Three-dimensional surveying device

Abstract

To provide a three-dimensional surveying device capable of increasing ranging precision of scanning.SOLUTION: A three-dimensional surveying device comprises: a light source section 31 for emitting ranging light 35; a light projection optical section 33 for applying the ranging light 35 onto a ranging optical axis 32; a scanning mirror 7 for rotatingly emitting the ranging light 35 within a surface crossing a rotation axis 6; a light reception optical section 41 for receiving reflected ranging light that is reflected by a measurement object and is guided via the scanning mirror 7; a reference light optical section 24 for receiving the ranging light 35 reflected by the scanning mirror 7 as internal reference light 36 and reflecting it and then changing the quantity of light of the internal reference light 36; and a light receiving element 42 for receiving reflected ranging light and the internal reference light 36. The reference light optical section 24 has: a filter 243 having density gradient in which optical density in an area through which the internal reference light 36 is transmitted is changed along a scanning line of the internal reference light 36; and a retroreflection reflection sheet 244 for reflecting the internal reference light 36 transmitted through the filter 243 having density gradient.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a three-dimensional surveying instrument that acquires three-dimensional data of a measurement object by irradiating the measurement object with distance measuring light, measuring the distance to the measurement object, and detecting the irradiation direction of the distance measuring light. [Background technology]

[0002] Patent Document 1 discloses a three-dimensional surveying device that acquires three-dimensional data (three-dimensional point cloud data) of multiple points on a measurement object. The three-dimensional surveying device described in Patent Document 1 irradiates a pulsed laser beam as a distance measurement light onto the measurement object and receives the reflected light of each pulsed laser reflected by the measurement object. The three-dimensional surveying device then measures the distance to the measurement object based on the received reflected light and an internal reference light, and acquires three-dimensional data of the measurement object by detecting the irradiation direction (horizontal angle and vertical angle) of the distance measurement light.

[0003] The three-dimensional surveying device described in Patent Document 1 corrects measured distance values ​​according to the amount of reflected distance-measuring light using a correction method such as range walk correction, thereby reducing errors in the measured distance values. Specifically, before starting the operation of acquiring three-dimensional data (i.e., scanning), the three-dimensional surveying device irradiates a laser beam toward a gradient density filter and a reflective sheet installed below the scanning unit. The three-dimensional surveying device then rotates the circular gradient density filter to change the amount of light passing through the gradient density filter (i.e., internal reference light) and obtains a table of correction values ​​corresponding to the amount of light for a known distance. The three-dimensional surveying device then starts the scanning operation and corrects the distance value according to the amount of light reflected from the object (i.e., reflected distance-measuring light) by using the table of correction values ​​corresponding to the amount of light.

[0004] The correction value may change depending on, for example, the warm-up state of the 3D surveying device. Therefore, the 3D surveying device updates the correction value by offsetting it when the laser beam passes through the gradient density filter during scanning. However, the 3D surveying device described in Patent Document 1 does not re-acquire the table of correction values ​​according to the light intensity during scanning. Therefore, there is room for improvement in terms of improving the distance measurement accuracy of scanning. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6953233 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made in view of the above circumstances, and has an object to provide a three-dimensional surveying device that can improve the distance measurement accuracy of scanning. [Means for solving the problem]

[0007] According to the present invention, the above-mentioned problem is solved by a three-dimensional surveying device that irradiates a measurement object with distance measurement light, measures a distance to the measurement object based on reflected distance measurement light that is formed when the distance measurement light is reflected by the measurement object and an internal reference light, and acquires three-dimensional data of the measurement object by detecting the irradiation direction of the distance measurement light, the three-dimensional surveying device comprising: a light source unit that emits the distance measurement light; a light projection optical unit that irradiates the distance measurement light emitted from the light source unit onto a distance measurement light axis; a scanning mirror that is rotatable about a rotation axis while tilted relative to the axis of the rotation axis, and that rotationally irradiates the distance measurement light guided from the light projection optical unit within a plane intersecting the rotation axis; and a light receiving optical unit that receives the reflected distance measurement light that is reflected by the measurement object and guided via the scanning mirror. The problem is solved by a three-dimensional surveying device comprising: a reference light optical unit that is arranged in a range within the irradiation range in which the distance measurement light is rotated and irradiated by the scanning mirror but other than the measurement range in which the distance measurement light is irradiated onto the object to be measured, and that receives and reflects the distance measurement light reflected by the scanning mirror as the internal reference light and is capable of changing the amount of light of the reflected internal reference light; and a light receiving element that receives the reflected distance measurement light and the internal reference light guided from the reference light optical unit, wherein the reference light optical unit has a density gradient filter in which the optical density of the area through which the internal reference light passes varies along the scanning line of the internal reference light, and a retroreflective reflective sheet that reflects the internal reference light that has passed through the density gradient filter.

[0008] According to the three-dimensional surveying device of the present invention, a reference beam optical unit that receives and reflects the distance measurement beam reflected by the scanning mirror as an internal reference beam is provided in a range outside the measurement range of the irradiation range of the distance measurement beam. The irradiation range is the range where the distance measurement beam is irradiated by the scanning mirror during rotation. The measurement range is the range where the distance measurement beam is irradiated onto the measurement object. The reference beam optical unit also has a gradient density filter in which the optical density of the area through which the internal reference beam passes varies along the scanning line of the internal reference beam, and the amount of reflected internal reference beam can be changed. Therefore, every time the scanning mirror rotates during a scanning operation, i.e., every time the scanning mirror rotates and irradiates the distance measurement beam during a scanning operation, the internal reference beam passes through the entire optical density of the gradient density filter that varies along the scanning line of the internal reference beam. Therefore, the three-dimensional surveying device of the present invention can obtain a table of correction values ​​corresponding to the light amount every time the scanning mirror rotates during a scanning operation. As a result, the three-dimensional surveying device of the present invention uses a precise table to correct the measured distance value according to the amount of reflected distance measuring light for each rotation of the scanning mirror, thereby improving the scanning distance measurement accuracy.

[0009] In the three-dimensional surveying instrument according to the present invention, the surface of the concentration gradient filter through which the internal reference light passes is preferably flat.

[0010] According to the three-dimensional surveying device of the present invention, the structure of the gradient density filter can be simplified and made smaller, which in turn allows the structure of the three-dimensional surveying device to be simplified and made smaller.

[0011] In the three-dimensional surveying device of the present invention, the optical density gradient on the plane is preferably changed according to the distance between the portion where the distance measurement light is reflected by the scanning mirror and the portion where the internal reference light passes through the surface.

[0012] In the three-dimensional surveying device according to the present invention, the gradient of optical density on the plane of the gradient density filter changes depending on the distance between the portion where the distance measurement light is reflected by the scanning mirror and the portion where the internal reference light passes through the surface of the gradient density filter, thereby improving the linearity or nonlinearity of the table of correction values ​​according to the light intensity.

[0013] In the three-dimensional surveying device of the present invention, the surface of the gradient concentration filter through which the internal reference light passes is preferably a spherical surface in which the distance between the portion where the distance measurement light is reflected by the scanning mirror and the portion where the internal reference light passes through the surface is constant.

[0014] In the three-dimensional surveying device according to the present invention, the surface of the gradient density filter through which the internal reference light passes is a spherical surface in which the distance between the portion where the distance measurement light is reflected by the scanning mirror and the portion where the internal reference light passes through the surface of the gradient density filter is constant, thereby improving the linearity or nonlinearity of the table of correction values ​​according to the light intensity.

[0015] In the three-dimensional surveying instrument according to the present invention, the gradient of the optical density on the spherical surface is preferably constant.

[0016] According to the three-dimensional surveying instrument of the present invention, the linearity or linearity of the table of correction values ​​according to the amount of light can be further improved.

[0017] In the three-dimensional surveying device of the present invention, the optical density preferably has a gradient that gradually increases the amount of light of the internal reference light that passes through the density gradient filter in the scanning direction of the internal reference light.

[0018] In the three-dimensional surveying device according to the present invention, the optical density of the gradient density filter has a gradient that gradually increases the amount of internal reference light passing through the gradient density filter in the scanning direction of the internal reference light. Therefore, in the initial stage of the internal reference light passing through the gradient density filter, a relatively large amount of internal reference light is prevented from entering the light receiving element, and a relatively large amount of light is prevented from remaining in circuits such as the control and calculation unit. As a result, the three-dimensional surveying device according to the present invention can improve the accuracy of the table of correction values ​​according to the amount of light, and improve the distance measurement accuracy of scanning.

[0019] In the three-dimensional surveying device of the present invention, the optical density preferably has a gradient in which the amount of light of the internal reference light passing through the density gradient filter gradually increases and then decreases in the scanning direction of the internal reference light.

[0020] According to the three-dimensional surveying device of the present invention, the optical density of the gradient-density filter has a gradient that gradually increases and then decreases the amount of light of the internal reference light passing through the gradient-density filter in the scanning direction of the internal reference light. Therefore, in the initial stage of the internal reference light passing through the gradient-density filter, a relatively large amount of the internal reference light is prevented from entering the light-receiving element, thereby preventing a relatively large amount of light from remaining in circuits such as the control and calculation unit. Furthermore, in the later stage of the internal reference light passing through the gradient-density filter, a relatively large amount of the internal reference light is prevented from entering the light-receiving element, thereby preventing a relatively large amount of light from remaining in circuits such as the control and calculation unit. Therefore, when the scanning mirror irradiates the reference light optical unit with a distance measurement light as the internal reference light during the next rotation, a relatively large amount of light is prevented from remaining in circuits such as the control and calculation unit. This allows the three-dimensional surveying device of the present invention to further improve the accuracy of the table of correction values ​​according to light amount, thereby further improving the distance measurement accuracy of scanning. [Effects of the Invention]

[0021] According to the present invention, it is possible to provide a three-dimensional surveying device that can improve the distance measurement accuracy of scanning. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is a block diagram illustrating a three-dimensional surveying device according to an embodiment of the present invention. [Figure 2] FIG. 2 is a block diagram illustrating a control system of the three-dimensional surveying instrument according to the present embodiment. [Figure 3] FIG. 2 is a diagram illustrating a reference light optical unit according to the present embodiment. [Figure 4] 4 is a diagram illustrating a reference light optical unit of a three-dimensional surveying device according to a comparative example of the present embodiment. FIG. [Figure 5] 10 is a graph illustrating an example of the relationship between the amount of light and a correction value. [Figure 6] FIG. 2 is a schematic diagram illustrating a density gradient filter according to a first specific example. [Figure 7] FIG. 2 is a plan view illustrating a gradient filter according to a first specific example. [Figure 8] FIG. 10 is a plan view illustrating a gradient filter according to a second specific example. [Figure 9] FIG. 10 is a schematic diagram illustrating a density gradient filter according to a third specific example. [Figure 10] FIG. 10 is a plan view illustrating a gradient filter according to a third specific example. [Figure 11] 10 is a flowchart illustrating a distance calculation process of the three-dimensional surveying device according to the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0023] Preferred embodiments of the present invention will now be described in detail with reference to the drawings. The embodiments described below are preferred examples of the present invention, and therefore various technically preferable limitations are applied thereto, but the scope of the present invention is not limited to these aspects unless otherwise specified in the following description to the effect that the present invention is particularly limited. Furthermore, in each drawing, similar components are designated by the same reference numerals, and detailed descriptions thereof will be omitted as appropriate.

[0024] FIG. 1 is a block diagram showing a three-dimensional surveying device according to an embodiment of the present invention. In the description of this embodiment, a case where the three-dimensional surveying device is a three-dimensional laser scanner will be taken as an example.

[0025] As shown in Figure 1, the three-dimensional surveying device 1 comprises a leveling unit 2 attached to a tripod (not shown), a base unit 3 attached to the leveling unit 2, a support unit 5 attached to the base unit 3 so as to be rotatable in the horizontal direction via a horizontal rotation unit 4, and a scanning mirror 7 attached to the support unit 5 so as to be rotatable in the vertical direction (height direction) around a vertical rotation axis 6.

[0026] The leveling unit 2 has, for example, three adjustment screws 8. The leveling unit 2 is leveled by adjusting the adjustment screws 8 so that an inclination sensor (not shown) provided on the support unit 5 detects horizontality.

[0027] The horizontal rotation unit 4 is rotatably mounted on the base unit 3 via a bearing 9 and has a horizontal rotation shaft 11 that is supported vertically. The support unit 5 is supported by the horizontal rotation shaft 11 and rotates integrally with the horizontal rotation shaft 11.

[0028] The horizontal rotation unit 4 houses a horizontal drive unit 13 including a horizontal drive motor 12, and a horizontal angle detector (e.g., an encoder) 14 that detects the rotation angle of the horizontal rotation shaft 11. The base unit 5 rotates around the horizontal rotation shaft 11 by the driving force transmitted from the horizontal drive motor 12. The rotation angle of the horizontal rotation shaft 11 relative to the base unit 3 (i.e., the rotation angle of the base unit 5) is detected by the horizontal angle detector 14.

[0029] The detection result (horizontal angle) of the horizontal angle detector is input to the control calculation unit 15. The driving of the horizontal drive motor 12 is controlled by the control calculation unit 15 based on the detection result of the horizontal angle detector .

[0030] A recess 16 is formed in the center of the base rack 5. A first chamber 5a and a second chamber 5b are formed on both sides of the recess 16. The first chamber 5a (the chamber on the left in FIG. 1) houses a vertical drive unit 17 and a vertical angle detector 18. The second chamber 5b (the chamber on the right in FIG. 1) houses a distance measurement light emitting unit 19, a common optical path unit 21, a distance measurement unit 22, an imaging unit 23, and a reference light optical unit 24. A control and calculation unit 15 is housed at a required position inside the base rack 5. Furthermore, a display unit 25 and an operation unit 26 are provided in required portions of the base rack 5.

[0031] The vertical rotation shaft 6 has an axis extending horizontally and is rotatably supported on the base part 5 via a bearing 27. One end of the vertical rotation shaft 6 protrudes into the recess 16. The scanning mirror 7 is provided on the end of the vertical rotation shaft 6 protruding into the recess 16 and is inclined at 45° with respect to the axis of the vertical rotation shaft 6. The scanning mirror 7 is supported within the recess 16 by the vertical rotation shaft 6 and can rotate in the vertical direction around the vertical rotation shaft 6.

[0032] The vertical drive unit 17 has a vertical drive motor 28 that rotates the vertical rotation shaft 6. The scanning mirror 7 rotates by a driving force transmitted from the vertical drive motor 28 via the vertical rotation shaft 6. The scanning unit 29 of this embodiment has the vertical rotation shaft 6, the scanning mirror 7, and the vertical drive motor 28.

[0033] A vertical angle detector 18 (e.g., an incremental encoder) is provided at the other end of the vertical rotation shaft 6. The rotation angle of the vertical rotation shaft 6 relative to the support unit 5 is detected by the vertical angle detector 18. The detection result (vertical angle) of the vertical angle detector 18 is input to the control calculation unit 15. The drive of the vertical drive motor 28 is controlled by the control calculation unit 15 based on the detection result of the vertical angle detector 18.

[0034] The distance measurement light emitting unit 19 has a distance measurement light source unit 31 and a light projecting optical unit 33 including an objective lens and the like. The distance measurement light source unit 31 is, for example, a semiconductor laser and emits distance measurement light 35 along a distance measurement optical axis 32. In this embodiment, the distance measurement light 35 is an invisible infrared pulsed laser beam. The distance measurement light source unit 31 is controlled by the control and calculation unit 15 and emits pulsed light in a required state including a required light intensity and a required pulse interval.

[0035] The common optical path section 21 has a first beam splitter 38 and a second beam splitter 39. The distance measuring section 22 has a light receiving optical section 41 including a condenser lens and the like, and a light receiving element 42. The light receiving element 42 receives reflected distance measuring light 37, which is formed when the distance measuring light 35 is reflected by a measurement object (not shown) and passes through the light receiving optical section 41, and converts it into an electrical signal. The light receiving element 42 also receives the internal reference light 36 guided from the reference light optical section 24 and converts it into an electrical signal. An example of the light receiving element 42 is an avalanche photodiode.

[0036] That is, distance measurement light 35 output from distance measurement light source unit 31 is guided to common optical path unit 21 via light projection optical unit 33. Distance measurement light 35 guided to common optical path unit 21 is reflected successively by first beam splitter 38 and second beam splitter 39 and guided to scanning mirror 7. Note that distance measurement light 35 transmitted through first beam splitter 38 and second beam splitter 39 is absorbed by an anti-reflection member (not shown).

[0037] The scanning mirror 7 is a deflection optical member that reflects the distance measurement light 35 incident from the horizontal direction at a right angle. The scanning mirror 7 also reflects the reflected distance measurement light 37 and internal reference light 36 incident on the scanning mirror 7 in the horizontal direction toward the second beam splitter 39.

[0038] The distance measurement light 35 guided from the common optical path section 21 to the scanning mirror 7 is reflected by the scanning mirror 7 and irradiated onto the measurement object. The distance measurement light 35 guided from the common optical path section 21 to the scanning mirror 7 is also reflected by the scanning mirror 7 and irradiated onto the reference beam optical section 24 as internal reference light 36. That is, in the measurement range of the irradiation range of the distance measurement light 35, the distance measurement light 35 is reflected by the scanning mirror 7 and irradiated onto the measurement object. On the other hand, in the range other than the measurement range of the irradiation range of the distance measurement light 35, the distance measurement light 35 is reflected by the scanning mirror 7 and is received and reflected by the reference beam optical section 24 as internal reference light 36. That is, the reference beam optical section 24 is provided in the range other than the measurement range of the irradiation range of the distance measurement light 35. The internal reference light 36 is a part of the distance measurement light 35 and is received and reflected by the reference beam optical section 24. In this specification, the term "irradiation range" refers to the range where the distance measuring light 35 is rotated and irradiated by the scanning mirror 7. Also, the term "measurement range" refers to the range where the distance measuring light 35 is irradiated onto the measurement object.

[0039] When the scanning mirror 7 rotates around the vertical rotation axis 6, the distance measuring light 35 is rotationally emitted within a plane intersecting the vertical rotation axis 6 (within a vertical plane in this embodiment). Furthermore, when the base unit 5 is rotated horizontally by the horizontal rotation unit 4, the distance measuring light 35 is rotationally emitted horizontally around the horizontal rotation axis 11. Therefore, by cooperation between the vertical rotation of the scanning mirror 7 and the horizontal rotation of the base unit 5, the three-dimensional surveying device 1 can scan the entire measurement range with the distance measuring light 35.

[0040] The reflected distance measuring light 37 reflected by the measurement object present within the measurement range is incident on the scanning mirror 7. The reflected distance measuring light 37 incident on the scanning mirror 7 is reflected by the scanning mirror 7 and incident on the common optical path section 21. The reflected distance measuring light 37 passes through the second beam splitter 39 and is guided to the distance measuring section 22. Furthermore, the internal reference light 36 reflected by the reference light optical section 24 provided in a range outside the measurement range is incident on the scanning mirror 7. The internal reference light 36 incident on the scanning mirror 7 is reflected by the scanning mirror 7 and incident on the common optical path section 21. The internal reference light 36 passes through the second beam splitter 39 and is guided to the distance measuring section 22.

[0041] The light-receiving element 42 of the distance measuring unit 22 receives the reflected distance measuring light 37 reflected by the object to be measured and the internal reference light 36 reflected by the reference light optical unit 24 via the light-receiving optical unit 41. In the light-receiving element 42, the reflected distance measuring light 37 and the internal reference light 36 are converted into a reflected distance measuring light electric signal and an internal reference light electric signal, respectively, and sent to the control and calculation unit 15. The distance to the object to be measured is measured based on the difference in time interval between the reflected distance measuring light electric signal and the internal reference light electric signal.

[0042] The control and calculation unit 15 calculates the coordinate values ​​of the measurement object based on the measured distance to the measurement object, the vertical angle detected by the vertical angle detector 18, and the horizontal angle detected by the horizontal angle detector 14. The control and calculation unit 15 also records the coordinate values ​​of the measurement object for each pulse of light, thereby obtaining point cloud data for the entire measurement range or point cloud data for the measurement object. The angle detection unit that detects the direction of the ranging light axis 32 includes the horizontal angle detector 14 and the vertical angle detector 18. That is, the irradiation direction of the ranging light 35 is detected by the angle detection unit that includes the horizontal angle detector 14 and the vertical angle detector 18.

[0043] An imaging element 45 is provided on the imaging optical axis of the imaging unit 23. The imaging element 45 has a collection of pixels and outputs a digital image signal. Examples of the imaging element 45 include a CCD or CMOS sensor. The position of each pixel of the imaging element 45 within the imaging element 45 is identifiable.

[0044] FIG. 2 is a block diagram illustrating a control system of the three-dimensional surveying instrument according to this embodiment. The control calculation unit 15 is electrically connected to the operation unit 26, the vertical angle detector 18, and the horizontal angle detector 14. The control calculation unit 15 receives the angle detection signals output from the vertical angle detector 18 and the horizontal angle detector 14, as well as the operation signal output from the operation unit 26 based on the operation of the operator.

[0045] The operator uses the operation unit 26 to set the conditions necessary to start measurement with the 3D surveying device 1. Examples of setting the necessary conditions include setting the measurement range, setting the point cloud data density (pitch), and setting the imaging conditions when capturing images. The setting conditions inputted through the operation unit 26 are displayed on the display unit 25. This allows the operator to check the setting conditions inputted through the operation unit 26 on the display unit 25. The operation unit 26 and the display unit 25 may be provided in the base unit 5, or may be provided independently of the base unit 5 and remotely operable via a signal transmission medium such as wireless or infrared.

[0046] The control and calculation unit 15 drives the distance measurement light source unit 31, the horizontal drive motor 12, and the vertical drive motor 28, and also controls the display unit 25 that displays the work status, measurement results, etc. The control and calculation unit 15 is also provided with an external storage device 46 such as a memory card, HDD, or SSD. The external storage device 46 may be fixedly provided to the control and calculation unit 15, or may be detachably provided.

[0047] The control and calculation unit 15 has a calculation unit 47, a memory unit 48, a distance measurement light emitting drive unit 49 that controls the light emission of the distance measurement light source unit 31, a horizontal drive unit 13 that drives and controls the horizontal drive motor 12, and a vertical drive unit 17 that drives and controls the vertical drive motor 28. The control and calculation unit 15 also has a distance data processing unit 51 that processes distance data obtained by the distance measurement unit 22, and an image data processing unit 52 that processes image data obtained by the imaging unit 23.

[0048] The calculation unit 47 is, for example, a CPU (Central Processing Unit), and performs program startup, signal control processing, calculations, drive control of the display unit 25, etc., based on signals (commands) sent from the operation unit 26. In other words, the calculation unit 47 controls the entire three-dimensional surveying device 1, and causes the display unit 25 to display surveying conditions, measurement results (distance measurement results and angle measurement results), image processing results (images of the collimation range), etc.

[0049] The storage unit 48 stores programs such as a sequence program for executing distance measurement, measurement of vertical angle, and measurement of horizontal angle, an arithmetic program for performing distance measurement calculations, a measurement data processing program for processing measurement data, an imaging program for controlling the imaging state of the imaging unit 23, an image processing program for performing image processing, an image display program for displaying data on the display unit 25, or a program for integrating and managing these programs. The storage unit 48 also stores data such as measurement data and image data.

[0050] The storage unit 48 may be, for example, a semiconductor memory built into the three-dimensional surveying device 1. Alternatively, the storage unit 48 may be any of various storage media connectable to the three-dimensional surveying device 1, such as a CD (Compact Disc), a DVD (Digital Versatile Disc), a RAM (Random access memory), a ROM (Read only memory), a hard disk, or a memory card.

[0051] Distance measurement light emitting drive unit 49, horizontal drive unit 13, vertical drive unit 17, distance data processing unit 51, and image data processing unit 52 are realized by calculation unit 47 executing a program stored (memorized) in storage unit 48. Note that distance measurement light emitting drive unit 49, horizontal drive unit 13, vertical drive unit 17, distance data processing unit 51, and image data processing unit 52 may be realized by hardware or a combination of hardware and software.

[0052] The program executed by a computer including the control and calculation unit 15 is an example of the "3D surveying device driving program" of the present invention. The "computer" here is not limited to a personal computer, but also includes a processing unit, a microcomputer, etc. included in information processing equipment, and is a general term for equipment and devices that can realize the functions of the present invention by a program.

[0053] The calculation unit 47 may have the functions of the distance data processing unit 51 and the image data processing unit 52. In this case, the distance data processing unit 51 and the image data processing unit 52 do not necessarily have to be provided.

[0054] Furthermore, the distance data processing unit 51 and the image data processing unit 52 may be provided separately from the control and calculation unit 15. For example, a personal computer separate from the control and calculation unit 15 may execute the functions of the distance data processing unit 51 and the image data processing unit 52. In this case, for example, the distance data and image data are transmitted from the three-dimensional surveying device 1 to the personal computer via communication means provided in the three-dimensional surveying device 1 and the personal computer. The personal computer then processes the distance data and the image data. Examples of the communication means include optical communication, wireless communication, and LAN.

[0055] FIG. 3 is a diagram illustrating the reference beam optical unit of this embodiment. FIG. 4 is a diagram illustrating a reference light optical unit of a three-dimensional surveying instrument according to a comparative example of this embodiment. FIG. 5 is a graph illustrating an example of the relationship between the amount of light and the correction value. For ease of explanation, the imaging unit 23 is omitted from FIG.

[0056] First, a reference beam optical unit 24A of a three-dimensional surveying device 1A according to a comparative example of this embodiment will be described with reference to Fig. 4. The reference beam optical unit 24A of the three-dimensional surveying device 1A according to this comparative example is provided in a range outside the measurement range within the irradiation range of the distance measurement beam 35, and receives and reflects the distance measurement beam 35 reflected by the scanning mirror 7 as internal reference beam 36. The reference beam optical unit 24A is also capable of changing the amount of the reflected internal reference beam 36.

[0057] Specifically, the reference beam optical unit 24A has a motor 241A, a gradient filter 243A, a reflection sheet 244, and a filter 245. The motor 241A has a shaft 242A and generates a rotational force. The gradient filter 243A is supported by the shaft 242A of the motor 241A and is rotatable about the shaft 242A of the motor 241A by the rotational force transmitted from the motor 241A.

[0058] The optical density of the gradient-concentration filter 243A varies in the circumferential direction. In other words, the gradient-concentration filter 243A has a concentration gradient in which the optical density varies in the circumferential direction. The optical density of the gradient-concentration filter 243A does not necessarily have to increase or decrease sequentially along the circumferential direction, as long as it varies in the circumferential direction.

[0059] When the gradient concentration filter 243A rotates due to the rotational force transmitted from the motor 241A, the optical density of the region through which the internal reference light 36 passes through the gradient concentration filter 243A changes. Therefore, the transmittance of the gradient concentration filter 243A to the internal reference light 36 is variable.

[0060] The reflective sheet 244 is provided on the opposite side of the scanning mirror 7 from the gradient concentration filter 243A, and reflects the distance measurement light 35 that has passed through the gradient concentration filter 243A. At this time, the reflective sheet 244 retroreflects the internal reference light 36. This eliminates the need for optical axis adjustment, unlike when a prism or mirror reflects the internal reference light 36. This saves the trouble of adjusting the optical axis.

[0061] The filter 245 is provided between the scanning mirror 7 and the gradient-concentration filter 243A, and is made of, for example, glass. The optical density of the filter 245 is fixed and does not change throughout the entire filter 245. The filter 245 can adjust the variation in the light intensity of the internal reference beam 36 caused by variations in the three-dimensional surveying device 1A. The filter 245 can also suppress reflection of the internal reference beam 36 on the surface of the gradient-concentration filter 243A. The filter 245 does not necessarily have to be provided.

[0062] The distance measurement light 35 reflected by the scanning mirror 7 and transmitted through the filter 245 and the gradient concentration filter 243A is reflected by the reflecting sheet 244. The internal reference light 36 reflected by the reflecting sheet 244 is transmitted through the gradient concentration filter 243A and the filter 245 and is reflected by the scanning mirror 7.

[0063] The three-dimensional surveying device 1A according to the comparative example adjusts and fixes the rotation angle of the scanning mirror 7 before starting the operation of acquiring three-dimensional data (i.e., the scanning operation), and irradiates the distance measurement light 35 toward the reference beam optical unit 24A. In other words, before the scanning operation, the distance measurement light 35 as the internal reference beam 36 remains irradiated onto the reference beam optical unit 24A. Furthermore, the three-dimensional surveying device 1A according to the comparative example rotates the concentration gradient filter 243A by the rotational force transmitted from the motor 241A.

[0064] As a result, when the internal reference light 36 passes through the gradient concentration filter 243A, the optical density of the region where the internal reference light 36 passes through the gradient concentration filter 243A changes. That is, when the internal reference light 36 passes through the gradient concentration filter 243A, the transmittance of the internal reference light 36 with respect to the gradient concentration filter 243A changes. As a result, the internal reference light 36 with different light intensities is guided to and acquired by the scanning mirror 7. The internal reference light 36 reflected by the scanning mirror 7 passes through the second beam splitter 39 and is guided to the light receiving element 42.

[0065] As a result, as shown in the graph in FIG. 5, the three-dimensional surveying device 1A according to the comparative example acquires the relationship between the light intensity of the internal reference light 36 and the distance-related correction value at a known distance. In other words, the three-dimensional surveying device 1A according to the comparative example acquires a correction value according to the light intensity for a known distance. In the graph shown in FIG. 5, the correction value is relatively large when the light intensity is relatively large. Then, the three-dimensional surveying device 1A according to the comparative example stores (memorizes) a table of correction values ​​according to the light intensity for a known distance in the memory unit 48 (see FIG. 2).

[0066] Thereafter, the three-dimensional surveying device 1A according to the comparative example stops the rotation of the gradient density filter 243A and starts the scanning operation, and corrects the distance value according to the amount of reflected distance measuring light 37 reflected by the object to be measured from the distance measuring light 35 by using a table stored in the memory unit 48, i.e., a table of correction values ​​according to the amount of light.

[0067] Here, the distance correction value (see FIG. 5) acquired before the scanning operation may change due to, for example, the warm-up state of the three-dimensional surveying device 1A. Therefore, the three-dimensional surveying device 1A according to the comparative example updates the correction value by offsetting it when the laser beam passes through the gradient density filter 243A during the scanning operation. However, the three-dimensional surveying device 1A according to the comparative example does not re-acquire the table of correction values ​​according to the light intensity during the scanning operation.

[0068] 3, in the three-dimensional surveying device 1 according to this embodiment, the reference light optical unit 24 is provided in a range outside the measurement range within the irradiation range of the distance measurement light 35, and receives and reflects the distance measurement light 35 reflected by the scanning mirror 7 as internal reference light 36. In addition, the reference light optical unit 24 has a gradient density filter 243 instead of the motor 241A and the gradient density filter 243A.

[0069] The gradient-concentration filter 243 is fixed at a predetermined position in the reference beam optical unit 24. The optical density of the gradient-concentration filter 243 varies along the scanning line of the internal reference beam 36 in the region through which the internal reference beam 36 passes. In other words, the optical density of the gradient-concentration filter 243 varies along the trajectory of the internal reference beam 36 passing through the gradient-concentration filter 243. The other structures are similar to those of the three-dimensional surveying device 1A according to the comparative example described above with reference to FIG. 4.

[0070] According to the three-dimensional surveying device 1 of this embodiment, every time the scanning mirror 7 rotates during a scanning operation, that is, every time the scanning mirror 7 rotates and irradiates the distance measurement light 35 during a scanning operation, the internal reference light 36 passes through all of the optical densities of the graded concentration filter 243 that change along the scanning line of the internal reference light 36. Therefore, the three-dimensional surveying device 1 of this embodiment can obtain a table of correction values ​​according to the light intensity every time the scanning mirror 7 rotates during a scanning operation. An example of the table of correction values ​​according to the light intensity, in other words, an example of a graph showing the relationship between the light intensity of the internal reference light 36 and the correction value for distance, is as described above with reference to FIG. 5.

[0071] The three-dimensional surveying device 1 according to this embodiment stores (memorizes) a table of correction values ​​corresponding to the light intensity for a known distance in the storage unit 48 every time the scanning mirror 7 makes one rotation during a scanning operation. As a result, the three-dimensional surveying device 1 according to this embodiment uses the precise table to correct the measured distance value according to the light intensity of the reflected distance measuring light 37 every time the scanning mirror 7 makes one rotation, thereby improving the distance measurement accuracy of scanning.

[0072] 4, there is no need for a driving unit such as the motor 241A. That is, there is no need for a mechanism or structure for driving the gradient filter 243. Therefore, the three-dimensional surveying device 1 according to this embodiment can be simplified in structure and made smaller in size.

[0073] Next, a specific example of the density gradient filter of this embodiment will be described with reference to the drawings. FIG. 6 is a schematic diagram illustrating a density gradient filter according to a first specific example. FIG. 7 is a plan view showing a gradient filter according to a first specific example. Fig. 6 is a plan view of the scanning mirror 7 and the gradient filter 243 as viewed along the direction of arrow A11 shown in Fig. 3. Fig. 7 is a plan view of the gradient filter 243 as viewed along the direction of arrow A12 shown in Fig. 6.

[0074] 6, in this specific example, the surface 246 of the gradient-concentration filter 243 through which the internal reference light 36 passes is flat. As shown in Fig. 7, the optical density of the gradient-concentration filter 243 varies along the scanning line 361 of the internal reference light 36 in the region through which the internal reference light 36 passes. Specifically, the optical density of the gradient-concentration filter 243 has a gradient that gradually increases the amount of the internal reference light 36 passing through the gradient-concentration filter 243 in the scanning direction A2 of the internal reference light 36.

[0075] The scanning line 361 corresponds to the trajectory of the internal reference light 36 passing through the surface 246 of the gradient concentration filter 243 when the scanning mirror 7 rotates vertically around the vertical rotation axis 6 (see Figure 1), as indicated by the arrow A1 in Figure 6.

[0076] The optical density gradient on the surface 246 (i.e., plane) of the gradient-concentration filter 243 may be constant or may vary along the scanning line 361 of the internal reference light 36. For example, the optical density gradient on the surface 246 of the gradient-concentration filter 243 may vary according to the distance L1 between the portion 71 (see FIG. 6 ) where the distance measurement light 35 is reflected by the scanning mirror 7 and the portion where the internal reference light 36 passes through the surface 246 of the gradient-concentration filter 243.

[0077] According to this example, the surface 246 of the gradient filter 243, through which the internal reference light 36 passes, is flat, which simplifies the structure and reduces the size of the gradient filter 243. As a result, the structure of the three-dimensional surveying device 1 can be simplified and reduced in size.

[0078] Furthermore, the optical density of the gradient-concentration filter 243 has a gradient that gradually increases the amount of internal reference light 36 passing through the gradient-concentration filter 243 in the scanning direction A2 of the internal reference light 36. Therefore, in the initial stage of the internal reference light 36 passing through the gradient-concentration filter 243, a relatively large amount of internal reference light 36 is prevented from entering the light receiving element 42, and a relatively large amount of light is prevented from remaining in circuits such as the control and calculation unit 15. As a result, the three-dimensional surveying device 1 having the gradient-concentration filter 243 of this specific example can improve the accuracy of the table of correction values ​​according to the amount of light, and can improve the distance measurement accuracy of scanning.

[0079] Furthermore, if the optical density gradient on the plane of the gradient filter 243 changes depending on the distance L1 between the portion 71 where the distance measurement light 35 is reflected by the scanning mirror 7 and the portion where the internal reference light 36 passes through the surface 246 of the gradient filter 243, the linearity or nonlinearity of the table of correction values ​​according to the amount of light can be improved.

[0080] FIG. 8 is a plan view showing a gradient filter according to a second example. 8 corresponds to a plan view of the gradient filter 243B of this example as viewed along the arrow A12 shown in FIG.

[0081] In this specific example, the surface 246B of the gradient concentration filter 243B through which the internal reference light 36 passes is flat, similar to the surface 246 of the gradient concentration filter 243 according to the first specific example described above with reference to Fig. 7. As shown in Fig. 8, the optical density of the gradient concentration filter 243B of this specific example has a gradient such that the amount of the internal reference light 36 passing through the gradient concentration filter 243B gradually increases and then decreases in the scanning direction A2 of the internal reference light 36.

[0082] Specifically, when viewed along the scanning direction A2 of the internal reference light 36, the amount of light of the internal reference light 36 passing through the gradient concentration filter 243B is relatively small in the early stage, relatively large in the middle stage (i.e., the stage when the internal reference light 36 passes through the center part of the gradient concentration filter 243B), and becomes relatively small again in the late stage. The rest of the structure is similar to that of the gradient concentration filter 243 according to the first specific example described above with reference to Figures 6 and 7.

[0083] According to this specific example, in the early stage when the internal reference light 36 passes through the gradient concentration filter 243B, a relatively large amount of the internal reference light 36 is prevented from entering the light-receiving element 42, and a relatively large amount of the internal reference light 36 is prevented from remaining in circuits such as the control and calculation unit 15. Furthermore, in the later stage when the internal reference light 36 passes through the gradient concentration filter 243B, a relatively large amount of the internal reference light 36 is prevented from entering the light-receiving element 42, and a relatively large amount of the internal reference light 36 is prevented from remaining in circuits such as the control and calculation unit 15. Therefore, when the scanning mirror 7 irradiates the reference light optical unit 24 with the distance measurement light 35 as the internal reference light 36 during the next rotation, a relatively large amount of the light is prevented from remaining in circuits such as the control and calculation unit 15. This further improves the accuracy of the table of correction values ​​according to the light amount, and further improves the distance measurement accuracy of scanning.

[0084] FIG. 9 is a schematic diagram illustrating a density gradient filter according to a third specific example. FIG. 10 is a plan view showing a gradient filter according to a third example. 9 corresponds to a plan view of the scanning mirror 7 and the gradient filter 243C as viewed along the direction of the arrow A11 shown in FIG 3. FIG 10 is a plan view of the gradient filter 243C as viewed along the arrow A13 shown in FIG 9.

[0085] 9, in this specific example, the surface 246C of the gradient concentration filter 243C through which the internal reference light 36 passes is a spherical surface. Specifically, the surface 246C of the gradient concentration filter 243C is a spherical surface in which the distance L2 between the portion 71 where the distance measurement light 35 is reflected by the scanning mirror 7 and the portion where the internal reference light 36 passes through the surface 246C of the gradient concentration filter 243C is constant.

[0086] 10, the optical density of the gradient concentration filter 243C varies along the scanning line 361 of the internal reference light 36 in the region through which the internal reference light 36 passes. Specifically, the optical density of the gradient concentration filter 243C has a gradient that gradually increases the amount of the internal reference light 36 passing through the gradient concentration filter 243C in the scanning direction A3 of the internal reference light 36. The gradient of the optical density on the surface 246C (i.e., the spherical surface) of the gradient concentration filter 243C is constant.

[0087] In addition, similar to the gradient concentration filter 243C according to the second specific example described above with reference to Figure 8, the optical density of the gradient concentration filter 243C may have a gradient in which the amount of internal reference light 36 passing through the gradient concentration filter 243C gradually increases and then decreases in the scanning direction A3 of the internal reference light 36.

[0088] According to this specific example, the surface 246C of the gradient-concentration filter 243C, through which the internal reference light 36 passes, is a spherical surface with a constant distance L2 between the portion 71B where the distance measurement light 35 is reflected by the scanning mirror 7 and the portion where the internal reference light 36 passes through the gradient-concentration filter 243C, so that the linearity or linearity of the table of correction values ​​according to the light amount can be improved. Furthermore, because the gradient of optical density on the spherical surface of the gradient-concentration filter 243C is constant, the linearity or linearity of the table of correction values ​​according to the light amount can be further improved.

[0089] Next, the calculation process (measurement process) of the distance to the measurement object will be described with reference to the drawings. FIG. 11 is a flowchart illustrating a distance calculation process of the three-dimensional surveying device according to this embodiment.

[0090] First, in step S11, the control and calculation unit 15 rotates or swings the scanning mirror 7 in the vertical direction, and irradiates the reference light optical unit 24 with the distance measurement light 35 as the internal reference light 36. As a result, the internal reference light 36 passes through all of the optical density of the concentration gradient filter 243 that changes along the scanning line of the internal reference light 36.

[0091] The internal reference light 36 received and reflected by the reference light optical unit 24 is reflected by the scanning mirror 7, passes through the second beam splitter 39, and is guided to the light receiving element 42. The distance data processing unit 51 then calculates the internal light distance based on the internal reference light (internal light) 36 received by the light receiving element 42. That is, the distance data processing unit 51 processes the internal light distance data based on the internal reference light 36 received by the light receiving element 42 and converted into an internal reference light electrical signal. As a result, the three-dimensional surveying device 1 can obtain a table of correction values ​​corresponding to the light amount for a known distance and store it in the memory unit 48 every time the internal reference light 36 passes through all of the optical densities of the concentration gradient filter 243 that have changed along the scanning line 361 of the internal reference light 36.

[0092] When a predetermined amount of data for the table of correction values ​​according to the light intensity has been stored in the memory unit 48, in step S12 following step S11, the control and calculation unit 15 rotates the base unit 5 in the horizontal direction to make it take off. By executing the process of step S12, the 3D surveying device 1 stabilizes the horizontal rotation speed of the base unit 5, thereby making the density (pitch) of the point cloud data acquired by the scanning operation described below uniform and preventing variations in the spacing of the point cloud data.

[0093] The process described above with respect to step S11, i.e., the process of obtaining a table of correction values ​​according to light amounts for known distances and storing the table in the storage unit 48, may be executed in step S12. In other words, the processes of step S11 and step S12 may be executed simultaneously.

[0094] Next, in step S13, the control and calculation unit 15 controls the scanning mirror 7 to irradiate the object to be measured with the distance measurement light 35 and also irradiate the reference light optical unit 24 with the distance measurement light 35 as the internal reference light 36. That is, the control and calculation unit 15 rotates the scanning mirror 7 in the vertical direction and rotates the base unit 5 in the horizontal direction to start the scanning operation.

[0095] The reflected distance measuring light 37 reflected by the measurement object is reflected by the scanning mirror 7, passes through the second beam splitter 39, and is guided to the distance measuring unit 22. Then, the distance data processing unit 51 calculates the external light distance based on the reflected distance measuring light (external light) 37 received by the light receiving element 42. That is, the distance data processing unit 51 processes the external light distance data based on the reflected distance measuring light 37 received by the light receiving element 42 and converted into a reflected distance measuring light electrical signal.

[0096] As described above with respect to step S11, the distance data processing unit 51 calculates the internal light distance based on the internal reference light (internal light) 36 received by the light receiving element 42. This allows the three-dimensional surveying device 1 to obtain a table of correction values ​​corresponding to the light intensity for a known distance and store it in the memory unit 48 every time the scanning mirror 7 makes one rotation during the scanning operation.

[0097] Next, in step S14, distance data processing unit 51 calculates the distance to the measurement object based on the internal light distance data and external light distance data stored in memory unit 48. That is, distance data processing unit 51 corrects the external light distance data according to the light intensity of reflected distance-measuring light 37 using a precise table stored in memory unit 48, and calculates the distance to the measurement object.

[0098] The above describes the embodiments of the present invention. However, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the scope of the claims. The configurations of the above embodiments can be partially omitted or arbitrarily combined in a different manner from the above. [Explanation of symbols]

[0099] 1: 3D surveying device, 1A: 3D surveying device, 2: leveling unit, 3: base unit, 4: horizontal rotation unit, 5: support unit, 5a: first chamber, 5b: second chamber, 6: vertical rotation axis, 7: scanning mirror, 8: adjusting screw, 9: bearing, 11: horizontal rotation axis, 12: horizontal drive motor, 13: horizontal drive unit, 14: horizontal angle detector, 15: control and calculation unit, 16: recess, 17: vertical drive unit, 18: vertical angle detector, 19: distance measurement light emitting unit, 21: common optical path unit, 22: distance measurement unit, 23: imaging unit, 24: reference light optical unit, 24A: reference light optical unit, 25: display unit, 26: operation unit, 27: bearing, 28: vertical drive motor, 29: scanning unit, 31: Distance measurement light source unit, 32: Distance measurement optical axis, 33: Light projecting optical unit, 35: Distance measurement light, 36: Internal reference light, 37: Reflected distance measurement light, 38: First beam splitter, 39: Second beam splitter, 41: Light receiving optical unit, 42: Light receiving element, 45: Image sensor, 46: External memory device, 47: Calculation unit, 48: Memory unit, 49: Distance measurement light emission drive unit, 51: Distance data processing unit, 52: Image data processing unit, 71: Part, 71B: Part, 241A: Motor, 242A: Shaft, 243: Concentration gradient filter, 243A: Concentration gradient filter, 243B: Concentration gradient filter, 243C: Concentration gradient filter, 244: Reflection sheet, 245: Filter, 246: Surface, 246B: Surface, 246C: Surface, 361: Scan line

Claims

1. A three-dimensional surveying device that irradiates a measurement object with distance measurement light, measures a distance to the measurement object based on reflected distance measurement light that is formed by the distance measurement light being reflected by the measurement object and an internal reference light, and acquires three-dimensional data of the measurement object by detecting an irradiation direction of the distance measurement light, a light source unit that emits the distance measurement light; a light projection optical unit that projects the distance measurement light emitted from the light source unit onto a distance measurement optical axis; a scanning mirror that is rotatable about the rotation axis while being tilted with respect to the axis of the rotation axis, and that rotates and irradiates the distance measurement light guided from the light projecting optical unit within a plane that intersects with the rotation axis; a light receiving optical unit that receives the reflected distance measuring light reflected by the object to be measured and guided via the scanning mirror; a reference light optical unit that is provided in a range other than a measurement range in which the distance measurement light is irradiated onto the measurement object within an irradiation range in which the distance measurement light is irradiated by the scanning mirror while being rotated, the reference light optical unit receiving and reflecting the distance measurement light reflected by the scanning mirror as the internal reference light, and that is capable of changing the amount of the reflected internal reference light; a light-receiving element that receives the reflected distance measuring light and the internal reference light guided from the reference light optical unit; Equipped with The reference light optical unit includes: a gradient density filter in which the optical density of an area through which the internal reference beam passes varies along a scanning line of the internal reference beam; a retroreflective sheet that reflects the internal reference light that has passed through the density gradient filter; A three-dimensional surveying device comprising:

2. 2. The three-dimensional surveying instrument according to claim 1, wherein the surface of the gradient density filter through which the internal reference light passes is a flat surface.

3. 3. The three-dimensional surveying instrument according to claim 2, wherein the optical density gradient on the plane changes according to the distance between the portion where the distance measurement light is reflected by the scanning mirror and the portion where the internal reference light is transmitted through the surface.

4. 2. The three-dimensional surveying device according to claim 1, wherein the surface of the gradient concentration filter through which the internal reference light passes is a spherical surface in which the distance between the portion where the distance measurement light is reflected by the scanning mirror and the portion where the internal reference light passes through the surface is constant.

5. 5. The three-dimensional surveying instrument according to claim 4, wherein the gradient of the optical density on the spherical surface is constant.

6. 2. The three-dimensional surveying instrument according to claim 1, wherein the optical density has a gradient such that the amount of the internal reference light passing through the density-graded filter gradually increases in the scanning direction of the internal reference light.

7. 2. The three-dimensional surveying instrument according to claim 1, wherein the optical density has a gradient in which the amount of light of the internal reference light passing through the density gradient filter gradually increases and then decreases in the scanning direction of the internal reference light.

Images