Apparatus, method and system for measuring a position on an object

Abstract

1. A system for monitoring survey reflectors positioned at multiple locations on an object, the system comprising: a camera including one or more light sources positioned to illuminate a field in space corresponding to at least 10% of the camera's field of view, preferably the entire field of view, an image sensor receiving a light beam from reflection of the beam by the survey reflector and providing data, a body with an optical entry system, the image sensor being positioned on a first side of the body and the light source being positioned on a second side of the body, and a processing unit for processing the data. The processing unit is configured to determine a position of the survey reflector from the image sensor data and to detect movement of the survey reflector based on a comparison of the determined position with a previously determined position.

Description

[Technical Field]

[0001]

[0001] The present invention relates to systems and methods for monitoring a position on an object, and may further relate to systems and methods for monitoring and / or detecting the movement of an object. [Background technology]

[0002] Systems and methods for determining the position of remote objects have long been known, for example in the field of surveying and / or monitoring structures.

[0003]

[0003] WO 2019 / 143249 and WO 2019 / 143250 disclose devices and methods for monitoring the position of an object, e.g., a structure, over time. The disclosed systems include beacons using active light sources placed at the positions to be measured. The publications present solutions for reducing the influence of distracting light sources, such as ambient light, and for efficiently distinguishing between different beacons.

[0004]

[0004] However, active light sources require a power source, which for long-term monitoring may require the use of batteries, battery replacement, or local energy harvesting (such as the use of solar panels).

[0005]

[0005] U.S. Patent Application Publication No. 2018 / 0224527 describes a coordinate measuring device for detecting the position of a movable object in space, the device having automatic object recognition. However, the device is very complex, and when measuring multiple objects, the measurement procedure takes a considerable amount of time.

[0006]

[0006] U.S. Patent No. 8,553,212 describes a geodesic measurement system and method for identifying a target unit having a geodesic measurement device. The publication focuses on identifying the target unit. However, when it is desired to measure and thereby identify multiple target units, the procedure appears to be relatively time-consuming. Summary of the Invention

[0007]

[0007] The problem addressed in this document is a method that allows the position of an object to be monitored over time. More particularly, the problem addressed relates to the monitoring of objects that have a fixed position relative to the Earth but move over time, such as buildings. The position on the object may show a position that changes slowly over time, and the entire object may even deform. Causes may be related to the soft ground on which the building stands, underground construction below the building (such as the construction of an underground car park or subway), or earthquakes (such as the extraction of natural gas from the ground below a building).

[0008]

[0008] More particularly, it is an object of the present invention to overcome the shortcomings of the prior art and to enable locations to be monitored over time while providing efficient and reliable monitoring while reducing power consumption at the monitored locations, particularly in remote locations. In particular, it is an object of the present invention to reduce dependency on power sources at the monitored locations.

[0009] A further object of the present invention is to enable more time-efficient monitoring of locations on an object.

[0010] It is a further object of the present invention to reduce the complexity of a system and / or method for monitoring a position on an object.

[0011]

[0011] Therefore, the present invention provides a system as defined in independent claim 1.

[0012]

[0012] The present invention also provides a method according to a further independent claim.

[0013]

[0013] Advantageous embodiments are set forth in the dependent claims.

[0014] According to a first aspect of the present invention, there is provided a system for monitoring survey reflectors positioned at a plurality of locations on an object, said system comprising: A camera, one or more first light sources for emitting first diverging beams, the one or more first light sources being positioned such that a field in space corresponding to at least 10% of a field of view of the camera is illuminated by the one or more first light sources; an image sensor for receiving a reflected light beam including reflections of the first divergent beam by the plurality of survey reflectors and providing data; a body having an optical entry system, the body having a first side facing an interior space of the camera and a second side facing away from the interior space, the image sensor being disposed in the interior space, the one or more first light sources being disposed on the second side of the body, the one or more first light sources being disposed at a first distance from the optical entry system; a camera, a processing unit configured to process the data; Equipped with The processing unit is configured to determine a position of each survey reflector from the data and detect movement of one or more of the plurality of survey reflectors based on a comparison of the determined position of each survey reflector with previously determined positions of the survey reflector.

[0015]

[0015] By using one or more light sources emitting diverging beams, the camera can simultaneously capture images of multiple survey reflectors located apart from one another without moving the camera and / or scanning one or more light beams. The one or more first light sources are positioned such that a cumulative light beam produced by the first diverging light beams emitted by each of the one or more first light sources covers a field of view within a space of at least 10% of the camera's field of view. This allows all survey reflectors within 10% of the camera's field of view to be simultaneously illuminated and monitored.

[0016] This eliminates the need to move the camera, such as by scanning the light beam emitted by the camera, to monitor multiple survey reflectors. This is in contrast to conventional systems that typically use collimated laser beams. The use of collimated laser beams has the advantage of providing high light intensity, but when provided to a camera for use with a reflector, requires the camera to be scanned, such as to monitor multiple survey reflectors.

[0017]

[0017] Each of the one or more first light sources emits a diverging beam, which is a beam whose cross section has non-negligible dimensions in two dimensions. In a preferred embodiment, the first diverging beam represents a cone, preferably a right circular cone, having a first solid angle greater than 0°. Alternatively, the first diverging beam may represent an elliptical cone. Because the light intensity or luminous flux of the diverging beam decreases with distance from the light source, a high-power light source, typically a high-power LED, must be used to maintain the desired operating distance, i.e., the distance at which the survey reflector can be detected.

[0018] In some embodiments, one first light source may be provided that emits a light beam having a solid angle large enough to cover at least 10% or more of the field of view of the camera.

[0019] According to one embodiment, the field in space corresponds to at least 50% of the field of view of the camera. In a preferred embodiment, the field in space illuminated by the one or more first light sources is substantially equal to or larger than the field of view of the camera. In some embodiments, one first light source may be provided, with the entire field of view of the camera illuminated by the first beam. In other embodiments, two or more first light sources are provided, with the assembly of each diverging light beam substantially covering the field of view of the camera.

[0020] This allows surveys to be performed more quickly compared to prior art techniques that rely on scanning systems, and also reduces system complexity by allowing surveys and / or monitoring of multiple survey reflectors to be performed without relying on moving parts and / or multiple cameras.

[0021] As described herein above, in a preferred embodiment, the camera may be provided with a non-refractive element, e.g., a pinhole, that functions as the objective. This has several advantages, such as reduced optical distortion, compared to cameras that use refractive optical elements, i.e., one or more lenses, to form the objective, as described in WO 2019 / 143250. In particular, cameras that use non-refractive optical elements have been observed to have several advantages over conventional cameras that use lenses as the objective, including: purely geometrical properties of optical elements, Minimal or no chromatic aberration, Near-infinite depth of field, The body with optical entry system has very low thermal resistance and low thermal mass, minimizing thermal sensitivity. The field of view depends only on the size of the image sensor and the distance between the pinhole or slit and the image sensor. The dimensions of the image sensor and optical entry system can be reduced; Extremely lightweight as the weight associated with lenses is avoided It is inexpensive because the cost of lenses is avoided, Relatively simple calibration procedure, etc.

[0022]

[0022] Having multiple first light sources can be advantageous. When the optical entry system includes non-refractive elements such as one or more pinholes, the camera becomes relatively sensitive to water droplets or dirt on the survey reflector. This is because the pinhole has an infinite depth of field. By providing the camera with multiple first light sources, the likelihood that the reflection of the first beam emitted by the camera will be adversely affected by disturbances on the prism can be reduced, leading to a more robust system.

[0023]

[0023] By using a survey reflector, a passive reflector such as a prism, at a monitored location remote from the camera to reflect light emitted by one or more light sources located on, i.e., included in, the camera, power to the monitored location can be eliminated. According to some embodiments described in more detail herein below, additional functionality can be provided at the monitored location that requires power, but these are low-power and / or configured to be active for only a limited time. Thus, power consumption at the monitored target location can be avoided all together, or at least significantly reduced, compared to systems that use beacons or other target objects with active light sources at the target location. This reduces maintenance and simplifies installation, especially for long-term measurements.

[0024]

[0024] The survey reflector advantageously includes a prism, such as a conventional survey prism. These are generally low cost and widely available, providing a cost-effective system. Preferably, a high-precision survey prism made entirely of glass may be used. Alternatively, the survey reflector may comprise a hollow mirror, also known as a cat's eye. As will be appreciated by those skilled in the art, other alternatives may be possible.

[0025]

[0025] Survey reflectors, for example, provided on beacons or target units, are located at multiple different remote locations, while one or more diverging light beams reflected by the survey reflectors are generated by a camera located at the surveillance setup in a central location, also referred to herein as the camera location. Locating one or more light sources at one central location allows for the use of significantly higher power levels than light sources located at multiple target locations, as described in the prior art. Providing a sufficient power source, such as batteries and / or a power harvesting system, at a central location is less expensive and requires less time and / or effort than providing power sources at multiple remote locations.

[0026]

[0026] The light source or light sources may be arranged entirely on one side of the body, or alternatively may be partially integrated into the body and arranged to emit light onto a side of the body facing away from the image sensor, i.e. the image sensor is arranged facing a first side of said body and a first beam is emitted in a direction perpendicular to a second, opposite side of said body.

[0027]

[0027] The first light source is positioned a first distance D1 from the optical entry system, i.e., from the center of the objective lens of the camera. As explained herein below with reference to the drawings, the first distance should be selected so that the reflection of the first diverging light beam from the survey reflector passes through the optical entry system into the camera and reaches the image sensor.

[0028]

[0028] By approximate definition, the first distance D1 is less than the dimension of the surface area of ​​the survey reflector where the first beam strikes the survey reflector, e.g., the diameter in the case of a circular surface area. This approximation is based on many assumptions about the surveillance setup, related to setups represented by mathematically ideal situations commonly used in physics modeling. Such assumptions include, for example, that the first light source is a point source and is located in the same plane as the body on which the optical entry system is located, that the optical entry system is infinitely small, and that the survey reflector projects a perfect conical beam centered on the first light source at the plane of the body holding the light source. However, to a first approximation, such a model provides a sufficient understanding and first approximation of the first distance.

[0029]

[0029] In practical situations, the diameter of the survey reflector ranges from 10 mm to 200 mm, and is usually 20 to 100 mm. The first distance must be smaller than the diameter of the survey reflector. When survey prisms of different diameters are used, the first distance must be smaller than the smallest diameter of the survey reflector. For target units such as those shown in Figures 11 to 15, the first distance must be smaller than the diameter of each individual survey reflector.

[0030] Advantageously, the first light source comprises a light-emitting diode, LED, preferably a high-power LED. The light emitted by the first light source is preferably in the infrared range, although other wavelengths may be possible. The first solid angle is preferably greater than 45 degrees, more preferably greater than 50 degrees, and most preferably greater than 60 degrees. The number of first light sources and their positions on the body may be selected according to the solid angle of the beam emitted by the first light sources, such that the light generated by the assembly of first light sources substantially covers the field of view of the camera. This allows all survey reflectors located within the field of view of the camera to be illuminated by one or more first light sources without the need to move the camera and / or the light beam.

[0031]

[0031] The image sensor is configured to receive and detect reflections of the one or more first divergent beams emitted by the one or more first light sources from all survey reflectors located within a portion of the field of view of the camera illuminated by the one or more first divergent beams, and for this purpose the image sensor may preferably be a two-dimensional sensor.

[0032]

[0032] By simultaneously illuminating multiple separately located survey reflectors with one or more diverging beams generated by one or more first light sources, multiple survey reflectors can be measured substantially simultaneously, thereby reducing system complexity and the time required for measurements.

[0033] According to some embodiments, the optical entry system of the body includes a non-refractive element, such as a slit or pinhole, that forms the objective lens of the camera. In further embodiments, the non-refractive objective optical element may include other diffractive elements, such as a Fresnel zone plate, a photon sieve, an arched slit, a mask, or a holographic element. The non-refractive element passes light, including ambient light as well as the light beam formed by reflection of the first beam on the survey reflector, to the camera and image sensor. Such non-refractive elements, and their advantages, are described herein above and in detail in WO 2019 / 143250.

[0034] According to an alternative embodiment, the optical entry system comprises a lens or lens system. Preferably, the optical entry system includes a single lens. If this lens is sufficiently thin, i.e., has low optical power, and is relatively easy and / or well-defined to be attached to the body, the temperature effects introduced by the lens and / or its attachment can be reduced and / or taken into account, for example, by modeling in the processing of data recorded by the image sensor.

[0035]

[0035] The body with the optical entry system may be substantially planar or may have any other shape in which the optical entry system or the camera objective lens can be placed.

[0036]

[0036] The processing unit may be located in or on the camera, for example in the interior space of the camera, close to the image sensor. Alternatively, the processing unit may be located remotely from the camera.

[0037]

[0037] The position and / or location of the survey reflector is advantageously determined by image processing of the data recorded by the image sensor.

[0038] The system can be used to record data substantially continuously and / or at predetermined sampling intervals. The integration time of the signal measured by the image sensor may be increased to compensate for the loss of light intensity due to the use of a diverging light beam instead of a collimated beam and the use of a non-refractive optical element such as a pinhole instead of a camera objective lens.

[0039]

[0039] The use of a survey reflector, such as a prism, instead of an active light source at the target location presents particular challenges, solutions of which are presented in different embodiments of the invention described herein below.

[0040] Environmental effects, including ambient (diffuse) light entering the camera, can create interference or noise in the measurement and / or monitoring of objects.

[0041] In one embodiment, the processing unit is further configured to apply a first code to the first diverging beam by modulating the beam, thereby applying or superimposing a predetermined code or pattern onto the first diverging beam. This first code can be applied in various ways known in the art of signal processing. Advantageously, the first code can be provided by amplitude modulation of the first diverging beam, so that the amplitude of the beam varies over time in a predetermined manner. For example, the beam can vary sinusoidally with a predetermined frequency and / or phase. By amplitude modulating the first diverging beam while sequentially recording data from the image sensor and applying filtering techniques during image processing of the recorded data frames, environmental effects can be suppressed. These filtering techniques reduce the ambient light (read as constant light) level in the processed image, preferably to a very low level, but do not suppress the modulated light in the processed image.

[0042]

[0042] It should be understood that modulation of the light beam can be performed in a variety of different ways, including amplitude modulation, phase and / or frequency modulation, different polarizations, etc. Modulation at different frequencies as described herein should be understood to encompass any suitable means of providing the beam with different codes that allow each reflected beam to be distinguished.

[0043]

[0043] Measurement and / or monitoring of objects can also be adversely affected by diffuse or specular reflections of the first diverging beam from surfaces other than the survey reflector. These reflections can interfere with the reflection from the prism or even appear as false targets.

[0044] However, reflections of the light emitted by the first light source from objects other than the survey reflector are not sufficiently suppressed by the above-mentioned techniques. Therefore, an object of the present invention may be to reduce the effect of reflections of the light generated by the camera on objects other than the survey reflector.

[0045] According to one embodiment, the apparatus further comprises one or more second light sources, each for emitting a second diverging beam, said one or more second light sources being arranged at a second distance D2 from the optical entry system that is greater than the first distance at which the one or more first light sources are located, and the processing unit is configured to apply a second code to the second diverging light beam, the second code being different from the first code. The second code may be applied in a manner similar to the first code. Like the first diverging beam, the second diverging beam is preferably conical with a solid angle Ω2 greater than zero.

[0046]

[0046] Thereby, the one or more second diverging light beams are distinguishable from the one or more first diverging light beams. In particular, reflections of the first diverging light beams detected by the image sensor are distinguishable from reflections of the second diverging light beams detected by the image sensor. This is advantageous and can be used as described in more detail elsewhere in this document.

[0047] The second distance must be selected so that the reflection of the second diverging light beam from the survey reflector does not enter the camera through the optical entry system. By a rough definition, similar to the rough definition of the first distance, the second distance is greater than the dimension of the surface area where the first beam impinges on the survey reflector, e.g., the diameter in the case of a circular surface area. Above in this specification, typical values ​​for the dimensions, i.e., the diameter, of the survey reflector were given. The second distance must be greater than this dimension. If multiple survey reflectors with different dimensions, i.e., different diameters, are used, the second distance must be greater than the largest dimension to prevent the reflection of the second diverging light beam from entering the optical entry system.

[0048]

[0048] Thus, the first and second beams can be distinguished from one another during image processing and / or by physical measurements in the system or measurement setup.

[0049]

[0049] According to one embodiment, the first beam is amplitude modulated at a modulation frequency, and the second beam is amplitude modulated in antiphase with this modulation frequency. This causes the camera objective, advantageously formed by a non-refractive element such as a pinhole, to see only the first light source reflected by the prism. However, all other objects in the field of view reflect the light of both light sources back to the objective. However, the in-phase and anti-phase modulated light added together appears as a constant light source and is largely suppressed in image processing (similar to ambient light).

[0050] According to a further embodiment, the first light source may emit light at a first wavelength λ1, and the second light source may emit light at a second wavelength λ2, different from the first wavelength. The first and second wavelengths are preferably relatively close to each other so that the image sensor has substantially the same sensitivity to both wavelengths. Only the first light beam is reflected by the survey reflector by attaching a bandpass filter to the survey reflector that passes the first wavelength λ1 but not the second wavelength λ2. In this embodiment, the one or more second light sources are preferably located close to the one or more first light sources, i.e., preferably at the first distance, rather than the second distance as described above, to avoid differences in illumination of the reflective surface by the first and second beams, respectively. However, this method may also provide acceptable results for second light sources located at the second distance. Also, in this embodiment, the first and second beams are provided with first and second codings, respectively. As described above, by subtracting the images associated with the first and second codes respectively, the reflection caused by the survey reflector can be obtained, excluding the influence of ambient light.

[0051] These different embodiments allow reflections from the survey reflector to be distinguished from specular reflections from surfaces other than the survey reflector, ie, false targets.

[0052]

[0052] It may also be desirable to measure the distance between the camera and the survey reflector, and in particular to do so in a time-efficient manner.

[0053] According to one embodiment, the system further comprises one or more third light sources configured to emit a third diverging beam, the one or more third light sources being positioned at a third distance from the optical entry system substantially similar to the first distance, and the processing unit is further configured to apply a third code to the third diverging beam, the third code being different from the first code. When used with the one or more second light sources described above, the third code is also different from the second code. Like the first diverging beam, the third diverging beam is preferably conical, having a solid angle Ω3 greater than zero. The first and third diverging beams have substantially the same wavelength. From images obtained from the first and third light sources, respectively, the distance between the image sensor, i.e., the camera, and different survey reflectors can be measured. The positions of the first and third light sources are known, as are the distance between the optical entry system and the image sensor and the optical characteristics of the optical entry system. This allows the distance between the camera and the survey reflector associated with a particular reflection detected by the image sensor to be determined. The one or more first and third light sources are preferably located on opposite sides of the optical entry system as this allows for maximizing the baseline between detected reflections.

[0054]

[0054] The second and third light sources described herein advantageously comprise light emitting diodes, as does the first light source. The first, second and third light sources preferably emit light of substantially the same wavelength, unless expressly stated otherwise.

[0055] The image sensor provides frames of raw data substantially continuously or at specified sampling intervals. Such a series of raw data frames, recorded at different sampling times, is subjected to various steps of image processing, such as filtering and mathematical operations, to generate an image representing the reflection of light emitted from the camera off the survey reflector. The series of frames includes at least two raw data frames, but preferably includes a larger number, which may be as many as 1,000, 10,000, or even more. As will be appreciated by those skilled in the art, one or more additional steps may be included. Images may be acquired for one or more first, second, or third light sources, each having a different encoding or modulation, as described herein above, while filtering out contributions from the other light sources. Various information can be obtained from the images representing the reflection of light resulting from the first, second, and / or third light sources, respectively.

[0056] For example, as described herein, an image associated with a second light source, i.e., reflected light bearing a second code detected by an image sensor, can be subtracted from an image associated with a first light source, i.e., reflected light bearing a first code reaching an image sensor. This allows for obtaining information derived from a first diverging light beam reflected by one or more survey reflectors. This technique has been shown to suppress reflections of the first diverging beam from reflective surfaces other than the survey reflector, i.e., so-called false targets. Using this technique, suppression of 10 dB or more, particularly 10-50 dB or more, has been achieved.

[0057] By combining the image associated with light of the first coding with the corresponding image associated with the third coding, the distance between the camera and the survey reflector can be determined, and the symmetry of the resulting image allows for the recognition of false targets.

[0058]

[0058] Additional processing steps may be applied to the data recorded by the image sensor and / or to the images obtained by processing this data, in particular correlation techniques may be applied where the images are compared with one or more previously acquired images and / or specification data to detect and / or determine the movement of one or more survey reflectors and / or deformation of the object.

[0059] According to an embodiment, the processing unit is further configured to apply a command code to the first diverging beam. This allows a command or signal providing instructions, information, and / or a request to be sent to the survey reflector. By applying this command or signal to the first diverging beam, it is simultaneously broadcast to all survey reflectors illuminated by the first diverging beam. For this purpose, the survey reflector may be provided with or located next to a target unit comprising a receiver for receiving the command, a target processing unit for detecting and processing it, and preferably one or more further features for performing an action in response to the command. For example, such a target unit may provide and / or comprise a survey reflector identification unit, as described herein below. An example of such a command or signal may be a command requesting the survey reflector to identify itself, for example, by transmitting an identification signal in response to the command. Alternatively or additionally, other types of information, such as telemetry data, may be requested from the survey reflector in this manner.

[0060]

[0060] A further object of the present invention may be to be able to distinguish different survey reflectors from one another.

[0061]

[0061] In one embodiment, the system further comprises a survey reflector identification unit configured to emit an identification signal in response to a request from the camera, the identification signal being unique for each survey reflector, the survey reflector identification unit configured to be disposed on the survey reflector.

[0062]

[0062] The survey reflector identification unit a receiver for receiving the first divergent beam emitted by the camera; a microcontroller coupled to the optical receiver; Advantageously, the microcontroller further comprises an identification unit emitter configured to emit said identification signal when a command is detected by said microcontroller. Advantageously, the identification signal may be emitted in the form of a code that is emitted for a limited time.

[0063]

[0063] The receiver may advantageously be an ultra-low power, high-sensitivity receiver having only low power consumption. An example of such a receiver is described in WO 2020 / 027660. The receiver may be configured to receive the first light beam substantially continuously, and the microcontroller determines whether a command or request for an identification signal is provided in the first light beam.

[0064]

[0064] The camera may advantageously be configured to issue a command or request for an identification signal via the light emitted by the first light source, for example as a signal or code added or superimposed on the first diverging light beam, whereby the request for identification is sent simultaneously to all survey reflectors within the part of the field of view covered by the other first diverging light beam, i.e. the same identification request is received by each survey reflector, which in response sends back their own unique identification signal to the camera.

[0065]

[0065] This enables each survey reflector to be identified substantially simultaneously within a portion of the camera's field of view illuminated by one or more first light sources in a substantially automated manner, thereby further facilitating automated surveying and / or monitoring of multiple survey reflectors.

[0066]

[0066] The identification unit light emitter, which may comprise, for example, a light emitting diode, only emits the identification signal in response to a request, thereby keeping the energy consumption of the identification unit low.

[0067]

[0067] The different embodiments described above can be combined as will be understood by those skilled in the art.

[0068] In a second aspect of the present invention, there is provided a method for monitoring a plurality of survey reflectors on an object, the method comprising: emitting, by each of one or more first light sources, a first diverging beam having a solid angle greater than zero toward the plurality of survey reflectors, wherein the plurality of survey reflectors are substantially simultaneously illuminated by the one or more first diverging beams from the one or more first light sources, and the one or more first light sources are maintained in a substantially fixed position; recording, with an image sensor, data representative of a reflected light beam including reflections of the first divergent beam by the plurality of survey reflectors; monitoring the location at a first camera position by determining a position of each survey reflector from the data by image processing of the data, and detecting movement of one or more of the plurality of survey reflectors based on a comparison of the determined position of each survey reflector with previously determined positions of the survey reflectors; Includes.

[0069]

[0069] The method according to the second aspect of the invention may be advantageously carried out using a system according to the first aspect, achieving corresponding effects and advantages.

[0070] In a preferred embodiment, the image processing of the data comprises one or more of the steps described in relation to the first aspect.

[0071]

[0071] In particular, the method may be further configured to reduce disturbances from environmental interference and / or false objects, as described above with reference to the first aspect.

[0072] In one embodiment, a first code is applied to the first diverging beam. This may be applied according to any of the methods described with reference to the first aspect. Filtering techniques may be applied during image processing of the data to distinguish light resulting from reflections of the first beam from other light sources and / or other reflections.

[0073] According to some embodiments, the method comprises: providing a body with an optical entry system that allows light to pass through, the body having a first side and a second side, and positioning the body such that the first side faces an interior space of the camera and the second side faces away from the interior space, such that the image sensor is positioned in the interior space on the first side of the body and the one or more first light sources are positioned on the second side of the body; positioning the one or more first light sources at a first distance D1 from the optical entry system; disposing one or more second light sources at a second distance D2 greater than the first distance D1, and emitting a second divergent beam by each of the one or more second light sources; applying a second code to the second diverging beam, the second code being different from the first code.

[0074]

[0074] The first and second distances are preferably defined as defined herein above with reference to the first aspect. The first and second codes may be applied according to one or more of the techniques described above with reference to the first aspect.

[0075] According to some embodiments, the method further comprises: generating a first image from the reflected light having a first code; generating a second image from the reflected light having a second code; subtracting the second image from the first image and determining the position and / or movement of the one or more survey reflectors from the resulting image; Further includes: This allows the image resulting from the reflection of the first beam, i.e. the measurement beam, to be separated from disturbances caused by environmental influences.

[0076] A further object of the present invention is to distinguish reflections from survey reflectors from other specular reflections, ie, false targets.

[0077] According to one embodiment, the method further comprises providing one or more third light sources and applying a third code, different from the first code, to the third diverging beam. The third light sources are positioned at a third distance D3 from the optical entry system, the third distance being comparable to the first distance. The process of applying the coding can be performed as described above. The method further comprises determining, based on the images obtained for the respective reflections of the first and third diverging beams, whether the detected image originates from the survey reflector or from a different reflective element. This can be determined based on whether the detected image is mirrored relative to the position of the light sources.

[0078]

[0078] The reflections of the first and second light beams, respectively, from the survey reflector appear as two separate, distinguishable objects in the image obtained by image processing of the data. When reflected from the prism, or from the hollow mirror if the light source is outside the focal length of the hollow mirror, the image is mirrored relative to the center of the prism or hollow mirror. This confirms that these reflections originate from the survey reflector and not from another reflective surface within the camera's field of view.

[0079] A further object of the present invention may be to determine the distance between the camera and the survey reflector.

[0080]

[0080] This can be achieved by embodiments in which the method further comprises providing one or more tertiary light sources as described herein above, preferably on an opposite side of the non-refractive element from the first light source. The distance between the camera and the survey reflector can be determined from the distance between a first point p1 in the resulting image resulting from reflection of light emitted from the first light source from the survey reflector and a second point p2 resulting from reflection of light emitted from the third light source from the survey reflector.

[0081]

[0081] In this embodiment, the positions of the first and third light sources relative to each other and relative to the optical entry system, e.g., a non-refractive element such as a pinhole, are determined so that the distance between the camera and the survey reflector can be determined. The first and third light sources do not have to be located on opposite sides of the non-refractive element, although this may be preferred as it maximizes the baseline between the two light sources while allowing both light sources to remain within a set maximum distance from the optical entry system.

[0082]

[0082] The embodiment for measuring distance can be advantageously combined with any one of the above-mentioned embodiments to suppress unwanted reflections, thereby allowing reflections to be identified and / or suppressed while at the same time measuring the distance between the camera and the survey reflector.

[0083] According to one embodiment, the distance is: providing a body with first and second optical entry systems; determining, from a baseline between the first and second optical entry systems, a distance between the camera and the survey reflector and a distance between the projected target images resulting from the first and second optical entry systems; The method can further include: The first and second optical entry systems may comprise non-refractive elements, such as pinholes or one or more lenses, preferably single lenses, that act as objective lenses for the camera, as described herein above.

[0084] According to another embodiment, the distance may be determined by using two cameras placed at different camera positions, the cameras being positioned to view the same set of survey reflectors with the optical axes of the respective cameras tilted relative to each other. monitoring the location with a second camera location located away from the first camera location, wherein a first line of sight between the first camera location and a reference survey reflector is oriented at an angle to a second line of sight between the second camera location and the reference survey reflector; determining three-dimensional coordinates of the survey reflector based on the observations at the first camera position and the second camera position; further comprising The monitoring at the second location is performed in the same manner as the monitoring at the first location.

[0085]

[0085] The three-dimensional coordinates can be determined according to various methods, as will be understood by those skilled in the art. For example, triangulation methods may be used. Typically, one or more parameters are known, such as the distance between one or more features and / or the orientation angle of one or more features relative to one another in the above setting.

[0086]

[0086] Determining the three-dimensional coordinates of the survey reflectors requires minimizing the number of survey reflectors monitored by both cameras and knowing one or more distances (between the two survey reflectors, between the two cameras, or between one of the cameras and one of the survey reflectors). This results in a set of equations with many unknowns, which can be solved using known mathematical methods. If necessary, the orientation or tilt (pitch and roll) of the cameras can also be measured, for example by tilt sensors mounted on the cameras. Knowing the tilt of the cameras reduces the number of survey reflectors needed to solve the equations.

[0087]

[0087] As mentioned above with reference to the first aspect, a further object of the invention may be to distinguish between different survey reflectors.

[0088] According to one embodiment, the method comprises: issuing a survey reflector identification command using the one or more first light sources; and emitting an identification signal in response to the survey reflector identification command by an identification unit light emitter disposed on the survey reflector.

[0089]

[0089] Advantageously, the identification signal is emitted in the form of a code and is emitted for a limited time only. The identification signal is preferably unique for each survey reflector, especially for adjacent survey reflectors. For survey reflectors located far enough apart that they can be distinguished from one another on the basis of distance, the identification signals or codes can be reused. In this case, they can be combined with additional codes or signals that provide a unique identification when detected and / or interpreted together with the identification signal.

[0090]

[0090] This can be achieved by using the survey reflector identification unit described above.

[0091] According to a third aspect, there is provided a system for monitoring survey reflectors positioned at a plurality of locations on an object, the system comprising: a camera configured to monitor the survey reflector, the camera comprising: one or more first light sources each for emitting a first diverging beam; one or more second light sources for emitting a second diverging beam; an image sensor for receiving a reflected light beam including reflections of the first divergent beam by the plurality of survey reflectors and providing data; a body including an optical entry system, the body having a first side facing an interior space of the camera and a second side facing away from the interior space, the image sensor being disposed in the interior space, and the first and second light sources being disposed on the second side of the body; a camera, a processing unit configured to process the data; Equipped with the first light source is positioned at a first distance D1 from the optical entry system, and the second light source is positioned at a second distance D2 from the optical entry system that is greater than the first distance; The processing unit is configured to apply a first code to the first diverging beam and a second code, different from the first code, to the second diverging beam.

[0092]

[0092] Features of the system according to the third aspect are preferably analogous or similar to corresponding features of the system according to the first aspect and may be combined with any of the features or embodiments thereof.

[0093] The first and second diverging beams may be diverging beams having a solid angle greater than zero, and may preferably be conical.

[0094]

[0094] In particular, the processing unit advantageously operates and / or functions in the manner described above with reference to the first aspect.

[0095] According to a fourth aspect, there is provided a method for monitoring a position on an object, the method comprising: providing a plurality of survey reflectors on the object, each survey reflector being provided at one of the locations; emitting, by each of one or more first light sources, a first diverging beam toward the plurality of survey reflectors; emitting, by each of one or more second light sources, a second diverging beam toward the plurality of survey reflectors; recording, with an image sensor, data representative of a reflected light beam including reflections of the first divergent beam by the plurality of survey reflectors; determining a position of each survey reflector from the data by image processing of the data, and detecting movement of one or more of the plurality of survey reflectors based on a comparison of the determined position of each survey reflector with previously determined positions of survey reflectors; monitoring the location by Including, The method further includes applying a first code to the first diverging beam and a second code to the second diverging beam, the second code being different from the first code.

[0096]

[0096] These features make it possible in particular to distinguish the reflection of the survey reflector from other reflections and / or ambient light entering the camera, and / or to reduce the influence and / or interference caused by environmental influences and / or reflections from surfaces other than the survey reflector.

[0097]

[0097] The method according to the fourth aspect may advantageously be carried out using the apparatus according to the third aspect, and may provide the technical effects and / or advantages as described above with reference to the third aspect.

[0098]

[0098] The method according to the fourth aspect may include one or more of the steps or features described with reference to the second aspect.

[0099]

[0099] According to a fifth aspect of the present invention, there is provided a beacon comprising the above-mentioned survey reflector. Further, the beacon may comprise the above-mentioned survey reflector identification unit. Furthermore, the beacon may be provided with a survey reflector as described above, i.e., may be fitted with an optical bandpass filter and / or an active modulator.

[0100] According to a sixth aspect, there is provided a system for monitoring a location on an object, comprising a system according to the first or third aspect and a plurality of beacons according to the fifth aspect.

[0101] As mentioned above, in contrast to conventional survey systems that use collimated laser beams, a wide diverging beam from an LED is preferably used. The use of a diverging light beam reduces the light intensity per luminous flux or cross-sectional area at the survey reflector. As a result, the intensity of the reflected light reaching the camera and image sensor is reduced. This can limit the operating range of the system. Particularly in preferred embodiments where the camera is provided with a pinhole or other non-refractive optical element as the objective lens, this can result in a very low light intensity at the image sensor. Therefore, it is desirable to increase the light intensity of the reflected light reaching the image sensor.

[0102] According to a seventh aspect, there is provided a target unit for use in any of the systems or methods described above, the target unit comprising a plurality of survey reflectors arranged in a single plane.

[0103]

[0103] Using a target unit consisting of multiple survey reflectors arranged in a single plane increases the amount of reflected light and the light intensity at the image sensor compared to using individual survey reflectors at each of multiple locations on the monitored target, thereby increasing the operating distance and detection range of a survey system, such as the survey system described herein. A target unit including multiple survey reflectors, such as survey prisms, can be viewed at a longer distance than the individual survey reflectors previously used.

[0104]

[0104] The survey reflectors are preferably high precision survey reflectors, for example of the glass type. These are high precision machined glass prisms that provide much greater accuracy and reflected light intensity than the low cost molded plastic prisms conventionally used in surveying applications.

[0105]

[0105] The survey reflectors are arranged in a single plane in the sense that corresponding points or locations on multiple survey reflectors are all arranged in the same plane, thereby effectively achieving a substantially planar survey reflector, which has a larger reflective area than a single survey reflector.

[0106]

[0106] It should be noted that to increase the intensity of the reflected light, multiple survey reflectors are required because increasing the size of a single survey reflector or prism does not result in an increase in intensity.

[0107]

[0107] As mentioned above, the minimum dimension of each survey reflector is considered to be determined by the distance between the first light source, usually an LED, and the pinhole or other non-refractive optical element used as the camera objective. According to theory, if a prism or survey reflector with a circular base facing the incident light beam is used, its diameter must be at least equal to this distance. If a prism with a triangular or hexagonal base is used, it must be sized so that the diameter of its imaginary inscribed circle is at least equal to this distance.

[0108]

[0108] According to one embodiment, the survey reflectors are arranged in an array with one of the survey reflectors located at the center of the array, the center representing the symmetry point of the array. An array arranged in a single plane as described above may have mirror symmetry and / or rotational symmetry with respect to the central reflector. For example, the survey reflectors may be arranged in a hexagonal array pattern. In this manner, the survey reflectors are arranged in an efficient arrangement, i.e., closely packed to maximize the reflective area of ​​the target unit. Due to the symmetrical arrangement of the survey reflectors, the increase in intensity or power of light reflected by multiple survey reflectors is substantially equal in both the vertical and horizontal directions compared to a single survey reflector.

[0109]

[0109] According to one embodiment, each survey reflector has a surface configured to receive an incident light beam, said surface being substantially circular. Alternatively, other shapes of receiving surfaces or reflector bases may be used, such as triangular or hexagonal.

[0110]

[0110] In particular, when the survey reflector, which is typically a prism, has a circular base or front surface and receives the incident light beam, a hexagonal arrangement provides an efficient arrangement of the reflectors. Also, for other shapes, such as triangular bases or front surfaces that receive the incident light, a hexagonal arrangement may provide the most efficient packing. Alternatively, when using survey prisms with triangular bases, the reflectors may be arranged so that the sides of the triangles touch each other.

[0111]

[0111] According to one embodiment, the multiple survey reflectors are realized by multiple survey prisms, which are preferably substantially identical, and the surfaces of the prisms configured to receive the incident light beam are arranged in the single plane.

[0112]

[0112] According to another embodiment, the multiple survey reflectors are realized by multiple hollow mirrors, each having a center point, the hollow mirrors being preferably substantially identical, and the center points of all mirrors being located in said single plane.

[0113] According to one embodiment, the plurality of survey reflectors includes 13 to 35 reflectors. The number of survey reflectors in the target unit is typically selected to provide efficient reflection of the light beam emitted by the camera and / or survey system while maintaining the reflective area of ​​the target unit so that it appears substantially point-like to the camera. The number of individual survey reflectors included in the target unit may be set according to the distance between the camera and the target unit. Increasing the number of survey reflectors in the target unit generally increases the operating distance or detection range of the system.

[0114]

[0114] Features of different embodiments of the target unit may be combined.

[0115]

[0115] According to an eighth aspect, a system according to the first and / or third aspects hereinabove further comprises a plurality of target units according to the seventh aspect.

[0116] In summary, according to an advantageous embodiment, there is provided a system according to the first and / or third aspect, wherein the camera uses a pinhole or other non-refractive optical element as an objective lens, and wherein a plurality of target units according to the seventh aspect are positioned on the monitored object. As described herein above, survey light reflected by a survey reflector of the target unit is generated at the camera as one or more diverging light beams, the one or more diverging light beams forming a diverging light beam having a solid angle such that at least 10%, preferably 50% or more of the field of view of the camera is illuminated by the diverging light beam. This system allows points or positions of objects such as buildings or other structures to be monitored with high angular accuracy, while the system avoids the use of any moving parts.

[0117]

[0117] The use of a wide beam, such as a diverging beam emitted by an LED, in combination with using a pinhole instead of a lens as the camera objective can result in a more reliable system with more accurate measurements compared to conventional systems using a collimated laser beam and a camera with a lens-based objective, although this can lead to light losses. As discussed above in this specification, light losses can be compensated for by using a high-power LED light source, integrating measurements, and / or using multiple survey reflectors at individual locations on the target.

[0118]

[0118] Embodiments of the present disclosure are described herein below with reference to the accompanying drawings. However, the embodiments of the present disclosure are not limited to the particular embodiments, and should be construed to include all modifications, variations, equivalent apparatus and methods, and / or alternative embodiments of the present disclosure.

[0119]

[0119] As used in this specification, the terms "have," "may have," "include," and "may include" indicate the presence of the corresponding feature (e.g., a value, function, operation, or element such as a component) and do not exclude the presence of additional features.

[0120] As used herein, the terms "A or B," "at least one of A and / or B," or "one or more of A and / or B" include all possible combinations of the items listed therewith. For example, "A or B," "at least one of A and B," or "at least one of A or B" means (1) including at least one A, (2) including at least one B, or (3) including both at least one A and at least one B.

[0121] As used herein, terms such as "first" and "second" may modify various elements and do not limit the corresponding elements, regardless of the order and / or importance of the corresponding elements. These terms may be used to distinguish one element from another. For example, a first element can be referred to as a second element, and similarly, a second element can be referred to as a first element, without departing from the scope of the present invention.

[0122]

[0122] When an element (e.g., a first element) is "operably or communicatively coupled with" or "connected to" another element (e.g., a second element), it will be understood that the element may be directly coupled with / to the other element, or that there may be intervening elements (e.g., third elements) between the element and the other element. Conversely, when an element (e.g., a first element) is "directly coupled with" or "directly connected to" another element (e.g., a second element), it will be understood that there are no intervening elements (e.g., third elements) between the element and the other element.

[0123]

[0123] As used herein, the phrase "configured to" may be used interchangeably with "suitable for," "capable of," "designed to," "adapted to," "created to," or "capable of," depending on the context. The term "configured to" does not necessarily mean "specifically designed to" at the hardware level. Instead, the phrase "an apparatus configured to..." may mean that an apparatus, in conjunction with other devices or components in a particular context, is "capable of..."

[0124]

[0124] The terms used in describing various embodiments of the present disclosure are intended to describe particular embodiments and are not intended to limit the present disclosure. As used herein, the singular form is intended to include the plural form unless the context clearly dictates otherwise. All terms used herein, including technical or scientific terms, have the same meaning as commonly understood by those skilled in the art unless otherwise defined. Terms defined in commonly used dictionaries should be interpreted as having the same or similar meaning in the context of the relevant technology, and should not be interpreted as having an ideal or exaggerated meaning unless expressly defined herein. Depending on the circumstances, even terms defined in this disclosure should not be interpreted as excluding embodiments of the present disclosure.

[0125]

[0125] For purposes of determining the scope of protection afforded by the claims of this document, appropriate consideration should be given to any elements equivalent to elements specified in the claims.

[0126]

[0126] The present invention will now be described in more detail with reference to the accompanying drawings. [Brief explanation of the drawings]

[0127] [Figure 1A] 1A-1C show some schematic configurations of a system for monitoring the position and / or movement of an object. [Figure 1B] 1A-1C show some schematic configurations of a system for monitoring the position and / or movement of an object. [Figure 1C] 1A-1C show some schematic configurations of a system for monitoring the position and / or movement of an object. [Figure 2] 1 is a diagram illustrating a system according to a general embodiment of the present invention; [Figure 3] FIG. 4 shows a schematic diagram of a system according to a further embodiment of the invention. [Figure 4] FIG. 1 shows a schematic diagram of a setup for reducing environmental interference. [Figure 5A] FIG. 1 shows a schematic diagram of a setup for distinguishing reflections from a survey reflector from other reflective elements. [Figure 5B] FIG. 5B is a diagram illustrating the principle of FIG. 5A. [Figure 5C] FIG. 5B is a diagram illustrating the principle of FIG. 5A. [Figure 5D] FIG. 5B is a diagram illustrating the principle of FIG. 5A. [Figure 5E] FIG. 5B is a diagram illustrating the principle of FIG. 5A. [Figure 6] FIG. 1 shows a schematic measurement setup according to one embodiment. [Figure 7] FIG. 10 shows a schematic diagram of an arrangement that allows for identification of a survey reflector, according to one embodiment. [Figure 8] FIG. 1 is a diagram showing an overview of the functions of a camera that can be used in the present invention. [Figure 9] 1 illustrates an exemplary housing for a camera according to the present invention. [Figure 10] FIG. 10 shows a flowchart of an example of the functionality of the system. [Figure 11] FIG. 2 illustrates a target unit according to one embodiment of the present invention. [Figure 12A] 12A-12C show schematic cross-sections of the target unit of FIG. 11 according to different embodiments. [Figure 12B] 12A-12C show schematic cross-sections of the target unit of FIG. 11 according to different embodiments. [Figure 12C] 12A-12C show schematic cross-sections of the target unit of FIG. 11 according to different embodiments. [Figure 13A] FIG. 10 illustrates the placement of survey reflectors within a target unit according to an embodiment of the present invention. [Figure 13B] FIG. 10 illustrates the placement of survey reflectors within a target unit according to an embodiment of the present invention. [Figure 13C] FIG. 10 illustrates the placement of survey reflectors within a target unit according to an embodiment of the present invention. [Figure 13D]FIG. 10 illustrates the placement of survey reflectors within a target unit according to an embodiment of the present invention. [Figure 14A] FIG. 10 illustrates the placement of survey reflectors within a target unit according to an embodiment of the present invention. [Figure 14B] FIG. 10 illustrates the placement of survey reflectors within a target unit according to an embodiment of the present invention. [Figure 14C] FIG. 10 illustrates the placement of survey reflectors within a target unit according to an embodiment of the present invention. [Figure 15] FIG. 14B is a rear view of the arrangement of FIG. 14A. DETAILED DESCRIPTION OF THE INVENTION

[0128]

[0143] Generally, the present invention relates to surveying an object or tracking the movement of an object by tracking one or more survey reflectors attached to the object. More particularly, the present invention is directed to an apparatus comprising a camera with one or more light sources configured to emit diverging light beams for surveying and / or tracking locations on an object.

[0129]

[0144] While the illustrated embodiments are described using a camera having an optical entry system, i.e., a camera objective, formed by a non-refractive element in the form of a pinhole in the camera objective, it should be understood that the non-refractive element may alternatively be any of the non-refractive elements described herein above. Alternatively, the optical entry system may be formed by a lens system, such as a lens system including a single lens. Similarly, while the embodiments are described using a prism as the survey reflector, it should be understood that a different reflective element, for example, another type of prism or a hollow mirror, may also be used.

[0130]

[0145] Figure 1A shows a possible setup of a system in which an object 3 is monitored. The system comprises a sensor device such as a camera 7. The system also comprises a number of survey reflectors 1 attached to the object 3 at a number of locations. The object 3 is shown as including one or more buildings to which the survey reflectors 1 are fixed. However, the object 3 may alternatively be other structures such as towers, tunnels (Figure 1B) or bridges (Figure 1C), but may also be vehicles (such as boats on land) or natural objects such as large rocks.

[0131]

[0146] The object 3 is monitored by monitoring or measuring the position of the survey reflector 1. By monitoring their position over time, movement of all or part of the object 3 can be detected. Preferably, the amount, degree and / or direction of movement can also be determined. This allows monitoring of conditions such as the stability or integrity or mechanical properties of the object 3.

[0132]

[0147] One camera 7 is shown, however the system may comprise multiple cameras 7.

[0133]

[0148] According to the present invention, camera 7 is positioned to generate and transmit diverging light beams 5, also referred to as first beams, to a plurality of survey reflectors 1. The survey reflectors 1 reflect portions of the diverging light beams 5 that impinge thereon, thereby forming reflected beams 6 that are reflected back to camera 7. As will be explained in more detail herein below, light beam 5 is generally substantially conical in shape and has a solid angle Ω1 that covers the field of view of camera 7. This allows multiple survey reflectors 1 to be monitored substantially simultaneously.

[0134]

[0149] Figure 1B shows the implementation in a tunnel 3. A railway with railway sleepers 12 is passing through the tunnel 3. Both the tunnel walls and the railway sleepers 12 are equipped with survey reflectors 1. The camera 7 is positioned to view all survey reflectors 1 within its field of view.

[0135]

[0150] FIG. 1C shows an implementation on a bridge 3. The bridge 3 is equipped with multiple survey reflectors 1. A camera 7 is positioned to view all of the survey reflectors 1.

[0136]

[0151] The survey reflector 1 shown in Figures 1A-1C may be realized by a single high-precision survey reflector such as a survey prism, or alternatively, each location may be provided with multiple survey reflectors advantageously realized by target units 1100, 1101, 1102, 1103, as described herein below with reference to Figures 11 and 12A-12C.

[0137]

[0152] FIG. 2 is a schematic diagram of the measurement principle of a system 20 for monitoring multiple locations on an object 3 according to a first aspect of the present invention. To facilitate the explanation and understanding of the optical principles, FIG. 2 shows the system 20 monitoring one survey reflector 21. However, as shown, for example, in FIGS. 1A-1C, the system 20, and in particular its camera 27, can be used to monitor multiple such survey reflectors. In the illustrated embodiment, the survey reflector 21 is formed by a prism, but other types of reflectors, such as hollow mirrors, can also be used. Further alternatively, instead of a single reflector 21, a target unit, such as that shown in FIGS. 11-15, can be used, which comprises multiple such reflectors.

[0138]

[0153] The system 20 comprises a camera 27 and a processing unit 29 that may be included in or located within the camera 27. Alternatively, the processing unit 29 may be located remotely from the camera 27.

[0139]

[0154] The camera 27 includes a first light source 22 that emits a diverging beam 25, also referred to as a first diverging beam. The first light source 22 typically includes a light-emitting diode (LED). The first beam 25 has a first solid angle Ω1, which is preferably large enough to substantially cover the entire field of view of the camera 27. Alternatively, as described above, multiple first light sources 22 may be provided to substantially cover the field of view of the camera. In such an embodiment, the solid angle of each beam need not necessarily cover the field of view, as long as the assembly of beams substantially covers the field of view. This allows all survey reflectors 21 located within the field of view of the camera, i.e., seen by the camera, to be illuminated by the first beam 25 without moving, rotating, or scanning the camera or the light beam (possibly excepting one or more survey reflectors that are shadowed by obstacles, such as pedestrians or vehicles when monitoring a building, as shown in FIG. 1A, or trains when monitoring a tunnel, as shown in FIG. 1B). If multiple first light sources 22 are provided, all survey reflectors are illuminated by a beam from at least one of the light sources.

[0140]

[0155] In some embodiments, the first diverging beam 25, or the accumulation of first diverging beams emitted by the plurality of first light sources 22, only partially covers the camera's field of view. For many surveying applications, this may be sufficient. The partial coverage may be, for example, at least 10% or more, and in some embodiments, at least 50%, depending on the application.

[0141]

[0156] The first beam 25 is preferably amplitude modulated, so as to exhibit a predetermined variation in its amplitude over time. Alternatively and / or additionally, other types of encoding may be applied to the first beam, as described in more detail in the overview section herein above. As mentioned above, environmental effects on the measurements, such as interference from ambient light, may be reduced by applying appropriate filtering techniques during image processing of the data.

[0142]

[0157] The survey reflector 21 reflects a portion of the received first beam 25 to form a reflected beam 26 that is reflected back towards a camera 27 .

[0143]

[0158] The apparatus 20 further comprises an image sensor 24 configured to receive reflected light, i.e., a portion 261 of the reflected beam 26, which enters the camera 27. As a result of receiving the reflected light 261, the image sensor 24 generates data in the form of, in a preferred embodiment, a two-dimensional image.

[0144]

[0159] Disposed between the image sensor 24 and the first light source 22, or at least its light-emitting surface, is a body 28, which in the illustrated embodiment is substantially planar. The body 28 is non-transparent to light and, in the illustrated embodiment, includes an optical entry system in the form of a non-refractive element such as a pinhole 23, forming the objective lens of the camera. In the illustrated embodiment, the body 28 forms part of the housing of the camera.

[0145]

[0160] Although the present description focuses on optical entry systems formed by pinholes, other types of non-refractive elements may be suitable as well, in particular those described in WO 2019 / 143250, as well as refractive elements such as single thin lenses.

[0146]

[0161] The processing unit 29 is configured to determine the position of each survey reflector from the data, typically by image processing of the data provided by the image sensor, based on a comparison of the determined position of each survey reflector with their previously determined positions, and to detect movement of one or more of the plurality of survey reflectors.

[0147]

[0162] By simultaneously illuminating all survey reflectors within the camera's field of view with diverging beams generated by one or more first light sources, all survey reflectors can be measured substantially simultaneously without the need to move the camera and / or scan the first beam. This reduces the complexity of the system and the time required for measurements. Because the survey reflectors are passive reflective elements, no power source is required.

[0148]

[0163] The first light source 22 is positioned a first distance D1 from the pinhole 22. Roughly speaking, the first distance D1 is smaller than the diameter, such as the diameter D, of the surface area or aperture of the survey reflector 21 onto which the first beam 26 is incident. If the light source is outside this radius, the observer, i.e., the pinhole 23, cannot "see" the reflection of the first light source, according to the principles of optics: The light source 22 can be assumed to be approximately a point source. A perfect survey prism reflects the divergent beam emitted by the first light source (if its beam width is wide enough to cover the entire prism aperture) back to the (point) source. The apparent distance of the reflected light source to an observer collocated with the source is twice the distance from the source to the prism. The beam width or solid angle (in degrees or steradians) of the reflected beam is limited by the prism aperture and the distance between the light source and the prism. The diameter of the reflected beam spot at the light source is twice the diameter of the prism opening (because the virtual light source 22v is located at twice the distance from the light source to the prism). The center of the spot of the virtual light source 22v is at the same location as the point light source 22. Therefore, an observer (or receiver) at the same distance from the prism as the light source can only "see" the reflected light source if the observer (or receiver) is within a radius of the prism diameter from the light source. In other words, the reflection 251 of the first beam 25 at the prism 21 appears at the pinhole 23 only if the first light source 22 is located within a distance of the pinhole equal to or less than the prism diameter. This principle is used in different embodiments to distinguish and / or reduce the effects of ambient light and / or reflections of the first beam from surfaces other than the survey reflector, as will be described in more detail below.

[0149]

[0164] FIG. 3 schematically illustrates a system 30 according to a further embodiment. The system 30 is similar to the device 20 illustrated in FIG. 2, except that the camera 37 is provided with an additional light source, also referred to as a second light source 322, in addition to the first light source 321. The second light source 322 is similar to the first light source and is positioned at a second distance D2 from the pinhole 33 that is greater than the first distance D1. Similar to the approximate definition of the first distance D1, the second distance D2 is greater than the diameter D of the prism 31. The first and second light sources 321, 322 can be positioned on opposite sides of the pinhole 33, but this is not required. Similar to the first light source 321, the second light source 322 also emits a diverging light beam in the form of a second beam 352 having a second solid angle Ω2, preferably large enough to cover the field of view of the camera. Further similar to the embodiment of FIG. 2, multiple first and second light sources 321, 322 may be provided. This means, following the theory summarized above with reference to Figure 2, that the reflection 362 of the second light source 322 by the prism 31 does not enter through the pinhole 33, but the reflection of the first light source 361 does (as described above with reference to Figure 2). As can be seen, the virtual light source 322v corresponding to the second light source 322 is not visible at the pinhole 33. This setup thereby facilitates the suppression of reflections from spurious objects, according to an embodiment of the present invention.

[0150]

[0165] Elements or surfaces other than the survey reflector 31 that are located within the field of view of the pinhole 33 and that are illuminated by the first beam 321 can also reflect light diffusely or as specular surfaces. These reflections can interfere with the reflection from the prism 31 or even create a false target. To obtain reliable measurement results, and thus reliable and proper monitoring of the monitored object, it is desirable to be able to distinguish between such unwanted reflections and the reflection of the first beam from the prism.

[0151]

[0166] This can be achieved as described above by applying a first code to the first beam, for example by amplitude modulating the first light beam 351 emitted from the first light source 321 at a particular modulation frequency and providing a second code to the second beam, so that only the reflection of the first light source 321 reaches the pinhole, and not the second light source 322 in the prism. Other elements in the field of view reflect light from both sources back to the pinhole.

[0152]

[0167] By providing different codes, Code 1 and Code 2, respectively, to the light emitted by the first and second light sources 321, 322, the signals originating from the first and second light sources respectively can be separated during processing of data from the image sensor, as explained in more detail in the overview section herein above.

[0153]

[0168] By subtracting the two images obtained after filtering the first and second codes respectively, it is possible to obtain the reflection caused by the prism 31. From the image obtained from the subtraction, the position and / or movement of the prism 31 can be determined.

[0154]

[0169] Alternatively, an optical bandpass filter can be placed in or before the prism 31 to pass light of one wavelength and block light of another wavelength. A first light beam having a first wavelength and a first code is reflected by the prism, but a second light beam having a second wavelength and a second code is not. This causes the prism to reflect only light from the first light source 321, while other elements in the camera's field of view reflect both light from the first light source 321 and light from the second light source 322. This method also works if the second light source is placed at a distance from the pinhole 33 that is less than the diameter of the prism.

[0155]

[0170] In a further embodiment shown in Figure 4, the influence of environmental interference on the survey reflector measurements is reduced by fitting the survey reflector 41 with an active modulator 412, for example a liquid crystal modulator that modulates the amplitude of the reflected light 46 at a specific frequency that is constant, i.e., distinguishable from the ambient light. Also, in this embodiment, a single light source 42 is sufficient. The light beam 45 emitted thereby does not need to be modulated, but may be.

[0156]

[0171] In the embodiment shown in FIG. 5A, the camera 57 includes a first light source 521 and an additional light source, also referred to herein as a third light source 522. Both light sources are located within a distance d from the pinhole 53. Using the approximate definition above, the distance d does not exceed the diameter D of the survey reflector 51. Thus, portions of the reflected beams 561 and 562 of both the first light beam 521 and the additional light beam 522 are reflected by the survey reflector 51 and enter the pinhole 53. Due to their different codes, their respective projections on the image sensor 54 can be distinguished using image processing. The light sources 521 and 522 are advantageously located on opposite sides of the pinhole 53, although this is not required. The camera 57 may further include one or more second light sources located away from the pinhole 53, as described with reference to FIG. 3, but details of such combinations will be omitted here.

[0157]

[0172] As shown in Figures 5B to 5E, this setup makes it possible to distinguish between reflections from the prism 51 or hollow mirror forming the survey reflector and reflections from other mirror-like surfaces, also called false targets, located in the field of view of the camera 57. For this purpose, the first beam 521 is provided with a first code and the beam 522 with a different code. The characteristics of the image resulting from the reflection of the two light sources, in particular the presence or absence of mirror symmetry, make it possible to distinguish whether the reflection comes from a prism or another mirror-like surface.

[0158]

[0173] 5B, when reflected from prism 51, a first light source 521, e.g., an LED to the right of pinhole 53, generates a virtual light source 521v that appears on the left, and light source 522, which may be an additional LED to the left of pinhole 53, generates a virtual light source 522v on the right. In other words, or more generally, the images of the two light sources are mirrored relative to the center of the prism.

[0159]

[0174] However, this is not the case when reflected from a flat mirror 5101 as shown in Figure 5C, or from a spherical, or convex, mirror 5102 as shown in Figure 5D. In these cases, the image is not mirrored.

[0160]

[0175] As shown in FIG. 5E, for a hollow or concave mirror surface 5103, the image will only be mirrored if the two light sources are located outside the focal length of the mirror.

[0161]

[0176] Furthermore, from the distance between the two images or objects recorded by the image sensor 54 in the embodiment shown in FIG. 5A, the distance D between the camera and the survey reflector can be calculated. T The distance between the images i1 and i2 recorded on the image sensor 54 can be determined by the known distance between the two light sources and the focal length D of the camera. f (i.e., the distance between the image sensor and the pinhole, which is known), and the absolute (two-dimensional) angle of the image sensor relative to the object, which can be measured according to other principles described herein and / or known to those skilled in the art, and the distance D between the pinhole and the prism, which can thus be determined. T Depends on.

[0162]

[0177] Another measurement setup capable of determining the distance between a camera and various survey reflectors is shown in FIG. 6. In this setup, two cameras 67A and 67B are used, positioned at different camera locations but viewing the same scene, i.e., the same set of survey reflectors 61. These cameras 67A, 67B may be any of the cameras described above and may therefore operate according to any of the methods described above. The cameras are positioned so that their respective optical axes are disposed at a preferably known angle α relative to one another. As will be appreciated by those skilled in the art, triangulation measurements can be used to determine the distance from the camera to the survey reflector 61. Furthermore, the three-dimensional coordinates of the survey reflector 61 can be determined, as described in the Overview section of this document.

[0163]

[0178] Furthermore, in each of the above-described embodiments, it may be desirable to identify each of the survey reflectors before commencing a measurement or monitoring session and / or while monitoring a series of survey reflectors over time, in order to distinguish reflections from each of the different survey reflectors. This may be made possible by the embodiment shown in Figure 7. It should be noted that the embodiment of Figure 7 may be applied to or incorporated into each of the embodiments described herein above.

[0164]

[0179] As shown in FIG. 7 , the survey reflector 71 comprises a light receiver 714 for receiving a portion of the first beam 75 emitted by the light source 72 of the camera 77, and a microcontroller 719 coupled to or forming part of the light receiver 714 and / or attached to or combined with the light receiver 714 for detecting and / or processing a signal generated by the light receiver upon receiving the light. Furthermore, an identification unit light emitter 712, e.g., an LED, is provided on the survey reflector and coupled to the microcontroller 719. The light receiver 714, the microcontroller 719, and the light emitter 712 may form a survey reflector identification unit 716. The processing unit 79 associated with the camera 77 is configured to control the first light source 72 so that a signal is added to the first light beam 75. This signal may include an identification request. When such a request signal is received by the light receiver 714, the identification unit light emitter 712 emits an identification signal, e.g., in the form of a short-lived code. This identification signal is unique to each survey reflector and, when received by the image sensor 74 of the camera 77, allows the survey reflector to be identified.

[0165]

[0180] The survey reflector 71 and the survey reflector identification unit 716 may be arranged in a survey reflector unit 718, which may also be called a beacon.

[0166]

[0181] The object 3 may be provided with a number of survey reflector units 718 at different positions on it in order to monitor these positions. In the embodiment shown, the survey reflector 71 is provided by a prism. However, it can be understood that other types of reflectors may be suitable as well, for example a hollow mirror, also known as a cat's eye.

[0167]

[0182] By configuring the processing unit 79 to cause the camera 77, and in particular its light source 72, to send an identification request to all survey reflector units within its range, each of these can be uniquely identified by an identification signal transmitted by the identification unit 716 of each survey reflector unit 718.

[0168]

[0183] The components according to the embodiment of camera 7 will now be described in more detail, in particular with regard to their functional aspects. This description applies equally to all cameras 27, 37, 47, 57, 67A, 67B, 77 described in the different embodiments herein above.

[0169]

[0184] FIG. 8 illustrates an example of a camera 7. The exemplary camera 7 includes non-refractive optics 101, an image sensor 120, a clock 123, a processing unit 9 connected to memory 15, one or more position and / or orientation measurement components 16, an output unit 17, an input unit (or user interface) 19, an electronic networking module 109, and one or more light sources 102. The non-refractive optics 101 is shown connected to the image sensor 120. This latter "connection" need not be a physical connection. Here, "connection" is intended to refer to a situation in which the non-refractive optics 101 is configured to receive ambient light such that the received ambient light is received by the image sensor 120. As can be understood from the embodiments described herein above, not all functional elements illustrated in FIG. 8 need be present.

[0170]

[0185] All connections intended for the transmission of data may be physical connections (wires), but may alternatively be wireless and based on the transmission of electromagnetic / optical radiation.

[0171]

[0186] The non-refractive optic 101 may be any type of non-refractive optical element described herein above. In a preferred embodiment, the non-refractive optic may include one or more pinholes. The pinhole diameter may be in the range of 50-400 μm. Alternatively, as described above, the non-refractive optic may be replaced by a lens, which is preferably a thin lens that allows for temperature modulation with low computational effort.

[0172]

[0187] The processing unit 9 may be any suitable processing unit known in the art.

[0173]

[0188] The image sensor 120 preferably includes a set of light-sensitive elements (pixels) arranged in a 2D matrix that forms the camera's image plane, such as a CCD or CMOS sensor. The image sensor 120 is positioned to receive the light beams 6 incident thereon through the non-refractive optical system 101. Each light beam 6 is focused onto a subset of these light-sensitive elements. Each such subset corresponds to the solid angle of one incident light beam 6, i.e., both the horizontal and vertical angles of incidence relative to the Earth. Of course, angles of incidence relative to other objects besides the Earth, such as a geostationary satellite, can also be measured. These subsets are static for each survey reflector 1, as long as both the camera 7 and the survey reflector 1 are in fixed positions.

[0174]

[0189] In an alternative embodiment, a line sensor can be used in combination with an optical slit as an objective lens rather than a pinhole. In such an embodiment, the optical slit is oriented essentially perpendicular to the lateral direction of the line sensor. Such an alternative embodiment can provide angular measurement in one dimension. To increase the number of dimensions available for measurement, two or more such devices equipped with line sensors can be arranged in various different orientations. For example, two such devices can be arranged perpendicularly, enabling measurements similar to those performed with a 2D matrix sensor. Such linear sensor arrangements have the advantage of consuming significantly less power than devices using 2D matrix sensors.

[0175]

[0190] Optionally, a temperature control system 103 may be provided to reduce thermal effects on the measurement data. The thermal capacity of the non-refractive optics 101 is relatively low compared to cameras 7 that use a lens system instead of the non-refractive optics 101. Thermal stability can be improved by implementing a temperature control system in the form of a thermostat 103. FIG. 8 shows an embodiment with a reversible (i.e., configured for both cooling and heating) Peltier element 103 for the non-refractive optics 101. The Peltier element 103 is connected to a processing unit 9, and its temperature is controlled by the processing unit 9 so that the non-refractive optics 101 is kept at a predetermined temperature. Alternatively, thermal stability can be increased by the design of the camera housing, in particular the materials used, and / or by measuring the temperature at various locations within the camera housing and using a model that accounts for thermal effects during processing of data from the image sensor.

[0176]

[0191] The following summarizes some general aspects of the system described hereinabove and how it operates.

[0177]

[0192] If the system is equipped with two or more cameras, as shown in Figure 6, the technique described here can be used to measure how far the survey reflector 1, 61 is from the camera. This can be done by triangulation measurements where one baseline is known. Measuring the distance between the cameras 7, 27, 37, 47, 57, 77 and the survey reflector 1 can also be done with other distance measurement techniques, such as time-of-flight measurements.

[0178]

[0193] The image sensors 24, 34, 44, 54, 74, 120 convert the received light beam 6 into an image. The image is a series of electronic signals, referred to herein as pixel signals. Each pixel signal is generated by one light receiving element and has a value that depends on the light intensity of the light received by the light receiving element. The pixel signals can therefore relate to the object 3 to which the survey reflector 1 is attached and its surroundings.

[0179]

[0194] The image sensor is positioned so that light entering the camera through the non-refractive element forms a diffraction pattern on the image sensor. The diffraction pattern depends on the properties of the non-refractive element and appears as dark or light areas on the image sensor depending on the distance and angle from each pixel of the image sensor to the non-refractive element. High-resolution measurements can be obtained by integrating multiple data frames containing a large number of pixels, typically at least 100.

[0180]

[0195] In embodiments using refractive optics, such as a lens, the image sensor is preferably positioned so that its photosensitive elements are near the focal plane of the lens. In another preferred embodiment, the image sensor 120 is positioned within the focal length of the lens, and the image is defocused a certain amount, resulting in a focus condition beyond infinity. In such an embodiment, image processing may include super-resolution imaging based on defocusing techniques, thereby enabling sub-pixel resolution. Resolutions of 1 / 100th of a pixel or better can be achieved.

[0181]

[0196] Processing unit 9 is configured to receive pixel signals from image sensor 120 and store them in memory 15. The pixel signals may be stored by processing unit 9 as a single image, preferably with a timestamp and / or position stamp indicative of the position of camera 7. Preferably, however, the pixel signals are stored by processing unit 9 as a series of images forming a video, each image being provided with a timestamp and / or position stamp indicative of the position of camera 7.

[0182]

[0197] The clock 23 supplies clock signals to the processing unit 9, as known to those skilled in the art. The clock signals are used for the normal processing of the processing unit 9. The processing unit 9 can generate timestamps based on these clock signals. However, the camera 7 may also be equipped with a GNSS unit that receives time signals from satellites, or may receive time signals from another suitable source.

[0183]

[0198] The memory 15 may include different types of sub-memories, such as ROM (Read Only Memory) / Flash-type memory, for storing appropriate program instructions and data for executing the processing unit 9. The memory may also include appropriate RAM (Random Access Memory)-type memory for storing temporary data, such as data received from the image sensor 120. The memory 15 may also include cache-type memory. Some or all of the sub-memories may be located physically separate from the other components. The processing unit 9 may also be configured to transmit all pixel signals via the electronic networking module 20 to a remote unit for external storage and processing. A local copy of these pixel signals may then be stored in the local memory 15 within the camera 7, but this is not required.

[0184]

[0199] The memory 15 stores initial position data indicating the initial position of the camera 7. Such initial position data may be established using a theodolite and saved by the user. Such initial position data may also be obtained from measurements made by the camera 7 itself. For example, the camera 7 may collect sequential photographs from a known "blinking" light source installed on a tall, well-known aviation obstacle marker. Such obstacle markers may be placed at a specified vertical distance from the tall structure, enabling triangulation. The memory 15 also stores a camera ID that identifies the camera 7 and is used by the processing unit 9 in external communications with other devices to identify the camera 7 to other external devices.

[0185]

[0200] The position and / or orientation measurement component 16 may include one or more accelerometers and / or gyrometers / gyroscopes, as known to those skilled in the art. It may also include the GNSS unit described above. Such accelerometers and / or gyrometers / gyroscopes measure the camera's own motion and derive an updated camera position and orientation from such measurements. The updated camera position and / or orientation is then stored in memory 15 by the processing unit 9. This allows changes in the camera's position and / or orientation to be taken into account when measuring the position of one or more survey reflectors 1. Accuracy may be on the order of 1 / 1000 of a degree. Tests have demonstrated accuracy of 2 millidegrees peak-to-peak. Furthermore, a 3-axis accelerometer package can also measure the direction of Earth's gravity when stationary. A 3D gyro package with sufficient performance can also measure the orientation of the Earth's rotation axis (even when stationary).

[0186]

[0201] The output unit 17 may include one or more sub-output units such as a display and a speaker.

[0187]

[0202] The input unit 19 may comprise one or more sub-input units, such as a keyboard and a microphone. The display and keyboard may be made as two separate touchscreens, but may also be implemented as a single touchscreen.

[0188]

[0203] The electronic networking module 20 may comprise one or more of LTE (Long Term Evolution), Ethernet, WiFi, Bluetooth, power line communication, low power wide area networks (e.g., Lora™ and Sigfox™), and NFC (Near Field Communication) modules. Technologies known in the Internet of Things (IoT) and proprietary communication protocols may also be used.

[0189]

[0204] The at least one light source 102 includes at least one light source, such as a light emitting diode (LED) source, configured to generate light. The processing unit 9 is configured to control each LED light source to generate a light beam.

[0190]

[0205] As shown in FIG. 9 , the camera may be provided with a housing configured to withstand high temperature and / or pressure environments (e.g., deep sea or geothermal environments) without introducing significant errors due to deformation of the optical elements. The housing (which may be used with any of the cameras 27, 37, 47, 57, 67A, 67B, and 77 described in different embodiments herein) includes at least one wall 600 surrounding a cavity 610. The image sensor 120 is mounted within the cavity 610. The housing is closed by a front wall or cover, also referred to herein as a body, within which a pinhole 102 (or another optical entry system) is provided. The pinhole 102 is configured to form an image with the sensor 120, as described herein above. The first, second, and third light sources described herein may be disposed on or within the front wall or body facing the exterior of the housing to emit their light beams in the exterior direction. The housing may further be provided with various additional features and / or elements, depending, for example, on the particular environment in which the camera will be used.

[0191]

[0206] The basic idea of ​​the device, and the method for using the device to monitor objects, is that camera 7, or any one of cameras 27, 37, 47, 57, 67A, 67B, 77 described in different embodiments herein, is placed in a fixed position so that it is stationary. The stationary position is then known and stored in memory 15 accessible by processing unit 9 of camera 7.

[0192]

[0207] All survey reflectors 1 described in the various embodiments herein above, or similarly survey reflectors 21, 31, 41, 51, 61, 71, or target units 1100, 1101, 1102, 1103 described further herein below and shown in Figures 11 to 15, when installed, have initial positions stored in the memory 15 of the camera.

[0193]

[0208] Thus, when the system is started, the camera knows all the initial positions of the survey reflectors that correspond to the initial positions and orientations of the objects 3 on which the survey reflectors are attached.

[0194]

[0209] The processing unit 9 is configured to calculate the initial solid angle of incidence of each of the reflected light beams 6. That is, the received reflected light beams are imaged via non-refractive optics onto one or more light-sensitive elements of the image sensor 120. The processing unit 9 determines which these light-sensitive elements are and establishes the solid angle of incidence of the corresponding light pulses. Techniques for doing so are known to those skilled in the art and need not be described in further detail here.

[0195]

[0210] If the object 3 is stable, i.e. does not move, the positions of all survey reflectors 1 are also stable. As a result, the solid angle of incidence of each reflected light beam on the image sensor of the camera is fixed. However, as soon as the object 3 or part of it moves, this solid angle of incidence of the reflected light beam 6 changes. The processing unit 9 is configured to calculate this change in the solid angle for each light beam 6.

[0196]

[0211] FIG. 10 shows an example of successive steps in image processing according to an embodiment of the present invention.

[0197]

[0212] The camera 7 receives reflected light beams 6 from the survey reflectors 1, 1100, 1101, 1102, 1103, 1401, 1402, 1403 which are projected onto the image sensor 120. Figure 10 shows a process flow according to one embodiment performed by the processing unit 9 to extract relevant survey reflector data. This process flow applies equally to any of the embodiments described herein above. It should be understood that Figure 10 shows a basic process and that further details may be added to one or more of the process steps and / or further process steps may be added to further optimize the method, particularly as described herein above and / or as would be understood by one of ordinary skill in the art.

[0198]

[0213] The first step 1001 in the process is to sequentially record or capture at least two, and preferably many, image frames, or raw data frames. Each image frame is essentially a 2D array of light values. By capturing a series of image frames, a 3D matrix of light values ​​is formed. The axes of the 3D matrix are X, Y, and time T. In one embodiment, a sequence of 100 images is captured at intervals of 1 / 60 seconds.

[0199]

[0214] In step 1002, digital processing is applied to the sequence of image frames to enhance the data associated with one particular light source or coded light beam while suppressing the contribution of other light received by the image sensor, as described herein above. The output of this process is a 2D image. Multiple light sources with different unique codes can be processed using the same 3D matrix of light values, each producing a unique 2D image.

[0200]

[0215] In step 1002a, the processed 2D image may include both the (diffusely) reflected light of the environment and the reflection from the survey reflector of the divergent light beams emitted by the one or more first light sources.

[0201]

[0216] In step 1002b, the 2D processed image associated with the light emitted by the second light source may include (diffusely) reflected light of the environment, rather than from the survey reflector, as described with reference to FIG. 3 herein above.

[0202]

[0217] In step 1002c, which may be optional, the processed 2D image may equally contain both the (diffusely) reflected light of the environment and the survey reflector, but it comes from a light source having a different position than in 1002a, e.g. one or more third light sources, so the position of the survey reflector in the 2D image will be slightly shifted compared to the image obtained in step 1002a.

[0203]

[0218] In step 1003, the two 2D images obtained in steps 1002a and 1002b, respectively, are subtracted from each other to reveal only the reflection of one particular light source by the survey reflector. By subtracting the image obtained in step 1002b, and optionally the image obtained in step 1002c, from the image obtained in step 1002a, the reflection of light emitted by the first light source from the survey reflector can be enhanced while reducing the effects of ambient light and diffusely reflected light from other light sources. The result is a single 2D image that substantially represents only the reflection of the first divergent light beam from the survey reflector, with other effects suppressed.

[0204]

[0219] In step 1004, the position of the survey reflector and / or one or more movements of the monitored survey reflector are determined. Light emitted by a particular light source, e.g., a first light source, or light having a particular coding, e.g., a first coding, reflected from the survey reflector generates a feature or blob, preferably comprising multiple pixels, for each survey reflector, or a diffraction pattern in the case of non-refractive optics. By correlating the feature or pattern in the 2D image obtained in step 1004 with predetermined (e.g., default) features or diffraction patterns and / or previously measured features or diffraction patterns, the position of the survey reflector and / or one or more of its movements can be identified.

[0205]

[0220] In step 1005, the resulting data, i.e., the precise 2D coordinates of each of the reflectors, is made available for other processes. These may include further processes to correct for errors such as camera movement, temperature compensation, estimating distance based on the two light sources, storing the data, displaying the data, etc.

[0206]

[0221] FIG. 11 illustrates a target unit 1100 according to one embodiment. The target unit 1100 includes multiple survey reflectors 111 arranged in the same plane, represented by dashed lines p1 or p2. As shown in FIG. 12A, the survey reflectors 111 can advantageously be survey reflectors 21, 31, 41, 51, 61, or 71 described hereinabove. As can be seen in FIG. 11, the multiple survey reflectors 111 are arranged symmetrically around a center of symmetry at which survey reflector 111c is located. In the illustrated embodiment, each survey reflector has six nearest neighbors, except for those located at the ends of the array. In other words, the reflectors are arranged in shifted or offset rows, and the rows may have different numbers of reflectors. Preferably, all of the survey reflectors 111 are substantially identical. A plurality of survey reflectors 111 are disposed or mounted in a holder 110, which may be mounted on a standard or tripod placed on the ground, or may be secured to an object or structure such as object 3 shown in Figures 1A-1C. Holder 110 is advantageously non-reflective and non-transparent to light emitted by survey camera 7.

[0207]

[0222] As shown in FIG. 11, the front surface of the survey reflector that receives the incident light can be circular, with a hexagonal arrangement providing the most efficient placement of the reflector.

[0208]

[0223] The plurality of target units 1100 shown in Figure 11 may advantageously form part of any one of the systems described with reference to Figures 2 to 4, 5A, 6 and 7 herein above.

[0209]

[0224] Figure 12A shows a cross section along aa in Figure 11. As can be seen, the target unit 1100 comprises a plurality of survey prisms 111. These may be advantageously represented by the survey prisms 21, 31, 41, 51, 61, 71 described herein above.

[0210]

[0225] Figures 12B and 12C show alternative embodiments 1102, 1103 of target unit 1100. These embodiments differ from the embodiment of Figure 12A by the type of survey reflector used. However, even in these embodiments, the survey reflectors may be arranged in the pattern shown in Figure 11.

[0211]

[0226] Figure 12B shows a target unit 1102 comprising multiple convex mirrors 11102. These may be similar to the survey reflector 5102 shown in Figure 5D.

[0212]

[0227] Figure 12C shows a target unit 1103 comprising multiple concave mirrors 11103. These may be similar to the survey reflector 5103 shown in Figure 5E.

[0213]

[0228] Figures 13A-13E show close-packed arrangements similar to Figure 11 for different numbers of individual survey reflectors 141. In the illustrated embodiment, the survey reflectors have circular bases facing the incident light beam, although similar arrangements are possible with bases of other shapes.

[0214]

[0229] 13A-13E show target unit arrangements including 3, 7, 19, 37, and 61 survey reflectors, respectively. Increasing the number of reflectors typically increases the operating distance of the system. As can be seen, the individual reflectors are arranged in an array with centers of rotational and / or mirror symmetry such that the reflected light intensity is substantially equal in different directions of the cross section of the reflected light beam. However, rectangular arrays or arrays with only one row of reflectors are also possible in certain applications.

[0215]

[0230] Figures 14A-14C show schematic packing configurations of prisms 141 with triangular bases. As can be seen, these may be arranged so that the sides of the bases of adjacent prisms touch each other. Figure 15 shows a schematic representation of the arrangement of Figure 14A from a rear view.

[0216]

[0231] The scope of the present invention is not limited to the foregoing examples, and it will be apparent to those skilled in the art that several modifications and variations thereof are possible without departing from the scope of the present invention as defined in the appended claims. While the present invention has been illustrated and described in detail in the drawings and description, such illustration and description are to be considered exemplary or illustrative only and not restrictive. The present invention is not limited to the disclosed embodiments, but includes advantageous combinations of the disclosed embodiments.

[0217]

[0232] Variations of the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, by studying the drawings, the description, and the appended claims. The features of the above-described embodiments and aspects can be combined unless such combination results in an obvious technical contradiction.

Claims

1. 1. A method for monitoring a plurality of survey reflectors (1, 21, 31, 41, 51, 5101, 5102, 5103, 61, 71) arranged at a plurality of positions on an object (3), comprising: The method includes receiving, by an image sensor (24, 34, 44, 54, 74, 120) of a camera (7, 27, 37, 47, 57, 67A, 67B, 77), a reflected light beam (26, 361, 46) including reflections of a first diverging beam by the plurality of survey reflectors to provide image sensor data; The reflected light beam one or more first light sources (22, 321, 42, 521, 72, 102) of the camera, each emitting a first diverging beam (5, 25, 351, 45, 551, 75) having a solid angle (Ω1) greater than zero, the one or more first light sources being positioned such that a field in space corresponding to at least 10% of the field of view of the camera is illuminated by the one or more first light sources; one or more second light sources (322) each emitting a second diverging beam (352); is formed by the image sensor is disposed in an interior space of a body (28, 38, 48, 58, 78) of the camera having an optical entry system (23, 33, 43, 53, 73), the body having a first side facing the interior space and a second side facing an opposite side to the interior space, the one or more first light sources are disposed on the second side of the body, and the one or more first light sources are disposed at a first distance (D1, d) from the optical entry system; the first distance is selected so that reflection of the first diverging beam from the survey reflector passes through the optical entry system into the camera and onto the image sensor; the one or more second light sources are positioned at a second distance (D2) from the optical entry system that is greater than the first distance, the second distance being such that a reflection (362) of the second diverging beam from the survey reflector does not pass through the optical entry system to the camera; the method comprising the steps of: processing the image sensor data by a processing unit (9, 29, 79) of the camera to determine a position of each survey reflector from the image sensor data; and detecting movement of one or more of the plurality of survey reflectors based on a comparison of the determined position of each survey reflector with previously determined positions of the survey reflectors; the processed image sensor data includes a first image including reflected light of an environment and the reflection of the first diverging beam by the survey reflector, and a second image including the reflected light of the environment; The method comprises: subtracting the second image from the first image to obtain a resulting image; determining a position and / or movement of the one or more survey reflectors of the plurality of survey reflectors based on the resulting images; Including, the processing unit is further configured to apply a first code to the first divergent beam by modulation of the first divergent beam and to apply filtering techniques during image processing of the recorded data; The method comprises: applying, by the processing unit, a second code to the second diverging beam; emitting a third diverging beam (552) by one or more third light sources (522), the one or more third light sources being positioned at a third distance (d) from the optical entry system that is substantially similar to the first distance (d); applying, by the processing unit, a third code to the third diverging beam, the third code being different from the first code and, if used, different from the second code; further comprising: method.

2. the optical entry system comprises a non-refractive optical element (101) forming an objective lens of the camera; The method of claim 1.

3. the field in space corresponds to at least 50% of the field of view of the camera, and preferably the field in space is substantially equal to or larger than the field of view of the camera; 3. The method according to claim 1 or 2.

4. the method further comprising applying, by the processing unit, a command code to the first diverging beam, the command code comprising instructions, information and / or requests to be transmitted to the survey reflector; The method according to any one of claims 1 to 3.

5. The method further comprises the step of providing a survey reflector identification unit (761) mounted on or included in a survey reflector, the survey reflector identification unit (761) comprising: a receiver (71) for receiving the first divergent beam; a microcontroller (719) coupled to the optical receiver; an identification unit emitter (712) configured to emit a unique identification signal in response to said microcontroller receiving a command; Including, The method according to any one of claims 1 to 4.

6. 1. A system for monitoring a plurality of survey reflectors (1, 21, 31, 41, 51, 5101, 5102, 5103, 61, 71) arranged at a plurality of positions on an object (3), said system comprising: a camera (7, 27, 37, 47, 57, 67A, 67B, 77) configured to monitor the survey reflector, the camera comprising: one or more first light sources (22, 321, 42, 521, 72, 102) each emitting a first diverging beam (5, 25, 351, 45, 551, 75) having a solid angle greater than zero; one or more second light sources (322) each emitting a second diverging beam (352) having a solid angle greater than zero; an image sensor (24, 34, 44, 54, 74, 120) for receiving a reflected light beam including reflections of the first diverging beam by the plurality of survey reflectors and providing data; a body (28, 38, 48, 58, 78) having an optical entry system (23, 33, 43, 53, 73); Including, the body has a first side facing an interior space of the camera and a second side facing away from the interior space, the image sensor is disposed in the interior space, and the first and second light sources are disposed on the second side of the body; The system comprises a processing unit (9, 29, 79) configured to process the data according to the method of any one of claims 1 to 5. system.

7. the system further comprises a survey object unit (1100, 1101, 1102, 1103) for use in the system, the survey object comprising a plurality of survey reflectors (21, 31, 41, 51, 5101, 5102, 5103, 61, 71, 111, 11101, 11102, 11103) arranged in a single plane (p1, p2); The system of claim 6.

8. the plurality of survey reflectors are arranged in the array with one of the plurality of survey reflectors (111c) being located at the center of the array, the center representing a point of symmetry of the array; 8. A system according to claim 6 or 7.

9. the plurality of survey reflectors are arranged in a hexagonal array pattern. A system according to any one of claims 6 to 8.

10. each survey reflector having a surface configured to receive an incident light beam, said surface being substantially circular; The system according to any one of claims 6 to 9.

11. the plurality of survey reflectors are realized by a plurality of survey prisms (21, 31, 41, 51, 61, 71, 111), the prisms being preferably substantially identical, and the surfaces of the prisms configured to receive the incident light beams being arranged in a single plane; A system according to any one of claims 6 to 10.

12. the plurality of survey reflectors are realized by a plurality of hollow mirrors (5102, 5103, 11102, 11103), each having a center point (c), the hollow mirrors preferably being substantially identical, and the center points of all mirrors being located in a single plane (p1, p2); A system according to any one of claims 6 to 11.

13. the plurality of survey reflectors includes 13 to 35 reflectors; A system according to any one of claims 6 to 12.

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