JP2026018120A - Airflow visualization device and airflow visualization method - Google Patents

Abstract

An airflow visualization device and an airflow visualization method are provided that are capable of easily analyzing airflow in a real environment and visualizing the airflow.
[Solution] Using an infrared camera 1 and an optical filter 3, infrared temperature data is obtained by capturing infrared rays in a wavelength band including wavelengths at which infrared rays are absorbed by _CO2 in the same measurement target space, and infrared temperature data is obtained by capturing infrared rays in a wavelength band in which the amount of infrared rays absorbed by _CO2 is smaller than that of the wavelength _band , and a difference image is generated and displayed as an image representing the airflow in the measurement target space by removing the temperature distribution image corresponding to the infrared temperature data capturing infrared rays in the wavelength band including wavelengths at which infrared rays are absorbed by _CO2 from the temperature distribution image corresponding to the infrared temperature data capturing infrared rays in the wavelength band in which the amount of infrared rays absorbed by CO2 is smaller.
[Selected Figure] Figure 1

Description

The present invention relates to an airflow visualization device and an airflow visualization method.

Generally, particle image spectroscopy (PIV) has been widely used as a method for analyzing fluid flow (see, for example, Patent Document 1). PIV uses particles called tracers, and analyzes the fluid flow by supplying the tracers into a fluid to be analyzed, irradiating the tracers in the fluid with laser light, and taking images in synchronization with the oscillation of the laser light.
Also, a method has been proposed in which the fluid itself is colored with two colors, and the two colors are alternately flowed to observe the stripe pattern, thereby observing the flow of the fluid (see, for example, Patent Document 2).

Furthermore, a method for visualizing airflow based on image processing using an infrared camera has also been proposed (see, for example, Patent Document 3). This method uses _CO2 , which is present in the atmosphere at approximately 400 ppm, as a tracer, and performs image processing calculations based on temperature fluctuations over a short period of time from an image in which a temperature image of _CO2 measured by an infrared camera is superimposed on a temperature image of the background, thereby extracting only an image of temperature fluctuations of _CO2 and using it to visualize airflow.

JP 2018-40571 A Japanese Patent Application Laid-Open No. 2006-71382 Patent No. 7065060 Patent No. 7393322

Previous fluid flow analysis methods (PIV methods) required large-scale equipment such as laser irradiation devices and were performed in environments with restricted access. In addition, the need to supply tracers made the process complicated, limiting measurements to laboratory use and limiting the time available for measurement.
As a result, flow analysis could not be effectively performed on actual structures and environments, such as inside or outside buildings that cover a wide area, inside factories, or public facilities such as train stations with large numbers of people.

In contrast, the method using an infrared camera (Patent Document 3) solves the above-mentioned problems. It is a simple measurement method that requires only an infrared camera and a computer, and is effective for measuring a wide range of objects, such as those inside large buildings or outdoors.

However, this method analyzes the distribution of temperature fluctuations over a short period of time, specifically, within a short time of around 1 to 2 seconds, to determine whether the temperature fluctuations were upward or downward. While it can visualize the airflow itself, it cannot visualize how the airflow stirs up the room and changes the temperature, or the range in which the airflow from an air conditioner or other device effectively acts. As a result, it was not possible to properly evaluate the impact and effect of airflow on the indoor environment.

The present invention was made in consideration of these circumstances, and aims to provide an airflow visualization device and airflow visualization method that enable simple analysis of airflow in real environments and visualize temperature changes such as how airflow stirs up indoor air and changes the temperature distribution, and the effects of convection caused by heating and cooling appliances, i.e., how indoor air is stirred up by convection from a circulator or the like and temperature variations are evened out, and the range and extent to which the room temperature rises due to warm air from an air conditioner.

According to one aspect of the present invention, there is provided an airflow visualization device including: _an imaging device that outputs first infrared temperature data obtained by capturing infrared rays in a first wavelength band that includes wavelengths at which infrared rays are absorbed by _CO2 , and second infrared temperature data obtained by capturing infrared rays in a second wavelength band in which the amount of infrared rays absorbed by CO2 is less than the amount of infrared rays absorbed by _CO2 in the first wavelength band, in the same measurement target space; and a visualization processing unit that generates a differential image by removing a temperature distribution image corresponding to the second infrared temperature data from a temperature distribution image corresponding to the first infrared temperature data, as an image representing the airflow in the measurement target space.

According to another aspect of the present invention, there is provided an airflow visualization method comprising the steps of: acquiring first infrared temperature data and second infrared temperature data from an imaging device that includes an infrared camera and outputs, from the _infrared camera, first infrared temperature data obtained by capturing infrared rays in a first wavelength band that includes wavelengths at which infrared rays are absorbed _{by CO2} , and second infrared temperature data obtained by capturing infrared rays in a second wavelength band in which the amount of infrared rays absorbed by CO2 is less than the amount of infrared rays absorbed by CO2 in the first wavelength band; and displaying, as an image representing airflow in the space to be measured, a difference image obtained by removing the temperature distribution image corresponding to the second infrared temperature data from the temperature distribution image corresponding to the first infrared temperature data, based on the acquired first infrared temperature data and second infrared temperature data.

One aspect of the present invention makes it easy to visualize airflow and resulting temperature changes in a real environment, such as how airflow stirs the air in a room and changes the temperature distribution, and the effects of convection caused by heating and cooling appliances, i.e., the temperature changes caused by convection.

1 is a schematic configuration diagram showing an example of an airflow visualization device according to an embodiment of the present invention. FIG. FIG. 1 is a schematic diagram illustrating an example of an infrared camera equipped with a filter wheel. FIG. 10 is a schematic configuration diagram showing another example of the airflow visualization device. FIG. 1 is a block diagram illustrating an example of an analysis processing device. 10 is a flowchart illustrating an example of a processing procedure for analysis processing. 10 is an example of an operation screen during analysis processing. 10 is an image for explaining a difference image. 10 is an image for explaining a difference image. 10 is an image for explaining a difference image. 10 is an example of a difference image. 10 is an example of a difference image. 10 is an example of a difference image. 10 is a flowchart showing another example of the processing procedure in the analysis processing unit. 10 is a flowchart showing another example of the processing procedure in the analysis processing unit. 10 is a flowchart showing another example of the processing procedure in the analysis processing unit. 10 is a flowchart showing another example of the processing procedure in the analysis processing unit. 10 is a flowchart showing another example of the processing procedure in the analysis processing unit.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
In the following detailed description, many specific configurations are described to provide a thorough understanding of the embodiments of the present invention. However, it is clear that other embodiments can be implemented without being limited to such specific configurations. Furthermore, the following embodiments do not limit the invention according to the claims. Furthermore, not all combinations of features described in the embodiments are necessarily essential to the solution of the invention.

<Embodiment>
First, the airflow visualization device according to the present invention will be described.
The airflow visualization device according to this embodiment visualizes airflows and temperature changes caused by these airflows by analyzing infrared temperature data (first infrared temperature data) (hereinafter also referred to as infrared temperature data corresponding to the infrared absorption wavelengths by _CO2 ) obtained from the infrared camera ₁ through an optical filter having an infrared transmission wavelength in a wavelength band (first wavelength band) that includes the infrared absorption wavelengths of _CO2 , and infrared temperature data (second infrared temperature data) (hereinafter also referred to as infrared temperature data corresponding to the wavelengths at which infrared absorption by _CO2 is small) obtained from the infrared camera 1 through an optical filter having an infrared transmission wavelength in a wavelength band (second wavelength band) in which the amount of infrared light absorbed by _CO2 is less than the amount of infrared light absorbed in the wavelength band that includes the infrared absorption wavelengths of CO2.

Here, "wavelengths at which infrared absorption by _CO2 is minimal" refer to wavelengths at which image information can be obtained that include only temperature images corresponding to thermal radiation from the walls of the measurement space, air conditioning equipment, etc., and do not include temperature images due to airflow. These wavelengths may be wavelengths at which infrared absorption by _CO2 is not present, or wavelengths at which infrared absorption by _CO2 occurs to some extent; specifically, they refer to wavelengths of approximately 3.0 μm or more and 4.0 μm or less, or 4.5 μm or more and 5.0 μm or less.

As shown in FIG. 1, the airflow visualization device 10 comprises an infrared camera 1 and an analysis processing device (visualization processing unit) 2. The analysis processing device 2 is composed of a personal computer or the like that performs calculations based on the infrared temperature data from the infrared camera 1 and displays a differential image representing the airflow. The analysis processing device 2 acquires infrared temperature data from the infrared camera 1, which captures infrared light that has passed through two types of optical filters with different infrared transmission wavelengths, at a predetermined cycle, and calculates the airflow in the space photographed by the infrared camera 1 from the acquired infrared temperature data, and visualizes and displays it on a display device, which will be described later.

One infrared camera 1 is used to acquire infrared temperature data. Since the infrared absorption wavelength of _CO2 is approximately 4.3 μm, the measurement wavelength of the infrared camera 1 includes the wavelength band of 3 to 5 μm. As shown in Figure 2, the infrared camera 1 is equipped with a filter wheel 3, which can be fitted with two or more optical filters 3a. The infrared camera 1 and the filter wheel 3 including the optical filters 3a constitute an imaging device.

At least one optical filter (first optical filter) 3 a having an infrared transmission wavelength that includes the infrared absorption wavelength of _CO2 is attached to the filter wheel 3, or the filter wheel 3 is left blank with no optical filter 3 a attached. Also, at least one optical filter (second optical filter) 3 a having an infrared transmission wavelength that is a wavelength at which infrared absorption by _CO2 is low or that does not include the infrared absorption wavelength is attached to the filter wheel 3. The optical filter 3 a having an infrared transmission wavelength that includes the infrared absorption wavelength of _CO2 has an infrared transmission wavelength of, for example, 4.1 μm or more and 4.4 μm or less.

By using the infrared camera 1 to take pictures while rotating the filter wheel 3, infrared temperature data corresponding to wavelengths at which _CO2 absorbs infrared rays and infrared temperature data corresponding to wavelengths at which _CO2 absorbs infrared rays less are alternately obtained.

Although the airflow visualization device 1 uses a filter wheel 3 to visualize airflow using a single infrared camera 1, this is not a limitation. For example, it is also possible to visualize airflow using multiple infrared cameras without using the filter wheel 3. For example, when two infrared cameras 1a and 1b are used as shown in FIG. 3, one of the infrared cameras is equipped with an optical filter having an infrared transmission wavelength that includes the infrared absorption wavelength of _CO2 , or no optical filter is provided. The other infrared camera is equipped with an optical filter having an infrared transmission wavelength that is less absorbed by _CO2 , or an infrared camera with a wavelength that is less absorbed by _CO2 is used. These two infrared cameras are then positioned so that their fields of view are the same, and processing is performed using the infrared temperature data acquired by the two infrared cameras.

<Method of calculating _CO2 temperature>
Next, a method for calculating the _CO2 temperature will be described.
First, the air in a space where the air flow is to be measured, such as a room, is photographed as a measurement target by the infrared camera 1 .

Here, although there is approximately 400 ppm of _CO2 in the atmosphere, according to Kirchhoff's law, absorption and radiation are equal in a state of thermal equilibrium, and therefore, in the infrared temperature data obtained by photographing the measurement target space with the infrared camera 1, the group of infrared temperature data corresponding to infrared rays that have passed through an optical filter that includes, as its infrared transmission wavelength, the infrared absorption wavelength of _CO2 is infrared temperature data that is a superposition of infrared temperature data corresponding to infrared rays radiated from _CO2 in the atmosphere and infrared temperature data corresponding to infrared rays radiated from the background in the measurement target space. In other words, this is infrared temperature data that is a superposition of infrared temperature data corresponding to the atmosphere in the measurement target space and infrared temperature data corresponding to the background of the measurement target, such as the walls of the room.

On the other hand, the infrared temperature data group corresponding to the infrared rays that have passed through an optical filter that has an infrared transmission wavelength that is low in infrared absorption by _CO2 will contain less infrared rays emitted from _CO2 , i.e., will mainly contain infrared temperature data corresponding to the background of the measurement space, such as the walls of a room.

Therefore, by taking the difference between "infrared temperature data corresponding to infrared rays that have passed through an optical filter that has an _infrared transmission wavelength that includes the infrared absorption wavelength of _CO2 as its infrared transmission wavelength" and "infrared temperature data corresponding to infrared rays that have passed through an optical filter that has an infrared transmission wavelength that is set to have a wavelength that is less absorbed by CO2," it is possible to remove the components of the infrared temperature data that correspond to the background of the measurement object, such as the walls of a room, and the infrared temperature data obtained as the difference will be a value that reflects the components of the infrared temperature data that correspond to _CO2 in the measurement object space (atmosphere).

Therefore, by subtracting the infrared temperature data corresponding to the wavelength at which _CO2 absorbs less infrared rays multiplied by coefficient k2 from the infrared temperature data corresponding to the wavelength at which _CO2 absorbs less infrared rays multiplied by coefficient k1, it is possible to obtain infrared temperature data obtained by infrared camera 1 that reflects the amount of infrared radiation emitted by _CO2 , i.e., infrared temperature data that reflects the state of the space being measured (atmosphere), with the components corresponding to the amount of infrared rays absorbed by background walls, etc. removed.

As a result, it is possible to obtain the flow of CO ₂ in the measurement target space (airflow) and the temperature change of CO ₂ (temperature change caused by the airflow).
Furthermore, by performing this series of processes in real time while taking images with the infrared camera 1, it is possible to display images of the airflow and the temperature change caused by the airflow in real time.

Furthermore, by measuring the atmospheric temperature using a thermocouple or the like while changing the airflow temperature value in several steps for the airflow in the space being measured, and simultaneously taking measurements using infrared camera 1, and correcting coefficients k1 and k2 based on this, a temperature distribution image can be obtained that shows the calibrated actual temperature distribution.

<Configuration of analysis processing device>
FIG. 4 is a block diagram showing an example of the analysis processing device 2.
The analysis processing device 2 includes a calculation processing unit 2a, a display device 2b, an input device 2c, and a storage device 2d. The calculation processing unit 2a includes a camera control unit 21, a filter wheel driving unit 22, and a temperature data processing unit 23. The input device 2c is configured with, for example, a keyboard, a touch panel displayed on the display device 2b, etc.

The camera control unit 21 controls the operation of the infrared camera 1 in response to input information from the input device 2c, sets the exposure time, and instructs the timing of infrared temperature data acquisition and switches the optical filter 3a in response to this acquisition timing. The filter wheel drive unit 22 activates the filter wheel 3 and switches the optical filter 3 in response to input information from the camera control unit 21.

The temperature data processing unit 23 inputs infrared temperature data from the infrared camera 1 and displays it on the display device 2b and stores it in the storage device 2d. As an initial process, the temperature data processing unit 23 displays a difference image on the display device _2b , which is the difference between infrared temperature data corresponding to wavelengths of infrared absorption by _CO2 and infrared temperature data corresponding to wavelengths where _CO2 absorbs infrared light to a lesser extent. The temperature data processing unit 23 then searches, in response to a user operation, for coefficients k1 and _k2 that will produce a desired image that represents only the airflow in the measurement target space. The temperature data processing unit 23 then uses the acquired coefficients k1 and k2 to generate a difference image based on the infrared temperature data input from the infrared camera 1, and displays this difference image on the display device 2b as an image representing the airflow in the measurement target space.

<Analysis processing>
Next, an example of the processing procedure in the calculation processing unit 2a will be described. Fig. 5 is a flowchart showing an example of the processing procedure of the analysis processing in the calculation processing unit 2a. Fig. 6 is an example of an operation screen on the display device 2b when the analysis processing is being executed. In Fig. 6, image f1 is a difference image, image f2 is a temperature distribution image based on infrared temperature data corresponding to infrared absorption wavelengths by _CO2 , and image f3 is a temperature distribution image based on infrared temperature data corresponding to wavelengths where infrared absorption by _CO2 is low.
In response to a user's operation, the processing unit 2a starts the infrared camera 1 (step S1) and starts the filter wheel 3 (step S2).

Next, initial adjustments are made to the infrared camera 1, such as calibrating for variations between pixels (step S3). For example, in accordance with user operation, an image of a blackbody plate captured by the infrared camera 1 is displayed on the display device 2b, and calibration is performed so that this image is uniform.

Next, the object to be measured is photographed in response to a user operation and displayed on the display device 2b (step S4). At this time, the filter wheel 3 is switched so that infrared temperature data corresponding to wavelengths at which _CO2 absorbs infrared rays and infrared temperature data corresponding to wavelengths at which _CO2 absorbs infrared rays less are acquired substantially simultaneously.

Next, the exposure time for infrared temperature data corresponding to wavelengths of infrared absorption by _CO2 (step S5) and the exposure time for infrared temperature data corresponding to wavelengths where _CO2 absorbs infrared light to a lesser extent are determined according to the temperature of the object to be measured (step S6). Specifically, when the temperature of the object to be measured is high, the exposure time is shortened because the amount of radiant energy that the infrared camera can measure may be exceeded. When the temperature of the object to be measured is low, the exposure time is lengthened to ensure the amount of radiant energy required to increase sensitivity. For example, as shown in FIG. 6 , the user operates the exposure time setting unit m1 on the display screen while referring to temperature distribution images f2 and f3 displayed on the display device 2b, thereby setting the exposure time so that the temperature distribution image consisting of infrared temperature data corresponding to wavelengths of infrared absorption by _CO2 and the temperature distribution image consisting of infrared temperature data corresponding to wavelengths where _CO2 absorbs infrared light to a lesser extent are both good images.

Next, infrared temperature data corresponding to multiple temperature distribution images is acquired to time-average the infrared temperature data corresponding to wavelengths of infrared absorption by _CO2 (step S7). Similarly, infrared temperature data corresponding to wavelengths where _CO2 has little infrared absorption is acquired, equivalent to multiple temperature distribution images (step S8). The number of infrared temperature data corresponding to temperature distribution images required to time-average the infrared temperature data differs between the infrared temperature data corresponding to wavelengths of infrared absorption by _CO2 and the infrared temperature data corresponding to wavelengths where _CO2 has little infrared absorption. The infrared temperature data corresponding to wavelengths where _CO2 has little infrared absorption represents the background, not the airflow, and the background image changes little over time. Therefore, it is preferable to acquire a certain number of such infrared temperature data for the purpose of noise reduction. Conversely, infrared temperature data corresponding to wavelengths of infrared absorption by _CO2 changes greatly over time, and averaging makes these changes less visible, so it is preferable to acquire a relatively small number of such data.

Next, the infrared temperature data corresponding to the wavelengths of infrared absorption by _CO2 corresponding to the multiple temperature distribution images acquired in step S7 is averaged (step S9), and similarly, the infrared temperature data corresponding to the wavelengths of infrared absorption by _CO2 that are low corresponding to the multiple temperature distribution images acquired in step S8 is averaged (step S10).

Then, a differential image is obtained by subtracting the infrared temperature data corresponding to wavelengths with less infrared absorption by _CO2 averaged in step S10 from the infrared temperature data corresponding to wavelengths with less infrared absorption by _CO2 averaged in step S9, and the obtained differential image is displayed on the display device 2b (step S11).

The difference image is obtained by subtracting the value obtained by multiplying the averaged infrared temperature data corresponding to the wavelengths where infrared absorption by _CO2 is low by the coefficient _k2 from the value obtained by multiplying the averaged infrared temperature data corresponding to the wavelengths where infrared absorption by CO2 is low by the coefficient k1, and this is the difference image.
By performing the differential processing, as shown in FIG. 6, for example, a differential image f1, a temperature distribution image f2 consisting of data obtained by multiplying the averaged infrared temperature data corresponding to the wavelengths of infrared radiation absorbed by _CO2 by a coefficient k1, and a temperature distribution image f3 consisting of data obtained by multiplying the averaged infrared temperature data corresponding to the wavelengths of infrared radiation with less absorption by CO2 by a coefficient _k2 are displayed on the display device 2b.

Next, the user changes the coefficients k1 and k2 while referring to the difference image f1 in Figure 6, searching for coefficients k1 and k2 that will make the background in the subject space invisible in the difference image f1. The coefficients k1 and k2 are searched for, for example, by performing a setting operation on the coefficient ratio setting unit m2 on the display screen. The calculation processing unit 2a performs difference processing each time the coefficients k1 and k2 are input, and displays the difference image f1 on the display device 2b. The determined coefficients k1 and k2 are then stored in a specified memory area (step S12).

It is possible to set both coefficients k1 and k2 as variables, but calculations can be made easier by setting one of the coefficients to the constant "1." Therefore, in Figure 6, coefficient k2 is set to "1," and coefficient k1 is adjusted by adjusting the coefficient ratio.

Next, the arithmetic processor 2a acquires infrared temperature data corresponding to wavelengths of infrared absorption by _CO2 and measures a temperature distribution image (step S13), acquires infrared temperature data corresponding to wavelengths where _CO2 has little infrared absorption, and measures a temperature distribution image (step S14). The acquired infrared temperature data is then stored in a predetermined storage area. Then, the most recent infrared temperature data stored in the storage area is averaged over a predetermined number of images corresponding to wavelengths where _CO2 has little infrared absorption (step S15). Similarly, the most recent infrared temperature data stored in the storage area is averaged over a predetermined number of images corresponding to wavelengths where _CO2 has little infrared absorption (step S16). A difference image is then acquired using the coefficient k1 determined in step S12 (step S17), and the acquired difference image is displayed on the display device 2b (step S18). The process then returns to step S13, sequentially displays the difference images, and ends when a measurement termination operation is performed (step S19).

By carrying out the above processing, it is possible to easily obtain a difference image that shows the airflow and the temperature change caused by the airflow.
Furthermore, by performing the above processing in real time while taking images with the infrared camera 1, it is possible to display a differential image showing the airflow and the temperature change that accompanies the airflow in real time.

However, what is obtained here is a relative value of temperature change, not an absolute temperature value. To convert this to an absolute temperature value, divide the airflow temperature value into several stages, measure the atmospheric temperature value using a thermocouple or similar device, and simultaneously measure it with an infrared camera. Determine the relationship between the measured atmospheric temperature values at multiple stages and the temperature change value measured by the infrared camera, and convert the temperature change value to the atmospheric temperature value based on this relationship.

Alternatively, the coefficients k1 and k2 can be corrected in advance based on the relationship between the measured atmospheric temperature values at multiple stages and the temperature change values measured by the infrared camera, and the atmospheric temperature value can be calculated directly without first calculating the temperature change values.

Measuring atmospheric temperature values is not limited to thermocouples, as long as it is possible to measure atmospheric temperature values. For example, temperature measurement may be performed using the temperature measurement device described in Patent Document 4. The temperature measurement device described in Patent Document 4 has the same device configuration as the airflow visualization device 1 according to this embodiment, and therefore can be easily implemented by installing a calculation processing unit for performing temperature measurement in the temperature measurement device described in Patent Document 4 in the airflow visualization device 1. Furthermore, by configuring the calculation processing for temperature measurement in the temperature measurement device described in Patent Document 4 and the calculation processing for airflow visualization in the airflow visualization device according to this embodiment to be switchable, the usability of the airflow visualization device can be further improved.

(Modification)
The filter wheel 3 is required to be equipped with at least one optical filter 3 a having an infrared transmission wavelength that includes the infrared absorption wavelength of CO ₂ , or to have a blank portion with no optical filter 3 a attached to the filter wheel 3 and at least one optical filter 3 a having an infrared transmission wavelength that is a wavelength at which infrared absorption by CO ₂ is low or that does not include the infrared absorption wavelength. For example, the filter wheel 3 may be equipped with an equal number of two types of optical filters 3 a, namely, optical filters 3 a having an infrared transmission wavelength that includes the infrared absorption wavelength of CO ₂ and optical filters 3 a having an infrared transmission wavelength that is a wavelength at which infrared absorption by CO ₂ is low, or may not be equipped with an equal number of two types of optical filters 3 a. Furthermore, the filter wheel 3 may be equipped with these two types of optical filters 3 a alternately or adjacently.

Alternatively, the two types of optical filters 3a may be attached in equal numbers, i.e., optical filters 3a having infrared transmission wavelengths that include the infrared absorption wavelength of CO ₂ and optical filters 3a having infrared transmission wavelengths that are less absorbed by CO _2. Furthermore, a plurality of types of optical filters having infrared absorption wavelengths that are the same as the infrared absorption wavelength of CO ₂ but different infrared transmission wavelengths may be used as the optical filters _3a having infrared transmission wavelengths that are the same as the infrared absorption wavelength of CO _2. In this case, a difference image may be displayed by removing the temperature distribution image based on infrared temperature data obtained by an optical filter having infrared transmission wavelengths that are less absorbed by CO _{2 from a temperature distribution image obtained by adding together a plurality of temperature distribution images based on infrared temperature data having different infrared transmission wavelengths, obtained by using a plurality of optical filters having infrared absorption wavelengths that are the same as the infrared absorption wavelength of CO 2} but different infrared transmission wavelengths, i.e., an image showing airflow and temperature changes caused by the airflow. As for the optical filter 3a having an infrared transmission wavelength that includes the infrared absorption wavelength of _CO2 , the wider the range of infrared transmission wavelength, the more noise can be reduced in the difference image obtained as an image of the airflow. Similarly, when multiple optical filters with different infrared transmission wavelengths that include the infrared absorption wavelength of _CO2 are provided and an image of the airflow is obtained using multiple infrared temperature data with different infrared transmission wavelengths, the more noise can be reduced.

<Example>
The airflow visualization device 10 has the configuration shown in Figures 1 and 2. An IR8350hp model manufactured by InfraTec was used as the infrared camera 1. The IR8350hp infrared camera 1 is a cooled type for the mid-infrared band, uses an InSb element, has a measurement wavelength of 1.5 μm to 5.7 μm, and has 640 x 512 pixels. In addition, as shown in Figure 2, a filter wheel 3 is provided between the lens and sensor of the infrared camera 1, which can accommodate a total of six optical filters.

An optical filter with an infrared transmission band of 4.15 μm to 4.37 μm was attached to the filter wheel 3 as the optical filter _3a having the infrared absorption wavelength of _CO2 as its infrared transmission wavelength, and an optical filter with an infrared transmission band of 3.28 μm to 3.45 μm was attached as an optical filter having an infrared transmission wavelength with little infrared absorption by CO2.
The imaging frame rate was 75 Hz, the exposure time was 3000 μsec, and the imaging time was 60 sec.

The filter wheel 3 can hold six optical filters 3a, allowing infrared temperature data to be acquired every 12.5 Hz through each optical filter 3a.

Figure 7 shows a digital camera image of the background in the measurement space. The flow of warm air discharged from an air conditioner was the measurement target.

Figure 8 is a temperature distribution image based on infrared temperature data obtained through an optical filter whose infrared transmission wavelength is the wavelength of infrared absorption by CO ₂ , and Figure 9 is a temperature distribution image based on infrared temperature data obtained through an optical filter whose infrared transmission wavelength is the wavelength at which infrared absorption by CO ₂ is low. The temperatures in both Figures 8 and 9 are digital level values from the infrared camera.

The temperature distribution image corresponding to the wavelength of infrared absorption by _CO2 shown in Figure 8 was obtained by averaging the past three temperature distribution images, and the temperature distribution image corresponding to the wavelength of infrared absorption by _CO2 at a low level shown in Figure 9 was obtained by averaging the past 50 temperature distribution images.

For the temperature distribution image corresponding to the wavelength of infrared absorption by _CO2 shown in Figure 8, a small number of images are averaged because if the number of images is increased, the airflow image due to _CO2 will also be averaged, making it difficult to recognize as a flow. On the other hand, for the temperature distribution image corresponding to the wavelength of infrared absorption by _CO2 shown in Figure 9, which is low, only a background image does not change significantly over time, so a large number of images are averaged in order to reduce noise.

It can be seen from Figure 8 that the temperature distribution image corresponding to the wavelength of infrared light absorbed by _CO2 consists of an image showing the warm air discharged from the air conditioner and the background temperature. On the other hand, it can be seen from Figure 9 that the temperature distribution image corresponding to the wavelength of infrared light with little absorption by _CO2 consists of an image showing only the background temperature, not including the warm air discharged from the air conditioner.

FIG. 10 shows a differential image obtained by multiplying the infrared temperature data corresponding to the wavelengths at which _CO2 absorbs infrared rays by a coefficient k1 = 2.5 and then subtracting from it the infrared temperature data corresponding to wavelengths at which _CO2 absorbs less infrared rays. In other words, it shows an image that shows only the temperature distribution due to the airflow, excluding the temperature distribution image of the air conditioner, etc. in the background.
Because the warm air blown from an air conditioner is pulsating, the generated difference image has variations in density, which can be recognized as airflow.

The airflow visualization image (= difference image) generated here has a temperature resolution of 64 levels using digital level values. If the goal is to visualize the effects of airflow and the resulting temperature changes, displaying the digital level values is sufficient, and conversion to Celsius or absolute temperature is not necessarily important.

Furthermore, since this processing is a low-load process that involves only averaging, multiplication, and subtraction, it is sufficient to keep up with the frame rate of 12.5 Hz for each optical filter, and airflow images can be displayed while taking photographs.
11 and 12 are visualization images of the airflow when the direction of the warm airflow discharged from the air conditioner is changed. This also allows us to grasp the change in indoor air temperature caused by the warm airflow, making it possible to quantitatively understand the effect of the airflow compared to conventional methods.
Furthermore, unlike conventional airflow visualization methods that are based on short-term temperature changes, this method displays airflow as a temperature change image in accordance with actual physical phenomena, making it possible to obtain an intuitive and easy-to-understand image of airflow.

When the warm air from the air conditioner was measured with a thermocouple, it was 42°C, while the original temperature of the space being measured was 22°C. Therefore, by converting the digital level value to a temperature resolution of 64 levels from 22°C to 42°C, it is possible to display the temperature on a Celsius or absolute temperature scale.

<Modification 1>
In the above embodiment, the analysis processing is described as being performed in real time, but it is also possible to store the infrared temperature data in the memory device 2d, save the infrared temperature data temporarily, and then analyze the saved infrared temperature data.
FIG. 13 is a flowchart showing an example of the processing procedure in the processing unit 2a when storing infrared temperature data.

In FIG. 13, the same parts as those in the real-time analysis process shown in FIG. 5 are given the same reference numerals, and detailed description thereof will be omitted.
In response to user operations, the processing unit 2a starts the infrared camera 1 (step S1), starts the filter wheel 3 (step S2), and performs initial adjustments of the infrared camera 1, such as calibrating for variations between pixels (step S3). Subsequently, the object to be measured is photographed and displayed on the display device 2b (step S4), and the exposure time is set according to the temperature of the object to be measured (steps S5 and S6).

Then, the process proceeds to step S6a, where saving of the infrared temperature data to the memory device 2d is started, and while switching the filter wheel 3, infrared temperature data corresponding to the infrared absorption wavelength by _CO2 is measured and stored in the memory device 2d (step S6b), and infrared temperature data at the infrared transmission wavelength where infrared absorption by _CO2 is low is measured and stored in the memory device 2d (step S6c).When the end operation is performed (step S6d), the process ends.

Figure 14 is a flowchart showing an example of the processing steps for analysis processing that analyzes infrared temperature data stored in the storage device 2d.

First, infrared temperature data is read from the storage device 2d (step S21). For example, infrared temperature data corresponding to the wavelength at which the initial _CO2 absorbs infrared rays and infrared temperature data corresponding to the wavelength at which the initial _CO2 absorbs infrared rays less are read. Next, a difference image is calculated for the read infrared temperature data (step S22). A search process for the coefficient k1 is performed while the difference image is displayed on the display device 2b in the same manner as in step S12 of FIG. 5 (step S23).

When the user issues an instruction to start the analysis process (step S24), a predetermined number of the oldest infrared temperature data are read from the storage device 2d (step S25), and the oldest infrared temperature data corresponding to wavelengths of infrared absorption by _CO2 are averaged in the same manner as in step S15 to obtain the averaged infrared temperature data corresponding to wavelengths of infrared absorption by _CO2 (step S26). Similarly, the oldest infrared temperature data corresponding to wavelengths of infrared absorption by _CO2 are averaged in the same manner as in step S16 to obtain the averaged infrared temperature data corresponding to wavelengths of infrared absorption by _CO2 (step S27). Then, a difference process is performed using the coefficient k1 identified in step S23 to obtain a difference image, which is stored in the storage device 2d (step S28).

If further analysis is to be performed, the process returns from step S29 to step S25, where a predetermined number of pieces of infrared temperature data are read, averaged (steps S25 to S27), and subtracted to obtain a subtraction image (step S28). At this time, the predetermined number of pieces of infrared temperature data read in step S25 may be the second-oldest piece of infrared temperature data excluding the oldest piece of infrared temperature data stored in the storage device 2d, or the next-oldest piece of infrared temperature data excluding the infrared temperature data used in the averaging in steps S26 and S27 may be read.

If an end operation is performed, the process ends (step S29).
When referring to the differential images, the differential images stored in the storage device 2d are read out and displayed in chronological order, thereby making it possible to display an image of the temperature distribution of the airflow.

<Modification 2>
15 is a flowchart showing an example of a processing procedure when further temperature calibration is performed in the above embodiment, in which a temperature distribution image expressed with a temperature resolution of 64 levels in digital level values is converted into an image corresponding to the actual temperature. This makes it possible to display the temperature on a scale of Celsius temperature or absolute temperature.

In FIG. 15, the same parts as those in the real-time analysis process shown in FIG. 5 are given the same reference numerals, and detailed description thereof will be omitted.
The processes in steps S1 to S12 are the same. After selecting the coefficient k1 in step S12, the process proceeds to step S12a, where temperatures are measured at two or more locations in the airflow using sensors such as thermocouples (step S12a). Then, a linear equation that expresses the relationship between the difference value and the temperature measurement value at each pixel of the difference image is found (step S12b).

Next, proceed to step S13, measure infrared temperature data while switching optical filters (steps S13 and S14), and perform differential processing to obtain a differential image (steps S15 to S17).

Next, the process proceeds to step S17a, where the linear equation detected in step S12b is used to convert the difference value for each pixel in the difference image obtained in step S17 into a temperature, and an image of the conversion results is displayed in real time on the display device 2b (step S18).
The processes of steps S13 to S17b are repeated, and when an operation to end the measurement is performed (step S19), the process ends.

<Modification 3>
16 and 17 are flowcharts showing an example of the processing procedure in the arithmetic processing unit 2a when analyzing infrared temperature data stored in the memory device 2d and performing temperature calibration, in which the temperature distribution expressed with a temperature resolution of 64 levels in digital level values is converted into actual temperature. This makes it possible to display the temperature on a scale of Celsius or absolute temperature.

16 and 17, the same parts as those in the analysis process without temperature calibration shown in FIGS. 13 and 14 are given the same reference numerals, and detailed description thereof will be omitted.
16 is a flowchart showing an example of the processing procedure for storing infrared temperature data. In FIG. 16, the processing in steps S1 to S6 is the same, and after setting the exposure time in step S6, the process proceeds to step S6aa, where temperatures are measured at two or more points in the airflow using sensors such as thermocouples, and the measured values are stored in the storage device 2d.

Next, the process proceeds to step S6a, where acquisition and storage of infrared temperature data is started, and the infrared temperature data is acquired and stored in the memory layer 2d while switching the filter wheel 3, and the process ends when an end operation is performed (steps S6a to S6d).
FIG. 17 is a flowchart showing an example of a processing procedure for analyzing infrared temperature data stored in the storage device 2d and performing temperature calibration.

In FIG. 17, the same parts as those in the analysis process without temperature calibration shown in FIG. 14 are given the same reference numerals, and detailed description thereof will be omitted.
The processing of steps S21 to S23 is the same. After searching for the coefficient k1, the process proceeds to step S23a, where a linear equation expressing the relationship between the difference value and the temperature measurement is detected based on the temperature measurement value stored together with the infrared temperature data in the processing of step S6aa in FIG. 16 and the difference image acquired in the processing of step S22, and the linear equation is stored in a specified memory area.

When the user issues an instruction to start the analysis process (step S24), a predetermined number of the oldest infrared temperature data are read from the storage device 2d (step S25), and the predetermined number of the oldest infrared temperature data at infrared transmission wavelengths, including wavelengths where infrared absorption by _CO2 is high, are averaged and subjected to difference processing (steps S26 to S28).Then, the process proceeds to step S28a, where the linear equation detected in step S23a is used to convert the difference values for each pixel in the difference image obtained in step S28 into temperatures, and the converted values are stored in a predetermined storage area.Then, when an operation to end the analysis is performed, the process ends (step S29).

When referring to the differential image, the differential image stored in the storage device 2d can be read out and displayed in chronological order, allowing for the display of an image of the temperature distribution of the airflow, and it is also possible to display the image with a scale of Celsius temperature and absolute temperature.

The scope of the present invention is not limited to the exemplary embodiments shown and described, but also includes all embodiments that achieve equivalent effects to those intended by the present invention. Furthermore, the scope of the present invention can be defined by any desired combination of specific features among all the respective features disclosed.

Furthermore, the present invention can have the following configurations, for example.
(1)
an imaging device that outputs first infrared temperature data obtained _by capturing infrared rays in a first wavelength band including wavelengths at which infrared rays are absorbed by _CO2 in the same measurement target space, and second infrared temperature data obtained by capturing infrared rays in a second wavelength band in which the amount of infrared rays absorbed by _CO2 is smaller than the amount of infrared rays absorbed by CO2 in the first wavelength band;
a visualization processing unit that generates a difference image by removing a temperature distribution image corresponding to the second infrared temperature data from a temperature distribution image corresponding to the first infrared temperature data, as an image representing an airflow in the measurement target space;
An airflow visualization device comprising:
(2)
The imaging device is
An infrared camera,
one or more first optical filters having the first wavelength band as an infrared transmission wavelength band;
one or more second optical filters having the second wavelength band as an infrared transmission wavelength band;
a filter wheel that switches between the first optical filter and the second optical filter to switch the wavelength band of the infrared light input to the infrared camera,
The airflow visualization device described in (1) above, wherein the infrared camera outputs data obtained by capturing infrared light that has passed through the first optical filter as the first infrared temperature data, and data obtained by capturing infrared light that has passed through the second optical filter as the second infrared temperature data.
(3)
The imaging device is
one or more infrared cameras having a first optical filter having the first wavelength band as an infrared transmission wavelength band, capturing an image of infrared light in the first wavelength band that has passed through the first optical filter and outputting the image as the first infrared temperature data;
one or more infrared cameras having a second optical filter having the second wavelength band as an infrared transmission wavelength band, capturing an image of infrared light in the second wavelength band that has passed through the second optical filter and outputting the image as the second infrared temperature data;
The airflow visualization device according to (1) above,
(4)
The airflow visualization device according to (2) or (3) above, wherein the measurement wavelength of the infrared camera includes a wavelength band of 3 μm or more and 5 μm or less.
(5)
The airflow visualization device according to any one of (2) to (4) above, wherein the first wavelength band is the same wavelength band as a measurable wavelength band of the infrared camera.
(6)
The airflow visualization device according to any one of (1) to (5), wherein the first wavelength band includes a wavelength band of 4.1 μm or more and 4.4 μm or less.
(7)
The imaging device is
An infrared camera,
a second optical filter having the second wavelength band as an infrared transmission wavelength band;
a filter wheel for switching between the second optical filter and a blank section where no optical filter is provided,
The airflow visualization device described in (1) above, wherein the infrared camera outputs data obtained by capturing infrared light that has passed through the blank portion as the first infrared temperature data, and data obtained by capturing infrared light that has passed through the second optical filter as the second infrared temperature data.
(8)
The imaging device is
one or more infrared cameras that capture infrared light in the measurement target space and output the first infrared temperature data;
one or more infrared cameras having a second optical filter having the second wavelength band as an infrared transmission wavelength band, capturing an image of infrared light in the second wavelength band that has passed through the second optical filter and outputting the image as the second infrared temperature data;
The airflow visualization device according to (1) above,
(9)
The airflow visualization device according to any one of (1) to (8), wherein the visualization processing unit creates the differential image based on differential data obtained by subtracting a value obtained by multiplying the second infrared temperature data by a second coefficient from a value obtained by multiplying the first infrared temperature data by a first coefficient.
(10)
A means for acquiring the temperature of CO ₂ in the measurement target space,
the visualization processing unit determines the first coefficient and the second coefficient based on a temperature of the _CO2 ;
The airflow visualization device according to (9) above, wherein the difference image is created using the first coefficient and the second coefficient.
(11)
The airflow visualization device according to any one of (1) to (10), wherein the visualization processing unit processes the first infrared temperature data and the second infrared temperature data in real time to create and display the difference image.
(12)
acquiring the first infrared temperature data and the second infrared temperature data from an imaging device including an infrared camera, the imaging device outputting first infrared temperature data obtained by capturing infrared rays in a first wavelength band including wavelengths at which infrared rays are absorbed by _{CO2 ,} and second infrared temperature data obtained by capturing infrared rays in a second wavelength band in which the amount of infrared rays absorbed by _CO2 is less than the amount of infrared rays absorbed by CO2 in the first wavelength band, in the same measurement target space;
a step of displaying a difference image obtained by removing the temperature distribution image corresponding to the second infrared temperature data from the temperature distribution image corresponding to the first infrared temperature data based on the acquired first infrared temperature data and the acquired second infrared temperature data as an image representing an airflow in the measurement target space;
An airflow visualization method comprising:

REFERENCE SIGNS LIST 1 Infrared camera 2 Analysis processing device 2a Arithmetic processing unit 2b Display device 2c Input device 2d Storage device 21 Camera control unit 22 Filter wheel driving unit 23 Temperature data processing unit 3 Filter wheel 3a Optical filter 10 Airflow visualization device

Claims (12)

an imaging device that outputs first infrared temperature data obtained _by capturing infrared rays in a first wavelength band including wavelengths at which infrared rays are absorbed by _CO2 in the same measurement target space, and second infrared temperature data obtained by capturing infrared rays in a second wavelength band in which the amount of infrared rays absorbed by _CO2 is smaller than the amount of infrared rays absorbed by CO2 in the first wavelength band;
a visualization processing unit that generates a difference image by removing a temperature distribution image corresponding to the second infrared temperature data from a temperature distribution image corresponding to the first infrared temperature data, as an image representing an airflow in the measurement target space;
An airflow visualization device comprising: The imaging device is
An infrared camera,
one or more first optical filters having the first wavelength band as an infrared transmission wavelength band;
one or more second optical filters having the second wavelength band as an infrared transmission wavelength band;
a filter wheel that switches between the first optical filter and the second optical filter to switch the wavelength band of the infrared light input to the infrared camera,
2. The airflow visualization device according to claim 1, wherein the infrared camera outputs, as the first infrared temperature data, data obtained by capturing infrared light that has passed through the first optical filter, and as the second infrared temperature data, data obtained by capturing infrared light that has passed through the second optical filter. The imaging device is
one or more infrared cameras having a first optical filter having the first wavelength band as an infrared transmission wavelength band, capturing an image of infrared light in the first wavelength band that has passed through the first optical filter and outputting the image as the first infrared temperature data;
one or more infrared cameras having a second optical filter having the second wavelength band as an infrared transmission wavelength band, capturing an image of infrared light in the second wavelength band that has passed through the second optical filter and outputting the image as the second infrared temperature data;
The airflow visualization device according to claim 1, further comprising: An airflow visualization device according to claim 2 or 3, characterized in that the measurement wavelength of the infrared camera includes a wavelength band of 3 μm or more and 5 μm or less. The airflow visualization device described in claim 2 or 3, characterized in that the first wavelength band is the same wavelength band as the measurable wavelength band of the infrared camera. An airflow visualization device according to any one of claims 1 to 3, characterized in that the first wavelength band includes a wavelength band of 4.1 μm or more and 4.4 μm or less. The imaging device is
An infrared camera,
a second optical filter having the second wavelength band as an infrared transmission wavelength band;
a filter wheel for switching between the second optical filter and a blank section where no optical filter is provided,
2. The airflow visualization device according to claim 1, wherein the infrared camera outputs, as the first infrared temperature data, data obtained by capturing an image of infrared light that has passed through the blank portion, and as the second infrared temperature data, data obtained by capturing an image of infrared light that has passed through the second optical filter. The imaging device is
one or more infrared cameras that capture infrared light in the measurement target space and output the first infrared temperature data;
one or more infrared cameras having a second optical filter having the second wavelength band as an infrared transmission wavelength band, capturing an image of infrared light in the second wavelength band that has passed through the second optical filter and outputting the image as the second infrared temperature data;
The airflow visualization device according to claim 1, further comprising: The airflow visualization device described in any one of claims 1 to 3, characterized in that the visualization processing unit creates the difference image based on difference data obtained by subtracting a value obtained by multiplying the second infrared temperature data by a second coefficient from a value obtained by multiplying the first infrared temperature data by a first coefficient. A means for acquiring the temperature of CO ₂ in the measurement target space,
the visualization processing unit determines the first coefficient and the second coefficient based on a temperature of the _CO2 ;
The airflow visualization device according to claim 9, wherein the difference image is created using the first coefficient and the second coefficient. The airflow visualization device described in any one of claims 1 to 3, characterized in that the visualization processing unit processes the first infrared temperature data and the second infrared temperature data in real time to create and display the difference image. acquiring the first infrared temperature data and the second infrared temperature data from an imaging device including an infrared camera, the imaging device outputting first infrared temperature data obtained by capturing infrared rays in a first wavelength band including wavelengths at which infrared rays are absorbed by _{CO2 ,} and second infrared temperature data obtained by capturing infrared rays in a second wavelength band in which the amount of infrared rays absorbed by _CO2 is less than the amount of infrared rays absorbed by CO2 in the first wavelength band, in the same measurement target space;
a step of displaying a difference image obtained by removing the temperature distribution image corresponding to the second infrared temperature data from the temperature distribution image corresponding to the first infrared temperature data based on the acquired first infrared temperature data and the acquired second infrared temperature data as an image representing an airflow in the measurement target space;
An airflow visualization method comprising: