BG67307B1 - Passive infrared motion sensor with one single focus fresnel lens and multiple zones - Google Patents

Abstract

The PIR motion sensors are widely used in security systems, as well as they are used to detect people and vehicles. The present invention relates to the use of a plurality of passive infrared two-element motion - detectors with only one single focus Fresnel lens. By positioning detectors near the central one (in focus) what is achieved is: increasing the number of zones and the detection area without increasing the size of the PIR sensor; solving the problem of the dependence for determining the angular velocity and direction of movement on the temperature difference between the object and the environment (the PIR-element inverts the signal if the temperature of the object is lower than that of the environment); improving the characteristics of the sensors - increasing the detection distance of the object and/or reducing false alarms; creation of a PIR sensor for specific needs by an appropriate geometric structure and an algorithm for signal processing.

Description

Field of technology

In optical systems, the condition is to place the focusing lens and the electromagnetic wave capture sensor on the optical axis, with the electromagnetic wave detection sensor in focus. The purpose of this geometric construction is to obtain a bright, contrasting and focused image. This principle is also used in the design of passive infrared motion sensors. Most often, a two-element infrared spectrum detector (DDFS) - 8-M4 pm - is used for the realization of such a device. In this sense, the present invention relates to Passive infrared two-element motion detectors using only one single-focus Fresnel lens. This geometric structure requires a change in the control electronics, as well as a change in the algorithms and signal processing in passive infrared detectors.

BACKGROUND OF THE INVENTION

Passive infrared (PIR) detectors are widely used motion sensors designed for automatic light and energy switches, alarm sensors, door openers, etc., areas in the home and industry. The advantages of PIR detectors are their small size, low cost, very low consumption and the fact that they do not emit anything. Detectors built into security systems typically respond to radiation in the far-infrared range of 7-14 pm and are used to detect the movement of people and vehicles.

The technology of passive infrared motion detectors has been known for more than 40 years. Over the years, a number of technological improvements and methods for signal processing and analysis have been made to achieve better parameters of the devices using this technology. For example, in his article Madura (2007) presents an original design of a large number of PIR sensors and the principle of operation of a passive infrared detector with a wide range of detection of slow-moving or crawling people at a distance of up to 140 t. uses a special method to analyze the signal from multiple DDCHS [1]. Shpater (2001) used two DDCHs with two lenses to prevent the alarm from being triggered by pets. The design of its detector is vertically arranged parallel elements located with opposite polarity to increase the sensitivity and reduce the noise of the device [2]. The DDCHS was used to determine the relative direction of a moving object by alternating the polarizations of the sensor elements, while a switch, counter and timer were additionally used to determine its speed [3]. U.S. Patents 2004/0140430 A1 and US006163025A deal with a complex system of PIR sensors based on multifocal Fresnel lenses and DDICs, which are intertwined in different configurations, achieving different output frequencies in order to distinguish lower than human objects (domestic pets) and reduce erroneous alarm events caused by shock, light or ambient temperature. Characteristic of this type of PIR sensor is the use of a complex optical system and complex technological implementation of the various configurations of the detector system [4,5]. A system of PIR sensors controlled by a common microcontroller used to screen signals from random events and / or pets by moving people was introduced by Tatsuoka. The emphasis of the patent proposal is to reduce the consumption of the device when using an autonomous power supply [6].

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Significant differences are the decisions cited above:

The main claim of the present patent is the use of methods and device based on many standard DDCHS placed behind a single-focus Fresnel lens, which are generally not located in its focus. The principle of spatial modulation (creation of a number of separate sensitive areas) is the main basis of PIR the technology so far, and this is achieved by the production of Fresnel lenses with multiple individual segments or by mirror optics with multiple segments (For example: US 2004/0140430 A1, US006163025A). In this sense, our proposal is a novelty.

The geometric construction of the device (one single-focus Fresnel lens and multiple DDCHS) allow for a stable solution in determining the angular velocity, which corresponds to the radial velocity of an object located at a certain distance from the device. For example, a device located on the sides of a road at a certain distance is used to determine the speed of vehicles on the road. The patent claims cited above do not provide a solution for determining the angular velocity of an object.

The difference in determining the direction of travel with the above patents is that the signal from the plurality of DDCHs is used instead of using the polarity reversal of one DDCHS (For example: Patent US 2004/0140430 A1 and US 5,291,020, 1994).

We do not know that a solution to the problem of changing the polarity of the signal of the DDCHS, obtained from the movement of an object with a lower temperature than the environment, has been presented.

A fundamental difference between the methods and algorithms for reducing false alarms with the above-mentioned patent proposals is not expected.

The difference with the classic PIR sensor is a multi-zone Fresnel lens consists in the use of multiple DDCHS and one single-focus Fresnel lens. This leads to the use of the entire area of the Fresnel lens, which is associated with an increase in the energy used (increase in the detection distance) entering the DDCHS. The many DDCHs are also used as separate sources of information. After algorithmic processing, false alarms are reduced.

Technical essence of the invention

The object of the invention is to provide a PIR motion sensor using a plurality of DDCHS and a single single-focus Fresnel lens.

The present patent proposal creates a geometric construction in which some FTTs are outside the optical axis and / or out of focus of the optical system. It is achieved through such a system.

1. Increasing the number of zones using only one single-focus Fresnel lens, which leads to an increase in the detection area;

2. The problem of the dependence for determining the direction of movement of the object on its temperature relative to that of the environment is solved. The direction of movement is correctly determined regardless of the outside temperature (the polarity of the pyroelement signal changes if the temperature of the object is lower than that of the environment, which is a problem in determining the direction of movement);

3. Determine in advance the angular velocity at which the object enters the central (focus) area. The angular velocity of a moving object is correctly determined (the polarity of the signal of the pyroelement changes,

BG 67307 Bl if the object temperature is lower than the ambient temperature, which is a problem when determining the angular velocity by other methods).

4. Improving the characteristics of the sensor - increasing the detection distance of the object and / or reducing false alarms.

5. More precise determination of the direction of movement of an object in the plane perpendicular to the optical axis of the PIR sensor, using a different geometric configuration of the DDCHS.

6. Screening of lower objects from a person (pets) by applying appropriate mathematical algorithms in the microprocessor control of a PIR sensor, using a different geometric configuration of the DDCHS, which improves the degree of recognition and reduces the possibility of false alarms .

Explanation of the attached figures

Figure 1: Example of a PIR sensor with seven DDCHS and one single-focus Fresnel lens.

Figure 2: Trigger diagram with the respective coverage areas for a PIR sensor with seven DDCHS and one single-focus Fresnel lens.

Figure 3: Example of the location of three DDCHS located at 120 ° to each other, while their directions of maximum sensitivity are also at 120 ° to each other in a PIR sensor with a single-focus Fresnel lens.

Figure 4: Diagram of actuation with the respective coverage areas for a PIR sensor with the location of three DDCHS, the location of three DDCHS located at 120 ° to each other, while their directions of maximum sensitivity are also at 120 ° relative to another.

Figure 5: Example of in-line placement of three DDCHS in a PIR sensor with a single-focus Fresnel lens.

Figure 6a: Simplified electronic circuit of a channel of a PIR sensor;

Figure 6b: Simplified electronic circuit of a PIR sensor with three DDCHS.

PIR - DDIC detectors; AMP - amplifiers; COM - two-threshold (window) comparators CPU microprocessor.

An embodiment of the invention

Exemplary embodiments of a PIR sensor have been developed, described below, and other geometric constructions are possible, depending on the need and tasks:

Example 1

A PIR sensor shown in Figure 1 is constructed, which is a schematic example of an arrangement with seven DDCHS and one single-focus Fresnel lens. The seven DDCHs are arranged in the following order: one is in the focus of a single-focus Fresnel lens, in the same horizontal plane, on the left and on the right, two more DDCHs are placed in close proximity, and below and above the focus are placed two more DDCHs. so that the outer DDICS form a hexagon. All DDCHS are oriented in the same way and have maximum sensitivity in a direction perpendicular to the elements of the DDCHS. Figure 2 shows what is the actuation diagram and the corresponding coverage areas of such a geometric implementation.

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Example 2

A PIR sensor has been built with the location of three DDCHS with one single-focus Fresnel lens, and the focus of the Fresnel lens is in the geometric center between the three DDCHS. The three DDCHS are located at 120 ° to each other, and at the same time their directions of maximum sensitivity are also at 120 to each other. This geometric structure is shown in Figure 3. The actuation diagram and the corresponding coverage areas for such a geometric structure are presented in Figure 4. In this way, with a suitable algorithm, the direction of motion can be determined in a plane perpendicular to the direction of the optical sensor axis.

Example 3

Figure 5 shows an embodiment of a sensor arranged in a line of three DDCHS and one single-focus Fresnel lens. The actuation diagram and the corresponding coverage areas are identical to the diagram in Figure 5 and are therefore not shown in a separate figure. In the building shown, the directions of maximum sensitivity are in the same plane.

Other locations and orientations of the DDCHS are also possible, depending on the need.

The control electronics of devices embodied by this patent may have the following form shown in Figure 6a and Figure 6b. Figure 6a shows a simplified electronic circuit of a channel of a PIR sensor, in which the infrared signal passed through the filter excites the two-element detector, the signal of which is amplified by an amplifier and transmitted to a window comparator. The comparator generates a logic signal when exiting the levels of the predefined window.

Figure 6b shows a simplified electronic circuit of a PIR sensor with three DDCHS. The scheme of Figure 6a was used for each DDCHS. A similar scheme is used for the implementation of a PIR sensor with more than three DDCHS.

Application of the invention

The variants of the created PIR sensor device, as well as the methods of operation determined by the geometric constructions are intended mainly for alarm sensors in the security systems. Different examples of PIR sensor implementations provide different sensor advantages.

Example 1 is intended to create a long-range PIR with many coverage areas using standard DDCHS and a single-focus Fresnel lens. Each of the DDCHS uses the entire area of the Fresnel lens, not just a portion, as is the case with multifocal Fresnel lenses. This leads to a longer distance to detect objects. That is, the sensor itself is more sensitive in length than a classic multi-zone sensor with the same Fresnel lens area. Due to the presence of many DDCHS, a much larger covered area is obtained, compared to a sensor, there is one DDCHS.

Example 2 is used for a high-positioned (downward-pointing PIR sensor) by which the direction of moving objects in the plane perpendicular to the optical axis of the PIR sensor can be determined.

Example 3 is intended for the registration of moving motor vehicles over long distances and can be used for incorporation into a vehicle counting system, including the determination of direction of travel or, as part of a guidance system or trigger of other sensors ( camera, lighting, etc.). The information provided by the PIR sensor is the direction of movement of the object and the angular velocity at which the object enters the central (focus) zone.

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For all variants of implementation of PIR sensor there are many DDCHS, the solution of the problem caused by the inversion of the polarity of the signal is valid if the temperature of the detected object is lower than that of the environment, which prevents the correct determination of the angular velocity and direction of movement. so far.

Claims (1)

Passive infrared motion sensor with one single-focus Fresnel lens and multiple zones, characterized in that a plurality of two-element infrared detectors are mounted in the focal plane of the Fresnel lens, forming multiple zones with the Fresnel lens, with a maximum of one detector located in the focus of the lens