JPS63309880A - Obstacle detecting system - Google Patents

Abstract

PURPOSE:To execute the position detection even if plural pieces of obstacles exist, by emitting modulated beams whose frequencies are different from each other, from plural light emitting elements, and detecting reflected beams reflected due to a fact that those modulated beams have irradiated the obstacle, with each light receiving element. CONSTITUTION:Modulated beams whose frequencies are different from each other, which is emitted from plural light emitting elements 12 irradiate an obstacle 14 and reflected, and the reflected beams are photodetected by plural light receiving elements 13 provided in accordance with the elements 12. An output of the element 13 detects only a specific modulation frequency by a frequency filter 16 through a current - voltage converting circuit 15. Subsequent ly, it is supplied to a display device 17, and from each detected frequency signal, a position of the obstacle 14 is displayed. Accordingly, even if plural pieces of obstacles 14 exist, its position can be detected, and also, since the modulated beams are used, this system is not influenced by an electromagnetic noise, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an obstacle detection system particularly suitable for detecting obstacles behind a motor vehicle.

[Conventional technology]

2. Description of the Related Art When detecting an obstacle behind a car or the like, a detection system as shown in FIG. 3, for example, is known. This is done by embedding a conductor 3 as a sensor in the rear bumper 2 of the car 1, and detecting the change in capacitance (C) that occurs between the conductor 3 and the obstacle 4 by converting it into a change in voltage value. The presence or absence of the obstacle 4 is then detected from the detected value.

Figure 4 is its equivalent circuit diagram, where the resistor (R) is connected to the power supply 5.
The voltage (V) appearing at the output terminal 6 through the sensor varies depending on the above-mentioned capacitance (C), and by detecting this voltage (V), the presence of the obstacle 4 can be known.

[Problem that the invention seeks to solve]

However, in the above-mentioned obstacle detection system, the capacitance (C) between the conductor 3, which is a sensor, and the reacted obstacle 4 is simply detected, so it is difficult to detect the presence of multiple obstacles. However, since it is a conductive sensor, it is susceptible to electromagnetic noise.

This invention was made with attention to such problems, and an object of the present invention is to provide an obstacle detection system that can detect a plurality of obstacles and their positions and is not affected by noise. The purpose is

[Means for solving problems]

The obstacle detection system of the present invention includes a frequency modulation circuit that causes a plurality of light emitting elements to emit modulated light of different frequencies, and a plurality of frequency modulation circuits that receive reflected light when the modulated light from each light emitting element hits an obstacle and is reflected. It is equipped with a light-receiving element, and the position of an obstacle is detected from the output of each light-receiving element.

[Effect]

In the obstacle detection system of the present invention, modulated light having different frequencies is emitted from a plurality of light emitting elements, and when these modulated lights hit an obstacle, the reflected light is detected by each light receiving element. Then, the frequency of the modulated light hitting the obstacle is detected from the output of each light receiving element, and the position of the obstacle is thereby detected.

〔Example〕

FIG. 1 is a block diagram showing a schematic configuration of an obstacle detection system according to the present invention. In the figure, 11 is a frequency modulation circuit that causes a plurality of light emitting elements 12 such as light emitting diodes to emit modulated light of different frequencies, and 13 is a light receiving element such as a plurality of photodiodes provided corresponding to each light emitting element 12. Each of the modulated lights hits the obstacle 14 and is reflected, and the reflected light is received. 15 is an IV conversion circuit that converts the output of the light receiving element 13, that is, the current (1) to voltage (V) of the photoelectrically converted electric signal; ) is a frequency filter that detects only the signal of the modulation frequency, and these are provided corresponding to each light receiving element 13. 17 is a display device that displays the position of the obstacle 14 from each detected frequency signal.

The detection system having the above configuration is suitable for application to an automobile, for example, as shown in FIG.

12b, -12,x and light receiving elements 13a, 13b.

. . . = 13 A sensing structure is provided in which a plurality of pairs of modules x are installed, that is, a plurality of pairs of light receiving and emitting modules each consisting of a light emitting section having a different modulation frequency and a light receiving section that detects only the modulation frequency. If there is an obstacle 14, the modulated light emitted from the light emitting section is diffusely reflected on the surface of the obstacle 14 and returns to each light receiving element 13. At this time, the returned reflected light reaches each light receiving section, but since it is frequency modulated, the position of the light receiving element 13 that can detect the frequency becomes the position of the rear obstacle 14, and its position is displayed on the display. It can be done at 17. At this time, as described above, the current of each light receiving element 13 is converted into voltage and detected, and the display device 1
7 to provide information to the driver.

In this way, obstacles behind the car can be reliably detected, and even if there are multiple obstacles, the position (distance) can be detected using modulated light. Therefore, it is not affected by electromagnetic noise, etc. Additionally, since there are no moving parts, it has a long lifespan, is highly reliable, and has fast detection speed.

〔Effect of the invention〕

As explained above, according to the present invention, modulated light with different frequencies is reflected from a plurality of light emitting elements, and the reflected light that is reflected when the modulated light hits an obstacle is detected by each light receiving element. Therefore, even if a plurality of obstacles exist, their positions (distance S) can be detected, and the effect of not being affected by noise can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing a schematic configuration of an obstacle detection system according to the present invention, Fig. 2 is a block diagram showing an example in which the system shown in Fig. 1 is applied to an automobile, and Fig. 3 is a block diagram showing a conventional example. , FIG. 4 is an equivalent circuit diagram of the circuit configuration of FIG. 3. 11 Frequency modulation circuit 12 Light emitting element 13 Light receiving element 14 Obstacle Applicant Stanley Electric Co., Ltd. Figure 4

Claims (1)

[Claims] A frequency modulation circuit that causes a plurality of light emitting elements to each emit modulated light of a different frequency, and a plurality of light receiving elements that receive reflected light when the modulated light from each light emitting element hits an obstacle and is reflected. An obstacle detection system characterized by detecting the position of an obstacle from the output of.