Fire detection system

Abstract

To enable accurate detection of smoke occurring within a monitored area to detect a fire even when the monitored area is dark or has uneven light distribution.SOLUTION: A fire detection system includes: a slit light source 12 that is installed within a monitored area at least partially enclosed by walls and emits predetermined slit light across the monitored area in a planar direction to project a light line section of a predetermined width onto the wall surface; a monitoring camera 14 that captures an image of the monitored area including the wall surface onto which the light line section is projected; an imaging control unit 20 that controls imaging operation for capturing an image of the monitored area as a first image 36 using the monitoring camera 14 while the slit light source is illuminated, and capturing an image of the monitored area as a second image 38 using the monitoring camera 14 while the slit light source is extinguished; and a smoke determination unit 26 that detects a fire by determining smoke when predetermined smoke determination conditions are met based on the first image 36 and the second image 38.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a fire detection system that detects fires by detecting smoke using an image of a monitored area captured by an imaging device. [Background technology]

[0002] Conventionally, various fire detection devices and systems have been proposed that apply predetermined image processing to images of a monitored area captured by an imaging device such as a surveillance camera, and determine smoke generated by a fire from the images to detect the fire (Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-114930 [Patent Document 2] Japanese Patent Publication No. 2020-057236 Summary of the Invention [Problem to be solved by the invention]

[0004] However, conventional fire detection systems that detect fires by detecting smoke from images captured by an imaging device have difficulty detecting smoke from images captured in dark places, such as at night, and are therefore unable to accurately detect fires. Even when lighting is present in the monitored area, particularly in high-ceiling spaces, sufficient light is not necessarily provided near the ceiling, resulting in uneven light distribution and making it difficult to detect smoke even when it is present. While installing separate infrared lighting or other devices to detect smoke in dark places is conceivable, this does not solve the problem of insufficient light being provided in some locations and uneven light distribution, as is the case when lighting is present in the monitored area.

[0005] Therefore, in order to make the distribution of light in the monitored area uniform, it is possible to increase the number of lighting devices or the light output of the lighting devices, but this would increase costs and power consumption, resulting in high economic costs.

[0006] The present invention aims to provide a fire detection system that can accurately determine smoke generated in a monitored area and detect fires, even in dark places or monitored areas with uneven light distribution. [Means for solving the problem]

[0007] (Fire detection system: first invention) A first invention is a fire detection system, a slit light source that is installed in a monitoring area at least a portion of which is surrounded by a wall, and that projects a predetermined slit light beam that crosses the monitoring area in a plane to project a light line portion with a predetermined width on the wall surface; an imaging device that captures an image of a monitoring area including a wall surface on which the light line portion is projected; an imaging control unit that controls an imaging operation in which an image of the monitoring area is captured as a first image by the imaging device with the slit light source turned on, and an image of the monitoring area is captured as a second image by the imaging device with the slit light source turned off; a smoke determination unit that determines that there is smoke and detects a fire when predetermined smoke determination conditions are satisfied based on the first image and the second image; The present invention is characterized in that:

[0008] (Smoke judgment) The smoke detection unit is calculating a first difference (ΔA) between a first brightness of the light line portion of the first image and a second brightness of the light line portion of the second image, and determining that the first difference (ΔA) is a first smoke candidate if the first difference (ΔA) satisfies a predetermined first smoke candidate determination condition; a second difference (ΔB) between a first brightness of a background portion not including the light line portion of the first image and a first brightness of a background portion not including the light line portion of the second image is calculated, and if the second difference (ΔB) satisfies a predetermined second smoke candidate determination condition, the result is determined to be a second smoke candidate; If both the first smoke candidate and the second smoke candidate are identified, the smoke identification condition is met and it is identified as smoke.

[0009] (Smoke detection using steady-state difference) The smoke detection unit is As a first smoke candidate determination condition, when the first difference (ΔA) is equal to or less than a predetermined threshold (α) that is smaller than the first steady difference (ΔAth) in a smoke-free state, it is determined to be a first smoke candidate; As a condition for determining whether a smoke is a second smoke candidate, if the second difference (ΔB) is equal to or exceeds a predetermined threshold (β) that is greater than the second steady difference (ΔBth) in a smoke-free state, the smoke is determined to be a second smoke candidate.

[0010] (steady-state difference) The smoke detection unit is A first steady difference (ΔAth) is calculated based on the first difference (ΔA) when the first smoke candidate is not determined; The second steady difference (ΔBth) is calculated based on the second difference (ΔB) when the second smoke candidate is not determined.

[0011] (Image capture position overlooking the optical path of the slit light) The imaging device is installed in a position where it looks down at a predetermined angle from diagonally above the optical path plane of the slit light that crosses the monitoring area in a plane.

[0012] (Image capture position looking up at the optical path of the slit light) The imaging device is installed at a position where it can be viewed from obliquely below at a predetermined angle, looking up at the optical path plane of the slit light that crosses the monitoring area in a plane.

[0013] (Setting imaging conditions) The imaging control unit sets the imaging conditions of the imaging device or the brightness of the slit light emitted from the slit light source so that the brightness of the light line portion in the first image does not saturate and is distinguishable from the brightness of the portion that does not include the light line portion.

[0014] (Determining smoke location) The smoke determination unit determines the position of smoke based on the position of a dimmed portion where brightness is reduced within the light line portion in the first image.

[0015] (Determining whether it is smoke or not) The smoke detection unit determines whether the object to be detected is smoke or not based on the position of the dimming area where the brightness is decreasing in the light line area in the first image and the position of the scattering area where the brightness is increasing in the background area in the first image.

[0016] (Fire detection system: second invention) A second invention is a fire detection system, a slit light source that is installed in a monitoring area at least a portion of which is surrounded by a wall, and that projects a predetermined slit light beam that crosses the monitoring area in a plane to project a light line portion with a predetermined width on the wall surface; an imaging device that captures an image of a monitoring area including a wall surface on which the light line portion is projected; an imaging control unit that controls an imaging operation in which an image of the monitoring area is captured as a first image by the imaging device with the slit light source turned on, and an image of the monitoring area is captured as a second image by the imaging device with the slit light source turned off; a smoke determination unit that calculates a difference (ΔA) between a first brightness of the light line portion of the first image and a second brightness of the light line portion of the second image, and determines that there is smoke and detects a fire when the difference (ΔA) satisfies a predetermined smoke determination condition; The present invention is characterized in that:

[0017] (Fire detection system: 3rd invention) A third invention is a fire detection system, a slit light source that is installed in a monitoring area at least a portion of which is surrounded by a wall, and that projects a predetermined slit light beam that crosses the monitoring area in a plane to project a light line portion with a predetermined width on the wall surface; an imaging device that captures an image of a monitoring area including a wall surface on which the light line portion is projected; an imaging control unit that controls an imaging operation in which an image of the monitoring area is captured as a first image by the imaging device with the slit light source turned on, and an image of the monitoring area is captured as a second image by the imaging device with the slit light source turned off; a smoke determination unit that determines a difference (ΔB) between a first brightness of a background portion not including the light line portion of the first image and a second brightness of a background portion not including the light line portion of the second image captured with the slit light source turned off, and determines that the difference (ΔB) is smoke and detects a fire if the difference (ΔB) satisfies a predetermined smoke determination condition; The present invention is characterized in that:

[0018] (Fire detection system: 4th invention) A fourth invention is a fire detection system, a light source that is installed in a monitoring area at least a portion of which is surrounded by a wall, and that irradiates the monitoring area with predetermined light to project a light projection unit onto a predetermined portion of the wall; a smoke determination unit that determines that smoke exists when a first smoke determination condition based on a difference in brightness between a predetermined portion of the wall surface when the light source is turned on and a predetermined portion of the wall surface when the light source is not turned on is satisfied; The present invention is characterized in that:

[0019] (Fire detection system: 5th invention) A fifth invention is a fire detection system, a light source that is installed in a monitoring area at least a portion of which is surrounded by a wall, and that irradiates the monitoring area with predetermined light to project a light projection unit onto a predetermined portion of the wall; a smoke determination unit that determines that smoke exists when a first smoke determination condition based on the difference in brightness between a predetermined portion of the wall surface when the light source is turned on and a predetermined portion of the wall surface when the light source is not turned on, and a second smoke determination condition based on the difference in brightness between the brightness of the wall surface other than the predetermined portion when the light source is turned on and a predetermined portion of the wall surface when the light source is not turned on, are satisfied; The present invention is characterized in that: [Effects of the Invention]

[0020] (Effects of the first invention of the fire detection system) The first invention is a fire detection system comprising: a slit light source that is installed in a monitoring area at least partially surrounded by a wall, and that emits a predetermined slit light that crosses the monitoring area in a plane, projecting a light line portion of a predetermined width onto the wall surface; an imaging device that images the monitoring area including the wall surface onto which the light line portion is projected; an imaging control unit that controls the photographing operation to cause the imaging device to capture an image of the monitoring area as a first image with the slit light source turned on, and to capture an image of the monitoring area as a second image with the slit light source turned off; and a smoke detection unit that determines the presence of smoke and detects a fire if predetermined smoke detection conditions are satisfied based on the first image and the second image.Therefore, smoke can be detected by determining, based on the first image with the slit light source turned on and the second image with the slit light source turned off, whether the slit light is dimmed by smoke, thereby reducing the brightness of the light line portion, or whether the slit light hits smoke and the background area not including the light line portion increases in brightness due to scattered light generated when the slit light hits smoke.This makes it possible to determine the presence of smoke and detect fires even if the monitoring area is dark or the light distribution is uneven.

[0021] (Smoke detection effect) In addition, the smoke detection unit calculates a first difference (ΔA) between a first brightness of the light line portion of the first image and a second brightness of the light line portion of the second image, and determines that it is a first smoke candidate if the first difference (ΔA) satisfies a predetermined first smoke candidate determination condition; calculates a second difference (ΔB) between a first brightness of the background portion not including the light line portion of the first image and a first brightness of the background portion not including the light line portion of the second image, and determines that it is a second smoke candidate if the second difference (ΔB) satisfies a predetermined second smoke candidate determination condition; and determines that it is smoke if both the first smoke candidate and the second smoke candidate are determined, as this satisfies the smoke determination condition.Therefore, by using the first difference, it is possible to determine an event in which the slit light is dimmed by smoke and the brightness of the light line portion decreases, after eliminating the effects of external light other than the slit light, such as background and indoor lighting, which are present even in a smoke-free state (a state in which smoke is not being generated), and it is possible to accurately capture the event and determine it as a first smoke candidate.

[0022] In addition, by using the second difference, it is possible to eliminate the influence of external light other than the slit light, such as the background and indoor lighting that are present even in a smoke-free state, and to determine the phenomenon in which the brightness of the background increases due to scattered light generated when the slit light hits smoke, making it possible to accurately identify the phenomenon and determine it as a second smoke candidate.

[0023] Furthermore, if both the first smoke candidate and the second smoke candidate are identified, the smoke identification condition is met and the result is identified as smoke, thereby enabling accurate identification of smoke and detection of a fire.

[0024] (Effect of smoke detection using steady-state difference) In addition, the smoke detection unit determines a first smoke candidate as a first smoke candidate determination condition when the first difference (ΔA) is less than or equal to a predetermined threshold (α) that is smaller than the first steady-state difference (ΔAth) in a smoke-free state, or is less than the threshold (α), and determines a second smoke candidate as a second smoke candidate as a second smoke candidate condition when the second difference (ΔB) is greater than or equal to a predetermined threshold (β) that is larger than the second steady-state difference (ΔBth) in a smoke-free state, or exceeds the threshold (β).Therefore, by determining the first smoke candidate and the second smoke candidate using a threshold based on the steady-state difference obtained steadily in a smoke-free state, it is possible to reliably determine the first smoke candidate and the second smoke candidate.

[0025] (Effect of steady-state difference) In addition, the smoke detection unit calculates the first steady-state difference (ΔAth) based on the moving average of the first difference (ΔA) when the first smoke candidate is not determined, and calculates the second steady-state difference (ΔBth) based on the moving average of the second difference (ΔB) when the second smoke candidate is not determined.As a result, the steady-state difference is updated using the first difference or second difference that is steadily obtained in a smoke-free state, and even if there are changes in the environment of the monitored area, it is possible to reliably determine the first smoke candidate and the second smoke candidate without being affected by those changes.

[0026] (Effect of the imaging position looking down on the optical path of the slit light) Furthermore, the imaging device is installed in a position where it can look down at a predetermined angle from diagonally above the optical path plane of the slit light that crosses the monitored area in a plane, so that the slit light source can be installed in a position close to the floor surface of the monitored area, making it possible to quickly identify smoke when it is first generated.

[0027] (Effect of imaging position looking up at the optical path of the slit light) In addition, the imaging device is installed in a position where the optical path plane of the slit light that crosses the monitoring area in a plane can be viewed from diagonally below at a specified angle, so that the slit light source can be installed at a high position in the monitoring area, thereby suppressing and preventing the slit light from being dimmed, blocked, or scattered by items placed in the monitoring area, such as shelves, making it possible to reliably determine that it is smoke.

[0028] (Effect of imaging condition settings) In addition, the imaging control unit sets the imaging conditions of the imaging device or the brightness of the slit light emitted from the slit light source so that the brightness of the light line portion in the first image does not saturate and is distinguishable from the brightness of the portion that does not include the light line portion, making it possible to capture the first and second images as images suitable for smoke detection without changing the imaging conditions.

[0029] (Effect of determining smoke position) In addition, the smoke detection unit determines the location of smoke based on the position of the dimming area where brightness is reduced within the light line area in the first image, making it possible to identify the location of smoke generation (location of fire generation) in the monitored area in addition to detecting smoke.

[0030] (Effect of determining whether or not there is smoke) The smoke detection unit determines whether the object to be detected is smoke or not based on the position of the dimming section where brightness decreases within the light line section in the first image and the position of the scattering section where brightness increases within the background section in the first image. Therefore, if the positional relationship between the dimming section and the scattering section is not what it would be when smoke is generated, for example, if there is a large discrepancy between the positions of the dimming section and the scattering section, it determines that a factor other than smoke has occurred, and makes it possible to prevent factors other than smoke from being mistakenly detected as smoke.

[0031] (Effects of the fire detection system of the second invention) The second invention is a fire detection system comprising: a slit light source that is installed in a monitoring area at least partially surrounded by a wall, and that emits a predetermined slit light that crosses the monitoring area in a plane, projecting a light line portion of a predetermined width onto the wall surface; an imaging device that images the monitoring area including the wall surface onto which the light line portion is projected; an imaging control unit that controls the photographing operation to cause the imaging device to capture an image of the monitoring area as a first image with the slit light source turned on, and to capture an image of the monitoring area as a second image with the slit light source turned off; and a smoke detection unit that calculates the difference (ΔA) between the first brightness of the light line portion of the first image and the second brightness of the light line portion of the second image, and determines that there is smoke and detects a fire if the difference (ΔA) satisfies a predetermined smoke detection condition.Therefore, it is possible to determine an event in which the slit light is dimmed by smoke and the brightness of the light line portion decreases, while eliminating the effects of external light other than the slit light, such as background and indoor lighting, that exists even in a smoke-free state, and to accurately identify the event and determine that it is smoke.

[0032] (Effects of the fire detection system of the third invention) Further, a third invention is a fire detection system comprising: a slit light source that is installed in a monitoring area at least partially surrounded by a wall, and that emits a predetermined slit light that crosses the monitoring area in a plane to project a light line portion of a predetermined width onto the wall surface; an imaging device that images the monitoring area including the wall surface onto which the light line portion is projected; an imaging control unit that controls the photographing operation to cause the imaging device to photograph an image of the monitoring area as a first image with the slit light source turned on, and to photograph an image of the monitoring area as a second image with the slit light source turned off; and a smoke detection unit that calculates a difference (ΔB) between a first brightness of a background portion that does not include the light line portion in the first image and a second brightness of the background portion that does not include the light line portion in a second image photographed with the slit light source turned off, and that determines that there is smoke and detects a fire if the difference (ΔB) satisfies a predetermined smoke determination condition. Therefore, it is possible to determine an event in which the brightness of the background portion increases due to scattered light generated when the slit light hits smoke, while eliminating the effects of ambient light other than the slit light, such as background and room lighting that exist even in a smoke-free state, and enables the event to be accurately identified and determined to be smoke.

[0033] (Fire detection system: 4th and 5th inventions) Furthermore, the fire detection systems of the fourth and fifth inventions are capable of detecting smoke without being limited to using a slit light source as the light source or to a configuration equipped with an imaging device for capturing the first and second images, and similar to the first to third inventions, they are capable of detecting smoke and fires without being affected by dark areas or uneven light distribution in the monitored area. [Brief explanation of the drawings]

[0034] [Figure 1] FIG. 1 is an explanatory diagram showing an example of a monitoring area where a slit light source and a monitoring camera of a fire detection system are installed. [Figure 2] FIG. 1 is an explanatory diagram showing the configuration of a fire detection system. [Figure 3] FIG. 1 is an explanatory diagram showing a fixed irradiation type slit light source. [Figure 4]FIG. 10 is an explanatory diagram showing a rotary scanning type slit light source. [Figure 5] 10 is an explanatory diagram showing, in a time chart, changes in brightness of a light line portion and a background portion. FIG. [Figure 6] 10A and 10B are explanatory diagrams showing a first image and a second image taken when a monitoring area is free of smoke. [Figure 7] 10A and 10B are explanatory diagrams showing a first image and a second image taken when a monitoring area is affected by ambient light and is free of smoke. [Figure 8] 10A and 10B are explanatory diagrams showing a first image and a second image taken when a monitoring area is photographed in a state where smoke is present. [Figure 9] 10A and 10B are explanatory diagrams showing a first image and a second image taken when a monitoring area is imaged in a smoky state affected by ambient light. [Figure 10] 10 is an explanatory diagram showing, in a table format, the brightness and difference between the light line portion and the background portion under the influence of ambient light; FIG. [Figure 11] 10 is an explanatory diagram showing the relationship between the brightness distribution of a light line portion including a dimming portion in a first image and the position of smoke. FIG. [Figure 12] FIG. 10 is an explanatory diagram showing an example of a smoke detection operation in the form of a flowchart. DETAILED DESCRIPTION OF THE INVENTION

[0035] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a fire detection system according to the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the following embodiments.

[0036] [Basic concept of the embodiment] First, the basic concept of the embodiment will be described. The embodiment relates to a fire detection system that detects fires by detecting smoke using an image of a general monitoring area. The term "fire detection system" encompasses the concepts of "fire detection equipment" and "fire detection device."

[0037] Here, a "monitored area" is an area to be monitored, and is an outdoor or indoor space with a certain extent. Since a fire detection system projects a light line onto a wall, the "monitored area" is at least surrounded by walls, and is a concept that includes areas such as rooms, corridors, and staircases of a building. Note that although the monitored area is surrounded by walls, it is not limited to monitored areas that are completely surrounded by walls, and also includes monitored areas that are partially open and surrounded. Furthermore, the "monitored area" includes concepts such as a "monitored space" and a "monitored section."

[0038] The first embodiment of the fire detection system corresponding to the first invention is characterized by comprising a slit light source, an imaging device, an imaging control unit, and a smoke determination unit. Note that, as modified examples of the invention (fourth and fifth inventions), the light source is not limited to a slit light source, and includes a fire detection system that uses, for example, an illuminance sensor that detects brightness instead of an image captured by an imaging device, but the embodiments mainly deal with fire detection systems that include a slit light source and an imaging device.

[0039] Here, the "slit light source" is a light source installed in the monitored area that projects a predetermined slit of light across the monitored area in a plane, projecting a line of light of a predetermined width onto the wall surface. The structure and type of the "slit light source" are arbitrary, and include, for example, a light source that optically widens and projects a beam of light from a light-emitting unit, or a light source that oscillates and scans the beam of light. The type of "slit light" is also arbitrary, and includes, for example, visible light and infrared light. When visible light is used, it is appropriate to provide a light output that is greater than that of ceiling lighting or the like present in the monitored area.

[0040] The "imaging device" is a device that images a monitoring area including a wall surface on which the optical line portion is projected, and is installed in the monitoring area because it images the monitoring area including the wall surface on which the optical line portion is projected, and includes the concept of a television camera that captures moving images, such as an ITV camera, or a monitoring camera. The "imaging device" is sensitive to the wavelength of the slit light emitted from the slit light source.

[0041] Furthermore, the "imaging control unit" controls the photographing operation of using the imaging device to capture an image of the monitored area as a first image with the slit light source turned on, and capturing an image of the monitored area as a second image with the slit light source turned off. For example, it includes a control unit that synchronizes the on / off operation of the slit light source with the imaging operation of the imaging device, and then controls the imaging device to repeat the operation of turning on the slit light source and causing the imaging device to capture a first image, and the operation of turning off the slit light source and causing the imaging device to capture a second image, and a control unit that turns the slit light source on and off at any timing without synchronizing the on / off operation of the slit light source with the imaging operation of the imaging device, and determines through image processing whether the image captured by the imaging device is an image with the light on or off, and classifies it into a first image which is an image with the light on and a second image which is an image with the light off.

[0042] In addition, the "smoke detection unit" determines that there is smoke and detects a fire when predetermined smoke detection conditions are met based on the first image and the second image; specifically, it calculates a first difference (ΔA) between a first brightness of the light line portion of the first image and a second brightness of the light line portion of the second image, and determines that there is a first smoke candidate when the first difference (ΔA) meets predetermined first smoke candidate detection conditions; it calculates a second difference (ΔB) between a first brightness of the background portion not including the light line portion of the first image and a first brightness of the background portion not including the light line portion of the second image, and determines that there is a second smoke candidate when the second difference (ΔB) meets predetermined second smoke candidate detection conditions; and when both the first smoke candidate and the second smoke candidate are detected, it determines that there is smoke as the smoke detection conditions are met.

[0043] Note that the second image is an image captured with the slit light source turned off and does not show any light line portions, so the "second brightness of the light line portions in the second image" refers to the brightness of the area in the first image where the light line portions were shown, and the "second brightness of the background area not including the light line portions in the second image" refers to the brightness of the same area as the background area in the first image. Furthermore, the "background area" refers to the area in the image that does not include any light line portions, and may refer to a part of the area other than the light line portions.

[0044] Here, the "first difference (ΔA)" is used to detect the phenomenon in which the slit light is dimmed by smoke, reducing the brightness of the light line portion in the first image, and the first difference (ΔA) in a smoke-present state (a state in which smoke is occurring) is smaller than the first difference (ΔA) in a no-smoke state (a state in which smoke is not occurring).

[0045] For this reason, the "first smoke candidate determination condition" may be any condition that can capture a decrease in the first difference, including, for example, determining that a first smoke candidate exists when the first difference (ΔA) is equal to or less than a predetermined threshold (α) that is smaller than the first steady-state difference (ΔAth) in a smoke-free state. Furthermore, the "first steady-state difference (ΔAth)" is calculated based on the first difference (ΔA) in a case where a first smoke candidate is not determined, and the first steady-state difference (ΔAth) is updated by calculating, for example, the moving average of the first difference (ΔA) in a case where a first smoke candidate is not determined, i.e., the first difference (ΔAth) in a smoke-free state, thereby enabling reliable determination of a first smoke candidate without being affected by any fluctuations in the environment of the monitored area.

[0046] In addition, the "second difference (ΔB)" is used to detect the phenomenon in which the brightness of the background area in the first image that does not include the light line portion increases due to scattered light generated when the slit light hits smoke, and the second difference (ΔB) in the smoke-present state is larger than the second difference (ΔB) in the smoke-free state.

[0047] For this reason, the "conditions for determining a second smoke candidate" are set to any conditions that can detect an increase in the second difference, including, for example, determining a second smoke candidate when the second difference (ΔB) is equal to or exceeds a predetermined threshold (β) that is greater than the second steady-state difference (ΔBth) in a smoke-free state. The "second steady-state difference (ΔBth)" is calculated based on the second difference (ΔB) in a case where a second smoke candidate is not determined, and the second steady-state difference (ΔBth) is updated by calculating, for example, the moving average of the second difference (ΔB) in a case where a second smoke candidate is not determined, i.e., the second difference (ΔB) in a smoke-free state, thereby enabling reliable determination of a second smoke candidate without being affected by any fluctuations in the environment of the monitored area.

[0048] Then, the first smoke candidate is judged based on the first difference (ΔA), and the second smoke candidate is judged based on the second difference (ΔB).If both the first and second smoke candidates are judged to be smoke, it is judged to be smoke.This makes it possible to eliminate the influence of external light other than the slit light from the background or indoor lighting that exists in a smoke-free state.In addition, even if the monitored area is dark or the light distribution is uneven, it is not affected and it is possible to accurately judge smoke and detect a fire.

[0049] Furthermore, the "slit light source" and "imaging device" of the fire detection system are installed at predetermined positions in the monitored area, but the relative positions of the "slit light source" and "imaging device" can be arbitrary. For example, the imaging device may be installed in a position where it overlooks the optical path of the slit light as it crosses the monitored area in a plane from diagonally above at a predetermined angle. In this case, the imaging device is installed at a higher position than the slit light source, and the slit light source can be installed close to the floor of the monitored area, making it possible to quickly identify smoke in its early stages.

[0050] In another embodiment, the imaging device is installed at a position where it looks up at a predetermined angle from diagonally below the optical path of the slit light that crosses the monitoring area in a plane. In this case, the imaging device is installed at a lower position than the slit light source, and the slit light source is installed at a higher position in the monitoring area, which can suppress or prevent the effects of dimming, blocking, or scattering of the slit light by items placed in the monitoring area, such as shelves, making it possible to reliably determine that there is smoke.

[0051] In addition, the "imaging control unit" sets the imaging conditions of the imaging device so that the brightness of the light line portion in the first image does not saturate, and by setting the imaging conditions or the brightness of the slit light irradiated from the slit light source to such that the brightness of the light line portion in the first image does not saturate and that the brightness can be distinguished from the brightness of the portion that does not include the light line portion, continuous imaging is possible without changing the imaging conditions or the brightness of the slit light.

[0052] The "smoke detection unit" determines the location of smoke based on the location of dimming areas where brightness is reduced in the light line areas in the first image. Any method can be used to determine the location of smoke (location of a fire) in the monitored area based on the location of dimming areas in the light line areas, but examples include dividing the monitored area into multiple sections and determining the location of smoke in each section. Specifically, one method associates each section with a position in the light line areas, calculates a brightness distribution (distribution of pixel values) along the light line areas in the first image, and determines in which section of the monitored area a fire has occurred based on the location in the brightness distribution where brightness (pixel values) is reduced (location of dimming areas).

[0053] Furthermore, the "smoke determination unit" determines whether the object to be determined is smoke or not based on the positions of dimming sections where brightness decreases within the light line section in the first image and the positions of scattering sections where brightness increases within the background section in the first image. For example, when dividing a monitoring area into multiple sections and determining the position of smoke by section, if the sections of smoke position determined by the positions of the dimming sections and the scattering sections are determined to be the same section, there is a high possibility that the object to be determined is smoke, whereas if there is a difference between the section of smoke position determined by the position of the dimming sections and the section of smoke position determined by the position of the scattering sections, there is a high possibility that the error is due to a factor other than smoke, and the error can be avoided.

[0054] In addition, in the first embodiment (first invention) of the fire detection system, a first smoke candidate is determined based on the first difference (ΔA), a second smoke candidate is determined based on the second difference (ΔB), and if both the first smoke candidate and the second smoke candidate are determined, it is determined to be smoke, but the fire detection system may also determine smoke using other methods.

[0055] A second embodiment of a fire detection system corresponding to the second invention determines whether smoke has occurred based on the first difference (ΔA), and like the first embodiment, is equipped with a slit light source, an imaging device, an imaging control unit, and a smoke detection unit, but the "smoke detection unit" determines the difference (ΔA) between the first brightness of the light line portion of the first image and the second brightness of the light line portion of the second image, and if the difference (ΔA) satisfies a predetermined smoke determination condition, determines whether smoke has occurred and detects a fire.

[0056] Furthermore, a third embodiment of a fire detection system corresponding to the third invention of the present application determines whether smoke has occurred based on the second difference (ΔB), and like the first embodiment, is equipped with a slit light source, an imaging device, an imaging control unit, and a smoke detection unit, but the "smoke detection unit" determines the difference (ΔB) between the first brightness of the background area other than the light line area of ​​the first image and the second brightness of the background area other than the light line area of ​​the second image captured with the slit light source turned off, and determines whether smoke has occurred and detects a fire if the difference (ΔB) satisfies predetermined smoke determination conditions.

[0057] The following describes specific embodiments. In the following embodiments, the target monitoring area is a "monitoring area (indoor space) surrounded by a floor, ceiling, and walls," the "slit light source" is a "slit light source that irradiates infrared slit light," the "imaging device" is a "monitoring camera that is sensitive to infrared light," and the imaging device is installed at a higher position than the slit light source.

[0058] [Specific details of the embodiment] The embodiments of the fire detection system will be described separately as follows. a. Location of the fire detection system slit light source and surveillance camera b. First embodiment of the fire detection system b1. Slit light source b2.Surveillance cameras b3. Fire detection equipment c. Smoke detection processing c1. Identification of the first smoke candidate c2. Identification of second smoke candidate c3. First and second images of the monitored area without smoke c4. First and second images of a smoke-free monitoring area affected by ambient light c5. First and second images of a monitoring area with smoke present c6. First and second images of a monitoring area with smoke and the influence of ambient light c7. Smoke position determination process d.Smoke judgment operation e. Second embodiment of fire detection system f. Third embodiment of fire detection system g. Modifications of the present invention

[0059] [a. Location of the fire detection system slit light source and surveillance camera] First, the installation locations of the slit light source and the monitoring camera of the fire detection system will be explained with reference to Fig. 1, which shows an example of a monitoring area where the slit light source and the monitoring camera of the fire detection system are installed.

[0060] 1, the X, Y, and Z directions are perpendicular to each other. Specifically, the wall on which the slit light source 12 and the monitoring camera 14 are installed is defined as the rear wall, the X direction of the coordinate axes is defined as the left-right direction, the Y direction is defined as the up-down direction, and the Z direction is defined as the front-to-back direction. The +X side of the X direction is defined as the right side, the -X side as the left side, the +Y side of the Y direction is defined as the top side, the -Y side as the bottom side, and the +Z side of the Z direction is defined as the front side, and the -Z side as the rear side. This also applies to FIGS. 3, 4, 6 to 9, and 11.

[0061] 1, the monitored area 10 is an indoor space surrounded by walls 1010, 1012, 1014, 1016, a floor 1020, and a ceiling 1030, and a slit light source 12 and a monitoring camera 14 are installed on the wall 1010 side, which is the rear surface of the monitored area 10. The monitoring camera 14 is installed at a high position in the monitored area 10, and the slit light source 12 is installed at a lower position than the monitoring camera 14.

[0062] The slit light source 12 irradiates a slit light 1210 that crosses the monitored area 10 in a plane (crosses the ZX plane in the Z direction) to project a light line portion 16 having a predetermined width (width in the vertical direction) on the wall surfaces 1012, 1014, and 1016. The slit light 1210 is light that contains a predetermined infrared wavelength, and is irradiated from the slit light source 12 spreading in the X direction.

[0063] The monitoring camera 14 is sensitive to the infrared wavelength of the slit light 1210, and is installed in a position where it looks down at a predetermined angle from diagonally above the optical path plane of the slit light 1210 that crosses the monitoring area 10 in a plane.

[0064] During fire monitoring, the slit light source 12 is repeatedly turned on and off, and the monitoring camera 14 repeatedly captures images of the monitoring area 10 with the slit light source 12 turned on and off.

[0065] [b. First embodiment of fire detection system] Next, the configuration of the first embodiment of the fire detection system will be described with reference to Fig. 2 showing the configuration of the fire detection system.

[0066] 2, the first embodiment of the fire detection system includes a slit light source 12, a surveillance camera 14, and a fire detection device 18, and the fire detection device 18 is provided with an imaging control unit 20, an image input unit 22, an image storage unit 24, and a smoke determination unit 26. The slit light source 12 and the surveillance camera 14 are installed in the monitored area 10 as shown in FIG.

[0067] (b1. Slit light source) First, we will explain the slit light source as a component of the fire detection system. In this explanation, we will refer to Figure 3, which shows a fixed-irradiation type slit light source, and Figure 4, which shows a rotary-scanning type slit light source. Note that Figure 3(A) shows the slit light source as seen from the plane (top), and Figure 3(B) shows the slit light source as seen from the right side.

[0068] The fixed irradiation type slit light source 12 shown in Fig. 3 includes a light emitter 28 and a cylindrical lens 30. The light emitter 28 includes an infrared light emitting element, such as an infrared LED, that emits light in the infrared wavelength band, and drives the infrared light emitting element to emit a cylindrical infrared beam of light into the cylindrical lens 30. The cylindrical lens 30 converts the incident infrared beam of light into a slit light 1210 that spreads in a fan shape at a predetermined angle in the ZX plane and irradiates it. Therefore, while the slit light source 12 is turned on, the slit light 1210 that spreads across the monitored area 10 shown in Fig. 1 in a plane is irradiated, and the light line portion 16 is fixedly formed.

[0069] 4 includes a light-emitting unit 28, a polygon mirror 32, a motor shaft 34, and an fθ lens 35. The polygon mirror 32 is attached to the motor shaft 34 and rotates at a predetermined speed. The infrared beam from the light-emitting unit 28 is incident on the mirror surface of the rotating polygon mirror 32, causing the reflected beam to scan a predetermined angular range in the ZX plane and then pass through the fθ lens 35 to project a slit beam 1214. Therefore, if the time axis is lengthened, the slit beam 1214 will essentially project a slit light 1210 that spreads across the monitoring area 10 shown in FIG. 1 in a plane while the slit light source 12 is turned on, and the light line portion 16 will also essentially be formed. Regardless of whether the slit light source 12 is a fixed-irradiation type or a rotary-scan type, the slit light source 12 can be realized using a known configuration as shown in FIGS. 3 and 4.

[0070] The slit light source 12 is also communicably connected to an imaging control unit 20 of the fire detection device 18, and is controlled to be turned on or off by a control instruction from the imaging control unit 20.

[0071] (b2. Surveillance cameras) Next, a description will be given of the monitoring camera 14 as a component of the fire detection system. The monitoring camera 14 captures an image of the monitoring area 10 so as to include the light line portion 16 projected on the wall surfaces 1012, 1014, and 1016 when the slit light source 12 is turned on.

[0072] Furthermore, surveillance camera 14 may be, for example, an infrared video camera that captures images in the infrared range. Surveillance camera 14 using an infrared video camera captures video of monitored area 10 sequentially at a frame rate of, for example, 30 frames per second or 60 frames per second, consisting of a series of infrared frame images, and transmits image data (hereinafter referred to as infrared image) of the infrared frame images of monitored area 10 at 30 frames per second or 60 frames per second from the captured video to fire detection device 18. The size of the infrared image transmitted from surveillance camera 14 to fire detection device 18 is arbitrary, but may be, for example, 1920 x 1080 pixels. Furthermore, the infrared image is a grayscale image whose gradation changes from black to gray to white depending on the intensity of the infrared light.

[0073] Furthermore, the surveillance camera 14 has the ability to arbitrarily adjust the shutter speed and aperture opening as imaging conditions, and also has the function of automatically changing the imaging conditions to obtain an optimal infrared image, but in this embodiment, the imaging conditions of the surveillance camera 14 are fixed to predetermined imaging conditions regardless of the on / off state of the slit light source 12. The imaging conditions of the surveillance camera 14 are, for example, fixedly set to the shutter speed and aperture opening so that when the slit light source 12 is on in the infrared image, the brightness of the light line portion 16 projected on the wall surfaces 1012, 1014, 1016 does not saturate and can be distinguished from the brightness of the portion not including the light line portion 16.

[0074] The surveillance camera 14 is also communicatively connected to an image input unit 22 of the fire detection device 18, and transmits infrared images to the image input unit 22. The surveillance camera 14 is also communicatively connected to an imaging control unit 20 of the fire detection device 18, and the imaging conditions may be changed in response to a control instruction from the imaging control unit 20.

[0075] Furthermore, communication between the slit light source 12 and the surveillance camera 14 and the fire detection device 18 may be wired or wireless, and any communication method may be adopted, such as communication via a wiring cable such as a USB cable or communication via wireless LAN, and in the embodiment, the slit light source 12 and the surveillance camera 14 and the fire detection device 18 are connected by a wiring cable.

[0076] (b3. Fire detection devices) Next, we will explain the fire detection device 18 as a component of the fire detection system. The fire detection device 18 is composed of hardware such as a computer circuit equipped with a CPU, memory, various input / output ports, etc., and as described above, includes the imaging control unit 20, image input unit 22, image storage unit 24, and smoke detection unit 26.

[0077] The imaging control unit 20 controls the slit light source 12 by switching it on and off at a predetermined timing. Here, the on and off times of the slit light source 12 are arbitrary, but to enable the smoke detection unit 26 to repeatedly perform smoke detection in a short period of time, for example, the on and off times are both set to one second, making it possible to perform smoke detection once for a total of two seconds of imaging time, one second when the slit light source 12 is on and one second when the slit light source 12 is off.

[0078] In addition, the imaging control unit 20 extracts a predetermined infrared image from the infrared images continuously transmitted from the surveillance camera 14 to the image input unit 22 in synchronization with each of the on and off states of the slit light source 12, and stores a first image 36, which is an infrared image with the slit light source 12 on, in the image memory unit 24, and also stores a second image 38, which is an infrared image with the slit light source 12 off, in the image memory unit 24.

[0079] Here, the first image 36 and the second image 38 stored in the image memory unit 24 are arbitrary, but since continuous infrared images are input from the surveillance camera 14 to the image input unit 22 at 30 frames per second or 60 frames per second, for example, the first infrared image of the infrared images input continuously during one second while the slit light source 12 is turned on is taken as the first image 36, and the first infrared image of the infrared images input continuously during one second while the slit light source 12 is turned off is taken as the second image 38.

[0080] The smoke determination unit 26 determines that there is smoke and detects a fire when predetermined smoke determination conditions are met based on the first image 36 and the second image 38 stored in the image storage unit 24.

[0081] [c. Smoke detection processing] Next, we will explain the smoke detection process performed by the smoke detection unit 26 of the fire detection device 18. The smoke detection process in the first embodiment performs a first smoke candidate determination, which detects an event in which the slit light is dimmed by smoke and the brightness of the light line portion decreases, and a second smoke candidate determination, which detects an event in which the slit light hits smoke and the brightness of the background portion not including the light line portion increases due to scattered light generated, and determines that there is smoke if both the first smoke candidate and the second smoke candidate are detected.

[0082] In this explanation, reference will be made to Figure 5, which shows a time chart of changes in the brightness of the light line portion and the brightness of the background portion. Figure 5(A) shows a time chart of the first difference indicating changes in the brightness of the light line portion, Figure 5(B) shows the determination of the first smoke candidate, Figure 5(C) shows a time chart of the second difference indicating changes in the brightness of the background portion, Figure 5(D) shows the determination of the second smoke candidate, and Figure 5(E) shows the determination of smoke.

[0083] (c1. First smoke candidate determination) First, a description will be given of the determination of a first smoke candidate, which detects an event in which the slit light is attenuated by smoke and the brightness of the light line portion decreases.

[0084] When smoke occurs due to a fire in the monitored area 10, the slit light 1210 emitted from the slit light source 12 is dimmed by the smoke, and the brightness of the light line portion 16 projected by the slit light 1210 decreases, so the smoke detection unit 26 determines a first smoke candidate as indicating the possibility of smoke. How to determine the first smoke candidate is arbitrary, but for example, the first smoke candidate is determined according to the following procedure.

[0085] First, a first brightness A1 of the light line portion 16 of the first image 36, which is an infrared image with the slit light source 12 turned on, is calculated. Second, a second brightness A2 of the light line portion 16 of the second image 38, which is an infrared image with the slit light source 12 turned off, is calculated.

[0086] Here, the "first brightness A1 of the light line portion 16" is the sum of the pixel values ​​(gradation values) of the pixels in the first image 36 where the light line portion 16 is located, and the "second brightness A2 of the light line portion 16" is the sum of the pixel values ​​(gradation values) of the pixels in the same area in the first image 36 as the area where the light line portion 16 was located.

[0087] Third, the difference between the first brightness A1 and the second brightness A2 of the light line portion 16 (=A1-A2) is calculated as the first difference ΔA. Fourth, it is determined whether the first difference ΔA satisfies a predetermined first smoke candidate determination condition, and if the first smoke candidate determination condition is satisfied, it is determined to be a first smoke candidate. Here, for example, a predetermined threshold value α is set as the first smoke candidate determination condition, and it is determined that the first smoke candidate determination condition is satisfied if the first difference ΔA is equal to or less than the predetermined threshold value α.

[0088] Such determination of the first smoke candidate will be explained below with reference to FIGS. 5(A) and 5(B).

[0089] First, in a smoke-free state (a state in which no smoke is generated) before time t1, the slit light 1210 is not affected by the attenuation caused by smoke, so the first difference ΔA is the wall scattering of the light line portion 16 projected onto the wall surface itself, and as shown in Figure 5(A), the first difference ΔA calculated at a period of, for example, once every two seconds remains at an approximately constant value.

[0090] Furthermore, the steady-state difference ΔAth is calculated by taking a moving average over time of the first difference ΔA calculated in a smoke-free state, and the threshold value α serving as the first smoke candidate determination condition is set based on the steady-state difference ΔAth. Here, the threshold value α is set to an arbitrary predetermined value based on the steady-state difference ΔAth, and for example, a value of 50% of the steady-state difference ΔAth is set as a predetermined ratio of the steady-state difference ΔAth. Furthermore, the number of moving averages of the first difference ΔA in a smoke-free state used to calculate the steady-state difference ΔAth is arbitrary, but for example, the steady-state difference ΔAth is calculated from a moving average of the first difference ΔA for one hour, taking into account fluctuations in the brightness of the optical line section 16 due to ambient light such as lighting in the monitored area 10 and external light.

[0091] Next, when smoke due to a fire occurs in the monitored area 10 at time t1, the slit light 1210 is dimmed by the smoke, and the brightness of the part of the light line portion 16 in the first image 36 corresponding to the position of the smoke (dimmed part) decreases.As time passes, the smoke concentration increases and diffuses, and the first brightness A1 of the light line portion 16 in the first image 36 gradually decreases.As a result, as shown in Figure 5(A), the first difference ΔA decreases as time passes from time t1.

[0092] Then, at time t2, when the first difference ΔA becomes equal to or less than the threshold α set based on the steady-state difference ΔAth, it is determined to be the first smoke candidate, and the determination value of the first smoke candidate changes from 0 to 1, as shown in Figure 5(B), for example.

[0093] (c2. Determining the second smoke candidate) Next, we will explain how to determine a second smoke candidate, which detects an event in which the brightness of the background area not including the light line portion increases due to scattered light generated when the slit light hits smoke. When smoke occurs due to a fire in the monitored area 10, scattered light is generated when the slit light 1210 emitted from the slit light source 12 hits the smoke, and the brightness of the background area not including the light line portion 16 increases. Therefore, the smoke determination unit 26 determines the second smoke candidate as indicating the possibility of smoke. How the second smoke candidate is determined is arbitrary, but for example, the second smoke candidate may be determined according to the following procedure.

[0094] First, a first brightness B1 of the background portion not including the light line portion 16 of the first image 36, which is an infrared image with the slit light source 12 turned on, is calculated. Second, a second brightness B2 of the background portion not including the light line portion 16 of the second image 38, which is an infrared image with the slit light source 12 turned off, is calculated.

[0095] Here, the "first brightness B1 of the background portion" is the sum of the pixel values ​​(gradation values) of pixels in the first image 36 where the light line portion 16 is not located, and the "second brightness B2 of the background portion" is the sum of the pixel values ​​(gradation values) of pixels in the same area in the first image 36 as the area where the light line portion 16 was not located.

[0096] Third, the difference between the first brightness B1 and the second brightness B2 of the background (=B1-B2) is calculated as the second difference ΔB. Fourth, it is determined whether the second difference ΔB satisfies a predetermined second smoke candidate determination condition, and if the second smoke candidate determination condition is satisfied, it is determined to be a second smoke candidate. Here, for example, a predetermined threshold value β is set as the second smoke candidate determination condition, and if the second difference ΔB is equal to or greater than the predetermined threshold value β, the second smoke candidate determination condition is satisfied.

[0097] Such determination of the second smoke candidate will be explained below with reference to FIGS. 5(C) and 5(D).

[0098] First, before time t1, when there is no smoke (when no smoke is generated), the slit light 1210 hits the smoke and no scattered light is generated, so the second difference ΔB remains at 0 or close to 0, as shown in Figure 5(C).

[0099] The second difference ΔB of the background portion is also calculated, for example, once every two seconds, in the same manner as the first difference ΔA of the light line portion 16. The steady-state difference ΔBth is calculated by taking a moving average over time of the second difference ΔB calculated in a smoke-free state, and a threshold value β serving as a second smoke candidate determination condition is set based on the steady-state difference ΔBth. In the same manner as the first difference ΔA, the steady-state difference ΔBth is calculated from the moving average of the second difference ΔB over, for example, one hour.

[0100] Next, when smoke from a fire appears in the monitored area 10 at time t1, the slit light 1210 hits the smoke, generating scattered light, which increases the brightness of the area in the background of the first image 36 corresponding to the position of the smoke. As time passes, the smoke becomes more concentrated and diffuses, and the first brightness B1 of the background of the first image 36 gradually increases. As a result, as shown in Figure 5(C), the second difference ΔB increases as time passes from time t1.

[0101] Then, when the second difference ΔB increasing at time t3 is equal to or exceeds the threshold β set based on the steady-state difference ΔBth, it is determined to be a second smoke candidate, and the determination value of the second smoke candidate changes from 0 to 1, as shown in Figure 5(D), for example.

[0102] Furthermore, since the first smoke candidate was already determined at time t2 and the determination value of the first smoke candidate changed from 0 to 1, the second smoke candidate is determined at time t3 and when the determination value of the second smoke candidate changes from 0 to 1, it is determined to be smoke based on the determinations of both the first and second smoke candidates, and the smoke determination value changes from 0 to 1, for example, as shown in Figure 5(E). Note that the time chart shown in Figure 5 is an example, and the first smoke candidate is determined at time t2, and then the second smoke candidate is determined at time t3, but the timing of determining the first and second smoke candidates will differ depending on the situation.

[0103] (c3. First and second images of the monitored area without smoke) Next, the first and second images taken of a smoke-free monitoring area, which are used in the smoke detection process, will be described. In this description, reference will be made to Fig. 6, which shows the first and second images taken of a smoke-free monitoring area. Fig. 6(A) shows the monitoring area as viewed from the right side, Fig. 6(B) shows the second image, and Fig. 6(C) shows the first image.

[0104] In the smoke-free monitored area 10 of Fig. 6(A), the second image 38, which is an infrared image with the slit light source 12 turned off, is, for example, the image shown in Fig. 6(B), and is a black image (image value is near 0) because the slit light 1210 is not irradiated and there is no infrared source in the monitored area 10. Note that in the second image 38 shown in Fig. 6(B), solid lines indicating the intersection positions of the wall and floor surfaces and dotted lines indicating the light line portions 16 are shown for reference, and the same is shown in Figs. 7(B) to 9(B).

[0105] 6(A), the first image 36, which is an infrared image when the slit light source 12 is turned on, becomes, for example, the image shown in FIG. 6(C), in which the slit light 1210 from the slit light source 12 is irradiated onto the wall surface without being dimmed by smoke and scattered by the wall surface, so that the light line portion 16 is displayed as a scattered image. Note that the background is black like the second image 38, because there is no smoke to generate scattered light.

[0106] Therefore, the first difference ΔA, which is the difference between the first brightness A1 of the light line portion 16 in the first image 36 and the second brightness A2 of the light line portion 16 shown by the dotted line in the second image 38, will maintain a predetermined high value corresponding to the brightness of the light line portion 16, as shown before time t1 in Figure 5(A).

[0107] On the other hand, the first brightness B1 of the background part of the first image 36 and the second brightness B2 of the background part of the second image 38 are approximately the same brightness, and as shown before time t1 in Figure 5 (C), the second difference ΔB, which is the difference between the two, remains at or near the 0 level.

[0108] (c4. First and second images of a smoke-free monitoring area affected by ambient light) Next, the first and second images taken when a smoke-free monitoring area is affected by ambient light will be described. In this description, reference will be made to Fig. 7, which shows the first and second images taken when a smoke-free monitoring area is affected by ambient light. Fig. 7(A) shows the monitoring area as viewed from the right side, Fig. 7(B) shows the second image, and Fig. 7(C) shows the first image.

[0109] In addition to the slit light 1210 from the slit light source 12, there may be external disturbance light in the monitored area 10, such as external light that enters the monitored area from outside through lighting containing infrared rays or windows, etc. For example, in the smoke-free monitored area 10 shown in Figure 7(A), external disturbance light 40 containing infrared rays is locally irradiated from the ceiling surface toward the floor surface.

[0110] Therefore, in the monitored area 10 in a smoke-free state shown in Fig. 7(A), the second image 38, which is an infrared image with the slit light source 12 turned off, becomes, for example, the image shown in Fig. 7(B), in which disturbance light scattering areas 42 caused by disturbance light are projected near the floor of the monitored area 10, forming part of the background. In the second image 38 shown in Fig. 7(B), the areas other than the disturbance light scattering areas 42 are black.

[0111] 7(A), the first image 36, which is an infrared image when the slit light source 12 is turned on, becomes, for example, the image shown in FIG. 7(C), in which the slit light 1210 from the slit light source 12 is irradiated onto the wall surface without being dimmed by smoke and scattered by the wall surface, so that the light line portion 16 is displayed as a scattered image. Furthermore, because the ambient light 40 is irradiated regardless of whether the slit light source 12 is on or off, the ambient light scattering portion 42 is displayed in the background portion, similar to the second image 38.

[0112] Since the disturbance light scattering section 42 is projected onto the background, the first difference ΔA, which is the difference between the first brightness A1 of the light line section 16 in the first image 36 and the second brightness A2 of the light line section 16 shown by the dotted line in the second image 38, is not affected by the disturbance light scattering section 42 and maintains a predetermined high value corresponding to the brightness of the light line section 16, as shown before time t1 in Figure 5(A).

[0113] On the other hand, the first brightness B1 of the background portion of the first image 36 and the second brightness B2 of the background portion of the second image 38 are affected by the disturbance light scattering portion 42, but since both are affected by the disturbance light scattering portion 42 to the same extent, the second difference ΔB, which is the difference between the two, is hardly affected by the disturbance light scattering portion 42 and maintains a value at or near the 0 level, as shown before time t1 in Figure 5(C).

[0114] Therefore, even if disturbance light scattering sections 42 caused by disturbance light 40 are present in the monitored area 10, the smoke determination is not affected by the disturbance light scattering sections 42, and the first and second smoke candidates are not erroneously determined based on the first and second images 36, 38 in a smoke-free state. Note that even if the disturbance light scattering sections 42 are projected in part of the light line section 16, the first difference ΔA is hardly affected by the disturbance light scattering sections 42, and therefore maintains a predetermined high value as shown before time t1 in FIG. 5(A).

[0115] (c5. First and second images of a monitoring area with smoke present) Next, the first and second images taken when a monitoring area is imaged in a smoke-containing state, which are used in the smoke detection process, will be described. In this description, reference will be made to Fig. 8, which shows the first and second images taken when a monitoring area is imaged in a smoke-containing state. Fig. 8(A) shows the monitoring area as viewed from the right side, Fig. 8(B) shows the second image, and Fig. 8(C) shows the first image.

[0116] In the monitored area 10 in a smoke-present state as shown in Figure 8(A), the second image 38, which is an infrared image when the slit light source 12 is turned off, becomes, for example, the image shown in Figure 8(B), and even though smoke 44 is present in the monitored area 10, the slit light 1210 is not irradiated and there is no source of infrared light, so the image is black.

[0117] 8(A), the first image 36, which is an infrared image of the monitored area 10 with smoke present and the slit light source 12 turned on, becomes, for example, the image shown in FIG. 8(C), in which the slit light 1210 from the slit light source 12 is illuminated on the wall surface while being attenuated by the smoke 44 and scattered by the wall, resulting in the projection of a light line portion 16 with a dimmed portion 46 of reduced brightness corresponding to the position of the smoke 44. Furthermore, the slit light 1210 strikes the smoke 44 and generates scattered light, resulting in the projection of a slit light smoke scattering portion 48 in part of the background. Note that the area of ​​the background of the first image 36 shown in FIG. 8(C) other than the slit light smoke scattering portion 48 is a black image.

[0118] Therefore, the first difference ΔA, which is the difference between the first brightness A1 of the light line portion 16 where the dimming portion 46 of the first image 36 exists and the second brightness A2 of the light line portion 16 shown by the dotted line in the second image 38, is a value that is lower by the amount of the decrease in brightness at the dimming portion 46 compared to the first difference ΔA in a smoke-free state.

[0119] As the concentration of smoke 44 increases and diffuses over time, the brightness of the dimming section 46 decreases further and the area of ​​the dimming section 46 expands, so that the first difference ΔA decreases as shown from time t1 onwards in Figure 5(A).As shown at time t2 in Figure 5(A), when the first difference ΔA is equal to or less than a predetermined threshold value α or less than the threshold value α (satisfying the first smoke candidate determination condition), it is determined to be a first smoke candidate.

[0120] On the other hand, the second difference ΔB, which is the difference between the first brightness B1 of the background area where the slit light smoke scattering area 48 of the first image 36 exists and the second brightness B2 of the background area of ​​the second image 38, is a value that increases by the amount of the slit light smoke scattering area 48 that has appeared compared to the second difference ΔB in a smoke-free state.

[0121] As the concentration of smoke 44 increases and diffuses over time, the brightness of the slit light smoke scattering section 48 further increases and the area of ​​the slit light smoke scattering section 48 expands, so that the second difference ΔB increases as shown from time t1 onwards in Figure 5(C).As shown at time t3 in Figure 5(C), when the second difference ΔB is equal to or exceeds a predetermined threshold β (satisfying the second smoke candidate determination condition), it is determined to be a second smoke candidate.

[0122] (c6. First and second images of a monitoring area with smoke and the influence of ambient light) Next, a first image and a second image taken when a monitoring area is imaged in a smoky state affected by ambient light will be described. In this description, reference will be made to FIG. 9, which shows the first and second images taken when a monitoring area is imaged in a smoky state affected by ambient light, and FIG. 10, which shows in table form the brightness and difference of the light line portion and background portion in a state affected by ambient light. Note that FIG. 9(A) shows the monitoring area as viewed from the right side, FIG. 9(B) shows the second image, and FIG. 9(C) shows the first image, and the brightness and difference shown in FIG. 10 are for the monitoring area shown in FIG. 9(A).

[0123] 9(A), in a monitored area 10 with smoke present, an illumination light source 50 is installed on the ceiling surface, and the illumination light source 50 irradiates illumination light (disturbance light) including infrared rays onto the monitored area 10. In addition, smoke 44 is occurring in the monitored area 10 due to a fire.

[0124] Therefore, in the monitored area 10 with smoke present as shown in Fig. 9(A), the second image 38, which is an infrared image with the slit light source 12 turned off, becomes, for example, the image shown in Fig. 9(B), in which illumination light smoke scattering areas 52, which are caused by the illumination light hitting and scattering by smoke 44, are projected in part of the background. Also, in the second image 38 shown in Fig. 7(B), the area other than the illumination light smoke scattering areas 52 is a black image.

[0125] 9(A), the first image 36, which is an infrared image when the slit light source 12 is turned on, becomes, for example, the image shown in FIG. 9(C), in which the slit light 1210 from the slit light source 12 is illuminated onto the wall surface while being attenuated by the smoke and scattered by the wall, resulting in the projection of a light line portion 16 with a dimmed portion 46 of reduced brightness corresponding to the position of the smoke 44. Furthermore, the slit light 1210 strikes the smoke 44 and generates scattered light, resulting in the projection of a slit light smoke scattering portion 48 generated by the scattered light in part of the background, and because illumination light is illuminated from the illumination light source 50 regardless of whether the slit light source 12 is on or off, an illumination light smoke scattering portion 52, similar to the second image 38, is projected in part of the background.

[0126] Here, with reference to FIG. 10, the smoke detection performed by the smoke detection unit 26 for the monitored area 10 equipped with the illumination light source 50 of FIG. 9 will be described in detail.

[0127] Figure 10(A) is a table showing the first brightness A1 of the light line portion 16 of the first image 36, the second brightness A2 of the light line portion 16 of the second image 38, and the first difference ΔA, which is the difference between them, which are used to determine the first smoke candidate.As shown in the left column, the first brightness A1, the second brightness A2, and the first difference ΔA are listed for ``smoke present'' and ``smoke absent.''

[0128] First, in a state without smoke, the first brightness A1 of the light line portion 16 of the first image 36 in a state in which the slit light source 12 is turned on is [First brightness A1] = [Background] + [Slit light scattering on the wall] The second brightness A2 of the light line portion 16 of the second image 38 in the state where the slit light source 12 is turned off is [2nd Brightness A2] = [Background] The first difference ΔA is [First difference ΔA] = [A1-A2] = [Wall scattering of slit light] As shown before time t1 in FIG. 5A, the first difference ΔA is maintained at a substantially constant value according to the wall scattering caused by the slit light.

[0129] On the other hand, in a state where there is smoke, the first brightness A1 of the light line portion 16 of the first image 36 in a state where the slit light source 12 is turned on is [First brightness A1] = [Background] + [Wall scattering of slit light] - [Attenuation of slit light by smoke] The second brightness A2 of the light line portion 16 of the second image 38 in the state where the slit light source 12 is turned off is [2nd Brightness A2] = [Background] The first difference ΔA is [First difference ΔA] = [A1 - A2] = [Wall scattering of slit light] - [Attenuation of slit light by smoke] As a result, the first difference ΔA is reduced by the amount of attenuation of the slit light due to the smoke, compared to when there is no smoke.

[0130] As the concentration and diffusion of smoke 44 increases over time, the amount of attenuation of the slit light caused by smoke 44 increases, and as shown from time t1 onwards in Figure 5(A), the first difference ΔA decreases.As shown at time t2 in Figure 5(A), when the first difference ΔA is equal to or less than a predetermined threshold value α or less than the threshold value α (satisfying the first smoke candidate determination condition), it is determined to be a first smoke candidate.

[0131] The "background" refers to infrared sources scattered within the monitored area, such as lighting and external light (such as sunlight) scattered or reflected by walls. Each object within the monitored area has its own characteristic wavelength and magnitude of reflection, but when captured by the monitoring camera 14, it appears as a reflection of light emitted from the light source. In other words, the brightness of the background is the result of the influence of infrared rays scattered within the monitored area on objects within the monitored area. The ambient light scattering portion 42 shown in FIG. 7(B) also appears as part of the background and is included in the "background." Furthermore, a portion of the illumination light smoke scattering portion 52 may be projected onto a portion of the light line portion 16. In this case, the "scattered illumination light" component is added to the background of the first brightness A1 and second brightness in the smokeless and smoke-present states, but does not affect the first difference ΔA.

[0132] Furthermore, Figure 10(B) is a table showing the first brightness B1 of the background part of the first image 36, the second brightness B2 of the background part of the second image 38, and the second difference ΔB, which is the difference between them, which are used to determine the second smoke candidate.As shown in the left column, the first brightness B1, second brightness B2, and second difference ΔB are listed separately for "smoke present" and "smoke absent."

[0133] First, in a state without smoke, the first brightness B1 of the background part of the first image 36 in a state in which the slit light source 12 is turned on is [First brightness B1] = [Background (including the effect of scattering of illumination light)] The second brightness B2 of the background portion of the second image 38 when the slit light source 12 is turned off is [Second brightness B2] = [Background (including the effect of scattering of illumination light)] The second difference ΔB is [Second difference ΔB]=[B1-B2]=[0] As shown before time t1 in FIG. 5C, the second difference ΔB is maintained at the 0 level or a value close to the 0 level.

[0134] On the other hand, in the smoke-present state, the first brightness B1 of the background portion of the first image 36 in the state where the slit light source 12 is turned on is: [First brightness B1] = [Background (including the effect of scattering of illumination light)] + [Scattering of slit light] The second brightness B2 of the light line portion 16 of the second image 38 in a state where the slit light source 12 is turned off is [Second brightness B2] = [Background (including the effect of scattering of illumination light)] The second difference ΔB is [Second difference ΔB] = [B1-B2] = [Scattering of slit light] As a result, the second difference ΔB increases by the amount of scattering of the slit light due to the smoke, compared to when there is no smoke.

[0135] As the concentration and diffusion of smoke 44 increases over time, the scattering of slit light by smoke 44 increases, and as shown from time t1 onwards in Figure 5(C), the second difference ΔB increases.As shown at time t3 in Figure 5(C), if the second difference ΔB is equal to or exceeds a predetermined threshold β (satisfies the second smoke candidate determination condition), it will be determined to be a second smoke candidate, and if both the first smoke candidate and the second smoke candidate are determined to be smoke, it will be determined to be smoke.

[0136] (c7. Smoke position determination process) Next, the process of determining the position of smoke will be explained. In this explanation, reference will be made to Fig. 11, which shows the relationship between the brightness distribution of the light line portion including the dimming portion in the first image and the position of smoke. Note that Fig. 11(A) shows the first image, and Fig. 11(B) shows the brightness distribution of the light line portion.

[0137] As described above, when the smoke detection unit 26 of the fire detection device 18 judges both the first smoke candidate and the second smoke candidate and determines that they are smoke, it may further perform a smoke position judgment process on the first image 36 in which the slit light source 12 is lit.

[0138] 11(B), the smoke position determination process by the smoke determination unit 26 obtains a pixel value distribution 60, which is a brightness distribution with the vertical axis representing "brightness (pixel value)" and the horizontal axis representing "position," for example, for the pixel arrangement along the light line portion 16 of the first image 36 (the pixel arrangement along a direction perpendicular to the up-down direction). Note that since the light line portion 16 is a line with a predetermined width in the up-down direction, the brightness at each position in the pixel value distribution 60 may be obtained as the sum of multiple pixels in the up-down direction of the light line portion 16 in the first image 36, or may be obtained for a predetermined single pixel.

[0139] Here, in the light line section 16 when smoke is present, a dimming section 46 is included at a predetermined position, for example, in Figure 11 (A), approximately in the center of the light line section 16 projected on the front wall surface, and in the pixel value distribution 60, there is a pixel value decrease section 62 where the pixel value (brightness) is decreased corresponding to the position of the dimming section 46, and the smoke detection section 26 determines the position of the smoke from the position of the pixel value decrease section 62 (position of the dimming section 46).

[0140] In determining the position of smoke based on the position of the pixel value decreasing portion 62, the resolution and range of the identified smoke position are arbitrary, for example, the monitoring area 10 is divided into arbitrary sections, and the smoke position is determined in each section. The method of dividing the sections is also arbitrary, for example, four boundary lines 64 are set when looking from the slit light source 12 to the light line portion 16, and the monitoring area 10 is divided into three sections P1 (left side), P2 (center), and P3 (right side) by the boundary lines 64, and the position in the pixel value distribution 60 is associated with each section.

[0141] In the pixel value distribution 60 of Figure 11 (B), the position of the pixel value decrease section 62 corresponding to the dimming section 46 is section P2 (center), so the smoke detection unit 26 determines section P2 as the smoke position and is able to also notify the smoke position.

[0142] Although the embodiment has been described in which the position of the smoke is determined from the position of the dimming section 46 of the light line section 16 in the first image 36, the position of the smoke may also be determined based on the position of the slit light smoke scattering section 48 in the background part of the first image 36, or the position of the smoke may also be determined based on the positions of both the dimming section 46 and the slit light smoke scattering section 48.

[0143] In addition, when determining the position of smoke based on the positions of both the dimming unit 46 and the slit light smoke scattering unit 48, the smoke determination unit 26 may determine whether the object to be determined is smoke or not based on the positional relationship between the dimming unit 46 and the slit light smoke scattering unit 48.

[0144] For example, in the first image 36 shown in Figure 11, the smoke position based on the position of the dimming section 46 and the smoke position based on the position of the slit light smoke scattering section 48 are determined to be in the same section P2 (center), and the smoke position based on the position of the dimming section 46 and the smoke position based on the position of the slit light smoke scattering section 48 are consistent, and the smoke determination section 26 determines that there is indeed smoke when the positions (smoke position section) of the dimming section 46 and the slit light smoke scattering section 48 are consistent, as in the first image 36 shown in Figure 7, and determines that there is no smoke when the positions of the dimming section 46 and the slit light smoke scattering section 48 are different.

[0145] In this way, by determining whether or not there is smoke in addition to determining the position of the smoke, it is possible to determine that there is no smoke when, for example, a change occurs in the image due to lighting or some other object, and the positions of the light-reducing section 46 and the slit light smoke scattering section 48 are different.

[0146] [d.Smoke judgment operation] Next, a description will be given of the smoke detection operation by the fire detection device 18 shown in Fig. 2. In this description, reference will be made to Fig. 12, which shows a flowchart of an example of the smoke detection operation.

[0147] As shown in FIG. 12, the imaging control unit 20 of the fire detection device 18 sets in advance the pixel area of ​​the light line unit 16 and the pixel area of ​​the background part for the infrared image of the monitoring area captured by the monitoring camera 14 (step S1).

[0148] Next, when the imaging control unit 20 determines that a predetermined smoke detection timing has been reached, for example, that two seconds set as the smoke detection period has elapsed, it turns on the slit light source 12 for a predetermined time, for example, one second, and stores, in the image memory unit 24, for example, the first infrared image from the infrared images captured while the slit light source 12 is on, as the first image 36 (steps S2 to S4).

[0149] Next, the imaging control unit 20 turns off the slit light source 12 for a predetermined time, for example, one second, and stores, from the infrared images captured while the slit light source 12 is off, for example, the first infrared image, as the second image 38 in the image storage unit 24 (steps S5 to S6).

[0150] Next, upon receiving instructions from the imaging control unit 20, the smoke detection unit 26 begins operation, reads out the first image 36 and the second image 38 from the image memory unit 24, calculates a first difference ΔA which is the difference between the first brightness A1 of the light line portion 16 of the first image 36 and the second brightness A2 of the light line portion 16 of the second image 38, and when it determines that the calculated first difference ΔA has decreased to below the first smoke candidate determination condition, for example, a predetermined threshold value α, it determines that it is the first smoke candidate (steps S7 to S10).

[0151] Next, the smoke detection unit 26 calculates a second difference ΔB, which is the difference between the first brightness B1 of the background part of the first image and the second brightness B2 of the background part of the second image, and when it determines that the calculated second difference ΔB has increased to or above the second smoke candidate detection condition, for example, a predetermined threshold value β, it determines that it is a second smoke candidate (steps S11 to S13).

[0152] Next, the smoke determination unit 26 determines that the first smoke candidate and the second smoke candidate have been determined to be smoke, outputs a fire detection signal to the outside, and returns to the step of determining the next smoke determination timing (steps S14, S2).

[0153] On the other hand, if the first difference ΔA calculated in step S9 does not satisfy the first smoke candidate determination condition, the steady-state difference ΔAth is calculated and updated by adding the first difference ΔA obtained at that time to the time-varying moving average, and the process returns to the step of determining the next smoke determination timing (steps S9, S15, S2).

[0154] Furthermore, if the second difference ΔB calculated in step S12 does not satisfy the second smoke candidate determination condition, the steady-state difference ΔBth is calculated and updated by adding the second difference ΔB obtained at that time to the time-varying moving average, and the process returns to the step of determining the next smoke determination timing (steps S12, S16, S2).

[0155] When the smoke detection unit 26 determines the position of smoke in step S14, it calculates the brightness distribution of the light line portion 16 of the first image 36 and determines the position of the smoke from the position of the pixel value decreasing portion (light-down portion) where the brightness is decreasing. Furthermore, when updating the steady-state difference ΔAth in step S15, it may calculate the second difference ΔB, and if the second difference ΔB is not equal to or greater than a predetermined threshold value β, it may also update the steady-state difference ΔBth.

[0156] [e. Second embodiment of fire detection system] Next, a second embodiment of the fire detection system will be described. The installation location and configuration of the fire detection system according to the second embodiment are the same as those of the first embodiment shown in Figures 1 and 2, and the smoke detection unit performs smoke detection based on an event in which the slit light is dimmed by smoke and the brightness of the light line portion decreases, i.e., the first smoke candidate in the first embodiment.

[0157] The installation location of the fire detection system of the second embodiment is as shown in FIG. 1, and the configuration is as shown in FIG. 2, which is the same as the first embodiment described above, so a description thereof will be omitted.

[0158] The smoke detection unit 26 of the second embodiment calculates a difference ΔA between a first brightness A1 of the light line portion 16 of a first image 36, which is an infrared image with the slit light source 12 turned on, and a second brightness A2 of the light line portion 16 of a second image 38, which is an infrared image with the slit light source 12 turned off, and determines that there is smoke and detects a fire if the difference ΔA satisfies a predetermined smoke detection condition, for example, if the difference ΔA is equal to or less than a predetermined threshold value α. Furthermore, in order to improve the accuracy of smoke detection, the smoke detection unit 26 determines that there is smoke and detects a fire if it determines that there is smoke a predetermined number of times in succession in smoke detection determinations obtained at a predetermined cycle of 2 seconds, for example.

[0159] Furthermore, in the fire detection system of the second embodiment, the background and external light do not affect the difference ΔA, so it is possible to accurately detect the phenomenon of a decrease in the brightness of the light line and determine that it is smoke.

[0160] [f. Third embodiment of fire detection system] Next, a third embodiment of the fire detection system will be described. The installation location and configuration of the fire detection system according to the third embodiment are the same as those of the first embodiment shown in Figures 1 and 2, and the smoke detection unit performs smoke detection based on an event in which the brightness of the background increases due to scattered light generated when slit light strikes smoke, i.e., the second smoke candidate in the first embodiment.

[0161] The installation location of the fire detection system of the third embodiment is as shown in FIG. 1, and the configuration is as shown in FIG. 2, which is the same as the first embodiment described above, so a description thereof will be omitted.

[0162] The smoke detection unit 26 of the third embodiment calculates a difference ΔB between a first brightness B1 of the background of a first image 36, which is an infrared image with the slit light source 12 turned on, and a second brightness B2 of the background of a second image 38, which is an infrared image with the slit light source 12 turned off, and determines that there is smoke and detects a fire if the difference ΔB satisfies a predetermined smoke detection condition, for example, if the difference ΔB is equal to or greater than a predetermined threshold β. Furthermore, in order to improve the accuracy of smoke detection, the smoke detection unit 26 determines that there is smoke and detects a fire if it determines that there is smoke a predetermined number of times in succession in smoke detection determinations obtained at a predetermined cycle of 2 seconds, for example.

[0163] Furthermore, in the fire detection system of the third embodiment, the background and external light do not affect the difference ΔB, so it is possible to accurately detect an increase in the brightness of the background and determine that it is smoke.

[0164] [f. Modifications of the present invention] Modifications of the fire detection system according to the present invention will now be described. In addition to the above-described embodiment, the fire detection system according to the present invention includes the following modifications.

[0165] (Location of the slit light source and surveillance camera) In the embodiment, the monitoring camera is installed at a position higher than the slit light source so as to look down at a predetermined angle from diagonally above the optical path plane of the slit light that crosses the monitoring area in a plane, but the installation location is not limited to this. For example, the monitoring camera may be installed lower than the slit light source so as to look up from below at the optical path plane of the slit light that crosses the monitoring area in a plane.

[0166] (Fire detection equipment) In the embodiment, the fire detection device is equipped with an image storage unit, but instead of the fire detection device having an image storage unit, an external storage device may be provided and the storage device may be freely connected to the fire detection device. The fire detection device may also be equipped with a display operation unit that can display infrared images captured by a surveillance camera as needed, and also enable operations such as setting the sensitivity of the surveillance camera, setting the areas of the light line and background in the image, and setting the thresholds used to determine the first and second smoke candidates.

[0167] (imaging control unit) In the embodiment, the imaging control unit controls the monitoring camera (imaging device) to repeatedly take a first image by turning on the slit light source and take a second image by turning off the slit light source, but this is not limited to this. For example, the image input unit may determine whether the slit light source is on or off based on images taken by the monitoring camera by turning on and off the slit light source at any timing, and then sort the images into a first image and a second image and store them in the image storage unit.

[0168] Furthermore, in the embodiment, the imaging control unit sets the imaging conditions of the surveillance camera so that the brightness of the light line portion in the first image does not saturate and is able to be distinguished from the brightness of the portion that is not the light line portion, but this is not limited to this. The slit light source may be adjusted so that the brightness of the light line portion in the first image does not saturate and is able to be distinguished from the brightness of the portion that is not the light line portion, or the amount of light from the slit light source may be reduced, or in a bright environment, the amount of light may be increased to ensure SN, or both the imaging conditions of the surveillance camera and the slit light source may be adjusted.

[0169] (Smoke judgment) In the embodiment, the smoke detection unit uses the difference in brightness between the first image and the second image (first difference ΔA, second difference ΔB) as the difference in brightness between the first image and the second image for detecting smoke, but this is not limiting. For example, smoke may be detected by determining whether the brightness when the slit light source is turned on and the brightness when the slit light source is turned off satisfy a predetermined conditional expression.

[0170] (steady-state difference) In the embodiment, for the sake of simplicity, the brightness of the light line portion and the background portion is calculated as the sum of the pixel values ​​of the pixels in the corresponding regions, and the steady-state difference between the light line portion and the background portion is common within the region, but this is not limited to this. In reality, the steady-state difference may differ for each portion of the light line depending on the distance between the slit light source and the wall surface, etc., so the steady-state difference value may be calculated for each arbitrary region, such as for each predetermined pixel in the image (e.g., 50 pixels), for each predetermined distance in real space (e.g., 5 m), or for each section into which the monitoring region is divided (e.g., three sections), and a threshold may be set based on the steady-state difference for each region.

[0171] In addition, in the embodiment, a simple moving average was used to calculate the steady-state difference ΔAth and the steady-state difference ΔBth, but they may also be calculated using a calculation such as a weighted average (past steady-state difference ΔAth × 0.9 + latest steady-state difference ΔA × 0.1).

[0172] (Fourth and fifth inventions) In the embodiment, the light source is a slit light source that emits a slit light that crosses the monitoring area in a plane, but is not limited to this. For example, the light source may be a light source that emits light that projects a predetermined light projection portion, such as a point, circle, or rectangle, onto a predetermined part of the wall surface.

[0173] In addition, an illuminance sensor may be used instead of a surveillance camera, and a first illuminance sensor that detects the brightness of a specific part of the wall surface onto which the light projection unit is projected may be used to obtain the difference in brightness of the specific part of the wall surface by acquiring the brightness of the specific part of the wall surface when the light source is turned on and the brightness of the specific part of the wall surface when the light source is turned off, and a second illuminance sensor that detects the brightness of areas other than the specific part of the wall may be used to obtain the brightness of areas other than the specific part of the wall surface when the light source is turned on and the brightness of areas other than the specific part of the wall surface when the light source is turned off, thereby acquiring the difference in brightness of areas other than the specific part of the wall surface.

[0174] The difference in brightness of a specified part of the wall surface when the light source is turned on and when the light source is turned off corresponds to the difference in brightness of the light line part in the embodiment, and the difference in brightness of the wall surface other than the specified part when the light source is turned on and when the light source is turned off corresponds to the difference in brightness of the background part in the embodiment.

[0175] In this case, only smoke present in the direction of light irradiation can be monitored, but by rotating the optical axis of the light source along the ZX plane around the Y axis and rotating the optical axes of the first illuminance sensor and second illuminance sensor coaxially with the optical axis of the light source, it becomes possible to monitor smoke over the entire monitoring area. Also, by performing smoke detection processing each time the light source, first illuminance sensor, and second illuminance sensor are rotated by a predetermined angle, it becomes possible to determine the direction in which smoke exists (smoke position).

[0176] In this way, the light source is not limited to a slit light source, and the means for detecting brightness (differences in brightness) is not limited to an image captured by an imaging device and may be an illuminance sensor, so that as modified examples of the invention that do not specify a means for detecting a light source and brightness, there are fire detection systems of the fourth invention (an invention corresponding to the second embodiment in which a means for detecting a light source and brightness is not specified) and the fifth invention (an invention corresponding to the first embodiment in which a means for detecting a light source and brightness is not specified). Note that the invention corresponding to the third embodiment in which a means for detecting a light source and brightness is not specified may also be adopted.

[0177] (others) Furthermore, the present invention includes appropriate modifications that do not impair the objects and advantages thereof, and is not limited to the numerical values ​​shown in the above embodiments. [Explanation of symbols]

[0178] 10: Monitoring area 1010, 1012, 1014, 1016: Wall 1020:Floor 1030: Ceiling surface 12: Slit light source 1210: Slit light 14: Surveillance camera 16: Optical line section 46: Dimming section 18: Fire detection device 20: Imaging control unit 22: Image input unit 24: Image storage unit 26:Smoke judgment section 28: Light-emitting part 30: Cylindrical lens 32: Polygon mirror 34: Motor rotating shaft 35: fθ lens 36: First image 38: Second image 40: Ambient light 42: Disturbance light scattering section 44:Smoke 46: Dimming section 48: Slit light smoke scattering part 50:Lighting light source 52: Illumination light and smoke scattering part 60: Pixel value distribution 62: Pixel value reduction section 64: Borderline

Claims

1. a slit light source that is installed in a monitoring area at least a portion of which is surrounded by a wall, and that irradiates a predetermined slit light that crosses the monitoring area in a plane to project a light line portion with a predetermined width on the wall; an imaging device that images a monitoring area including a wall surface onto which the light line portion is projected; an imaging control unit that controls a photographing operation in which the imaging device photographs an image of the monitoring area as a first image with the slit light source turned on, and the imaging device photographs an image of the monitoring area as a second image with the slit light source turned off; a smoke determination unit that determines that there is smoke and detects a fire when a predetermined smoke determination condition is satisfied based on the first image and the second image; A fire detection system comprising:

2. 2. The fire detection system of claim 1, The smoke detection unit calculating a first difference between a first brightness of the light line portion of the first image and a second brightness of the light line portion of the second image, and determining the first difference as a first smoke candidate when the first difference satisfies a predetermined first smoke candidate determination condition; calculating a second difference between a first brightness of a background portion of the first image that does not include the light line portion and a second brightness of a background portion of the second image that does not include the light line portion, and determining that the second difference is a second smoke candidate when the second difference satisfies a predetermined second smoke candidate determination condition; A fire detection system characterized in that, when both the first smoke candidate and the second smoke candidate are determined, the smoke determination condition is satisfied and the system determines that the smoke is smoke.

3. 3. The fire detection system according to claim 2, The smoke detection unit As the first smoke candidate determination condition, when the first difference is equal to or less than a predetermined threshold value that is smaller than a first steady difference in a smoke-free state, the first smoke candidate is determined; A fire detection system characterized in that the second smoke candidate determination condition is that the second difference is greater than or equal to a predetermined threshold value that is greater than the second steady-state difference in a smoke-free state, or if it exceeds the threshold value.

4. 4. The fire detection system according to claim 3, The smoke detection unit The first steady difference is calculated based on the first difference when the smoke is not determined to be the first smoke candidate; A fire detection system characterized in that the second steady-state difference is calculated based on the second difference when the second smoke candidate is not determined.

5. 2. The fire detection system of claim 1, A fire detection system characterized in that the imaging device is installed in a position that overlooks the optical path plane of the slit light that crosses the monitoring area in a plane from diagonally above at a predetermined angle.

6. 2. The fire detection system of claim 1, A fire detection system characterized in that the imaging device is installed in a position where it looks up at a predetermined angle from diagonally below the optical path plane of the slit light that crosses the monitoring area in a plane.

7. 2. The fire detection system of claim 1, A fire detection system characterized in that the imaging control unit sets the imaging conditions of the imaging device or the brightness of the slit light emitted from the slit light source so that the brightness of the light line portion in the first image does not saturate and is distinguishable from the brightness of parts that do not include the light line portion.

8. 3. The fire detection system according to claim 2, A fire detection system characterized in that the smoke detection unit determines the position of smoke based on the position of the dimming part where brightness is reduced within the light line part in the first image.

9. 3. The fire detection system according to claim 2, A fire detection system characterized in that the smoke detection unit determines whether the object to be detected is smoke based on the position of the dimming area where brightness decreases in the light line area in the first image and the position of the scattering area where brightness increases in the background area in the first image.

10. a slit light source that is installed in a monitoring area at least a portion of which is surrounded by a wall, and that irradiates a predetermined slit light that crosses the monitoring area in a plane to project a light line portion with a predetermined width on the wall; an imaging device that images the monitoring area including a wall surface on which the light line unit is projected; an imaging control unit that controls a photographing operation in which the imaging device photographs an image of the monitoring area as a first image with the slit light source turned on, and the imaging device photographs an image of the monitoring area as a second image with the slit light source turned off; a smoke determination unit that calculates a difference between a first brightness of the light line portion of the first image and a second brightness of the light line portion of the second image, and determines that the difference is smoke and detects a fire when the difference satisfies a predetermined smoke determination condition; A fire detection system comprising:

11. a slit light source that is installed in a monitoring area at least a portion of which is surrounded by a wall, and that irradiates a predetermined slit light that crosses the monitoring area in a plane to project a light line portion with a predetermined width on the wall; an imaging device that images the monitoring area including a wall surface on which the light line unit is projected; an imaging control unit that controls a photographing operation in which the imaging device photographs an image of the monitoring area as a first image with the slit light source turned on, and the imaging device photographs an image of the monitoring area as a second image with the slit light source turned off; a smoke determination unit that calculates a difference between a first brightness of a background portion of the first image that does not include the light line portion and a second brightness of a background portion of the second image that does not include the light line portion, and determines that the difference is smoke and detects a fire when the difference satisfies a predetermined smoke determination condition; A fire detection system comprising:

12. a light source that is installed in a monitoring area at least a portion of which is surrounded by a wall, and that irradiates the monitoring area with predetermined light to project a light projection unit onto a predetermined portion of the wall; a smoke determination unit that determines that smoke exists when a first smoke determination condition based on a difference in brightness between the brightness of a predetermined portion of the wall surface when the light source is turned on and the brightness of the predetermined portion of the wall surface when the light source is not turned on is satisfied; A fire detection system comprising:

13. a light source that is installed in a monitoring area at least a portion of which is surrounded by a wall, and that irradiates the monitoring area with predetermined light to project a light projection unit onto a predetermined portion of the wall; a smoke determination unit that determines that smoke exists when a first smoke determination condition based on a difference in brightness between a predetermined portion of the wall surface when the light source is turned on and a predetermined portion of the wall surface when the light source is not turned on, and a second smoke determination condition based on a difference in brightness between a portion of the wall surface other than the predetermined portion when the light source is turned on and a portion of the wall surface other than the predetermined portion when the light source is not turned on, are satisfied; A fire detection system comprising:

Images