JP6221197B2 - Laser tracker - Google Patents

Description

  The present invention relates to a laser tracker.

  Patent Documents 1, 2, and 3 disclose laser trackers that measure the three-dimensional coordinates of a measurement target while tracking the measurement target using laser light emitted from a main body.

  The laser tracker emits laser light to a target attached to a measurement object, and the main body receives the reflected light of the laser light reflected from the target. Thus, the distance to the target (measurement object) and the two angles (elevation angle and azimuth angle) of the reflected light are measured, and the three-dimensional coordinates of the measurement object are measured. Hereinafter, laser light emitted from the main body of the laser tracker is referred to as “laser light”, and reflected light of the laser light reflected from the target is referred to as “measurement light”.

  The distance from the main body to the target is measured relative or absolutely by a distance measuring device such as a laser interferometer, an optical comb distance meter, or a two-color interferometer. Also, the two angles of the measurement light are measured by a rotary encoder. Further, the laser tracker includes a gimbal beam operation mechanism (see Patent Document 3), and the gimbal beam operation mechanism directs the laser beam to the target. Thereby, the laser tracker can measure the three-dimensional coordinates of the measurement object while tracking the measurement object.

  As the target, a right-angle prism mirror or a corner cube prism that can be retroreflected is used. The laser light is incident on the perpendicularly combined surfaces of the target, and a part of the laser light is reflected in the incident direction as measurement light by several reflections.

JP 2010-54429 A JP 2012-112919 A Special table 2013-505542 gazette

  As described above, the laser trackers of Patent Documents 1 to 3 use a rotary encoder as means for measuring two angles of measurement light. That is, the conventional laser tracker measures (converts) two angles of the measurement light based on the angle signal output from the rotary encoder after detecting the direction of the measurement light.

  Therefore, the direction measurement accuracy (also referred to as measurement direction accuracy) of measurement light by a conventional laser tracker is limited to the accuracy of the angle signal output from the rotary encoder, that is, mechanical accuracy (also referred to as resolution). There is a disadvantage that only an accuracy of about 500 μm can be obtained at a distance of 100 m.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a laser tracker that can improve measurement direction accuracy as compared with a conventional laser tracker using a rotary encoder.

  In one aspect of the present invention, in order to achieve the above object, a target attached to a measurement target, and a distance from a main body to the target while emitting the laser beam to the target and tracking the target Measuring means; angle adjusting means capable of adjusting the radiation angle of the laser light around two orthogonal axes; and planar light receiving capable of detecting the position of the measuring light reflected by the target. A space of the target based on an angle measuring means that receives the light by the means and measures two angles of the measuring light; a distance measured by the distance measuring means; and two angles measured by the angle measuring means. A calculation means for calculating coordinates, and a position of the measurement light reflected by the target are detected and moved with the amount of movement of the target. And an optical position detecting means for outputting a signal corresponding to the direction, and the angle adjusting means is controlled based on the signal from the optical position detecting means so that the optical axis of the laser beam and the optical axis of the measuring light coincide And a control means for providing a laser tracker.

  According to one aspect of the present invention, a planar light receiving means capable of detecting a position is used as a means for measuring two angles of measurement light. That is, the measurement light is received by the light receiving surface of the planar light receiving means capable of detecting the position, and the position of the laser spot on the light receiving surface is detected. That is, angle data is allocated in advance for each of a large number of light receiving elements, and two angles of the measurement light are measured (detected) based on the light receiving elements that receive the laser spot. Thereby, it can measure directly, without converting two angles of measurement light. Therefore, according to one aspect of the present invention, the measurement direction accuracy of the measurement light can be improved as compared with a conventional laser tracker using a rotary encoder.

  In one aspect of the present invention, the light receiving unit of the angle measuring unit is preferably a hemispherical organic imaging device.

  According to one embodiment of the present invention, two angles of measurement light can be accurately measured by a hemispherical organic imaging device.

  In one aspect of the present invention, the angle adjusting unit reflects a part of the laser light and transmits a part of the measurement light, and rotates the beam splitter around two orthogonal axes. It is preferable that the light receiving unit of the angle measuring unit receives a part of the measurement light transmitted through the beam splitter.

  According to one aspect of the present invention, by using a beam splitter, laser light can be reflected toward a target, and a part of the measurement light can be effectively used as a measurement direction detection tool.

  In one aspect of the present invention, the measurement object includes a GPS receiver and a transmitter that transmits position data received by the GPS receiver, and the control means includes a transmitter from the transmitter. It is preferable that a receiver for receiving position data is provided, and the control unit controls an angle of the laser beam about two axes by the angle adjusting unit based on the position data received by the receiver.

  According to one aspect of the present invention, the latitude, longitude, and altitude position data of the measurement object is acquired by the GPS receiver. The position data of the measurement object is output from the transmitter and is always received by the receiver of the control means. Then, the control means controls the angle of the laser beam around two axes by the angle adjusting means based on the position data received by the receiver. Thereby, the laser tracker can always track without losing sight of the measurement object.

  According to the laser tracker of the present invention, it is possible to improve measurement direction accuracy as compared with a conventional laser tracker using a rotary encoder.

Explanatory drawing which showed the structure of the laser tracker of 1st Embodiment. Explanatory drawing which showed the optical path of the laser beam in the laser tracker of FIG. Explanatory drawing which showed the optical path of the measurement light in the laser tracker of FIG. Explanatory drawing which expanded and showed the structure of the principal part of the laser beam of 2nd Embodiment. Flow chart showing the procedure of the measurement method by laser tracker

  Hereinafter, preferred embodiments of a laser tracker according to the present invention will be described in detail with reference to the accompanying drawings.

[Configuration of Laser Tracker 10]
FIG. 1 is an explanatory diagram showing the configuration of the laser tracker 10 of the first embodiment. Figure 2 is an explanatory view showing the optical path of the laser beam L ₁ in the laser tracker 10 of FIG. 1, FIG. 3 is an explanatory view showing the optical path of the measurement light L ₂ in the laser tracker of FIG. The laser beam L ₁ in FIG. 2 are indicated by solid arrows, the measurement light L ₂ in FIG. 3 are indicated by the dashed arrows.

  As shown in FIG. 1, a laser tracker 10 includes a cylindrical main body 14 supported by a support member 12 such as a tripod, an angle rotation amount detection unit 16 mounted on the upper part of the main body 14, and a signal detector 18. (Calculation means, control means) 20 and a corner cube prism (hereinafter referred to as “CCP”) 24 as a target attached to the measurement object 22.

  Inside the main body 14, a distance measuring device (distance measuring means) 26 having a laser light source 25, a half mirror 28, and a two-dimensional semiconductor position detector (Position Sensitive Detector: hereinafter referred to as “two-dimensional PSD”) 30. Is placed.

  The distance measuring device 26 is a known laser interferometer, optical comb distance meter, or two-color interferometer that measures the distance between the main body 14 of the laser tracker 10 and the CCP 24 using laser light. It is a distance measuring device.

The half mirror 28 is disposed on the optical axis of the laser beam L ₁ emitted from the distance measuring device 26 as shown in FIG. 2, and has a function of transmitting the laser beam L ₁ . The half mirror 28 also has a function of reflecting the measurement light L ₂ reflected by the CCP 24 and reflected by a beam splitter (hereinafter referred to as “BS”) 32 to the two-dimensional PSD 30 as shown in FIG. The measurement light L ₂ is probe light for measuring the distance from the main body 14 of the laser tracker 10 to the CCP 24 by the distance measurement device 26. Further, CCP24 is 2, parallel to the incident direction of the laser light L ₁ that as emitted from the distance measuring device 26 of FIG. 3, a function of reflecting the measurement light L ₂ in the opposite direction. The BS 32 will be described later.

2D PSD30 comprises receiving surface for reading the position of the optical axis of the measurement light L ₂ as shown in FIG. 3. 2D PSD30, the position data of the measuring light L _2, is that is one that recognizes a positional displacement amount of the reference position of the measurement light L _2. Here, the “position data” of the measurement light L ₂ represents the amount of displacement of the laser spot in two orthogonal directions on the light receiving surface of the two-dimensional PSD 30.

The arithmetic and control unit 20 makes the laser spot of the measurement light L ₂ incident on the light receiving surface of the two-dimensional PSD 30 return to the center of the light receiving surface of the two-dimensional PSD 30, that is, with respect to the optical axis of the measurement light L ₂ of the CCP 24. The orthogonal biaxial motor (drive unit) 34 of the BS 32 is controlled so that the amount of movement in the orthogonal biaxial direction becomes zero.

  As shown in FIGS. 2 and 3, the biaxial motor 34 includes a first motor 36 for adjusting the elevation angle having a rotation axis in the horizontal direction and a second motor 38 for adjusting the azimuth angle having a rotation axis in the vertical direction. It consists of. The arithmetic and control unit 20 controls the rotation amounts of the first motor 36 and the second motor 38, respectively, so that the BS 32 can be directed to a desired elevation angle and azimuth angle.

  Since the method for adjusting the angle of the BS 32 using the two-dimensional PSD 30 and the two-axis motor 34 is known, the description thereof is omitted here. Further, instead of the two-dimensional PSD 30, an imaging element such as a four-division photodiode may be applied.

The angular rotation amount detection unit 16 illustrated in FIG. Further, the case 40 is provided with a window 42 for emitting the laser beam L ₁ and for entering the measuring beam L ₂ . And the inside of the case 40, BS32,2 axis motor 34 described above, two-dimensional PSD44 for detecting the rotation angle of BS32, and the two-dimensional PSD to detect the elevation angle and azimuth angle of the measuring light _{L 2} directly (planar Light receiving means) 46 is disposed at a predetermined position.

BS32 has a function of the laser beam L ₁ from the distance measuring device 26 which has passed through the half mirror 28 as shown in FIG. 2, reflected by a proportion, and transmits. The laser light L ₁ reflected by the BS 32 is emitted toward the CCP 24 through the window 42. Then, as shown in FIG. 3, a part of the measurement light L ₂ reflected by the CCP 24 and incident on the BS 32 through the window 42 passes through the BS 32 and is incident on the light receiving surface of the two-dimensional PSD 46. Then, the remaining measurement light L ₂ excluding the part is reflected toward the half mirror 28.

Part of the remaining measurement light L ₂ is reflected by the half mirror 28 and is incident on the light receiving surface of the two-dimensional PSD 30. Further, the measurement light L ₂ transmitted through the half mirror 28 is incident on the distance measuring device 26. The distance measuring device 26 measures the distance from the main body 14 to the CCP 24 based on the emitted laser light L ₁ and the incident measuring light L ₂ . Since the distance measuring method by the distance measuring device 26 is also known, its description is omitted here.

2D PSD44 as shown in FIG. 2 is disposed above the BS32, the laser beam _{L 1} having passed through the BS32 to the light receiving surface is incident. Depending on the rotation angle of BS32, the light receiving surface of the two-dimensional PSD 44, the incident position of the laser beam _{L 1} having passed through the BS32 (laser spot position) is different. By outputting the position data to the arithmetic and control unit 20, the rotation amount of the BS 32 is calculated by the arithmetic and control unit 20. Further, instead of the two-dimensional PSD 44, an imaging element such as a four-division photodiode may be applied.

2D PSD46 as shown in FIG. 3 is disposed on the back side of the BS32, the measuring light _{L 2} having passed through the incident BS32 on its light receiving surface. Since the incident position (laser spot position) of the measurement light L ₂ transmitted through the BS 32 on the light receiving surface of the two-dimensional PSD 46 differs according to the rotation angle amount of the two axes of the BS 32, the position data is sent to the arithmetic and control unit 20. By output, the elevation angle and the azimuth angle of the measurement light L ₂ are measured by the arithmetic and control unit 20. Further, instead of the two-dimensional PSD 46, a hemispherical thin film organic imaging device 48 shown in FIG. 4 may be applied, or an imaging device such as a quadrant photodiode may be applied. That is, any planar light receiving means can be applied as a light receiving means for measuring an elevation angle and an azimuth angle.

  An embodiment to which the organic imaging element 48 is applied is a second embodiment. In this case, the center of the sphere of the hemispherical organic imaging element 48 is set to the center of the BS 32.

  On the other hand, a GPS (Global Positioning System) receiver 50 and a transmitter 52 are attached to the measurement object 22.

The transmitter 52 wirelessly outputs the latitude, longitude, and altitude position data of the measurement object 22 received by the GPS receiver 50. The arithmetic and control unit 20 includes a receiver 54 that receives the position data. The arithmetic and control unit 20 controls the biaxial motor 34 of the BS 32 based on the position data received by the receiver 54 so that the laser light L ₁ is always emitted toward the measurement target 22. Thereby, the laser tracker 10 can always track without losing sight of the measurement object 22.

[Operation of Laser Tracker 10]
As shown in FIG. 2, the laser light L ₁ emitted from the distance measuring device 26 enters the CCP 24 attached to the measurement object via the half mirror 28 and the BS 32. Then, as shown in FIG. 3, the measurement light L ₂ reflected by the CCP 24 is returned through the same path as the laser light L ₁ and enters the distance measurement device 26. Thereby, the distance between the main body 14 and the CCP is measured by the distance measuring device 26. Then, the distance data is transmitted from the distance measuring device 26 to the arithmetic control device 20.

The laser light _{L 1} is reflected by CCP24, when returning the measurement light _{L 2} to the distance measuring device 26, is reflected part of the measurement light _{L 2} by BS32, 2-dimensional measuring light _{L 2} through a half mirror 28 PSD 30 Is incident on the light receiving surface. When the CCP 24 moves in a direction perpendicular to the optical axis of the laser light L ₁ incident on the CCP 24, the incident position of the measurement light L ₂ incident on the light receiving surface of the two-dimensional PSD 30 changes according to the moving amount and the moving direction. The change of the incident position of the measurement light L ₂ is detected by using the two-dimensional PSD 30, and the arithmetic and control unit 20 causes the biaxial motor 34 so that the incident position of the measurement light L ₂ is always located at the center of the light receiving surface. To control the direction of the BS 32. Thus, the laser tracker 10 can track the measurement target 22 by using the laser beam L _1.

  When the laser tracker 10 is tracking the measurement object 22, two relative angle data (elevation angle data and azimuth angle data) between the BS 32 and the CCP 24 are directly detected by the two-dimensional PSD 46. These two angle data are transmitted to the arithmetic and control unit 20.

  The arithmetic and control unit 20 calculates the three-dimensional coordinates of the measurement object 22 using these two angle data and the distance data from the distance measuring device 26.

  The above is the operation of the laser tracker 10.

The feature of the laser tracker 10 of the embodiment is that the elevation angle data and the azimuth angle data of the measurement light L ₂ are directly obtained by the two-dimensional PSD 46 or the organic imaging device 48. As a result, the laser tracker 10 of the embodiment has improved measurement direction accuracy compared to a conventional laser tracker that uses a rotary encoder with limited resolution. That is, more accurate angle measurement can be performed.

  For example, when the distance from the center of the BS 32 to the two-dimensional PSD 46 is 0.1 m and the position resolution (pixel size 5 μm + 1/100 subpixel method) of the two-dimensional PSD 46 is 0.05 μm, the elevation angle of the laser tracker 10 of the embodiment and The measurement direction accuracy of the azimuth can be reduced to about 50 μm at a distance of 100 m. Therefore, the accuracy is improved 10 times as compared with the conventional laser tracker.

  FIG. 5 is a flowchart showing the procedure of the measurement method using the laser tracker 10.

According to FIG. 5, first, two-dimensional PSD46 or create the detected position data by organic image sensor 48 calibration data in the optical axis direction of the measurement light _{L 2} (Step 1: S1).

  Next, the position of the CCP 24 of the measurement object 22 is detected by receiving position data from the transmitter 52 (S2).

Then, radiate toward the laser beam _{L 1} in CCP24 (S3).

Then, for centering the CCP24, it detects the position of the optical axis of the measurement light _{L 2} by a two-dimensional PSD30 for centering (S4).

  Next, in order to center the CCP 24, the BS 32 is rotated by the biaxial motor 34 (S5).

  Next, the distance from the main body 14 to the CCP 24 is measured by the distance measuring device 26 (S6).

  Next, the calculation control device 20 calculates the three-dimensional coordinate position of the measurement object 22 from the two angle data obtained by the two-dimensional PSD 46 or the organic imaging device 48 and the distance data from the distance measurement device 26 (S7).

  And the measuring object 22 is moved and the step of S2-S7 is repeated.

  Thereby, the laser tracker 10 of the embodiment can measure the accurate three-dimensional coordinates of the measurement object while tracking the measurement object 22.

DESCRIPTION OF SYMBOLS 10 ... Laser tracker, 12 ... Support member, 14 ... Main body, 16 ... Angular rotation amount detection part, 18 ... Signal detector, 20 ... Calculation control apparatus, 22 ... Measurement object, 24 ... CCP, 25 ... Laser light source, 26 ... Distance measuring device, 28 ... Half mirror, 30 ... Two-dimensional PSD, 32 ... BS, 34 ... Two-axis motor, 36 ... First motor, 38 ... Second motor, 40 ... Case, 42 ... Window, 44 ... 2D PSD, 46 ... 2-D PSD, 48 ... organic imaging device, 50 ... GPS receiver, 52 ... transmitter, 54 ... receiver, L 1 _... laser light, L 2 _... measurement light

Claims (3)

A target attached to the measurement object;
Distance measuring means for measuring the distance from the main body to the target while emitting the laser beam to the target and tracking the target;
Angle adjustment means capable of adjusting the radiation angle of the laser light around two orthogonal axes;
Angle measuring means for measuring the two angles of the measurement light by receiving the measurement light of the laser beam reflected by the target by a planar light receiving means capable of detecting a position;
A computing means for computing the spatial coordinates of the target based on the distance measured by the distance measuring means and the two angles measured by the angle measuring means;
A light position detecting means for detecting a position of the measurement light reflected by the target and outputting a signal corresponding to a moving amount and a moving direction of the target;
Control means for controlling the angle adjusting means so that the optical axis of the laser light and the optical axis of the measurement light coincide with each other based on a signal from the optical position detecting means;
Equipped with a,
The angle adjusting means includes a beam splitter that reflects part of the laser light and transmits part of the measurement light, and a drive unit that rotates the beam splitter around two orthogonal axes,
The laser tracker according to claim 1 , wherein the light receiving means of the angle measuring means receives a part of the measurement light transmitted through the beam splitter .   The laser tracker according to claim 1, wherein the light receiving means of the angle measuring means is a hemispherical organic imaging device. The measurement object includes a GPS receiver and a transmitter that transmits position data received by the GPS receiver.
The control means includes a receiver for receiving position data from the transmitter,
3. The laser tracker according to claim 1, wherein the control unit controls an angle around the two axes of the laser beam by the angle adjusting unit based on the position data received by the receiver.

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