EP3938801A1

EP3938801A1 - A method for locating a retro-reflecting object on a tool

Info

Publication number: EP3938801A1
Application number: EP20717335.2A
Authority: EP
Inventors: Björn Edlund
Original assignee: Beotop Innovation AB
Current assignee: Beotop Innovation AB
Priority date: 2019-03-12
Filing date: 2020-03-01
Publication date: 2022-01-19
Also published as: WO2020185143A4; WO2020185143A1

Abstract

The invention discloses a method and a system for locating a retro-reflecting object (6) on a manufacturing tool within a volume, said volume consisting of a transparent medium and being limited by the boundary of the field-of-view (FOV) (5) from a lens-equipped aperture (4) of a base station (1), and by non-transparent obstructions within said FOV (5). Pixels (53) on a surface (52) behind said aperture (4) is associated, one-to-one, with sets of pair-of-angles in relation to the normal plane of said aperture (4) within said volume. Said base station (1) furthermore consisting of image capturing means (20) that detect reflected light signals from objects, said signals are filtered by filtering means (51). Said base station (1) tracks the movement of said object (6) and estimates the position of a tool end based on reflections from at least one retro-reflecting object (6) on said tool.

Description

A METHOD FOR LOCATING A RETRO-REFLECTING OBJECT ON A TOOL

Various wireless technologies based on the propagation of waves in free air have been exploited for determining the location of a device in space. The majority of said devices in these technologies are powered, e.g. by batteries or similar, and connected to controlling means. Examples of waves are Ultra-wideband (UWB), and U ltrasonic waves, both of which are used with trilateration and Time-of- Flight (ToF) techniques for determining the location of a device. GPS and GFONASS, also utilizing these methods with radio waves, are used for finding an electronic device' position on the surface of the earth. Another, more modern technology is Bluetooth, which have been seen in local positioning applications. Other technologies have also been exploited for the same purpose, such as inertia sensitive technology (I MU) as well as image recognition technologies, often in connection with efforts to exploit artificial intelligence (Al). The number of potentially fruitful technologies is thus large, which is an indication that this challenge is a field of interest for many companies. Flowever, the mentioned methods are either expensive or inaccurate to some degree, or both.

For the manufacturing industry, we have suggested to use the emerging technology of asymmetric free space optical (FSO) data communicating systems for coming to terms with the mentioned problems above. Flence, this technology also has capacity to wirelessly transfer data. The challenge of achieving a high level of traceability and control of tool operations in this industry on one hand, and to achieve a reliable wireless data communication system on the other hand, is met with the

"directional" properties of this technology. Such a system has been suggested to include a stationary base station which is interrogating a potentially moving modulating retro-reflector (MRR) integrated on said tool. The base station would do that with a directional light source carrying data signals for establishing an asymmetric FSO data link.

For such applications, a challenge is to direct said directional light source from a base station to said MRR with high accuracy. If the MRR is not stationary but moves around in space, said challenge can be broken down into the method for the base station to finding it and efficiently tracking it with said directional light source. As soon as it has been found, the interrogating and thus handshaking procedures of establishing an FSO data link can be started. Before the MRR has been found, no data can be interchanged and no knowledge of the direction or distance from the base station to the MRR can been achieved. Therefore, it is crucial for the base station to use a method that quickly enables it to find the MRR with high reliability and with high accuracy. It shall be mentioned that the desired method, which is the object of this invention, is not limited to said tool positioning application. It is considered to have a clear purpose of its own. Thus, also in many non-FSO applications, a method for finding a retro-reflecting object is wanted, and it does not matter whether said object has MRR capabilities or not. The desired method is thus a positioning method for reflecting objects, where the distance between the base station and the reflecting object has line-of- sight between them, or line-of-sight between them and mirrors in the system implying that light from the base station reaches the reflecting object and vice versa. More than one base station may also be used for increasing the likelihood of finding the reflective device. Also, a subsequent task to the finding of the reflector is for the system to perform an effective tracking of the reflecti ng object. To know the accurate position of a retro-reflector is important for a base station, e.g. in the mentioned field of asymmetric Free Space Optical (FSO) applications.

PRIOR ART

The document US20060060651 (Dl) discloses a laser scanner that rapidly scans pre-programmed points of retro-reflecting targets for permitting the exact locations and the identity of the targets to be confirmed. The purpose of the system is to make sure that the cooperative target is still present and that its position has not changed. Also, the retro-reflecting targets also modulate the reflected light for purposes of returning additional information back to the location of the scanner.

Although having features reminding of the disclosed field of interest, Dl does not discuss the problem of trying to find a retro-reflective target within a volume when a 'pre-programmed point' does not contain such a target. The invention in Dl is thus limited to certain activities based on whether a target has been found or not, not to find the target when it is lost'. Flowever, Dl does discuss data sending capabilities when a target has been found.

SUMMARY OF THE INVENTION

The invention discloses a method for locating a retro-reflecting object (6) on a manufacturing tool in a volume, said volume consisting of a transparent medium, said volume furthermore being partly limited by boundaries of the field-of-view (FOV) (5) of a lens-equipped aperture (4) of a base station (1), and partly by non-transparent obstructions within said FOV (5), said base station (1) furthermore containing data processing means (9), at least one data memory (7, 8), a light source (46), image capturing means (20), and means for communicating data with a controlling unit (48) , said method is accomplished by said light source (46) shedding light on said volume, said image capturing means (20) capturing an image of reflected light signals from said obstructions in said volume, the method comprising:

predetermining one-to-one associations between multiple sets of pair-of-angles (23, 24) within said FOV (5) and pixels (25) on a surface (2) behind said lens (4) in said base station (1), each said set of pair-of-angles (23, 24) fully determining a direction (22) in 3-dimensional space in relation to the normal of said lens-equipped aperture (4), and storing said associations in compounds in one of said at least one data memory (7, 8),

predetermining at least one property of reflected light signals, said property being indicative of a found retro-reflecting object (6), and storing data specifying said at least one property in one of said at least one data memory (7, 8) of said base station (1),

detecting reflected light signals on said image capturing means (20) when a pixel (25) is activated, said pixel (25) having a said one-to-one association to a set of pair-of-angles (23, 24) directed to a reflecting object (6),

determining at least one set of pair-of-angles (23, 24) corresponding to reflected light signals from at least one retro-reflecting object (6), and storing said determined set of pair-of-angles (23, 24) in one of said at least one data memory (7, 8), said pair-of-angles (23, 24) constituting a 2- dimensional position data estimation of said retro-reflecting object (6), and setting an identity of said retro-reflecting object (6) and storing said identity linked to said stored determined pair-of- angles (23, 24)

The method further comprising:

said base station (1) containing at least one directional light source and at least one directional light source direction adjusting means, said light source containing distance measurement means, said directional light source direction adjusting means directing said directional light source to one of said at least one reflecting object (6) defined by one of said at least one determined pair-of- angles (23, 24),

measuring the distance (40) to said retro-reflecting object (6), and storing said distance linked to said determined set of pair-of-angles in one of said at least one data memory (7, 8),

said processing means (9) estimating the 3-dimensional position of said retro-reflecting object (6), said estimation calculation using said determined set of pair-of-angles (23, 24) and said measured distance (40), said 3-dimensional position estimation being in relation to the location and the orientation of said base station (1),

in one of said at least one data memory (7, 8), storing said 3-dimensional position linked to said stored distance (40) and said stored determined pair-of-angles (7, 8) Furthermore, the method is comprising:

said at least one property being specifications on the amplitude of said reflected light signals, said specifications stating what amplitudes of said reflected light signals from any pair-of-angles must be for said pair-of-angles to be determined,

said at least one property being specifications on the wavelengths or polarity of said reflected light signals, said specifications stating what wavelengths or polarity said reflected light signals from any pair-of-angles must have for said pair-of-angles to be determined,

If said base station detects that at least two pixels are associated with at least two sets of determined pair-of-angles, and that at least one of said properties of the reflected light signals corresponding to said at least two pixels does not differ more than a predetermined amount, and that said at least two pixels do not have more than a predetermined amount of pixels between them, said at least two sets of determined pair-of-angles are grouped,

said grouping meaning setting the identities of the retro-reflecting objects corresponding to said determined pair-of-angles to same group identity, storing said group identity linked to said stored determined pair-of-angles in said at least one data memory (7, 8)

The method comprising additionally:

said image capturing means continuously measuring at least one of said properties of said reflected light signals from at least one set of determined pair-of-angles corresponding to a stored identity of at least one retro-reflecting object (6),

setting and storing an attribute meaning "moving retro-reflector" linked to said stored identity of said retro-reflecting object (6) in one of said at least one memory (7, 8) if the following conditions are fulfilled:

o within a predetermined time period, at least one property of reflected light signals on one pixel (a) goes from indicative of a retro-reflecting object corresponding to said pixel (a) to not indicative of a retro-reflecting object corresponding to said pixel (a),

o within said time period, at least one property of reflected light signals on another pixel (b) goes from not indicative of a retro-reflecting object corresponding to said pixel (b) to indicative of a retro-reflecting object corresponding to said pixel (b)

o said pixels a and b do not have more than a predetermined number of pixels between them unselecting said determined pair-of-angles for not being part of said sets of determined pair-of- angles when said at least one property of said reflected light signals are not indicative of a corresponding retro-reflecting object anymore,

Also, the method comprising:

investigating whether there are retro-reflecting objects in said volume by shedding light in the directions of at least one pair-of-angles at a time and measuring at least one of said properties of reflected light signals corresponding to said at least one pair-of-angles predetermining and storing a 'tool indicative retro-reflections distance interval' meaning allowed distances between retro-reflecting objects attached to a tool, and storing said 'tool indicative retro-reflections distance interval' in one of said at least one data memory (7, 8),

predetermining a 'tool end distance' meaning the distance and the direction from the set of retro- reflecting objects on a tool to an end of said tool,

said retro-reflecting objects having been detected by said image capturing means and the identities of said retro-reflecting objects have been stored in said at least one data memory, said data processing means estimating the distance between said reflecting objects and if said distance does not differ more than a predetermined amount from said 'tool indicative retro- reflections distance interval', estimating the tool end position based on the positions of said retro- reflecting objects,

storing said tool end position in one of at least one data memory (7, 8)

The method is also comprising:

said base station further comprising Free Space Optical (FSO) data communication interrogation means consisting of a light source being directed to a determined reflecting object,

said interrogation means interrogating said determined reflecting object for aiming to establish an asymmetric FSO data communication link

The invention does also contain a Computer program comprising instructions which, when executed by a computer, cause the computer to carry out the method according to any of the preceding claims. The invention also contains a Computer-readable medium comprising instructions which, when executed by a computer, cause the computer to carry out the method according to any of the claims

1-10 Thus, what is claimed system-wise is a system consisting of a base station (1) for finding a retro- reflecting object (6) on a manufacturing tool in a volume, said volume consisting of a transparent medium, said base station (1) containing at least one data memory (7, 8), data processing means (9) and a lens-equipped aperture (4), behind said lens a surface (2) is disclosed, said surface (2) containing identifiable areas, pixels (25), each of said pixels (25) having a one-to-one association to one set of pair-of-angles (23, 24), said set of pair-of-angles (23, 24) fully determining a direction (22) in 3- dimensional space measured from the normal of said aperture (4), all of said sets of pair-of-angles (23, 24) determining the field-of-view (FOV) (5) from said aperture (4), said base station (1) furthermore containing at least one light shedding device (46) for shedding light on a volume covering said FOV (5), said base station also containing image capturing means (20), said image capturing means (20) capturing images of reflections from non-transparent obstructions within said FOV (5), said base station (1) comprising:

in one of said at least one data memory (7, 8), said sets of pair-of-angles (23, 24) and data identifying said associated pixels (25) are stored in data compounds,

means for determining and outputting at least one pair-of-angles (23, 24) when reflected light signals from at least one retro-reflecting object (6) are captured by said image capturing means (20)

The base station furthermore contains

light shedding means (57) containing said lens-equipped aperture (4), pixels (25) on said surface (2) and at least one light source (46),

said at least one light source (46) is directed to said pixels (53) of said surface within said light shedding means (57), said pixels (53) manipulating the light from said light source (46) for subsequently transporting said light via said lens-equipped aperture (4) to cover said FOV said base station furthermore containing at least one directional light source and directional light source direction adjusting means,

said at least one data memory and said data processing means are interconnected with said directional light source direction adjusting means for the data processing means to send determined pair-of-angles to said directional light source direction adjusting means,

said directional light source direction adjusting means capable of adjusting the direction of said directional light source to point towards the direction defined by said received determined pair- of-angles within said FOV.

Optionally, said directional light source direction adjusting means is a galvanometer. Said directional light source direction adjusting means can also be at least one digital micromirror device (DMD) being part of a micro-electromechanical system (MEMS). Said at least one light source is a laser rangefinder. Said surface in said base station can consist of digital micromirror devices (DMD) or an LCD screen Finally, said at least one light source is an interrogating laser for establishing an asymmetric Free Space Optical (FSO) data communication link with a modulating retro-reflector (MRR).

To summarize, what is claimed is a positioning system for locating a retro-reflecting object (6) on a manufacturing tool in a volume according to above, wherein:

said positioning system containing at least two base stations according to above,

said at least two base stations being installed in one common coordinate system, with determined orientations and locations of said base stations in said coordinate system,

said at least two base stations being interconnected for communicating between each other the position of said retro-reflecting object, said position being a point in said coordinate system

BRIEF DESCRI PTION OF THE DRAWINGS

Fig 1. shows a high-level overview of the method and system

Fig 2. presents the overall principle of the method and system

Fig 3. shows an overview of the functionality of the light shedding means and the image capturing means

Fig 4. shows a surface of pixels and the principles of the tracking functionality

Fig 5. presents the base station in more detail, according to a first embodiment of the invention

Fig 6. shows a surface of pixels and the functionality of said first embodiment of the invention

Fig 7. presents the base station in more detail, according to a second embodiment of the invention

Fig 8. shows a high-level situation when a retro-reflecting object has been found by the base station

Fig 9. shows the invention in the application of locating a manufacturing tool

Fig 10. shows an example of an array of retro-reflecting objects

DETAILED DESCRIPTION OF THE INVENTION

Referring to fig 1, the main idea of the method and the system in the invention is to find at least one retro-reflecting object (6) within a three-dimensional volume by optical means in a base station (1). A retro-reflector is an object being part of the obstructions in said volume as viewed from said base station (1), said vol ume being limited partly by said obstructions and the boundary surface of the field of view (FOVbs) (5) from said base station (1). Light (11) is shed on said volume from light shedding means in said base station (1) and said retro-reflector (6) reflects said light if said light is covered within the field of view (FOVrr) (12) of said retro-reflecting object (6). Said base station (1) is optionally connected to a controlling unit (48) via a network (47).

As can be seen in fig 2, the obstructions in said volume within said FOVbs (5) corresponds to specific pixels (3) on a surface (2) behind a lens-equipped aperture (4) within said base station (1). Flowever, depending on the resol ution of the system, each pixel covers a certain part size of said FOVbs, said part size thus forming a small field of view (FOVp) per pixel. Flence, each said pixel (25) corresponds to a fixed direction (22) which is pointed in the center of said FOVp, said direction being outside of said base station (1) and being defined by a set of pair-of-angles (23, 24), said pair-of-angles (23, 24) being measured from the normal of said lens-equipped aperture (4). One set of pair-of-angles (23, 24) determines fully a direction in three-dimensional space. Preferably the pair-of-angles (23, 24) consist of an azimuthal angle and a polar angle, said angles preferably thus being perpendicular to each other. The lens-equipped aperture (4) and the pixels (3) on the surface form a certain field-of-view (FOVbs) (5) outside of the base station (1). It is within this FOVbs (5) that the pair-of-angles (23, 24) are directed.

There are existing but different technologies for associating the following two entities with each other:

1) line-of-sight obstructions within a FOV (5) from a point in space to a volume

2) pixels (3) on a surface (2) at (or just behind) said point in space

where said associations are updated frequently so that the pixel representation of the corresponding volume in said FOV is done in real-time, not just at any specific point in time.

Such existing technologies are known in the art: on one hand different types of projectors exist. In DLP (Digital Light Processing) projectors the total amount of pixels consist of a matrix of small mirrors, so called digital micromirror devices (DMD), also called micro-electromechanical system mirrors (or MEMS mirrors), said mirrors can be repositioned rapidly one-by-one to reflect light of different colors either through the lens or onto a heat sink. The DLP technology was developed by Texas

Instruments™. Another type of projectors is based on LCD (Liquid Crystal Display) technology. Some of these are sometimes called LED projectors depending on the light source type. A successful LCD technology in projectors has by Epson™ received the brand name '3LCD' where a series of dichroic filters separates light to three polysilicon panels. As polarized light passes through the panels

(combination of polarizer, LCD panel and analyzer), individual pixels can be opened to allow light to pass or closed to block the light.

On the other hand, however, also cameras, such as motion picture cameras or video cameras, are known in the art which also do this association between pixels and line-of-sight obstructions within the FOV. The camera has a lens that projects an image onto a sensor that creates a video signal. Said video signal from the sensor consists of a number of images per second, each consisting of horizontal lines and pixels.

The disclosed invention utilizes said feature, however said feature being defined by the association of a direction from a lens on one hand, with a pixel on a surface on the other hand, said surface often being 2-dimensional and forming a matrix of pixels, on a grid. Important to note however, is that in the mentioned technologies the actual "directions" has not been emphasized. In these developed technologies, it has been the image of real objects being represented by groups of pixels that is the interesting feature, not the actual directions defined by angles from the lens. It is this feature that is utilized for arriving at the purpose of the invention, which is to search and subsequently find a retro- reflecting object in space within line-of-sight from the searching unit. Flowever, the technology used for associating a direction to a pixel can be any one of the mentioned types in the state of the art, in principle described by projectors OR cameras. Although different purposes in those technologies (they can even be argued to have opposite purposes) their functionalities are still based on one and the same principle as they fulfill said one-to-one association between a certain direction (22) from the lens (4) to a certain 'pixel' (25) behind the lens (4). The disclosed invention is based on said principle and the invention has embodiments from both mentioned types. Each pixel (25) is thus associated with a unique set of pair-of-angles (23, 24).

Said base station also comprises a light source shedding light (11) on said volume. When a retro- reflecting object (6) is hit by said light, said retro-reflecting object (6) will reflect said light back to the base station (1). A condition for the retro-reflecting object to reflect said light is that the field-of-view (FOVrr) (12) of said retro-reflector covers the light from the base station, meaning that the back-to- the-source-reflecting property of said retro-reflector is only effective if the light (11) to be reflected is found within a certain FOVrr (12) in relation to the normal of said retro-reflecting surface. Said FOVrr (12) is different depending on the type of retro-reflector, whether it consists of corner-cubes, cat-eye- lenses or other types, but is normally around +-15 degrees, exact specification of said angle width in said FOVrr (12) is not important for the utilization of the invention. When said retro-reflecting object (6) is found by the base station (1), said retro-reflecting object (6) will reflect light back to the base station (1).

Furthermore, said base station (1) contains data processing means (9) and at least one data memory (7, 8), said at least one data memory normally being at least one volatile and at least one non-volatile memory. Said base station (1) is calibrated during its installation, in an orientation and at a location where said base station (1) is to operate from. Said associations between pixels and corresponding sets of pair-of-angles are stored as multiple compounds in one of at least one data memory (7, 8), normally in a non-volatile memory. Each said compound thus containing a pair-of-angles and data identifying the corresponding pixel. Thus, when said retro-reflecting object (6) is found by the base station (1), the pixel (25) corresponding to the direction (22) to the location of said retro-reflector (6) is identified. The identification data of said pixel (25) will be used for picking up the corresponding pair-of-angles (23, 24) among said compounds from the storage of compounds in said at least one data memory (7) of said base station (1). Said pair-of-angles (23, 24) is thus determined as

corresponding to a found reflecting object (6), said determined pair-of-angles now being stored in a data memory (7, 8), normally in one of the at least one volatile memories, in said base station (1) .

In order to describe the principle of the functionality of said base station (1), it is important to describe the image capturing means which is also embedded in said base station (1). Also, said light shedding means in said base station (1) has an important role. However, said image capturing means and said light shedding means are not specifically shown in fig 2. This is because said image capturing means and said light shedding means look somewhat different in the different embodiments. Thus, they will be described more in detail in relation to the descriptions of said different embodiments. However, in fig 3, an overview of the principle of said light shedding means (11) and said image capturing means (10) in said base station (1) is shown. Said light shedding means (11) sheds light (68) on said retro- reflecting object (6). Said retro-reflecting object (6) reflects light (69) back to said base station (1). Said image capturing means (10) captures the reflected light (69) from said reflecting object (6) and alerts said data processing means (9) that a certain pixel shall be associated to a retro-reflecting object (6).

Said determined pair-of-angles (23, 24) representing said direction (22) to said reflecting object (6) will be used by processing means (9) in said base station (1) for controlling beam direction means (42) to be directed to said reflecting object (6). Said beam direction means (42) is used by electronic distance measurement (EDM) means (43), e.g. consisting of a laser rangefinder in said base station (1), for measuring the distance, characterized by the straight line (13), and macroscopically by the distance (40) in Fig 8, from the base station (1) to the retro-reflecting object (6). Said distance calculation is normally carried out by processing means (9) in said base station (1), said distance calculation is at least using the time-of-flight method, which is known in the art of laser rangefinders. Said distance measurement result data is updated frequently and is stored in a data memory (8) (normally a volatile memory). The location expressed in 3-dimensional coordinates of said retro-reflecting object is calculated, using known trigonometric formulas, by said data processing means (9) based on said distance (40) and said pair-of-angles (23, 24). Said pair-of-angles (23, 24) and the angles indicated by said straight line (13) in fig 2 are very different from each other. The purpose of fig 2 is however for emphasizing the principal functionality of said base station (1) which requires a view of said base station (1) and said retro-reflecting object (6) which may look unrealistic. Normally said retro-reflecting object (6) is much further away from said base station (1) meaning that the mentioned angles are less different from each other. However, there may still be a small difference of angles between said pair-of-angles (23, 24) and the angles formed by said straight line (13), said difference being due to difference in location of the lenses (4, 45). Said differences are accounted for when calibrating the base station (1) at installation, said calibration is done via trigonometric calculations by said data processing means (9). These differences are represented by data that is stored in a memory (7), normally a non-volatile memory in said base station (1). Furthermore, the invention according to the claims is also considered to cover a base station (1) where same aperture (4) and where also same 'pixels' are used for locating said retro- reflecting object and for directing beams with specific purposes to it.

Referring now to fig 4, apart from fig 1 - 3. If a retro-reflecting object (6) is moving and its FOVrr (12) still covers the base station (1), some pixels are triggered, e.g. pixel (31), and some other are

"untriggered", e.g. pixel (33). The base station (1) then acts to recalculate the location of the retro- reflecting object (6) similarly as above, but in a tracking procedure. For the reflecting object to be perceived as moving, the pixels that are triggered and the pixels that are untriggered must be closer than a certain number of pixels from each other, for example maximum 2 pixels as shown in fig 5. Said number of pixels are derived from the size of a retro-reflecting object that is searched for and said number is predetermined. Furthermore, to be perceived as moving in a certain speed or acceleration, the time period between triggered pixels and untriggered pixels must be within a certain

predetermined time period interval. Said predetermined time period interval and said predetermined number of pixels are stored in at least one of said at least one data memory (7, 8). In said tracking procedure some pair-of-angles are selected to be determined and others are unselected for not being part of said sets of pair-of-angles as from a certain point in time. Crucial is also that said image capturing means (10) has a sufficiently frequent update interval for being able to capture fast moving reflecting objects. Said determining of 'new' sets of pair-of-angles indicating a moving object are stored in one of at least one data memory together with attribute data indicating a 'moving' object. When, or if, the FOV of either said retro-reflecting object (6) (FOVrr) or said base station (1) (FOVbs) does not cover its counterpart, the tracking is lost and the base station (1) aims to find said retro- reflector (6) again, as has been described above. To distinguish said retro-reflected light from all light sources and reflections in said volume, the light entered into the image capturing system is filtered in different ways by distinguishing filters of different sorts. One type of said distinguishing filters is a polarizing filter that enables identification of a certain reflected light due to its polarity. Said polarizing properties of said retro-reflected light corresponds to data stored in a memory (7) of said base station (normally a non-volatile memory) as said polarizing properties is predetermined by the design of said retro-reflecting object (6) being searched for. Another type of said distinguishing filters is an amplitude filter, only enabling processing of reflected light above a certain threshold amplitude, said reflected light from said retro-reflector (6) has an amplitude above said threshold. Other examples are wavelength filters, detecting and filtering light differently depending on said light's wavelength. Such distinguishing of a desired type of reflecting object is thus also accomplished by modifying the wavelength of the transmitted light (11) from said light source of said base station (1). There could also be other types of distinguishing filters, enabling said base station to identify said retro-reflecting objects in said volume. Many filters have supporting functionalities in part of the software running in said processing means (9) in said base station (1). Said part of said software is using configuration data stored in a data memory (7). Said configuration data is configured by a user via a graphical user interface (GU I) in advance to the operation of said base station (1), said GUI occasionally being connected to said base station (1) via an interface (14). With said software, a dynamic configuration of settings on what to filter is done. Other manipulations are also managed with said software. Said at least one filtering means (61) is schematically shown in fig 3.

When said base station (1) determines that at least one set of pair-of-angles corresponding to at least one reflecting object (6) within the FOVbs (5), said base station assigns an identity to each determined set of pair-of-angles (23, 24) and stores said identity in one of said at least one data memory (7, 8). Said identity of said determined pair-of-angles (23, 24) being interpreted as a retro-reflecting object. Furthermore, if said base station detects that at least two adjacent pixels, or pixels with not more than a predetermined number of pixels between them, according to said stored compounds correspond to determined sets of pair-of-angles, and that the properties of said corresponding reflections does not differ more than a predetermined amount, said object identities of said sets of pair-of-angles are grouped into corresponding to one and the same object. If sets of pair-of-angles are being grouped this way, the pair-of-angles corresponding to the reflections of the highest amplitude is being selected as the main pair-of-angles corresponding to that reflecting object.

Furthermore, a directional light source direction adjusting means (42) is included in said base station for being instructed to direct at least one directional light source (43, 44) to the retro-reflecting object (6) defined by said determined pair-of-angles (23, 24). One of said at least one directional light source controlled by said direction adjusting means (42) is the EDM means (43) as has been described.

An interrogating signal in a modulated laser beam from an interrogating data communicating laser source (44) within said base station is also pre-programmed to be directed to said retro-reflecting object (6) when said retro-reflecting object (6) has been found. Said interrogation is considered successful when said retro-reflecting object (6) returns modulated signals according to predetermined properties implying that FSO data communication has been initiated.

Said directional light direction adjusting means (42) can consist of a galvanometer controlled mirror or a M EMS mirror. It could also be a tip-tilt device controlled by a couple of servo motors, or controlled by a step motors. It could also be controlled via the pixels on the surface (2)

Said base station (1) is also containing beam shape modifying means (45) on the beam created by any of said at least one directional light source (43, 44). Said beam shape modifying means (45) consists of an adjustable lens arrangement for beam collimation, controlled by said data processing means (9), and modifies the beam of corresponding directional light when it has been directed to a reflecting object by the light source direction adjusting means (42). Said modification of said beam is represented in fig 2 by a thin beam (15) and a thicker beam (35). Said modification of said beam thickness (15, 35) is done by the collimating properties of the lens within said beam shape modifying means (45). During said beam thickness modifications, frequent measurements of the amplitude of said corresponding reflections are done. The aim for modifying said collimated beam thickness (15,

35) is to find the beam shape implying the highest reflection amplitude, by keeping same signal strength from the at least one light source and modifying the beam thickness (15, 35).

When said highest amplitude has been found, said light source direction adjusting means (42) optionally finetunes the beam direction along the line corresponding to the boundaries of the pixel (25) associated to said main determined pair-of-angles (23, 24) corresponding to said reflecting object (6). Said finetuning algorithm is done by said processing means (9) ordering said direction adjusting means (42) to move the beam according to the average of the determined pair-of-angles (23, 24) and the sets of the pair-of-angles of the pixels surrounding said pixel (25). During said finetuning algorithm, the amplitude of the reflected light is frequently measured for finding said largest amplitude of said reflections. When found, the pair-of-angles of said light source direction adjusting means (42) is the most accurate pair-of-angles corresponding to said reflecting object. Said accurate pair-of-angles is used for accurate position calculation together with data on said distance (40), said accurate position data being stored in a data post in one of said at least one data memory (8), normally a volatile memory, said post also containing a data attribute meaning 'accurate'.

With similar arguments as above, the claims of the invention are considered to cover also the case where said directional beam with its direction adjusting means (42) is embedded within same aperture (4) from which the pair-of-angles are determined, meaning also that the beam shape modifying means (45), the EDM means (43) and the FSO interrogating laser source (44) may be embedded for reaching out through said aperture (4).

Thus, said functionalities described above are common to all embodiments of the invention even if the function of the different parts of the system differ according to the differences between said embodiments. Said embodiments are shown in fig 5 and 7, which now will be described.

In a first embodiment of the invention, presented in fig 5, said surface (52) of "pixels" (53) is used for shedding light on said volume within said FOVbs (5). To this end, said light shedding means (57) includes a light source (46) shedding light on the surface (52) of pixels (53). Said pixels (53) are controlled by the data processing means (59) how to shed light on the volume defined by the FOVbs (5). The feature of having each pixel associated to a particular set of pair-of-angles from said base station is still valid as it is a crucial part of the invention. In this method, light from light shedding means (57) is shed on the volume sequentially, one part of the FOVbs (5) at a time in a scanning movement, said part consisting of at least one pixel. An example is shown in fig 6 where four pixels (34, 35, 36, 37) forming a square are used for the lighting up one at a time, lightening up one small volume at a time within said FOVbs (5). Flowever, it could be just one pixel at the time being lit up as well. Said image capturing means (20) does or does not detect the presence of a reflecting object for every scanning step. Said at least one filter (51) is also at work within said image capturing means (20) for enable said data processing means (59) to determine whether a reflecting object fulfills the at least one condition to be considered as an interesting retro-reflecting object candidate or not. If said image capturing means (20) detecting a reflecting object (6) when a specific pixel (55) has been "lit up", said data processing means (59) receives a signal from said image capturing means (20) about said detection . Said processing means (59) then fetches the corresponding pair-of-angles (23, 24) from the relevant data compound in the memory (7, 8), determines and stores said pair-of-angles temporarily in one of said at least one memory (7, 8) and sends said pair-of-angles to said directional light source direction adjusting means (42) which is instructed to be directed to said reflecting object (6). Said processing means (9) also sends activation signal to the at least one directional light source (43, 44) for further processing. It shall be mentioned that for the first embodiment, the beam shape collimation modifying means, the EDM means using a laser source, and/or the FSO interrogating laser source may be embedded for reaching out through said lens-equipped aperture (4). According to this first embodiment this is preferably accomplished by utilizing the pixel controlling features of the described technologies, meaning that the light source (46) contains a laser source.

For said first embodiment a special filter shall be described which has another function than the already mentioned other filters. It is described by using secondary image capturing means such as a photo detector, which is physically located further away from the lens-equipped aperture (4) than the original image capturing means. The purpose of being located further away from the light source is that retro-reflected light originating from the base station (1) will not hit this secondary photo detector, which is a fact utilized by distinguishing non-interesting reflecting objects from interesting retro-reflecting objects.

As described, said sequentially lightened part of the FOVbs (5) could be selected to be as small as corresponding to one single pixel or corresponding to a group of pixels (34, 35, 36, 37), said selection depending on how fast and/or with what resolution of said scanning movement that is desired. The selection of said part size is predetermined in one of said at least one data memory (7) of said base station, also being configurable via said GU I. If selecting a group of pixels (34, 35, 36, 37), and said image capturing means detect a reflecting object, the scanning movement is changed into performing a scanning within said group of pixels, said pixels representing said reflecting object. Said scanning within said group using a smaller part size within said group of pixels for finding the pair-of-angles corresponding to the largest amplitude of said reflecting object, where said smaller part size can be as small as one pixel. Thus, a form of finetuning is performed until finding the pixel corresponding to the reflection with the highest amplitude.

In this embodiment, the capturing system (20) consists of at least one photo detector or similar means and it is integrated within, or very close to, the light shedding aperture lens (4). In general, said light shedding light source (57) is located behind same lens or so close to the capturing system that light reflected by said retro-reflecting object (6) within said volume finds its way to said image capturing means (20).

In a second embodiment of the invention, i.e. shown in fig 7, the capturing means (67) consists of a surface (62) of pixels (63) that are responsible for capturing images from said volume. Flowever, said pixels (63) in said second embodiment are not necessarily used for the shedding of the light towards said vol ume. One pixel (65) still, however, corresponds to the direction (66) to said retro-reflecting object (6) in relation to the orientation of the base station (1), as in all other embodiments of the invention. Said image capturing means (67) contains at least one filter (71) for distinguishing reflecting objects with certain properties. Said properties are stored in a memory (7) in said base station (1) as has been described. Said image capturing means (67) detects and identifies the pixel (65) that corresponds to the direction of said reflecting object, and thus the processing means (89) receives the identity of said pixel (65). Said data processing means (89) fetches the pair-of-angles (23, 24) in the data compound including said pixel (65), determines and stores said pair-of-angles (23, 24) temporarily in a memory (8) corresponding to said reflecting object (6). Said pair-of-angles (23, 24) is then sent by the processing means of said base station to directional light direction adjusting means (42) of at least one directional light source (43, 44), for being adjusted so that a distance measuring directional light source and/or an interrogating data communication directional light source being part of said at least one light source (43, 44) can use direction adjusting means (42) for directing light (or radiation) to said retro-reflecting object (6). Said distance measurement and said interrogation can both use same said directional light direction adjusting means (42), or they are part of systems separated from each other. Said separate system parts are still part of said base station (1), however. Furthermore, in this embodiment of the invention, the light source shedding means (60), shedding light on the volume, is not specified further - it can be any light source with sufficient strength for causing a retro-reflector (6) within the volume to reflect light detectable by said capturing means (67). Said light source (6) may also be positioned within or very close to said lens-equipped aperture (4).

During tracking of a moving retro-reflector (6) in said second embodiment of the invention, as stated earlier, referring to fig 3, at least one determined pair-of-angles is replaced one after the other by other determined pair-of-angles, corresponding signals are sent to said directional light direction adjusting means (42) for tracking, i.e. following, said reflecting object. When said reflecting object is lost, at least one directional light source (43, 44) is shutoff by said data processing means (67) until said reflecting object is found again.

Naturally, the light source and the capturing system on one side and the retro-reflecting object on the other side, are preferably within line-of-sight of each other. Flowever, the line-of-sight requirement shall not be regarded as a limiting factor for the system to be effective. By using at least one mirror between said base station and said retro-reflecting object that routes the light between said base station and said retro-reflector, the system is still effective, although it is associated to a more complicated installation. An important purpose of the invention, for all embodiments, is not only to determine the position of a device carrying a retro-reflecting object (6). It also aims to determine the orientation of said device or, more specifically, to determine the position of certain parts or ends on the device, since the positions of said parts or ends may be interesting to know for a user. By using at least one retro-reflecting surface, with properties that enables the detection of the orientation of said at least one retro- reflecting surface, the system shall calculate the position of said at least one device end or device part. If attaching a retro-reflecting object on a device, such as a tool, said orientation may be detected by the base station (1) by means of detecting a certain pattern or shape of groups of determined pixels that matches a predetermined pattern of pixels, said pattern of pixels having been predetermined and stored in a memory (7) in the base station (1). Said data processing means is configured to specifically react on said pattern and hence to calculate the position of said at least one end using trigonometric calculations, said position being related to said pattern according to known and predetermined data in said memory. Said pattern can be of different sorts, however predetermining a certain distance between reflecting objects is one such pattern, e.g. accomplished by using at least two reflecting surfaces attached to said device.

Other general embodiments of the invention are to use more than one base station interconnected via a network for transferring data between each other, preferably on a network (47) with a controlling unit (48) as main coordinator of the base stations (1). In fig 1, there is only one base station shown, however, for simplicity. Although that would make the system somewhat more complicated and expensive, clear advantages are also achieved. One of said advantages is that the positioning capacity is enhanced with better accuracy if light from light sources of more than one base station is reflected by a retro-reflecting object. Then, the position of said retro-reflecting object is calculated by means of both trilateration and Time-of-Flight (ToF) methodology. A retro-reflecting object may then also be found faster, something also supported by the fact that there might be obstructions between at least one base station and said retro-reflecting object, but not between at least one other base station and said retro-reflecting object. As soon as the retro-reflecting object is found by one base station, its position is transmitted to the other base stations via the data network. Two or more apertures can also be used in the same housing of said base station and using trilateration

methodology as above.

Naturally, the higher number of pixels that corresponds to a complete view of a certain FOVbs of said lens, the higher capacity of representing a high-resolution image for the complete image. Thus, the pixels are preferably small, densely organized as well as being many, which together with the lens characteristics pays for a high-resolution complete image. E.g. in the DMD (or MEMS) case, the mirrors are very small and densely organized.

AN APPLICATION OF THE INVENTION

As was mentioned in the beginning, the invention is preferably used in the manufacturing industry. To narrow it down even further, the engineering manufacturing industry exemplified by the automotive industry has appropriate environments. Here follows some more background information on the production sites in the facilities of this industry. The need for an invention such as the disclosed one is described. Although the retro-reflecting object in the following description is a modulation retro- reflector (MRR) and thus fulfills the data communication capacity between the tool and an upper level system, the disclosed invention is also applicable for a production system where the retro-reflecting object is merely a passive retro-reflector, and the data communication is done with other means, such as RF based communication technology, or a wired connection.

In the manufacturing industrial facilities, the operations that are performed on the 'workpieces' (i.e. parts and/or sub-parts eventually forming the final products) are from various sorts, like pressing, welding, painting, assembling etc. Typically, an operation is performed by at least one special tool, designed to be capable of performing a specific task. Examples of such tools are wrenches, fastening tools, riveting tools, paint nozzle tools, pressing tools, imprinting tools, stamping tools, drilling tools and others. The tools can be powered manually, electrically (from battery or mains) or pneumatically, as they perform their specific operations on workpieces. Furthermore, the tools can be handled manually, by a human operator, or by a machine or robot.

A key concept to achieve a desirable and reliable quality of the produced items, in all their details, is the level of control in the production. High level of control is reached when using well designed and controllable tools for specific purposes, having capability of storing operational data, and maintaining a low level of ambiguity. A sub-concept to the level of control in production is the level of traceability, i.e. the ability to know in detail what operations have been done on a workpiece and when.

A tool type that is commonly used in many different assembling production facilities, on many different applications, are power tools, so called 'nut runners', or 'fastening tools' where the actual operations are defined by fastening parts together via threaded joints. Such power tool system is known e.g. from Dl: US 2002003043 (Al), which presents a portable electric power tool, connected via a power cable to an operation control device (controller). The controller constitutes an intelligent system that can be programmed for making the tool to behave in different ways.

In a large and advanced production facility where a tool system such as the one described in D1 is used, the controller also communicates with an upper level production system, partly to receive production data (also called 'build data') that defines the characteristic parameters for the tool settings adapted for the operation that the tool is about to perform. After an operation, result data are transferred from the tool's sensors, via the controller to the upper level production system for providing the desirable traceability regarding the performed operation .

Another embodiment of the tool system in D1 is a tool powered by a battery and equipped with an embedded control device and thus no "wired" connection to external control devices, but still with capability to wirelessly commu nicate operational tool data with external devices and an upper level production system. The wireless communication technology is normally radio based, such as WLAN, Bluetooth, Zigbee etc. Such radio-frequency (RF) based communication has had an enormous development the past decades considering the high quantities of communicating devices, and the number of such devices in the industrial world is expected to increase further, not least due to the concept of 'internet-of-things' (IOT) which has become a subject of interest for many companies. RF communication, however, suffers from some problems which tend to increase as the number of RF communicating devices increases. Particularly in facilities where the radio traffic is dense, the problems of extensive use of RF communication can be discerned.

Symptoms of the mentioned problems are among others an increasing number of interference issues between the many electronic devices in facilities that are commonly communicating via RF based technologies. Furthermore, the growing use of RF com has led to an increasing number of cases where occupied frequency channels are causing problems for many companies and third-party suppliers working with RF communicating equipment in said facilities. The task to find available effective frequency channels and/or the obligation to apply for licenses regarding the use of certain RF channels sometimes implies time consuming and thus costly circumstances. The extensive use of RF communication according to the popular WLAN standard resulted in the introduction of the 5 GFIz band, due to the limitations of the 2,4 GFIz band. I n that process, extra bandwidth was made available. Flowever, the 5 GFIz band is also not limitless. I n addition to that, the use of higher RF com frequencies implies increasing signal strengths, which in combination with an increasing number of communicating devices in general may be suspected to affect the working environment for human operators in facilities negatively. A counter-measure to these problems is to use a non-RF based technology to focus on enabling data communication only when specific "spatial" conditions are fulfilled. It states the importance of when and where data shall be interchanged, not just anytime and anywhere or 'as soon as possible'. Data communication related to traceability and control of tool operations is an example where such conditions can be stated. Traceability and control often require system knowledge of the whereabouts of the tool.

An interesting environment is a manufacturing production facility where workpieces are worked upon in working sites by means of tools. Figure 9 shows the system setup of the invention in said working site: A workpiece (105) is to be worked upon by means of a tool (107), here held by a human operator (122), aiming to perform specific operations on specific operation points (106a, 106b, 106c). An upper level production system (101) is connected to a base station (110) via a network (102). Said base station (110) includes data processing means (103a), data memory means (103b) and furthermore a directional light source (104) such as a laser transmitting light of e.g. the near infrared and/or light in the visible spectrum. The light source (104) is preferably embedded in said base station (110) with electric distance measurement (EDM) means (131) and theodolite means (130) together with steering means (133) and a light sensor (132). If activating the tool trigger (129), the tool (107) performs an operation at its operation end (108) if said tool is configured to do so. The kind of operation that is performed can be of various sorts as the present invention is not limited to a certain type of tool operations. Flowever, important is that said tool (107) contains at least one sensor for producing data that carries result information on the performed tool operation. Said tool also comprises processing means (128) and memory means (127). Furthermore, and crucial to the invention, said base station (110) and said tool (107) have means for transferring data between each other via a free space optical (FSO) communication link. A light source in the base station serves as the interrogating part and a structure of modulating retro-reflectors (MRR) (109) on the tool (107) is the other part of said link.

The light source being the interrogating part of the FSO com link is preferably the same light source as the mentioned light source (104), as is described by fig. 9 and as is described in the following text, but it could also be another light source located close to it.

It is important to come to terms with interference related problems caused by extensive use of RF based data communication technologies in industrial environments such as between a mobile tool and stationary communication devices as in said system setup. To this end, data is interchanged only when specific conditions are fulfilled, and such conditions can be found in a working site as in environments such as these. A tool such as said tool (7) needs to report its operational result data to external devices after an operation, normally the sooner the better for an upper level production system (1) to have quickest possible updated status information on said tool operation. Furthermore, the tool needs to be programmed, or configured, with correct production data prior to an operation to perform said operation correctly. Flowever, since tool movements often are suffering from ambiguity to some degree, the verification of correct production data in said tool is preferably done as close in time before each operation as possible. Thus, by involving the art of determining the position of a tool, the traceability and even the control of the tool operations are achieved through the very use of the FSO com technique, as the sending and receiving of data occur only under very specific conditions, direction- and space -wise as well as timewise.

An ability of data communication via light, known as FSO com technology, is to send large amount of data in short time. A high data bit rate pays for low latency which is highly desirable in the current application. Apart from providing high bandwidth for data communication, FSO com has low susceptibility for interference, it is license-free and difficult to intercept.

It would be very beneficial to provide a method and a system to achieve a high level of traceability of operations done by a tool (7) on operation points (6a-c) on a workpiece (5) in a working site of a manufacturing facility. Part of the base station (10) utilize functionality that can be found e.g. in products known as "total stations". With such products, very precise measurements of distances and 'direction describing' angles are achieved with electronic distance measurement (EDM) means and theodolite means by directing a laser beam to a retro-reflecting item such as a prism. Said prism corresponds to said MRR structure (9). When said beam (12) is directed from said light source (4) to said MRR structure (9) and the base station (10) has detected that proper modulation of light is received by said light sensor (32), said base station determines that said light source (4) is pointed directly to said MRR structure (9). The location of said MRR structure (9) is then measured by said base station (10). Said EDM means (31) is used for measuring the distance, and said theodolite means (30) is used for determining the direction (i.e. the angles), from said light source (4) to said MRR structure (9). The location of the MRR structure (9) is calculated as space coordinates. The space coordinates may be 3D coordinates, i.e. x, y and z coordinates, but more preferably polar coordinates, i.e. r, Q and f (where“x" is radial distance, "Q" is polar angle and "f" is azimuthal angle). The installation of the base station (10) must be done firmly in the working site with appropriate calibrations of the location measuring means to determine, with high accuracy, the space coordinates of said MRR structure (9) in relation to said base station (10). The workpiece (5), and if appl icable also its carriage, must have a location that is well-defined in relation to said working site and said base station, thus the used coordinate system also involves said workpiece (5).

The location of said operation points (6a-c) on said workpiece (5) are often already known in advance, and are thus previously stored in said data memory means (3b) of said base station (10). Alternatively, if said workpiece (5) is moving on an assembly line or similar, arrays of space coordinates are stored together with arrays of time stamps representing movement of said operation points (6a-c) and said arrays describing the location of each operation point (6a-c) at any point in time. If using only one set of location measurement means, said EDM means (31) or said theodolite means (30), one may still utilize some benefits of the system, however with less accuracy. In such a simple interpretation of the system, preferably polar coordinates are used. For determining location only by distance, i.e. by the EDM means, "r" (i.e. radial distance) is used. For determining location only by direction, i.e. by the theodolite means, "Q" (i.e. polar angle) and "f" (i.e. azimuthal angle) are used.

When a workpiece (5) has entered a working site, a trigger signal is sent for the base station (10) to be activated. The trigger signal could be a digital relay or digital input activated by sensors such as proximity sensors or obstructed photo cell beams detecting the workpiece. It could also be a signal from the upper level production system or from a line PLC having information on the general whereabouts of the workpieces or any other source sending said triggering signal to the base station (10). Said trigger signal uses state of the art technology.

When the base station (10) becomes activated, its task is first to search for said MRR structure (9) to find it. Said base station (10) controls the steering means (33) of the light source (4) to scan light on the volume covering said at least one operation point (6a) and its surroundings. The scanning light rays fol low a predetermined scanning pattern and are exemplified in figure 9 as a zig-zag pattern (13) within a rectangular boundary (14), but they could also be defined by other movements (e.g. a spiral from smaller to larger circles) within other form of boundary (e.g. a circular boundary).

The purpose of said scanning is for said base station (10) to detect the presence of a light communication device of said tool (7). Said light communication device being in the form of a structure of modu lating retro-reflectors (MRR) (9). When detected, said light source (4) locks on said MRR structure (9) being the target. Said locking is managed by said light sensor (32) giving input to the steering means (33) of the base station when said light sensor (32) sensing the retro-reflected light. Said reflected light from said MRR structure (9) is detected by said light sensor (32) as a gaussian spot with a certain size, and said input consists of signals to said steering means (33) aiming to keep said spot in the middle of said light sensor. Elence, if said spot is detected as diverted from the middle of said light sensor, but still is detected by said light sensor, signals are sent from said light sensor (32) to said steering means (33) for adjusting the direction of said light to keep said retro-reflected light from said MRR structure (9) in the middle of said light sensor. If said light sensor (32) does not detect said retro-reflected light at all, the movement of said steering means (and said light from said light source) reverts to an MRR searching scanning pattern, aimed for finding said MRR structure (9) as soon as possible. When said light being focused on said MRR structure, the base station (10) measures and determines the location of said device (9) by means of the theodolite means (30) and/or the EDM means (31). In this situation, it is also time for said FSO com link to be established.

In symmetrical FSO com applications the communicating parts are similarly equipped with a signal source (emitter) and a signal detector (receiver) plus data processing means on both sides. Flere, however, the link is asymmetrical, i.e. one part contains the light source (4), the light sensor (receiver) (32) plus some optics for providing the highly directional laser beam, and said part constitutes the interrogating part of the communication system together with said data processing means and said data memory. The other part of the FSO com link, said MRR structure (9), is physically located on the tool (7) and electrically connected to the tool processing means (28). When said MRR structure (9) is hit by said light and detects the interrogating data, encryption of the signal takes place by means of the MRR structure (9) and the processing means (28) of the tool (7), and a beam with modulated encoded information is sent back to the interrogator. Thus, the Modulated Retro-Reflector (MRR) is the key component of the two communicating parts for modulating the signal according to the input data sequence, while ensuring that the beam will be reflected back in exactly the same direction, or more precisely in the direction defined by 180 degrees in relation to the original direction of the light from the light source (4). The idea behind using such an asymmetrical link instead of a symmetrical one is the strong requirement in the current environment of keeping the weight and complexity low at the tool side of the communication, as well as using a robust component - the MRR structure (9). Suitable designs in the art of MRR:s in FSO communication have been studied and successfully used, such as corner cube reflectors (CCR) or cat eye optics as MRR components.

As soon as light from said light source (4) has been locked onto said MRR structure (9) by the method described, data communication handshaking procedure starts between the base station (10) and said tool (7). Said handshaking procedure aiming to establish said FSO com link. The data interchanged in said handshaking procedure is similar as handshaking procedures in any kind of data communication link and contain e.g. time synchronization and/or information on the identities of the two

communicating parties. Other application relevant data may also be interchanged.

The system technical idea behind FSO communications using MRR have been known for a long time, but it is not until recently that the development of the MRR:s has reached an interesting level. The design of many of them requires nanotechnology for which advanced research centers with skilled personnel and modern labs are necessary. Apart from being functioning in an FSO com link in general, the MRR structure (9) and the processing means (28) of the tool (7) are required to have a sufficiently fast response time to the interrogating data from the base station (10) for establishing the FSO link in short time. Apart from other already mentioned important requirements on an M RR structure (9), integrated on a tool (7), like having low complexity and being light as well as robust, there are three specific topics that needs to be addressed :

1) The modulation capacity which defines the possible maximum bit rate in the established communication link

2) The field-of-view (FOV) of the complete MRR structure which defines its general

communication abilities when receiving incoming light from different directions in the point of view from the tool

3) The ability of the MRR structure to supply information on the orientation of said MRR

structure to the base station, when receiving light from different directions in the point of view from the tool

High modulation capacity is achieved with multiple quantum well (MQW) based electro-absorption modulators (EAM) in MRR:s. GaAs and InP based semiconductor technologies are used. Chosen communication bands have operational wavelengths of around 850 nm using GaAs and around 1550 nm using I nP. Furthermore, to achieve a high bit rate it is a lso necessary for the MRR structure to be embedded in a tool system that is well designed in terms of system architecture and competitive hardware components (e.g. the processing means and other electronic components are required to be sufficiently fast) which is considered to be known to a person skilled in the art. To conclude, a high bit rate fulfills the needs described by topic no. 1 above.

Said MRR structure consists of at least one MRR unit. One MRR unit is enough for being part of an established FSO com link, but the robustness of this solution benefits from using more than one MRR unit. More than one FSO com sub link is then created between said MRR structure (9) and said base station (10), with one MRR unit in each FSO com sub link. The described FSO com link may thus consist of more than one FSO com sub link.

In the following, an example of an MRR structure (9) consisting of MQW modulated Corner Cube Reflectors (CCR) will be described. The retro-reflecting type shall not be limited to corner cubes although it here serves as an example. Thus, in the following, the concepts 'CCR unit' and 'CCR array' are used as terms instead of the more generally 'MRR unit' and 'MRR structure' (the latter terminology are used in the claims). It is important to note however that the field-of-view (FOV) is different among different modulating retro-reflector types. The FOV of an FSO communicating MRR unit is defined as the direction boundaries, from the MRR unit point of view, within which data communication via light is possible, i.e. within which the MRR 'sees' the light source. These boundaries are defined by the features of the specific type of retro-reflecting MRR u nit.

Said CCR are non-complex, robust, light and economically produced, however suffering from a Field- Of-View (FOV) of about ±15 degrees. This FOV feature may falsely be considered disadvantageous in the current application. Flowever, by arranging some small CCR units next to each other, forming an array in a certain 3-dimensional manner, a complete FOV is created which is larger than the FOV from a single CCR unit. The tool, with said CCR array firmly integrated on it, can thus be turned in many directions while maintaining communication via at least one of said FSO com sub links. More specifically, depending on how the array is physically arranged, the complete FOV may also have any shape, adapted to the application so that data communication is enabled when the tool (107) is oriented in its most common ways.

The different images of figures lOa-c shows an example of the features of a CCR array consisting of single CCR units. Compounds of such CCR units are beneficial when the FOV of each unit is small. As is shown in figure 10a and 10b, each circular single CCR unit (141) has a FOV (143) of around ±15 degrees from the normal of its own plane, which implies a small FOV. In the example of fig. 10a the upper part of the CCR array (142) has the form of a rather flat tetrahedron and it consists of three CCR units (141a-c). The height of the tetrahedron is chosen so that the CCR units (141a-c) are integrated on the three tetrahedron planes turning upwards, but inclined to each other in such a way that their FOV:s are overlapping, yielding a FOV from the complete CCR array to be larger than ±15 degrees, as can be seen in fig. 10c, disposed in a pattern created by the special form of the CCR array (142) structure. Important is also that the virtual volume covered by the total FOV, at the point of view from the light sensor (132), is cohesive, i.e. it does not contain any holes, weak spots or similar. As is shown in fig. 10c, the FOV of a single "cone" forms an "ellipse" at a (virtual) plane parallel to the base plane (144) of said CCR array at a certain distance from said CCR array, since each CCR unit is inclined to the base plane. A large total FOV meets well the demands indicated in topic no. 2 above.

By modulating the reflected light from one or more identified CCR units, and not from CCR units whose FOV does not cover light from the light source, the base station (110) draws some conclusions (based on elimination) about the orientation of the CCR array, and thus the orientation of the tool (107). To this end, each CCR unit (141a, b, c) has its own unique identity and is connected to said processing means of said tool (107). The identity consists of an identification key, associated to each CCR u nit, and said identification key is included in said FSO com sub link between corresponding CCR unit and said base station (110). The FSO communicating sections of the structure of ellipses is used by the data processing means (103a) in the base station (110) to furthermore determine the orientation of the CCR array. E.g. if all CCR units in such a compound are communicating with the base station (110), the light source is located in the middle of the pattern of said total FOV shown in fig 10c, it is determined that the CCR array is oriented with its base plane more or less perpendicular to the light of said light source (104).

However, the orientation of said CCR array (and said tool) can never be fully determined with the described method only, as it is possible for said tool (107) to be "turned" around a vector from said CCR unit to said light source (104). It merely defines a certain inclination of said tool.

Therefore, the base station (110) also uses another method to determine the orientation of the CCR array (and thus the tool) which is the art of triangulation. By measuring the distance and direction to each CCR unit, by using the EDM means and the theodolite means, and by fully knowing the spatial relation between communicating CCR units, said orientation of sail tool is calculated. To this end, said spatial relations between communicating CCR units are stored as vector parameters in said data memory means (103b) of said base station (110). It shall also be mentioned that a CCR array may consist of more than one CCR unit where each unit is located a certain distance from each other and not included in the same "package", as is indicated by the embodiment of fig. lOa-c. Such concept is applicable when the size and shape of the tool supports it, but it implies a better accuracy when determining the tool orientation through triangulation.

Many involving CCR units makes a CCR array more complicated and heavier than an array with fewer units, but on the other hand a more reliable method for meeting said described topic no. 3 is discerned.

Having determined the orientation of the tool (107), and by knowing the position of the operation end (108) of the tool (107) in relation to said communication CCR units, an object is met: i.e. to achieve reliable traceability of said tool operation. The location of the operation end (8) is known by previously stored vector parameters in said data memory (127) in said tool, and in said data memory (103b) of said base station (110), said vector parameters refer to vectors between each CCR unit and said operation end (106a). However, to associate an operation with an operation point (106a) on a workpiece (105) there is a need to associate said operation point (106a) with the operation end (108) of the tool. For said calculation to be as accurate as possible, said orientation of said tool (107) needs to be determined as accurate as possible. It shall also be mentioned that if a CCR unit is located close to the operation end (108) and maintains an effective FSO com sub link with the base station (110), topic no. 3 loses its importance as the tool orientation loses part of its importance. Being able to determine the location of that CCR unit (close to the operation end) a good opinion is achieved also regarding the location of said operation end. Such an example also reduces the need for using other CCR units in the CCR array, at least when it comes to topic no. 3; however, for topic no. 2, i.e. achieving a large FOV in general, it may still be important to have more than one CCR u nit (or using a MRR unit with large FOV).

Many different three-dimensional structures with integrated CCR arrays would be able to provide different shapes and sizes of the FOV. Depending on the wanted features for a certain application, the appropriate CCR array structure is chosen. The simplest CCR array is one which only contain one CCR unit (appropriately positioned as close to the operation end as possible). A small FOV is here compensated by low weight and low complexity, and it can be produced at a lower cost than more advanced structures.

Traceability: For a tool operation to be unambiguously associated with said operation point (106a), said operation end (108) of said tool (107) needs to be located sufficiently close to said operation point (106a) at the time of the creation of the operational result data. To this end, a parameter called "allowed association distance" is stored in advance of said operation in said data memory (103b) of said base station (110).

After having performed an operation, operational result data including magnitudes from at least one tool sensor and/or diagram data is created and stored in the storage means (127) of said tool (107). Said operational result data is sent from the tool (107) to the base station (110) via the existing FSO com link. The coordinates of the tool's operation end (108), now known to the base station (110), are stored together with said operational result data as linked posts in said data memory (103b). Said base station (110) now uses the 'allowed association distance' value for determining whether at least one operation point can be connected (i.e. associated) to said posts. If there are none, said allowed association distance may be too small; if there are more than one, it may be too big. A primary goal is to enable the connection/association of one ambiguous operation point (106a) to each operation. Complete operational result data including location data and operation point identity is then transmitted to the upper level production system (101) via the plant network (102). This is how the described method provides traceability of the performed tool operations, at least for the operations performed during the time when an FSO communication link is maintained.

If, for some reason, said FSO com link goes down prior to said operation causing said operation to be performed without an available FSO com link, said base station may also continuously send determined location of said tool's operation end (108) to said tool (107) when said FSO com link exists for the tool to be updated frequently on its whereabouts. Then, at the failure of said FSO com link, the probability increases for the tool to store its operational result data together with the location of its operation end in said tool's own data memory (127) as linked posts, thereby maintaining traceability.

In this scenario, the tool must not move much after the failing FSO com link to be effective.

Alternatively, the system may also be used to achieve control of a tool operation that said tool (107) performs at an operation point (106a) on a workpiece (105). In this embodiment said tool is normally disabled from performing any operation at all when said tool is located more than an 'allowed association distance' from said operation point (106a) covered by the light source (104). In this embodiment, said tool is enabled for performing an operation only when said tool operation end (108) is located less than said allowed association distance from said operation point (106a). For unambiguous reasons, in this embodiment it is important that only one operation point (106a) is 'associated' to said operation end (108) of said tool (107) before enabling said tool (107) for operation. Said tool enabling data consisting of either all necessary production data adapted for said operation point (106a), or, when the tool already has the correct parameter settings in general, said data merely consisting of a tool enabling signal. Note; if more than one operation point (e.g. 106a-c) all have same requirements regarding production data, and more detailed traceability is not necessary, the allowed association distance may be set to a larger value.

The operational result data is sent from the tool (107) to said base station (110) directly after said operation, via said full duplex FSO com link. Packaged together with the identity of the corresponding operation point (106a) or points (e.g. 106a-c) the complete operational result data is further transferred to said upper level production system (101). Control of the tool operation has been achieved.

An upper level production system sending production data to a tool short before a tool operation, and receiving tool result data short after the operation, with full traceability, implies a flexible and an efficient production process where decisions by the upper level production system on what tool operations to be performed can be done at the right time, according to the just-in-time production philosophy which constitutes the conditions for low set times in modern LEAN manufacturing. If the data communication is done wirelessly with the benefits of FSO communication compared to RF communication technology, the advantages are clear.

Finally, some remarks must be made to emphasize the purpose and the intended use of the disclosed invention when applying it to the described field of engineering manufacturing tools. A 2-D or 3-D position of retro-reflecting objects is found through the method in the invention, independent on whether said retro-reflecting objects are modulating or passive retro-reflecting objects, and through this knowledge the position of the corresponding tool operation end is estimated. To know the position of the tool operation end in real-time is useful since this information is used in the production related data traffic in a manufacturing facility. For traceability purposes, the position of the tool operation end at the time of the operation, is transferred to controlling units, preferably in the same data packet as the result data from said tool. For control purposes, the tool is disabled for use until its operation end is estimated to be unambiguously close to a well-defined operation point, where it is enabled with correct production parameters - the corresponding data is sent to the tool at the right time when it has correct position. The important aspect here is that the transfer of this operational tool data is independent on what communication technology that is used, it could be RF based, FSO based or via a wired connection. The base station (1) initiates the relevant communication when having established the tool operation end position. If the tool communicates with external controlling units through an RF link, this controlling unit could be a part of said base station, or just connected to the base station. In the latter case, the method consists of an activity where the controlling unit sends the tool result data at a certain point in time to the base station so that said base station can establish a data package where the position of the tool operation end is linked to the tool result data. The base station can also send the tool operation end position to a controlling unit, either continuously in real time, or at certain times. In such systems it is the controlling unit that uses the tool operation end position in traceability or control purposes for the tool operation activities.

Other important properties of the scanning activities of the base station in order to establish position data of a tool's operation end is to use different light wavelengths that shall be reflected by said at least one retro-reflecting object on the tool, which has been described earlier. Flowever, for this light shedding to be non-disturbing for the operator the light used shall have wavelengths outside of the visible spectrum, such as in the ultra-violet spectrum or in the infrared or the near-infrared spectrum. The described existing technologies containing said surface of pixels are not exploited with light outside of the visible spectrum, which is something that also indicates the inventive step of the disclosed invention.

In the preferred embodiment, the transmitted light from the base station shall be pulsed according to pulse-width modulation (PWM), and the frequency as well as the duty cycle of that pulsed light shall be possible to modify as a means for filtering out other pulsed light in the current environment, such as light from fluorescent lamps. The image capturing means in the base station discerns the base station initiated light shedding from other light sources.

Claims

1. A method for locating a retro-reflecting object (6) on a manufacturing tool in a volume, said volume consisting of a transparent medium, said volume furthermore being partly limited by boundaries of the field-of-view (FOV) (5) of a lens-equipped aperture (4) of a base station (1), and partly by non-transparent obstructions within said FOV (5), said base station (1) furthermore containing data processing means (9), at least one data memory (7, 8), a light source (46), image capturing means (20), and means for communicating data with a controlling unit (48) , said method is accomplished by said light source (46) shedding light on said volume, said image capturing means (20) capturing an image of reflected light signals from said obstructions in said volume, the method comprising:

predetermining one-to-one associations between multiple sets of pair-of-angles (23, 24) within said FOV (5) and pixels (25) on a surface (2) behind said lens (4) in said base station (1), each said set of pair-of-angles (23, 24) fully determining a direction (22) in 3-dimensional space in relation to the normal of said lens- equipped aperture (4), and storing said associations in compounds in one of said at least one data memory (7, 8),

detecting reflected light signals on said image capturing means (20) when a pixel (25) is activated, said pixel (25) having a said one-to-one association to a set of pair- of-angles (23, 24) directed to a reflecting object (6),

determining at least one set of pair-of-angles (23, 24) corresponding to reflected light signals from at least one retro-reflecting object (6), and storing said determined set of pair-of-angles (23, 24) in one of said at least one data memory (7, 8), said pair-of-angles (23, 24) constituting a 2-dimensional position data estimation of said retro-reflecting object (6), and setting an identity of said retro- reflecting object (6) and storing said identity linked to said stored determined pair- of-angles (23, 24)

2. A method as claimed in claim 1 further comprising: said base station (1) containing at least one directional light source (44) and at least one directional light source direction adjusting means (42), said light source containing distance measurement means (43),

said directional light source direction adjusting means (42) directing said directional light source (44) to one of said at least one reflecting object (6) defined by one of said at least one determined pair-of-angles (23, 24),

measuring the distance (40) to said retro-reflecting object (6), and storing said distance (40) linked to said determined set of pair-of-angles (23, 24) in one of said at least one data memory (7, 8),

said processing means (9) estimating the 3-dimensional position of said retro- reflecting object (6), said estimation calculation using said determined set of pair- of-angles (23, 24) and said measured distance (40), said 3-dimensional position estimation being in relation to the location and the orientation of said base station (1),

in one of said at least one data memory (7, 8), storing said 3-dimensional position linked to said stored distance (40) and said stored determined pair-of-angles (7, 8)

3. A method as claimed in claim 1 or 2 further comprising:

4. A method as claimed in any of claims 1 - 3 further comprising:

said at least one property being specifications on the wavelengths of said reflected light signals, said specifications stating what wavelengths said reflected light signals from any pair-of-angles must have for said pair-of-angles to be determined,

5. A method as claimed in any of claims 1 - 4 further comprising:

said at least one property being specifications on the polarity of said reflected light signals, said specifications stating what polarity said reflected light signals from any pair-of-angles must have for said pair-of-angles to be determined,

6. A method as claimed in any of claims 1 - 5 further comprising:

7. A method as claimed in any of claims 1 - 6 further comprising:

said image capturing means measuring at least one of said properties of said reflected light signals from at least one set of determined pair-of-angles corresponding to a stored identity of at least one retro-reflecting object (6), creating an attribute meaning "moving retro-reflector",

setting and storing said attribute linked to said stored identity of said retro- reflecting object (6) in one of said at least one memory (7, 8) if the following conditions are fulfilled:

o said pixels a and b do not have more than a predetermined number of pixels between them

unselecting said determined pair-of-angles for not being part of said sets of determined pair-of-angles when said at least one property of said reflected light signals are not indicative of a corresponding retro-reflecting object anymore,

8. A method as claimed in any of claims 1 - 7 further comprising:

investigating whether there are retro-reflecting objects in said volume by shedding light in the directions of at least one pair-of-angles at a time and measuring at least one of said properties of reflected light signals corresponding to said at least one pair-of-angles

9. A method as claimed in any of claims 1 - 8 further comprising:

predetermining and storing a 'tool indicative retro-reflections distance interval' meaning allowed distances between retro-reflecting objects attached to a tool, and storing said 'tool indicative retro-reflections distance interval' in one of said at least one data memory (7, 8),

predetermining a 'tool end distance' meaning the distance and the direction from the set of retro-reflecting objects on a tool to an end of said tool,

said retro-reflecting objects having been detected by said image capturing means and the identities of said retro-reflecting objects have been stored in said at least one data memory (7, 8),

said data processing means estimating the distance between said reflecting objects and if said distance does not differ more than a predetermined amount from said 'tool indicative retro-reflections distance interval', estimating the tool end position based on the positions of said retro-reflecting objects,

storing said tool end position in one of at least one data memory (7, 8)

10. A method as claimed in any of claims 1-9 further comprising:

11. Computer program comprising instructions which, when executed by a computer, cause the computer to carry out the method according to any of the preceding claims

12. Computer-readable medium comprising instructions which, when executed by a computer, cause the computer to carry out the method according to any of the claims 1-10

13. A base station (1) for finding a retro-reflecting object (6) on a manufacturing tool in a volume, said volume consisting of a transparent medium, said base station (1) containing at least one data memory (7, 8), data processing means (9) and a lens-equipped aperture (4), behind said lens a surface (2) is disclosed, said surface (2) containing identifiable areas, pixels (3), each of said pixels (25) having a one-to-one association to one set of pair-of-angles (23, 24), said set of pair-of-angles (23, 24) fully determining a direction (22) in 3-dimensional space measured from the normal of said aperture (4), all of said sets of pair-of-angles (23, 24) determining the field-of-view (FOV) (5) from said aperture (4), said base station (1) furthermore containing at least one light shedding device (46) for shedding light on a volume covering said FOV (5), said base station also containing image capturing means (20), said image capturing means (20) capturing images of reflections from non-transparent obstructions within said FOV (5), said base station (1) comprising:

in one of said at least one data memory (7, 8), said sets of pair-of-angles (23, 24) and data identifying said associated pixels (25) are stored in data compounds, means for determining and outputting at least one pair-of-angles (23, 24) when reflected light signals from at least one retro-reflecting object (6) are captured by said image capturing means (20)

14. A base station (1) according to claim 13, wherein :

light shedding means (57) containing said lens-equipped aperture (4), pixels (53) on said surface (2) and at least one light source (46),

said at least one light source (46) is directed to said pixels (53) of said surface within said light shedding means (57), said pixels (53) manipulating the light from said light source (46) for subsequently transporting said light via said lens-equipped aperture (4) to cover said FOV

15. A base station (1) according to claim 13 or 14, wherein :

said base station furthermore containing at least one directional light source (43, 44) and directional light source direction adjusting means (42),

said directional light source direction adjusting means (42) capable of adjusting the direction of said directional light source to point towards the direction defined by said received determined pair-of-angles (23, 24) within said FOV

16. A base station (1) according to any of claims 13 - 15, wherein :

said directional light source direction adjusting means is a galvanometer

17. A base station (1) according to any of claims 13 - 16, wherein said directional light source direction adjusting means (42) is at least one digital micromirror device (DMD) being part of a micro-electromechanical system (MEMS)

18. A base station (1) according to any of claims 13 - 17, wherein:

said at least one light source (43) is a laser rangefinder

19. A base station (1) according to claim 13-18, wherein:

said surface consisting of digital micromirror devices (DMD)

20. A base station (1) according to claim 13-18, wherein:

said surface consisting of at least one LCD panel

21. A base station (1) according to any of claims 13 - 20, wherein

said at least one light source is an interrogating laser for establishing an asymmetric Free Space Optical (FSO) data communication link with a modulating retro-reflector (MRR)

22. A positioning system containing at least one base station (1) for locating a retro-reflecting object (6) on a manufacturing tool in a volume according to any of claims 13 - 21, wherein:

If said positioning system containing at least two base stations according to any of claims 13-20, said at least two base stations being installed in one common coordinate system, with determined orientations and locations of said base stations in said coordinate system,