JPH02278131A - Pyroelectric-type infrared detector - Google Patents

Abstract

PURPOSE:To enable execution of detection being strong to white light noise and applicable at a wide angle of field irrespective of the direction of movement by disposing an element of a balanced differential type annularly and by increasing or decreasing a part or more of it intentionally. CONSTITUTION:An element of a balanced differential type is disposed annularly and a part or more of it is increased or decreased intentionally. In a pair of infrared detectors of the balanced differential type thus prepared, one of the elements is made to have a plus polarity (a) and the other a minus polarity (b). When a heat source moves in the direction of the detectors, first the plus polarity is outputted by the element (a) and then the minus polarity by (b). When the heat source moves in the direction Y, an output is made by the increased part of the annular element (b), and although it is canceled in the central part, the output is made again by the increased part of the element (a). In the case when the heat source moves across with an inclination of 45 deg., moreover, the output is made by the increased part, not being canceled, and thus detection can be executed. The area of the increased part of the element can be adjusted in regard to a detection distance etc. when the detector is designed, and thus the detection at a wide angle of field can be executed.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention is a detection type pyroelectric device that is used for intrusion alarms, fire detectors, etc., and has a wide viewing angle and is particularly installed on a ceiling or the like. This relates to a type of infrared detector.

(Conventional Technique #i) A pyroelectric infrared detector utilizes the pyroelectric effect of a ferroelectric material in which an electric signal appears in response to temperature changes caused by infrared energy.

When using this pyroelectric infrared detector as a human body or flame detection detector, the current mainstream method is to connect two elements in series with opposite polarities in order to compensate for changes in room temperature. In this case, two types are often used: a balanced differential type shown in FIG. 2 and a single compensation type shown in FIG.

In FIG. 2(b), infrared energy passes through a selective transmission filter 1, enters an element 2a, and then enters an element 2a.
incident on b. Since the polarities of the elements 2a and 2b are opposite, the output of 2a appears in the + direction, and the output of 2b appears in one direction.

Since this signal has high capacitive impedance, bias resistor 3 and F
ET4 is connected, and through these parts 2a,
The combined signal of 2b is output to the outside of the detector. pyroelectric element,
Electrical components such as FET and Rg are housed in a hermetically sealed metal package 5.

FIG. 2(a) shows the positions of the selective transmission filter 1 and the pair of t-poles 2a and 2b when the detector is viewed from above. As is clear from Figure 2 (a), with this type, output can be obtained in the Y direction that crosses the two elements, but in the X direction rotated by 90'', the cancellation moves because the light enters the two elements at the same time. I can't get any output.

On the other hand, the detector shown in Fig. 3 allows infrared rays to enter only one light-receiving element located in the center, and a temperature compensation element is provided on the outer periphery of the light-receiving element at a position where no light enters. Can detect movement in all directions.

However, although such a single compensation type uses a 5-selective transmission filter (transmits only 7 to 14 μm), the two filters on the light-receiving element are sensitive to car headlights, direct sunlight, etc. It is output due to secondary radiation, and false alarms are likely to occur.

On the other hand, in the case of the balanced differential type shown in FIG. 2, the output for secondary radiation appears in both elements at the same time, so cancellation works and there is no problem.

In order to solve these problems, as shown in Figure 4, we have two elements, an inner ring and an outer ring, on concentric circles, and the dividing axis of both is rotated by 90'. One half of the elements of the inner ring and half of the outer ring are connected with the same polarity to form one element of a balanced differential type, and then the remaining half of the inner ring and half of the outer ring are connected to the same polarity. A balanced differential type detector was devised in which one element is connected in a reverse radial manner to form the other element of the balanced differential type, and finally both elements are connected in series.

FIG. 5(a) shows the output waveform of this detector when it is moved in the direction a in FIG. 4. Next, FIG. 5(b) shows the output waveform when moving at the same speed in the direction b in FIG. 4.

At this time, if the threshold value of the detection signal is set to 1, an alarm will be issued even if the vehicle moves in both directions. However, if the threshold value is V, the outputs of elements 7b and 6a overlap, and an alarm is issued in the a direction where the peak value is increasing, but it is lost in the b direction where the outputs of elements 7b and 6b overlap and are canceled. It becomes news.

In this way, the above-mentioned detector may cause cancellation depending on the moving direction and moving speed, resulting in a false alarm.

(5! Problems that Ming attempts to solve) The present invention is a focused infrared detector that is resistant to white light noise caused by car headlights, sunlight, etc., and that can detect with a wide viewing angle regardless of the direction of movement. It is intended to provide.

(Means for Solving the Problems) The present invention is characterized in that balanced differential elements are arranged in a circumferential ring as shown in FIG. 1, and at least a portion thereof is intentionally increased or decreased.

In addition, the present invention is characterized by intentionally increasing or decreasing a portion or more of not only the circumferential annular shape but also the deformed elliptical circumferential annular shape as shown in FIG. 6, or a U-shaped element. .

(Function) Regardless of the moving direction and speed of the heat source, it has a wide viewing angle like the single compensation type, and when light enters both elements at the same time, such as a car's driver and sunlight, it is flat. Cancellation works as an N-hydrostatic type, and no output appears.

(Example) A more detailed explanation will be given below using the drawings.

FIG. 1 shows an example of implementing the present invention. In such a pair of balanced differential type infrared detectors, one of the elements is decapolar a, and the other is unipolar. In this detector, when the heat source moves in the X direction, element a first outputs fertilization, and then element b outputs unipolarity. Further, when the heat source moves in the Y direction, the heat is outputted by the enlarged portion of the circumference of element b, and is canceled in the central portion, but is output again by the enlarged portion of element a. Furthermore, even when the beam crosses at an inclination of 45 degrees, the increased portion is not canceled and is output, making it possible to detect it.

FIG. 7 shows an example of the output with respect to the angle of entry of the heat source into the element.

The area of the increased portion can be adjusted appropriately to the detection distance of the detector and the expected moving speed of the human body when designing the detector. Therefore, detection patterns with various wide viewing angles are possible.

Furthermore, since the areas of the pair of elements are equal, positive and negative cancellation works for light that is simultaneously incident on both elements, such as car headlights and sunlight.

Similar effects can be obtained by using the shape of the element as shown in FIG. The same applies to the case of polygonal shapes.

(Effects of the Invention) As explained above, the flat tWi differential pyroelectric infrared detector has a characteristic shape in a certain direction part of the circumferential ring in which the element is divided into two from the center. Due to the unique shape, uniform characteristics can be obtained over a wide viewing angle regardless of the direction in which the heat source moves, and the output does not appear in response to white light noise (car headlights, sunlight, etc.), eliminating false alarms. It has become possible.

[Brief explanation of drawings]

FIG. 1 shows an element pattern of an embodiment of the present invention. FIG. 2 shows an element pattern and an electric circuit diagram of a balanced differential type detector in a conventional method, and FIG. 3 shows an element pattern and an electric circuit diagram of a single compensation type detector in a conventional method. FIG. 4 shows an element pattern of a balanced differential type detector having an inner ring and an outer ring arranged on concentric circles, and FIG. 5 shows an example of its output waveform. FIG. 6 shows an element pattern of another embodiment of the present invention. FIG. 7 shows an example of output characteristics with respect to the penetration angle obtained by implementing the present invention.

Claims (1)

[Claims] In a balanced differential pyroelectric infrared detector in which two elements of opposite polarity are connected and arranged, the element configuration is a circumferential ring that is divided into two from the center, and one of the elements is divided into two from the center. A pyroelectric infrared detector characterized by increasing and decreasing area.