CN110312924B - Dryness sensor - Google Patents
Dryness sensor Download PDFInfo
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- CN110312924B CN110312924B CN201880012541.2A CN201880012541A CN110312924B CN 110312924 B CN110312924 B CN 110312924B CN 201880012541 A CN201880012541 A CN 201880012541A CN 110312924 B CN110312924 B CN 110312924B
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- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 35
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- 238000010521 absorption reaction Methods 0.000 claims abstract description 24
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- 238000002835 absorbance Methods 0.000 claims description 15
- 238000011088 calibration curve Methods 0.000 claims description 13
- 238000002834 transmittance Methods 0.000 claims description 9
- 238000001035 drying Methods 0.000 claims description 7
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- 229920000728 polyester Polymers 0.000 description 2
- -1 polyethylene terephthalate Polymers 0.000 description 2
- 229920000139 polyethylene terephthalate Polymers 0.000 description 2
- 239000005020 polyethylene terephthalate Substances 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 239000004065 semiconductor Substances 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- 244000025254 Cannabis sativa Species 0.000 description 1
- 235000012766 Cannabis sativa ssp. sativa var. sativa Nutrition 0.000 description 1
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- 229920000742 Cotton Polymers 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
- G01N21/27—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands using photo-electric detection ; circuits for computing concentration
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
- G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
- G01N21/35—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light
- G01N21/3554—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light for determining moisture content
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/02—Details
- H01L31/0232—Optical elements or arrangements associated with the device
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/08—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof in which radiation controls flow of current through the device, e.g. photoresistors
- H01L31/10—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof in which radiation controls flow of current through the device, e.g. photoresistors characterised by at least one potential-jump barrier or surface barrier, e.g. phototransistors
Abstract
A dryness sensor (1) is provided with: a first band-pass filter (32) that extracts light of a first wavelength band in which absorption by water is large; a second band-pass filter (42) that extracts light of a second wavelength band, which is absorbed by water and is smaller than the first wavelength band; a first light receiving unit (33) that converts light of a first wavelength band, which is reflected by the object (2) and transmitted through the first band-pass filter (32), into a first electric signal; a second light receiving unit (43) that converts light of a second wavelength band, which is reflected by the object (2) and has passed through the second band-pass filter (42), into a second electric signal; and an arithmetic processing unit (56) that detects the dryness of the object (2) on the basis of the first electric signal and the second electric signal. The center wavelength of the first wavelength band and the center wavelength of the second wavelength band are a combination selected from 1400nm to 1600nm, and the combination is a combination in which a change in signal ratio is obtained from each of a plurality of material candidates which become the object (2).
Description
Technical Field
The present invention relates to a dryness sensor.
Background
Conventionally, for example, an infrared moisture meter is known which measures the amount of moisture contained in an object by using absorption of infrared light by moisture (for example, see patent document 1). If the amount of water contained in an object can be measured, the dryness of the object can also be detected.
Documents of the prior art
Patent document
Patent document 1: japanese laid-open patent publication No. 5-118984
Disclosure of Invention
Problems to be solved by the invention
However, since the infrared absorption characteristics vary depending on the material of the object, it is practical that a variation occurs in the detection result of the dryness sensor depending on the difference in the material. The detection of dryness also lacks accuracy if dispersion occurs in the detection result of the dryness sensor.
Therefore, an object of the present invention is to suppress dispersion of the result of moisture amount detection due to a difference in material of an object and improve the accuracy of dryness detection.
Means for solving the problems
In order to achieve the above object, a dryness sensor according to an aspect of the present invention is a dryness sensor that emits light to an object and detects dryness of the object based on reflected light from the object, the dryness sensor including: a light emitting unit that emits, toward the object, 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; a first band pass filter for extracting the light of the first wavelength band; a second band-pass filter for extracting the light of the second wavelength band; a first light receiving unit that receives the detection light reflected by the object and transmitted through the first band pass filter, and converts the detection light into a first electric signal; a second light receiving unit that receives the reference light reflected by the object and transmitted through the second band-pass filter, and converts the reference light into a second electric signal; and a calculation processing unit that calculates a signal ratio of the first electrical signal and the second electrical signal, and detects dryness of the object based on a change in the signal ratio; the center wavelength defined by the center value of the wavelength that is the half value of the maximum transmittance of the optical band-pass filter is a combination in which the center wavelength of the first wavelength band and the center wavelength of the second wavelength band are selected from 1400nm or more and 1600nm or less, and the change in the signal ratio is obtained from each of a plurality of material candidates that are the object.
Effects of the invention
The dryness sensor according to the present invention can suppress dispersion of the result of moisture amount detection due to a difference in material of the object, and improve the accuracy of dryness detection.
Drawings
Fig. 1 is a schematic diagram showing a structure of a dryness sensor and an object according to an embodiment.
Fig. 2 is a block diagram showing a control structure of the dryness sensor according to the embodiment.
Fig. 3 is a graph showing the absorption spectra of water and water vapor.
Fig. 4 is a diagram showing absorption spectra of a plurality of material candidates as an object according to the embodiment.
Fig. 5 is a graph showing a relationship between a change rate of the normalized signal ratio and dryness.
Detailed Description
Hereinafter, a dryness sensor according to an embodiment of the present invention will be described in detail with reference to the drawings. The embodiments described below are all preferred specific examples of the present invention. Therefore, the numerical values, shapes, materials, constituent elements, arrangement and connection forms of the constituent elements, and the like shown in the following embodiments are examples, and do not limit the present invention. Thus, among the constituent elements of the following embodiments, constituent elements that are not recited in the independent claims indicating the uppermost concept of the present invention are described as arbitrary constituent elements.
The drawings are schematic and not necessarily strictly illustrated. Therefore, for example, the scales and the like do not always match in each drawing. In the drawings, substantially the same components are denoted by the same reference numerals, and redundant description is omitted or simplified.
(embodiment mode)
[ summary ]
First, an outline of the dryness sensor according to the embodiment will be described.
Fig. 1 is a schematic diagram showing a structure of a dryness sensor 1 according to an embodiment and an object 2. Fig. 2 is a block diagram showing a control configuration of 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 fig. 1 and 2, the dryness sensor 1 detects moisture contained in the object 2 located at a distance from each other with the space 3 therebetween.
The object 2 is not particularly limited, and may be clothing, for example. Examples of the object 2 other than clothes include bed clothes such as a bed sheet and a pillow cover. For example, by attaching the dryness sensor 1 to a clothes drying device or the like, the dryness of clothes can be confirmed. This can suppress the occurrence of damage to clothes due to excessive drying.
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 housing 10 of the dryness sensor 1.
As shown in fig. 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.
Hereinafter, each constituent element of the dryness sensor 1 will be described 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 formed of a light-shielding material. This can suppress the incidence of the external light into the housing 10. Specifically, the housing 10 is formed of a resin material or a metal material having 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 in 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 attached to these openings.
[ light-emitting part ]
The light emitting unit 20 emits, toward the object 2, detection light having a first wavelength band in which the absorption of water is greater than a predetermined value and reference light having a second wavelength band in which the absorption of water is equal to or less than the predetermined value. Specifically, the light emitting unit 20 includes a lens 21 and a light source 22.
The lens 21 is a condenser lens for condensing the light emitted from the light source 22 on the object 2. The lens 21 is a convex lens made of resin, but is not limited thereto.
The Light source 22 is an LED (Light Emitting Diode) Light source that emits continuous Light including a first wavelength band to be detection Light and a second wavelength band to be reference Light, and having 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 graph showing the absorption spectra of water and water vapor. As shown in fig. 3, moisture has absorption peaks at wavelengths of about 1450nm and about 1940 nm. The water vapor has an absorption peak at a wavelength slightly lower than the absorption peak of water, specifically, at a wavelength of about 1350nm to 1400nm or about 1800nm to 1900 nm.
Therefore, a wavelength band having a high water absorbance is selected as a first wavelength band to be used as the detection light, and a wavelength band having a lower water absorbance than the first wavelength band is selected as a second wavelength band to be used as the reference light. The average wavelength of the second wavelength band is made longer than the average wavelength of the first wavelength body. Further, the center wavelength defined by the center value of the wavelength at half the maximum transmittance of the optical band-pass filter is a combination of the center wavelength of the first wavelength band and the center wavelength of the second wavelength band selected from 1400nm to 1600 nm. This combination will be described in detail.
Fig. 4 is a diagram showing absorption spectra of a plurality of material candidates as the object 2 according to the embodiment. FIG. 4 is a reference to the subject matter set 4Pp063 lectured from the general discussion of molecular architecture 2003. Here, examples of the material candidates include cotton, hemp, PEs (polyester), PET (polyethylene terephthalate), cuprammonium fiber, acetate fiber, PP (polypropylene), rayon, silk, vinylon, and wool. Materials other than these materials may be used as candidates for the material for forming the object 2.
The center wavelength of the first wavelength band is selected from the range of 1450nm to 1500 nm. For example, in the present embodiment, the center wavelength of the first wavelength band is 1450nm, and corresponds to L1 in fig. 4. On the other hand, the central wavelength of the second wavelength band is selected from a range of 1530nm to 1580nm, in which the absorbance of water is smaller than the selected range of the central wavelength of the first wavelength band. For example, in the present embodiment, the center wavelength of the second wavelength band is 1550nm, which corresponds to L2 in fig. 4.
In fig. 4, if the absorption spectra of the material candidates are compared at the center wavelength L1 of the first wavelength band and the center wavelength L2 of the second wavelength band, the absorbances of both the center wavelength L1 and the center wavelength L2 are substantially equal for any of the material candidates. In other words, the difference between the absorbance at the center wavelength L1 and the absorbance at the center wavelength L2 is small for any one material candidate. In this way, by using the first wavelength band of the center wavelength L1 as the detection light and the second wavelength band of the center wavelength L2 as the reference light, the influence of the difference in the materials in the dryness detection can be suppressed.
Further, as described above, since the selection range of the center wavelength of the first wavelength band is set to the range of 1450nm to 1500nm, and the selection range of the center wavelength of the second wavelength band is set to the range of 1530nm to 1580nm, the influence of the difference in the materials in the dryness detection can be tolerated by the combination of the ranges. However, in order to further reduce the influence of the difference in the materials, the combination of the center wavelength of the first wavelength band and the center wavelength of the second wavelength band may be selected so that the difference in absorbance of each material candidate as a whole becomes minimum. The "difference in absorbance of each material candidate is minimized as a whole" includes, for example, a case where 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 obtained for all the material candidates, and the total value thereof is minimized.
In this way, since the light source 22 irradiates light continuously including the first wavelength band and the second wavelength band, the object 2 is irradiated with detection light including the first wavelength band in which absorption by water is large and reference light including the second wavelength band in which absorption by water is smaller than the first wavelength band. Further, the influence of the difference in the material of the 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 condenser lens for condensing the reflected light reflected by the object 2 toward 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 convex lens made of resin, but is not limited thereto.
The first band pass filter 32 is a band pass filter that extracts light of the first wavelength band from the reflected light. Specifically, the first bandpass filter 32 is disposed between the lens 31 and the first light receiving unit 33, and is provided on the optical path of the reflected light that has passed through the lens 31 and entered the first light receiving unit 33. The first band pass filter 32 transmits light of the first wavelength band and absorbs light of other wavelength bands.
The first light receiving unit 33 is a light receiving element that receives light of 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 of the first wavelength band to generate a first electric signal corresponding to the amount (i.e., intensity) of the received light. 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 part 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 condenser lens for condensing the reflected light reflected by the object 2 toward 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 convex lens made of resin, but is not limited thereto.
The second band-pass filter 42 is a band-pass filter that extracts light of 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 provided on the optical path of the reflected light that passes through the lens 41 and enters the second light receiving unit 43. The second band-pass filter 42 transmits light of the second wavelength band and absorbs light of other wavelength bands.
The second light receiving unit 43 is a light receiving element that receives the light of 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 of the second wavelength band to generate a second electric signal corresponding to the amount (i.e., intensity) of the received light. 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 part 33 is a photodiode, the second light receiving part 43 is also a photodiode.
[ Signal processing Circuit ]
The signal processing circuit 50 is a circuit that controls the light source 22 of the light emitting unit 20 to be turned on, 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 to detect dryness.
The signal processing circuit 50 may be housed in the casing 10, or may be mounted on the outer surface of the casing 10. Alternatively, the signal processing circuit 50 may have a communication function such as wireless communication, and 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 processing unit 56.
The light source control unit 51 is composed of a drive circuit and a microcontroller. The light source control unit 51 includes a nonvolatile memory in which a control program for the light source 22 is stored, a volatile memory which 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 such that turning on and off of the light source 22 is repeated at a predetermined light emission cycle. Specifically, the light source control unit 51 outputs a pulse signal of a predetermined frequency (for example, 1kHz) to the light source 22, thereby turning on and off the light source 22 at a predetermined light emission period.
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 amplification unit 52 is an operational amplifier that amplifies the first electric signal.
The first signal processing section 54 is constituted by a microcontroller. The first signal processing unit 54 includes a nonvolatile memory in which a processing program for the first electric signal is stored, a volatile memory which is a temporary storage area for executing the program, an input/output port, a processor for executing the program, and the like. The first signal processing unit 54 performs passband limitation on the first electric signal, corrects the phase delay due to the passband limitation, and then performs multiplication with the light emission period of the light source 22. The processing for this first electrical signal is a so-called lock-in amplifier processing. Thus, noise caused by disturbance light can be suppressed from the first electric signal.
The second amplifier 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 amplification unit 53 is an operational amplifier that amplifies the second electric signal.
The second signal processing section 55 is constituted 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 which is a temporary storage area for executing the program, an input/output port, a processor for executing the program, and the like. The second signal processing unit 55 performs passband limitation on the second electric signal, corrects the phase delay due to the passband limitation, and then performs multiplication with the light emission period of the light source 22. The processing for this second electrical signal is a so-called lock-in amplifier processing. This can suppress noise caused by disturbance light 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) of the voltage level of the first electric signal to the voltage level of the second electric signal. In the present embodiment, the arithmetic processing unit 56 detects the amount of water contained in the object 2 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 arithmetic processing unit 56 detects the dryness of the object 2 based on the detected moisture amount. A specific method of detecting (calculating) the dryness is explained 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 which is a temporary storage area for executing the program, an input/output port, a processor for executing the program, and the like.
The arithmetic processing unit 56 outputs the detected dryness of the object 2 to an external device through the input/output port. Further, the dryness sensor 1 itself may be provided with a display unit, and the dryness may be displayed on the display unit.
[ Signal processing (detection processing) ]
Next, the signal processing (the process of detecting the dryness) performed by the arithmetic processing unit 56 will be described.
In the present embodiment, the arithmetic processing unit 56 detects the amount of the component included in the 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 optical energy Pd corresponds to the intensity of the first electrical signal output from the first photoreceiver 33, and the optical energy Pr corresponds to the intensity of the second electrical signal output from the second photoreceiver 43.
The optical energy Pd is represented by (formula 1) below.
(formula 1) Pd (Pd0 × Gd × Rd × Td × Aad × Ivd)
Here, Pd0 is the optical energy of light in the first wavelength band that becomes detection light among the light emitted by the light source 22. Gd is the binding efficiency (light condensing ratio) of light in the first wavelength band to the first photoreceivers 33. Specifically, Gd corresponds to the proportion of a part of the light emitted from the light source 22 that is a component diffusely reflected by the object 2 (i.e., 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. And Ivd is the light receiving sensitivity of the first light receiving unit 33 with respect to the detection light included in the reflected light.
Aad represents the absorbance of the detection light by the component (moisture) contained in the object 2, and is represented by the following (formula 2).
(formula 2) Aad ═ 10－αa×Ca×D
Here, α a is a predetermined absorption coefficient, specifically, an absorption coefficient of the component (moisture) with respect to the detection light. Ca is the volume concentration of a component (moisture) contained in the object 2. D is a contributing thickness 2 times the thickness of a component contributing to the absorption of the detection light.
More specifically, in the object 2 in which the moisture is uniformly dispersed, Ca corresponds to the volume concentration included in the component of the object 2 when light enters the object 2, is internally reflected, and is emitted from the object 2. D corresponds to the optical path length from the inside to the exit from the object 2 after being reflected. For example, when the object 2 is a mesh-like solid material such as a fiber or a porous solid material such as a sponge, it is assumed that light is reflected by the surface of the solid material. In this case, for example, Ca is the concentration of moisture contained in the liquid phase coated with the solid matter. D is a contribution thickness converted as an average thickness of the liquid phase covering the solid matter.
Therefore, α a × Ca × D corresponds to the amount of components (water content) contained in the object 2. As is clear from the above, the optical 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, the absorbance of moisture is extremely small compared to moisture, and therefore, it can be ignored.
Similarly, the optical energy Pr of the reference light incident on the second light receiving unit 43 is represented by the following (equation 3).
(formula 3) Pr-Pr 0 XGrXRr XTr X Ivr
In the present embodiment, the absorbance Aad of moisture is obtained from the difference between the absorption of the detection light of the first wavelength band by the component (moisture) contained in the object 2 and the absorption of the reference light of the second wavelength band. Since the reference light can be considered to be substantially not absorbed by the components contained in the object 2, it is understood that the term corresponding to the absorption rate Aad due to moisture is not included in (formula 3) as compared with (formula 1).
In the formula (3), Pr0 is the optical energy of the light of the second wavelength band which becomes the reference light among the light emitted from the light source 22. Gr is the coupling efficiency (light condensing ratio) of the reference light emitted from the light source 22 to the second light receiving unit 43. Specifically, Gr corresponds to a proportion of a portion of the reference light that is a component diffusely reflected by the object 2 (i.e., 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 denotes the light receiving sensitivity of the second light receiving unit 43 with respect to the reflected light.
In the present embodiment, since the detection light and the reference light, which are the light emitted from the light source 22, are emitted coaxially and in the same spot size, the coupling efficiency Gd of the detection light and the coupling efficiency Gr of the reference light are substantially equal. Since the peak wavelengths of the detection light and the reference light are relatively close to each other, the reflectance Rd of the detection light and the reflectance Rr of the reference light are substantially equal to each other.
Therefore, by taking the ratio of (expression 1) to (expression 3), the following (expression 4) is derived.
(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) x (Ivd/Ivr)
The light energies Pd0 and Pr0 are preset to the initial outputs of the light sources 22. The transmittance Td and the transmittance Tr are preset by the transmittance 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 preset by the light receiving characteristics of the first light receiving unit 33 and the second light receiving unit 43, respectively. Thus, Z represented by (equation 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 electrical signal corresponds to the optical energy Pd, and the signal level (voltage level) of the second electrical signal corresponds to the optical energy Pr.
Therefore, the arithmetic processing unit 56 can calculate the absorptance Aad of the water contained in the object 2 based on (equation 4). Thus, the arithmetic processing unit 56 can calculate the water content based on (equation 2).
Here, as described above, since the first wavelength band of the center wavelength L1 is used as the detection light and the second wavelength band of the center wavelength L2 is used as the reference light, the moisture content of the object 2 is detected without being affected by the difference in the materials. In other words, the moisture content of the object 2 can be accurately detected regardless of the material of the object 2.
Further, moisture (water vapor) is also present in the space 3, and it is also assumed that the detection light and the reference light are absorbed by the water vapor. For example, even when the central wavelength of the first wavelength band is selected from the range of 1450nm to 1500nm, and the central wavelength of the second wavelength band is selected from the range of 1530nm to 1580nm, the influence of the absorption by water vapor can be suppressed from the relationship of the absorption spectrum of water vapor in fig. 3.
The arithmetic processing unit 56 detects the dryness of the object 2 based on the moisture content. For example, if the weight of the object 2 during drying is W1 and the amount of water contained in the object 2 is W2 (corresponding to α a × Ca × D), the dryness Dr can be determined from Dr ═ W1/(W1+ W2) × 100 [% ].
Even if the moisture content is not determined, if a table indicating a relationship between the rate of change of the signal ratio (the ratio of the voltage level of the first electrical signal to the voltage level of the second electrical signal) and the dryness of the object 2 is stored in advance in the nonvolatile memory of the arithmetic 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, a calibration curve representing the relationship between the rate of change in the signal ratio and the dryness Dr is defined. Specifically, the dryness Dr when the weight of the object 2 at the time of drying is W1 and the amount of water contained in the object 2 is W2 (corresponding to α a × Ca × D) is represented by Dr ═ W1/(W1+ W2) × 100 [% ]. The signal ratio R when the first electrical signal is S1 and the second electrical signal is S2 is represented by R — S1/S2. When the dryness is 100%, the reference signal ratio r is represented by r ═ s1/s2, where s1 is the first electrical signal and s2 is the second electrical signal. The rate of change of the signal ratio is represented by a ratio of the signal ratio R to the reference signal ratio R (normalized signal ratio) R/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 rate of change of the normalized signal ratio (Δ R/R) and the dryness Dr. As shown in fig. 5, if the dryness Dr becomes larger than 60%, the rate of change Δ R/R shows a substantially linear change. Therefore, the first approximate straight line C of the change rate Δ R/R with the dryness Dr of 60% or more and the dryness Dr is taken 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.
[ Effect and the like ]
As described above, according to the present embodiment, the dryness sensor 1 that emits light to the object 2 and detects the dryness of the object 2 based on the reflected light from the object 2 includes: a light emitting unit 20 that emits, toward the object 2, 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; a first band pass filter 32 that extracts light of a first wavelength band; a second band-pass filter 42 for extracting light of a second wavelength band; a first light receiving unit 33 that receives the detection light reflected by the object 2 and transmitted through the first band pass filter 32, and converts the light into a first electric signal; a second light receiving unit 43 for receiving the reference light reflected by the object 2 and transmitted through the second band-pass filter 42, and converting the reference light into a second electric signal; and an arithmetic processing unit 56 for calculating a signal ratio of the first electric signal and the second electric signal and detecting the dryness of the object based on a change in the signal ratio; the center wavelength defined by the center value of the wavelength at half maximum transmittance of the optical band-pass filter is selected from the range of 1450nm to 1500nm as the center wavelength of the first wavelength band, and 1530nm to 1580nm as the center wavelength of the second wavelength band.
According to this configuration, since the center wavelength of the first wavelength band is selected from the range of 1450nm to 1500nm, and the center wavelength of the second wavelength band is selected from the range of 1530nm to 1580nm, the influence of the difference in the material in the dryness detection can be suppressed. Therefore, the accuracy of the dryness detection can be improved.
The arithmetic processing unit 56 converts the signal ratio into the dryness degree based on a calibration curve indicating the relationship between the change rate of the signal ratio and the dryness degree.
According to this configuration, the signal ratio detected by the arithmetic processing unit 56 is converted into the dryness based on the calibration curve, so that the processing efficiency can be improved compared with the case where the dryness is calculated one by one.
The dryness Dr when the weight of the object 2 at the time of drying is W1 and the amount of water contained in the object 2 is W2 is represented by Dr ═ W1/(W1+ W2) × 100 [% ]; assuming that the signal ratio R when the first electrical signal is S1 and the second electrical signal is S2 is represented by R — S1/S2; let r be s1/s2 as a reference signal ratio r when the first electric signal is s1 and the second electric signal is s2 when the dryness is 100%; the rate of change is represented by the ratio R/R of the signal ratio R to the reference signal ratio R; the calibration curve is obtained from the relationship between 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 of the object 2 at the time of drying.
The calibration curve is a first approximate straight line of the ratio R/R and the dryness Dr when the dryness Dr is 60% or more.
According to this configuration, the first order approximation straight line C of the ratio R/R and the dryness Dr when the dryness Dr is 60% or more is taken as the calibration curve, so that the relationship between the ratio R/R and the dryness Dr can be simplified. Therefore, the watch can be easily produced.
For example, the light emitting unit 20 includes an LED light source (light source 22) that emits continuous light including light of the first wavelength band and light of the second wavelength band and having a peak wavelength on the second wavelength band side.
According to this configuration, light of the first wavelength band and light of the second wavelength band can be irradiated by 1 light source 22. In addition, since the light source 22 is an LED light source, the energies of the first and second wavelength bands change at the same rate due to aging. This can suppress the influence of aging as compared with a thermal light source. Further, since the light source 22 has the second wavelength band side where the absorption of moisture is small as the peak wavelength, the temperature change of the attenuation factor due to the moisture amount can be suppressed.
For example, the first light receiving unit 33 and the second light receiving unit 43 include light receiving elements of the same type as each other.
According to this configuration, since the first light receiving unit 33 and the second light receiving unit 43 include the same type of light receiving elements, the sensitivity of the first light receiving unit 33 and the sensitivity of the second light receiving unit 43 tend to be the same as each other, and the influence of the aging can be suppressed.
(others)
The dryness sensor 1 according to the present invention has been described above based on the above-described embodiments, but the present invention is not limited to the above-described embodiments.
For example, in the above-described embodiment, a case where the center wavelength of the first wavelength band is selected from the range of 1450nm to 1500nm inclusive, and the center wavelength of the second wavelength band is selected from the range of 1530nm to 1580nm inclusive has been exemplified. However, the center wavelength of the first wavelength band and the center wavelength of the second wavelength band may be a combination selected from 1400nm to 1600nm, and a combination in which a change in the signal ratio is obtained from each of a plurality of material candidates as the object 2. In this case, the center wavelength of the second wavelength band is a longer wavelength than the center wavelength of the first wavelength band. The change in the signal ratio described here is a change in the signal ratio with respect to the reference signal ratio. If the combination satisfies this, the influence of the difference in the material in the dryness detection can be suppressed to an acceptable level.
In the above embodiment, the case where the light source 22 is an LED light source is exemplified, but the light source may be a semiconductor laser element, an organic EL element, or the like.
In the above embodiment, the case where 1 light source 22 emits continuous light including the first wavelength band to be detection light and the second wavelength band to be reference light has been described as an example. However, a plurality of light sources may be provided, with 1 light source emitting detection light and the other light sources emitting reference light.
In the above-described embodiment, the case where the light source control unit 51, the first signal processing unit 54, the second signal processing unit 55, and the arithmetic processing unit 56 provided in the signal processing circuit 50 are each configured by a dedicated microcontroller has been described as an example, but the signal processing circuit may be realized by 1 microcontroller as a whole.
In addition, the present invention includes a form obtained by implementing various modifications that will occur to those skilled in the art to each embodiment, or a form realized by arbitrarily combining the components and functions of each embodiment within a scope that does not depart from the gist of the present invention.
Description of the reference symbols
1 dryness sensor
2 object
20 light emitting part
22 light source (LED light source)
30 first light receiving module
32 first band-pass filter
33 first light receiving part
40 second light receiving module
42 second band-pass filter
43 second light receiving part
56 arithmetic processing unit
Claims (4)
1. A dryness sensor for emitting light to an object and detecting dryness of the object based on reflected light from the object,
the dryness sensor includes:
a light emitting unit that emits, toward the object, 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;
a first band pass filter for extracting the light of the first wavelength band;
a second band-pass filter for extracting the light of the second wavelength band;
a first light receiving unit that receives the detection light reflected by the object and transmitted through the first band pass filter, and converts the detection light into a first electric signal;
a second light receiving unit that receives the reference light reflected by the object and transmitted through the second band-pass filter, and converts the reference light into a second electric signal; and
a calculation processing unit that calculates a signal ratio between the first electric signal and the second electric signal and detects dryness of the object based on a change in the signal ratio;
with respect to the center wavelength defined by the center value of the wavelength that is the half value of the maximum transmittance of the optical band-pass filter,
a center wavelength of the first wavelength band and a center wavelength of the second wavelength band are combinations of changes in the signal ratio obtained from each of a plurality of material candidates as the object, and the center wavelength of the first wavelength band is selected from a range of 1450nm to 1500nm so that a difference between an absorbance at the center wavelength of the first wavelength band and an absorbance at the center wavelength of the second wavelength band among the material candidates becomes minimum as a whole; the central wavelength of the second wavelength range is selected from the range of 1530nm to 1580nm,
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 represented by Dr ═ W1/(W1+ W2) × 100 [% ];
assuming that the signal ratio R when the first electrical signal is S1 and the second electrical signal is S2 is represented by R — S1/S2;
when the dryness is 100%, a reference signal ratio r when the first electric signal is s1 and the second electric signal is s2 is represented by r-s 1/s 2;
the rate of change is represented by a ratio R/R of 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.
2. The dryness sensor according to claim 1,
the calibration curve is a first approximate straight line of the ratio R/R where the dryness Dr is 60% or more and the dryness Dr.
3. Dryness sensor according to claim 1 or 2,
the light emitting unit is an LED light source that emits continuous light having a wavelength band corresponding to the detection light and a wavelength band corresponding to the reference light, and having a peak wavelength on the second wavelength side.
4. Dryness sensor according to claim 1 or 2,
the first light receiving unit and the second light receiving unit include light receiving elements of the same type.
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| JP2017034176 | 2017-02-24 | ||
| JP2017-034176 | 2017-02-24 | ||
| PCT/JP2018/005161 WO2018155289A1 (en) | 2017-02-24 | 2018-02-15 | Dryness sensor |
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| CN110312924A CN110312924A (en) | 2019-10-08 |
| CN110312924B true CN110312924B (en) | 2021-11-23 |
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| JP (1) | JP6712792B2 (en) |
| CN (1) | CN110312924B (en) |
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| JPWO2018155289A1 (en) | 2019-11-07 |
| JP6712792B2 (en) | 2020-06-24 |
| CN110312924A (en) | 2019-10-08 |
| MY193492A (en) | 2022-10-17 |
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