JP2012073033A - Water level detection device with infrared array sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water level detection device and a water level detection method capable of easily and accurately detecting a water level without contact.SOLUTION: A water level detection device 100 including an infrared array sensor 20, an output unit 10 for outputting an output of the infrared array sensor 20 as two-dimensional information, and a signal processing unit 30 obtains a water level based on a height of the infrared array sensor 20 installed and a detection angle of it. The infrared array sensor 20 arranged on a specified position above a case housing water as liquid detects infrared ray based on heat emission from the inner wall of the case and the surface of the liquid housed in the case. The output unit 10 outputs the output of the infrared array sensor 20 as two-dimensional information based on a difference in reflection rate between the liquid and the case. The signal processing unit 30 calculates a water level of the liquid based on the two-dimensional information, the height of the infrared array sensor 20 installed and the detection angle of the infrared array sensor 20.

Description

  The present invention relates to a water level detection device using an infrared array sensor.

  Various methods for detecting the water level have been proposed, but generally, a method of directly contacting the liquid using a float, a pressure sensor or the like has been common. However, when detecting the water level of a liquid related to food such as a rice cooker or pot, there is a problem in detecting the water level in direct contact from the viewpoint of hygiene.

  Therefore, a method for detecting the water level in a non-contact manner has been proposed. For example, as a method for non-contact temperature detection, there has conventionally been proposed a method for measuring the molten steel surface level by detecting a change in the amount of heat radiation and measuring the molten metal surface level by detecting thermal radiation. (Patent Document 1).

JP 58-150826 A

In the method of Patent Document 1, since the molten metal surface level is measured by the change in the amount of heat radiation, the amount of heat radiation is also changed depending on the temperature of the molten steel surface, and sufficient measurement accuracy cannot be obtained.
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a water level detection device capable of detecting a water level easily and with high accuracy without contact.

  The present invention is arranged at a predetermined position above a case in which a liquid is stored and receives an infrared array sensor that receives an infrared signal, infrared rays based on thermal radiation from the inner wall of the case and the liquid surface stored in the case. An output unit that detects and outputs two-dimensional information based on a difference in reflectance between the liquid and the case, the two-dimensional information, the installation height of the infrared array sensor, and the detection angle of the infrared array sensor. And a signal processing unit for determining the water level of the liquid.

  Further, the present invention includes the water level detection device described above, which includes a protection member that protects the infrared sensor array from a gas generated from the liquid.

  The present invention also includes the water level detection device, wherein the protection member is a shutter that thermally blocks the infrared sensor array.

  According to the water level detection device of the present invention, it is possible to detect the water level with high accuracy without contact. At the same time, the water temperature (liquid temperature) can be detected. Furthermore, the problem of hygiene can be solved.

The figure which shows the water level detection apparatus of Embodiment 1 of this invention (when a water level is high), (a) is a figure which shows an apparatus structure, (b) is a figure which shows a measurement result The figure which shows the water level detection apparatus of Embodiment 1 of this invention (when a water level is low), (a) is a figure which shows an apparatus structure, (b) is a figure which shows a measurement result The figure which shows the rice cooker using the water level detection apparatus of Embodiment 1 of this invention. The figure which shows the rice cooker using the water level detection apparatus of Embodiment 1 of this invention. It is a figure which shows the infrared array sensor used for the water level detection apparatus of Embodiment 1 of this invention, (a) is a partially broken schematic perspective view, (b) is a schematic perspective view which shows the state which removed the package cover. , (C) is a schematic side view showing a state in which the package lid is removed, and (d) is a schematic sectional view. Sectional drawing of the principal part of the infrared sensor chip mounted in the infrared array sensor of the water level detection apparatus of Embodiment 1 of this invention. The figure which shows the plane layout of the infrared sensor chip Equivalent circuit diagram of the infrared sensor chip

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1A and FIG. 2A are explanatory diagrams showing a water level detection device according to an embodiment of the present invention, and the water level detection device measures the water level of the liquid contained in the case by 8 rows and 8 columns. An infrared array sensor having the pixels is provided. FIG. 2 shows a state where the water level is lower than in FIG. FIG.3 and FIG.4 is explanatory drawing and external appearance perspective view which show the rice cooker carrying this water level detection apparatus. FIG. 1B and FIG. 2B are diagrams showing measurement results in the case of the water level corresponding to the states of FIG. 1A and FIG. 5 to 8 are diagrams showing an infrared array sensor used here.

  The water level detection device 100 includes an infrared array sensor 20, an output unit 10 that outputs the output of the infrared array sensor 20 as two-dimensional information, and a signal processing unit 30. The water level is determined based on the angle. The external line array sensor 20 is disposed at a predetermined position above the case 110 that stores water 111 as a liquid, and detects infrared rays based on thermal radiation from the inner wall of the case and the surface of the liquid stored in the case. . Then, the output unit 10 outputs the output of the infrared array sensor 20 as two-dimensional information based on the difference in reflectance between the liquid and the case. Further, the signal processing unit 30 calculates the liquid level based on the two-dimensional information, the installation height of the infrared array sensor 20, and the detection angle of the infrared array sensor 20. This case is made of polyimide resin, and its water 111 and its reflectance are different. The signal processing unit 30 receives a signal from the infrared array sensor 20 and calculates the water level using the signal value, the installation height of the infrared array sensor 20, and the detection angle of the infrared array sensor 20.

  And this water level detection apparatus 100 is mounted in the rice cooker 1000, as shown in FIG.3 and FIG.4. The rice cooker includes a container main body 200 having a case 110 and a lid 300 that matches the container main body 200. The lid 300 is provided with an infrared wall sensor 20 of the water level detection device on the inner wall, and includes a shutter 40 that is a transparent steam blocking unit.

The shutter 40 as the protective member protects the infrared array sensor 20 from a gas generated from the liquid.
The measurement results are shown in FIGS. 1 (b) and 2 (b). FIG. 1B shows infrared two-dimensional information in which only infrared energy from the liquid surface is detected when the water level is high as shown in FIG. FIG. 2B shows infrared two-dimensional information in which only infrared energy is detected in a state where the water level is low as shown in FIG. Here, the central portion R1 detects infrared energy from the liquid surface, and the outer peripheral portion R2 detects infrared energy from the case 110.

  At this time, due to the difference in the amount of radiation, the amount of infrared energy differs between the liquid water 111 and the case 110 containing water even at the same temperature, and the detection result of the infrared two-dimensional image differs. .

  In this manner, by extracting the infrared image detected from the infrared array sensor 20, the height of the liquid surface can be detected. For example, an infrared two-dimensional image at the reference water level is set as a reference image, and the image is set so as to be an image of only the liquid surface as shown in FIG. When the water level becomes lower than that, the inner wall of the case 110 can be seen around as shown in FIG. 2B, and the outer periphery of the infrared image becomes an image of the case 110. From the ratio between the outer radius a1 of the central portion R1 and the outer radius a2 of the outer peripheral portion R2, the angle facing the infrared array sensor 20 is calculated, and the water level can be calculated.

Next, a method for calculating the water level will be described.
First, as shown in FIGS. 1 (a) and 1 (b), when at the reference water level, the height from the sensor to the liquid level when the detection angle of the inner wall of the container is θ ₀ is h _0, and the inner wall of the container at that time The distance from the container center to the container is b2. The radius of the output image at this time is assumed to be a2.
When the water level is lowered, as shown in FIG. 2B, the output image shows the inner wall of the case 110 in the periphery, and the outer periphery becomes an image of the case 110. On the other hand, as shown in FIG. 2A, what is actually desired to be measured is the height h from the sensor to the liquid level when the detection angle of the inner wall of the container is θ, from the inner wall of the container to the center of the container at that time. Is the distance b1. Based on the radius a1 of the outer periphery of the central portion R1 and the radius a2 of the outer periphery of the outer peripheral portion R2, and assuming that the radius of the output image at this time is a1, the height h from the sensor to the liquid level is calculated by the following equation. The
h = h ₀ · (b2 / b1)
= H ₀ · (a2 / a1)
And the depth h1 from the reference plane of the actual container is
h1 = h−h ₀
Thus, the height of the liquid level can be easily detected.

  In this way, the signal processing unit 30 determines the position of the liquid level from the sensor installation height based on the detection angle of the infrared array sensor installed on the upper part of the liquid level based on the output data from the output unit 10 and the detected temperature information. Can be detected.

  Next, the infrared array sensor 20 constituting the water level detection device 100 will be described. 5A and 5B are diagrams showing the infrared array sensor, in which FIG. 5A is a partially broken schematic perspective view, FIG. 5B is a schematic perspective view showing a state in which the package lid is removed, and FIG. 5C is a diagram with the package lid removed. FIG. 6 is a schematic side view showing the state, FIG. 6D is a schematic cross-sectional view, FIG. 6 is a cross-sectional view of the main part of the infrared sensor chip mounted on this infrared array sensor, and FIG. 8 is an equivalent circuit diagram of the infrared sensor chip.

  The infrared array sensor 20 is an infrared image sensor, and includes an infrared sensor chip 1, an IC chip 2 that processes an output signal of the infrared sensor chip 1, and a package 3 that houses the infrared sensor chip 1 and the IC chip 2. It has. Here, a thermistor (not shown) for measuring the absolute temperature is also housed in the package 3.

  This infrared sensor chip 1 has a thermal infrared detector formed in a silicon substrate as a base substrate 11. The thermal infrared detector is a thermocouple that connects dissimilar metals and generates a temperature difference between the junctions of these metals due to the heat of infrared rays. (Effect) is used to detect infrared rays as a voltage. This thermal infrared detector converts the received infrared light into heat with an infrared absorption film, and adds this heat to a number of thermocouples connected in series. Output as voltage. In this thermal infrared detector, as a material of the infrared absorbing film that absorbs infrared rays, a black film or a carbon film having a high infrared absorption rate is used.

  The package 3 is configured such that a package body 4 formed of a wiring board on which the infrared sensor chip 1, the IC chip 2, and the thermistor are mounted and a package lid 5 are hermetically bonded to block moisture. The package lid 5 is provided with a window 9 a, and a lens 9 is provided in this window so that the condensed infrared light is guided to the infrared sensor chip 1. Further, a cover member 6 having good thermal conductivity is provided inside the package 3 so as to relieve the temperature change of the infrared sensor chip 1. Infrared light passes through the infrared transmission window 7 and is guided to the infrared sensor chip 1.

  In this infrared sensor chip, as shown in FIGS. 7 and 8, pixels Cp having a thermal infrared detector Th and a MOS transistor Tr serving as a pixel selection switching element are arranged in an array on one surface side of the base substrate 11 (here Then, they are arranged in a two-dimensional array. Here, the base substrate 11 is formed using a silicon substrate. In the present embodiment, m × n (8 × 8 in the illustrated example) pixels Cp are formed on the one surface side of one base substrate 11, but the number and arrangement of the pixels are particularly limited. Not what you want.

The infrared sensor is provided with a plurality of vertical read lines L _v, and a plurality of horizontal signal lines S _H, and a plurality of ground lines, and the common ground line Gnd, and a plurality of reference bias lines V _ref, all The output of the temperature sensing part of the thermal infrared detection part Th can be read out in time series. The plurality of vertical read lines L _v is one in which one end of the temperature sensitive portion of the plurality of thermal infrared detector Th of each row are commonly connected to each column via the MOS transistor Tr described above. A plurality of horizontal signal lines S _H is to the gate electrode of the MOS transistor Tr corresponding to the temperature sensing portion of the thermal infrared detector Th of each row are commonly connected for each row. The plurality of ground lines are obtained by commonly connecting the p ^{+ -type} well regions of the MOS transistors Tr of each column for each column. The ground lines are connected in common to form a common ground line Gnd. Further, the plurality of reference bias lines _Vref are obtained by commonly connecting the other ends of the temperature sensing units of the plurality of thermal infrared detection units in each column for each column.

As described above, the infrared sensor of the present embodiment is arranged in parallel with the thermal infrared detector Th and the thermal infrared detector Th on the one surface side of the base substrate 11, and outputs the thermal infrared detector Th. A plurality of pixels Cp having MOS transistors Tr for reading are formed. Here, in the MOS transistor Tr, the gate electrode is connected to the horizontal signal line, and the source electrode is connected to the reference bias line _Vref via the temperature sensing unit. Each reference bias line V _ref is commonly connected to the common reference bias line, and the drain electrode is connected to the vertical readout line. Each horizontal signal line is electrically connected to a different pixel selection pad. Each vertical readout line is electrically connected to a separate output pad. The common ground line is electrically connected to the ground pad. The common reference bias line is electrically connected to the reference bias pad, and the silicon substrate is electrically connected to the substrate pad.

  In this way, the output voltage of each pixel Cp can be read sequentially by controlling the potential of each pixel selection pad Vsel so that the MOS transistors Tr are sequentially turned on. For example, the reference bias pad potential is 1.65, the ground pad potential is 0 V, and the substrate pad potential is 5 V. At this time, if the potential of the pixel selection pad is 5 V, the MOS transistor Tr is turned on, and the output voltage of the pixel Cp (1.65 V + the output voltage of the temperature sensing unit) is read from the output pad. On the other hand, when the potential of the pixel selection pad is set to 0 V, the MOS transistor Tr is turned off, and the output voltage of the pixel Cp is not read from the output pad.

  The structures of the thermal infrared detector Th and the MOS transistor Tr will be described below. In the present embodiment, a single crystal silicon substrate having an n-type conductivity and a (100) surface is used as the silicon substrate.

  The thermal infrared detector Th is formed in a region for forming the thermal infrared detector Th in each of the pixels Cp on the one surface side of the silicon substrate. The MOS transistor Tr is formed in a region for forming the MOS transistor Tr in each pixel Cp on the one surface side of the silicon substrate.

  The thermal infrared detecting portion Th is a thin film structure portion having an infrared absorbing portion that is formed by being spatially separated by the base substrate 11 and the cavity 12 on the one surface side of the base substrate 11 based on a silicon substrate and absorbs infrared rays. 13 and a thermocouple-type temperature sensing unit that includes a thermocouple and detects a temperature difference between the infrared absorption unit and the base substrate 11. The temperature sensing part includes a p-type polysilicon layer 15, an n-type polysilicon layer 14 formed over the infrared absorption part and the base substrate 11, and a thermocouple. The thermocouple includes a connection portion (a hot junction T1 and a cold junction T2) in which the p-type polysilicon layer 15 and the n-type polysilicon layer 14 are electrically joined on the infrared incident surface side of the infrared absorption portion.

  In this way, by capturing the output from the infrared sensor as an infrared image, it is possible to easily output a two-dimensional infrared image as shown in FIGS. Can be detected.

  As described above, according to the water level detection device of the present invention, since the water level can be detected in a non-contact manner, application to utensils used for storage or cooking of food such as rice cookers and pots is extremely effective. It is. Since it is non-contact, it does not cause deterioration even if it is used continuously for a long time.

  Therefore, the present invention can be applied to a water level detection device or the like in a safety confirmation system that remotely confirms the safe living of an elderly person using a communication line. For example, it can be used as a sensor over a long period of time by detecting the rate of change of the pot water level and confirming the water supply to the pot, the use of hot water, and the like.

  Further, since the detection is performed based on the two-dimensional infrared information, for example, even if some of the pixels in the 8 rows and 8 columns are deteriorated, the contours as shown in FIGS. 1B and 2B are obtained. Since information can be acquired, it has the feature that there are very few malfunctions.

1 Infrared sensor chip 2 IC chip 3 Package 4 Package body 5 Package lid 6 Cover member
7 Infrared transmitting window 9 Lens 9a Window 10 Output unit 11 Base substrate 12 Cavity 13 Thin film structure unit 14 n-type polysilicon layer 15 p-type polysilicon layer 20 Infrared array sensor 30 Signal processing unit 40 Shutter 100 Water level detection device 110 Case 1000 Rice cooking Container 200 Container body 300 Cover

Claims (3)

An infrared array sensor that is disposed at a predetermined position above the case containing the liquid and receives an infrared signal;
An output unit that detects infrared rays based on thermal radiation from the inner wall of the case and the surface of the liquid stored in the case, and outputs two-dimensional information based on a difference in reflectance between the liquid and the case;
The water level detection apparatus which has a signal processing part which calculates | requires the water level of the said liquid based on the said two-dimensional information, the installation height of the said infrared array sensor, and the detection angle of the said infrared array sensor. The water level detection device according to claim 1,
The water level detection apparatus provided with the protection member which protects the said infrared sensor array from the gas produced | generated from the said liquid. The water level detection device according to claim 1,
The water level detection device, wherein the protection member is a shutter that thermally blocks the infrared sensor array.

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