JPS6177781A - Object detector - Google Patents

Abstract

PURPOSE:To enable the detection of a long-range object to the detection limit, by judging that the detection light receiving output is below the limit level to control the gate through which an object detection signal passes. CONSTITUTION:The reflected light from an object X to be detected corresponding to the light projected from a projection means 1 is received by a detection light receiving means 3 and the phase difference corresponding to the distance from a reference passive reflector Y between the light receiving and reference wave light receiving output with a reference wave light receiving means 2 is detected by a phase difference detection means 4 and outputted via a discrimination means 6 for a detection output 5 with the object X existing in a specified distance range and a gate 8 and the like. A level discrimination means 7 determines whether the output of the means 3 is below the detection limit level or not and the gate 8 is closed by the discrimination output of the means 7 when it is below to shut down the detection output from a means 6. Thus, the detection of a long-range object to the detection limit is accomplished accurately.

Description

[Detailed Description of the Invention] [Technical Field] The present invention transmits an optical signal modulated at an appropriate frequency from a light projecting means, and detects when the detected object is within the detection area based on the phase delay of the reflection from the detected object. Object detection that determines whether or not the object is present and outputs an object detection signal! &It is related to placement.

[Background Art] Conventionally, this type of object detection device has the following features, as shown in FIG.
A light projecting means 1 for projecting an optical signal modulated at an appropriate frequency; a reference wave receiving means 2 provided in a reference optical path P;
A detection wave light receiving means 3 provided on the detected optical path P2 and a phase difference detecting means 4 for detecting the phase difference between the outputs of both light receiving means 2 and 3.
, an integrating means 5 that integrates the output of the phase difference detecting means 4, and a determining means 6 that determines whether the output level of the integrating means 5 is at a predetermined level and detects whether the object to be measured X exists within the detection area. It is made up of. The light projecting means 1 is formed by an oscillation circuit 10, a driver circuit 11, and a light emitting element 12 made of an LED. The detected optical signal is projected onto a reference optical path P and a detected optical path P2. The reference wave light-receiving means 2 includes a light-receiving element 20 composed of seven photodiodes that receives the light passing through the reference optical path P1, that is, the light reflected by the reference reflector Y, and an amplifier circuit 21 that amplifies the output of the light-receiving element 20 at high frequency. , amplifier circuit 2
It is formed by a frequency conversion circuit 22 that converts one output into an intermediate frequency signal, and an amplifier circuit 23 that amplifies the intermediate frequency signal,
The detected wave light-receiving means 3 includes a light-receiving element 30 composed of seven otodiodes that receives the light passing through the detected optical path P2, that is, the light reflected by the detected object X, and an amplifier circuit 31 that amplifies the output of the light-receiving element 30 at high frequency. , a frequency conversion circuit 32 that converts the output of the amplifier circuit 31 into an intermediate frequency signal, and an amplifier circuit 33 that amplifies the intermediate frequency signal, and a local oscillation circuit that generates a local oscillation frequency for obtaining the intermediate frequency signal. The circuit 40 is shared by both light receiving means 2.3. Also,
The determining means 6 is formed by a threshold circuit.

The operation will be explained below using FIGS. 3 to 6. Now, as shown in FIG. 3, the distance between the detected object X and the object detection device A is d, and the distance sid between the reference reflector Y and the object detection signal 8 can be illuminated.
．． The phase difference φ(.

) is φ=(2d/λ)X 360 and input=3X10'/f0, so φ= +2
d/(3X 10”/f.)lx 360=(2d
-f, /3X10'') d can be calculated.In addition, the light receiving means 2.3
In the frequency conversion circuit 22.32, the light receiving element 20.3
Although the high frequency signal output from 0 is converted into an intermediate frequency signal, it goes without saying that the phase difference φ between the reference wave and the detected wave is preserved. This phase difference φ is detected by the phase difference detecting means 4, integrated by the integrating means 5, and its level is determined by the determining means 6. When it becomes below a preset threshold level, that is, when it approaches An object detection signal is output when an incoming detected object X enters the detection area.

By the way, in the conventional example in which the level of the output of the phase difference detection means 4 is determined through the integration means 5,
The output V of the integrating means 5 with respect to the distance d is as shown in FIG. 7, and as the distance d increases, the detection limit Q, (
After passing the value determined by the modulation frequency f0 of the optical signal, the output of the integrating means 5 is no longer directly proportional to the distance, and as the distance tad increases further, an output V corresponding to a phase difference of 90° is obtained. It has become. In this case, the range to the right of the 00 point is a noise range, and the output ■ of the integrating means 5 in this range is related to the distance d (does not include 1 m. Therefore, the threshold level Vth of the discriminating means 6 is the phase difference φ When the output of the integrating means 5 corresponding to 90° is set to be larger than 5, there is an inconvenience that it becomes impossible to distinguish between a and β, resulting in malfunction.0 For example,
When the maximum detectable distance is set to Q as shown in Figure 7, even though we want to detect object X that is closer than point Q, object X that is farther away than point Q is also detected. There was this inconvenience. Therefore, the detection area was set within the range where the phase difference φ does not exceed 90°, but when the phase difference φ is 90' or more, the detection limit Q0 is reached (the output V of the integrating means 5 is at the distance d). (range directly proportional to)
There is a problem in that the output of the phase difference detection means 4 is not effectively used, making it impossible to detect objects over long distances.

E. OBJECT OF THE INVENTION The present invention has been made in view of the above points, and its purpose is to provide an object detection device capable of detecting an object over a long distance up to the detection limit.

[Disclosure of the Invention 1 (Embodiment) Fig. 1 shows an embodiment of the present invention, in which in an object detection device A similar to the conventional example, the output of the detection wave receiving means 3 becomes below the detection limit level. and gate means 8 for preventing an object detection signal from being output when the output cuff of the level discriminating means is obtained.The level discriminating means 7 is a signal level detecting circuit. 7a and a threshold circuit 7b, gate hand y, 8 is formed by discriminating means 6 and level discriminating means #51.7.
It is formed by an AND circuit to which the output of is input.

In the embodiment, the level detection is performed before the amplifier circuit 33 of the light receiving means 3, but it may be performed after the amplifier circuit 33 of the light receiving means 3.

Now, in the present invention, the level determination means 7 determines whether the signal level (inversely proportional to the distance d) of the intermediate frequency signal output from the frequency r&conversion circuit 32 of the light receiving means 3 is below a predetermined detection limit level. When the detection limit level is lower than the detection limit level, that is, when the detected object become.

This prevents the object detection signal from being output even if the gate means 8 is closed and the discrimination means 6 outputs the object detection signal. Therefore, as shown in FIG. 2, the maximum detectable distance Q is equal to the detection limit Q when the thread 7 threshold level Vth of the discriminating means 6 is lower than the maximum detectable distance Q as shown in FIG. Even if the limb detection object X is in the noise range (Q, to the right of the point) even if
) is prevented, and the detection limit is reduced to Q. This results in an object detection device 17A capable of detecting objects over long distances.

[Effect of the Invention 1] As described above, the present invention includes a light projecting means for transmitting an optical signal modulated at an appropriate frequency, a reference wave receiving means provided in the reference optical path, and a detection device provided in the detected optical path. a phase difference detection means for detecting a phase difference between the outputs of both light reception means; an integration means for integrating the output of the phase difference detection means; In an object detection device, the object detecting device includes a discriminating means for discriminating whether the detected wave is detected and outputting an object detection signal. Since the gate means is provided to prevent the output of an object detection signal when the object detection signal is ,
It is possible to prevent malfunctions due to the output of the integrating means when the liquid sensing object force is within the range of noise, and to obtain an object detecting device capable of detecting an object over a long distance up to the detection limit.

[Brief explanation of drawings]

Fig. 1 is a block circuit diagram of an embodiment of the present invention, Fig. 2 is an explanatory diagram of the same operation as above, Fig. 3 is a block circuit diagram of a conventional example,
Figure fB4 to Figure tj117 are explanatory diagrams of the same operation. 1 is a light projecting means, 2 is a reference wave receiving means, 3 is a detection wave receiving means, 4 is a phase difference detecting means, 5 is an integrating means, 6 is a discriminating means, 7 is a level discriminating means, and 8 is a gate means.

Claims (1)

[Claims] (1) A light projecting means for transmitting an optical signal modulated at an appropriate frequency, a reference wave receiving means provided on the reference optical path, a detected wave receiving means provided on the detected optical path, and an output of both light receiving means. A phase difference detection means for detecting a phase difference, an integration means for integrating the output of the phase difference detection means, and an output of an object detection signal by determining whether or not a detected object exists within the detection area based on the output of the integration means. In an object detection device, the object detection device includes a level discrimination means for discriminating when the output of the detected wave receiving means has become below a detection limit level, and a level discriminating means for discriminating that the output of the detected wave light receiving means has become below the detection limit level, and a level discriminating means for disabling the output of an object detection signal when the output of the level discriminating means is obtained. An object detection device characterized in that it is provided with a gate means for detecting an object.