EP4643094A1

EP4643094A1 - Reflective target

Info

Publication number: EP4643094A1
Application number: EP23838104.0A
Authority: EP
Inventors: Andreas Winter
Original assignee: Hilti AG
Current assignee: Hilti AG
Priority date: 2022-12-31
Filing date: 2023-12-22
Publication date: 2025-11-05
Also published as: EP4394318A1; WO2024141500A1

Abstract

Reflective target (150) configured to be used in measuring and surveying applications, comprising a base element (151) having a central axis (152), and a prism section (153) including a plurality of corner cube prisms (154) having light entrance surfaces, wherein the corner cube prisms (154) are arranged around the central axis (152) in a circumferential direction (155) and configured to reflect light beams of a range of wavelengths. The target (150) further comprises a cat-eye section (156) including a plurality of cat-eyes (157) arranged around the central axis (152) in the circumferential direction (155), wherein the cat-eyes (157) are configured to reflect light beams of a first range of wavelengths and formed by a plurality of prism elements having light entrance surfaces.

Description

Reflective target

The present invention relates to a reflective target according to the definition of claim 1.

Background of the invention

Reflective targets are widely used in measuring and surveying applications, such as in the construction sector. A reflective target may be applied to a landmark or a position of interest and aimed at using a laser instrument, such as a theodolite or robotic total station, having a light emitting element for emitting light such as laser light along an optical axis towards the reflective target. The laser instrument includes an optical arrangement for receiving the reflected light from the reflective target. Based on the reflected light the laser instrument may be accurately oriented towards the target.

US 6,185,055 B1 discloses a known reflective target configured to be used in measuring and surveying applications. The target comprises a base element having a central axis, and a prism section including a plurality of corner cube prisms. The corner cube prisms are arranged around the central axis in a circumferential direction and configured to reflect light beams of a range of wavelengths. The disadvantage of the reflective target known from US 6,185,055 B1 is that an identification of the target during tracking is not supported.

Summary of the invention

Therefore, what is desired is a reflective target that supports the identification of the target during tracking. What is also desired is to support the identification of a passive target.

These objects are achieved by realizing the features of the independent claim. Features which further develop the invention in an advantageous manner are described in the dependent claims.

According to an aspect of the present invention, there is provided a reflective target configured to be used in measuring and/or surveying applications. The target further comprises a cat-eye section including a plurality of cat-eyes arranged around the central axis in the circumferential direction, wherein the cat-eyes are configured to reflect light beams of a first range of wavelengths and formed by a plurality of prism elements having light entrance surfaces.

The target according to the invention comprises a prism section including a plurality of corner cube prisms and a cat-eye section including a plurality of cat-eyes. The optical properties of the corner cube prisms (prism section) differ from the cat-eyes (cat-eye section). The cat-eye section supports the identification of the target during tracking.

Preferably, the target further comprises a further cat-eye section including a plurality of further cat-eyes arranged around the central axis in the circumferential direction, wherein the further cat-eyes are configured to reflect light beams of a second range of wavelengths and formed by a plurality of further prism elements having further light entrance surfaces, wherein the cat-eye section is arranged at a first height level of the target and the further cat-eye section is arranged at a second height level of the target, the second height level being different from the first height level. By using a target that includes a cat-eye section with a plurality of cat-eyes and a further cat-eye section with a plurality of further cat-eyes, the target can be easily distinguished during tracking from reflecting surfaces or other targets. The combination of two cat-eye sections which are configured to reflect different wavelength allows to identify the target in an image captured by a total station and showing different colored reflexes.

Preferably, the target further comprises a foil section including a reflective foil arranged around the central axis in the circumferential direction, the reflective foil being formed by multiple prisms. The foil section with the reflective foil supports measuring of distances between a laser instrument and the target.

Preferably, the foil section is arranged between the cat-eye section and the further cat-eye section. By using a target that includes a cat-eye section with a plurality of cat-eyes, a further cat-eye section with a plurality of further cat-eyes, and a foil section between the cat-eye sections, the target can be easily distinguished during tracking from reflecting surfaces or other targets. The foil section arranged between the two cat-eye sections separates the cat-eye sections and allows to identify the different colored reflexes in an image captured by a total station.

Preferably, the target further comprises a further prism section including a plurality of further corner cube prisms having light entrance surfaces, wherein the further corner cube prisms are arranged around the central axis in the circumferential direction. The further corner cube prisms of the further prism section may have the same optical properties as the corner cube prisms of the prism section. Using a target having two prism sections can reduce the effort of searching a target during tracking. Preferably, the prism section and the further prism section are arranged at different height levels of the target in the length direction of the target. The prism section may be arranged at a first height level of the target and the further prism section may be arranged at a second height level of the target, the second height level being different from the first height level.

In a preferred embodiment, the cat-eyes of the cat-eye section and/or the further cat-eyes of the further cat-eye section are formed as planar cat-eyes.

In a preferred embodiment, the cat-eyes of the cat-eye section are formed as planar cateyes, and the corner cube prisms of the prism section are arranged in the planar cat-eyes in such a way that the light entrance surfaces are parallel to the cat-eyes.

Brief Description of the drawings

The aspects of the invention are described or explained in more detail below, purely by way of example, with reference to working examples shown schematically in the drawing. Identical elements are labelled with the same reference numerals in the figures. The described embodiments are generally not shown true in scale, and they are also not to be interpreted as limiting the invention. Specifically,

FIG. 1 shows a system for measuring and surveying comprising a reflective target according to the present invention, a laser instrument, and a supervisory device, which is integrated in a remote controller,

FIGS. 2A, B show an exemplary version of the laser instrument used in the system of FIG. 1 (FIG. 2A) and a block diagram of the main components of the laser instrument as illustrated in FIG. 2A (FIG. 2B),

FIGS. 3A, B show an exemplary version of the remote controller used in the system of FIG. 1 (FIG. 3A) and a block diagram of the main components of the remote controller as illustrated in FIG. 3A (FIG. 3B),

FIG. 4 shows a first exemplary version of a reflective target according to the present invention comprising first and second prism sections, first and second cat-eye sections, and a foil section,

FIG. 5 shows a second exemplary version of a reflective target according to the present invention comprising a prism section, a cat-eye section, and a foil section, and FIG. 6 shows a third exemplary version of a reflective target according to the present invention comprising a prism section and a cat-eye section.

Detailed Description

Reference will now be made in detail to the present preferred embodiment, an example of which is illustrated in the accompanying drawings. It is to be understood that the technology disclosed herein is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. The technology disclosed herein is capable of other embodiments and of being practiced or of being carried out in various ways.

Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. All definitions, as defined and used herein, should be understood to control over dictionary definitions, definitions in documents incorporated by reference, and/or ordinary meanings of the defined terms. The indefinite articles "a" and "an", as used herein in the specification and in the claims, unless clearly indicated to the contrary, should be understood to mean "at least one". The phrase "and/or", as used herein in the specification and in the claims, should be understood to mean "either or both" of the elements so conjoined, i.e., elements that are conjunctively present in some cases and disjunctively present in other cases. Multiple elements listed with "and/or" should be construed in the same fashion, i.e., "one or more" of the elements so conjoined. Other elements may optionally be present other than the elements specifically identified by the "and/or" clause, whether related or unrelated to those elements specifically identified.

The use of "including, or "comprising, or "having" and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless limited otherwise, the terms "connected", "coupled", and "mounted", and variations thereof herein are used broadly and encompass direct and indirect connections, couplings, and mountings. In addition, the terms "connected" and "coupled", and variations thereof are not restricted to physical or mechanical connections or couplings.

FIG. 1 schematically illustrates a typical measuring and surveying application in the construction sector as an example of a system 10 for measuring and surveying applications in a worksite environment.

The system 10 comprises a laser instrument 12 having distance and angle measuring functionality, a remote controller 13 that is connected via a first communication link 14 to the laser instrument 12, and a reflective target 15 that is connected via a second communication link 16 to the remote controller 13. The laser instrument 12 is formed as a total station and com- prises a measuring unit 17 that is mounted on a mounting support structure in the form of a tripod 18. Alternatively, the measuring unit 17 can be mounted on other mounting support structures.

Typically, the communications via the first communication link 14 between the laser instrument 12 and remote controller 13 and via the second communication link 16 between the target 15 and remote controller 13 are wireless, such as using WiFi format or Bluetooth format. In FIG. 1, the first communication link 14 and second communication link 16 are depicted as wireless link, although it certainly could be constructed by use of an electrical cable, an optical cable, or any other type of suitable cable.

FIGS. 2A, B show an exemplary version of the measuring unit 17 of the laser instrument 12 used in the system 10 of FIG. 1 in a perspective view (FIG. 2A) and a block diagram of the main components of the measuring unit 17 as illustrated in FIG. 2A (FIG. 2B).

The laser instrument 12 is designed as robotic total station and comprises a measuring head 21 , a main housing 22, and a battery pack 23 configured to power the laser instrument 12. The measuring head 21 is enclosed by a housing 24, which includes an exit window 25. In the housing 24, a distance measuring device that emits a laser beam 26 and a tracking device that emits optical radiation 27 are arranged. The laser beam 26 and the optical radiation 27 are emitted through the exit window 25 to leave the housing 24.

The laser beam 26 is also called first light beam, and the optical radiation 27 is also called second light beam. The first light beam 26 is within a first range of wavelengths and has a first angle of aperture, and the second light beam 27 is within a second range of wavelengths and has a second angle of aperture.

The main housing 22 is Il-formed and includes a bottom portion 30, a first side portion 31, and a second side portion 32. The measuring head 21 is pivotably mounted to the main housing 22 about a pivoting axis 33 and is arranged between the first side portion 31 and the second side portion 32. The main housing 22 can rotate completely around its circumference at a full 360° angle with respect to a disc 34 about a rotating axis 35.

An azimuth motor device and a first angle measuring device are located in the bottom portion 30 of the main housing 22 and allow to rotate the laser instrument 12 about the rotating axis 35 and to determine the direction of the laser beam 26 in a horizontal plane perpendicular to a local direction of gravitation 36. An elevation motor device and a second angle measuring device are located in the first side portion 31 of the main housing 22 and allow the measuring head 21 to pivot about the pivoting axis 33 and to determine the direction of the laser beam 26 in a vertical plane parallel to the local direction of gravitation 36. To make the laser in- strument 12 fully automatic, it is preferred to include a self-leveling device, which may be arranged in the bottom portion 30 of the main housing 22.

FIG. 2B shows a block diagram of the main components of the laser instrument 12. The laser instrument 12 may include a first electronic device 41 , a distance measuring device 42, a first angle measuring device 43 configured to measure the orientation of the laser beam in the horizontal plane (horizontal angle), an azimuth motor device 44, a second angle measuring device 45 configured to measure the orientation of the laser beam in the vertical plane (vertical angle), an elevation motor device 46, an overview camera device 47, and a tracking device 48 configured to track a target via the laser instrument 12.

The laser instrument 12 shown in FIG. 2A is a robotic total station. A total station is called robotic if it is able automatically to follow a target through the worksite environment. To allow following of a target, a robotic total station comes equipped with the azimuth and elevation motor devices 44, 46 for automatically rotating the laser instrument horizontally and vertically, and the tracking device 48 for tracking the target.

The first electronic device 41 comprises a first processing circuit (pP) 49, a first memory circuit 50 that may include associated random-access memory (RAM) and read only memory (ROM), a first communications circuit 51 , and a first input/output (I/O) interface circuit 52. The first processing circuit 49, also called device control unit, may communicate with the first memory circuit 50 and first communications circuit 51 and is configured to control the laser instrument 12. The first communications circuit 51 includes a first transmitter circuit 53 and a first receiver circuit 54 and is configured to be connected to a communications circuit of the remote controller via the communication link. The first input/output interface circuit 52 is an interface between the first processing circuit 49 and the various types of motor driver circuits and sensor circuits of the laser instrument 12.

The distance measuring device 42 includes a laser transmitter 56, a laser driver circuit 57, a photosensor 58, and a laser receiver interface circuit 59. The laser driver circuit 57 provides current for the laser transmitter 56 which emits the laser beam 26. The photosensor 58 receives at least a part of the laser beam 26 reflected at a target or a surface of the worksite environment, and the current signal that is outputted by the photosensor 58 is directed to the laser receiver interface circuit 59. After appropriate amplification and demodulation, the signal is sent via the first input/output interface circuit 52 to the first processing circuit 49.

The first angle measuring device 43 includes a first angle encoder 61 , which will provide input signals to the first processing circuit 49, so that it knows exactly in which horizontal angle the laser transmitter 56 is arranged in the horizontal plane; the output signal of the first angle encoder 61 is directed to the first input/output interface circuit 52. The azimuth motor device 44 includes an azimuth motor 62, which is the motive force to rotate the main housing 22 of the laser instrument 12 about the first rotating axis 32, and an azimuth motor driver circuit 63, which will provide the proper current and voltage to drive the azimuth motor 62.

The second angle measuring device 45 includes a second angle encoder 64, which will provide input signals to the first processing circuit 49, so that it knows exactly in which vertical angle the laser transmitter 56 is arranged in the vertical plane; the output signal of the second angle encoder 64 is directed to the first input/output interface circuit 52. The elevation motor device 46 includes an elevation motor 65, which is the motive force to pivot the measuring head 21 about the first pivoting axis 30, and an elevation motor driver circuit 66, which will provide the proper current and voltage to drive the elevation motor 65.

The overview camera device 47 may be arranged in the measuring head 21 of the laser instrument 12 for capturing an image or a video feed generally in the direction of a sighting axis of the laser instrument 12. The overview camera device 47 may include optical elements, such as, but not limited to, an objective and a focusing lens, a graphics processing unit (GPU) 68, and a first imaging sensor 69, which may comprise or be constituted by a CCDbased sensor, an active pixel-sensor, a CMOS-based sensor, and/or by any other type of suitable imaging sensors.

The tracking device 48 includes an optical radiation source 70, such as, but not limited to, an infrared (IR) transmitter or a visible light transmitter, a driver circuit 71, a second imaging sensor 72, and a receiver interface circuit 73. The driver circuit 71 provides current for the optical radiation source 70 which emits optical radiation, such as, but not limited to, infrared radiation or visible radiation. The second imaging sensor 72 receives at least a part of the optical radiation reflected at a target, and the current signal that is outputted by the second imaging sensor 72 is directed to the receiver interface circuit 73. After appropriate amplification and processing, the signal is sent via the first input/output interface circuit 52 to the first processing circuit 49 for further processing and/or analyzing. The optical radiation source 70 may be configured to emit modulated optical radiation in accordance with characteristics, such as, but not limited to, a frequency.

FIGS. 3A, B show an exemplary version of the remote controller 13 used in the system 10 of FIG. 1 in a front view (FIG. 3A) and a block diagram of the main components of the remote controller 13 as illustrated in FIG. 3A (FIG. 3B).

The remote controller 13 is designed as tablet computer and includes a housing 81 , a touch screen display 82, a battery 83, a set of buttons 84, e.g., volume control button, power on/off button, and display control button, a set of indicators 85, e.g., for operating status, data storage status, and battery status, a set of connectors 86, e.g., for docking, data storage, and USB, and a card slot 87.

FIG. 3B shows a block diagram of the main components of the remote controller 13. The remote controller 13 may include a second electronic device 91 , a display device 92, and an input device 93.

The second electronic device 91 comprises a second processing circuit (pP) 96, a second memory circuit 97 that may include associated random-access memory (RAM), read only memory (ROM), and some type of bulk memory (BULK), a second communications circuit 98, and a second input/output (I/O) interface circuit 99. The second processing circuit 96 may communicate with the second memory circuit 97 and second communications circuit 98 and is configured to control the remote controller 13. The second communications circuit 98 includes a second transmitter circuit 100 and a second receiver circuit 101 and is configured to be connected to the first communications circuit 51 of the laser instrument 12 via the communication link 14. The second input/output interface circuit 99 is an interface between the second processing circuit 96 and the various driver circuits of the remote controller 13.

In the second memory circuit 97 several program codes having computer-executable instructions for performing a method may be stored. The stored program codes may include a program code for performing a method for tracking a reflective target or for identifying a reflective target. The methods maybe performed by a supervisory device of the system 10, the supervisory device having evaluation, data processing and control functionality. In the system 10, the supervisory device is integrated into the second processing circuit 96 of the second electronic device 91 of the remote controller 13. Alternatively, the supervisory device maybe integrated into the first processing circuit 49, or into the first and second processing circuits 49, 96, or in any other type of suitable processing circuit.

The display device 92 includes a display 103 and a display driver circuit 104. The display driver circuit will be in communication with the second I/O interface circuit 99 and provides the correct interface and data signals for the display 103. If the remote controller 13 is a laptop computer, for example, then this would be the standard display seen in most laptop computers. Or, if the remote controller 13 is a tablet computer or a smart phone, in which case the display device is a much smaller physical device, the display device 103 could be a touch screen display.

The user-operated input device 93 includes a keypad 105 and a keypad driver circuit 106.

The keypad driver circuit will be in communication with the second I/O interface circuit 99 and controls the signals that interface to the keypad 105. If the display device 103 is a touch screen display, then there may not be a separate keypad on the remote controller 13, because most of the command or data to input functions will be available by touching the display itself and the keypad is integrated in the touch screen display. There may be some type of power on/off button, but that would not necessarily be considered a true keypad and typically would not be used for entering data.

FIG. 4 shows a first exemplary version of a reflective target 110 according to the present invention, the reflective target 110 being configured to be used in measuring and surveying applications.

The target 110 comprises a base element 111 having a central axis 112, a prism section 113 including a plurality of corner cube prisms 114 arranged around the central axis 112 in a circumferential direction 115, and a cat-eye section 116 including a plurality of cat-eyes 117 formed by a plurality of prism elements having light entrance surfaces, the cat-eyes being arranged around the central axis 112 in the circumferential direction 115. The corner cube prisms 114 are configured to reflect light beams of a range of wavelengths, and the cat-eyes 117 are configured to reflect light beams of a first range of wavelengths.

In the exemplary version shown in FIG. 4, the target 110 further comprises a foil section 118 including a reflective foil 119 arranged around the central axis 112 in the circumferential direction 115, a further cat-eye section 121 including a plurality of further cat-eyes 122 formed by a plurality of further prism elements having further light entrance surfaces, and a further prism section 123 including a plurality of further corner cube prisms 124.

To differ between the prism section 113 including the plurality of corner cube prisms 114 and the further prism section 123 including the plurality of further corner cube prisms 124, the prism section 113 is called "first prism section" including first corner cube prisms 114, and the further prism section 123 is called "second prism section" including second corner cube prisms 124. To differ between the cat-eye section 116 including the plurality of cat-eyes 117 and the further cat-eye section 121 including the plurality of further cat-eyes 122, the cat-eye section 116 is called "first cat-eye section" including first cat-eyes 117, and the further cateye section 121 is called "second cat-eye section" including second cat-eyes 122.

The first corner cube prisms 114 and second corner cube prisms 124 are configured to reflect light beams, the first cat-eyes 117 are configured to reflect light beams of a first range of wavelengths, the second cat-eyes 122 are configured to reflect light beams of a second range of wavelengths, and the retroreflective foil 119 is configured to reflect the light beam used for distance measuring, preferably in the infrared spectrum. The second corner cube prisms 124 of the second prism section 123 have the same optical properties as the first corner cube prisms 114 of the first prism section 113.

The first cat-eye section 116 is arranged at a first height level of the target 110 and the second cat-eye section 121 is arranged at a second height level of the target 110 in a length direction 125 of the target that is parallel to the central axis 112, wherein the second height level is different from the first height level. The combination of two cat-eye sections which are configured to reflect different wavelengths allows to identify the target in an image captured by a total station and showing different colored reflexes.

In the exemplary version shown in FIG. 4, the foil section 118 is arranged between the first cat-eye section 116 and the second cat-eye section 121 . The target 110 that includes the first cat-eye section 116 with the plurality of first cat-eyes 117, the second cat-eye section 121 with the plurality of second cat-eyes 122, and the foil section 118 arranged between the first and second cat-eye sections 116, 121 can be easily distinguished during tracking from reflecting surfaces or other targets. The foil section arranged between the two cat-eye sections 116, 121 separates the first and second cat-eye section 116, 121 and allows to identify the different colored reflexes in an image captured by a total station.

The first prisms 114, the first cat-eyes 117, and the reflective foil 119 differ in their optical properties. The reflective foil 119 and the cat-eyes 119 are composed of multiple prisms arranged next to each other. A cat-eye is a target having a planar reflective section that includes a plurality of prisms, each prism is constituted by a corner cube having three surfaces being oriented perpendicular to one another and each prism is oriented such that a common edge formed by two of the three surfaces is in the same plane as the target axis.

FIG. 5 shows a second exemplary version of a reflective target 130 according to the present invention, the reflective target 130 being configured to be used in measuring and/or surveying applications.

The target 130 comprises a base element 131 having a central axis 132, a prism section 133 including a plurality of corner cube prisms 134 arranged around the central axis 132 in a circumferential direction 135, and a cat-eye section 136 including a plurality of cat-eyes 137 formed by a plurality of prism elements having light entrance surfaces, the cat-eyes 137 being arranged around the central axis 132 in the circumferential direction 135. The corner cube prisms 134 are configured to reflect light beams, and the cat-eyes 137 are configured to reflect light beams of a first range of wavelengths.

In the exemplary version shown in FIG. 5, the target 130 further comprises a foil section 138 including a reflective foil 139 arranged around the central axis 132 in the circumferential di- rection 135. The reflective foil 139 is cylindrically formed with a circular cross-section; alternatively, the cross-section of the reflective foil 139 may be formed as hexagon, octagon, or any other type of polygon. The foil section 138 with the reflective foil 139 supports measuring of distances between a laser instrument and the target 130. FIG. 6 shows a third exemplary version of a reflective target 150 according to the present invention, the reflective target 150 being configured to be used in measuring and/or surveying applications.

The target 150 comprises a base element 151 having a central axis 152, a prism section 153 including a plurality of corner cube prisms 154 arranged around the central axis 152 in a cir- cumferential direction 155, and a cat-eye section 156 including a plurality of cat-eyes 157 formed by a plurality of prism elements having light entrance surfaces, the cat-eyes 157 being arranged around the central axis 152 in the circumferential direction 155.

The corner cube prisms 154 and the cat-eyes 157 are configured to reflect different ranges of wavelengths. The optical properties of the corner cube prisms (prism section 153) differ from the cat-eyes (cat-eye section 156). The cat-eye section 156 can support the identification of the target 150 during tracking.

Claims

1. A reflective target (15; 110; 130; 150) configured to be used in measuring and surveying applications, comprising:

■ a base element (111 ; 131 ; 151) having a central axis (112; 132; 152), and

■ a prism section (113; 133; 153) including a plurality of corner cube prisms (114; 134; 154) having light entrance surfaces, wherein the corner cube prisms (114; 134; 154) are arranged around the central axis (112; 132; 152) in a circumferential direction (115; 135; 155) and configured to reflect light beams, characterized in that the target (110; 130; 150) further comprises a cat-eye section (116; 136; 156) including a plurality of cat-eyes (117; 137; 157) arranged around the central axis (112; 132; 152) in the circumferential direction (115; 135; 155), wherein the cat-eyes (117; 137; 157) are configured to reflect light beams of a first range of wavelengths and formed by a plurality of prism elements having light entrance surfaces.

2. The target according to claim 1 , further comprising a further cat-eye section (121) including a plurality of further cat-eyes (122) arranged around the central axis (112) in the circumferential direction (115), wherein the further cat-eyes (122) are configured to reflect light beams of a second range of wavelengths and formed by a plurality of further prism elements having further light entrance surfaces, wherein the cat-eye section (116) and the further cat-eye section (121) are arranged at different height levels of the target (110) in a length direction (125) parallel to the central axis (112) of the target (110).

3. The target according to any of claims 1 to 2, further comprising a foil section (118; 138) including a reflective foil (119; 139) arranged around the central axis (112; 132) in the circumferential direction (115; 135), the reflective foil (119; 139) being formed by multiple prisms.

4. The target according to claim 3, wherein the foil section (118) is arranged between the cat-eye section (116) and the further cat-eye section (121).

5. The target according to any of claims 1 to 4, further comprising a further prism section (123) including a plurality of further corner cube prisms (124) having light entrance surfaces, wherein the further corner cube prisms (124) are arranged around the central axis (112) in the circumferential direction (115).

6. The target according to claim 5, wherein the prism section (113) and the further prism section (123) are arranged at different height levels of the target in the length direction

7. The target according to any of claims 1 to 6, wherein the cat-eyes (117; 137) and/or the further cat-eyes (122; 132) are formed as planar cat-eyes.

8. The target according to claim 1 , wherein the cat-eyes (137) are formed as planar cateyes and the corner cube prisms (134) of the prism section (133) are arranged in the pla- nar cat-eyes (137) in such a way that the light entrance surfaces are parallel to the cateyes (137).