JPS62245932A - Photodetector - Google Patents

Abstract

PURPOSE:To accurately detect the passage of a body to be measured by arranging a light collection cylinder whose internal surface is formed into a reflecting surface in front of a photodetecting element. CONSTITUTION:The light collecting cylinder 12 is arranged in front of the detection surface of the photodetecting element 10 which detects light beams such as an infrared ray. A filter 14 where only an infrared ray is passed when light to be measured is the infrared ray is provided on the front end surface of the light collecting cylinder 12. The entire surface 2 or specific pattern surface of the internal surface of the light collection cylinder 12 is formed into the light reflecting surface. This pattern varies depending upon the internal diameter and effective length of the light collecting cylinder 12. Further, the pattern of the intensity of the light is converted by the element 10 into the pattern of the level of a current, which is amplified by a proper amplifier and led out. When the body moves across in front of the light collecting cylinder 12, the light beams emitted by the body enter the light collection cylinder 12 and are recognized as a specific pattern by the element 10.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a photodetection device, and preferably to an infrared detection device.

(Prior art) Temperature needles, etc. that measure temperature by detecting infrared rays,
Infrared rays emitted from the object to be measured are focused by a lens and an aperture onto an infrared detection element to form a spot of about 1 mraφ.

In addition, when determining the average value of infrared rays emitted from a wide area, or in devices that detect the intrusion of a person into a detection space, there are devices that condense the light using a multi-mirror, Fresnel lens, or the like.

However, optical systems such as lenses, multi-mirrors, and Fresnel lenses require complicated devices. Therefore, the optical system tends to shift slightly due to vibrations, temperature changes, etc., and there are many problems such as the need to readjust the focal position.

The present invention provides a device that can replace the conventional photodetection device described above, and its purpose is to provide a device that is equipped with a simple cylindrical body that focuses light in a predetermined pattern, and that detects the pattern by detecting the pattern. An object of the present invention is to provide a photodetection device that can confirm the passage of an object.

(Summary of the invention) The present invention includes the following configuration to achieve the above object.

That is, a photodetecting device having a photodetecting element is characterized in that a condensing tube whose inner surface is formed as a reflective surface is disposed in front of the photodetecting element.

Further, in a photodetecting device having a photodetecting element, a condensing tube whose inner surface is formed as a reflective surface is disposed in front of the photodetecting element, and the inner surface of the condensing tube just in front of the photodetecting element reflects a predetermined amount of light. It is characterized by being formed on a light-shielding surface that absorbs reflected light more than the number of times.

Furthermore, the photodetecting device having a photodetecting element is characterized in that a light collecting tube whose inner surface is divided into a light shielding surface and a reflecting surface in the circumferential direction is disposed in front of the photodetecting element.

(effect) Next, we will discuss the effects.

In the present invention, the inner surface of the condenser w112 is formed as a reflective surface.

Therefore, the destinations that pass through the light collecting tube 12 and reach the photodetecting element are the light that directly enters the light detecting element and the inner surface of the light collecting tube.
The reflected light is reflected once, twice, three times, and so on.

Reflected light that is repeatedly reflected more than a predetermined number of times is so weak that it is no longer detected by the photodetecting element.

Therefore, the condenser tube 12 provides a constant viewing angle to the photodetector.

Furthermore, since the detection surface of the photodetecting element has a certain area, the non-reflected light and each reflected light overlap to form a pattern of light intensity. The pattern is determined by the aperture and effective length of the condenser tube 12.

Therefore, when an object enters the viewing angle, the photodetection element recognizes the pattern and detects the intrusion of the object.

Furthermore, if a light shielding surface is provided that absorbs reflected light a predetermined number of times or more, noise will be cut and detection accuracy will be improved.

If the inner surface of the condenser tube is divided into a light shielding surface and a reflecting surface in the circumferential direction,
The light measurement space can be further subdivided within a predetermined viewing angle.

(Embodiments) Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The device of the present invention includes a photodetecting element 10 that detects light such as infrared rays.
A condenser tube 12 is disposed in the front direction of the detection surface (FIG. 1).

If the light to be measured is infrared rays, a filter 14 is provided on the front end surface of condensing tube 2, which passes only infrared rays. The filter 14 is also provided for the purpose of preventing dust and the like from entering the light collecting tube 12.

The inner surface of the condenser tube 12 has a light reflecting surface formed on the entire surface or a predetermined pattern surface to be described later.

FIG. 2 shows the reflection path of light when it enters the condenser tube 12. FIG.

In the figure, among the light that reaches the detection part (pointed for convenience) of the photodetector 10, the light that enters the condenser tube 12 within an angle of O (0') with respect to the optical axis reaches the detection part. Light enters without reflection.

Similarly, among the light reaching the detection part, with respect to the optical axis,
Light entering the condenser tube 12 at an inclination angle between the inclination angle of the straight line 0 and the inclination angle of the straight line 1 is reflected once on the inner surface of the light condenser tube 2, and then enters the detection section.

Similarly, light at an angle of inclination between straight lines 1 and 2 is reflected twice, and light at an angle of inclination between straight lines 2 and 3 is reflected three times and enters the detection section.

The same applies to the case of four or more reflections, and the inclination angle gradually increases. Therefore, by repeating reflection, light from all directions in front of the condenser tube 12 can theoretically reach the detection section. However, due to reflectance, light that is reflected many times is absorbed halfway through the process.

As is clear from the figure, the reflection position immediately before the light enters the detection part of photodetector element 0 is the range L for the one reflection, the range M for the one reflected twice, and the range M for the one reflected three times. The range is N. Therefore, if the N range of the inner surface of the condenser tube 12 is shielded from light, the three-times reflected light will be absorbed and will not enter, and only the non-reflected, once-reflected, and twice-reflected light will enter the detection section. It turns out.

Figure 3 is a drawing in which the incident light path is further broken down by the number of reflections, where (a> is one reflection, (b) is two reflections, and (c)
indicates a ray of light that is reflected three times.

For reference, the calculation of each ray angle is as follows.

<0AC=jan-'DO/AD <0BC= <to18C= tan-'Do/^口/3<BIBC= <A2AC= Lan-'DO/
To 8D1<B20C-tarl-'DO/^D/7th 4th
In the figure, the inner diameter of the condenser tube 12 is 20+++m, and the effective length is 100m.
The beam pattern is drawn on the plane xY, which is 500 mm away from the objective side of the condenser tube 12, where m is the beam pattern.

For convenience, the size of the photodetector was ignored, and only the optical path converging at the center point O of the photodetector was assumed. Furthermore, since the diameter of the condenser tube 12 is sufficiently small compared to the distance to the x-y plane, the objective side window of the condenser tube 12 is also considered as one point.

The area surrounded by Fl is the non-reflective area and is the brightest. F
The donut-shaped area surrounded by 1 and F2 is the one-time reflection area, and the area surrounded by F2 and 13 is the two-time reflection area, which gradually becomes darker.

In the above explanation, the size of the photodetecting element has been ignored, but since an actual photodetecting element has an area of 1 to 21IllIlφ, the beam pattern with an element diameter of 21I1mφ will have a non-reflective area as shown in Figure 5. There are formed areas where the and one-time reflection areas overlap, the one-time reflection areas and the two-time reflection areas, and the two-time reflection areas and the three-time reflection areas.

In other words, if we consider that the element surface moves forward and backward by a distance of a/lan O (a/element radius), the angular deviation △θ of the ray AP in Fig. 3 becomes O △θ-tar1-'□ .

AD± □ tanθ Therefore, beam patterns that overlap by the above angle are generated.

Therefore, a ring-shaped pattern of light intensity is generated in the detection section of the actual photodetection element. This pattern varies depending on the inner diameter (aperture) and effective length of the condenser tube 12. Further, this light intensity pattern becomes a current intensity pattern by the photodetector, and can be amplified and extracted by an appropriate amplifier (not shown).

Therefore, when an object crosses in front of the condenser tube 12, light (infrared rays, etc.) emitted from the object enters the condenser tube 12, and is recognized by the photodetector element 10 as a predetermined pattern.

Further, the pattern is always constant regardless of the distance between the object and the condenser tube 12.

6 to 14 show the condenser tube 12 (outer diameter 9.5 mm,
Inner diameter 8.5mm, brass layer) length 15ROM, 20
1.40mm.

Set to 60nu11, attach it to an infrared detector, detect infrared rays emitted from a pedestrian moving in front of the infrared detector, amplify the signal from the detector with an amplifier, and create a synchroscope with memory. This is a graph obtained by observing the voltage amplitude. 1m and 2.5m from the detector
The amplitude was observed when it passed through two locations.

Note that a dual type pyroelectric infrared sensor was used as the infrared detection element.

It is clear from the above graph that by attaching the condenser tube 12, the amplitude increases and the detection accuracy improves. Note that the detection range became narrower when the light collecting tube 12 became fuller.

By the way, the region of the reflective surface formed on the inner surface of the light collecting tube 12 may be the entire surface of the light collecting tube 12. Even in this case, as mentioned above, the reflected light more than a predetermined number of times becomes extremely weak due to the reflectance and is not detected by the photodetector 10, so that it is substantially within a certain viewing angle range in front of the condenser tube 12. This means that only objects that are detected are detected. In other words, an object that falls within the viewing angle can be detected.

In addition, in order to prevent noise, the condenser tube 1 immediately in front of the photodetector element 10
2. The inner surface is light-shielded and, as described above, the reflected light that is reflected more than a predetermined number of times is cut when h>A. In order to block infrared rays, an infrared absorbing paint may be applied to the inner surface of the condenser tube 12.

Further, the inner surface of the condenser tube 12 may be divided into a reflective surface and a light shielding surface in the circumferential direction.

This makes it possible to further divide the light detection range within a predetermined viewing angle in front of the condenser tube 12.

Further, the inner surface on the front end side of the condenser tube 12 may be shielded from light over a certain length. This allows you to simply narrow down the viewing angle.

Note that the cross-sectional shape of the condenser tube 12 is not limited to a circular shape, but may be formed into a polygonal shape.

The reflective surface may be a metal mirror surface, or a mirror may be attached thereto.

By detecting infrared rays emitted from humans, the present invention can be widely applied to various home security systems, visitor alarms, automatic doors, automatic lighting lights, human detection devices in robot robot arm rotation, etc.

(Effects of the Invention) As described above, according to the light detection device according to the present invention, since light can be focused in a strong and weak pattern using a simple light collecting tube, passage of the object to be measured can be detected with high accuracy.

Furthermore, by forming a light-shielding surface that cuts reflected light more than a predetermined number of times, noise generation can be suppressed and pattern recognition can be performed more accurately.

Furthermore, by dividing the inner surface of the condenser cylinder into a light shielding surface and a reflecting surface in the circumferential direction, the detection space can be narrowed down arbitrarily.
Light can be focused (detected) only in the necessary areas, allowing for more detailed responses depending on the installation location, etc.

Although the present invention has been variously explained above with reference to preferred embodiments, the present invention is not limited to these embodiments, and it goes without saying that many modifications can be made without departing from the spirit of the invention. That's true.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of the apparatus of the present invention. Figure 2 is an explanatory diagram showing the path of the light that entered the condenser tube. Figure 3 is an exploded view of the reflected light. (a) is reflected once, (b) is reflected twice.
(C) shows three reflections. FIG. 4 is a principle diagram of a beam pattern condensed by a condenser tube, and FIG. 5 is an explanatory diagram showing the overlapping of beam patterns. Figures 6 to 14 are synchroscope diagrams of the amplitude of each voltage for an infrared detector, when a condenser tube is not used, and when a condenser tube is used and the length of the condenser tube is changed. be. 10... Photodetection element, 12... Condenser tube, 14...
· ·filter.

Claims (1)

[Scope of Claims] 1. A photodetecting device having a photodetecting element, characterized in that a condensing tube whose inner surface is formed as a reflective surface is disposed in front of the photodetecting element. 2. The photodetecting device according to claim 1, wherein the inner surface on the front end side of the condenser tube is formed as a light-shielding surface. 3. In a photodetecting device having a photodetecting element, a condensing tube whose inner surface is formed as a reflective surface is disposed in front of the photodetecting element,
A photodetection device characterized in that an inner surface of the condenser tube immediately in front of the photodetection element is formed as a light-shielding surface that absorbs reflected light a predetermined number of times or more. 4. A photodetecting device having a photodetecting element, characterized in that a condensing tube whose inner surface is divided into a light shielding surface and a reflecting surface in the circumferential direction is disposed on the front side of the photodetecting element. Detection device.