JPS59183388A - Optical object detector - Google Patents

Abstract

PURPOSE:To enhance detection resolving power and to exclude the influence of extraneous light by clearing a detection point, by such simple constitution that a light emitting drive current is controlled corresponding to the detection state in a light receiving point. CONSTITUTION:A current flows the LEDLD of the light emitting part and the photo-transistor P of the light receiving part of an optical type matter detector 10 connected to a constant-current circuit 14 in common in a mutually differential manner and, when a part of the light from LEDLD is blocked by matter and the current flowing the transistor P is reduced, a light emitting drive current flowing LEDLD increases and voltage V0 detected by the transistor P is not abruptly changed. On the other hand, when light emitted from LEDLD is further blocked by matter, the brightness of LEDLD is saturated and the voltage V0 detected by the transistor P abruptly becomes large to clear a detection point. By this mechanism, the detection point is cleared by simple constitution, detection resolving power becomes high, the influence of extraneous light is excluded and the enhancement in the accuracy and reliability of an optical type object detector can be achieved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an optical object detector used, for example, for positioning a movable part.

[Background technology]

2. Description of the Related Art Optical object detectors, particularly optical object detectors in which a light emitting part and a light receiving part are optically opposed, are widely used for, for example, determining the stop position of a handling device. 1 and 2 show an example of this type of optical object detector.

In the detector 10 shown in the figure, a light emitting part LD and a light receiving part P are arranged in a pair of legs of a U-shaped casing in a state where they are optically opposed to each other.

When the detected object 12 is located in the optical path between the light emitting part LD and the light receiving part 2, the light (arrow) from the light emitting part LD is blocked and the amount of light received by the light receiving part P decreases. This appears as a change in the photodetection output of section P. Therefore,
A power supply V is applied to the light receiving section P via a suitable load resistor R1. 0, the object detection output V is output from the connection end with the resistor R3.
. can be obtained. The light emitting section LD is connected to the power source (-) through the current limiting resistor R2. By supplying a constant drive current from 0, it emits light with a constant brightness.

However, in the object detector described above, as shown in FIG. 3, the relationship between the light shielding rate by the detected object 12 and the detection output (■o) is the detection output (■). However, the detected object 1
According to the light shielding rate by 2, the curve changes smoothly in a nearly linear manner.

For this reason, the detection point becomes very vague, which has been a major obstacle in increasing the detection resolution. This also limits the accuracy of positioning, for example. Furthermore, since this object detector is an optical type, it is susceptible to the effects of extraneous light, which, along with the ambiguity of the detection point mentioned above, is a major factor that impedes the accuracy and reliability of its detection. was.

[Purpose of the invention]

This invention was made in view of the above problems.
The aim is to make it possible to clarify the detection point, increase detection resolution, and significantly improve the accuracy and reliability of external light detection by simply adding a relatively simple additional configuration. An object of the present invention is to provide an optical object detector.

The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

[Summary of the invention]

A brief overview of typical inventions disclosed in this application is as follows.

That is, in an optical object detector in which a light emitting part and a light receiving part are optically opposed to each other and an object intervening in the optical path between the two is detected by a change in the light detection output of the light receiving part, By increasing or decreasing the drive current according to the light detection state of the light receiving section, by adding a relatively simple additional configuration, the detection point can be clarified and the detection resolution can be increased, and the detection resolution can be improved. This achieves the objective of significantly increasing the accuracy and reliability of detection.

〔Example〕

Hereinafter, typical embodiments of the present invention will be described with reference to the drawings.

In addition, the same or corresponding parts are indicated by the same reference numerals in the drawings.

The optical object detector according to the embodiment of the present invention has the same structure as described above in terms of its appearance. That is, as shown with reference to FIG. 1, the light emitting part LD and the light receiving part P are disposed in a pair of legs of the U-shaped casing in a state where they are optically opposed to each other. The object to be detected 1 is placed in the optical path between the light emitting part LD and the light receiving part P.
2, its detection output is obtained as a change in the light detection state of the light receiving section P.

Here, in the optical object detector according to the embodiment of the present invention, as shown in FIG.
The drive current I2 flowing to the light emitting portion LD and the light emitting portion LD are distributed from a common constant current source. The constant current source is the power supply V.

0 and the constant current circuit 14. Light emitting part LD
A light emitting diode is used and is connected between the power source cc and the constant current circuit 140. The light receiving section P uses a phototransistor and is connected to a power supply V through a load resistor R. 0 and the constant current source 14. And the detection output v
0 is taken out from both ends of the light receiving section P.

As a result, the currents I, , I, flowing through the light receiving section P and the light emitting section LD, respectively, have a total current value L+I, which is a constant current I controlled by the constant current circuit 14. limited to. As a result, the currents I, , I2 have a differential relationship and change complementary to each other. That is, the drive current I of the light emitting section LD.

increases or decreases with changes in the photodetection output of the light receiving section P.

Now, in the optical object detector configured as above,
First, when the object to be detected 12 approaches a detection position that blocks the light entering the light receiving part P from the light emitting part LD, the amount of light received by the light receiving part P also partially decreases due to the partial light blocking state.

As a result, the current I flowing through the light receiving part P also decreases, but
When this current I2 decreases, the light emitting portion L
The drive current (2) of D increases. As a result, the light emitting part LD
The brightness of the light receiving section P increases to compensate for the decrease in the amount of light received by the light receiving section P. As a result, at the partial light shielding stage, the above detection output ■. changes will be kept small. However, when the object to be detected 12 comes to a detection position that blocks most of the light from the light receiving section P, the brightness of the light emitting section LD is saturated, and as a result, the light detection output of the light receiving section P becomes larger than before. It starts to change. As a result, as the detected object 12 approaches the detection position, the light shielding rate and the detection output (2) increase. As shown in FIG. 5, the relationship changes little at first, but suddenly changes midway through. This makes the detection point clear and allows the detection resolution to be significantly increased.

Furthermore, even if the amount of light received by the light receiving section P is changed by external light, the drive current It of the light emitting section LD changes, and the brightness of the light emitting section LD changes so as to reduce the change in the amount of light received. Therefore, the detection output V.

This also has the effect of reducing the influence of external light that appears on the screen.

[effect]

As described above, in the optical object detector according to the present invention,
By simply adding a relatively simple additional configuration, it is possible to clarify the detection point, increase the detection resolution, and make it less susceptible to the effects of extraneous light, thereby improving the accuracy and reliability of detection. can be improved.

Although the invention made by the present inventor has been specifically explained above based on examples, it goes without saying that this invention is not limited to the above-mentioned examples, and can be modified in various ways without departing from the gist thereof. Nor. For example, the light receiving section may be a photodiode.

[Application field]

In the above explanation, the invention made by the present inventor was mainly explained with respect to a positioning detector, which is the field of application behind the invention, but it is not limited thereto.
For example, it can be applied to a detector used for counting articles or for intrusion alarm.

[Brief explanation of drawings]

FIG. 1 is a side view showing an example of the appearance of an optical object detector according to the present invention. FIG. 2 is a circuit diagram showing an example of an optical object detector other than the present invention. FIG. 3 is a graph showing its operating characteristics. FIG. 4 is a circuit diagram showing an embodiment of the optical object detector according to the present invention. FIG. 5 is a graph showing an example of its operating characteristics. 10... Optical object detector, 12... Object to be detected,
LD... Light emitting part (light emitting diode), P... Light receiving part (phototransistor), ■Cc... Power supply, ■1...
・Operating current of the light receiving part, ■,...Detection current of the light emitting part, R
7...Load resistance, R7...Current limiting resistance, ■.・・・
・Detection output, 14...constant current circuit, ■o...constant current. 527 Figure 1 Figure 2 '17cc Figure 3 Figure 5/' Shio/Temple /ρθㅅ・ 4

Claims (1)

[Scope of Claims] 1. An optical object detector in which a light-emitting part and a light-receiving part are optically opposed to each other, and an object interposed in the optical path between the two is detected by a change in the light detection output of the light-receiving part. . An optical object detector, characterized in that the driving current of the light emitting section is increased or decreased depending on the light detection state of the light receiving section. 2. In the detector according to claim 1, a phototransistor is used in the light receiving section, and an operating current flowing through the phototransistor and a driving current flowing through the light emitting section are changed in a complementary manner. Features of optical object detector. 3. In the detector according to claim 1 or 2, a phototransistor is used in the light receiving section, and currents flowing through the phototransistor and the light emitting section are distributed from a common constant current source. An optical object detector featuring: