Patent Description:
A surveying instrument such as a laser scanner or a total station has an electronic distance meter which detects a distance to an object which is to be measured by the prism distance measurement using reflecting a prism having the retro-reflective property as the object or the non-prism distance measurement using no reflecting prism.

There are surveying instruments which use a multi-stack laser as a light source of the surveying instrument, in which a plurality of light emitters, for instance, laser diodes are laminated (stacked) and emit lights simultaneously. The multi-stack laser purposes for an increase a light amount of a distance measuring light by combining lights from the plurality of light emitters and for an increase in distance capable of being measured.

However, even if the respective light emitters are controlled in such a manner that the respective light emitters emit lights simultaneously, there may be a gap in timing of the light emission due to manufacturing errors and the like. Further, due to this gap, a difference of, for instance, approximately ±<NUM> may be produced in a distance measurement value for each light emitter.

On the other hand, in case of the prism distance measurement using a reflecting prism or the like having the retro-reflective property as an object, in a state where a beam profile (an intensity distribution) of the distance measuring light being maintained a distance measuring light is reflected by the prism. Therefore, in a case where the prism measurement using the multi-stack laser as a light source is performed, errors could possibly occur in distance measurement results depending on which part of the distance measuring light is reflected, that is, the light of which light emitter is a light to be reflected.

<CIT> discloses a surveying device comprising a light emitting unit using an array of solid-state lasers or LEDs sharing a common collimator optical unit.

It is an object of the present invention to provide a surveying instrument which achieves for uniforming beam profiles of distance measuring lights and reducing errors in distance measurement results.

To attain the object as described, a surveying instrument according to claim <NUM> is provided.

Further, in the surveying instrument according to a preferred embodiment, the one-dimensional diffusion optical member is a slit plate having a slit extending in a direction orthogonal to a laminating direction of the light emitters.

Further, in the surveying instrument according to a preferred embodiment, the object is a corner cube having the retro-reflective property, and the distance measuring light diffused by the one-dimensional diffusion optical member is configured in such a manner that an overlapping portion in which lights emitted from the respective light emitters are all overlapped is formed, and the arithmetic control module is performed the distance measurement of the corner cube by the overlapping portion.

Further, in the surveying instrument according to a preferred embodiment, the surveying instrument further comprises a frame unit configured to horizontally rotate around a horizontal rotation shaft by a horizontal rotation motor, a scanning mirror configured to vertically rotate around a vertical rotation shaft by a vertical rotation motor provided in the frame unit, to irradiate the corner cube with the distance measuring light, and to receive the reflected distance measuring light from the corner cube, a horizontal angle encoder configured to detect a horizontal angle of the frame unit, and a vertical angle encoder configured to detect a vertical angle of the scanning mirror, wherein the arithmetic control module is configured to calculate a gravity center position of the corner cube based on a received light amount, a horizontal angle, and a vertical angle of the reflected distance measuring light at the time of scanning the corner cube with the distance measuring light and perform the angle measurement of the corner cube based on the gravity center position.

Further, in the surveying instrument according to a preferred embodiment, the arithmetic control module is configured to determine whether the corner cube has been performed the distance measurement with the overlapping portion based on a received light amount of the reflected distance measuring light, and discard a distance measurement result in which distance measurement is determined to have not been performed with the overlapping portion.

Further, in the surveying instrument according to a preferred embodiment, the arithmetic control module is configured to calculate a gravity center position of the corner cube based on a light amount distribution obtained at the time of scanning the corner cube with the distance measuring light, to determine whether the corner cube has been performed the distance measurement with the overlapping portion based on whether the corner cube is within a preset threshold range set in advance to the gravity center position, and to discard a distance measurement result in which distance measurement is determined to have not been performed by the overlapping portion.

Further, in the surveying instrument according to a preferred embodiment, the distance measuring light projecting module further comprises a driving mechanism, and the driving mechanism is configured to insert or remove the one-dimensional diffusion optical member with respect to an optical axis of the distance measuring light.

Further, in the surveying instrument according to a preferred embodiment, the distance measuring light receiving module further has a light receiving prism configured to internally reflect the reflected distance measuring light more than once and then cause the reflected distance measuring light to be received by the photodetector.

Further, in the surveying instrument according to a preferred embodiment, the slit plate has one slit hole.

Further, in the surveying instrument according to a preferred embodiment, the slit plate is a plurality of slit holes.

Furthermore, in the surveying instrument according to a preferred embodiment, an aperture width of the slit hole is changeable in a laminating direction of the light emitters, and the arithmetic control module is configured to change the aperture width of the slit hole in the laminating direction of the light emitters.

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

First, by referring to <FIG>, a description will be given on a surveying instrument according to a first embodiment of the present invention.

A surveying instrument <NUM> is, for instance, a laser scanner. The surveying instrument <NUM> is constituted of a leveling module <NUM> mounted on a tripod (not shown) and a surveying instrument main body <NUM> mounted on the leveling module <NUM>.

The leveling module <NUM> has leveling screws <NUM>, and the surveying instrument main body <NUM> is leveled up by the leveling screws <NUM>.

The surveying instrument main body <NUM> includes a fixing unit <NUM>, a frame unit <NUM>, a horizontal rotation shaft <NUM>, a horizontal rotation bearing <NUM>, a horizontal rotation motor <NUM> as a horizontal rotation driving module, a horizontal angle encoder <NUM> as a horizontal angle detector, a vertical rotation shaft <NUM>, a vertical rotation bearing <NUM>, a vertical rotation motor <NUM> as a vertical rotation driving module, a vertical angle encoder <NUM> as a vertical angle detector, a scanning mirror <NUM> which is a vertical rotation module, an operation panel <NUM> which serves as both an operation module and a display module, an arithmetic control module <NUM>, a storage module <NUM>, a distance measuring unit <NUM> and others. It is to be noted that, as the arithmetic control module <NUM>, a CPU specialized for this instrument or a general-purpose CPU is used.

The horizontal rotation bearing <NUM> is fixed to the fixing unit <NUM>. The horizontal rotation shaft <NUM> has a vertical axis 6a, and the horizontal rotation shaft <NUM> is rotatably supported by the horizontal rotation bearing <NUM>. Further, the frame unit <NUM> is supported by the horizontal rotation shaft <NUM>, and the frame unit <NUM> integrally rotates with the horizontal rotation shaft <NUM> in the horizontal direction.

The horizontal rotation motor <NUM> is provided between the horizontal rotation bearing <NUM> and the frame unit <NUM>, and the horizontal rotation motor <NUM> is controlled by the arithmetic control module <NUM>. The arithmetic control module <NUM> rotates the frame unit <NUM> around the axis 6a by the horizontal rotation motor <NUM>.

A relative rotation angle of the frame unit <NUM> with respect to the fixing unit <NUM> is detected by the horizontal angle encoder <NUM>. A detection signal from the horizontal angle encoder <NUM> is input to the arithmetic control module <NUM>, and the horizontal angle data is calculated by the arithmetic control module <NUM>. The arithmetic control module <NUM> performs the feedback control of the horizontal rotation motor <NUM> based on the horizontal angle data.

Further, in the frame unit <NUM>, the vertical rotation shaft <NUM> having a horizontal axis 11a is provided. The vertical rotation shaft <NUM> can rotate via the vertical rotation bearing <NUM>. It is to be noted that an intersection of the axis 6a and the axis 11a is a projecting position for a distance measuring light, and the intersection is an origin of a coordinate system of the surveying instrument main body <NUM>.

A recess portion <NUM> is formed in the frame unit <NUM>. One end portion of the vertical rotation shaft <NUM> extends to the inside of the recess portion <NUM>. Further, the scanning mirror <NUM> is fixed to the one end portion, and the scanning mirror <NUM> is accommodated in the recess portion <NUM>. Further, the vertical angle encoder <NUM> is provided at the other end portion of the vertical rotation shaft <NUM>.

The vertical rotation motor <NUM> is provided on the vertical rotation shaft <NUM>, and the vertical rotation motor <NUM> is controlled by the arithmetic control module <NUM>. The arithmetic control module <NUM> rotates the vertical rotation shaft <NUM> by the vertical rotation motor <NUM>. Further, and the scanning mirror <NUM> is rotated around the axis 11a.

A rotation angle of the scanning mirror <NUM> is detected by the vertical angle encoder <NUM>, and a detection signal is input to the arithmetic control module <NUM>. The arithmetic control module <NUM> calculates the vertical angle data of the scanning mirror <NUM> based on the detection signal, and performs the feedback control of the vertical rotation motor <NUM> based on the vertical angle data.

Further, the horizontal angle data and the vertical angle data calculated by the arithmetic control module <NUM>, and the measurement results are stored in the storage module <NUM>. As the storage module <NUM>, 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 memory card and a USB memory as a semiconductor storage device, and other storage devices. The storage module <NUM> may be attachable to and detachable from the frame unit <NUM>. Alternatively, the storage module <NUM> may enable transmitting the data to an external storage device or an external data processing device via a not shown communicating means.

In the storage module <NUM>, various types of programs are used. These programs include: a control program for controlling the driving of light emitters of a light emitting module (to be described later), a sequence program for controlling a 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 three-dimensional coordinates of a desired measuring point based on a distance and an angle, a calculation program for calculating the center of gravity of an object based on a measurement result, a control program for discarding a distance measurement result having an error based on a received light amount of a reflected distance measuring light and other programs. Further, when the various types of programs stored in the storage module <NUM> are executed by the arithmetic control module <NUM>, various types of processing are performed.

The operation panel <NUM> is, for instance, a touch panel. The operation panel <NUM> serves as both an operation module which performs, for instance, changing distance measurement instructions or measurement conditions such as a measuring point interval and a display module which displays distance measurement results, images and the like.

Next, a description will be given on the distance measuring unit <NUM> by referring to <FIG>.

The distance measuring unit <NUM> has a distance measuring light projecting module <NUM> and a distance measuring light receiving module <NUM>. It is to be noted that the distance measuring light projecting module <NUM> and the distance measuring light receiving module <NUM> configure a distance measuring module.

The distance measuring light projecting module <NUM> has a distance measuring optical axis <NUM>. Further, the distance measuring light projecting module <NUM> has a light emitting module <NUM>, a collimator lens <NUM>, the beam shaping optical element <NUM> which provided on the distance measuring optical axis <NUM>, a one-dimensional diffusion optical element <NUM> as a one-dimensional diffusion optical member provided on a reflected optical axis of the beam shaping optical element <NUM>, a reflecting prism <NUM> as a deflection member, and a fixing member <NUM> configured to fix the reflecting prism <NUM>. Further, the scanning mirror <NUM> is provided on the distance measuring optical axis <NUM> reflected by the reflecting prism <NUM>. The fixing member <NUM> is formed with the use of a transparent material such as a glass plate. Further, a window unit <NUM> which is formed of a transparent material and integrally rotates with the scanning mirror <NUM> is provided on a reflected optical axis of the scanning mirror <NUM>.

It is to be noted that the collimator lens <NUM>, the beam shaping optical element <NUM>, the one-dimensional diffusion optical element <NUM>, the reflecting prism <NUM>, and the like constitute a light projecting optical system <NUM>. Further, in the first embodiment, the distance measuring optical axis <NUM>, the distance measuring optical axis <NUM> reflected by the beam shaping optical element <NUM>, and the distance measuring optical axis <NUM> reflected by the reflecting prism <NUM> are generically referred to as the distance measuring optical axis <NUM>.

Further, a distance measuring light receiving module <NUM> has a light receiving optical axis <NUM>. The distance measuring light receiving module <NUM> has a photodetector <NUM> and a light receiving prism <NUM> provided on the light receiving optical axis <NUM>, and has a focusing lens <NUM> with a predetermined NA provided on the light receiving optical axis <NUM> reflected by the light receiving prism <NUM>. It is to be noted that the light receiving prism <NUM> and the focusing lens <NUM> constitute a light receiving optical system <NUM>. Further, in the first embodiment, the light receiving optical axis <NUM> and a reflected optical axis reflected by the light receiving prism <NUM> are generically referred to as a light receiving optical axis <NUM>.

The light emitting module <NUM> is a multi-stack laser light source in which a plurality of light emitters, for instance, laser diodes (LDs) are laminated. The light emitting module <NUM> is constituted of, for instance, three laminated (stacked) light emitters, and controlled in such a manner that laser beams are simultaneously pulse-emitted from the respective light emitters and a combined pulsed light is projected as a distance measuring light <NUM> (to be described later). When the three light emitters simultaneously emit lights and the combined distance measuring light <NUM> is projected, a light amount of the distance measuring light <NUM> emitted from the light emitting module <NUM> is assured, and the long-distance measurement by the surveying instrument <NUM> is enabled.

It is to be noted that the number of the light emitters constituting the light emitting module <NUM> may be two, four, or five. The number of the light emitters is appropriately set in correspondence with an assumed distance to the object.

The beam shaping optical element <NUM> is, for instance, a reflective or transmissive anamorphic prism. The distance measuring light <NUM> projected from the light emitting module <NUM> and turned to a parallel light flux by the collimator lens <NUM>. In this time, the distance measuring light <NUM> has an elliptical beam shape, and the beam shaping optical element <NUM> is configured to correct the elliptical distance measuring light <NUM> into a circular shape and more deflect the distance measuring light <NUM> at a right angle.

The one-dimensional diffusion optical element <NUM> is configured to diffuse the distance measuring light <NUM> deflected by the beam shaping optical element <NUM> in a predetermined direction (a one-dimensional direction). The direction of diffusion of the distance measuring light <NUM> by the one-dimensional diffusion optical element <NUM> is a laminating direction (a stacking direction) of the respective light emitters of the light emitting module <NUM>.

It is to be noted that, as the one-dimensional diffusion optical element <NUM>, it is possible to use various lenses or optical elements. These lenses or optical elements include: a cylindrical lens, a lenticular lens, a micro-cylindrical lens array, an elliptical diffusion film, a binary optical element, a diffractive optical element and others. The micro-cylindrical lens array is obtained by arranging tiny cylindrical lenses in an array. Further, in the following description, as the one-dimensional diffusion optical element <NUM>, any one of an elliptical diffusion film, a binary optical element, and a diffractive optical element is used.

The distance measuring unit <NUM> is controlled by the arithmetic control module <NUM>. When the pulsed distance measuring light <NUM> is projected onto the distance measuring optical axis <NUM> from the light emitting module <NUM>, the distance measuring light <NUM> is turned to a parallel light flux by the collimator lens <NUM> and deflected at a right angle while correcting the beam shape of the distance measuring light <NUM> by the beam shaping optical element <NUM>. The distance measuring light <NUM> reflected by the beam shaping optical element <NUM> is diffused in a one-dimensional direction by the one-dimensional diffusion optical element <NUM>, and reflected at a right angle by the reflecting prism <NUM>. The distance measuring optical axis <NUM> of the distance measuring light <NUM> projected from the reflecting prism <NUM> via the fixing member <NUM> coincides with the axis 11a. And the distance measuring light <NUM> is deflected at a right angle by the scanning mirror <NUM> and irradiated to the object via the window unit <NUM>. By rotating the scanning mirror <NUM> around the axis 11a, the distance measuring light <NUM> becomes orthogonal to the axis 11a, and the distance measuring light <NUM> is rotated (used for a scan) within a plane including the axis 6a.

It is to be noted that the window unit <NUM> is tilted at a predetermined angle with respect to the distance measuring optical axis <NUM> in such a manner that the distance measuring light <NUM> reflected by the window unit <NUM> does not enter the photodetector <NUM>.

The distance measuring light <NUM> reflected by the object (hereinafter a reflected distance measuring light <NUM>) is reflected at a right angle by the scanning mirror <NUM>, and the reflected distance measuring light <NUM> is received by the photodetector <NUM> through the light receiving optical system <NUM>. The photodetector <NUM> is, for instance, an avalanche photodiode (APD) or an equivalent photoelectric conversion element.

The arithmetic control module <NUM> performs the distance measurement for each pulse of the distance measuring light <NUM> based on a time lag between a light emission timing of the light emitting module <NUM> and a light reception timing of the photodetector <NUM> (that is, a round-trip time of a pulsed light) and a light velocity (Time of Flight). It is to be noted that the operation panel <NUM> can change the light emission timing of the light emitting module <NUM>, that is, a pulse interval.

It is to be noted that an internal reference light optical system (to be described later) is provided in the distance measuring unit <NUM>. By performing the distance measurement based on a time lag between the light reception timing for an internal reference light (to be described later) received from the internal reference light optical system and the reception timing of a reflected distance measuring light and the light velocity, the distance measuring unit <NUM> enables the further accurate distance measurement.

The frame unit <NUM> and the scanning mirror <NUM> are rotated at a constant speed, respectively. A two-dimensional scan by the distance measuring light <NUM> is performed by the cooperation between the vertical rotation of the scanning mirror <NUM> and the horizontal rotation of the frame unit <NUM>. Further, 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 encoder <NUM> and the horizontal angle encoder <NUM>, the arithmetic control module <NUM> enables calculating the vertical angle data and the horizontal angle data. Three-dimensional coordinates of the object and 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.

Next, a description will be given on the light receiving optical system <NUM>. It is to be noted that, in <FIG>, only a chief ray (the distance measuring optical axis <NUM>) of the distance measuring light <NUM> and a chief ray (the light receiving optical axis <NUM>) of the reflected distance measuring light <NUM> alone are shown.

The light receiving prism <NUM> is a square prism having a predetermined refractive index, Further, the receiving prism <NUM> has a first surface 35a which the reflected distance measuring light <NUM> transmitted through the focusing lens <NUM> enters, a second surface 35b which reflects the reflected distance measuring light <NUM> transmitted through a plane of the first surface 35a, a third surface 35c which the reflected distance measuring light <NUM> reflected by the second surface 35b and the first surface 35a enters, and a fourth surface 35d as a transmission surface which the reflected distance measuring light <NUM> reflected by the third surface 35c is transmitted through. The reflected distance measuring light <NUM> transmitted through the fourth surface 35d enters the photodetector <NUM>. It is to be noted that, the third surface 35c reflects the reflected distance measuring light <NUM> in such a manner that the reflected distance measuring light <NUM> crossed the reflected distance measuring light <NUM> entered the first surface 35a.

Further, a reference prism <NUM> having the retro-reflective property is provided below the scanning mirror <NUM>. In a process of the rotational irradiation of the distance measuring light <NUM> via the scanning mirror <NUM>, a part of the distance measuring light <NUM> enters the reference prism <NUM>. The distance measuring light <NUM> retro-reflected by the reference prism <NUM> is configured to enter the light receiving optical system <NUM> via the scanning mirror <NUM>, and to be received by the photodetector <NUM>.

Here, an optical path length from the light emitting module <NUM> to the reference prism <NUM> and an optical path length from the reference prism <NUM> to the photodetector <NUM> are known. Therefore, the distance measuring light <NUM> reflected by the reference prism <NUM> can be used as an internal reference light <NUM>. The scanning mirror <NUM> and the reference prism <NUM> configure an internal reference light optical system <NUM>.

Next, by referring to <FIG>, a description will be given on a case where the measurement is performed by the surveying instrument <NUM> having the distance measuring unit <NUM>. Various types of operations of the distance measuring unit <NUM> are performed when the arithmetic control module <NUM> executes various types of programs. It is to be noted that a case where the prism measurement is performed will be described below.

The object, for instance, a corner cube <NUM> is irradiated with the distance measuring light <NUM> emitted from each light emitter of the light emitting module <NUM> via the collimator lens <NUM>, the beam shaping optical element <NUM>, the one-dimensional diffusion optical element <NUM>, the reflecting prism <NUM>, the fixing member <NUM>, and the scanning mirror <NUM>. The reflected distance measuring light <NUM> which has been reflected by the corner cube <NUM> and entered the light receiving optical system <NUM> via the scanning mirror <NUM> is refracted in a process of being transmitted through the focusing lens <NUM> and the first surface 35a. Further, the reflected distance measuring light <NUM> is sequentially reflected by the second surface 35b and the first surface 35a in the light receiving prism <NUM>, and enters the third surface 36c. Further, the reflected distance measuring light <NUM> is reflected by the third surface 35c so that the reflected distance measuring light <NUM> crosses the reflected distance measuring light <NUM> entered the first surface 35d, and the reflected distance measuring light <NUM> is then transmitted through the fourth surface 35d, and received by the photodetector <NUM>.

The arithmetic control module <NUM> calculates three-dimensional coordinates of the corner cube <NUM> based on a distance measurement result of the distance measuring unit <NUM> and detection results of the horizontal angle encoder <NUM> and the vertical angle encoder <NUM>.

It is to be noted that the measurement of the corner cube <NUM> may be performed by scanning the whole circumference or the periphery of the corner cube <NUM> with the distance measuring light <NUM> and determining a position at which the reflected distance measuring light <NUM> has been received as a position of the corner cube <NUM>.

Here, <FIG> shows a beam profile of the distance measuring light <NUM> in a case where the one-dimensional diffusion optical element <NUM> is not used, and <FIG> shows a beam profile of the distance measuring light <NUM> in a case where the one-dimensional diffusion optical element <NUM> is used. Further, <FIG> shows a comparison between beam profile section intensities of the respective distance measuring lights <NUM> at a position of a line "A", in which solid lines represent a case where the one-dimensional diffusion optical element <NUM> is used and dashed lines represent a case where the one-dimensional diffusion optical element <NUM> is not used.

As shown in <FIG>, in a case where the one-dimensional diffusion optical element <NUM> is not used, the distance measuring lights <NUM> of the respective light emitters are independently projected with the shapes of the distance measuring light <NUM> being maintained. Further, since the beam profile section intensities at that time are independently detected for each of the distance measuring lights <NUM> of the respective light emitters, beam intensities of beam sections of the distance measuring lights <NUM> greatly vary.

On the other hand, in a case where the one-dimensional diffusion optical element <NUM> is used, the distance measuring lights <NUM> of the respective light emitters are expanded in a laminating direction (a stacking direction) of the light emitters, and the distance measuring lights <NUM> of the respective light emitters are superimposed, averaged, and then projected. Further, since the profile section intensities at that time are detected with the distance measuring lights <NUM> of the respective light emitters being superimposed and averaged, the beam intensities of the beam sections of the distance measuring lights <NUM> are substantially constant.

Further, <FIG> show a relationship in position between the corner cube <NUM> and the beam profiles of the distance measuring lights <NUM> in a case where the one-dimensional diffusion optical element <NUM> is used and in a case where the one-dimensional diffusion optical element <NUM> is not used. It is to be noted that, in <FIG>, a reference numeral <NUM> denotes a light receiving range of the photodetector <NUM>.

As shown in <FIG>, the distance measuring light <NUM> consists of distance measuring lights 41a, 41b and 41c pulse-emitted from three light emitters. On the other hand, due to an error or the like of the light emission timing of each light emitter based on a manufacturing error or the like, a distance measurement result based on the distance measuring lights 41a, 41b and 41c produces errors.

Therefore, in a case where the corner cube <NUM> has reflected the distance measuring light 41a (a corner cube 46a) and in a case where the corner cube <NUM> has reflected the distance measuring light 41c (a corner cube 46c), an error of approximately ±<NUM> is produced with respect to a case where the corner cube <NUM> has reflected the distance measuring light 41b (a corner cube 46b).

On the other hand, as shown in <FIG>, the distance measuring lights 41a, 41b and 41c diffused by the one-dimensional diffusion optical element <NUM> only in the laminating direction (one direction) of the light emitters are superimposed on each other, combined, and uniformed. Further, an overlapping portion 41d, where all the distance measuring lights 41a, 41b and 41c are superimposed on each other, is received within the light receiving range <NUM>.

If the distance measuring light <NUM> from the overlapping portion 41d is reflected, no matter which corner cube <NUM> (the corner cube 46d, 46e, 46f, <NUM>, <NUM> and 46i) reflects the distance measuring light <NUM>, as shown in <FIG>, the beam profile of the distance measuring light <NUM> is substantially uniformed, and hence no error is produced in a distance measurement result.

On the other hand, in a case where the corner cube <NUM> is measured while performing a scan with the distance measuring light <NUM> by the cooperation of the frame unit <NUM> and the scanning mirror <NUM>, like corner cubes <NUM> and 46j, the distance measuring light <NUM> from a portion where any one of the distance measuring lights 41a, 41b and 41c or any two of the distance measuring lights 41a, 41b and 41c overlap each other may be reflected by the corner cube <NUM>.

In this case, as compared with a case where the distance measuring light <NUM> of the overlapping portion 46d is reflected by the corner cube <NUM>, an error is produced in a distance measurement result. On the other hand, a difference is produced in received light amount when the photodetector <NUM> has received the reflected distance measuring light <NUM>. Therefore, the arithmetic control module <NUM> is capable of determining whether the distance measuring light <NUM> of the overlapping portion 41d has been reflected by the corner cube <NUM> based on the difference in received light amount of the reflected distance measuring light <NUM>. Further, the arithmetic control module <NUM> is capable of discarding a distance measurement result as an erroneous distance measurement result, in which the distance measurement has been determined which have been performed with the distance measuring light <NUM> of any other portion than the overlapping portion 41d.

Alternatively, based on a light amount distribution when the corner cube <NUM> has been scanned with the distance measuring light <NUM> by the arithmetic control module <NUM>, whether the corner cube <NUM> has been performed the distance measurement by the distance measuring light <NUM> of the overlapping portion 41d. In this case, the arithmetic control module <NUM> calculates a horizontal angle and a vertical angle of a gravity center position of the corner cube <NUM> based on a horizontal angle and a vertical angle of each point at which a light amount distribution has been obtained, and can determine whether the corner cube <NUM> has been measured the distance with the distance measuring light <NUM> of the overlapping portion 41d based on whether the corner cube <NUM> is located within a predetermined angle range (a threshold range set in advance) centered on the gravity center position.

The arithmetic control module <NUM> can calculate a gravity center position of the corner cube <NUM> based on the horizontal angle and the vertical angle of each point from which the light amount distribution has been obtained. Further, the arithmetic control module <NUM> can determine whether each distance measurement result is within the threshold range from the gravity center position of the corner cube <NUM> based on an angle threshold value as set in advance, and discarding the distance measurement result determined to be out of the threshold range as an erroneous distance measurement result.

<FIG> are graphs to show a relationship between a horizontal angle of the frame unit <NUM>, a vertical angle of the scanning mirror <NUM>, and a received light amount of the reflected distance measuring light <NUM> in a case where the corner cube <NUM> is measured while scanning the distance measuring light <NUM> without using the one-dimensional diffusion optical element <NUM>. Further, <FIG> are graphs to show a relationship between a horizontal angle of the frame unit <NUM>, a vertical angle of the scanning mirror <NUM>, and a received light amount of the reflected distance measuring light <NUM> in a case where the corner cube <NUM> is measured while scanning the distance measuring light <NUM> with the one-dimensional diffusion optical element <NUM> provided.

It is to be noted that, in <FIG> and <FIG>, triangular plots <NUM> represent received light amounts in a "V" axis direction (a vertical direction) and cross-shaped plots <NUM> represent received light amounts in an "H" axis direction (a horizontal direction).

As shown in <FIG>, in a case where the one-dimensional diffusion optical element <NUM> is not provided, by discretely sampling light reception signals, the received light amounts in the H axis direction have a continuous distribution, but the received light amounts in the "V" axis direction, that is, the received light amounts in the laminating direction of the light emitters have a discontinuous distribution. Therefore, an error at the time of calculating of the gravity center position of the corner cube <NUM> increases, and an error is also produced in an angle measurement result of the corner cube <NUM>.

On the other hand, as shown in <FIG>, in a case where the one-dimensional diffusion optical element <NUM> is provided, by discretely sampling the light reception signals, both the received light amounts in the "V" axis direction and the received light amount in the "H" axis direction have continuous distributions. Therefore, it is possible to prevent an error at the time of calculating of the gravity center position of the corner cube <NUM>, and likewise prevent an error in an angle measurement result of the corner cube <NUM>.

As described above, the multi-stack laser light source which has a plurality of light emitters laminated in one direction as the light emitting module <NUM> and causes the respective light emitters to simultaneously emit lights is used. Therefore, by totaling light reception signals when the distance measuring lights <NUM> are projected from the respective light emitters and the respective reflected distance measuring lights <NUM> are received by the photodetector <NUM>, it is possible to substantially increase the received light amounts to correspond with the number of the light emitters. Thereby it is possible to extend a reached distance of the distance measuring light <NUM>, and it is possible to extend a measurable distance.

Further, since the one-dimensional diffusion optical element <NUM> which diffuses the distance measuring light <NUM> in the only laminating direction (one direction) of the light emitters as the light projecting optical system <NUM> is used, it is possible to superimpose all the distance measuring lights 41a, 41b and 41c emitted from the respective light emitters and form the overlapping portion 46d in which beam profiles are uniformed.

Therefore, even if any portion of the distance measuring light <NUM> of the overlapping portion 46d is used and the corner cube <NUM> is measured, it is possible to obtain uniform distance measurement results regardless of the number of laminated light emitters and improve a distance measurement accuracy.

Further, even in a case where a scan is performed with the distance measuring light <NUM> and the corner cube <NUM> is measured, it is possible to obtain a distribution of the received light amounts continuous in both the "V" axis direction and the "H" axis direction, the arithmetic control module <NUM> can calculate an accurate gravity center position of the corner cube <NUM> and improve an angle measurement accuracy of the corner cube <NUM>. Therefore, since it is possible to improve the distance measurement accuracy and the angle measurement accuracy by the one-dimensional diffusion optical element <NUM>, the measurement accuracy of the surveying instrument <NUM> is improved.

Further, in a case whrer the corner cube <NUM> is measured with the distance measuring light <NUM> of any other portion than the overlapping portion 46d, a difference is produced in received light amounts of the reflected distance measuring light <NUM> as compared with a case where the corner cube <NUM> is measured with the distance measuring light <NUM> of the overlapping portion 46d.

Therefore, by discarding a measurement result of the corner cube <NUM> measured with the distance measuring light <NUM> of any portion other than the overlapping portion 46d based on the difference in received light amounts of the reflected distance measuring light <NUM>, it is possible to eliminate a measurement result having an error and improve the measurement accuracy.

Further, the one-dimensional diffusion optical element <NUM> is a one-dimensional diffusion optical element which diffuses the distance measuring light <NUM> in one direction alone, and it is capable of allowing a beam diameter of the distance measuring light <NUM> to be smaller than that of two-dimensional diffusion optical element which diffuses the distance measuring light <NUM> in two directions.

Therefore, it is possible to increase a received light amount of the reflected distance measuring light <NUM> and extend a measurable distance.

Further, the light receiving prism <NUM> is used as the light receiving optical system <NUM>, and the reflected distance measuring light <NUM> is internally reflected in the light receiving prism <NUM> more than once. Thereby, an optical path of the reflected distance measuring light <NUM> is bent, and an optical path length for a focal distance of the focusing lens <NUM> is assured.

Therefore, since a length in an optical axis direction of the light receiving optical system <NUM> can be shortened, it is possible to miniaturize an optical system of the light distance measuring unit <NUM> and also miniaturize the entire surveying instrument.

It is to be noted that, in the first embodiment, the multi-stack laser light source which has three light emitters laminated in one direction is used as the light emitting module <NUM>. On the other hand, the light emitting module <NUM> may be a multi-stack laser light source in which two light emitters are laminated or may be a multi-stack laser light source in which four or five light emitters are laminated.

Further, in the first embodiment, the one-dimensional diffusion optical element <NUM> is provided on the distance measuring optical axis <NUM>, and the one-dimensional diffusion optical element <NUM> may be insertable into and removable from the distance measuring optical axis <NUM> by a driving mechanism such as a solenoid. By making the one-dimensional diffusion optical element <NUM> insertable and removable, it is possible to proper use of the distance measuring light <NUM> depending on an object. For instance, the one-dimensional diffusion optical element <NUM> enables inserting onto the distance measuring optical axis <NUM> in case of performing the prism measurement and the one-dimensional diffusion optical element <NUM> enables removing from the distance measuring optical axis <NUM> in case of performing the non-prism measurement, the workability can be improved.

Further, in the first embodiment, the surveying instrument <NUM> is a laser scanner, but it is needless to say that the configuration of the first embodiment enables performing even if a total station is used.

In the first embodiment, the one-dimensional diffusion optical element <NUM> is arranged between the beam shaping optical element <NUM> and the reflecting prism <NUM>, but the one-dimensional diffusion optical element <NUM> may be provided at other positions. For instance, as shown in <FIG>, the one-dimensional diffusion optical element <NUM> may be arranged between the collimator lens <NUM> and the beam shaping optical element <NUM>.

Further, in a case where a use of the surveying instrument <NUM> is restricted to the prism measurement alone, that is, in a case where the one-dimensional diffusion optical element <NUM> is fixed with respect to the distance measuring optical axis <NUM>, the one-dimensional diffusion optical element <NUM> may be arranged between the fixing member <NUM> and the scanning mirror <NUM>, or the one-dimensional diffusion optical element <NUM> may be arranged between the scanning mirror <NUM> and the window unit <NUM>. Further, in place of the one-dimensional diffusion optical element <NUM>, a thin film having an optical action to diffuse a light in a one-dimensional direction may be formed on the reflecting prism <NUM>, on the fixing member <NUM>, on the scanning mirror <NUM>, or on the window unit <NUM>.

Further, in the first embodiment, an elliptic diffusion film, a binary optical element, or a diffractive optical element is used as the one-dimensional diffusion optical element <NUM>. On the other hand, a cylindrical lens, a lenticular lens, or a micro-cylindrical lens array may be used as the one-dimensional diffusion optical element <NUM>.

In a case where the cylindrical lens, the lenticular lens, or the micro-cylindrical lens array is used and they are further aspherized and optimized, like the profile section intensity of each distance measuring light show in <FIG>, it is possible to uniform a beam profile of the distance measuring light <NUM> over its entire area. Therefore, the measurement accuracy can be improved.

Next, by referring to <FIG>, a description will be given on a second embodiment of the present invention. It is to be noted that, in <FIG>, the same components as shown in <FIG> are referred by the same symbols, and detailed description thereof will be omitted.

In the second embodiment, a slit plate <NUM> is used as a one-dimensional diffusion optical member. The slit plate <NUM> is provided between a beam shaping optical element <NUM> and a reflecting prism <NUM> like the one-dimensional diffusion optical element <NUM> (see <FIG>) in the first embodiment.

Further, as shown in <FIG>, the slit plate <NUM> is, for instance, a circular disk having a slit hole <NUM> formed at the center. By passing a distance measuring light <NUM> deflected by the beam shaping optical element <NUM> through the slit hole <NUM>, the distance measuring light <NUM> is configured to be diffracted by the slit hole <NUM>, and to be diffused in a predetermined direction (a one-dimensional direction). In the second embodiment, the slit hole <NUM> is a slit extending in a direction orthogonal with respect to a laminating direction (a stacking direction) of a light emitting module <NUM>, and a diffusing direction of the distance measuring light <NUM> is the laminating direction of respective light emitters.

It is to be noted that an aperture size of the slit hole <NUM> is appropriately set from <NUM>×<NUM> to <NUM>×<NUM> in correspondence with a distance to an object. For instance, the aperture size of the slit hole <NUM> sets to <NUM>×<NUM>.

A distance measuring unit <NUM> is controlled by an arithmetic control module <NUM> (see <FIG>). When the pulsed distance measuring light <NUM> is projected onto a distance measuring optical axis <NUM> from the light emitting module <NUM>, the distance measuring light <NUM> is turned to a parallel light flux by a collimator lens <NUM> and deflected at a right angle while correcting its beam shape by the beam shaping optical element <NUM>. The distance measuring light <NUM> reflected by the beam shaping optical element <NUM> is diffused in a laminating direction of light emitters by the slit hole <NUM> of the slit plate <NUM>, and then reflected at a right angle by a reflecting prism <NUM>. The distance measuring light <NUM> projected from the reflecting prism <NUM> is deflected at a right angle by the scanning mirror <NUM> and irradiated to an object, for instance, a corner cube <NUM> via a window unit <NUM>.

A reflected distance measuring light <NUM> reflected by the corner cube <NUM> is received by a photodetector <NUM> via the scanning mirror <NUM> and a light receiving optical system <NUM>, and the distance measurement of the corner cube <NUM> is performed.

In the second embodiment, the slit plate <NUM> having the slit hole <NUM> extending in a direction orthogonal to the laminating direction (the stacking direction) of the light emitters is used. Therefore, the distance measuring lights <NUM> of the respective light emitters are diffused only in a one-dimensional direction, namely, the laminating direction (the stacking direction) of the light emitters, and the distance measuring lights <NUM> of the respective light emitters are superimposed, averaged, and then projected. Further, since the profile section intensities at that time are detected with the distance measuring lights <NUM> of the respective light emitters being superimposed and combined, beam intensities of beam sections of the distance measuring lights <NUM> are substantially constant.

An overlapping portion 41d (see <FIG>) of the distance measuring lights 41a, 41b and 41c, which have been superimposed due to the diffraction when passing through the slit hole <NUM>, is configured to be received in a light receiving range <NUM> (see <FIG>). Therefore, in the second embodiment, likewise, it is possible to obtain the same effects as the configuration in the first embodiment. For instance, by reflecting the overlapping portion 41d by the corner cube <NUM>, the errors in distance measurement result are prevented.

It is to be noted that, in the second embodiment, the slit plate <NUM> is provided on the distance measuring optical axis <NUM>. On the other hand, the slit plate <NUM> may be insertable into and removable from the distance measuring optical axis <NUM> by a driving mechanism such as a solenoid. By making the slit plate <NUM> insertable and removable, it is possible to proper use of a beam profile of the distance measuring light <NUM> corresponding with an object, for instance, to insert of the slit plate <NUM> onto the distance measuring optical axis <NUM> in case of performing the prism measurement and to remove of the slit plate <NUM> from the distance measuring optical axis <NUM> in case of performing the non-prism measurement, the workability can improve.

Further, in the second embodiment, the slit plate <NUM> is arranged between the beam shaping optical element <NUM> and the reflecting prism <NUM>, but the slit plate <NUM> may be provided at other positions. For instance, similar to <FIG> in the first embodiment, the slit plate <NUM> may be arranged between the collimator lens <NUM> and the beam shaping optical element <NUM>.

Further, in a case where a use of the surveying instrument <NUM> is restricted to the prism measurement alone, that is, in a case where the slit plate <NUM> is fixed with respect to the distance measuring optical axis <NUM>, the slit plate <NUM> may be arranged between a fixing member <NUM> and the scanning mirror <NUM>, or the slit plate <NUM> may be arranged between the scanning mirror <NUM> and the window unit <NUM>. Further, in place of the slit plate <NUM>, a thin film having a slit portion formed may be formed on the reflecting prism <NUM>, on the fixing member <NUM>, or on the window unit <NUM>. The thin film is formed in such a manner that, for instance, the distance measuring light <NUM> is not transmitted through portions other than the slit portion.

Further, in the second embodiment, as the one-dimensional diffusion optical member, the slit plate <NUM> having the slit hole <NUM> formed is used. On the other hand, the one-dimensional diffusion optical member is not restricted to the slit plate <NUM>.

For instance, as shown in <FIG>, a slit plate <NUM> which formed a plurality of slit holes <NUM> in a circular disk may be used. By using the slit plate <NUM>, the distance measuring lights 41a, 41b and 41c emitted from the respective light emitters are diffracted and combined when the distance measuring lights 41a, 41b and 41c pass through the slit holes <NUM>, and resulted the distance measuring light <NUM> including the overlapping portion 41d. It is to be noted that, in <FIG>, the five slit holes <NUM> are formed in the slit plate <NUM>, but the number of the slit holes <NUM> may be four or less, or may be six or more.

Further, a parallel flat glass plate having slits formed by an etching process may be used, instead of forming slit holes in a circular disk, as in the slit plate <NUM> or the slit plate <NUM>.

Claim 1:
A surveying instrument comprising: a distance measuring light projecting module (<NUM>) having a light emitting module (<NUM>) configured to project a distance measuring light (<NUM>) to an object (<NUM>) and a one-dimensional diffusion optical member (<NUM>, <NUM>, <NUM>, <NUM>) configured to diffuse said distance measuring light in a one-dimensional direction, a distance measuring light receiving module (<NUM>) having a photodetector (<NUM>) configured to receive a reflected distance measuring light (<NUM>) from said object, and an arithmetic control module (<NUM>) configured to control said light emitting module and calculate a distance to said object based on a light reception result of said reflected distance measuring light with respect to said photodetector, wherein said light emitting module is a multi-stack laser, in which a plurality of light emitters, for instance, laser diodes, are laminated, i.e. stacked, in one direction, in the following called laminating direction, and emit lights simultaneously, and said one-dimensional diffusion optical member is configured to diffuse said distance measuring light in said laminating direction of said light emitters.