is made of a light shielding material. Thereby, it can suppress that external light injects into the housing | casing 10. FIG. Specifically, the housing 10 is formed of a resin material or a metal material that has a light shielding property with respect to light received by the first light receiving module 30 and the second light receiving module 40.

  A plurality of openings are provided on the outer wall of the housing 10, and the lens 21 of the light emitting unit 20, the lens 31 of the first light receiving module 30, and the lens 41 of the second light receiving module 40 are provided in these openings. It is attached.

[Light emitting part]
The light emitting unit 20 emits detection light including a first wavelength band in which absorption by water is larger than a predetermined value and reference light including a second wavelength band in which absorption by water is equal to or less than a predetermined value toward the object 2. It is a light emitting part. Specifically, the light emitting unit 20 includes a lens 21 and a light source 22.

  The lens 21 is a condensing lens that condenses the light emitted from the light source 22 onto the object 2. The lens 21 is a resin convex lens, but is not limited thereto.

  The light source 22 is an LED (Light Emitting Diode) light source that emits continuous light having a first wavelength band that forms detection light and a second wavelength band that forms reference light, and a peak wavelength on the second wavelength band side. Specifically, the light source 22 is an LED light source made of a compound semiconductor.

  FIG. 3 is a diagram showing absorption spectra of moisture and water vapor. As shown in FIG. 3, moisture has absorption peaks at wavelengths of about 1450 nm and about 1940 nm. Water vapor has absorption peaks at wavelengths slightly lower than the absorption peak of moisture, specifically at wavelengths of about 1350 nm to 1400 nm and about 1800 nm to 1900 nm.

  For this reason, a wavelength band with a high water absorbance is selected as the first wavelength band for the detection light, and a wavelength band with a lower water absorbance than the first wavelength band is selected as the second wavelength band for the reference light. select. And the average wavelength of a 2nd wavelength band is made longer than the average wavelength of a 1st wavelength body. Regarding the center wavelength defined by the center value of the wavelength that is half the maximum transmittance of the optical bandpass filter, the center wavelength of the first wavelength band and the center wavelength of the second wavelength band are 1400 nm to 1600 nm. It is a combination selected from. This combination will be described in detail.

  FIG. 4 is a diagram illustrating an absorption spectrum of a plurality of material candidates constituting the object 2 according to the embodiment. FIG. 4 is a quote from 4Pp063, Abstracts of Lecture 2003, General Meeting of Molecular Structures. Here, examples of material candidates include cotton, hemp, PEs (polyester), PET (polyethylene terephthalate), cupra, acetate, PP (polypropylene), rayon, silk, vinylon, and wool. It is also possible to use materials other than these as material candidates for the object 2.

  The center wavelength of the first wavelength band is selected from the range of 1450 nm to 1500 nm. For example, in the present embodiment, the center wavelength of the first wavelength band is 1450 nm, which corresponds to L1 in FIG. On the other hand, the center wavelength of the second wavelength band is selected from a range of 1530 nm or more and 1580 nm or less in which the absorbance of water is smaller than the selection range of the center wavelength of the first wavelength band. For example, in the present embodiment, the center wavelength of the second wavelength band is 1550 nm, which corresponds to L2 in FIG.

  In FIG. 4, when the absorption spectrum of each material candidate is compared between the center wavelength L1 of the first wavelength band and the center wavelength L2 of the second wavelength band, the center wavelength L1 and the center The absorbance is almost equivalent to the wavelength L2. In other words, the difference between the absorbance at the center wavelength L1 and the absorbance at the center wavelength L2 is small in any material candidate. Thus, by using the first wavelength band of the center wavelength L1 as the detection light and using the second wavelength band of the center wavelength L2 as the reference light, it becomes possible to suppress the influence of the difference in the material in the dryness detection. .

  As described above, the selection range of the center wavelength of the first wavelength band is in the range of 1450 nm to 1500 nm, and the selection range of the center wavelength of the second wavelength band is in the range of 1530 nm to 1580 nm. In the case of the combination in the above, the influence of the difference in the material on the dryness detection is acceptable. However, in order to further reduce the influence of the difference in material, the combination of the center wavelength of the first wavelength band and the center wavelength of the second wavelength band is made so that the difference in absorbance between the material candidates is the smallest overall. Just choose. “The difference in absorbance of each material candidate as a whole is the smallest” means, for example, that the difference between the absorbance at the center wavelength of the first wavelength band and the absorbance at the center wavelength of the second wavelength band is the same for all materials. A case where it is obtained by a candidate and the total value becomes the smallest is mentioned.

  Thus, since the light source 22 irradiates light including the first wavelength band and the second wavelength band continuously, the object 2 has detection light including the first wavelength band that is largely absorbed by water, Reference light including a second wavelength band whose absorption by water is smaller than the first wavelength band is irradiated. Furthermore, the influence by the difference in the material of the target object 2 is also suppressed.

[First light receiving module]
As shown in FIG. 1, the first light receiving module 30 includes a lens 31, a first band pass filter 32, and a first light receiving unit 33.

  The lens 31 is a condensing lens for condensing the reflected light reflected by the object 2 on the first light receiving unit 33. The lens 31 is fixed to the housing 10 such that the focal point is located on the light receiving surface of the first light receiving unit 33, for example. The lens 31 is, for example, a resin convex lens, but is not limited thereto.

  The first band pass filter 32 is a band pass filter that extracts light in the first wavelength band from the reflected light. Specifically, the first band pass filter 32 is disposed between the lens 31 and the first light receiving unit 33, and is on the optical path of the reflected light that passes through the lens 31 and enters the first light receiving unit 33. Is provided. The first band pass filter 32 transmits light in the first wavelength band and absorbs light in other wavelength bands.

  The first light receiving unit 33 is a light receiving element that receives light in the first wavelength band reflected by the object 2 and transmitted through the first band pass filter 32 and converts the light into a first electric signal. The first light receiving unit 33 photoelectrically converts the received light in the first wavelength band to generate a first electrical signal corresponding to the amount of light received (that is, intensity). The generated first electric signal is output to the signal processing circuit 50. The first light receiving unit 33 is, for example, a photodiode, but is not limited thereto. For example, the first light receiving unit 33 may be a phototransistor or an image sensor.

[Second light receiving module]
The second light receiving module 40 includes a lens 41, a second band pass filter 42, and a second light receiving unit 43.

  The lens 41 is a condensing lens for condensing the reflected light reflected by the object 2 on the second light receiving unit 43. The lens 41 is fixed to the housing 10 such that the focal point is located on the light receiving surface of the second light receiving unit 43, for example. The lens 41 is, for example, a resin convex lens, but is not limited thereto.

  The second bandpass filter 42 is a bandpass filter that extracts light in the second wavelength band from the reflected light. Specifically, the second band pass filter 42 is disposed between the lens 41 and the second light receiving unit 43, and is on the optical path of the reflected light that passes through the lens 41 and enters the second light receiving unit 43. Is provided. The second bandpass filter 42 transmits light in the second wavelength band and absorbs light in other wavelength bands.

  The second light receiving unit 43 is a light receiving element that receives light in the second wavelength band reflected by the object 2 and transmitted through the second band pass filter 42 and converts the light into a second electric signal. The second light receiving unit 43 photoelectrically converts the received light in the second wavelength band, thereby generating a second electric signal corresponding to the amount of light received (that is, intensity). The generated second electric signal is output to the signal processing circuit 50. The second light receiving unit 43 is a light receiving element having the same shape as the first light receiving unit 33. That is, when the first light receiving unit 33 is a photodiode, the second light receiving unit 43 is also a photodiode.

[Signal processing circuit]
The signal processing circuit 50 controls the lighting of the light source 22 of the light emitting unit 20 and processes the first electric signal and the second electric signal output from the first light receiving unit 33 and the second light receiving unit 43, thereby reducing the dryness. Is a circuit for detecting

  The signal processing circuit 50 may be housed in the housing 10 or may be attached to the outer surface of the housing 10. Alternatively, the signal processing circuit 50 may have a communication function such as wireless communication, and may receive the first electric signal from the first light receiving unit 33 and the second electric signal from the second light receiving unit 43.

  Specifically, as shown in FIG. 2, the signal processing circuit 50 includes a light source control unit 51, a first amplification unit 52, a second amplification unit 53, a first signal processing unit 54, a second signal processing unit 55, and an arithmetic operation. A processing unit 56 is provided.

  The light source control unit 51 includes a drive circuit and a microcontroller. The light source control unit 51 includes a non-volatile memory in which a control program for the light source 22 is stored, a volatile memory that is a temporary storage area for executing the program, an input / output port, a processor for executing the program, and the like.

  The light source control unit 51 controls the light source 22 so that turning on and off of the light source 22 is repeated at a predetermined light emission period. Specifically, the light source control unit 51 outputs a pulse signal having a predetermined frequency (for example, 1 kHz) to the light source 22 to turn on and off the light source 22 at a predetermined light emission cycle.

  The first amplifying unit 52 amplifies the first electric signal output from the first light receiving unit 33 and outputs the amplified first electric signal to the first signal processing unit 54. Specifically, the first amplifying unit 52 is an operational amplifier that amplifies the first electric signal.

  The first signal processing unit 54 is configured by a microcontroller. The first signal processing unit 54 is a non-volatile memory in which a processing program for the first electric signal is stored, a volatile memory that is a temporary storage area for executing the program, an input / output port, a processor for executing the program, and the like Have The first signal processing unit 54 performs a multiplication process with the light emission period of the light source 22 after limiting the passband and correcting the phase delay due to the passband restriction on the first electric signal. The process for the first electric signal is a so-called lock-in amplifier process. Thereby, the noise based on disturbance light can be suppressed from the first electric signal.

  The second amplifying unit 53 amplifies the second electric signal output from the second light receiving unit 43 and outputs the amplified second electric signal to the second signal processing unit 55. Specifically, the second amplifying unit 53 is an operational amplifier that amplifies the second electric signal.

  The second signal processing unit 55 is configured by a microcontroller. The second signal processing unit 55 includes a nonvolatile memory in which a processing program for the second electric signal is stored, a volatile memory that is a temporary storage area for executing the program, an input / output port, a processor for executing the program, and the like. Have The second signal processing unit 55 performs a multiplication process with the light emission period of the light source 22 after performing the passband restriction and correcting the phase delay due to the passband restriction on the second electric signal. The process for the second electric signal is a so-called lock-in amplifier process. Thereby, the noise based on disturbance light can be suppressed from the second electric signal.

  The arithmetic processing unit 56 detects a component included in the object 2 based on the first electric signal output from the first light receiving unit 33 and the second electric signal output from the second light receiving unit 43. Specifically, the arithmetic processing unit 56 detects the dryness of the object 2 based on the ratio (signal ratio) between the voltage level of the first electric signal and the voltage level of the second electric signal. In the present embodiment, the arithmetic processing unit 56 is based on the first electric signal processed by the first signal processing unit 54 and the second electric signal processed by the second signal processing unit 55. The amount of water contained in is detected. And the arithmetic processing part 56 detects the dryness of the target object 2 based on the detected moisture content. A specific dryness detection (calculation) method will be described later.

  The arithmetic processing unit 56 is, for example, a microcontroller. The arithmetic processing unit 56 includes a nonvolatile memory in which a signal processing program is stored, a volatile memory that is a temporary storage area for executing the program, an input / output port, and a processor that executes the program.

  The arithmetic processing unit 56 outputs the detected dryness of the object 2 from the input / output port to an external device. In addition, a display part may be provided in dryness sensor 1 itself, and a dryness may be displayed on the said display part.

[Signal processing (detection processing)]
Next, signal processing (dryness detection processing) by the arithmetic processing unit 56 will be described.

  In the present embodiment, the arithmetic processing unit 56 detects the amount of component included in the target object 2 by comparing the light energy Pd of the detection light included in the reflected light with the light energy Pr of the reference light. The light energy Pd corresponds to the intensity of the first electric signal output from the first light receiving unit 33, and the light energy Pr corresponds to the intensity of the second electric signal output from the second light receiving unit 43.

  The light energy Pd is expressed by the following (Formula 1).

  (Formula 1) Pd = Pd0 × Gd × Rd × Td × Aad × Ivd

  Here, Pd0 is the light energy of the light in the first wavelength band that forms the detection light among the light emitted from the light source 22. Gd is the coupling efficiency (condensing rate) of the light in the first wavelength band to the first light receiving unit 33. Specifically, Gd corresponds to the proportion of the light emitted from the light source 22 that becomes a part of the component that is diffusely reflected by the object 2 (that is, the detection light included in the reflected light).

  Rd is the reflectance of the detection light from the object 2. Td is the transmittance of the detection light by the first band pass filter 32. Ivd is the light receiving sensitivity for the detection light included in the reflected light in the first light receiving unit 33.

  Aad is the absorptance of the detection light by the component (moisture) contained in the object 2, and is expressed by the following (Expression 2).

(Formula 2) Aad = 10 ^{−αa × Ca × D}

  Here, αa is a predetermined extinction coefficient, specifically, the extinction coefficient of the detection light by the component (water). Ca is a volume concentration of a component (moisture) contained in the object 2. D is a contribution thickness that is twice the thickness of the component that contributes to the absorption of the detection light.

  More specifically, in the target object 2 in which moisture is uniformly dispersed, when light enters the target object 2 and is reflected and emitted from the target object 2, Ca is included in the components of the target object 2. This corresponds to the volume concentration. Further, D corresponds to the optical path length from the reflection inside to the emission from the object 2. For example, when the object 2 is a mesh-like solid such as a fiber or a porous solid such as a sponge, it is assumed that light is reflected on the surface of the solid. In this case, for example, Ca is the concentration of water contained in the liquid phase covering the solid. Moreover, D is the contribution thickness converted as an average thickness of the liquid phase which covers the solid substance.

  Therefore, αa × Ca × D corresponds to the amount of component (water content) contained in the object 2. From the above, it can be seen that the light energy Pd corresponding to the intensity of the first electric signal changes according to the amount of water contained in the object 2. In addition, since the light absorbency of moisture is extremely small compared with moisture, it can be disregarded.

  Similarly, the optical energy Pr of the reference light incident on the second light receiving unit 43 is expressed by the following (Expression 3).

  (Formula 3) Pr = Pr0 * Gr * Rr * Tr * Ivr

  In the present embodiment, the absorption rate Aad due to moisture is obtained from the difference between the absorption of the detection light in the first wavelength band by the component (water) contained in the object 2 and the absorption of the reference light in the second wavelength band. . In addition, since it can be considered that reference light is not substantially absorbed by the component contained in the target object 2, the term corresponding to the absorption rate Aad due to moisture is ( It is not included in Equation 3).

  In (Expression 3), Pr0 is the light energy of the light in the second wavelength band that forms the reference light among the light emitted from the light source 22. Gr is the coupling efficiency (condensation rate) of the reference light emitted from the light source 22 to the second light receiving unit 43. Specifically, Gr corresponds to the proportion of the portion of the reference light that becomes part of the component diffusely reflected by the object 2 (that is, the reference light included in the reflected light). Rr is the reflectance of the reference light by the object 2. Tr is the transmittance of the reference light by the second band pass filter 42. Ivr is the light receiving sensitivity with respect to the reflected light of the second light receiving unit 43.

  In the present embodiment, the light emitted from the light source 22, that is, the detection light and the reference light are irradiated coaxially and at the same spot size, so that the detection light coupling efficiency Gd and the reference light coupling efficiency Gr are It becomes almost equal. Further, since the peak wavelengths of the detection light and the reference light are relatively close, the detection light reflectance Rd and the reference light reflectance Rr are substantially equal.

  Therefore, the following (Expression 4) is derived by taking the ratio of (Expression 1) and (Expression 3).

  (Formula 4) Pd / Pr = Z × Aad

  Here, Z is a constant term and is represented by (Equation 5).

  (Formula 5) Z = (Pd0 / Pr0) × (Td / Tr) × (Ivd / Ivr)

  Each of the light energies Pd0 and Pr0 is predetermined as an initial output of the light source 22. Further, the transmittance Td and the transmittance Tr are predetermined by the transmission characteristics of the first band-pass filter 32 and the second band-pass filter 42, respectively. The light receiving sensitivity Ivd and the light receiving sensitivity Ivr are predetermined by the light receiving characteristics of the first light receiving unit 33 and the second light receiving unit 43, respectively. Therefore, Z shown in (Expression 5) can be regarded as a constant.

  The arithmetic processing unit 56 calculates the light energy Pd of the detection light based on the first electric signal, and calculates the light energy Pr of the reference light based on the second electric signal. Specifically, the signal level (voltage level) of the first electric signal corresponds to the light energy Pd, and the signal level (voltage level) of the second electric signal corresponds to the light energy Pr.

  Therefore, the arithmetic processing unit 56 can calculate the absorption rate Aad of moisture contained in the target object 2 based on (Equation 4). Thereby, the arithmetic processing part 56 can calculate a moisture content based on (Formula 2).

  Here, as described above, since the first wavelength band of the center wavelength L1 is the detection light and the second wavelength band of the center wavelength L2 is the reference light, the target is not affected by the difference in material. The water content of the object 2 is detected. In other words, it is possible to accurately detect the moisture content of the object 2 without considering the material of the object 2.

  In addition, although moisture (water vapor | steam) also exists in the space 3, the case where detection light and reference light are absorbed by water vapor | steam is assumed. For example, when the center wavelength of the first wavelength band is selected from the range of 1450 nm to 1500 nm and the center wavelength of the second wavelength band is selected from the range of 1530 nm to 1580 nm, the relationship of the water vapor absorption spectrum of FIG. Therefore, it is also possible to suppress the influence of light absorption by water vapor.

  And the arithmetic processing part 56 detects the dryness of the target object 2 based on a moisture content. For example, when the weight of the object 2 during drying is W1 and the amount of water contained in the object 2 is W2 (corresponding to αa × Ca × D), the dryness Dr is Dr = W1 / (W1 + W2) × 100. [%].

  Further, a table indicating the relationship between the rate of change of the signal ratio (ratio between the voltage level of the first electrical signal and the voltage level of the second electrical signal) and the dryness of the object 2 is calculated without obtaining the moisture content. If stored in advance in the nonvolatile memory of the processing unit 56, the arithmetic processing unit 56 can detect the dryness Dr of the object 2 based on the detected signal ratio and the table.

  For example, the table is defined by a calibration curve indicating the relationship between the change rate of the signal ratio and the dryness Dr. Specifically, the dryness Dr when the weight of the object 2 during drying is W1 and the amount of water contained in the object 2 is W2 (corresponding to αa × Ca × D) is Dr = W1 / (W1 + W2). ) × 100 [%]. The signal ratio R when the first electric signal is S1 and the second electric signal is S2 is represented by R = S1 / S2. When the dryness is 100%, the reference signal ratio r when the first electric signal is s1 and the second electric signal is s2 is represented by r = s1 / s2. The rate of change of the signal ratio is indicated by the ratio (standardized signal ratio) R / r between the signal ratio R and the reference signal ratio r. The calibration curve is obtained from the relationship between the ratio R / r and the dryness Dr.

  FIG. 5 is a graph showing the relationship between the change rate (ΔR / r) of the normalized signal ratio and the dryness Dr. As shown in FIG. 5, when the dryness Dr becomes larger than 60%, the change rate ΔR / r shows a substantially linear change. Therefore, a linear approximation line C between the change rate ΔR / r when the dryness Dr is 60% or more and the dryness Dr is used as a calibration curve. A table may be created based on the calibration curve and stored in advance in the nonvolatile memory of the arithmetic processing unit 56.

[Effects, etc.]
As described above, according to the present embodiment, the dryness sensor 1 emits light to the target object 2 and detects the dryness of the target object 2 based on the reflected light from the target object 2. A light emitting unit 20 that emits detection light including a first wavelength band in which absorption by water is greater than a predetermined value and reference light including a second wavelength band in which absorption by water is equal to or less than a predetermined value toward the object 2; The first bandpass filter 32 that extracts light in the first wavelength band, the second bandpass filter 42 that extracts light in the second wavelength band, and the first bandpass filter 32 that is reflected by the object 2. The first light receiving unit 33 that receives the detected light and converts it into a first electric signal, and the reference light reflected by the object 2 and transmitted through the second bandpass filter 42 is received and converted into a second electric signal. The second light receiving unit 43, the first electric signal and the second electric signal And a calculation processing unit 56 that detects the dryness of the object based on the change in the signal ratio, and the center value of the wavelength that is a half value of the maximum transmittance of the optical bandpass filter The center wavelength of the first wavelength band is selected from the range of 1450 nm to 1500 nm, and the center wavelength of the second wavelength band is selected from the range of 1530 nm to 1580 nm.

  According to this configuration, the center wavelength of the first wavelength band is selected from the range of 1450 nm to 1500 nm, and the center wavelength of the second wavelength band is selected from the range of 1530 nm to 1580 nm. It becomes possible to suppress the influence of the difference. Therefore, the accuracy of dryness detection can be improved.

  In addition, the arithmetic processing unit 56 converts the signal ratio into the dryness based on a calibration curve indicating the relationship between the change rate of the signal ratio and the dryness.

  According to this configuration, since the signal ratio detected by the arithmetic processing unit 56 is converted into the dryness based on the calibration curve, the processing efficiency can be improved compared to the case where the dryness is calculated one by one.

  Further, the dryness Dr when the weight of the object 2 during drying is W1 and the water content of the object 2 is W2 is shown by Dr = W1 / (W1 + W2) × 100 [%] The signal ratio R when one electric signal is S1 and the second electric signal is S2 is indicated by R = S1 / S2, and when the dryness is 100%, the first electric signal is s1, and the second electric signal is The reference signal ratio r when s2 is represented by r = s1 / s2, the rate of change is represented by the ratio R / r of the signal ratio R and the reference signal ratio r, and the calibration curve is represented by the ratio R / r. And the dryness Dr.

  According to this configuration, since the calibration curve is obtained from the relationship between the ratio R / r and the dryness Dr, the dryness Dr can be obtained in consideration of the reference signal ratio r. That is, the dryness Dr can be obtained without knowing the weight W1 when the object 2 is dried.

  The calibration curve is a linear approximation line of the ratio R / r when the dryness Dr is 60% or more and the dryness Dr.

  According to this configuration, since the linear approximation line C between the ratio R / r at a dryness Dr of 60% or more and the dryness Dr is used as a calibration curve, the relationship between the ratio R / r and the dryness Dr is simplified. can do. Therefore, creation of the table can be facilitated.

  In addition, for example, the light emitting unit 20 includes an LED light source (light source 22) that emits continuous light that includes light in the first wavelength band and light in the second wavelength band and has a peak wavelength on the second wavelength band side.

  According to this configuration, it is possible to irradiate light in the first wavelength band and light in the second wavelength band by one light source 22. Further, since the light source 22 is an LED light source, the energy of the first wavelength band and the second wavelength band due to aging changes at the same rate. Thereby, the influence by secular change can be suppressed compared with a heat-type light source. Furthermore, since the light source 22 has the peak wavelength on the second wavelength band side where moisture absorption is small, it is possible to suppress the temperature change of the attenuation rate due to the amount of moisture.

  In addition, for example, the first light receiving unit 33 and the second light receiving unit 43 include light receiving elements of the same type.

  According to this configuration, since the first light receiving unit 33 and the second light receiving unit 43 are provided with light receiving elements having the same shape, the secular change in sensitivity between the first light receiving unit 33 and the second light receiving unit 43 has the same tendency. Thus, the influence of secular change can be suppressed.

(Other)
As mentioned above, although the dryness sensor 1 which concerns on this invention was demonstrated based on said embodiment, this invention is not limited to said embodiment.

  For example, in the above embodiment, the case where the center wavelength of the first wavelength band is selected from the range of 1450 nm to 1500 nm and the center wavelength of the second wavelength band is selected from the range of 1530 nm to 1580 nm is exemplified. explained. However, the center wavelength of the first wavelength band and the center wavelength of the second wavelength band are combinations selected from 1400 nm to 1600 nm, and each of the plurality of material candidates constituting the object 2 has a signal ratio of Any combination that provides a change may be used. At this time, the center wavelength of the second wavelength band is longer than the center wavelength of the first wavelength band. The change of the signal ratio here is a change of the signal ratio with respect to the reference signal ratio. If it is a combination satisfying this, it is possible to suppress the influence of the difference in the material in the dryness detection to an allowable level.

  Moreover, although the case where the light source 22 was an LED light source was illustrated in the said embodiment, a semiconductor laser element or an organic EL element etc. may be sufficient as a light source.

  Moreover, in the said embodiment, the case where the one light source 22 emitted the continuous light containing the 1st wavelength band which makes detection light, and the 2nd wavelength band which makes reference light demonstrated. However, a plurality of light sources may be provided so that one light source emits detection light and another light source emits reference light.

  Moreover, in the said embodiment, the case where the light source control part 51 with which the signal processing circuit 50 is equipped, the 1st signal processing part 54, the 2nd signal processing part 55, and the arithmetic processing part 56 each consist of a dedicated microcontroller is illustrated. Although described, the signal processing circuit may be realized by a single microcontroller as a whole.

  In addition, the embodiment can be realized by arbitrarily combining the components and functions in each embodiment without departing from the scope of the present invention, or a form obtained by subjecting each embodiment to various modifications conceived by those skilled in the art. Forms are also included in the present invention.

DESCRIPTION OF SYMBOLS 1 Dryness sensor 2 Object 20 Light emission part 22 Light source (LED light source)
30 first light receiving module 32 first band pass filter 33 first light receiving unit 40 second light receiving module 42 second band pass filter 43 second light receiving unit 56 arithmetic processing unit

Claims (7)

A dryness sensor that emits light to an object and detects the dryness of the object based on reflected light from the object,
A light emitting unit that emits detection light including a first wavelength band in which absorption by water is greater than a predetermined value and reference light including a second wavelength band in which absorption by water is equal to or less than the predetermined value toward the object;
A first bandpass filter for extracting light in the first wavelength band;
A second bandpass filter for extracting light in the second wavelength band;
A first light receiving unit that receives the detection light reflected by the object and transmitted through the first bandpass filter, and converts the detection light into a first electrical signal;
A second light receiving unit that receives the reference light reflected by the object and transmitted through the second bandpass filter, and converts the reference light into a second electrical signal;
An arithmetic processing unit that calculates a signal ratio between the first electric signal and the second electric signal, and detects a dryness of the object based on a change in the signal ratio;
For the center wavelength defined by the center value of the wavelength, which is half the maximum transmittance of the optical bandpass filter,
The center wavelength of the first wavelength band and the center wavelength of the second wavelength band are combinations selected from 1400 nm to 1600 nm, and each of the plurality of material candidates constituting the object includes the signal ratio. The dryness sensor is a combination that can change The center wavelength of the first wavelength band is selected from the range of 1450 nm to 1500 nm,
The dryness sensor according to claim 1, wherein the center wavelength of the second wavelength band is selected from a range of 1530 nm to 1580 nm. The dryness sensor according to claim 1 or 2, wherein the arithmetic processing unit converts the signal ratio into the dryness based on a calibration curve indicating a relationship between a change rate of the signal ratio and the dryness. The dryness Dr when the weight of the object at the time of drying is W1 and the amount of water contained in the object is W2 is shown by Dr = W1 / (W1 + W2) × 100 [%],
The signal ratio R when the first electric signal is S1 and the second electric signal is S2 is represented by R = S1 / S2.
When the dryness is 100%, the reference signal ratio r when the first electric signal is s1 and the second electric signal is s2, is represented by r = s1 / s2.
The rate of change is indicated by a ratio R / r between the signal ratio R and the reference signal ratio r;
The dryness sensor according to claim 3, wherein the calibration curve is obtained from a relationship between the ratio R / r and the dryness Dr. The dryness sensor according to claim 4, wherein the calibration curve is a linear approximation line between the ratio R / r and the dryness Dr when the dryness Dr is 60% or more. The light emitting unit is an LED light source that emits continuous light having a wavelength band that forms the detection light and a wavelength band that forms the reference light, and a peak wavelength on the second wavelength band side. The dryness sensor according to any one of the above. The dryness sensor according to any one of claims 1 to 6, wherein the first light receiving unit and the second light receiving unit include light receiving elements of the same type.

Images