JPS6298225A - Optical device for heat ray type detector - Google Patents

Abstract

PURPOSE:To eliminate a dead zone and to obtain high reliability by providing the two condensing means which makes the detecting area one and has a different focus on the optical system and by arranging the position of both means at the same position. CONSTITUTION:The condensing means 1a, 1b which are composed of a Fresnel lens or convex lens are arranged coaxially. The focus of the condensing means 1b of the outer periphery is then taken as the optical detecting face by focusing the image in the out-of-focus shape on the photodetecting surface by locating the focus of the condensing means 1a of small diameter at the center part at the front side from the photodetecting surface of a two element type pyroelectric heat ray detecting element 2. Consequently the detecting area near the detector is enlarged as X, the delay in the detecting time of each element can be made larger and the detecting output is obtd. because of even in case of a man body M passing through the detecting area with quick steps the simultaneous input being not caused.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an optical device for a heat ray detector that detects heat rays generated from a human body or the like.

[Background technology] Unlike infrared (near-infrared) detectors, heat-ray detectors are passive detectors; for example, if we consider a long-range molded detector, infrared detectors are This can be achieved by placing photodetectors on both sides, but when using hot-wire detector A, in order to detect long distances, the detection area must be narrowed down as shown in Figure 8 (,). As shown in (b), if the detection area expands at far tm, even if the human body M enters the detection area, the temperature change will be averaged over the entire detection area and the temperature change will be small, making it difficult to detect the temperature change. The problem is that it is no longer possible to do so.

Therefore, an optical system is generally constructed to narrow down the detection area using a parabolic mirror or a 7-lens lens, but in reality, due to the characteristics of the optical system, there may be some blurring at long distances. This creates a detection area that is larger than theoretically possible, making it possible to secure a sufficient area to detect a human body. However, in the area near heat-ray detector A, the blur is small and the optical system (parabolic mirror or 7 Lens lens)
In many cases, the opening area of the sensor is equal to the detection area, resulting in a problem that the detection area becomes extremely narrow. Also, if the number of divisions in the optical system is increased as shown in Figure ll59,
There is a problem in that the opening area of each detection area B becomes increasingly narrow.

By the way, a pyroelectric heat ray detection element is often used as the detection element of the heat ray detector A, and especially for human body detection, it does not output a detection signal in response to simultaneous inputs (high frequencies are applied to the element). It is common to use a two-element type (or four-element type) that does not output a signal even if a sudden temperature change occurs or disturbance light enters.

Here, the two-element type pyroelectric heat ray detection element is the first one.
As shown in Figure 0, a and b are juxtaposed and the first
As shown in Figure 1, the polarities are reversed so that the outputs of elements a and b cancel each other out against simultaneous input.

Since the detection areas of these two elements) a and b are shifted, when the human body M moves in the direction of the arrow as shown in Figure 10, the output of each element) a and b is as shown in Figure 12 (
The waveform will be as shown in a).

And the combined output of these two elements) a and b is tIrJ
The waveform becomes as shown in FIG. 12(b).

As can be seen from this waveform, as the difference L between the detection times of elements a and b becomes smaller, the cancellation component becomes larger and the output signal becomes smaller.

Then, when t=0, simultaneous inputs occur.

Therefore, as mentioned above, the detection area is narrow near the detector A, and when the human body M passes there (especially when passing at a fast pace), almost simultaneous inputs occur and no detection output is obtained from the heat ray detection element. , it can be seen that it becomes undetectable.

Currently, the heat-ray detector A that is generally available on the market does not have any measures against the rapid passage of a human body M at close range, and therefore has a dead zone, making it unreliable when used for crime prevention. It has become less sexual. The detection area near hot-wire detector A is narrow not only in long-distance types but also in short-distance types (wide-angle type, all-around type), and is a fatal flaw in a detector with only one division. It's watery.

[Object of the Invention] The present invention has been made in view of the above-mentioned problems, and its purpose is to provide an optical device for a hot-ray detector that can ensure sufficient detection sensitivity near the detector within the detection area. is to provide.

[Disclosure of the invention 1 The present invention will be explained below with reference to Examples.

This embodiment corresponds to the first invention, and as shown in FIG. 1, condensing means 1a and 1b each consisting of a 7-lens lens or a convex lens are arranged concentrically, and as shown in FIG. As the small-diameter condensing means 1a of the section, for example, a 2-element type pyroelectric heat ray detecting element 2 with a pyroelectric heat ray detection element 2 whose pyroelectric heat ray detection element 2 is located in front of the light receiving surface is used as the small diameter focusing means 1a, and a blurred image is focused on the light receiving surface. , the light-receiving surface is the light-receiving surface of the condensing means 1b around the Tato.

As a result, the image formed on the light receiving surface by the condensing means 1a becomes blurred, and the detection area near the detector is expanded as shown by X, and the difference in detection time of each element can be increased. Even if the human body M passes through X quickly, simultaneous input will not occur and a detection output will be obtained.

(K) This embodiment corresponds to the first invention like the first embodiment, and as shown in FIG. The pyroelectric heat ray detection element 2 is arranged in front and behind the axis so that the respective foci and α are exactly located on the light receiving surface of the 2-element type pyroelectric heat ray detection element 2. The detection area is expanded as shown by X, and the same effects as in the first embodiment are obtained.

This embodiment corresponds to the f52 invention in which the detection area is divided into a long-range area X1, a medium-range area X2, and a short-range area X3 as shown in FIG. Concentrating means 1 b, 1 consisting of a 7-lens lens or a convex lens corresponding to area X1 and medium distance area X2, respectively.
The focal length of the light collecting means 1a consisting of a 7-lens lens or a convex lens corresponding to the short-distance area The focal length is set so that the focal length and α are shifted backward from the light receiving surface of the pyroelectric heat ray detection element 2,
This is to make the short distance area X3 wider.

Therefore, the image formed on the light-receiving surface by the condensing means 1a becomes blurred, and even if the human body M passes quickly through the short-distance area X, simultaneous input will not occur and a detection output will be obtained.

[Actual] [Example] L In this example, as shown in Fig. 6, a plurality of condensing means 1 each consisting of a 7-lens lens are pasted together all around the body, and the detection area is divided by each condensing means 1. As shown in FIG. The image is focused on the light-receiving surface of the pyroelectric heat ray detection probe 2 provided on the surface, and the focal length of the condensing means 1b is set so that the focal point is exactly on the light-receiving surface. By utilizing the reflections 113a and 3b, it is possible to lengthen the focal and direct distances of the condensing means 1b, thereby extending the detection area to a far distance.

On the other hand, the light condensing means 1a″Ch corresponding to the short distance area
The concentrated heat rays are reflected by reflecting mirrors 3a and 3b inside the vessel body 4.
Instead of being reflected by the pyroelectric heat ray detection element 2, the image is directly focused on the light receiving surface of the pyroelectric heat ray detection element 2, thereby eliminating attenuation due to reflection and increasing sensitivity. Then, the focal point of the condensing means 1a is removed from the light-receiving surface of the pyroelectric heat ray detection element 2, and the short-distance operation is performed.

, and the same effects as in Example 3 are obtained.

[Effect of the invention 1 In the first invention, the detection area is one, two light condensing means with different focal points are provided in the optical system, and the positions of both light condensing means are set to the same position, or In the second invention, the detection area is divided into a short distance area and a long distance area, and the focal point of the focusing means of the optical system in the short distance area is set to a pyroelectric type. Since the light receiving surface of the heat ray detection element is shifted from the light receiving surface of the heat ray detection element, and the focal point of the light condensing means of the long-distance area optical system is set to the light receiving surface of the pyroelectric heat ray detection element, it is possible to detect heat rays of the same detection area type or the split Erica type. In a type detector, it is possible to expand the short distance area and prevent simultaneous human input to the pyroelectric heat ray detection element, and as a result, temperature changes can be reliably detected even if a human body passes quickly near the detector. This makes it possible to eliminate the so-called dead zone, resulting in the effect that high reliability can be obtained even when used for crime prevention.

[Brief explanation of drawings]

FIG. 1 is a front view of the optical system of Example 1 corresponding to the first invention, FIG. 2 is a schematic diagram for explaining the same operation (1η diagram), and FIG. 3 is an explanation of the operation of Example 1 corresponding to the first invention. FIG. 4 is a side view of Embodiment 3 corresponding to the second invention, FIG. 5 is a schematic diagram of the same operation 1 as above, and FIG. 6 is Embodiment 4 corresponding to the second invention. Figure 7 is a sectional view of the main parts of the same as above.
8 and 9 are explanatory diagrams of a conventional example, and FIGS. 10, 11, and 12 are explanatory diagrams of the operation of a two-element type pyroelectric heat ray detection element, 1a, 11]... is a light collecting means,
2 is a pyroelectric heat ray detection element. Agent Patent Attorney Ishi 1) Ai 7 Figure 3 Figure 4 Figure 5 ^3 Figure 6 Figure 10 Figure 11 Figure 12

Claims (2)

[Claims] (1) In a heat-ray detector using a pyroelectric heat-ray detection element having multiple elements, the detection area is one,
Two light condensing means having different focal points are provided in the optical system, and the positions of both light condensing means are set at the same position, or the respective focal points are set at positions that match the light receiving surface of the pyroelectric heat ray detection element. The optical device of the hot wire type detector is characterized by: (2) In a heat-ray detector using a pyroelectric heat-ray detection element having multiple elements, the detection area is divided into short-range and long-range areas, and the focal point of the condensing means of the optical system in the short-range area is focused. The optics of a heat-ray type detector is characterized in that the light-receiving surface of the pyroelectric heat-ray detection element is shifted from the light-receiving surface of the electric-type heat-ray detection element, and the focal point of the light condensing means of the optical system for a long distance area is set to the light-receiving surface of the pyroelectric type heat-ray detection element. Device.