Laser measuring method and laser measuring system having fan-shaped tilted laser beams and three known points of photodetection system

A laser measuring method in a laser measuring system, which comprises a rotary laser system for projecting a laser beam by rotary irradiation and at least one photodetection system having at least one photodetector for receiving the laser beam, comprising a step of emitting at least two fan-shaped laser beams by the rotary laser system, at least one of the fan-shaped laser beams being tilted, a step of receiving the laser beams at least at three known points by the photodetection system, a step of obtaining elevation angles with respect to the rotary laser system based on photodetection signals which are formed when the photodetector receives the laser beam, and a step of measuring an installing position of the rotary laser system based on elevation angles and position data at the three known points.

BACKGROUND OF THE INVENTION

The present invention relates to a laser measuring method and a laser measuring system, by which a laser beam is projected by rotary irradiation for the purpose of forming a horizontal reference plane or a reference plane tilted with respect to the horizontal reference plane at a predetermined angle and by which it is possible to measure a position by receiving the laser beam.

As a representative system for forming a reference plane by projecting a laser beam by rotary irradiation, a rotary laser system installed at a known point and a photodetection system installed at a measuring point and used for receiving a laser beam from the rotary laser system have been known in the past.

A rotary laser system forms a reference plane by projecting a laser beam with a cross-section of luminous flux in spot-like shape. For instance, when the laser beam is projected in a horizontal plane by rotary irradiation, a horizontal reference plane is formed. When the laser beam is projected within a vertical plane by rotary irradiation, a vertical reference plane is formed. When the laser beam is projected within a tilted plane by rotary irradiation, a tilted reference plane is formed.

The photodetection system comprises a photodetection unit for receiving and detecting a laser beam. Based on the laser beam detected by the photodetection unit, a horizontal reference position, a vertical reference position, etc. are measured.

When measurement as required is performed by projecting a laser beam from a rotary laser system by rotary irradiation, accuracy of installation of the rotary laser system gives direct influence on a measured value. Therefore, it is important to install the rotary laser system at a known point with high accuracy. However, accurate installation requires skill and is difficult to perform. Also, measurement is based on the assumption that the rotary laser system is installed at a known point. Depending on the circumstances, there may be no adequate known point for installing the rotary laser system or there may be environmental condition not suitable for installing the rotary laser system at a known point. In such cases, there has been such problem that measuring operation itself is often difficult to carry out.

When the rotary laser system can be installed, there is no effective method to verify whether the rotary laser system has been accurately installed or not. Further, when the rotary laser system is installed in tilted condition, error may occur with respect to the known point but there has been no effective method to detect such error. Also, when deviation of position occurs due to later cause after the system has been installed, there has been no effective method to detect such deviation.

A laser measuring system is disclosed in JP-A 2002-39755, in which a laser beam is projected by rotary irradiation to form a horizontal reference plane or a reference plane tilted at a predetermined angle with respect to the horizontal reference plane, and by which position can be measured by receiving the laser beam at a photodetection system.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a laser measuring system, in which a rotary laser system can be installed at any desired point and by which it is possible to perform accurate measurement without being influenced by installing conditions such as tilting of the rotary laser system, and deviation of the rotary laser system can be confirmed and corrected when positional deviation occurs at a later time after the installation.

To attain the above object, the present invention provides a laser measuring method in a rotary laser system, which comprises a rotary laser system for projecting a laser beam by rotary irradiation and at least one photodetection system having at least one photodetector for receiving the laser beam, comprising a step of emitting at least two fan-shaped laser beams by the rotary laser system, at least one of the fan-shaped laser beams being tilted, a step of receiving the laser beams at least at three known points by the photodetection system, a step of obtaining elevation angles with respect to the rotary laser system based on photodetection signals which are formed when the photodetector receives the laser beam, and a step of measuring an installing position of the rotary laser system based on elevation angles and position data at the three known points.

Also, the present invention provides a laser measuring system, which comprises a rotary laser system for projecting a laser beam by rotary irradiation and at least one photodetection system for receiving the laser beam, wherein the rotary laser system has a laser projector for emitting at least two fan-shaped laser beams, at least one of the fan-shaped laser beams being tilted, the photodetection system comprises at least one photodetector for receiving the fan-shaped laser beams, the photodetection system is installed at least at three known points, elevation angles with respect to the rotary laser system are calculated based on photodetection signals which are formed when the photodetector receives the laser beam, and an installing position of the rotary laser system is calculated based on elevation angles and position data at the three known points. Further, the present invention provides the laser measuring system as described above, wherein the photodetection system comprises a GPS position measuring system, and a position of the photodetection system is measured by the GPS position measuring system.

According to the present invention, a laser measuring method is provided, which comprises a rotary laser system for projecting a laser beam by rotary irradiation and at least one photodetection system having at least one photodetector for receiving the laser beam, comprising a step of emitting at least two fan-shaped laser beams by the rotary laser system, at least one of the fan-shaped laser beams being tilted, a step of receiving the laser beams at least at three known points by the photodetection system, a step of obtaining elevation angles with respect to the rotary laser system based on photodetection signals which are formed when the photodetector receives the laser beam, and a step of measuring an installing position of the rotary laser system based on elevation angles and position data at the three known points. As a result, there is no need to install the rotary laser system at a known point. This contributes to the improvement of working efficiency and to the elimination of error, which may occur during installation. Also, when the position of the rotary laser system is deviated after installation, the installing position can be corrected.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Description will be given below on the best aspect to carry out the present invention referring to the drawings.

First, description will be given on general features of a rotary laser system and a photodetection system used in the present embodiment referring toFIG. 1toFIG. 3.

A rotary laser system1projects a plurality of fan-shaped laser beams by rotary irradiation. A photodetection system2comprises a photodetection unit41(to be described later). The photodetection unit41comprises at least one photodetector (in the figure, two photodetectors are shown), which receives the fan-shaped laser beams.

A tripod5is installed at a position to approximately align with an approximately known point X, and the rotary laser system1is mounted on the tripod5. The rotary laser system1comprises a main unit6and a rotating unit7rotatably mounted on the main unit6. A laser beam3is projected by rotary irradiation from the rotating unit7. The photodetection system2is supported by a supporting means as required.FIG. 1shows operating condition in outdoor conditions. The photodetection system2is installed on a rod8, which can be manually handled by an operator.

The laser beam3comprises a plurality of fan-shaped beams (fan-shaped laser beams). For instance, the laser beam3is arranged in N-shaped configuration, comprising vertical fan-shaped beams3aand3band a fan-shaped beam3ctilted at an angle of θ on a diagonal line with respect to the fan-shaped beams3aand3b. Each of the fan-shaped beams3aand3bare projected with a spreading angle of α in a direction of ±δ (SeeFIG. 6). The fan-shaped beams3aand3bare not necessarily vertical in so far as the fan-shaped beams3aand3bare parallel to each other and cross a horizontal plane.

Referring toFIG. 2andFIG. 3, description will be given on the rotary laser system1.

The rotary laser system1according to the present invention comprises a casing10and a laser projector12having a projection optical axis11(to be described later). The laser projector12is tiltably accommodated in the casing10.

A recessed portion13in truncated conical shape is formed at a center of an upper surface of the casing10, and the laser projector12is penetrating through a center of the recessed portion13in an up-to-bottom direction. The laser projector12is supported on the recessed portion13via a spherical seat14so that the laser projector12can be tilted. On an upper portion of the laser projector12, the rotating unit7is rotatably mounted, and a pentagonal prism15is provided on the rotating unit7.

A scanning gear16is arranged on the rotating unit7. The laser projector12is provided with a scanning motor18having a driving gear17. The rotating unit7can be rotated and driven by the scanning motor18via the driving gear17and the scanning gear16.

Two sets of tilting mechanisms19(only one of the tilting mechanisms19is shown in the figure), which are arranged around the laser projector12, are accommodated within the casing10. The tilting mechanism19comprises a motor for tilting21, a screw for tilting22having a center of rotation in parallel to the laser projector12, and a tilting nut23threaded on the screw for tilting22.

The laser projector12comprises two tilting arms24(only one of the tilting arms24is shown in the figure), which are extended in a direction perpendicularly crossing the projection optical axis11, and the tilting arms24perpendicularly cross each other. At a tip of each of the tilting arms24, a pin with circular cross-section is protruded, and the tilting arm24is engaged with the tilting mechanism19via the pin.

The motor for tilting21can rotate the screw for tilting22via a driving gear25and a gear for tilting26. When the screw for tilting22is rotated, the tilting nut23is moved up or down. When the tilting nut23is moved up or down, the tilting arm24is tilted, and the laser projector12is tilted. The other set of the tilting mechanism not shown in the figure tilts the laser projector12in a direction perpendicular to the tilting direction of the tilting mechanism19by a mechanism similar to the mechanism of the tilting mechanism19.

On an intermediate portion of the laser projector12, there are provided a fixed tilt sensor27in parallel to the tilting arm24and a fixed tilt sensor28in a direction perpendicular to the tilting arm24. By the fixed tilt sensor27and the fixed tilt sensor28, a tilt angle of the laser projector12in any direction can be detected. Based on the result of the detection by the fixed tilt sensor27and the fixed tilt sensor28, the laser projector12is tilted by the two sets of the tilting mechanisms19via two tilting arms24, and the laser projector12can be controlled so that the laser projector12is always maintained in a vertical direction. Also, the laser projector12can be tilted at any desired angle.

Referring toFIG. 3, description will be given now on the laser projector12and the rotating unit7.

A projection optical system33comprises a laser beam emitting unit31and a collimator lens32, etc. arranged along the projection optical axis11, and the projection optical system33is accommodated in the laser projector12.

The rotating unit7has a prism holder34. The prism holder34holds the pentagonal prism15and a diffraction grating (BOE)35provided under the pentagonal prism15.

The laser beam3emitted from the laser beam emitting unit31is turned to parallel beams by the collimator lens32, and the laser beam3enter the diffraction grating35. The incident laser beam3is divided so as to form three fan-shaped beams3a,3b, and3cby the diffraction grating35. The fan-shaped beams3a,3band3care deflected in a horizontal direction by the pentagonal prism15and are projected through a projection window36of the prism holder34.

The diffraction grating35may be arranged at a position where the laser beam3passes through after being deflected by the pentagonal prism15. InFIG. 2, reference numeral37denotes an encoder for detecting a rotation angle of the rotating unit7, and38denotes a transparent cover in cylindrical shape.

Light emitting condition of the laser beam emitting unit31is controlled by a light emission control unit39. For instance, communication data can be superimposed on the laser beam3by a method, e.g. a method to modulate the laser beam3. Thus, data such as positional information on the direction of rotary projection of the rotary laser system1detected by the encoder37can be sent to the photodetection system2via optical communication.

A wireless communication equipment may be separately provided as a communication means, and data may be transmitted to the photodetection system2via wireless communication.

Next, description will be given on the photodetection system2referring toFIG. 4andFIG. 5.

The photodetection system2comprises a photodetection unit41for detecting the fan-shaped beams3a,3band3c, a display unit42, a mark display unit43, an alarm unit44such as a buzzer, and an input unit45such as input keys. The photodetection unit41comprises a plurality of, for instance, two photodetectors41aand41barranged above and under, each comprising a light emitting element such as a laser diode. A distance D between the photodetector41aand the photodetector41bis a known value. Further, a storage unit46, an arithmetic operation unit47, a photodetection signal processing circuit48, and a photodetection signal output unit49are incorporated in the photodetection system2.

On the display unit42, an angle (elevation angle γ (SeeFIG. 8)) formed by a straight line, which connects a center point of rotation of the laser beam3with the photodetector41, and a horizontal reference plane is displayed, and a distance between the photodetection system2and the rotary laser system1is also displayed. The mark display unit43comprises marks, i.e. a central line and triangles, which are arranged at symmetrical positions with respect to the central line. The central line is lighted up when scanning position of the laser beam3is at the center of the horizontal line. When a scanning position of the laser beam3is above or under the center of the horizontal line, a corresponding mark is lighted up.

In the storage unit46, there are provided calculation programs necessary for surveying operation such as a program to calculate the elevation angle γ (to be described later) based on a signal from the photodetection unit41, a program to calculate a distance between the rotary laser system1and the photodetection system2, and a program to identify position of the rotary laser system1.

When the fan-shaped beams3a,3band3care received, a photodetection signal from the photodetection unit41is inputted to the photodetection signal processing circuit48, and it is detected whether the light has been received or not. Required signal processing such as A/D conversion is performed, and communication data superimposed on the fan-shaped beams3a,3band3care extracted and analyzed, and the results are inputted to the arithmetic operation unit47. As to be described later, the arithmetic operation unit47calculates the elevation angle γ based on the signal from the photodetection signal processing circuit48. Further, based on positional relation between the photodetectors41aand41b, a distance L between the rotary laser system1and the photodetection system2and tilting of the rod8is calculated. Further, the arithmetic operation unit47inputs the calculation results to the storage unit46and the results are displayed on the display unit42. Also, calculation results are transmitted to the rotary laser system1by optical communication via the photodetection signal output unit49.

Positional information of a point such as the known point X may be inputted in advance to the storage unit46by the input unit45. When the rotary laser system1has a wireless communication equipment as a communication means, a wireless receiver is provided on the photodetection system2.

The results of the calculation by the arithmetic operation unit47are outputted by the photodetection signal output unit49. An output from the photodetection signal output unit49is used as a signal to drive the mark display unit43.

Now, such calculations in the photodetection system2are described below as calculation of a distance between the rotary laser system1and the rod8, and calculation of a height of the photodetection system2and the like.

The rotary laser system1is installed via the tripod5at a predetermined point. Based on the results of detection by the fixed tilt sensors27and28, the tilting mechanism19is driven, and adjustment is made so that the laser projector12is maintained at vertical position.

The rod8is set at a measuring point. The photodetection system2is mounted at a predetermined height on the rod8, i.e. at a known height from the ground surface. Therefore, a distance between the lower end of the rod8and the photodetector41ais already known. The distance D between the photodetectors41aand41band the distance between the lower end of the rod8and the photodetector41aare inputted to the photodetection system2by the input unit45. The data such as the distance D are stored in the storage unit46via the arithmetic operation unit47.

A height of the photodetection system2, i.e. a difference of height of the photodetectors41aand41bwith respect to the horizontal reference plane, a distance L between the rotary laser system1and the photodetection system2, and elevation angles γ1and γ2with respect to the photodetectors41aand41bare calculated based on the receiving condition of the photodetection signals of the photodetectors41aand41band based on the distance D.

The elevation angles γ1and γ2are calculated by the arithmetic operation unit47based on photodetection signals emitted when the photodetectors41aand41brespectively receive the fan-shaped beams3a,3band3c. When the photodetection unit41is deviated from a photodetection range of the laser beam3or the like, the alarm unit44issues buzzer, etc. to attract the attention of the operator.

Now, description will be given on the elevation angle γ and the height difference with respect to the horizontal reference plane at the position of the photodetection system2referring toFIG. 6.FIG. 6shows the relation between the photodetector41and the laser beam3. The height H represents a height of the reference plane, i.e. a height of the center of the laser beam3. In other words, the height H is the height to the horizontal line.

The laser beam3is projected by rotary irradiation, and the laser beam3crosses the photodetection unit41, e.g. the photodetector41a. Because the laser beam3comprises the fan-shaped beams3a,3band3c, photodetection can be performed even when the photodetector41ais a spot-like photodetection element, and there is no need to perform accurate positioning of the photodetection system2.

When the laser beam3crosses over the photodetector41a, each of the fan-shaped beams3a,3band3cpasses through the photodetector41a. From the photodetector41a, photodetection signals51a,51band51ccorresponding to the fan-shaped beams3a,3band3crespectively are issued.

When the photodetector41ais at a position of a point A as shown inFIG. 6toFIG. 9with respect to the laser beam3, i.e. when the photodetector41ais at the center of the laser beam3, the photodetection signal is as shown inFIG. 10(A), and a time interval “t” between two each of three photodetection signals51a,51cand51bis equal to each other (=t0/2). The rotating unit7is driven by at a constant rotation speed. In the figure, the symbol T represents a period, during which the laser beam3is rotated by one turn.

When the photodetector41ais deviated from the center of the laser beam3and is at a position of a point B shown inFIG. 6toFIG. 9, the time interval between two each of the photodetection signals51a,51cand51bis different (FIG. 10(B)). When it is assumed that the photodetector41ais relatively moved from the right to the left inFIG. 7(i.e. the laser beam3moves from the left to the right in the figure), the time interval “t” between the photodetection signal51aand the photodetection signal51cbecomes shorter, and the interval between the photodetection signal51cand the photodetection signal51bbecomes longer.

The shapes formed by the laser beam3inFIG. 6are similar to each other regardless of the distance between the photodetection system2and the rotating unit7. By determining the ratio of the time intervals, a light-passing position in the figure can be calculated in the figure, which is turned to dimensionless. Therefore, regarding to the photodetector41a, the elevation angle γ1to the position of the point B with the rotating unit7at the center can be calculated according to the equation (1).
γ1=δ(1−2t1/t0)tan θ  (1)

Similarly, the elevation angle γ2of the photodetector41bcan be calculated by the equation (2).
γ2=δ(1−2t2/t0)tan θ  (2)

Further, based on the elevation angles γ1and γ2and on the distance D, the distance L between the rotary laser system1and the photodetection system2can be calculated by the equations given below.

Description will be given below on calculation of the distance L referring toFIG. 11.

Here, it is supposed that a distance from the horizontal position to the photodetector41ais d1, and a distance from the horizontal position to the photodetector41bis d2. Then, the distance L can be calculated from the following equations:
d1=Ltan(γ1)  (3)
d2=Ltan (γ2)  (4)
D+d1=d2  (5)

When the distance L is obtained, height differences d1and d2up to the photodetectors41aand41brespectively can be calculated by the equations (3) and (4).

As described above, when the laser beam3is projected by rotary irradiation at a constant speed, the laser beam3comprising a plurality of fan-shaped beams (fan-shaped laser beams) (e.g. the laser beam3comprises vertical fans-shaped beams3aand3band a fan-shaped beam3ctilted at an angle of θ on a diagonal line with respect to the fan-shaped beams3aand3b, thus being arranged in N-shaped configuration), and when the laser beam3is received by the photodetection system2, it is possible to determine the distance between the rotary laser system1and the photodetection system2, the values of heights d1and d2of the photodetection system2, and the elevation angle γ.

Therefore, because the position of installation of the rotary laser system1is already known, measurement on the photodetection system2can be made.

Next, description will be given on operation when the rotary laser system1is installed referring toFIG. 12.

As described above, when the photodetection system2comprises at least one photodetector41, the elevation angle γ can be measured. Further, by installing the photodetection system2at a known point, 3-dimensional coordinates (x, y, z) can be obtained from a single photodetection system2or from the photodetection system2installed at one point, and the elevation angle ω between the rotary laser system1and the photodetection system2can be obtained. The known point is defined as a point, which has been measured and installed in advance and which is obtained by surveying operation each time, etc.

When the rotary laser system1is installed at a predetermined point (X, Y, Z) and at least three photodetection systems2are installed at known points or the photodetection systems2are sequentially installed at three known points, it is possible to obtain coordinate values and elevation angles at the three known points, i.e. (x1, y1, z1, ω1), (x2, y2, z2, ω2) and (x3, y3, z3, ω3). Data of these three known values of coordinates and elevation angles are transmitted to the rotary laser system1, or these data are collected at the predetermined photodetection system2via the rotary laser system1.

The coordinate (unknown point) where the rotary laser system1is installed can be obtained from the three known coordinate values and the elevation angles by the equations given below.
(X−x1)2+(Y−y1)2=[(Z−z1)/tan ω1]2
(X−x2)2+(Y−y2)2=[(Z−z2)/tan ω2]2
(X−x3)2+(Y−y3)2=[(Z−z3)/tan ω3]2

As a result, coordinates of the installation point of the rotary laser system1can be accurately determined. Subsequently, it is possible to perform measurement by installing the photodetection system2at any desired point.

Surveying operation can be performed without installing the rotary laser system1at a known point, and the installing position of the rotary laser system1can be confirmed. If there may be an error, it can be corrected.

When the values of coordinates and elevation angles, i.e. (x1, y1, z1, ω1), (x2, y2, z2, ω2) and (x3, y3, z3, ω3) can be determined at three points on the photodetection system2respectively, it is possible to calculate the installing position of the rotary laser system1on the photodetection system2. Thus, the operation of the rotary laser system1can be limited only to the projection of the laser beam by rotary irradiation.

If there is communication function between the rotary laser system1and the photodetection system2, the installing position of the rotary laser system1can be calculated either at the arithmetic operation unit on the rotary laser system1or on the arithmetic operation unit of the photodetection system2. By installing the photodetection system2at three or more known points and obtaining the installing position of the rotary laser1can be determined with higher accuracy, the accuracy can be increased.

FIG. 13shows a case where the photodetection system2is provided with a GPS position measuring system52.

The GPS position measuring system52may be provided on the photodetection system2. The GPS position measuring system52is installed, for instance, on an upper end of the rod8, and a distance between the GPS position measuring system52and the lower end of the rod8is already known. By providing the GPS position measuring system52, an absolute plane position of the GPS position measuring system52can be measured. From the position measured by the GPS position measuring system52and the position of the known point where the rotary laser system1is installed, a distance between the photodetection system2and the rotary laser system1can be calculated. Further, the tilting of the rod8can be measured by the photodetection system2. Because the distance between the lower end of the rod8and the GPS position measuring system52is already known, an error caused from the tilting of the rod8can be corrected, and this makes it possible to measure the distance with high accuracy.

When the photodetection system2is provided with the GPS position measuring system52, there is no need to install the photodetection system2at a known point when the installing position of the rotary laser system1is to be measured. Because the result of measurement from the GPS position measuring system52is obtained, the condition equivalent to the condition where the photodetection system2is installed at a known point can be obtained. Thus, the installing position of the rotary laser system1can be accurately calculated.

As described above, if the photodetection system2is provided with two photodetectors41, a distance between the rotary laser system1and the photodetection system2can be measured. Because the projecting direction can be identified by the encoder37, it would suffice if installing position of the photodetection system2is known at least at one point.

The configuration of a plurality of the fan-shaped beams may not be an N-shaped configuration. It would suffice if at least one of the fan-shaped beams is tilted and the values about configurations such as a tilt angle are already known. For instance, the configurations shown in FIG. (A) toFIG. 14(R)or the like may be used.