Method and apparatus for detecting active organisms

Abstract

To provide a method for passively detecting an active body such as a vehicle located in the back of a shielding object such as a wall.SOLUTION: A method for detecting an active body uses an image formation optical system for forming infrared light into an image and an image sensor in which pixel elements made of an infrared light sensing element having a photoelectric conversion layer for converting the infrared light into an electric signal are arranged in a matrix, forms the infrared light into an image on the image sensor by the image optical system, captures gas discharged from an active body located in the back of an object or in a shieling body, and detects the active body.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a moving object detection method and an apparatus therefor.

Background Art

[0002] There is a demand for detecting moving objects such as vehicles, weapons, and animals hidden behind obstacles such as walls. With moving object detection technology, it becomes possible to detect a child jumping out from behind an object and protect them from traffic accidents, protect oneself from a fierce bear hiding in the bushes, trace and destroy weapons hidden in bushes or shelters and waiting in a standby state, and rescue people or pets buried under rubble due to an earthquake and unable to be searched for.

[0003] As methods for detecting moving objects, there are methods of capturing images in the visible light and infrared wavelength ranges by active or passive methods that are being put into practical use as vehicle collision avoidance systems, methods of irradiating electromagnetic wave reflected waves such as microwaves and analyzing the reflected waves, and methods of passively monitoring heat sources from reconnaissance aircraft or artificial satellites using infrared rays, which are being developed for military applications. As a system of this kind, for example, an active type detection system that detects using infrared sensors with the light of a strobe light device is disclosed in Patent Document 1. However, these methods have a problem that it is difficult to detect a moving object if there is an obstacle such as a wall or bushes, particularly a shield object maintained at room temperature, between the site where detection is performed and the location where the moving object is placed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Non-Patent Documents

[0005]

Non-Patent Document 1

[0006] The object of the present invention is to provide an activity detection method and apparatus for passively detecting active objects such as cars and animals, even when they are obscured by obstacles such as shadows. Furthermore, this invention aims to address the limitations on the measurement target and environment, and to enable the determination of whether the type of active entity is an engine-powered system such as a car, or an animal system such as a human, bear, or deer. Therefore, the object of the present invention is to provide a method and apparatus that can detect active objects hidden behind obstacles that are difficult to detect with visible light, radar, or sound collectors, without using a light source such as laser light, and without requiring safety considerations even in spaces where people are present. [Means for solving the problem]

[0007] The configuration of the present invention for solving the problem is shown below. (Composition 1) An imaging optical system that forms an image of infrared light, An image sensor is used in which pixel elements, each consisting of an infrared light sensing element having a photoelectric conversion layer that converts the aforementioned infrared light into an electrical signal, are arranged in a matrix. The infrared light is imaged onto the image sensor via the imaging optical system. A method for detecting moving objects that are behind objects or shielding. (Configuration 2) The method for detecting an active organism according to configuration 1, wherein the wavelength of the infrared light is 4.15 μm or more and 4.40 μm or less. (Composition 3) The method for detecting an active organism according to configuration 1, wherein the wavelength of the infrared light is 4.20 μm or more and 4.35 μm or less. (Composition 4) The infrared light consists of light from two or more different wavelength bands, and each wavelength band is individually imaged onto the image sensor. Furthermore, the wavelengths of light in the aforementioned wavelength bands are 2.4 μm to 3.6 μm, 2.5 μm to 2.9 μm, 2.9 μm to 3.2 μm, 3.1 μm to 3.5 μm, 4.15 μm to 4.40 μm, 4.15 μm to 4.90 μm, 4.4 μm to 5.5 μm, 4.45 μm to 4.95 μm, 4.6 μm to 10 μm, and 5.0 μm. A method for detecting active organisms according to Configuration 1, comprising two or more elements selected from the group consisting of m to 7.5 μm, 5.0 μm to 6.5 μm, 5.1 μm to 5.6 μm, 6.0 μm to 6.5 μm, 6.0 μm to 7.1 μm, 7.2 μm to 8.2 μm, 7.6 μm to 8.2 μm, 8 μm to 13 μm, and 14 μm to 16 μm. (Composition 5) The method for detecting an active organism according to configuration 4, which identifies and detects the type of active organism by comparing the intensity changes caused by light of two or more different wavelength bands. (Composition 6) The method for detecting an active organism according to configuration 4 or 5, wherein the first wavelength band, which is one of the aforementioned wavelength bands, is 4.15 μm or more and 4.40 μm or less. (Composition 7) The method for detecting an active organism according to configuration 6, wherein the first wavelength band is 4.20 μm or more and 4.35 μm or less. (Composition 8) The method for detecting an active organism according to any one of the configurations 1 to 7, wherein the photoelectric conversion layer is made of InSb. (Composition 9) A bandpass filter that transmits only infrared light of the aforementioned wavelength is placed before or after the imaging optical system. The method for detecting an active object according to any one of configurations 1 to 8, wherein the infrared light is imaged onto the image sensor via the bandpass filter. (Composition 10) The method for detecting an active object according to configuration 9, wherein the bandpass filter is cooled. (Composition 11) The method for detecting an active object according to configuration 10, wherein the cooling temperature is 50K or more and 250K or less. (Configuration 12) Comprising a camera and image processing means, The camera includes an imaging optical system for infrared light with a wavelength of 2.4 μm or more and 16 μm or less, and has an image sensor in which pixel elements each comprising an infrared light sensing element having a photoelectric conversion layer for converting the infrared light into an electric signal are arranged in a matrix, The image processing means is a moving object detection device that analyzes the intensity distribution acquired by the image sensor to perform region extraction processing. (Configuration 13) The moving object detection device according to Configuration 12, wherein the wavelength of the infrared light is 4.15 μm or more and 4.40 μm or less. (Configuration 14) The moving object detection device according to Configuration 12, wherein the wavelength of the infrared light is 4.20 μm or more and 4.35 μm or less. (Configuration 15) The infrared light consists of light in two or more different wavelength bands, and is imaged on the image sensor separately according to the light in each wavelength band, and the wavelengths of the light in the wavelength bands are selected from the group consisting of 2.4 μm or more and 3.6 μm or less, 2.5 μm or more and 2.9 μm or less, 2.9 μm or more and 3.2 μm or less, 3.1 μm or more and 3.5 μm or less, 4.15 μm or more and 4.40 μm or less, 4.15 μm or more and 4.90 μm or less, 4.4 μm or more and 5.5 μm or less, 4.45 μm or more and 4.95 μm or less, 4.6 μm or more and 10 μm or less, 5.0 μm or more and 7.5 μm or less, 5.0 μm or more and 6.5 μm or less, 5.1 μm or more and 5.6 μm or less, 6.0 μm or more and 6.5 μm or less, 6.0 μm or more and 7.1 μm or less, 7.2 μm or more and 8.2 μm or less, 7.6 μm or more and 8.2 μm or less, 8 μm or more and 13 μm or less, 14 μm or more and 16 μm or less, and are two or more. The moving object detection device according to Configuration 12. (Configuration 16) The image processing means compares the intensity changes due to the light in the two or more different wavelength bands, and specifies and outputs the type of the moving object from the ratio of the change amounts. The moving object detection device according to Configuration 15. (Configuration 17) The active body detection device according to Configuration 15 or 16, wherein a first wavelength band, which is one of the first wavelength bands, is 4.15 μm or more and 4.40 μm or less. (Configuration 18) The active body detection device according to Configuration 17, wherein the first wavelength band is 4.20 μm or more and 4.35 μm or less. (Configuration 19) The active body detection device according to any one of Configurations 12 to 18, wherein the photoelectric conversion layer is made of InSb. (Configuration 20) A band-pass filter that transmits only infrared light of the wavelength is installed in front of or behind the imaging optical system, The active body detection device according to any one of Configurations 12 to 19, wherein the infrared light is imaged on the image sensor through the band-pass filter. (Configuration 21) The active body detection device according to Configuration 20, wherein the band-pass filter is cooled.

Advantages of the Invention

[0008] According to the present invention, there are provided an active body detection method and an apparatus therefor that passively detect and detect an active body such as a vehicle or an animal even when it is blocked by an obstacle such as a shaded area. Further, according to the present invention, there is no limitation on the measurement object or the environment, and it is possible to discriminate whether the type of the active body is an internal combustion engine-mounted system such as a vehicle, an animal system such as a person, a bear or a deer, or a living system. Furthermore, the device of the present invention is also characterized in that it is compact and can be easily carried around in a real environment.

Brief Description of the Drawings

[0009] [Figure 1] It is an explanatory diagram for explaining a method of detecting an active body hidden by an obstacle. [Figure 2] It is a block diagram showing the schematic configuration of the device of the present invention. [Figure 3] It is an explanatory diagram showing the configuration of the camera unit of the device of the present invention. [Figure 4] It is a block diagram showing the configuration of the image processing means of the present invention. [Figure 5] These characteristic diagrams show the absorption spectra of various gases, with (a) representing CO2 gas, (b) representing water vapor, (c) representing CH4 gas, and (d) representing NH3 gas. [Figure 6] These are characteristic diagrams showing the absorption spectra of various gases. (a1) shows CO2 gas at room temperature, (a2) shows CO2 gas at 2000°C, (b1) shows H2O (water vapor) at room temperature, and (b2) shows H2O at 2000°C. [Figure 7] These characteristic diagrams show the absorption spectra of various gases at room temperature, with (a) showing the case for CO gas, (b) for NO gas, and (c) for NO2 gas. [Figure 8] These characteristic diagrams show the absorption spectra of various gases at 2000°C, with (a) showing the case for CO gas, (b) for NO gas, and (c) for NO2 gas. [Figure 9] This is a photograph of the portable measuring device used in the example. [Figure 10] This is a characteristic diagram showing the transmission spectrum of the bandpass filter used in the example. [Figure 11] This is a characteristic diagram showing the temperature characteristics of the radiant intensity of the bandpass filter used in the example. [Figure 12] This is a photograph showing an observation example according to the present invention. [Figure 13] This is a photograph showing an observation example according to the present invention. [Figure 14] This is a photograph showing an observation example according to the present invention. [Figure 15] This is a photograph showing an observation example according to the present invention. [Figure 16] This is a photograph showing an observation example according to the present invention. [Modes for carrying out the invention]

[0010] The embodiments for carrying out the present invention will be described below with reference to the drawings. Note that AB in the text represents A or greater and B or less.

[0011] <Detection principle> In the present invention's method for detecting active objects, gas leaking from a shielding object is detected by visualizing it with a camera that passively responds to a specific wavelength. In other words, as shown in Figure 1, the present invention's method for detecting active objects uses an activity detection device 4 equipped with a camera that acquires images in response to specific wavelengths in the infrared light region. By capturing how gases 5 emitted by active objects such as animals 2 or cars 3 hiding behind a shield 1, leak out and spread around the shield 1, the device detects, identifies, and identifies the active object. Because it is a passive measurement method that utilizes infrared light naturally emitted from the outside world, it is a simple detection method that can be used even in darkness and has a wide range of applications. Here, a shielding object (shielding body) refers to a shielding material such as a wall or bush that prevents direct viewing of the target activity using visible light, infrared light, ultraviolet light, microwaves, etc. Furthermore, an "active entity" refers to an object that can move using an internal combustion engine, fuel cell, or biological organs. Specific examples include cars, airplanes, mobile weapons (combat vehicles, fighter jets, robotic weapons, etc.), humans, animals such as bears, wild boars, and deer, and living organisms.

[0012] <<First specific wavelength>> The first specific wavelength of infrared light mentioned above is the absorption spectral band of CO2 molecules, which is between 4.15 μm and 4.40 μm, and in particular, the wavelength band with relatively high absorbance within that band, which is between 4.20 μm and 4.35 μm. Since CO2 molecules are emitted by internal combustion engines and animals alike, monitoring the presence of CO2 molecules in this wavelength band allows for the detection of active organisms.

[0013] The primary characteristic of CO2 molecules is their visibility and identifiability. As evidenced by its status as a leading greenhouse gas, CO2 gas is an absorber with strong absorption in the infrared region. The absorbance of CO2 molecules is shown in Figures 5(a) and 6(a1) for room temperature and in Figure 6(a2) for 2000°C. Within the sensitivity wavelength range of 3-5 μm for the InSb infrared sensor mainly discussed in this patent, there is a sharp, strong absorption at wavelengths of 4.20-4.35 μm. This absorbance is the absorbance of CO2 contained in air at 1 atmosphere and 25°C with a column density of 100 ppm·m, and the base of the exponent is 10 (common logarithm is used, not natural logarithm). Column density is a quantity that substantially defines the attenuation of light, taking into account both the concentration and optical path length necessary to specify the absorbance of an absorbent gas. For example, a column density of 100 ppm·m is the state in which a gas with a volume concentration of 100 ppm is distributed over a length of 1 m. In this patent, the state of 1 atmosphere and 25°C is referred to as the standard state. There are no major gas molecules present in the air that have a strong absorption in the same wavelength range. Therefore, by focusing on this wavelength, it is possible to detect the amount of CO2 gas with high sensitivity, and to identify and obtain information about CO2 specifically from other gases. Here, the absorbance of all gases, including CO2, at room temperature is calculated using the HANST gas quantification database of ST Japan Co., Ltd., with a resolution of 1.0 cm². -1 The following was used. Furthermore, the absorbance of all gases at 2000°C was measured using the publicly available database HITEMP (Non-Patent Document 1) with a resolution of 1.0 cm. -1 This was the request.

[0014] The second characteristic of the CO2 molecule is its light weight and flexibility. CO2, being a molecule, easily mixes with the surrounding air and accurately tracks its location. To be precise, its molecular weight of 44 is heavier than the average molecular weight of air (28.8), so in principle, it would eventually settle in the air under static conditions. However, in normal environments, turbulent mixing occurs, causing it to remain rather than settle. This is self-evident considering that the composition of the Earth's air, including CO2 concentration, is constant in homogeneous areas up to an altitude of 80 km. In flowing conditions, sedimentation due to molecular weight differences is completely negligible, and CO2 acts as an excellent tracer, faithfully indicating the presence of active materials by riding on air currents flowing from behind shields.

[0015] The third characteristic of CO2 molecules is their quantity. The concentration of CO2 in the atmosphere tends to increase year by year due to the effects of global warming, but as of 2020 it was approximately 400 ppm (0.04%). This amount of CO2 is naturally present even in standard conditions, such as untouched outdoor air or air inside unoccupied buildings, and according to the absorbance values ​​in Figures 5(a) and 6(a1), even fluctuations in CO2 in standard conditions result in intensity changes that can be sufficiently detected. As you can see, even trace amounts of CO2 present in the environment can be detected, but active objects emit orders of magnitude more CO2 than the environment. For example, the CO2 concentration in human exhaled breath is said to be 4%, which is 100 times the standard concentration. The CO2 concentration in indoor environments where people are present, such as inside a car or tent, is lower, but it can easily reach around 1000 ppm. Therefore, that amount of CO2 is released outside each time a person enters or leaves a room. Exhaust gases from internal combustion engines and combustion devices are 10%, 250 times the standard concentration. In addition, carbon dioxide cylinders used to power portable devices and carbonated beverages emit 100%, 2500 times the standard concentration of CO2. Thus, the presence of active objects leads to the emission of easily detectable amounts of CO2 due to various factors.

[0016] As an image sensor for measuring infrared light in the first specific wavelength band, a sensor in which the photoelectric conversion layer is made of InSb is preferred from the viewpoint of sensitivity. Furthermore, it is preferable to place a bandpass filter that transmits only infrared light of a specific wavelength before or after the imaging optical system, so that the infrared light is imaged onto the image sensor via the bandpass filter, thereby enabling efficient acquisition of images in the desired wavelength range. In this case, it is preferable that the bandpass filter is cooled, as this reduces noise.

[0017] If there is an absorber that absorbs light of a specific wavelength between the background and the activity detection device 4, the intensity of the light of the wavelength in the absorption band that passes through the absorber will change. Since the background emits light over a wide range of wavelengths, the change in the overall effect is negligible if only light in a narrow absorption band is absorbed. However, if the wavelength to be detected is limited to the absorption wavelength band of the absorber, the intensity of the infrared light reaching the activity detection device 4 will change sensitively with a large contrast due to the presence of the absorber. In this way, the presence of the absorber can be visualized. The absorbance of the absorber follows the Via-Lambert law and is proportional to the molecular molar extinction coefficient, the concentration of the molecule, and the thickness of the absorbing layer (the product of concentration and thickness is the column density). The absorbance of CO2 at a column density of 100 ppm·m under standard conditions is shown in Figures 5(a) and 6(a1), and this height changes in proportion to the concentration and thickness.

[0018] If the absorber's temperature is equal to or lower than the background temperature, the absorber simply absorbs infrared light from the background, and the intensity of infrared light reaching the camera decreases. However, if the absorber's temperature is higher than the background, according to Kirchhoff's laws, which show the reversibility of absorption and thermal radiation, the absorber actually emits light at its absorption wavelength, and the intensity of infrared light reaching the camera increases. More precisely, the way in which the intensity of infrared light reaching the camera changes due to the presence of an absorber varies depending on various factors, including not only temperature, but also the absorbance and emissivity of the absorber (both are equal according to Kirchhoff's laws), the emissivity of the background, and optical relationships determined by the imaging lens 12, etc. In any case, the presence of an absorber is perceived as a change in the intensity of infrared light.

[0019] In this invention, CO2 is used as a tracer, and fluctuations in its concentration are captured to detect active organisms 2 and 3. The advantage of focusing on concentration here lies in its overwhelmingly large range of change (dynamic range).

[0020] <<Other specific wavelengths>> Other specific wavelengths of infrared light mentioned above can be listed below, based on the gas and its temperature environment. Here, the rationale for the selected wavelength band is described after the wavelength band. Furthermore, the data supporting the selection of the wavelength band is shown in Figures 5 to 7. For high temperatures, a case of 2000°C is given as an example, assuming emissions from an internal combustion engine.

[0021] (a) 2.4 μm to 3.6 μm: High-temperature H2O short-wavelength peak (i) 2.5 μm to 2.9 μm: Short wavelength peak of H2O at room temperature (c) 2.9 μm or more and 3.2 μm or less: Selective high-temperature H2O (The profile shows the lower end of the high-temperature H2O spectrum, but does not detect room-temperature H2O.) (e) 3.1 μm to 3.5 μm: CH4 short wavelength peak (O) 4.15 μm to 4.40 μm: CO2 short wavelength peak (k) 4.15 μm to 4.90 μm: High-temperature CO2 short-wavelength peak (Ki) 4.4 μm to 5.5 μm: High temperature CO (Ku) 4.45 μm or more and 4.95 μm or less: CO (Ke) 4.6 μm to 10 μm: High-temperature H2O long-wavelength peak (C) 5.0 μm to 7.5 μm: H2O long wavelength peak (S) 5.0 μm or more and 6.5 μm or less: High temperature NO (S) 5.1 μm or more and 5.6 μm or less: NO (c) 6.0 μm to 6.5 μm: NO2 short wavelength peak (So) 6.0 μm to 7.1 μm: High-temperature NO2 (T) 7.2 μm to 8.2 μm: CH4 long wavelength peak (C) 7.6 μm to 8.2 μm: NO2 long wavelength peak (T) 8μm to 13μm: NH3 (Te) 14 μm to 16 μm: CO2 long wavelength peak

[0022] Among these, CO2, H2O, CH4, and NH3 at room temperature are emissions from living organisms such as humans and animals. Therefore, to detect animals and living organisms, it is preferable to select the wavelength bands (i), (e), (o), (ku), (ko), (ta), (tsu), and (te) in which these gases are detected. On the other hand, CO2 (especially at high temperatures), H2O (especially at high temperatures), CO, NO X These are emissions from internal combustion engines, and in order to detect active objects such as internal combustion engines and fuel cell systems in cars and airplanes, it is preferable to select the wavelength bands (A), (B), (E), (F), (G), (H), (I), (J), (S), (S), (E), (G), (C), (T), where these gases are detected. Furthermore, the wavelength band in (c) is the tail end of the high-temperature H2O spectrum, but room-temperature H2O is not detected to a significant degree, so it can be particularly favored for the detection, detection, and measurement of active elements in internal combustion engine systems.

[0023] Furthermore, it is preferable to individually image and detect light from two or more different wavelength bands, consisting of groups (a) to (t), on an image sensor, as this makes it possible to distinguish between the type of active entity, such as an internal combustion engine or a living organism (animal). In this case, the accuracy of identifying the type of active entity is improved by comparing the intensity changes of two or more different wavelength bands. Furthermore, to obtain high sensitivity, it is preferable to use a CO2 gas absorption range of 4.15 μm to 4.40 μm, more preferably 4.20 μm to 4.35 μm, as one of the two or more different wavelength bands mentioned above. From the above, the method of the embodiment described herein allows for monitoring of gases emitted from active organisms by selecting the wavelength of infrared light, making it possible to detect and locate active organisms hiding behind shielding objects.

[0024] In this invention, while it is difficult to detect motor-driven entities using power sources that do not employ internal combustion engines or fuel cells, changes in magnetic fields and sound are generally observed when a motor is driven, even with shielding objects such as walls. Therefore, by performing detection and measurement of magnetic fields and sound according to this invention, it becomes possible to determine whether the entity is a living organism, an internal combustion engine system, a motor-driven system, or a combination of these.

[0025] <Measuring device and its configuration> This section describes the configuration and characteristics of the activity detection device.

[0026] Figure 2 is a schematic diagram showing the configuration of the activity detection device 201, which comprises a camera 51 and an image processing means 52.

[0027] As shown in Figure 3(a), the camera 51 has an imaging optical system 12 for infrared light 11 in the specific wavelength range, and an image sensor 13 in which pixel elements 14, each consisting of an infrared light sensing element having a photoelectric conversion layer that converts infrared light into an electrical signal, are arranged in a matrix.

[0028] The imaging means 12 is not specifically defined as long as it has sufficient imaging performance as a camera, but for example, a lens imaging system using optical lenses made of Ge, Si, ZnSe, ZnS, or sapphire, a reflective optical system using mirrors, or a composite optical system using both mirrors and lenses can be used. It can be either a short focal length lens or a zoom lens. There are no particular limitations on magnification, f-number, or permissible aberrations, and an appropriate selection should be made considering cost, ease of use, weight, resolution, field of view, etc.

[0029] As the pixel element 14 (infrared light sensing element), photoelectric conversion elements such as InSb, HgCdTe, InAs / GaSb superlattices, InGaAs / InAlAs quantum wells, GaAs / AlGaAs quantum wells, InAs, PbS, and PbSe can be used. Alternatively, thermal infrared light sensing elements using bolometers, thermopiles, or pyroelectric elements may be used. Among these, InSb is particularly preferred due to its excellent sensitivity and signal-to-noise ratio characteristics. There are no particular limitations on the pixel size and number of pixels of the pixel element 14. Reducing the pixel size also reduces the size of the image sensor 13, making it easier to miniaturize the imaging means 12. A larger pixel size makes it easier to improve sensitivity and signal-to-noise ratio, and also to increase resolution. For example, a pixel size of 10 × 10 to 30 × 30 μm is possible. 2 That is acceptable. There are no particular limitations on the number of pixels; it should be set appropriately considering the size of the device and the required resolution. For example, the number of pixels can range from 64x64 to 1920x1536.

[0030] To narrow the wavelength of the infrared light 11 to be measured to below a predetermined range, it is effective to use a bandpass filter. Bandpass filters are small, lightweight, easy to handle, and can be removed as needed. For example, a multilayer film composed of SiO, ZnS, Ge, etc., deposited on a sapphire or germanium substrate can be used as a bandpass filter. The bandpass filter can be placed in front of the imaging means 12 as seen from the image sensor 13, as shown in the bandpass filter 15a in camera 102 in Figure 3(b), or behind the imaging means 12, as shown in the bandpass filter 15b in camera 103 in Figure 3(c). Placing it in front has the advantage of making it easy to replace or attach / detach the bandpass filter, while placing it behind allows for a smaller bandpass filter and, if cooling is performed as described later, it can be cooled together with the image sensor 13.

[0031] It is preferable that the bandpass filters 15a and 15b and the image sensor 13 be cooled. Cooling reduces noise caused by thermal radiation from the environment and components. In particular, if the bandpass filters 15a and 15b are at room temperature, the thermal radiation from them superimposed as a large baseline on the signal of the image sensor 13, significantly reducing the contrast of the resulting image. Cooling methods include Stirling coolers, Peltier elements, and liquid nitrogen cooling. Stirling coolers and Peltier elements are preferred due to their ease of use. In particular, Stirling coolers are especially preferred because they can cool to below 80K even in a handy size and can be operated by battery.

[0032] The cooling temperature is preferably between 50K and 250K. By setting it below 250K, the noise level can be improved by more than an order of magnitude. The lower the temperature, the lower the noise level, but at 50K the noise level drops by more than 20 orders of magnitude compared to normal temperature operation, and at this level, noise from other factors such as voltage fluctuations becomes dominant. Since extremely low temperatures reduce convenience and ease of handling, use at 50K or higher is preferable.

[0033] The image processing means 52 analyzes the intensity distribution acquired by the image sensor 13 of the camera 51 and performs extraction processing of regions where gas emitted from an active object is floating. As shown in Figure 4, it consists of an image interface unit 31, a calculation unit 32 equipped with a CPU, a memory unit 33 equipped with DRAM, a display / output unit 34 equipped with a GPU and a display, and a condition input / control unit 35 that gives instructions and sets exposure time, frame rate, contrast enhancement, spatial filtering, spatial differential processing, temporal differential processing, density calculation, ratio calculation, discrimination processing, etc. This process allows for the identification of the location (activity area) and type of active organisms, and by tracing the temporal changes in the activity area extracted by the image processing means 52, it also becomes possible to track the movement of active organisms hidden behind obstacles. Based on the above, the activity detection device 201 of this embodiment is a device that can detect, identify, and distinguish activity objects that are difficult to find because they are obscured by shielding objects, and furthermore, by tracking changes over time, it is possible to track the movement of the activity objects. [Examples]

[0034] (Example 1) Example 1 describes the apparatus configuration and an example of using it to observe a person hiding behind a wall. Naturally, the present invention is not limited to such a specific form, and the technical scope of the present invention is defined by the claims.

[0035] A photograph of the entire apparatus used is shown in Figure 9. The device is a portable system consisting of a camera, a PC for control, observation, and display, a battery to power them, and a tripod to hold the camera. The camera weighs approximately 2.5 kg, and the battery weighs approximately 5 kg. This camera allows for easy shooting, similar to shooting with a home video camera.

[0036] The configuration of camera 103 is shown in Figure 3(c). Camera 103 is a FLIR A6796 model, and has an image sensor 13 in which an image element 14 consisting of an imaging means (imaging lens) 12 adapted to infrared light in the wavelength range of 3-5 μm, a bandpass filter 15b with a transmission center wavelength of around 4.25 μm, and an infrared light sensing element using InSb is arranged in a 640 × 512 matrix. Here, the bandpass filter 15b is cooled to 80K along with the image sensor 13 (pixel element 14) by a battery-powered Stirling cooler. The image sensor 13 (pixel element 14) has 14-bit grayscale and a sensitive wavelength band of 3-5 μm. For the imaging lens 12, for example, lenses with focal lengths of 25 mm, 50 mm, 100 mm, and an F-number of 2.5 are available.

[0037] Figure 10 shows the transmission wavelength characteristics of the bandpass filter 15b cooled to 80K. It transmits infrared light in the wavelength range of 4.0-4.4 μm. Figure 11 also shows the effect of cooling the bandpass filter 15b. The vertical axis represents the total amount of infrared light intensity emitted by this bandpass filter within the sensitivity wavelength range of 3-5 μm of the InSb infrared light sensing element, i.e., the infrared light signal level originating from the bandpass filter. It is shown that cooling the filter to 80K results in a clear image with high contrast and a baseline reduced by more than 10 orders of magnitude compared to room temperature (300K).

[0038] The inventor conducted an experiment to detect a person hiding behind a wall using a camera with the above configuration, which had a cooled bandpass filter, made to match the absorption wavelength of CO2, installed between the imaging means and the image sensor.

[0039] Figure 12 shows still images extracted from a series of videos taken using the camera in Figure 9 equipped with the bandpass filter in Figure 10. The shooting conditions were: exposure time 45ms, frame rate 22.2Hz, lens focal length 25mm, and f-number 2.5. Figure 12(b) shows a corner of an indoor corridor. Objects at room temperature naturally emit infrared light of this wavelength, so such images can be passively acquired without using any illumination. However, a person is hiding behind the corner indicated by the white dashed line on the left, but their presence is not detected. The hidden person is emitting heat at a temperature higher than room temperature and could be easily visualized if their image were directly captured, but due to the presence of an obstruction, the person cannot be detected in the thermal image. However, by applying time differentiation processing to the same video to remove fixed images and extracting only the parts that have changed, it is possible to visualize the emission of CO2 gas from behind the corner (indicated by the white dashed line) as shown in Figure 12(a). In fact, if you go around and look behind the corner, you can see that a person is hiding there, as shown in Figure 12(c). As shown in Figure 13, the activity detection device 201 of the present invention allows for clear, non-contact monitoring of CO2 gas originating from human exhalation from a distance. Therefore, the results shown in Figure 12 demonstrate the detection of an activity hidden behind an obstacle by capturing the way in which CO2 gas from exhalation leaks and spreads beyond the obstacle.

[0040] (Example 2) In Example 2, we investigated whether it was possible to detect and visualize H2O contained in a high-temperature flame, assuming an internal combustion engine. The apparatus is almost the same as the activity detection device 201 shown in Example 1, but the camera and bandpass filter are slightly different. The camera 103 is a FLIR A6751 model, and the camera 103 has an image sensor 13 in which an image element 14 consisting of an imaging means (imaging lens) 12 adapted to infrared light in the wavelength range of 3-5 μm and an infrared light sensing element using InSb is arranged in a 640 × 512 matrix. The image sensor 13 (pixel element 14) has 14-bit grayscale and a sensitive wavelength band of 3-5 μm, and is cooled to 80K by a battery-powered Stirling cooler. For the imaging lens 12, for example, lenses with focal lengths of 25 mm, 50 mm, 100 mm, and an F-number of 2.5 are available. The bandpass filter 15b is positioned behind the imaging lens 12 as shown in Figure 3(c), but unlike in Example 1, it is not cooled. The bandpass filter 15b has a transmission band of 2.9 μm to 3.2 μm. As mentioned above, this band is a high-temperature H2O selective spectral band that does not show significant absorbance for H2O at room temperature but does have absorbance for high-temperature H2O.

[0041] Figure 14 shows the results of observing the flame of a lighter. The shooting conditions were: exposure time 1.2 ms, frame rate 30 Hz, lens focal length 25 mm, and F-number 2.5. The material used in a lighter is butane gas, which produces CO2 and H2O upon combustion. This image captures H2O, and first, since it is observed as luminescence rather than absorption, it can be seen that the gas is at least at a temperature higher than room temperature. Furthermore, as shown in Figures 5(b) and 6(b1), the absorbance of H2O at room temperature does not show absorption (luminescence) in this wavelength range, so as shown in Figure 6(b2), it can be seen that H2O gas at a high temperature of 2000°C or close to it is present. Thus, it can be seen that the combustion of a material containing hydrogen atoms at high temperatures can be clearly detected and monitored non-contact from a distance.

[0042] (Example 3) In Example 3, we investigated whether various gases emitted from active organisms could be detected and visualized. The results are shown in Figures 15 and 16.

[0043] Figure 15(a) is a still image extracted from a series of videos of CO2 contained in the exhaust gas of a gasoline engine vehicle, captured using the camera in Figure 9 equipped with the bandpass filter in Figure 10. The shooting conditions were: exposure time 40ms, frame rate 24.9Hz, lens focal length 25mm, and f-number 2.5. This image has undergone time differentiation processing, and the black and white stripes visible in the gas are a result of this processing. In the unprocessed image, the gas appears brighter because its temperature is higher than room temperature.

[0044] Figure 15(b) shows an image of CO2 in the exhaust gas of the same automobile, captured with a different camera at a different wavelength. The camera used is an Optris PI-160 model, which has an image sensor 13 in which image elements 14 consisting of infrared light sensing elements using microbolometers are arranged in a 160 × 120 matrix. The imaging lens 12 has a focal length of 10 mm and transmits light in the wavelength range of 12 μm to 16 μm. The hot muffler and the emitted gas are observed to be bright. This is a visualization of CO2 in the exhaust gas by capturing the peak on the long wavelength side of 14-16 μm in Figures 5(a) and 6(a1).

[0045] Figure 15(c) shows an example of detecting CO from the same automobile using the camera from Example 2. The bandpass filter 15b used has a transmission band of 4.5 μm to 4.9 μm. The shooting conditions were an exposure time of 40 ms, a frame rate of 24.9 Hz, a lens focal length of 25 mm, and an F-number of 2.5. This wavelength band also overlaps with high-temperature CO2 as shown in Figure 6(a2), but basically no gas was observed in this experiment. This is because in a normal automobile, the exhaust gas emitted from the muffler is cooled to a sufficiently low temperature. However, at the moment the accelerator was pressed hard, gas emission was observed as shown in Figure 15(c). The gas is observed brightly because it is at a higher temperature than room temperature. This is thought to be a visualization of CO emission due to incomplete combustion during rapid acceleration.

[0046] Figure 15(d) shows an example of detecting CH4 gas using the camera of Example 2. The bandpass filter 15b used has a transmission bandwidth of 3.18 μm to 3.45 μm. The shooting conditions were an exposure time of 2.3 ms, a frame rate of 30 Hz, a lens focal length of 25 mm, and an F-number of 2.5. CH4 gas from a cylinder was ejected to the right from the nozzle visible on the left. In this example, an infrared light source (blackbody light source at a temperature of 55°C) is placed in the background for easier observation, but it is expected that similar images can be recorded against a natural background at room temperature by cooling the bandpass filter to improve the signal-to-noise ratio. The gas is observed as dark because it is at a lower temperature than the background. This shows that components volatile from animal breath or fuel from internal combustion engines (normal fuels are mixtures of hydrocarbons, and their absorption spectra do not differ significantly from those of CH4) can be detected.

[0047] Figure 15(e) shows an image of the same CH4 gas captured with the camera used in Figure 15(b) at a different wavelength range. Here, the region between 7 μm and 12 μm wavelengths is transmitted. A blackbody light source at 55°C was placed in the background for easier observation. Because the gas is cooler than the background, it is observed as dark. It is expected that similar images can be recorded even with a room-temperature background by combining a high-performance camera with a cooling filter.

[0048] Figure 15(f) shows an image of water vapor at approximately 100°C captured by the camera used in Figure 15(b). The water vapor was generated by boiling H2O and ejected to the right from the nozzle visible on the left. Here, the region with wavelengths between 7 μm and 8 μm is being observed. The camera's specifications are for wavelengths above 8 μm, so this wavelength range should not be observable, but it actually has a slight sensitivity, which allows for a faint visualization. The background is at room temperature, and the gas is observed brightly because it is hotter than the background. Water vapor is constantly emitted by living organisms, as well as by the combustion of fuel. This allows us to observe living organisms hidden behind shielding, internal combustion engines, or fuel cells in operation.

[0049] Figure 16(a) shows an example of detecting NO gas using the camera of Example 2. The observation wavelength is between 5 μm and 6 μm. The shooting conditions were an exposure time of 2.4 ms, a frame rate of 30 Hz, a lens focal length of 50 mm, and an F-number of 2.5. The NO gas was generated by dissolving copper in dilute nitric acid and ejected from the nozzle visible on the left. The wavelength range exceeds the 3-5 μm wavelength band of the camera, which is a wavelength range that should not normally be observable. However, due to the very small amount of sensitivity that actually exists, visualization was possible by placing a circular blackbody light source at a temperature of 227°C in the background. The gas appears darker because it is cooler than the background. It is expected that if a camera with a matching bandwidth is used, observation will be clearer even if the background is at room temperature.

[0050] Figure 16(b) shows an image of NO2 gas captured by the camera used in Figure 15(b). The observed wavelength is between 7 μm and 8 μm. The NO2 gas was generated by dissolving copper in concentrated nitric acid and ejected from the nozzle visible on the left. The camera's specifications are for wavelengths above 8 μm, so it is normally in a wavelength range that cannot be observed, but in reality, it has a slight sensitivity to the NO2 long-wavelength peak, which is why it is visible. The background is at room temperature, and the gas is also at room temperature, so it is observed as dark due to absorption. Since both NO and NO2 are emitted from internal combustion engines, it is possible to detect the presence of an internal combustion engine operating behind a shielding object.

[0051] Figure 16(c) shows an image of NH3 gas captured by the camera used in Figure 15(b). The observation wavelength is between 8 μm and 13 μm. The NH3 gas was obtained by placing 25% ammonia water in a beaker and allowing it to evaporate naturally. A blackbody light source at 55°C was placed in the background for easier observation. Because the gas is cooler than the background, it appears dark. It is expected that similar images can be recorded even with a background at room temperature by combining a high-performance camera with a cooling filter. NH3 is produced from the sweat and urine of humans and animals, and is also expected to be used as a fuel in the future, so it is anticipated that it may volatilize from the fuel of internal combustion engines. Therefore, it may be possible to detect the presence of living organisms or internal combustion engines hidden behind obstacles.

[0052] Furthermore, the detected gas combinations can also be used to identify activity behind the shielding. CO2 and H2O, or CO2 and NH3, suggest the presence of living organisms. CO2 and CH4, or CH4 and NH3, suggest the presence of animals such as deer or cows. CO2 and CO, CO2 and NO2, or CO2 and NO suggest the presence of an internal combustion engine. Also, if CO2 and H2O or CO2 and CH4 are particularly high in concentration or in large quantities, an internal combustion engine is more likely than living organisms. Additionally, NH3 and NO2, NH3 and NO, or NH3 and H2O suggest the presence of an internal combustion engine that uses NH3 as fuel. Furthermore, considering combinations of three or more gases and their relative ratios allows for a more detailed identification of the type of activity present behind the shielding. [Industrial applicability]

[0053] The present invention provides a method for detecting an active object present behind an obstacle such as a wall, and an apparatus for that method. This method and device are expected to have a variety of applications, such as detecting cars, people, and animals that suddenly appear from behind a wall, detecting tanks and fighter jets waiting hidden in bushes, and rescuing injured people buried under rubble in buildings and other structures during disasters such as earthquakes. Therefore, we believe that this invention will have a significant social impact and a major influence on industry. [Explanation of symbols]

[0054] 1: Shield (wall) 2:Animals, Activities 3: Cars, activities 4: Activity detection device 5: Gases emitted by the organism 11: Infrared light 12: Imaging means (imaging lens) 13: Image sensor 14: Pixel element (infrared light sensing element) 15a: Bandpass filter 15b: Bandpass filter 31: Image Interface Section 32: Arithmetic section 33: Memory section 34: Display / Output Section 35: Condition Input / Control Unit 51: Camera 52: Image processing means 101: Camera 102: Camera 103: Camera 201: Activity detection device

Claims

1. A method for detecting an active object hidden behind an obstacle that is difficult to detect with visible light, radar, or a sound collector, A tracer is used to obtain one or more gases selected from the group consisting of CO₂, H₂O, CH₄, CO, NO, NO₂, and NH₃, which leak out and spread around the shielding object as emitted by the active body during its activity. Using infrared light A, which is either infrared light naturally emitted from the outside environment, or infrared light emitted by the gas when the gas is at a higher temperature than the surroundings, An imaging optical system for imaging the aforementioned infrared light A, The device uses an image sensor in which pixel elements, each consisting of an infrared light sensing element having a photoelectric conversion layer that converts infrared light guided by the imaging optical system into an electrical signal, are arranged in a matrix. The image of the gas is formed on the image sensor via the imaging optical system. A method for detecting an active organism, which detects the active organism from a change in the intensity of light in the absorption wavelength band of the gas.

2. The method for detecting an active organism according to claim 1, wherein the gas is CO2.

3. The method for detecting an active organism according to claim 1, wherein the absorption wavelength band is 4.15 μm or more and 4.40 μm or less.

4. The method for detecting an active organism according to claim 1, wherein the absorption wavelength band is 4.20 μm or more and 4.35 μm or less.

5. The absorption wavelength band consists of two or more different wavelength bands, and each of these wavelength bands is individually imaged on the image sensor according to the light of that wavelength band. Furthermore, the wavelength bands are 2.4 μm to 3.6 μm, 2.5 μm to 2.9 μm, 2.9 μm to 3.2 μm, 3.1 μm to 3.5 μm, 4.15 μm to 4.40 μm, 4.15 μm to 4.90 μm, 4.4 μm to 5.5 μm, 4.45 μm to 4.95 μm, 4.6 μm to 10 μm, and 5.0 μm or more. The method for detecting an active organism according to claim 1, comprising two or more particles selected from the group consisting of 7.5 μm or less, 5.0 μm to 6.5 μm, 5.1 μm to 5.6 μm, 6.0 μm to 6.5 μm, 6.0 μm to 7.1 μm, 7.2 μm to 8.2 μm, 7.6 μm to 8.2 μm, 8 μm to 13 μm, and 14 μm to 16 μm.

6. The method for detecting an active organism according to claim 5, wherein the type of active organism is identified and detected by comparing the intensity changes caused by light of two or more different wavelength bands.

7. The method for detecting an active organism according to claim 5 or 6, wherein the first wavelength band, which is one of the aforementioned wavelength bands, is 4.15 μm or more and 4.40 μm or less.

8. The method for detecting an active organism according to claim 7, wherein the first wavelength band is 4.20 μm or more and 4.35 μm or less.

9. The method for detecting an active object according to any one of claims 1 to 8, wherein the photoelectric conversion layer is made of InSb.

10. A bandpass filter that transmits only light in the absorption wavelength band is installed before or after the imaging optical system, The method for detecting an active object according to any one of claims 1 to 9, wherein light in the absorption wavelength band is imaged onto the image sensor via the bandpass filter.

11. The method for detecting an active object according to claim 10, wherein the bandpass filter is cooled.

12. The method for detecting an active object according to claim 11, wherein the cooling temperature is 50K or more and 250K or less.

13. A method for detecting an active organism according to any one of claims 1 to 12, comprising determining fluctuations in the concentration of the gas from changes in the intensity of light in the absorption wavelength band of the gas, and detecting the active organism from the fluctuations in the concentration of the gas.

14. An apparatus for use in the method for detecting an active object according to claim 1, Equipped with a camera and image processing means, The camera comprises an imaging optical system for infrared light B, which has a wavelength of 2.4 μm or more and 16 μm or less, The image sensor has pixel elements, each consisting of an infrared light sensing element having a photoelectric conversion layer that converts the infrared light B into an electrical signal, arranged in a matrix. The image processing means is an active object detection device that analyzes the intensity distribution acquired by the image sensor and performs region extraction processing.

15. The activity detection device according to claim 14, wherein the wavelength of the infrared light B is 4.15 μm or more and 4.40 μm or less.

16. The activity detection device according to claim 15, wherein the wavelength of the infrared light B is 4.20 μm or more and 4.35 μm or less.

17. The infrared light B consists of light from two or more different wavelength bands, and each wavelength band is individually imaged on the image sensor. Furthermore, the wavelengths of light in the aforementioned wavelength bands are: 2.4 μm to 3.6 μm, 2.5 μm to 2.9 μm, 2.9 μm to 3.2 μm, 3.1 μm to 3.5 μm, 4.15 μm to 4.40 μm, 4.15 μm to 4.90 μm, 4.4 μm to 5.5 μm, 4.45 μm to 4.95 μm, 4.6 μm to 10 μm, and 5.0 μm. The activity detection device according to claim 14, comprising two or more elements selected from the group consisting of 7.5 μm or less, 5.0 μm or more and 6.5 μm or less, 5.1 μm or more and 5.6 μm or less, 6.0 μm or more and 6.5 μm or less, 6.0 μm or more and 7.1 μm or less, 7.2 μm or more and 8.2 μm or less, 7.6 μm or more and 8.2 μm or less, 8 μm or more and 13 μm or less, and 14 μm or more and 16 μm or less.

18. The activity detection device according to claim 17, wherein the image processing means compares the intensity changes caused by light of two or more different wavelength bands, identifies the type of activity from the ratio of the amounts of change, and outputs it.

19. The activity detection device according to claim 17 or 18, wherein the first wavelength band, which is one of the aforementioned wavelength bands, is 4.15 μm or more and 4.40 μm or less.

20. The active organism detection device according to claim 19, wherein the first wavelength band is 4.20 μm or more and 4.35 μm or less.

21. The active object detection device according to any one of claims 14 to 20, wherein the photoelectric conversion layer is made of InSb.

22. A bandpass filter that transmits only the infrared light B is placed before or after the imaging optical system. The motion detection device according to any one of claims 14 to 21, wherein the infrared light is imaged onto the image sensor via the bandpass filter.

23. The activity detection device according to claim 22, wherein the bandpass filter is cooled.

Images