JP2019045186A - Moisture content detection unit - Google Patents

Abstract

To provide a downsized moisture content detection unit.SOLUTION: A moisture detection unit 1 comprises: a light source section 10 which emits to a subject 2, a light including a first wavelength band at which absorption caused by water is greater than a predetermined value and a second wavelength band at which the same is equal to or less than the predetermined value; a first filter 30a through which a light in the first wavelength band passes; a first light receiving element 30b which receives the light reflected by the subject 2 and passed through the first filter 30a, and thereby outputs a detection signal; a second filter 31a through which a light in the second wavelength band passes; a second light receiving element 31b which is connected in series with the first light receiving element 30b, receives the light passed through the second filter 31a, and thereby outputs a reference signal; a signal amplifying section 40 which is connected to a connection point C of the first and the second light receiving elements 30b, 31b, and outputs amplifier signals which the inputted signals are amplified; a lock-in amplifier 50 which extracts predetermined signals from the amplifier signals, and outputs extracted signals; and an A/D converter 60 which converts the extracted signals, and outputs digital signals.SELECTED DRAWING: Figure 3B

Description

  The present invention relates to a water content detection device.

  Conventionally, it has been performed to calculate the water content of an object using near infrared light. For example, in Patent Document 1, a measuring device that irradiates light of three wavelengths from a light source to an object, calculates the water content using light that has been transmitted through the object and is incident on a light detection element (light receiving element) It is disclosed.

JP, 2012-26746, A

  However, in the configuration described in Patent Document 1, three lock-in amplifiers are provided in order to discriminate the light incident on the light detection element for each wavelength from the light source, and there is a problem that the measurement apparatus becomes large.

  Then, an object of the present invention is to provide a miniaturized water content detection device.

  In order to achieve the above object, the water content detection device according to one aspect of the present invention is characterized in that the first wavelength band in which the absorption by water is larger than a predetermined value and the absorption by water is the second or less A semiconductor light emitting element emitting light including a wavelength band of the light source, the light source unit emitting the light which blinks at a predetermined frequency toward the object, and the light beam reflected by the light reflected by the object A first filter for transmitting light of one wavelength band, a first light receiving element for receiving the light of the first wavelength band transmitted through the first filter, and outputting a detection signal, and the object A second filter for transmitting the light of the second wavelength band contained in the light reflected by the light source, and the first light receiving element connected in series with the second filter; A second light receiving element that receives light in a second wavelength band and outputs a reference signal; An amplifier connected to the connection point of the first light receiving element and the second light receiving element and outputting an amplifier signal obtained by amplifying the signal input from the connection point; and the amplifier signal being input; A lock-in amplifier for extracting the signal of the predetermined frequency and outputting an extraction signal, and an A / D converter for receiving the extraction signal, A / D converting the extraction signal, and outputting a digital signal .

  According to the present invention, a miniaturized water content detection device can be realized.

It is a perspective view showing a schematic structure of a clothes drying device concerning an embodiment. It is a control block diagram of the clothes drying device concerning an embodiment. It is a schematic diagram which shows the structure and target object of the water content detection apparatus which concern on embodiment. It is a figure which shows the detailed structure of the broken line area | region of FIG. 3A. It is a figure which shows an example of the relationship between the electric current value which concerns on embodiment, and a moisture content.

  Below, the moisture content detection apparatus which concerns on embodiment of this invention is demonstrated in detail using drawing. Each of the embodiments described below shows a preferable specific example of the present invention. Therefore, numerical values, shapes, materials, components, arrangements of components, connection configurations and the like shown in the following embodiments are merely examples, and are not intended to limit the present invention. Therefore, among the components in the following embodiments, components that are not described in the independent claims indicating the highest concept of the present invention are described as optional components.

  Further, each drawing is a schematic view, and is not necessarily illustrated exactly. Therefore, for example, the scale and the like do not necessarily match in each figure. Further, in each of the drawings, substantially the same configuration is given the same reference numeral, and overlapping description will be omitted or simplified.

  In addition, the description of “almost **” is intended to include what is substantially recognized as **, and for example, when describing “generally rectangular parallelepiped” as an example, not only a perfect rectangular parallelepiped but also a rectangular parallelepiped substantially. It is intended to include what is permitted.

Embodiment
Hereinafter, the moisture content detection device according to the present embodiment will be described with reference to FIGS. 1 to 4. In the present embodiment, an example in which a moisture content detection device is mounted on a clothes drying device will be described as an example.

[1. Composition of clothes dryer]
First, a clothes drying apparatus 100 equipped with the water content detection device 1 according to the present embodiment will be described with reference to FIGS. 1 and 2.

  FIG. 1 is a perspective view showing a schematic configuration of a clothes drying apparatus 100 according to the present embodiment.

  As shown in FIG. 1, the clothes drying apparatus 100 sucks in the room air, dehumidifies it, and blows the air into the room again to dry the object 2 dried in the room. Here, the object 2 is, for example, clothing or the like when not particularly limited. As objects 2 other than clothing, bedding, such as a sheet and a pillow cover, may be mentioned.

  The clothes drying apparatus 100 includes a substantially rectangular main body 101 and a lid 102 that opens and closes at an upper portion of the main body 101. At an upper portion of the main body 101, a blower 103 (see FIG. 2) exposed when the lid 102 is in the open state is provided. The blower unit 103 dries the target 2 present in the space 3 by sending the wind W to the space 3 in the room. Space 3 is a space (free space) between the clothes drying apparatus 100 and the object 2.

  Further, at the upper part of the main body 101, a suction port 104 for taking in the outside air is provided at a position away from the lid portion 102. Inside the main body 101, a flow path for guiding the air from the suction port 104 to the air blowing portion 103 is formed, and a dehumidifying portion 105 (see FIG. 2) for dehumidifying the air is provided for the flow path. There is. Further, the lid portion 102 is provided with a water content detection device 1 for detecting the water content of the object 2.

  FIG. 2 is a control block diagram of the clothes drying apparatus 100 according to the present embodiment. As shown in FIG. 2, the clothes drying apparatus 100 includes a dehumidifying unit 105, a blowing unit 103, a water content detection device 1, and a drying control unit 106.

  The dehumidifying unit 105 is, for example, a vapor compression type heat pump, and dehumidifies air flowing through the flow path of the main body 101. The blower 103 blows the air dehumidified by the dehumidifier 105 toward the space 3. At least one drying condition such as a blowing range, a wind direction, a blowing intensity (wind force), and a blowing temperature in the blowing unit 103 can be changed. Details of the water content detection device 1 will be described later.

  The drying control unit 106 is configured by a microcomputer. The drying control unit 106 is a non-volatile memory in which a general operation program of the clothes drying apparatus 100 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 Etc.

  Specifically, the drying control unit 106 controls the drying condition of the blower unit 103 based on the water content of the object 2 detected by the water content detection device 1. Thus, appropriate drying conditions are selected in accordance with the water content of the object 2. In addition, as shown in FIG. 1, when there are a plurality of objects 2, the wind direction and the like can be adjusted according to the water content of the plurality of objects 2 detected by the water content detection device 1. That is, it is possible to dry the target 2 having a large amount of water from the plurality of targets 2 in a focused manner. Therefore, the clothes drying apparatus 100 can perform more efficient clothes drying. Below, the moisture content detection apparatus 1 with which the clothes drying apparatus 100 is provided is demonstrated.

[1-1. Configuration of Water Content Detection Device]
Next, each component of the moisture content detection device 1 will be described with reference to FIGS. 3A to 4.

  FIG. 3A is a schematic view showing the configuration of the water content detection device 1 according to the present embodiment and the object 2.

  The water content detection device 1 is a water content detection device that emits light to the object 2 and detects the water content of the object 2 based on the light (reflected light) reflected by the object 2. In the present embodiment, as shown in FIG. 1 and FIG. 2, the moisture content detection device 1 detects the moisture content contained in the object 2 arranged with the space 3 therebetween.

  As shown in FIG. 3A, the moisture content detection device 1 includes a light source unit 10, a light source control unit 20, a first light receiving unit 30, a second light receiving unit 31, a signal amplification unit 40, and a lock-in amplifier. 50, an A / D converter 60, and a signal processing unit 70. Although the details will be described later, the moisture content detection device 1 is characterized by the connection between the first light receiving unit 30 and the second light receiving unit 31.

[1-2. Light source section]
The light source unit 10 is a semiconductor light emitting element that emits detection light including a first wavelength band whose absorption by water is larger than a predetermined value, and reference light including a second wavelength band whose absorption by water is smaller than a predetermined value. , And is a light source unit that emits light flickering at a predetermined frequency toward the object 2. An example of the light emitted from the light source unit 10 to the object 2 is shown by the irradiation light L in FIG. 3A. The semiconductor light emitting element is a semiconductor chip in which a semiconductor layer is stacked on a growth substrate and emits near infrared light. In the following, the semiconductor light emitting element is also referred to as a light emitting element.

  Water has high absorption at a wavelength of about 1450 nm and low absorption at a wavelength of about 1300 nm. For this reason, a wavelength band in which the light absorbance of water is high is selected as the first wavelength band forming detection light, and a light absorbance of water is smaller than the first wavelength band as the second wavelength band forming reference light Select a wavelength band. Then, for example, the central wavelength of the first wavelength band is 1450 nm, and the central wavelength of the second wavelength band is 1300 nm.

  As described above, since the light emitting element emits light continuously including the first wavelength band and the second wavelength band, the object 2 is detected to include the first wavelength band in which the absorption by water is large. The light and the reference light including a second wavelength band whose absorption by water is smaller than the first wavelength band are irradiated.

  In the present embodiment, the light source unit 10 includes an LED (Light Emitting Diode) element that emits detection light including a first wavelength band and reference light including a second wavelength band as an example of a semiconductor light emitting element. .

  The light source unit 10 may have a lens (not shown) that condenses the light emitted from the light emitting element on the object 2. For example, although a lens is a resin-made convex lens, it is not restricted to this. In addition, the light source unit 10 may have a scanning unit (not shown) for irradiating the light emitted from the light emitting element to a desired position. For example, as the scanning unit, the light source unit 10 may have a structure for scanning light by adjusting the attitude of the light emitting element, or may have another structure. For example, the scanning unit is controlled by the light source control unit 20. That is, the light source unit 10 may irradiate the object 2 while scanning the light.

  The light emitted from the light source unit 10 to the object 2 may be, for example, light emitted from a light emitting element and reflected by a reflector or the like.

[1-3. Light source control unit]
The light source control unit 20 is a control device that controls the light source unit 10 and causes the light source unit 10 to emit light toward the object 2. The light source control unit 20 controls the light emitting element so that lighting and extinguishing of the light emitting element are repeated in a predetermined light emitting cycle. That is, the light source control unit 20 performs control to blink the light source unit 10 at a predetermined frequency (for example, 1 kHz). Specifically, the light source control unit 20 outputs a pulse signal of a predetermined frequency to the light emitting element to turn on and off the light emitting element at a predetermined light emitting cycle. Further, the light source control unit 20 also outputs the above pulse signal to the lock-in amplifier 50 as a reference signal. The pulse signal is an example of a control signal with which the light source control unit 20 controls the light emission of the light source unit 10. Also, hereinafter, a predetermined frequency that causes the light source unit 10 to blink is also referred to as a light emission frequency.

  In addition, the light source control unit 20 may cause the light source control unit 20 to irradiate light toward the object 2 while scanning the light, for example. The light source control unit 20 scans light from the light emitting element, for example, by controlling the scanning unit and changing the attitude of the light emitting element.

  The light source control unit 20 includes a drive circuit and a microcomputer. The light source control unit 20 includes a light emitting element, a non-volatile memory storing a control program for the scanning unit, a volatile memory as a temporary storage area for executing the program, an input / output port, a processor for executing the program, etc. Have.

[1-4. First and second light receiving units]
Each of the first light receiving unit 30 and the second light receiving unit 31 is a photoelectric conversion unit that receives the reflected light emitted from the light source unit 10 and reflected by the object 2 and converts the light into an electrical signal. An example of light reflected by the object 2 and received by the first light receiving unit 30 and the second light receiving unit 31 is shown as the reflected light R in FIG. 3A. Each of the first light receiving unit 30 and the second light receiving unit 31 photoelectrically converts the light in the received wavelength band to generate an electric signal according to the amount of light received (that is, the intensity).

  Here, the first light receiving unit 30 and the second light receiving unit 31 will be described in detail with reference to FIG. 3B.

  FIG. 3B is a diagram showing a detailed configuration of the broken line area A of FIG. 3A.

  As shown in FIG. 3B, the first light receiving unit 30 includes a first filter 30a and a first light receiving element 30b.

  The first filter 30a is a band pass filter that extracts light of a first wavelength band from the reflected light. Specifically, the first filter 30a is disposed on the incident side of the reflected light with respect to the first light receiving element 30b, and provided on the optical path of the reflected light incident on the first light receiving element 30b. There is. Then, the first filter 30a transmits the light of the first wavelength band, and absorbs or reflects the light of the other wavelength bands. The light in the first wavelength band is shown as the reflected light R1 in FIG. 3B.

  The first light receiving element 30 b is a light receiving element that receives the light of the first wavelength band that is reflected by the object 2 and transmitted through the first filter 30 a and converts the light into a first electric signal. The first light receiving element 30 b photoelectrically converts the received light of the first wavelength band to generate and output a first electric signal according to the amount of light received (that is, the intensity) of the light. The first light receiving element 30b is, for example, a photodiode, but is not limited thereto. For example, the first light receiving element 30b may be a phototransistor or an image sensor. The first electric signal generated and output by the first light receiving element 30b is an example of a detection signal.

  In addition, the first light receiving unit 30 may have a condensing lens (not shown) for condensing the reflected light on the first light receiving element 30b. The lens is, for example, fixed so that the focal point is located on the light receiving surface of the first light receiving element 30b. A lens is arrange | positioned at the incident side of the reflected light of the 1st filter 30a, and is being fixed to the housing | casing of the clothes dryer 100, for example. Although a lens is a resin-made convex lens, for example, it is not restricted to this.

  As described above, the first light receiving unit 30 is a photoelectric conversion unit that receives the detection light reflected by the object 2 and converts the light into a first electric signal.

  As shown in FIG. 3B, the second light receiving unit 31 includes a second filter 31a and a second light receiving element 31b.

  The second filter 31a is a band pass filter that extracts light of a second wavelength band from the reflected light. Specifically, the second filter 31a is disposed on the incident side of the reflected light with respect to the second light receiving element 31b, and is provided on the optical path of the reflected light incident on the second light receiving element 31b. There is. Then, the second filter 31a transmits the light of the second wavelength band, and absorbs or reflects the light of the other wavelength bands. The light in the second wavelength band is shown as the reflected light R2 in FIG. 3B.

  The second light receiving element 31 b is a light receiving element that receives the light of the second wavelength band reflected by the object 2 and transmitted through the second filter 31 a and converts the light into a second electric signal. The second light receiving element 31 b photoelectrically converts the received light of the second wavelength band to generate and output a second electric signal according to the amount (ie, intensity) of light received. The second light receiving element 31 b is a light receiving element having the same shape as the first light receiving element 30 b. That is, when the first light receiving element 30b is a photodiode, the second light receiving element 31b is also a photodiode. The first light receiving element 30b and the second light receiving element 31b may be light receiving elements having the same light receiving sensitivity characteristic. In this case, the same light receiving sensitivity characteristics are intended to include those in which the light receiving sensitivity characteristics are regarded as substantially the same. The second electric signal generated and output by the second light receiving element 31 b is an example of a reference signal.

  In addition, the second light receiving unit 31 may have a condensing lens (not shown) as the first light receiving unit 30 does.

  As described above, the second light receiving unit 31 is a photoelectric conversion unit that receives the reference light reflected by the object 2 and converts the light into a second electric signal.

  With such a configuration, the water content detection device 1 is less susceptible to factors other than the water content of the object 2, such as the influence of the environment of the space 3 for detecting the water content, in the detection of the water content. For example, when the temperature of the space 3 changes, the amount of light received by the light receiving element changes even if the amount of moisture of the object 2 is constant. For example, when the temperature of the space 3 changes, the amount of light received by the first light receiving element 30 b and the second light receiving element 31 b changes in the same manner. Therefore, the temperature change of the space 3 is calculated by calculating the difference or ratio between the first electric signal generated by the first light receiving element 30b and the second electric signal generated by the second light receiving element 31b. The influence can be suppressed. That is, the accuracy of the water content detected by the water content detector 1 is improved.

  Here, the connection relationship between the first light receiving element 30 b and the second light receiving element 31 b will be described. As shown to FIG. 3B, the 1st light receiving element 30b and the 2nd light receiving element 31b are connected in series. Specifically, the anode of the first light receiving element 30b and the cathode of the second light receiving element 31b are connected. The cathode of the first light receiving element 30b is connected to the positive side of the power supply, and the anode of the second light receiving element 31b is connected to the negative side of the power supply. That is, a reverse bias voltage is applied to the first light receiving element 30b and the second light receiving element 31b.

  When light in the first wavelength band is incident on the first light receiving element 30b connected as described above, a first current i1 flows from the positive side of the power supply toward the second light receiving element 31b. The first current i1 is an example of a first electrical signal. When light in the second wavelength band is incident on the second light receiving element 31b, a second current i2 flows from the first light receiving element 30b toward the negative side of the power supply. The second current i2 is an example of a second electrical signal.

  A signal amplifier 40 is connected between the lock-in amplifier 50 and a connection line connecting the anode of the first light receiving element 30 b and the cathode of the second light receiving element 31 b in series. With such a configuration, in the signal amplification unit 40, the difference between the first current i1 generated by the first light receiving element 30b and the second current i2 generated by the second light receiving element 31b. Current is output. The present invention is characterized in that a current of a difference is output to the signal amplification unit 40. In the following, the current of the difference between the first current i1 and the second current i2 is also referred to as a difference current. The differential current is shown at i1-i2 in FIG. 3B. The differential current is an example of a differential signal input to the signal amplification unit 40.

  Here, the differential current will be described with reference to FIG.

  FIG. 4 is a view showing an example of the relationship between the current value and the water content. The alternate long and short dash line in FIG. 4 indicates the first current i1, the broken line indicates the second current i2, and the solid line indicates the differential current. The vertical axis in FIG. 4 indicates the magnitude of the current (current value), and the horizontal axis indicates the amount of water contained in the object 2.

  As shown in FIG. 4, as the amount of water contained in the object 2 increases, the current value of the first current i1 decreases. This is because the light of the first wavelength band is absorbed by water as the amount of water contained in the object 2 increases. On the other hand, regardless of the amount of water contained in the object 2, the second current i2 has a substantially constant current value. This is because light in the second wavelength band is difficult to be absorbed by water. That is, due to the difference in the amount of water contained in the object 2, a difference also occurs in the current value of the difference current which is the difference between the first current i1 and the second current i2. Therefore, depending on the amount of water contained in the object 2, the signal output to the signal amplification unit 40 is different.

  In FIG. 3B, the first light receiving element 30b that receives light in the first wavelength band is connected to the positive side of the power supply, and the second light receiving element 31b that receives light in the second wavelength band is the power supply. Although an example of connection on the negative side is shown, the connection relationship is not limited to this. For example, the first light receiving element 30b that receives light in the first wavelength band is connected to the negative side of the power supply, and the second light receiving element 31b that receives light in the second wavelength band is the positive side of the power supply It may be connected to That is, the first light receiving unit 30 may be connected to the negative side of the power supply, and the second light receiving unit 31 may be connected to the positive side of the power supply.

  In addition, when the light source control unit 20 controls the light source unit 10 to irradiate light while scanning the object 2, the first light receiving unit 30 and the second light receiving unit 31 synchronize with the scanning to detect the object 2. Receive the light reflected by. That is, the first light receiving unit 30 and the second light receiving unit 31 receive the light reflected by the object 2 for each position of the object 2 irradiated with the light from the light source unit 10. Thus, the water content detection device 1 can detect the water content in a wider area. For example, the amount of water can be detected in each of a plurality of ranges or a plurality of objects 2 in the object 2. The light source control unit 20 can specify, for example, the position of the object 2 currently detecting the amount of water (for example, the direction in which the object 2 is viewed from the clothes drying apparatus 100) from the posture of the light emitting element. . Thereby, the drying condition such as the blowing range or the wind direction in the blowing unit 103 can be changed. The detection of the water content will be described later.

[1-5. Signal amplification unit]
Again referring to FIG. 3B, the signal amplification unit 40 is an amplifier that outputs an amplification signal obtained by amplifying the input electric signal at a predetermined amplification rate to the lock-in amplifier 50. For example, the signal amplification unit 40 is a current-voltage conversion circuit having a resistor 41 and an operational amplifier 42. For example, the signal amplification unit 40 outputs a signal corresponding to the difference current to the lock-in amplifier 50. The signal corresponding to the differential current may be, for example, a voltage corresponding to the differential current or a signal obtained by amplifying the differential current. The predetermined amplification factor is a predetermined amplification factor.

  The signal amplification unit 40 is connected to a connection point C of the first light receiving element 30 b and the second light receiving element 31 b. Specifically, one end of the signal amplification unit 40 is connected to a connection line connecting the anode of the first light receiving element 30b and the cathode of the second light receiving element 31b, and the other end is connected to the lock-in amplifier 50 There is. With such a configuration, a differential current that is the difference between the first current i1 and the second current i2 is input to the signal amplification unit 40. The signal amplification unit 40 amplifies the differential current input from the connection point C and outputs the amplified current to the lock-in amplifier 50.

  As described above, the differential current is input to the signal amplification unit 40. For example, a smaller current is input to the signal amplification unit 40 than when only the first current i1 flows. Specifically, the current flowing through the resistor 41 of the signal amplification unit 40 is reduced. When the current flowing through the resistor 41 is small, the resistance value of the resistor 41 can be set large.

  Further, as noise caused by the resistor 41, there is thermal noise. The magnitude of the thermal noise is determined based on the thermal noise current in expressed by the following equation. The thermal noise current in, where k is a Boltzmann constant, T is an absolute temperature, and the resistance value of the resistor 41 is Rf,

で求められる。式１に示すように、抵抗４１の抵抗値Ｒｆを大きくすることで、熱雑音電流ｉｎを小さくすることができる。上記に示すように、信号増幅部４０には差分電流が流れるので、抵抗４１の抵抗値を大きく設定することができ、それにより式１に示すように熱雑音電流ｉｎの値を小さくすることができる。これにより、熱雑音が少ない、つまりノイズの少ない高Ｓ／Ｎの信号を実現することができる。また、信号増幅部４０に入力される差分電流は、例えば第一の受光素子３０ｂで生成された第一の電流ｉ１より小さい電流である。そのため、第一の受光素子３０ｂで生成された第一の電流ｉ１が信号増幅部４０に入力されている場合に比べ、水分量検出装置１は高ダイナミックレンジを実現することができる。

It is determined by As shown in Equation 1, the thermal noise current in can be reduced by increasing the resistance value Rf of the resistor 41. As described above, since the differential current flows in the signal amplification unit 40, the resistance value of the resistor 41 can be set large, whereby the value of the thermal noise current in can be reduced as shown in equation 1. it can. This makes it possible to realize a high S / N signal with less thermal noise, that is, less noise. The differential current input to the signal amplification unit 40 is, for example, a current smaller than the first current i1 generated by the first light receiving element 30b. Therefore, as compared with the case where the first current i1 generated by the first light receiving element 30b is input to the signal amplification unit 40, the moisture content detection device 1 can realize a high dynamic range.

[1-6. Lock-in amplifier]
Referring again to FIG. 3A, lock-in amplifier 50 receives the amplification signal output from signal amplification unit 40, and extracts an extraction signal obtained by extracting a signal of a predetermined frequency (for example, light emission frequency) from the amplification signal. This is a circuit that outputs to the A / D converter 60. As shown in FIG. 3A, the lock-in amplifier 50 includes a band pass filter 51, a mixer 52, and a low pass filter 53.

  The band pass filter 51 is a filter for suppressing the noise component contained in the amplifier signal. By arranging the band pass filter 51 between the signal amplification unit 40 and the mixer 52, an amplifier signal in which noise components outside the pass band of the band pass filter 51 are suppressed is input to the mixer 52. The band pass filter 51 is realized by, for example, a circuit using an RLC circuit or an operational amplifier. The noise is, for example, noise due to disturbance light such as illumination light.

  The mixer 52 is a circuit that extracts synchronized signal components of two signals from the amplifier signal that has passed through the band pass filter 51 and the pulse signal that is output from the light source control unit 20 to the mixer 52. The mixer 52 can extract a signal component synchronized with the pulse signal, that is, a signal component in the same phase, from the amplifier signal including noise. That is, the mixer 52 can further suppress the noise included in the amplifier signal.

  The low pass filter 53 is a filter for removing an AC component from the signal component extracted by the mixer 52. The low pass filter 53 is realized by, for example, a circuit using an RC circuit or an operational amplifier.

  The process by the lock-in amplifier 50 as described above is a so-called lock-in amplifier process. Thereby, noise components such as disturbance light included in the amplifier signal amplified by the signal amplifier 40 can be suppressed. That is, by providing the lock-in amplifier 50, it is possible to extract a signal of high signal-to-noise ratio from the electric signal including noise. Also, since noise components can be suppressed before the signal is input to A / D converter 60, the signal input to A / D converter 60 exceeds the dynamic range of A / D converter 60. Can be suppressed. The lock-in amplifier 50 has a function similar to that of a narrow-band band pass filter that extracts a specific frequency from the received light signal (extracts only the frequency components of light on and off of the light emitted from the light source unit 10).

  The pass band of the low pass filter 53 is a fixed band. For example, the cutoff frequency of the low-pass filter 53 is the center frequency of the signal whose center frequency is the light ON / OFF frequency (for example, 1 kHz) of the light emitted from the light source unit 10 and the bandwidth for passing the signal. It is decided appropriately according to

[1-7. A / D converter]
The A / D converter 60 is a circuit that receives the extraction signal lock-in-amplified by the lock-in amplifier 50, A / D converts the extraction signal, and outputs a digital signal to the signal processing unit 70. .

[1-8. Signal processing unit]
The signal processing unit 70 is a processing unit that receives the digital signal converted by the A / D converter 60 and performs signal processing on the digital signal. The signal processing unit 70 has a non-volatile memory in which a processing program for digital signals 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 signal processing unit 70 converts the digital signal into the amount of water, for example, by calculating a predetermined constant for the signal intensity indicated by the digital signal. For example, the predetermined constant means the signal intensity indicated by the light of the first wavelength band forming the detection light and the light of the second wavelength band forming the reference light emitted by the light source unit 10, the first filter 30a and the second Of the first filter 31a and the light receiving characteristics of the first light receiving element 30b and the second light receiving element 31b. In addition, at least one of addition, subtraction, multiplication and division is performed in the operation. Further, the processing program for the digital signal stored in the non-volatile memory includes the above-mentioned predetermined constant. A plurality of predetermined constants may be stored.

  Here, as a comparative example, when the digital signal based on the first current and the digital signal based on the second current are respectively input to the signal processing unit, the signal processing unit uses the two digital signals. It is necessary to perform signal processing. For example, the signal processing unit needs to perform signal processing to calculate the difference or ratio between two digital signals. On the other hand, in the present invention, the digital signal input to the signal processing unit 70 is a signal generated based on the differential current. Therefore, the signal processing unit 70 does not need to perform the signal processing for calculating the difference or the ratio as described above. That is, the moisture content detection device 1 can reduce the processing amount of the signal processing performed by the signal processing unit 70.

[2. effect]
The water content detection device 1 according to the present embodiment emits light including a first wavelength band in which the absorption by water is larger than a predetermined value, and a second wavelength band in which the absorption by water is smaller than the predetermined value. And a light source unit 10 for emitting light flickering at a predetermined frequency toward the object 2, and transmitting light of a first wavelength band included in the light reflected by the object 2 It is included in the first filter 30a and the first light receiving element 30b that receives the light of the first wavelength band transmitted through the first filter 30a and outputs a detection signal, and the light reflected by the object 2 The second filter 31a that transmits the light of the second wavelength band and the first light receiving element 30b are connected in series, and receive the light of the second wavelength band transmitted through the second filter 31a, A second light receiving element 31b for outputting a reference signal, a first light receiving element 30b, and A signal amplification unit 40 is connected to a connection point of the second light receiving element 31b and outputs an amplification signal obtained by amplifying the signal input from the connection point C, and an amplification signal is input. A lock-in amplifier 50 that extracts a signal and outputs an extraction signal, and an A / D converter 60 that receives the extraction signal, A / D converts the extraction signal, and outputs a digital signal.

  As a result, even if the two light receiving elements of the first light receiving element 30 b and the second light receiving element 31 b are provided, one signal (specifically, a differential current) is output to the signal amplification unit 40. That is, the moisture content detection device 1 does not have to include a circuit such as the lock-in amplifier 50 for each wavelength band or each light receiving element. Therefore, the water content detection device 1 according to the present embodiment can be miniaturized even when two light receiving elements are provided. Further, since the number of lock-in amplifiers 50 can be reduced, cost reduction of the water content detection device 1 can be realized.

  The first light receiving element 30b and the second light receiving element 31b are light receiving elements having the same light receiving sensitivity characteristic.

  Thereby, the moisture content detection device 1 can be realized using two light receiving elements having the same light receiving sensitivity characteristic.

  In addition, the light source unit 10 irradiates light while scanning.

  Thereby, the water content can be detected in a plurality of ranges of the object 2 or a plurality of objects 2. Therefore, the drying control unit 106 can efficiently perform drying, such as drying mainly at a position where the amount of water is large, based on the detection result.

  In addition, the semiconductor light emitting element is an LED element.

  Thereby, the moisture content detection device 1 can be realized using the LED elements that can be turned on and off corresponding to the light emission cycle of lighting and off controlled by the light source control unit 20.

(Other embodiments)
As mentioned above, although the moisture content detection apparatus 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, an example in which the water content detection device 1 is mounted on the clothes drying device 100 has been described as an example, but the water content detection device 1 is mounted on electrical devices other than the clothes drying device 100 It is also good. For example, it may be used for an electrical device used in an indoor environment. For example, the apparatus may be used in an apparatus used for blowing air to dry an object (e.g., a floor of a bathroom) such as a bathroom dryer.

  In the above embodiment, although the example in which the light source unit 10 includes the LED element has been described, the light source unit 10 is a light source other than the LED element if it can be turned on and off in the light emission cycle controlled by the light source control unit 20 May be included. For example, the light source unit 10 may have a semiconductor laser element or an organic EL element.

  In the above embodiment, the light source control unit 20 controls the light emission cycle for turning on and off the light emitting element and an example of controlling the attitude of the light emitting element, but the control by the light source control unit 20 is not limited thereto. For example, the light source control unit 20 may control the intensity of light emitted from the light emitting element by controlling the amount of current supplied to the light emitting element.

  Further, in the above embodiment, an example in which the moisture content detection device 1 is integrally mounted on the clothes drying device 100 has been described, but the moisture content detection device is a dedicated device. It may be an attachable configuration.

  In the above embodiment, the water content detection device 1 receives the light reflected by the object 2 and detects the water content. However, the light transmitted through the object 2 is received, and the water content is detected. The amount may be detected.

  Moreover, although the light source part 10 demonstrated the example comprised with one type of light emitting element in the said embodiment, it is not limited to this. For example, the light source unit 10 may have a first light emitting element that emits light of a first wavelength band and a second light emitting element that emits light of a second wavelength band. Furthermore, only the first light receiving element receives the light emitted from the first light emitting element and reflected by the object 2, and the light emitted from the second light emitting element and reflected by the object 2 is received from the second light receiving element When only the element has a structure for receiving light, the moisture content detection device 1 may not include the first filter 30a and the second filter 31a.

  Moreover, although the signal processing part 70 demonstrated the example which detects a moisture content by computing a predetermined constant to the signal intensity which a digital signal shows in the said embodiment, detection of a moisture content is not limited to this. For example, the non-volatile memory of the signal processing unit 70 stores a table in which the signal intensity indicated by the digital signal and the moisture content are associated, and the signal processing unit 70 reads the table from the non-volatile memory The amount of water may be detected. For example, the non-volatile memory may store a table corresponding to the graph shown in FIG. For example, a table may be stored in which the electric signal and the amount of moisture input to the signal processing unit 70 correspond to each other. When a signal based on a voltage corresponding to the differential current is input to the signal processing unit 70, a table in which the signal based on the voltage and the amount of moisture correspond may be stored in the non-volatile memory.

  Further, in the above embodiment, each component may be configured by dedicated hardware or implemented by executing a software program suitable for each component. Each component may be realized by a program execution unit such as a processor reading and executing a software program recorded on a recording medium such as a hard disk or a semiconductor memory. The processor is configured of one or more electronic circuits including a semiconductor integrated circuit (IC) or a large scale integration (LSI). The plurality of electronic circuits may be integrated on one chip or may be provided on a plurality of chips. The plurality of chips may be integrated into one device or may be provided to a plurality of devices.

  In addition, the present invention can be realized by arbitrarily combining components and functions in each embodiment without departing from the scope of the present invention or embodiments obtained by applying various modifications that those skilled in the art may think to each embodiment. The form is also included in the present invention.

DESCRIPTION OF SYMBOLS 1 water content detection apparatus 2 object 10 light source part 30a 1st filter 30b 1st light receiving element 31a 2nd filter 31b 2nd light receiving element 40 signal amplification part (amplifier)
50 lock-in amplifier 60 A / D converter C connection point i1 first current (detection signal)
i2 second current (reference signal)

Claims (4)

A semiconductor light emitting device emitting light including a first wavelength band in which the absorption by water is larger than a predetermined value and a second wavelength band in which the absorption by water is equal to or less than the predetermined value; A light source unit that emits the light that flickers at a predetermined frequency;
A first filter for transmitting the light of the first wavelength band included in the light reflected by the object;
A first light receiving element that receives the light of the first wavelength band transmitted through the first filter and outputs a detection signal;
A second filter that transmits the light of the second wavelength band included in the light reflected by the object;
A second light receiving element connected in series to the first light receiving element, receiving the light of the second wavelength band transmitted through the second filter, and outputting a reference signal;
An amplifier connected to a connection point of the first light receiving element and the second light receiving element and outputting an amplifier signal obtained by amplifying a signal input from the connection point;
A lock-in amplifier that receives the amplification signal, extracts a signal of the predetermined frequency from the amplification signal, and outputs an extraction signal;
An A / D converter that receives the extraction signal, A / D converts the extraction signal, and outputs a digital signal. The water content detection device according to claim 1, wherein the first light receiving element and the second light receiving element are light receiving elements having the same light receiving sensitivity characteristic. The moisture content detection device according to claim 1, wherein the light source unit irradiates while scanning the light. The moisture content detection device according to any one of claims 1 to 3, wherein the semiconductor light emitting element is an LED element.

Images