JPS589083A - Optical detection for object - Google Patents

Abstract

PURPOSE:To detect accurately whether an object exists on an optical path or not, by irradiating the light from a light projector to a retroreflection plate obliquely through a half mirror and receiving this reflected light through the half mirror by a photodetector provided in the orthogonal direction. CONSTITUTION:The light emitted and driven from a light projector 7 of a single light detecting device A passes a light transmitting hole 12 through a half mirror 9 and is irradiated to a retroreflection plate B obliquely. The reflected light from the retroreflection plate B is returned to the half mirror 9 through the same optical path and is received by a photodetector 8 provided in the orthogonal direction. When an object C to be detected exists on the optical path, the quantity of received light of the photodetector 8 is reduced considerably, and its existence is detected. Since the light is irradiated to the object C obliquely also, the reflected light from the object C does not go in the same direction as the projected light, and thus, its existence is detected accurately.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for detecting the presence or absence of an object by combining a retroreflector and a photodetector.

Conventional cases of detecting the presence or absence of an object using light as a medium 1. One method uses light to irradiate the object to be detected and uses the reflection of the light, and another method uses the object to be detected to block the light. is common. In order to detect objects using the reflection of this light, we have a structure in which the emitter and receiver are placed side by side on the same side, and the optical path from the emitter to the receiver is created via a reflective surface. In reality, reflective optical sensors are widely used, but the amount of reflected light from an object to be detected varies depending on the surface condition and color of the object. is widespread. Therefore, it is difficult to obtain a constant amount of reflected light. Therefore, when the reflected light is received by a receiver and the output is converted into a digital signal to detect the presence or absence of an object to be detected, there may be limitations depending on the level of the amount of reflected light of the object to be detected, and therefore the signal processing This is a major drawback. Moreover, it may cause malfunctions such as failure to detect the object to be detected. In addition, reflective type optical sensors cannot detect objects that do not reflect light. On the other hand, in conventional fast-acting optical sensors that utilize the interception of light, a floodlight (light-emitting element) is used as shown in Figure 1.
2 and a light receiver (light-receiving element) 3 are placed facing each other at a fixed interval and housed in the same housing, and the presence or absence of an object to be detected on the optical path is detected by checking whether or not light reaches the light receiver. However, as shown in FIG. 1, this combination has a structure in which the projector 2 and the receiver 3 are connected at regular intervals by supports, so for example, the slits 5.
When assuming the detection of the presence or absence of the slit, the position of the slit cannot be larger than the distance l between the optical axis of the optical sensor and the support 1 from the outer periphery of the disk. However, it is clear that the force ζ implementation, which theoretically poses no problem if the distance l is increased, is at a major disadvantage. Although this is just an example, a major disadvantage of fast-acting optical sensors is that they are restricted by the mounting location and the size of the object to be detected. Furthermore, when detecting the presence or absence of an object using a cut-off type optical sensor, both sides of the object to be detected are always optically involved. This has the drawback that the optical sensor cannot be mounted on only one side of the object to be detected.

The present invention eliminates the drawbacks of both reflective and blocking optical sensors, and provides a method for detecting objects that relies on the detection of objects, which simultaneously combines the functions of both.

For this purpose, the present invention provides a photodetecting device (hereinafter referred to as a single optical path photodetecting device) having an optical system in which the optical paths of light emitting and receiving light can follow the same path, a retroreflector, and its projection. The object is detected by combining the detection and light reception method.

The present invention will be explained below with reference to the drawings. FIG. 2 is a block diagram of the entire apparatus used in the method of detecting an object using light according to the present invention. That is, it consists of one single photodetector A and a retroreflector B that is in the form of a piece. First, set the retroreflector B at a predetermined position, and emit a single beam of light from the outer retroreflector B at a distance D as shown in the figure, so that the light is irradiated obliquely to the retroreflector B. Set the detection devices A facing each other. The single photodetector A in the figure shows its cross-sectional view. To explain its structure, as shown in the figure, it consists of a light emitter (light emitting diode) 7, a light receiver (phototransistor) 8, and a half mirror for forming an optical path. - Consists of a (semi-transparent mirror) 9 and a main body 6 that houses them.

The main body 6 has a cubic shape obtained by molding a suitable material, and has circular holes 10, 11, 12, and the like of the same size for light passage as a light path as shown in the figure. are provided through the outside, and in the holes 10 and 11 for light passage on adjacent surfaces, the emitter 7 and the light receiver 8 are provided with circular holes for light passage to, it, respectively.
It is attached in connection with. In this case, the light projector 7 and the light receiver 8 are mounted with their light projecting and light receiving surfaces facing toward the center of the cube.

On the other hand, the half mirror 9 has support portions 13, 14, 13, 14, and 14 provided inside the cubic shape. Fixed. And the half mirror 9 has 4 mirrors for the emitter 7 and the receiver 8.
It is important to maintain the angular relationship of 5°. The main body 6 is not limited to what is shown in the drawings, and it is sufficient that the half mirror is arranged in a 45@ relationship with respect to the light projector 7 and the light receiver 8. It goes without saying that the internal surface of the main body must be appropriately treated to prevent reflection.

Next, the single light detection device A and the retroreflection plate B formed as described above were combined to face each other, and the single light detection device was installed so that light was irradiated obliquely to the retroreflection plate. Regarding the operation in this case, the almost parallel light emitted from the light projector 7 of the single light detection device A is emitted from the half mirror 9.
Almost half of the amount of light passes straight through the light passage hole 12 and is irradiated obliquely onto the retroreflector plate B.

The reflected light from the retroreflector B follows the same optical path as the original optical path in reverse according to the principle of the retroreflector and is lined up at the nouf mirror 9.
Then, approximately half of the amount of reflected light travels in one direction via the -7 mirror 9 and is received by the light receiver 8.

With the combination of the single light detection device A and the retroreflector B as described above, an optically opposing positional relationship is formed between the retroreflector B and the light receiver 8.

When considering only the facing relationship between the retroreflector B and the light receiver 8, the reflected light from the retroreflector B is apparently reflected by the retroreflector B.
acts as a light projector as a light emitting source, and forms a direct optical path toward the opposing light receiver 8 so that the light can reach it. Moreover, each time a constant amount of light is received by the light receiver 8. Moreover, as mentioned earlier, the light from the projector follows the same optical path (strictly speaking) - between the mirror 9 and the retroreflector B) as the one that irradiates the retroreflector. .

Next, the operation of the present invention will be described. Using a single photodetector A having the above-described structure, a recursive temporary projection plate B is set in advance at a distance D from the single photodetector A. A detected object C exists on the optical path where a beam of light is irradiated and the reflected light follows the same optical path as the emitted light in the opposite direction and is received by the single light detection device A again. When passing across the optical path, the object C can be detected depending on whether the light reaches the light receiver 8 or not, depending on the 8N ratio (difference in reflection) of the amount of reflected light between the retroreflector B and the object C to be detected. . However, it is assumed that the detected object C moves in parallel with the retroreflector B, and in this case, the detected object C is irradiated with the same oblique light as the light that is irradiated on the retroreflector B. Needless to say.

In the above case, it is important that the object to be detected is irradiated with light obliquely. For example, if we assume that the gold wave detection object C is planar and has a mirror-like reflective surface larger than the irradiation area, although it depends on the state and aspect of the detection object, the detection object C
The incident light is specularly reflected in the -1 direction with respect to the normal to the plane of the plane, and the reflected light is theoretically stopped at the photodetector A.
No light is received. This is due to the fact that the retroreflector B and the receiver 8 are in an opposing position, and that the light reflected from the retroreflector B is regularly blocked from the optical path that is always received by the receiver 8. Therefore, the presence or absence of the object C to be detected before and after that determines whether or not the light reaches the light receiver 8, so that it can be reliably detected. Therefore, if the light is irradiated perpendicularly to the object to be detected, instead of diagonally, the single light detection device will function as a reflective photosensor, and the reflected light from the object will not be received and will be blocked. This results in a loss of effectiveness. As already mentioned, this leads to drawbacks as a reflective optical sensor. In addition, when the light is irradiated carefully, even when the object to be detected has a flat surface like a blank sheet of paper with an uneven diffusive reflection surface or a flat surface with some unevenness, as will be described in the example below. Compared to the constant amount of reflected light from the retroreflector, the amount of reflected light from these objects to be detected shows a very small value, that is, a large value of 8N ratio is obtained, and a very good rapid-cutting effect of light can be obtained. It was done. Needless to say here, in conventional reflective optical sensors, the reflected light from the retroreflector is generally difficult to receive, or theoretically not received at all. Next, Examples will be described. 7 Example 1 A coin (10 yen) was used as the retroreflector B and the object to be detected.

100 yen coin), the irradiation angle of the light from the single photodetector A is 30°, and the detection distance is 5 mm. The ratio was approximately 10:1.21. Also, under the same conditions as above, the ratio of the amount of light reflected from the retroreflector to the amount of light reflected from the matte black paper is approximately 1.
A value of 0:1.08 was obtained. 8N compared to the former 8:
1, the latter was 9.2:1. In the case of a coin, which is the object to be detected in this example, the surface has irregular patterns on the front and back, and ephemeral and diffusely reflected light appears, but compared to matte black paper, the amount of reflected light is close to O. , results were obtained with no significant difference in the value of the amount of reflected light.

Example 2 Under the same conditions as in Example 1, a standard white (KodehkN
The ratio of the amount of light reflected from the retroreflector to the amount of light reflected from Kodak's standard white paper was approximately 10:1.3, and the 8N ratio was 7:1. This standard white paper made by Kodak is close to a completely diffusing surface.Therefore, it is possible to create a condition in which the reflected light from the object enters the single light detection device more easily than from other objects to be detected. It is something.

Example 1.2 shows the effect of obtaining a very large S/N ratio between the amount of light reflected from a specular reflection surface, a diffused surface, and a surface with uneven surfaces and the amount of light reflected from a retroreflector. Therefore, when converting the output signal into a digital signal, it tends to be easy and reliable9, and therefore the object can be detected reliably.

) Also, because of this configuration, there is no restriction on the location or size of the object to be detected during implementation.

As explained above, in the present invention, the light is obliquely irradiated onto a retroreflector plate installed opposite to the photodetector using a photodetector whose light paths for emitting and receiving light can pass along the same path. The presence or absence of an object is detected using a configuration in which the reflected light retraces its original path and is received by a photodetector. This has the effect of preventing the dependence of the amount of reflected light on the strength and weakness of the reflected light, and that it can be mounted freely without being restricted by the location or the size of the object to be detected, which is a drawback of conventional cut-off type optical sensors.

Since the present invention has the above-mentioned effects, it can be applied to, for example, telephones that function by detecting coins, various vending machines, coin sorting machines, counter machines for various objects, position detection systems, computer human output systems, etc. If so, we can expect great effects.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an example of a cut-off type optical sensor according to the prior art, and FIG. 2 is a configuration diagram and a sectional view of a part of the device, showing an embodiment according to the present invention. Mu10. Cross section of photodetector, 13. ,, retroreflector C
10, Detected object

Claims (1)

[Claims] The light from the projector is irradiated through the half mirror, and the reflected light retraces its original path and returns to the half mirror, and then is received by the receiver installed at right angles through the half mirror. Detection of an object using light, which is characterized in that the light detecting device is characterized in that the projector illuminates a retroreflector plate obliquely and detects the presence or absence of an object on the optical path. Method.