JPH076549Y2 - Infrared sensor - Google Patents

Description

[Detailed Description of the Invention] (a) Industrial Application Field The present invention relates to an infrared sensor, and more specifically,
The present invention relates to an infrared sensor capable of detecting passage of an object to be detected and its passing direction by a pyroelectric infrared detector.

(B) Conventional Technology Regarding the infrared sensor of this type, the applicant of the present application has already proposed a sensor as shown in FIGS. 3 and 4. This is because two surfaces in which the polarities of surface charges are opposite to each other are electrically connected in parallel (hereinafter referred to as dual connection) so that surface charges generated when infrared rays are simultaneously incident on each other cancel each other. A first pyroelectric infrared detector (1) having pyroelectric elements (1a) (1b) and a first pyroelectric infrared detector (1) arranged side by side so as to detect the passing direction of an object to be detected. Based on the detected signals from the second pyroelectric infrared detector (2) and the first and second pyroelectric infrared detectors (1) and (2), the detection signals of each pyroelectric infrared detector And an output rank determining means for determining the output rank of. Such an infrared sensor is used for one-way detection, which informs the first pyroelectric infrared detector (1) dually connected when a detection signal is first generated.

This infrared sensor body (10) has pyroelectric elements (1a) (1b) (2a) of these pyroelectric infrared detectors (hereinafter simply referred to as detectors) (1) and (2) on a substrate (14). They are arranged side by side in a straight line, and are covered with a metal cover (13) equipped with an infrared transmission filter (12). Then, for example, as shown in FIG. 5, the infrared rays from the respective detection areas are converted into the respective pyroelectric elements (1a) by the optical parts such as the convex lens (15).
It is incident on (1b) and (2a).

In FIG. 5, the detection areas of the pyroelectric elements (1a) (1b) (2a) are designated as (Z1a) (Z1b) (Z2). In the figure, arrow A
The detected object (for example, human body) that has advanced in the direction of (Z1
a) (Z1b) and (Z2) are passed through the detection area in this order. The detection signals generated by the detectors (1) and (2) as the object to be detected passes are as shown in FIG. 6 (A). That is, first, a detection signal as shown in (A) and (i) of the same figure is generated in the first detector (1). The detection signals are (A) and (o) in FIG.
The signal of the pyroelectric element (1a) shown in (1) (indicated by a chain line in the figure) and the signal of the subsequent pyroelectric element (1b) (indicated by a broken line in the figure) are combined. Furthermore, a pyroelectric element (1
Following the signal of b), the second detector (2) is shown in FIG.
The detection signal shown in (ii) is generated. On the contrary, the detection signal when the detected object advances in the direction of arrow B is shown in FIG.
The detection signal (ii) of the second detector (2) is generated first, and then the detection signal of the first detector (1) is generated by combining the signals generated by the pyroelectric elements (1b) and (1a). The signal (i) will be generated. Therefore, by comparing the generation times of the detection signals from the detectors (1) and (2), the passing direction of the detected object can be determined. That is, if the detection signal of the first detector (1) is early, the passing direction of the detected object is the direction of arrow A, and if the detection signal of the second detector (2) is early, it is the direction of arrow B. According to this configuration, even if the temperature relationship between the detected object and the background surroundings is reversed, the positive / negative of the signal is reversed, the time relationship is not changed, and the first detector (1) is dual-connected. Since no detection signal is generated even if the ambient temperature or brightness changes, the passage of the object to be detected in the direction of arrow A is notified, and arrow B
One-way detection can be performed stably with respect to temperature changes without notifying the passage in the direction.

However, the distance between the pyroelectric elements of the infrared sensor is about
While the infrared radiation source such as the human body, which is the object to be detected, is not point-like, it is a spread with a certain intensity distribution, while it is as narrow as 0.5 mm.It also occurs in optical components such as convex lenses or concave mirrors used for focusing light. Detection of the passing direction of the detected object may be difficult due to defocusing, the influence of aberration, and the like.

For example, when the object to be detected advances in the direction of arrow A in FIG. 5, the two defocusing elements of the first detector (1) are close to each other due to the defocusing of the convex lens (15). It is conceivable that infrared rays are incident on each of the two) substantially at the same time, and the time difference between the pyroelectric elements (1a) and (1b) generating signals becomes short as shown in FIG. 7 (o). At this time, the signals of the two pyroelectric elements (1a) (1b) dually connected cancel each other out, and the detection signal of the first detector (1) becomes as shown in FIG. 7 (i). The peak (P ") is the sixth
It becomes smaller than the peaks (P) and (P ′) in the case of FIG. This becomes remarkable in combination with the characteristics of the pyroelectric element in which the signal gradually rises due to the electric charges that have started to be generated when the infrared rays are incident, especially when the passing speed of the object to be detected is high. Therefore, when the detection signal is pulsed and digitally processed, the small peak (P ″) cannot be extracted as a signal, and the approach direction may not be detected.

In addition, the detection signal of the first detector (1) and the second detector shown in FIG.
The time difference from the detection signal of the detector (2) is t _{A in the} A direction,
Although it is t _{B in the} B direction, this corresponds to the distances d _A and d _B in FIG. 5, respectively. In this case, since the time difference between the detection signals when the detection target advances in the B direction is short, the direction detection by the time difference detection becomes more difficult.

On the other hand, if the spacing between the pyroelectric elements is widened, the above-mentioned problem can be solved, but in this case, the entire device including the infrared sensor body (10) and the convex lens (15) must be large. Instead, there was inconvenience such as taking up a place for installation.

(C) Problems to be solved by the present invention The present invention aims to provide an infrared sensor capable of accurate direction detection without increasing the size of the sensor body.

(D) Means for Solving the Problems The infrared sensor of the present invention comprises a first pyroelectric infrared detector 1 composed of two pyroelectric elements 1a and 1b which are connected so that surface charges cancel each other. , A second pyroelectric infrared detector 2 arranged side by side with the first pyroelectric infrared detector 1 to detect the passage direction of the object to be detected, and the two pyroelectric elements 1a, 1
Pyroelectric element 1 on the side of the second pyroelectric infrared detector 2 of b
and a shielding means 16 provided separately in front of b, dividing the fields of view of the first and second pyroelectric infrared detectors 1 and 2 so that the first and second pyroelectric infrared detectors 1 and 2 are separated when the object to be detected passes. It is characterized in that the pyroelectric infrared detectors 1 and 2 of FIG.

(E) Operation According to the above configuration, signals do not cancel each other out in the dual-connected first detectors, and the distance between the first detector and the second detector is substantially expanded. .

(F) Embodiment An embodiment shown in FIGS. 1 and 2 of the present invention will be described below. Incidentally, the same or corresponding parts as those of the conventional example described above are designated by the same reference numerals, and the description thereof will be omitted.

(16) is a light-shielding tape attached on the surface of the infrared transmission filter (12), which is the second detector of the two pyroelectric elements (1a) (1b) constituting the first detector (1). It is attached to the front part of the pyroelectric element (1b) on the side adjacent to. The light-shielding tape (16) does not transmit infrared rays, and as shown in FIG. 1, in the vicinity of the optical axis incident on the pyroelectric element (1b), in the direction perpendicular to the arrows A and B, which are the passage directions of the object to be detected. Infrared that is attached to the pyroelectric element (1b) for a long time, that is, infrared rays that are about to enter the pyroelectric element (1b) when the object to be detected is positioned in front of the pyroelectric element (1b). Shield.

When the infrared sensor main body (10) has such a structure, the detection signal waveforms generated in the first and second detectors (1) and (2) when the object to be detected passes in the directions of arrows A and B are shown in FIG. Will be things. The waveform (i) generated in the first detector (1) is
Since the infrared rays from the object to be detected, which are incident on the pyroelectric element (1b), are almost shielded, the pyroelectric element (1b) has substantially the same shape as that of one pyroelectric element that is not dual-connected. Therefore, according to this structure, the outputs of the pyroelectric elements (1a) and (1b) do not cancel each other and the peak (P ″) of the signal waveform does not become small as shown in FIG. And the distances d _A and d _B corresponding to the time difference between the detection signals of the second detectors (1) and (2).
Are large enough, almost the same size. This means that the distance between the first detector (1) and the second detector (2) is substantially increased. Therefore, regardless of the direction of passage of the object to be detected in either direction of arrows A and B, the time differences t _A and t _B at which the detectors (1) and (2) generate detection signals are sufficient as shown in FIG. It becomes large, and direction detection can be performed reliably.

As shown by the broken line in FIG. 1 (a), the light shielding tape (1
It is possible to attach 6 ') directly to the pyroelectric element (1b) instead of on the infrared transmission filter (12), but in this case, for example, when the brightness of the entire surroundings changes and becomes brighter, If an output signal is generated at the pyroelectric elements (1a) and (2a), and if a time difference occurs between these output signals for some reason, erroneous detection may occur. However, if the light shielding tape (16) is attached to the infrared transmission filter (12) as in the present invention, the light shielding tape (16) and the pyroelectric element (1b) are separated from each other, and the entire surrounding becomes bright. In that case, the light also enters the pyroelectric element (1b) from the light-transmitting portion other than the portion where the light-shielding tape (16) is attached to generate an output, which cancels each other out with the output of the pyroelectric element (1a). Therefore, no output is generated in the first detector (1), and erroneous detection does not occur.

It is also conceivable that the pyroelectric element (1b) is omitted and the first and second detectors (1) and (2) are composed of only the pyroelectric elements (1a) and (2a), respectively. Is the first detector (1) for the cause of infrared light changes such as fluorescent light and curtain movement, and temperature changes around the pyroelectric element.
Output is generated and false detection is made. According to the present invention, such an erroneous detection does not occur, and the passage direction of the object to be detected can be reliably detected.

The above description is based on the dual-connected first detector (1).
In the case where the unidirectional detection is performed by using the second detector (2) including one pyroelectric element (2a), the bidirectional detection is performed by using two detectors connected in dual. Not to mention that it can also be used in cases.

(G) Effect of the Invention According to the present invention, since the light-shielding means is provided in front of one of the two dual-connected pyroelectric elements and is spaced apart, it is possible to reliably detect the passing direction of the object to be detected, There is no risk of false detection.

[Brief description of drawings]

1 (a) is a sectional view showing an embodiment of the present invention, FIG. 1 (b) is a front view thereof, FIG. 2 is a signal waveform diagram thereof, and FIGS. 3 to 7 show conventional examples. 3 (a) is a sectional view of the infrared sensor main body, FIG. 3 (b) is a front view thereof, and FIG. 4 is a circuit diagram.
FIG. 5 is a sectional view, and FIGS. 6 and 7 are waveform diagrams. (1) …… First detector, (2) …… Second detector, (1a)
(1b) (2a) …… Pyroelectric element, (16) …… Shading tape.

Claims (1)

[Scope of utility model registration request] 1. A first pyroelectric infrared detector 1 comprising two pyroelectric elements 1a, 1b connected so that surface charges thereof cancel each other, and a first pyroelectric infrared detector 1 for detecting a passing direction of an object to be detected. A second pyroelectric infrared detector 2 arranged side by side with the first pyroelectric infrared detector 1 and the second pyroelectric infrared detector 2 side of the two pyroelectric elements 1a, 1b And a shielding means 16 provided separately in front of the pyroelectric element 1b.
The field of view of the pyroelectric infrared detectors 1 and 2 is divided, and the direction detection is performed by providing the operation time difference between the first and second pyroelectric infrared detectors 1 and 2 when the object to be detected passes. Infrared sensor characterized in that.