JP2018128318A - Gas detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas detector with which it is possible to easily obtain the aptitude information of gas detection with high accuracy.SOLUTION: A gas detector T0 includes an imaging device DU and an absorber OE. The imaging device DU forms an infrared image of a subject and detects, from the infrared image, a gas that is the object to be detected in the subject. The absorber OE has an infrared absorption characteristic that corresponds to the gas. The imaging device DU forms information that indicates the aptitude of gas detection on the basis of a difference between a first infrared image acquired by imaging via the absorber OE and a second infrared image acquired by imaging without going through the absorber OE, and outputs the resultant information.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a gas detection device, for example, a gas detection device that detects gas from an infrared image obtained by an infrared camera.

  In gas consumption places such as petrochemical plants, gas manufacturing factories, and power plants, it is required to detect and deal with gas leaks promptly in order to prevent gas leak accidents. Conventionally, various types of techniques for detecting leaked gas have been known. For example, Patent Document 1 proposes a technique for visualizing and detecting gas with an infrared camera. According to the gas detection technology, the state of gas leakage can be displayed in real time, so that the position of gas leakage can be grasped intuitively.

JP 2013-122389 A

  The suitability (gas detection performance) of gas detection by an infrared camera varies greatly depending on various factors (background objects, weather conditions, etc.) in the shooting environment. Therefore, when installing the infrared camera, it is necessary to confirm whether or not a desired gas detection performance is obtained. However, since the above factors are complicated, it is difficult to perform a high-precision simulation. Even if gas is actually ejected and confirmation is performed, it is not practical to perform it in the entire imaging area. When it is poisonous gas, it is dangerous.

  In addition, since gas detection technology using an infrared camera has not yet become widespread, it is not well known that the gas detection performance changes greatly, and the concept of diagnosing gas detection performance does not exist. Therefore, in the conventional gas detection apparatus as described in Patent Document 1, it is impossible to confirm whether or not a desired gas detection performance is obtained unless gas leakage actually occurs.

  This invention is made | formed in view of such a condition, The objective is to provide the gas detection apparatus which can obtain the suitability information of gas detection easily with high precision.

To achieve the above object, a gas detection device according to a first aspect of the invention corresponds to an imaging device that forms an infrared image of a subject and detects a gas to be detected in the subject from the infrared image, and the gas. An absorber having infrared absorption characteristics; and a gas detection device comprising:
Based on the difference between the first infrared image acquired by the imaging device through imaging through the absorber and the second infrared image acquired through imaging without the absorber, the suitability of gas detection is improved. The information to be shown is formed and output.

  The gas detector according to a second aspect of the present invention is the gas detector according to the first aspect, wherein the absorber is configured so as to cover all or part of the imaging angle of view of the imaging device during imaging via the absorber. It is arranged on the subject side of the imaging device.

  According to a third aspect of the present invention, there is provided the gas detector according to the first or second aspect, wherein the absorber is installed at an angle at which a reflected image of the imaging device itself does not overlap an infrared image of a subject. To do.

  According to a fourth aspect of the present invention, there is provided the gas detector according to the third aspect, further comprising a black body plate in a state adapted to the temperature, wherein the absorption image is formed at an angle where the reflected image of the black body plate overlaps the infrared image of the subject. It is characterized by being installed in a state where the body is adapted to the temperature.

  A gas detector according to a fifth aspect of the present invention is the gas detector according to any one of the first to fourth aspects, wherein the absorber is composed of a gas cell and a gas sealed in the gas cell. The gas sealed in is the same gas as the gas to be detected.

  In the gas detection device according to a sixth aspect of the present invention, in any one of the first to fifth aspects, the second infrared image is an infrared image acquired by photographing through a gas cell in which no gas is sealed. It is characterized by that.

  The gas detector according to a seventh aspect of the present invention is the gas detector according to the fifth or sixth aspect, wherein the transmittance of the portion through which infrared rays are transmitted in the material constituting the gas cell is 30% or more in the infrared absorption wavelength band of the gas. It is characterized by being.

  In the gas detector of the eighth invention according to the fifth invention, the type, concentration or thickness of the gas sealed in the gas cell corresponds to the type, concentration or thickness of the gas to be detected. A plurality of settings are set.

  According to a ninth aspect of the present invention, there is provided the gas detection device according to the eighth aspect, wherein the first infrared image is acquired by changing the concentration or thickness of the gas sealed in the gas cell in stages, and the gas detection is performed. It is characterized in that the concentration or thickness at the lower limit of detection is calculated as information indicating the suitability of the detection.

  In the gas detection device according to a tenth aspect of the present invention, in any one of the first to ninth aspects, the information indicating the suitability of the gas detection is calculated from the luminance values of the first and second infrared images. / N ratio.

  According to an eleventh aspect of the present invention, there is provided the gas detector according to any one of the first to tenth aspects, wherein information indicating the suitability of the gas detection is output in a map display.

  A gas detector according to a twelfth aspect of the present invention is the gas detector according to any one of the first to eleventh aspects, wherein the absorber is moved between the time of photographing through the absorber and the time of photographing not through the absorber. It further has a drive mechanism.

  The gas detector according to a thirteenth aspect of the present invention is characterized in that, in any one of the first to twelfth aspects, the first and second infrared images are average images of 5 frames or more.

  According to a fourteenth aspect of the present invention, there is provided the gas detector according to any one of the first to thirteenth aspects, wherein the first and second infrared images are alternately acquired and each is based on a difference between the average images of two or more times. Thus, information indicating suitability of the gas detection is formed.

  According to the present invention, it is possible to easily obtain suitability information for gas detection with high accuracy while having a simple configuration in which an absorber is combined with an imaging device. Thereby, selection of the installation place of an imaging device and determination of whether introduction is possible can be easily performed. Further, if the infrared absorption characteristics of the absorber are set so as to correspond to the type, concentration or thickness of the gas to be detected, it is possible to estimate what kind of gas can be detected up to which concentration.

The schematic block diagram which shows embodiment of a gas detection apparatus. The flowchart which shows the specific example of the measurement procedure by embodiment of a gas detection apparatus. 1 is a schematic cross-sectional view showing a first embodiment of a gas detection device. The schematic sectional drawing which shows 2nd Embodiment of a gas detection apparatus. The schematic sectional drawing which shows 3rd Embodiment of a gas detection apparatus. The top view which shows the relationship between the imaging area and absorber area in embodiment of a gas detection apparatus. The image figure which shows an example of the S / N ratio map by embodiment of a gas detection apparatus.

  Hereinafter, the gas detection apparatus etc. which implemented this invention are demonstrated, referring drawings. In addition, the same code | symbol is mutually attached | subjected to the part which is the same in each embodiment etc., and the corresponding part, and duplication description is abbreviate | omitted suitably.

  FIG. 1 schematically shows a schematic cross-sectional structure of a gas detection device T0 according to an embodiment of the present invention. As shown in FIG. 1, the gas detection device T0 includes an imaging device DU, an absorber OE, and the like. The imaging device DU has sensitivity to an electromagnetic wave in a specific wavelength band among electromagnetic waves radiated or reflected by a subject surface (object surface) having an absolute temperature of zero degrees or more, and brightness of a subject image including the electromagnetic wave in the specific wavelength band It is acquired as information. The absorber OE disposed in front of the field of view of the imaging device DU has an absorption characteristic equivalent to that of the detection target gas with respect to electromagnetic waves in a specific wavelength band.

  A typical example of the electromagnetic waves in the specific wavelength band is infrared rays, and a specific example of the imaging device DU is an infrared imaging device (that is, an infrared camera having sensitivity in the infrared wavelength region). Therefore, as a specific example of the gas detection device T0, an imaging device DU that forms an infrared image of a subject and detects a gas to be detected in the subject from the infrared image, and an infrared absorption characteristic corresponding to the detection target gas are provided. And an absorber OE having a gas detection system. As a further specific example of the imaging device DU, an infrared imaging device capable of detecting at least a part of wavelengths in a wavelength band of 1 to 16 μm is exemplified. For example, an uncooled far-infrared imaging device that detects 8 to 16 μm, A cooling-type mid-infrared imaging device that detects 3 to 5 μm is included. That is, a specific wavelength range may be set according to the observation target and the purpose of use, and an imaging device DU having detection sensitivity in the specific wavelength range may be selected.

  As an example of the absorber OE, a gas cell in which a detection target gas is sealed can be cited. That is, the absorber OE can be configured by enclosing the same gas as the detection target gas in the gas cell. The surface of the gas cell is preferably made of a material such as a glass plate, a plastic plate, or an optical film, and has a high transmittance for a specific wavelength region. For example, the transmittance of the portion of the material constituting the gas cell that transmits infrared rays (for example, each portion on the subject side and imaging device side of the gas) is 30% or more in the infrared absorption wavelength band of the detection target gas. Is desirable. The absorber OE is not limited to a gas cell. For example, an optical element having absorption characteristics equivalent to the detection target gas may be used as the absorber OE.

  The imaging device DU includes a lens unit LU that optically captures a subject image and outputs it as an electrical signal for still image shooting and moving image shooting of the subject. The lens unit LU, in order from the object (subject) side, picks up an imaging lens LN (AX: optical axis) that forms an optical image (subject image) of the object and an optical image formed by the imaging lens LN from the infrared of the subject. And an imaging sensor SR that converts an electrical signal as an image.

  In addition to the lens unit LU, the imaging device DU includes a signal processing unit 1, an operation control unit 2, a memory 3, an operation unit 4, a display unit 5, and the like. The signal generated by the image sensor SR is subjected to predetermined digital image processing, image compression processing, and the like as required by the signal processing unit 1 and recorded as a digital video signal in the memory 3 (semiconductor memory, optical disk, etc.) Via a cable or converted into an infrared signal or the like, it is transmitted to another device by a communication function. The arithmetic control unit 2 is composed of a microcomputer, and centrally performs control of functions such as a luminance information processing function, a photographing function, and an image reproduction function; and control of a moving mechanism of the imaging lens LN and the absorber OE. The operation unit 4 is a part including operation members such as operation buttons, and transmits information input by the operator to the calculation control unit 2. The display unit 5 includes a display such as a liquid crystal monitor, and displays an image using the image signal and recorded image information converted by the image sensor SR (information display such as gas leak notification, information display of gas detection suitability). I do.

  The parts other than the lens unit LU in the imaging device DU are in a digital device such as a control terminal device, a personal computer (stationary type, portable type, etc.), a portable device (smart phone, tablet terminal, touch pad, etc.) in the central monitoring room. At least a part thereof can be easily configured by a central processing unit (CPU), a random access memory (RAM), a read only memory (ROM), a hard disk drive (HDD), and the like. Then, the CPU reads out an information processing program suitable for gas detection stored in the HDD, develops it in the RAM, and executes it, thereby realizing the functions of the respective units.

  The suitability of gas detection by an infrared camera (gas detection performance) varies greatly depending on various factors in the photographing environment such as background objects and weather conditions as described above. Therefore, when installing the infrared camera, it is necessary to confirm whether or not a desired gas detection performance is obtained. Therefore, in the gas detection device T0, the imaging device DU that performs gas detection using infrared imaging images acquires the first infrared image acquired by imaging through the absorber OE and the imaging not through the absorber OE. Based on the difference from the second infrared image, information indicating the suitability of gas detection is formed and output.

  In FIG. 2, the specific example of the measurement procedure by gas detection apparatus T0 is shown. Since the temperature of the absorber OE greatly affects the measurement of information indicating the suitability for gas detection, the temperature of the absorber OE is first made equal to the temperature at the start of measurement (# 10). For example, after the measurement is started, the temperature of the absorber OE is made equal to the air temperature by waiting until a predetermined time elapses. This predetermined time is obtained in advance by calculation simulation or experiment in consideration of the heat capacity of the absorber OE, the surface area of the absorber OE, and the like. Alternatively, after the measurement is started, the temperature of the absorber OE is made equal to the air temperature by waiting until the change with time in the temperature of the absorber OE falls within an allowable range (near the temperature change of zero). The temperature measurement of the absorber OE is performed using, for example, a temperature measuring device such as a thermocouple.

  In a specific example of the measurement procedure, when the absorber OE is adjusted so as to have the same temperature as the air temperature (# 10), a first infrared image is acquired by photographing through the absorber OE (# 20), and the absorber OE is obtained. A second infrared image is acquired by photographing without passing through (# 30). Based on the difference between the acquired first and second infrared images, information indicating the suitability of gas detection is formed and output (# 40), and the measurement is terminated (# 50). Although this gas detection device T0 has a simple configuration in which the imaging device DU is combined with the absorber OE, the gas detection aptitude information can be easily obtained with high accuracy. This makes it possible to easily select the installation location of the imaging device DU and determine whether or not to introduce the imaging device DU. Note that the order of obtaining the first infrared image and obtaining the second infrared image may be reversed.

  In order to acquire a first infrared image by imaging through the absorber OE (# 20) and acquire a second infrared image by imaging without the absorber OE (# 30), infrared rays from the subject are absorbed. It is necessary to configure an optical path that does not pass through the body OE and an optical path that does not pass through the body OE. As a more specific configuration for that purpose, gas detectors T1 to T3 corresponding to the first to third embodiments are shown in FIGS.

  The gas detection device T1 shown in FIG. 3 inserts the absorber OE into the field of view of the imaging device DU (FIG. 3A) and retracts the absorber OE outside the field of view of the imaging device DU (FIG. 3 ( B)), the insertion / extraction mechanism 10 for switching is provided. The insertion / removal mechanism 10 is a drive mechanism that moves the absorber OE between photographing through the absorber OE and photographing without using the absorber OE. An example of the insertion / extraction mechanism 10 is one that moves the absorber OE in a straight line. Moreover, the absorber OE is arrange | positioned at a rotation member, and what rotates the rotation member and puts the absorber OE in the visual field of the imaging device DU is mentioned.

  When the absorber OE is inserted into the field of view of the imaging device DU as shown in FIG. 3A, the absorber OE completely covers the field of view of the imaging device DU, so that a subject image is formed through the absorber OE. 1 infrared image can be acquired. As shown in FIG. 3B, when the absorber OE is retracted out of the field of view of the imaging device DU, the absorber OE is completely out of the field of view of the imaging device DU, so that a subject image is formed without passing through the absorber OE. Thus, the second infrared image can be acquired.

  4 includes insertion of the absorber OE into the field of view of the imaging device DU (FIG. 4A), and removal of the absorber OE outside the field of view of the imaging device DU (FIG. 4 ( B)) is performed manually or automatically. In the gas detectors T0 and T1 (FIGS. 1 and 3), the absorber OE is arranged perpendicular to the optical axis AX (that is, the normal of the optical surface that transmits infrared rays is parallel to the optical axis AX). However, in such an arrangement, unless the transmittance of the surface of the absorber OE is ideal 100%, a reflection image of the surface of the absorber OE is captured. Therefore, in the gas detection device T2, the absorber OE is disposed with an inclination as shown in FIG. 4A in order to prevent a narcissus effect that captures a reflected image of the imaging device DU itself (here, The inclination angle is 45 degrees.) That is, the absorber OE is installed at an angle at which the reflected image of the imaging device DU itself does not overlap the infrared image of the subject. Therefore, it is possible to perform measurement with higher accuracy.

  When the absorber OE is inclined as described above, electromagnetic waves may enter from the periphery of the absorber OE. Therefore, in order to block electromagnetic waves incident from the periphery of the absorber OE, it is desirable to dispose the black body plate B1 at the surface reflection destination of the absorber OE. At this time, it is further desirable that the absorber OE is installed at an angle at which the reflected image of the black body plate B1 overlaps the infrared image of the subject. That is, here, the black body plate B1 is imaged together with the subject by setting the inclination angle of the absorber OE to 45 degrees. As described above, it is desirable that the absorber OE be installed in a state in which it is adapted to the temperature. Similarly, it is desirable that the black body plate B1 is also installed in a state that is sufficiently adapted to the temperature.

  In imaging through the absorber OE, the absorber OE is disposed on the subject side of the imaging device DU so as to cover all or part of the imaging field angle (that is, in the field of view) of the imaging device DU. desirable. In the gas detection device T1, the absorber OE is arranged on the subject side of the imaging device DU so as to cover the entire imaging field angle of the imaging device DU, but covers only a specific area as necessary. You may do it.

  FIG. 6 shows the relationship between the imaging area A0 and the absorber area A1. 6A shows a state where the absorber OE covers the entire range of the shooting angle of view, and FIG. 6B shows a state where the absorber OE covers a part of the shooting angle of view (in the imaging area A0). The state in which the absorber area A1 is located in the center portion) is shown. In the gas detection device T2, only the size and shape of the absorber OE can be changed, so that only a part of the shooting angle of view can be covered with the absorber OE, and the first infrared image can be obtained only for that portion. it can.

  The gas detection device T3 shown in FIG. 5 includes insertion of the absorber OE into the field of view of the imaging device DU (FIG. 5A), and insertion of an empty gas cell GC into the field of view of the imaging device DU (FIG. 5). (B)) is switched manually or automatically. The absorber OE is composed of a gas cell GC and a gas GS enclosed in the gas cell GC. The gas GS enclosed in the gas cell GC is the same gas as the gas to be detected. In the gas cell GC, it is desirable that the materials located on the subject side and the imaging device DU side of the gas GS transmit at least 30% of infrared rays in the infrared absorption wavelength band of the gas GS.

  In the gas detection device T3, similarly to the gas detection device T2, an angle (inclination angle) at which the reflected image of the imaging device DU itself does not overlap the infrared image of the subject in order to prevent a narcissus effect that captures a reflected image of the imaging device DU itself. : 45 degrees), the absorber OE (FIG. 5A) and the gas cell GC (FIG. 5B) are arranged. Also, the black body plate B1 is arranged in the same manner as the gas detection device T2.

  In the gas detection device T2, the second infrared image is acquired by photographing with the absorber OE removed outside the field of view of the imaging device DU. In the gas detection device T3, the second infrared image is empty in the field of view of the imaging device DU. A second infrared image is acquired by photographing with the gas cell GC inserted. That is, the second infrared image used in the gas detection device T3 is an infrared image acquired by photographing through the gas cell GC in which the gas GS is not sealed. When the gas cell GC in which the gas GS is not enclosed is used, the conditions other than the presence or absence of the gas GS are the same, so that the influence of the reflected image on the surface of the gas cell GC can be canceled. Therefore, suitability information for gas detection can be obtained with higher accuracy.

  It is desirable that a plurality of types, concentrations or thicknesses of the gas GS enclosed in the gas cell GC are set so as to correspond to the types, concentrations or thicknesses of the gas to be detected. Thereby, the suitability information of the gas detection with respect to various gas types, concentrations or thicknesses can be easily obtained. In other words, by setting the infrared absorption characteristics of the absorber OE so as to correspond to the type, concentration, or thickness of the gas GS to be detected, it is possible to estimate what concentration of gas GS can be detected. . Therefore, the first infrared image is obtained by changing the concentration or thickness of the gas GS enclosed in the gas cell GC in a stepwise manner (for example, measuring a plurality of times using a gas having a thickness corresponding to each concentration). It is desirable to calculate the concentration or thickness at the lower limit of detection as information indicating the suitability of gas detection. If several concentrations or thicknesses are measured, other concentrations or thicknesses can be estimated. For example, if detection is possible with an S / N ratio of 3 or more by an algorithm, the density corresponding to the S / N ratio of 3 is the detection lower limit density.

  In the gas detection devices T1 to T3 described above, a first infrared image is acquired by imaging through the absorber OE (# 20 in FIG. 2), and a second infrared image is acquired by imaging not through the absorber OE. At that time (# 30 in FIG. 2), in order to reduce an error between the first infrared image and the second infrared image, the first and second infrared images are preferably average images of 5 frames or more. . Moreover, in order to reduce the influence of time drift, the first and second infrared images are alternately acquired, and information indicating the suitability of gas detection can be formed based on the difference between the average images of two or more times. desirable.

  In the gas detection devices T1 to T3, as described above, information indicating the suitability of gas detection is obtained based on the difference between the first infrared image and the second infrared image (# 40 in FIG. 2). In each pixel of the obtained first and second infrared images, a difference in luminance information between the first infrared image and the second infrared image is calculated. The absolute value of the difference in information is information indicating the suitability of gas detection, and the larger the value, the better the suitability of gas detection.

The information indicating the suitability for gas detection is preferably the S / N ratio calculated from the luminance values of the first and second infrared images, and is preferably output in a map display. For example, by displaying a map with the S / N ratio, it is possible to output the suitability of gas detection more easily. The S / N ratio is calculated by the following formula (F1).
S / N ratio = | S1-S2 | / N (F1)
S1: Luminance value of the first infrared image,
S2: luminance value of the second infrared image,
N: NETD (Noise Equivalent Temperature Difference) luminance value,
It is. The brightness value N may be a catalog value or may be obtained by actual measurement. The luminance values S1, S2 and N may be used as they are, or may be used after being converted into temperature values.

  When gas detection is automated by an algorithm, if the lower limit value of the S / N ratio that can be detected by the algorithm is known, it is possible to display a detectable area and an undetectable area. For example, if the threshold of the S / N ratio that can be detected by the algorithm is 3, it can be seen that an area with an S / N ratio of 3 or more can be detected and an area with an S / N ratio of less than 3 cannot be detected. .

  By displaying the S / N ratio calculated for each pixel in a color scale or gray scale, the user can easily and intuitively detect the suitability of gas detection for all or a part of the imaging area A0 (FIG. 6). Can know. FIG. 7 shows an example of the S / N ratio map. Here, the following apparatus configuration is assumed.

  For example, the detection target gas is methane gas, and the detection target concentration is one tenth of the lower explosion limit, that is, 0.5% (the lower explosion limit of methane is 5%). Since it is the concentration thickness product (concentration × thickness) that can be detected by a system such as the gas detection devices T1 to T3 described above, the concentration thickness product is 0.5% · m (0.5% gas is 1 m thick). Equivalent to exist). Methane gas has an absorption characteristic in the wavelength region of 3.2 μm to 3.4 μm, and images a signal in that wavelength region. When the gas cell GC in which the gas GS is sealed is used as the absorber OE, an optical film (an FEP film NR0538-03 manufactured by Freon Chemical) that transmits the wavelength region is used on the surface of the gas cell GC. The thickness of the gas cell GC is set to 3.5 mm so as to be equivalent to 0.5% · m (inclined by 45 degrees and the optical path length is 5 mm).

  As can be understood from the above description, each of the above-described embodiments includes the following characteristic configurations (C1) to (C3) and the like.

(C1): Gas detection including an imaging device that forms an infrared image of a subject and detects a gas to be detected in the subject from the infrared image, and an absorber having infrared absorption characteristics corresponding to the gas. A device,
Based on the difference between the first infrared image acquired by the imaging device through imaging through the absorber and the second infrared image acquired through imaging without the absorber, the suitability of gas detection is improved. A gas detector characterized by forming and outputting information to be displayed.

(C2): A method for diagnosing the suitability of gas detection when detecting a gas to be detected in the subject from an infrared image of the subject,
First and second infrared images are acquired by photographing through an absorber having infrared absorption characteristics corresponding to the gas and photographing without using the absorber, and the first infrared image and the second infrared image are obtained. A gas detection suitability diagnostic method comprising forming and outputting information indicating suitability of gas detection based on a difference from an image.

(C3): A program for diagnosing the suitability of gas detection when detecting a gas to be detected in the subject from an infrared image of the subject,
A process of acquiring a first infrared image by imaging through an absorber having infrared absorption characteristics corresponding to the gas, a process of acquiring a second infrared image by imaging without passing through the absorber, and the first A gas detection aptitude diagnosis program that causes a computer to execute a process of forming and outputting information indicating the suitability of gas detection based on a difference between the infrared image and the second infrared image.

  As can be seen from each of the above-described embodiments, according to the embodiment of the gas detection device, the gas detection aptitude information can be easily obtained with high accuracy while the imaging device DU is combined with the absorber OE. It is possible to obtain. This makes it easy to select the installation location of the imaging device DU and determine whether or not to introduce the imaging device DU. In addition, if the infrared absorption characteristics of the absorber OE are set so as to correspond to the type, concentration, or thickness of the gas GS to be detected, it is possible to estimate what concentration of gas GS can be detected. These effects can be similarly obtained even when the gas detection suitability diagnosis method or the gas detection suitability diagnosis program is used.

T0, T1, T2, T3 Gas detection device OE Absorber GC Gas cell GS Gas DU Imaging device LU Lens unit LN Imaging lens SR Imaging sensor AX Optical axis A0 Imaging area A1 Absorber area B1 Black body plate 1 Signal processing unit 2 Operation control Part 3 Memory 4 Operation part 5 Display part 10 Insertion / extraction mechanism (drive mechanism)

Claims (14)

A gas detection apparatus comprising: an imaging device that forms an infrared image of a subject and detects a gas to be detected in the subject from the infrared image; and an absorber having infrared absorption characteristics corresponding to the gas. ,
Based on the difference between the first infrared image acquired by the imaging device through imaging through the absorber and the second infrared image acquired through imaging without the absorber, the suitability of gas detection is improved. A gas detector characterized by forming and outputting information to be displayed.   The imaging device via the absorber is characterized in that the absorber is arranged on the subject side of the imaging device so as to cover all or part of the imaging field angle of the imaging device. The gas detector according to 1.   The gas detector according to claim 1 or 2, wherein the absorber is installed at an angle at which a reflected image of the imaging device itself does not overlap an infrared image of a subject.   It further has a black body plate that is adapted to the temperature, and the absorber is installed at an angle at which the reflected image of the black body plate overlaps the infrared image of the subject in a state that is adapted to the temperature. The gas detector according to claim 3.   The absorber is composed of a gas cell and a gas sealed in the gas cell, and the gas sealed in the gas cell is the same gas as the gas to be detected. Item 5. The gas detection device according to any one of Items 1 to 4.   The gas detection apparatus according to claim 1, wherein the second infrared image is an infrared image acquired by photographing through a gas cell in which no gas is sealed.   7. The gas detection device according to claim 5, wherein a transmittance of a portion of the material constituting the gas cell that transmits infrared light is 30% or more in an infrared absorption wavelength band of the gas.   6. The gas according to claim 5, wherein a plurality of types, concentrations or thicknesses of the gas sealed in the gas cell are set so as to correspond to the types, concentrations or thicknesses of the gas to be detected. Detection device.   Obtaining the first infrared image by stepwise changing the concentration or thickness of the gas sealed in the gas cell, and calculating the concentration or thickness of the detection lower limit as information indicating the suitability of the gas detection The gas detection device according to claim 8, wherein   10. The gas according to claim 1, wherein the information indicating suitability of the gas detection is an S / N ratio calculated from luminance values of the first and second infrared images. Detection device.   The gas detection device according to claim 1, wherein information indicating suitability of the gas detection is output in a map display.   12. The driving mechanism according to claim 1, further comprising a drive mechanism that moves the absorber between the time of shooting through the absorber and the time of shooting not through the absorber. Gas detector.   The gas detection device according to any one of claims 1 to 12, wherein the first and second infrared images are average images of 5 frames or more, respectively.   The first and second infrared images are alternately acquired, and information indicating suitability of the gas detection is formed based on a difference between the average images of two or more times. The gas detection device according to any one of claims.