JPH087261B2 - Lightwave distance measuring method and lightwave distance meter - Google Patents

Description

TECHNICAL FIELD The present invention generally relates to a technique for measuring a distance by using a light wave, and more specifically, to shorten the measurement time and improve the measurement accuracy. The present invention relates to a lightwave distance measuring method and a lightwave distance meter.

[Prior Art] FIG. 21 schematically shows the configuration of a typical conventional optical distance meter. In this figure, 100 is a light emitting element, 101 is a light receiving element, 102 is a light transmitting lens, 103 is a light receiving lens, and 104 is a triangular prism attached to a target (not shown). Reference numeral 105 denotes an optical path switching shutter that intermittently rotates a disc 106 having an opening for external measurement and an opening for internal measurement by a drive motor 110 so as to switch between the optical path for external measurement and the optical path for internal measurement. It is configured. Electric circuit section 111
Is a circuit for supplying an electric signal having a modulation frequency to the light emitting element 100, a circuit for further converting a photoelectric conversion signal from the light receiving element 101 into a frequency signal (measurement signal) for arithmetic processing, and the measurement signal as a reference It includes a circuit for obtaining an external measurement value from the phase difference of the frequency signal (reference signal), a circuit for calibrating the external measurement value with an internal measurement value, and the like.

FIG. 22 is a plan view showing the arrangement structure of the openings provided in the disc 106 of the optical path switching shutter 105. Further, FIG. 23 is a partial cross-sectional perspective view showing a state of a main part when the disc 106 is rotated 90 ° from the state of FIG.

In FIG. 22, a pair of openings 107a and 107b are for external measurement, and another pair of openings 108a and 108b are for internal measurement. As shown in FIG. 23, a prism with a trapezoidal cross section is provided on the disc 106 between the internal measurement openings 108a and 108b.
109 is fixed, and an opening 108 is formed at the bottom end of the prism 109.
a and 108b are facing each other.

At the time of external measurement, as shown in FIG. 21, the external measurement openings 107a and 107b face the light emitting element 100 and the light receiving element 101, respectively, and the light wave emitted from the light emitting element 100 is opened by the opening 107.
a through the light-transmitting lens 102 to the target-side prism 10
The light wave propagating in the atmosphere toward 4 and reflected by the prism 104 and returning returns to the light receiving element 101 through the light receiving lens 103 and the opening 107b. However, during the internal measurement, as shown in FIG. 23, the internal measurement openings 107a and 107b face the light emitting element 100 and the light receiving element 101, respectively, and the light wave from the light emitting element 100 passes through the opening 108a to form a trapezoidal prism. A light wave that enters one end of the prism 109 and is reflected inside the prism 109 as shown in the figure and exits from the other end passes through the aperture 108b and the light receiving element 101.
Incident on.

FIG. 24 shows a specific example of the measurement sequence in the conventional lightwave rangefinder. First, the optical path switching shutter 105
In the state as shown in Fig. 1, a light wave with a 15 MHz frequency is emitted to the outside for a time of 666 msec, and external measurement is performed (201). Next, the drive motor 110 is operated to switch the shutter 105 to the state shown in FIG. 23 (202). About 0.5 for switching this shutter
It takes sec. Under the condition shown in Fig. 23, 666 msec
A light wave with a frequency of 15 MHz is passed through the optical path of the trapezoidal prism 109 only for the time of (1) and internal measurement is performed (204). Next, with the shutter 105 kept in the state shown in FIG. 23, the frequency switching circuit in the electric circuit section 111 is controlled to switch the frequency of the light wave to 150 KHz (204). This frequency switching takes about 0.2 sec.
Then, under the condition shown in FIG. 23, the internal measurement is now performed at the frequency of 150 KHz (205). Finally, set the frequency to 150KHz
Shutter shutter 105 to the 21st
After switching to the state shown in the figure (206), perform external measurement (2
07). After this, the internal measurement value is subtracted from the external measurement value to obtain the net measurement value.

Two types of frequencies (modulation frequency) of 15MHz and 150KHz
Is used to measure roughly at a frequency of 150 KHz with a long wavelength (scale) and to perform detailed measurement at a frequency of 15 MHz with a short wavelength (scale). In addition, the measurement time in each measurement mode is 666 msec.
This is because sampling is performed 10,000 times in each measurement mode when the frequency of the measurement signal is 15 KHz (the cycle is 66.66 μsec). Therefore, when the number of samplings is 1000, the measurement time should be 66.6msec. In this example, the total measurement time is about 3.86 seconds, of which about 1.0 seconds is spent for shutter switching.

[Problems to be Solved by the Invention] As described above, in the conventional optical distance meter, each measurement mode is executed in a batch method, and the disc 106 of the optical path switching shutter 105 is intermittently rotated to change the measurement mode. I was switching. Therefore, each time the measurement mode is switched, the measurement process is interrupted for a long time, and the total measurement process time is also long. Further, since the switching (interruption) time is long, there is a possibility that the movement of the target cannot be followed, which is also a problem in terms of measurement accuracy and reliability.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a lightwave distance measuring method and a lightwave distance meter that can obtain highly accurate measurement values in a short measurement time.

[Means for Solving the Problems] In order to achieve the above-mentioned object, the lightwave distance measuring method of the present invention uses a reflected light that returns to a light receiving element after projecting a modulated light onto an object via an external optical path. The distance value to the target is obtained from the phase difference with the modulated light, and the calibration measurement value is obtained from the phase difference between the modulated light and the modulated light that has reached the light receiving element via the internal calibration optical path of the modulated light. In the lightwave distance measuring method in which the external light path and the calibration light path are switched to calibrate the distance value with the calibration measurement value, n distance values and one calibration measurement value are calculated for each measurement cycle. However, n is an integer of 2 or more, and the average distance value is obtained by adding and averaging the distance values of the n times, and the average distance value is calibrated with the calibration measurement value.

Further, in order to achieve the above object, the optical distance meter of the present invention includes a light emitting element that projects a modulated light onto an object through an external optical path, and a light receiving element that receives reflected light reflected by the object. An element, a means for obtaining a distance value to the target from the phase difference between the modulated light and the reflected light, calibration light that reaches the light receiving element via the internal calibration optical path for the modulated light, and the modulated light Means for obtaining a calibration measurement value from the phase difference with light, and means for switching the external optical path and the calibration optical path to calibrate the distance value with the calibration measurement value, the opening of the external optical path for each measurement cycle The time is switched to n times that of the calibration optical path, where n is an integer greater than or equal to 2, optical shutter means, n memories for storing distance values n times in the opening of the external optical path, and the calibration Stores one calibration measurement value in the aperture of the optical path A calibration memory, an addition circuit for adding the contents of the n memories and outputting a cumulative distance value, a division circuit for dividing the cumulative distance value by n to obtain an average distance value, And a subtraction circuit for subtracting the average distance value by the calibration measurement value in the calibration memory.

The optical shutter means in the optical distance meter of the present invention is formed or provided with a light shield that rotates at a constant speed, and the light shield has an opening time of the external light path that is n times that of the calibration light path. And light transmitting or reflecting means for distance measurement and calibration.

Another optical shutter means includes a first liquid crystal shutter that selectively forms the external optical path and a second liquid crystal shutter that selectively forms the calibration optical path.

[Operation] In the present invention, the external measurement and the internal measurement are time-divisionally performed at a predetermined time ratio (for example, 10: 1) in one measurement cycle. In the initialization measurement prior to the main measurement, for example, 10
Only a number of internal measurements or calibrations are performed and written to, for example, 10 calibration memories each. Therefore, in the initialization measurement, for example, when the rotary shutter is used, 100 external measurement values are ignored.

When the main measurement is started, for example, 10
The external measurement values for one batch are sequentially written to the 10 external measurement memories, the arithmetic mean is calculated, and the internal measurement values for one batch are written to one of the calibration memories. Therefore, one of the ten calibration memories is updated to calibrate the averaged external measurement value that is averaged by the moving average value of the calibration values that are averaged.

As described above, in the present invention, the time ratio of, for example, n times of external measurement and 1 time of calibration measurement in one measurement cycle is provided for external and calibration measurement. However, n is an integer of 2 or more. Therefore, the main measurement time can be shortened as compared with the case where n times of external measurement and n times of calibration measurement are alternately repeated in order to obtain the same degree of accuracy as the measurement of the present invention. On the other hand, for a calibration measurement value that does not cause a sudden change in measurement, the contents of the calibration memory are partially updated for each measurement cycle, and the same number of calibration values as the external measurement value are obtained. A measurement value of is obtained, which makes it possible to guarantee a reliable measurement.

Further, according to the optical shutter means of the present invention, the external measurement mode and the internal measurement mode can be continuously switched rather than intermittently, which also shortens the cycle of the measurement cycle and thus the total measurement time. Can be shortened.

[Embodiment] An embodiment of the present invention will be described below with reference to FIGS. 1 to 20.

FIG. 1 is a partial cross-sectional perspective view schematically showing a configuration of a main part of a lightwave distance meter according to an embodiment. In this figure,
Reference numeral 10 is a light emitting element such as a light emitting diode, 11 is a light receiving element such as a phototransistor, 12 is a continuous rotation type optical path switching shutter according to the present invention, 19 is a light amount variable filter, 20 is a light transmitting lens, and 21 is a light receiving lens. is there. Also,
Reference numeral 22 is a surface reflection mirror for forming an optical path for calibration. The electric circuit section 23 will be described later with reference to FIG.

The shutter 12 is configured to continuously rotate at a constant speed by driving a drive motor (not shown) about a rotation shaft 13. The shutter 12 is of a cylindrical type, and a glass plate 14 is arranged at a predetermined inclination (for example, 45 °) with respect to the light emitting element 10, and a bottom surface thereof has a predetermined range (for example, 45 °) as shown in FIG. An external measuring opening 15 having an incomplete annular shape is formed over 300 °, and the side surface thereof has a predetermined position (for example, a portion where the opening 15 is missing) as shown in FIGS. 2 and 3.
A rectangular internal measurement opening 16 is formed at a predetermined length (for example, a length corresponding to 30 °) at a position (opposite to 15 '), and an index indicating the starting point of the opening 15 is attached, for example. As a result, when the time (cycle) required for the shutter 12 to make one rotation (360 ° rotation) is T, the time for which the light wave is emitted from the external measurement opening 15 to the light transmitting lens 20 side during one cycle period. Is T × 0.833 (300 ° / 360 °), and the light wave from the internal measurement aperture 16 is the surface reflection mirror of the optical path for calibration.
The time to go to the 22 side is T × 0.0833 (30 ° / 360 °).

2 is a side view of the shutter 12 of FIG. 1 viewed from the direction of arrow A, and FIG. 3 is a top view of the shutter 12 of FIG. 2 viewed from the direction of arrow B. As shown in FIG.
A magnet for detecting the rotational position at a predetermined position on the outer peripheral surface of the shutter 12.
17 is attached. The rotation phase of the shutter 12 is detected based on the timing when the magnet 17 passes through the rotation position detector 18 including a magnetic sensor. In addition, in FIG. 2, LB represents a beam of light waves.

1 to 3 show the state during external measurement. During external measurement, most of the light waves emitted from the light emitting element 10 pass through the glass 14 in the shutter 12 and travel from the opening 15 toward the light transmitting lens 20 side. Then, the light wave reflected and returned by the target (not shown) enters the light receiving element 11 via the light receiving lens 21. On the other hand, a part of the light wave reflected by the glass 14 hits the inner surface of the shutter 12 and is blocked there, and does not go outside.

4 to 6 show the state at the time of internal measurement. The state shown is from the state shown in FIGS. 1 to 3 to the shutter.
This is the state when 12 is rotated 180 °. At the time of internal measurement, the non-opening portion 15 ′ on the bottom surface of the shutter 12 is located beyond the glass 14 as viewed from the light emitting element 10. As a result, the light wave transmitted through the glass 14 hits the non-opening portion 15 'and is shielded there. On the other hand, the light wave reflected by the glass 14 enters the surface reflection mirror 22 through the side opening 16 of the shutter 12, is reflected there, and then enters the light receiving element 11. 5 is a side view of the shutter 12 of FIG. 4 seen from the direction of arrow A, and FIG.
The drawing is a bottom view of the shutter 12 seen from the direction of arrow B in FIG.

As described above, the optical path switching shutter 12 according to this embodiment is
Rotates continuously around the rotary shaft 13 at a constant speed, and gives an external measurement time and an internal measurement time at a time ratio of 10: 1 within each rotation cycle (measurement cycle).

FIG. 7 is a block diagram showing a circuit configuration example of the electric circuit section 23 according to this embodiment. The electric circuit section 23 includes a modulated wave generating section (24 to 27, 10), a modulated wave receiving section (11, 28 to 32),
It is composed of an arithmetic control unit (33 to 37), a display 38 and a rotational position detector 18.

The modulated wave generator includes a reference oscillator 24, a frequency generator circuit 25,
It is composed of a frequency switch 26, a drive circuit 27 and a light emitting element 10. The reference oscillator 24 generates a modulation frequency signal of 15 MHz, which is generated by the frequency generation circuit 25 and the gate circuit of the arithmetic control unit.
Give to 33 and. The frequency generation circuit 25 divides the input 15MHz signal to generate 150KHz and 15KHz signals, and
A 150KHz signal and 15KH
The z signal is used for the gate circuit 33 of the arithmetic control unit and the PLL of the modulated wave receiving unit.
And the circuit 32. The frequency switching device 26 operates in accordance with the switching control signal from the sequence control unit 37 of the control unit, 15 MHz, 1
Select either 50KHz signal. The modulation frequency signal output from the frequency switch 26 is amplified by the drive circuit 27 and then supplied to the light emitting element 10. The light emitting element 10 generates modulated wave light corresponding to this modulation frequency signal.

The modulated wave receiving unit includes a light receiving element 11, a preamplifier 28, a frequency converter 29, an amplifier 30, a waveform shaping circuit 31, and a PLL circuit 32.
Consists of The light receiving element 11 photoelectrically converts the input modulated wave light and outputs an electrical modulated wave signal. This modulated wave signal is
The frequency converter 29 converts the signal into a signal having a predetermined frequency (for example, 15 KHz). Then, this 15 KHz signal is amplified by an amplifier 30 and then shaped by a waveform shaping circuit 31 into a rectangular wave.
The rectangular wave signal of z is supplied to the gate circuit 33 of the arithmetic control unit as a measurement signal. The PLL circuit 32 functions as a local oscillation circuit and supplies a signal of a constant frequency (reception frequency + 15 KHz) to the frequency conversion circuit 29.

The arithmetic control unit includes a gate circuit 33, a counter 34, a memory 3
5, consisting of a microprocessor 36 and a sequence controller 37. The gate circuit 33 is 15KH from the frequency generation circuit 25.
In addition to inputting the z signal as the reference signal, the 15KHz signal from the waveform shaping circuit 31 is also input as the measurement signal, and the 15MHz signal from the reference oscillator 24 is output only during the period corresponding to the phase difference between the two 15KHz signals. Pass through. This phase difference is a measured value per sampling, and it is the time until the modulated wave generated by the modulated wave generation unit is emitted from the light emitting element, reflected by the target, and then returned to the light receiving element, or The time is 1 / N (N is an integer). The counter 34 counts the 15 MHz signal from the gate circuit 33 and outputs the cumulative count value to the memory 35 at a predetermined timing. As will be described later, the memory 35 includes a memory for external measurement and a memory for internal measurement, stores the measured value (count value) of external measurement in the memory for external measurement, and the measured value of internal measurement for internal measurement. Store in memory. Then, every predetermined cycle, for example, every time the optical path switching shutter 12 is rotated by 360 °, the data (externally measured value / internally measured value) in both memories is taken into the microprocessor 36. The microprocessor 36 corrects (calibrates) the external measurement value with the internal measurement value to determine the net distance measurement value, and displays the calculated measurement value on the display 38. The rotational position detector 18 provides a timing signal representing the rotational phase of the shutter 12 to the microprocessor 36.

Next, the operation of this embodiment will be described with reference to FIGS.

FIG. 8 is a timing chart for explaining the operation from when the power is turned on to when the main measurement is started. First, when the power supply voltage is turned on (FIG. 8 (a)), a self-check in the system is performed by the program of the microprocessor 36 (FIG. 8 (b)). Next, within the period in which the external measurement is prohibited (Fig. 8 (c)), only the internal measurement is executed and the internal measurement value is written in the internal measurement memory in the memory 35 (Fig. 8 (d). )). The internal measurement value acquisition period t is selected during a period in which the same number of internal measurement values as the number of external measurement values obtained in one measurement cycle in the main measurement are obtained. Next, after a lapse of a certain waiting time (Fig. 8 (e)), when a command to start the main measurement is given (Fig. 8 (f)), the main measurement is started in response to the command.
In each measurement cycle, external measurement and internal measurement are performed in a time division manner at a predetermined time ratio (10: 1).

FIG. 9 is a diagram showing the timing of the internal measurement time of the external measurement time in this embodiment. When the rotation speed of the shutter 12 is 10 rotations / second, the shutter 12 rotates once (360
It takes 100msec to rotate (° rotation), of which 8.33m
Sec is used for internal measurement and 83.3msec is used for external measurement. In this embodiment, the frequency of the reference signal / measurement signal is 15 KHz, so the sampling frequency is 15 KHz.
Hz, the sampling period is 66.7 μsec. Then
Using the time of 6.67msec within the internal measurement time (8.33msec)
100 times sampling was performed and the external measurement time (83.3mse
Within c8), sampling is performed 1000 times using a time of 66.7 msec.

FIG. 10 shows a configuration example of the memory 35 according to one embodiment.
The memory 35 includes an external measurement memory 35A and an internal measurement memory 35B. The external measurement memory 35A is configured to store a cumulative count value (external measurement value data) for 1000 samplings. Internal measurement memory 35B
Has 10 memory blocks m1 to m10, and is configured to store a cumulative count value (internal measurement value data) Cj for 100 samplings in each memory block mi.

Then, the internal measurement value acquisition operation after power-on (8th
(D)), internal measurement value data C1, C2 for 100 samplings are obtained each time the shutter 12 makes one rotation, and internal measurement value data C1 for 10 rotations of the shutter 12 (1000 samplings) C10 is stored in each of the blocks m1 to m10 of the internal measurement memory 35B.

When the main measurement is started (FIG. 8 (g)), the internal measurement value data C for 100 samplings is collected from the counter 34 at each measurement cycle, that is, every time the shutter 12 makes one rotation.
11 (C12, ...) and external measurement value data for 1000 samplings are obtained. The external measurement value data for 1000 times of sampling is written in the external measurement memory 35A, whereby all the data in the memory 35A is updated. on the other hand,
Internal measurement value data C11 (C12, C12,
...) is written in the internal measurement memory 35B, and this partially updates the data in the memory 35B.

Figure 11 shows the internal measurement memory 35B for each measurement cycle.
A part of the internal measurement value data is updated. As shown, internal measurement value data C11 (C12, ...) for 100 new samplings is written, and at the same time, the oldest data C1 (C2, C2, ...
...) is pushed out and erased. This enables sampling 1 from the data stored in the memory 35A.
A moving average value of 000 internal measurement data is obtained.

The microprocessor 36 captures the data in the external measurement memory 35A and the data in the internal measurement memory 35B updated as described above for each measurement cycle,
Based on these data, the average value of the external measurement values is calibrated by the moving average value of the internal measurement values to calculate the net distance measurement value, and the calculated distance measurement value is displayed on the display 38.

FIG. 12 shows another configuration example of the memory 35 for dual frequency measurement. In this configuration example, two internal measurement memories 35
B and 35C are provided, while one memory 35B has a modulation frequency of 15MH
It is used for internal measurement when z, and the other memory 35C is used for internal measurement when the modulation frequency is 150 KHz. When this memory 35 is used for two-frequency measurement, in the internal measurement value acquisition operation immediately after the power is turned on, the internal measurement value data of the shutter 10 rotations (1000 sampling times) at the frequency of 15 MHz is first stored in the first internal measurement memory 35B. Write, then 150KHz
The internal measurement value data of the shutter 10 rotations (1000 samplings) at the frequency is written in the second internal measurement memory 35C. Then, when the main measurement is started, the first shutter 1
In rotation, the modulation frequency is set to 15 MHz to obtain the moving average value of the internal measurement values from the first internal measurement memory 35B and the average value of the external measurement values from the external measurement value memory 35A.
The modulation frequency is set to 150 KHz by the next one rotation of the shutter to obtain the moving average value of the internal measurement values from the second internal measurement memory 35C and the average value of the external measurement values from the external measurement value memory 35A. When performing a plurality of measurement cycles, the above operation is repeated. Thus, in the case of dual frequency measurement,
One measurement cycle can be performed by rotating the shutter twice. However, when the measurement cycle is repeated many times, one frequency measurement (for example, measurement of 150 KHz frequency) can be thinned out if necessary.

FIG. 13 is a perspective view showing a modified example of the optical path switching shutter according to the present invention. Further, FIG. 14 is a bottom view showing the structure of the shutter 40, and FIG. 15 is a top view (FIG. 15 (a)) and a side view (FIG. 15 (b)) showing the shape of the circular mirror. .

In FIG. 13, the shutter 40 is formed in a disc shape, and is configured to be continuously rotated at a constant speed about a shaft 42 by a drive motor 41. This shutter 40 has
Similar to the shutter 12 of the embodiment shown in FIG. 1, an incomplete annular opening 4 in a predetermined range (for example, 300 °) is provided as an opening for external measurement. Then, on the surface (lower surface) facing the light emitting element 10, the surface reflection mirror 44 is attached to the part where the opening 43 is missing. This mirror 44 is the 15th
The surface is formed into a curved surface, which corresponds to a part (for example, a portion indicated by a dotted line 46) of the circular mirror 45 cut out as shown in the figure. Due to this curved surface, even if the angle of the light receiving surface of the mirror 44 is moved with respect to the optical axis from the light emitting element 10, the light wave from the light emitting element 10 is always at a constant reflection angle to the surface reflection mirror 22 side of the calibration optical path. It is supposed to be reflected.

Incidentally, as shown in FIG. 19, by disposing the cylindrical lens 47 and the spherical lens 48 in front of the surface reflection mirror 22 in the calibration optical path, a normal 45 instead of the curved reflection mirror 44 of FIG. It is also possible to use a right angle prism.

FIG. 16 is a perspective view showing another modification of the optical path switching shutter. Further, FIG. 17 shows the optical path switching shutter of FIG.
FIG. 18 is a plan view showing the structure of 54, and FIG. 18 is a plan view showing the structure of the optical path mask 56 of FIG.

In FIG. 16, 50 is a light emitting element, 51 is a light receiving element, 52 is a light transmitting lens, 53 is a light receiving lens, 54 is an optical path switching shutter,
55 is a drive motor, 56 is an optical path mask, 57 is a prism beam splitter, 58 is a light quantity adjusting filter, 59 is a mirror, 6
Reference numerals 0 and 61 denote light transmitting and receiving lenses. The shutter 54 is configured to continuously rotate at a constant speed by the drive motor 55. Then, as shown in FIG. 17, the shutter 54 is formed with an incomplete annular opening 62 for external measurement over a predetermined range (for example, 300 °), and is close to the lacking portion of the opening 62. A certain area on the edge (for example, 30
A notch 63 for internal measurement is formed over the angle.
The optical path mask 56 is fixedly arranged. This optical path mask
At 56, as shown in FIG.
An opening 64 for external measurement is formed at a predetermined position corresponding to, and an opening 65 for internal measurement is formed at a predetermined position corresponding to the notch 63 of the shutter 54.

Thus, when the external measurement opening 62 of the shutter 54 faces the external measurement opening 64 of the optical path mask 58 (during external measurement), the light wave from the light emitting element 50 is emitted from the shutter 54 and the optical path mask.
56, the light wave sent out to the target side via the beam splitter 57 and returned from the target is the beam splitter
The light is reflected by the light receiving lens 53 side at 57 and enters the light receiving element 51.
At this time, the notch 63 for internal measurement of the shutter 54 and the optical path mask 56
Since the internal measurement openings 65 of the optical path do not face each other, the light wave passing through the notch 63 is blocked by the non-opening portion of the optical path mask 56.

However, the internal measurement notch 63 of the shutter 54 is
When facing the internal measurement opening 65 of 56 (during internal measurement), the external measurement opening 62 of the shutter 54 does not face the external measurement opening 64 of the optical path mask 56 this time. At this time, no light wave goes to the beam splitter 57, and instead the shutter 54
Internal measurement notch 63 and optical path mask 56 internal measurement opening 65
A light wave directly passes through the light receiving lens 53 and enters the light receiving element 51.

Therefore, when the ranges of the external measurement opening 62 and the internal measurement notch 63 of the shutter 54 are set to 300 ° and 30 °, respectively, the shutter 54 is rotated within one cycle (measurement cycle).
External measurement time and internal measurement time are obtained at a 10: 1 time ratio.

FIG. 20 is a perspective view showing another modification of the optical path switching shutter. In FIG. 20, 70 is a light emitting element, 71 is a light receiving element, 72 is a light transmitting lens, 73 is a light receiving lens, 74 is white plate glass, 75 is a surface reflection mirror, 76 and 77 are liquid crystal shutters, and 78 is an electric circuit section. is there. The feature of this configuration example is the liquid crystal shutter.
The point is that an optical path switching shutter is configured using 76 and 77.

When performing external measurement, use the liquid crystal shutter 76 in the exit optical path.
ON, the liquid crystal shutter 77 in the calibration optical path is turned OFF. Then, the light wave transmitted through the white plate glass 74 is reflected by the liquid crystal shutter 76.
Exits to the light transmitting lens 72 side. However, white sheet glass 74
The light wave reflected by is blocked by the liquid crystal shutter 77 and does not reach the surface reflection mirror 75.

When performing internal measurement, use the liquid crystal shutter 77 in the calibration optical path.
ON, the liquid crystal shutter 76 in the emission optical path is turned OFF. Then, the light wave that has passed through the white plate glass 74 is transmitted to the liquid crystal shutter 77.
The light is blocked by and does not go out. On the other hand, the light wave reflected by the white plate glass 74 enters the surface reflection mirror 75 through the liquid crystal shutter 77, is reflected there and enters the light receiving element 71.

According to such a liquid crystal shutter system, both shutters 7
By controlling ON / OFF time of 6,77, external measurement time,
The internal measurement times and their time ratio can be arbitrarily selected.

In the embodiment described above, the range of the external measurement opening in the optical path switching shutter is 300 °, the range of the internal measurement opening or notch is 30 °, and the time ratio of the external measurement time to the internal measurement time is 10: 1. Although the case has been described, these values are merely examples, and the shutter can be configured to obtain an arbitrary time ratio.

[Effects of the Invention] As described above, according to the lightwave distance measuring method or the lightwave distance meter in the invention of the present application, for example, the average value of the external measurement values of 10 times is converted into the internal measurement value of 1 time in one measurement cycle. Since the calibration is performed with the updated moving average calibration value, a highly accurate measurement value can be obtained in a short measurement time.

Further, according to the optical shutter means of the present invention, the external measurement mode and the internal measurement mode can be continuously switched rather than intermittently, so that the cycle of the measurement cycle is shortened, and consequently the total measurement time is shortened. be able to.

Therefore, it is possible to follow the movement of the target object, and highly reliable measurement can be performed.

[Brief description of drawings]

1 to 20 are views for explaining an embodiment of a lightwave distance meter in the invention of the present application, FIG. 1 is a perspective view showing a configuration of a main part of the lightwave distance meter, and FIG. A plan view of the optical path switching shutter shown in FIG. 1 as seen from the direction of arrow A in FIG. 1, and FIG. 3 shows the optical path switching shutter shown in FIG. 2 as indicated by arrow B in FIG.
4 is a side view as seen from the direction of FIG. 4, FIG. 4 is a perspective view showing a state where the shutter has rotated a predetermined angle from the first state, and FIG. 5 shows the optical path switching shutter shown in FIG. 6 is a plan view seen from the direction of FIG. 6, FIG. 6 is a side view of the optical path switching shutter shown in FIG. 5 seen from the direction of arrow B in FIG. 5, and FIG. 7 is a circuit configuration of the electric circuit section shown in FIG. FIG. 8 is a block diagram showing an example, FIG. 8 is a timing diagram for explaining the operation of the lightwave rangefinder shown in FIG. 1, and FIG. 9 is a relation between the external measurement time and the internal measurement time given by the lightwave switching shutter of the embodiment. 10 is a block diagram showing a configuration example of the memory shown in FIG. 1, FIG. 11 is a diagram showing changes in internal measurement value data stored in the internal measurement memory shown in FIG. 10, FIG. 12 is a block diagram showing a modification of the internal measurement memory, and FIG. 13 is an optical path switching system. A perspective view showing a modified example of the cutter,
FIG. 14 is a plan view showing the structure of the shutter shown in FIG.
FIG. 15 is a view showing the shape of a circular mirror for explaining the surface reflection mirror shown in FIG. 13, FIG. 16 is a perspective view showing another modification of the optical path switching shutter, and FIG. 17 is shown in FIG. 18 is a plan view showing the structure of the shutter, FIG. 18 is a plan view showing the structure of the optical path mask shown in FIG. 16, FIG. 19 is a perspective view showing a modification of the configuration example shown in FIG. 13, and FIG. It is a perspective view which shows the other modification of an optical path switching shutter. 21 to 24 are views for explaining a conventional optical distance meter, FIG. 21 is a perspective view showing a configuration of a main part of the optical distance meter, and FIG. 22 is an optical path shown in FIG. FIG. 23 is a plan view showing the structure of the switching shutter, FIG. 23 is a side view showing a state in which the shutter is rotated by a predetermined angle from the state shown in FIG. 21, and FIG. 24 is a diagram for explaining the measuring operation of the optical rangefinder shown in FIG. It is a flow chart for. In the reference numerals used in the drawings, 10,50,100 ... light emitting element 11, 51,101 ... light receiving element 12,40, 54 ... optical path switching shutter 35 ... memory, 35B, 35C ... internal configuration memory 76, 77 ...... It is a liquid crystal shutter.

Claims (4)

[Claims] 1. A distance value to the target object is obtained from a phase difference between the reflected light returning to a light receiving element after projecting the modulated light onto the target object through an external optical path and the modulated light, A calibration measurement value is obtained from the phase difference between the calibration light that has reached the light receiving element via the internal calibration optical path and the modulated light, and the distance value is calibrated by switching the external optical path and the calibration optical path. In a lightwave distance measuring method in which measurement values are calibrated, n distance values and one calibration measurement value are obtained for each measurement cycle, where n is an integer of 2 or more, and the n distance values are added. A lightwave distance measuring method characterized in that an average distance value is obtained by averaging, and the average distance value is calibrated with the calibration measurement value. 2. A light-emitting element for projecting modulated light onto an object via an external optical path, a light-receiving element for receiving reflected light reflected by the object, and a position between the modulated light and the reflected light. Means for obtaining a distance value from the phase difference to the target object, calibration light that reaches the light receiving element via the internal calibration optical path for the modulated light, and means for obtaining a calibration measurement value from the phase difference between the modulated light and In the lightwave rangefinder having means for calibrating the distance value with the calibration measurement value by switching the external optical path and the calibration optical path, the opening time of the external optical path is set to be smaller than that of the calibration optical path for each measurement cycle. Switching to n times, where n is an integer greater than or equal to 2, optical shutter means, n memories for storing measured values n times in the opening of the external optical path, and 1 time in the opening of the calibration optical path. A calibration memory that stores calibration measurement values, An adder circuit for adding the contents of the n memories and outputting a cumulative distance value; a divider circuit for dividing the cumulative distance value by n to obtain an average distance value; And a subtraction circuit for subtracting the calibration measurement value in the calibration memory. 3. The light shutter means is a light shield that rotates at a constant speed, and a distance formed or provided in the light shield so that the opening time of the external light path is n times that of the calibration light path. The optical distance meter according to claim 2, further comprising a light transmitting or reflecting means for measurement and calibration. 4. The optical shutter means comprises a first liquid crystal shutter that selectively forms the external optical path and a second liquid crystal shutter that selectively forms the calibration optical path. Lightwave rangefinder.