Surveying instrument, distance measurement method and computer program product for determining 3D coordinates

Abstract

The invention relates to a surveying instrument for determining 3D coordinates, a distance measurement method and a computer program product, as well as a surveying instrument and a method for accurately determining the distance to a target (retroreflecting target) at close range for a specific setting of the surveying instrument. The central part of the received beam is blocked by components of the optical unit of the surveying instrument. When aiming at the target in the hit-target state, the distance measurement accuracy decreases at close range. Aiming at the target in the misaligned aiming state causes the reflected measurement beam to impinge on the unobstructed part of the detector surface, thereby obtaining an improved measurement accuracy. By shifting the impact position of the reflected measurement beam on the detector surface, that is, by averaging the distance measurement values ​​of the spatially inhomogeneous beam profile, the impact position is moved out of the obstructed part of the detector. To improve the measurement accuracy, the distance measurement values ​​can be averaged over time. It also relates to a computer program product stored on a machine-readable carrier or a computer data signal.

Description

Technical Field

[0001] The invention relates to a surveying instrument for determining the 3D coordinates of an object, in particular a surveying instrument to be used for close-range measurements. Furthermore, the invention relates to a method for determining the 3D coordinates of an object. The surveying instrument according to the invention is in particular one selected from the group consisting of a theodolite, a total station, a laser tracker and a Building Information Modeling (BIM) machine. The fields of the invention are geodesy and industrial metrology, as well as construction and monitoring. Background Art

[0002] Coordinate measuring devices (e.g., surveying instruments) for measuring the 3D coordinates of a target object often work on the basis of an optoelectronic measuring system. These devices usually emit optical radiation (usually laser radiation) in the direction of the target object to be measured in order to determine the distance between the device and the target. Using an angle measuring device, the direction in which the target object is located can also be determined. By measuring the distance and angular position of the target, the 3D coordinates of the target (e.g., given in polar coordinates) are determined and usually subsequently further processed. In the process, the target object to be measured reflects a portion of the emitted radiation back to the device, where it is received and converted into an electrical signal for distance determination. In addition to measuring naturally occurring targets, artificial targets (e.g., such as special target markers or reflectors) can also be attached to the target object, or a mobile measuring rod equipped with a reflector (e.g., a single retroreflector or a retroreflector structure) can be used as the target object. Retroreflectors have the following properties: when aiming at the center of the retroreflector, the direction of the incoming light beam is simply reversed, while when aiming at the peripheral area of ​​the retroreflector, the incoming light beam is reflected in the opposite direction with a beam offset.

[0003] The emitted optical radiation is configured for electro-optical distance measurement, for example based on the time-of-flight or phase measurement principle or a combination of these principles, as described, for example, in EP1757956, JP4843128 or other documents.

[0004] Optical radiation is also used for target identification and / or angle measurement of the direction of the target object. The target marker can be, for example, embodied as a retroreflector or a visual feature of the target object (such as a corner, an edge, a boundary of a contrasting area, etc.), such as described in WO2011 / 1414447 or EP1791082. In this regard, the optical radiation emitted by the measuring device in a pulsed or continuous manner can support the identification of the target in the field of view of the measuring device. A position-sensitive optical receiving element in the device (e.g., a structure having an area sensor in CCD or CMOS technology, a PSD based on the lateral photoelectric effect, or one or more photoreceptors (such as photodiodes, dual cells, orthogonal diodes, SPAD arrays, etc.)) can be used to identify and / or measure this type of target object in angular coordinates. This sensor is called an automatic target recognition and fine alignment module (ATR).

[0005] For angle determination, the measuring device is usually provided with one or more angle measuring devices (for example a goniometer or a clinometer), with which the angular position of the rotating part or the orientation of the aiming axis of an optical unit of the measuring device can be determined when the device or a part of the device is rotated for aiming purposes.

[0006] For distance and angle determination, the device to be used can emit separate or common radiation, for example a measuring beam or radiation source can be used for both purposes, or one measuring beam can be used for distance measurement and one beam can be used for angle determination or target recognition. For measurements on non-cooperative targets, the divergence of the measuring beam must be as small as possible, preferably diffraction-limited, otherwise the distance measurement may not provide the required measurement accuracy due to undefined illumination of the target object.

[0007] For example, velocimeters or total stations used in the field of surveying or geodesy can measure distances with an accuracy of a few millimeters or even less than one millimeter when measuring prisms or retroreflective target markers over several kilometers. The accuracy of angle measurements is usually in the range of less than 2 arc seconds to 10 arc seconds or less. These requirements are hindered by the fact that such measurement equipment is usually used in harsh environments where the environmental conditions vary greatly according to parameters such as temperature, humidity, etc.

[0008] In order to improve the accuracy of the angle measurement, the position difference between the center of the retroreflector and the impact point of the measuring beam (e.g., laser beam) on the reflector can be determined using the now increasingly standardized aiming status indicators (e.g., so-called fine aiming units). For example, a position-sensitive detector is used to determine the deviation of the received measuring beam from a zero position. Using this measurable deviation, the aiming of the measuring device can be adjusted to reposition the direction of the outgoing laser beam according to the deviation in a way that reduces the deviation on the fine aiming sensor (e.g., "zeroing") so that the beam is oriented toward the center of the reflector. Another way to correct for the deviation of the received measuring beam from the zero position is to determine an aiming error and to correct the measured angle with respect to the target based on the aiming error.

[0009] Some coordinate measuring instruments, in particular surveying instruments, have a common exit and receiver optical unit, which means that at least one component is used in both the exit and receiver optical unit or affects both the exit and receiver optical unit. An arrangement known from the prior art is an arrangement in which a measuring beam emitted by a radiation source is arranged off-axis with respect to an aiming axis, wherein the measuring beam is coupled to the aiming axis or to an axis parallel to the aiming axis by means of a deflection element in the aiming unit. Due to the specific arrangement, the deflection element, which initially deflects the outgoing measuring beam towards the target, is also present in the receiving beam path and prevents a portion of the reflected measuring beam from reaching the detector. In this context, preventing a portion of the reflected measuring beam from reaching the detector due to the presence of the deflection element is referred to as shielding or partial shielding of the detector, because the deflection element shields at least a portion of the detector, for example making at least a portion of the detector surface out of the line of sight of the reflected measuring beam and therefore inaccessible to at least a portion of the measuring beam.

[0010] When performing measurements using a surveying instrument having the described arrangement, the influence of partial obstruction of the return beam cross section is greater the closer the target and the smaller the measurement distance, and the influence of partial obstruction of the return beam cross section is smaller the farther the target and the larger the measurement distance. The far field can be defined as a range of distances where the obstructed portion of the return beam cross section is small compared to the portion of the beam cross section that impinges on the detector, and the distance can be measured with the required accuracy using a surveying instrument having the described arrangement. The close range can be defined as a range of distances where the obstructed portion of the detector is large compared to the impinging beam cross section, so that the error or noise in the distance measurement exceeds a tolerable limit. For standard prior art surveying instruments, the transition from far field to close range is typically between 5m and 35m.

[0011] When the amount of incident light decreases, the distance measurement accuracy decreases or the distance cannot be measured at all. This is due to the (spatial) inhomogeneity of the laser profile. Due to the spatial inhomogeneity of the laser profile, the measured distance value varies within the cross section of the laser beam. When a reasonable amount of the measurement beam impinges on the detector, the measured values ​​can be averaged based on the spatial distribution of the beam, resulting in a relatively accurate result for the measured distance. However, when part of the beam is blocked, the relevant part of the return beam is ignored, and if the pulse shape is laterally non-uniform, systematic distance errors are likely to occur. The local blockage of the return beam behaves like a spatial filter. This leads to the following effect: the measured distance varies greatly, depending on the position within the cross section of the beam profile. The larger the blocked part is compared to the part of the laser beam cross section that impinges on the detector, the greater the impact of ignoring the relevant part of the detection beam, and the less accurate the measured distance.

[0012] In order to minimize the systematic errors of the laser beam wavefront and to improve the accuracy of short-range distance measurements, different attempts have been made to solve the above-mentioned problems, which mainly occur at short distances. According to the prior art, for example, it is known that asymmetric emitter openings reduce the problems, because the emission beam is point-asymmetrically mirrored. Another possibility to avoid the problem of occlusion of at least a part of the detector is to use an emitter with parallax. When using an emitter with parallax, the problem of occlusion of the detector due to different settings can be reduced. Another solution is to use an emitter with an emitter zone that also transmits at least part of the reflected light, for example, a 90:10 beam splitter. JP3634772B2 discloses an attempt to use a transmissive emitter.

[0013] However, there is a need for further improved surveying instruments and distance measurement methods, in particular at close range, for determining the distance between the surveying instrument and a target with suitable accuracy (in particular, a sufficiently small distance measurement error).

[0014] Depending on the type of survey task, a total station, theodolite, laser tracker or building information modeling (BIM) machine is required. In addition, surface scanning and the precise determination of the target position on the surface or on the surface of another object may be required within the scope of a single measurement. Summary of the invention

[0015] The object of the present invention is to provide a surveying instrument with improved measurement accuracy at close ranges by solving the problem of reflected (retroreflected) beams being blocked by components of the optical unit. In addition, the object of the present invention is to provide a distance measurement method which provides improved measurement accuracy, especially at close ranges.

[0016] Within the scope of this document, the term "optical axis" will be used for optical systems in general and for any type of telescope. The term "sighting axis" will be used in the specific case of an optical system of a surveying instrument. Furthermore, within the scope of this document, the expressions "distance measuring beam" and "measuring beam" will be used in parallel. The invention is not limited to the embodiments described herein.

[0017] The invention relates to a surveying instrument for determining 3D coordinates of a retroreflective target, in particular a theodolite, a total station, a laser tracker or a building information modeling (BIM) machine, the surveying instrument comprising: a radiation source for generating a measuring beam; an optical unit for emitting and receiving at least a portion of the measuring beam and defining an aiming axis; a detector suitable for distance measurement, wherein the detector is configured to detect at least a portion of the measuring beam reflected by the retroreflective target, wherein the detector is shielded by at least one component of the optical unit; and an aiming status indicator configured to Outputting information indicative of an aiming state of transmitting a measuring beam with respect to a retroreflective target, wherein a hit target state is given, in which the aiming state indicator outputs information indicative of reflection of the measuring beam by the retroreflective target without a beam offset, wherein the surveying instrument is configured to automatically aim the retroreflective target with the measuring beam when performing a distance measurement in such a way that the aiming state indicator outputs information indicative of an unaimed aiming state, in which the aiming state indicator outputs information indicative of reflection of the measuring beam by the retroreflective target with a beam offset, and in which the reflected measuring beam is detected with a detector in the unaimed aiming state. When referring to an obscured portion of the detector, this means that a portion of the receiving aperture or pupil (e.g., a central portion) is obscured, and in the unaimed aiming state, the reflected measuring beam is displaced such that obscuration on the receiving device is reduced compared to prior art devices. Thus, when referring to a detector obscured by at least one component of the optical unit, this means that the optical path to the detector is obscured.

[0018] In the unaligned aiming state, the distance measurement beam is moved out of the blocked portion of the receiving aperture or pupil to increase the amount of light that strikes the detector, thereby reducing measurement errors and improving distance measurement. The expressions of moving out of the receiving aperture or pupil and moving out of the detector are used interchangeably in this article. In the case of moving out of the blocked portion of the detector, this means shifting the measurement beam so that the measurement beam is laterally shifted relative to the blocked portion of the receiver channel, so that the relevant part of the beam can bypass the blocking optical device in the receiver channel and reach the detector. The measurement beam can be moved away from the blocked portion of the detector in a manner that a portion of the reflected measurement beam is still blocked but the signal strength can be enhanced compared to the well-aligned prior art survey system. However, the measurement beam is preferably moved away from the blocked portion of the detector so that no part of the distance measurement beam is blocked by any component of the exit optical unit. In addition, the measurement beam should only be shifted by a small amount, which means that the entire measurement beam strikes the detector and the measurement beam will not be partially or completely shifted across the edge of the photosensitive detector. Therefore, the surveying instrument is configured to aim at the retroreflective target when performing distance measurements in such a way that the measuring beam, in particular the reflected beam, moves out of the obstructed part of the detector so that when impinging on the detector surface of the detector, the measuring beam is at most partially obstructed, preferably not obstructed at all. Increasing the amount of light impinging on the detector, such as the amount of reflected distance measuring beam reaching the detector, reduces distance measurement errors and thus improves the accuracy of the distance measurement.

[0019] The aiming state indicator may be any device configured to output information indicating the aiming state of the emitted measuring beam. According to one aspect of the invention, the aiming state indicator comprises: an area detector, in particular a position-sensitive area detector, for generating an indication of the aiming state, wherein a hit-target state is given if a reflection spot of the reflected measuring beam hits a defined servo control point position of the area detector, in particular defined by calibration data, and wherein a misaligned aiming state is given if a reference servo control point reflection spot position hits dispersedly; or a camera, wherein the camera comprises a photosensitive detector (e.g. CCD or CMOS), and wherein a hit-target state is given if an image of the retroreflected target is generated at a defined servo control point position of the photosensitive detector, in particular defined by calibration data, and wherein a misaligned aiming state is given if the reference servo control point position image is generated dispersedly. Furthermore, the aiming state may also be indicated by other methods, for example by using crosshairs if an appropriate vision system is present, wherein the center of the crosshairs defines the aiming axis. The operator can then adjust the surveying instrument, for example manually, so that a hit-target status is given, or so that a misalignment status is given. When the crosshairs are exactly on the target, then a hit-target status will be indicated, and when the crosshairs are not exactly on the target, a misalignment status will be given. The aiming status indicator can also be given by the detector of the surveying instrument of the invention itself, for example, if the detector is position-sensitive.

[0020] According to one aspect of the invention, the measuring beam comprises two local measuring beams, wherein the first local measuring beam is suitable for generating an aiming status indication on an aiming status indicator and the second local measuring beam is suitable for performing a distance measurement. For example, the first local measuring beam may be a beam having a specific wavelength λ 1 The laser beam of wavelength λ 1 The distance measuring beam can be a beam with a specific wavelength λ 2 The distance can then be measured using a photosensitive detector suitable for distance measurement, which is sensitive to the wavelength λ 2 sensitive.

[0021] The present invention also relates to a surveying instrument for coordinating the position of a target, in particular a retroreflective target, the surveying instrument comprising: a base; a support member, which is rotatably mounted on the base so that the support member can rotate around a first rotation axis; a carrier, which is rotatably mounted on the support member so that the carrier can rotate around a second rotation axis; an angle determination unit for obtaining first angle data about the support member rotating around a first rotation angle; an angle determination unit for obtaining second angle data about the carrier rotating around a second rotation angle, wherein a measuring beam is emitted from the carrier.

[0022] According to one aspect of the present invention, a surveying instrument comprises: a radiation source for generating a transmitted radiation beam; a base; a support member rotatably mounted on the base so that the support member can rotate around a first rotation axis; a carrier rotatably mounted on the support member so that the carrier can rotate around a second rotation axis, the second rotation axis being substantially orthogonal to the first rotation axis; an exit optical unit for emitting a distance measurement beam provided by at least a portion of the transmitted radiation and defining an aiming axis; a receiving optical unit for receiving a reflected distance measurement beam, the exit optical unit and the receiving optical unit being at least partially shared; and a detector configured to detect a distance measurement beam based on at least a portion of the reflected distance measurement beam. Acquiring distance measurement data; an angle determination unit for acquiring first angle data about a rotation of a support around a first rotation axis; at least one beam deflection element, the at least one beam deflection element being designed to deflect or manipulate the distance measurement beam in such a way that at least the transmitted distance measurement beam or the received distance measurement beam is offset and / or tilted relative to the aiming axis by means of an actuating device of the beam deflection element; an angle determination unit for acquiring second angle data about a rotation of the carrier around a second rotation angle; an angle determination unit for acquiring third angle data and determining the angle of the manipulated measurement beam relative to the defined aiming axis; and an evaluation device, the evaluation device being configured to obtain the position of a target based on the distance measurement data and the first angle data, the second angle data and the third angle data.

[0023] According to the invention, the surveying instrument is designed to change the direction of the measuring beam or to displace the measuring beam relative to the sighting axis, in particular in an automatic manner, so that the measuring beam moves out of the obstructed part of the detector and impinges on the surface of the receiving aperture from the periphery. In order to change the direction of the measuring beam or to displace the measuring beam relative to the sighting axis, the surveying instrument comprises a beam deflecting element, an evaluation device and a device (in particular a control device) for adjusting, in particular automatically adjusting, the beam deflecting element, so that the reflected measuring beam is deflected in such a way that a measuring error of the distance measurement is reduced. The evaluation device can be, for example, an evaluation unit; the control device can be, for example, a control unit. In particular, the evaluation device and the control device can be combined into an evaluation and control device.

[0024] The beam deflection element can influence the transmitted measurement beam or the reflected measurement beam or both. It is also possible to have more than one beam deflection element and for example to place one beam deflection element in such a way as to influence the transmitted measurement beam and another beam deflection element in such a way as to influence the reflected measurement beam. The beam deflection element can be any element suitable for a controlled change of the orientation of the distance measurement beam or for shifting the distance measurement beam relative to the aiming direction and thus any element suitable for shifting and / or tilting the measurement beam relative to the aiming axis in a controlled manner.

[0025] The beam deflection element can be, for example, a strongly deflecting object inserted into the optical path, but can also be any object that allows a movement (e.g. a rotation of the entire optical system or the carrier relative to the target) so that the measuring beam is tilted and / or shifted relative to the sighting axis, however, the desired changes can also be achieved by deflecting the emitter, while emitters and radiation sources are used in a similar manner within the scope of the invention. These elements can also be combined according to the invention.

[0026] According to one aspect of the invention, the misaligned aiming state is generated by a rotation of the carrier about at least the first rotation axis or the second rotation axis. Thus, the measuring beam can be deflected by a movement of the entire optical system or the carrier. For example, assuming that the surveying instrument is well aligned with the optical center of the retroreflective target before the movement so that a hit target state is given, the carrier can be slightly rotated about the rotation axis of a support, which can be rotatably mounted on a base, or slightly rotated about the rotation axis of the carrier, which can be rotatably mounted on a support, slightly meaning that the measuring beam still impinges on the retroreflective target but with a beam offset, and the retroreflected measuring beam impinges on the detector in the misaligned aiming state.

[0027] According to another aspect of the invention, the misaligned aiming state is generated by pivoting a beam deflecting element into the optical path of the measuring beam, in particular wherein the beam deflecting element is comprised in the optical unit, in particular at least one beam deflecting element is a mirror, a prism, a polygon, a double wedge, a refractive element, a movable optical fiber or a MOEMS element, wherein the beam deflecting effect is obtained in particular by a displacement and / or a tilting of the beam deflecting element and / or an electro-optical control of the optical (refractive) properties of the beam deflecting element. For example, the beam deflecting element can be a mirror, which is mounted inside a carrier such that the mirror can be pivoted in the optical path of the emitted measuring beam.

[0028] According to another aspect of the invention, the beam is deflected by deflection of the emitter. In a certain type of arrangement, the position of the reflected measuring beam on the receiving aperture can be shifted by tilting the emitter. For example, if the radiation source is a laser diode and thus generates a laser beam, and the laser beam is emitted via an exit optical unit having a mirror that is tilted 45° relative to the laser beam (such as to change the direction of the laser beam by 90°), and if the orientation or position of the laser diode changes so that the angle of the laser beam relative to the mirror changes to an angle ≠ 45°, the position of the reflected measuring beam impinging on the detector changes accordingly. According to this embodiment of the invention, the surveying instrument is configured to deflect, in particular automatically deflect the beam by deflection of the emitter depending on the indicated aiming state.

[0029] The optical paths of the transmitted measurement beam and the reflected measurement beam can be configured so that the beam deflection element affects the reflected measurement beam or the transmitted measurement beam, for example, the beam deflection element can be positioned so that it only affects the transmitted measurement beam, for example, the mapping characteristics of the receiving channel are basically independent of the control of the beam deflection element, or there can be a beam deflection element that affects the transmitted measurement beam and a beam deflection element that affects the reflected measurement beam, each of the beam deflection elements being independently controllable, or a single beam deflection element affects both the transmitted measurement beam and the reflected measurement beam.

[0030] An optical unit for transmitting and receiving at least a portion of a measuring beam includes a component for transmitting a distance measuring beam and a component for receiving a reflected distance measuring beam. An exit optical unit for transmitting a distance measuring beam and a receiving optical unit for receiving a reflected distance measuring beam are at least partially shared. For example, the exit optical unit can be constructed in the following manner: the radiation source is positioned so that the measuring beam emitted by the radiation source and transmitted to the exit optical unit is orthogonal to the beam emitted by the exit optical unit along the aiming axis. The component that changes the direction of the measuring beam can be a mirror. In order to shape or improve the beam characteristics, a lens or a lens group can be inserted into the optical path of the measuring beam, for example, after the mirror and before the measuring beam is emitted toward the target. Before the reflected measuring beam hits the detector, the receiving unit uses the same lens to improve the beam characteristics. In this setup, because both optical units use lenses, the lens and the mirror are components shared by the exit optical unit and the receiving optical unit, and the mirror is not only necessary for the exit optical unit, but also affects the receiving optical unit by blocking at least part of the detector, which has a negative impact on the receiving optical unit, especially in the case of close-range measurement.

[0031] The detector may be a photoelectric sensor that is large enough to allow peripheral displacement of the measurement beam on a sensitive area of ​​the detector surface. The photoelectric sensor may be, for example, a photocell, a PIN photodiode, an avalanche photodiode (APD), a semiconductor photomultiplier (such as, for example, a SiPM or SPAD array). The detector needs to be configured to detect the optical signal and convert the optical signal into an electrical signal. Therefore, the photoelectric sensor needs to be adjusted to the characteristics of the reflected measurement beam, in particular it needs to be sensitive within a specific wavelength range so that the wavelength of the reflected measurement beam lies within said wavelength range.

[0032] Several methods for performing electro-optical distance measurement are known, such as, for example, the time-of-flight (TOF) measurement principle, such as the frequency modulated continuous wave (FMCW) principle or the coherent frequency modulated continuous wave (CFMCW) principle, optical coherence distance measurement using a modulation scheme (e.g., as used for frequency modulated continuous wave light detection and ranging (LiDAR)), the phase measurement principle or measuring the distance by laser triangulation. For surveying instruments, for example, the time-of-flight (TOF) measurement principle or the phase measurement principle or a combination thereof is used to meet high demands on the measurement accuracy.

[0033] The radiation source can basically be any component that converts electrical energy into optical radiation energy, i.e. a light emitting diode (LED), a laser, in particular an actively triggered solid-state laser or a laser diode, such as a gallium arsenide (GaAs) or indium phosphide (InP) laser diode. However, the radiation source must be adapted to the distance measurement method and several other parameters, such as, for example, distance range, required accuracy, etc. Laser diodes, in particular GaAs laser diodes, are commonly used in instruments for distance measurement based on the time of flight (TOF) or phase difference principle. Most lasers emit spatially coherent light, thereby providing high light focusing sharpness or pulses with high energy density. Today, fiber lasers, seed fiber amplifiers and comb lasers are commonly used as radiation sources for precise distance measurement.

[0034] According to one embodiment of the invention, the evaluation and control device is included in the computer unit and is configured to obtain the position of the target based on the distance measurement data and the orientation of the distance measurement beam. The distance can be measured by several methods known in the prior art, for example, by a phase measurement principle or by a time of flight (TOF) method. The spatial orientation of the measurement beam can be determined by obtaining first angle data about the rotation of the support around a first rotation angle and obtaining second angle data about the rotation of the carrier around a second rotation angle, wherein any angle measurement device can be used. In addition, for example, the inclination angle of the measurement beam relative to the sighting axis (such as sometimes found in a misaligned sighting state) can be determined by using an aiming state indicator (such as a camera or an area detector). The determination of the alignment of the sighting axis, the precise determination of the vertical angle and the horizontal angle, and the inclination of the vertical axis and the determination of the inclination angle of the measurement beam relative to the sighting axis can be completed in an automated manner, for example, using sensors. The internal processing is then completely controlled by a microprocessor, and in particular the results of the horizontal angle measurement and the vertical angle measurement are provided in binary or digital form. Its output can be provided using a serial interface or can be displayed on a display (if present).

[0035] According to one aspect of the invention, the surveying instrument comprises a diffractive optical element, which is inserted into the optical path of the measuring beam, the diffractive optical element being in particular a moving diffuser, an optical wedge, in particular a close-range optical wedge, or a close-range diverging lens. The diffractive optical element is inserted into the optical path to homogenize the measuring beam before impinging on the reflector, in particular to perform a spatial and / or temporal homogenization. The measuring beam properties or the measuring beam quality (for example, the planarity of the modulated wavefront or the pulse wavefront) play an important role for the measurement accuracy. The properties of the measuring beam can be improved, for example, by mixing the measuring beam, in particular in order to generate a plurality of at least partially overlapping partial beams, which are arranged one next to the other. Due to the temporal and spatial mixing, the uneven distribution is flattened, as it were, and a uniform or at least more uniform measuring beam is obtained, i.e. a spatially homogenized measuring beam. In one embodiment, the surveying device is configured for temporal homogenization of the measuring beam. The relative position of the measurement beam and the diffractive optical element can be dynamically, in particular periodically variable, in particular by arranging or enabling the diffractive optical element to be arranged in the beam path so as to be movable, such that the element can be dynamically moved across the measurement beam. For example, the diffractive optical element can be oscillating, in particular perpendicular to the propagation axis of the measurement beam, and / or rotatable, in particular rotatable about the propagation axis of the measurement beam or about an axis with a parallel offset or with an eccentricity relative thereto.

[0036] The invention further relates to a surveying instrument for coordinated determination of the position of a target, wherein the difference between an on-target state and a misaligned state is adjusted, in particular automatically, as a function of the distance to the target or based on a signal strength of a reflected measuring beam, which signal strength depends on the indicated aiming state, detected by a detector. For example, a beam deflecting element implemented as a mirror can be mounted inside a carrier such that the mirror can be pivoted in the optical path of the emitted measuring beam. The surveying instrument can then be configured to generate a misaligned aiming state by changing the angle of the mirror relative to the measuring beam, in particular automatically, for example, depending on a previously performed measurement of the distance to the target according to the prior art, which indicates that the target is located at a close distance.

[0037] The invention relates in particular to a surveying instrument for the coordinated determination of the position of a retroreflecting target, wherein the difference between an on-target state and a misaligned state is adjusted, in particular automatically, as a function of the distance to the retroreflecting target or based on the signal strength of a reflected measuring beam, which depends on the indicated aiming state, detected by a detector.

[0038] Furthermore, the invention relates to a distance measuring method for determining the distance between a surveying instrument and a target. Depending on the distance to the target, a beam deflecting element is adjusted, in particular automatically adjusted, so that the measuring beam is displaced and / or tilted in such a way that the measuring beam is moved out of the obstructed part of the detector and impinges on the receiving aperture from the periphery.

[0039] In particular, the present invention relates to a distance measurement method for determining the distance between a surveying instrument, in particular a theodolite, a total station, a laser tracker or a building information modeling (BIM) machine, and a retroreflective target, the surveying instrument having: a radiation source; an optical unit, the optical unit defining an aiming axis; a detector, the detector being suitable for distance measurement, wherein the detector is configured to detect at least a portion of the measuring beam reflected by the retroreflective target, wherein the detector is shielded by at least one component of the optical unit; and an aiming status indicator for indicating an aiming status with respect to the retroreflective target, wherein a hit target status is given, in which the aiming status indicator generates an output defined, in particular defined by calibration data, indicating that no misalignment with respect to the retroreflective target has occurred, the method comprising the following steps: Aiming at a retroreflective target and detecting an aiming state with an aiming state indicator; generating a measuring beam in a radiation source; transmitting and receiving at least a portion of the measuring beam through an optical unit, wherein the transmitted measuring beam is transmitted toward at least one retroreflective target; and receiving at least a portion of the retroreflective measuring beam and detecting the at least a portion of the retroreflective measuring beam with a detector, thereby measuring the distance between the surveying instrument and the retroreflective target, wherein when performing the distance measurement: aiming at the retroreflective target in a manner such that the aiming state indicator indicates a misaligned aiming state, in which the aiming state indicator generates a defined output indicating that the retroreflective target reflects the measuring beam in a manner such that misalignment with respect to the retroreflective target occurs, and in the misaligned aiming state, a step of detecting the reflected measuring beam with the detector is completed.

[0040] According to one aspect of the present invention, the method includes the following steps: aiming at a retroreflective target using a measuring beam in such a manner that an aiming status indicator indicates a hit target status; determining an aiming direction based on the indicated hit target status; performing distance measurement, wherein the surveying instrument aims at the retroreflective target using a measuring beam in such a manner that an aiming status indicator indicates a misaligned aiming status, in which the aiming status indicator generates a defined output indicating that the retroreflective target reflects the measuring beam in such a manner that a misalignment occurs with respect to the retroreflective target, and detecting the reflected measuring beam using a detector in the misaligned aiming status.

[0041] According to a further aspect of the invention, the measuring beam is deflected relative to the sighting axis by pivoting a deflection object into the beam path of the measuring beam.

[0042] The present invention also relates to a method, wherein the surveying instrument also has a base; a support member, which is rotatably mounted on the base so that the support member can rotate around a first rotation axis; a carrier, which is rotatably mounted on the support member so that the carrier member can rotate around a second rotation axis; an angle determination unit for obtaining first angle data regarding a rotation of the support member around a first rotation angle; and an angle determination unit for obtaining second angle data regarding a rotation of the carrier around a second rotation angle, wherein a measuring beam is emitted from the carrier and the carrier rotates at least around the first rotation axis or the second rotation axis so that the measuring beam is manipulated in a manner that generates a misaligned state.

[0043] The invention also relates to a method in which a diffractive optical element is inserted into the beam path of the measuring beam, in particular a moving diffuser, an optical wedge or a close-diverging lens, so that the measuring beam is homogenized before it impinges on a detector surface of a retroreflector and / or a detector.

[0044] The invention also relates to a method, wherein the misalignment level of the measuring beam is automatically adjusted depending on the distance to the retroreflecting target or based on the angle-dependent signal strength of the reflected measuring beam detected by a detector.

[0045] The surveying instrument and method of the present invention can also be applied to targets that diffusely reflect light. When impinging on such a target, the measuring beam is reflected in such a way that the reflected or scattered light propagates as a spherical wave in all possible directions and only a certain amount of the transmitted measuring beam is reflected towards the detector. Therefore, the amount of light from the reflected measuring beam that impinges on the detector is less than when a retroreflective target is used. In addition, the impinging measuring beam is not focused. In order to avoid the problem of shading of the detector of the diffusely reflecting target, the distance measuring beam can be deflected or manipulated in such a way that at least the transmitted distance measuring beam or the received measuring beam is tilted relative to the aiming axis. It is assumed that the surveying instrument includes: a base; a support, which is rotatably mounted on the base, so that the support can rotate around a first rotation axis; and a carrier, which is rotatably mounted on the support, so that the carrier can rotate around a second rotation axis, which can be achieved, for example, by rotating the entire carrier around at least the first rotation axis or the second rotation axis.

[0046] The invention further relates to a computer program product with a program code stored on a machine-readable carrier, in particular on a surveying instrument according to the invention, or on a computer data signal for carrying out the method according to the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] The inventive surveying instrument and method according to the invention will be described subsequently with the aid of schematically represented embodiments shown in the drawings, but further advantages of the invention are disclosed. In these embodiments, the terms collimated measuring beam and divergent measuring beam are mainly used to compare aspects of a rather divergent measuring beam with a more focused or collimated measuring beam in comparison. As known to the person skilled in the art, every laser beam exhibits a certain divergence, even a collimated beam with diffraction-limited wavefront characteristics. Due to the divergence, the laser beam diameter depends on the distance traveled by the laser beam. This is shown in detail in the drawings:

[0048] Figure 1a to Figure 1d It shows that when the target is hit, at a distance of 18m from the target ( Figure 1a and Figure 1c ) and the distance to the target of 2m ( Figure 1b and Figure 1d ) case, the obstruction of the lens of the beam is measured for the reflected divergence at the telescope lens ( Figure 1a and Figure 1b ) and the obstruction of the lens for the reflected collimated measurement beam at the telescope lens ( Figure 1c and Figure 1d )

[0049] Figure 2 A schematic diagram of a beam path in an embodiment of a prior art arrangement is shown, wherein a measurement is performed in the on-target state.

[0050] Figure 3a to Figure 3c The distance to the target of 2 m measured with the divergent measuring beam is shown in the hit target state ( Figure 3a ) and the distance to the target is 18m ( Figure 3c ), an exemplary visualization of the occlusion of the lens, and the general trend of the distance measurement between 0 m and 18 m to the target using a divergent measuring beam using an embodiment of the surveying instrument of the present invention when performing a hit target distance measurement using a divergent reflected measuring beam ( Figure 3b ).

[0051] Figures 4a to 4c The distance to the target of 2 m measured with the collimated measurement beam is shown in Figure 2. Figure 4a ) and the distance to the target is 18m ( Figure 4c ), an exemplary visualization of the occlusion of the lens, and the general trend of the distance measurement between 0 m and 18 m to the target using a collimated measuring beam using an embodiment of the surveying instrument of the present invention when performing a distance measurement in a misaligned aiming state using a collimated reflected measuring beam ( Figure 4b ).

[0052] Figure 5 A schematic diagram of a beam path in an embodiment of an arrangement according to the invention is shown, in which a measurement is performed in a misaligned aiming state and the misaligned aiming state is generated by tilting a beam deflecting element, for example a mirror.

[0053] Figure 6 A schematic diagram of a beam path of an embodiment of the surveying instrument of the invention is shown, wherein the measurement is performed in a misaligned aiming state and the misaligned aiming state is generated by a rotation of the carrier.

[0054] Figure 7 A schematic diagram of a beam path of an embodiment of the surveying instrument of the invention is shown, wherein the measurement is performed in a misaligned aiming state and the misaligned aiming state is generated by a deflection of the transmitter.

[0055] Figure 8 A schematic diagram showing an embodiment of a beam path in a surveying instrument of the present invention when performing distance measurement in a misaligned aiming state. DETAILED DESCRIPTION

[0056] Figure 1a to Figure 1d The diverging measurement beam ( Figure 1a and Figure 1b ) and collimated measurement beam ( Figure 1c and Figure 1d ) is performed at a distance of 2 m from the target ( Figure 1b and Figure 1d ) and 18m( Figure 1a and Figure 1c ), an exemplary visualization of the obstruction 3 at the aperture of the telescope front lens 8, wherein the measurement is performed in the on-target state, so that the aiming axis of the telescope is aligned with the optical center of the retroreflector. Figure 1a shows a shadowing or blockage 3 at the aperture of a telescope lens or lens group 8 of a diverging measurement beam 2 at a distance of 18 m from the target, and Figure 1b The obstruction 3 at the telescope lens 8 of the diverging measuring beam 2 at a distance of 2 m from the target is shown as seen from inside the telescope. Figure 1c shows the obstruction 3 at the telescope lens 8 of the collimated measurement beam 4 at a distance of 18 m from the target, and Figure 1dThe obstruction 3 at the telescope lens 8 is shown as seen from inside the telescope at a distance of 2 m to the target. The transmitted measurement beam 2 behind the obstruction 3 shows a ring-shaped shape, with the central part being blocked and only a small amount of energy being able to pass through and reach the optical detector. The obstruction 3 at the telescope lens 8 is caused by components of the optical system, so that ultimately only the boundary parts of the reflected measurement beam reach the receiver, resulting in higher measurement errors. This is the case, for example, when the laser beam exhibits spatial modulation errors, so that the flight time varies within the beam cross section. If the central part of the beam is blocked due to the obstruction 3, only the ring-shaped part of the beam contributes to the distance measurement, resulting in systematic errors. From Figure 1b and Figure 1d It can be seen from the figure that compared with the boundary part of the reflected measurement beam when measuring the distance to the target at 18m ( Figure 1a and Figure 1c ), the boundary portion of the reflected measurement beam when measuring a distance of 2m from the target is smaller. Therefore, the accuracy of the distance measurement of the target at a distance of 2m is lower than the accuracy of the distance measurement of the target at a distance of 18m. When comparing the divergent measurement beam 2 and the collimated measurement beam 4, it can be seen that the amount of light from the boundary portion of the reflected measurement beam 5 in the case of the divergent measurement beam 2 is higher than that of the collimated measurement beam 4. In this example, the distance of 2m from the target is classified as a close distance, while the distance of 18m from the target is classified as a far field. Although the transition range between the close distance and the far field may be different for the collimated measurement beam 4 and the divergent measurement beam 2, the problem of limited distance measurement accuracy within a close distance occurs for both the divergent measurement beam 2 and the collimated measurement beam 4.

[0057] Figure 2 A schematic diagram of a beam path in an embodiment of a prior art arrangement is shown, wherein the measurement is performed in the on-target state. The lengths and size ratios of the components are selected only for explaining the principle and are not limiting in any way. The transmitter 9 generates a measuring beam which is transmitted to the exit optical unit. In order to collimate or collimate the measuring beam, a lens 20 can be inserted into the beam path. Figure 2 It can be seen that in this example, according to Figure 1a to Figure 1dAs explained above, the measuring beam is not yet completely parallel after the lens 20. The beam deflecting element 6 (e.g., a mirror or a reflecting prism) deflects the measuring beam by 90° in such a way that it is deflected toward another lens or lens group 8 in an orientation parallel to the sighting axis 7. The lens 8 is inserted to further parallelize the measuring beam. The divergence of the emitted measuring beam can be selected to be, for example, between 1 mrad and 3 mrad. The measuring beam is emitted 18 along the sighting axis 7 toward a target 12 (shown as a retroreflective target 12 in this embodiment). Since the retroreflective target 12 is made to reflect the incoming beam in a completely opposite direction, the direction of the reflected measuring beam 5 is reversed by 180° with respect to the emitted measuring beam 18. The edge portion of the emitted measuring beam 18 hits the target 12 in a lateral offset with respect to its center and is reflected with a point-symmetrical lateral offset relative to the emitted edge portion of the measuring beam 18. The divergence of the measuring beam remains unchanged by the retroreflection, resulting in a further increase in diameter when the reflected measuring beam propagates from the target 12 back to the surveying instrument. The reflected measurement beam 5 enters the receiving optical unit in an approximately parallel manner through the lens 8. An additional lens can be inserted in front of the receiver 19 to focus the reflected measurement beam 5 onto the receiver 19, which is usually very small (that is to say of the order of several hundred μm). It can be seen that only the boundary part of the reflected measurement beam 5 finally reaches the receiver 19 due to the occlusion 3 generated by the beam deflection element 6. Since the transmitted measurement beam 18 has a selected, optimized divergence, the diameter of the transmitted measurement beam 18 increases with increasing distance from the target 12. Therefore, the problem of occlusion 3 becomes worse the smaller the distance to the target 12. The measurement beam shown in the figure is a collimated measurement beam, however, diverging measurement beams can also suffer from occlusion problems.

[0058] Figure 3a to Figure 3c The distance to the target of 2 m measured with the divergent measuring beam is shown in the hit target state ( Figure 3a ) and the distance to the target is 18m ( Figure 3c ), and the general trend of distance measurements at distances to the target between 0 m and 18 m using a divergent measuring beam 2 using an embodiment of the surveying instrument according to the invention when performing a hit-target distance measurement using a divergent measuring beam 2. Such a hit-target distance measurement can also be performed using a surveying instrument of the prior art. Figure 3a The figure shows the obstruction 3 at the telescope lens 8 at a distance of about 2 m from the target 12. Figure 3c The obstruction 3 at the telescope lens 8 is shown at a distance of about 18 m from the target 12 . Figure 3b The overall trend of the systematic error of the distance measurement as a function of the distance is shown when measuring with a diverging measuring beam 2 . Figure 3bThe two horizontal lines in the figure represent the required accuracy. It can be seen that for distances smaller than the intersection of the upper horizontal line with the line indicating the distance measurement error, the accuracy requirement cannot be met. Some sources of error that reduce the distance measurement accuracy are, for example, at least partial shading and stray light due to light scattering from the surface of the beam deflecting element.

[0059] Figures 4a to 4c The distance to the target of 2 m measured with the collimated measuring beam 4 is shown in FIG. Figure 4a ) and the distance to the target is 18m ( Figure 4c ), an exemplary visualization of an obstruction 3 at the telescope lens 8, and the overall trend of distance measurements between 0 m and 18 m to the target using a collimated measuring beam 4, using an embodiment of the surveying instrument according to the invention, when performing distance measurements in a misaligned aiming state using the collimated measuring beam 4 ( Figure 4b ). Figure 4a The figure shows the obstruction 3 at the telescope lens 8 at a distance of about 2 m from the target. Figure 4c The obstruction 3 at the telescope lens 8 is shown at a distance of about 18 m from the target. Figure 4b The general trend of the distance measurement error as a function of the distance is shown when measuring with a collimated measuring beam 4 . Figure 4b The two horizontal lines above and below the central thick horizontal line in the figure represent the required accuracy. It can be seen that the accuracy requirement can be met when measuring the distance without aiming.

[0060] Figure 5 A schematic diagram of the beam path in an embodiment of the arrangement according to the invention is shown, in which the measurement is performed in a non-aimed aiming state. The lengths and the proportions of the sizes of the components are only chosen to explain the principle and are not limiting in any way. The emitter 9 generates a measuring beam which is transmitted to the exit optical unit. In order to efficiently collect the light from the optical unit and to generate a measuring beam which is as parallel as possible, a lens 20 can be inserted into the beam path. Figure 5As can be seen in FIG. 1 , in this example, the measuring beam is not yet completely parallel after the lens 20. A beam deflecting element 6 (e.g., a mirror) located on the sighting axis 7 deflects or steers the measuring beam in such a way that the measuring beam is deflected towards a further lens 8 in a non-parallel manner relative to the sighting axis 7. For example, if the beam deflecting element 6 is a mirror, the mirror can be tilted relative to its position in the on-target state to deflect the measuring beam. The beam deflecting element 6 is preferably located very close to the lens 8 so that the measuring beam leaves the lens 8 at a certain angle relative to the target axis 7, but approximately passes through the center of the lens 8. The emitted measuring beam 18 then passes through the lens 8 and is emitted towards the target 12 (shown as a retroreflective target 12 in this embodiment). Since the retroreflective target 12 is made to reflect the incoming beam in a parallel manner, the axis or chief ray of the reflected measuring beam 5 is parallel to the emitted measuring beam 18, except for the inevitable beam expansion (which depends on the distance from the target 12). The reflected measurement beam 5 enters the receiving optical unit through the lens 8 in an approximately parallel manner and is focused before hitting the receiver 19, which in this example is embodied as an array of avalanche photodiode (APD) arrays or SPAD-arrays. It can be seen that when measuring in the unaligned aiming state described herein, the occlusion 3 generated by the beam deflection element 6 does not affect the reflected measurement beam 5 and therefore does not affect the distance measurement. The beam optical path is configured so that the reflected measurement beam 5 bypasses the beam deflection element 6, so that the receiver 19 receives not only the boundary part of the reflected measurement beam 5 (such as in the on-target state), but also the receiver 19 receives the fully reflected measurement beam 5. The measurement beam shown in this figure is a collimated measurement beam, however, the same effect occurs for a divergent measurement beam (e.g., an emitted divergent beam with a total divergence angle of about 2 mrad).

[0061] Figure 6A schematic diagram of the beam path of an embodiment of the surveying instrument of the present invention is shown, wherein the measurement is performed in a non-aligned aiming state. The length and size ratios of the components are selected only for explaining the principle and are not limiting in any way. The emitted measurement beam 18 passes along the aiming axis 7 in the non-aligned aiming state, so in order to make the figure clearer, the aiming axis 7 in the non-aligned aiming state is not shown in the figure. Instead, the direction 7' ​​to the center of the target is shown. The emitted measurement beam 18 passes through the lens 8 of the exit optical unit toward the target 12 (shown herein as a retroreflective target 12). The emitted measurement beam 18 hits the retroreflective target 12 eccentrically (for example, with a lateral beam offset relative to the center of the retroreflective target 12). The reflected measurement beam 5 is projected in the opposite direction, and the lateral beam offset of the reflected measurement beam 5 with respect to the center of the retroreflective target 12 is equal to the lateral beam offset of the emitted measurement beam 18 with respect to the center of the retroreflective target 12. The amount of misalignment with respect to the target 12 (more specifically, the angle between the sighting axis 7 and the direction 7' ​​to the center of the target) can be generated, for example, in such a way that the reflected measurement beam 5 has a predetermined lateral dislocation at the lens 8, which can be selected to be, for example, one quarter of the lens diameter (e.g., 10 mm). In this embodiment, the beam offset is generated by a movement, in particular a rotation, of the entire optical system or carrier 15. The rotation is achieved by rotating the support 14 around a first rotation angle 16 or by rotating the carrier 15 around a second rotation angle 17 or a combination thereof. Alternatively, the base 13 can be rotated to rotate the entire surveying instrument. The rotation of the entire optical system affects the transmitted measurement beam 18 and the reflected measurement beam 5. The transmitted measurement beam 18 is not completely centered on the retroreflective target 12, but is offset with respect to the retroreflective target 12. Since the retroreflective target 12 is manufactured to reflect the incoming beam in a parallel manner, the reflected measurement beam 5 is parallel to the transmitted measurement beam 18. The reflected measurement beam 5 finally re-enters the telescope through the lens 8. Manipulation of the telescope pivoting allows to repeatedly perform distance measurements and calculate the ratio of the ideal angular misalignment by calculating the ratio of the required measurement beam offset to the actual original distance. The measurement beam shown in the figure is a collimated measurement beam, however, a surveying instrument of the type described in the invention can also be used to measure the distance to the target 12 using a divergent measurement beam. In this embodiment, the surveying instrument determines the angle between the sighting axis 7 and the direction 7' ​​to the target, for example by using an automatic angle measurement system (ATR), which directly measures the angle about the center of the target object despite being in a misaligned sighting state. In an alternative procedure, the retroreflector is centered in a first step, and the on-target state is ensured using an aiming state indicator, and in a second step a misaligned sighting state is generated (for example, by rotation as described above), and the distance to the target 12 is measured in the misaligned sighting state.

[0062] Figure 7A schematic diagram of a beam optical path in an embodiment of the arrangement of the present invention is shown, wherein measurement is performed in a non-aligned aiming state. The lengths and size ratios of the components are selected only for explaining the principle and are not limiting in any way. The transmitter 9 generates a measuring beam, which is transmitted to an exit optical unit. In order to generate a measuring beam that is as parallel as possible, a lens 20 can be inserted into the beam optical path. However, in this example, the measuring beam is not yet completely parallel after the lens 20. The beam deflection element 6 (e.g., a mirror) deflects or manipulates the measuring beam in the following manner: the measuring beam is deflected toward another lens 8 in a non-parallel manner relative to the aiming axis 7. In this embodiment, the beam deflection element 6 is in the same position and orientation as in the on-target state. The deflection of the measuring beam is achieved by deflecting or translating the transmitter 9. Positioning the emitter 9 in such a way that it emits the measuring beam at an angle ≠ 90° relative to the target axis 7 ensures that the measuring beam is tilted relative to the sighting axis 7 after being deflected on the beam deflecting element 6, assuming that the beam deflecting element 6 (in this case a mirror) is located on the sighting axis 7 and is not tilted. The beam deflecting element 6 is preferably located very close to the lens 8, so that the measuring beam leaves the lens at a certain angle relative to the target axis 7, but approximately passes through the center of the lens 8. The emitted measuring beam 18 then passes through the lens 8 and is emitted towards the target 12 (shown as a retroreflective target 12 in this embodiment). Since the retroreflective target 12 is manufactured to reflect the incoming light beam in a parallel manner, the reflected measuring beam 5 is parallel to the emitted measuring beam 18. The reflected measuring beam 5 enters the optical unit through the lens 8, where it is focused. The reflected measuring beam 5 enters the receiving optical unit through the lens 8 in an approximately parallel manner. In this embodiment, an additional beam deflection element or beam steering element 21 that affects the reflected measurement beam 5 is inserted in front of the receiver 19 to focus the reflected measurement beam 5 onto the receiver 19, which is usually very small (e.g., about 50 μm to 500 μm). The beam steering element 21 can consist of one optical component or can include multiple optical components, some of which are, for example, moving lenses, negative lenses, liquid lenses, transmission or reflection polygons, prisms or micro-electromechanical (MEMS) beam steering elements. It can be seen that when measuring in the misaligned aiming state described herein, the occlusion 3 generated by the beam deflection element 6 does not affect the reflected measurement beam 5 and therefore does not affect the distance measurement. The beam optical path is configured so that the reflected measurement beam 5 bypasses the beam deflection element 6, so that the receiver 19 receives not only the boundary part of the reflected measurement beam 5 (such as in the on-target state), but also the receiver 19 receives the fully reflected measurement beam 5. The measuring beam shown in the figure is a collimated measuring beam, however, a surveying instrument of the type described can also be used to measure distances with a diverging measuring beam.

[0063] Figure 8 A schematic diagram of an embodiment of a beam path in a surveying instrument of the present invention when performing distance measurements in a misaligned aiming state is shown. The transmitter 9 transmits a measuring beam towards the beam deflection element 6, where it is transmitted to the lens 8. In this embodiment, an additional lens 20 is inserted into the beam path directly after the transmitter 9 to generate a parallel measuring beam. The transmitted measuring beam 18 impinges on the retroreflective target 12 with a beam offset relative to the center of the retroreflective target 12 and is reflected in a parallel manner relative to the transmitted measuring beam 18. The beam offset is caused by the misalignment given by the angle between the direction 7' ​​and the aiming axis 7, neither of which is shown in the figure. The reflected measuring beam 5 enters the receiving optical unit and is focused towards the flat plate 22, which reflects the measuring beam towards the beam deflection element 6 (herein a mirror). The mirror 6 then reflects the reflected measuring beam 5 to the receiver 19. Since the receiver 19 is usually very small (e.g. in the range of 50 μm to 500 μm), an additional lens can be inserted in the beam path in front of the receiver 19 to focus the reflected measurement beam 5. The measurement beam shown in the figure is a focused measurement beam, however, a surveying instrument of the type described in the invention can also be used to measure distances with a diverging measurement beam.

[0064] Although the present invention has been illustrated above in part with reference to some preferred embodiments, it must be understood that various modifications and combinations may be made to the different features of the embodiments. All these modifications are within the scope of the appended claims. It goes without saying that the illustrated figures are only schematic diagrams of possible exemplary embodiments.

Claims

1. A surveying instrument for determining the 3D coordinates of a retroreflective target, the surveying instrument include: a radiation source for generating a measuring beam; an optical unit for emitting and receiving at least a part of the measuring beam and defining a sighting axis; a detector adapted for distance measurement, wherein the detector is configured to detect at least a portion of the measuring beam reflected by the retroreflective target, wherein the detector is obscured by at least one component of the optical unit; and an aiming state indicator configured to output information indicating an aiming state of the emitted measuring beam with respect to the retroreflective target, wherein a hit target state is given if a reflection spot of the reflected measuring beam strikes a defined servo control point position or if an image of the retroreflective target is generated at a defined servo control point position, in which the aiming state indicator outputs information indicating that the measuring beam is reflected by the retroreflective target without a beam offset, and a misaligned aiming state is given if the reflection spot strikes dispersedly with respect to the servo control point position or the image is dispersedly generated with respect to the servo control point position; The surveying instrument is configured to automatically perform the following operations when performing distance measurement: aiming the retroreflective target with the measuring beam in a manner such that the aiming state indicator outputs information indicating the misaligned aiming state in which the aiming state indicator outputs information indicating that the measuring beam was reflected by the retroreflective target with a beam offset, and In the misaligned aiming state, the reflected measuring beam is detected by means of the detector.

2. The surveying instrument according to claim 1, It is characterized in that The surveying instrument is a theodolite, a total station, a laser tracker or a Building Information Modeling (BIM) machine.

3. The surveying instrument according to claim 1, It is characterized in that The surveying instrument is configured to aim at the retroreflective target when performing the distance measurement in such a way that the measuring beam is displaced such that upon impingement on a detector surface of the detector, the measuring beam is at most partially obscured.

4. The surveying instrument according to claim 1, It is characterized in that The surveying instrument is configured to aim at the retroreflective target when performing the distance measurement in such a way that the measuring beam is displaced such that upon impingement on a detector surface of the detector, the measuring beam is not obscured at all.

5. The surveying instrument according to any one of claims 1 to 4, It is characterized in that The aiming status indicator comprises: an area detector for generating an indication of the aiming state, wherein the on-target state is given if a reflection spot of the reflected measuring beam impinges on a defined servo control point position of the area detector, and wherein the off-target state is given if the reflection spot impinges dispersedly with respect to the servo control point position; or A camera, wherein the camera includes a photosensitive detector, and wherein the hit target status is given if the image of the retroreflective target is generated at a defined servo control point position of the photosensitive detector, and wherein the misaligned aiming status is given if the image is generated dispersedly with respect to the servo control point position.

6. The surveying instrument according to any one of claims 1 to 4, It is characterized in that The aiming status indicator comprises: an area detector for generating an indication of the aiming state, wherein the on-target state is given if a reflection spot of the reflected measuring beam impinges on a servo control point position of the area detector defined by calibration data, and wherein the off-target state is given if the reflection spot impinges dispersedly about the servo control point position; or A camera, wherein the camera includes a photosensitive detector, and wherein the hit target state is given if the image of the retroreflective target is generated at a servo control point position of the photosensitive detector defined by calibration data, and wherein the misaligned aiming state is given if the image is generated dispersedly with respect to the servo control point position.

7. The surveying instrument according to any one of claims 1 to 4, It is characterized in that The measuring beam comprises two partial measuring beams, wherein a first partial measuring beam is adapted to be used for generating an aiming status indication on the aiming status indicator and a second partial measuring beam is adapted to be used for performing the distance measurement.

8. The surveying instrument according to any one of claims 1 to 4, It is characterized in that The surveying instrument comprises: Pedestal; a support member rotatably mounted on the base so that the support member can rotate about a first rotation axis; a carrier rotatably mounted on the support so that the carrier can rotate about a second rotation axis; an angle determination unit for acquiring first angle data regarding the rotation of the support member around a first rotation angle; an angle determination unit for acquiring second angle data regarding rotation of the carrier around a second rotation angle; Therein, the measuring beam is emitted from the carrier.

9. The surveying instrument according to claim 8, It is characterized in that The misaligned aiming state is generated by: The carrier rotates at least about the first rotation axis or the second rotation axis; or A beam deflecting element is pivoted into the optical path of the measuring beam, wherein the beam deflecting element is included in the optical unit, wherein the beam deflecting effect is obtained by a displacement and / or tilting of the beam deflecting element and / or an electro-optical control of the optical properties, i.e. the refractive properties, of the beam deflecting element.

10. The surveying instrument according to claim 9, It is characterized in that The at least one beam deflecting element is a mirror, a prism, a polygon, a double wedge, a refractive element, a movable optical fiber or a MOEMS element.

11. The surveying instrument according to any one of claims 1 to 4, It is characterized in that A diffractive optical element is inserted into the beam path of the measuring beam.

12. The surveying instrument according to claim 11, It is characterized in that The diffractive optical element is a moving diffuser, an optical wedge or a close diverging lens.

13. The surveying instrument according to any one of claims 1 to 4, It is characterized in that The difference between the on-target state and the off-target state is adjusted according to the distance to the retroreflective target or is adjusted based on the signal strength of the reflected measurement beam detected by the detector depending on the indicated aiming state.

14. A surveying instrument according to any one of claims 1 to 4, It is characterized in that The difference between the on-target state and the off-target state is automatically adjusted according to the distance to the retroreflective target or based on the signal strength of the reflected measurement beam detected by the detector depending on the indicated aiming state.

15. A distance measurement method for determining the distance between a surveying instrument and a retroreflective target, the surveying instrument having: Radiation sources; an optical unit, the optical unit defining a sighting axis; A detector, the detector being suitable for distance measurement, wherein the detector being configured to detect at least a portion of the measuring beam reflected by the retroreflective target, wherein the detector is obscured by at least one component of the optical unit; and an aiming state indicator for indicating an aiming state with respect to the retroreflective target, wherein a hit target state is given if a reflection spot of the reflected measuring beam strikes a defined servo control point position or if an image of the retroreflective target is generated at a defined servo control point position, in which the aiming state indicator generates a defined output indicating that no misalignment with respect to the retroreflective target has occurred, and a misaligned aiming state is given if the reflection spots strike dispersedly with respect to the servo control point position or the image is dispersedly generated with respect to the servo control point position; The method comprises the following steps: aiming at the retroreflective target and detecting an aiming state using the aiming state indicator; generating a measuring beam in the radiation source; emitting and receiving at least a portion of the measuring beam by the optical unit, wherein the emitted measuring beam is emitted toward at least one retroreflective target; receiving and detecting, with the detector, at least a portion of the reflected measurement beam, thereby measuring the distance between the surveying instrument and the reflective target; It is characterized in that when performing distance measurement: accomplishing aiming of the retroreflective target in a manner such that the aiming status indicator indicates the misaligned aiming status in which the aiming status indicator generates a defined output representing that the retroreflective target reflects the measurement beam in a manner such that a misalignment with respect to the retroreflective target occurs; and In the misaligned aiming state, the step of detecting the reflected measuring beam with the detector is performed.

16. The distance measurement method according to claim 15, It is characterized in that The surveying instrument is a theodolite, a total station, a laser tracker or a Building Information Modeling (BIM) machine.

17. The distance measurement method according to claim 15, It is characterized in that An on-target condition is given in which the aiming condition indicator generates an output defined by the calibration data, the defined output indicating that no misalignment with respect to the retroreflective target has occurred.

18. The distance measurement method according to claim 15, It is characterized in that By pivoting a beam-deflecting element into the beam path of the measuring beam, the measuring beam is deflected relative to the sighting axis.

19. The distance measurement method according to any one of claims 15 to 18, wherein the surveying instrument further comprises: Pedestal; a support member rotatably mounted on the base so that the support member can rotate about a first rotation axis; a carrier rotatably mounted on the support so that the carrier can rotate about a second rotation axis; an angle determination unit for acquiring first angle data regarding the rotation of the support member around a first rotation angle; an angle determination unit for acquiring second angle data regarding rotation of the carrier around a second rotation angle; Characterized in that the measuring beam is emitted from the carrier and that the carrier is rotated at least about the first rotation axis or the second rotation axis in order to steer the measuring beam in such a way that a misalignment state is generated.

20. The distance measurement method according to any one of claims 15 to 18, It is characterized in that A diffractive optical element is inserted into the beam path of the measuring beam, so that the measuring beam is homogenized before it impinges on the retroreflector or on the detector surface of the detector.

21. The distance measurement method according to claim 20, It is characterized in that The diffractive optical element is a moving diffuser, an optical wedge or a close diverging lens.

22. The distance measurement method according to any one of claims 15 to 18, It is characterized in that The misalignment level of the measuring beam is automatically adjusted depending on the distance to the retroreflective target; or is automatically adjusted based on the angle-dependent signal strength of the reflected measuring beam detected by the detector.

23. A distance measurement method, It is characterized in that The distance measurement method comprises the following steps: aiming the retroreflective target with the measuring beam in such a manner that the aiming status indicator indicates an on-target status; determining an aiming direction based on the indicated targeting status; The distance measurement method according to claim 15 is performed.

24. The distance measurement method according to claim 23, It is characterized in that By pivoting a beam-deflecting element into the beam path of the measuring beam, the measuring beam is deflected relative to the sighting axis.

25. The distance measurement method according to claim 23 or 24, wherein the surveying instrument further comprises: Pedestal; a support member rotatably mounted on the base so that the support member can rotate about a first rotation axis; a carrier rotatably mounted on the support so that the carrier can rotate about a second rotation axis; an angle determination unit for acquiring first angle data regarding the rotation of the support member around a first rotation angle; an angle determination unit for acquiring second angle data regarding rotation of the carrier around a second rotation angle; Characterized in that the measuring beam is emitted from the carrier and that the carrier is rotated at least about the first rotation axis or the second rotation axis in order to steer the measuring beam in such a way that a misalignment state is generated.

26. The distance measurement method according to claim 23 or 24, It is characterized in that A diffractive optical element is inserted into the beam path of the measuring beam, so that the measuring beam is homogenized before it impinges on the retroreflector or on the detector surface of the detector.

27. The distance measurement method according to claim 26, It is characterized in that The diffractive optical element is a moving diffuser, an optical wedge or a close diverging lens.

28. The distance measurement method according to claim 23 or 24, It is characterized in that The misalignment level of the measuring beam is automatically adjusted depending on the distance to the retroreflective target; or is automatically adjusted based on the angle-dependent signal strength of the reflected measuring beam detected by the detector.

29. A computer program product having a program code, It is characterized in that The computer program product is stored on a machine-readable carrier or a computer data signal for implementing the distance measurement method according to claims 15 to 28.

30. The computer program product according to claim 29, It is characterized in that The machine readable carrier is a surveying instrument according to any one of claims 1 to 14.

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