JP2016161363A - Optical coordinate measurement device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure spatial coordinates of a point of interest in a spatial coordinate system with an arbitrary origin using a simple device configuration and method.SOLUTION: A coordinate measurement device measures coordinates of a point of interest by; providing a photoemitter at a point of interest; providing a plurality of photoreceivers positioned at known coordinates to receive light emitted by the photoemitter; receiving the light emitted by the photoemitter using photoreceiver pairs, each consisting of an arbitrary pair of photoreceivers selected from the plurality of photoreceivers; computing a travel path distance difference, or a difference between a distance from the photoemitter to a first photoreceiver and a distance from the photoemitter to a second photoreceiver, for one photoreceiver pair; similarly computing a travel path distance difference for each of a plurality of photoreceiver pairs; and computing coordinates of the photoemitter from the known coordinates of the plurality of photoreceivers and the travel path distance differences of the photoreceiver pairs.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an apparatus for measuring the coordinates of a target point with light in a coordinate system having an arbitrary point as an origin.

As means for obtaining the three-dimensional coordinates, there are various methods such as optical, ultrasonic, radio, mechanical, magnetic, and GPS (global positioning system). However, each system has advantages and disadvantages, and an inexpensive, easy-to-use and accurate system has not been put into practical use and does not exist as a product.

In the field of basic construction surveying in the construction industry such as housing, the surveying point is pointed by an indicator (such as a pole) equipped with a reflecting prism, and the reflecting prism is tracked by analyzing the image obtained from the built-in camera. There are products that derive three-dimensional coordinates from distance information obtained by laser measurement and angle information obtained from each built-in two-axis servo motor.

However, this method requires a very high-performance encoder, which increases the cost. In measurement, it is necessary to track the measurement point indicator using the motor as described above, and thus the indicator must be moved within a trackable range, which is inconvenient. In addition, it is impossible to simultaneously measure a plurality of locations by a plurality of people.

Accordingly, the inventor of the present application has made an invention to solve these problems, and has applied for Japanese Patent Application No. 2012-227909 (Japanese Patent Application Laid-Open No. 2014-081232) “Wireless Coordinate Measuring Device”.

JP 2014/081232 A

The technique of Patent Document 1 uses radio. Wireless is less affected by obstacles and is one of the preferred means for 3D coordinate measurement, but it is affected by noise such as interference and harmonics in any frequency band, and multipath Therefore, it is necessary to limit the field to be used, and the versatility is lowered.

Therefore, the present invention has been made to solve the above problems.
The coordinate measuring device according to the present invention is:
“A light emitting part that emits light,
A plurality of light receiving units arranged at known coordinates in an arbitrary spatial coordinate system and receiving light emitted by the light emitting unit;
Based on the light received by the light receiving unit included in the light receiving unit pair, the first light reception of the light receiving unit pair from the light emitting unit based on the light received by the light receiving unit included in the light receiving unit pair. A propagation path distance difference calculating unit that calculates a propagation path distance difference that is a difference between a distance from the light emitting unit and a distance from the light emitting unit to the second light receiving unit of the light receiving unit pair;
A light emitting unit coordinate calculating unit that calculates the coordinates of the light emitting unit based on the known coordinates of the plurality of light receiving units and the propagation path distance difference calculated for each of the plurality of light receiving unit pairs;
With "
It is characterized by that.

The light emitting unit of the coordinate measuring device of the present invention is
"The light emitting part is provided separately from the plurality of light receiving parts."
It is characterized by that.

Furthermore, the coordinate measuring apparatus of the present invention is
“Light is amplitude modulated with a sine wave of a certain frequency”
It is characterized by that.

According to the present invention, three-dimensional coordinate measurement can be performed using light that is amplitude-modulated with a sine wave having a specific frequency.

Before the detailed description, common matters in the present specification will be described.
In the present invention, the light emitted from the light emitting unit is visible light, infrared light, ultraviolet light, X-rays, and the like, and the coordinates mean coordinates in a three-dimensional (three-dimensional) space orthogonal coordinate system unless otherwise specified.

It is a figure which shows the concept of this invention. It is a figure which shows the structure of a light-receiving part. It is a figure which shows the synthesis | combination of the signal waveform of the light received with the light-receiving part pair, and the oscillation waveform of a local oscillator.

FIG. 1 illustrates the basic concept of the present invention.
The reference module is handled so as not to move during a series of coordinate measurements, and can be regarded as the origin (or specific coordinates) of the virtual coordinate system. The reference module has a plurality of light receiving portions, and in FIG. 1, there are five light receiving portions. However, the reference module is not particularly limited to this.
The virtual coordinate system assumes that the horizontal direction is the X axis, the vertical direction is the Y axis, and the depth horizontal direction is the Z axis.
The measurement module includes a measurement point indicating unit that indicates a point whose coordinates are to be measured, a light emitting unit that emits light, and a measurement result display unit that displays a result of coordinate measurement. The user moves with this measurement module, points to the point to be coordinate-measured by the measurement point instruction unit, and instructs the measurement module to start measurement by pressing a measurement start switch (not shown). The result of coordinate measurement in the virtual coordinate system is displayed on the measurement result display unit.

FIG. 2 shows the structure of the light receiving portion of the reference module.
First, light is emitted from the light emitting unit of the measurement module. In FIG. 2, the light is amplitude-modulated with a 1 GHz sine wave as an example, but of course there is no reason limited to this. As is obvious, a 1 GHz local oscillator (not shown) is provided in the measurement module.
The reference module has five light receiving portions, which are light receiving portions R1 to R5, respectively.
Each of the light receiving portions R1 to R5 receives light emitted from the light emitting portion of the measurement module.

The light received by each of the light receiving portions R1 to R5 is converted into an electrical signal, and a signal component (1 GHz sine wave in this embodiment) used for amplitude modulation is extracted and input to the mixer.
In the reference module, a clock (local oscillator) of 1.00001 GHz (= 1 GHz + 10 kHz) is provided, and each mixer is applied to the 1 GHz sine wave signal received by the light receiving units R1 to R5 of the sine wave signal generated by the local oscillator. Mix with. Although the line lengths from the local oscillator to the mixer are all different in the figure, the circuits are actually adjusted so that the signals reach all the mixers at the same timing.
A signal mixed by each mixer is read by a microcomputer through an A / D (analog-digital) converter. The microcomputer processes the read signal as data.

FIG. 3 shows a waveform when a sine wave of 1 GHz and a sine wave of 1.00001 GHz (= 1 GHz + 10 kHz) are mixed by a mixer.
When two sine waves having similar frequencies are mixed, a signal whose amplitude varies with a frequency difference as a period (so-called “swell”) is obtained. Since the frequency difference is 10 kHz, the swell frequency is 10 kHz. The aforementioned microcomputer detects the envelope of this amplitude variation and analyzes the waveform.
Hereinafter, based on the above-mentioned prior art document (Japanese Patent Application No. 2012-227909 / Japanese Patent Application Laid-Open No. 2014-081232), common points will be treated only by reference and different points will be mainly described.

The gist of the prior art is to assume four receiving unit pairs, calculate the difference in distance between each of the two receiving units of the receiving unit pair and the transmitting unit, and calculate the transmitting unit with the difference in distance between the four receiving unit pairs. The three-dimensional coordinates are obtained.
In order to construct four receiver pairs, a system in which four receivers are arranged in a triangular pyramid shape was adopted in consideration of cost reduction. However, in the present invention, five light receiving parts are arranged in a quadrangular pyramid shape in order to improve measurement accuracy. It was set as the method to arrange in.
First, as described above, the signal mixed by the mixer has a beat of 10 kHz. By applying FFT (Fast Fourier Transform) processing to the envelope waveform of this signal by a microcomputer, the frequency of the envelope and the mixer The phase difference between the two signals mixed together can be obtained.

At this time, the frequency of the sine wave for amplitude modulation of the light emitted from the light emitting unit is f, the speed of light is c, the phase value of the reference signal among the signals mixed in the mixer is θ1, and the phase value of the other signal is When θn, the distance between the light emitting unit and the light receiving unit that receives the θ1 signal is d1, and the distance between the light emitting unit and the light receiving unit that receives the θn signal is dn, the distance difference Dm = dn−d1 is expressed by the following equation. Can be calculated (m = 1 to 4).
The subscripts n and m frequently used in the following formulas are as follows.
n is a number indicating a specific one of the plurality of light receiving portions. In this embodiment, there are five light receiving portions, and therefore n is in the range of 1 to 5.
Among these, a light receiving unit with n = 1 is treated as a center, and a light receiving unit pair is configured by a combination with light receiving units other than n = 1 (n = 2 to 5). In other words, when the light receiving part is represented as Rn, there are four light receiving part pairs: “R1 pair R2”, “R1 pair R3”, “R1 pair R4”, and “R1 pair R5”. These four combinations of light receiving part pairs are denoted by m. For example, “R1 vs. R2” is m = 1. When there are five light receiving parts, m is in the range of 1-4. If the writing method is different using m, it also means that the light receiving unit pair “R1 pair R (m + 1)” is shown.

From this, if the frequency f of the sine wave that modulates the amplitude of the light emitted from the light emitting unit and the frequency of the local oscillator in the reference module (= determines the swell frequency when mixed by the mixer) are known, The difference D between the “distance between the light emitting part and one light receiving part of the light receiving part pair” and the “distance between the light emitting part and the other light receiving part in the light receiving part pair” is known.
Since the same can be said for the relationship with the signals of the other light receiving parts, the difference in distance between the light receiving parts R1 to R5 with respect to the light emitting part is also obtained in the same manner.

In the prior art, four receiving units are configured by four receiving units. However, in the present invention, four light receiving units are configured by five light receiving units, and therefore a part corresponding to Equation 4 in the prior art document. Is as follows.

Based on the contents so far, a method for obtaining the coordinates of the light emitting unit from the distance difference Dm will be described.
The coordinates of the light emitting unit l are assumed to be l (x, y, z).
The coordinates of the light receiving parts R1 to R5 are known, and this is assumed to be Rn (x, y, z) (n = 1 to 5).
The linear distance between the light receiving part Rn and the light emitting part 1 is dn (n = 1 to 5).
The difference (distance difference) between d1 and d2 to d4 is rm (m = 1 to 4).
Am (m = 1 to 4) is obtained by converting a known delay factor on the circuit generated between the light receiving portions R1 and Rn into a distance.
A phase value obtained by subjecting the mixer output waveform to A / D conversion and FFT is θn (n = 1 to 5).

At this time,
T1 = D1-A1
T2 = D2-A2
T3 = D3-A3
T4 = D4-A4
Then,
C, X, Y, and Z can be defined as intermediate variables as follows.

Based on the above-mentioned intermediate variables, the coordinates l (x, y, z) of the light emitting unit are obtained by the following equations.

In this way, the coordinates of the light emitting unit are obtained by substituting the known coordinates of the five light receiving units and the propagation path distance difference measured in each pair of the light receiving units composed of the respective light receiving units into the mathematical formula. Is possible.

In the measurement module of FIG. 1, the target of the three-dimensional coordinate measurement is a part where the light emitting unit exists. However, if an accelerometer or the like is provided in the measurement module so as to acquire a posture in the direction of gravity, light emission Since the distance from the unit to the measurement point instruction unit is known, the coordinates of the measurement point instruction unit can also be calculated.

Further, although the measurement is performed on the reference module side, the measurement result may be notified to the measurement module side by communication means. In the example shown in FIG. 2, the result of measurement using Bluetooth (registered trademark) is transmitted to the measurement module.

The present invention has been described with reference to preferred embodiments. However, the present invention is not limited to these embodiments, and many modifications can be made without departing from the spirit of the invention. Of course.

Coordinate measurement at a specific location can be easily performed by using a light emitting unit and a light receiving unit that can be mass-produced, and there is an effect of improving the efficiency of operations such as dimension measurement and surveying.

Claims (3)

A light emitting unit that emits light;
A plurality of light receiving units arranged at known coordinates in an arbitrary spatial coordinate system and receiving light emitted from the light emitting unit;
A plurality of light receiving unit pairs each including two arbitrary light receiving units among the plurality of light receiving units, and based on light received by the light receiving units included in the light receiving unit pair, A propagation path distance difference calculation unit that calculates a propagation path distance difference that is a difference between a distance to the first light receiving unit and a distance from the light emitting unit to the second light receiving unit of the light receiving unit pair;
A light emitting unit coordinate calculating unit that calculates coordinates of the light emitting unit based on known coordinates of the plurality of light receiving units and the propagation path distance difference calculated for each of the plurality of light receiving unit pairs;
A coordinate measuring apparatus comprising: The coordinate measuring apparatus according to claim 1, wherein the light emitting unit is provided separately from the plurality of light receiving units. The coordinate measuring apparatus according to claim 1, wherein the light is amplitude-modulated with a sine wave having a specific frequency.