JPH06294863A - Distance measuring device - Google Patents

Abstract

PURPOSE:To achieve a high resolution without using a high-frequency clock and to obtain measurement data inexpensively and in real time in a distance measuring instrument for obtaining the distance to an object to be measured according to the turn around time of electromagnetic wave. CONSTITUTION:The electromagnetic wave pulse of a transmitter 2 which is transmitted to an object to be measured and the reflection wave pulse received by a receiver 3 are synthesized by a pulse synthesizing circuit 4, a pulse signal corresponding to the time difference between transmission and reception is generated, and a capacitor is charged by the amount of the pulse signal by a constantcurrent charging circuit 8. Then. the peak voltage of the capacitor is held for a constant amount of time by a peak hold circuit 9 and then the distance from the peak voltage to the object to be measured is calculated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distance measuring device for calculating the distance from a round trip time of electromagnetic waves to an object to be measured in an electromagnetic wave radar or the like.

[0002]

2. Description of the Related Art FIGS. 4 and 5 are views showing a basic measuring principle when measuring a distance to an object to be measured using electromagnetic waves.

As shown in FIG. 4, an electromagnetic wave is radiated (transmitted) to an object to be measured 1 at a distance L and the reflected wave is received. At this time, as shown in FIG. 5, when the time from the transmission of electromagnetic waves to the reception thereof is t, the distance L to the DUT 1 can be expressed by L = C × t / 2. However, C is the speed of light.

Therefore, the distance L to the DUT 1 can be obtained by measuring the time difference (t) between the transmission signal and the reception signal. As a method of measuring this time t, generally, a clock for comparison is input and the clock is counted by a counter only for the time t. Therefore, the resolution of the distance to be measured depends on the frequency of the clock, and for example, when trying to obtain a resolution of 1 m, a frequency of 150 MHz is required.

FIG. 6 is a block diagram showing a schematic configuration of a conventional distance measuring apparatus for obtaining the time difference between signals by counting clocks by a counter as described above. In the figure, 2 is a transmitter for irradiating an electromagnetic wave pulse to an object to be measured, and the output pulse of the transmitter 2 and the output pulse of the receiver 3 which receives the reflected wave pulse are input to a pulse synthesizing circuit 4, where A pulse signal is generated according to the time difference between transmission and reception.

Next, the output of the pulse synthesizing circuit 4 and the clock from the clock generating circuit 5 are compared by the AND gate 6, and the output clock of the AND gate 6 is counted by the counter 7.
Count with. Then, the distance to the object to be measured can be obtained based on the output (count value) of the counter 7.

[0007]

However, in the above-described conventional distance measuring device using electromagnetic waves, the time difference between the transmission and reception of electromagnetic waves is obtained by counting the clocks, so that a resolution of 1 m is obtained. 150 MH to get
z high frequency is required, circuit design and mounting technology are advanced, and parts used are special,
There was a problem that it became expensive.

Although the resolution may be improved by statistical processing, in this case, it is necessary to repeat the measurement 100 times or more in order to obtain 10 times the resolution, and the output interval of the measurement data is significantly long. Therefore, there is a problem that measurement data cannot be obtained in real time.

The present invention has been made by paying attention to the above-mentioned problems, and it is possible to design a circuit by incorporating high frequency technology.
It is an object of the present invention to provide a distance measuring device that does not require structural design, requires no special parts, can be manufactured at low cost, and can obtain measured data in real time.

[0010]

SUMMARY OF THE INVENTION A distance measuring apparatus according to the present invention comprises a transmitter for transmitting an electromagnetic wave pulse to an object to be measured, a receiver for receiving a reflected wave pulse from the object to be measured, and the electromagnetic wave pulse. A pulse circuit that generates a pulse signal according to the time difference between transmission and reception, a constant current charging circuit that charges a capacitor only for the time of the pulse signal, and a peak hold circuit that holds the peak voltage of the output of this constant current charging circuit. And is configured to calculate the distance from the held peak voltage to the object to be measured.

[0011]

In the distance measuring apparatus of the present invention, a pulse signal is generated according to the time difference between the transmission and the reception of the electromagnetic wave pulse, and the capacitor of the constant current charging circuit is charged for the time of the pulse signal. Then, the peak voltage of the output of the constant current charging circuit is held by the peak hold circuit, and the distance from the peak voltage to the object to be measured is calculated.

[0012]

FIG. 1 is a block diagram showing the circuit configuration of an embodiment of the present invention. In the figure, 2 is a transmitter for transmitting a single electromagnetic wave pulse to the DUT, 3 is a receiver for receiving a reflected wave pulse from the DUT, and 4 is a time difference between the transmission and reception of the electromagnetic pulse. In a pulse synthesizing circuit for generating a pulse signal, an outgoing pulse signal S1 of the oscillator 2 and a received pulse signal S2 of the receiver 3 are input and synthesized, and the time t required for the electromagnetic wave to make a round trip with the object to be measured. Only the pulse signal S3 that becomes H (high level) or L (low level) is output.

Reference numeral 8 is a constant current charging circuit that charges the capacitor only for the time of the pulse signal S3, and 9 is a peak hold circuit that holds the peak voltage of the output signal S4 of the constant current charging circuit 8. Voltage output signal S
The distance from 5 to the object to be measured is calculated.

FIG. 2 is a timing chart showing the operation of the above circuit, showing the waveforms of the output signals S1 to S5 of the respective parts of FIG. The method until the pulse synthesizing circuit 4 generates the pulse signal S3 according to the time difference between the transmission and the reception of the electromagnetic wave is the same as that of the circuit of FIG. 6, but here the electromagnetic wave becomes H only for the time t required for the round trip. The pulse signal S3 is output.

The pulse current S3 operates the constant current charging circuit 8 for a predetermined time t to charge the capacitor with a constant current. At this time, the voltage Vc across the capacitor rises in proportion to time t (see S4 in FIG. 2), and Vc = a
It can be expressed as xt. However, with a = (1 / C1) · i,
C1 is the capacity of the capacitor, and i is the charging current.

Since the time t is very short at 667 ns even at a distance of 100 m, the peak value of the voltage Vc across the capacitor is held for a fixed time by the peak hold circuit 9 in the next stage, and the voltage value is held. I try to read it. Then, the distance from the read voltage value to the measured object is calculated.

As described above, it is possible to obtain a sufficient distance resolution without using a high clock frequency, and it is not necessary to introduce a high frequency technology to design a circuit and a structure. In addition, no special parts are required, the device can be manufactured at low cost, and since it is not necessary to increase the resolution by statistical processing using a low clock frequency, measurement data can be obtained in real time.

FIG. 3 shows a concrete example of the circuit shown in FIG. The pulse synthesizing circuit 4 is composed of an OR gate 11 and a flip-flop 12. The OR gate 11 mixes the transmission signal and the reception signal, and the flip-flop 12
Is input to the clock (CLK) terminal. This allows
A signal that becomes H or L for the time t described above is generated.

The constant current charging circuit 8 includes a voltage dividing resistor 13,
14, an operational amplifier 15, a current limiting resistor 16, a transistor 17, an analog switch 18, and the above-described charging capacitor 19. The analog switch 18 connected to both ends of the capacitor 19 charges the capacitor 19 with a constant current only when the inverted output of the flip-flop 12 is L.

The peak hold circuit 9 includes an operational amplifier 20 to which the collector output of the transistor 17 is input, a diode 21 connected to the output side of the operational amplifier 20, a parallel circuit of an analog switch 22 and a capacitor 23, and a capacitor 2.
It is composed of an operational amplifier 24 to which the terminal voltage of 3 is inputted, and holds the peak voltage of the capacitor 19 until time-voltage conversion is performed and the subsequent CPU reads the voltage. Then, after the CPU reads the voltage,
The analog switch 22 discharges the capacitor 23 and resets the flip-flop 12.

[0021]

As described above, according to the present invention, a pulse signal is generated according to a time difference between transmission and reception of an electromagnetic wave pulse, and a constant current charging circuit charges a capacitor only for the time of the pulse signal. Since the peak value of the terminal voltage of this capacitor is held and the distance from the peak value to the DUT is calculated, sufficient distance resolution can be obtained without using a high clock frequency, and high-frequency technology can be used. Since there is no need to incorporate and design circuits and structures, no special parts are required, it can be manufactured at low cost, and there is no need to increase the resolution by statistical processing, there is the effect that measurement data can be obtained in real time.

[Brief description of drawings]

FIG. 1 is a block diagram showing a circuit configuration of an embodiment of the present invention.

FIG. 2 is a timing chart showing the operation of the circuit of FIG.

FIG. 3 is a circuit diagram showing a specific example of the circuit of FIG.

FIG. 4 is an explanatory diagram showing the measurement principle when measuring a distance using electromagnetic waves.

FIG. 5 is an explanatory diagram showing the measurement principle when measuring a distance using electromagnetic waves.

FIG. 6 is a block diagram showing a conventional example.

[Explanation of symbols]

 1 DUT 2 Transmitter 3 Receiver 4 Pulse synthesis circuit 8 Constant current charging circuit 9 Peak hold circuit 19 Capacitor

Claims (1)

[Claims] 1. A transmitter for transmitting an electromagnetic wave pulse to an object to be measured, a receiver for receiving a reflected wave pulse from the object to be measured, and a pulse signal according to a time difference between transmission and reception of the electromagnetic wave pulse. Pulse circuit, a constant current charging circuit that charges the capacitor only for the time of the pulse signal, and a peak hold circuit that holds the peak voltage of the output of this constant current charging circuit, and the measured object from the held peak voltage. Distance measuring device characterized by calculating the distance to.