JPH0416236Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention is an infrared detector for detecting moving objects, which is suitable for use in crime prevention devices that monitor intruders using infrared energy emitted by the human body, and is particularly suitable for detecting changes in ambient temperature. This paper relates to an improvement of a dual-type infrared detector that cancels common mode noise input such as noise and vibration.

That is, as shown in FIG. 6, the dual type infrared detector has a pair of infrared receiving electrodes B and C seated on a single pyroelectric material A with a required gap between them.
As these infrared receiving electrodes B and C are irradiated with infrared rays radiated from a moving object, the amount of infrared energy that reaches each electrode B and C due to a change in the spontaneous polarization value of the pyroelectric material A, In other words, it is configured to induce an output current according to the area of infrared irradiation in electrodes B and C, and to extract the output difference between electrodes B and C at this time as a moving object detection signal. By designing the areas of electrodes B and C to be the same, when common mode noise such as ambient temperature changes or vibrations is input to both electrodes B and C, the outputs of both electrodes B and C can be canceled out. The above detection output is not output, thereby eliminating the influence of noise.

However, in the conventional dual-type infrared detector, since the infrared receiving electrodes B and C, which are rectangular and have the same area, are arranged in parallel as shown in FIG. When a moving object approaches as a heat source, there will be a difference between the amount of infrared energy received by electrode B and that of electrode C. Therefore, the moving object can be detected without trouble due to the difference in output between electrodes B and C. However, when approaching from the direction shown by arrow B, the infrared rays are incident equally on both electrodes B and C, and there is no difference in the light-receiving area of both electrodes B and C. If the edge of the infrared light beam radiated from the electrode B is shown as a virtual straight line P in the figure, this virtual straight line P will move in parallel along the direction of arrow B as the moving object moves. If C has the shape shown in the figure, the electrode portion B' cut by the virtual straight line P,
Since the areas of C' are kept equal regardless of the position of the virtual straight line P, there is no difference in output between electrodes B and C, and moving objects cannot be detected. In other words, with conventional dual-type infrared detectors,
Blind spots occur in specific directions within the detection field of view.

This invention was devised in view of these points,
By simply changing the shape of a pair of electrodes that receive infrared rays, a difference in output always occurs between the two electrodes in response to infrared rays input from any direction, thereby eliminating the blind spot of the infrared detector described above. The purpose is to

Hereinafter, embodiments of the present invention will be described based on the drawings.

FIG. 1 shows a dual-type infrared detector for detecting moving objects, and FIG. 2 shows its circuit configuration.
In FIG. 1, numeral 1 is a single pyroelectric material formed by a thin piece of ferroelectric crystal. Pyroelectric material 1
On one side (surface) thereof, there are a first infrared receiving electrode 2 (hereinafter referred to as the first electrode) and a second infrared receiving electrode 2 which have the same area and each receives infrared rays and outputs a signal. Infrared receiving electrode 3 (hereinafter referred to as
A counter electrode 4 common to both the electrodes 2 and 3 is provided on the other surface (back surface). The first and second electrodes 2 and 3 are connected in series as shown in FIG. 2, and their polarization directions are opposed to each other.
In Figure 2, 5 is an impedance conversion FET, R
is the resistance, V _DD is the supply voltage, Vout is the signal output, and E is the ground.

In this embodiment, in the infrared detector having the above configuration, the first and second electrodes 2 and 3 are formed in the following shapes.

That is, as shown in FIG. Assuming virtual straight lines P ₁ , P ₂ , P _{3 . .} . in the directions, no matter which direction the imaginary straight lines P ₁ , P 2 , P ₃ . The area of the part of the electrode 2 cut by the virtual straight line (the part cut by the virtual straight line _P1 is indicated by diagonal lines) and the area of the second electrode 3 cut by the virtual straight line (the part cut by the virtual straight line _P1) The shape is such that the areas of the parts shown by diagonal lines are not equal to each other.

Examples of electrode shapes that satisfy the above conditions include arranging the scalene triangular electrodes 2 and 3 symmetrically with respect to O in the figure as shown in Fig. 4, a.
As shown in Fig. 5b, the L-shaped or tomoe-shaped electrodes 2 and 3 are arranged point-symmetrically, or as shown in Fig. Various shapes can be adopted, such as a circle, an isosceles triangle and a concave shape, a hollow square and a solid square, and other mutually different shapes.

According to the above embodiment, since the areas of the electrodes 2 and 3 are equal, sunlight, brightness of lighting equipment, and other ambient temperature changes that are incident on both the electrodes 2 and 3 at the same time,
Alternatively, the outputs of both electrodes 2 and 3 due to vibration are mutually canceled out and compensated, and at the same time, a virtual straight line that moves both electrodes 2 and 3 in parallel on the arrangement area of both electrodes can be viewed from any direction. Even when the electrodes are crossed at the same time, the shape is such that the area of the first infrared receiving electrode cut by the virtual straight line is not equal to the area of the second infrared receiving electrode cut by the virtual straight line. So,
Even if infrared rays radiated from a moving object, such as a human body, are simultaneously incident on both electrodes 2 and 3 from any direction, there will be a difference in the light-receiving areas of both electrodes 2 and 3, as shown by diagonal lines in FIG. An output difference occurs between both electrodes 2 and 3. Therefore, no matter from which direction a moving object such as an intruder or heat source enters the detection field of view, it can be detected.

It should be noted that the present invention can be similarly implemented in a dual-type infrared detector in which the first and second electrodes 2 and 3 are connected in parallel.

As described above, according to the present invention, it is possible to not only compensate for changes in ambient temperature and vibrations, but also to compensate for changes in ambient temperature and vibrations, using a simple structure that consists of a pair of electrodes with the same area. Even in response to infrared irradiation, an output difference can be generated between the two electrodes, so that a moving object can be detected no matter which direction it enters the detection field of view.

[Brief explanation of drawings]

1 to 3 show an embodiment of the present invention,
Fig. 1 is a schematic side view of the main parts, Fig. 2 is a circuit diagram, Fig. 3 is a plan view showing the shape of the electrode, Fig. 4 a, b, and Fig. 5 a, b, c show the shape of the electrode. It is a top view which shows a modification. FIG. 6 is an explanatory diagram of a conventional example. DESCRIPTION OF SYMBOLS 1... Pyroelectric material, 2... First infrared receiving electrode, 3... Second infrared receiving electrode, P ₁ , P ₂ , P ₃
...A virtual straight line.

Claims (1)

[Scope of utility model registration request] A first infrared receiving electrode and a second infrared receiving electrode, each of which has an equal area and receives infrared rays and outputs a signal, are arranged close to each other on one surface of a single pyroelectric material, A counter electrode common to both the electrodes is provided on the other surface, and the shape of the first and second infrared receiving electrodes is changed so that a virtual straight line moving in parallel on the arrangement area of both electrodes can be viewed from any direction. The area of the first infrared receiving electrode cut by the imaginary straight line is not equal to the area of the second infrared receiving electrode cut by the imaginary straight line, even when the electrodes cross simultaneously. An infrared detector for detecting moving objects.