FR3091583A1 - INFRARED LAYER DETECTOR UNDER CEILING - Google Patents

Abstract

The invention relates to an infrared detector (100) with the implementation and the arrangement within the same box of a set of several mirrors reflecting in the infrared, in order to form an image of the ceiling layer of a room. Figure for the abstract: Fig. 2

Description

Title of the invention: INFRARED LAYER DETECTOR UNDER CEILING

Technical area

The present invention relates to the field of optical systems comprising one or more optical components suitable for reflecting or making converge or diverge infrared radiation.

The invention aims more particularly to propose an infrared detector intended to be installed on the ceiling of a room and whose field of vision is suitable for observing the layer under the ceiling of the room.

In another of its aspects, the invention also relates to a detector combining a ceiling layer detector and a smoke detector.

In yet another of its aspects, the invention relates to a detector combining a ceiling layer detector and an occupancy detector.

The main application targeted by the invention consists in observing the ceiling layer of a room using an infrared sensor of moderate resolution, comprising for example 64 × 64 or 80 × 80 sensitive elements. This type of sensor has sufficient resolution to allow basic imaging functionality.

Although described with reference to the main application, the invention applies to any type of infrared detector for which there is a need to obtain a lateral and panoramic field of vision.

By "ceiling layer" means a layer located directly under a ceiling of a room, and which has a small thickness compared to the height of the room. Typically, a ceiling layer has a thickness of less than 15% of the height of the room, directly under the ceiling.

Prior art

Several technologies can be used to manufacture sensors operating in the infrared field. Thus, pyroelectric sensors and thermopiles are widely used for very low resolution detectors conventionally comprising only a few sensitive elements. Sensors incorporating microbolometers are used in medium and high resolution sensors that can be used as imagers.

There is a growing interest in sensors of moderate resolution, which allow the implementation of basic imaging functions such as the location of an infrared source.

Such sensors can have a resolution between 16x16 pixels and 80x80 pixels and can operate on the basis of one of the aforementioned technologies.

The execution of many functions of very low resolution detectors can be improved by the use of moderate resolution sensors. In addition, this type of sensor allows new applications.

Existing applications of infrared sensors mainly consist of monitoring an interior to determine the presence of a hot spot.

One of the main applications of existing pyroelectric type infrared sensors is motion detection.

This is the principle implemented for example by anti-intrusion detectors, which are installed in a large number of buildings. An intrusion alarm system typically relies on a pyroelectric sensor comprising two or four sensitive elements associated with a simple and inexpensive optical device defining the detector's field of vision. This optical device can in particular be a matrix of Fresnel lenses made of polyethylene or a set of mirrors each made from a plastic substrate, such as polymethyl methacrylate (PMMA) or polycarbonate (PC), at least metallized on its functional surface.

An anti-intrusion detector of this type is qualified as a passive detector because it emits no radiation.

The operation of an anti-intrusion detector is based on the observation of a variation of the ambient infrared flux simultaneously in all the sensitive elements of the sensor.

Several configurations of anti-intrusion detector are possible: installation on the ceiling, in which case the field of vision is typically of the order of 360 ° in azimuth and approximately 45 ° in elevation, on either side from the vertical, or a wall installation, in which case the detector's field of vision can be determined according to the configuration of the walls of the room in which it is installed.

Occupancy detectors, which usually control the automatic switching on of lights, are similar to anti-intrusion detectors in their operation.

There are also, for fire alarms, so-called thermovelocimetric detectors, sensitive to an abnormal increase in the temperature of the walls of a room which characterizes the presence of a heat source. Although reliable, these detectors are limited in that they do not allow the location of the heat source.

In addition, a growing interest in applications for counting people or managing queues can be observed, for example for reasons of security or space management. In this context, the company Irisys has developed a pyroelectric sensor with a resolution of 16x16 pixels. This sensor, which can for example be installed above a store queue, is associated with a germanium or chalcogenide glass lens which makes it possible to obtain a field of vision having a limited opening, of the '' from 50 ° to 60 °. The resolution of the sensor, although relatively low, is nevertheless sufficient to obtain a good approximation of the number of people and their location in the queue.

Figure 1 schematically shows an infrared detector 1 according to the state of the art comprising an imager of moderate resolution and intended to be arranged on a room ceiling. Infrared radiation enters the detector through the optical system 2, which in particular comprises an input lens and an infrared sensor.

The opening angle a of the field of vision of such a detector is conventionally between 70 ° and 90 °.

In many practical applications, the different types of detectors mentioned above are installed on the ceiling of a room.

However, the inventors have determined that there is an interest in monitoring the ceiling layer of a room.

Indeed, the ceiling layer plays a key role in the comfort of a living place. This is the boundary layer of convection, where an accumulation of heat can take place, especially in summer.

On the other hand, cold spots can appear there, for example when windows are opened in winter weather.

In other words, monitoring the layer under the ceiling produces important information for managing the thermal comfort of a room.

In addition, monitoring the layer under the ceiling improves safety in the context of preventing or detecting the start of a fire. It makes it possible to observe the thermo-velocimetry of the walls, that is to say the speed of temperature change of the walls, and therefore to detect an abnormal rise in their temperature characteristic of a pre-fire situation. In addition, the accumulation of hot smoke in the ceiling layer in the event of a fire can also be detected.

Compared to existing solutions of fire detectors whose field of vision is directed towards the floor of a room, a fire detector observing the layer under the ceiling has the advantage of not being able to trigger an alarm on the basis of a false signal from, for example, the occupants of the room or hot objects that they are likely to handle, such as for example a cup filled with hot coffee.

Therefore, there is a need for an infrared detector solution for monitoring the ceiling layer of a room.

The object of the invention is to meet this need at least in part.

Statement of the invention

To do this, the invention relates to an infrared detector intended to be arranged on a ceiling of a room to observe a layer under the ceiling, comprising:

A generally cylindrical case comprising an upper part and a lower part connected by at least one connecting means and defining between them side openings, a primary mirror in the form of a crown, arranged on the lower part of the case, and comprising a circular opening in its center, a secondary mirror in the form of a crown, integral with the housing and / or the primary mirror, and comprising a circular opening in its center, a third mirror in the form of a crown, arranged between the central opening the primary mirror and the central opening of the secondary mirror, integral with the housing and / or the primary mirror and / or the secondary mirror, and comprising a circular opening in its center, a fourth mirror arranged opposite the central opening of the mirror primary, integral with the secondary housing and / or mirror, and

- an infrared sensor arranged in the center of the lower part of the housing, the primary and secondary mirrors, the third and fourth mirrors being adapted to reflect radiation in the infrared; and

The side openings and the primary mirror defining the detector's field of vision, and the primary mirror, the secondary mirror, the third mirror and the fourth mirror being configured to form an image of the layer under the ceiling on the infrared sensor.

Thus, the invention essentially consists in the implementation and arrangement within a single housing of a set of several mirrors reflecting in the infrared, in order to form an image of the layer under the ceiling d 'a piece.

The detector's field of vision is determined on the one hand by the configuration of the side openings which allow infrared radiation to enter the detector, and by the configuration of the primary mirror.

An image of the ceiling layer is formed on the sensor of the detector after reflection on each of the plurality of mirrors, judiciously configured.

The use of mirrors makes it possible on the one hand to avoid the use of expensive infrared lenses, and on the other hand to allow the obtaining of a purely reflective optics.

In addition, aspheric image corrections can advantageously be obtained.

Advantageously, the side openings do not allow infrared radiation from the ground to enter the detector. The sensor therefore only receives signals from the ceiling layer: the floor and any occupants of the room are completely hidden.

Thanks to the invention, an infrared detector is thus obtained making it possible to observe the layer under the ceiling of a room and to provide a clear, corrected image thereof and with masking of the ground.

Preferably, the field of vision of the detector as described above has an angle between 5 ° and 10 °.

The detector advantageously consists of a single piece of injection molded plastic, such as polymethyl methacrylate (PMMA) or polycarbonate (PC), at least the surfaces of the plurality of mirrors being metallized.

The invention further relates to a detection assembly intended to be installed on a ceiling of a room, comprising an infrared layer detector under the ceiling as described above and a smoke detector arranged on an external face of the lower part of the ceiling layer detector housing.

The invention also relates to a detection assembly intended to be installed on a ceiling of a room, comprising an infrared layer detector under the ceiling as described above and an occupancy detector arranged on an outer face of the part bottom of the ceiling layer detector housing.

The invention finally relates to the use of an infrared detector as described above to detect an accumulation of heat or a cold spot in the ceiling layer of a room, as well as the use of an infrared detector as previously described to detect an accumulation of hot smoke in the ceiling layer of a room or an abnormal change in the temperature of the walls of a room at the level of the ceiling layer.

Brief description of the drawings

[Fig.l] is a schematic profile view of an infrared detector according to the state of the art;

[Fig.2] is a schematic view of an infrared layer ceiling detector according to the invention;

[Fig.3] is a side view of an infrared detector according to the invention;

[Fig.4] is a schematic view in longitudinal section of an infrared detector according to the invention in a sectional view;

[Fig.5] is an image obtained by an infrared detector according to the state of the art;

[Fig.6] is a simulation of the image obtained by an infrared detector according to the invention; [Fig.7] is a side view of an infrared detector according to the invention associated with a smoke detector;

[Fig.8] is a photographic reproduction of an infrared detector according to the invention associated with an occupancy detector.

detailed description

Throughout the present application, the terms "vertical", "lower", "upper", "bottom", "top", "below" and "above" are to be understood by reference with respect to a infrared detector in operating configuration installed on a ceiling and facing the ground. Thus, in an operating configuration, the lateral openings of the infrared detector overlook the ceiling layer of the room.

Figure 1 has already been described in the preamble and is therefore not commented on below.

We will now describe, with reference to Figures 2 to 4, an infrared detector according to the invention.

FIG. 2 schematically represents a detector 100 according to the invention, which has a field of vision measured by the angle opening onto the layer under the ceiling of the room where the detector is installed.

The field of vision is continuous over 360 ° in azimuth, that is to say in the plane orthogonal to the vertical direction.

The embodiment of Figure 3 illustrates the different elements that make up a detector 100 according to the invention.

As can be seen in this figure, the detector 100 comprises a housing 10 consisting of an upper part 11 and a lower part 12. At least one connecting means 13 assembles the upper 11 and lower 12 parts of the housing 10, while defining side openings 14. The side openings 14 allow infrared radiation from the ceiling layer to enter the detector.

In the illustrated embodiment, the connecting means 13 are rigid connecting means, constituted by four elongated supports, distributed equiangularly around the circumference of the housing 10, each attached by one of their ends to the upper part of the housing and through the other end to the lower part of the housing. The lower and upper parts of the housing as well as the supports can be made in one piece.

A set of four mirrors 15, 17, 19, 21 is arranged in the housing 10 in a fixed manner. The primary mirror 15, the secondary mirror 17 and the third mirror 19 each have a circular opening in their center, respectively designated by the references 16, 18, 20.

The primary mirror 15 is arranged on the lower part 12 of the housing, so as to return the infrared radiation from the field of view of the aperture angle detector a to the secondary mirror.

Thus, the side openings 14 and the reflecting surface of the primary mirror 15 are shaped so that the primary mirror reflects the incident radiation from the layer under the ceiling to direct it towards the secondary mirror 19.

The reflecting surface of the secondary mirror 19 faces the reflecting surface of the primary mirror 15. It is shaped, so as to capture the radiation coming from the primary mirror in order to return it to the third mirror 19.

The third mirror 19 is arranged above the central opening 16 of the primary mirror 15 and below the central opening 18 of the secondary mirror 17. Its reflecting surface is shaped to receive the infrared radiation returned by the secondary mirror and to transmit it to the fourth mirror 21.

The fourth mirror 21 is arranged above the central opening 18 of the secondary mirror 17. Its reflecting surface is generally parabolic in shape, without central opening, and is shaped to return the radiation from the third mirror 19 to the infrared sensor 22, arranged in the center of the lower part of the housing 10 under the central opening 16 of the primary mirror 15.

The detector's field of vision is determined by the configuration of the lateral openings 14 and by that of the primary mirror 15, as visible in FIG. 3. The detector's field of vision extends continuously over 360 ° around the vertical and has a field of vision on the ceiling layer whose angle a is between 5 ° and 10 °.

The mirrors are shaped so that the image obtained is clear, with aspherical corrections.

Figure 4 shows the optical traces of infrared rays from the ceiling layer. It can be seen that the path of an infrared ray in the detector 1 has four reflections, one on each of the mirrors 15, 17, 19, 21, and ends on the infrared sensor 22.

Thus, thanks to the invention, a device based solely on mirrors is implemented in order to obtain a field of vision open on the layer under the ceiling. In particular, the use of infrared lenses, which can be expensive, is avoided.

Figure 5 is a photographic reproduction of the infrared image obtained by a detector according to the state of the art as shown in Figure 1. The detector is installed on the ceiling and its field of vision is directed towards the room floor. The opening angle of the field of vision does not exceed 90 °.

In contrast, FIG. 6 is a simulation of the image obtained by a detector according to the invention installed in the same place as the detector in FIG. 5. Thanks to the detector according to the invention, an image of the layer under the room ceiling.

It can be seen that the image obtained comprises total masking of the ground at the center of the image: the field of vision of the detector covers only the layer under the ceiling. In the case of a fire detection application, this central masking avoids any risk of inadvertent triggering of the alarm by a false signal caused for example by an occupant of the room or by a hot object that would be likely to handle, such as a cup filled with hot coffee.

The invention can be implemented to fulfill a fire alarm function. In fact, infrared surveillance of the ceiling layer authorizes the detection of hot smoke and makes it possible to observe the thermo-velocimetry of the walls of a room, that is to say the rate of rise of their temperature, which to indicate a pre-fire situation.

The invention can also be implemented with the aim of improving the thermal comfort of a room: infrared monitoring of the layer under the ceiling can indicate an accumulation of heat or makes it possible to detect a window that has remained open when the outdoor weather conditions are winter.

It is particularly advantageous to combine an infrared detector according to the invention with other types of devices intended to be installed on the ceiling of a room. This makes it possible to take advantage of the characteristics of each device and to combine their effects. It also helps limit the unsightly effect that comes from having multiple instruments on the ceiling of a room.

As shown in Figure 7, it is possible to combine a detector 100 according to the invention with a smoke detector 111 to obtain a single detector 110. The smoke detector 111 is a detector according to the state of the art , comprising in particular a smoke chamber 112 whose obscuration, due for example to the accumulation of smoke, is the trigger for the alarm signal.

The smoke detector is arranged on the underside of the lower part 12 of the housing 10 of the detector 100: it is its outer face which is facing the ground of the room in the detector's mounted configuration.

Advantageously, this arrangement of the smoke detector makes it possible to simplify the mechanical and electronic architecture of the detector 110. Indeed, the electronic components of each of the detectors 100 and 111 can then be arranged on two opposite sides of a printed circuit, which may in particular be a four-layer printed circuit.

By combining the information received by the ceiling layer detector and the smoke detector, the single detector 110 makes it possible to minimize the risks of inadvertent triggering of an alarm signal.

FIG. 8 illustrates the combination in a single detector 120 of a ceiling layer detector 100 according to the invention and of an occupancy detector 121.

An occupancy detector according to the state of the art makes it possible to carry out several functions related to the management of the comfort of an interior: we can cite for example the lighting control or even the modulation control ventilation.

The combination of a ceiling layer detector according to the invention and a occupancy detector according to the state of the art makes it possible to integrate functionalities for managing thermal comfort with the functionalities linked to detection. of occupation.

Occupancy detectors as well as state of the art smoke detectors are typically installed toward the center of a room. However, this is advantageously a favorable placement position for a ceiling layer detector: the combination of these detectors into a single detector makes it possible to take advantage of this fact.

In addition, the combination of the ceiling layer detector with either a smoke detector or an occupancy detector allows new functionalities without the need to add a new detector to the ceiling of a room. . This therefore avoids the proliferation of ceiling detectors, which can have an unsightly effect.

Other variants and advantages of the invention can be achieved without departing from the scope of the invention. The invention is thus not limited to the examples described above.

Although described with reference to the main intended application, namely the observation of the ceiling layer of a room, the invention is also applicable to any field in which it is advantageous to obtain a field of lateral vision extending continuously over a whole periphery, ie 360 °. The detector as described above can for example be used in the automotive field and in transport in general.

Claims (1)

Claims [Claim 1] Infrared detector (100) comprising: - a generally cylindrical housing (10) comprising an upper part (11) and a lower part (12) connected by at least one connecting means (13) and defining between them lateral openings (14), - a primary mirror (15) in the form of a crown, arranged on the lower part of the housing, and comprising a circular opening (16) in its center, a secondary mirror (17) in the form of a crown, integral with the housing and / or the primary mirror, and comprising a circular opening (18) at its center, - A third mirror (19) in the shape of a crown, arranged between the central opening of the primary mirror and the central opening of the secondary mirror, integral with the housing and / or the primary mirror and / or the secondary mirror, and comprising an opening circular (20) in its center, - a fourth mirror (21) arranged opposite the central opening of the primary mirror, integral with the housing and / or the secondary mirror, -an infrared sensor (22) arranged in the center of the part lower case, primary and secondary mirrors, the third and fourth mirrors being adapted to reflect infrared radiation; and the side openings and the primary mirror defining the field of vision of the detector, and the primary mirror, the secondary mirror, the third mirror and the fourth mirror being configured to form on the infrared sensor an image of the layer under the ceiling. [Claim 2] Infrared detector according to claim 1, the field of vision of the detector having an angle between 5 ° and 10 °. [Claim 3] Infrared detector according to one of the preceding claims, consisting of a single piece of injection molded plastic, such as polymethyl methacrylate (PMMA) or polycarbonate (PC), at least the surfaces of the plurality of mirrors being metallized . [Claim 4] Detection assembly (110), intended to be installed on a room ceiling, comprising an infrared layer detector (100) according to one of the preceding claims and a smoke detector (111) arranged on an external face from the bottom of the housing of the ceiling layer detector. [Claim 5] Detection assembly (120), intended to be installed on a ceiling of a room, comprising an infrared layer detector (100) according to one of claims 1 to 3 and an occupancy detector (121) arranged on an outer face of the lower part of the ceiling layer detector housing. [Claim 6] Use of an infrared detector according to one of claims 1 to 3, to detect an accumulation of heat or a cold spot in the ceiling layer of a room. [Claim 7] Use of an infrared detector according to one of claims 1 to 3, to detect an accumulation of hot smoke in the ceiling layer of a room or an abnormal change in the temperature of the walls of a room at the level of the layer ceiling. 1/3