JPH02223825A - Passive type infrared direction decision sensor - Google Patents

Abstract

PURPOSE:To increase the difference of incidence time of infrared rays to respective pyroelectric elements and to increase the output levels of both pyroelectric elements by composing the direction decision sensor of a couple of pyroelectric elements which are connected in reverse series, a couple lenses corresponding to them, and a light shield plate which inhibits infrared rays passed through the lenses from being incident on elements other than their corresponding pyroelectric elements. CONSTITUTION:The couple of pyroelectric elements 3a and 3b which are connected reversely in series are put in a package 4 to constitute a pyroelectric sensor 1, which generates a negatively large output when a body moves from one element 3a to the other element 3b and a positively large output when the body moves in the opposite direction. Thus, the sensor 1 is constituted, the couple of lenses 2a and 2b are provided at an interval in the array direction of the elements 3a and 3b, and the distance between the lenses is made variable. Further, the light shield plate 6 is provided between the elements 3a and 3b at right angles to the array plane and the infrared rays passed through both the lenses 2a and 2b are made incident on the elements 3a and 3b independently of each other to generate the time difference in timing between the incident infrared rays.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to an infrared passive direction determination sensor that uses a pair of pyroelectric elements to detect the moving direction of an object that generates heat rays.

[Conventional technology]

BACKGROUND ART Conventionally, there has been provided a pyroelectric sensor called a dual type in which a pair of pyroelectric elements are housed in one package. In such a pyroelectric sensor, when an object that generates infrared rays, such as a human body, moves in the direction in which both pyroelectric elements are arranged, there is a difference in the time at which the infrared rays are incident on each pyroelectric element. Detection becomes possible. For example, as shown in FIG. 5, consider a case where a lens 2 is disposed in front of a pyroelectric sensor 1 to detect infrared rays from an object moving in the direction of the arrow in the figure. In this case, infrared rays are incident on one pyroelectric element 3a when an object passes through detection area A, and infrared rays are incident on the other pyroelectric element 3b when an object passes through detection area B. This causes a difference in the incident time of infrared rays to both pyroelectric elements 3a and 3b.

[Problem to be solved by the invention]

By the way, since the distance between the pyroelectric elements 3a and 3b in the pyroelectric sensor 1 is small, in the above configuration, each pyroelectric element 3a, 3b
The distance between the detection areas A and B corresponding to this also becomes smaller. As a result, when the moving speed of the object is fast, both pyroelectric elements 3a
, 3b, the difference in time for detecting an object becomes smaller and the output signal also becomes smaller, resulting in a problem that false alarms and missed alarms are more likely to occur. On the other hand, as shown in FIG. 6, in front of the pyroelectric sensor 1 is a pair of lenses 2a spaced apart in the arrangement direction of the pyroelectric elements 3a and 3b.
, 2b are also considered. In this configuration, as the object moves, each pyroelectric element 3a of the pyroelectric sensor 1,
3b, infrared rays are incident on each of them twice, making it possible to reliably detect the movement of an object. However, since the difference in the timing of incidence of infrared rays on both pyroelectric elements 3a and 3b is the same as in the configuration shown in FIG. 5, the performance is not improved in the moving direction of the object. The present invention aims to solve the above problems,
The object of the present invention is to provide an infrared passive direction determination sensor that detects the moving direction of an object without causing false alarms or missed alarms by increasing the difference in the time of incidence of infrared rays on each pyroelectric element. .

[Means to solve the problem]

In order to achieve the above object, the present invention includes a pair of pyroelectric elements connected in anti-series, a pair of lenses corresponding to each pyroelectric element, and a pair of pyroelectric elements between both pyroelectric elements. A light shielding plate is provided which is disposed perpendicular to the array plane and prevents infrared rays passing through each lens from entering other than the corresponding pyroelectric element. Further, instead of the lens, a slit plate having a pair of slits corresponding to each pyroelectric element may be provided.

[Effect]

According to the above configuration, by placing a light shielding plate between each pyroelectric element, it is possible to make a large difference in the time of incidence of infrared rays on each pyroelectric element, regardless of the distance between the two pyroelectric elements. Even if the object is moving at a high speed, the output level of both pyroelectric elements can be increased, and the presence and direction of the moving object can be reliably detected.

[Example 1] As shown in FIG. 1, a pair of pyroelectric elements 3a and 3b are packaged in one package 4 to form a pyroelectric sensor 1. Both pyroelectric elements 3a and 3b are reversed. are connected in series,
When an object moves from one pyroelectric element 3a toward the other pyroelectric element 3b in the arrangement direction of both pyroelectric elements 3a and 3b, a large output is generated on the negative side as shown in FIG. 4(a). If the object moves in the opposite direction, the fourth
As shown in Figure (b), a large output can be obtained on the positive side. Therefore, as shown in FIG. 3, by comparing the output of the pyroelectric sensor 1 with the positive and negative thresholds T, , T- set in the comparator 5, the moving direction of the object can be determined. In front of the pyroelectric sensor 1, as shown in FIG. 1, a pair of lenses 2a and 2b are provided which are spaced apart in the arrangement direction of the pyroelectric elements 3a and 3b. They are arranged so that the distance between them is variable. Further, a light shielding plate 6 is disposed between the pyroelectric elements 3a and 3b so as to be perpendicular to the arrangement plane of the pyroelectric elements 3a and 3b. This light shielding plate 6 is provided so that the infrared rays passing through both lenses 2a and 2b are independently incident on each pyroelectric element 3a and 3b, respectively. That is, each lens 2a. The infrared rays that have passed through 2b pass through the corresponding pyroelectric blocker 3.
It is incident only on a and 3b and not on the other. Therefore, the detection area A corresponding to each pyroelectric element 3a, 3b, depending on the distance of the lenses 2a, 2brffI,
Since the distance between the detection areas A and B can be adjusted, the distance between the detection areas A and B can be set larger than before. In other words, the time difference between the timings at which infrared rays are incident on each pyroelectric element 3a and 3b can be made larger than in the past, and the output signal level of the pyroelectric sensor 1 increases, which reduces the occurrence of false alarms and missed alarms. It becomes less. The area width W in each of the detection areas A and B is set to be approximately equal to the width of the object to be detected. In addition, the distance between the front lenses 2a and 2b is set according to the speed of the object to be detected6.Normally, both detection areas A and B
The distance between them is set to several times the area width W.

Embodiment 2 In this embodiment, a slit plate 8 in which a pair of slits 7a and 7b are formed is used in place of the lenses 2a and 2b. Generally, the slit plate 8 on which the slits 7a and 7b are formed is cheaper than the lenses 2a and 2b, so the cost of this embodiment can be lower than that of the first embodiment. Furthermore, by adjusting the distance between the slits 7a and 7b, the distance between the detection areas A and B can be adjusted.Furthermore, by adjusting the width of the slits 7a and 7b, the area width W of the detection areas A and B (J adjustment Since the operation is the same as in Example 1,
The explanation will be omitted. [Effects of the Invention] As described above, the present invention includes a pair of pyroelectric elements connected in anti-series, a pair of lenses corresponding to each pyroelectric element, and a pair of pyroelectric elements connected between both pyroelectric elements. A light shielding plate is provided perpendicularly to the array plane of the lens to prevent infrared rays passing through each lens from entering other than the corresponding pyroelectric element, and a light shielding plate is provided in the darkness of each pyroelectric element. By doing this, it is possible to make a large difference in the time at which infrared rays are incident on both pyroelectric elements, so even if the object is moving at a high speed, the output level of both pyroelectric elements can be made large, and the presence of a moving object can be This has the advantage that it is possible to reliably detect both the direction of movement and the direction of movement. In addition, the same effect can be obtained by providing a slit plate with a pair of slits corresponding to each pyroelectric element instead of the lens, and the cost can be lower than when using lenses. It is.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing a first embodiment of the present invention, FIG. 2 is a schematic configuration diagram showing a second embodiment of the present invention, and FIG. 3 is a usage example of the infrared passive direction determination sensor according to the present invention. The block diagram shown in FIG. 4 is an explanatory diagram of the operation of the pyroelectric sensor used in the above,
FIG. 5 is a schematic configuration diagram showing a conventional example, and FIG. 6 is a schematic configuration diagram showing another conventional example. 1... Pyroelectric sensor, 2a, 2b... Lens, 3a,
3b... Pyroelectric element, 6... Light shielding plate, 7a, 7b...
- Slit, 8...Slit plate, A, B...Detection area. Figure 3 Agent Patent Attorney Ishi 1) Head 7 Figure 4 7a, 7b...Slit 8...Slit O feet A, B...Detection area 1st 2nd leap

Claims (2)

[Claims] (1) A pair of pyroelectric elements connected in anti-series, a pair of lenses corresponding to each pyroelectric element, and a pair of lenses arranged between both pyroelectric elements perpendicular to the arrangement plane of both pyroelectric elements. An infrared passive direction determination sensor comprising: a light shielding plate that prevents infrared rays passing through each lens from entering other than a corresponding pyroelectric element. (2) A pair of pyroelectric elements connected in anti-series, a slit plate with a pair of slits corresponding to each pyroelectric element, and a slit plate arranged between both pyroelectric elements perpendicular to the array plane of both pyroelectric elements. 1. An infrared passive direction determination sensor comprising: a light shielding plate which is arranged as a slit and prohibits infrared rays passing through each slit from entering other than a corresponding pyroelectric element.