CN118470892A

CN118470892A - Smoke detection device

Info

Publication number: CN118470892A
Application number: CN202410812461.2A
Authority: CN
Inventors: 乔宁; 王帆; 张�林; 迪兰·理查德·缪尔; 米娜·科伊; 邢雁南
Original assignee: Ningbo Shishi Technology Co ltd
Current assignee: Ningbo Shishi Technology Co ltd
Priority date: 2024-06-21
Filing date: 2024-06-21
Publication date: 2024-08-09

Abstract

The invention discloses a smoke detection device. In order to avoid erroneous judgment, the smoke detection apparatus of the present invention includes: the body is provided with a cavity and an air inlet gap; a light emitting module emitting light and forming a light path in the cavity; the detection module comprises an event camera, and the field of view of the event camera and the light path overlap and form a sensing area of the event camera; and determining whether to issue an alarm according to whether the event issue rate exceeds an alarm threshold. The invention discloses a brand new smoke alarm detection device scheme, which can effectively avoid false triggering or false judgment and is suitable for the field of fire alarm.

Description

Smoke detection device

Technical Field

The invention relates to the field of fire alarm, in particular to a smoke detection device.

Background

Fire early warning is an extremely important task for household, forest and warehouse fire prevention. The traditional smoke sensor mainly utilizes ionization effect, photoelectric effect, thermistor and other means to generate/amplify induced current and the like so as to detect smoke; in other embodiments, neural networks (e.g., YOLO) that consume significant energy and hardware costs are used to detect fires.

There is currently a new type of sensor, so-called event cameras or dynamic vision sensors. An attempt was made in prior art 1 to detect smoke using an event camera. The prior art 1 senses rising smoke to a monitoring area (factory, living room, parking lot, etc.) through a dynamic vision sensor, spreads to flames, and judges whether there is smoke or fire according to intensity data.

Prior art 1: DE102017207852A1 (ROBERT BOSCH)

According to the scheme, the sensor is prevented from being subjected to data analysis by using the neural network, and the neural network is easy to false alarm or miss alarm and has low reliability because of extremely large fire scene difference. However, in addition to smoke and flame, various moving objects in the monitored area may cause intensity data to be within the characteristic frequency range, and thus make false decisions as well.

How to use an event camera to achieve direct or indirect detection of smoke, fog, or/and fire is a completely new task challenge.

Disclosure of Invention

In order to alleviate or partially alleviate the above technical problem, the solution of the present invention is as follows:

A smoke detection apparatus comprising: the body is provided with a cavity and an air inlet gap; a light emitting module emitting light and forming a light path in the cavity; the detection module comprises an event camera, and the field of view of the event camera and the light path overlap and form a sensing area of the event camera; and determining whether to issue an alarm according to whether the event issue rate exceeds an alarm threshold.

Further, the event issuing rate is the number of events issued per pixel per unit time.

Further, whether the event issue rate exceeds the alarm threshold is determined by whether the count value exceeds the threshold.

Further, the light emitting module emits infrared light or visible light.

Further, the smoke detection device comprises an optical path guiding device, so that light rays emitted by the light emitting module form an optical path in the cavity.

Further, the smoke detection device includes an optical path guiding device so that only light traveling in a set direction can be sensed by the event camera.

Further, the optical path guiding means may include a chute in the body, a projection having a passage therein, or a boss in the cavity.

Further, the alarm threshold is a first threshold or a second threshold, wherein the first threshold is higher than the second threshold; when the duration of time that the event release rate exceeds the first threshold exceeds the first set duration, the smoke detection device gives an alarm and sets the alarm threshold to the second threshold.

Further, after the duration that the principle release rate exceeds the second threshold exceeds the second set duration, the smoke detection device upgrades the alarm; the second set time length is longer than the first set time length.

Further, the light emitting module emits infrared light, non-laser type visible light, or laser light at a set frequency.

Further, the body comprises a shell and a cover, and a shading baffle is arranged outside or inside the air inlet gap; or/and the light-emitting module and the body are separated, the light-emitting module emits laser, and the laser enters the cavity of the body through the gap on the body.

Further, at least in the body region where the light path is directed, a light absorbing material is used.

Further, a component for promoting air flow disturbance is arranged in the cavity of the body.

The technical scheme of the invention has one or more of the following beneficial technical effects:

(1) A new smoke alarm detection scheme is disclosed.

(2) False triggering/false judgment is effectively avoided, and false triggering caused by various uncertain things in a monitoring range in the traditional scheme is effectively avoided.

(3) And the alarm leakage is effectively avoided. In some embodiments, the sensor is susceptible to more aggressive event delivery in the case of low concentrations of smoke.

Furthermore, other advantageous effects that the present invention has will be mentioned in the specific embodiments.

Drawings

FIG. 1 is a diagram of a first example of a smoke detection device of the present invention;

FIG. 2 is a diagram of a second example of a smoke detection device of the present invention;

FIG. 3 is a third exemplary illustration of a smoke detection device of the present invention;

FIG. 4 is a diagram of an example of a compressed frame image of an event output by an event camera in accordance with the present invention;

FIG. 5 is a schematic diagram of sampling of different concentrations of smoke versus event delivery rates in certain types of embodiments;

FIG. 6 is a distribution plot of the number of pixels of the intensity of event delivery in some types of embodiments.

Detailed Description

For the purpose of making the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings, and it is apparent that the described embodiments are some embodiments of the present invention, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

In order to clearly describe the technical solution of the embodiments of the present invention, in the embodiments of the present invention, the words "first", "second", etc. are used to distinguish the same item or similar items having substantially the same function and effect. Those skilled in the art will appreciate that the words "first," "second," and the like do not limit the number and order of execution.

In the present invention, the term "smoke detection" refers to the detection of the presence of "smoke" or "fog" in an environment. Hereinafter, embodiments of the present invention will be described by taking "smoke" as an example.

The smoke detection device of the present invention comprises a body having a cavity. The local area may be constituted by a housing and a cover, for example. An air inlet gap is arranged in the body.

Fig. 1 is a diagram of a first example of a smoke detection device of the present invention. The smoke detection device may include a housing and a cover (not shown). The housing may also be considered a base.

The shell can be a pentagonal cuboid or a cylinder. On one side of the housing, such as the bottom, several air intake slots are included.

In the present invention, the air intake gap allows particles (e.g., smoke particles) in the environment to fly away and diffuse into the housing cavity.

The smoke detection device comprises a light emitting module which emits a laser, for example visible light, such as green laser, red laser.

The laser forms a beam or path within the cavity. And the detection module comprises an event camera, and the light beam passes through the field of view of the event camera. In other words, the optical path of the laser is within the field of view of the event camera.

By means of the cover, the light emitting module, the detection module and the light beam can be enclosed within the cavity of the smoke detection device.

For the scheme adopting laser, the scheme is easier to support a large field range, such as fire prevention and disaster prevention of a warehouse, because the laser has better directivity. In an exemplary embodiment in this scenario, the light emitting module is not placed inside or on the surface of the housing, but may be placed further outside and into the cavity through a slit (which may be an air intake slit) in the housing. The separate lighting module and body exist as a complete set of smoke detection devices.

Further, the light emitting module may be a light source (such as a nearby light) emitted by other devices in the environment, and transmitted into the cavity through a specially designed hole in the body, and forms a light path.

Fig. 2 is a diagram of a second example of the smoke detection device of the present invention. The smoke detection device also comprises a light-emitting module and a detection module. The light source in the light emitting module may be a laser source that does not need to emit laser light, and may be an infrared light source that emits infrared light by a conventional LED that emits non-laser type visible light.

Illustratively, on the cover, a number of air intake apertures are also designed to allow particles in the environment to drift, diffuse into the cavity of the smoke detection device.

Since the conventional light source does not have very good directivity as a laser source, a light-passing channel for guiding light propagation is provided in a housing of the smoke detection device, so that an optical path is formed. Based on the design, the conventional LED and infrared light source also have certain directivity.

For the event camera to receive light, the light channel can be designed to ensure that the light in a specific direction can be incident into the event camera in the detection module.

The light-passing channel of the light-emitting module for outgoing light and the light-passing channel of the detection module for incoming light overlap in the cavity to form a sensing area.

In the invention, particles in the sensing area can transmit light rays emitted by the light source in the light emitting module along the light transmission channel of the emergent light to the event camera in the detection module through the light transmission channel of the incident light by reflection and diffuse reflection.

Illustratively, the light-passing channel is a chute within the body.

Preferably, for non-laser type visible light, infrared light or laser light, this approach may increase the imaging significance of the particles in the event camera by controlling the light emission frequency of the light source to have a certain flicker frequency (e.g. 1Hz, 10Hz, 30 Hz), even if the flow rate of the particles is not high.

In some embodiments, a normally open light source may also be selected.

The light source emits light with a wavelength of 850n, 940nm, for example.

Fig. 3 is a diagram of a third example of the smoke detection device of the present invention. In this smoke detection device, the light emitting module and the detection module are designed in two protruding parts outside the housing, but by means of the guidance or limitation of the protruding parts on the light path, the light emitted by the light emitting module forms a light path in the cavity, while the detection module can also only sense a partial area inside the cavity, the light path and the partial area overlapping, constituting the sensing area of the invention. Particles within the sensing region may transfer photons in the optical path into an event camera in the detection module.

Further, the protruding member has a channel inside.

In order to avoid interference of light, a boss is designed in the cavity of the shell, which can avoid or reduce adverse propagation of light in the cavity. The boss may be a sector boss and the sector angle α may be 90 degrees, 120 degrees, or other angles, etc.

Preferably, the fan angle α is non-180 degrees or near 180 degrees, so that direct light from the light source to the event camera is avoided.

Further, a light shielding block (not shown) is arranged on the outer side or the inner side of the air inlet gap, so that external light is prevented from interfering with light in the cavity.

Further, the material of the present invention from which the body is constructed has poor diffuse reflection properties, in other words, the material of the body is constructed, or at least in the body region where the light source is directed, is a light absorbing material with good light absorbing properties.

The optical path in the present invention refers to a photon flow having directivity. Such as laser light, is a photon stream with very good directivity. In the examples of fig. 2 and 3, the laser light may not be necessary, but the light emitted by the light source is guided by mechanical means to form an optical path. The aforementioned protruding members, as well as the light-passing channels, all constitute the light path guiding means.

In one aspect, the light path guiding device causes light emitted by the light emitting module to form a light path in the cavity. On the other hand, the optical path guiding device enables only light propagating in the set direction to be sensed by the event camera.

Fig. 4 is a diagram of an example of a compressed frame image of an event output by an event camera in accordance with the present invention. For the embodiment in fig. 1, fig. 4 shows event information captured by an event camera in the case of no smoke, low concentration smoke, high concentration smoke. In the case of smoke, the generated pulse events are typically noise events. The low concentration smoke is shown in fig. 4 to produce more (pulsed) events.

Fig. 5 is a schematic diagram of sampling of different concentrations of smoke versus event delivery rates in some types of embodiments. When there is no smoke, the event issue rate is approximately equal to 0. Statistically, low concentrations of smoke do generally result in higher event delivery rates, and high concentrations of smoke yield fewer event delivery rates. The phenomenon shows that the invention can accurately and early warn by applying the scheme of executing smoke detection by the event camera under the condition of low-concentration smoke.

Alternatively, during long-term smoke detection waiting, an alarm threshold may be set to a higher first threshold, and an alarm is raised when the event issue rate exceeds the alarm threshold (equal to the first threshold). And once an alarm is raised, the alarm threshold may be changed to a lower second threshold to avoid premature release of the alarm due to the detected (smoke concentration getting higher due to fire deterioration) event release rate being below the first threshold. When the alarm is completely released, the alarm threshold value is restored to the first threshold value.

Further, when the alarm release rate exceeds the alarm threshold for a first set period of time (for example, 5 seconds), an alarm is sent out, so that false triggering of interference factors is avoided. When the event issue rate continues to exceed the alarm threshold for a second set period of time (e.g., 90 seconds), the alarm may be escalated to take the user's attention and avoid greater losses. The second set time length is longer than the first set time length.

In the present invention, the event issuing rate refers to the average number of (impulse) events issued per pixel per unit time. The total number of pixels considered here may be the physical resolution of the event camera or the number of pixels that can be activated effectively (in a laser-like embodiment, the optical path is limited in the number of pixels that can activate the event camera, only the middle area pixels, not all pixels, as illustrated in fig. 4).

In an exemplary embodiment, as a simplified design, because the event camera resolution is fixed, or the pixel area that can be activated is fixed or nearly fixed with the design parameters determined, it is only necessary to count whether the number of events generated by the event camera (i.e., characterizing the event issue rate in one count value) exceeds a threshold value per unit time (e.g., 20 milliseconds). Thus, solutions with different specific design parameters often have quite different thresholds.

Further, for a thermal pixel, the effect on the accuracy of the result can be eliminated by shielding the thermal pixel output.

FIG. 6 is a distribution plot of the number of pixels of the intensity of event delivery in some types of embodiments. In the figure, the horizontal axis represents the event issue rate per pixel, i.e., the number of events issued by a pixel for a set period of time (10 seconds), indicating the intensity of event issue for that pixel for that period of time. The vertical axis is the number of pixels with a particular event issue rate. This type of embodiment light source has a wavelength of 940nm and blinks at a frequency of 10Hz, db representing different smoke concentrations.

Further, for schemes using a blinking light source, the event camera may also generate a certain amount of events in a scene without smoke (db=0) due to aerosol, diffuse reflection inside the body, etc., which may result in a reference event emission rate. An alarm may be triggered when it is detected that the event issue rate exceeds the reference event issue rate by a certain level (alarm threshold).

The reference event issuing rate may be detected in advance, such as more than by detection before shipment; or after a calibration operation prior to use, for which the alarm threshold is often meant, may be non-stationary in different products.

Further, a component may be provided in the body cavity that encourages airflow disruption. Some known designs may create turbulence or turbulence, depending on the aerodynamics, which may cause the gas to create various disturbances. Such embodiments facilitate significant imaging of particles in an event camera, enhancing detection performance.

Numerous specific details are set forth in the above description in order to provide a better illustration of the invention. It will be understood by those skilled in the art that the present invention may be practiced without some of these specific details. In some instances, well known methods, procedures, components, and circuits have not been described in detail so as not to obscure the present invention.

The foregoing is merely illustrative of the present invention, and the present invention is not limited thereto, and any person skilled in the art will readily recognize that variations or substitutions are within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A smoke detection apparatus, comprising:

The body is provided with a cavity and an air inlet gap;

A light emitting module emitting light and forming a light path in the cavity;

the detection module comprises an event camera, and the field of view of the event camera and the light path overlap and form a sensing area of the event camera; and

Whether to issue an alarm is determined according to whether the event issue rate exceeds an alarm threshold.

2. The smoke detection apparatus according to claim 1, wherein:

the event distribution rate is the average number of events distributed per pixel in a unit time.

3. A smoke detection device according to claim 2, wherein:

Whether the event issuing rate exceeds the alarm threshold value is judged by whether the count value exceeds the threshold value.

4. A smoke detection apparatus according to any one of claims 1 to 3 wherein:

the light emitting module emits infrared light, non-laser type visible light, or laser light.

5. The smoke detection apparatus of claim 4 wherein:

the smoke detection device comprises a light path guiding device, so that light rays emitted by the light emitting module form a light path in the cavity.

6. The smoke detection device of claim 5 wherein:

the smoke detection device includes an optical path guiding device so that only light traveling in a set direction can be sensed by the event camera.

7. The smoke detection apparatus according to claim 6, wherein:

The light path guiding device comprises a chute in the body, a protruding part with a channel inside or a boss in the cavity.

8. A smoke detection apparatus according to any one of claims 1 to 3 wherein:

the alarm threshold is a first threshold or a second threshold, wherein the first threshold is higher than the second threshold;

when the duration that the event release rate exceeds the first threshold exceeds the first set duration, the smoke detection device gives an alarm and sets the alarm threshold as a second threshold;

When the duration that the event release rate exceeds the second threshold exceeds the second set duration, the smoke detection device upgrades the alarm; the second set time length is longer than the first set time length.

9.A smoke detection apparatus according to any one of claims 1 to 3 wherein:

The light emitting module emits infrared light, non-laser type visible light, or laser light at a set frequency.

10. The smoke detection apparatus according to claim 9 wherein:

The body comprises a shell and a cover, and a shading baffle is arranged on the outer side or the inner side of the air inlet gap; or/and the combination of the two,

The light-emitting module and the body are separated, the light-emitting module emits laser, and the laser enters the cavity of the body through a gap on the body.