JP2012103192A - Light wave distance meter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light wave distance meter capable of shortening a distance measurement time without making a filter position setting time longer.SOLUTION: The light wave distance meter which has a variable density filter 25 for light reception quantity adjustment arranged between distance measurement optical paths 23 and is a phase difference type stores a distance measurement value, a filter position of the variable density filter 25, and a signal rejection rate of a distance measurement signal in storage means 51 each time a measurement is taken. When a measurement is taken, an arithmetic processing part 50 compares a sample distance measurement value calculated through sampling of the distance measurement signal with the distance measurement value in the storage means 51. Filter position adjustment means sets the variable density filter 25 at a most closing filter position among distance measurement value data when the difference is equal to or less than 1 m, and starts taking a distance measurement at the filter position when the signal rejection rate at the filter position is 0% or with a density a little larger than that at the filter position when the signal rejection rate is not 0%. A suitable filter position is determined by adjusting the filter position several times, so the signal rejection rate becomes lower to decrease the number of times of distance measurement, so that the distance measurement time can be shortened eventually.

Description

  The present invention relates to a phase difference type light wave distance meter, and more particularly to a light wave distance meter in which a variable light receiving density filter that adjusts the amount of received light is disposed between distance measuring optical paths.

  For example, those disclosed in the following Patent Documents 1 and 2 are known as phase difference type lightwave distance meters. As shown in FIG. 5, this type of lightwave distance meter modulates the intensity of the signal output from the oscillator 1 through reference numerals 2 to 4 and transmits it as light from the light emitting element 11. Such light becomes distance measuring light obtained by being reflected by the target reflector 22 such as a prism disposed at the measurement point, and reference light obtained by being emitted to the reference light path 26, and is alternatively received by the light receiving element 30. The received light is converted into a distance measurement signal and a reference signal, respectively, and the received light signal is converted from an analog signal to digital data through reference numerals 32 to 40, and the CPU 50, which is an arithmetic processing unit, converts the digital signals of the distance measurement light and the reference light The phase difference is calculated, and the linear distance (distance value) to the target reflector 22 is measured.

  A variable light reception density filter 25 having a continuous density gradient and controlled by the arithmetic processing unit 50 is disposed between the target reflector 22 and the light receiving element 30. When the amplitude of the distance measurement signal obtained by sampling a part of the signal in a short time is larger than a predetermined range suitable for the measurement, the filter is closed (increasing the filter density), and conversely, if the amplitude is small, the filter is opened. The filter position is adjusted step by step in the direction of decreasing the filter density. When the filter position adjustment is performed at least once and the variable density filter 25 is set to the filter position suitable for the distance measurement from the initial filter position, the linear distance measurement (distance measurement) to the target reflector 22 is performed. Is called.

Japanese Patent Publication No.51-8340 (FIG. 2) Japanese Patent Application No. 2009-137788 (paragraph number 0019, FIG. 1)

  However, for example, if the distance from the optical wave distance meter to the target reflector 22 is long, the distance measuring optical path is bent greatly due to the influence of atmospheric fluctuation, the distance measuring signal of the distance measuring light is attenuated, and the variable density filter 25 is There is a tendency to be determined at an open position rather than when the atmospheric fluctuation is small. For this reason, it is difficult to adjust the filter position, which takes time, and the desired distance measurement specification time may be exceeded.

  On the other hand, if the initial filter position of the variable density filter 25 is set to an open position from the beginning, there is a high possibility that the optimum filter position is quickly set when the atmospheric fluctuation is large. When the fluctuation is small or the distance to the target reflector 22 is short, the distance measurement signal level exceeds the distance measurement possible range, and such a signal cannot be used for distance measurement (rejected). The signal rejection rate increases.

  In order to prevent the distance measurement signal level from exceeding the distance measurement possible range, the variable density filter 25 may be set to a closed position from the beginning, but the filter is excessively closed. The signal-to-noise ratio of the distance measurement signal is increased, and the problem that the distance measurement accuracy is deteriorated occurs.

  The present invention has been made in view of such problems, and a first object of the invention is to quickly set the variable density filter to the optimum filter position, so that the filter position setting is not delayed. Is to provide. The second purpose is to set the optimum filter position for each distance measurement, thereby increasing the number of distance measurement signal samples effective for distance value calculation and reducing the number of distance measurement times. As a result, the distance measurement accuracy is improved. An object of the present invention is to provide a lightwave distance meter with a reduced distance measurement time without lowering.

  The lightwave distance meter according to claim 1 is one selected from a light transmission means for transmitting light modulated at a plurality of modulation frequencies, and a target reflector or a reference light path in which the light of the light transmission means is arranged at a measurement point. An optical path switching means for transmitting to the optical path; a variable light reception density filter for adjusting the amount of received light having a continuous density gradient, disposed between the distance measurement optical paths of the distance measurement light reflected by the target reflector; and the distance measurement A light receiving means that receives light or reference light that has passed through the reference light path and outputs a distance measurement signal or a reference signal; and a distance measurement value that is a linear distance to a target reflector by a phase difference between the distance measurement signal and the reference signal An optical distance meter comprising: an arithmetic processing unit for calculating at least a distance value calculated for each distance measurement, a filter position of the variable density filter, and a light receiving light amount exceeding the range capable of distance measurement. The number of distance signal samples and A storage means for storing measurement data of a signal rejection rate that represents a ratio to the number of samples used for the distance is provided, and the arithmetic processing unit is provided with a short-time ranging signal from sampling data including at least one period of the ranging signal. The difference between the short-time measurement means for calculating the amplitude and the sample distance measurement value and the sample distance measurement value obtained by the short-time measurement means with reference to the past distance measurement value stored in the storage means is 1 m. When the following distance measurement data is not available, normal distance measurement is started. When there is distance measurement data with a difference of 1 m or less, the filter position where the variable density filter is most closed among the distance measurement data. The variable density filter is set at the filter position, and the signal rejection rate at the filter position is referenced from the storage means. When the signal rejection rate is 0%, ranging is performed at the filter position. Open However, when the signal rejection rate is not 0%, filter position adjusting means for starting distance measurement by making the filter density higher than 0 to 1% higher than the filter position, and the variable density filter by the filter position adjusting means After the position adjustment, the distance is measured and the signal rejection rate is calculated, and the signal rejection rate is calculated by the distance measurement and rejection rate calculation means. After the distance measurement and rejection rate calculation means, the calculated distance value is obtained by the filter position adjustment means. Measurement data storage instructing means for storing the measurement data of the filter position of the obtained variable density filter and the signal rejection rate of the distance measurement signal calculated by the distance measurement and rejection rate calculating means is provided in the storage means.

  (Function) In general, the position of the variable density filter tends to be determined to be an open position (a position where the filter density is low) than when the atmospheric fluctuation is small enough to be affected by the atmospheric fluctuation. It will also be difficult.

  However, the distance measurement value in the past measurement and the measurement data of the filter position of the variable density filter are stored in the storage means, and a value close to the sample distance measurement value obtained by the short-time measurement means (the difference is 1 m or less). When the distance measurement value is referred to from past measurement data and the most closed filter position is adopted, the best filter position that is not affected by atmospheric fluctuation in the measurement of the linear distance (distance measurement) Measurement can be performed at the same time, and the optimum filter position can be quickly determined without being affected by atmospheric fluctuations.

  Furthermore, if the measurement data of the signal rejection rate of the ranging signal in the past measurement is also stored, the ranging signal level may exceed the distance measurement range unless the signal rejection rate is 0%. If the signal rejection rate is not 0%, close the variable density filter by a small amount (above 0 to 1%) from the best filter position, so that the signal exceeding the range can be measured without closing the filter too much. Since it can be further reduced, it is possible to perform measurement at a more suitable filter position. Even when such adjustment is included, the filter position is determined by several adjustments, so that the time required for the filter position adjustment is not prolonged.

  As a result, as the past measurement data to be compared increases (as the distance is measured), the optimum filter position for the distance measurement is learned.

  In addition, since the filter position is optimal, the ranging means can obtain many ranging signal samples that are effective in calculating the ranging value (the signal rejection rate of the ranging signal is reduced), so that almost all sample data can be measured. It can be used for distance value calculation. For this reason, the number of times of distance measurement can be reduced while maintaining the conventional distance measurement accuracy, and as a result, the time required for distance measurement can also be shortened.

  According to a second aspect of the present invention, in the light wave distance meter according to the first aspect, the arithmetic processing unit includes a variable density filter having a difference between the current distance measurement value and the distance measurement value stored in the storage means of 1 m or less. A stored data deleting means for comparing the filter positions and deleting data other than the measurement data having the filter position where the variable density filter is most closed is provided.

  (Operation) Among the past measurement data stored in the storage means, the measurement data having the filter position data in which the variable density filter is most closed among the ones having a close distance value (difference is 1 m or less) Is the best measurement data that was not affected by the fluctuation of the atmosphere at the distance measurement. Therefore, by leaving only one set of the best measurement data (ranging value, filter position of variable density filter, signal rejection rate) and deleting others, the capacity of the storage means can be efficiently emptied.

  According to the lightwave distance meter of the first aspect, the distance measurement time can be shortened without delaying the filter position setting time, so that the entire distance measurement specification time is significantly shortened compared with the conventional one, and the working efficiency is remarkably improved. To improve.

  For users who measure substantially the same straight line distance, the optimum filter position is learned earlier, so the usability is improved.

  According to the lightwave distance meter of the second aspect, there is no problem associated with the allowable capacity exceeding of the storage means.

The block diagram of the optical wave distance meter which concerns on this invention. The figure which shows an example of the ranging signal waveform sampled with the AD converter at the time of long-distance ranging with the conventional lightwave rangefinder. It is a figure which shows the relationship between the linear distance of a light wave distance meter and a measurement object, and the filter position of a variable density filter, Comprising: The figure explaining the influence of fluctuation of the atmosphere. The flowchart figure which shows the procedure of the distance measurement which concerns on this invention. The block diagram of the conventional lightwave distance meter.

  Next, an optimal embodiment of the optical wave distance meter will be described with reference to FIG. FIG. 1 is a block diagram of an optical distance meter according to the present invention. The lightwave distance meter of the embodiment includes a light sending unit 100, an optical path switching unit 102, a light receiving unit (light receiving element 30), a local signal sending unit 101, an arithmetic processing unit (CPU 50), and a storage unit (storage device 51) shown below. Etc. are included in the components.

  The oscillator 1, the frequency divider 2, the frequency superimposing circuit 3, the drive circuit 4, the load resistor 8, and the light emitting element 11 are connected in order as shown in FIG.

  The oscillator 1 generates a reference signal F1 having a predetermined frequency. The frequency divider 2 divides the signal F1 to generate signals F2 and F3 having different frequencies. The signals F1, F2, and F3 are superimposed by the frequency superimposing circuit 3. The drive circuit 4 that receives the voltage supply drives the light emitting element 11 with an AC signal based on the superimposed signals (F1, F2, and F3). The light emitting element 11 is also driven by a DC power supply via a load resistor 8 having a constant resistance value, and sends out light whose intensity is modulated with the amplitude of the superimposed signals (F1, F2, F3).

  On the other hand, a PLL (Phase Locked Loop) 5, a local signal oscillator 6, and a frequency generation circuit 7 constitute a local signal transmission unit 101. The PLL 5 is connected to the oscillator 1, and the local signal oscillator 6 is connected to the PLL 5 through a bidirectional signal line. The frequency generation circuit 7 is connected to the oscillator 1 and the local signal oscillator 6 respectively. The local signal oscillator 6 is connected to a frequency converter 32 described later, and the frequency generation circuit 7 is connected to frequency converters (35, 38) described later.

  The local signal oscillator 6 receives the reference signal F1 from the oscillator 1 via the PLL 5, and outputs a frequency signal F1 + Δf1 whose frequency is shifted by a minute value Δf1 from the signal F1 to the frequency converter 32. The frequency generation circuit 7 receives the signal F 1 from the oscillator 1 and further receives the frequency signal F 1 + Δf 1 from the local signal oscillator 6. Then, the frequency generation circuit 7 first divides the reference signal F1 into signals F2 and F3, and based on the frequency signal F1 + Δf1, the frequency is shifted by a minute value Δf2 and Δf3 from the signals F2 and F3. Signals F2 + Δf2 and F3 + Δf3 are output, respectively. The frequency signals (F2 + Δf2, F3 + Δf3) are input to the frequency converters (35, 38), respectively.

  The light transmitted from the light emitting element 11 is alternatively emitted by the optical path switching means 102 including the beam splitter 20 and the switching shutter 28. That is, the beam splitter 20 divides the distance into two directions, ie, the distance measuring optical path 21 direction and the reference optical path 26 direction. By switching the switching shutter 28, the beam is sent to the optical path not shielded by the shutter 28.

  Since the reference optical path 26 side is shielded by the switching shutter 28, the light transmitted to the distance measuring optical path 21 is reflected to the distance measuring optical path 23 by the target reflector 22 such as a prism disposed at the measurement point. The reflected light (hereinafter referred to as distance measuring light) is collected by a light receiving optical 24 (a condensing lens or the like), subjected to light amount adjustment by a variable density filter 25, and then received by a light receiving element 30 (light receiving means). Received light.

  The variable density filter 25 is a thin disk-shaped transparent light receiving light amount adjusting means, and is formed so that the filter concentration is continuously increased from 0% to 99% in the circumferential direction. . Thereby, the diaphragm effect of the light quantity gradually increases from one end in the circumferential direction to the other end in the circumferential direction, and rotates in the direction to increase the filter density (close the filter) or in the direction to decrease the filter density (filter The position is adjusted and the concentration is adjusted step by step. Note that the density change of the variable density filter 25 can be changed linearly, quadratic, or exponentially, as long as there is a correspondence between the angle change and the density change. good. Such filter position adjustment is performed by rotating a disk by driving an actuator 52 (not shown) or the like controlled by a CPU 50 described later.

  On the other hand, by switching the switching shutter 28 and shielding the distance measuring optical path 21 side, the light transmitted to the reference optical path 26 (hereinafter referred to as reference light) is made constant by a density filter 27 having a predetermined light amount attenuation rate of an open / close type. Is received by the light receiving element 30.

  An amplifier 31 is connected to the light receiving element 30, and for each signal (F1, F2, F3), a frequency converter (32, 35, 38), a low-pass filter (33, 36, 39), an AD converter (34, 37, 40) is connected. The AD converters (34, 37, 40) are each connected to the CPU 50, and a storage device 51 is connected to the CPU 50. The CPU 50 is also connected to the variable density filter 25 via an actuator 52 (not shown).

  The distance measuring light and the reference light received by the light receiving element 30 are output as electric signals (ranging signal, reference signal), respectively.

  The distance measurement signal and the reference signal are respectively amplified by the amplifier 31, and then input to the frequency converter (32, 35, 38) for each of the signals indicating F1, F2, and F3.

  The frequency converter (32, 35, 38) converts the signals (F1, F2, F3) input as ranging signals or reference signals into frequency signals (F1 + Δf1, F2 + Δf2, F3 + Δf3) on the local signal transmission means 101 side. To generate intermediate frequency signals (Δf1, Δf2, Δf3) that have a lower frequency band and are easy to handle. The intermediate frequency signals (Δf1, Δf2, Δf3) are sent to the AD converters (34, 37, 40) after the high frequency components are removed as noises by the bandpass filters (33, 36, 39). Here, the distance measurement signal or the reference signal is converted from an electrical signal to a digital signal and input to the CPU 50.

  The CPU 50, which is an arithmetic processing unit, analyzes the signal amplitude and phase information from the input ranging signal and the reference signal digital signal, and is generated inside the optical distance meter by the phase difference between the ranging light and the reference light. The error is corrected, and a linear distance (ranging value) from the light wave rangefinder to the target reflector 22 is calculated.

  The CPU 50 performs short-time measurement means, filter position adjustment means, distance measurement and rejection rate calculation means, and measurement data storage instruction means, which will be described later, in the process of distance measurement value calculation. Further, a storage data deleting unit to be described later is appropriately performed on the storage device 51.

  The storage device 51, which is a storage means connected to the CPU 50, stores various programs necessary for the distance measurement value calculation in the CPU 50, and the calculated distance measurement value and the variable obtained by the filter position adjustment means. Each measurement data of the filter position of the density filter 25 and a signal rejection rate indicating the number of distance measurement signal samples exceeding the distance measurement possible range are stored.

  Hereinafter, the properties of the lightwave distance meter will be described with reference to FIGS. 2 and 3, and the distance measurement procedure of the lightwave distance meter according to the embodiment and the variable density which is a characteristic part of the present invention will be described with reference to the flowchart of FIG. The adjusting means of the filter 25 will be described in detail.

  Generally, an appropriate amount of light is determined for a lightwave distance meter according to specifications. Specifically, the threshold value of the maximum amplitude value and the minimum amplitude value of the distance measurement signal is set in advance so that the distance measurement signal level obtained through the light receiving element 30 is within an appropriate range (range measurement possible range) that can be analyzed by the CPU 50. It is set and stored in the storage device 51.

  FIG. 2 is a diagram showing an example of a ranging signal waveform sampled by an AD converter (34, 37, 40) when a long-range distance measurement is performed with a conventional optical wave rangefinder, where the horizontal axis indicates time, and the vertical axis indicates time. The axis indicates the signal amplitude of the ranging signal. A signal in which the distance measurement signal obtained from the light receiving element 30 exceeds the specified maximum amplitude value is rejected as data that cannot be used by the CPU 50 for distance measurement calculation. The ratio of the number of signals exceeding the maximum amplitude value among the total number of samples of the distance measurement signal obtained within the distance measurement time is referred to as a signal rejection rate.

  In order to reduce the signal rejection rate, the CPU 50 calculates the short-range ranging signal amplitude from the sampling data for several cycles of the ranging signal obtained in a short time, and compares it with the set value of the storage device 51. By measuring the difference and issuing a control signal to the actuator 52 so that the distance measurement signal falls within the threshold, the filter is closed (the filter density is increased) if the short-range distance signal amplitude is greater than the maximum amplitude value. If the direction of the filter is small, the filter position is adjusted stepwise in the direction of opening the filter (decreasing the filter density). When such adjustment is performed at least once and the variable density filter 25 is set to a filter position suitable for the measurement of the linear distance, distance measurement is started.

However, the relationship between the linear distance to the target reflector 22 and the filter position of the variable density filter 25 is generally as shown in FIG. FIG. 3 is a diagram illustrating the relationship between the linear distance between the optical distance meter and the measurement object 22 and the filter position of the variable density filter 25, and is a diagram illustrating the influence of atmospheric fluctuations. The horizontal axis represents the linear distance from the light wave distance meter to the target reflector 22, and the vertical axis represents the filter position of the variable density filter 25, that is, the filter density. From FIG.
(I) When the distance from the light wave rangefinder to the target reflector 22 is short (in the case of short-range distance measurement), the variable density filter 25 is controlled in the closing direction.
(Ii) If the atmospheric fluctuation at the time of distance measurement is large, the distance measuring optical path is bent, the distance measurement signal of the distance measuring light is attenuated, and the variable density filter 25 is determined to be opened more than when the atmospheric fluctuation is small. Is done.
(iii) The greater the distance from the light wave rangefinder to the target reflector 22 (far-distance measurement), the greater the influence of atmospheric fluctuations.

  I understand that. For this reason, particularly in the case of long-distance ranging, it is difficult to adjust the filter position of the variable density filter 25 due to the influence of atmospheric fluctuations.

  On the other hand, if the initial filter position of the variable density filter 25 is set to an open position from the beginning, there is a high possibility that the optimum filter position is quickly set when the atmospheric fluctuation is large. When the fluctuation is small or the distance to the target reflector 22 is short, the distance measurement signal level exceeds the distance measurement possible range, and the signal rejection rate increases. Further, if the initial filter position of the variable density filter 25 is set to a closed position from the beginning so that the distance measurement signal level does not exceed the distance measurement possible range, the filter is excessively closed. The problem is that the ratio increases and the ranging accuracy deteriorates.

  Here, even if the atmospheric fluctuation at the time of distance measurement is large, if there is filter position data of the variable density filter 25 when the atmospheric fluctuation has been small at that distance in the past, the filter position is determined for that distance. A suitable filter position. Then, in the distance measurement value, it can be seen that the filter position that has not been most affected by atmospheric fluctuations so far is the most closed filter position.

  That is, if the past distance measurement value and the measurement data of the filter position are stored as a set, the same (near value) distance measurement values are compared, and the best filter that is most closed among them is compared. Position can be employed.

  Furthermore, if the measurement data of the signal rejection rate of the distance measurement signal in the past measurement is also stored, the distance measurement signal level may exceed the distance measurement range unless the signal rejection rate is 0%. That is. Therefore, by further closing the variable density filter 25 by a small amount from the past best filter position, it is possible to reduce the distance measurement signal exceeding the distance measurement range without excessively closing the filter. It becomes possible to measure.

  Hereinafter, based on the flowchart of FIG. 4, the procedure of distance measurement of the lightwave distance meter according to the embodiment will be described in detail.

  When the distance measurement is started, the distance measurement signal or reference signal received by the light receiving element 30 through the reference numerals 100, 101, 102 is input to the CPU through reference numerals 31-40, and the CPU 50 starts the short-time measurement means. The

  The short-time measuring means calculates the short-range ranging signal amplitude as usual from the sampling data for several cycles of the ranging signal obtained in a short time. In addition to this, the ranging value is also calculated from the sampling data. (Hereinafter, this is referred to as a sample ranging value).

  Next, as in the past, the short-time ranging signal amplitude value is compared with the maximum amplitude value and the minimum amplitude value stored in the storage device 51, the difference is measured, and the ranging signal falls within the threshold value. Then, the control signal is output, and the actuator 52 sets the variable density filter 25 to the optimum position (initial filter position) from the short-time measurement.

  Next, the filter position adjusting means is started.

  In the filter position adjustment means, first, the sample distance measurement value obtained by the short time measurement means is compared with the past distance measurement value stored in the storage device 51, and the difference from the sample distance measurement value is within 1 m. A search is made as to whether distance measurement value data having a close value is stored in the storage device 51. Here, the reason for determining whether or not the values are close is within a difference of 1 m from the viewpoint of obtaining sufficiently reliable accuracy and the balance of the storage capacity of the storage device 51. Note that it is preferable to increase the storage capacity of the storage device 51 by 10 times so that the difference is within 0.1 m because accuracy is further improved.

  When there is no distance measurement data having a difference of 1 m or less in the storage device 51, the distance of the current sample distance measurement is a linear distance measured for the first time. Move on.

  On the other hand, when there is distance measurement data having a difference of 1 m or less in the storage device 51, the distance of the current sample distance measurement value is the second or more measurement, and thus past measurement data exists in the storage device 51. . Therefore, first, the filter position at which the variable density filter 25 is most closed is determined from the distance measurement data having a difference of 1 m or less, and the variable density filter 25 is reset by using this as the secondary filter position. Next, the signal rejection rate in the measurement adopted for the secondary filter position is referred from the storage device 51.

  When the signal rejection rate of the measurement adopted for the secondary filter position is 0%, if the secondary filter position is adopted for that distance, the distance measurement signal level will not exceed the distance measurement possible range. Therefore, the secondary filter position is the optimum filter position for the distance measurement. Therefore, the distance measurement and rejection rate calculation means are moved to the secondary filter position.

  Conversely, when the signal rejection rate is not 0%, it means that there is still a signal exceeding the distance measurement possible range even if the secondary filter position is adopted. Therefore, the filter density is closed by a little more, specifically 1% (more preferably 0.1%), so that a more suitable filter position is obtained, and the filter density is further increased to a position (third-order filter position). Adjust and move to ranging and rejection rate calculation means.

  As a result, the first-stage light intensity is attenuated from the secondary filter position, and the signal amplitude of the obtained distance measurement signal is reduced, so that the signal rejection rate can be made closer to 0%. Further, the variable density filter 25 does not become excessively thick with respect to the distance.

  When the variable density filter is adjusted according to the case by the filter position adjusting means, the distance measurement and the rejection rate calculating means measure the distance, and from the phase difference between the obtained distance measurement signal and the reference signal to the target object 22 A distance measurement value is calculated, and a signal rejection rate in the distance measurement is calculated from the obtained distance measurement signal. Here, the distance measurement signal obtained by such distance measurement has a much lower signal rejection rate than the distance measurement signal obtained by the conventional lightwave distance meter, so that the number of times of measurement is less than the number of conventional samples.

  Finally, in the measurement data storage instruction means, the calculated distance measurement value, the filter position of the variable density filter 25 obtained by the filter position adjustment means, and the calculated signal rejection rate of the distance measurement signal are stored in the storage means 51. Store and finish the distance measurement.

  By using the sample distance measurement value obtained by the short-time measurement means as described above, if there is a value close to this, by referring to the most closed filter position from the past distance measurement value, Since the optimum filter position can be quickly determined by three adjustments at the maximum without being affected by atmospheric fluctuations, the time for adjusting the filter position is not prolonged.

  Further, if the signal rejection rate of the distance measurement signal is used and the signal rejection rate is not 0%, the filter position is further reset. Therefore, the more the measurement is performed, the closer the signal rejection rate becomes to 0%. The filter position is learned.

  Further, since the distance measurement signals within the distance measurement possible range (within the threshold value) are increased by the optimum filter position, almost all sample data obtained by distance measurement can be used for distance measurement value calculation. For this reason, since the number of times of distance measurement (number of samples of the distance measurement signal) can be reduced while maintaining the conventional distance measurement accuracy, the time required for distance measurement can be shortened in the lightwave distance meter of the present invention.

  In any linear distance measurement, the variable density filter is gradually closed to reduce the influence of atmospheric fluctuations as the past measurement data to be compared increases (the more distance measurement is performed). Therefore, it is no longer affected by atmospheric fluctuations (dashed arrows in FIG. 3).

  Therefore, the filter position setting time is not delayed, and the distance measurement time can be further shortened, so that the overall distance measurement specification time is significantly shortened compared to the conventional method, and the work efficiency is greatly improved for the user. .

  In addition, for users who measure the distance of substantially the same linear distance, the optimum filter position is learned earlier, so that the distance measurement specification time is extremely shortened and the usability is improved.

  In addition, since the storage capacity of the storage unit 51 is limited, if measurement data is accumulated for each distance measurement, there is a possibility that problems such as operation delay and freeze due to insufficient capacity may occur. Therefore, the CPU 50 deletes unnecessary measurement data as needed by the stored data deletion means.

  Among the past measurement data, the measurement data having the data of the most closed variable density filter 25 among the measurement values close to the current distance measurement value is the least affected by the fluctuation of the atmosphere. Since this is the best measurement data, no other measurement data is required.

  Therefore, the stored data deleting means compares the filter positions of the variable density filters 25 whose difference between the current distance measurement value and the past distance measurement value stored in the capacity storage device 51 is 1 m or less. Among them, measurement data other than a set of measurement data (ranging value, filter position of the variable density filter 25, signal rejection rate) having the filter position where the variable density filter 25 is most closed, for example, at the timing of the end of distance measurement. delete.

  As a result, the capacity of the storage device 51 is efficiently emptied, so that there is no problem associated with exceeding the allowable capacity.

DESCRIPTION OF SYMBOLS 11 Light emitting element 22 Target reflector 21, 23 Ranging optical path 25 Variable density filter 26 Reference optical path 30 Light receiving element (light receiving means)
50 CPU (arithmetic processing unit)
51 Storage device (storage means)
100 Optical transmission means 102 Optical path switching means

Claims (2)

A light sending means for sending light modulated at a plurality of modulation frequencies; a light path switching means for sending the light of the light sending means to a selected one of a target reflector or a reference light path arranged at a measurement point;
A variable light reception density filter for adjusting the amount of received light having a continuous density gradient, disposed between the distance measurement optical paths of the distance measurement light reflected by the target reflector;
A light receiving means for receiving the distance measuring light or the reference light that has passed through the reference light path and outputting a distance measuring signal or a reference signal;
A calculation unit that calculates a distance value, which is a linear distance to the target reflector, based on a phase difference between the distance measurement signal and the reference signal; and a distance value calculated at least for each distance measurement in the optical distance meter A memory for storing measurement data of a filter position of the variable density filter and a signal rejection rate representing a ratio between the number of samples of the ranging signal and the number of samples used for ranging in which the amount of received light exceeds the range capable of ranging Providing means,
In the arithmetic processing unit,
A short-time measuring means for calculating a short-range ranging signal amplitude and a sample ranging value from sampling data including at least one period of the ranging signal;
With reference to the past distance measurement values stored in the storage means, if there is no distance measurement data whose difference from the sample distance measurement value obtained by the short-time measurement means is 1 m or less, normal distance measurement is performed. When there is distance measurement data having a difference of 1 m or less, the variable density filter is referred to the most closed filter position in the distance measurement data, and the variable density filter is set at the filter position. At the same time, the signal rejection rate at the filter position is referred from the storage means, and when the signal rejection rate is 0%, ranging starts at the filter position, but when the signal rejection rate is not 0% Filter position adjusting means for starting distance measurement by setting the filter density to be more than 0 to 1% higher than the filter position;
Ranging after the position adjustment of the variable density filter by the filter position adjusting means, ranging to calculate the signal rejection rate and the rejection rate calculation means,
After the distance measurement and rejection rate calculation means, the calculated distance measurement value, the filter position of the variable density filter obtained by the filter position adjustment means, and the distance measurement signal calculated by the distance measurement and rejection rate calculation means An optical distance meter characterized by comprising measurement data storage instruction means for storing measurement data of a signal rejection rate in the storage means.   The calculation processing unit compares the filter positions of the variable density filters whose difference between the current distance value and the distance value stored in the storage means is 1 m or less, and among them, the variable density filter 2. The optical distance meter according to claim 1, further comprising stored data deleting means for deleting data other than measurement data having a filter position that is most closed.

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