Target objects with improved angular incidence range for retroreflection

Abstract

Target object with improved angular incidence range for retro-reflection. The invention relates to a target object providing a large angular incidence range for retro-reflection and a reduced amount of disturbing reflections, configured to provide a 360° omni-directional retro-reflection around a vertical axis and an angular incidence range of ±45° with respect to the horizontal. The target object comprises eight tri-prisms 4-11 arranged around an arrangement axis in such a way that the outlines of the tri-prisms are embedded in an octahedron shape, wherein four tri-prisms are arranged embedded in a first cone 26 and wherein the other four tri-prisms 8-11 are arranged embedded in a second cone 27. Each of the first and second cones comprises a cone base and four side surfaces, the cone bases of the first and second cones being arranged parallel to each other. A shielding member is arranged axially between the first and second cones and ensures that, in case of oblique light incidence with respect to the arrangement axis, one of the first and second cones is at least partially shielded by the shielding member.

Description

Technical Field

[0001] The present invention relates to a target object, particularly a target object for geodetic surveying, construction surveying or industrial surveying, wherein the target object provides a large angle of incidence for retroreflection and a reduced amount of interference reflection. Background Technology

[0002] For example, in geodesy, the location of a target point to be measured or laid out occurs indirectly, such as when the target object on a measuring rod (e.g., provided by a retroreflector such as a prism, foil, or spherical reflector) is measured using a coordinate measuring device (e.g., by using a total station or stadia). Since the tip of the measuring rod is placed on the actual target point in the terrain, the location of that target point can be derived from the determinable spatial relationship between the target object and the tip of the rod. This method particularly allows for the measurement and recording or laying out of points that cannot be directly measured or laid out due to obstacles between the coordinate measuring device and the point.

[0003] Current practice involves ensuring the pole is perfectly vertical at the point of interest and compensating for the position of the pole's length. However, leveling the pole takes time, and it would be desirable to take measurements of the target position without leveling the pole.

[0004] Surveying instruments (such as theodolites, automatic total stations (TPS), laser trackers, automatic alignment devices, distance measuring devices, and laser scanners) have been used for decades to measure natural objects and target marking devices. For example, they are used to measure the horizontal distance, height difference, orientation angle, or relative coordinates between the measuring device and the target object.

[0005] Aiming can be performed manually using a visual aiming device, or fully automatically using an electro-optical sensor, such as a quadrant diode or an image camera.

[0006] The measuring instrument has at least one light emitter that emits radiation along the instrument's target axis in the direction reflecting the target object. The measuring instrument includes an optical arrangement (Automatic Target Recognition, ATR) for receiving the reflected radiation. Based on the reflected light, the instrument automatically aligns itself with the target object. This alignment should be as accurate as possible towards the optical marks and calibration center on the reflector unit. The angular measurement of the alignment between the instrument and the target object is performed in two dimensions (horizontal and vertical). Furthermore, a ranging unit (LiDAR) determines the tilt distance between the measuring instrument and the target object. This determines the spatial coordinates of the target object relative to the instrument.

[0007] The measuring instruments may optionally be equipped with a target search unit (so-called powersearch function). These sensors also require a sufficiently good reflector arrangement, especially at long distances of 500m or 1000m, to generate sufficiently high reflected signals.

[0008] For example, the target marking device is configured as a handheld pole equipped with a reflector unit and a bubble level. Alternatively or additionally, a GNSS or GPS antenna and / or target marking unit is attached to the upper end of the pole (a so-called smart pole).

[0009] If the poles are moved, for example, by being carried or attached to a mobile vehicle (and without a GPS antenna), they can be tracked using a surveying instrument such as a total station. During the tracking process, the surveying instrument is continuously aligned with a reflective element on the target unit, and the path is followed by a motorized alignment unit along both horizontal and vertical orientations. The complete surveying system consists of a combination of a robotic total station and pole units, with the user positioned at the pole (also known as a rover).

[0010] The lever is typically not used to determine the coordinates of the reflector's center, but rather to determine the coordinates of a point connected to the reflector. Such a point could be the lever's anchor point or the bucket of a construction vehicle. Therefore, a lever arm exists between the measuring point and the reflector's center, through which measurement errors can be gradually introduced when determining the coordinates of that point.

[0011] Existing solutions typically suffer from drawbacks regarding oblique light incidence, for example, where retroreflection is limited to a vertical measurement range of ±30° from perpendicular incidence. Other problems include interference reflections in the absence of a reference reflector center and a fixed positional reference. Such reflections complicate automatic alignment to the reflector center and, in the worst case, result in loss of the target object.

[0012] Typically, existing solutions are optimized for vertical pole mounting, where accuracy decreases with tilted mounting. By rotating around the yaw angle, the reflection center of the reflector changes laterally, for example, varying in both the horizontal and vertical directions. Measurement accuracy is typically reduced to 5mm to 10mm.

[0013] The reflected beams are arranged separately, which makes accurate auto-aiming difficult. As the vehicle rotates around the yaw angle, the signal strength used for distance measurement and auto-aiming also changes.

[0014] The entry area of ​​a retroreflector used for retroreflection is only a small fraction of the total light entering the surface. For example, if the entry surface is perfectly aligned with the measuring instrument, the edges are ineffective. However, if the reflector is tilted relative to the line of sight, the aperture of the reflected beam decreases. Therefore, the prism needs to be of a certain size, which implies greater weight.

[0015] Applications with tilted poles and therefore tilted reflector arrangements have generally not been a problem until now. The most common use of the target object previously was in a vertical setting using a plumb bob or IMU, which was simultaneously aimed with the aiming beam of an automatic target recognition (ATR) laser tracker or total station to determine the horizontal and vertical orientation of the reflector center, and thus indirectly determine the foothold on the pole as well.

[0016] To simplify the surveyor's measurement process, a new reflector arrangement should provide measurement accuracy for both vertical and inclined rod settings. Known 360° reflector arrangements have the drawback of not being able to mark target points with sufficient accuracy, particularly in terms of orientation accuracy depending on the rod's orientation and therefore the orientation of the reflector arrangement. Therefore, the object of this invention is to provide a target object that enables more accurate and cheaper spatial detection of target points.

[0017] Surveying using a standard GNSS RTK joystick is slow and involves multiple steps. For each measurement, it is typically necessary to keep the pole vertical while reading the measurement data on the controller screen and moving the pole to the correct position. The position of the reflector or GPS antenna attached to the 1.8m or 2m pole is calculated. To obtain the correct measurement data displayed on the screen (i.e., to show the position of the pole tip), the pole must be kept vertical.

[0018] Recently, modern poles have appeared in locations where the position no longer needs to be perfectly vertical. To accurately determine or indicate the tip of a pole or control stick (a pole with a GNSS unit), the pole can be kept tilted during measurement. The vertical setting of the target object and thus the vertical setting of the reflector unit must ensure the accuracy of previous coordinate measurements under this tilted setting.

[0019] For example, tilt compensation between the pole tip and the pole foot can be performed using specialized IMU sensor technology (e.g., combining IMU and GNSS data), or using a visual-inertial system that combines data from a camera, IMU, and optionally GNSS sensors and processes it. This visual-inertial system addresses the six degrees of freedom of a solid in space by applying algorithms known from Simultaneous Localization and Mapping (SLAM).

[0020] Points such as building corners, walls, fences, lampposts, or under obstacles such as cars cannot typically be measured directly using a vertical pole. For example, to measure a building corner, nearby points must be identified, and a compensated measurement must be performed for that point.

[0021] For various applications, it has proven advantageous to form target objects in such a way that they can be aimed at and measured advantageously from all directions, not just one. Therefore, surveyors carrying the target object and erecting it at different points do not need to ensure correct orientation relative to the measuring instrument each time the target object is erected. Moreover, when measuring the same fixed point with varying instrument settings, the target object positioned at that point is aimed at from different directions. In the construction of traffic routes (e.g., in the construction of road tunnels), the same measurement point or target object is often measured from substantially opposite directions, and in each case, reorientation of the target object is undesirable. Target objects that can be measured from a large angular range (particularly 360° horizontally and greater than ±45° vertically) are also ideal for measuring moving objects.

[0022] Since modern reflectors do not require vertical alignment, the angle between the reflector and the line of sight can result in any value. Therefore, new reflectors should have a large field of view in both azimuth and elevation directions.

[0023] The simplest case of such a target object is one with a spherical reflector; however, the potential uses of spherical reflectors are limited because they can only be used for measurements at short distances. For measurements even at long distances, large retroreflective foils or prisms are typically used. Their substantially higher degree of retroreflection allows for distance measurements over hundreds or thousands of meters. However, unlike spherical reflectors, they only reflect the beam within a limited vertical range within the finite azimuth alignment range of the prism or reflective foil. Typically, the beam is reflected with high intensity within a horizontal range of ±45° and a vertical range of ±35°. To obtain what is called a 360° or omnidirectional reflector, a target object consisting of multiple retroreflectors can be used.

[0024] EP 0846278 describes a 360° reflector with multiple prisms. The prisms are arranged such that the side surfaces of adjacent prisms are in contact with each other, resulting in the pupils of adjacent prisms at least partially contacting each other during a retroreflection from one prism to an adjacent prism. Therefore, this arrangement acts as an omnidirectional reflector, reflecting light from all incident directions in the azimuth plane (e.g., the horizontal plane in the case of a vertical arrangement of a target / pole). This patent... Figure 5An omnidirectional reflector in a retainer is shown. However, omnidirectional reflectors are not well-suited for close-range measurements because the measurement can be tampered with at short distances due to interference or disruptive reflections.

[0025] DE 10209895 describes an omnidirectional reflector comprising an arrangement of eight prisms in the form of two pyramids oriented with their bases facing each other. Due to this specific arrangement of the prisms, interfering reflections, particularly double reflections, are reduced within the horizontal angular range. However, interfering reflections still exist at large vertical angles deviating from the horizontal plane, posing a significant hindrance, especially in the case of automated guidance and control of construction machinery. The interfering reflections are not generated by triple reflections but by any other periscopic optical path, where the beam is reflected back to the total station in a specific orientation. To form a locatable target object, a retaining portion is provided in the prism arrangement, on which a plumb bob can be mounted. The retaining portion is mounted directly on the prism arrangement from below, which means that, for example, when the plumb bob is roughly placed on a surface, forces acting on the fragile prisms must be considered.

[0026] A common drawback of the described prior art arrangements is the occurrence of interfering reflections at vertical angles (e.g., exceeding ±30°) deviating from the horizontal plane. These interfering reflections are back reflections emitted by the reflector units, but without a reference mark center and a fixed position reference. Only the triple-reflected beam is anchored to the reflection center of the physical right-angle prism. Therefore, reflections may occur originating from prisms positioned laterally relative to the actual working prism and not aligned in the direction of the measuring beam.

[0027] Another problem with existing arrangements is their sensitivity to damage from external mechanical forces to reflective components, typically made of glass. This sensitivity stems in particular from the fact that arrangements for omnidirectional reflection of radiation must utilize glass sections whose light-entry surfaces cover a 360° azimuth range without external protection. To hold the glass sections, most arrangements have retaining portions directly attached to them, resulting in the transmission of external forces to the fragile glass sections, especially to the mirror surfaces. The three mirror surfaces of the glass prism are ground and polished so that their relative angles are orthogonal within sub-radian seconds of accuracy to generate a retroreflected beam with a deviation from the incident beam typically less than 5 radian seconds. Moreover, the flatness of each surface is in the micrometer or sub-micrometer range. External forces caused by the retaining portions or adhesive reduce the flatness of the mirror surfaces, leading to angular expansion of the reflected beam and shortening the maximum measuring distance of the measuring instrument.

[0028] Because target objects are typically used in a manner where they are set up and moved by surveyors in the terrain, they must be handheld and portable, and therefore as lightweight as possible. Consequently, lightweight holding devices, such as plumb bobs, are commonly used. The high weight of the reflector arrangement and the low weight of the plumb bob result in an unbalanced target object that is prone to falling, and the sensitive glass parts are easily broken. This problem is exacerbated in cases where the reflector arrangement additionally carries the GPS target object. During traffic route construction where the target object is mounted on construction machinery, considerable forces are also applied to the target object due to vibrations, causing stress, particularly at the connection between the holding part and the reflector arrangement.

[0029] Another problem with existing technology is that interference reflections occur when light from a prism enters a wet surface. Water droplets on the prism surface, especially those caused by rain, snow, or splashes, can cause this. The effective size of the reflected beam's aperture is reduced by the sum of all the cross-sections of the water droplet. In the worst case, the remaining free aperture can be reduced to almost zero. Summary of the Invention

[0030] The purpose of this invention is to provide an improved target object that eliminates the defects of the prior art.

[0031] One particular objective is to provide a target object that offers high-intensity retroreflection over an angular range of up to 360° and an increased range for oblique incidence.

[0032] These objectives are achieved by implementing at least a portion of the features of the independent claims. Further development of the features of the invention in alternative or advantageous manner is described in the appended patent claims.

[0033] This invention relates to a target object, particularly for geodetic surveying, construction surveying, and industrial surveying, having an arrangement of four prisms, each prism having a light-entering surface and three reflecting surfaces. The four prisms are arranged around an axis such that their (outer) contours can be fitted into a cone (e.g., their contours can be adapted to fit the cone's shape or form the cone), the cone having a pyramid base and four side surfaces in different planes, wherein the common intersection of these planes forms a pyramid tip opposite the pyramid base (e.g., the common intersection of the four side surfaces forms the pyramid tip).

[0034] For each of the four prisms, one of its reflecting surfaces is aligned parallel to the base of the cone, and the other two reflecting surfaces are aligned parallel to the reflecting surfaces of their respective adjacent prisms.

[0035] According to one aspect of the invention, the target object includes a shielding member arranged axially (relative to the arrangement axis) on one side of the cone base (e.g., adjacent to the cone), wherein, in a direction perpendicular to the arrangement axis, the opaque portion of the shielding member extends beyond the maximum extension of four reflective surfaces arranged parallel to the cone base.

[0036] According to another aspect of the invention, the target object includes an opaque blocking component disposed in a region surrounding the tip of the cone, wherein the blocking component blocks light from entering the surface of the prism, thereby reducing the effective usable size of the light-entering surface of each prism in the prism.

[0037] Alternatively, instead of having an opaque blocking component for the target object, each prism in the prism is configured to have an additional prism surface different from the light-entering surface and the three reflecting surfaces. This additional prism surface is positioned opposite to the base of the cone, and in particular, it is parallel to the base of the cone, which, for example, results in the four prisms having a truncated cone shape in their profiles.

[0038] Another possible use of the shielding member is an arrangement in which the target object includes a first retroreflector and a second retroreflector (e.g., where the first and second retroreflectors are configured as prisms), and the first and second retroreflectors are arranged axially adjacent to each other on the arrangement axis. The shielding member is axially positioned between the first and second retroreflectors, wherein the opaque portion of the shielding member extends radially beyond the radial extension range of both the first and second retroreflectors in a direction perpendicular to the arrangement axis. In the case of oblique light incident relative to the arrangement axis, one of the first and second retroreflectors is at least partially shielded by the opaque portion of the shielding member.

[0039] For example, each prism in the prism has a light-entering surface and three reflecting surfaces oriented at right angles to each other in each case. The prism is configured such that the distance between the reflection center (for a triple-reflected beam) and the prism vertex is no greater than 5 mm, and especially no greater than 3 mm.

[0040] The target object is configured to provide backscattering for light incident over a 360° range around the axis of the arrangement, particularly for light incident perpendicular to the axis of the arrangement, and more particularly wherein the target object has four prisms.

[0041] In another embodiment, the target object comprises eight prisms, each prism having a light-entering surface and three reflecting surfaces. The eight prisms are arranged around an axis such that their outlines can be fitted into an octahedral shape, wherein four of the eight prisms are arranged to fit into a first cone, and the other four are arranged to fit into a second cone. Each of the first and second cones includes a base and four side surfaces, wherein the bases of the first and second cones are arranged parallel to each other.

[0042] The first cone is formed in such a way that one reflective surface of each of the four prisms embedded in the first cone is arranged parallel to the base of the cone, and the other two corresponding reflective surfaces of each of the four prisms embedded in the first cone are arranged adjacent to the reflective surfaces of the neighboring prisms embedded in the first cone.

[0043] The second cone is formed in such a way that one reflective surface of each of the four prisms embedded in the second cone is arranged parallel to the base of the cone, and the other two corresponding reflective surfaces of each of the four prisms embedded in the second cone are arranged adjacent to the reflective surfaces of the neighboring prisms embedded in the second cone.

[0044] In other words, four of the eight prisms embedded in one of the two cones efficiently reflect light from the angle of the upper hemisphere, and four of the eight prisms efficiently reflect light from the angle of the lower hemisphere, wherein the shielding member is arranged axially between the first and second cones, and ensures that in the case of oblique light incident relative to the arrangement axis, one of the first and second cones is at least partially shielded by the shielding member.

[0045] Each of the eight prisms has a vertex formed by the common intersection of the three reflecting surfaces of the prism, and the vertex is arranged on the corresponding base of the first and second cones, respectively.

[0046] In another embodiment, the target object includes an opaque blocking component disposed in the region surrounding the tip of at least one of the first and second cones. This blocking component blocks light from entering the surface through the prisms of the at least one of the first and second cones, thereby reducing the size of the light entering the surface from each of the prisms in the at least one of the first and second cones.

[0047] In another embodiment, each of the prisms in at least one of the first and second cones is configured to have an additional prism surface different from the light-entering surface and the three reflecting surfaces. This additional prism surface is arranged such that it is opposite to the base of the cone, and in particular, it is parallel to the base of the cone, resulting in the profiles of the four prisms in at least one of the first and second cones being truncated cones.

[0048] In another embodiment, the shielding member includes a mark disposed on an opaque portion extending beyond the maximum extent of the four reflective surfaces arranged parallel to the base of the cone. This mark provides a positional indication of the reflection center (for a triple-reflected beam) of one of the prisms. For example, in the case of eight prisms arranged as described above, the shielding member is axially disposed between one cone and another (e.g., adjacent to the first cone and another cone on the base side).

[0049] In another embodiment, the shielding component includes a mark disposed on an opaque portion of the shielding component, wherein the mark provides a positional indication of the reflection center of one of the retroreflectors.

[0050] In another embodiment, the shielding member (e.g., completely) surrounds the arrangement axis, and in particular, the opaque portion of the shielding member is specifically implemented as a planar annular surface.

[0051] In another embodiment, the shielding component may, for example, completely surround the arrangement axis. For instance, the opaque portion extending radially beyond both the first and second retroreflectors is specifically implemented as a planar annular surface.

[0052] In another embodiment, the target object includes a support frame comprising four reception sections, and, where applicable, eight reception sections, arranged around an arrangement axis such that the contours (common outer contours) of these reception sections match the cone and, where applicable, another cone. Each of the reception sections is defined by three mutually perpendicular planes. The support frame includes clip mounts disposed at the corners of the cone and, where applicable, at the corners of another cone, configured to hold the four prisms, and, where applicable, four additional prisms, in a tension-free and fixed arrangement within the reception sections.

[0053] The three mutually perpendicular planes forming the support frame are configured as solid, and preferably non-perforated, plates, particularly solid metal plates / sheets. Therefore, each receiving portion in the receiving section is defined by three mutually perpendicular solid plates, particularly solid metal plates.

[0054] The support frame provides high stability and rigidity. For example, the support frame is made of metal injection molding material or fiber-reinforced material. The support frame for the target object is configured to dissipate forces along the rod from the bottom to the top of the target object, and thus can robustly support, for example, a GNSS sensor.

[0055] Instead of using clip-on mounts, the prisms can be glued together or glued to the support frame. However, this can cause undesirable thermal and mechanical stresses on the optics and damage the wavefront of the reflected laser, which is avoided by using a support frame with clip-on mounts as described above. In any case, it is conceivable that two reflective surfaces of each of the four prisms (and, in applicable cases, eight prisms) are glued together (which are arranged adjacent to one of the reflective surfaces of another of the four prisms (and, in applicable cases, eight prisms)). In this arrangement, each of the four prisms and each of the other four prisms has a prism vertex formed by the common intersection of the three reflective surfaces of that prism. This prism vertex is arranged on a corresponding cone base, and in particular, it is arranged on an arrangement axis.

[0056] Because of the support frame described above, the target object does not require any direct adhesion between the prisms, thus eliminating photomechanical stress. Easily machinable glass types such as N-BK7 are sufficient as materials for the prisms without causing any interfering reflections.

[0057] For example, the target object also includes an interface located at one of the distal ends on the arrangement axis, and the interface is configured to connect the target object to a mating object, particularly a surveyor's rod or protective cap.

[0058] In another embodiment, the target object includes a protective cap disposed at one of the distal ends and configured to protect the target object from axially impacting water droplets. The protective cap includes a drainage channel, for example, wherein the protective cap has a frustoconical shape. A cross-section perpendicular to the arrangement axis narrows from one of the distal ends to the other distal end, and the maximum cross-section perpendicular to the arrangement axis is greater than the radial extension of the retroreflector or prism.

[0059] In another embodiment, the protective cap has an air inlet and an exhaust outlet. The exhaust outlet is arranged from one of the distal ends toward the other distal end, for example, wherein the exhaust outlet is configured to generate an airflow parallel to one of the light-entry surfaces of the prism. The target object also has a pneumatic nozzle configured to generate an air jet onto the light-entry surface.

[0060] In another embodiment, the light-entering surface is equipped with a hydrophobic optical coating.

[0061] In another embodiment, the (e.g., upper) protective cap has an adapter for GNSS antennas and / or visual inertial system accessories.

[0062] In another embodiment, the protective cap has an adapter for an automated target identifier.

[0063] In another embodiment, the protective cap has a target identifier configured to provide target object information related to the target object and / or target ID. For example, the prism type indicates a so-called additional constant of the reflection center, which has a value other than zero. Especially for compensated measurements, it is important that the correct reflector type is known and that the correct optical specifications and compensation parameters are applied in the context of measurements using a coordinate measuring machine. A unique target ID can be used to identify a target object within a group of multiple target objects. Target object information is provided by the optical characteristics defined by the target identifier, such as a defined reflectivity pattern, color coding, polarization coding, and / or by means of a transmitted signal to be detected by a total station.

[0064] As outlined above, when prisms are mentioned in connection with this invention, they should be understood in the broadest sense as different shaped bodies of transparent material for reflecting beams of light, having, in principle, any desired form of pupil cross-section or aperture region (e.g., trapezoidal, triangular, or hexagonal), which allows the beams of light to enter or exit the shaped body, and in each case, three flat reflective surfaces oriented at right angles to each other, and the beams having triple reflection.

[0065] The retroreflection effect of a prism derives from the retroreflection effect of a three-sided mirror, where, in each case, the three mirrors are adjacent to each other at right angles. If light falls into such a three-sided mirror, the light is reflected at all three mirrors, and the light rays exiting the three mirrors extend parallel to each other and are laterally deflected relative to the incident light. The parallelism is achieved within a few radian seconds over long distances of several kilometers. This retroreflection is possible within a specific range of incident angles relative to the normal to the surface into which the light enters.

[0066] Not all light falling onto the surface is reflected back. Only light falling into the pupil of the prism is reflected back. This pupil is defined by the (straight and kinked) lines generated by the point reflection of the light entering the surface from the side edge of the surface at the vertex of the virtual prism. The vertex of the virtual prism is the prism vertex visible when looking into the prism, but it is only apparent due to the refraction of the prism glass.

[0067] For example, when light is incident perpendicular to the surface of a prism, a rotationally symmetric prism generates the largest pupil or aperture area, and thus the largest amount of light backscattering.

[0068] As the angle of incidence of light into the prism changes, the shape and size of the pupil change. With increasing angle of incidence, the pupil surface becomes smaller and more located at the edge of the light-entering surface. Finally, at a specific angle of incidence, this area disappears, and no more light is reflected back.

[0069] Another conceivable arrangement is that of multiple prisms with triangular light-entry surfaces arranged such that the side surfaces of adjacent prisms are in contact with each other. In this case, the prisms can have different sizes, and their light-entry surfaces can have different angles relative to the spatial diagonal passing through the vertices of the prisms. This is useful for specific, defined angle ranges in the case of retroreflection.

[0070] When combining multiple prisms for a 360° target object, it is also conceivable to ensure that the pupils of the light travel a relatively long path when the light is reflected from one prism to an adjacent prism. As the angle of incidence changes, the pupil area of ​​one prism decreases, while the pupil areas of adjacent prisms increase, and the sum of the pupil areas always remains large. Thus, a large amount of light is continuously reflected back at the angle of incidence that the light enters in the prism arrangement.

[0071] Furthermore, because the edge lines of the pupil regions adjacent to the prisms are aligned parallel over a relatively large area, the reflected light beams are positioned close to each other in space. This provides high measurement accuracy, for example, in cases where prism arrangements are used to determine coordinates in three dimensions, and is suitable for automated measurements.

[0072] Since interference reflections may originate from prisms that are laterally positioned relative to the actual working prism and not aligned with the direction of the measurement beam, precisely shielding these adjacent prisms can reduce interference reflections even if the vertical angle deviates from the horizontal plane by more than ±30°.

[0073] As summarized above, one aspect of the invention is that eight prisms are arranged around an arrangement axis in such a way that the outlines of these prisms can be fitted into an octahedral shape, wherein four of the eight prisms are arranged to be fitted into a first cone, and the other four of the eight prisms are arranged to be fitted into a second cone. Each of the first and second cones includes a base and four side surfaces, wherein the bases of the first and second cones are arranged parallel to each other. A shielding member is axially arranged between the first and second cones, and ensures that in the case of oblique light incident relative to the arrangement axis, one of the first and second cones is at least partially shielded by the shielding member.

[0074] It is also conceivable to arrange the retroreflectors (especially prisms) as reflective elements of the target object by arranging the shielding component axially between them, for retroreflecting light radiation along an arrangement axis configured to retroreflect light incident from a direction perpendicular to the arrangement axis. By configuring the shielding component radially larger than the first and second retroreflectors in a direction perpendicular to the arrangement axis, and positioning it away from the arrangement axis, it ensures that in the case of oblique light incident relative to the arrangement axis, some of the retroreflectors are at least partially shielded by the shielding component.

[0075] Since only the pupil area of ​​the light-entering surface provides the desired retroreflection, the corner regions of the prism are ineffective even if the measuring instrument is correctly aligned. However, if these regions are illuminated by a beam of light with a large angle to the normal of the light-entering surface, it can cause interfering reflections. To reduce these interfering reflections, it is advantageous to reduce the light-incident surface towards the corners of the prism, especially for the corners near the upper and lower end bars of the support frame. This reduction can be achieved by covering these corners with an opaque material (e.g., paint) or by using so-called truncated right-angle prisms.

[0076] In the case of conventional aiming mark arrangements, additional reflections occur at the spatially separated prisms, which also leads to erroneous distance measurements. This is particularly evident at short distances (e.g., less than 25m), for which a minimum distance must be maintained in the case of such aiming mark arrangements. In contrast, by means of a prism arrangement according to one aspect of the invention, a reliable measurement range can be achieved even at short distances, as the prisms are positioned very closely together and reflect each other.

[0077] To maintain the stability and compactness of the prism, the target object has a mounting or retaining element. The prism can then be positioned in a manner that prevents light from being blocked from entering the surface by the mounting element. The 360° horizontal angular range is thus effectively reflected. Furthermore, the prism and mounting element are advantageously designed and arranged such that a specific vertical angular range (particularly at least ±45° or greater) is reflective. Attached Figure Description

[0078] The invention will now be illustrated in more detail by way of example, with reference to the schematic examples shown in the accompanying drawings. The same reference numerals are used to label the same elements in the drawings. The embodiments described are generally not shown to scale, and these embodiments should not be construed as limiting the invention.

[0079] Figure 1 An exemplary layout workflow for the target object according to the present invention, using a total station and attached to a pole.

[0080] Figure 2 According to an embodiment of the target object of the present invention, the target object has eight prisms arranged in an octahedral shape and is equipped with a shielding component, a blocking assembly, a support frame, and an interface.

[0081] Figure 3 Possible designs for the support frame.

[0082] Figure 4 According to an embodiment of the target object of the present invention, an example is provided for a region on the surface into which reflected light enters.

[0083] Figure 5 Possible designs for right-angle prisms.

[0084] Figure 6 According to an embodiment of the target object of the present invention, the target object has eight prisms arranged in an octahedral shape, and is also equipped with a shielding component, a blocking assembly, a support frame, and a protective cap.

[0085] Figure 7 Visualization of the effective aperture at two vertical incident angles.

[0086] Figure 8 : Solution to omit unnecessary parasitic or interfering reflections. Detailed Implementation

[0087] Figure 1 An exemplary stakeout workflow using a total station 3 and a surveying rod 2 is depicted. The surveying rod 2 has a rigid rod-shaped body with an indicator tip 23 for contacting a surveying point on the ground. The body defines a rod axis 24. The rod 2 includes a target object 1 (e.g., a retroreflector device) as a position-giving device to make the coordinates of a reference position at the rod 2 available. The target object 1 is located on the body at a known position relative to the tip 23. The total station 3 is used to repeatedly determine the reference position of the target object 1.

[0088] The total station 3 includes a telescope unit adapted to measure the distance and orientation angle of the target object 1 to the measuring rod 2. Aiming at the retroreflector device of the rod can be performed visually via an optical telescope or via an Automatic Target Recognition (ATR) sensor unit also located within the telescope unit of the total station 3.

[0089] In the past, the most common use of measuring rod 2 was in vertical mounting to determine the horizontal and vertical orientation of target object 1, for example, the center of the reflector of a retroreflector, and thus indirectly to determine the bottom of the rod.

[0090] To simplify the surveying process for surveyors or civil engineers, the new total station-rod system is configured to work with a rod set at a certain angle.

[0091] For example, the measuring rod 2 also includes an inertial measurement unit (IMU) placed on the body in a defined spatial relationship relative to the position-giving device. For instance, the IMU is configured as a microelectromechanical system (MEMS) and includes an IMU sensor comprising an accelerometer and a gyroscope. The rod 2 includes an evaluation device for deriving the position of the measurement point based at least on a determined reference position and on the defined spatial relationship of the target object relative to the tip 23. The high-quality rod is equipped with a visual-inertial system that calculates the rod's six degrees of freedom in real time based on information provided by an imaging camera and the IMU sensor.

[0092] Typically, target objects (especially 360° retroreflectors, which measure 360° in a plane perpendicular to the rod axis) have the disadvantage of not being able to mark target points with sufficient accuracy when the beam is incident at an angle (i.e., when the rod is tilted). Therefore, the accuracy of direction determination (angle) is insufficient depending on the alignment of the measuring rod and thus on the alignment of the reflector device.

[0093] Figure 2 An exemplary embodiment of the target object 1 is depicted, comprising eight prisms 4, 5, 6, 7, 8, 9, 10, and 11 of identical design arranged axially adjacent to each other around an arrangement axis 25 and providing an octahedral shape. The arrangement axis 25 extends along the vertices of the octahedron and through its center. A horizontal plane is arranged perpendicular to the arrangement axis 25 and also passes through the center of the octahedron. The octahedron is formed such that four prisms 4 to 7 are arranged to be embedded in a first cone 26, and another four prisms 8 to 11 are arranged to be embedded in another cone 27. The bases of the cones are arranged parallel to each other in the horizontal plane, wherein one of the two cones is formed such that a reflecting surface of each of the four prisms is arranged parallel to the cone base, and the other two corresponding reflecting surfaces of each of the four prisms are arranged in each case to be adjacent to one of the reflecting surfaces of the other of the four prisms. The prism apex is oriented to the base of the cone, and the prism apex is specifically located in the base of the cone, wherein the light-entering surfaces of the four prisms are all deflected relative to the reflecting surfaces of the side surfaces forming the cone.

[0094] The target object has an opaque blocking component 13 arranged in the region surrounding the tips of the two cones 26, 27. Alternatively, prisms 4, 5, 6, 7, 8, 9, 10, 11 can be configured to have a truncated cone shape (see, for example, see...). Figure 5 ).

[0095] For example, target object 1 also has interfaces 15 and 16, which are located at the vertices of the octahedron and axially arranged relative to the arrangement axis 25. These interfaces are used to receive mating objects, specifically the surveyor's rod 2. The interfaces are adapted to the shape of a pyramid apex.

[0096] Target object 1 also includes Figure 3 The support frame 14 shown comprises three orthogonal metal plates, with the arrangement axis along the intersection line of two vertical metal plates. The outer edge of the plate extends to the light-entering surface of the prism and forms a clamp-on mounting 30 for eight prisms 4 to 11, wherein the prisms are held in a fixed arrangement by, for example, a bracket located at the end of the thin wall, in such a way that the free aperture size of the prism is not reduced. Other types of mounting mechanisms can also be used to fix the prism position in a stress-free manner.

[0097] in other words, Figure 3 The support frame 14 shown includes eight receiving portions arranged around the arrangement axis 25 in such a way that the outlines of these receiving portions match the cone 26 and another cone 27. Each of the receiving portions is defined by three mutually perpendicular planes. The support frame 14 includes clamp-mount members 30 arranged at the corners of the cone 26 and the other cone 27. The clamp-mount members are configured to hold the four prisms and four other prisms in a tension-free and fixed arrangement within the receiving portions.

[0098] like Figure 2 As depicted, the shielding member 12 is arranged axially adjacent to the cone and another cone on one side of the cone base. In principle, it coincides with a third horizontally placed metal sheet. The opaque portion of the shielding member 12 extends beyond the maximum extension of the four reflective surfaces, which are arranged parallel to the cone base and away from the arrangement axis 25. This ensures that, in the case of oblique light incident relative to the arrangement axis 25, one of the first cone 26 and the second cone 27 is at least partially shielded by the shielding member 12.

[0099] Figure 4 Another embodiment of the target object 1 according to the invention is depicted, wherein the area of ​​the so-called effective light entering the surface 17 of the prisms 4 to 11, which provide the desired retroreflection, is reduced relative to the theoretically achievable size. Even if the measuring instrument is correctly aligned, the corner regions of the prisms 4 to 11 are ineffective, but may provide interference reflections. The prism 5 also generates interfering reflections at certain specific steep angles of incidence of the measuring beam.

[0100] To reduce the aforementioned interference reflections, it is advantageous to reduce the light incident area toward the cone apex and to impart a certain characteristic to the light entering surface 28. Figure 2 The trapezoidal shape is shown. This reduction can be achieved by designing interfaces 15 and 16 such that they cover the apex of the cone to a certain extent, or by using so-called truncated right-angle prisms.

[0101] Figure 5 A possible implementation of the so-called truncated right-angle prism 19 is shown. It has another surface 29, different from the light-entering surface 28 and the three reflecting surfaces. This surface 29 is arranged opposite to the base of the cone, and in particular, it is parallel to the base of the cone. In the case of a conical arrangement of four right-angle prisms around an arrangement axis 25, a truncated cone shape is generated.

[0102] Because there is no [condition] when using a truncated right-angle prism. Figure 2 The cone vertex of the target object 1 is shown, thus the entire arrangement has a reduced weight. In this way, when using an unmodified prism, the size of the retroreflection prism can be increased by 25% without increasing the initial weight and size of the target object 1. For example, this results in a stronger retroreflection, leading to an increased measurement distance.

[0103] exist Figure 6 In another embodiment of the invention shown, protective caps 20 and 21 are attached to interfaces 15 and 16, which are designed to ensure impact-resistant installation of the target object 1. For this purpose, the protective caps 20 and 21 are designed such that if an external force or torque is applied (e.g., when the target object 1 is dropped), the protective caps 20 and 21 are impacted first, and the force is directly directed to the rod. No force component from the outside is directed to the glass prism (unless there is an inertial force accelerating the prism mass), and therefore almost no force is transmitted to the prisms 4 to 11.

[0104] In one embodiment, protective caps 20 and 21 are implemented, wherein the protective caps 20 and 21 have a frustoconical shape, wherein the top surface of the frustocon is directed toward the center of an octahedron, and the bottom of the frustocon is designed to be radially larger than the reflector arrangement.

[0105] In addition to protecting against external forces, the protective cap 20 also protects the light-entering surface from water droplets, which reduce the optically clean prism aperture and / or cause interfering reflections. Furthermore, the protective cap 20 is provided with drainage channels, thereby allowing a larger amount of water that may accumulate on the protective cap to drain from the prism surface.

[0106] exist Figure 6In the illustrated embodiment, the protective cap 20 is provided with an air inlet 22 and an exhaust outlet. The exhaust outlet is arranged toward, and particularly parallel to, the light-entering surfaces. The target object 1 is equipped with a pneumatic nozzle that allows air to be sprayed onto the light-entering surfaces. Surface drying is particularly efficient thanks to the pneumatic nozzle oriented parallel to the light-entering surfaces. Short pulses of air, ranging from 5 mN to 50 mN, remove not only large water droplets from the light-entering surfaces but also small water droplets.

[0107] To facilitate the free flow of water droplets on the light-entry surfaces, these surfaces are equipped with a hydrophobic optical coating on their outward-facing sides. The hydrophobic coating reduces the contact area of ​​the water droplets by several orders of magnitude, resulting in a corresponding decrease in adhesion, and a weak air jet is sufficient to keep the inlet surface water-free.

[0108] For example, the shielding member 12 also has markings 18 on its upper and lower sides. These markings provide a positional indication of the center of reflection defined by one of the prisms. When aiming the total station through the eyepiece of the telescope, the markings simplify visual aiming at the tilted positioning rod. In another embodiment of the shielding member 12, the shielding member is made of rubber, which provides additional protection against mechanical shocks.

[0109] Typically, when the structure of target object 1 (for example, such as...) Figure 6 As shown, the height point is symmetrical, which is advantageous because it allows the target object 1 to be used in an inclined setting, as opposed to the vertical setting commonly used to date. By implementing several aspects of the invention, the target object 1 can be constructed to provide omnidirectional retroreflection of 360° in the horizontal angular range and at least ±45° in the vertical angular range, wherein the occurrence of interfering reflections is significantly reduced. Moreover, the target object 1 can be used in rainy or snowy weather conditions because the light-entering surfaces of the prisms 4 to 11 can be kept free of water droplets by the protective caps 20 and 21 and the active air jet device.

[0110] Figure 7 The diagram shows a so-called unfolded representation of the beam path in a "conventional" prism, i.e., without the shielding component 12 according to the invention. Figure 2 ) and at the tip of the cone, there is no blocking component 13 according to the invention. Figure 2 ) / Without the use of the truncated cone 19 according to the present invention ( Figure 5A prism in the shape of (). This unfolded representation allows light rays to be drawn as continuous lines without reflection, making the aperture, vignetting, etc., more visible. Using this representation, the path of light entering surface 28 within the aperture of the prism can be better understood. Regions a, b, and c correspond to a representation of a mirrored image of the prism. Two effective apertures (= ray boundaries) of two different incident beams 31, 31' are depicted, which enter the prism of the target object at two selected incident angles along the elevation direction and have corresponding retroreflected exit beams 32, 32'.

[0111] In variant x, the incident beam 31 enters the prism at a vertical angle close to 0°, that is, the incident beam 31 is approximately perpendicular to the arrangement axis 25. Figure 2 In variant y, the incident beam 31' enters the prism at a vertical angle of 90°, that is, the incident beam 31' is parallel to the arrangement axis 25 (e.g., when the arrangement axis is vertically oriented, it illuminates from the zenith or nadir direction).

[0112] Figure 8 A representation of the unfolded prism in a target object according to an embodiment of the present invention is depicted, wherein, by means of the shielding member 12 according to the present invention ( Figure 2 ) and the blocking component at the tip of the cone (13) / using a truncated cone 19 ( Figure 5 A prism in the shape of a triangle is used to suppress parasitic internal reflections and pseudo-reflections that occur in the direction of a certain incident elevation angle of a beam.

[0113] For example, by removing the so-called far-end prism corner (by means of blocking component 13 or a prism in the shape of a truncated cone 19) and shielding component 12 blocking light reflected from a steep angle of incidence (near the zenith or nadir) that would otherwise interfere with the reflection from the corresponding prism in the other hemisphere (e.g., blocking a steep beam of light incident on a prism in the lower hemisphere, since that beam is better reflected by a prism in the upper hemisphere). Additionally, the removed prism corner and shielding component also provide a reduction in interfering reflections (e.g., no triple retroreflection).

[0114] Although the invention has been illustrated above, reference has been made in part to some preferred embodiments. It must be understood that many modifications and combinations of different features can be made to these embodiments. All such modifications fall within the scope of the appended claims.

Claims

1. An object (1) having an arrangement of four triangular prisms (4 to 7), each of the triangular prisms (4 to 7) having a light entry surface and three reflecting surfaces, wherein the common intersection of the planes forms a cone tip opposite the cone base, and for each of the four triangular prisms (4 to 7) one of the reflecting surfaces of the triangular prism is arranged parallel to the cone base and each of the other two reflecting surfaces of the triangular prism is arranged parallel to a reflecting surface of a respective adjacent triangular prism, characterized in that the object (1) comprises a shielding member (12) arranged axially on one side of the cone base, wherein in a direction perpendicular to the arrangement axis (25) an opaque portion of the shielding member (12) extends beyond the maximum extension of the four reflecting surfaces (4 to 7) arranged parallel to the cone base, wherein the object (1) comprises an opaque blocking assembly (13) arranged in a region surrounding the cone tip, wherein the blocking assembly (13) blocks light from passing through the light entry surface of the triangular prisms (4 to 7), thereby reducing the effective available size of the light entry surface of each of the triangular prisms (4, 7), or each of the triangular prisms (4 to 7) is configured to have a further prism surface different from the light entry surface and the three reflecting surfaces, wherein the further prism surface is arranged opposite the cone base. The object is an object for geodetic, constructional and industrial surveying. The further prism surface is parallel to the cone base. The triangular prisms are configured in such a way that the distance between the reflecting center and the vertex of the triangular prism is not greater than 5 mm. The distance between the reflecting center and the vertex of the triangular prism is not greater than 3 mm. The four prisms (4 to 7) are arranged around an arrangement axis (25) in such a way that the contours of the four prisms can be embedded in a cone (26) having a cone base and four side surfaces lying in different planes, wherein 6. The object (1) according to claim 1, characterized in that the object (1) comprises a further four triangular prisms (8, 9, 10, 11), each of the further four triangular prisms (8 to 11) having a light entry surface and three reflecting surfaces, the further four triangular prisms (8 to 11) are arranged around the arrangement axis (25) in such a way that the contour of the further four triangular prisms can be embedded into a further cone (27) having a further cone base and a further four side surfaces lying in different planes, wherein the common intersection of the planes forms a further cone tip opposite the further cone base, for each of the further four triangular prisms (8 to 11) one of the reflecting surfaces of the triangular prism is arranged parallel to the further cone base and each of the other two reflecting surfaces of the triangular prism is arranged parallel to a reflecting surface of a respective adjacent triangular prism (8 to 11), and the further four triangular prisms (8 to 11) are arranged in such a way that the distance between the reflecting center and the vertex of the triangular prism is not greater than 5 mm. ​ ​ ​ ​ ​ ​ 2. The target object (1) according to claim 1, characterized in that ​ 3. The target object (1) according to claim 1, characterized in that ​ 4. The target object (1) according to claim 1, characterized in that ​ 5. The target object (1) according to claim 4, characterized in that ​ ​ ​ ​ ​ The four triangular prisms and the further four triangular prisms (4 to 11) are arranged in such a way that the contours of these triangular prisms can be embedded in an octahedron shape, wherein the cone base and the further cone base are arranged parallel to each other.

7. The target object (1) according to any one of claims 1 to 6, characterized in that The shielding component (12) comprises a marking (18) arranged on the opaque portion of the shielding component (12), wherein the marking provides an indication of the position of the reflection center for one of the triangular prisms.

8. The target object (1) according to any one of claims 1 to 6, characterized in that The shielding component (12) surrounds the arrangement axis (25).

9. The target object (1) according to claim 8, characterized in that The shielding component (12) completely surrounds the arrangement axis (25).

10. The target object (1) according to claim 8, characterized in that The opaque portion of the shielding component (12) is embodied as a planar annular surface.

11. The target object (1) according to any one of claims 1 to 6, characterized in that The opaque blocking assembly (13) or the triangular prisms (4 to 11) are configured to arrange the individual light entry surfaces of the triangular prisms (4 to 11) in a trapezoidal shape.

12. The target object (1) according to any one of claims 1 to 6, characterized in that The target object (1) comprises a support frame (14), wherein the support frame (14) comprises four and, if applicable, eight receptacles which are arranged around the arrangement axis (25) in such a way that the contours of these receptacles match the cone (26) and, if applicable, the further cone (27), wherein each of the receptacles is delimited by three mutually perpendicular planes, wherein the support frame (14) comprises a clip mount (30) which is arranged at the corners of the cone (26) and, if applicable, at the corners of the further cone (27), which is configured to hold the four and, if applicable, further four triangular prisms in a tension-free and fixed arrangement in the receptacles.

13. The target object (1) according to claim 12, characterized in that The receptacles are delimited by three mutually perpendicular solid plates.

14. The target object (1) according to claim 13, characterized in that The solid plates are solid metal plates.

15. The target object (1) according to any one of claims 1 to 6, characterized in that The target object (1) comprises an interface at one of the distal ends of the arrangement axis (25) and which is configured to connect the target object (1) to a counterpart.

16. The target object (1) according to claim 15, characterized in that The counterpart is a rod (2) or a protective cap of a surveyor.

17. The target object (1) according to claim 16, characterized in that The target object (1) comprises a protective cap arranged at one of the distal ends and configured to protect the target object (1) from axial impact water droplets, wherein the protective cap comprises a drainage channel, wherein a cross section perpendicular to the arrangement axis (25) narrows from the one of the distal ends to the other distal end and the largest cross section perpendicular to the arrangement axis (25) is larger than the radial extension of the triangular prisms (4 to 11).

18. The target object (1) according to claim 17, characterized in that The protective cap has a truncated conical shape.

19. The target object (1) according to claim 17, characterized in that The protective cap (20, 21) has an air inlet (22) and an air outlet, and the air outlet is arranged from the one of the distal ends towards the other distal end, and the target object has a pneumatic nozzle configured to generate an air jet onto the light entry surface.

20. The target object (1) according to claim 19, characterized in that The exhaust port is configured to generate an air flow parallel to one of the light entry surfaces.

21. The target object (1) according to any one of claims 1 to 6, characterized in that The light entry surface is equipped with a hydrophobic optical coating.

22. The target object (1) according to any one of claims 17 to 20, characterized in that The protective cap (20) has an adapter for a GNSS antenna and / or a visual inertial system accessory.

23. The target object (1) according to any one of claims 17 to 20, characterized in that The protective cap (20) has an adapter for an automated target identifier.

24. The target object (1) according to any one of claims 17 to 20, characterized in that The protective cap (20, 21) has a target identifier configured to provide target object information about a prism type and / or a target ID of the target object.

25. The target object (1) according to claim 24, characterized in that The target object information is provided by defined optical properties of the target identifier and / or by means of a transmitted signal to be detected by the total station.

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