JPS6177780A - Object detector - Google Patents

Abstract

PURPOSE:To prevent malfunctioning with a simple construction, by setting the modulation frequency of light signal so that the phase difference between a reference wave light receiving output and the detection wave light receiving output is within 90 deg.. CONSTITUTION:The oscillation frequency of an oscillation circuit 10 of a projection means 1 is adjusted according to the setting of the detection area so that the phase difference between the reflected light from an object X to be detected and a reference light from the reference reflection surface Y will be within 90 deg. at the longest detectable distance. This eliminates the need for using the area where the phase difference causing the malfunctioning is above 90 deg. thereby permitting a simple construction. It combines a phase difference detection output by a phase difference detection means 4 for the reference light receiving output and the detection wave light receiving output, an integration means 5 for integrating the output, a discrimination means 6 for determining whether an object exists or not in a specified distance area based on the level of the integration results and prevents a malfunctioning to detect the existence of an object satisfactorily.

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 whether the optical signal is within a detection area based on the phase delay of the reflected light from an object to be detected. The present invention relates to an object detection device that outputs an object detection signal by determining whether or not the object is detected.

[Background Art J] Conventionally, this type of object detection device, as shown in the fjSL diagram, includes a light projecting means 1 for projecting a steam light signal modulated with a suitable circumference tr&, and a reference light path P1 provided with A reference wave light receiving means 2 and a detection wave light receiving hand 1 provided in the detected optical path P2.
23, both light receiving means 2.2.3, a phase difference detecting means 4 for detecting the phase difference between the outputs of the light receiving means 2.3, an integrating means 5 for integrating the output of the phase difference detecting means 4, and determining whether the output level of the integrating means 5 is at a predetermined level. and a determining means 6 for detecting whether or not the object to be measured X exists within the detection area. The light projecting means 1 includes an oscillation circuit 10, a driver circuit 11, and an LED.
The oscillation circuit 1 is formed with a light emitting cord 12 consisting of
The optical signal modulated by blinking the light emitting element 12 at a frequency of 0 is transmitted to the reference optical path P and the detected optical path P.
It is designed to project light onto 2. The reference wave photodetector Vi2 includes a light receiving element 20 made up of seven otodiodes that receives the light passing through the reference optical path P, that is, the light reflected by the base wall reflector Y, and an amplifier circuit that amplifies the output of the light receiving element 20 at high frequency. 21, a frequency conversion circuit 22 that converts the output of the amplifier circuit 21 into an intermediate frequency signal, and an amplifier circuit 23 that amplifies the intermediate frequency signal.
A light-receiving element 30 consisting of seven otodiodes that receives the light that has passed through 2, that is, the light reflected by the object to be detected It is formed of a frequency conversion circuit 32 that performs frequency conversion and an amplifier circuit 33 that amplifies an intermediate frequency signal, and a local oscillation circuit 40 that generates a local oscillation frequency for obtaining an intermediate frequency signal is connected to both light receiving means 2.3. It is shared by Further, the determining means 6 is formed of a shield circuit.

The operation will be explained below using FIGS. 3 to 6. Now, as shown in FIG. 3, when the distance between the detected object X and the object detection device A is d, and the distance ad between the reference reflector Y and the object detection device A can be ignored, the light receiving means 2,
:(The phase difference of the output of φ(.

) is φ=(2d/λ)X 360 and input=3X10'/f, so φ12d/
(3x 10'/r.) IX 360=(2d-fo
/3X, 10'')X360.If the modulation frequency of the optical signal [. It should be noted that the frequency conversion circuit 22.32 of the light receiving means 2.3 converts the high frequency signal output from the light receiving element 20.30 into an intermediate frequency signal. It goes without saying that the phase difference φ is preserved, and this phase difference φ is detected by the phase difference detection means 4, integrated by the integration means 5, and determined by the discrimination means 6.
The level is determined at , and an object detection signal is output when the level does not reach a preset threshold level, that is, when the 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 of the integrating means 5 with respect to the distance d is as shown in FIG. Means 5 output ■ 5 is directly proportional to the distance (and furthermore, the distance #
As ld increases, the output corresponding to a phase difference φ of 90°■
, is now obtained. Therefore, in the case where the threshold level vth of the discriminating means 6 is set to be thicker than the output V of the integrating means 5 corresponding to l [φ is 90°, it becomes impossible to distinguish between the 0 point and the β point. There was a problem that malfunctions occurred.1 For example, if the maximum detectable distance is set to Q as shown in Figure 6, even if you want to detect the object X that is closer than point Q,
There is a problem in that the detected object X that is further away than the point is also detected. Therefore, it has been considered to identify the α and β points by utilizing the fact that the detection wave level received by the light receiving element 30 of the light receiving means 3 decreases in inverse proportion to the distance d. There is a problem in that a soil level detection means, a gate means, etc. are required, making the configuration complicated.

[Object of the Invention J The present invention has been made in view of the above points, and its object is to provide an object detection device that has a simple configuration and does not malfunction.

Disclosure of the Invention 1 (Example) Figure PIIl1 shows an example of the present invention, and the object detection is similar to the conventional example! At position A, the phase difference φ between the light reflected by the detected object X at the longest detectable distance Q and the reference wave is 9.
The modulation frequency r0 of the optical signal is set to be within 0°, and the oscillation frequency of the oscillation circuit 10 of the light projecting means 1 is adjusted when setting the detection area.

Now, in the present invention, since the modulation frequency r0 of the optical signal is set so that the phase difference φ is always within 90 degrees, level detection means and gate means for detecting the detection limit level are provided. Therefore, it is possible to reliably detect the object X to be detected. In other words, the detection area is set so as not to use an area where the phase difference φ is 90° or more, which may cause malfunction (modulation frequency is set to 10).
By doing so, it is possible to obtain an object detection device A that has a simple configuration and is free from malfunctions.

[Effects of the Invention] As described above, the present invention provides variable 51! a reference wave light receiving means provided in the reference optical path, a detection plate light receiving means provided in the detected path, and a phase difference detecting the phase difference between the outputs of both light receiving means. It consists of a detecting means, an integrating means for integrating the output of the phase difference detecting means, and a determining means for determining whether the output level of the integrating means is at a predetermined level and detecting whether the object to be measured exists within the detection area. In an object detection device, the phase difference between the light reflected by the detected object at the longest detectable distance and the reference wave is 90
Since the frequency of the optical signal is set so that the detection limit level is within This has the effect of providing an object detection device that can detect objects, has simple V# configuration, and is free from malfunctions.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the operation of one embodiment of the present invention, FIG. 2 is a block circuit diagram of a conventional example, and FIGS. 3 to 6 are explanatory diagrams of the same operation. 1 is a light projecting means, 2 is a reference wave receiving means, 3 is a detection plate light receiving means, 4 is a phase difference detecting means, 5 is an integrating means, and 6 is a discriminating 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 a determination as to whether or not the output level of the integration means is at a predetermined level to determine whether or not the object to be measured exists within the detection area. In an object detection device comprising a discrimination means for detection, the modulation frequency of the optical signal is set so that the phase difference between the light reflected by the object to be detected at the longest detectable distance and the reference wave is within 90 degrees. Object detection device.