JP2007155660A - Light wave range finder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve precision without changing modulation signals. <P>SOLUTION: When a distance measuring light, modulated by modulation signals F1, F2, F3 from a light-emitting element 10A, is emitted and then the reflection light is received by a light receiving element 18, distance measuring signals f1, f2, f3 and a distance measuring signal f1×n are outputted from the light-receiving element 18. When respective distance measuring signals are mixed with local signals L1×n, L1, L2, L3 by mixers 20-26; a distance measuring signal (IF signal) Δf at an intermediate frequency is outputted from respective mixers 20-26; each distance measuring signal is compared with a reference signal Δf by a computing unit 36, and the distance to a measuring point is computed, based on the phase difference among them. In this case, since the distance measuring signal (IF signal) is generated from the distance measuring signals f1, f2, f3, and the distance measuring signal (IF signal) is generated from the distance measuring signal f1×n that is a harmonic component of the distance measuring signal f1, accuracy accompanying increase in the measuring information can be improved without changing the modulation signals. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a light wave distance meter suitable for obtaining a distance to a measurement point based on a phase difference between a distance measurement signal and a reference signal.

  Conventionally, in a phase-difference optical distance meter, light is modulated using three types of modulation signals, for example, 75 MHz, 3.75 MHz, and 250 kHz, and the modulated light is reflected at a measuring point. Light is emitted sequentially toward the mirror (corner prism or reflecting sheet), and the reflected light reflected by the reflecting mirror is received by the light receiving element. The light is received and converted into an electrical signal. ) Is converted into an intermediate frequency ranging signal (IF signal), and the phase difference between the IF signal and the reference signal is measured. In addition, an accurate value is obtained by correcting a distance error inside the machine by using a reference signal.

  In this case, when 75 MHz is used as the modulation signal, the phase difference is measured 25,000 times as a precise measurement, and when a 3.75 MHz signal is used as the modulation signal, it is 5,000 times as an intermediate measurement. When the phase difference is measured and 250 kHz is used as the modulation signal, the phase difference is measured 2500 times as a rough measurement. Actually, since there is a calibration measurement, each measurement measures a phase difference of about twice.

  In order to obtain the distance to a measuring point using an optical wave distance meter by a phase difference method, in recent years, high accuracy and high measurement time have been demanded. In order to cope with such a request, the conventional technique uses a 75 MHz signal as a modulation signal in order to obtain an accuracy of several millimeters, and transmits the modulation signal as a pulse signal from a laser diode (LD). Is adopted. In this case, when the transmitted light is reflected by the reflector and received by the light receiving element as reflected light, and converted into an electric signal as a distance measuring signal, it is twice the actual transmission distance (L) of the light. A corresponding phase delay (θ) occurs. On the other hand, when the ranging signal output from the light receiving element is converted to an intermediate frequency of 6.25 kHz by a mixer, the phase delay (θ) becomes a phase delay with respect to 6.25 kHz. Therefore, the delay time is 75 MHz / 6.25 kHz = 12,000 times, the resolution is also 12,000 times, and an accuracy of several mm can be realized.

  However, when more accurate distance measurement is required, the modulation signal must be set to a frequency higher than 75 MHz. However, in order to further increase the modulation signal, the circuit for oscillating the light transmission LD becomes complicated and difficult.

  The present invention has been made in view of the above-described problems of the prior art, and an object thereof is to provide an optical rangefinder that can achieve high accuracy without changing a modulation signal.

  In order to achieve the object, the optical distance meter according to claim 1 emits ranging light modulated by any one of a plurality of types of modulation signals having different frequencies generated from a reference signal. A light emitting means; a light receiving means for performing photoelectric conversion upon receiving the distance measuring light and outputting a distance measuring signal; a reference signal generating means for generating a reference signal; and the plurality of types of modulation signals, respectively. A plurality of local signal generating means for generating local signals having different frequencies by the signal component of the reference signal, a distance measuring signal output from the light receiving means, and a local signal generated by the plurality of local signal generating means are mixed. A plurality of mixing means for outputting intermediate frequency ranging signals, a reference signal generated by the reference signal generating means, and an intermediate frequency output by the plurality of mixing means In a lightwave range finder comprising a calculation means for calculating a phase difference from a distance signal and calculating a distance to a measurement point based on each phase difference, n times the modulation signal among the modulation signals (n is An auxiliary local signal generating means for generating an auxiliary local signal having a frequency different from that of the reference signal with respect to a modulation signal of an integer of 2 or more, a distance measurement signal by the output of the light receiving means, and the auxiliary local signal generating means And an auxiliary mixing unit that mixes the auxiliary local signal generated by the generation of the signal and outputs a ranging signal having an intermediate frequency, and the calculation unit is configured to output the reference signal generated by the reference signal generating unit and the output of the auxiliary mixing unit. A phase difference with the intermediate frequency ranging signal is obtained, and the distance to the measuring point is corrected based on this phase difference.

  (Operation) When the ranging light is emitted (transmitted) toward the measuring point, if the modulation signal is a rectangular wave, a harmonic component of n times the modulation signal is superimposed on the ranging light, and the harmonic component Is also transmitted together with the modulation signal, and by mixing the distance measurement signal by the output of the light receiving means and the auxiliary local signal by the generation of the auxiliary local signal generation means by the auxiliary mixing means to generate the intermediate frequency distance measurement signal, A ranging signal including the modulation signal and its harmonic components can be extracted as the ranging signal of the intermediate frequency, and the accuracy can be improved as the measurement information increases without changing the modulation signal. Is possible.

  According to a second aspect of the present invention, there is provided a light wave distance meter that emits distance measuring light modulated by any one of a plurality of types of modulation signals having different frequencies generated from a reference signal, and the measurement signal. A light receiving means for performing photoelectric conversion when receiving distance light and outputting a distance measurement signal, a reference signal generating means for generating a reference signal, and only a signal component of the reference signal for each of the plurality of types of modulation signals A plurality of local signal generating means for generating local signals having different frequencies, a distance measuring signal output from the light receiving means, and a local signal generated by the plurality of local signal generating means to mix each of the intermediate signals. A plurality of mixing means for outputting a signal, and a phase difference between a reference signal generated by the reference signal generating means and an intermediate frequency ranging signal output by the plurality of mixing means. And an optical distance meter provided with a calculation means for calculating a distance to a measuring point based on each phase difference, and n times the modulation signal having the highest frequency among the modulation signals (n is an integer of 2 or more) ) Auxiliary local signal generating means for generating an auxiliary local signal having a frequency different from the modulation signal by the signal component of the reference signal, and a distance measurement signal generated by the output of the light receiving means and auxiliary by the generation of the auxiliary local signal generating means An auxiliary mixing unit that mixes a local signal and outputs a ranging signal of an intermediate frequency, and the calculating unit measures the intermediate frequency by the reference signal generated by the reference signal generating unit and the output of the auxiliary mixing unit. The phase difference with the distance signal is obtained, and the distance to the measurement point is corrected based on this phase difference.

  (Operation) When the distance measuring light is emitted (transmitted) toward the measuring point, if the modulation signal is a rectangular wave, a harmonic component of n times the modulation signal is superimposed on the distance measuring light, and the harmonic wave Since the component is also transmitted along with the modulation signal, the distance measurement signal generated by the light receiving means and the auxiliary local signal generated by the auxiliary local signal generating means are mixed by the auxiliary mixing means to generate the intermediate frequency distance measurement signal. As the intermediate frequency ranging signal, the modulation signal having the highest frequency among the modulation signals and the ranging signal including the harmonic components thereof can be extracted, and the measurement information can be increased without changing the modulation signal. As a result, higher accuracy can be achieved.

  As described above, according to the first aspect of the present invention, the ranging signal including the modulation signal and its harmonic component can be extracted, and the measurement information can be increased without changing the modulation signal. Accordingly, it becomes possible to achieve high accuracy.

  According to the second aspect of the present invention, the modulation signal having the highest frequency among the modulation signals and the ranging signal including the harmonic component thereof can be extracted, and the measurement can be performed without changing the modulation signal. As the information increases, higher accuracy can be achieved.

  Hereinafter, embodiments of the present invention will be described based on examples. FIG. 1 is a block diagram of a light wave distance meter showing an embodiment of the present invention. In FIG. 1, a phase difference type lightwave distance meter includes a light emitter 10, a frequency divider 12, 14, a reference signal generator 16, a light receiving element 18, a mixer 20, 22, 24, 26, and amplifiers 28, 30, 32. , 34, an arithmetic unit 36, and signal generators 38, 40, 42, 44.

  The light emitter 10 includes, for example, a laser diode (LD) as the light emitting element 10A, an oscillator that oscillates the light emitting element, a modulator that modulates light, and the like. A modulation signal F1 with a frequency of 75 MHz, a modulation signal F2 with a frequency of 3.75 MHz, and a modulation signal F3 with a frequency of 250 kHz are input, and each of the input modulation signals is selected in a specified order, and the selected modulation signal is made into a rectangular wave. As a light emitting means that narrows the pulse width and oscillates the laser diode in multimode, modulates the light with a modulation signal to produce distance measuring light, and emits (transmits) the distance measuring light toward the measuring point It is configured. The light emitter 10 is supplied with a modulation signal F1 having a frequency of 75 MHz from the reference signal generator 16, and a modulation signal F2 obtained by dividing the modulation signal F1 by the frequency divider 12 and the modulation signal F1. A modulation signal F3 obtained by frequency division by the frequency divider 14 is input.

  The light receiving element 18 emits distance measuring light from the light emitting element 10A toward the measuring point, and when the distance measuring light is reflected by the reflecting mirror of the measuring point and receives the reflected light, the light receiving element 18 performs photoelectric conversion to measure. As the distance signal, for example, a distance measurement signal f1 having a frequency of 75 MHz, a distance measurement signal f2 having a frequency of 3.75 MHz, a distance measurement signal f3 having a frequency of 250 kHz, and n times (n is an integer of 2 or more) the distance measurement signal f1. It is configured as a light receiving means for outputting a distance measurement signal f1 × n by harmonics, and each distance measurement signal is output to the mixers 20, 22, 24, and 26.

  The mixer 20 sends an auxiliary local signal L1 × n (= F1 ×) whose frequency is higher by the signal component of the reference signal Δf than the modulation signal (reference signal) F1 × n (n is an integer of 2 or more) from the signal generator 38. n + Δf), a local signal L1 (= F1 + Δf) having a frequency higher than that of the modulation signal F1 by the signal component of the reference signal Δf is input from the signal generator 40 to the mixer 22, and the signal is input to the mixer 24. A local signal L2 (= F2 + Δf) having a frequency higher than the modulation signal F2 by the signal component of the reference signal Δf is input from the generator 42, and the mixer 26 receives the reference signal Δf from the signal generator 44 rather than the modulation signal F3. A local signal L3 having a higher frequency than the signal component is input.

  In this case, the signal generator 38 receives the reference signal F1 from the reference signal generator 16, multiplies the reference signal F1 by n (n is an integer equal to or greater than 2), and also generates a reference signal from the n-fold multiplied reference signal F1. The auxiliary local signal generating means generates an auxiliary local signal L1 × n (= F1 × n + Δf) having a high frequency by the signal component Δf. The signal generator 40 receives a reference signal F1 from the reference signal generator 16, and generates a local signal L1 (= F1 + Δf) having a higher frequency than the reference signal F1 as a signal component of the reference signal Δf. It is configured. The signal generator 42 receives and divides the reference signal F1 from the reference signal generator 16, and the local signal L2 (= F2 + Δf) whose frequency is higher by the signal component of the reference signal Δf than the modulation signal F2 obtained by frequency division. The signal generator 44 receives and divides the reference signal F1 from the reference signal generator 16, and the signal generator 44 generates a reference signal Δf rather than the modulation signal F3 obtained by the division. It is configured as a local signal generating means for generating a local signal L3 (= F3 + Δf) having a high frequency by the signal component.

  The mixer 20 mixes the ranging signal f1 × n output from the light receiving element 18 with the auxiliary local signal L1 × n output from the signal generator 38 to generate a ranging signal Δf having an intermediate frequency, for example, 6 or 25 kHz. It is configured as an auxiliary mixing means for outputting, and the intermediate frequency ranging signal Δf is inputted to the amplifier 28. The mixer 22 is configured as a mixing unit that mixes the distance measurement signal f1 output from the light receiving element 18 and the local signal L1 output from the signal generator 40 to output a distance measurement signal Δf having an intermediate frequency (6, 25 kHz). The intermediate frequency ranging signal Δf is input to the amplifier 30. The mixer 24 is configured as a mixing unit that mixes the distance measurement signal f2 output from the light receiving element 18 and the local signal L2 output from the signal generator 42 to output a distance measurement signal Δf having an intermediate frequency (6, 25 kHz). The mixer 26 mixes the distance measurement signal f3 output from the light receiving element 18 and the local signal L3 output from the signal generator 44 to output a distance measurement signal Δf having an intermediate frequency (6, 25 kHz). Each ranging signal Δf is input to amplifiers 32 and 34, respectively.

  The amplifiers 28, 30, 32, and 34 extract specified signal components, for example, 6.25 kHz signal components, from the signals output from the mixers 20 to 26 using a filter, and each ranging signal Δf extracted by the filter. Is amplified at a predetermined amplification degree and output to the computing unit 36.

  The arithmetic unit 36 sequentially inputs distance measurement signals (IF signals) Δf output from the amplifiers 28 to 34, obtains a phase difference between the input distance measurement signal (IF signal) Δf and the reference signal Δf, and calculates each phase difference. Is configured as a calculation means for calculating the distance to the measuring point based on the above.

  In this case, by using the distance measurement signal (IF signal) obtained from the distance measurement signal f3, for example, distance measurement from 0 to 600 m can be performed, and the distance measurement signal (IF signal) obtained from the distance measurement signal f2. Can be used for ranging from 0 to 40 m, and by using a ranging signal (IF signal) obtained from the ranging signal f 1, ranging from 0 to 2 m can be performed, and ranging signal f 1 × By using the ranging signal (IF signal) obtained from n, ranging from 0 to 0.5 m can be performed. That is, when a distance measurement signal (IF signal) having an intermediate frequency is obtained using f1, f2, and f3 as distance measurement signals, for example, even if the distance to the measurement point is 321.53 m, it is only up to 321 m. It cannot be measured accurately. On the other hand, when a distance measurement signal (IF signal) of an intermediate frequency is obtained using f1 × n, f1, f2, and f3 as distance measurement signals, it can be accurately measured up to 321.5 m.

  This is because when 75 MHz is used as one of the three types of modulation signals and this modulation signal is used as a rectangular wave, and the light is modulated by narrowing the pulse width of the rectangular wave, the ranging light is broadband. This is because harmonics of n times (n is an integer of 2 or more) of 75 MHz are also transmitted, and using this harmonic component as information makes it possible to achieve high accuracy.

  In the above configuration, the light emitter 10 sequentially selects any one of the modulation signals F1, F2, and F3, and the ranging light modulated by the selected modulation signal is emitted from the light emitting element 10A toward the measurement point. When the reflected light is received by the light receiving element 18, the distance measuring signal f1 × n is output from the light receiving element 18 together with the distance measuring signals f1, f2, and f3. 26 is mixed with the local signals L1 × n, L1, L2, L3. As a result, each of the mixers 20 to 26 outputs an intermediate frequency ranging signal (IF signal) Δf, and the computing unit 36 compares each ranging signal (IF signal) with the reference signal Δf, and the phase difference between them. Based on, the distance to the station is calculated. At this time, in addition to generating a ranging signal (IF signal) from the ranging signals f1, f2, and f3, a ranging signal (IF signal) from the ranging signal f1 × n that is a harmonic component of the ranging signal f1. Therefore, it is possible to increase the accuracy as the measurement information increases without changing the modulation signal.

  In the above-described embodiment, the case where each of the mixer 20, the amplifier 28, and the signal generator 38 is used as one that uses the harmonic component of the modulation signal has been described. By doing so, higher accuracy can be achieved. In this case, each mixer has a different frequency and is configured to correspond to n times the distance measurement signal f1 (n is an integer of 2 or more), and each signal generator has a different frequency and a local frequency. It is necessary to configure the signal corresponding to n times the signal L1 (n is an integer of 2 or more).

  According to the present embodiment, since the harmonic component of n times (n is an integer of 2 or more) of the 75 MHz modulation signal is used for measurement information, high accuracy can be achieved without changing the modulation signal. become.

It is a block block diagram of the light wave distance meter of one Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Light emitter 10A Light emitting element 12, 14 Frequency divider 16 Reference signal generator 18 Light receiving element 20, 22, 24, 26 Mixer 28, 30, 32, 34 Amplifier 36 Operation unit 38, 40, 42, 44 Signal generator

Claims (2)

  Light emitting means for emitting distance measuring light modulated by any one of a plurality of types of modulation signals having different frequencies generated from a reference signal, and photoelectric conversion when receiving the distance measuring light. A light receiving means for outputting a ranging signal, a reference signal generating means for generating a reference signal, and a plurality of local signals for generating local signals having different frequencies corresponding to the signal components of the reference signal for the plurality of types of modulation signals, respectively. Generating means; and a plurality of mixing means for mixing each of the ranging signals output from the light receiving means and the local signals generated by the plurality of local signal generating means to output intermediate frequency ranging signals; and the reference Obtain the phase difference between the reference signal generated by the signal generating means and the intermediate frequency ranging signal output from the plurality of mixing means, and obtain the measuring point based on each phase difference. An optical distance meter comprising a computing means for computing a distance, wherein the frequency of the signal component of the reference signal is n times the modulation signal of any one of the modulation signals (n is an integer of 2 or more). Auxiliary local signal generating means for generating different auxiliary local signals, and a distance measuring signal output from the light receiving means and an auxiliary local signal generated by the auxiliary local signal generating means are mixed to output an intermediate frequency ranging signal. And an auxiliary mixing means for calculating a phase difference between a reference signal generated by the reference signal generating means and an intermediate frequency ranging signal output by the auxiliary mixing means, and based on the phase difference. A light wave distance meter obtained by correcting a distance to the measuring point.   Light emitting means for emitting distance measuring light modulated by any one of a plurality of types of modulation signals having different frequencies generated from a reference signal, and photoelectric conversion when receiving the distance measuring light. A light receiving means for outputting a ranging signal, a reference signal generating means for generating a reference signal, and a plurality of local signals for generating local signals having different frequencies corresponding to the signal components of the reference signal for the plurality of types of modulation signals, respectively. Generating means; and a plurality of mixing means for mixing each of the ranging signals output from the light receiving means and the local signals generated by the plurality of local signal generating means to output intermediate frequency ranging signals; and the reference Obtain the phase difference between the reference signal generated by the signal generating means and the intermediate frequency ranging signal output from the plurality of mixing means, and obtain the measuring point based on each phase difference. In a lightwave distance meter comprising a computing means for computing a distance, only the signal component of the reference signal with respect to a modulation signal n times (n is an integer of 2 or more) of the modulation signal having the highest frequency among the modulation signals. Auxiliary local signal generating means for generating auxiliary local signals having different frequencies, and a distance measuring signal output from the light receiving means and an auxiliary local signal generated by the auxiliary local signal generating means are mixed to obtain a distance measuring signal having an intermediate frequency. An auxiliary mixing means for outputting, and the calculating means obtains a phase difference between the reference signal generated by the reference signal generating means and the intermediate frequency ranging signal output by the auxiliary mixing means, and based on the phase difference. A light wave distance meter obtained by correcting the distance to the measuring point.

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