JPH077081B2 - Time measuring method and apparatus - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a time measuring method and apparatus capable of measuring time with high resolution.

[Conventional technology]

The distance measuring device using the optical pulse shown in FIG. 3 will be described as an example. The device includes a light emitting unit (for example, an LED) 1 for generating the optical pulse and a photodiode for receiving the optical pulse, for example. The light receiving element 2 is formed. When an optical pulse is transmitted from the LED 1 toward the measuring object 3 and compared with the pulse received by the light receiving element 2, it is t
There is a time difference of only. This is the time required for light to travel back and forth the distance L. Therefore, assuming that the speed of light is c, L = c · t / 2. Therefore, the distance L can be obtained by measuring the time t.

As shown in the timing chart of FIG. 4, the time t is measured by opening the gate from the time of transmission to the time of reception and counting clock pulses for time measurement passing during the time. be able to.
For example, if the frequency of the clock pulse is 100 MHz and the count value is f, then t = f / 100 × 10 ⁶ .

[Problems to be Solved by the Invention]

By the way, the time resolution is determined by the frequency of the clock pulse, and is 100 nanoseconds at 100 MHz. In order to increase the resolution (accuracy) with the same frequency, conventionally, a method has been adopted in which the above measurement is performed n times and the average value thereof is obtained. In this case, the clock pulse and the transmitted signal must be completely asynchronous, and the resolution under this condition is statistically It is known that That is, in order to obtain a resolution of 1/100, it is necessary to perform 10,000 measurements and average them, and to obtain a resolution of 1 / N, N ² measurements must be performed.

[Means for Solving the Problems]

In order to solve the above-mentioned problems, in the present invention, a signal generation unit that generates a signal of a predetermined frequency, a reception unit that receives the signal, and a time measurement from the signal generation time to the reception time of the signal are used. A time measuring method having a counter for counting clock pulses and measuring time from the count value, comprising: a first reference oscillator for generating a first clock pulse of frequency A (Hz); A second reference oscillator for generating a second clock pulse having a high frequency B (Hz), and a signal is generated from the signal generating unit at every A / (BA) th of the second clock pulse. Until the signal is received by the receiving unit, the counter counts the first clock pulse, and the counter counts A / (B-
This is repeated A) times to cause the counter to cumulatively count the first clock pulse.

Further, the time measuring device according to the present invention has a frequency A (Hz).
A first reference oscillator for generating a first clock pulse of the second clock, and a second reference oscillator of a frequency B (Hz) higher than the first clock pulse.
A second reference oscillator for generating a clock pulse;
From the frequency divider that divides the clock pulse into A / (BA), the signal generator that generates a signal at the output of this divider, the receiver that receives the signal, and the signal generator From the time when the signal is generated to the time when the signal is received by the receiving unit.
A gate circuit for passing the clock pulse, a first counter for counting the clock pulse, and a second counter for closing the gate circuit when the number of measurements by opening the gate circuit becomes A / (BA) times. Is equipped with.

[Action]

As described above, the second clock pulse is divided and A / (B-
By transmitting every A) and measuring this A / (BA) times, the resolution becomes 1 / A-1 / B (second).

〔Example〕

Hereinafter, an embodiment of the present invention will be described in detail with reference to FIGS. 1 and 2.

As shown in FIG. 1, the device comprises a first reference oscillator 10 and a second reference oscillator 11. In this embodiment, the first reference oscillator 10 outputs a first frequency of 100 MHz.
A clock pulse is output, while the second reference oscillator 11 outputs a second clock pulse having a frequency of 100.1 MHz. The second clock pulse is divided into 1/1000 by the frequency divider 12, and its output is applied to the LED driver 13 which is the light emitting section, whereby an optical pulse is emitted from the LED 14 every 1000th second clock pulse. Is irradiated.

The light pulse reflected by the measurement object (not shown) is received by the receiving circuit 16 via the light receiving element (for example, photodiode) 15.
To be received. The reception signal output from this reception circuit is input to the reset terminal R of the set / reset flip-flop circuit 17. This flip-flop circuit
The pulse output from the frequency divider 12 is input to the set terminal S of 17.

The output terminal Q of the flip-flop circuit 17 is connected to one input terminal of the first AND gate 18. The first reference oscillator 10 is connected to the other input terminal of the first AND gate 18. The output terminal of the first AND gate 18 is connected to one input terminal of the second AND gate 19, and between the other input terminal and the output terminal Q of the flip-flop circuit 17,
A second counter 20 for counting the measuring circuit is connected.

A first counter 21 for counting the first clock pulse is connected to the output terminal of the second AND gate 19.

Next, the operation of the present invention will be described with reference to the timing chart of FIG. Note that FIG. 1 shows FIG. 2 (a).
Portions where the pulse waveforms of (f) to (f) are generated are shown with the same symbols.

First, the first clock pulse (a) and the second clock pulse (b) rise simultaneously, and the frequency divider 12 outputs the transmission pulse (c). As a result, an optical pulse is emitted from the LED 14, the flip-flop circuit 17 is set, and the output (e) of the output terminal Q thereof becomes "H". Along with this, the output (f) of the second counter 19 also becomes “H”, and the first counter 21 counts the first clock pulse (a).

When the light pulse returned by the light receiving element 15 is detected, the reset terminal R of the flip-flop circuit 17 from the receiving circuit 16 is detected.
A reset signal (d) is output to reset the flip-flop circuit 17, and the output (e) of its output terminal Q becomes "L". As a result, the first AND gate 18 is turned off and the passage of the first clock pulse (a) is blocked. That is, the first counter 21 counts the first clock pulse (a) while the first AND gate 18 is open.
The output (f) of the second counter 20 is held in the “H” state until the number of measurements reaches a predetermined number, for example, 1000 times.

Then, from the frequency divider 12 to 1000 of the second clock pulse (b).
The output (c) corresponding to the output is output, and the first counter 21 counts the first clock pulse (a) in the same manner as described above. This measurement is repeated, and when the second counter 20 counts the number of measurements 1000 times, the output (f) of the counter 20 becomes "L" and the second AND gate 19 is closed.

In this case, the first clock pulse (a) is 100 MHz, the second clock pulse (b) is 100.1 MHz, and the transmission output (c) of the frequency divider 12 is 1/1000 of the second clock pulse (b). The first clock pulse (a) counted while the first AND gate 18 is open is the timing n
9.99 picoseconds (1/10
0.1MHz-1 / 100MHz) faster. Therefore, by measuring this 1000 times, the time can be measured with a resolution of 9.99 picoseconds.

Thus, for example, by using two clock pulses of 100MHz and 100.1MHz, as described above, 100M
Hz, the resolution of one measurement was 10 nanoseconds,
By measuring 1000 times and averaging, 9.99 picoseconds (10
Nanosecond / 1001) resolution will be obtained.

Here, assuming that the first clock pulse is A Hz and the second clock pulse is B Hz (≠ A Hz), both pulses appear at the same timing because the first clock pulse is
A / (BA) occurrence, the second clock pulse is B / (BA)
It is the time of the start. Therefore, the second clock pulse
A / (B-A) The transmission signal is output at every cycle and the measurement is performed A / (B-A) times, resulting in a resolution of (1 / A)-(1 / B) (seconds). Will be obtained.

It should be noted that although this embodiment describes a distance measuring device using an optical pulse, the present invention is not limited to this.

〔The invention's effect〕

As described above, according to the present invention, by using two clock pulses having different frequencies, time measurement can be performed with high resolution in a shorter time.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the time measuring device according to the present invention, FIG. 2 is its timing chart, and FIG.
FIG. 4 is a schematic diagram for explaining a conventional example, and FIG. 4 is a timing chart for explaining the time measuring method. In the figure, 10 and 11 are reference oscillators, 12 is a frequency divider, 14 is an LED, 15 is a light receiving element, 17 is a flip-flop circuit, 18 and 19 are AND gates, and 20 and 21 are counters.

Claims (2)

[Claims] 1. A signal generating section for generating a predetermined pulse signal, a receiving section for receiving the pulse signal, and counting time-measuring clock pulses from the pulse signal generation time to the signal reception time. In a time measuring method having a counter and measuring time from the count value, a first reference oscillator that generates a first clock pulse of frequency A (Hz) and a frequency B (Hz that is higher than the first clock pulse ) A second reference oscillator for generating a second clock pulse, and a signal is generated from the signal generating section for each pulse A / (BA) of the second clock, and the signal is generated by the receiving section. The first clock pulse is counted by the counter until it is received by A / (B-
A) A time measuring method characterized in that the counter is cumulatively counted the first clock pulse by repeating A) times. 2. A first reference oscillator for generating a first clock pulse of frequency A (Hz), and a second reference oscillator for generating a second clock pulse of frequency B (Hz) higher than the first clock pulse. , The second clock pulse is A / (B-
A) a frequency divider for frequency division, a signal generator for generating a signal at the output of the frequency divider, and a receiver for receiving the signal,
A gate circuit that allows the first clock pulse to pass from the time when the signal is generated from the signal generator to the time when the signal is received by the receiver, and a first circuit that counts the clock pulse.
The number of measurements made by opening the counter and the above gate circuit is A /
The second time the gate circuit is closed at the time of (BA) times
A time measuring device comprising: a counter.