JP2019039924A - Light wave rangefinder - Google Patents

Abstract

To provide a light wave rangefinder that enables measurements in a short time.SOLUTION: A light wave rangefinder comprises: a light emitting element 11 that emits rangefinder light 28; signal generators 33, 34 that generate a plurality of proximity frequencies; an emission optical system that sequentially switches intermittent modulation rangefinder light having each of the plurality of proximity frequencies intermittently pulsed to a prescribed width for each proximity frequency to emit the intermittent modulation rangefinder light; a light reception unit 21 that receives reflection rangefinder light 28' from a measurement object to generate an intermittent light reception signal 29; a reference signal generator 31 that outputs a reference frequency signal; frequency conversion units 39, 43, and 48 that mix the intermittent light reception signal with the reference frequency signal to obtain an intermittent conversion signal; and a computation control unit 47. The computation control unit is configured to: obtain a phase of the intermittent light reception signal with respect to the plurality of proximity frequencies to compute a precision measurement distance; or obtain a phase difference between each intermittent conversion signal to compute a rough measurement distance value; and measure a distance on the basis of the rough measurement distance value and a precision measurement distance value.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a lightwave distance meter that irradiates a measurement object with modulated measurement light, receives reflected measurement light from the measurement object, and measures a distance to the measurement object based on a phase difference between the measurement light and the reflected measurement light. It is about.

  In a light wave rangefinder that measures the distance by detecting the phase difference between the measurement light and the reflected measurement light, the measurable distance and measurement accuracy are determined by the modulation frequency. Therefore, in order to be able to measure from a short distance to a long distance, it is necessary to irradiate distance measuring light having a plurality of modulation frequencies.

  For example, when a modulation frequency of 30 MHz and a modulation frequency of 300 KHz are used, distances up to 5 m and 500 m can be measured at each frequency. In order to measure distances beyond this, additional frequencies are required. In the past, the heterodyne method was used to measure the high frequency phase, and the phase was measured after the frequency was lowered. For example, for phase measurement at 30 MHz and 300 KHz, frequencies of 30 MHz-30 KHz and 300 KHz-30 KHz are generated, and phase measurement is performed at the difference frequency of 30 KHz. If 300 KHz-30 KHz generated at that time is used as the third modulation frequency, the phase difference from the 300 KHz modulation signal is obtained, which is equivalent to the phase modulated at 30 KHz in a pseudo manner. Distance measurement was possible.

  In the conventional optical wave distance meter, since a plurality of frequencies are generated, and a distance measuring light is emitted for each of the plurality of frequencies and the distance is measured, there is a problem that the circuit configuration becomes complicated and the measurement time becomes long. .

JP-A-5-232232 JP 2004-219285 A

  In view of such circumstances, the present invention provides a lightwave distance meter that efficiently creates signals necessary for measurement and enables measurement in a short time.

The present invention relates to a light emitting element that emits distance measuring light, a signal generator that generates a plurality of adjacent frequencies, a modulation signal that is intermittently pulsed to a plurality of the adjacent frequencies, and a predetermined width based on the modulation signal. An emission optical system that sequentially switches and emits intermittent modulation ranging light pulsed to a width for each adjacent frequency, and a light receiving unit that receives reflected ranging light from a measurement object and generates an intermittent light reception signal having a predetermined pulse width And a reference signal generator for generating a reference frequency signal having a difference between the respective predetermined frequencies, and the intermittent light reception signal from the light receiving unit is frequency-converted by mixing with the reference frequency signal, and each of the adjacent frequency signals is converted. Correspondingly, a frequency conversion unit for obtaining an intermittent conversion signal having a pulse width and an arithmetic control unit are provided, and the pulse width of the intermittent light reception signal is longer than the period of the intermittent conversion signal. Is set as the previous SL arithmetic control unit calculates a precise measured distance for a plurality of proximate frequencies obtains a phase of the intermittent light signal, and each intermittent converted signal mutual seeking retardation rough measurement distance value And a light wave distance meter configured to measure the distance by combining the rough measurement distance value and the precise measurement distance value.

  Further, the present invention generates an intermittent pattern that makes a round of the intermittent modulation ranging light with a predetermined number of intermittent, integrates the intermittent conversion signal a plurality of times for each intermittent pattern, the intermittent width of the obtained integrated waveform, the intermittent period From the above, specify a plurality of adjacent frequencies, determine the average phase of each intermittent conversion signal, determine the precise measurement distance value from the average phase, determine the coarse measurement distance value from the average phase difference between the intermittent conversion signals, The present invention relates to a lightwave distance meter that measures the distance of a measurement object from a measurement distance value and a rough measurement distance value.

  The present invention also relates to a lightwave distance meter in which the frequencies of intermittent conversion signals corresponding to at least two of a plurality of adjacent frequencies are the same.

  Further, the present invention relates to a light wave distance meter in which the arithmetic control unit performs distance measurement with a delay time of a light reception pulse of the intermittent modulation distance measuring light.

  Further, the present invention relates to the light wave distance meter for generating an abnormal signal when the difference between the precision measurement distance value and the rough measurement distance value obtained from a plurality of adjacent frequencies is not within a predetermined value. .

  Further, according to the present invention, the intermittent switching of a plurality of adjacent frequencies is performed by shifting a predetermined cycle for each frequency, and the intermittent conversion signal subjected to frequency conversion performs phase measurement after shifting the predetermined cycle. It is related to.

According to the present invention, a light emitting element that emits distance measuring light, a signal generator that generates a plurality of adjacent frequencies, a modulation signal that is intermittently pulsed to a predetermined width, and the modulation signal And an emission optical system that sequentially switches and emits intermittent modulation ranging light that has been pulsed to a predetermined width for each adjacent frequency, and receives reflected ranging light from a measurement object, and generates an intermittent light reception signal having a predetermined pulse width. The light receiving unit, a reference signal generator that generates a reference frequency signal having a difference between the respective predetermined frequencies, and the intermittent light reception signal from the light receiving unit are frequency-converted by mixing with the reference frequency signal, and each adjacent frequency A frequency conversion unit corresponding to the signal and obtaining an intermittent conversion signal having a pulse width, and an arithmetic control unit, wherein the pulse width of the intermittent light reception signal is longer than the period of the intermittent conversion signal Is set so as to be, pre-Symbol arithmetic control unit calculates a precise measured distance for a plurality of proximate frequencies obtains a phase of the intermittent light signal, also rough measurement seeking phase difference between the respective intermittent converting signals mutually Since the distance value is calculated and the distance is measured by combining the rough measurement distance value and the precision measurement distance value, all the modulation frequencies are used for the precision measurement and the rough measurement, and the measurement efficiency is high. Also, the measurement time is shortened. Furthermore, by using the ranging light as intermittent light, it is possible to concentrate only on the time during which the optical output is modulated, the peak power can be increased, and the light emission time is shortened, so the S / N is improved and the measurement accuracy is improved. Will improve .

  Further, according to the present invention, the intermittent modulation ranging light is generated in an intermittent pattern that makes a round with a predetermined number of intermittent, the intermittent conversion signal is integrated multiple times for each intermittent pattern, the intermittent width of the obtained integrated waveform, From the intermittent period, identify multiple adjacent frequencies, determine the average phase of each intermittent conversion signal, determine the precise measurement distance value from the average phase, and determine the coarse measurement distance value from the average phase difference between the intermittent conversion signals. Since the distance of the measurement object is measured from the precision measurement distance value and the rough measurement distance value, the number of intermittent points can be set as appropriate in accordance with the required measurement accuracy.

  Further, according to the present invention, since the frequency of the intermittent conversion signal corresponding to at least two of the plurality of adjacent frequencies is the same, the component on the electric circuit may correspond to one frequency, and the circuit configuration Since the frequency is close, one filter with a low Q is sufficient, and since the Q is low, the influence of the adjacent frequency on each phase shift is reduced, and the difference between the precision measurement and the coarse measurement is reduced. Abnormal measurement due to is difficult to occur.

  Further, according to the present invention, the arithmetic control unit measures the distance by the delay time of the light receiving pulse of the intermittent modulation ranging light, so that a long distance measurement is possible, and the modulation required for the long distance measurement. Frequency can be omitted.

  According to the present invention, the arithmetic control unit generates an abnormal signal when the difference between the fine measurement distance value and the coarse measurement distance value obtained from a plurality of adjacent frequencies is not within a predetermined value. It can be eliminated and the reliability of the measurement is improved.

  Furthermore, according to the present invention, intermittent switching of a plurality of adjacent frequencies is performed by shifting a predetermined cycle for each frequency, and the phase conversion is performed after shifting the intermittent conversion signal subjected to frequency conversion by a predetermined cycle. It exhibits an excellent effect that measurement with less error becomes possible.

It is the schematic of the optical system of the lightwave distance meter which concerns on a present Example. It is the schematic of the measuring circuit of the light wave distance meter which concerns on a present Example. (A) is an explanatory view showing a pulsed state-finding light, (B) is an explanatory view showing a light reception signal, (C) is an explanatory view showing a light emission pattern, and (D) is a signal after signal conversion of the light emission pattern. (E) is an explanatory diagram showing enlarged pulse modulated light after passing through a low-pass filter, and is a diagram showing a light reception signal and an internal signal after A / D conversion. It is explanatory drawing of distance measurement by delay time measurement, (A) is explanatory drawing of a light emission pattern, (B) is explanatory drawing which shows a light reception signal. It is the figure which changed the phase for every proximity frequency, (A) is a figure which shows a light emission pattern, (B) is explanatory drawing which shows a light reception signal.

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

  First, referring to FIG. 1, a distance measuring optical system 1 of a lightwave distance meter according to an embodiment of the present invention will be described.

  In FIG. 1, the distance measuring optical system 1 includes an emission optical system 2, a light receiving optical system 3, and a collimating optical system 4. FIG. 1 shows a prism whose measurement object 5 is a retroreflector.

  The distance measuring optical system 1 has a distance measuring optical axis 6 directed toward the measurement object 5, the emission optical system 2 is an emission optical axis 7, the light receiving optical system 3 is a light receiving optical axis 8, and the collimating optics. The system 4 has a collimating optical axis 9.

  A light emitting element 11, a condenser lens 12, a half mirror 13, and a light amount adjuster 14 are disposed on the emission optical axis 7, and deflecting mirrors 15 and 16 are disposed on the emission optical axis 7. The optical axis 7 is deflected by the deflection mirrors 15 and 16 so as to coincide with the distance measuring optical axis 6.

  The light emitting element 11 is a laser diode, for example, and emits invisible ranging light.

  An objective lens 17 and a dichroic mirror 18 are provided on the distance measuring optical axis 6. The dichroic mirror 18 transmits visible light and reflects distance measuring light. A portion of the distance measuring optical axis 6 that has passed through the dichroic mirror 18 is the collimating optical axis 9, and an eyepiece 19 is provided on the collimating optical axis 9.

  The objective lens 17, the dichroic mirror 18, the eyepiece lens 19, and the like constitute the collimating optical system 4.

  The condenser lens 12, the half mirror 13, the light amount adjuster 14, the deflection mirrors 15 and 16, the objective lens 17, and the like constitute the emission optical system 2.

  The portion of the distance measuring optical axis 6 reflected by the dichroic mirror 18 is the light receiving optical axis 8, and a light receiving element 21 is provided on the light receiving optical axis 8.

  The objective lens 17, the dichroic mirror 18 and the like constitute the light receiving optical system 3.

  The reflected optical axis of the half mirror 13 is guided to the light receiving element 21 through the reflecting mirror 22 as the internal reference optical axis 23. The half mirror 13 and the reflecting mirror 22 constitute an internal reference optical system 24.

  An optical path switch 25 is provided across the emission optical axis 7 and the internal reference optical axis 23. The optical path switch 25 selectively cuts off and opens the exit optical axis 7 and the internal reference optical axis 23, and the distance measuring light transmitted through the half mirror 13 by the optical path switch 25. Is selected, or whether a part of the distance measuring light reflected by the half mirror 13 is emitted to the internal reference optical system 24 is selected.

  The light emitting element 11 and the light receiving element 21 are electrically connected to the arithmetic processing unit 27, respectively.

  Hereinafter, the operation of the distance measuring optical system 1 will be described.

  A modulated distance measuring light 28 is emitted from the light emitting element 11, and the distance measuring light 28 converted into a parallel light beam by the condenser lens 12 is adjusted in light amount by the light amount adjuster 14, and then the objective lens 17. Is transmitted through the center of the measurement object 5 and emitted to the measurement object 5.

  The distance measuring light reflected by the measurement object 5 is incident on the objective lens 17 as reflected distance measuring light 28 ′, condensed by the objective lens 17, reflected by the dichroic mirror 18 and incident on the light receiving element 21. To do. The reflected distance measuring light 28 ′ is received by the light receiving element 21, and the light receiving element 21 generates an intermittent light receiving signal 29.

  A part of the ranging light 28 emitted from the light emitting element 11 (internal reference light 28 ″) is reflected by the half mirror 13. When the internal reference optical axis 23 is opened by switching the optical path of the optical path switch 25, the internal reference light 28 ″ enters the light receiving element 21. The light receiving element 21 emits a light receiving signal of the internal reference light 28 ''.

  Visible light incident through the objective lens 17 passes through the dichroic mirror 18 and is collected by the eyepiece lens 19. The surveyor can collimate the measurement object 5 through the eyepiece lens 19.

  The arithmetic processing unit 27 drives the light emitting element 11 to emit modulated light. Further, the distance to the measurement object 5 is measured based on the intermittent light receiving signal 29 of the reflected distance measuring light 28 ′ input from the light receiving element 21, and the internal light is detected based on the intermittent light receiving signal 29 of the internal reference light 28 ″. The optical path length of the reference optical system 24 is measured. The final measurement value is obtained as a difference between the measurement result based on the reflected distance measuring light 28 'and the measurement result of the internal reference light 28 ". By obtaining the difference between the measurement result of the reflected distance measuring light 28 ′ and the measurement result of the internal reference light 28 ″, the influence due to the drift of the electric circuit can be eliminated.

  Next, the arithmetic processing unit 27 will be described with reference to FIG.

  In FIG. 2, the same components as those shown in FIG.

  The reference signal generator 31 generates a reference frequency signal s1 having a predetermined frequency. In addition, the numerical value shown below can be suitably changed according to the measurement distance and the measurement accuracy. For example, in the following description, 240 MHz is the reference frequency.

  The reference frequency signal s1 emitted from the reference signal generator 31 is 1/32 of 240 MHz by the frequency divider 32 to generate a 7.5 MHz divided frequency signal s2. The frequency-divided signal s2 is input to the first signal generator 33 and the second signal generator 34.

  The first signal generator 33 generates a first modulation signal s3 of 240 MHz + 7.5 MHz from the divided frequency signal s2 and the reference frequency signal s1, and outputs the first modulation signal s3 to the first intermittent pulse generator 35. The second signal generator 34 generates a second modulated signal s4 of 240 MHz-7.5 MHz from the divided frequency signal s2 and the reference frequency signal s1, and outputs the second modulated signal s4 to the second intermittent pulse generator 36.

  The first signal generator 33 and the second signal generator 34 generate two modulated signals having frequencies close to each other, 240 MHz + 7.5 MHz and 240 MHz-7.5 MHz.

  The first intermittent pulse generator 35 converts the first modulated signal s3, which is a continuous signal, into an intermittent signal that is generated at predetermined time intervals with a predetermined time width. That is, the first modulated signal s3 as a continuous signal is converted into a pulse signal. The first pulse modulation signal s5 pulsed from the first intermittent pulse generator 35 to the AND circuit 37 is input.

  Therefore, the pulse of the first pulse modulation signal s5 includes a frequency of 240 MHz + 7.5 MHz, and the pulse is composed of a frequency of 240 MHz + 7.5 MHz.

  Similarly, in the second intermittent pulse generator 36, the second modulation signal s4, which is a continuous signal, is converted into an intermittent signal that is generated at predetermined time intervals with a predetermined time width, and converted into a pulse signal. The second pulse modulated signal s6 is input from the second intermittent pulse generator 36 to the AND circuit 37. Similarly to the first pulse modulation signal s5, the pulse of the second pulse modulation signal s6 includes a frequency of 240 MHz to 7.5 MHz, and the pulse has a frequency of 240 MHz to 7.5 MHz.

  The reference frequency signal s1 generated by the reference signal generator 31 is also input to the timing signal generator 39. The timing signal generator 39 generates various timing signals to be described later based on the reference frequency signal s1.

  The timing signal generator 39 issues a timing signal to the first intermittent pulse generator 35 and the second intermittent pulse generator 36, and the first intermittent pulse generator 35 and the second intermittent pulse generator 36 output the timing signal. Control is performed so that the one-pulse modulated signal s5 and the second pulse-modulated signal s6 are output alternately and at predetermined time intervals.

  The timing signal from the timing signal generator 39 is input to the switching gate 40. A switching signal is input to the AND circuit 37 from the switching gate 40.

  The AND circuit 37 alternately outputs a first pulse modulation signal s5 and a second pulse modulation signal s6 to the driver 38 in response to the switching signal from the switching gate 40.

  The driver 38 drives the light emitting element 11 based on the first pulse modulation signal s5 and the second pulse modulation signal s6, ranging light modulated by 240 MHz + 7.5 MHz, ranging measured by 240 MHz-7.5 MHz. Light is emitted alternately at predetermined time intervals and at predetermined time intervals (see FIG. 3C).

  The light emitting element 11 intermittently emits the distance measuring light 28, and the distance measuring light 28 becomes pulsed light. Further, alternately emitted pulsed light is composed of 240 MHz + 7.5 MHz modulated light and 240 MHz-7.5 MHz modulated light (hereinafter referred to as pulse modulated light).

  FIGS. 3A and 3C show a state in which 240 MHz + 7.5 MHz modulated light and 240 MHz-7.5 MHz modulated light are emitted alternately. In this embodiment, the pulse width is set to 933 ns. Here, the switching timing of 240 MHz + 7.5 MHz modulated light and 240 MHz-7.5 MHz modulated light is switched at a higher speed than the moving speed when the measuring object is a moving object. It is set so that the movement does not affect the measurement result.

  Here, when the modulated light is intermittent, the pulse width is set to be longer than one period of the difference frequency. Further, the intermittent period (pulse generation period) is set to a speed at which the phase change of the difference frequency signal due to the movement of the moving body can be ignored.

  Further, the distance measuring light 28 is intermittently emitted, that is, pulsed, thereby reducing the light emission load factor of the light emitting element (laser diode: LD) 11. Since the peak value can be increased by the decrease in the light emission load factor, the light intensity of the distance measuring light can be increased and the long distance measurement can be performed without impairing the safety for the eyes. The predetermined time width and the predetermined time interval are appropriately selected according to the measurement situation.

  The distance measuring light 28 is emitted toward the measurement object 5, reflected by the measurement object 5, and received by the light receiving element 21 through the light receiving optical system 3. The light receiving element 21 generates an intermittent light receiving signal 29. As the light receiving element to be used, for example, a photodiode and further an avalanche photodiode (APD) are used.

  Further, the optical path is switched by the optical path switch 25, and a part of the distance measuring light 28 is received by the light receiving element 21 through the internal reference optical system 24 as internal reference light 28 ″. Since the processing of the received light signal when the reflected distance measuring light 28 'is received and the processing of the received light signal for the internal reference light 28' 'are the same, the following is the processing of the received light signal of the reflected distance measuring light 28'. Will be described.

  The light receiving element 21 alternately receives 240 MHz + 7.5 MHz pulse-modulated light and 240 MHz-7.5 MHz pulse-modulated light as the reflection distance measuring 28 ′. Therefore, the light receiving signal of the light receiving element 21 becomes a pulse output and the inside of the pulse becomes an intermittent light receiving signal 29 having frequencies of 240 MHz + 7.5 MHz and 240 MHz-7.5 MHz.

  FIG. 3B shows the generation state of the received light signal. In the light reception signal, a delay time (pulse delay) corresponding to the distance occurs between the light emission pulse.

  The received light signal is amplified by the amplifier 42, and the amplified signal is input to the mixing circuit 43. The mixing circuit 43 receives a reference frequency signal s1 of 240 MHz from the reference signal generator 31 via the AND circuit 48. The input timing of the reference frequency signal s1 is mixed with a light receiving signal (intermittent signal) of 240 MHz + 7.5 MHz pulse modulated light and a light receiving signal (intermittent signal) of 240 MHz-7.5 MHz pulse modulated light, respectively. Further, the timing signal is controlled by the timing signal from the timing signal generator 39.

  The frequency conversion is performed by mixing the light receiving signal of 240 MHz + 7.5 MHz pulse modulated light, the light receiving signal of pulse modulated light of 240 MHz-7.5 MHz and the reference frequency signal s1, and the frequency of ± 7.5 MHz and the added frequency 240 MHz + 240 MHz + 7. 5 MHz and a frequency of 240 MHz + 240 MHz-7.5 MHz are obtained. Further, the high-frequency component is removed through the low-pass filter 44, and a difference frequency of ± 7.5 MHz remains. The ± 7.5 MHz difference frequency signal corresponds to 240 MHz + 7.5 MHz pulse-modulated light and 240 MHz-7.5 MHz pulse-modulated light, and thus becomes a pulse-like difference frequency signal (intermittent conversion signal). ing.

  Further, of the two difference frequencies, one is a 7.5 MHz difference frequency signal whose phase advances in time, and the other is a 7.5 MHz difference frequency signal whose phase reverses in time (see FIG. 3 (E)). Therefore, a phase shift (phase difference) corresponding to the distance (time) occurs between the two difference frequencies.

  Here, the reference signal generator 31, the timing signal generator 39, the AND circuit 48, the mixing circuit 43 and the like function as a frequency conversion unit.

  Each difference frequency passes through the low-pass filter 44, is removed from the high frequency, and is input to the A / D converter 45. The band of the low-pass filter 44 is set to about 10 MHz, which is sufficient for the difference frequency of 7.5 MHz. After the conversion by the A / D converter 45, it is stored in a memory 46 as a storage means.

  FIG. 3E shows that the signal contained in the pulse is a signal having a difference frequency of 7.5 MHz by mixing in the mixing circuit 43.

  The signal stored in the memory 46 is read by the calculation control unit 47 for distance calculation, and the phase difference is calculated for each difference frequency signal. That is, the phase is obtained for each waveform of one cycle and each frequency of 240 MHz + 7.5 MHz and 240 MHz-7.5 MHz included in each pulse signal, and each phase is used for precision measurement. Further, a phase difference is detected for each of the two types of difference frequency signals and for each difference frequency of one cycle, and a phase difference between the two difference frequencies is obtained, and the phase difference is used for rough measurement. The calculation control unit 47 calculates the distance based on the speed of light using the phase for precise measurement and the phase difference for coarse measurement (see FIG. 3E).

  Further, by averaging the difference frequencies of the difference frequency of 7.5 MHz and the difference frequency of −7.5 MHz, a waveform having no phase shift at the starting point can be obtained. In addition, it is possible to perform highly accurate phase measurement by averaging the corresponding frequencies.

  The maximum measurement distances obtained from the phases of the respective frequencies of 240 MHz + 7.5 MHz and 240 MHz-7.5 MHz are 60.6 cm and 64.5 cm, respectively, and short-range and high-precision measurement is possible. Further, since the measurement time interval is extremely short, the distance of the moving body can be measured.

  Furthermore, the maximum measurement distance obtained from the phase difference between the ± 7.5 MHz difference frequencies is 10 m, and a medium distance measurement (coarse distance measurement) is possible. Therefore, high-precision distance measurement from short distance to medium distance by combining distance measurement by phase detection of 240MHz + 7.5MHz, 240MHz-7.5MHz and distance measurement by detection of phase difference between ± 7.5MHz difference frequency Is possible.

  In addition, the combination of distance measurement supplements the distance below the minimum unit of medium distance measurement (coarse measurement) with precision measurement, but the medium distance measurement value (coarse measurement distance value) and the precision distance measurement value If the difference is not within a predetermined value, a signal indicating that the measurement is abnormal may be issued. It can be determined that the measured value is abnormal, and the reliability of the measurement is improved.

  In addition, the circuit for calculating the phase and the circuit for calculating the distance based on the calculated phase are frequencies close to 240 MHz + 7.5 MHz and 240 MHz-7.5 MHz, and the ± 7.5 MHz difference frequency is the same difference frequency. A common processing circuit may be used. Therefore, the circuit configuration of the arithmetic control unit 47 is simplified.

  Furthermore, the measurement accuracy is similar at the adjacent frequencies of 240 MHz + 7.5 MHz and 240 MHz-7.5 MHz, and the distance measurement results measured at both frequencies can be used as data to be averaged. Thus, with a small circuit configuration, many distance measurement results can be averaged, and the measurement accuracy is improved.

  As described above, the distance measurement based on the phase and the phase difference is performed for each frequency, and the measurement results obtained for each frequency are averaged. Therefore, the distance measurement is performed according to the number of frequencies included in the pulse modulated light. The number of measurements is determined. Therefore, when the average number of times is increased to improve the accuracy of the measurement value, the pulse width may be widened to increase the number of times of measurement. The determination of the pulse width and the pulse interval can be changed by taking the measurement accuracy into consideration.

  Next, a case where long distance measurement is performed will be described.

  In long-distance measurement, the pulse-modulated light is processed as pulsed light, and distance measurement can be performed based on the round-trip time (delay time) of the pulsed light (TOF: Time of Flight).

  As shown in FIG. 4A, the pulse width of the pulse-modulated light is changed every predetermined time interval. For example, the normal pulse width is set to 933 ns, the pulse interval is set to 20 μs, and the pulse width is set to 800 ns every 160 μs interval, that is, for each pulse modulated light. 160 μs is 6.2 KHz and corresponds to a pulse delay time of 24 km. Although the pulse width may be narrowed or widened, the pulse that can be identified from other pulses is set as the reference pulse light.

  Thus, by detecting the reference pulse light, an intermittent pattern is formed that makes a round every 8 pulses (every 8 intermittent numbers). Needless to say, the intermittent number is set as appropriate.

  Since pulse-modulated light of 240 MHz + 7.5 MHz and 240 MHz-7.5 MHz are alternately emitted, the pulse interval itself is 10 μs.

  By detecting the delay time of the received light signal of the reference pulse light having a pulse width of 800 ns, it is possible to measure up to 24 km in both directions (see FIG. 4B). Since the emission interval of the reference pulse light can be set arbitrarily, it can be set as appropriate according to the required maximum distance.

  Furthermore, by forming an intermittent pattern, it integrates multiple times for each intermittent pattern, obtains an integrated waveform, specifies multiple adjacent frequencies from the intermittent width and intermittent period of the obtained integrated waveform, and determines each intermittent conversion signal An average phase may be obtained, a precise measurement value may be obtained from the average phase, a coarse measurement distance value may be obtained from the average phase difference, and a distance of the measurement object may be measured from the precise measurement value and the coarse measurement distance value.

  In the above embodiment, two adjacent frequencies are generated. However, three or more adjacent frequencies may be generated, or two or more sets of adjacent frequencies may be generated.

  FIG. 5A shows a light emission pattern in which the phase is shifted by 1/2 cycle every 240 MHz + 7.5 MHz and 240 MHz-7.5 MHz, and the received light signal shifted by 1/2 cycle is 240 MHz + 7.5 MHz, 240 MHz-7. Accurate phase measurement is possible by performing averaging for every 5 MHz (see FIG. 5B).

  As described above, in the present invention, all modulation frequencies are used for precision measurement and coarse measurement, so that the measurement efficiency is high and the measurement time is shortened. Furthermore, by using the ranging light as intermittent light, it is possible to concentrate only on the time during which the optical output is modulated, the peak power can be increased, and the light emission time is shortened, so the S / N is improved and the measurement accuracy is improved. Will improve.

  In addition, since the distance measurement is performed using the distance measuring light of two modulation frequencies which are close to each other, signal processing and distance calculation can be performed by a common processing circuit, and the circuit configuration is simplified.

  Furthermore, since continuous modulated waves are used as intermittent signals and emitted in pulses, the peak value of emitted ranging light can be increased, the amount of received light is increased, measurement accuracy is improved, and long-distance measurement is performed. It becomes possible.

  In addition, by emitting pulses, long distance measurement can be performed based on the round trip time of the pulsed light, and the light emission interval of the pulsed light that is the object of distance measurement can be arbitrarily set, so the maximum measurement distance can be measured. It can be easily changed according to the situation.

  In the above embodiment, two adjacent frequencies are generated. However, three or more adjacent frequencies may be generated, or two or more sets of adjacent frequencies may be generated.

  The period of the intermittent signal is set to a speed at which the phase change of the intermittent conversion signal due to the movement of the moving object is negligible when the measuring object is a moving object. Even if it exists, distance measurement becomes possible.

  In addition, an intermittent pattern that makes a cycle of intermittent modulation ranging light at a predetermined intermittent number is generated, and the intermittent conversion signal is integrated a plurality of times for each intermittent pattern, and from the intermittent width and intermittent period of the obtained integrated waveform, a plurality of proximity patterns are obtained. The frequency is specified, the average phase of each intermittent conversion signal is obtained, the precise measurement value is obtained from the average phase, the coarse measurement distance value is obtained from the average phase difference, and the measurement object is obtained from the precise measurement distance value and the coarse measurement distance value. Therefore, the intermittent number can be set as appropriate according to the required measurement accuracy.

  Also, the components on the electric circuit may correspond to one frequency, the circuit configuration is simplified, and the frequencies are close to each other, so only one filter with a low Q is sufficient, and the Q is low, so The influence on each phase shift is reduced, and abnormal measurement due to the shift between the precise measurement and the coarse measurement is less likely to occur.

  In addition, since distance measurement is performed with the delay time of the light reception pulse of intermittent modulation ranging light, long distance measurement is possible, the modulation frequency required for long distance measurement can be omitted, and the pulse light emission interval can be arbitrarily set Therefore, the maximum measurement distance can be easily changed according to the measurement situation.

  Further, when the difference between the precise measurement distance value and the rough measurement distance value obtained from a plurality of adjacent frequencies is not within a predetermined value, an abnormal signal is generated, so that the abnormal measurement value can be eliminated and the measurement reliability is improved.

  In addition, intermittent switching of multiple adjacent frequencies is performed with a predetermined period shifted for each frequency, and the phase conversion is performed after shifting the predetermined frequency of the intermittent conversion signal after frequency conversion. It becomes.

DESCRIPTION OF SYMBOLS 1 Distance measuring optical system 2 Emission optical system 3 Light receiving optical system 4 Collimating optical system 5 Measuring object 6 Distance measuring optical axis 7 Ejecting optical axis 8 Receiving optical axis 9 Collimating optical axis 11 Light emitting element 14 Light quantity adjuster 18 Dichroic mirror DESCRIPTION OF SYMBOLS 21 Light receiving element 24 Internal reference optical system 25 Optical path switch 27 Operation processing part 31 Reference signal generator 33 1st signal generator 34 2nd signal generator 35 1st intermittent pulse generator 36 2nd intermittent pulse generator 39 Timing signal Generator 43 Mixing circuit 47 Operation control unit

Claims (6)

A light emitting element that emits distance measuring light, a signal generator that generates a plurality of adjacent frequencies, a modulation signal that is intermittently pulsed to each of the plurality of adjacent frequencies, and pulsed to a predetermined width by the modulation signal An emission optical system that sequentially switches and emits the intermittent modulation ranging light for each proximity frequency, a light receiving unit that receives reflected ranging light from the measurement object, and generates an intermittent light reception signal having a predetermined pulse width; A reference signal generator that emits a reference frequency signal having a predetermined frequency difference, and frequency conversion of the intermittent light reception signal from the light receiving unit by mixing with the reference frequency signal, corresponding to each adjacent frequency signal, pulse A frequency conversion unit that obtains an intermittent conversion signal having a width; and an arithmetic control unit, wherein the pulse width of the intermittent light reception signal is set to be longer than the period of the intermittent conversion signal. It is, before Symbol arithmetic control unit calculates a precise measured distance for a plurality of proximate frequencies obtains a phase of the intermittent light signal, also the calculated coarse measurement distance value seeking phase difference between the intermittent converted signals mutually A light wave distance meter configured to measure a distance by combining the rough measurement distance value and the precision measurement distance value.   The intermittent modulation ranging light is generated with an intermittent pattern that makes a round with a predetermined number of intermittent pulses, the intermittent conversion signal is integrated multiple times for each intermittent pattern, and a plurality of proximity is obtained from the intermittent width and intermittent period of the obtained integrated waveform. Specify the frequency, determine the average phase of each intermittent conversion signal, determine the precise measurement distance value from the average phase, determine the coarse measurement distance value from the average phase difference between each of the intermittent conversion signals, precise measurement distance value, The light wave distance meter according to claim 1, wherein the distance of the measurement object is measured from the rough measurement distance value.   The light wave rangefinder according to claim 1, wherein the frequencies of the intermittent conversion signals corresponding to at least two of the plurality of adjacent frequencies are the same.   The lightwave distance meter according to claim 1, wherein the arithmetic control unit performs distance measurement based on a delay time of a light reception pulse of the intermittent modulation ranging light.   2. The optical rangefinder according to claim 1, wherein the arithmetic control unit generates an abnormal signal when a difference between a precision measurement distance value and a coarse measurement distance value obtained from a plurality of adjacent frequencies is not within a predetermined value.   2. The optical distance meter according to claim 1, wherein intermittent switching of a plurality of adjacent frequencies is performed with a predetermined period shifted for each frequency, and the phase conversion is performed after shifting the intermittent conversion signal subjected to frequency conversion by a predetermined period. .

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