JP2004325373A - Distance measuring instrument - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To dispense with a large number of counters, and to precisely measure a distance at a low electric power consumption without carrying out complicated processing. <P>SOLUTION: A start signal is transmitted to a counter means 13 when transmitting a measuring signal to a measuring object O, a stop signal is transmitted to the counter means 13 when receiving the measuring signal reflected by the measuring object, leading-up or tailing-down of the nearest clock signal is recognized out of a clock signal generated by a clock signal generating means 1 and clock signals generated by N-number of clock signal delaying means 2, when the stop signal is transmitted, and a count value counted by the counter means from a start signal reception time to a stop signal reception time is corrected to measure the distance up to the measuring object. Measuring precision of N-times is obtained compared with the case where the clock signal generated by the clock signal generating means is counted by the counter means. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a distance measuring device, and in particular, detects a time difference between a time when a pulsed laser beam is irradiated to a measurement target and a time when a laser beam reflected from the measurement target is detected, and detects a time difference between the time and the measurement target. The present invention relates to a distance measuring device for measuring a distance.
[0002]
[Prior art]
There are various techniques for calculating a distance to a measurement target by irradiating the measurement target with a laser beam and measuring a time until the reflected light is received.
[0003]
For example, the distance measuring device described in Patent Document 1 gives a start signal by emitting laser light, gives a stop signal at the time of receiving a reflected laser light from an object, and measures the time between them by, for example, 10 counters. To count. Here, each counter counts according to clock pulses of a plurality of clocks, and these clocks have a certain phase difference, and the sum of the phase differences is set to be substantially equal to the clock cycle T1. For this reason, a deviation occurs in each count value when the stop signal is given, and by averaging each count value, it is possible to obtain a measurement result similar to the resolution of 1/10 of the clock cycle T1. Thus, an inexpensive and high-performance distance measuring device can be provided.
[0004]
In addition, the distance measuring device described in Patent Document 2 irradiates a laser beam from a light emitting element such as a laser diode to enable a wide range and high precision distance measurement without using a high-frequency counter. The reflected light from the light is received by a light-receiving element such as a photodiode, converted into an electric signal, and the time from the emission of the laser light to the reception of the light is measured. A clock pulse is input to the digital counter at the same time that irradiation is detected, and the time from the detection of laser beam irradiation until the first clock pulse enters the digital counter and the digital counter starts counting is integrated. It is measured with an analog circuit using a device.
[0005]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 7-294462
[Patent Document 2]
JP 2001-83250 A
[Problems to be solved by the invention]
However, the distance measuring device described in Patent Document 1 has a problem that a large number of counters are required when the resolution is improved. Further, in the distance measuring device described in Patent Literature 2, the measurement result by the terminal integrator that measures the reception timing of the reflected pulse and the time until the rise of the clock pulse is transmitted to the microcomputer simultaneously with the counting result by the digital counter. There is a problem in that the final distance measurement data is calculated and processed by a computer, which complicates the processing, and that the power consumption increases due to the use of a microcomputer.
[0008]
Therefore, the present invention has been made in view of the problems in the above-described conventional distance measuring apparatus, and does not require a large number of counters, and digitizes acquired data and performs complicated processing by a CPU or the like. An object of the present invention is to provide a distance measuring device that enables high-precision distance measurement with low power without performing the measurement.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the present invention is a distance measuring device, a measuring signal transmitting means for transmitting a measuring signal to a measuring object, and reflected from the measuring object, from the measuring signal transmitting means Measurement signal receiving means for receiving the emitted measurement signal, and a time required from transmission of the measurement signal by the measurement signal transmission means to reception of the measurement signal by the measurement signal reception means, to the measurement object. Distance calculating means for calculating a distance, the distance calculating means generating a clock signal, and a clock signal generated by the clock signal generating means having a signal having a plurality of different delay times. A plurality of clock signal delay means for generating the clock signal and a clock signal generating means for supplying a start signal to a stop signal. Counter means for counting and outputting the number of clocks of the generated clock signal, and start signal sending means for sending the start signal to the counter means when the measurement signal sending means sends a measurement signal to the object to be measured. A stop signal transmitting means for transmitting the stop signal to the counter means when the measurement signal receiving means receives the measurement signal reflected from the measurement object; and a stop signal transmitted by the stop signal transmitting means. When the clock signal generated by the clock signal generating means and the plurality of clock signals generated by the clock signal delaying means are recognized, a rising or falling edge of the nearest clock signal is recognized, and the nearest clock signal is detected. Clock signal specifying means for specifying A count value of the means, and calculates the distance to the object to be measured based on the delay time of the clock signal generated by the specified clock signal and the clock signal generating means.
[0010]
According to the present invention, when the stop signal is issued, the clock signal generated by the clock signal generating means and the clock signal generated by the N clock signal delay means, the rising or falling of the closest clock signal. , It is possible to obtain N times higher measurement accuracy as compared with the case where the clock signal generated by the clock signal generating means is counted by the counter means. Further, unlike the conventional case, a large number of counters are not required.
[0011]
The clock signal specifying unit includes a plurality of flip-flops that latch the stop signal, and an OR circuit that outputs a latch signal to a subsequent flip-flop when one of the plurality of flip-flops latches the stop signal. You can do so. Accordingly, when the stop signal is issued, the clock signal having the closest rising or falling edge of the clock signal can be specified, and a distance measuring device with a simple configuration and low power consumption can be provided.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, embodiments of the present invention will be described with reference to the drawings.
[0013]
FIG. 1 shows an embodiment of a distance measuring device according to the present invention. The distance measuring device comprises a clock generator 1, delay lines (1 to N) 2, a pulse generator 3, a laser light generator, A unit 4, a light transmitting optical system 5, a light receiving optical system 6, a detector 7, a flip-flop circuit (FF0 to N-1,2) 8, an OR gate 9, a flip-flop (FF) 10, It is composed of a 2N → N encoder 11, a lower register 12, a distance measuring counter 13, and an upper register 14.
[0014]
A clock generator (clock signal generating means) 1 generates various laser signals for irradiating the object to be measured 0 with a pulse laser beam and measures the time from the irradiation time to the reception time of the received light signal.
[0015]
The delay lines (1 to N) 2 as clock signal delay means give N kinds of delay times to the “sample clock signal 0” generated by the clock generator 1. Assuming that the cycle of “sample clock 0” is T, each of the delay lines (1 to N) 2 has a delay time of T × N / (N + 1). Here, the number N of delay lines is determined according to the required distance measurement resolution. The sample clocks 0 to N give the latch timings of the flip-flop circuits (FF0 to N-1, 2) 8, respectively, which constitute clock signal specifying means described later.
[0016]
The pulse generator 3 generates a laser emission control signal required for laser generation of the laser light generator 4 based on a clock signal from the clock generator 1 and simultaneously generates a clear signal of the distance measuring counter 13 (counter means). I do.
[0017]
When the laser emission control signal synchronized with the sample clock 0 is output from the pulse generation unit 3, the laser light generation unit 4 generates a pulsed laser. Irradiated toward zero. The laser light generator 4 functions as a start signal transmitting unit and outputs a start signal for recognizing a pulse generation timing to the distance measuring counter 13.
[0018]
The light receiving optical system 6 receives a signal reflected from the object to be measured 0 and guides the signal to the detector 7. After converting the weak input signal due to light into an electric signal, the detector 7 outputs a stop signal for notifying the timing at which the received signal reaches a peak value to the distance measuring counter 13 and the flip-flop circuits (FF0 to N -1) Output to 8.
[0019]
FIG. 2 shows a laser transmission / reception timing and a distance measurement target section. The distance measuring counter 13 counts each time the sample clock 0 rises from the start signal to the stop signal, and registers the result in the upper register 14. At this time, the laser emission control signal and the emitted pulse laser are synchronized with the sample clock 0 and always have a fixed value. The measurement target distance to be obtained is from the laser transmission time to the time when the reception signal reaches a peak, and the time from the last rising of the sample clock 0 at which the distance measurement counter 13 stops counting by the stop signal to the peak value of the reception signal. It measures by the method mentioned later.
[0020]
The flip-flop circuits (FF0-1 to FFN-1) 8 sequentially latch the stop signals at the rising timing of the sample clocks 0 to N. The latched signals enter the second-stage flip-flop circuits (FF0-2 to FFN-2) and are latched again at the next rising edge of each sample clock. This two-stage configuration is a means for avoiding the risk that the latch output is uncertain only at the first stage (FF0-1 to FFN-1) because the stop signal and the sample clock are asynchronous.
[0021]
The flip-flop circuits (FF0-2 to FFN-2) output the latch outputs to the OR gate 9 and the flip-flop (FF) 10.
[0022]
The OR gate 9 operates faster than the elements used in the flip-flop circuits (FF0-1 to FFN-1) 8, and is the first of the flip-flop circuits (FF0-2 to FFN-2). When the detection of the stop signal changes from the “L” level to the “H” level, the “L” level changes to “H” level before the latch signal of the flip-flop (FF) that changes to the “H” level for the second time is input. The signal changes to the H level, and at the rising edge, the data input to the flip-flop (FF) 10 is latched. The OR gate 9 outputs a rising signal only once in one transmission / reception cycle, and only the signal which first detects the stop signal is held at the "H" level.
[0023]
The output of the flip-flop (FF) 10 enters the 2N → N encoder 11. The encoder 11 converts a channel having only one “H” level among 2N powers into an N-bit encoded value.
[0024]
FIG. 3 shows the latch timing of the stop signal (for the sake of convenience, the timing is shown on the assumption that the sample clock 1 rises immediately after the stop signal) and the distance measurement value detection timing by the encoder 11. The encoder 11 has 2N channel inputs (CH0 to CH2N-1) and an N-bit output, and converts the input channel number into an N-bit signal and outputs it. The output of the encoder 11 is registered in the lower register 12, and the distance measurement data to be obtained is obtained by combining the output with the data registered in the upper register 14.
[0025]
Next, as an embodiment of the distance measuring apparatus according to the present invention, a case where the number of delay lines is seven and the peak level of the received signal (rising of the stop signal) falls between the rising of the sample clock 1 and the rising of the sample clock 2 will be described. I do.
[0026]
FIG. 4 shows the overall configuration of one embodiment of the distance measuring device of the present invention. This distance measuring device includes a clock generator 31, delay lines (1 to 7) 32, a pulse generator 33, a laser light generator 34, a light transmission optical system 35, a light receiving optical system 36, a detector 37, a flip-flop circuit (FF0-7-1, 2) 38, an OR gate 39, a flip-flop (FF) 40, a 23 → 3 encoder 41, a lower register 42, a distance measuring counter 43, an upper And a register 44.
[0027]
The clock generator 31 generates pulsed laser light for irradiating the distance measurement target 30 and generates various clock signals for measuring the time from the irradiation time to the reception time of the light receiving signal.
[0028]
The delay lines (1 to 7) 32 give seven kinds of delay times to the “sample clock signal 0” generated by the clock generator 31. Assuming that the cycle of “sample clock 0” is T, the delay lines (1 to 7) 32 each have a delay time of N × T / 8 (N = 1 to 7). The sample clocks 0 to 7 give latch timings of flip-flop circuits (FF0 to FF7-1, 2) 38 described later.
[0029]
The pulse generator 33 generates a laser emission control signal required for laser generation of the laser light generator 34 based on a clock signal from the clock generator 31 and, at the same time, generates a clear signal of the distance measuring counter 43.
[0030]
When the laser emission control signal synchronized with the sample clock 0 is output from the pulse generation unit 33, the laser light generation unit 34 generates a pulsed laser. Irradiated toward Further, the laser light generator 34 outputs a start signal for recognizing the pulse generation timing to the distance measuring counter 43.
[0031]
The light receiving optical system 36 receives a signal reflected from the distance measurement target 30 and guides the signal to the detector 37. After converting a weak input signal due to light into an electric signal, the detector 37 outputs a stop signal indicating the timing when the received signal reaches a peak value to the distance measuring counter 43 and the flip-flop circuits (FF0 to FF7-1) 38. I do.
[0032]
The distance measuring counter 43 counts each time the sample clock 0 rises from the start signal to the stop signal, and registers the result in the upper register 44. At this time, the laser emission control signal and the emitted pulse laser are synchronized with the sample clock 0 and always have a fixed value. The measurement target distance to be obtained is from the laser transmission time to the time when the received signal reaches a peak, and the time from the rising edge of the last sample clock 0 at which the distance measuring counter 43 stops counting by the stop signal to the peak value of the received signal. It measures by the method mentioned later.
[0033]
The flip-flop circuits (FF0-1 to FF7-1) 38 sequentially latch the stop signals at the rising timing of the sample clocks 0 to 7. The latched signal enters each of the second-stage flip-flop circuits (FF0-2 to FF7-2) and is latched again at the next rising edge of each sample clock. This two-stage configuration is a means for avoiding the risk that the latch output becomes indefinite at only the first stage (FF0-1 to FF7-1) because the stop signal and the sample clock are asynchronous.
[0034]
The flip-flop circuits (FF0-2 to FF7-2) output the latch outputs to the OR gate 39 and the flip-flop (FF) 40.
[0035]
The OR gate 39 operates faster than the elements used in the flip-flop circuits (FF0-1 to FF7-1) 38, and is the first of the flip-flop circuits (FF0-2 to FF7-2). When the detection of the stop signal changes from the “L” level to the “H” level, the “L” level changes to “H” level before the latch signal of the flip-flop (FF) that changes to the “H” level for the second time is input. The signal changes to the H level, and at the rising edge, the data input to the flip-flop (FF) 40 is latched. The OR gate 39 outputs a rise only once in one transmission / reception cycle, and only the signal which first detects the stop signal is held at the "H" level.
[0036]
The output of the flip-flop (FF) 40 enters the 23 → 3 encoder 41. The encoder 41 converts a channel which is only at the “H” level among the input powers of 2 to the power of 3 into a 3-bit encoded value.
[0037]
FIG. 5 shows the latch timing of the stop signal (the timing is shown on the assumption that the sample clock 2 rises immediately after the stop signal) and the timing of detecting the distance measurement value by the encoder 41. The encoder 41 has an input of 8 channels (CH0 to CH7) and a 3-bit output, converts the input channel number into a 3-bit code, and outputs the code. For example, when CH0 becomes "H", the output code becomes "000", and when CH2 becomes "H" as in this example, the output code becomes "010". The output of the encoder 41 is registered in the lower register 42, and by combining this with data registered in the upper register 44, distance measurement data to be obtained is obtained.
[0038]
In the above embodiment, the distance measuring counters 13 and 43 count each time the sample clock 0 rises from the start signal to the stop signal, and stop when calculating the distance to the measurement target. Although the time from the rising edge of the last sample clock 0 when the distance measurement counters 13 and 43 stopped counting by the signal to the peak value of the received signal was measured, the counting was performed at each falling edge of the sample clock 0, and the last The time from the falling of sample clock 0 to the peak value of the received signal may be measured. Also, when the stop signals are latched by the flip-flop circuits (FF0-1 to FFN-1) 8 and 38, they may be latched sequentially at the falling timing of the sample clocks 0 to N.
[0039]
【The invention's effect】
As described above, according to the present invention, a distance measurement that does not require a large number of counters, does not require digitization of acquired data, and does not require complicated processing by a CPU or the like, enables low-power, high-precision distance measurement. An apparatus can be provided.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram showing one embodiment of a distance measuring device according to the present invention.
FIG. 2 is an explanatory diagram of laser transmission / reception timing and a distance measurement target section of the distance measuring device of FIG. 1;
FIG. 3 is an explanatory diagram of latch timing of a stop signal and encoder output timing of the distance measuring device of FIG. 1;
FIG. 4 is an overall configuration diagram showing one embodiment of a distance measuring device according to the present invention.
FIG. 5 is an explanatory diagram of latch timing of a stop signal and encoder output timing of the distance measuring device of FIG. 4;
[Explanation of symbols]
0 Distance measuring object 1 Clock generator 2 Delay line (1 to N)
Reference Signs List 3 pulse generating unit 4 laser beam generating unit 5 light transmitting optical system 6 light receiving optical system 7 detector 8 flip-flop circuit (FF0 to N-1, 2)
9 OR gate 10 Flip-flop (FF)
11 2N → N encoder 12 Lower register 13 Distance measuring counter 14 Upper register 30 Distance measuring object 31 Clock generator 32 Delay line (1-7)
33 pulse generator 34 laser light generator 35 light transmitting optical system 36 light receiving optical system 37 detector 38 flip-flop circuit (FF0-7-1, 2)
39 OR gate 40 Flip-flop (FF)
41 23 → 3 encoder 42 Lower register 43 Distance measuring counter 44 Upper register

Claims (2)

A measurement signal transmitting means for transmitting a measurement signal to a measurement object,
Measurement signal receiving means for receiving a measurement signal emitted from the measurement signal transmission means, reflected by the measurement object,
Distance measurement means for calculating a distance to the object to be measured, based on a time required from transmission of the measurement signal by the measurement signal transmission means to reception of the measurement signal by the measurement signal reception means,
The distance calculating means,
Clock signal generating means for generating a clock signal;
A plurality of clock signal delay means for generating a signal obtained by giving a plurality of different delay times to the clock signal generated by the clock signal generation means;
Counter means for counting and outputting the number of clocks of the clock signal generated by the clock signal generation means from when the start signal is supplied to when the stop signal is supplied;
Start signal transmitting means for transmitting the start signal to the counter means when the measurement signal transmitting means transmits a measurement signal to the measurement object,
Stop signal transmitting means for transmitting the stop signal to the counter means when the measurement signal receiving means receives a measurement signal reflected from the measurement object,
When the stop signal transmitted by the stop signal transmitting means is issued, the nearest one of the clock signal generated by the clock signal generating means and the plurality of clock signals generated by the clock signal delaying means, Clock signal specifying means for recognizing the falling edge and specifying the closest clock signal,
A distance measuring device for calculating a distance to the object to be measured based on a count value of the counter unit, a delay time of the specified clock signal and a clock signal generated by the clock signal generating unit. . The clock signal specifying means includes:
A plurality of flip-flops for latching the stop signal;
2. The distance measuring apparatus according to claim 1, further comprising: an OR circuit that outputs a latch signal to a subsequent flip-flop when one of the plurality of flip-flops latches a stop signal.

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