Surveying instrument

There are provided a horizontal angle detector for detecting a horizontal angle, an elevation angle detector for detecting an elevation angle, a dynamic displacement detector for detecting posture displacement of a surveying instrument main unit in two horizontal directions, and a calculating unit, wherein the dynamic displacement detector detects displacement with respect to standard posture of the surveying instrument main unit 1, the calculating unit calculates the horizontal angle and the elevation angle corresponding to dynamic displacement detected by the dynamic displacement detector, and compensates the horizontal angle and the elevation angle obtained by the horizontal angle detector and the elevation angle detector respectively are compensated based on the calculated horizontal angle and the calculated elevation angle.

BACKGROUND OF THE INVENTION

The present invention relates to a surveying instrument, by which it is possible to perform a measurement with high accuracy and quickly by compensating a deviation of an optical axis of a measuring light when the deviation occurs on the optical axis of the measuring light due to vibration.

A surveying instrument is used to perform a distance measurement and a measurement of a horizontal angle and a vertical angle by directing the optical axis of the measuring light of a distance measuring light optical system toward an object to be measured. A surveying instrument with tracking function has a rotator, and the rotator is rotated to follow the movement of the object to be measured. The optical axis of the measuring light is directed toward the object to be measured, and the measurement can be performed on the object to be measured.

When the surveying instrument is installed, leveling is carried out on the surveying instrument so that a vertical axis of the surveying instrument concurs with a gravitational direction. The leveling operation is carried out by using a tilt sensor provided on the surveying instrument. The surveying operation is performed with the surveying instrument under leveled condition.

In the meantime, even when the surveying instrument is leveled accurately in standard condition, a posture of the surveying instrument may be deviated, although slightly, when the rotator driven or stopped. Also, a slight angular error may occur during the driving due to an inertial force of a driving unit. In case the measurement is performed dynamically, the error may exert influence on a measured value. Or, the deviation may occur in the leveling condition of the surveying instrument due to causes subsequently occurred, such as the vibration from outside or the like. Under the condition where the deviation has occurred in the leveling condition, an error may be included in the measured value, and an accurate measurement may not be carried out.

Therefore, in the past, in case the deviation occurs in the leveling condition of the surveying instrument—for instance, in case the device is tilted, it has been practiced to detect the tilting and to compensate a measurement result based on a result of the detection.

In the past, to detect the tilting of the surveying instrument, the tilting has been detected with high accuracy by using an air bubble tube type tilt sensor or a tilt sensor to detect the tilting of liquid surface, which are provided on the surveying instrument for the purpose of leveling,

The tilt sensor can detect the tilting of the surveying instrument with high accuracy, but it requires longer time for detecting. Further, because a tracking operation is carried out or the like, immediately after the rotator is driven and stopped, a signal from the tilt sensor is not stable due to the vibration caused at the time of stopping. Thus, it is not possible to accurately detect the tilting. Accordingly, it is necessary to wait for some time until the vibration ceases to exist and the tilt sensor can be stabilized. Further, the measurement error may occur during operation.

Also, the tilt sensor does not exhibit high responsiveness and does not response accurately to the vibration from outside—for instance, to the vibration caused by the passing of an automobile on a road near the point where the surveying instrument is installed. Therefore, it has been practiced to perform averaged processing in view of time to the detection signal from the tilt sensor. The tilting in average has been determined, and the measured value has been compensated based on the tilting obtained by the averaged processing.

For this reason, variations in the measurement data are increased because of the vibration.

In some type of the surveying instrument, a pulsed distance measuring light is projected at high speed by rotary irradiation via the rotator and the position of the object to be measured is measured. In this type of surveying instrument, the high inertial force occurs due to stopping or driving of a motor and the rotator, and the posture of the surveying instrument is changing at every moment. In this respect, the tilt sensor as described above exhibits low responsiveness, and the change of posture cannot be detected accurately. Thus, compensation cannot be made with high accuracy.

As the surveying instrument to detect the tilting and to compensate the tilting of the instrument by using the tilt sensor is disclosed in JP-A-06-347271, JP-A-08-43098 and JP-A-2006-78416. The surveying instrument to measure the position of the object to be measured by projecting a laser beam for a position measurement by rotary irradiation is disclosed in JP-A-2004-212058 and JP-A-2007-170902.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a surveying instrument, by which it is possible to detect the change in the posture of the instrument at high speed and to perform the measurement with high accuracy even when installation posture of the surveying instrument is changed due to the causes occurred subsequently after the leveling of the surveying instrument or even during the operation of the driving unit.

To attain the above object, the surveying instrument according to the present invention comprises a horizontal angle detector for detecting horizontal angle, an elevation angle detector for detecting elevation angle, a dynamic displacement detecting means for detecting posture displacement of a surveying instrument main unit in two horizontal directions, and a calculating unit, wherein the dynamic displacement detecting means detects displacement with respect to standard posture of the surveying instrument main unit, the calculating unit calculates horizontal angle and elevation angle corresponding to dynamic displacement detected by the dynamic displacement detecting means, and compensates the horizontal angle and the elevation angle obtained by the horizontal angle detector and the elevation angle detector respectively based on the calculated horizontal angle and the calculated elevation angle.

Also, the surveying instrument according to the present invention, wherein the dynamic displacement detecting means comprises two sets of image pickup units which are provided on the surveying instrument main unit, wherein optical axes of the two sets of image pickup units are arranged to perpendicularly cross each other in a horizontal plane, and wherein the calculating unit acquires two image data before and after the transition of time by each of the image pickup units, obtains dynamic displacement of the surveying instrument main unit by a comparison of the two image data, and calculates the horizontal angle and the elevation angle corresponding to dynamic displacement, and compensates the horizontal angle and the elevation angle obtained by the horizontal angle detector and the elevation angle detector based on the calculated horizontal angle and the calculated elevation angle.

Further, the surveying instrument according to the present invention, wherein a photodetection element for outputting image data, which is provided in the image pickup unit, is an image detecting element having pixels with coordinate positions and having a photodetection area as required. Also, the surveying instrument according to the present invention, wherein said image pickup unit provides the photodetection elements, and wherein said photodetection element for outputting image data is two line sensors perpendicularly crossing each other. Also, the surveying instrument according to the present invention, wherein the two image data used for comparison are data along two lines perpendicularly crossing each other as set up on the photodetection element. Further, the surveying instrument according to the present invention, wherein the dynamic displacement detecting means is an acceleration sensor.

The present invention provides the surveying instrument, which comprises a horizontal angle detector for detecting horizontal angle, an elevation angle detector for detecting elevation angle, a dynamic displacement detecting means for detecting posture displacement of a surveying instrument main unit in two horizontal directions, and a calculating unit, wherein the dynamic displacement detecting means detects displacement with respect to standard posture of the surveying instrument main unit, the calculating unit calculates horizontal angle and elevation angle corresponding to dynamic displacement detected by the dynamic displacement detecting means, and compensates the horizontal angle and the elevation angle obtained by the horizontal angle detector and the elevation angle detector respectively based on the calculated horizontal angle and the calculated elevation angle. As a result, even when dynamic displacement occurs due to the error in the posture caused by the vibration and by the driving of the instrument itself, it is possible to compensate the horizontal angle and the elevation angle to match the displacement and to measure the elevation angle and the horizontal angle with high accuracy by eliminating an influence from the vibration.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the attached drawings, description will be given below on the best aspect of the invention when the present invention is carried out.

First, referring toFIG. 1toFIG. 3, description will be given on an example of a surveying instrument, in which the present invention is carried out. The surveying instrument shown inFIG. 1is a three-dimensional measuring instrument, for instance. A distance measuring light is projected by rotary irradiation, and the distance measuring light reflected from an object to be measured is detected and received, and the elevation angle and the horizontal angle are measured.

The surveying instrument1is installed via a tripod2. The central axis of the surveying instrument1concurs with the vertical line, and its posture is set in such manner that the central axis passes through a known point3.

The surveying instrument1primarily comprises a leveling unit4, a surveying instrument main unit5installed on the leveling unit4, and a rotary projecting unit6rotatably mounted on a top of the surveying instrument main unit5.

The leveling unit4supports the surveying instrument main unit5at three points, for instance. The surveying instrument main unit5can be freely tilted around one supporting point, and positions in height of the other two supporting points can be adjusted by an actuator (motor) respectively. By adjusting the position in height of each of the two supporting points by the actuator, the surveying instrument main unit5can be tilted in two directions.

Inside the surveying instrument main unit5, a tilt sensor7for detecting the tilting of the surveying instrument main unit5is provided. Based on the result of detection by the tilt sensor7, the leveling unit4performs leveling of the surveying instrument main unit5so that the central axis of the surveying instrument main unit5concurs with the vertical line.

Inside the surveying instrument main unit5, there are provided a distance measuring unit8comprising a light projecting unit25(seeFIG. 3) and a photodetection unit26(seeFIG. 3), a rotary driving unit9, a posture detecting device10, a control unit11, etc.

The light projecting unit25comprises a projection light optical system including a light emitting source and a vertical optical axis12, and a distance measuring light14is projected in a direction toward an object to be measured (e.g. a prism)27. The photodetection unit26comprises a photodetection element and a photodetection optical system, and the distance measuring light reflected by the object to be measured27is detected and received. The distance measuring unit8measures a distance to the object to be measured27and the elevation angle based on the reflected distance measuring light detected by the photodetection unit26.

The rotary driving unit9rotates the rotary projecting unit6at a constant speed in horizontal direction, which is a part of the projection light optical system. It comprises rotation angle detecting means, e.g. a horizontal angle encoder28(seeFIG. 3) for detecting the horizontal angle, for instance, and an elevation angle encoder29(seeFIG. 3). The rotation angle detecting means detects a direction of the distance measuring light projected from the rotary projecting unit6, and the result of detection is transmitted to the control unit11. The rotary projecting unit6is designed to rotate around the optical axis12of the light projecting unit, and it is provided with a deflecting optical member, e.g. a mirror13. The mirror13is arranged on the optical axis12and it is rotatably supported around the horizontal axis. The distance measuring light14projected along the optical axis12is deflected by the mirror13in horizontal direction and is projected. When the rotary projecting unit6is rotated, the distance measuring light14is scanned in horizontal direction. The mirror13is rotated, and the distance measuring light14is scanned in vertical direction.

The control unit11controls the leveling unit4, the distance measuring unit8and the rotary driving unit9. The control unit11also controls a leveling operation of the surveying instrument main unit5and projects the distance measuring light by controlling the distance measuring unit8. By receiving the reflection light from the object to be measured27, the control unit11measures the distance to the object to be measured27. Then, based on the result of detection by the rotation angle detecting means, the control unit11measures the horizontal angle and the elevation angle of the object to be measured27.

The posture detecting device10detects dynamic displacement of the surveying instrument main unit5caused by the vibration. The posture detecting device10comprises two sets of image pickup units16and17. Each of the two sets of image pickup units16and17has the same arrangement, and optical axes of these two sets of image pickup units16and17are directed in horizontal direction and are directed in the directions crossing perpendicularly to each other. For instance, the optical axis18of the image pickup unit16is directed in the direction of X-axis, and an optical axis19of the image pickup unit17is directed in the direction of Y-axis.

Now, description will be given on the image pickup unit16. The image pickup unit17has the same configuration as that of the image pickup unit16, and description is not given here.

The image pickup unit16comprises an image forming lens21and a photodetection element22arranged along the optical axis18. The image forming lens21forms an image of a scene around the surveying instrument1on the photodetection element22. The photodetection element22is an image detecting element which has an area and is composed of a multiple of pixels, for instance, CCD. Each pixel has a position identified in a coordinate system having the optical axis18as the origin on the photodetection element22. Similarly to the image pickup unit16, the image pickup unit17has an image forming lens23and a photodetection element24.

The distances from the image forming lens21and from the photodetection element22to a photodetection plane are already known. Therefore, when the position of a pixel is identified, field angle on the identified pixel can be determined.

It is so designed that a photodetection signal from the photodetection element22is transmitted to the control unit11together with coordinate signal of each pixel for each pixels.

FIG. 3represents approximate arrangement of a control system in the surveying instrument according to the present invention.

The control unit11primarily comprises a horizontal angle and elevation angle calculating unit31, a main calculating unit32, a storage unit33, an image analyzing unit34, a measured distance calculating unit35, a tilt analyzing unit36, and a driving control unit37. The measuring conditions, measurement results, etc. are displayed on a display unit38.

The storage unit33is semiconductor memory, HDD, etc. Various types of programs are stored in the storage unit33. These programs include: a sequence program for instructing the surveying instrument1to measure distance, an image processing program for detecting the deviation of horizontal angle and the deviation of elevation angle based on an image signal from the photodetection element22and from the photodetection element24, a compensation calculating program for compensating the measurement results based on the deviation of horizontal angle and the deviation of elevation angle calculated, and other programs. Further, data such as distance measurement data as measured, the detected horizontal angle and elevation angle, the deviation of horizontal angle, the deviation of elevation angle, etc. are stored.

The horizontal angle and the elevation angle detected respectively by the horizontal angle encoder28and the elevation angle encoder29are inputted to the horizontal angle and elevation angle calculating unit31. The elevation angle and the horizontal angle are calculated at the horizontal angle and elevation angle calculating unit31, and the results of calculation are inputted to the main calculating unit32.

The results obtained by images taken by the image pickup unit16and the image pickup unit17are transmitted to the image analyzing unit34as photodetection signals from the photodetection element22and the photodetection element24respectively. Blurring of images is detected at the image analyzing unit34. Based on the blurring of the image, the deviation of horizontal angle (i.e. a deviation in X direction) and the deviation of elevation angle (i.e. a deviation in Y direction) are calculated respectively. The deviation of horizontal angle and the deviation of elevation angle thus calculated are transmitted to the main calculating unit32.

The results of detection from the tilt sensor7are inputted to the main calculating unit32via the tilt analyzing unit36. The main calculating unit32performs leveling through driving control of the leveling unit4via the driving control unit37.

Referring toFIG. 4andFIG. 5, description will be given below on an operation.

First, the leveling unit4is driven via the driving control unit37, and the leveling operation is carried out.

Tilting of the surveying instrument main unit5is detected by the tilt sensor7, and the result of detection is inputted to the tilt analyzing unit36. The tilt analyzing unit36judges in which direction and how far the surveying instrument is tilted, and the result of judgment on the tilting is inputted to the main calculating unit32. At the main calculating unit32, the leveling unit4is driven via the driving control unit37based on the result of the judgment on tilting, and the leveling unit4is controlled so that the horizontal line is detected by the tilt sensor7.

When the surveying instrument main unit5has been leveled and when the optical axis12is turned to the vertical direction, scenes in X direction and in Y direction are taken by the image pickup unit16and the image pickup unit17respectively. The results of image pickup are stored in the storage unit33as standard images (FIG. 4(A) andFIG. 4(B)).

The rotary projecting unit6is driven to project the light by rotary irradiation, the distance measuring unit8is driven, and the measurement operation is started. Distance data obtained by distance measurement are stored in the storage unit33. As the result of rotation of the rotary projecting unit6, the vibration occurs, and dynamic displacement of the surveying instrument main unit5is caused by the vibration.

During the measurement operation, image pickup operations on the scenes by the image pickup unit16and the image pickup unit17are continued, and image data are stored in the storage unit33. The image data are acquired in synchronization with the measurement by the distance measuring unit8, and the distance data are associated with the image data.

When mechanical displacement occurs on the surveying instrument main unit5as the results of the vibration, displacement of the surveying instrument main unit5appears as blurring of images taken by the image pickup unit16and the image pickup unit17.FIG. 5(A) shows images taken by the image pickup unit16when displacement occurs in horizontal direction. InFIG. 5(A), the images indicated by solid lines represent X-standard images41, and images indicated by broken lines show X-displaced images42where the vibration has occurred. Image data of the X-standard images41and image data of the X-displaced images42are transmitted respectively to the image analyzing unit34. At the image analyzing unit34, amount of displacement of the surveying instrument main unit5in horizontal direction is obtained based on the X-standard images41and the X-displaced images42.

If a deviation of images between the X-standard images41and the X-displaced images42, i.e. the deviation of images on the photodetection element22, is obtained as number of pixels, the change of field angle can be obtained. From the field angle thus changed, the amount of displacement of the surveying instrument main unit5in horizontal direction is obtained. The deviation of images as given above represents instantaneous displacement changing at every moment, i.e. dynamic displacement.

It is assumed here that both the tripod2and the surveying instrument main unit5have sufficient rigidity, and that twisting displacement around the optical axis12and the falling of the optical axis12do not occur by the vibration.

FIG. 5(B) represents images taken by the image pickup unit17when displacement occurs in the vertical direction. InFIG. 5(B), the images indicated by solid lines represent Y-standard images43, and images indicated by broken lines represent Y-displaced images44when the vibration has occurred.

Similarly, displacement in the vertical direction can be obtained on the photodetection element24by the Y-standard images43and the Y-displaced images44.

When displacement occurs in two directions, i.e. in horizontal direction and in vertical direction, horizontal displacement component and vertical displacement component are obtained, and by synthesizing these components, the direction of displacement and amount of displacement can be determined.

For the purpose of determining the displacement on images, a simple and convenient method as shown inFIG. 6(A) andFIG. 6(B) may be used. As the method to obtain displacement inFIG. 6(A) andFIG. 6(B), vertical lines45aand45band horizontal lines46aand46bare set up on the images, and displacement between the images on the two lines is obtained. To facilitate the comparison of the images, edge processing or the like may be adopted on the images.

In case a method to compare image data by specifying the vertical line45and the horizontal line46is adopted, line sensors may be used as the photodetection element22and the photodetection element24.

The amount of displacement obtained at the image analyzing unit34is transmitted to the main calculating unit32. The main calculating unit32compensates the horizontal angle obtained by the horizontal angle encoder28and the elevation angle obtained by the elevation angle encoder29based on the amount of displacement determined from the result of distance measurement. By this compensation, the influence of the vibration from the results of the distance measurement can be eliminated, and the measurement accuracy can be improved.

It may be so designed that an image data found one frame before is used as the standard image, and the amount of displacement may be determined based on the blurring of the images between the frames.

The means for detecting the elevation angle is not limited to the elevation angle encoder29. As described in JP-A-2004-212058, at least three fan beams, with at least one of them tilted at a known tilt angle, are projected at constant speed by rotary irradiation, and based on the time difference between the moments when three fan beams are received at the photodetection element, the elevation angle may be detected.

Referring toFIG. 7, concrete description will be given below on a case where the amount of displacement is obtained based on the images.

On the photodetection element22, it is apparent that the X-displaced image42is deviated in upward direction by 6 pixels according toFIG. 7(A), and the X-displaced image42is deviated in rightward direction by three pixels according toFIG. 7(B).

Also, it is evident that, on the photodetection element24, there is no deviation in top-to-bottom direction according toFIG. 7(C), and that it is deviated by three pixels in rightward direction according toFIG. 7(D).

In this case, focuses are adjusted to infinity on the image pickup unit16and the image pickup unit17. Accordingly, the deviation of the image represents tilting of the elevation angle in the image optical system respectively, and left-to-right direction represents the deviation of each of the images in horizontal rotating direction. Therefore, amount of the deviation of images on the photodetection element22and amount of the deviation of images on the photodetection element24basically agree with each other. By finding the number of pixels to correspond to the amount of the deviation, the value can be converted to the angle to match the field angle.

For example, it is supposed here that field angle of the opposite angle of the photodetection element22, the photodetection element24are 1° respectively, and when it is in size of 640 pixels×480 pixels, field angle of one pixel is obtained as:
1/(√{square root over ((640×640+480×480)))}=0.001250°=4.5″

Thus, it is found that it is tilted by:

4.5″×6=27″ in X-axis elevation angle; and

As described above, it can be detected how the surveying instrument main unit5is tilted for each frame or for each measurement data. By using this tilting, the elevation angle and the horizontal angle can be compensated.

In case the processing is performed—not on the line, which is set up by image processing, but on the images for one frame or for a required range of one frame, processing speed is decreased, but the amount of information is increased. This results in the increase of resolving power and contributes to the improvement of accuracy.

It may be so arranged that image processing by line and image processing by area are simultaneously used, and a processing method may be selected to match the measuring conditions.

If the amount of the deviation is detected based on the pixel signal only on the line as set up on the photodetection element22and the photodetection element24, the amount of the data to be processed is decreased, and this contributes to the calculation at higher speed.

As described above, if line sensors are used as the photodetection element22and the photodetection element24, the processing can be performed at higher speed and the cost can be reduced.

In the embodiment as described above, the displacement caused by the vibration is obtained based on the images acquired in two directions. However, as the means to obtain displacement, it may be so designed that an acceleration sensor is used and displacement can be determined by integrating the results of detection.

FIG. 8shows a case where the present invention is carried out on a total station. InFIG. 8, the same component as shown inFIG. 1is referred by the same symbol.

The main unit5comprises a leveling unit4, a base unit48, and a rotary projecting unit6. A tilt sensor7, a control unit11, a posture detecting device10, etc. are accommodated in the base unit48. The rotary projecting unit6is rotatably mounted around a vertical axis47on the base unit48, and the rotary projecting unit6is rotated in horizontal direction by a horizontal rotary driving unit9a.

The rotary projecting unit6has a lens barrel unit49, which is rotatable around horizontal axis, stores a distance measuring unit (not shown), which comprises the distance measuring light optical system, a distance measuring light emitting unit, a photodetection unit, etc. The lens barrel unit49is designed to be rotated in vertical direction by a vertical rotary driving unit9b. The lens barrel unit49is directed toward the object to be measured by the horizontal rotary driving unit9aand the vertical rotary driving unit9b.

In this embodiment, images in two directions, i.e. in X-axis direction and Y-axis direction are acquired by the posture detecting device10, a dynamic displacement of the image is determined, the elevation angle and the horizontal angle are compensated by the displacement obtained, and the result of the distance measurement is compensated. As a result, the measurement can be performed with high accuracy.

The surveying instrument, to which the present invention is applied, may be the three-dimensional measuring device as described above, or a total station, or a surveying instrument with the tracking function, or a scanner to determine three-dimensional configuration of an object by driving a mirror at high speed. In brief, the present invention can be applied for compensation of the horizontal angle and the elevation angle in a surveying instrument, which has source of the vibration.