Surveying instrument

A surveying instrument including a light projecting optical system which projects the distance measuring light, a light receiving optical system which receives the reflected distance measuring light from an object, a frame unit 5 which horizontally rotates around a horizontal rotation shaft, a scanning mirror which is provided in the frame unit, vertically rotates, a horizontal angle detector which detects a horizontal angle of the frame unit, a vertical angle detector which detects a vertical angle of the scanning mirror and an arithmetic control module which calculates the three-dimensional coordinates of the object, in which the light receiving optical system has a reflecting mirror having a reflecting surface which is an off-axis paraboloidal surface or an off-axis free-form surface, and the reflected distance measuring light is configured to be led to a light receiving module by the reflecting mirror while being condensed.

BACKGROUND OF THE INVENTION

The present invention relates to a surveying instrument which can acquire the three-dimensional coordinates of an object.

A surveying instrument such as a laser scanner or a total station has an electro-optical distance measurement device which detects a distance to an object by the prism distance measurement using a reflecting prism as the object or the non-prism distance measurement using no reflecting prism.

A light receiving module of the electro-optical distance measurement device has an optical system including a lens, and the incident light is imaged on a light receiving surface by a refracting action of the lens. An objective lens of the optical system has a focal distance “f”, and the focal distance “f” is determined based on the performance required for the electro-optical distance measurement device. For instance, in case of performing the vertical measurement, an aperture of the lens increases to assure a light receiving amount, and a focal distance also becomes longer with an increase in aperture of the lens.

For this reason, the light receiving module of the electro-optical distance measurement device requires a size which enables accommodating the optical system and a length in an optical axis direction which enables assuring the focal distance “f”. Therefore, the miniaturization of the light receiving module has been difficult due to the limitation in the size of the optical system and the focal distance.

SUMMARY OF INVENTION

It is an object of the present invention to provide a surveying instrument which miniaturizes an optical system and attains the miniaturization of the entire instrument.

To attain the object as desired, a surveying instrument according to the present invention includes a light projecting optical system which projects the distance measuring light emitted from a distance measuring light source onto a projecting optical axis, a light receiving optical system which receives a reflected distance measuring light from an object and leads the reflected distance measuring light to a light receiving module, a frame unit which horizontally rotates around a horizontal rotation shaft, a scanning mirror which is provided in the frame unit, vertically rotates around a vertical rotation shaft, irradiates the object with the distance measuring light from the light projecting optical system, and receives the reflected distance measuring light from the object by the light receiving optical system, a horizontal angle detector which detects a horizontal angle of the frame unit, a vertical angle detector which detects a vertical angle of the scanning mirror and an arithmetic control module which calculates the three-dimensional coordinates of the object based on a light reception result of the reflected distance measuring light, a detection result of the horizontal angle detector, and a detection result of the vertical angle detector, wherein the light receiving optical system has a reflecting mirror having a reflecting surface which is an off-axis paraboloidal surface or an off-axis free-form surface, and the reflected distance measuring light is configured to be to a light receiving module by the reflecting mirror while being condensed.

Further, in the surveying instrument according to a preferred embodiment, a multilayer film optical element having a predetermined glass thickness is provided on the projecting optical axis, the multilayer film optical element has a first incidence surface which exists at a close position from the distance measuring light source and a second incidence surface which exists at an away position from the distance measuring light source, a beam splitter film which reflects a part of the distance measuring light and transmits a remaining part of the distance measuring light is formed on an incidence portion of the distance measuring light on the second incidence surface, an antireflective film is formed on a portion excluding the beam splitter film, wherein the distance measuring light is configured to be reflected by the beam splitter film, and the reflected distance measuring light is configured to be transmitted through the beam splitter film and the antireflective film.

Further, in the surveying instrument according to a preferred embodiment, a reference light receiving module and an internal reference light optical system which separates a part of the light from the distance measuring light source as the internal reference light and leads the internal reference light to the reference light receiving module, wherein the internal reference light optical system is configured to separate the internal reference light by a beam splitter provided on the projecting optical axis, and the arithmetic control module is configured to calculate a distance to the object based on a time lag between the light reception timing of the reflected distance measuring light and the light reception timing of the internal reference light.

Further, in the surveying instrument according to a preferred embodiment, a reference light receiving module and an internal reference light optical system which separates a part of the light from the distance measuring light source as the internal reference light and leads the internal reference light to the reference light receiving module, wherein the internal reference light optical system is configured to separate the internal reference light by the beam splitter film, and the arithmetic control module is configured to calculate a distance to the object based on a time lag between the light reception timing of the reflected distance measuring light and the light reception timing of the internal reference light.

Further, in the surveying instrument according to a preferred embodiment, a tracking light projecting optical system which deflects the tracking light emitted from a tracking light source coaxially with the distance measuring light, and a tracking light receiving optical system which receives the reflected tracking light from the object and leads the reflected tracking light to an image pickup element, wherein the arithmetic control module is configured to control the frame unit and the scanning mirror based on a light receiving position of the reflected tracking light on the image pickup element in such a manner that the object is tracked.

Further, in the surveying instrument according to a preferred embodiment, a long-pass filter which reflects the infrared light or the near-infrared light and transmits through the visible light is provided on the first incidence surface, the distance measuring light is the infrared light or the near-infrared light, the tracking light is the visible light, and the multilayer film optical element is arranged in such a manner that the second incidence surface is placed on a common optical axis of the distance measuring light and the tracking light.

Further, in the surveying instrument according to a preferred embodiment, the tracking light projecting optical system has a spread angle adjusting module configured to adjust a spread angle of the tracking light, and the spread angle adjusting module is configured to be able to switch between the tracking light having a predetermined spread angle and the laser pointer light which is a parallel light flux.

Further, in the surveying instrument according to a preferred embodiment, an external light reflected by the scanning mirror is configured to enter the image pickup element via the tracking light receiving optical system, and an image having an optical axis of the distance measuring light as a center is configured to be acquired based on the external light which has entered the image pickup element.

Furthermore, in the surveying instrument according to a preferred embodiment, a window glass which rotates integrally with the scanning mirror, wherein the window glass tilts with respect to the optical axis of the distance measuring light.

According to the present invention, a surveying instrument including a light projecting optical system which projects the distance measuring light emitted from a distance measuring light source onto a projecting optical axis, a light receiving optical system which receives a reflected distance measuring light from an object and leads the reflected distance measuring light to a light receiving module, a frame unit which horizontally rotates around a horizontal rotation shaft, a scanning mirror which is provided in the frame unit, vertically rotates around a vertical rotation shaft, irradiates the object with the distance measuring light from the light projecting optical system, and receives the reflected distance measuring light from the object by the light receiving optical system, a horizontal angle detector which detects a horizontal angle of the frame unit, a vertical angle detector which detects a vertical angle of the scanning mirror and an arithmetic control module which calculates the three-dimensional coordinates of the object based on a light reception result of the reflected distance measuring light, a detection result of the horizontal angle detector, and a detection result of the vertical angle detector, wherein the light receiving optical system has a reflecting mirror having a reflecting surface which is an off-axis paraboloidal surface or an off-axis free-form surface, and the reflected distance measuring light is configured to be to a light receiving module by the reflecting mirror while being condensed. As a result, a length in the optical axis direction of the light receiving optical system can be reduced, and the downsizing of the optical system and the downsizing of the entire instrument can be achieved.

DESCRIPTION OF EMBODIMENT

A description will be given on an embodiment of the present invention by referring to the attached drawings.

First, inFIG.1, a description will be given on a surveying instrument according to an embodiment of the present invention.

A surveying instrument1is, for instance, a laser scanner, and constituted of a leveling module2mounted on a tripod (not shown) and a surveying instrument main body3mounted on the leveling module2. It is to be noted that, as the measurement, the non-prism measurement is carried out.

The leveling module2has the leveling screws10, and the surveying instrument main body3is leveled up by the leveling screws10.

The surveying instrument main body3includes a base unit4, a frame unit5, a horizontal rotation shaft6, a horizontal rotation bearing7, a horizontal rotation motor8as a horizontal rotation driving module, a horizontal angle encoder9as a horizontal angle detector, a vertical rotation shaft11, a vertical rotation bearing12, a vertical rotation motor13as a vertical rotation driving module, a vertical angle encoder14as a vertical angle detector, a scanning mirror15as a vertical rotation module, an operation panel16which serves as both an operation module and a display unit, an arithmetic control module17, a storage module18, a distance measuring unit19and others. It is to be noted that, as the arithmetic control module17, a CPU specialized for this instrument or a general-purpose CPU is used.

The horizontal rotation bearing7is fixed to the base unit4. The horizontal rotation shaft6has a vertical axis6a, and the horizontal rotation shaft6is rotatably supported by the horizontal rotation bearing7. Further, the frame unit5is supported by the horizontal rotation shaft6, and the frame unit5integrally rotates with the horizontal rotation shaft6in the horizontal direction.

The horizontal rotation motor8is provided between the horizontal rotation bearing7and the frame unit5, and the horizontal rotation motor8is controlled by the arithmetic control module17. The arithmetic control module17rotates the frame unit5around the axis6aby the horizontal rotation motor8.

A relative rotation angle of the frame unit5with respect to the base unit4is detected by the horizontal angle encoder9. A detection signal from the horizontal angle encoder9is input to the arithmetic control module17, and the horizontal angle data is calculated by the arithmetic control module17. The arithmetic control module17performs the feedback control of the horizontal rotation motor8based on the horizontal angle data.

Further, in the frame unit5, the vertical rotation shaft11having a horizontal axis11ais provided. The vertical rotation shaft11can rotate via the vertical rotation bearing12. It is to be noted that an intersection of the axis6aand the axis11ais a projecting position of the distance measuring light, and the intersection is an origin of a coordinate system of the surveying instrument main body3.

A recess portion21is formed in the frame unit5. One end portion of the vertical rotation shaft11extends to the inside of the recess portion21, and the scanning mirror15is fixed to the one end portion. Therefore, the scanning mirror15is accommodated in the recess portion21.

Further, the vertical angle encoder14is provided at the other end portion of the vertical rotation shaft11. The vertical rotation motor13is provided on the vertical rotation shaft11, and the vertical rotation motor13is controlled by the arithmetic control module17. The arithmetic control module17rotates the vertical rotation shaft11by the vertical rotation motor13, and the scanning mirror15is rotated around the axis11a.

A rotation angle of the scanning mirror15is detected by the vertical angle encoder14, and a detection signal is input to the arithmetic control module17. The arithmetic control module17calculates the vertical angle data of the scanning mirror15based on the detection signal, and performs the feedback control of the vertical rotation motor13based on the vertical angle data.

Further, the horizontal angle data and the vertical angle data calculated by the arithmetic control module17, the measurement results, the measuring point intervals (to be described later), and the measuring angle intervals (to be described later) are saved in the storage module18. As the storage module18, various types of storage devices are used. These storage devices include: an HDD as a magnetic storage device, a CD or DVD as an optical storage device, a RAM, a ROM, a DRAM, a memory card and a USB memory as a semiconductor storage device and other storage devices. The storage module18may be attachable and detachable the frame unit5. Alternatively, the storage module18may be configured to enable transmitting the data to an external storage device or an external data processing device via a non-illustrated communicating means.

In the storage module18are stored various types of programs are stored. These programs include: a sequence program for controlling the distance measuring operation, a calculation program for calculating a distance by the distance measuring operation, a calculation program for calculating an angle based on the horizontal angle data and the vertical angle data, a calculation program for calculating the three-dimensional coordinates of a desired measuring point based on a distance and an angle, a tracking program for tracking an object, a setting program for setting an interval of the measuring points or an interval of the measuring angles, a spread angle adjustment program for adjusting a spread angle of the distance measuring light or the tracking light (to be described later) and other programs. Further, when the various types of programs stored in the storage module18are executed by the arithmetic control module17, the various types of processing are performed.

The operation panel16is, for instance, a touch panel. The operation panel16serves as both an operation module which performs, for instance, changing the distance measurement instructions or the measurement conditions such as a measuring point interval or a measuring angle interval and a display module which displays a distance measurement result and the like.

Next, a description will be given on the distance measuring unit19by referring toFIG.2.

The distance measuring unit19mainly has a distance measuring light projecting module22, a distance measuring light receiving module23, an internal reference light receiving module24, a tracking light projecting module25and a tracking light receiving module26.

The distance measuring light projecting module22has a projecting optical axis27and a light emitter28, and the light emitter28which is a distance measuring light source, for instance, a laser diode (LD) is provided on the projecting optical axis27. Further, the distance measuring light projecting module22has a first plane-parallel plate29, a light projecting lens31, a first beam splitter32and a multilayer film optical element33as a deflecting optical element33which are provided on the projecting optical axis27. It is to be noted that the first plane-parallel plate29, the light projecting lens31, the first beam splitter32and the multilayer film optical element33constitute a light projecting optical system.

The light emitter28pulse-emits a laser beam having an infrared or near-infrared wavelength. Alternatively, the light emitter28burst-emits the laser beam.

The first plane-parallel plate29is, for instance, the tabular glass having a predetermined thickness, and the first plane-parallel plate29can be inserted into or removed from the projecting optical axis27by a non-illustrated driving mechanism. When the first plane-parallel plate29is inserted onto the projecting optical axis27, a spread angle of the distance measuring light increases. When the first plane-parallel plate29is removed from the projecting optical axis27, the spread angle of the distance measuring light decreases. Therefore, at the time of performing the non-prism distance measurement, the first plane-parallel plate29is removed from the projecting optical axis27, and the distance measuring light having a small beam diameter is used. Further, at the time of performing the prism measurement, the first plane-parallel plate29is inserted onto the projecting optical axis27, and the distance measuring light having a large beam diameter is used.

The first beam splitter32has the optical characteristics to reflect approximately 1% of the light and transmit approximately 99% of the light. The first beam splitter32deflects (reflects) a part of the laser beam emitted from the light emitter28as the internal reference light toward an internal reference optical axis34(to be described later), and transmits a remaining greater part of the light therethrough as the distance measuring light.

The multilayer film optical element33is, for instance, the tabular glass having a predetermined glass thickness, and the multilayer film optical element33tilts at, for instance, 45° with respect to the projecting optical axis27The thickness of the multilayer film optical element33is approximately 15 mm at the time of, for instance, 40ϕ. Further, one surface (a first incidence surface) of the multilayer film optical element33which is provided at a position close to the light emitter28is a long-pass filter surface35. A long-pass filter film which transmits the infrared light or the near-infrared light therethrough and makes reflected the visible light is provided on the long-pass filter surface35.

The other surface (a second incidence surface) of the multilayer film optical element33which is provided at a position away from the light emitter28is a beam splitter surface36. A beam splitter film53is provided on the beam splitter surface36. As shown inFIG.3, the beam splitter film53is formed only at a position in the beam splitter surface36which the distance measuring light enters. That is, the beams splitter film53having an elliptical shape which is substantially the same as a light flux of the distance measuring light is formed on the beam splitter surface36, and an antireflective film54is formed on a portion excluding the beam splitter film53. The beam splitter film53has the optical characteristics to reflect approximately 80% of the light and transmit approximately 20% of the light. Further, on the multilayer film optical element33, the chamfered portions37provided by chamfering the corner portions are formed.

Further, the distance measuring light receiving module23has a light receiving optical axis38, the multilayer film optical element33, a reflecting mirror39and a light receiving module41. Further, on the light receiving optical axis38, the multilayer film optical element33and the reflecting mirror39are provided. Further, on a reflecting optical axis38′ of the reflecting mirror39, the light receiving module41, for instance, a light receiving fiber is provided. The light receiving module41leads the received light to a photodetector. It is to be noted that the photodetector may be provided at a light receiving position of the light receiving module41. Further, the multilayer film optical element33and the reflecting mirror39constitute a light receiving optical system.

The reflecting mirror39is an off-axis paraboloidal mirror having a reflecting surface which is an off-axis paraboloid. The reflecting mirror39is configured to deflect (reflect) the light receiving optical axis38with an off-axis amount of approximately 30° to 60°, for instance, 45° while focusing the reflected distance measuring light.

The internal reference light receiving module24has the internal reference optical axis34, a reference light receiving module42, a light receiving lens43and a first beam splitter32. On the internal reference optical axis34, the reference light receiving module42, for instance, a light receiving fiber, the light receiving lens43and the first beam splitter32are provided. The reference light receiving module42leads the internal reference light to a photodetector. It is to be noted that the first beam splitter32and the light receiving lens43constitute an internal reference light optical system.

The tracking light projecting module25has a tracking projecting optical axis44. Further, the tracking light projecting module25has a tracking light emitter45, a second plane-parallel plate46, a light projecting lens47and a second beam splitter48which are provided on the tracking projecting optical axis44, and the multilayer film optical element33which are provided on a reflecting optical axis of the second beam splitter48. The tracking light emitter45which is a tracking light source is, for instance, a laser diode (LD) which emits the visible light. It is to be noted that the second plane-parallel plate46, the light projecting lens47, the second beam splitter48, and the multilayer film optical element33constitute a tracking projecting optical system.

The second plane-parallel plate46is, for instance, the tabular glass having a predetermined thickness, and the second plane-parallel plate46can be inserted into or removed from the tracking projecting optical axis44by a non-illustrated driving mechanism. When the second plane-parallel plate46is inserted onto the tracking projecting optical axis44, a spread angle is adjusted in such a manner that the light emitted from the tracking light emitter45becomes the tracking light having a predetermined spread angle. Further, when the second plane-parallel plate46is removed from the tracking projecting optical axis44, the light emitted from the tracking light emitter45is projected as the laser pointer light which is a parallel light flux having no spread angle.

Further, the second beam splitter48has the optical characteristics to reflect approximately 50% of the light and transmit approximately 50% of the light. Further, the tracking light (the laser pointer light) transmitted through the second beam splitter48is deflected (reflected) coaxially with the distance measuring light (onto the projecting optical axis27) by the long-pass filter surface35of the multilayer film optical element33. That is, the long-pass filter surface35is placed on a common optical path of the distance measuring light and the tracking light.

The tracking light receiving module26has a tracking receiving optical axis49. Further, the tracking light receiving module26has the multilayer film optical element33, the second beam splitter48, a plurality of receiving light lenses51constituted of multiple lenses and an image pickup element52which are provided on the tracking light receiving optical axis49. The multilayer film optical element33, the second beam splitter48, and the plurality of receiving light lenses51constitute a tracking light receiving optical system.

The image pickup element52is a CCD or a CMOS sensor which is an aggregation of pixels, and each pixel can specify a position on the image pickup element52can be identified. For instance, each pixel has the pixel coordinates having the center of the image pickup element52as an origin, and the position on the image pickup element52can be specified by the pixel coordinates. The receiving signal and the pixel coordinate output from each pixel are input to the arithmetic control module17.

In a state where the second plane-parallel plate46has been inserted on the tracking projecting optical axis44, the tracking light projecting module25and the tracking light receiving module26constitute a tracking module. When the arithmetic control module17drives the horizontal rotation motor8and the vertical rotation motor13based on a light receiving position of the reflected tracking light on the image pickup element52and a positional deviation from the center of the image pickup element52, the object can be tracked.

Further, in a state where the second plane-parallel plate46has been removed from the tracking projecting optical axis44, the tracking light projecting module25constitutes a laser pointer irradiating module, and the tracking light receiving module26constitutes an image pickup module. The tracking light (the laser pointer light) projected from the tracking light emitter45is deflected coaxially with the distance measuring light by the long-pass filter surface35. Therefore, an irradiating position of the distance measuring light can be confirmed by the laser pointer light. Further, when the external light which has entered via the scanning mirror15is received by the image pickup element52, an image which is coaxial with the distance measuring light (an image having the optical axis of the distance measuring light as a center) can be acquired.

Next, a description will be given on a case where the measurement and the tracking are performed by the surveying instrument1having the distance measuring unit19. It is to be noted that, in the present embodiment, the prism measurement in which a prism having the retroreflective properties is determined as an object. Further, the first plane-parallel plate29is inserted onto the projecting optical axis27, and the second plane-parallel plate46is inserted onto the tracking projecting optical axis44.

The light emitter28pulse-emits or burst-emits an infrared or near-infrared laser beam. A diameter of the laser beam is expanded so that a predetermined spread angle is provided in a process of being transmitted through the first plane-parallel plate29. Then, the laser beam is turned to a parallel light flux by the light projecting lens31, and enters the first beam splitter32.

A part of the laser beam which has entered the first beam splitter32is reflected onto the internal reference optical axis34as the internal reference light. The reflected internal reference light is received by the reference light receiving module42via the light receiving lens43.

Further, a remaining part of the laser beam which has entered the first beam splitter32enters the multilayer film optical element33as the distance measuring light. The distance measuring light is deflected at the time of being transmitted through the long-pass filter surface35, and the distance measuring light is reflected on the beam splitter film53of the beam splitter surface36. An optical axis (the projecting optical axis27) of the distance measuring light reflected on the beam splitter film53is deflected in such a manner that the optical axis of the distance measuring light coincides with the axis11awhen the distance measuring light is projected from the long-pass filter surface35. The optical axis of the deflected distance measuring light strikes upon the scanning mirror15. When the scanning mirror15rotates around the axis11a, the distance measuring light reflected on the scanning mirror15at a right angle becomes orthogonal with the axis11a, and the distance measuring light is rotated (scanned) within a plane including the axis6a.

The distance measuring light reflected by the object (hereinafter a reflected distance measuring light) strikes upon the scanning mirror15, and the reflected distance measuring light is reflected (deflected) at a right angle by the scanning mirror15. The reflected distance measuring light deflected by the scanning mirror15is sequentially transmitted through the long-pass filter surface35and the beam splitter surface36. Then, the reflected distance measuring light is reflected and deflected by the reflecting mirror39, further focused, and received by the light receiving module41.

Here, the distance measuring light has a predetermined spread angle, and the reflected distance measuring light also has a predetermined spread angle. Therefore, a light flux diameter of the reflected distance measuring light decreases in case of performing the short-distance measurement, and the light flux diameter of the reflected distance measuring light increases in case of performing the long-distance measurement.

For this reason, in case of measuring a long distance, a proportion of the reflected distance measuring light which enters the beam splitter film53is slight, and a sufficient light amount can be assured only from the reflected distance measuring light which has been transmitted through the antireflective film54. On the other hand, in case of measuring a short distance, since a proportion of the reflected distance measuring light which enters the beam splitter film53increases, a sufficient light amount cannot be assured only from the reflected distance measuring light which has been transmitted through the antireflective film54.

In the present embodiment, since a part of the reflected distance measuring light which has entered the beam splitter film53is transmitted through the beam splitter film53, a sufficient light amount can be assured even in case of the short-distance measurement.

It is to be noted that the window glass55which integrally rotates with the scanning mirror15is provided on the optical axis of the distance measuring light reflected by the scanning mirror15. The window glass55tilts at a predetermined angle with respect to the optical axis of the distance measuring light, and prevents the distance measuring light (the stray light) reflected by the window glass55from entering the light receiving module41.

The distance measuring unit19performs the distance measurement for each pulse of the distance measuring light based on a time lag between the light emission timing of the light emitter28and the light reception timing of the light receiving module41(that is, round-trip time of the pulsed light) and a light velocity (Time of Flight). The light emission timing, that is, a pulse interval of the light emitter28is changeable.

Further, the distance measuring unit19has the internal reference light receiving module24. Therefore, by performing the distance measurement based on a time lag between the light reception timing of the internal reference light received by the reference light receiving module42and the light reception timing of the reflected distance measuring light received by the light receiving module41and the light velocity, the further accurate distance measurement can be performed.

Since the frame unit5and the scanning mirror15rotate at the constant speeds, respectively, a two-dimensional scan by the distance measuring light is performed by the cooperation between the vertical rotation of the scanning mirror15and the horizontal rotation of the frame unit5. Further, since the distance measurement data (a slope distance) is acquired by the distance measurement for each pulsed light, by detecting a vertical angle and a horizontal angle for each pulsed light by the vertical angle encoder14and the horizontal angle encoder9, the arithmetic control module17enables calculating the vertical angle data and the horizontal angle data. The three-dimensional point cloud data corresponding to the object can be acquired based on the vertical angle data the horizontal angle data and the distance measurement data.

Further, in parallel with the distance measurement operation, the tracking light is projected from the tracking light emitter45. The tracking light is slightly diffused in a process of being transmitted through the second plane-parallel plate46and the light projecting lens47. The diffused tracking light is reflected by the second beam splitter48, and then strikes upon the multilayer film optical element33. The tracking light reflected by the long-pass filter surface35of the multilayer film optical element33is reflected at a right angle by the scanning mirror15, and irradiated to the object while being diffused.

The reflected tracking light reflected by the object is sequentially reflected by the scanning mirror15and the long-pass filter surface35. The reflected tracking light reflected by the scanned mirror15and the long-pass filter surface35is sequentially transmitted through the second beam splitter48and the plurality of receiving light lenses51, and enters the image pickup element52. The arithmetic control module17calculates a deviation between the center of the image pickup element52and an incidence position of the reflected tracking light, and controls the driving of the horizontal rotation motor8and the vertical rotation motor13so that the incidence position of the reflected tracking light becomes the center of the image pickup element52. Thereby, the surveying instrument main body3tracks the object.

Further, when the second plane-parallel plate46has been removed from the tracking projecting optical axis44, a measuring point is irradiated with the tracking light as the laser pointer light, and an image having the measuring point as a center can be acquired by the tracking light receiving module26.

As described above, in the present embodiment, the off-axis paraboloidal mirror having an off-axis amount of approximately 30° to 60° is used as the reflecting mirror provided in the light receiving optical system. For this reason, since the light receiving optical axis38can be reflected at an acute angle exceeding a right angle, the light receiving module41can be arranged between the multilayer film optical element33and the reflecting mirror39.

Therefore, since a length in the optical axis direction of the distance measuring unit19(the light receiving optical system) can be shortened, the optical system of the distance measuring unit19can be miniaturized, and the entire surveying instrument can be miniaturized.

Further, the window glass55rotated integrally with the scanning mirror15tilts with respect to the optical axis of the distance measuring light. Therefore, a measurement error due to the reception of the distance measuring light, which is reflected by the window glass55, with respect to the light receiving module41can be prevented, and a measurement accuracy can be improved.

Further, the insertion or removal of the first plane-parallel plate29enables adjusting a spread angle of the distance measuring light. Therefore, it is possible to properly use the non-prism distance measurement adopting the distance measuring light of a small beam diameter and the prism distance measurement adopting the distance measuring light of a large beam diameter.

Further, by the insertion or removal of the second plane-parallel plate46, the tracking light projecting module25and the tracking light receiving module26serve both a laser pointer irradiation module and an image pickup module. Therefore, the laser pointer irradiation module or the image pickup module does not have to be additionally provided, and a reduction of the number of components and a decrease in manufacturing cost can be achieved.

Further, a prism or the like having the retroreflective properties can be automatically tracked. Therefore, one worker can perform the tracking and the measurement, and the workability can be improved.

Further, the image pickup element52can receive the external light via the scanning mirror15. Therefore, it is possible to acquire an image of the entire circumference, except for the lower part that is blocked by the frame unit5.

Further, on the beam splitter surface36of the multilayer film optical element33, a part the distance measuring light enters is the beam splitter film53. Therefore, the reflected distance measuring light can be transmitted through the beam splitter film53, and a light receiving amount in the short-distance measurement can be assured.

It is to be noted that, in the present embodiment, by the insertion or removal of the first plane-parallel plate29and the second plane-parallel plate46each of which is the tabular glass, the changeover between the prism distance measurement and the non-prism distance measurement and the changeover between the tracking light and the laser pointer light are performed. On the other hand, the liquid lenses may be used in place of the first plane-parallel plate29and the second plane-parallel plate46. Changing the focal distances of the liquid lenses enables the changeover between the prism distance measurement and the non-prism distance measurement and the changeover between the tracking light and the laser pointer light without inserting or removing the liquid lenses. The first plane-parallel plate29, the second plane-parallel plate46and the liquid lenses are generically referred to as a spread angle adjusting module.

Further, the tracking light projecting module25and the tracking light receiving module26may be counterchanged with each other. That is, the tracking light receiving module26may be provided on a reflecting optical axis of the second beam splitter48, and the tracking light projecting module25may be provided on a transmitting optical axis of the second beam splitter48.

Further, in the present embodiment, the tracking light projecting module25also serves as a laser pointer irradiating module, but the laser pointer irradiating module may be additionally provided with respect to the tracking light projecting module25. In this case, when a filter which can receive the invisible light is provided with respect to the image pickup element52, the tracking light can be the invisible light. Further, the second plane-parallel plate46can be omitted.

Further, in the present embodiment, the off-axis paraboloidal mirror is used as the reflecting mirror39, but an off-axis free-form mirror having a reflecting surface which is an off-axis free-form surface may be used.

It is to be noted that the distance measuring light projecting module22and the internal reference light receiving module24are not restricted with respect to the configurations in the present embodiment. For instance, as shown inFIG.4A, a mirror56may be provided on the reflecting optical axis of the first beam splitter32, and the light receiving lens43and the reference light receiving module42may be provided on the reflecting optical axis of the mirror56. Alternatively, as shown inFIG.4B, the first beam splitter32may have the optical characteristics of transmitting approximately 1% of the light and reflecting approximately 99% of the light, and the light receiving lens43and the reference light receiving module42may be provided on the transmitting optical axis of the first beam splitter32.

Further, the distance measuring light projecting module22and the distance measuring light receiving module23may be configured like a modification shown inFIG.5.

In the modification ofFIG.5, the light receiving lens43and the reference light receiving module42are provided on the transmitting optical axis of the beam splitter film53of the multilayer film optical element33. That is, the beam splitter film53also serves as the function of the first beam splitter32.

Therefore, the first beam splitter32can be omitted, the number of components can be reduced, and hence the simplification of the instrument structure and a decrease in manufacturing cost can be achieved.