Lightwave distance meter

Abstract

To provide a light wave distance meter with which it is possible to improve the rejection ratio of errors of measured distance values.SOLUTION: The light wave distance meter comprises a ranging light emission unit, a received light signal generation unit for generating a received light signal, and a control computation unit for computing the distance to a measurement object. The received light signal includes a first intermittent received light signal 411 corresponding to first ranging light, a second intermittent received light signal 412 corresponding to second ranging light, a third intermittent received light signal 413 corresponding to third ranging light, and a fourth intermittent received light signal 414 corresponding to fourth ranging light. The control computation unit executes error determination control for acquiring shift signals 413b, 414b derived by shifting the phase of at least one of the first to fourth intermittent received light signals by 2π*n-π / 2 or 2π*n+π / 2 and comparing the phases of the shift signals 413b, 414b and the phases of intermittent received light signals 411a, 412a with each other in either a first or a second frequency.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to an optical distance meter that generates a signal having a desired phase difference with respect to a reference signal. [Background technology]

[0002] Conventionally, there has been known an optical distance meter that switches an intermittently modulated signal, which is a pulse of a plurality of adjacent frequencies, for each adjacent frequency to cause a light-emitting element to emit light, and receives reflected distance-measuring light from an object to be measured with a light-receiving element (see, for example, Patent Document 1, Patent Document 2, and Patent Document 3).

[0003] For example, the optical distance meter disclosed in Patent Document 1 calculates a precisely measured distance value by determining the phase of intermittently received light signals corresponding to multiple nearby frequencies, calculates a coarsely measured distance value from the phase difference between each intermittently received light signal, and measures the distance by combining the coarsely measured distance value and the precisely measured distance value.

[0004] However, when the object to be measured has a step or a slope, the electronic distance meters described in Patent Documents 1 to 3 may produce errors in the measured distance value, and may not be able to completely eliminate the errors in the measured distance value. In this respect, there is room for improvement in the electronic distance meters described in Patent Documents 1 to 3. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6410258 [Patent Document 2] Patent No. 6841726 [Patent Document 3] Japanese Patent Application Publication No. 2018-169371 Summary of the Invention [Problem to be solved by the invention]

[0006] SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has as its object to provide an electronic distance meter that can improve the rate of eliminating errors in measured distance values. [Means for solving the problem]

[0007] The object is to provide a distance measuring device comprising: a distance measuring light emitting unit having a light emitting element and emitting distance measuring light by driving the light emitting element; a light receiving signal generating unit having a light receiving element that receives reflected light from an object to be measured and emits a light receiving signal; and a control and calculation unit that calculates the distance to the object to be measured based on the light receiving signal, wherein the distance measuring light emitting unit includes a reference signal generator that generates a reference frequency signal that is a continuous signal of a predetermined reference frequency, and a control and calculation unit that generates a first modulated signal modulated at a first frequency by the reference frequency signal and a second modulated signal modulated at a second frequency close to the first frequency. a frequency divider that generates a first pulse modulated signal by pulsing the first modulated signal and a second pulse modulated signal by pulsing the second modulated signal; a phase shifter that generates a third pulse modulated signal by shifting the first pulse modulated signal by a time corresponding to 2π·n-π / 2 or 2π·n+π / 2 and a fourth pulse modulated signal by shifting the second pulse modulated signal by a time corresponding to 2π·n-π / 2 or 2π·n+π / 2; the light-emitting element is configured to emit a first distance measurement light based on the first pulse modulated signal, a second distance measurement light based on the second pulse modulated signal, a third distance measurement light based on the third pulse modulated signal, and a fourth distance measurement light based on the fourth pulse modulated signal in a time-division alternating manner, the light-receiving signals including a first intermittent light-receiving signal corresponding to the first distance measurement light, a second intermittent light-receiving signal corresponding to the second distance measurement light, a third intermittent light-receiving signal corresponding to the third distance measurement light, and a fourth intermittent light-receiving signal corresponding to the fourth distance measurement light, and the control and calculation unit obtains a shifted signal obtained by shifting the phase of at least one of the first to fourth intermittent light-receiving signals by 2π·n-π / 2 or 2π·n+π / 2, and performs error determination control to compare the phase of the shifted signal with the phase of the intermittent light-receiving signal at least between the first frequencies and between the second frequencies.

[0008] In the electronic distance meter according to the present invention, the control and calculation unit acquires a shift signal obtained by shifting the phase of at least one of the following by 2π·n-π / 2 or 2π·n+π / 2: a first intermittent light-receiving signal corresponding to the first distance-measuring light emitted in response to the first pulse-modulated signal, a second intermittent light-receiving signal corresponding to the second distance-measuring light emitted in response to the second pulse-modulated signal, a third intermittent light-receiving signal corresponding to the third distance-measuring light emitted in response to the third pulse-modulated signal shifted by a time equivalent to 2π·n-π / 2 or 2π·n+π / 2, and a fourth intermittent light-receiving signal corresponding to the fourth distance-measuring light emitted in response to the fourth pulse-modulated signal shifted by a time equivalent to 2π·n-π / 2 or 2π·n+π / 2. As a result, if the object to be measured does not have a step, no time-series change occurs in the phase of the acquired data, and the phase of the shift signal matches the phase of the intermittent light-receiving signals, which are modulated at the same frequency. Therefore, the control and calculation unit executes error determination control to compare the phase of the shift signal with the phase of the intermittently received light signal modulated at the same frequency. In this way, the electronic distance meter according to the present invention uses data with phases that are spaced apart in time series for error determination, thereby improving the accuracy of error determination and increasing the rate of error removal in measured distance values.

[0009] In the optical distance meter according to the present invention, it is preferable that the control and calculation unit compares the phase of the shift signal obtained by frequency analyzing the central part of the signal width of the intermittent light receiving signal from which the shift signal is obtained with the phase of the intermittent light receiving signal obtained by frequency analyzing the central part of the signal width of the intermittent light receiving signal.

[0010] According to the electronic distance meter of the present invention, the control and calculation unit can compare the phase of the shift in the relatively clean stable region with the phase of the intermittent light receiving signal in the relatively clean stable region, thereby further improving the accuracy of error determination and the rate of error elimination in the measured distance value.

[0011] In the electronic distance meter according to the present invention, it is preferable that the control and calculation unit executes control to remove the intermittent light receiving signal when the phase difference between the phase of the shift signal and the phase of the intermittent light receiving signal is equal to or greater than a predetermined threshold value.

[0012] According to the electronic distance meter of the present invention, the control and calculation unit eliminates the intermittent light-receiving signal when the phase difference between the phase of the shift signal and the phase of the intermittent light-receiving signal is equal to or greater than a predetermined threshold. Therefore, the electronic distance meter of the present invention can more efficiently eliminate errors in the measured distance value by using valid light-receiving signals whose phase difference between the phase of the shift signal and the phase of the intermittent light-receiving signal is less than the predetermined threshold, and eliminating light-receiving signals whose phase difference between the phase of the shift signal and the phase of the intermittent light-receiving signal is equal to or greater than the predetermined threshold.

[0013] In the control and calculation unit according to the present invention, the control and calculation unit preferably sets the predetermined threshold value in accordance with the distance to the object to be measured.

[0014] According to the electronic distance meter of the present invention, the control and calculation unit uses a predetermined threshold value set according to the distance to the object to be measured, and uses valid received light signals whose phase difference between the phase of the shift signal and the phase of the intermittent received light signal is less than the predetermined threshold value, while eliminating received light signals whose phase difference between the phase of the shift signal and the phase of the intermittent received light signal is equal to or greater than the predetermined threshold value, thereby enabling the electronic distance meter of the present invention to more efficiently eliminate errors in the measured distance value.

[0015] In the control calculation unit of the present invention, it is preferable that the control calculation unit executes control to align the center position of the first intermittent light receiving signal and the third intermittent light receiving signal with the center position of the second intermittent light receiving signal and the fourth intermittent light receiving signal.

[0016] According to the control calculation unit of the present invention, the center position of the first intermittent light receiving signal and the third intermittent light receiving signal coincides with the center position of the second intermittent light receiving signal and the fourth intermittent light receiving signal, so the electronic distance meter of the present invention can prevent errors from occurring in the acquired data. [Effects of the Invention]

[0017] According to the present invention, it is possible to provide an electronic distance meter that can improve the rate of eliminating errors in measured distance values. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a block diagram showing a schematic configuration of an electronic distance meter according to an embodiment of the present invention; [Figure 2] 3A and 3B are explanatory diagrams showing a pulse-modulated signal and an intermittent light-receiving signal according to the present embodiment. [Figure 3] FIG. 10 is a schematic diagram illustrating a case where the object to be measured has a step. [Figure 4] FIG. 4 is a schematic diagram showing an example of a light reception signal according to the present embodiment. [Figure 5] 5 is a schematic diagram illustrating error determination control executed by a control calculation unit according to the present embodiment. FIG. [Figure 6] FIG. 10 is a schematic diagram illustrating a case where the object to be measured has an inclination. DETAILED DESCRIPTION OF THE INVENTION

[0019] Preferred embodiments of the present invention will now be described in detail with reference to the drawings. The embodiments described below are preferred examples of the present invention, and therefore various technically preferable limitations are applied thereto, but the scope of the present invention is not limited to these aspects unless otherwise specified in the following description to the effect that the present invention is particularly limited. Furthermore, in each drawing, similar components are designated by the same reference numerals, and detailed descriptions thereof will be omitted as appropriate.

[0020] FIG. 1 is a block diagram showing a schematic configuration of an electronic distance meter according to an embodiment of the present invention. FIG. 2 is an explanatory diagram showing a pulse modulated signal and an intermittent light receiving signal according to this embodiment.

[0021] In recent years, in order to ensure the amount of received light, a burst light emission method has been adopted in electronic distance meters, in which light intensity is increased and light is emitted intermittently (burst light emission) so that the light emission load rate is below a predetermined value. As will be explained below, the electronic distance meter 20 according to this embodiment is an electronic distance meter that employs the burst light emission method.

[0022] In the electronic distance meter 20 according to this embodiment, the reference signal generator 40 generates a reference frequency signal s1 with a predetermined reference frequency fc. The values ​​shown below can be changed as appropriate depending on the measurement distance and measurement accuracy. For example, in the following description, the reference frequency fc is set to 120 MHz.

[0023] The reference frequency signal s1 generated by the reference signal generator 40 is divided by the first frequency divider 42a and the second frequency divider 42b to generate a frequency-divided signal with a frequency f by dividing the reference frequency fc by n. If the frequency f is fc / n and the first frequency divider 42a and the second frequency divider 42b are each frequency dividers that divide the 120 MHz reference frequency fc by 1 / 16, the frequency f will be 7.5 MHz.

[0024] The first frequency divider 42a generates a first modulated signal modulated at fc-f [Hz] (120-7.5 MHz in this embodiment) using the divided frequency signal and the reference frequency signal s1. The first frequency divider 42a also pulses the continuous first modulated signal, converting it into a first pulse modulated signal s2, an intermittent signal generated at predetermined time intervals. Therefore, the pulses of the first pulse modulated signal s2 contain a frequency of fc-f (120 MHz-7.5 MHz). For example, the first pulse modulated signal s2 becomes a signal with a cosine waveform based on the position at which the first modulated signal is pulsed. The first frequency divider 42a then outputs the first pulse modulated signal s2 to the light-emitting element drive circuit 32 and the first phase shifter 43a. The fc-f [Hz] (120-7.5 MHz) in this embodiment is an example of the "first frequency" in the present invention.

[0025] The second frequency divider 42b generates a second modulated signal modulated at fc+f [Hz] (120+7.5 MHz in this embodiment) using the divided frequency signal and the reference frequency signal s1. The second frequency divider 42b also pulses the continuous second modulated signal, converting it into a second pulse modulated signal s3, which is an intermittent signal generated at predetermined time intervals. Therefore, the pulses of the second pulse modulated signal s3 contain a frequency of fc+f (120 MHz+7.5 MHz). For example, the second pulse modulated signal s3 becomes a signal with a cosine waveform based on the position at which the second modulated signal is pulsed. The second frequency divider 42b then outputs the second pulse modulated signal s3 to the light-emitting element drive circuit 32 and the second phase shifter 43b. In this embodiment, fc+f [Hz] (120+7.5 MHz) is an example of the "second frequency" of the present invention.

[0026] In this way, the first frequency divider 42a and the second frequency divider 42b generate two modulated signals with close frequencies, fc+f [Hz] and fc-f [Hz], and also generate a pulse modulated signal by pulsing the modulated signal.

[0027] First phase shifter 43a calculates a shift time corresponding to the phase difference based on first pulse modulated signal s2 and the set phase difference, and generates third pulse modulated signal s4 by shifting first pulse modulated signal s2 by the set shift time in the set shift direction, and outputs the third pulse modulated signal s4 to light-emitting element drive circuit 32. In this embodiment, first phase shifter 43a shifts first pulse modulated signal s2 by a time corresponding to a -π / 2 (-90°) phase to generate third pulse modulated signal s4, and outputs the third pulse modulated signal s4 to light-emitting element drive circuit 32. Like first pulse modulated signal s2, third pulse modulated signal s4 contains a frequency of fc-f [Hz] (120-7.5 MHz in this embodiment). Because third pulse modulated signal s4 is a signal obtained by shifting first pulse modulated signal s2 by a time corresponding to a -π / 2 (-90°) phase, it becomes, for example, a signal having a sin waveform depending on the position at which third pulse modulated signal s4 is pulsed.

[0028] Second phase shifter 43b calculates a shift time corresponding to the phase difference based on second pulse modulation signal s3 and the set phase difference, and generates fourth pulse modulation signal s5 by shifting second pulse modulation signal s3 by the set shift time in the set shift direction, and outputs the fourth pulse modulation signal s5 to light-emitting element drive circuit 32. In this embodiment, second phase shifter 43b generates fourth pulse modulation signal s5 by shifting second pulse modulation signal s3 by a time corresponding to a π / 2 (90°) phase, and outputs the fourth pulse modulation signal s5 to light-emitting element drive circuit 32. Like second pulse modulation signal s3, fourth pulse modulation signal s5 contains a frequency of fc+f [Hz] (120+7.5 MHz in this embodiment). Because fourth pulse modulation signal s5 is a signal obtained by shifting second pulse modulation signal s3 by a time corresponding to a π / 2 (90°) phase, it becomes a signal having a −sin waveform, for example, based on the position at which fourth pulse modulation signal s5 is pulsed.

[0029] The shift time by which each of the first phase shifter 43a and the second phase shifter 43b shifts is not limited to a time corresponding to a phase of ±π / 2 (±90°), but may be a time corresponding to a phase expressed by the following formula: Formula: 2π n+k 2π / a (n=natural number, k=1,2,...,a, a=constant)

[0030] For example, first phase shifter 43a generates third pulse modulated signal s4 by shifting first pulse modulated signal s2 by a time equivalent to 2π·n-π / 2 or 2π·n+π / 2. Furthermore, for example, second phase shifter 43b generates fourth pulse modulated signal s5 by shifting second pulse modulated signal s3 by a time equivalent to 2π·n-π / 2 or 2π·n+π / 2. The following description will be given as an example in which first phase shifter 43a generates third pulse modulated signal s4 by shifting first pulse modulated signal s2 by a time equivalent to a -π / 2 (-90°) phase, and second phase shifter 43b generates fourth pulse modulated signal s5 by shifting second pulse modulated signal s3 by a time equivalent to a π / 2 (90°) phase.

[0031] The light-emitting element drive circuit 32 causes the light-emitting element 21 to emit burst light (intermittent light) using a light-emitting drive signal including the first pulse-modulated signal s2, the second pulse-modulated signal s3, the third pulse-modulated signal s4, and the fourth pulse-modulated signal s5. 32 drives the light emitting element 21 with a light emission drive signal including a first pulse modulated signal s2 generated based on a first modulated signal modulated at 120-7.5 MHz, a second pulse modulated signal s3 generated based on a second modulated signal modulated at 120+7.5 MHz, a third pulse modulated signal s4 modulated at 120-7.5 MHz and time shifted by a phase of -90°, and a fourth pulse modulated signal s5 modulated at 120+7.5 MHz and time shifted by a phase of 90°. The light emitting element drive circuit 32 of this embodiment is an example of the "light emitting drive unit" of the present invention.

[0032] The light-emitting element 21 (e.g., a laser diode: LD) is driven by a light-emitting element drive circuit 32 and emits a laser beam whose intensity is modulated to a predetermined frequency. The laser beam is split by a half mirror (not shown) into distance-measuring beams 23a and 23b and an internal reference beam. The distance-measuring beams 23a and 23b that pass through the half mirror are irradiated onto a measurement object (not shown) through an objective lens (not shown). The reflected distance-measuring beams 23a' and 23b' that are reflected by the measurement object are received by a light-receiving element 27 through the objective lens and half mirror. Note that a photodiode, for example, an avalanche photodiode (APD), is used as the light-receiving element 27.

[0033] The light-emitting element 21, the light-emitting element drive circuit 32, etc. constitute the "distance measuring light emitting section" of the present invention. The light-receiving element 27, the light-receiving circuit 33, etc. constitute the "light-receiving signal generating section" of the present invention.

[0034] For example, as shown in Fig. 2A, the burst light emission period (burst period) is 10 µs (100 kHz), and the burst light emission time is 266 ns.

[0035] Furthermore, the light-emitting element drive circuit 32 alternately emits light in a time-division manner based on a first pulse modulation signal s2 of 120 MHz - 7.5 MHz (cos component), a second pulse modulation signal s3 of 120 MHz + 7.5 MHz (cos component), a third pulse modulation signal s4 of 120 MHz - 7.5 MHz (sine component) that is time-shifted by a -90° phase, and a fourth pulse modulation signal s5 of 120 MHz + 7.5 MHz (sine component) that is time-shifted by a 90° phase (see FIG. 2(A)).

[0036] Compared to the first pulse modulated signal s2 of 120 MHz - 7.5 MHz and the second pulse modulated signal s3 of 120 MHz + 7.5 MHz shown in FIG. 2(A), the third pulse modulated signal s4 of 120 MHz - 7.5 MHz and the fourth pulse modulated signal s5 of 120 MHz + 7.5 MHz, which are issued with a delay, are modulated signals that are shifted in time by -90° phase and 90° phase, respectively.

[0037] Therefore, the light emitting element 21 emits distance measurement light 23a modulated at 120 MHz - 7.5 MHz and 120 MHz - 7.5 MHz with the time shifted by -90° phase, and distance measurement light 23b modulated at 120 MHz + 7.5 MHz and 120 MHz + 7.5 MHz with the time shifted by 90° phase, alternately in bursts at a burst emission period (10 μs) by time division.

[0038] As described above, the laser beam emitted from the light-emitting element 21 is split by a half mirror (not shown) into distance measurement beams 23a and 23b and internal reference beam. The signal processing for the distance measurement beams 23a and 23b is the same as the signal processing for the internal reference beam. Therefore, the following description will focus on the distance measurement beams 23a and 23b.

[0039] 1, reflected distance-measuring lights 23a' and 23b' are incident on the light-receiving element 27. As shown in Fig. 2(B), intermittent light-receiving signals 41a and 41b are alternately emitted from the light-receiving element 27. The intermittent light-receiving signals 41a and 41b correspond to the distance-measuring lights 23a and 23b.

[0040] That is, the reflected distance-measuring light 23a' is pulse-modulated light based on the first pulse-modulated signal s2 and the third pulse-modulated signal s4 of fc-f (120 MHz-7.5 MHz). Therefore, the light-receiving signal emitted from the light-receiving element 27 is a pulse output, and the inside of the pulse is an intermittent light-receiving signal 41a having a frequency of fc-f (120 MHz-7.5 MHz). Also, the reflected distance-measuring light 23b' is pulse-modulated light based on the second pulse-modulated signal s3 and the fourth pulse-modulated signal s5 of fc+f (120 MHz+7.5 MHz). Therefore, the light-receiving signal emitted from the light-receiving element 27 is a pulse output, and the inside of the pulse is an intermittent light-receiving signal 41b having a frequency of fc+f (120 MHz+7.5 MHz).

[0041] The intermittent photodetection signal 41a is a photodetection signal having a signal width of 266 ns and including 120 MHz - 7.5 MHz and 120 MHz - 7.5 MHz which is phase-shifted by -π / 2 (-90°).Similarly, the intermittent photodetection signal 41b is a photodetection signal having a signal width of 266 ns and including 120 MHz + 7.5 MHz and 120 MHz + 7.5 MHz which is phase-shifted by π / 2 (90°).

[0042] As mentioned above, the light emitting element 21 has a light emission cycle of 10 μs (100 kHz). Therefore, the generation cycle (generation interval) of the intermittent light receiving signals 41a and 41b is 10 μs. The light emission interval is set to be sufficiently longer than the time it takes for the distance measuring light to travel to and from the object to be measured, and is set appropriately to correspond to the required maximum distance measurement distance.

[0043] The intermittent light receiving signals 41a and 41b are amplified by amplifier 49 and mixed with a 120 MHz reference frequency signal in mixing circuit 46 to become +7.5 MHz and −7.5 MHz intermittent modulated signals. The ±7.5 MHz intermittent modulated signals are amplified by amplifier 44 and output to light receiving circuit 33.

[0044] Of the ±7.5 MHz intermittent modulated signals, those that have been time-shifted by ±90° phase are subjected to signal processing (restoration processing) by the photodetector circuit 33, which advances the intermittent received signal, which is delayed in time by ±90°, by ±90°. The ±7.5 MHz intermittent modulated signal is also subjected to the required signal processing, such as A / D conversion, by the photodetector circuit 33, and then input to the control and calculation unit 37. By performing restoration processing on the ±7.5 MHz intermittent modulated signal that has been time-shifted by ±90° phase, the ±7.5 MHz and the ±7.5 MHz signal with a different phase are input without any time delay.

[0045] The control and calculation unit 37 executes various programs stored in the storage unit 38 and performs necessary calculations for distance measurement. The control and calculation unit 37 also controls the light-emitting element drive circuit 32 and controls the light-emitting state of the light-emitting element 21 via the light-emitting element drive circuit 32. The control and calculation unit 37 also switches between the reflected distance-measuring light 23a', 23b' and the internal reference light incident on the light-receiving element 27.

[0046] Furthermore, the control and calculation unit 37 calculates the distance by determining the phase difference (light-receiving time difference) between the internal reference light and the reflected distance-measuring light 23a', 23b' from the light-receiving signal. Also, by determining the phase difference between the internal reference light and the reflected distance-measuring light 23a', 23b', the control and calculation unit 37 eliminates unstable elements in the circuit, such as drift of the light-receiving circuit 33. Details of the operation of the control and calculation unit 37 in this embodiment will be described later.

[0047] The memory unit 38 stores various programs for calculations required for measurement. For example, a signal processing program for performing signal processing such as amplifying and A / D converting the signal output from the light receiving element 27, a calculation program for performing a discrete Fourier transform (DFT) on the burst signal, a program for converting the result of the DFT into phase and amplitude, and a calculation program for extracting the phase and amplitude of the primary frequency, secondary frequency, etc. obtained by performing the DFT are stored in the memory unit 38. The memory unit 38 also stores various data such as distance measurement results and calculation results.

[0048] The main control unit 39 controls the distance measurement operation of the electronic distance meter 20 and also controls the calculation processing of the control and calculation unit 37. The main control unit 39 and the control and calculation unit 37 may be integrated into one control unit.

[0049] An internal reference light including 120 MHz + 7.5 MHz and 120 MHz + 7.5 MHz time-shifted by a phase of 90°, and an internal reference light including 120 MHz - 7.5 MHz and 120 MHz - 7.5 MHz time-shifted by a phase of -90°, are time-divisionally incident on the light receiving element 27. The light receiving signal emitted from the light receiving element 27 upon which the internal reference light is incident is also processed in the same way as the distance measuring lights 23 a and 23 b.

[0050] The optical path length of the internal reference light is constant. Therefore, when circuits such as the light-receiving circuit 33 are stable, the timing of generating the light-emission drive signal and the timing of generating the light-receiving signal that the light-receiving circuit 33 receives and emits after receiving the internal reference light are fixed. Therefore, when circuits such as the light-receiving circuit 33 are stable, the relationship between the timing of generating the intermittent light-receiving signal that the light-receiving circuit 33 receives and emits after receiving the internal reference light and the timing of generating the light-emission drive signal is also fixed. Therefore, the light-receiving signal of the internal reference light that the light-receiving circuit 33 emits is a signal based on the light-emission drive signal.

[0051] Therefore, the light emitting drive signal generated by the light emitting element drive circuit 32 may be used as a reference signal.

[0052] Next, the operation of the control calculation unit 37 of this embodiment will be described with reference to the drawings. FIG. 3 is a schematic diagram illustrating a case where the object to be measured has a step. FIG. 4 is a schematic diagram showing an example of a light reception signal according to this embodiment. FIG. 5 is a schematic diagram illustrating the error determination control executed by the control calculation unit of this embodiment.

[0053] An example of the operation of the control and calculation unit 37 when the measurement object 70 has a step will be described with reference to FIGS. In the following explanation, for convenience of explanation, the distance measurement light 23a emitted from the light-emitting element 21 based on the first pulse modulation signal s2 of 120 MHz - 7.5 MHz (cos component) will be referred to as "first distance measurement light 231." The distance measurement light 23b emitted from the light-emitting element 21 based on the second pulse modulation signal s3 of 120 MHz + 7.5 MHz (cos component) will be referred to as "second distance measurement light 232." The distance measurement light 23a emitted from the light-emitting element 21 based on the third pulse modulation signal s4 of 120 MHz - 7.5 MHz (sine component) shifted in time by -90° phase will be referred to as "third distance measurement light 233." The distance measurement light 23b emitted from the light-emitting element 21 based on the fourth pulse modulation signal s5 of 120 MHz + 7.5 MHz (sine component) shifted in time by 90° phase will be referred to as "fourth distance measurement light 234."

[0054] 2A, the first distance measurement light 231, the second distance measurement light 232, the third distance measurement light 233, and the fourth distance measurement light 234 are alternately emitted in this order from the light-emitting element 21. After the fourth distance measurement light 234 is emitted, the first distance measurement light 231, the second distance measurement light 232, the third distance measurement light 233, and the fourth distance measurement light 234 are alternately emitted again in this order from the light-emitting element 21. Therefore, the first distance measurement light 235 shown in FIG. 3 corresponds to the first distance measurement light 231. In the example shown in FIG. 3, the electronic distance meter 20 scans the distance measurement light from left to right across the measurement object 70.

[0055] In the following description, the light receiving signal corresponding to the first distance measurement light 231 will be referred to as the "first intermittent light receiving signal 411." The light receiving signal corresponding to the second distance measurement light 232 will be referred to as the "second intermittent light receiving signal 412." The light receiving signal corresponding to the third distance measurement light 233 will be referred to as the "third intermittent light receiving signal 413." The light receiving signal corresponding to the fourth distance measurement light 234 will be referred to as the "fourth intermittent light receiving signal 414." Since each light receiving signal corresponds to a respective distance measurement light, the first intermittent light receiving signal 411, second intermittent light receiving signal 412, third intermittent light receiving signal 413, and fourth intermittent light receiving signal 414 are alternately emitted in this order from the light receiving element 27, as shown in FIG. 4 . Since the first distance measurement light 235 corresponds to the first distance measurement light 231 , the first intermittent light receiving signal 415 corresponding to the first distance measurement light 235 corresponds to the first intermittent light receiving signal 411 .

[0056] 4, the control and calculation unit 37 of this embodiment acquires a comparison signal 411a from the light reception signal in the center portion of the signal width (266 ns in this embodiment) of the first intermittent light reception signal 411. Similarly, the control and calculation unit 37 acquires a comparison signal 412a from the light reception signal in the center portion of the signal width of the second intermittent light reception signal 412. The control and calculation unit 37 acquires a comparison signal 413a from the light reception signal in the center portion of the signal width of the third intermittent light reception signal 413. The control and calculation unit 37 acquires a comparison signal 414a from the light reception signal in the center portion of the signal width of the fourth intermittent light reception signal 414.

[0057] Furthermore, the control and calculation unit 37 of this embodiment acquires a shift signal obtained by shifting the phase of at least one of the first to fourth intermittent light-receiving signals 411, 412, 413, and 414 by -π / 2 or π / 2. In the example shown in Fig. 5, the control and calculation unit 37 acquires a shift signal 413b obtained by shifting the phase of the comparison signal 413a by π / 2 (90°) from the light-receiving signal in the center part of the signal width of the third intermittent light-receiving signal 413. Similarly, the control and calculation unit 37 acquires a shift signal 414b obtained by shifting the phase of the comparison signal 414a by -π / 2 (-90°) from the light-receiving signal in the center part of the signal width of the fourth intermittent light-receiving signal 414.

[0058] The control and calculation unit 37 then executes error determination control to compare the phase of the shifted signal 413b, which has been modulated at the same frequency of 120 MHz-7.5 MHz, with the phase of the comparison signal 411a. Specifically, the control and calculation unit 37 executes error determination control to compare the phase of the shifted signal 413b, which has been determined by frequency analyzing the central portion of the signal width (i.e., the stable region) of the third intermittent light-receiving signal 413, with the phase of the comparison signal 411a, which has been determined by frequency analyzing the central portion of the signal width (i.e., the stable region) of the first intermittent light-receiving signal 411, both at the same frequency of 120 MHz-7.5 MHz. As shown in FIG. 3, the measurement points P1 and P3 are located on the same plane within the measurement object 70. In this case, since there is no time-series change in the phase of the acquired data, as shown in FIG. 5, the phase of the shift signal 413b obtained by frequency analyzing the central part of the signal width (i.e., the stable region) of the third intermittent light-receiving signal 413 matches the phase of the comparison signal 411a obtained by frequency analyzing the central part of the signal width (i.e., the stable region) of the first intermittent light-receiving signal 411.

[0059] In response to this, the control and calculation unit 37 executes error determination control to compare the phase of the shifted signal 414b and the phase of the comparison signal 412a, both of which are modulated at the same frequency of 120 MHz + 7.5 MHz. Specifically, the control and calculation unit 37 executes error determination control to compare the phase of the shifted signal 414b, which is obtained by frequency analyzing the central portion of the signal width (i.e., the stable region) of the fourth intermittent light-receiving signal 414, with the phase of the comparison signal 412a, which is obtained by frequency analyzing the central portion of the signal width (i.e., the stable region) of the second intermittent light-receiving signal 412, both of which are modulated at the same frequency of 120 MHz + 7.5 MHz. As shown in FIG. 3, there is a step in the measurement object 70 between measurement point P2 and measurement point P4. As a result, a time-series change occurs in the phase of the acquired data, and as shown in Figure 5, the phase of the shift signal 414b obtained by frequency analysis of the central part of the signal width (i.e., the stable region) of the fourth intermittent light-receiving signal 414 does not match the phase of the comparison signal 412a obtained by frequency analysis of the central part of the signal width (i.e., the stable region) of the second intermittent light-receiving signal 412.

[0060] The control and calculation unit 37 then executes control to remove the intermittent light-receiving signal when the phase difference between the shift signal and the intermittent light-receiving signal is equal to or greater than a predetermined threshold. The control and calculation unit 37 also sets the predetermined threshold in accordance with the distance to the measurement object 70. The control and calculation unit 37 of this embodiment sequentially executes such error determination control.

[0061] Note that the phase of the shift signal 413b acquired by the control and calculation unit 37 may be inverted relative to the phase of the comparison signal 411a. That is, the phase of the shift signal 413b acquired by the control and calculation unit 37 may be shifted by π (180°) relative to the phase of the comparison signal 411a. For example, the shift signal 413b may have a −cosine waveform, and the comparison signal 411a may have a cosine waveform. In this case, the control and calculation unit 37 inverts the phase of either the shift signal 413b or the comparison signal 411a, and performs error determination control by comparing the phase of either the phase-inverted shift signal 413b or the comparison signal 411a with the phase of the other phase-uninverted shift signal 413b or the comparison signal 411a. This allows the control and calculation unit 37 to perform error determination control similar to the error determination control described above. The same applies to the error determination control that compares the phase of the shift signal 414b with the phase of the comparison signal 412a.

[0062] In the example shown in FIG. 5 , the control and calculation unit 37 acquires the shift signal 413b from the third intermittent light-receiving signal 413. Alternatively, the control and calculation unit 37 may acquire a shift signal obtained by shifting the phase of the comparison signal 411a by −π / 2 (−90°) from the light-receiving signal in the center portion of the signal width of the first intermittent light-receiving signal 411. In this case, the control and calculation unit 37 performs error determination control by comparing the phase of the shift signal with the phase of the comparison signal 413a. Furthermore, the control and calculation unit 37 acquires the shift signal 414b from the fourth intermittent light-receiving signal 414. Alternatively, the control and calculation unit 37 may acquire a shift signal obtained by shifting the phase of the comparison signal 412a by π / 2 (90°) from the light-receiving signal in the center portion of the signal width of the second intermittent light-receiving signal 412. In this case, the control and calculation unit 37 performs error determination control by comparing the phase of the shift signal with the phase of the comparison signal 414a.

[0063] In the electronic distance meter 20 according to this embodiment, the control and calculation unit 37 acquires shift signals 413b, 414b obtained by shifting the phase of at least one of the following (the third and fourth intermittent light reception signals 413, 414 in this embodiment): the first intermittent light reception signal 411 corresponding to the first distance measurement light 231 emitted in response to the first pulse modulation signal s2; the second intermittent light reception signal 412 corresponding to the second distance measurement light 232 emitted in response to the second pulse modulation signal s3; the third intermittent light reception signal 413 corresponding to the third distance measurement light 233 emitted in response to the third pulse modulation signal s4 shifted by a time equivalent to 2π·n-π / 2 or 2π·n+π / 2; and the fourth intermittent light reception signal 414 corresponding to the fourth distance measurement light 234 emitted in response to the fourth pulse modulation signal s5 shifted by a time equivalent to 2π·n-π / 2 or 2π·n+π / 2) by 2π·n-π / 2 or 2π·n+π / 2. As a result, when the measurement target 70 does not have a step, the phase of the acquired data does not change over time, and the phases of the shift signals 413b and 414b match the phases of the intermittent light receiving signals modulated at the same frequency (comparison signals 411a and 412a of the first and second intermittent light receiving signals 411 and 412 in this embodiment). Therefore, the control and calculation unit 37 executes error determination control to compare the phases of the shift signals 413b and 414b with the phases of the intermittent light receiving signals modulated at the same frequency (comparison signals 411a and 412a of the first and second intermittent light receiving signals 411 and 412 in this embodiment). In this way, the electronic distance meter 20 according to this embodiment uses data with phases spaced apart over time for error determination, thereby improving the accuracy of error determination and increasing the rate of error removal in the measured distance value.

[0064] Furthermore, the control and calculation unit 37 compares the phases of the shift signals 413b and 414b, which are obtained by performing frequency analysis on the central portion of the signal width (266 ns in this embodiment), with the phases of the first and second intermittent light-receiving signals 411 and 412, which are obtained by performing frequency analysis on the central portion of the signal width (266 ns in this embodiment). Therefore, the control and calculation unit 37 can compare the phases of the shift signals 413b and 414b in a relatively clean stable region with the phases of the first and second intermittent light-receiving signals 411 and 412 in a relatively clean stable region. This allows the electronic distance meter 20 according to this embodiment to further improve the accuracy of error determination and further improve the rate of error removal in measured distance values.

[0065] Furthermore, the control and calculation unit 37 removes the intermittent light receiving signals (the second intermittent light receiving signal 412 and the fourth intermittent light receiving signal 414 in this embodiment) when the phase difference between the phase of the shift signals 413b, 414b and the phase of the first and second intermittent light receiving signals 411, 412 is equal to or greater than a predetermined threshold. Therefore, the electronic distance meter 20 according to this embodiment can more efficiently remove errors in the measured distance value by using valid light receiving signals in which the phase difference between the phase of the shift signals 413b, 414b and the phase of the first and second intermittent light receiving signals 411, 412 is less than the predetermined threshold, while removing light receiving signals in which the phase difference between the phase of the shift signals 413b, 414b and the phase of the first and second intermittent light receiving signals 411, 412 is equal to or greater than the predetermined threshold.

[0066] Furthermore, the control and calculation unit 37 uses a predetermined threshold value set according to the distance to the measurement object 70 to use valid received light signals in which the phase difference between the phase of the shift signals 413b, 414b and the phase of the first and second intermittent received light signals 411, 412 is less than the predetermined threshold value, while eliminating received light signals in which the phase difference between the phase of the shift signals 413b, 414b and the phase of the first and second intermittent received light signals 411, 412 is equal to or greater than the predetermined threshold value. This allows the electronic distance meter 20 according to this embodiment to more efficiently eliminate errors in the measured distance value.

[0067] Next, other operations of the control calculation unit 37 of this embodiment will be described with reference to the drawings. FIG. 6 is a schematic diagram illustrating a case where the measurement object has an inclination.

[0068] First, the first distance measurement light 231, the second distance measurement light 232, the third distance measurement light 233, and the fourth distance measurement light 234 emitted by the light-emitting element 21 are as described above with reference to Fig. 3. Also, the first intermittent light-receiving signal 411, the second intermittent light-receiving signal 412, the third intermittent light-receiving signal 413, and the fourth intermittent light-receiving signal 414 emitted from the light-receiving element 27 are as described above with reference to Fig. 3.

[0069] 6, when the measurement target 70 is inclined, the center position of the first intermittent light receiving signal 411 and the third intermittent light receiving signal 413, which have the same frequency band of 120 MHz-7.5 MHz, may deviate from the center position of the second intermittent light receiving signal 412 and the fourth intermittent light receiving signal 414, which have the same frequency band of 120 MHz+7.5 MHz. Specifically, as shown by deviation value S11 in FIG. 6, the center position C1 between the distance to measurement point P1 calculated based on the first intermittent light receiving signal 411 and the distance to measurement point P3 calculated based on the third intermittent light receiving signal 413 may deviate from the center position C2 between the distance to measurement point P2 calculated based on the second intermittent light receiving signal 412 and the distance to measurement point P2 calculated based on the fourth intermittent light receiving signal 414. When the center position C1 deviates from the center position C2, an error occurs in the acquired data.

[0070] In such a case, the control and calculation unit 37 of this embodiment changes the selection of data used to calculate the distance value to the measured object 70, and performs control to align the center position C3 of the first intermittent light receiving signals 411, 415 corresponding to the first distance measuring light 231, 235 and the third intermittent light receiving signal 413 corresponding to the third distance measuring light 233 with the center position C2 of the second intermittent light receiving signal 412 corresponding to the second distance measuring light 232 and the fourth intermittent light receiving signal 414 corresponding to the fourth distance measuring light 234.

[0071] For example, the control calculation unit 37 determines the center position of the first intermittent light receiving signal 411 and the first intermittent light receiving signal 415, and then determines the center position C3 between this center position and the third intermittent light receiving signal 413. By doing so, the control calculation unit 37 matches the center position C3 based on the first intermittent light receiving signal 411, the third intermittent light receiving signal 413, and the first intermittent light receiving signal 415 with the center position C2 between the second intermittent light receiving signal 412 and the fourth intermittent light receiving signal 414.

[0072] According to the electronic distance meter 20 of this embodiment, the center position C3 of the first intermittent light-receiving signals 411, 415 and the third intermittent light-receiving signal 413 coincides with the center position C2 of the second intermittent light-receiving signal 412 and the fourth intermittent light-receiving signal 414. Therefore, the electronic distance meter 20 of this embodiment can suppress errors from occurring in the acquired data.

[0073] The above describes the embodiments of the present invention. However, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the scope of the claims. The configurations of the above embodiments can be partially omitted or arbitrarily combined in a different manner from the above. [Explanation of symbols]

[0074] 20: Optical distance meter, 21: Light-emitting element, 23a: Distance measuring light, 23a': Reflected distance measuring light, 23b: Distance measuring light, 23b': Reflected distance measuring light, 27: Light receiving element, 32: Light-emitting element drive circuit, 33: Light receiving circuit, 37: Control and calculation unit, 38: Memory unit, 39: Main control unit, 40: Reference signal generator, 41a, 41b: Intermittent light receiving signal, 42a: First frequency divider, 42b: Second frequency divider, 43a: First phase shifter, 43b: Second phase shifter, 44: Amplifier, 46: Mixing circuit, 49: Amplifier, 70: Measurement object, 231: First distance measuring light, 232: Second distance measuring light, 233: Third distance measuring light, 234: Fourth distance measuring light, 235: first distance measuring light, 411: first intermittent light receiving signal, 411a: comparison signal, 412: second intermittent light receiving signal, 412a: comparison signal, 413: third intermittent light receiving signal, 413a: comparison signal, 413b: shift signal, 414: fourth intermittent light receiving signal, 414a: comparison signal, 414b: shift signal, 415: first intermittent light receiving signal, C1, C2, C3: center position, P1, P2, P3, P4: measurement point, S11: deviation value, s1: reference frequency signal, s2: first pulse modulated signal, s3: second pulse modulated signal, s4: third pulse modulated signal, s5: fourth pulse modulated signal

Claims

1. a distance measurement light emitting unit having a light emitting element and emitting distance measurement light by driving the light emitting element; a light-receiving signal generating unit having a light-receiving element that receives reflected light from the object to be measured and generates a light-receiving signal; a control and calculation unit that calculates a distance to the object to be measured based on the light receiving signal; Equipped with The distance measurement light emitting unit a reference signal generator that generates a reference frequency signal that is a continuous signal of a predetermined reference frequency; a frequency divider that generates a first modulated signal modulated at a first frequency by the reference frequency signal and a second modulated signal modulated at a second frequency close to the first frequency, and also generates a first pulse modulated signal obtained by pulsing the first modulated signal and a second pulse modulated signal obtained by pulsing the second modulated signal; The first pulse modulated signal is modulated for a time corresponding to 2π·n−π / 2 or 2π·n+π / 2. a phase shifter for generating a third pulse modulated signal obtained by shifting the second pulse modulated signal by a time corresponding to 2π·n−π / 2 or 2π·n+π / 2, and a fourth pulse modulated signal obtained by shifting the second pulse modulated signal by a time corresponding to 2π·n−π / 2 or 2π·n+π / 2; a light-emitting driver that drives the light-emitting element based on the first pulse modulated signal, the second pulse modulated signal, the third pulse modulated signal, and the fourth pulse modulated signal, and alternately emits a first distance-measuring light based on the first pulse modulated signal, a second distance-measuring light based on the second pulse modulated signal, a third distance-measuring light based on the third pulse modulated signal, and a fourth distance-measuring light based on the fourth pulse modulated signal in a time-division manner; and the first distance measurement light, the second distance measurement light, the third distance measurement light, and the fourth distance measurement light are irradiated in different directions, The received light signal is a first intermittent light receiving signal corresponding to the first distance measuring light; a second intermittent light receiving signal corresponding to the second distance measuring light; a third intermittent light receiving signal corresponding to the third distance measuring light; a fourth intermittent light receiving signal corresponding to the fourth distance measuring light; Including, the control and calculation unit acquires a shift signal obtained by shifting the phase of at least one of the first to fourth intermittent light receiving signals by 2π·n−π / 2 or 2π·n+π / 2; an optical distance meter that performs error determination control to compare the phase of the shift signal with the phase of the intermittently received light signal at least between the first frequencies and between the second frequencies;

2. 2. The optical distance meter according to claim 1, wherein the control and calculation unit compares a phase of the shift signal obtained by frequency-analyzing a central portion of a signal width of the intermittent light-receiving signal from which the shift signal is acquired with a phase of the intermittent light-receiving signal obtained by frequency-analyzing the central portion of the signal width of the intermittent light-receiving signal.

3. 3. The optical distance meter according to claim 1, wherein the control and calculation unit executes control to remove the intermittent light receiving signal when a phase difference between the phase of the shift signal and the phase of the intermittent light receiving signal is equal to or greater than a predetermined threshold.

4. 4. The electronic distance meter according to claim 3, wherein the control and calculation unit sets the predetermined threshold value in accordance with the distance to the object to be measured.

5. The optical distance meter according to any one of claims 1 to 4, characterized in that the control calculation unit performs control to align the center position of the first intermittent light receiving signal and the third intermittent light receiving signal with the center position of the second intermittent light receiving signal and the fourth intermittent light receiving signal.

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