DE102024105237A1 - Monitoring system and laser processing machine arrangement - Google Patents

Abstract

The invention relates to a monitoring system (1) comprising: a plurality of monitoring units (2, 3), wherein the monitoring system (1) is designed to monitor a line of sight (4) between a first and a second monitoring unit (2, 3) by means of a signal transmission between the first monitoring unit (2) and the second monitoring unit (3). The monitoring system (1) is designed to monitor the line of sight (4) by means of a signal transmission in the form of a radio transmission, in particular by means of a UWB radio transmission, between the first monitoring unit (2) and the second monitoring unit (3). The invention also relates to a laser processing machine arrangement having such a monitoring system (1).

Description

The present invention relates to a monitoring system comprising: a plurality of monitoring units, wherein the monitoring system is configured to monitor a line of sight between a first and a second monitoring unit by signal transmission between the first monitoring unit and the second monitoring unit. The invention also relates to a laser processing machine arrangement with such a monitoring system.

In the EP 2886242 A1 A laser processing machine arrangement is described that has a monitoring system that registers entry into a controlled area. The controlled area comprises at least one danger zone around a laser processing head. The monitoring system is designed to automatically shut down the laser processing head when it registers entry into the controlled area.

The monitoring system can be an optical monitoring system comprising a light grid or a light barrier to monitor at least one boundary section that allows access to the controlled area. The optical monitoring system can comprise two sub-devices, for example, a transmitter device and a receiver device. The transmitter device can emit one or more control beams, which are registered by the receiver device. Passage through the boundary section can be registered by interrupting a respective control beam.

When monitoring a line of sight or a controlled area with a light barrier or light grid, the problem is that the transmitter and receiver must be precisely aligned and can potentially become misaligned. This can lead to the control beam not being received by the receiver, even though it is not interrupted (a so-called false positive).

Object of the invention

The invention is based on the object of providing a monitoring system in which precise alignment of the monitoring units to one another is not necessary. The invention is also based on the object of providing a laser processing arrangement with such a monitoring system.

Subject of the invention

This object is achieved by a monitoring system of the type mentioned above, which is designed to monitor the line of sight by means of a signal transmission in the form of a radio transmission between the first monitoring unit and the second monitoring unit.

In the monitoring system according to the invention, a radio barrier is used instead of a light barrier for monitoring the line of sight. Instead of a light beam for monitoring the line of sight, the radio barrier uses radio transmission in the form of radio signals. The radio-based monitoring system or a respective monitoring unit is designed to detect when a radio-absorbing body, for example a person, obscures or interrupts the line of sight, i.e., a generally straight, direct line between the two monitoring units. In the event that the line of sight is partially interrupted by a radio-absorbing body, the radio signal takes a detour via a reflection from other objects in the room, which becomes visible in the measurement of the radio transmission, more precisely in the signal propagation times of the radio signals. The reliability of such monitoring is based on the fact that common reflections of the radio signal during radio transmission between the monitoring units can be detected and do not lead to false positives. The radio barrier described here can replace a light barrier. Likewise, light grids that monitor multiple lines of sight can be replaced by a radio grid or a radio-based safety fence, as described in more detail below.

In one embodiment, the monitoring units are configured for UWB (ultra-wideband) radio transmission. The detection of small objects that partially obscure the line of sight requires high accuracy in measuring the radio signals, more precisely in measuring the signal propagation times of the radio signals or, equivalently, the distance between the monitoring units determined from the respective signal propagation times. The required accuracy is typically on the order of a few millimeters. With the help of suitable measures (see below), distance measurement with a resolution or measurement accuracy in the millimeter range can be realized using UWB radio transmission.

So far, UWB radio transmission has typically only achieved a resolution of approximately 10 cm. However, even UWB radio transmission with such accuracy is much more precise than other The radio technologies used for localization. The further development of UWB radio transmission to millimeter accuracy (see below) increases the advantage that UWB radio transmission has over other short-range radio technologies such as Wi-Fi and BLE (Bluetooth Low Energy) when it comes to precise localization.

Furthermore, because UWB radio transmission operates in a cleaner, higher frequency band than Wi-Fi and BLE, it does not interfere with the operation of other wireless protocols. UWB radio transmission, or UWB localization, can be integrated into existing wireless operating environments without causing disruptive signal interference. Another advantageous feature of UWB technology is its inherently high level of security. While other technologies use signal strength (RSSI) to determine distance and location, UWB technology is based on time-of-flight or time-of-arrival calculations. Therefore, it is much more difficult to alter UWB measurements and the technology is far less vulnerable to relay attacks. Furthermore, UWB technology can potentially bridge longer distances. In principle, radio transmission can also be achieved using methods other than UWB, such as radar, but long-wave radio frequencies are generally unsuitable due to their low resolution.

In a further embodiment, the monitoring units have a transceiver, preferably a UWB transceiver, or are designed as a transceiver, preferably as a UWB transceiver or UWB anchor. In principle, a first monitoring unit can be designed only as a transmitter and a second monitoring unit can be designed only as a receiver, or vice versa. However, for the distance measurement methods described below and for the use of the monitoring units as nodes of a monitoring network (see below), it is advantageous if the monitoring units are designed as transceivers or have a transceiver, i.e., both a transmitter and a receiver. UWB transceivers transmit and receive omnidirectionally and therefore do not need to be aligned. The cover of the monitoring units or the UWB transceivers does not have to be optically transparent and therefore also enables new design variants if necessary.

The monitoring units of the surveillance system can generally be connected to a central unit that evaluates the radio transmission to detect a line-of-sight interruption. However, it is also possible for the monitoring units to be autonomous, i.e., they themselves detect a line-of-sight interruption and initiate or trigger appropriate measures upon detection. In this case, the surveillance system generally does not have a central monitoring unit.

In a further embodiment, the monitoring system is designed to monitor the line of sight based on a signal propagation time of the radio transmission between the first monitoring unit and the second monitoring unit, in particular based on a distance between the first monitoring unit and the second monitoring unit determined from the signal propagation time. Based on the signal propagation time of the radio transmission, more precisely, on one or more radio signals sent from one monitoring unit to the other, a distance measurement between the two monitoring units can be realized in a known manner. The transmission of radio signals between the two monitoring units takes place with the highest possible repetition frequency to ensure continuous monitoring of the line of sight.

In a further development of this embodiment, the monitoring system is designed to detect an interruption of the line of sight based on a deviation of the signal propagation time from a target signal propagation time, in particular based on a deviation of the distance determined from the signal propagation time from a target distance between the first and second monitoring units. Due to the precise distance measurement using UWB radio technology, a radio-absorbing body, e.g., a person or a part of a person's body, positioned between the two monitoring units and obscuring or interrupting the line of sight can be detected or registered. In this case, the measured distance deviates from the target distance between the two monitoring units, or a complete packet loss may occur during radio transmission. If this is the case, the radio barrier is triggered, i.e., the monitoring system detects the interruption of the line of sight.

The target distance typically corresponds to the actual, i.e., minimum distance between the two monitoring units, which are usually fixed. It is theoretically also possible for the target distance to be determined based on a path that passes over a reflector for the radio signals. In this case, the monitored line of sight also passes over the reflector. The target distance can be determined using the monitoring units or, if necessary, by another type of distance measurement. Typically, the measured distance is greater than the target distance when the line of sight is interrupted. The monitoring units can be installed stationary, However, it is also possible for these devices, for example in the form of portable UWB transceivers, to be detachably attached to walls or other objects to monitor a line of sight. In this way, a mobile surveillance system can be realized.

If a target distance to another monitoring unit is set or specified on a monitoring unit and saved there, or if the target distance is measured using the monitoring units along an uninterrupted line of sight, each monitoring unit can autonomously decide whether there is a significant deviation of the signal propagation time from the target signal propagation time or the distance from the target distance, or whether there is a complete loss of packet during radio transmission, and detect whether the line of sight has been obscured or interrupted. For example, it can be checked whether the deviation from the target distance exceeds a threshold. If this is the case, the respective monitoring unit can trigger an alarm, for example by generating an acoustic and/or visual alarm signal itself. Alternatively or additionally, an alarm signal can be transmitted to an alarm center, which can be part of the monitoring system or an external alarm center.

In a further development, the monitoring units are designed to measure the distance using a time-stamp-based distance measurement method, preferably two-way ranging, i.e., two-way distance measurement, and/or a phase-based distance measurement method. The distance between two non-synchronized monitoring units can be determined, for example, using so-called two-way ranging, see, for example, the article " https://en.wikipedia.org/wiki/Symmetrical_double-sided_two-way_ranging” or the article “Error Corrections for Ultrawideband Ranging”, J. Sidorenko et al., IEEE Transactions on Instrumentation and Measurement, Vol. 69, No. November 11, 2020 , each of which is incorporated in its entirety by reference into this application. For measuring the distance between the two monitoring units, a phase-based distance measuring method can be used, as described in DE 102022202846A1 , which is incorporated by reference in its entirety into this application. In particular, the method described therein enables distance measurement accuracy in the millimeter range to be achieved; see also the link "https://www.nxp.com/company/blog/nxp-continues-to-advance-uwbtaking-accuracy-to-mm-level:BL-NXP-ADVANCE-UWB-ACCURACY-MM-LEVEL." The UWB transceivers marketed by NXP enable distance resolution in the low millimeter range, regardless of the distance covered.

In a further embodiment, the monitoring system is designed to monitor lines of sight between at least two pairs of monitoring units by radio transmission between the two monitoring units of a respective pair of monitoring units. As is common with light barriers, several radio barriers, each monitoring a line of sight, can form a radio grid and, for example, create a radio-based fence that serves to monitor a surface area. Particularly when implementing such a radio grid, it is advantageous that the monitoring units do not have to be aligned relative to one another. It is understood that the lines of sight do not necessarily have to run in a common area, but can also run in three or more different directions to monitor a controlled volume or a controlled area.

Preferably, at least one monitoring unit is designed to monitor at least two lines of sight between the monitoring unit and at least two other monitoring units by radio transmission between the monitoring unit and the at least two other monitoring units. Unlike light barriers or light grids, in which a respective transmitter or receiver can only be used to monitor one line of sight due to the requirement of mutual alignment, the monitoring units described here, particularly in the form of transceivers, can serve as nodes or (multidimensional) nodes of a monitoring network and monitor multiple lines of sight simultaneously. The two or more pairs of monitoring units described above therefore do not necessarily have to be different monitoring units; rather, one and the same monitoring unit can be assigned to two or more pairs of monitoring units, each of which monitors a common line of sight.

In a further development, for monitoring a surface area, in particular a boundary section of a control area, a first group of monitoring units is arranged at a first edge of the surface area and a second group of monitoring units is arranged at a second edge of the surface area in order to monitor lines of sight between the monitoring units of the first group of monitoring units and the monitoring units of the second group of monitoring units. In this case The area can be monitored by arranging several monitoring units, e.g. in a matrix. For example, the monitoring units of one group can be arranged one above the other in a monitoring column or the like in order to monitor a plurality of lines of sight to the monitoring units of the other group. In principle, a one-to-one assignment can be made between the monitoring units of the respective groups, i.e. each pair of monitoring units monitors exactly one line of sight. As a rule, however, it is advantageous if an N-to-N assignment is made between the N monitoring units of the respective groups, i.e. if each monitoring unit of the first group monitors a number of N lines of sight to the N monitoring units of the second group. If the monitoring units of a respective group or of both groups are synchronized in time, an optimized measuring method can be used to increase the measuring frequency and/or the measuring accuracy. For example, a common clock signal can be used for the temporal synchronization. It goes without saying that the number of monitoring units in the two groups can also be different.

The monitored area may, for example, be a boundary section of a control area in the form of a working area that includes a danger zone around a laser processing head, as described in the EP 2886242 A1 which is incorporated by reference in its entirety into this application. The monitoring system, particularly with the N-to-N line connection, can detect entry into the controlled area and, if necessary, shut down the laser processing head. The monitoring system, particularly with the N-to-N line connection, can be used not only to secure the working areas of machines, especially machine tools, but also as a security device, e.g., for theft protection in larger rooms.

In a further embodiment, the monitoring units are designed for radar monitoring, particularly in the form of proximity sensors. In addition to using the monitoring units as nodes for monitoring lines of sight, they can serve as radar devices or proximity sensors, particularly if they are designed in the form of UWB transceivers or have UWB transceivers. The radar can be used, for example, to monitor whether people are present in a monitored room. In this way, the monitoring system also enables spatial monitoring of a controlled area or a monitored volume in addition to or in parallel to access monitoring.

In a further embodiment, the monitoring units are designed for tracking, positioning, and/or navigating mobile objects, which preferably have a UWB tag. The monitoring system is switchable, in particular, between a first operating mode for monitoring the at least one line of sight and a second operating mode for locating, positioning, and/or navigating the mobile objects. The monitoring system can be designed for locating and/or positioning mobile objects, which are generally provided with a UWB tag, which enables localization, positioning, or navigation using the monitoring units in the form of UWB anchors. In the first operating mode, which is activated, for example, at night, the monitoring system can serve as an alarm system and monitor access to a monitored control area, e.g., in a museum: As soon as a line of sight is breached, the monitoring system triggers an alarm. In the second operating mode, which is activated during the day or during the museum's opening hours, objects such as visitors can be located and positioned or navigated through the museum (e.g., based on omlox or fira). In this case, the monitoring units are used in dual-use mode. It is also possible to position one or more mobile objects, such as a drone, in the second operating mode to conduct an automatic inventory in a warehouse or the like, and to use the alarm function of the monitoring system in the first operating mode. Regardless of whether switching between the two operating modes is possible or not, objects such as valuables can also be tagged with a UWB tag and located or tracked. It is also possible to use a "projected light barrier," in which one or more lines of sight between a mobile monitoring unit and one or more stationary monitoring units are monitored, and an interruption of the line of sight(s) triggers an alarm.

The invention also relates to a laser processing machine arrangement, comprising: a control area in which a laser processing head is arranged, and a monitoring system configured as described above for detecting entry into the control area, preferably for detecting passage through a boundary section of the control area. The monitoring system can be configured to automatically deactivate the laser processing head when it detects entry into the control area. The monitoring system can, in particular, detect a passage through the boundary section of the controlled area, which can be located, for example, between two groups of monitoring units that create a radio-based protective fence in the boundary section. It is understood that the monitoring system can also be designed to monitor areas other than the controlled areas of laser processing machines, for example, to monitor areas in buildings or the like.

Further advantages of the invention will become apparent from the description and the drawings. Likewise, the above-mentioned and further listed features can be used individually or in combination. The embodiments shown and described are not intended to be exhaustive, but rather serve as examples for describing the invention.

• 1a,b eine schematische Darstellung eines Überwachungssystems, das zwei Überwachungseinheiten zur Überwachung einer Sichtlinie durch UWB-Funkübertragungen aufweist,
• 2 eine schematische Darstellung eines Überwachungssystems, das zur Überwachung eines Flächenbereichs zwei Gruppen von Überwachungseinheiten an Rändern des Flächenbereichs aufweist, und
• 3 eine schematische Darstellung einer Laserbearbeitungsmaschinen-Anordnung mit einem Überwachungssystem zum Detektieren des Betretens eines Kontrollbereichs.

They show:

• 1a ,b a schematic representation of a surveillance system comprising two monitoring units for monitoring a line of sight by UWB radio transmissions,
• 2 a schematic representation of a monitoring system having two groups of monitoring units at the edges of an area for monitoring the area, and
• 3 a schematic representation of a laser processing machine arrangement with a monitoring system for detecting entry into a controlled area.

In the following description of the drawings, identical reference symbols are used for identical or functionally identical components.

1a ,b show a radio-based surveillance system 1 comprising two monitoring units 2, 3 in the form of UWB transceivers. The two stationary monitoring units 2, 3 are arranged along a line of sight 4 at a distance A, which in the example shown is 10 meters. The surveillance system 1 is configured to monitor the line of sight 4 by transmitting signals in the form of UWB radio transmission between the two monitoring units 2, 3, both of which are configured for UWB radio transmission.

The monitoring of the line of sight 4 using UWB radio transmission is carried out based on a signal propagation time or propagation times T, T' of UWB radio signals exchanged between the two monitoring devices 2, 3. As in 1a As can be seen, the transmission of the UWB radio signals between the two monitoring units 2, 3 can take place on two different signal paths 5, 5', whereby the first, shorter signal path 5 runs along the line of sight 4 and the second, longer signal path 5' runs via a reflector 6. The reflector 6 is not arranged for the purpose of radio transmission between the two monitoring units 2, 3; rather, the UWB radio signals are reflected by practically every object present in a room.

The signal propagation time T' along the second signal path 5', which leads via the reflector 6, is longer than along the first signal path T. The two monitoring units 2, 3 are designed to determine a distance A _T between the two monitoring units 2, 3 based on the signal propagation time T, T', whereby only the shorter or minimum signal propagation time T is taken into account when determining the distance A _T. The distance A _T determined via the signal propagation time T, T' corresponds to a target distance that corresponds to the actual distance A between the two monitoring units 2, 3 of A = 10 m.

While in 1a shown example, the line of sight 4 between the two monitoring units 2, 3 is not interrupted, in the case of 1b In the example shown, the line of sight 4 between the two monitoring units 2, 3 is interrupted because a person 7 is located on the line of sight 4. Since the shorter signal path 5 running along the line of sight 4 is interrupted, the signal transmission can only take place along the second, longer signal path 5' with the longer signal propagation time T'. The distance A _T' determined by the monitoring units 2, 3 due to the longer signal propagation time via the reflector 6 lies in the 1b shown example, in which the reflector 6 is arranged in the middle between the two monitoring units 2, 3 and is at a distance of 10 cm from the line of sight 4, at A _T' = 10.002 m.

In the 1b In the example shown, an interruption of the line of sight 4 is detected by the monitoring system 1 based on the deviation of the signal propagation time T' from the target signal propagation time T along the line of sight 4, more precisely based on the deviation of the distance A _T' determined from the signal propagation time T' from the target distance A _T (which corresponds to the actual distance). The monitoring system 1 or a respective monitoring unit 2, 3 can trigger an alarm and/or take or initiate other measures upon detecting the interruption of the line of sight 4.

Based on the 1a ,b described example, it becomes clear that the accuracy in determining the distance A _T , A _T' should be in the range of a few millimeters, so that the interruption the line of sight 4 can be reliably detected. To enable this accuracy, the monitoring units 2, 3 are designed to measure the distance A _T , A _T , by a time stamp-based distance measuring method, more precisely by two-way ranging, and/or by a phase-based distance measuring method, as is the case, for example, in the DE102022202846A1 The target signal propagation time T, which corresponds to the signal propagation along the line of sight 4, can be stored in the two monitoring units 2, 3. The target signal propagation time T can be determined, for example, in a calibration operation of the monitoring system 1, in which it is ensured that the line of sight 4 is not interrupted. However, the target signal propagation time T can also be determined in another way.

2 shows a surveillance system 1 having two groups G1, G2, each with four monitoring units 2a-d, 3a-d, which serve to monitor a surface area F. The monitoring units 2a-d of the first group G1 are arranged one above the other in a monitoring column 8a at a first, left edge of the surface area F. Correspondingly, the monitoring units 3a-d of the second group G2 are arranged one above the other in a monitoring column 8b at a second, right edge of the surface area F in order to monitor lines of sight 4 between the monitoring units 2a-d of the first group G1 of monitoring units 2a-d and the monitoring units 3a-d of the second group G2 of monitoring units 3a-d. Due to the large number of monitored lines of sight 4, the entire surface area F between the two monitoring columns 8a, 8b can be monitored.

A respective monitoring unit 2a-d of the first group G1 is designed for the simultaneous monitoring of four lines of sight 4 to one of the four monitoring units 3a-d of the second group G2. Similarly, a respective monitoring unit 3a-d of the second group G2 is designed for the simultaneous monitoring of four lines of sight 4 to one of the four monitoring units 3a-d of the first group G1. 2 The surveillance system 1 shown thus serves to monitor 4 x 4 = 16 lines of sight 4, which form a planar network or a radio-based protective fence for monitoring the area F. The surveillance system 1 can thus detect a person passing through the area F.

The area F can, for example, be one of four boundary sections 9a-d of a 3 shown control area 10, the entry to which is monitored by means of a monitoring device 1, which has four of the 2 shown monitoring columns 8a-d, which are in 3 are shown in a plan view. Between each two of the monitoring columns 8a-d, a surface area in the form of a boundary section 9a-d is formed. The passage through the respective boundary section 9a-d is limited to the distances mentioned above in connection with 2 monitored in the manner described.

A laser processing machine 11 is arranged in the control area 10. The machine has a laser processing head 12 that emits laser radiation during laser processing. If the monitoring system 1 detects a passage through one of the boundary sections 9a-d, the laser processing head 12 is switched off. The laser processing machine 11, together with the monitoring device 1, forms a laser processing machine arrangement 13.

The surveillance system 1 can also be used to monitor other rooms or areas and for purposes other than monitoring lines of sight 4 or surface areas F. This utilizes the fact that the surveillance units 2, 3 in the form of UWB transceivers can also be used for other purposes. For example, one or more of the surveillance units 2a-d, 3a-d, ... of a respective surveillance column 8a-d can also be used for radar surveillance or as proximity sensors and detect when a person or object approaches the respective surveillance column 8a-d to within a predetermined distance D, as shown in 3 is shown as an example for the first monitoring column 8a.

The monitoring system 1, more precisely the monitoring units 2, 3, 2a-d, 3a-d, can also be used to locate and/or position mobile objects, which usually have a UWB tag. Such a mobile object 14, which is located outside the control area 10, is shown, for example, in 3 It is possible for the surveillance system 1 to be switchable between a first operating mode for monitoring at least one line of sight 4 and a second operating mode for locating, positioning, and/or navigating mobile objects 14. For example, when using the surveillance system 1 in a museum or the like, the second operating mode can be activated during the day to navigate people through the museum, and the first operating mode can be activated at night to use the surveillance system 1 as an alarm system.

QUOTES CONTAINED IN THE DESCRIPTION

This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 2886242 A1 [0002, 0021]
• DE 102022202846A1 [0017, 0033]

Cited non-patent literature

• https://en.wikipedia.org/wiki/Symmetrical_double-sided_two-way_ranging” or the article “Error Corrections for Ultrawideband Ranging”, J. Sidorenko et al., IEEE Transactions on Instrumentation and Measurement, Vol. 69, No. November 11, 2020 [0017]

Claims (12)

Monitoring system (1), comprising: a plurality of monitoring units (2, 2a-d, 3, 3a-d), wherein the monitoring system (1) is designed to monitor a line of sight (4) between a first and a second monitoring unit (2, 3) by means of a signal transmission between the first monitoring unit (2) and the second monitoring unit (3), characterized in that the monitoring system (1) is designed to monitor the line of sight (4) by means of a signal transmission in the form of a radio transmission between the first monitoring unit (2) and the second monitoring unit (3). Monitoring system according to Claim 1 , in which the monitoring units (2, 2a-d, 3, 3a-d) are designed for UWB radio transmission. Monitoring system according to Claim 1 or 2 , in which the monitoring units (2, 2a-d, 3, 3a-d) have a transceiver, preferably a UWB transceiver, or are designed as a transceiver, preferably as a UWB transceiver. Monitoring system according to one of the preceding claims, which is designed to monitor the line of sight (4) based on a signal propagation time (T, T') of the radio transmission between the first monitoring unit (2) and the second monitoring unit (3), in particular based on a distance (A _T , A _T' ) between the first monitoring unit (2) and the second monitoring unit (3) determined from the signal propagation time (T, T'). Monitoring system according to Claim 4 which is designed to detect an interruption of the line of sight (4) on the basis of a deviation of the signal propagation time (T') from a target signal propagation time (T), in particular on the basis of a deviation of the distance (A _{T '} ) determined from the signal propagation time (T') from a target distance (A T ) between the first and the second monitoring unit (2, 3). Monitoring system according to Claim 4 or 5 , in which the monitoring units (2, 3) are designed to measure the distance (A _T , A _T' ) by a time stamp-based distance measuring method, preferably by two-way ranging, and/or by a phase-based distance measuring method. Monitoring system according to one of the preceding claims, which is designed to monitor lines of sight (4) between at least two pairs of monitoring units (2a-d, 3a-d) by radio transmission between the two monitoring units (2a-d, 3a-d) of a respective pair of monitoring units (2a-d, 3a-d). Monitoring system according to one of the preceding claims, which has at least one monitoring unit (2a-d, 3a-d) which is designed to monitor at least two lines of sight (4) between the monitoring unit (2a-d, 3a-d) and at least two other monitoring units (3a-d, 2a-d) by radio transmission between the monitoring unit (2a-d, 3a-d) and the at least two other monitoring units (3a-d, 2a-d). Monitoring system according to Claim 7 or 8 , in which, for monitoring a surface area (F), in particular a boundary section (9a-d) of a control area (10), a first group (G1) of monitoring units (2a-d) is arranged at a first edge of the surface area (F) and a second group (G2) of monitoring units (3a-d) is arranged at a second edge of the surface area (F) in order to monitor lines of sight (4) between the monitoring units (2a-d) of the first group (G1) of monitoring units (2a-d) and the monitoring units (3a-d) of the second group (G2) of monitoring units (3a-d). Monitoring system according to one of the preceding claims, in which the monitoring units (2, 3, 2a-d, 3a-d) are designed for radar monitoring, in particular in the form of proximity sensors. Surveillance system according to one of the preceding claims, in which the monitoring units (2, 3, 2a-d, 3a-d) are designed for locating, positioning and/or navigating mobile objects (14), which preferably have a UWB tag, wherein the monitoring system (1) is preferably switchable between a first operating mode for monitoring one or more lines of sight (4) and a second operating mode for locating, positioning and/or navigating the mobile objects (14). A laser processing machine arrangement (13), comprising: a control area (10) in which a laser processing head (12) is arranged, and a monitoring system (1) according to one of the preceding claims for detecting entry into the control area (10), preferably for detecting passage through a boundary section (9a-d) of the control area (10).