JPS60253992A - Range measuring device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Technical field of invention] The present invention relates to an optical distance measuring device.

[Prior art]

The first method of measuring distance by emitting light is the same method as radar, as shown in Figure 1, in which a short pulsed light beam is emitted from a light source 1 such as a laser, light emitting diode, or arc tube. By measuring the round trip time t from the time the light is emitted to when the light is reflected by the target object 2 and detected by the light receiver 3, the distance R can be determined by the formula R = evil. Here, C is the speed of light, which is about 300,000]i4/19.

The second method is to modulate the intensity of the light and emit it continuously, as shown in Figure 2. There is a method to detect phase difference. That is, if the phase difference between the reference point a of the emission waveform A and the point corresponding to the reference point of the reception waveform B is θ, and the wavelength λ and θ, then the distance R to the object can be calculated using the formula 7202. I can't stand it. However, if the object or the light emitting source is moving, a troubling effect will appear and the wavelength 2 will change, so correction is required. Additionally, relative speed can be detected by detecting the Doppler frequency, making it convenient as a distance meter for automobiles.

A third method involves triangulation. As shown in Fig. 3, this method is based on the fact that when an image of an object is formed on a detector 4 installed at a distance from the light emitting source 1, the image at the position hit by the light beam deviates from the center line. Kara 2 R=L
" f is the distance from the V-lens 5 of the detector 4 to the imaging plane.

However, in the distance measuring device described above, the first method emits the pulse as a single pulse, so it is easy to produce a relatively large output, but it is susceptible to various kinds of noise, which can cause errors. In addition, in the case of continuous wave modulation of light as in the second method, it is sufficient to use a laser to modulate at several MHz to several MHz, but especially for automobiles, the operating temperature must be high and Doppler correction is complicated. become. In addition, phase difference detection is essentially a time measurement similar to radar, so a high-speed processing device is required, and errors become large at short distances. Furthermore, triangulation using the third method is relatively simple, but in the case of a single pulse, it is still susceptible to noise and easily causes errors. For this reason, several pulses are emitted in succession to confirm that this pulse is indeed an image of the emitted light beam, but it is often impossible to measure if it is disturbed by noise. .

By the way, automobile distance meters often measure distances of several ROMs. For example, there is a need for a device that can instantly measure the distance between vehicles and the distance to an obstacle in front, issue a warning to the driver, or apply the brakes without making any mistakes.

The cause of the error is that the signal is weak and the S/N ratio with respect to noise is small, which often causes detection errors. Of course,
Although it is possible to increase the intensity of the emitted light, suitable light emitting sources are often difficult to use for automobiles because they are expensive and have a short lifespan.

[Summary of the invention]

This invention was made with the aim of improving this drawback, and since the light emission intensity from the light emitting source is modulated with a high frequency and the light is emitted as a pulsed light beam, even a relatively weak light emitting source can improve the S/N ratio. It is an object of the present invention to provide a distance measuring device which is improved and free from errors caused by noise.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings.

The same reference numerals as in FIG. 3 indicate the same parts. When the pulse beam emitted in the third method explained above is modulated with a high frequency of about 100 KH2O.

A pulse waveform as shown in FIG. 5 is emitted. As shown in FIG. 4, this pulse is generated by an oscillator 6 to generate a sine wave of about 100 KHz, which is inputted to a power amplifier 8 through a pulse gate circuit 7, and the output thereof is inputted to a light emitter 1 to cause it to emit light. As the light emitter 1, a light emitting element such as an LED is used.

In order to form this light into a beam, a parabolic reflecting mirror 9 may be used, or a V lens (not shown) may be used.

A light emission pulse with a width of several m5ec illuminates a part of the object 2 and forms an image on the detector 4. The signal of the detector 4 is essentially a modulated pulse of about 100 KI (Z), even if it contains some noise.

In this way, what degrades the S/N ratio is generally pulse-like random noise or a certain level of bank ground signal, but by modulating the signal with a high frequency, the output of the detector 4 can peak at about 100KH2. The S/N ratio can be increased by amplifying the signal through a filter 10f having a filter 10f. The filter 10 may be composed of an inductor and a capacitor, or may be a solid filter using a resistor and a capacitor or a surface acoustic wave. By increasing the S/N ratio as described above, it is possible to obtain a distance measuring instrument that can measure long distances without error. The detected signals can be processed in a manner similar to conventional schemes. For example, in the embodiment of the present invention, the imaged position can be detected by using a light receiving element array as a detector. Then, the detected position is read into the computer 12 through the shift register 11, for example, and calculated using a predetermined constant, and the distance is displayed on the display device 13, and the alarm device 14 gives an alarm by voice, buzzer, etc. Of course, the method according to the present invention can also be applied to the first radar type. [Effects of the Invention] As explained above, according to the present invention, the light emission intensity from the light source can be modulated with high frequency. Since the light is emitted as a pulsed light beam, the light emission ratio is improved even with a weak light source.
A highly reliable distance measuring device for automobiles that can use inexpensive and long-life general light emitting elements, can stably measure distances over long distances, and is free from errors due to noise can be obtained.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of a conventional distance measuring method using one type of radar, Fig. 2 is a diagram of emitted light waveforms and received light waveforms of the method using the second method, and Fig. 3 is an explanatory diagram of the method using the third method. Fourth
The figure is a block diagram of a distance measuring device according to the present invention, and FIG. 5 is a pulse waveform diagram. ■... Light source, 2... Target, 4... Detector, 6
...Oscillator, 7...Pulse gate circuit, 8...Power amplifier, 9...Reflection! , 10...filter, 11
Mountain shift V register, 12... computer, 13...
・Display device. 14...Alarm device. In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] In a device that measures the distance between the light source and the object by emitting a light beam such as infrared rays, visible light, or ultraviolet light from a light source and detecting the light beam reflected by an object, the intensity of the light emitted from the light source is measured using a high frequency A distance measuring device characterized in that it emits light as a pulsed light beam modulated by.