Retroreflector device

Abstract

Provided is a retroreflector device. Reflector device (1) for determining a position and / or for marking a target point having at least two retroreflective elements (10), each of the at least two retroreflective elements comprising a respective front boundary surface (11), which causes measurement light to enter the respective retroreflective element (10), and a respective rear boundary surface (12), which reflects the measurement light as reflected measurement light, the front boundary surface (11) and the rear boundary surface (12) are on opposite sides of the respective retroreflective element (10), and the respective optical axis (13) is defined by an arrangement of the front boundary surface and / or the rear boundary surface of the respective retroreflective element (10). The front and rear boundary surfaces of each of the at least two retroreflective elements have a curved shape, and for each of the at least two retroreflective elements, the angle of incidence of the measurement light with respect to its optical axis (13) is equal to the angle of emergence of the reflected measurement light with respect to its optical axis.

Description

Field of the Invention

[0001] The present invention generally relates to an optical device, preferably for the fields of industrial metrology or geodetic surveying, which provides retroreflection of received measurement light. Background Art

[0002] Surveying systems for determining positions in the field of geodetics or in the field of building or construction are known in different ways. An example thereof is a system consisting of a static surveying device having a direction determination unit and a distance meter (such as a total station) and a surveying aid instrument for marking points to be measured or characterized (such as poles). For example, prior art geodetic equipment is described in the published document EP1686350. Also known is a layout system consisting of static laser transmitters, which generate a position reference by means of laser beams, which can be received by a laser receiver at the point to be marked. Thus, surveying activities are performed by the interaction of static devices having known positions and thus providing position references with receiving or marking or calibratable surveying aid devices, so that the positions of individual terrain points (such as land survey points or points on construction site objects, for example in the interior or exterior areas of a building or in road construction) can be accurately determined for position measurement or staking-out.

[0003] Regarding the configuration of surveying devices, many different embodiments are known. For example, modern total stations have a microprocessor for digital post-processing and storage of the recorded measurement data. The devices usually have a compact and integrated design, and in the devices there are usually coaxial distance measurement elements as well as a calculation unit, a control unit and a storage unit. Depending on the development level of the total station, in the case of using a retroreflector (such as a full-circle prism) as the target object, a device for automatic target search and tracking can also be integrated. As a man-machine interface, a total station can include an electronic display / control unit - usually a microprocessor calculation unit having an electronic data storage device - having a display and an input device, such as a keyboard. The display / control unit is provided with the measurement data recorded by an electrical sensor, so that the position of the target point can be determined, optically displayed and stored by the display / control unit. A total station known from the prior art can also have a radio data interface for establishing a radio link to external peripheral components, such as a radio link to a surveying aid instrument or to a hand-held data recording device, which can be configured, for example, as a data recorder or a field computer.

[0004] To aim or align at a target point to be surveyed, a general type of geodetic surveying device includes a target telescope (e.g., an optical telescope) as the aiming device. The target telescope is typically rotatable relative to the base of the surveying device about a vertically upright axis and a horizontal tilt axis, such that the telescope can be aligned with the point to be measured by swivelling and tilting. In addition to the optical observation channel, modern devices can also include a camera for recording images integrated into the target telescope and, for example, co-axially or parallel-aligned. In this case, the recorded images can be represented as real-time images, in particular on the display of a display / control unit and / or on the display of a peripheral device (e.g., a data recorder for remote control).

[0005] As standard, current surveying devices now include an automatic target tracking function using a prism as a target reflector (ATR: "Automatic Target Recognition"). For this purpose, for example, another separate ATR light source and a special ATR detector sensitive to that wavelength (e.g., a CCD surface sensor, a CMOS image sensor (CIS, CMOS image sensor) or a SPAD array) are additionally integrated into the telescope.

[0006] In many geodetic surveying applications, point surveying is carried out by placing a specially configured surveying aid instrument or target object (e.g., a surveying rod) at the target point. This typically consists of a rod with a reflector (e.g., a full-circle prism or a 360-degree prism) for defining the survey path or survey point. For such surveying tasks, data, instructions, voice, and other information items are usually transmitted between the target object and the central surveying device in order to control the surveying process and establish or record survey parameters. Examples of such data are identification information items of the target object (examples from the type of prism used), the inclination of the rod, the height of the reflector above the ground, the reflector constant, or measured values (such as temperature or air pressure). These information or situation-contingent parameters are required in order to allow highly precise alignment and surveying of the survey point defined by the rod with the prism.

[0007] Furthermore, it is necessary to determine or adjust the spatial orientation or inclination of the relative relevant spatial direction with respect to the corresponding auxiliary instrument in a defined manner (e.g., vertically) in order to derive, together with the position of the reflector arranged on the auxiliary instrument that has been determined, the survey point to be determined by means of the instrument. This orientation can be determined, for example, by means of an inclination sensor provided at the determined position and placement relative to the reflector.

[0008] The use of an inclination sensor allows for simple position determination in two rotational degrees of freedom. In this way, the roll and pitch of a measuring aid instrument can be determined, i.e., the respective rotations about the corresponding horizontal axes.

[0009] Disadvantages of known surveying targets such as full-circle prisms are generally that these targets have a relatively heavy weight. This heavy weight is caused by the long-distance requirements of the retroreflectors. They enable 3D measurements to be carried out in the field from any direction within a yaw range of 360° and a pitch range of 60° at distances typically up to 300 m without adjusting the target orientation. To provide such characteristics, targets of this type usually consist of six glass corner cubes, which are polished by a high-precision machine and manually assembled, and thus are expensive to produce. Accordingly, the number of glass prisms (6 or 8) as well as the support structure for protecting against impacts also contribute to the relatively large weight.

[0010] Furthermore, for many use cases, a GNSS antenna needs to be mounted on top of the target, and the mechanical construction must be robust enough so that the pole can withstand the tipping of the GNSS antenna. To achieve this, 360° targets usually have large dimensions and are rather heavy. Another disadvantage of corner cubes is that the lateral aiming error of an ATR camera is relatively high due to the refraction effect and fly spots mainly caused by secondary reflections (instead of regular triple reflections) at the prism angles. The arrangement of six individual prisms also results in errors because the apparent positions of the prisms are not in the same point. This is due to the radial offset from the polar axis as well as the vertical offset between the upper and lower prism groups. Summary of the Invention

[0011] Accordingly, it is an object of the present invention to provide an improved reflector device that allows for reliable and robust measurements while avoiding the above-mentioned disadvantages.

[0012] Another object of the present invention is to provide an improved reflector device that provides improved retroreflective characteristics within a wide angular range (field of view) and has improved handling characteristics, particularly with regard to weight and mounting stability.

[0013] The present invention relates to a reflector device for determining the position of a target point and / or for marking a target point, particularly for industrial or geodetic surveys. The reflector device has at least two retroreflective elements, wherein each of the at least two retroreflective elements includes a respective front boundary surface and a respective rear boundary surface, the front boundary surface being configured to allow measurement light to enter the respective retroreflective element, and the rear boundary surface being configured to reflect the measurement light as reflected measurement light. The front boundary surface and the rear boundary surface are arranged on opposite sides of the respective retroreflective element. Furthermore, each of the at least two retroreflective elements includes a respective optical axis defined by the arrangement of the front boundary surface and / or the rear boundary surface of the respective retroreflective element.

[0014] The front boundary surface and the rear boundary surface of each of at least two retroreflective elements have a curved shape. In particular, the front boundary surface has a convex curvature with respect to the irradiation direction of the measurement light, and the rear boundary surface has a convex shape. In particular, the centers of curvature of the front boundary surface and the rear boundary surface are in the same position to provide a single-center optical design.

[0015] For each of at least two retroreflective elements, the incident angle of the measurement light with respect to its optical axis is equal to the exit angle of the reflected measurement light with respect to its optical axis. This means that the incident light is retroreflected (parallel).

[0016] Due to the possible offset between the incident measurement light and the reflected measurement light, the corresponding incident angle and exit angle at the curved front boundary surface may be different. However, the incident angle and the exit angle with respect to the reflector device are equal. In other words, the directions of the measurement light and the reflected light are exactly opposite.

[0017] The measurement light is preferably provided as a collimated laser, especially emitted by a measurement device (such as a surveying device (such as a total station or a laser scanner) or a metrology device (such as a laser tracker)). The laser can have a specific wavelength, for example, a wavelength in the visible spectrum VIS (e.g. 658 nm) or the infrared spectrum IR.

[0018] In one embodiment, the rear boundary surface can provide a coating to provide reflectivity. The coating can be a dielectric or a metal coating. The coating can be provided on the rear boundary surface of the retroreflective element.

[0019] In one embodiment, at least two of the retroreflective elements can be arranged in different orientations. In one embodiment, the reflector device can include a plurality of retroreflective elements, each retroreflective element being arranged to have a specific orientation different from the orientation of the other retroreflective elements. The orientation of the retroreflective element can preferably be defined by its optical axis and the facing direction of the reflected rear boundary surface.

[0020] In an embodiment, each of at least two retroreflective elements can be arranged in a specific orientation different from the orientation of the other retroreflective elements. Additionally or alternatively, the optical axes of each of at least two retroreflective elements are provided with different orientations.

[0021] In an alternative embodiment, at least two of the retroreflective elements can be arranged in the same orientation. This is especially the case when the reflector device has a cylindrical shape and the beads (retroreflective elements) are not tilted up or down.

[0022] In one embodiment, at least one of the retroreflective elements can be configured such that the measurement light entering the retroreflective element at the front boundary surface is focused on the rear boundary surface.

[0023] According to one embodiment, the front boundary surface and the rear boundary surface of at least one of the retroreflective elements may be spherical in shape. According to some embodiments, at least one of the boundary surfaces, the front boundary surface, and / or the rear boundary surface may be formed in a spherical, elliptical, parabolic, or hyperbolic shape.

[0024] According to an embodiment, at least one of the retroreflective elements may include a sphere having a refractive index n, where 1.9 < n < 2.1, particularly where n = 2 or n ~ 2 (n is approximately 2; n is a function of lambda λ). In particular, the sphere provides the front boundary surface and the rear boundary surface. The sphere may be made of an optical material that allows manipulation of the propagation of the measurement light such that the measurement light is focused onto the (inner) rear boundary surface by entering and passing through the sphere (e.g., by refraction).

[0025] In particular, the retroreflective element may be made of glass.

[0026] According to one embodiment, at least one of the retroreflective elements may include at least two optical elements, where the front boundary surface is provided by the first optical element of the at least two optical elements, and the rear boundary surface is provided by the second optical element of the at least two optical elements. In particular, each of the at least two optical elements may have a refractive index n, where n < 2.1.

[0027] In particular, the front boundary surface may include a radius of curvature different from that of the rear boundary surface. The radius of curvature of the front boundary surface may preferably be less than the radius of curvature of the rear boundary surface.

[0028] In one embodiment, each of the at least two optical elements may define a center point, particularly an optical or geometric center, and the at least two optical elements may be arranged such that the center points of the at least two optical elements coincide and provide a single center distance between the front boundary surface and the rear boundary surface. This single center design provides that the chief ray from any field angle travels through the same center point of the single center system. Thus, due to spherical symmetry, the focusing and retroreflective performance across the entire FOV is constant. The same focusing and retroreflective performance can be achieved with a larger aperture while the size can remain significantly smaller than a classical imaging lens.

[0029] In one embodiment, each of the at least two optical elements may be configured such that the center points of the at least two optical elements are set with a specific offset and the distance between the front boundary surface and the rear boundary surface is less than the single center distance. Thereby, an apochromatic retro-reflecting element for a specific measurement and illumination wavelength of the survey device can be provided.

[0030] According to one embodiment, the reflector device may include a carrier that bears at least two retroreflective elements. The at least two retroreflective elements are arranged at the carrier.

[0031] In particular, the carrier may include a central mount, and the at least two retroreflective elements may be arranged in different orientation directions, in particular, where the mount is provided by a rod extending through the carrier. The mount may preferably be designed to connect another component to the reflector device. In particular, the mount may be arranged (oriented) and configured to hold a GNSS antenna on top of the reflector device.

[0032] In one embodiment, the carrier may have a spherical or cylindrical shape and may include at least two recesses. Each recess may be configured to bear one retroreflective element, and a respective one of the retroreflective elements may be arranged at each recess. In particular, the carrier may include a plurality of recesses, and the recesses are distributed uniformly and / or equidistantly on the surface of the carrier (with respect to the surface of the carrier).

[0033] The carrier may be constructed in a lightweight design. The carrier may include, for example, a lightweight metal material such as aluminum, or may even be made of it. Using such a material to construct the carrier provides improved robustness and structural stability of the carrier and the entire reflector device. Thereby, the GNSS antenna can be relatively easily mounted on the carrier. In addition, due to the spatial extension of the carrier, the rod-shaped mount may be at least partially arranged inside the carrier, in particular extending throughout the carrier, in order to also provide for the mounting of the reflector device on, for example, a surveying pole.

[0034] The invention also relates to a retroreflective element for the above-described reflector device. The retroreflective element includes: a front boundary surface configured to allow measurement light to enter the retroreflective element; and a rear boundary surface configured to reflect the measurement light as reflected measurement light, where the front boundary surface and the rear boundary surface are arranged on opposite sides of the retroreflective element. The optical axis is defined by the arrangement of the front boundary surface and / or the rear boundary surface of the retroreflective element.

[0035] The front boundary surface and the rear boundary surface of the retroreflective element have a curved shape. The retroreflective element includes a mounting element arranged at the rear boundary surface and protruding from the rear boundary surface, and the mounting element provides for the mounting of the retroreflective element at the reflector device.

[0036] Such a design of the retroreflective element provides, for example, an efficient and precise arrangement of one or more such retroreflective elements at the carrier of the reflector device. Thus, the components of the reflector device can be manufactured separately and combined in a later step. In addition, in the case where one of the retroreflective elements is damaged, the corresponding element can be quickly replaced, and the accuracy of the reflector device can be restored.

[0037] In one embodiment, the mounting element may include a first end and a second end, wherein the first end includes a reflective surface facing away from the mounting element, the first end is attached to the rear boundary surface, and the reflective surface of the first end provides a reflected rear boundary surface. In particular, the second end is configured to be connected to a recess of the reflector device.

[0038] For example, a pin (mounting element) may have a reflective concave spherical shape at one end. The pin may be fixed to the optical element of the retroreflective element with an optically transparent adhesive, and the optical element provides the rear boundary surface. In particular, the optical element is embodied as a sphere, such as an N2 sphere.

[0039] The present invention also relates to a method of providing a reflector device. The method includes providing at least one retroreflective element including a front boundary surface configured to allow measurement light to enter the retroreflective element, a rear boundary surface configured to reflect the measurement light as reflected measurement light, and a mounting element disposed at and protruding from the rear boundary surface, wherein the front boundary surface and the rear boundary surface are disposed on opposite sides of the retroreflective element.

[0040] The method further includes providing a carrier having at least one recess for carrying at least one retroreflective element, wherein the recess is configured to receive the mounting element of the retroreflective element, and arranging a plurality of retroreflective elements corresponding to the number of recesses at the carrier by inserting each mounting element of the retroreflective element into a corresponding recess.

[0041] In one embodiment, at least two recesses may be provided such that each recess includes a specific orientation different from the orientation of the other recesses, wherein the orientation of the recess is defined by an insertion axis and an opening of the corresponding recess. Providing recesses with specific orientations provides relatively easy assembly of the reflector device because no additional alignment of individual reflective elements is required.

[0042] The mounting element may be provided by a post, a pin, a bolt, a rod, etc. In one embodiment, the mounting element may include a reflective end face as described above.

[0043] In one embodiment, the method includes: providing a mounting plate including at least one recess; providing an optically transparent bead in the recess, in particular an optically transparent bead that is optically transparent with respect to a wavelength range associated with a specific measurement light; providing a sealing cap on the optically transparent bead to define a surface area of the bead to be coated; and applying a reflective coating on the bead and thereby providing a coated bead. Further, the method includes: providing a guiding plate having a guiding member on the coated bead, wherein the guiding plate and the mounting plate are arranged such that the guiding member is centeredly arranged with respect to the coated surface area of the coated bead; providing a mounting element in the guiding member such that the mounting element contacts the coated bead; applying an adhesive at the mounting element and at the coated bead to provide a connection between the mounting element and the coated bead and providing a retroreflective element through this connection.

[0044] By manufacturing a retroreflective element according to the above method, an initial non-reflective element can be processed (i.e., coated) to provide a reflective element. The initial element is selected with respect to material, dimensions, and shape such that the coating has provided a retroreflective element. Further, the method also provides for precisely connecting and orienting the mounting element with respect to the coated area of the retroreflective element. In particular, the mounting element is connected and oriented such that the extension of the mounting element is parallel to the optical axis of the retroreflective element. The mounting element is preferably arranged on the rear boundary surface and points away from the coated area.

[0045] The invention also relates to a reflector device for determining a position and / or for marking a target point, in particular for industrial or geodetic surveys, which reflector device is obtained by performing the above method. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The various aspects of the invention are described or explained in more detail below only by way of example with reference to working examples schematically shown in the drawings. Identical elements are marked with the same reference numerals in the figures. The described embodiments are generally not shown to scale and they should not be construed as limiting the invention. Specifically,

[0047] Figure 1 : shows a geodetic surveying system having a reflector device according to the invention;

[0048] Figure 2 : shows an exemplary embodiment of a reflector device according to the invention;

[0049] Figures 3a to 3b : shows a further exemplary embodiment of a reflector device according to the invention;

[0050] Figures 4a to 4b : shows an embodiment of a retroreflective element of a reflector device according to the invention;

[0051] Figures 5a to 5c: A method for adjusting the optical properties of a retroreflective element of a reflector device according to the present invention is shown;

[0052] Figures 6a to 6b : A method for adjusting the optical properties of a retroreflective element of a reflector device according to the present invention is shown; and

[0053] Figures 7a to 7c : A method for assembling a reflector device according to the present invention is shown. Detailed Description

[0054] Figure 1 A surveying device 50 is shown, particularly configured as a total station or multi-station. The surveying device has a base, a support unit, and a sighting unit. The support unit can rotate relative to the base about a vertical rotation axis, and the sighting unit can rotate about a horizontal axis and rotate about the vertical axis by means of the support unit. A measuring laser beam 21 (measurement light) is emitted from the sighting unit and impinges on a reflector device 1 of a measuring aid instrument 51 configured as a rod. Generally, (collimated) laser radiation generated by a laser diode or a gas laser provided on the surveying device 50 is used as the measurement light 21. The reflector device 1 is constructed as a retroreflector and is shown and described in more detail below.

[0055] For distance measurement, the measurement light 21 is reflected back parallel by the retroreflector, recorded by the surveying device 50, and evaluated for distance information, for example, by means of time-of-flight measurement. The position of the measuring aid instrument 51 can be determined by determining the angular setting of the sighting unit (i.e., the emission direction of the laser 21).

[0056] The reflector device 1 of the measuring aid instrument 51 includes a plurality of retroreflective elements, each of which includes a curved front boundary surface and a reflectively coated rear boundary surface, and the incident angle of the measurement light 21 relative to its optical axis is equal to the exit angle of the reflected measurement light relative to its optical axis. The retroreflective elements are arranged in different orientations. Thereby, a retroreflector providing a 360° (horizontal) angular range of retroreflection 52 (similar to a field of view) can be provided around a yaw axis 5 (carrier axis). In addition, a relatively large angular range of retroreflection 53 (retroreflective field) is provided around a pitch axis (orthogonal to the yaw axis 5). This also provides a great advantage for some usage cases where there is a large height difference between the target (including the reflector device) and the surveying equipment.

[0057] Figure 2 An exemplary embodiment of the reflector device 1 according to the present invention is shown. The reflector device 1 is partially shown and shown in a cross-sectional view.

[0058] The reflector device 1 includes a plurality of retroreflective elements 10. Each retroreflective element 10 includes a front boundary surface 11 (exemplarily shown only for one of the retroreflective elements), which is configured and oriented to allow measurement light to enter the corresponding retroreflective element 10. In addition, each retroreflective element 10 includes a corresponding rear boundary surface 12, which is configured to reflect the measurement light as reflected measurement light. The front boundary surface 11 and the rear boundary surface 12 are arranged on opposite sides of the retroreflective element 10.

[0059] Each retroreflective element 10 defines an optical axis 13 through its front boundary surface 11 and rear boundary surface 12. In particular, the optical axis 13 intersects the center point of the retroreflective element 10 and the center point of the rear boundary surface 12. The center point of the rear boundary surface 12 is preferably defined by the center point of the reflective coating area representing the rear boundary surface 12.

[0060] In another embodiment, the back side of the retroreflective element is not coated, but the reflectivity can be provided by an alternative solution, for example, the reflective inner surface of a recess of a mounting element or carrier attached to the reflective end of the retroreflective element.

[0061] The front boundary surface 11 and the rear boundary surface 12 are curved. According to the illustrated embodiment, the retroreflective element 10 is designed as a sphere, where the reflective coating is arranged on one side of the sphere, and the opposite two sides are optically transparent for measuring light of a specific wavelength or wavelength range.

[0062] The retroreflective element 10 is also configured such that the incident angle of the measurement light with respect to the optical axis 13 is equal to the exit angle of the reflected measurement light with respect to the optical axis 13, that is, the measurement light is retroreflected.

[0063] In addition, the reflector device 1 includes a carrier 2. The retroreflective elements 10 are mounted on the carrier 2, where each retroreflective element 10 provides a specific orientation different from that of the other retroreflective elements 10.

[0064] In the illustrated embodiment, the carrier 2 provides a spherical shape, and the retroreflective elements 10 are evenly and / or equidistantly distributed on the surface of the carrier 2. As shown, the retroreflective elements 10 are arranged such that the rear boundary surface 12 of the elements 10 faces the center of the spherical carrier 2, and the front boundary surface 11 points away from the carrier 2. In particular, the retroreflective elements 10 are arranged such that their optical axes 13 intersect in a common intersection region (for example, with a spatial tolerance of about 2 mm) or point, where the intersection point coincides with the center point of the carrier 2.

[0065] One benefit of this embodiment is that since the center of gravity of the signal (associated with the ATR camera image) remains centered as the carrier 2 rotates, the lateral measurement can become independent of pitch. This can be particularly advantageous compared to a cylindrical arrangement where the signal can move up / down, since all spheres reflect with the same intensity and are offset from the pole axis.

[0066] The carrier 2 also includes a central mount 3. The mount 3 can preferably be arranged such that additional survey elements (e.g., GNSS or GNSS antennas) can be mounted on top of the carrier 2.

[0067] The carrier can include or can be made of a metal-containing material, particularly an aluminum-based material. Thereby, the carrier 2 can provide structural robustness and stability as well as a relatively low weight. By using aluminum, the mechanical structure of the carrier can be designed in such a way that the total weight is lower than that of a conventional prism, where most of the volume is occupied by a large amount of glass.

[0068] The mount 3 can be attached on top of the carrier 2 or can extend into the internal volume of the carrier 2, particularly through the entire carrier.

[0069] The design of the reflector device 1 provides retroreflection of the measurement light over a wide angular range, particularly more than 360° (yaw angle) around the carrier axis 5 (yaw axis) and more than 180° around the pitch axis 6, the pitch axis 6 being orthogonally oriented with respect to the carrier axis 5.

[0070] The retroreflection of the measurement light is provided by at least one of the retroreflective elements 10. In particular, the retroreflection of the measurement light can be provided simultaneously by at least two or more retroreflective elements 10. The number of retroreflective elements 10 and / or which retroreflective element provides the reflection depends on the incident angle of the measurement light relative to the reflector device 1 (particularly also on the offset). In other words, when the incident angle of the measurement light changes, the retroreflective elements 10 that contribute to total retroreflection also change.

[0071] The idea of the reflector device 1 (hereinafter also: bead reflector) is to arrange at least two, preferably a plurality of beads (retroreflective elements 10) in a spherical layout to cover a sufficient angular range (FOV), particularly at least close to 4π steradians. The FOV of each bead is designed to be large enough to overlap with sufficiently neighboring beads. Compared to a typical corner cube prism retroreflector, the retroreflection mechanism here is based on refraction rather than reflection. The incident light can be focused on the rear surface of each bead and reflected back to the receiver. Each bead can act like an afocal imaging lens. Its aberration is preferably selected to be as small as possible over the entire FOV to achieve a constant bright signal independent of the reflector orientation. In other words, each bead provides a large aperture, a large FOV, consistently good imaging performance, and at the same time small size and weight.

[0072] Figure 3a and Figure 3b shows two further embodiments of the reflector device 1 according to the present invention.

[0073] Figure 3a Shows a reflector device 1 having a carrier 2, wherein the carrier provides a cylindrical shape. A plurality of retroreflective elements 10 are arranged at the carrier 2. The retroreflective elements 10 are arranged in different orientations such that the measurement light directed at the reflector device 1 is retroreflected over a wide field of view.

[0074] The specific design of the reflector device 1 provides a retroreflection of more than 360° around the carrier axis 5. In addition, due to the orientation of the retroreflective elements 10, the range of (sufficient) retroreflection around the pitch axis 6 remains relatively large, i.e., retroreflection can be provided up to 120° (±60°) or even up to 140° (±70°).

[0075] In an alternative embodiment, the retroreflective elements 10 are oriented along the normal of the cylindrical surface, i.e., not tilted up / down. This can provide easier manufacturing of the components and / or a stronger signal at normal incidence, while still providing a sufficient FOV since each bead has a large angular range.

[0076] Figure 3b Shows a reflector device 1 having a carrier 2, wherein the carrier provides a spherical shape. A plurality of retroreflective elements 10 are arranged at the carrier 2. The retroreflective elements 10 are arranged in different orientations such that the measurement light directed at the reflector device 1 is retroreflected over a wide field of view.

[0077] and Figure 3a Compared with the design of the reflector device 1 of , the total reflection range related to the pitch axis and yaw axis can be further expanded here. Due to the spherical shape, the retroreflective elements 10 can be oriented over a wider range related to the pitch angle. In particular, in the upper and lower regions of the carrier 2, the retroreflective elements 10 can even be oriented straight up and / or straight down, i.e., having an orientation angle of +90° or -90° related to the pitch axis 6.

[0078] In addition, the design of the spherical carrier 2 provides an advantageous manufacturing method, wherein each retroreflective element 10 can be oriented such that its corresponding optical axis is coaxial with the surface normal defined by the surface area where the retroreflective element 10 is arranged. The spherical shape allows for effectively providing recesses for respectively mounting the retroreflective elements 10, for example, by drilling (orthogonally) in the carrier.

[0079] In an alternative embodiment (not shown), the reflector device 1 with the carrier 2 can provide a non-uniform arrangement of a plurality of retroreflective elements 10 (beads) on the carrier 2. Thereby, retroreflection over a wide angular range can still be provided (as described above). In addition, such a non-uniform (but known) distribution of the retroreflective elements 10 can also be used to determine the orientation of the reflector device 1.

[0080] For example, an image of the reflector device 1 (irradiated and thus reflected) can be captured, and thereby the reflections of a set of retroreflective elements 10 can be imaged. The image can be processed, and the pattern of the reflections can be determined based on the image. Due to the non-uniform arrangement of the retroreflective elements 10, such a pattern can be uniquely assigned to the set of retroreflective elements 10 (which are arranged at the carrier 2 in the corresponding pattern respectively). As a result, the orientation of the reflector device 1 can be derived based on the shape and / or orientation of the pattern in the image.

[0081] In addition, the specific intensity of the reflections can be taken into account during the image processing to derive the detected set of retroreflective elements 10.

[0082] The retroreflective elements 10 can also be designed to provide different and / or individual reflectivities. Such a variation in reflectivity can be detected and resolved (in the image by image processing). Therefore, the orientation of the reflector device 1 can also be derived based on the pattern of the reflectivities.

[0083] The above method for determining the orientation of the reflector device 1 can preferably be applied, and the surveying device measures distances up to about 50 m. Here, an ATR of the focusing surveying device can be provided to resolve the retroreflective elements 10.

[0084] Figure 4a and Figure 4b Two embodiments of the bead-shaped retroreflective elements 10 of the reflector device according to the invention are shown.

[0085] Figure 4a An embodiment of the retroreflective element 10 with a front boundary surface 11 and a rear boundary surface 12 is shown. The retroreflective element 10 has a spherical shape, in particular, the retroreflective element 10 is constructed as a sphere.

[0086] The retroreflective element 10 is provided as a spherical lens with a refractive index of at least close to 2. By fine-tuning the refractive index, the position of the focal plane can be adjusted for the wavelength. The sphere radius can be freely selected because the focal plane always coincides with the sphere surface, regardless of the sphere radius. Therefore, the spherical lens can have an angular range of retroreflectivity (field of view (FOV)) of ±90 degrees.

[0087] In the shown embodiment, the rear boundary surface 12 of the reflection is coated with a metal coating. In particular, the coating covers the hemisphere. The coating provides a reflectivity of at least 95% within an angular range close to 2π steradians.

[0088] Beneficial properties of the bead retroreflective element 10 are, for example, a large aperture, a large FOV, good imaging performance, and at the same time small size and weight, which can be provided by the given single-center design of the retroreflective element 10. The single-center design is characterized in that all its components (including the aperture, the lens, and the image plane) are symmetrically shaped and positioned relative to a single center point where the aperture is virtually located. The chief ray from any field angle travels through the same center point of the single-center system. Due to the spherical symmetry, the imaging performance over the entire FOV can be constant. According to the present invention, these properties are provided by a single optical lens having two optical surfaces.

[0089] Measurement light 21 emitted by a surveying device such as a total station or a rangefinder can be provided, for example, to enter the bead 10 at the front surface 11. The measurement light 21 is focused onto the rear boundary surface 12 and is reflected back as reflected measurement light 22. The incident angles of the incident measurement light 21 and the reflected measurement light 22 with respect to the optical axis 13 of the bead 10 are the same.

[0090] Figure 4b Another embodiment of the retroreflective element 10 having a front boundary surface 11 and a rear boundary surface 12 is shown. Here, the retroreflective element 10 has an elongated shape.

[0091] The elongated retroreflective element 10 has two spherical surfaces, namely, the front boundary surface 11 and the rear boundary surface 12, having different radii. The radius 11a of the front boundary surface 11 is smaller than the radius 12a of the rear boundary surface 12.

[0092] The centers of curvature of the two surfaces 11 and 12 are in the same position, so the design is also single-center. The radius of the rear surface 12 is correspondingly adapted to the refractive index of the optical material and the radius of curvature of the front surface such that the focal plane coincides with the rear surface 12. Therefore, the choice of refractive index is flexible so that any type of plastic and glass material can be used. The refractive index is preferably chosen to be less than 2.

[0093] Thereby, the retroreflective element 10 can be manufactured more easily and efficiently. Glass and plastic molding are preferred techniques instead of classical grinding and polishing (e.g., PGM, precision glass molding).

[0094] Figures 5a to 5c A method is shown of how to adjust the optical properties of the retroreflective element 10 according to the present invention to meet specific properties required for use with a surveying device.

[0095] Surveying equipment such as total stations can provide three optical subsystems (EDM, ATR, and power search) operating at three different wavelengths (e.g., 658 nm, 785 nm, and 850 nm). To achieve consistently good radiometric measurements over a spectral range of approximately 200 nm, the configuration of the retroreflective element 10 can be specifically adjusted to overcome negative effects caused, for example, by the dispersion of the manufacturing material.

[0096] The radiation response to wavelength changes is asymmetric. The radiometric measurement towards longer wavelengths decreases significantly more slowly than when moving in the opposite direction (see Figure 5a ). When moving in the slowly changing direction, after reflection over a wide spectral range of several hundred nanometers, the radiometric measurement remains at approximately 20% of the total power on the detector.

[0097] Based on this finding, it is proposed to design the achromatic bead 10 by shifting the response curve in such a way that the three relevant wavelengths are located to the right of the peak position.

[0098] According to the present invention, the elongated retroreflective element 10 is designed such that a negative thickness offset is introduced for the bead design. In other words, the regular distance between the front boundary surface 11 and the rear boundary surface 12 (as Figure 4b shown) is reduced (see Figure 5b ).

[0099] As a result, the power distribution at the detector is shifted relative to the measurement wavelength such that for each wavelength, the power at the detector is at least 10% - 20% of the detectable peak power (see Figure 5c ).

[0100] Figures 6a to 6b Another method is shown of how to adjust the optical properties of the retroreflective element 10 according to the present invention to meet specific characteristics required for use with surveying equipment.

[0101] Here, the retroreflective element is constructed as a sphere or bead (as Figure 4a shown). It has been found that to meet the optical surveying characteristics, the retroreflective element 10 should preferably be configured as a spherical lens made of an optical material with an adjusted refractive index. The retroreflective characteristics of the retroreflective element 10 directly depend on the refractive index.

[0102] From Figure 6a it can be seen that after reflection at a sphere with a refractive index of approximately 2.022, the total power of the measurement light with a wavelength of 658 nm approaches zero. Therefore, for example, the measurement light of a total station used to determine the distance to a reflector (with a wavelength of 658 nm) will be reflected with insufficient intensity. By changing the optical material of the bead and changing the refractive index, a solution to this problem has been found.

[0103] Thus, the retroreflective element 10 can be made of a material with a slightly different refractive index provided as 2.0033. Thereby, the reflection characteristics of the retroreflective element 10 are shifted such that sufficient power can be provided at the detection unit after reflection at the bead 10 to reflect all three relevant wavelength regions. For example, by selecting glass with a refractive index n = 2.0033, the thickness variation (diameter variation of the sphere) of the bead design has no influence on the wavelength dependence. This is an advantage of being spherical compared to designs with different radii.

[0104] The corresponding tuning of the refractive index of the material may be the result of the spherical aberration effect. For a finite range of the angle of incidence / offset with respect to the optical axis of the bead, the reflected ray 22 can be only parallel to the incident measurement light 21. For example, for a wavelength of n = 2, the rays close to the bead center are retroreflected, but for longer wavelengths, the refractive index becomes n < 2, and retroreflection occurs at a larger offset, where the spherical aberration adds additional refractive power. At shorter wavelengths with n > 2, the retroreflection effect disappears.

[0105] Figures 7a to 7c A method of manufacturing a reflector device 1 having a plurality of retroreflective elements 10 according to the present invention is shown. First, the retroreflective element 10 must be manufactured to provide sufficient retroreflection, and in the next step, the retroreflective element must be arranged at the reflector device 1 with a specific orientation.

[0106] A mounting plate 31 is provided. The plate 31 includes at least one recess, and an optically transparent bead 32 is arranged in the recess. Here, optically transparent refers to the wavelength range related to the specific measurement light of the above surveying device. Next, a sealing cover 33 is placed on the optically transparent bead 32 to define the surface area of the bead to be coated. The sealing cover 33 includes a seal 34 or a spacer ring, such as an O-ring, etc., which contacts the bead 32 and thereby separates a part of the bead 32 (see Figure 7a ).

[0107] This arrangement coats the sealed area by applying a reflective (mirror) coating. The coating can be applied by spraying, painting, or other deposition techniques. In particular, the coating is then dried or cured. The coated retroreflective element 10 is produced by this process.

[0108] In the next step, a guide plate 35 with a guide 36 is set on the coated bead 10, wherein the guide plate 35 and the mounting plate 31 are arranged such that the guide 36 is arranged centrally with respect to the coated surface area of the bead 10.

[0109] The basic step is to bond the guide post 37 (mounting element) directly in a single step after coating the bead. Thus, the post 37 is set in the guide 36 such that the post 37 contacts the coated bead 10. Instead of the post, bolts or pins, etc. can also be used.

[0110] Apply an adhesive (e.g., glue) such that it covers at least a portion of the post and at least a portion of the coated bead 10 to provide a connection between the post 37 and the coated bead 10 (see Figure 7b ). For example, if the post is provided as a hollow guide post, it can be centered and glued on top of the coating area, and the adhesive can be applied through the holes of the post 37.

[0111] By avoiding any active alignment of the coated bead and / or the post, a cost-effective, scalable, precise, and robust assembly concept can be provided.

[0112] As described above, the alignment accuracy between the post axis and the coating area is ensured by the precisely positioned guide plate 33. As Figure 7c shown, the connected guide post 37 allows for effortless and automatic assembly of the coated ball lens 10 in the bead carrier 2. This process can be carried out and parallelized by using state-of-the-art machine automation and / or robotics to achieve high volume and high throughput.

[0113] The retroreflective element 10 with the glued post can be easily arranged at the carrier 2 of the reflector device 1. For this purpose, the carrier can include a number of recesses 38, where each recess 38 is configured to carry one retroreflective element 10 (see Figure 7c ). Such an assembly can ensure the desired distribution of the retroreflective elements 10 above the carrier 2 by the corresponding arrangement of the recesses 38. In addition, due to the individual configuration of the retroreflective elements 10, the desired orientation of each of these elements 10 can also be provided in a reliable and robust manner.

[0114] Although the above part illustrates the present invention with reference to some preferred embodiments, it must be understood that many modifications and combinations of different features of the embodiments can be made. All such modifications are within the scope of the appended claims.

Claims

1. A reflector device (1) for determining a position and / or for marking a target point, the reflector device being used in particular for industrial or geodetic surveying, the reflector device having at least two retroreflective elements (10), wherein: Each of the at least two retroreflective elements (10) comprises a respective front boundary surface (11) and a respective rear boundary surface (12), wherein the respective front boundary surface is configured to allow measurement light (21) to enter the respective retroreflective element (10), and the respective rear boundary surface is configured to reflect the measurement light into reflected measurement light (22), wherein the front boundary surface (11) and the rear boundary surface (12) are arranged on opposite sides of the respective retroreflective element (10), and a respective optical axis (13), the respective optical axis being defined by the arrangement of the front boundary surface (11) and / or the rear boundary surface (12) of the respective retroreflective element (10), Features The front boundary surface (11) and the rear boundary surface (12) of each of the at least two retroreflective elements (10) are curved, and For each of the at least two retroreflective elements (10), an incident angle of the measuring light (21) relative to its optical axis (13) is equal to an exit angle of the reflected measuring light (22) relative to its optical axis (13).

2. The reflector device (1) according to claim 1, Features At least two of the at least two retroreflective elements (10) are arranged in different orientations, in particular, each of the at least two retroreflective elements (10) is arranged in a specific orientation that is different from the orientation of the other retroreflective elements (10), and / or The reflector device (1) comprises a plurality of retroreflective elements, each retroreflective element being arranged in a specific orientation different from the orientations of the other retroreflective elements, and / or The optical axis (13) of each of the at least two retroreflective elements (10) is provided with a different orientation.

3. The reflector device (1) according to any one of the preceding claims, Features At least one of the retroreflective elements (10) is configured such that the measuring light (21) entering the retroreflective element (10) at the front boundary surface (11) is focused on the rear boundary surface (12).

4. The reflector device (1) according to any one of the preceding claims, Features The front boundary surface (11) of at least one of the at least two retroreflective elements (10) and said rear boundary surface (12) is spherical in shape, and / or At least one of the at least two retroreflective elements (10) comprises a sphere having a refractive index n of 1.9<n<2.1, in particular wherein n=2.

5. The reflector device (1) according to any one of the preceding claims, Features At least one of the at least two retroreflective elements (10) comprises at least two optical elements, wherein the front boundary surface (11) is provided by a first optical element of the at least two optical elements and the rear boundary surface (12) is provided by a second optical element of the at least two optical elements, in particular wherein each of the at least two optical elements has a refractive index n, n<2.

1.

6. The reflector device (1) according to claim 5, Features The front boundary surface (11) comprises a radius of curvature that is different from the radius of curvature of the rear boundary surface (12), in particular wherein the radius of curvature of the front boundary surface is smaller than the radius of curvature of the rear boundary surface.

7. The reflector device (1) according to claim 5 or 6, Features Each of the at least two optical elements (10) has a center point, and the at least two optical elements (10) are arranged such that The center points of the at least two optical elements (10) coincide with each other, and the front boundary surface (11) and the rear boundary surface (12) have a single center distance therebetween, or The center points of the at least two optical elements (10) are provided with a certain offset, and the distance between the front boundary surface (11) and the rear boundary surface (12) is smaller than the single center distance.

8. The reflector device (1) according to any one of the preceding claims, Features The reflector device (1) comprises a carrier (2) carrying the at least two retroreflective elements (10), and the at least two retroreflective elements are arranged on the carrier.

9. The reflector device (1) according to claim 8, Features The carrier (2) comprises a central mounting (3) and the at least two retroreflective elements (10) are arranged in different orientation directions, in particular wherein the mounting (3) is provided by a rod extending through the carrier (2).

10. The reflector device (1) according to claim 8 or 9, Features The carrier (2) comprises a spherical or cylindrical shape and at least two recesses (38), wherein Each recess (38) is configured to carry a retroreflective element (10), and A corresponding retroreflective element (10) is arranged at each recess (38), In particular, The carrier (2) comprises a plurality of recesses (38), and the recesses are evenly and / or equidistantly distributed with respect to the surface of the carrier (2).

11. A retroreflective element (10) for use in a reflector device (1) according to any one of the preceding claims, the retroreflective element (10) comprising a front boundary surface (11) and a rear boundary surface (12), the front boundary surface being configured to allow measurement light (21) to enter the retroreflective element (10), and the rear boundary surface being configured to reflect the measurement light into reflected measurement light (22), wherein The front boundary surface (11) and the rear boundary surface (12) are arranged on opposite sides of the retroreflective element (10), and an optical axis (13), the optical axis being defined by the arrangement of the front boundary surface (11) and / or the rear boundary surface (12) of the retroreflective element (10), Features The front boundary surface (11) and the rear boundary surface (12) of the retroreflective element (10) are curved, and The retroreflective element (10) comprises a mounting element (37) arranged at the rear boundary surface (12) and protruding from the rear boundary surface (12), the mounting element (37) providing mounting of the retroreflective element (10) at the reflector device (1).

12. The retroreflective element (10) according to claim 11, Features The mounting element (37) comprises a first end and a second end, wherein The first end includes a reflective surface facing away from the mounting element (37), The first end is attached to the rear boundary surface (12); and The reflective surface of the first end provides the reflective rear boundary surface (12), In particular, the second end is configured to be connected to a recessed portion of the reflector device (1).

13. A method for providing a reflector device (1), the method comprising: At least one retroreflective element (10) is provided, the retroreflective element (10) comprising: a front boundary surface (11) configured to allow measurement light (21) to enter the retroreflective element (10), a rear boundary surface (12) configured to reflect the measurement light as reflected measurement light (22), wherein the front boundary surface (11) and the rear boundary surface (12) are arranged on opposite sides of the retroreflective element (10), and a mounting element (37) arranged at the rear boundary surface (12) and protruding from the rear boundary surface, providing a carrier (2) having at least one recess (38) carrying the at least one retroreflective element (10), wherein the at least one recess (38) is configured to accommodate the mounting element (37) of the retroreflective element (10), and Arranging a plurality of retroreflective elements (10) corresponding to a plurality of the recesses (38) on the carrier (2) by inserting each mounting element (37) of the retroreflective element into a corresponding recess (38), In particular, at least two recesses are provided such that each recess comprises a specific orientation that is different from the orientations of the other recesses, wherein said orientation of the recesses is defined by the insertion axis and the opening of the respective recess.

14. The method according to claim 13, Features The method comprises: providing a mounting plate (31) comprising at least one recess, providing an optically transparent bead (32) in the recess, in particular optically transparent with respect to a wavelength range relevant for the specific measurement light, providing a sealing cover (33) on the optically transparent bead (32) to define the surface area of ​​the bead to be coated, applying a reflective coating to the optically transparent beads (32), thereby providing coated beads, providing a guide plate (35) having a guide (35) on the coated bead, wherein the guide plate (35) and the mounting plate (31) are arranged such that the guide (35) is centrally arranged relative to the coated surface area of ​​the coated bead, placing the mounting element (37) in the guide (35) such that the mounting element (37) contacts the coated bead, Adhesive is applied at the mounting element (37) and the coated bead to provide a connection between the mounting element (37) and the coated bead, and the retroreflective element (10) is provided through the connection.

15. A reflector device for determining a position and / or for marking a target point, in particular for industrial or geodetic surveying, obtained by carrying out the method according to claim 13 or 14.

Images